WO2023066394A1 - 正极活性材料、正极极片、二次电池、电池模块、电池包和用电装置 - Google Patents

正极活性材料、正极极片、二次电池、电池模块、电池包和用电装置 Download PDF

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WO2023066394A1
WO2023066394A1 PCT/CN2022/126838 CN2022126838W WO2023066394A1 WO 2023066394 A1 WO2023066394 A1 WO 2023066394A1 CN 2022126838 W CN2022126838 W CN 2022126838W WO 2023066394 A1 WO2023066394 A1 WO 2023066394A1
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cladding layer
optionally
positive electrode
elements
active material
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PCT/CN2022/126838
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English (en)
French (fr)
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蒋耀
欧阳楚英
张欣欣
邓斌
王志强
袁天赐
徐波
陈尚栋
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宁德时代新能源科技股份有限公司
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Priority claimed from PCT/CN2021/125898 external-priority patent/WO2023065359A1/zh
Priority claimed from PCT/CN2021/130350 external-priority patent/WO2023082182A1/zh
Priority claimed from PCT/CN2021/140462 external-priority patent/WO2023115388A1/zh
Priority claimed from PCT/CN2022/084907 external-priority patent/WO2023184511A1/zh
Priority claimed from PCT/CN2022/084923 external-priority patent/WO2023184512A1/zh
Priority claimed from PCT/CN2022/099484 external-priority patent/WO2023240603A1/zh
Priority claimed from PCT/CN2022/099516 external-priority patent/WO2023240613A1/zh
Priority claimed from PCT/CN2022/099523 external-priority patent/WO2023240617A1/zh
Priority claimed from PCT/CN2022/099868 external-priority patent/WO2023245345A1/zh
Priority to KR1020247007998A priority Critical patent/KR20240046889A/ko
Priority to CN202280013384.3A priority patent/CN116964781A/zh
Application filed by 宁德时代新能源科技股份有限公司 filed Critical 宁德时代新能源科技股份有限公司
Publication of WO2023066394A1 publication Critical patent/WO2023066394A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B25/00—Phosphorus; Compounds thereof
    • C01B25/16—Oxyacids of phosphorus; Salts thereof
    • C01B25/26—Phosphates
    • C01B25/45—Phosphates containing plural metal, or metal and ammonium
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    • C01G45/00—Compounds of manganese
    • C01G45/006—Compounds containing, besides manganese, two or more other elements, with the exception of oxygen or hydrogen
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
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    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H01M4/1397—Processes of manufacture of electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/582—Halogenides
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
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    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
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    • C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
    • C01P2002/74—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by peak-intensities or a ratio thereof only
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    • C01P2004/80—Particles consisting of a mixture of two or more inorganic phases
    • C01P2004/82—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases
    • C01P2004/84—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases one phase coated with the other
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    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the technical field of lithium batteries, and in particular to a positive electrode active material, a positive electrode sheet containing the same, a secondary battery, a battery module, a battery pack and an electrical device.
  • secondary batteries have been widely used in energy storage power systems such as hydraulic, thermal, wind and solar power plants, as well as electric tools, electric bicycles, electric motorcycles, electric vehicles, Military equipment, aerospace and other fields. Due to the great development of secondary batteries, higher requirements have been put forward for their energy density, cycle performance and safety performance. As the existing positive electrode active materials for secondary batteries, the performance of materials with active transition metal doping elements such as lithium manganese phosphate needs to be improved.
  • the current positive electrode active material as well as the positive electrode sheet, secondary battery, battery module, battery pack and electrical device containing the same still need to be improved.
  • the present application is made in view of the above problems, and its purpose is to provide a lithium manganese phosphate positive electrode active material, so that the secondary battery using the positive electrode active material has a higher gram capacity, good cycle performance and safety performance.
  • the present application provides a lithium manganese phosphate positive electrode active material and a preparation method thereof, as well as related positive electrode sheets, secondary batteries, battery modules, battery packs and electrical devices.
  • the first aspect of the present application provides a positive electrode active material with a core-shell structure, including an inner core and a shell covering the inner core, wherein the chemical formula of the inner core is Li m A x Mn 1 -yByP1 -zCzO4 - nDn , said A includes one or more elements selected from Zn, Al, Na, K, Mg, Nb, Mo and W, said B Including one or more elements selected from Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb and Ge, the C includes selected from B (boron), S, Si and One or more elements in N, said D includes one or more elements selected from S, F, Cl and Br, said m is selected from the range of 0.9 to 1.1, and said x is selected from 0.001 to the range of 0.1, the y is selected from the range of 0.001 to 0.5, the z is selected from the range of 0.001 to 0.1, the
  • a positive electrode active material with a core-shell structure including an inner core and a shell covering the inner core, wherein the chemical formula of the inner core is Li a A x Mn 1-y B y P 1-z C z O 4-n D n , said A includes one or more elements selected from Zn, Al, Na, K, Mg, Nb, Mo, and W, and said B includes elements selected from Ti , V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, Nb and Ge in one or more elements, the C includes one selected from B (boron), S, Si and N One or more elements, the D includes one or more elements selected from S, F, Cl and Br, the a is selected from the range of 0.9 to 1.1, and the x is selected from the range of 0.001 to 0.1, The y is selected from the range of 0.001 to 0.5, the z is selected from the range of 0.001 to 0.1, the n is selected from the range of 0.00
  • a positive electrode active material with a core-shell structure which includes an inner core and a shell covering the inner core, the inner core comprising Li 1+x Mn 1-y A y P 1 -z R z O 4 , wherein, the x is any value within the range of -0.100 to 0.100, the y is any value within the range of 0.001 to 0.500, and the z is any value within the range of 0.001 to 0.100, so Said A is one or more elements selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and Ge.
  • the R is one or more elements selected from B, Si, N and S;
  • the The shell comprises a first cladding layer covering the inner core and a second cladding layer covering the first cladding layer; wherein the first cladding layer comprises crystalline pyrophosphate Ma P 2 O 7 and crystalline oxide M' b O c , wherein, said a is greater than 0 and less than or equal to 4, said b is greater than 0 and less than or equal to 2, said c is greater than 0 and less than or equal to 5, said M is one or more elements selected from Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb and Al, optionally one element selected from Li, Fe and Zr One or more elements, said M' is one or more elements selected from alkali metals, alkaline earth metals, transition metals, Group IIIA elements, Group IVA elements, lanthanides and Sb, optional
  • a positive electrode active material having a core-shell structure which includes an inner core and a shell covering the inner core, the inner core comprising Li 1+x Mn 1-y A y P 1 -z R z O 4 , wherein, the x is any value within the range of -0.100-0.100, the y is any value within the range of 0.001-0.600, and the z is any value within the range of 0.001-0.100, so Said A is one or more elements selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and Ge.
  • the shell includes a first cladding layer covering the inner core, a second cladding layer covering the first cladding layer, and a cladding layer covering the The third cladding layer of the second cladding layer, wherein the first cladding layer comprises crystalline pyrophosphate Li a MP 2 O 7 and/or M b (P 2 O 7 ) c , wherein the a is greater than 0 and less than or equal to 2, said b is any value within the range of 1-4, said c is any value within the range of 1-3, said crystalline pyrophosphate Li a MP 2 O 7 and M M in b (P 2 O 7 ) c is each independently one or more elements selected from Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb and Al,
  • a positive electrode active material having a core-shell structure which includes an inner core and a shell covering the inner core, the inner core comprising Li m A x Mn 1-y By y P 1 -z C z O 4-n D n , wherein, the m is selected from any value within the range of 0.5-1.2, optionally any value selected from the range of 0.9-1.1, and the x is selected from 0.001-0.5 Any value within the range, optionally any value selected from the range of 0.001-0.1, the y selected from any value within the range of 0.001-0.5, the z selected from any value within the range of 0.001-0.2, may Optionally be selected from any value within the range of 0.001-0.1, said n is selected from any value within the range of 0.001-0.5, optionally selected from any value within the range of 0.001-0.1, said A is selected from Zn , one or more elements of Al, Na, K, Mg, Nb, Mo and W, optionally one or more
  • a positive electrode active material with a core-shell structure which includes an inner core and a shell covering the inner core, the inner core comprising Li m A x Mn 1-y By y P 1 -z C z O 4-n D n , wherein, the m is selected from any value within the range of 0.9-1.1, the x is selected from any value within the range of 0.001-0.1, and the y is selected from the range of 0.001-0.6 Any value within, optionally any value selected from the range of 0.001-0.5, said z is selected from any value within the range of 0.001-0.1, said n is selected from any value within the range of 0.001-0.1, said A is one or more elements selected from Zn, Al, Na, K, Mg, Nb, Mo and W, optionally one or more elements selected from Al, Mg, Nb, Mo and W element, the B is one or more elements selected from Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn
  • a positive electrode active material which has the chemical formula Li a A x Mn 1-y By y P 1-z C z O 4-n D n , wherein, the A includes selected from One or more elements in Zn, Al, Na, K, Mg, Nb, Mo and W, and the B includes elements selected from Ti, V, Zr, Fe, Ni, Mg, Co, Ga, Sn, Sb, One or more elements in Nb and Ge, the C includes one or more elements selected from B (boron), S, Si and N, and the D includes one or more elements selected from S, F, Cl and Br One or more elements in, said a is selected from the range of 0.9 to 1.1, said x is selected from the range of 0.001 to 0.1, said y is selected from the range of 0.001 to 0.5, and said z is selected from the range of 0.001 to 0.1 The range of n is selected from the range of 0.001 to 0.1, and the positive electrode active material is electrical
  • a positive electrode active material with a core-shell structure which includes an inner core and a shell covering the inner core, and the chemical formula of the inner core is Li 1+x Mn 1-y A y P 1-z R z O 4 , where x is any value within the range of -0.100-0.100, y is any value within the range of 0.001-0.500, z is any value within the range of 0.001-0.100, the A One or more elements selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and Ge, can be One or more elements of Fe, Ti, V, Ni, Co and Mg, said R is one or more elements selected from B, Si, N and S, optionally, said R is selected from from one of B, Si, N, and S; the values of x, y, and z satisfy the following conditions: the entire inner core is kept electrically neutral; the shell includes
  • the method for providing the core material includes the following steps: Step (1): dissolving and stirring the source of manganese, the source of element B and acid in a solvent to generate doping element B The suspension of the manganese salt, the suspension is filtered and the filter cake is dried to obtain the manganese salt doped with the element B; step (2): the lithium source, the phosphorus source, the source of the element A, the source of the element C Add the source of element D, the solvent and the manganese salt doped with element B obtained by step (1) into the reaction vessel and grind and mix to obtain a slurry; step (3): transfer the slurry obtained by step (2) Spray drying and granulation in spray drying equipment to obtain granules; step (4): sintering the granules obtained in step (3) to obtain the inner core Li m A x Mn 1-y By y P 1-z C z O 4 -n D n .
  • the source of element A is selected from at least one of the simple substance, oxide, phosphate, oxalate, carbonate and sulfate of element A
  • the source of element B is selected from element B
  • the source of element C is selected from at least one of sulfate, borate, nitrate and silicate of element C
  • the source of element D is selected from at least one of element D and ammonium salt.
  • a positive electrode active material is proposed, an inner core and a shell covering the inner core, the inner core including a ternary material, d Li 2 MnO 3 ⁇ (1-d)LiMO 2 and LiMPO 4 At least one of them, 0 ⁇ d ⁇ 1, the M includes one or more selected from Fe, Ni, Co, Mn, the shell contains crystalline inorganic substances, and the crystalline inorganic substances use X
  • the full width at half maximum of the main peak measured by ray diffraction is 0-3°
  • the crystalline inorganic substance includes one or more selected from metal oxides and inorganic salts.
  • the shell includes at least one of the metal oxide and the inorganic salt, and carbon. Thereby, the conductivity as well as cycle performance and rate performance of the cathode active material can be improved.
  • the inner core includes LiMPO 4 and M includes Mn and non-Mn elements, and the non-Mn elements satisfy at least one of the following conditions: the ionic radius of the non-Mn element is a, the ionic radius of the manganese element is b,
  • the present application can at least obtain at least one of the following beneficial effects by regulating the doping site, element type and content of the doped non-Mn element: improving the conductivity and capacity of the positive electrode active material of the material, and to a certain extent Improve and even overcome its disadvantages of poor stability and cycle performance.
  • at least one of the Mn site and the P site, especially the Mn site is doped with non-Mn elements, which can reduce the lattice change rate of the positive electrode active material, improve interface performance, and reduce interface side reactions with the electrolyte. and increase capacity.
  • Doping non-Mn elements at the Li site and the O site can help improve the performance of the positive active material.
  • the positive electrode active material can have significant improvement in cycle performance and/or high temperature stability, as well as larger gram capacity and higher High compaction density.
  • the non-Mn element includes one or both of a first doping element and a second doping element
  • the first doping element is a manganese-site doping
  • the second doping element The element is phosphorus doped.
  • the first doping element and the second doping element can not only effectively reduce the dissolution of manganese, thereby reducing the migration of manganese ions to the negative electrode, reducing the consumption of electrolyte due to the decomposition of the SEI film, and improving the cycle performance and safety performance of the secondary battery. It can promote the adjustment of Mn-O bonds, reduce the migration barrier of lithium ions, promote the migration of lithium ions, and improve the rate performance of secondary batteries.
  • the first doping element satisfies at least one of the following conditions: the ionic radius of the first doping element is a, the ionic radius of the manganese element is b, and
  • the lattice change rate of the positive electrode active material can be further reduced.
  • the second doping element satisfies at least one of the following conditions: the chemical activity of the chemical bond formed between the second doping element and O is not less than the chemical activity of the P-O bond; the second doping element The highest valence of an element is not greater than 6.
  • the change rate of the Mn-O bond can be increased, the small polaron migration barrier of the positive electrode active material can be improved, and the electronic conductivity can be improved.
  • the doping of the second element can also reduce the concentration of antisite defects in the material, improve the dynamic performance and gram capacity of the material, and change the morphology of the material, thereby increasing the compaction density of the material.
  • the positive electrode active material contains at least two kinds of the first doping elements.
  • the first doping element includes Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and One or more elements in Ge.
  • the first doping element includes at least two selected from Fe, Ti, V, Ni, Co and Mg. Therefore, by doping two or more metals within the above range, the doping at the manganese site is beneficial to enhance the doping effect, further reduce the surface oxygen activity, and thereby inhibit the dissolution of manganese.
  • the doping of multiple elements can increase the synergistic effect between elements, such as increasing the battery capacity while reducing the lattice change rate of the material and enhancing the kinetic performance of the battery.
  • the first doping element includes Fe element and trivalent element, and the molar ratio of the trivalent element to the positive electrode active material is 0.001-0.05.
  • the second doping element includes one or more elements selected from B (boron), S, Si and N.
  • the positive electrode active material includes Li 1+x Mn 1-y A y P 1-z R z O 4 , x is any value in the range of -0.100-0.100, and y is in the range of 0.001-0.500 Any value within , z is any value within the range of 0.001-0.100, said A includes Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga , one or more elements of Sn, Sb, Nb and Ge, and said R includes one or more elements selected from B (boron), S, Si and N.
  • the manganese doped element A is selected from the above elements, which helps to reduce the lattice change rate of lithium manganese phosphate in the process of deintercalating lithium, improves the structural stability of lithium manganese phosphate positive electrode material, greatly reduces the dissolution of manganese and Reduce the oxygen activity on the surface of the particle;
  • the element R doped at the phosphorus position is selected from the above elements and also helps to change the difficulty of the change of the Mn-O bond length, thereby improving the electronic conductance and reducing the migration barrier of lithium ions. Migrate to improve the rate performance of the secondary battery. If the value of x is too small, the lithium content of the entire inner core system will decrease, which will affect the gram capacity of the material.
  • the value of y will limit the total amount of all doping elements. If y is too small, that is, the amount of doping is too small, the doping elements will have no effect. If y exceeds 0.5, the Mn content in the system will be less, which will affect the quality of the material. voltage platform.
  • the R element is doped at the P position, and since the PO tetrahedron is relatively stable, an excessive z value will affect the stability of the material. Therefore, when x, y, and z are selected from the above-mentioned ranges, the cathode active material may have better performance.
  • the positive electrode active material includes Li 1+x C m Mn 1-y A y P 1-z R z O 4-n D n , wherein the C is selected from Zn, Al, Na, One or more elements in K, Mg, Nb, Mo and W, said A includes Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Mg, One or more elements of Co, Ga, Sn, Sb, Nb and Ge, the R includes one or more elements selected from B (boron), S, Si and N, and the D includes the selected One or more elements from S, F, Cl and Br, x is any value in the range of -0.100-0.100, y is any value in the range of 0.001-0.500, z is in the range of 0.001-0.100 Any value of n, n is any value within the range of 0.001 to 0.1, m is any value within the range of 0.9 to 1.1.
  • the ratio of y to 1-y is 1:10 to 1:1, optionally 1:4 to 1:1.
  • the energy density and cycle performance of the positive electrode active material can be further improved.
  • (1+x):m is in the range of 9 to 1100, optionally in the range of 190-998. As a result, the energy density and cycle performance of the positive electrode active material can be further improved.
  • the ratio of z to 1-z is 1:9 to 1:999, optionally 1:499 to 1:249.
  • the cycle performance and rate performance of the secondary battery using the positive electrode active material are further improved.
  • said C, R and D are each independently any element within the above respective ranges, and said A is at least two elements within its range; optionally, said C is selected from Any element from Mg and Nb, and/or, the A is at least two elements selected from Fe, Ti, V, Co and Mg, optionally Fe and selected from Ti, V, Co and one or more elements in Mg, and/or, the R is S, and/or, the D is F.
  • the rate performance, gram capacity and/or high temperature performance of the secondary battery can be further improved.
  • the x is selected from the range of 0.001 to 0.005; and/or, the y is selected from the range of 0.01 to 0.5, optionally selected from the range of 0.25 to 0.5; and/or, the z selected from the range of 0.001 to 0.005; and/or, said n is selected from the range of 0.001 to 0.005.
  • the gram capacity, rate performance and/or kinetic performance of the material can be further improved, and/or the rate performance of the battery and/or the high temperature performance of the battery can be further improved.
  • the lattice change rate of the positive electrode active material is less than 8%, optionally less than 4%, optionally less than 3.8%, more preferably 2.0-3.8%.
  • the gram capacity and rate performance of the battery cell can be improved.
  • the Li/Mn antisite defect concentration of the positive electrode active material is 4% or less, may be 2.2% or less, more may be 1.5-2.2%, may be 2% or less, more may Preferably, it is 0.5% or less.
  • Mn 2+ can be prevented from hindering the transport of Li + , and at the same time, the gram capacity and rate performance of the positive electrode active material can be improved.
  • the surface oxygen valence state of the positive electrode active material is -1.89 to -1.98, optionally -1.90 to -1.98, more preferably -1.90 or less, more preferably -1.82 or less .
  • the surface energy of the highly active surface can be increased, and the ratio of the highly active surface can be reduced. Reduce the interface side reaction between the positive electrode material and the electrolyte, thereby improving the cycle performance of the battery cell, high-temperature storage and gas production, and then improving the cycle performance and high-temperature stability of the battery cell.
  • the positive electrode active material has a compacted density at 3T of 2.0 g/cm 3 or more, optionally 2.2 g/cm 3 or more, optionally 2.2 g/cm 3 or more and 2.8 g /cm 3 or less. Thereby, the volumetric energy density of the battery cell can be improved.
  • the crystalline inorganics include pyrophosphate QP 2 O 7 and phosphate XPO 4 , and the metal oxide includes Q' e O f , wherein each of Q and X is independently selected from Li , Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb or Al in one or more;
  • said Q includes Li and is selected from Fe, Ni, Mg, Co, Cu , one or more of Zn, Ti, Ag, Zr, Nb or Al;
  • Q' is selected from Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb and Al
  • One or more elements, optionally one or more elements selected from Li, Fe and Zr, said M' is selected from alkali metals, alkaline earth metals, transition metals, group IIIA elements, group IVA
  • One or more elements in group elements, lanthanide elements and Sb optionally selected from Li, Be, B, Na, Mg, Al, Si, P,
  • the pyrophosphate includes Li a QP 2 O 7 and/or Q b (P 2 O 7 ) c , wherein 0 ⁇ a ⁇ 2, 1 ⁇ b ⁇ 4, 1 ⁇ c ⁇ 6 , the values of a, b and c satisfy the following conditions: the Li a QP 2 O 7 or Q b (P 2 O 7 ) c is kept electrically neutral, and the Li a QP 2 O 7 and Q b ( Q in P 2 O 7 ) c is each independently one or more elements selected from Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb or Al.
  • the interplanar spacing of the phosphate is 0.244-0.425nm, optionally 0.345-0.358nm, and the included angle of the crystal direction (111) is 20.00°-37.00°, optionally 24.25°-26.45°;
  • the interplanar spacing of pyrophosphate is 0.293-0.470nm, optionally 0.293-0.326nm, and the included angle of crystal direction (111) is 18-32.57°, optionally 18-32°, optionally 19.211 °-30.846°, more preferably 26.41°-32.57°.
  • the interplanar spacing and included angle range of the crystalline material are within the above range, the impurity phase in the cladding layer can be effectively avoided, thereby improving the gram capacity, cycle performance and rate performance of the material, thereby reducing the lithium intercalation and deintercalation more effectively.
  • the lattice change rate of the positive electrode active material and the amount of manganese ion dissolution can improve the high-temperature cycle performance and high-temperature storage performance of the battery.
  • the shell contains a carbon coating layer
  • the crystalline inorganic substance is located between the inner core and the carbon coating layer
  • the carbon of the carbon coating layer is SP2 form carbon and SP3 form carbon.
  • a mixture of carbon, optionally, the molar ratio of SP2 form carbon to SP3 form carbon is any value within the range of 0.07-13, optionally any value within the range of 0.1-10, optionally within 2.0 Any value in the range -3.0.
  • the overall performance of the secondary battery is improved by limiting the molar ratio of the SP2 form carbon to the SP3 form carbon within the above range.
  • the shell comprises a first cladding layer covering the inner core and a second cladding layer covering the first cladding layer, wherein the first cladding layer comprises pyrophosphoric acid Salt QP 2 O 7 and phosphate XPO 4 , the second coating layer is a coating carbon layer.
  • the coating amount of the first coating layer is greater than 0% by weight and less than or equal to 7% by weight, optionally 4-5.6% by weight, based on the weight of the inner core.
  • the weight ratio of pyrophosphate to phosphate in the first coating layer is 1:3 to 3:1, optionally 1:3 to 1:1.
  • the coating amount of the second coating layer is greater than 0% by weight and less than or equal to 6% by weight, optionally 3-5% by weight, based on the weight of the inner core.
  • the coating amount of the first coating layer is greater than 0% by weight and less than or equal to 7% by weight, optionally 4-5.6% by weight, based on the weight of the inner core.
  • the coating amount of the first coating layer is within the above range, the function of the first coating layer can be effectively exerted, and at the same time, the kinetic performance of the secondary battery will not be affected due to the over thickness of the coating layer.
  • the weight ratio of pyrophosphate to phosphate in the first coating layer is 1:3 to 3:1, optionally 1:3 to 1:1. Therefore, by using pyrophosphate and phosphate in a suitable weight ratio range, it can not only effectively hinder the dissolution of manganese, but also effectively reduce the content of lithium impurities on the surface and reduce the side reaction at the interface, thereby improving the high-temperature storage performance and safety performance of the secondary battery. and cycle performance.
  • the crystallinity of the pyrophosphate and phosphate salts are each independently 10% to 100%, optionally 50% to 100%. Therefore, the pyrophosphate and phosphate having the crystallinity in the above-mentioned range are conducive to fully exerting the functions of pyrophosphate to hinder manganese dissolution and phosphate to reduce the content of lithium impurities on the surface and reduce the side reaction at the interface. Pyrophosphate and phosphate with a certain degree of crystallinity are not only conducive to giving full play to the ability of the pyrophosphate coating layer to hinder the dissolution of manganese and the excellent ability of the phosphate coating layer to conduct lithium ions, and to reduce the interface side reactions. Phosphate cladding and phosphate cladding enable better lattice matching, thereby enabling tighter bonding of the cladding layers.
  • the coating amount of the second coating layer is greater than 0% by weight and less than or equal to 6% by weight, optionally 3-5% by weight, based on the weight of the inner core.
  • the shell includes a first cladding layer covering the inner core and a second cladding layer covering the first cladding layer, wherein the first cladding layer includes a crystalline pyrophosphate QP 2 O 7 and metal oxide Q' e O f , the second coating layer is a coating carbon layer.
  • the coating amount of the first coating layer is greater than 0% by weight and less than or equal to 7% by weight, optionally 4-5.6% by weight, based on the weight of the inner core.
  • the weight ratio of pyrophosphate to oxide in the first coating layer is 1:3 to 3:1, optionally 1:3 to 1:1.
  • the coating amount of the second coating layer is greater than 0% by weight and less than or equal to 6% by weight, optionally 3-5% by weight, based on the weight of the inner core.
  • the shell includes a first cladding layer covering the inner core, a second cladding layer covering the first cladding layer, and a third cladding layer covering the second cladding layer.
  • a cladding layer, the first cladding layer comprises crystalline pyrophosphate, the second cladding layer comprises metal oxide Q' e O f , and the crystalline pyrophosphate comprises Li a QP 2 O 7 and /or Q b (P 2 O 7 ) c , wherein said a is greater than 0 and less than or equal to 2, said b is any value within the range of 1-4, and said c is any value within the range of 1-3 ; the third cladding layer comprises carbon.
  • the coating amount of the first coating layer is greater than 0 and less than or equal to 6% by weight, optionally greater than 0 and less than or equal to 5.5% by weight, more optionally greater than 0 and less than or equal to Equal to 2% by weight, based on the weight of the inner core; and/or the coating amount of the second coating layer is greater than 0 and less than or equal to 6% by weight, optionally greater than 0 and less than or equal to 5.5% by weight , more optionally 2% by weight-4% by weight, based on the weight of the inner core; and/or the coating amount of the third coating layer is greater than 0 and less than or equal to 6% by weight, optionally greater than 0 and less than or equal to 5.5 wt%, more optionally greater than 0 and less than or equal to 2 wt%, based on the weight of the inner core.
  • the thickness of the first cladding layer is 2-10nm; and/or the thickness of the second cladding layer is 3-15nm; and/or the thickness of the third cladding layer The thickness is 5-25nm.
  • the manganese content is in the range of 10% by weight to 35% by weight, optionally in the range of 15% by weight to 30% by weight, more optionally in the range of 17% by weight to 20% by weight.
  • the content of phosphorus element is in the range of 12 weight %-25 weight %, optionally in the range of 15 weight %-20 weight %; optionally, the weight ratio of manganese element and phosphorus element is in the range of 0.90-1.25 Within, more preferably within the range of 0.95-1.20.
  • the content of manganese element within the above range can effectively avoid problems such as deterioration of material structure stability and density decrease that may be caused if the content of manganese element is too large, thereby improving the performance of the secondary battery such as cycle, storage and compaction density; And it can avoid problems such as low voltage platform that may be caused if the manganese content is too small, thereby improving the energy density of the secondary battery.
  • the positive electrode active material includes a first cladding layer covering the inner core, a second cladding layer covering the first cladding layer, and a cladding layer covering the second cladding layer.
  • the third cladding layer wherein the first cladding layer includes crystalline pyrophosphate Li a QP 2 O 7 and/or Q b (P 2 O 7 ) c , and the second cladding layer includes crystalline Phosphate XPO 4 , the third coating layer is carbon.
  • the coating amount of the first coating layer is greater than 0 and less than or equal to 6% by weight, optionally greater than 0 and less than or equal to 5.5% by weight, more optionally greater than 0 and less than or equal to Equal to 2% by weight, based on the weight of the inner core; and/or the coating amount of the second coating layer is greater than 0 and less than or equal to 6% by weight, optionally greater than 0 and less than or equal to 5.5% by weight , more optionally 2-4% by weight, based on the weight of the inner core; and/or the coating amount of the third coating layer is greater than 0 and less than or equal to 6% by weight, optionally greater than 0 and Less than or equal to 5.5 wt%, more optionally greater than 0 and less than or equal to 2 wt%, based on the weight of the inner core.
  • the thickness of the first cladding layer is 1-10 nm; and/or the thickness of the second cladding layer is 2-15 nm; and/or the thickness of the third cladding layer is 2-25nm.
  • the manganese element content is in the range of 10% by weight to 35% by weight, optionally in the range of 15% by weight to 30% by weight, more optionally in the range of 17% by weight
  • the content of phosphorus element is in the range of 12% by weight - 25% by weight, optionally in the range of 15% by weight - 20% by weight
  • the weight ratio of manganese element and phosphorus element is in the range of 0.90-1.25, which can be Selected as 0.95-1.20.
  • a method for preparing a cathode active material includes the steps of forming an inner core, and forming a shell on at least the surface of the inner core, the inner core includes at least one of a ternary material, d Li 2 MnO 3 ⁇ (1-d)LiMO 2 and LiMPO 4 , 0 ⁇ d ⁇ 1, the M includes one or more selected from Fe, Ni, Co, Mn, the shell contains crystalline inorganic substances, and the crystalline inorganic substances use the full width at half maximum of the main peak measured by X-ray diffraction is 0-3°, and the crystalline inorganic substance includes one or more selected from metal oxides and inorganic salts.
  • the non-Mn element includes first and second doping elements
  • the method includes: mixing a manganese source, a dopant of the manganese-site element, and an acid to obtain a dopant having the first doping element.
  • Manganese salt particles of heteroelements mixing the manganese salt particles with the first doping element with lithium source, phosphorus source and the dopant of the second doping element in a solvent to obtain a slurry, in an inert gas
  • the lithium manganese phosphate compound with the doping element M is obtained after sintering under the protection of atmosphere.
  • the source of element C is selected from at least one of elemental C, oxides, phosphates, oxalates, carbonates and sulfates
  • the source of element A is selected from elemental A
  • the source of element R being selected from sulfates of element R , borate, nitrate and silicate, organic acid, halide, organic acid salt, oxide, hydroxide at least one
  • the source of element D is selected from at least one of element D and ammonium salt A sort of.
  • the obtained manganese salt particles with the first doping element meet at least one of the following conditions: at 20-120°C, optionally 40-120°C, optionally 60-120°C, more preferably
  • the manganese source, the manganese site element and the acid are mixed optionally at a temperature of 25-80°C; and/or the mixing is carried out under stirring at 200-800rpm, optionally at 400-700rpm , more optionally 500-700 rpm for 1-9h, alternatively 3-7h, more alternatively alternatively 2-6h.
  • mixing the manganese salt particles having the first doping element with the lithium source, the phosphorus source and the dopant of the second doping element in a solvent is carried out at 20-120°C, optionally 1-10h at a temperature of 40-120°C.
  • the prepared inner core and the positive electrode active material made from it have higher crystallinity and fewer lattice defects, which are beneficial to inhibit the dissolution of manganese and reduce the interface side reaction between the positive electrode active material and the electrolyte, thereby improving the cycle performance of the secondary battery and safety performance.
  • the manganese salt particles with the first doping element are combined with lithium
  • the source, the phosphorus source and the dopant of the second dopant element are milled and mixed in a solvent for 8-15 hours.
  • the shell includes a first cladding layer covering the inner core and a second cladding layer covering the first cladding layer, the first cladding layer containing the pyrophosphate salt QP 2 O 7 and said phosphate XPO 4 , said second coating layer comprises carbon, said method comprising: providing QP 2 O 7 powder and a suspension of XPO 4 comprising a source of carbon, said inner core , QP 2 O 7 powder is added to the XPO 4 suspension containing carbon sources and mixed, and sintered to obtain positive electrode active materials.
  • the providing QP 2 O 7 powder includes: adding the source of element Q and the source of phosphorus to the solvent to obtain a mixture, adjusting the pH of the mixture to 4-6, stirring and fully reacting, and then drying , obtained by sintering, and the QP 2 O 7 powder provided meets at least one of the following conditions: the drying is at 100-300°C, optionally at 150-200°C for 4-8h; the sintering is at 500- Sinter at 800°C, optionally at 650-800°C, for 4-10 hours in an inert gas atmosphere.
  • the sintering temperature for forming the cladding layer is 500-800° C., and the sintering time is 4-10 hours.
  • forming the shell comprises: providing Li a QP 2 O 7 and/or Q b (P 2 O 7 ) c and XPO 4 suspensions respectively, adding the inner core to the suspension and mixed, and sintered to obtain the positive electrode active material.
  • forming the shell comprises: dissolving a source of element Q, a phosphorus source and an acid, and optionally a lithium source in a solvent to obtain a suspension of the first coating layer; combining the inner core with the The suspension of the first coating layer is mixed and sintered to obtain the material covered by the first coating layer; the source of element X, the phosphorus source and the acid are dissolved in a solvent to obtain the suspension of the second coating layer; The material coated with the first coating layer is mixed with the suspension of the second coating layer and sintered to obtain a material coated with two coating layers; the carbon source is dissolved in a solvent to obtain a third coating layer solution; adding the materials covered by the two layers of coating layers into the third coating layer solution, mixing, drying and sintering to obtain the positive electrode active material.
  • the pH of the solution dissolved with the source of element Q, phosphorus source and acid, and optionally lithium source is controlled to be 3.5-6.5, stirred and reacted for 1 -5h, the temperature of the solution is raised to 50-120°C and maintained for 2-10h, and/or, the sintering is carried out at 650-800°C for 2-6 hours.
  • the solution when forming the material covered by the two-layer coating layer, after dissolving the source of element X, phosphorus source and acid in the solvent, stirring and reacting for 1-10 h, the solution is heated to 60- 150°C for 2-10 hours, and/or, sintering at 500-700°C for 6-10 hours.
  • the sintering in the step of forming the third cladding is carried out at 700-800° C. for 6-10 hours.
  • the shell includes a first cladding layer covering the inner core, a second cladding layer covering the first cladding layer, wherein the first cladding layer includes a crystalline pyrophosphate QP 2 O 7 and said metal oxide Q' e O f , said second cladding layer comprising carbon, forming said shell comprises: providing a powder comprising crystalline pyrophosphate QP 2 O 7 and comprising A suspension of carbon source and oxide Q'eOf , mixing the inner core, powder comprising crystalline pyrophosphate QP2O7 and a suspension comprising carbon source and oxide Q'eOf , Sintering to obtain positive electrode active material.
  • the shell includes a first cladding layer covering the inner core, a second cladding layer covering the first cladding layer, and a second cladding layer covering the second cladding layer.
  • Three cladding layers wherein, the first cladding layer includes crystalline pyrophosphate QP 2 O 7 , the second cladding layer includes the metal oxide Q' e O f , and the third cladding layer
  • the layer comprises carbon, forming the shell comprising: providing a first mixture comprising pyrophosphate Li a QP 2 O 7 and/or Q b (P 2 O 7 ) c , mixing the core material with the first mixture, drying, sintering , obtain the material covered by the first cladding layer; provide the second mixture comprising the metal oxide Q' e O f , mix the material covered by the first cladding layer with the second mixture, dry, and sinter , to obtain the material coated with the second coating layer; providing a third mixture containing carbon source, mixing the material coated with the second coating
  • the source of element Q, phosphorus source, acid, optional lithium source and optional solvent are mixed to obtain the first mixture; and/or, to form the
  • the source of the element Q' is mixed with a solvent to obtain a second mixture; and/or, when the third cladding layer is formed, a carbon source is mixed with a solvent to obtain a third mixture; optionally, forming
  • the source of element Q, phosphorus source, acid, optional lithium source and optional solvent are mixed at room temperature for 1-5 hours, then heated to 50°C-120°C and kept at this temperature mixing for 2-10 hours, and the above-mentioned mixing is carried out at a pH of 3.5-6.5; optionally, when forming the second coating layer, the source of the element Q' and the solvent are mixed at room temperature for 1-10 hours, Then raise the temperature to 60°C-150°C and keep mixing at this temperature for 2-10h.
  • the sintering in the first cladding step, is carried out at 650-800° C. for 2-8 hours; and/or, in the second cladding step, the sintering is carried out at 400-750° C. °C for 6-10 hours; and/or, in the third coating step, the sintering is performed at 600-850 °C for 6-10 hours.
  • the shell includes a first cladding layer covering the inner core, a second cladding layer covering the first cladding layer, wherein the first cladding layer includes a crystalline pyrophosphate QP 2 O 7 and said metal oxide Q' e O f , said second cladding layer comprising carbon, forming said shell comprises: providing a powder comprising crystalline pyrophosphate QP 2 O 7 and comprising A suspension of carbon source and oxide Q'eOf , mixing the inner core, powder comprising crystalline pyrophosphate QP2O7 and a suspension comprising carbon source and oxide Q'eOf , Sintering to obtain positive electrode active material.
  • the shell includes a first cladding layer covering the inner core, a second cladding layer covering the first cladding layer, and a second cladding layer covering the second cladding layer.
  • Three cladding layers wherein, the first cladding layer includes crystalline pyrophosphate QP 2 O 7 , the second cladding layer includes the metal oxide Q' e O f , and the third cladding layer
  • the layer comprises carbon, forming the shell comprising: providing a first mixture comprising pyrophosphate Li a QP 2 O 7 and/or Q b (P 2 O 7 ) c , mixing the core material with the first mixture, drying, sintering , obtain the material covered by the first cladding layer; provide the second mixture comprising the metal oxide Q' e O f , mix the material covered by the first cladding layer with the second mixture, dry, and sinter , to obtain the material coated with the second coating layer; providing a third mixture containing carbon source, mixing the material coated with the second coating
  • the source of element Q, phosphorus source, acid, optional lithium source and optional solvent are mixed to obtain the first mixture; and/or, to form the
  • the source of the element Q' is mixed with a solvent to obtain a second mixture; and/or, when the third cladding layer is formed, a carbon source is mixed with a solvent to obtain a third mixture; optionally, forming
  • the source of element Q, phosphorus source, acid, optional lithium source and optional solvent are mixed at room temperature for 1-5 hours, then heated to 50°C-120°C and kept at this temperature mixing for 2-10 hours, and the above-mentioned mixing is carried out at a pH of 3.5-6.5; optionally, when forming the second coating layer, the source of the element Q' and the solvent are mixed at room temperature for 1-10 hours, Then raise the temperature to 60°C-150°C and keep mixing at this temperature for 2-10h.
  • the sintering in the first cladding step, is carried out at 650-800° C. for 2-8 hours; and/or, in the second cladding step, the sintering is carried out at 400-750° C. °C for 6-10 hours; and/or, in the third coating step, the sintering is performed at 600-850 °C for 6-10 hours.
  • the doping elements can be uniformly distributed, and the crystallinity of the material after sintering is higher, thereby improving the gram capacity and rate performance of the material.
  • the present application proposes a secondary battery, wherein the positive electrode active material described above or the positive electrode active material prepared by the method described above or the positive electrode sheet described above are included.
  • the present application proposes a battery module, which includes the aforementioned secondary battery.
  • the present application proposes a battery pack, which includes the aforementioned battery module.
  • the present application proposes an electrical device, which includes at least one selected from the foregoing secondary battery, battery module, or battery pack.
  • Fig. 1 is the X-ray diffraction spectrum (XRD) pattern of undoped LiMnPO4 and the cathode active material prepared in Example 2.
  • Example 2 is an X-ray energy dispersive spectrum (EDS) diagram of the positive electrode active material prepared in Example 2.
  • EDS X-ray energy dispersive spectrum
  • FIG. 3 is a schematic diagram of the positive electrode active material having a core-shell structure described in the present application.
  • FIG. 4 is a schematic diagram of a positive electrode active material with a core-shell structure according to an embodiment of the present application.
  • FIG. 5 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG. 6 is an exploded view of the secondary battery according to one embodiment of the present application shown in FIG. 5 .
  • FIG. 7 is a schematic diagram of a battery module according to an embodiment of the present application.
  • FIG. 8 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG. 9 is an exploded view of the battery pack according to one embodiment of the present application shown in FIG.
  • FIG. 10 is a schematic diagram of an electrical device in which a secondary battery is used as a power source according to an embodiment of the present application.
  • ranges disclosed herein are defined in terms of lower and upper limits, and a given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive and may be combined arbitrarily, ie any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are contemplated. Additionally, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, the following ranges are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-5.
  • the numerical range “a-b” represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers.
  • the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article, and "0-5" is only an abbreviated representation of the combination of these values.
  • a certain parameter is an integer ⁇ 2
  • "about" a certain numerical value represents a range, which means the range of ⁇ 10% of the numerical value.
  • all the implementation modes and optional implementation modes of the present application can be combined with each other to form new technical solutions. If there is no special description, all the technical features and optional technical features of the present application can be combined with each other to form a new technical solution.
  • all steps in the present application can be performed sequentially or randomly, preferably sequentially.
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed in sequence, and may also include steps (b) and (a) performed in sequence.
  • step (c) means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c) , may also include steps (a), (c) and (b), may also include steps (c), (a) and (b) and so on.
  • the "comprising” and “comprising” mentioned in this application mean open or closed.
  • the “comprising” and “comprising” may mean that other components not listed may be included or included, or only listed components may be included or included.
  • the term “or” is inclusive unless otherwise stated.
  • the phrase “A or B” means "A, B, or both A and B.” More specifically, the condition “A or B” is satisfied by either of the following: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists) ; or both A and B are true (or exist).
  • coating layer and “coating” refer to a material layer coated on core materials such as lithium manganese phosphate, and the material layer can completely or partially cover the core, using “Cover layer” is just for convenience of description and is not intended to limit the present invention.
  • each cladding layer can be fully clad or partially clad.
  • thickness of the coating layer refers to the thickness of the material layer coated on the inner core in the radial direction of the inner core.
  • the present application proposes a positive electrode active material, which has an inner core and a shell covering the inner core, and the inner core includes a ternary material, d Li 2 MnO 3 ⁇ (1-d)LiMO 2 And at least one of LiMPO 4 , 0 ⁇ d ⁇ 1, the M includes one or more selected from Fe, Ni, Co, Mn, the shell contains crystalline inorganic matter, and the crystalline inorganic
  • the full width at half maximum of the main peak measured by X-ray diffraction of the compound is 0-3°
  • the crystalline inorganic compound includes one or more selected from metal oxides and inorganic salts.
  • the crystal lattice structure of the material in the crystalline state is stable, and it has a better interception effect on the active metal ions that are easy to dissolve, such as Mn.
  • the inventors of the present application have found that the positive active materials currently used in lithium-ion secondary batteries are often used in ternary positive active materials or may be used in order to improve battery performance, such as increasing capacity, improving rate performance, cycle performance, etc.
  • Doping elements are added to LiMPO 4 in a high-voltage system, such as LiMnPO 4 , LiNiPO 4 , LiCoPO 4 , or Li-rich manganese-based positive electrode active materials.
  • the above-mentioned doping elements can replace the active transition metal and other sites in the above-mentioned materials, so as to improve the battery performance of the materials.
  • Mn elements may be added to materials such as lithium iron phosphate, but the addition or doping of the above-mentioned active transition metals and other elements may easily lead to the dissolution of active metals such as Mn ions during the deep charge and discharge process of the material.
  • the dissolved active metal elements will further migrate to the electrolyte, causing a catalyst-like effect after the negative electrode is reduced, leading to the dissolution of the SEI film (solid electrolyte interphase, solid electrolyte interphase film) on the surface of the negative electrode.
  • the dissolution of the above-mentioned metal elements will also lead to the loss of the capacity of the positive active material, and after the dissolution, the crystal lattice of the positive active material will have defects, resulting in problems such as poor cycle performance. Therefore, it is necessary to improve the positive electrode materials based on the above-mentioned active metal elements to alleviate or even solve the above-mentioned problems.
  • the inventors found that the main peak of X-ray diffraction measurement has the above-mentioned full width at half maximum.
  • the crystalline inorganic substance has a better ability to intercept and dissolve active metal ions, and the crystalline inorganic substance and the aforementioned core material can be well combined, and has a stable
  • the bonding force is not easy to cause the problem of detachment during use, and a coating layer with an appropriate area and good uniformity can be realized by a relatively simple method.
  • the inventors of the present application have found in actual operation that the existing lithium manganese phosphate positive electrode active material suffers from serious dissolution of manganese ions during deep charging and discharging. Although there is an attempt in the prior art to coat lithium manganese phosphate with lithium iron phosphate to reduce interfacial side reactions, this coating cannot prevent the dissolved manganese ions from continuing to migrate into the electrolyte. The dissolved manganese ions are reduced to metal manganese after migrating to the negative electrode.
  • the metal manganese produced in this way is equivalent to a "catalyst", which can catalyze the decomposition of the SEI film (solid electrolyte interphase, solid electrolyte interphase film) on the surface of the negative electrode to produce by-products; a part of the by-products is gas, so it will cause secondary battery damage.
  • another part of the by-product is deposited on the surface of the negative electrode, which will hinder the passage of lithium ions in and out of the negative electrode, causing the impedance of the secondary battery to increase, thereby affecting the kinetic performance of the secondary battery.
  • the electrolyte and the active lithium inside the battery are continuously consumed, which will have an irreversible impact on the capacity retention of the secondary battery.
  • a new type of positive electrode active material with a core-shell structure can be obtained, and the positive electrode active material can achieve significantly reduced manganese ion dissolution and reduce
  • the crystal lattice change rate, which is used in secondary batteries, can improve the cycle performance, rate performance, safety performance of the battery and increase the capacity of the battery.
  • the inner core includes LiMPO 4 and M includes Mn and non-Mn elements, and the non-Mn elements meet at least one of the following conditions: the ionic radius of the non-Mn elements is a, and the ions of manganese elements The radius is b,
  • lithium manganese phosphate As the positive electrode active material of lithium-ion secondary batteries, compounds that can be applied to high-voltage systems in the future, such as lithium manganese phosphate, lithium iron phosphate, or lithium nickel phosphate, have lower costs and better application prospects. But taking lithium manganese phosphate as an example, its disadvantage compared with other positive electrode active materials is its poor rate performance, which is usually solved by means of coating or doping. However, it is still hoped that the rate performance, cycle performance, and high temperature stability of lithium manganese phosphate cathode active materials can be further improved.
  • the inventors of the present application have repeatedly studied the effects of doping with various elements at the Li-site, Mn-site, P-site and O-site of lithium manganese phosphate, and found that by controlling the doping site and specific elements, doping Impurities can improve the gram capacity, rate performance and cycle performance of positive electrode active materials.
  • selecting an appropriate doping element at the Mn site can improve the lattice change rate of lithium manganese phosphate in the process of intercalation and deintercalation of lithium, improve the structural stability of the positive electrode material, greatly reduce the dissolution of manganese, and reduce the particle surface.
  • Oxygen activity can increase the gram capacity of the material, reduce the interface side reaction between the material and the electrolyte during use, and improve the cycle performance of the material.
  • selecting an element with an ionic radius similar to that of the Mn element as the doping element at the Mn site, or selecting an element whose valence variable valence range is within the valence variable valence range of Mn for doping can control the bond length between the doping element and O
  • the amount of change in the length of the bond with the Mn-O bond is conducive to stabilizing the lattice structure of the doped positive electrode material.
  • a vacancy element at the Mn site to support the lattice, such as the valence of the element is greater than or equal to the sum of the valence of Li and Mn, which is equivalent to introducing an incompatible element at the active and easy-to-dissolve Mn site.
  • the vacant sites where Li is combined can play a supporting role in the crystal lattice.
  • choosing an appropriate P-site doping element can help change the difficulty of changing the Mn-O bond length, thereby improving electronic conductivity and reducing the migration barrier of lithium ions, promoting lithium ion migration, and increasing the rate of secondary batteries performance.
  • the tetrahedral structure of the P-O bond itself is relatively stable, making it difficult to change the length of the Mn-O bond, resulting in a high barrier to lithium ion migration in the material as a whole, and appropriate P-site doping elements can improve the robustness of the P-O bond tetrahedron. degree, thereby promoting the improvement of the rate performance of the material.
  • the chemical activity of the chemical bond formed with O can be selected to be not less than that of the P-O bond to be doped at the P site, thereby improving the difficulty of changing the length of the Mn-O bond.
  • the chemical activity of the chemical bond formed with O is not less than the chemical activity of the P-O bond
  • the valence state is not significantly higher than P, for example, elements lower than 6 can be doped at the P site, which is beneficial to reduce the repulsion of Mn and P elements, and can also improve the gram capacity and rate performance of the material.
  • appropriate element doping at the Li site can also improve the lattice change rate of the material and maintain the battery capacity of the material.
  • O-site doping elements can help to improve the interface side reactions between the material and the electrolyte, reduce the interface activity, and thus help to improve the cycle performance of the positive electrode active material.
  • O can also be doped to improve the corrosion resistance of materials such as HF, which is beneficial to improve the cycle performance and life of materials.
  • the non-Mn element doped at the above-mentioned site may include one or both of the first doping element and the second doping element, and the first doping element is manganese site-doped, so The second doping element is phosphorus doping.
  • the first doping element satisfies at least one of the following conditions: the ionic radius of the first doping element is a, the ionic radius of the manganese element is b, and
  • the valence change voltage is U, 2V ⁇ U ⁇ 5.5V.
  • the second doping element satisfies at least one of the following conditions: the chemical activity of the chemical bond formed by the second doping element and O is not less than the chemical activity of the P-O bond; the highest valence of the doping element M and the second doping element No more than 6.
  • the positive electrode active material may also contain two kinds of first doping elements at the same time.
  • the Mn site and the P site among the above positions can be doped at the same time. As a result, it can not only effectively reduce the dissolution of manganese, and then reduce the migration of manganese ions to the negative electrode, reduce the consumption of electrolyte due to the decomposition of the SEI film, improve the cycle performance and safety performance of the secondary battery, and also promote the adjustment of the Mn-O bond. Reduce the lithium ion migration barrier, promote lithium ion migration, and improve the rate performance of the secondary battery.
  • the cathode active material of the present application can be used in lithium ion secondary batteries, for example.
  • the first doping element includes one or more selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and Ge element.
  • the first doping element includes at least two selected from Fe, Ti, V, Ni, Co and Mg.
  • the second doping element includes one or more elements selected from B (boron), S, Si, and N.
  • the above-mentioned doping elements should keep the system electrically neutral, so as to ensure that there are as few defects and impurity phases in the positive electrode active material as possible. If there is an excess of transition metals (such as manganese) in the positive electrode active material, since the structure of the material system itself is relatively stable, the excess transition metals are likely to be precipitated in the form of simple substances, or form impurity phases inside the lattice to maintain electrical neutrality. Sex can make such impurity as little as possible. In addition, ensuring the electrical neutrality of the system can also generate lithium vacancies in the material in some cases, so that the kinetic performance of the material is better.
  • transition metals such as manganese
  • the inventors of the present application have found in actual operation that the existing lithium manganese phosphate positive electrode active material suffers from severe manganese dissolution during the deep charge and discharge process. After a lot of research, the inventors found that a new type of positive electrode active material can be obtained by modifying lithium manganese phosphate, and the positive electrode active material can achieve significantly reduced manganese dissolution and reduced lattice change rate, which is used for In secondary batteries, the cycle performance, rate performance, and safety performance of the battery can be improved, and the capacity of the battery can be increased.
  • the entire inner core system maintains electrical neutrality, which can ensure that the defects and impurity phases in the positive electrode active material are as small as possible.
  • transition metals such as manganese
  • the excess transition metals are likely to be precipitated in the form of simple substances, or form impurity phases inside the lattice to maintain electrical neutrality. Sex can make such impurity as little as possible.
  • ensuring the electrical neutrality of the system can also generate lithium vacancies in the positive electrode active material in some cases, so that the kinetic performance of the positive electrode active material is better.
  • the above-mentioned positive electrode active material may have a compound of the chemical formula Li 1+x Mn 1-y A y P 1-z R z O 4 , wherein x is any value in the range of -0.100-0.100, and y It is any value in the range of 0.001-0.500, z is any value in the range of 0.001-0.100, and the A includes Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe , one or more elements of Ni, Co, Ga, Sn, Sb, Nb and Ge, and the R includes one or more elements selected from B (boron), S, Si and N.
  • the values of x, y and z satisfy the following condition: the whole compound remains electrically neutral.
  • the positive electrode active material may have a chemical formula of Li 1+ xC m Mn 1-y A y P 1-z R z O 4-n D n , wherein the C includes Zn , Al, Na, K, Mg, Nb, Mo and W in one or more elements, said A includes Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe , one or more elements in Ni, Mg, Co, Ga, Sn, Sb, Nb and Ge, the R includes one or more elements selected from B (boron), S, Si and N,
  • the D includes one or more elements selected from S, F, Cl and Br, x is any value within the range of 0.100-0.100, y is any value within the range of 0.001-0.500, and z is any value within the range of 0.001 Any value within the range of -0.100, n is any value within the range of 0.001 to 0.1, and m is any value within the range of 0.9 to 1.1.
  • the C
  • the above-mentioned limitation of the numerical range of x, y, z or m is not only for each element as the site.
  • the limitation of the stoichiometric number is also the limitation of the sum of the stoichiometric numbers of each element as the site.
  • A is selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and Ge
  • G, D, E, K are each independently selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb , one of Nb and Ge, optionally, at least one of G, D, E and K is Fe.
  • one of n1, n2, n3, n4 is zero, and the rest are not zero; more optionally, two of n1, n2, n3, n4 are zero, and the rest are not zero; also optionally, Three of n1, n2, n3, n4 are zero, and the rest are not zero.
  • doping a One, two or three of the above-mentioned A elements in addition, it is advantageous to dope one or two R elements at the phosphorus site, which is conducive to uniform distribution of doping elements.
  • Mn sites can have both Fe and V doping.
  • the ratio of y to 1-y is 1:10 to 1:1, optionally 1:4 to 1:1.
  • y represents the sum of the stoichiometric numbers of the Mn-site doping elements A.
  • the ratio of z to 1-z is 1:9 to 1:999, optionally 1:499 to 1:249.
  • z represents the sum of the stoichiometric numbers of the P-site doping elements R.
  • the positive electrode active material may contain Li 1+x C m Mn 1-y A y P 1-z R z O 4-n D n .
  • the size of x is affected by the valence size of A and R and the size of y and z, so as to ensure that the whole system is electrically neutral. If the value of x is too small, the lithium content of the entire inner core system will decrease, which will affect the gram capacity of the material. The value of y will limit the total amount of all doping elements. If y is too small, that is, the amount of doping is too small, the doping elements will have no effect.
  • y exceeds 0.5, the Mn content in the system will be less, which will affect the quality of the material. voltage platform.
  • the R element is doped at the position of P. Since the PO tetrahedron is relatively stable, but too large a z value will affect the stability of the material, so the z value is limited to 0.001-0.100. More specifically, x is any value within the range of 0.100-0.100, y is any value within the range of 0.001-0.500, z is any value within the range of 0.001-0.100, n is any value within the range of 0.001 to 0.1 Value, m is any value in the range of 0.9 to 1.1.
  • the 1+x is selected from the range of 0.9 to 1.1, such as 0.97, 0.977, 0.984, 0.988, 0.99, 0.991, 0.992, 0.993, 0.994, 0.995, 0.996, 0.997, 0.998, 1.01
  • the x is selected from The range of 0.001 to 0.1, such as 0.001, 0.005, said y is selected from the range of 0.001 to 0.5, such as 0.001, 0.005, 0.02, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.34, 0.345, 0.349, 0.35 , 0.4
  • the z is selected from the range of 0.001 to 0.1, such as 0.001, 0.005, 0.08, 0.1
  • the n is selected from the range of 0.001 to 0.1, such as 0.001, 0.005, 0.08, 0.1, and the positive electrode activity
  • the material is electrically neutral.
  • the positive electrode active material of the present application is obtained by element doping in the compound LiMnPO 4 etc., without wishing to be bound by theory, it is believed that the performance improvement of lithium manganese phosphate is related to the reduction of lithium manganese phosphate in the lithium deintercalation process.
  • the lattice change rate is related to the reduced surface activity. Reducing the lattice change rate can reduce the lattice constant difference between the two phases at the grain boundary, reduce the interfacial stress, and enhance the Li + transport capacity at the interface, thereby improving the rate performance of the positive electrode active material.
  • high surface activity can easily lead to serious interface side reactions, aggravate gas production, electrolyte consumption, and interface damage, thereby affecting battery cycle performance.
  • the lattice change rate is reduced by Li and Mn site doping.
  • Mn-site doping can also effectively reduce surface activity, thereby inhibiting the dissolution of Mn and the interface side reaction between the positive electrode active material and the electrolyte.
  • P-site doping makes the change rate of the Mn-O bond length faster, lowers the small polaron migration barrier of the material, and thus is beneficial to the electronic conductivity.
  • O-site doping has a good effect on reducing the side reactions at the interface. The doping of P site and O site also affects the Mn stripping and kinetic properties of antisite defects.
  • doping reduces the concentration of antisite defects in the material, improves the dynamic performance and gram capacity of the material, and can also change the morphology of the particles, thereby increasing the compaction density.
  • the applicant unexpectedly found that by simultaneously doping a specific element in a specific amount at the Li site, Mn site, P site, and O site of the compound LiMnPO 4 , significantly improved rate performance can be obtained while significantly reducing the Mn and Mn site Dissolution of doping elements results in significantly improved cycle performance and/or high temperature stability, and the gram capacity and compacted density of the material can also be increased.
  • the lattice change rate during the delithiation process can be further reduced, thereby further improving the rate performance of the battery.
  • the Mn-site doping elements within the above range the electronic conductivity can be further improved and the lattice change rate can be further reduced, thereby improving the rate performance and gram capacity of the battery.
  • the P-site doping element within the above range the rate performance of the battery can be further improved.
  • the side reactions at the interface can be further reduced, and the high-temperature performance of the battery can be improved.
  • the x is selected from the range of 0.001 to 0.005; and/or, the y is selected from the range of 0.01 to 0.5, optionally selected from the range of 0.25 to 0.5; and/or, the z selected from the range of 0.001 to 0.005; and/or, said n is selected from the range of 0.001 to 0.005.
  • the value of y within the above range the gram capacity and rate performance of the material can be further improved.
  • the value of x within the above range the dynamic performance of the material can be further improved.
  • the z value within the above range the rate performance of the secondary battery can be further improved.
  • the value of n within the above range the high temperature performance of the secondary battery can be further improved.
  • the positive electrode active material having four sites all doped with non-Mn elements satisfies: (1-y): y is in the range of 1 to 4, optionally in the range of 1.5 to 3, And (1+x):m is in the range of 9 to 1100, optionally in the range of 190-998.
  • y represents the sum of stoichiometric numbers of Mn-site doping elements.
  • the positive electrode active material can have Li 1+x Mn 1-y A y P 1-z R z O 4 and Li 1+x C m Mn 1-y A y P 1-z R z O At least one of 4-n D n .
  • the ratio of y to 1-y is 1:10 to 1:1, optionally 1:4 to 1:1.
  • the ratio of z to 1-z is 1:9 to 1:999, optionally 1:499 to 1:249.
  • C, R and D are each independently any element within the above respective ranges, and said A is at least two elements within its range; optionally, said C is any one selected from Mg and Nb one element, and/or, the A is at least two elements selected from Fe, Ti, V, Co and Mg, optionally Fe and one or more elements selected from Ti, V, Co and Mg , and/or, the R is S, and/or, the D is F.
  • x is selected from the range of 0.001 to 0.005; and/or, the y is selected from the range of 0.01 to 0.5, optionally selected from the range of 0.25 to 0.5; and/or, the z is selected from the range of 0.001 to 0.005 range; and/or, said n is selected from the range of 0.001 to 0.005.
  • x is selected from the range of 0.001 to 0.005; and/or, the y is selected from the range of 0.01 to 0.5, optionally selected from the range of 0.25 to 0.5; and/or, the z is selected from the range of 0.001 to 0.005 range; and/or, said n is selected from the range of 0.001 to 0.005.
  • the lattice change rate of the positive electrode active material is less than 8%, optionally, the lattice change rate is less than 4%.
  • the rate of lattice change can be measured by methods known in the art, such as X-ray diffraction (XRD).
  • XRD X-ray diffraction
  • the lithium-deintercalation process of LiMnPO 4 is a two-phase reaction. The interfacial stress of the two phases is determined by the lattice change rate. The smaller the lattice change rate, the smaller the interfacial stress and the easier Li + transport. Therefore, reducing the lattice change rate of doped LiMnPO4 will be beneficial to enhance the transport ability of Li+, thereby improving the rate performance of secondary batteries.
  • the average discharge voltage of the positive electrode active material is above 3.5V, and the discharge gram capacity is above 140mAh/g; optionally, the average discharge voltage is above 3.6V, and the discharge gram capacity is above 145mAh /g or more.
  • the average discharge voltage of undoped LiMnPO 4 is above 4.0V, its discharge gram capacity is low, usually less than 120mAh/g, so the energy density is low; adjusting the lattice change rate by doping can make it The discharge gram capacity has been greatly improved, and the overall energy density has increased significantly under the condition of a slight drop in the average discharge voltage.
  • the Li/Mn antisite defect concentration of the positive electrode active material is less than 2%, and optionally, the Li/Mn antisite defect concentration is less than 0.5%.
  • the so-called Li/Mn antisite defect refers to the exchange of the positions of Li + and Mn 2+ in the LiMnPO4 lattice.
  • the Li/Mn antisite defect concentration refers to the percentage of Li + that is exchanged with Mn 2+ in the total Li + in the cathode active material.
  • the Mn 2+ of antisite defects will hinder the transport of Li + , which is beneficial to improve the gram capacity and rate performance of positive electrode active materials by reducing the concentration of Li/Mn antisite defects.
  • the Li/Mn antisite defect concentration can be measured by methods known in the art, such as XRD.
  • the surface oxygen valence state of the positive electrode active material is below -1.82, optionally between -1.89 and -1.98.
  • EELS electron energy loss spectroscopy
  • the positive electrode active material has a compacted density of 2.0 g/cm3 or more at 3T (ton), optionally 2.2 g/cm3 or more.
  • the compacted density can be measured according to GB/T 24533-2009.
  • the average particle size range of the inner core prepared by the present application is 50-500nm, and the Dv50 is 200-300nm.
  • the primary particle size of the core is in the range of 50-500nm, and the Dv50 is 200-300nm. If the average particle size of the inner core is too large (over 500nm), the gram capacity of the battery using the material will be affected; Cover evenly.
  • the inventors of the present application cut out the middle region (core region) of the prepared positive electrode active material particles by focusing ion beam (abbreviated as FIB), and examined them by transmission electron microscope (abbreviated as TEM) and X-ray energy spectrum analysis (abbreviated as EDS) test found that the distribution of each element is uniform and no aggregation occurs.
  • FIB focusing ion beam
  • EDS X-ray energy spectrum analysis
  • the positive electrode active material inner core of the present application is basically consistent with the position of the main characteristic peak before doping with LiMnPO , illustrates that the lithium manganese phosphate positive active material inner core of doping has no impurity phase, and the improvement of battery performance mainly comes from element doping, and not caused by impurities.
  • the cathode active material has a core-shell structure, wherein the shell contains at least one of a crystalline inorganic substance and a metal oxide.
  • the crystalline inorganic substance includes pyrophosphate QP 2 O 7 and phosphate XPO 4
  • the metal oxide includes Q' e O f .
  • said Q and X are each independently selected from one or more of Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb or Al; optionally said Q includes Li And one or more selected from Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb or Al; Q' is selected from Li, Fe, Ni, Mg, Co, Cu, Zn , one or more elements of Ti, Ag, Zr, Nb and Al, optionally one or more elements selected from Li, Fe and Zr, and the M' is selected from alkali metals, alkaline earth One or more of metals, transition metals, Group IIIA elements, Group IVA elements, lanthanides and Sb, optionally selected from the group consisting of Li, Be, B, Na, Mg, Al, Si, P , K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, As, Se, Sr, Y, Zr, Nb,
  • the pyrophosphate includes Li a QP 2 O 7 and/or Q b (P 2 O 7 ) c , where 0 ⁇ a ⁇ 2, 1 ⁇ b ⁇ 4, 1 ⁇ c ⁇ 6, and
  • the values of a, b and c satisfy the following conditions: the Li a QP 2 O 7 or Q b (P 2 O 7 ) c is kept electrically neutral, and the Li a QP 2 O 7 and Q b (P 2 Q in O 7 ) c is each independently one or more elements selected from Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb or Al.
  • pyrophosphate as a coating layer can effectively isolate doped metal ions from the electrolyte. And the structure of crystalline pyrophosphate is stable, therefore, the coating of crystalline pyrophosphate can effectively inhibit the dissolution of transition metals and improve cycle performance.
  • Crystalline phosphate and crystalline pyrophosphate have a high degree of lattice matching (mismatch degree is only 3%), good stability and excellent ability to conduct lithium ions, and coating the core with it can improve the positive electrode active material.
  • the stability of the electrolyte can effectively reduce the interface side reaction of the electrolyte, thereby improving the high-temperature cycle and storage performance of the battery.
  • oxides can also play a role in stabilizing the dissolution of active doped metals, and oxides are easy to synthesize and have low cost.
  • the appropriate ratio of oxides and crystalline inorganic substances such as pyrophosphates is It is beneficial to give full play to the synergistic effect of the two, and can further inhibit the dissolution of manganese, while maintaining a low impedance of the secondary battery.
  • the pyrophosphate and phosphate salts each independently have a crystallinity of 10% to 100%, optionally 50% to 100%.
  • the interplanar spacing of the phosphate is 0.244-0.425nm, optionally 0.345-0.358nm, and the included angle of the crystal direction (111) is 20.00°-37.00°, optionally 24.25°-26.45°;
  • the interplanar spacing of the pyrophosphate is 0.293-0.470nm, optionally 0.293-0.326nm, and the included angle of the crystal direction (111) is 18-32.57°, optionally 19.211°-30.846°, more optional
  • the ground is 26.41°-32.57°.
  • Pyrophosphate and phosphate with a certain degree of crystallinity are not only beneficial to give full play to the ability of the pyrophosphate coating layer to hinder the dissolution of manganese ions and the excellent ability of the phosphate coating layer to conduct lithium ions, and to reduce the interface side reactions.
  • the pyrophosphate coating and the phosphate coating enable better lattice matching, thereby enabling a tighter bonding of the coatings.
  • the inorganic salts in the cladding layer in the shell are all crystalline substances.
  • the crystalline pyrophosphate and crystalline phosphate in the cladding layer can be characterized by conventional technical means in the art, and can also be characterized, for example, by means of a transmission electron microscope (TEM). Under TEM, the inner core and the cladding layer can be distinguished by measuring the interplanar spacing.
  • TEM transmission electron microscope
  • the specific test method of the interplanar spacing and the included angle of the crystalline pyrophosphate in the cladding layer and the crystalline phosphate can comprise the following steps: get a certain amount of coated positive electrode active material sample powder in a test tube, and Inject a solvent such as alcohol into the test tube, then fully stir and disperse, and then use a clean disposable plastic straw to take an appropriate amount of the above solution and drop it on a 300-mesh copper grid. At this time, some powder will remain on the copper grid.
  • the difference between the interplanar spacing range of crystalline pyrophosphate and the existence of crystalline phosphate can be directly judged by the value of interplanar spacing. Crystalline pyrophosphate and crystalline phosphate within the range of the aforementioned interplanar spacing and included angle can more effectively reduce the lattice change rate and manganese ion dissolution rate of the positive electrode active material in the lithium-deintercalation process, thereby improving the battery life. Excellent high temperature cycle performance and high temperature storage performance.
  • the coating may also contain carbon.
  • Carbon materials have good electronic conductivity. When used in secondary batteries, electrochemical reactions occur, which require the participation of electrons. Therefore, in order to increase the electron transport between particles and the electron transport at different positions of the particles, Carbon, which has excellent electrical conductivity, may be used to coat the cathode active material. Therefore, carbon coating can effectively improve the electrical conductivity and desolvation ability of cathode active materials.
  • the carbon in the inner cladding layer is a mixture of SP2 carbon and SP3 carbon
  • the molar ratio of SP2 carbon to SP3 carbon is in the range of 0.1-10 Any value within , which can be any value within the range of 2.0-3.0.
  • the molar ratio of SP2 form carbon to SP3 form carbon may be about 0.1, about 0.2, about 03, about 0.4, about 0.5, about 0.6, about 0.7, about 0.8, about 0.9, about 1, about 2, about 3 , about 4, about 5, about 6, about 7, about 8, about 9, or about 10, or within any range of any of the above values.
  • the comprehensive electrical performance of the secondary battery is improved.
  • the carbon in the coating layer is all amorphous SP3 If they are all in the form of graphitized SP2, the conductivity is good, but there are few lithium ion paths, which is not conducive to the deintercalation of lithium.
  • limiting the molar ratio of SP2 carbon to SP3 carbon within the above range can not only achieve good electrical conductivity, but also ensure the passage of lithium ions, which is beneficial to the realization of the function of the secondary battery and its cycle performance.
  • the mixing ratio of the SP2 form and the SP3 form of the coating carbon can be controlled by sintering conditions such as sintering temperature and sintering time.
  • sintering conditions such as sintering temperature and sintering time.
  • sucrose as the carbon source to prepare the third coating
  • the proportion of SP2 carbon and SP3 carbon can be adjusted by selecting pyrolysis conditions and sintering conditions.
  • coating layer carbon can be measured by Raman (Raman) spectrum, and concrete test method is as follows: by the energy spectrum that Raman tests is carried out peak splitting, obtain Id/Ig (wherein Id is the peak intensity of SP3 form carbon, Ig is the peak intensity of SP2 form carbon), thereby confirming the molar ratio of the two.
  • the shell includes an inorganic cladding layer and a carbon cladding layer, the inorganic cladding layer is disposed close to the inner core, and the inorganic cladding layer has the aforementioned phosphate and pyrophosphate, metal oxide at least one of the .
  • phosphate and pyrophosphate may be used to form an inorganic salt coating layer, and the outer side of the inorganic salt coating layer may further have a carbon layer.
  • pyrophosphate and pyrophosphate both form independent cladding layers, one of them is set close to the inner core, the other is clad with the crystalline inorganic salt cladding layer set close to the inner core, and a carbon layer is set on the outermost side.
  • the core-shell structure may only contain an inorganic salt coating layer composed of phosphate or pyrophosphate, and a carbon layer is arranged on the outside.
  • the bond between the inorganic cladding layer and the core is similar to a heterojunction, and the firmness of the bond is limited by the degree of lattice matching.
  • the lattice mismatch is below 5%, the lattice matching is better, and the two are easy to combine closely.
  • the tight combination can ensure that the coating layer will not fall off in the subsequent cycle process, which is beneficial to ensure the long-term stability of the material.
  • the measurement of the binding degree between the cladding layer and the core is mainly carried out by calculating the mismatch degree of each lattice constant between the core and the cladding.
  • the matching degree between the core and the cladding layer is improved compared with that without doping elements, and the core and the cladding layer are improved.
  • the coating layers of crystalline inorganic salt can be combined more tightly.
  • the shell includes a first cladding layer, a second cladding layer and a third cladding layer
  • the first cladding layer envelops the inner core and includes crystalline pyrophosphate.
  • the second coating layer includes crystalline phosphate and covers the first coating layer, and the third coating layer is carbon.
  • Pyrophosphate as the first coating layer can effectively isolate the doped metal ions from the electrolyte.
  • the structure of crystalline pyrophosphate is stable, therefore, the coating of crystalline pyrophosphate can effectively inhibit the dissolution of transition metals and improve cycle performance.
  • Crystalline phosphate as the second coating layer has a higher degree of lattice matching with the first layer of coating crystalline pyrophosphate (the mismatch degree is only 3%), and its stability is better than that of pyrophosphate and has excellent
  • the ability to conduct lithium ions is conducive to improving the stability of the positive electrode active material and reducing the interface side reactions between the positive electrode active material and the electrolyte.
  • the third coating layer can improve the electronic conductivity of the positive electrode active material, and the carbon coating can also effectively improve the electrical conductivity and desolvation ability of the positive electrode active material.
  • the coating amount of the first coating layer is greater than 0 and less than or equal to 6% by weight, optionally greater than 0 and less than or equal to 5.5% by weight, more optionally greater than 0 and less than or equal to 2 % by weight, based on the weight of the inner core.
  • the coating amount of the second coating layer is greater than 0 and less than or equal to 6% by weight, optionally greater than 0 and less than or equal to 5.5% by weight, more optionally 2-4% by weight , based on the weight of the kernel.
  • the coating amount of the third coating layer is greater than 0 and less than or equal to 6% by weight, optionally greater than 0 and less than or equal to 5.5% by weight, more optionally greater than 0 and less than or equal to Equal to 2% by weight, based on the weight of the inner core. In this application, the coating amount of each layer is not zero.
  • the coating amount of the three-layer coating layer is preferably within the above range, so that the inner core can be fully coated without sacrificing the positive electrode activity. Under the premise of the gram capacity of the material, the kinetic performance, cycle performance and safety performance of the battery are further improved.
  • the coating amount if the coating amount is within the above range, the following situations can be effectively avoided: too little coating means that the thickness of the coating layer is relatively thin, which may not be able to effectively hinder the migration of transition metals; If the coating amount is too large, it means that the coating layer is too thick, which will affect the migration of Li+, thereby affecting the rate performance of the positive electrode active material.
  • the coating amount if the coating amount is within the above-mentioned range, the following situations can be effectively avoided: if the coating amount is too much, the plateau voltage of the positive electrode active material as a whole may be affected; if the coating amount is too small, it may not be possible to achieve sufficient coverage.
  • the carbon coating mainly plays the role of enhancing the electron transport between particles.
  • the structure also contains a large amount of amorphous carbon, the carbon density is low. Therefore, if the coating amount is too large Large, it will affect the compaction density of the pole piece.
  • the thickness of the first cladding layer is 1-10 nm. In some embodiments, the thickness of the second cladding layer is 2-15 nm. In some embodiments, the thickness of the third cladding layer is 2-25 nm. In some embodiments, the thickness of the first cladding layer may be about 2 nm, about 3 nm, about 4 nm, about 5 nm, about 6 nm, about 7 nm, about 8 nm, about 9 nm or about 10 nm, or within any of the above values. within any range.
  • the thickness of the second cladding layer may be about 2 nm, about 3 nm, about 4 nm, about 5 nm, about 6 nm, about 7 nm, about 8 nm, about 9 nm, about 10 nm, about 11 nm, about 12 nm, About 13nm, about 14nm, about 15nm, or within any range of any of the above numerical values.
  • the thickness of the third cladding layer may be about 2 nm, about 3 nm, about 4 nm, about 5 nm, about 6 nm, about 7 nm, about 8 nm, about 9 nm, about 10 nm, about 11 nm, about 12 nm , about 13nm, about 14nm, about 15nm, about 16nm, about 17nm, about 18nm, about 19nm, about 20nm, about 21nm, about 22nm, about 23nm, about 24nm or about 25nm, or within any range of any of the above numerical values.
  • the thickness of the first cladding layer is in the range of 1-10nm, it can avoid the adverse effect on the kinetic performance of the positive electrode active material that may be generated when it is too thick, and may not be able to effectively hinder transition metal ions when it is too thin. migration problem.
  • the thickness of the second coating layer is in the range of 2-15nm, the surface structure of the second coating layer is stable, and the side reaction with the electrolyte is small, so the side reaction at the interface can be effectively reduced, thereby improving the performance of the battery. High temperature cycle performance and high temperature storage performance.
  • the electrical conductivity of the positive electrode active material can be improved and the compacted density of the positive electrode sheet prepared by using the positive electrode active material can be improved.
  • the thickness test of the coating layer is mainly carried out by FIB.
  • the specific method may include the following steps: randomly select a single particle from the positive electrode active material powder to be tested, cut a thin slice with a thickness of about 100 nm from the middle position of the selected particle or near the middle position, and then Carry out TEM test on the sheet, measure the thickness of the cladding layer, measure 3-5 positions, and take the average value.
  • the manganese content is in the range of 10% by weight to 35% by weight, optionally in the range of 15% by weight to 30% by weight, more optionally in the range of 17% by weight to 20% by weight. in the weight % range.
  • the content of phosphorus is in the range of 12 wt%-25 wt%, optionally in the range of 15 wt%-20 wt%.
  • the weight ratio of the manganese element to the phosphorus element is in the range of 0.90-1.25, optionally 0.95-1.20.
  • the content of manganese may correspond to that of the inner core.
  • Limiting the content of the phosphorus element within the above range can effectively avoid the following situation: if the content of the phosphorus element is too large, it may cause the covalency of P-O to be too strong and affect the conduction of small polarons, thereby affecting the positive electrode active material. electrical conductivity; if the content of phosphorus element is too small, it may stabilize the lattice structure of the pyrophosphate in the inner core, the first cladding layer and/or the phosphate in the second cladding layer The performance decreases, thereby affecting the overall stability of the positive electrode active material.
  • the weight ratio of manganese to phosphorus content has the following effects on the performance of the battery: if the weight ratio is too large, it means that there is too much manganese element, and the dissolution of manganese ions increases, which affects the stability of the positive electrode active material and the gram capacity, and then affects the cycle of the battery. Performance and storage performance; if the weight ratio is too small, it means that there is too much phosphorus, and it is easy to form an impurity phase, which will reduce the discharge voltage platform of the positive electrode active material, thereby reducing the energy density of the battery.
  • the measurement of manganese and phosphorus elements can be carried out by conventional technical means in this field.
  • the cathode active material is dissolved in dilute hydrochloric acid (concentration 10-30%), utilize the content of each element of ICP test solution, then the content of manganese element is measured and Convert to get its weight ratio.
  • the inorganic cladding layer includes a first cladding layer covering the inner core and a second cladding layer covering the first cladding layer, wherein the first cladding layer
  • the cladding layer includes pyrophosphate QP 2 O 7 and phosphate XPO 4
  • the second cladding layer is a cladding carbon layer.
  • the coating amount of the first coating layer is greater than 0% by weight and less than or equal to 7% by weight, optionally 4-5.6% by weight, based on the weight of the inner core.
  • the weight ratio of pyrophosphate to phosphate in the first coating layer is 1:3 to 3:1, optionally 1:3 to 1:1.
  • the coating amount of the second coating layer is greater than 0% by weight and less than or equal to 6% by weight, optionally 3-5% by weight, based on the weight of the inner core.
  • the wrapping amount of each layer is non-zero.
  • the coating amount of the first coating layer is within the above range, the dissolution of manganese can be further suppressed, and at the same time, the transport of lithium ions can be further promoted. And can effectively avoid the following situation: if the coating amount of the first coating layer is too small, it may cause insufficient inhibition of pyrophosphate on manganese dissolution, and the improvement of lithium ion transport performance is not significant; if the second If the coating amount of the first coating layer is too large, the coating layer may be too thick, which increases the battery impedance and affects the kinetic performance of the battery. The proper ratio of pyrophosphate and phosphate is conducive to giving full play to the synergistic effect of the two.
  • pyrophosphate and phosphate with a certain degree of crystallinity are beneficial to keep the structure of the first coating layer stable and reduce lattice defects. On the one hand, this is beneficial to give full play to the role of pyrophosphate in hindering the dissolution of manganese. On the other hand, it is also beneficial to phosphate to reduce the content of lithium on the surface and the valence state of oxygen on the surface, thereby reducing the interface side reactions between the positive electrode material and the electrolyte, and reducing the The consumption of electrolyte improves the cycle performance and safety performance of the battery.
  • the interplanar spacing of the phosphate of the first cladding layer is 0.345-0.358nm, and the included angle of the crystal direction (111) is 24.25°-26.45°.
  • the first cladding layer The interplanar spacing of the pyrophosphate in the layer is 0.293-0.326nm, and the included angle of the crystal direction (111) is 26.41°-32.57°.
  • the crystallinity of pyrophosphate and phosphate can be adjusted, for example, by adjusting the process conditions of the sintering process, such as sintering temperature, sintering time, and the like.
  • the crystallinity of pyrophosphate and phosphate salts can be measured by methods known in the art, such as by methods such as X-ray diffraction, densitometry, infrared spectroscopy, differential scanning calorimetry, and nuclear magnetic resonance absorption methods.
  • the carbon-containing layer as the second coating layer can play a "barrier" function to avoid direct contact between the positive electrode active material and the electrolyte, thereby reducing the corrosion of the active material by the electrolyte and improving the safety performance of the battery at high temperatures.
  • it has strong electrical conductivity, which can reduce the internal resistance of the battery, thereby improving the kinetic performance of the battery.
  • the gram capacity of the carbon material is low, when the amount of the second coating layer is too large, the gram capacity of the entire positive electrode active material may be reduced. Therefore, when the coating amount of the second coating layer is in the above range, the kinetic performance and safety performance of the battery can be further improved without sacrificing the gram capacity of the positive electrode active material.
  • the shell of the positive electrode active material can also have a first coating layer and a second coating layer, the first coating layer includes crystalline pyrophosphate QP 2 O 7 and metal oxide Q' e O f , the second cladding layer is a cladding carbon layer.
  • first coating layer includes crystalline pyrophosphate QP 2 O 7 and metal oxide Q' e O f
  • the second cladding layer is a cladding carbon layer.
  • the first cladding layer 12 includes crystalline pyrophosphate and crystalline oxide; due to the high migration barrier (>1eV) of transition metal in pyrophosphate, it can effectively inhibit the transition metal Dissolution; crystalline oxides have high structural stability and low surface activity. Therefore, coating with crystalline oxides can effectively reduce interface side reactions, thereby improving the high-temperature cycle and high-temperature storage performance of the battery.
  • the second cladding layer 13 is a carbon-containing layer, it can effectively improve the electrical conductivity and desolvation ability of the inner core 11 .
  • the "barrier" function of the second coating layer 13 can further hinder the migration of manganese ions into the electrolyte, and reduce the corrosion of the active material by the electrolyte.
  • the positive electrode active material of this application can reduce the generation of Li/Mn antisite defects by performing specific element doping and surface coating on lithium manganese phosphate, and effectively inhibit At the same time, it promotes the migration of lithium ions, thereby improving the rate performance of the battery cell, and improving the cycle performance, high temperature performance and safety performance of the secondary battery.
  • FIG. 3 is a schematic structural diagram of the cathode active material proposed in the present application, and is not limited to the foregoing embodiments.
  • the positive electrode active material has two coating layers, it can have the structure shown in FIG. 3 .
  • the coating layer (12 and 13 as shown in the figure) can realize complete coating or partial coating to the inner layer structure, and the coating amount or area can be 100%, 90%, or 100% of the inner layer structure. 80%, 70%, 60%, 50%, etc.
  • the interplanar spacing of the pyrophosphate in the first coating layer is 0.293-0.326 nm, and the included angle of the crystal direction (111) is 26.41°-32.57°; optionally, the first coating
  • the interplanar spacing of the pyrophosphate in the layer is 0.300-0.310 nm (for example, 0.303 nm); and/or, optionally, the included angle of the crystal direction (111) of the pyrophosphate in the first cladding layer is 29.00 °-30.00° (eg 29.496°).
  • the interplanar spacing of the pyrophosphate in the first coating layer and the included angle of the crystal direction (111) are in the above range, the impurity phase in the coating layer can be effectively avoided, thereby increasing the gram capacity of the material and improving the secondary battery capacity. cycle performance and rate performance.
  • the coating amount of the first coating layer is greater than 0% by weight and less than or equal to 7% by weight, optionally 4-5.6% by weight, based on the weight of the inner core.
  • the coating amount of the first coating layer is within the above range, the dissolution of manganese can be further suppressed, and at the same time, the transmission of lithium ions can be further promoted, so as to maintain the low impedance of the secondary battery and improve the kinetic performance of the secondary battery.
  • the weight ratio of pyrophosphate to oxide in the first coating layer is 1:3 to 3:1, optionally 1:3 to 1:1.
  • the proper ratio of pyrophosphate and oxide is conducive to giving full play to the synergistic effect of the two, which can further inhibit the dissolution of manganese, while maintaining a low impedance of the secondary battery.
  • the coating amount of the second coating layer is greater than 0% by weight and less than or equal to 6% by weight, optionally 3-5% by weight, based on the weight of the inner core.
  • the performance and advantages of the carbon coating layer are similar to those in the aforementioned embodiments, and will not be repeated here.
  • the thickness of the first cladding layer is 1-100 nm. Therefore, the migration barrier of the transition metal in the first cladding layer is relatively high, which can effectively reduce the dissolution of the transition metal.
  • the oxide has high stability, which can effectively reduce the side reaction at the interface, thereby improving the high temperature stability of the material.
  • the thickness of the second cladding layer is 1-100 nm.
  • the crystallinity of the pyrophosphate in the first coating layer is 10% to 100%, optionally 50% to 100%.
  • the pyrophosphate with a certain degree of crystallinity is beneficial to keep the structure of the first coating layer stable and reduce lattice defects. On the one hand, this is beneficial to give full play to the role of pyrophosphate in hindering the dissolution of manganese. On the other hand, it is also beneficial to reduce the content of lithium on the surface and the valence state of oxygen on the surface, thereby reducing the interface side reaction between the positive electrode material and the electrolyte and reducing the impact on the electrolyte. The consumption of liquid improves the cycle performance and safety performance of the secondary battery.
  • the shell may further include a first cladding layer covering the inner core, a second cladding layer covering the first cladding layer, and a second cladding layer covering the second cladding layer.
  • the third cladding layer of the layer similarly, at this time, the positive electrode active material may have a structure as shown in FIG. 4 .
  • the first cladding layer 12 includes crystalline pyrophosphate
  • the second cladding layer 13 includes metal oxide Q' e O f
  • the crystalline pyrophosphate includes Li a QP 2 O 7 and/or Q b (P 2 O 7 ) c , wherein, said a is greater than 0 and less than or equal to 2, said b is any value within the range of 1-4, and said c is any value within the range of 1-3
  • the third coating layer 13 contains carbon.
  • the specific composition of crystalline pyrophosphate including Li a QP 2 O 7 and/or Q b (P 2 O 7 ) c and metal oxide Q' e O f has been described in detail above, and will not be repeated here repeat.
  • the bond between the first cladding layer and the core is similar to a heterojunction, and the firmness of the bond is limited by the degree of lattice matching.
  • Crystalline oxide as the second cladding layer has a higher degree of lattice matching with the first cladding crystalline pyrophosphate (the mismatch degree is only 3%) and its stability is better than that of pyrophosphate.
  • Pyrophosphate coating is beneficial to improve the stability of the material. Coating with crystalline oxide can effectively reduce the interfacial side reactions on the surface of the positive electrode active material, thereby improving the high-temperature cycle and storage performance of the secondary battery.
  • the lattice matching mode between the second cladding layer and the first cladding layer, etc. is similar to the above-mentioned combination between the first cladding layer and the core.
  • the lattice mismatch is below 5%, the lattice matching is relatively strong. Well, the two are easy to combine tightly.
  • the main reason why carbon is used as the third coating layer is that the electronic conductivity of the carbon layer is better.
  • the coating amount of the first coating layer is greater than 0 and less than or equal to 6% by weight, optionally greater than 0 and less than or equal to 5.5% by weight, more optionally greater than 0 and less than or equal to Equal to 2% by weight, based on the weight of the inner core; and/or the coating amount of the second coating layer is greater than 0 and less than or equal to 6% by weight, optionally greater than 0 and less than or equal to 5.5% by weight , more optionally 2% by weight-4% by weight, based on the weight of the inner core; and/or the coating amount of the third coating layer is greater than 0 and less than or equal to 6% by weight, optionally greater than 0 and less than or equal to 5.5 wt%, more optionally greater than 0 and less than or equal to 2 wt%, based on the weight of the inner core.
  • the wrapping amount of each layer is non-zero.
  • the coating amount of the three-layer coating layer is preferably within the above range, so that the inner core can be fully coated, and at the same time, the kinetic performance and safety of the secondary battery can be further improved without sacrificing the gram capacity of the positive electrode active material. performance.
  • the first coating layer if the coating amount is within the above range, the dissolution of transition metals can be reduced, and the smooth migration of lithium ions can be ensured, thereby improving the rate performance of the positive electrode active material.
  • the second coating layer when the coating amount is within the above range, the positive electrode active material can maintain a certain plateau voltage and ensure the coating effect.
  • the carbon coating mainly plays the role of enhancing the electron transport between particles. However, because the structure also contains a large amount of amorphous carbon, the density of carbon is low, and the coating amount is within the above range. Inside, the compaction density of the pole piece can be guaranteed.
  • the thickness of the first cladding layer is 2-10 nm; and/or the thickness of the second cladding layer is 3-15 nm; and/or the thickness of the third cladding layer is 5-25nm.
  • the thickness of the first cladding layer can be about 2 nm, about 3 nm, about 4 nm, about 5 nm, about 6 nm, about 7 nm, about 8 nm, about 9 nm, or about 10 nm, or within any range of any of the above values.
  • the thickness of the second cladding layer can be about 3 nm, about 4 nm, about 5 nm, about 6 nm, about 7 nm, about 8 nm, about 9 nm, about 10 nm, about 11 nm, about 12 nm, about 13 nm, about 14 nm , about 15 nm, or within any range of any of the above numerical values.
  • the thickness of the third cladding layer can be about 5 nm, about 6 nm, about 7 nm, about 8 nm, about 9 nm, about 10 nm, about 11 nm, about 12 nm, about 13 nm, about 14 nm, about 15 nm, About 16 nm, about 17 nm, about 18 nm, about 19 nm, about 20 nm, about 21 nm, about 22 nm, about 23 nm, about 24 nm, or about 25 nm, or within any range of any of the above numerical values.
  • the thickness of the first coating layer is in the range of 2-10 nm, it can effectively reduce the dissolution of transition metals and ensure the kinetic performance of the secondary battery.
  • the thickness of the second coating layer is in the range of 3-15nm, the surface structure of the second coating layer is stable, and the side reaction with the electrolyte is small, so the side reaction at the interface can be effectively reduced, thereby improving the high temperature performance of the secondary battery .
  • the thickness of the third cladding layer is in the range of 5-25 nm, the electrical conductivity of the material can be improved and the compaction performance of the battery electrode sheet prepared by using the positive electrode active material can be improved.
  • the thickness measurement of cladding layer is mainly carried out by FIB.
  • the manganese element content is in the range of 10% by weight to 35% by weight, optionally in the range of 15% by weight to 30% by weight, and more optionally in the range of 17% by weight to 20% by weight.
  • the content of phosphorus element is in the range of 12 weight %-25 weight %, optionally in the range of 15 weight %-20 weight %; optionally, the weight ratio of manganese element and phosphorus element is in the range of 0.90-1.25 Within, more preferably within the range of 0.95-1.20.
  • the content of manganese may correspond to that of the inner core.
  • limiting the content of the manganese element within the above range can ensure the stability and high density of the positive electrode active material, thereby improving the cycle, storage and compaction performance of the secondary battery, and maintaining a certain voltage Platform height, thereby increasing the energy density of the secondary battery.
  • limiting the content of phosphorus element within the above range can effectively improve the electrical conductivity of the material and improve the overall stability of the material.
  • the content weight ratio of manganese to phosphorus is within the above range, which can effectively reduce the dissolution of elements such as transition metal manganese, improve the stability and gram capacity of the positive electrode active material, and then improve the cycle performance and storage performance of the secondary battery. It helps to reduce the impurity phase in the material and maintain the discharge voltage plateau height of the material, thereby increasing the energy density of the secondary battery.
  • the positive electrode active material includes a first cladding layer covering the inner core, a second cladding layer covering the first cladding layer, and a second cladding layer covering the second cladding layer.
  • the coating amount of the first coating layer is greater than 0 and less than or equal to 6% by weight, optionally greater than 0 and less than or equal to 5.5% by weight, more optionally greater than 0 and less than or equal to 2% by weight, based on the weight of the inner core; and/or the coating amount of the second coating layer is greater than 0 and less than or equal to 6% by weight, optionally greater than 0 and less than or equal to 5.5% by weight %, more optionally 2-4% by weight, based on the weight of the inner core; and/or the coating amount of the third coating layer is greater than 0 and less than or equal to 6% by weight, optionally greater than 0 and less than or equal to 5.5 wt%, more optionally greater than 0 and less than or equal to 2 wt%, based on the weight of the inner core.
  • the thickness of the first cladding layer is 1-10 nm; and/or the thickness of the second cladding layer is 2-15 nm; and/or the thickness
  • the content of manganese element is in the range of 10% by weight-35% by weight, optionally in the range of 15% by weight-30% by weight, more optionally in the range of 17% by weight-20% by weight, phosphorus
  • the element content is in the range of 12 wt%-25 wt%, optionally in the range of 15 wt%-20 wt%, and the weight ratio of manganese and phosphorus is in the range of 0.90-1.25, optionally 0.95-1.20.
  • the average particle diameter of the primary particles of the positive electrode active material is in the range of 50-500 nm, and the volume median particle diameter Dv50 is in the range of 200-300 nm. Since the particles will be agglomerated, the actual measured secondary particle size after agglomeration may be 500-40000nm.
  • the particle size of the cathode active material affects the processing of the material and the compacted density performance of the electrode sheet.
  • the average particle diameter of the primary particles of the positive electrode active material is too small, which may cause particle agglomeration, difficulty in dispersion, and more bonding agent, resulting in poor brittleness of the pole piece; the average particle size of the primary particles of the positive electrode active material is too large, which may cause larger gaps between the particles and reduce the compacted density.
  • the second aspect of the present application relates to a method for preparing the cathode active material of the first aspect of the present application.
  • the method comprises the steps of forming an inner core, and forming a shell on at least the surface of the inner core, the inner core comprising at least one of a ternary material, d Li 2 MnO 3 ⁇ (1-d)LiMO 2 and LiMPO 4 , 0 ⁇ d ⁇ 1, the M includes one or more selected from Fe, Ni, Co, Mn, the shell contains crystalline inorganic matter, and the crystalline inorganic matter uses the main peak measured by X-ray diffraction The full width at half maximum is 0-3°, and the crystalline inorganic substance includes one or more selected from metal oxides and inorganic salts.
  • each cladding layer in the core and the shell has been described in detail above, and will not be repeated here.
  • the inner core contains LiMPO 4 and M includes Mn and non-Mn elements as an example, the steps of the method are described in detail:
  • the method includes the operation of forming a LiMPO 4 compound, wherein the LiMPO 4 compound may have all the features and advantages of the aforementioned LiMPO 4 compound, which will not be repeated here.
  • the M includes Mn and non-Mn elements, and the non-Mn elements meet at least one of the following conditions: the ionic radius of the non-Mn element is a, the ionic radius of the manganese element is b,
  • the non-Mn element includes first and second doping elements
  • the method includes: mixing a manganese source, a dopant of the manganese-site element, and an acid to obtain a dopant having the first doping element
  • Manganese salt particles are mixed with lithium source, phosphorus source and the dopant of the second doping element in a solvent to obtain a slurry, in an inert gas
  • the LiMPO 4 compound is obtained after sintering under the protection of atmosphere.
  • the types of the first doping element and the second doping element have been described in detail above, and will not be repeated here.
  • the first doping element comprises Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and Ge
  • the second doping element includes one or more elements selected from B (boron), S, Si and N.
  • the LiMPO 4 compound is formed according to the formula Li 1+x Mn 1-y A y P 1-z R z O 4 , and in other embodiments, according to the formula Li 1+x C m Mn 1 -y A y P 1-z R z O 4-n D n forms the LiMPO 4 compound.
  • the elements of each substitution site and their selection principles, beneficial effects, and atomic ratio ranges have been described in detail above, and will not be repeated here.
  • the source of element C is selected from at least one of the simple substance, oxide, phosphate, oxalate, carbonate and sulfate of element C
  • the source of element A is selected from the simple substance of element A, oxide, phosphoric acid
  • the source of element R is selected from sulfate, borate of element R , at least one of nitrate and silicate, organic acid, halide, organic acid salt, oxide, hydroxide
  • the source of element D is selected from at least one of element D and ammonium salt.
  • the acid is selected from one or more of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, and organic acids such as oxalic acid, for example, oxalic acid.
  • the acid is a dilute acid having a concentration of 60% by weight or less.
  • the manganese source can be a manganese-containing substance known in the art that can be used to prepare lithium manganese phosphate, for example, the manganese source can be selected from elemental manganese, manganese dioxide, manganese phosphate, manganese oxalate, carbonic acid One or a combination of manganese.
  • the lithium source can be a lithium-containing substance known in the art that can be used to prepare lithium manganese phosphate, for example, the lithium source can be selected from lithium carbonate, lithium hydroxide, lithium phosphate, lithium dihydrogen phosphate one or a combination of them.
  • the phosphorus source can be a phosphorus-containing substance known in the art that can be used to prepare lithium manganese phosphate, for example, the phosphorus source can be selected from diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium phosphate and phosphoric acid one or a combination of them.
  • the addition amount of the source of each site doping element depends on the target doping amount, and the ratio of the amount of lithium source, manganese source and phosphorus source conforms to the stoichiometric ratio.
  • the obtained manganese salt particles with the first doping element meet at least one of the following conditions: at 20-120°C, optionally 40-120°C, optionally 60-120°C, more preferably
  • the manganese source, the manganese site element and the acid are mixed optionally at a temperature of 25-80°C; and/or the mixing is carried out under stirring at 200-800rpm, optionally at 400-700rpm , more optionally 500-700 rpm for 1-9h, alternatively 3-7h, more alternatively alternatively 2-6h.
  • the positive active material may have a first doping element and a second doping element.
  • the method may be carried out by grinding and mixing the manganese salt particles having the first doping element with the lithium source, the phosphorus source and the dopant of the second doping element in a solvent for 8-15 hours.
  • mixing the manganese salt particles with the first doping element with the lithium source, the phosphorus source and the dopant of the second doping element in a solvent is carried out at 20-120° C., optionally 40-120° C. °C temperature for 1-10h.
  • the method can form a LiMPO 4 compound according to the chemical formula Li 1+ xC x Mn 1-y A y P 1-z R z O 4-n D n .
  • the manganese salt particles having the first doping element may be ground and mixed with a lithium source, a phosphorus source, and a dopant of the second doping element in a solvent for 8-15 hours.
  • a manganese source, a source of element A and an acid can be dissolved in a solvent to form a suspension of a manganese salt doped with element A, and the suspension is filtered and dried to obtain a manganese salt doped with element A; mixing a lithium source, a phosphorus source, a source of element C, a source of element R, a source of element D, a solvent, and the manganese salt doped with element A plus a solvent to obtain a slurry; spray drying the slurry Granulating to obtain granules; sintering the granules to obtain the positive electrode active material. Sintering may be performed at a temperature range of 600-900° C. for 6-14 hours.
  • the doping elements By controlling the reaction temperature, stirring rate and mixing time during doping, the doping elements can be evenly distributed, and the crystallinity of the material after sintering is higher, which can improve the gram capacity and rate performance of the material.
  • the operation of forming the inner core may include the following steps: (1) dissolving and stirring the source of manganese, the source of element B and acid in a solvent to generate a suspension of manganese salt doped with element B, The suspension is filtered and the filter cake is dried to obtain a manganese salt doped with element B; (2) the source of lithium source, phosphorus source, element A, source of element C and element D, solvent and by steps (1) The obtained manganese salt doped with element B is added into a reaction vessel for grinding and mixing to obtain a slurry; (3) the slurry obtained by step (2) is transferred to a spray drying device for spray drying and granulation to obtain particles; (4) sintering the particles obtained in step (3).
  • the solvents described in step (1) and step (2) can each independently be a solvent routinely used by those skilled in the art in the preparation of manganese salts and lithium manganese phosphate, for example, they can each independently select At least one of ethanol, water (such as deionized water), etc.
  • the stirring in step (1) is performed at a temperature in the range of 60-120°C. In some embodiments, the stirring in step (1) is performed at a stirring rate of 200-800 rpm, or 300-800 rpm, or 400-800 rpm. In some embodiments, the agitation of step (1) is performed for 6-12 hours. In some embodiments, the milling and mixing of step (2) is performed for 8-15 hours.
  • the doping elements By controlling the reaction temperature, stirring rate and mixing time during doping, the doping elements can be evenly distributed, and the crystallinity of the material after sintering is higher, which can improve the gram capacity and rate performance of the material.
  • the filter cake may be washed before drying the filter cake in step (1).
  • the drying in step (1) can be carried out by methods and known conditions known to those skilled in the art, for example, the drying temperature can be in the range of 120-300°C.
  • the filter cake may be ground into particles after drying, for example, until the median diameter Dv50 of the particles is in the range of 50-200 nm.
  • the median particle diameter Dv50 refers to the particle diameter corresponding to when the cumulative volume distribution percentage of the positive electrode active material reaches 50%.
  • the median particle diameter Dv50 of the positive electrode active material can be measured by laser diffraction particle size analysis. For example, with reference to the standard GB/T 19077-2016, use a laser particle size analyzer (such as Malvern Master Size 3000) to measure.
  • a carbon source is also added to the reaction vessel for grinding and mixing.
  • the method can obtain a positive electrode active material whose surface is coated with carbon.
  • the carbon source includes one or a combination of starch, sucrose, glucose, polyvinyl alcohol, polyethylene glycol, and citric acid.
  • the amount of the carbon source relative to the amount of the lithium source is usually in the range of 0.1%-5% molar ratio.
  • the grinding can be carried out by suitable grinding means known in the art, for example, it can be carried out by sand grinding.
  • the temperature and time of the spray-drying in step (3) can be the conventional temperature and time for spray-drying in the art, for example, at 100-300° C. for 1-6 hours.
  • the sintering is performed at a temperature range of 600-900° C. for 6-14 hours.
  • the crystallinity of the material can be controlled, and the dissolution of Mn and Mn-site doping elements after cycling of the positive electrode active material can be reduced, thereby improving the high-temperature stability and cycle performance of the battery.
  • the sintering is performed under a protective atmosphere, which may be nitrogen, inert gas, hydrogen or a mixture thereof.
  • the core of the positive electrode active material may only have Mn-site and P-site doping elements.
  • the step of providing the positive electrode active material may include: step (1): mixing and stirring the manganese source, the dopant of element A and acid in a container to obtain manganese salt particles doped with element A; step (2) : the manganese salt particle doped with element A is mixed with the dopant of lithium source, phosphorus source and element R in a solvent to obtain a slurry, which is obtained after sintering under the protection of an inert gas atmosphere. The kernel of element R.
  • the dopant of element A and the acid are reacted in a solvent to obtain a manganese salt suspension doped with element A
  • the suspension is filtered, drying and sanding to obtain manganese salt particles doped with element A with a particle size of 50-200 nm.
  • the slurry in step (2) is dried to obtain a powder, and then the powder is sintered to obtain a positive electrode active material doped with element A and element R.
  • the step (1) is mixed at a temperature of 20-120°C, optionally 40-120°C; and/or the stirring in the step (1) is carried out at 400-700rpm 1-9h, optionally 3-7h.
  • the reaction temperature in the step (1) can be at about 30°C, about 50°C, about 60°C, about 70°C, about 80°C, about 90°C, about 100°C, about 110°C or about 120°C °C; the stirring in the step (1) is carried out for about 2 hours, about 3 hours, about 4 hours, about 5 hours, about 6 hours, about 7 hours, about 8 hours or about 9 hours; optionally,
  • the reaction temperature and stirring time in the step (1) can be within any range of the above-mentioned arbitrary values.
  • the step (2) is mixed at a temperature of 20-120°C, optionally 40-120°C, for 1-12h.
  • the reaction temperature in the step (2) can be at about 30°C, about 50°C, about 60°C, about 70°C, about 80°C, about 90°C, about 100°C, about 110°C or about 120°C °C; the mixing described in the step (2) was carried out for about 2 hours, about 3 hours, about 4 hours, about 5 hours, about 6 hours, about 7 hours, about 8 hours, about 9 hours, about 10 hours, About 11 hours or about 12 hours;
  • the reaction temperature and mixing time in the step (2) can be within any range of any of the above-mentioned values.
  • the prepared positive electrode active material has fewer lattice defects, which is conducive to inhibiting the dissolution of manganese, reducing the interface side reactions between the positive electrode active material and the electrolyte, thereby improving Cycle performance and safety performance of secondary batteries.
  • the pH of the solution is controlled to be 3.5-6, optionally, the pH of the solution is controlled to be 4-6, more preferably Optionally, the pH of the solution is controlled to be 4-5. It should be noted that in this application, the pH of the resulting mixture can be adjusted by methods commonly used in the art, for example, by adding acid or base.
  • the molar ratio of the manganese salt particles to the lithium source and the phosphorus source is 1:0.5-2.1:0.5-2.1, more optionally, the doped
  • the molar ratio of manganese salt particles doped with element A to lithium source and phosphorus source is about 1:1:1.
  • the sintering conditions during the preparation of lithium manganese phosphate doped with elements A and R are: sintering at 600-950°C for 4-10 hours under an atmosphere of inert gas or a mixture of inert gas and hydrogen. hours; alternatively, the sintering can be performed at about 650°C, about 700°C, about 750°C, about 800°C, about 850°C or about 900°C for about 2 hours, about 3 hours, about 4 hours, about 5 hours hours, about 6 hours, about 7 hours, about 8 hours, about 9 hours or about 10 hours; optionally, the sintering temperature and sintering time can be within any range of any of the above values.
  • the protective atmosphere is a mixed gas of 70-90 vol% nitrogen and 10-30 vol% hydrogen.
  • the particles having the chemical composition described above may serve as an inner core, and the method further includes the step of forming a shell surrounding the inner core.
  • the coating step may include the step of forming a carbon coating layer.
  • the carbon source includes one or more of starch, sucrose, glucose, polyvinyl alcohol, polyethylene glycol, and citric acid. The combination.
  • the amount of the carbon source relative to the amount of the lithium source is usually in the range of 0.1%-5% molar ratio.
  • the grinding can be carried out by suitable grinding means known in the art, for example, it can be carried out by sand grinding.
  • the method further includes the step of forming the aforementioned inorganic coating layer.
  • the coating layer includes a first coating layer and a second coating layer covering the first coating layer, the first coating layer contains pyrophosphate QP 2 O 7 and phosphate XPO 4 , the second The coating layer contains carbon as an example, the method includes: providing QP 2 O 7 powder and XPO 4 suspension containing carbon source, adding the lithium manganese phosphate oxide and QP 2 O 7 powder to the carbon containing Source XPO 4 suspension and mixed, sintered to obtain positive active material.
  • said QP 2 O 7 powder is a commercially available product, or alternatively said providing QP 2 O 7 powder includes: adding a source of element Q and a source of phosphorus to a solvent to obtain a mixture, and adjusting the pH of the mixture to 4-6, stirring and fully reacting, then obtained by drying and sintering, and the QP 2 O 7 powder provided meets at least one of the following conditions: the drying is at 100-300°C, optionally 150-200°C Drying for 4-8 hours; the sintering is at 500-800° C., optionally 650-800° C., in an inert gas atmosphere for 4-10 hours.
  • the sintering temperature for forming the coating layer is 500-800° C.
  • the sintering time is 4-10 h.
  • the XPO 4 suspension comprising a source of carbon is commercially available, or alternatively, prepared by combining a source of lithium, a source of X, phosphorus The source of carbon and the source of carbon are uniformly mixed in a solvent, and then the reaction mixture is heated to 60-120° C. for 2-8 hours to obtain the XPO 4 suspension containing the source of carbon.
  • the pH of the mixture is adjusted to 4-6.
  • the median particle diameter Dv50 of the primary particles of the double-layer coated lithium manganese phosphate positive electrode active material of the present application is 50-2000 nm.
  • the coating layer includes a first coating layer coating the LiMPO 4 compound, a second coating layer coating the first coating layer, and a coating layer coating the second coating layer.
  • the third cladding layer wherein the first cladding layer includes crystalline pyrophosphate Li a QP 2 O 7 and/or Q b (P 2 O 7 ) c , where 0 ⁇ a ⁇ 2, 1 ⁇ b ⁇ 4, 1 ⁇ c ⁇ 6, the values of a, b and c satisfy the following conditions: to keep the crystalline pyrophosphate Li a QP 2 O 7 or Q b (P 2 O 7 ) c Neutral, the Q in the crystalline pyrophosphate Li a QP 2 O 7 and Q b (P 2 O 7 ) c are each independently selected from Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag , one or more elements in Zr, Nb or Al; the second cladding layer includes crystalline phosphate XPO 4 , wherein, the X is selected
  • the pH of the solution dissolved with the source of element Q, phosphorus source and acid, and optionally lithium source is controlled to be 3.5-6.5, then stirred and reacted for 1-5h, and then the solution is The temperature is raised to 50-120° C. and maintained at this temperature for 2-10 hours, and/or, the sintering is carried out at 650-800° C. for 2-6 hours.
  • the reaction proceeds substantially.
  • the reaction is performed for about 1.5 hours, about 2 hours, about 3 hours, about 4 hours, about 4.5 hours or about 5 hours.
  • the reaction time of the reaction may be within any range of any value mentioned above.
  • the pH of the solution is controlled to be 4-6.
  • the solution is heated to about 55°C, about 60°C, about 70°C, about 80°C, about 90°C, about 100°C, about 110°C or about 120°C, and maintained at this temperature for about 2 hours, about 3 hours, about 4 hours, about 5 hours, about 6 hours, about 7 hours, about 8 hours, about 9 hours or about 10 hours; optionally, the first coating In the step, the temperature and holding time of the heating can be within any range of any of the above-mentioned values.
  • the sintering may be performed at about 650°C, about 700°C, about 750°C, or about 800°C for about 2 hours, about 3 hours, about 4 hours, about 5 hours or about 6 hours; optionally, the sintering temperature and sintering time can be within any range of any of the above-mentioned values.
  • the first cladding step by controlling the sintering temperature and time within the above range, the following situation can be avoided: when the sintering temperature in the first cladding step is too low and the sintering time is too short, it will cause The crystallinity of the first cladding layer is low, and there are many amorphous substances, which will lead to a decrease in the effect of inhibiting metal dissolution, thereby affecting the cycle performance and high-temperature storage performance of the secondary battery; and when the sintering temperature is too high, it will cause the second The appearance of impurity phases in the first coating layer will also affect its effect of inhibiting metal dissolution, thereby affecting the cycle and high-temperature storage performance of the secondary battery; when the sintering time is too long, the thickness of the first coating layer will increase, affecting The migration of Li+ affects the gram capacity and rate performance of the material.
  • the reaction time of the reaction may be within any range of any value mentioned above.
  • the solution is heated to about 65°C, about 70°C, about 80°C, about 90°C, about 100°C, about 110°C, about 120°C, about 130°C, about 140°C or about 150°C and maintaining at that temperature for about 2 hours, about 3 hours, about 4 hours, about 5 hours, about 6 hours, about 7 hours, about 8 hours, about 9 hours or about 10 hours;
  • the heating temperature and holding time may be within any range of any of the above-mentioned values.
  • the reaction temperature is too low, the reaction cannot take place or the reaction rate is relatively slow; When it is too high, the product will decompose or form a heterogeneous phase; when the reaction time is too long, the particle size of the product will be larger, which may increase the time and difficulty of the subsequent process; if the reaction time is too short, the reaction will be incomplete and less products will be obtained.
  • the sintering may be sintering at about 550°C, about 600°C or about 700°C for about 6 hours, about 7 hours, about 8 hours, about 9 hours or about 10 hours;
  • the sintering temperature and sintering time may be within any range of any of the above-mentioned values.
  • the second cladding step by controlling the sintering temperature and time within the above range, the following situation can be avoided: when the sintering temperature in the second cladding step is too low and the sintering time is too short, it will cause The crystallinity of the second cladding layer is low, and the amorphous state is more, which reduces the performance of reducing the surface reactivity of the material, thereby affecting the cycle and high-temperature storage performance of the secondary battery; and when the sintering temperature is too high, it will cause the second cladding layer
  • the appearance of impurity phases in the coating will also affect its effect of reducing the surface reactivity of the material, thus affecting the cycle and high-temperature storage performance of the secondary battery; when the sintering time is too long, the thickness of the second coating layer will increase, affecting The voltage platform of the material, thereby reducing the energy density of the material, etc.
  • the sintering in the third cladding step is performed at 700-800° C. for 6-10 hours.
  • the sintering may be sintering at about 700°C, about 750°C or about 800°C for about 6 hours, about 7 hours, about 8 hours, about 9 hours or about 10 hours;
  • the sintering temperature and sintering time may be within any range of any of the above-mentioned values.
  • the third cladding step by controlling the sintering temperature and time within the above range, the following situation can be avoided: when the sintering temperature in the third cladding step is too low, it will cause the third cladding layer The degree of graphitization of the lower coating layer will affect its conductivity, thereby affecting the gram capacity of the material; when the sintering temperature is too high, the degree of graphitization of the third cladding layer will be too high, which will affect the transmission of Li+, thereby affecting the gram capacity of the material When the sintering time is too short, the cladding layer will be too thin, which will affect its conductivity, thereby affecting the gram capacity of the material; if the sintering time is too long, the cladding layer will be too thick, which will affect the compaction density of the material. wait.
  • the drying temperature is from 100°C to 200°C, optionally from 110°C to 190°C, more preferably from 120°C to 180°C , even more preferably at a drying temperature of 120°C to 170°C, most preferably at a drying temperature of 120°C to 160°C, the drying time is 3-9h, optionally 4-8h, more preferably 5-7h, most preferably Optionally about 6h.
  • the shell of the aforementioned positive electrode active material includes a first cladding layer covering the inner core and a second cladding layer covering the first cladding layer, wherein the first cladding layer includes crystalline coke Phosphate QP 2 O 7 and said metal oxide Q' e O f , said second cladding layer comprising carbon
  • forming said shell comprises: providing a powder comprising crystalline pyrophosphate QP 2 O 7 and comprising carbon source and oxide Q' e O f suspension, the inner core, powder comprising crystalline pyrophosphate QP 2 O 7 and a suspension comprising carbon source and oxide Q' e O f are mixed and sintered , to obtain the positive electrode active material.
  • the suspension of the oxide Q' e O f may be a suspension formed by mixing commercially available metal oxides and raw materials including but not limited to carbon sources such as sucrose in a solvent.
  • the aforementioned shell of the positive electrode active material includes a first cladding layer covering the inner core, a second cladding layer covering the first cladding layer, and a first cladding layer covering the second cladding layer.
  • Three cladding layers wherein, the first cladding layer includes crystalline pyrophosphate QP 2 O 7 , the second cladding layer includes the metal oxide Q' e O f , and the third cladding layer
  • the layer comprises carbon, forming the shell comprising: providing a first mixture comprising pyrophosphate Li a QP 2 O 7 and/or Q b (P 2 O 7 ) c , mixing the core material with the first mixture, drying, sintering , obtain the material covered by the first cladding layer; provide the second mixture comprising the metal oxide Q' e O f , mix the material covered by the first cladding layer with the second mixture, dry, and sinter , to obtain the material coated with the second coating layer; providing a third mixture containing carbon source
  • the first cladding layer mixes a source of element Q, a phosphorus source, an acid, an optional lithium source, and an optional solvent to obtain the first mixture; And/or, when forming the second cladding layer, mix the source of the element Q' with a solvent to obtain a second mixture; and/or, when forming the third cladding layer, mix a carbon source with a solvent to obtain a third mixture ;
  • the source of the element Q, phosphorus source, acid, optional lithium source and optional solvent are mixed at room temperature for 1-5h, and then heated to 50°C -120°C and keep the temperature for mixing for 2-10 hours.
  • the above mixing is all carried out under the condition of pH 3.5-6.5; optionally, when forming the second coating layer, the source of the element Q' and the solvent Mix at low temperature for 1-10h, then raise the temperature to 60°C-150°C and keep mixing at this temperature for 2-10h.
  • the sintering is carried out at 650-800° C. for 2-8 hours; and/or, the second cladding step In, the sintering is carried out at 400-750° C. for 6-10 hours; and/or, in the third coating step, the sintering is carried out at 600-850° C. for 6-10 hours.
  • sintering is performed at 650-800°C (eg, about 650°C, about 700°C, about 750°C, or about 800°C) for 2-8 hours (about 2 hours, about 3 hours, about 4 hours, about 5 hours, about 6 hours, about 8 hours); and/or, in the second coating step, sintering at 400-750°C (such as about 400°C, about 450°C, about 500°C °C, about 550°C, about 600°C, about 700°C, about 750°C) for 6-10 hours (eg, about 6 hours, about 7 hours, about 8 hours, about 9 hours or about 10 hours); and/or , in the third coating step, sintering is carried out at 600-850°C (eg about 600°C, about 650°C, about 700°C, about 750°C, about 800°C, about 850°C) for 6-10 hours (eg about 6 hours, about 7 hours, about 8 hours
  • the drying temperature is from 80°C to 200°C, optionally from 80°C to 190°C, more preferably from 120°C to 180°C, or even More preferably, it is carried out at a drying temperature of 120°C to 170°C, most preferably at a drying temperature of 120°C to 160°C, and the drying time is 3-9h, preferably 4-8h, more preferably 5-7h, most preferably For about 6h.
  • the third aspect of the present application provides a positive electrode sheet, which includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, the positive electrode film layer includes the positive electrode active material according to the first aspect of the present application or obtained through the present application.
  • the content of the positive electrode active material in the positive electrode film layer is 95-99.5% by weight, based on the total weight of the positive electrode film layer.
  • the fourth aspect of the present application provides a secondary battery, which includes the positive electrode active material of the first aspect of the present application or the positive electrode active material prepared by the method of the second aspect of the present application or the positive electrode sheet of the third aspect of the present application.
  • a secondary battery typically includes a positive pole piece, a negative pole piece, an electrolyte, and a separator.
  • active ions are intercalated and extracted back and forth between the positive electrode and the negative electrode.
  • the electrolyte plays the role of conducting ions between the positive pole piece and the negative pole piece.
  • the separator is arranged between the positive pole piece and the negative pole piece, which mainly plays a role in preventing the short circuit of the positive and negative poles, and at the same time allows ions to pass through.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode collector, and the positive electrode film layer includes the positive electrode active material according to the first aspect of the present application.
  • the positive electrode current collector has two opposing surfaces in its own thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposing surfaces of the positive electrode current collector.
  • the positive electrode current collector can be a metal foil or a composite current collector.
  • aluminum foil can be used as the metal foil.
  • the composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base.
  • the composite current collector can be formed by forming metal materials (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyethylene terephthalic acid It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene glycol ester
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the positive electrode film layer may further optionally include a binder.
  • the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene At least one of ethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • the positive electrode film layer may also optionally include a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the positive electrode sheet can be prepared in the following manner: the above-mentioned components used to prepare the positive electrode sheet, such as positive electrode active material, conductive agent, binder and any other components, are dispersed in a solvent (such as N - Methylpyrrolidone) to form positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.
  • a solvent such as N - Methylpyrrolidone
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material.
  • the negative electrode current collector has two opposing surfaces in its own thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposing surfaces of the negative electrode current collector.
  • the negative electrode current collector can use a metal foil or a composite current collector.
  • copper foil can be used as the metal foil.
  • the composite current collector may include a base layer of polymer material and a metal layer formed on at least one surface of the base material of polymer material.
  • Composite current collectors can be formed by metal materials (copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyethylene terephthalic acid It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • the negative electrode active material can be a negative electrode active material known in the art for batteries.
  • the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material, lithium titanate, and the like.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon-oxygen compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys.
  • the tin-based material may be selected from at least one of simple tin, tin oxide compounds and tin alloys.
  • the present application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials of batteries can also be used. These negative electrode active materials may be used alone or in combination of two or more.
  • the negative electrode film layer may further optionally include a binder.
  • the binder can be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), poly At least one of methacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the negative electrode film layer may also optionally include a conductive agent.
  • the conductive agent can be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the negative electrode film layer may optionally include other additives, such as thickeners (such as sodium carboxymethylcellulose (CMC-Na)) and the like.
  • thickeners such as sodium carboxymethylcellulose (CMC-Na)
  • CMC-Na sodium carboxymethylcellulose
  • the negative electrode sheet can be prepared in the following manner: the above-mentioned components used to prepare the negative electrode sheet, such as negative electrode active material, conductive agent, binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.
  • a solvent such as deionized water
  • the electrolyte plays the role of conducting ions between the positive pole piece and the negative pole piece.
  • the present application has no specific limitation on the type of electrolyte, which can be selected according to requirements.
  • electrolytes can be liquid, gel or all solid.
  • the electrolyte is an electrolytic solution.
  • the electrolyte solution includes an electrolyte salt and a solvent.
  • the electrolyte salt may be selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, trifluoromethane At least one of lithium sulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium difluorooxalate borate, lithium difluorodifluorooxalatephosphate and lithium tetrafluorooxalatephosphate.
  • the solvent may be selected from ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, Butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate At least one of ester, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • the electrolyte may optionally include additives.
  • additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain performances of the battery, such as additives that improve battery overcharge performance, additives that improve high-temperature or low-temperature performance of batteries, and the like.
  • a separator is further included in the secondary battery.
  • the present application has no particular limitation on the type of the isolation membrane, and any known porous structure isolation membrane with good chemical stability and mechanical stability can be selected.
  • the material of the isolation film can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the separator can be a single-layer film or a multi-layer composite film, without any particular limitation. When the separator is a multilayer composite film, the materials of each layer may be the same or different, and there is no particular limitation.
  • the positive pole piece, the negative pole piece and the separator can be made into an electrode assembly through a winding process or a lamination process.
  • the secondary battery may include an outer package.
  • the outer package can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the secondary battery may be a hard case, such as a hard plastic case, aluminum case, steel case, and the like.
  • the outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag.
  • the material of the soft case may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
  • FIG. 5 shows a secondary battery 5 having a square structure as an example.
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plates enclose to form an accommodating cavity.
  • the housing 51 has an opening communicating with the accommodating cavity, and the cover plate 53 can cover the opening to close the accommodating cavity.
  • the positive pole piece, the negative pole piece and the separator can be formed into an electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the accommodating cavity. Electrolyte is infiltrated in the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.
  • the secondary battery can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.
  • FIG. 7 is a battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 .
  • the plurality of secondary batteries 5 may be fixed by fasteners.
  • the battery module 4 may also include a case having a housing space in which a plurality of secondary batteries 5 are accommodated.
  • the above-mentioned battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3 , the upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery module 4 .
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • the present application also provides an electric device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application.
  • the secondary battery, battery module, or battery pack can be used as a power source of the electric device, and can also be used as an energy storage unit of the electric device.
  • the electric devices may include mobile devices (such as mobile phones, notebook computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, etc.) , electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but not limited thereto.
  • a secondary battery, a battery module or a battery pack can be selected according to its use requirements.
  • FIG. 10 is an example of an electrical device.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • a battery pack or a battery module may be used.
  • a device may be a cell phone, tablet, laptop, or the like.
  • the device is generally required to be light and thin, and a secondary battery can be used as a power source.
  • the positive electrode active material sample was prepared as a button charge, and the above charge charge was carried out at a small rate of 0.05C until the current was reduced to 0.01C. Then take out the positive pole piece in the battery, and soak it in DMC for 8 hours. Then dry, scrape the powder, and screen out the particles whose particle size is less than 500nm. Take a sample and calculate its lattice constant v1 in the same way as the above-mentioned test fresh sample, and (v0-v1)/v0 ⁇ 100% is shown in the table as the lattice change rate before and after it completely deintercalates lithium.
  • the Li/Mn antisite defect concentration is obtained. Specifically, import the XRD results tested in the "Measurement Method of Lattice Change Rate” into the General Structural Analysis System (GSAS) software, and automatically obtain the refined results, which include the occupancy of different atoms. By reading the refined As a result, the Li/Mn antisite defect concentration is obtained.
  • GSAS General Structural Analysis System
  • a 5 g positive electrode active material sample was taken to prepare a button electrode according to the button electrode preparation method described in the above examples. Charge the button with a small rate of 0.05C until the current decreases to 0.01C. Then take out the positive pole piece in the battery, and soak it in DMC for 8 hours. Then dry, scrape the powder, and screen out the particles whose particle size is less than 500nm. The obtained particles were measured by electron energy loss spectroscopy (EELS, the instrument model used was Talos F200S), and the energy loss near-edge structure (ELNES) was obtained, which reflected the density of states and energy level distribution of the elements. According to the density of states and energy level distribution, the number of occupied electrons is calculated by integrating the data of the valence band density of states, so as to calculate the valence state of the charged surface oxygen.
  • EELS electron energy loss spectroscopy
  • ELNES energy loss near-edge structure
  • the full battery was discharged to a cut-off voltage of 2.0V at a rate of 0.1C after being cycled at 45°C until the capacity decayed to 80%. Then the battery was disassembled, and the negative pole piece was taken out. On the negative pole piece, 30 discs with a unit area (1540.25mm 2 ) were randomly selected, and the inductively coupled plasma emission spectrum (ICP) was tested with Agilent ICP-OES730. According to the ICP results, the amounts of Fe (if the Mn site of the positive electrode active material is doped with Fe) and Mn are calculated, so as to calculate the dissolution amount of Mn (and Fe doped at the Mn site) after cycling.
  • the test standard is based on EPA-6010D-2014.
  • Full cells were stored at 100% state of charge (SOC) at 60°C.
  • the open circuit voltage (OCV) and AC internal resistance (IMP) of the cell are measured before, after and during storage to monitor the SOC, and the volume of the cell is measured.
  • the full battery was taken out after every 48 hours of storage, and the open circuit voltage (OCV) and internal resistance (IMP) were tested after standing for 1 hour, and the cell volume was measured by the drainage method after cooling to room temperature.
  • the battery of the embodiment always maintains an SOC of more than 99% during the experiment until the end of storage.
  • Dissolve 5 g of the positive electrode active material prepared above in 100 ml of aqua regia (concentrated hydrochloric acid: concentrated nitric acid 1:3) (concentration of concentrated hydrochloric acid ⁇ 37%, concentration of concentrated nitric acid ⁇ 65%), and use ICP to test the elements of the solution. content, and then measure and convert the content of manganese or phosphorus (amount of manganese or phosphorus/amount of positive electrode active material*100%) to obtain its weight ratio.
  • the thickness test of the coating layer is mainly to cut a thin slice with a thickness of about 100nm from the middle of the single particle of the positive electrode active material prepared above through FIB, and then conduct a TEM test on the thin slice to obtain the original picture of the TEM test, and save the original picture format (xx.dm3) .
  • the thickness was measured at three locations on the selected particle and the average value was taken.
  • the test is performed by Raman spectroscopy. By splitting the energy spectrum of the Raman test, Id/Ig is obtained, where Id is the peak intensity of SP3 form carbon, and Ig is the peak intensity of SP2 form carbon, thereby confirming the molar ratio of the two.
  • ACSTEM spherical aberration electron microscope
  • Li2FeP2O7 solution To prepare Li2FeP2O7 solution, dissolve 7.4 g of lithium carbonate, 11.6 g of ferrous carbonate, 23.0 g of ammonium dihydrogen phosphate and 12.6 g of oxalic acid dihydrate in 500 mL of deionized water, control the pH to 5, then stir and The reaction was carried out at low temperature for 2 hours to obtain a solution, and then the solution was heated to 80° C. and maintained at this temperature for 4 hours to obtain a suspension of the first coating layer.
  • step S2 Take 10mol (about 1574g) of the co-doped lithium manganese phosphate core material obtained according to the step S2 process and add it to the first cladding layer suspension obtained in step S3 (the content of the first cladding layer substance is 15.7g), fully Stir and mix for 6 hours. After mixing evenly, transfer to a 120° C. oven to dry for 6 hours, and then sinter at 650° C. for 6 hours to obtain a pyrophosphate-coated material.
  • step S4 Add the pyrophosphate-coated material obtained in step S4 to the second coating layer suspension (the content of the second coating layer substance is 47.1 g) obtained in step S5, stir and mix thoroughly for 6 hours, and mix After uniformity, transfer to a 120°C oven to dry for 6 hours, and then sinter at 700°C for 8 hours to obtain a two-layer coated material.
  • step S6 Add the two-layer coated material obtained in step S6 to the sucrose solution obtained in step S7, and stir and mix together for 6 hours. After mixing evenly, transfer to a 150°C oven to dry for 6 hours, and then sinter at 700°C for 10 Hour obtains the material after three layers of coating.
  • Negative electrode active material artificial graphite, hard carbon, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), thickener sodium carboxymethyl cellulose (CMC) are 90:5:2:2:1 according to weight ratio Dissolve in deionized water as a solvent, stir and mix evenly to prepare negative electrode slurry.
  • the negative electrode slurry was evenly coated on the copper foil of the negative electrode current collector at a ratio of 0.117g/1540.25mm 2 , and then dried, cold pressed, and cut to obtain the negative electrode sheet.
  • a commercially available PP-PE copolymer microporous film with a thickness of 20 ⁇ m and an average pore diameter of 80 nm was used.
  • the positive electrode sheet, separator, and negative electrode sheet obtained above are stacked in order, so that the separator is in the middle of the positive and negative electrodes to play the role of isolation, and the electrode assembly is obtained by winding.
  • the electrode assembly is placed in an outer package, and the electrolyte solution is injected and packaged to obtain a full battery (hereinafter also referred to as "full battery").
  • a lithium sheet is used as the negative electrode, and a solution of 1mol/L LiPF 6 in ethylene carbonate (EC), diethyl carbonate (DEC) and dimethyl carbonate (DMC) with a volume ratio of 1:1:1 is used as the electrolyte , and assembled into a button battery (hereinafter also referred to as "button") in a button box together with the above-mentioned positive pole piece prepared.
  • EC ethylene carbonate
  • DEC diethyl carbonate
  • DMC dimethyl carbonate
  • step S1 and step S2 FeSO 4 .
  • other conditions were the same as in Example 1.
  • step S1 and step S2 except that in step S1 and step S2, the amount of Li 2 CO 3 is changed to 0.496mol, Mo(SO 4 ) 3 is replaced by W(SO 4 ) 3 , and H 4 SiO 4 is replaced by H 2 SO 4 , other conditions are identical with embodiment 1.
  • step S1 and step S2 change the amount of Li 2 CO 3 to 0.4985 mol, change 0.001 mol of Mo(SO 4 ) 3 to 0.0005 mol of Al 2 (SO 4 ) 3 , change NH 4 HF 2 into NH 4 HCl 2 , other conditions are the same as in Example 1.
  • step S1 and step S2 FeSO 4 .
  • Change the amount of H 2 O to 0.69 mol change the amount of Li 2 CO 3 to 0.4965 mol, change 0.001 mol of Mo(SO 4 ) 3 to 0.0005 mol of Nb 2 (SO 4 ) 5 , change the amount of H 4 SiO 4 Instead of H 2 SO 4 , and adding 0.01 mol of VCl 2 when preparing the doped manganese oxalate in step S1, the other conditions are the same as in Example 1.
  • step S1 and step S2 FeSO 4 .
  • step S1 and step S2 MgSO 4 is replaced by CoSO 4 , other conditions are the same as in embodiment 6.
  • step S1 and step S2 MgSO 4 was replaced by NiSO 4 , other conditions were the same as in Example 6.
  • step S1 and step S2 FeSO 4 .
  • step S1 and step S2 FeSO 4 .
  • step S1 and step S2 FeSO 4 .
  • step S1 and step S2 MnSO 4 .
  • the amount of H 2 O is changed to 1.36mol, FeSO 4 .
  • step S1 and step S2 MnSO 4 .
  • the amount of H 2 O is changed to 1.16mol, FeSO 4 .
  • the amount of H 2 O was changed to 0.8 mol, other conditions were the same as in Example 12.
  • step S1 and step S2 MnSO 4 . Except that the amount of H 2 O was changed to 1.3 mol, and the amount of VCl 2 was changed to 0.1 mol, other conditions were the same as in Example 12.
  • step S1 and step S2 MnSO 4 .
  • the other conditions are the same as in Example 1.
  • step S1 and step S2 MnSO 4 .
  • step S1 and step S2 MnSO 4 .
  • Change the amount of 0NH 4 HF 2 to 0.0025 mol, and add 0.1 mol of VCl 2 when preparing the doped manganese oxalate in step S1, and the other conditions are the same as in Example 1.
  • step S1 and step S2 FeSO 4 .
  • Change the amount of NH 4 HF 2 to 0.0025 mol, and add 0.1 mol of VCl 2 and 0.1 mol of CoSO 4 when preparing the doped manganese oxalate in step S1, and other conditions are the same as in Example 1.
  • step S1 and step S2 FeSO 4 . Except that the amount of H 2 O was changed to 0.4 mol and the amount of CoSO 4 was changed to 0.2 mol, other conditions were the same as in Example 18.
  • step S1 and step S2 MnSO 4 .
  • the amount of H 2 O is changed to 1.5mol, FeSO 4 .
  • the amount of H 2 O was changed to 0.1 mol and the amount of CoSO 4 was changed to 0.3 mol, other conditions were the same as in Example 18.
  • step S1 and step S2 MnSO 4 .
  • the amount of H 2 O is changed to 1.5mol, FeSO 4 .
  • the amount of H 2 O was changed to 0.2 mol, and 0.1 mol of CoSO 4 was replaced with 0.2 mol of NiSO 4 , other conditions were the same as in Example 18.
  • step S1 and step S2 MnSO 4 .
  • the amount of H 2 O is changed to 1.4mol, FeSO 4 .
  • the amount of H 2 O was changed to 0.3 mol, and the amount of CoSO 4 was changed to 0.2 mol, other conditions were the same as in Example 18.
  • step S1 and step S2 MnSO 4 .
  • the amount of H 2 O is changed to 1.2mol, FeSO 4 .
  • the amount of H 2 O was changed to 0.5 mol, and the amount of CoSO 4 was changed to 0.2 mol, other conditions were the same as in Example 18.
  • step S1 and step S2 MnSO 4 .
  • the amount of H 2 O is changed to 1.0mol, FeSO 4 .
  • the amount of H 2 O was changed to 0.7 mol and the amount of CoSO 4 was changed to 0.2 mol, other conditions were the same as in Example 18.
  • step S1 and step S2 MnSO 4 .
  • the amount of H 2 O is changed to 1.4mol, FeSO 4 .
  • Change the amount of H 2 O to 0.3 mol change the amount of Li 2 CO 3 to 0.4825 mol, change 0.001 mol of Mo(SO 4 ) 3 to 0.005 mol of MgSO 4 , change the amount of H 4 SiO 4 to 0.1 mol, change the amount of phosphoric acid to 0.9mol, change the amount of NH 4 HF 2 to 0.04mol, and add 0.1mol of VCl 2 and 0.2mol of CoSO 4 when preparing doped manganese oxalate in step S1, other The conditions are the same as in Example 1.
  • step S1 and step S2 MnSO 4 .
  • the amount of H 2 O is changed to 1.4mol, FeSO 4 .
  • Change the amount of H 2 O to 0.3 mol change the amount of Li 2 CO 3 to 0.485 mol, change 0.001 mol of Mo(SO 4 ) 3 to 0.005 mol of MgSO 4 , change the amount of H 4 SiO 4 to 0.08 mol, change the amount of phosphoric acid to 0.92mol, change the amount of NH 4 HF 2 to 0.05mol, and add 0.1mol of VCl 2 and 0.2mol of CoSO 4 when preparing doped manganese oxalate in step S1, other The conditions are the same as in Example 1.
  • steps S3 to S6 different first coating layer substances or second coating layer substances are selected for coating, other conditions are the same as in embodiment 1. See Table 1 and Table 2 for the preparation method of each coating material.
  • step S4 step S6, and step S8, the amount of each raw material used was adjusted according to the amount of coating shown in Table 8, other conditions were the same as in Example 1.
  • step S4 the sintering temperature in the powder sintering step was adjusted to 550°C, the sintering time was adjusted to 1 hour to control the crystallinity of Li2FeP2O7 to 30%, and the coating sintering temperature was adjusted in step S5 The temperature is 650°C, the sintering time is adjusted to 2 hours to control the crystallinity of LiFePO 4 to 30%, other conditions are the same as in Example 1.
  • step S4 the sintering temperature in the powder sintering step was adjusted to 550°C, the sintering time was adjusted to 2 hours to control the crystallinity of Li2FeP2O7 to 50%, and the coating sintering temperature was adjusted in step S5 The temperature is 650° C., the sintering time is adjusted to 3 hours to control the crystallinity of LiFePO 4 to 50%, other conditions are the same as in Example 1.
  • step S4 the sintering temperature in the powder sintering step was adjusted to 600°C, the sintering time was adjusted to 3 hours to control the crystallinity of Li2FeP2O7 to 70%, and the coating sintering temperature was adjusted in step S5 The temperature is 650° C., the sintering time is adjusted to 4 hours to control the crystallinity of LiFePO 4 to 70%, other conditions are the same as in Example 1.
  • Preparation of positive electrode active material take 1 mol of the above-mentioned manganese oxalate particles, 0.45 mol of lithium carbonate, 0.005 Nb 2 (SO 4 ) 5 , 85% phosphoric acid aqueous solution containing 1 mol of phosphoric acid, 0.025 mol of NH 4 HF 2 and 0.01 mol of sucrose Add to 20L deionized water. The mixture was transferred to a sand mill and thoroughly ground and stirred for 10 hours to obtain a slurry. The slurry was transferred to a spray drying device for spray drying and granulation. The drying temperature was set at 250° C. and dried for 4 hours to obtain granules. In a protective atmosphere of nitrogen (90 vol%) + hydrogen (10 vol%), the above powder was sintered at 700°C for 10 hours to obtain carbon-coated Li 0.90 Nb 0.01 Mn 0.6 Fe 0.4 PO 3.95 F 0.05 .
  • Preparation of positive electrode active material Take 1 mol of the above-mentioned manganese oxalate particles, 0.499 mol of lithium carbonate, 0.001 mol of MgSO 4 , 0.999 mol of phosphoric acid in an 85% phosphoric acid aqueous solution, 0.001 mol of H 4 SiO 4 , 0.0005 mol of NH 4 HF 2 and 0.01mol sucrose were added to 20L deionized water. The mixture was transferred to a sand mill and thoroughly ground and stirred for 10 hours to obtain a slurry. The slurry was transferred to a spray drying device for spray drying and granulation. The drying temperature was set at 250° C. and dried for 4 hours to obtain granules.
  • Preparation of positive electrode active material Take 1 mol of the above-mentioned manganese oxalate particles, 0.474 mol of lithium carbonate, 0.001 mol of MgSO 4 , 0.93 mol of phosphoric acid in an 85% phosphoric acid aqueous solution, 0.07 mol of H 4 SiO 4 , 0.06 mol of NH 4 HF 2 and 0.01mol sucrose were added to 20L deionized water. The mixture was transferred to a sand mill and thoroughly ground and stirred for 10 hours to obtain a slurry. The slurry was transferred to a spray drying device for spray drying and granulation. The drying temperature was set at 250° C. and dried for 4 hours to obtain granules.
  • Preparation of positive electrode active material Take 1 mol of the above-mentioned manganese oxalate particles, 0.497 mol of lithium carbonate, 0.001 mol of Mo(SO 4 ) 3 , 0.999 mol of phosphoric acid in an 85% phosphoric acid aqueous solution, 0.001 mol of H 4 SiO 4 , 0.0005 mol of Add NH 4 HF 2 and 0.01 mol sucrose to 20 L of deionized water. The mixture was transferred to a sand mill and thoroughly ground and stirred for 10 hours to obtain a slurry. The slurry was transferred to a spray drying device for spray drying and granulation. The drying temperature was set at 250° C.
  • step S4 is changed and steps S5 and S6 are not performed.
  • step S2 Take 10mol (about 1574g) of the co-doped lithium manganese phosphate core material obtained according to the step S2 process and add it to the first cladding layer suspension (the first cladding layer substance content is 62.8g) obtained in step S3, fully Stir and mix for 6 hours. After mixing evenly, transfer to a 120°C oven to dry for 6 hours, and then sinter at 500°C for 4 hours to control the crystallinity of Li 2 FeP 2 O 7 to 5%, and obtain amorphous Li 2 FeP 2 O 7 coated material.
  • step S6 is changed and steps S3 and S4 are not performed.
  • step S2 Take 10mol (about 1574g) of the co-doped lithium manganese phosphate core material obtained according to the step S2 process and add it to the first cladding layer suspension obtained in step S3 (the content of the first cladding layer substance is 15.7g), fully Stir and mix for 6 hours. After mixing evenly, transfer to a 120°C oven to dry for 6 hours, and then sinter at 500°C for 4 hours to control the crystallinity of Li 2 FeP 2 O 7 to 5%, and obtain amorphous Li 2 FeP 2 O 7 coated material.
  • the amorphous Li 2 FeP 2 O 7 coated material obtained in step S4 was added to the second coating layer suspension obtained in step S5 (the content of the second coating layer substance was 47.1g), fully Stir and mix for 6 hours. After mixing evenly, transfer to a 120°C oven to dry for 6 hours, and then sinter at 600°C for 4 hours to control the crystallinity of LiFePO 4 to 8%, and obtain amorphous Li 2 FeP 2 O 7 and Amorphous LiFePO 4 coated material.
  • Table 3 shows the positive electrode active material compositions of Comparative Examples 1 to 12.
  • Table 4 shows the performance data of the positive electrode active material, positive electrode sheet, button charge or full charge of Comparative Examples 1 to 12 measured according to the above performance test method.
  • Table 5 shows the positive electrode active material compositions of Examples 1-44.
  • Table 6 shows the performance data of the positive electrode active material, positive electrode sheet, button charge or full charge of Examples 1-44 measured according to the above performance test method.
  • the present application modifies the Li site, Mn site, P site, and O site of lithium manganese phosphate with a specific amount of doping specific elements at the same time and performs multi-layer coating on lithium manganese phosphate.
  • the resulting cathode active material achieves a smaller lattice change rate, a smaller Li/Mn antisite defect concentration, a larger compaction density, a surface oxygen valence closer to -2 valence, and less
  • the amount of Mn and Fe released after cycling so that the battery of the present application has better performance, such as higher capacity, better high-temperature storage performance and high-temperature cycle performance.
  • FIG. 7 shows the X-ray diffraction pattern (XRD) pattern of undoped LiMnPO 4 and the inner core of the positive electrode active material prepared in Example 2.
  • XRD X-ray diffraction pattern
  • FIG. 8 shows an X-ray energy dispersive spectrum (EDS) diagram of the core of the positive electrode active material prepared in Example 2. Dotted distribution in the figure is each doping element. It can be seen from the figure that elements are uniformly doped in the inner core of the positive electrode active material prepared in Example 2.
  • Table 7 shows the interplanar distances and included angles of the first cladding material and the second cladding material of Examples 32 to 44.
  • Table 8 shows the positive electrode active material compositions of Examples 45 to 59.
  • Table 9 shows the performance data of the positive electrode active material, positive electrode sheet, button charge or full charge of Examples 45 to 59 measured according to the above performance test method.
  • Table 10 shows the performance data of the positive electrode active material, positive electrode sheet, button charge or full charge of Examples 60 to 62 measured according to the above performance test method.
  • the shell includes the first cladding layer (pyrophosphate and phosphate), the second cladding Specific examples where the layer comprises carbon:
  • Each parameter is the same as the S1 step of embodiment 1.
  • the parameters are the same as the step S2 of Example 1 to obtain Li 0.994 Mo 0.001 Mn 0.65 Fe 0.35 P 0.999 Si 0.001 O 3.999 F 0.001 , that is, co-doped lithium manganese phosphate core.
  • Example 2 The parameters are the same as in Example 1, and a full battery (hereinafter also referred to as “full battery”) and a button battery (hereinafter also referred to as “button battery”) are obtained.
  • full battery hereinafter also referred to as “full battery”
  • button battery hereinafter also referred to as “button battery”.
  • step S1 and step S2 FeSO 4 .
  • other conditions were the same as in Example 1-A.
  • step S1 and step S2 except that in step S1 and step S2, the amount of Li 2 CO 3 is changed to 0.496mol, Mo(SO 4 ) 3 is replaced by W(SO 4 ) 3 , and H 4 SiO 4 is replaced by H 2 SO 4 , other conditions are identical with embodiment 1-A.
  • step S1 and step S2 change the amount of Li 2 CO 3 to 0.4985 mol, change 0.001 mol of Mo(SO 4 ) 3 to 0.0005 mol of Al 2 (SO 4 ) 3 , change NH 4 HF 2 into NH 4 HCl 2 , other conditions are the same as in Example 1-A.
  • step S1 and step S2 FeSO 4 .
  • Change the amount of H 2 O to 0.69 mol change the amount of Li 2 CO 3 to 0.4965 mol, change 0.001 mol of Mo(SO 4 ) 3 to 0.0005 mol of Nb 2 (SO 4 ) 5 , change the amount of H 4 SiO 4 Instead of H 2 SO 4 , and adding 0.01 mol of VCl 2 when preparing the doped manganese oxalate in step S1, the other conditions are the same as in Example 1-A.
  • step S1 and step S2 FeSO 4 .
  • step S1 and step S2 MgSO 4 was replaced by CoSO 4 , other conditions were the same as in Example 6-A.
  • step S1 and step S2 MgSO 4 was replaced by NiSO 4 , other conditions were the same as in Example 6-A.
  • step S1 and step S2 FeSO 4 .
  • step S1 and step S2 FeSO 4 .
  • step S1 and step S2 FeSO 4 .
  • step S1 and step S2 MnSO 4 .
  • the amount of H 2 O is changed to 1.36mol, FeSO 4 .
  • Change the amount of H 2 O to 0.6 mol change the amount of Li 2 CO 3 to 0.4985 mol, change Mo(SO 4 ) 3 to MgSO 4 , change H 4 SiO 4 to HNO 3 , and prepare the doped During the manganese oxalate, also add the VCl of 0.04mol Except that, other conditions are identical with embodiment 1-A.
  • step S1 and step S2 MnSO 4 .
  • the amount of H 2 O is changed to 1.16mol, FeSO 4 .
  • the amount of H 2 O was changed to 0.8 mol, other conditions were the same as in Example 12-A.
  • step S1 and step S2 MnSO 4 . Except that the amount of H 2 O was changed to 1.3 mol, and the amount of VCl 2 was changed to 0.1 mol, other conditions were the same as in Example 12-A.
  • step S1 and step S2 MnSO 4 .
  • other conditions are the same as in Example 1-A.
  • step S1 and step S2 MnSO 4 .
  • MnSO 4 Change the amount of H 2 O to 1.2 mol, change the amount of Li 2 CO 3 to 0.492 mol, change 0.001 mol of Mo(SO 4 ) 3 to 0.005 mol of MgSO 4 , change H 4 SiO 4 to H 2 SO 4. Change the amount of 0NH 4 HF 2 to 0.0025 mol, and add 0.1 mol of VCl 2 when preparing the doped manganese oxalate in step S1, and the other conditions are the same as in Example 1-A.
  • step S1 and step S2 FeSO 4 .
  • Change the amount of NH 4 HF 2 to 0.0025 mol, and add 0.1 mol of VCl 2 and 0.1 mol of CoSO 4 when preparing doped manganese oxalate in step S1, and other conditions are the same as in Example 1-A.
  • step S1 and step S2 FeSO 4 . Except that the amount of H 2 O was changed to 0.4 mol, and the amount of CoSO 4 was changed to 0.2 mol, other conditions were the same as in Example 18-A.
  • step S1 and step S2 MnSO 4 .
  • the amount of H 2 O is changed to 1.5mol, FeSO 4 .
  • the amount of H 2 O was changed to 0.1 mol, and the amount of CoSO 4 was changed to 0.3 mol, other conditions were the same as in Example 18-A.
  • step S1 and step S2 MnSO 4 .
  • the amount of H 2 O is changed to 1.5mol, FeSO 4 .
  • the amount of H 2 O was changed to 0.2 mol, and 0.1 mol of CoSO 4 was replaced with 0.2 mol of NiSO 4 , other conditions were the same as in Example 18-A.
  • step S1 and step S2 MnSO 4 .
  • the amount of H 2 O is changed to 1.4mol, FeSO 4 .
  • the amount of H 2 O was changed to 0.3 mol, and the amount of CoSO 4 was changed to 0.2 mol, other conditions were the same as in Example 18-A.
  • step S1 and step S2 MnSO 4 .
  • the amount of H 2 O is changed to 1.2mol, FeSO 4 .
  • the amount of H 2 O was changed to 0.5 mol, and the amount of CoSO 4 was changed to 0.2 mol, other conditions were the same as in Example 18-A.
  • step S1 and step S2 MnSO 4 .
  • the amount of H 2 O is changed to 1.0mol, FeSO 4 .
  • the amount of H 2 O was changed to 0.7 mol and the amount of CoSO 4 was changed to 0.2 mol, other conditions were the same as in Example 18-A.
  • step S1 and step S2 MnSO 4 .
  • the amount of H 2 O is changed to 1.4mol, FeSO 4 .
  • Change the amount of H 2 O to 0.3 mol change the amount of Li 2 CO 3 to 0.4825 mol, change 0.001 mol of Mo(SO 4 ) 3 to 0.005 mol of MgSO 4 , change the amount of H 4 SiO 4 to 0.1 mol, change the amount of phosphoric acid to 0.9mol, change the amount of NH 4 HF 2 to 0.04mol, and add 0.1mol of VCl 2 and 0.2mol of CoSO 4 when preparing doped manganese oxalate in step S1, other The conditions were the same as in Example 1-A.
  • step S1 and step S2 MnSO 4 .
  • the amount of H 2 O is changed to 1.4mol, FeSO 4 .
  • Change the amount of H 2 O to 0.3 mol change the amount of Li 2 CO 3 to 0.485 mol, change 0.001 mol of Mo(SO 4 ) 3 to 0.005 mol of MgSO 4 , change the amount of H 4 SiO 4 to 0.08 mol, change the amount of phosphoric acid to 0.92mol, change the amount of NH 4 HF 2 to 0.05mol, and add 0.1mol of VCl 2 and 0.2mol of CoSO 4 when preparing doped manganese oxalate in step S1, other The conditions were the same as in Example 1-A.
  • step S3 and step S4 the raw materials used are adjusted according to the coating amount shown in Table 5, so that the dosages of Li 2 FeP 2 O 7 /LiFePO 4 in Examples 28 to 32 are respectively Except for 12.6g/37.7g, 14.1g/42.4g, 18.8g/56.5g, 22.0/66.0g and 25.1g/75.4g, other conditions are the same as in Example 1-A.
  • step S4 the amount of sucrose was adjusted to 74.6g, 149.1g, 186.4g and 223.7g respectively so that the corresponding coating amounts of the carbon layer as the second coating layer were 31.4g, 62.9g, 78.6g And 94.3g, other conditions are identical with embodiment 1-A.
  • step S3 and step S4 the raw materials used are adjusted according to the coating amount shown in Table 5, so that the dosages of Li 2 FeP 2 O 7 /LiFePO 4 in Examples 37 to 40 are respectively Except for 23.6g/39.3g, 31.4g/31.4g, 39.3g/23.6g and 47.2g/15.7g, other conditions are the same as in Example 1-A.
  • step S4 the sintering temperature in the powder sintering step was adjusted to 550°C, the sintering time was adjusted to 1 hour to control the crystallinity of Li2FeP2O7 to 30%, and the coating sintering temperature was adjusted in step S5 The temperature is 650°C, the sintering time is adjusted to 2 hours to control the crystallinity of LiFePO 4 to 30%, other conditions are the same as in Example 1-A.
  • step S4 the sintering temperature in the powder sintering step was adjusted to 550°C, the sintering time was adjusted to 2 hours to control the crystallinity of Li2FeP2O7 to 50%, and the coating sintering temperature was adjusted in step S5 The temperature is 650°C, the sintering time is adjusted to 3 hours to control the crystallinity of LiFePO 4 to 50%, other conditions are the same as in Example 1-A.
  • step S4 the sintering temperature in the powder sintering step was adjusted to 600°C, the sintering time was adjusted to 3 hours to control the crystallinity of Li2FeP2O7 to 70%, and the coating sintering temperature was adjusted in step S5 The temperature is 650°C, the sintering time is adjusted to 4 hours to control the crystallinity of LiFePO 4 to 70%, other conditions are the same as in Example 1-A.
  • step S1 prepares doped manganese oxalate, and the time of grinding and stirring in a sand mill, sintering temperature and sintering time when step S2 prepares a co-doped lithium manganese phosphate core
  • step S2 prepares a co-doped lithium manganese phosphate core
  • the sintering temperature and sintering time were adjusted to 680°C/4h, 750°C/6h, and 800°C, respectively. Except °C/8h, other conditions are the same as Example 38-A.
  • step S2 Take 10mol (about 1570g) of the co-doped lithium manganese phosphate core obtained according to the process of step S2 and add it to the LiFePO4 suspension (containing 37.3g of sucrose and 62.8g of LiFePO4) obtained in step S4, stir and mix evenly Dry in a vacuum oven at 150°C for 6 hours. The resulting product was then dispersed by sand milling. After dispersion, the obtained product was sintered at 600° C. for 4 hours in a nitrogen atmosphere to obtain an amorphous lithium iron phosphate and carbon-coated positive electrode active material.
  • the resulting product was sintered in a nitrogen atmosphere at 600°C for 4 hours to control the crystallinity of LiFePO 4 to 8%, to obtain amorphous lithium iron pyrophosphate, amorphous lithium iron phosphate, carbon-coated Positive active material.
  • the button battery prepared above in a constant temperature environment of 25°C let it stand for 5 minutes, discharge it at 0.1C to 2.5V, let it stand for 5 minutes, charge it at 0.1C to 4.3V, and then charge it at a constant voltage of 4.3V to
  • the current is less than or equal to 0.05mA, let stand for 5 minutes; then discharge to 2.5V according to 0.1C, the discharge capacity at this time is the initial gram capacity, denoted as D0, the discharge energy is the initial energy, denoted as E0, and the average discharge voltage V That is E0/D0.
  • Table 1-A shows the compositions of positive electrode active materials of Examples 1-A to 11-A and Comparative Examples 1-A to 12-A.
  • Table 2-A shows the performance data of Examples 1-A to 11-A and Comparative Examples 1-A to 12-A of the positive electrode active material, positive electrode sheet, buckle charge or full charge measured according to the above performance test method.
  • the present application modifies Li-site, Mn-site, P-site and O-site of lithium manganese phosphate with a specific amount of doping specific elements at the same time and performs multi-layer coating on lithium manganese phosphate.
  • the resulting positive electrode active material achieves a smaller lattice change rate, a smaller Li/Mn antisite defect concentration, a larger compaction density, a surface oxygen valence closer to -2 valence, and fewer cycles. Therefore, the battery of the present application has better performance, such as higher capacity, better high-temperature storage performance and high-temperature cycle performance.
  • Table 3-A shows the positive electrode active material compositions of Examples 12-A to 27-A.
  • Table 4-A shows the performance data of the positive electrode active material, positive electrode sheet, button charge or full charge of Examples 12-A to 27-A measured according to the above performance test method.
  • (1-y):y is in the range of 1 to 4 and a:x is in the range of 9 to 1100, optionally, (1-y):y
  • a:x is in the range of 1.5 to 3 and a:x is in the range of 190 to 998, the energy density and cycle performance of the battery can be further improved.
  • Table 5-A shows the positive electrode active material compositions of Examples 28-A to 40-A.
  • Table 6-A shows the performance data of the positive electrode active material, positive electrode sheet, button charge or full charge of Examples 28-A to 40-A measured according to the above performance test method.
  • Example 1-A Combining Example 1-A and Examples 28-A to 32-A, it can be seen that as the amount of the first coating layer increases from 3.2% to 6.4%, the Li/Mn anti-site defect concentration of the obtained positive electrode active material gradually decreases, After cycling, the dissolution of Fe and Mn gradually decreased, and the safety performance and cycle performance of the corresponding battery were also improved, but the gram capacity decreased slightly.
  • the total amount of the first coating layer is 4-5.6% by weight, the overall performance of the corresponding battery is the best.
  • Example 1-A and Examples 33-A to 36-A it can be seen that as the amount of the second coating layer increases from 1% to 6%, the Li/Mn anti-site defect concentration of the obtained positive electrode active material gradually decreases, After cycling, the dissolution of Fe and Mn gradually decreased, and the safety performance and cycle performance of the corresponding battery were also improved, but the gram capacity decreased slightly.
  • the total amount of the second coating layer is 3-5% by weight, the overall performance of the corresponding battery is the best.
  • Example 1-A and Examples 37-A to 40-A it can be seen that when Li 2 FeP 2 O 7 and LiFePO 4 exist in the first cladding layer, especially the weight of Li 2 FeP 2 O 7 and LiFePO 4 The improvement of battery performance is more obvious when the ratio is 1:3 to 3:1, and especially when it is 1:3 to 1:1.
  • Table 7-A shows the performance data of the positive electrode active material, positive electrode sheet, button charge or full charge of Examples 1-A, 41-A to 43-A measured according to the above performance test method.
  • Examples 44-A to 57-A except changing the stirring speed and heating temperature when preparing the doped manganese oxalate in step S1, and the time of grinding and stirring in a sand mill when preparing the co-doped lithium manganese phosphate core in step S2, and sintering Temperature and sintering time, and other conditions are the same as in Example 1-A, specifically as shown in Table 8-A below.
  • Table 9-A shows the performance data of the positive electrode active material, positive electrode sheet, button charge or full charge of Examples 44-A to 57-A measured according to the above performance test method.
  • Example 58-A to 61-A except for changing the drying temperature, drying time, sintering temperature and sintering time when preparing lithium iron pyrophosphate powder in step S3, other conditions are the same as in Example 1-A, as shown in Table 10- As shown in A.
  • Table 11-A shows the performance data of the positive electrode active material, positive electrode sheet, button charge or full charge of Examples 58-A to 61-A measured according to the above performance test method.
  • Examples 62-A to 64-A are the same as Example 38 except that the drying temperature, drying time, sintering temperature and sintering time in step S5 are changed, and the details are shown in Table 12-A below.
  • Table 13-A shows the performance data of the positive electrode active material, positive electrode sheet, button charge or full charge of Examples 62-A to 64-A measured according to the above performance test method.
  • the core is Li 1+ xMn 1-y A y P 1-z R z O 4
  • the shell includes the first cladding layer including crystalline pyrophosphate QP 2 O 7 and metal oxide Q' e O f
  • the reaction kettle was heated to 80° C. and stirred at 600 rpm for 6 hours until the reaction was terminated (no bubbles were generated), and a Fe, Co and V co-doped manganese oxalate suspension was obtained. Then filter the suspension, dry the filter cake at 120° C., and then grind to obtain Fe, Co and V co-doped manganese oxalate dihydrate particles with a median diameter Dv50 of 100 nm.
  • lithium iron pyrophosphate powder 4.77 g of lithium carbonate, 7.47 g of ferrous carbonate, 14.84 g of ammonium dihydrogen phosphate and 1.3 g of oxalic acid dihydrate were dissolved in 50 ml of deionized water. The pH of the mixture was 5, and the reaction mixture was stirred for 2 hours to fully react. Then the temperature of the reacted solution was raised to 80°C and maintained at this temperature for 4 hours to obtain a suspension containing Li 2 FeP 2 O 7 , which was filtered, washed with deionized water, and dried at 120°C for 4 hours , to obtain powder. The powder was sintered at 650° C. under a nitrogen atmosphere for 8 hours, cooled naturally to room temperature, and then ground to obtain Li 2 FeP 2 O 7 powder.
  • Example 1-1 the ratio of the coating amount shown in Example 1-1 is correspondingly adjusted, so that the amount of Li 2 FeP 2 O 7 /Al 2 O 3 in Examples 1-2 to 1-6 is 12.6g/ 37.68g, 15.7g/47.1g, 18.8g/56.52g, 22.0/65.94g and 25.1g/75.36g, except that the amount of sucrose in Examples 1-2 to 1-6 is 37.3g, other conditions are the same as in Example 1 -1 is the same.
  • Examples 1-15 were the same as those of Examples 1-14.
  • Example 1-16 Except that in Example 1-16, 466.4g of NiCO 3 , 5.0g of zinc carbonate and 7.2g of titanium sulfate were used instead of ferrous carbonate during the preparation of the co-doped lithium manganese phosphate core, and in co-doping
  • the ferrous carbonate of 455.2g and the vanadium dichloride of 8.5g are used in the preparation process of the lithium manganese phosphate inner core, and the ferrous carbonate of 455.2g is used in the preparation process of the co-doped lithium manganese phosphate inner core in embodiment 1-18 , 4.9g of vanadium dichloride and 2.5g of magnesium carbonate, the conditions of Examples 1-16 to 1-18 are identical to those of Example 1-7.
  • embodiment 1-19 uses the lithium carbonate of 369.4g in the preparation process of co-doped lithium manganese phosphate inner core, and replaces dilute sulfuric acid with the dilute nitric acid of 60% concentration of 1.05g
  • embodiment 1-20 is in co-doped
  • the conditions of embodiments 1-19 to 1-20 are the same as in embodiment 1-18
  • Examples 1-21 632.0g of manganese carbonate, 463.30g of ferrous carbonate, 30.5g of vanadium dichloride, 21.0g of magnesium carbonate and 0.78g of silicate were used in the preparation process of the co-doped lithium manganese phosphate core.
  • Embodiment 1-22 uses 746.9g manganese carbonate, 289.6g ferrous carbonate, 60.9g of vanadium dichloride, 42.1g of magnesium carbonate and 0.78g of silicate in the preparation process of co-doped lithium manganese phosphate core
  • the conditions of Examples 1-21 to 1-22 are the same as those of Example 1-20.
  • embodiment 1-23 uses 804.6g manganese carbonate, 231.7g ferrous carbonate, 1156.2g ammonium dihydrogen phosphate, 1.2g boric acid (mass fraction 99.5%) and 370.8 g lithium carbonate; embodiment 1-24 uses 862.1g manganese carbonate, 173.8g ferrous carbonate, 1155.1g ammonium dihydrogen phosphate, boric acid (mass fraction 99.5% of 1.86g) in the preparation process of co-doped lithium manganese phosphate core ) and 371.6g lithium carbonate, the conditions of embodiment 1-23 to 1-24 are identical with embodiment 1-22.
  • Example 1-25 uses 370.1g of lithium carbonate, 1.56g of silicic acid and 1147.7g of ammonium dihydrogen phosphate in the preparation process of the co-doped lithium manganese phosphate core, the conditions of Example 1-25 are the same as those of Example 1-20 are the same.
  • embodiment 1-26 uses 368.3g lithium carbonate, 4.9g mass fraction to be 60% dilute sulfuric acid, 919.6g manganese carbonate, 224.8g ferrous carbonate, 3.7g dichloro Except the ammonium dihydrogen phosphate of vanadium, 2.5g magnesium carbonate and 1146.8g, the condition of embodiment 1-26 is identical with embodiment 1-20.
  • embodiment 1-27 uses 367.9g lithium carbonate, 6.5g concentration to be 60% dilute sulfuric acid and 1145.4g ammonium dihydrogen phosphate in the preparation process of co-doped lithium manganese phosphate inner core, the conditions of embodiment 1-27 Same as Example 1-20.
  • embodiment 1-28 to 1-33 uses 1034.5g manganese carbonate, 108.9g ferrous carbonate, 3.7g vanadium dichloride and 2.5g magnesium carbonate in the preparation process of co-doped lithium manganese phosphate inner core, the use of lithium carbonate
  • the amounts are: 367.6g, 367.2g, 366.8g, 366.4g, 366.0g, and 332.4g
  • the amounts of ammonium dihydrogen phosphate are: 1144.5g, 1143.4g, 1142.2g, 1141.1g, 1139.9g, and 1138.8g
  • Concentration is that the consumption of the dilute sulfuric acid of 60% is respectively: except 8.2g, 9.8g, 11.4g, 13.1g, 14.7g and 16.3g, the conditions of embodiment 1-28 to 1-33 are identical with embodiment 1-20 .
  • the raw materials used are according to the coating amount shown in Table 1
  • the ratio of the coating amount corresponding to Example 1-1 is adjusted accordingly, so that the amount of Li 2 FeP 2 O 7 /MgO in Example 1-34 is 15.72g/47.1g, Li 2 in Example 1-35
  • the dosages of FeP 2 O 7 /ZrO 2 are 15.72g/47.1g respectively
  • the dosages of Li 2 FeP 2 O 7 /ZnO in Examples 1-36 are 15.72g/47.1g respectively
  • the amount of 2 O 7 /SnO 2 is 15.72g/47.1g
  • the amount of Li 2 FeP 2 O 7 /SiO 2 in Example 1-38 is 15.72g/47.1g
  • the dosages of 2 O 7 /V 2 O 5 are 15.72g/47.1g respectively, and other conditions are the same as in Example 1
  • Example 1-40 the preparation of inner core LiMn 0.999 Fe 0.001 P 0.995 N 0.005 O 4 .
  • Fe-doped manganese oxalate 1148.0g of manganese carbonate (calculated as MnCO3 , the same below) and 11.58g of ferrous carbonate (calculated as FeCO3 , the same below) were fully mixed in a mixer for 6 hours. The mixture was transferred to a reaction kettle, and 5 liters of deionized water and 1260.6 g of oxalic acid dihydrate (calculated as C 2 H 2 O 4 .2H 2 O, the same below) were added. The reactor was heated to 80° C. and stirred at 600 rpm for 6 hours until the reaction was terminated (no bubbles were generated), and Fe-doped manganese oxalate suspension was obtained. Then the suspension was filtered, the filter cake was dried at 120° C., and then ground to obtain Fe-doped manganese oxalate dihydrate particles with a median diameter Dv50 of 100 nm.
  • Example 1-4 the preparation of inner core LiMn 0.50 Fe 0.50 P 0.995 N 0.005 O 4 .
  • Fe-doped manganese oxalate 574.7g of manganese carbonate (calculated as MnCO3 , the same below) and 579.27g of ferrous carbonate (calculated as FeCO3 , the same below) were fully mixed in a mixer for 6 hours. The mixture was transferred to a reaction kettle, and 5 liters of deionized water and 1260.6 g of oxalic acid dihydrate (calculated as C 2 H 2 O 4 .2H 2 O, the same below) were added. The reactor was heated to 80° C. and stirred at 600 rpm for 6 hours until the reaction was terminated (no bubbles were generated), and Fe-doped manganese oxalate suspension was obtained. Then the suspension was filtered, the filter cake was dried at 120° C., and then ground to obtain Fe-doped manganese oxalate dihydrate particles with a median diameter Dv50 of 100 nm.
  • Example 1-1 For other conditions of Example 1-39 to Example 1-41, refer to Example 1-1.
  • zirconium pyrophosphate 123.2g of zirconium dioxide (calculated as ZrO 2 , the same below) and 230.6g of phosphoric acid (calculated as 85% H 3 PO 4 , the same below) were fully mixed. It was heated to 350°C while stirring continuously for 2 hours to fully react the reaction mixture. Then the reacted solution was kept at 350°C for 4 hours to obtain a viscous paste containing ZrP2O7 , which finally became a solid, and was washed with deionized water , and the resulting product was placed in a ball mill equipped with ethanol Grinding was carried out for 4 hours, and the obtained product was dried under an infrared lamp to obtain ZrP 2 O 7 powder.
  • Example 1-1 In addition to using 104.5g of manganese carbonate, 1138.5g of ammonium dihydrogen phosphate and 371.3g of lithium carbonate in the preparation process of the inner core, and additionally adding 1052.8g of ferrous carbonate, 5.25g of dilute nitric acid (in 60% HNO3 , the same below) Other than that, it is the same as Example 1-1.
  • Example 1-1 In addition to using 1034.3g of manganese carbonate, 1138.5g of ammonium dihydrogen phosphate and 371.3g of lithium carbonate in the preparation process of the inner core, additionally add 115.8g of ferrous carbonate, 5.25g of dilute nitric acid (in 60% HNO3 , the same below) Other than that, it is the same as Example 1-1.
  • the sintering temperature in the powder sintering step is 550°C, and the sintering time is 1h to control the crystallinity of Li 2 FeP 2 O 7 to 30%.
  • the sintering temperature in the coating sintering step during the preparation of Al 2 O 3 is 650° C., and the sintering time is 2 h to control the crystallinity of Al 2 O 3 to 100%.
  • Other conditions are the same as in Example 1-1.
  • the sintering temperature in the powder sintering step is 550°C, and the sintering time is 2h to control the crystallinity of Li 2 FeP 2 O 7 to 50%.
  • the sintering temperature in the coating sintering step during the preparation of Al 2 O 3 is 650° C., and the sintering time is 3 h to control the crystallinity of Al 2 O 3 to 100%, other conditions are the same as in Example 1-1.
  • the sintering temperature in the powder sintering step is 600°C, and the sintering time is 3h to control the crystallinity of Li 2 FeP 2 O 7 to 70%.
  • the sintering temperature in the coating sintering step during the preparation of Al 2 O 3 is 650° C., and the sintering time is 4 hours to control the crystallinity of Al 2 O 3 to 100%, other conditions are the same as in Example 1-1.
  • the sintering temperature in the powder sintering step is 650°C, and the sintering time is 4h to control the crystallinity of Li 2 FeP 2 O 7 to 10%.
  • the sintering temperature in the coating sintering step during the preparation of Al 2 O 3 is 500° C., and the sintering time is 6 h to control the crystallinity of Al 2 O 3 to 100%, other conditions are the same as in Example 1-1.
  • the heating temperature/stirring time in the reactor of Example 3-1 was respectively 60°C/120 minutes; the heating in the reactor of Example 3-2 Temperature/stirring time is respectively 70 °C/120 minutes; The heating temperature/stirring time in embodiment 3-3 reactor is respectively 80 °C/120 minutes; The heating temperature/stirring time in embodiment 3-4 reactor is respectively 90°C/120 minutes; the heating temperature/stirring time in the reactor of Example 3-5 was 100°C/120 minutes respectively; the heating temperature/stirring time in the reactor of Example 3-6 was 110°C/120 minutes respectively; The heating temperature/stirring time in the reactor of embodiment 3-7 is respectively 120 °C/120 minutes; The heating temperature/stirring time in the reactor of embodiment 3-8 is respectively 130 °C/120 minutes; Embodiment 3-9 reaction The heating temperature/stirring time in the kettle is respectively 100 DEG C/60 minutes; The heating temperature/stir
  • Embodiment 4-1 to 4-4 are identical to Embodiment 4-1 to 4-4:
  • the drying temperature/drying time in the drying step are 100°C/4h, 150°C/6h, 200°C/6h and 200°C/6h respectively;
  • the sintering temperature and sintering time in the sintering step are 700°C/6h, 700°C/6h, 700°C/6h and 600°C/6h, respectively, Other conditions are the same as in Example 1-7.
  • Embodiment 4-5 to 4-7 are identical to Embodiment 4-5 to 4-7:
  • drying temperature/drying time in the drying step during the cladding process were 150°C/6h, 150°C/6h and 150°C/6h respectively;
  • sintering temperature and sintering time in the sintering step during the cladding process were respectively Except for 600°C/4h, 600°C/6h and 800°C/8h, the other conditions are the same as in Examples 1-12.
  • Preparation of carbon-coated lithium manganese phosphate take 1789.6g of manganese oxalate dihydrate particles obtained above, 369.4g of lithium carbonate (calculated as Li 2 CO 3 , the same below), 1150.1g of ammonium dihydrogen phosphate (calculated as NH 4 H 2 PO 4 meter, the same below) and 31 g of sucrose (calculated as C 12 H 22 O 11 , the same below) were added to 20 liters of deionized water, and the mixture was stirred for 10 hours to make it evenly mixed to obtain a slurry.
  • lithium carbonate calculated as Li 2 CO 3 , the same below
  • 1150.1g of ammonium dihydrogen phosphate calculated as NH 4 H 2 PO 4 meter, the same below
  • sucrose calculated as C 12 H 22 O 11 , the same below
  • Comparative Example 2 Except for using 689.5g of manganese carbonate and additionally adding 463.3g of ferrous carbonate, other conditions of Comparative Example 2 were the same as those of Comparative Example 1-1.
  • lithium iron pyrophosphate powder when preparing lithium iron pyrophosphate powder, dissolve 9.52g of lithium carbonate, 29.9g of ferrous carbonate, 29.6g of ammonium dihydrogen phosphate and 32.5g of oxalic acid dihydrate in 50ml of deionized water. The pH of the mixture was 5, and the reaction mixture was stirred for 2 hours to fully react. Then the temperature of the reacted solution was raised to 80°C and maintained at this temperature for 4 hours to obtain a suspension containing Li 2 FeP 2 O 7 , which was filtered, washed with deionized water, and dried at 120°C for 4 hours , to obtain powder.
  • the powder was sintered at 500°C under a nitrogen atmosphere for 4 hours, cooled naturally to room temperature, and then ground. Control the crystallinity of Li 2 FeP 2 O 7 to 5%.
  • Li 2 FeP 2 O 7 The consumption of other conditions is identical with comparative example 1-4 except that the consumption of 62.8g.
  • amorphous lithium iron pyrophosphate powder 2.38 g of lithium carbonate, 7.5 g of ferrous carbonate, 7.4 g of ammonium dihydrogen phosphate and 8.1 g of oxalic acid dihydrate were dissolved in 50 ml of deionized water. The pH of the mixture was 5, and the reaction mixture was stirred for 2 hours to fully react. Then the temperature of the reacted solution was raised to 80°C and maintained at this temperature for 4 hours to obtain a suspension containing Li 2 FeP 2 O 7 , which was filtered, washed with deionized water, and dried at 120°C for 4 hours , to obtain powder. The powder was sintered at 500° C. under a nitrogen atmosphere for 4 hours, cooled naturally to room temperature, and then ground to control the crystallinity of Li 2 FeP 2 O 7 to 5%.
  • the drying temperature/drying time in the drying step was 80°C/3h and 80°C/3h in Comparative Examples 1-8 to 1-10, respectively , 80°C/3h; the sintering temperature and sintering time in the sintering step during the coating process were 400°C/3h, 400°C/3h, and 350°C/2h in Comparative Examples 8-10; Comparative Examples 1-11
  • the drying temperature/drying time in the drying step during the coating process was 80°C/3h; the weight ratios of Li 2 FeP 2 O 7 /Al 2 O 3 in Comparative Examples 8-9 were 1:3, 1:3, respectively. 1; only Li 2 FeP 2 O 7 was used in Comparative Example 10; only Al 2 O 3 was used in Comparative Example 1-11, other conditions were the same as in Examples 1-1 to 1-7.
  • Example 1-A All parameters are the same as those in Example 1-A to obtain a positive electrode sheet.
  • Negative electrode active material artificial graphite, conductive agent superconducting carbon black (Super-P), binder styrene-butadiene rubber (SBR), thickener carboxymethylcellulose sodium (CMC-Na) are 95% according to mass ratio: 1.5%: 1.8%: 1.7% was dissolved in deionized water, and after fully stirring and mixing, a negative electrode slurry with a viscosity of 3000mPa.s and a solid content of 52% was obtained; the negative electrode slurry was coated on a 6 ⁇ m negative electrode current collector copper foil , and then baked at 100° C. for 4 hours to dry, and rolled to obtain a negative electrode sheet with a compacted density of 1.75 g/cm 3 .
  • the above obtained positive electrode sheet, separator, and negative electrode sheet are stacked in order, so that the separator is in the middle of the positive and negative electrodes to play the role of isolation, and the bare cell is obtained by winding. Place the bare cell in the outer package, inject the above electrolyte and package it to obtain a full battery (hereinafter also referred to as "full battery").
  • Example 1-A The parameters are the same as in Example 1-A, and a button battery (hereinafter also referred to as "button”) is assembled in a button box.
  • button hereinafter also referred to as "button"
  • Table 1-1 The performance test results of Examples 1-1 to 1-52 and Comparative Examples 1-1 to 1-7
  • the presence of the first cladding layer is beneficial to reduce the concentration of Li/Mn antisite defects and the dissolution of Fe and Mn after cycling. , improve the charge capacity and compaction density of the battery, and improve the safety performance and cycle performance of the battery.
  • the lattice change rate, antisite defect concentration and Fe and Mn dissolution amount of the obtained material can be significantly reduced, the gram capacity and compaction density of the battery can be increased, and the battery performance can be improved.
  • Safety performance and cycle performance is beneficial to reduce the concentration of Li/Mn antisite defects and the dissolution of Fe and Mn after cycling. , improve the charge capacity and compaction density of the battery, and improve the safety performance and cycle performance of the battery.
  • Table 4-1 The performance test results of Examples 4-1 to 4-7 and Comparative Examples 1-8 to 1-11
  • the shell includes the first cladding layer contains crystalline pyrophosphate, and the second cladding layer contains metal oxide Q' eOf , the preparation and performance test of the embodiment in which the third coating layer contains carbon , wherein unless otherwise specified, the sources of the reagents involved are the same as the actual sources of Examples 1-1 to 1-52:
  • Step S1 Preparation of Fe, Co, V and S co-doped manganese oxalate
  • Step S2 Prepare inner core Li 0.997 Mn 0.60 Fe 0.393 V 0.004 Co 0.003 P 0.997 S 0.003 O 4
  • Step S3 Preparation of the first coating layer suspension
  • Li2FeP2O7 solution Dissolve 7.4 g of lithium carbonate, 11.6 g of ferrous carbonate, 23.0 g of ammonium dihydrogen phosphate and 12.6 g of oxalic acid dihydrate in 500 mL of deionized water, control the pH to 5, then stir and The reaction was carried out for 2 hours to obtain a solution, and then the solution was heated to 80° C. and maintained at this temperature for 4 hours to obtain a suspension of the first coating layer.
  • Step S4 Coating of the first coating layer
  • step S2 Add 1571.9 g of the doped lithium manganese phosphate core material obtained in step S2 to the suspension of the first coating layer obtained in step S3 (the content of the coating substance is 15.7 g), stir and mix thoroughly for 6 hours, and mix evenly Afterwards, it was dried in an oven at 120°C for 6 hours, and then sintered at 650°C for 6 hours to obtain a pyrophosphate-coated material.
  • Step S5 Preparation of the second coating layer suspension
  • nanoscale Al 2 O 3 (particle size about 20 nm) was dissolved in 1500 mL of deionized water, and stirred for 2 hours to obtain a suspension of the second coating layer.
  • Step S6 Coating of the second coating layer
  • step S4 Add 1586.8 g of the pyrophosphate-coated material obtained in step S4 to the second coating layer suspension (coating substance content: 47.1 g) obtained in step S5, stir and mix thoroughly for 6 hours, and mix well Afterwards, it was dried in an oven at 120°C for 6 hours, and then sintered at 700°C for 8 hours to obtain a two-layer coated material.
  • Step S7 Preparation of the third coating layer aqueous solution
  • Step S8 Coating of the third coating layer
  • step S6 Add 1633.9 g of the two-layer coated material obtained in step S6 to the sucrose solution obtained in step S7, stir and mix together for 6 hours, after mixing evenly, transfer to an oven at 150°C to dry for 6 hours, and then sinter at 700°C for 10 hours A three-layer coated material is obtained.
  • Examples 2-B to 62-B and Comparative Examples 1-B to 11-B were made in a method similar to that of Example 1-B, and the differences in the preparation of positive electrode active materials are shown in Table 1-B to 6-B.
  • Comparative Examples 1-B to 2-B, 4-B to 10-B and Example 58B are not coated with the first layer, so there are no steps S3-S4; Comparative Examples 1-B to 10-B and Example 57 -B is not clad with the second layer, so there are no steps S5-S6.
  • Table 1-B Preparation of Fe, Co, V and S co-doped manganese oxalate and preparation of inner core (steps S1-S2)
  • the above obtained positive electrode sheet, separator, and negative electrode sheet are stacked in order, so that the separator is in the middle of the positive and negative electrodes to play the role of isolation, and the bare cell is obtained by winding. Place the bare cell in the outer package, inject the above electrolyte and package it to obtain a full battery (hereinafter also referred to as "full battery").
  • the above-mentioned positive pole piece, negative pole and electrolyte are assembled into a button battery in a button box.
  • Table 8-B Interplanar spacing and (111) included angle of crystalline pyrophosphate in the first cladding layer
  • Table 9-B The thickness of each layer of the positive electrode active material and the weight ratio of manganese and phosphorus
  • the sintering temperature range of step S4 is 650-800°C and the sintering time is 2-6 hours
  • the sintering temperature of step S6 is 400-600°C and the sintering time is 6-10 hours
  • the sintering temperature of step S8 is When the temperature is 700-800°C and the sintering time is 6-10 hours, it can achieve smaller lattice change rate, smaller Li/Mn antisite defect concentration, less dissolution of manganese and iron elements, better 3C charging constant current ratio, larger battery capacity, better battery cycle performance, and better high temperature storage stability.
  • Example II-1 (the sintering temperature of step S4 is 750°C and the sintering time is 4h) achieves Better positive electrode active material performance and battery performance are obtained, which indicates that when the sintering temperature in step S4 is 750° C. or greater than 750° C., it is necessary to control the sintering time to be less than 4.5 hours.
  • the positive electrode active material and battery preparation of the examples in the following table are similar to Example 1-B, and for the differences in the preparation of the positive electrode active material, please refer to the method parameters in the following table. See also the table below for the results.
  • Table 11-B Influence of reaction temperature and reaction time on the performance of positive electrode active materials in core preparation
  • the inner core is Li 1+x C m Mn 1-y A y P 1-z R z O 4-n D n as detailed below, and the shell includes the first cladding layer comprising crystalline pyrophosphate and metal oxide Q' e O f , the preparation and performance test of the positive electrode active material containing carbon in the second coating layer:
  • Step S1 Preparation of doped manganese oxalate
  • Each parameter is the same as the preparation of the doped manganese oxalate of embodiment 1.
  • Step S2 Preparation of an inner core comprising Li 0.994 Mo 0.001 Mn 0.65 Fe 0.35 P 0.999 Si 0.001 O 3.999 F 0.001
  • Step S3 Preparation of lithium iron pyrophosphate powder
  • Step S4 Prepare a suspension comprising aluminum oxide and sucrose
  • Step S5 Preparation of two coating layers
  • the positive electrode active materials of Examples 1C-2 to 1C-59 and Comparative Examples 1C to 12C were prepared in a method similar to that of Example 1C-1, and the differences in the preparation of the positive electrode active materials are shown in Tables 1C to 4C.
  • Comparative Examples 1C to 9C do not involve Steps S3-S5; Comparative Example 10C does not involve Step S4; Comparative Example 11C does not involve Step S3.
  • Table 1C Preparation of doped manganese oxalate and preparation of inner cores (steps S1-S2)

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Abstract

正极活性材料、正极极片、二次电池(5)、电池模块(4)、电池包(1)和用电装置。正极活性材料具有内核(11)及包覆内核(11)的壳，内核(11)包括三元材料、dLi 2MnO 3·(1-d)LiMO 2以及LiMPO 4中的至少一种，0＜d＜1，M包括选自Fe、Ni、Co、Mn中的一种或多种，壳含有结晶态无机物，结晶态无机物使用X射线衍射测量的主峰的半高全宽为0-3°，结晶态无机物包括选自金属氧化物以及无机盐中的一种或多种。

Description

正极活性材料、正极极片、二次电池、电池模块、电池包和用电装置 技术领域
本申请涉及锂电池技术领域，尤其涉及一种正极活性材料、以及包含其的正极极片、二次电池、电池模块、电池包和用电装置。
背景技术
近年来，随着二次电池的应用范围越来越广泛，二次电池广泛应用于水力、火力、风力和太阳能电站等储能电源系统，以及电动工具、电动自行车、电动摩托车、电动汽车、军事装备、航空航天等多个领域。由于二次电池取得了极大的发展，因此对其能量密度、循环性能和安全性能等也提出了更高的要求。作为二次电池现有的正极活性材料，磷酸锰锂等具有活泼过渡金属掺杂元素的材料的性能还有待提升。
因此，目前的正极活性材料、以及包含其的正极极片、二次电池、电池模块、电池包和用电装置仍有待改进。
发明内容
本申请是鉴于上述课题而进行的，其目的在于，提供一种磷酸锰锂正极活性材料，使得应用所述正极活性材料的二次电池具有较高的克容量、良好的循环性能和安全性能。
为了达到上述目的，本申请提供了一种磷酸锰锂正极活性材料及其制备方法，以及相关的正极极片、二次电池、电池模块、电池包和用电装置。
为了达到上述目的，本申请的第一方面提供了一种具有核-壳结构的正极活性材料，包括内核及包覆所述内核的壳，其中，所述内核的化学式为Li mA xMn 1-yB yP 1-zC zO 4-nD n，所述A包括选自Zn、Al、Na、K、Mg、Nb、Mo和W中的一种或多种元素，所述B包括选自Ti、V、Zr、Fe、Ni、Mg、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素，所述C包括选自B(硼)、S、Si和N中的一种或多种元素，所述D包括选自S、F、Cl和Br中的一种或多种元素，所述m选自0.9至1.1的范围，所述x选自0.001至0.1的范围，所述y选自0.001至0.5的范围，所述z选自0.001至0.1的范围，所述n选自0.001至0.1的范围，并且所述内核为电中性的；所述壳包括包覆所述内核的第一包覆层、包覆所述第一包覆层的第二包覆层以及包覆所述第二包覆层的第三包覆层，其中，所述第一包覆层包括晶态焦磷酸盐Li aMP 2O 7和/或M b(P 2O 7) c，0≤a≤2，1≤b≤4，1≤c≤6，所述a、b和c的值满足以下条件：使晶态焦磷酸盐Li aMP 2O 7或M b(P 2O 7) c保持电中性，所述晶态焦磷酸盐Li aMP 2O 7 和M b(P 2O 7) c中的M各自独立地为选自Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb和Al中的一种或多种元素，所述第二包覆层包括晶态磷酸盐XPO 4，所述X为选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb和Al中的一种或多种元素；所述第三包覆层为碳。
本申请的另一方面，提供了一种具有核-壳结构的正极活性材料，包括内核及包覆所述内核的壳，其中，所述内核的化学式为Li aA xMn 1-yB yP 1-zC zO 4-nD n，所述A包括选自Zn、Al、Na、K、Mg、Nb、Mo和W中的一种或多种元素，所述B包括选自Ti、V、Zr、Fe、Ni、Mg、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素，所述C包括选自B(硼)、S、Si和N中的一种或多种元素，所述D包括选自S、F、Cl和Br中的一种或多种元素，所述a选自0.9至1.1的范围，所述x选自0.001至0.1的范围，所述y选自0.001至0.5的范围，所述z选自0.001至0.1的范围，所述n选自0.001至0.1的范围，并且所述内核为电中性的；所述壳包括包覆所述内核的第一包覆层以及包覆所述第一包覆层的第二包覆层，其中，所述第一包覆层包括焦磷酸盐MP2O7和磷酸盐XPO 4，所述M和X各自独立地选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb和Al中的一种或多种；所述第二包覆层包含碳。
在本申请的又一方面，提出了一种具有核-壳结构的正极活性材料，其包括内核及包覆所述内核的壳，所述内核包含Li 1+xMn 1-yA yP 1-zR zO 4，其中，所述x为-0.100～0.100范围内的任意数值，所述y为0.001～0.500范围内的任意数值，所述z为0.001～0.100范围内的任意数值，所述A为选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素、可选地为选自Zn、Fe、Ti、V、Ni、Co和Mg中的一种或多种元素，所述R为选自B、Si、N和S中的一种或多种元素；所述壳包括包覆所述内核的第一包覆层以及包覆所述第一包覆层的第二包覆层；其中，所述第一包覆层包含晶态焦磷酸盐M aP 2O 7和晶态氧化物M′ bO c，其中，所述a大于0且小于或等于4，所述b大于0且小于或等于2，所述c大于0且小于或等于5，所述M为选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb和Al中的一种或多种元素、可选地为选自Li、Fe和Zr中的一种或多种元素，所述M′为选自碱金属、碱土金属、过渡金属、第IIIA族元素、第IVA族元素、镧系元素和Sb中的一种或多种元素、可选地为选自Li、Be、B、Na、Mg、Al、Si、P、K、Ca、Sc、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Ga、Ge、As、Se、Sr、Y、Zr、Nb、Mo、Tc、Ru、Rh、Pd、Ag、Cd、In、Sn、Sb、Te、W、La和Ce中的一种或多种元素、更可选地为选自Mg、Al、Si、Zn、Zr和Sn中的一种或多种元素；所述第二包覆层包含碳。
在本申请的又一方面，提供了一种具有核-壳结构的正极活性材料，其包括内核及包覆所述内核的壳，所述内核包含Li 1+xMn 1-yA yP 1-zR zO 4，其中，所述x为-0.100-0.100范围内的任意数值，所述y为0.001-0.600范围内的任意数值，所述z为0.001-0.100范围内的任意数值，所述A为选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素、可选地为选自Fe、V、Ni、Co和Mg中一种或多种元素，所述R为选自B、Si、N和S中的一种或多种元素、可选地为选自Si、N和S中的一种或多种元素；所述壳包括包覆所述内核的第一包覆层、包覆所述第一包覆层的第二包覆层以及包覆所述第二包覆层的第三包覆层，其中，所述第一包覆层包含晶态焦磷酸盐Li aMP 2O 7和/或M b(P 2O 7) c，其中，所述a大于0且小于或等于2，所述b为1-4范围内的任意数值，所述c为1-3范围内的任意数值，所述晶态焦磷酸盐Li aMP 2O 7和M b(P 2O 7) c中的M各自独立地为选自Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb和Al中的一种或多种元素、可选地为选自Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr和Al中的一种或多种元素；所述第二包覆层包含晶态氧化物M′ dO e，其中，所述d大于0且小于或等于2，所述e大于0且小于或等于5，所述M′为选自碱金属、碱土金属、过渡金属、第IIIA族元素、第IVA族元素、镧系元素和Sb中的一种或多种元素，可选地为选自Li、Be、B、Na、Mg、Al、Si、P、S、K、Ca、Sc、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Ga、Ge、As、Se、Sr、Y、Zr、Nb、Mo、Tc、Ru、Rh、Pd、Ag、Cd、In、Sn、Sb、Te、W、La和Ce中的一种或多种元素，更可选地为选自Mg、Al、Si、Ti、V、Ni、Cu、Zr和W中的一种或多种元素；所述第三包覆层包含碳。
在本申请的又一方面，提供了一种具有核-壳结构的正极活性材料，其包括内核及包覆所述内核的壳，所述内核包含Li mA xMn 1-yB yP 1-zC zO 4-nD n，其中，所述m选自0.5-1.2范围内的任意数值、可选地为选自0.9-1.1范围内的任意数值，所述x选自0.001-0.5范围内的任意数值、可选地为选自0.001-0.1范围内的任意数值，所述y选自0.001-0.5范围内的任意数值，所述z选自0.001-0.2范围内的任意数值、可选地为选自0.001-0.1范围内的任意数值，所述n选自0.001-0.5范围内的任意数值、可选地为选自0.001-0.1范围内的任意数值，所述A为选自Zn、Al、Na、K、Mg、Nb、Mo和W中的一种或多种元素、可选地为选自Al、Mg、Nb、Mo和W中的一种或多种元素，所述B为选自Ti、V、Zr、Fe、Ni、Mg、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素、可选地为选自Ti、V、Fe、Ni、Mg和Co中的一种或多种元素，所述C为选自B、S、Si和N中的一种或多种元素、可选地为选自S、Si和N中的一种或多种元素，所述D为选自S、F、Cl和Br中的一种或多种元素、可选地为选自F、Cl和Br中的一种或多种元素；所述壳包括包覆所述内核的第一 包覆层以及包覆所述第一包覆层的第二包覆层；其中，所述第一包覆层包含晶态焦磷酸盐M aP 2O 7和氧化物M′ bO c，其中，所述a大于0且小于或等于4、可选地为大于0且小于或等于3，所述b大于0且小于或等于2，所述c大于0且小于或等于5，所述M为选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb和Al中的一种或多种元素、可选地为选自Li和Fe中的一种或多种元素，所述M′为选自碱金属、碱土金属、过渡金属、第IIIA族元素、第IVA族元素、镧系元素和Sb中的一种或多种元素、可选地为选自Li、Be、B、Na、Mg、Al、Si、P、K、Ca、Sc、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Ga、Ge、As、Se、Sr、Y、Zr、Nb、Mo、Tc、Ru、Rh、Pd、Ag、Cd、In、Sn、Sb、Te、W、La和Ce中的一种或多种元素、更可选地为选自Mg、Al、V、Cu、Zn、Zr和W中的一种或多种元素；所述第二包覆层包含碳。
在本申请的又一方面，提出了一种具有核-壳结构的正极活性材料，其包括内核及包覆所述内核的壳，所述内核包含Li mA xMn 1-yB yP 1-zC zO 4-nD n，其中，所述m选自0.9-1.1范围内的任意数值，所述x选自0.001-0.1范围内的任意数值，所述y选自0.001-0.6范围内的任意数值、可选地为选自0.001-0.5范围内的任意数值，所述z选自0.001-0.1范围内的任意数值，所述n选自0.001-0.1范围内的任意数值，所述A为选自Zn、Al、Na、K、Mg、Nb、Mo和W中的一种或多种元素、可选地为选自Al、Mg、Nb、Mo和W中的一种或多种元素，所述B为选自Ti、V、Zr、Fe、Ni、Mg、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素、可选地为选自Ti、V、Fe、Ni、Mg和Co中的一种或多种元素，所述C为选自B、S、Si和N中的一种或多种元素、可选地为选自S、Si和N中的一种或多种元素，所述D为选自S、F、Cl和Br中的一种或多种元素、可选地为选自F、Cl和Br中的一种或多种元素；所述壳包括包覆所述内核的第一包覆层、包覆所述第一包覆层的第二包覆层以及包覆所述第二包覆层的第三包覆层，其中，所述第一包覆层包含晶态焦磷酸盐Li aMP 2O 7和/或M b(P 2O 7) c，其中，所述a大于0且小于或等于2，所述b为1-4范围内的任意数值，所述c为1-3范围内的任意数值，所述晶态焦磷酸盐Li aMP 2O 7和M b(P 2O 7) c中的M各自独立地为选自Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb和Al中的一种或多种元素，可选地为选自Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr和Al中的一种或多种元素；所述第二包覆层包含氧化物M′ dO e，其中，所述d大于0且小于或等于2，所述e大于0且小于或等于5，所述M′为选自碱金属、碱土金属、过渡金属、第IIIA族元素、第IVA族元素、镧系元素和Sb中的一种或多种元素，可选地为选自Li、Be、B、Na、Mg、Al、Si、P、S、K、Ca、Sc、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Ga、Ge、As、Se、Sr、Y、Zr、Nb、Mo、Tc、Ru、Rh、Pd、Ag、Cd、In、Sn、Sb、Te、W、La和Ce中的一种 或多种元素，更可选地为选自Mg、Al、Ca、Ti、V、Co、Ni、Cu、Zn和Zr中的一种或多种元素；所述第三包覆层包含碳。
在本申请的又一方面，提供了一种正极活性材料，其具有化学式Li aA xMn 1-yB yP 1-zC zO 4-nD n，其中，所述A包括选自Zn、Al、Na、K、Mg、Nb、Mo和W中的一种或多种元素，所述B包括选自Ti、V、Zr、Fe、Ni、Mg、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素，所述C包括选自B(硼)、S、Si和N中的一种或多种元素，所述D包括选自S、F、Cl和Br中的一种或多种元素，所述a选自0.9至1.1的范围，所述x选自0.001至0.1的范围，所述y选自0.001至0.5的范围，所述z选自0.001至0.1的范围，所述n选自0.001至0.1的范围，并且所述正极活性材料为电中性的。
在本申请的又一方面，提供了一种具有核-壳结构的正极活性材料，其包括内核及包覆所述内核的壳，所述内核的化学式为Li 1+xMn 1-yA yP 1-zR zO 4，其中x为在-0.100-0.100范围内的任意数值，y为在0.001-0.500范围内的任意数值，z为在0.001-0.100范围内的任意数值，所述A为选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素，可选为Fe、Ti、V、Ni、Co和Mg中一种或多种元素，所述R为选自B、Si、N和S中的一种或多种元素，可选地，所述R为选自B、Si、N和S中的一种元素；所述x、y和z的值满足以下条件：使整个内核保持电中性；所述壳包括包覆所述内核的第一包覆层、包覆所述第一包覆层的第二包覆层以及包覆所述第二包覆层的第三包覆层，其中，所述第一包覆层包括晶态焦磷酸盐Li aMP 2O 7和/或M b(P 2O 7) c，其中，0≤a≤2，1≤b≤4，1≤c≤6，所述a、b和c的值满足以下条件：使晶态焦磷酸盐Li aMP 2O 7或M b(P 2O 7) c保持电中性，所述晶态焦磷酸盐Li aMP 2O 7和M b(P 2O 7) c中的M各自独立地为选自Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb或Al中的一种或多种元素，所述第二包覆层包括晶态磷酸盐XPO4，其中，所述X为选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb或Al中的一种或多种元素；所述第三包覆层为碳。
在本申请的又一方面，提供了一种具有核-壳结构的正极活性材料，其包括内核及包覆所述内核的壳，所述内核包括Li 1+xMn 1-yA yP 1-zR zO 4，其中x＝-0.100～0.100，y＝0.001～0.500，z＝0.001～0.100，所述A选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种，可选为Fe、Ti、V、Ni、Co和Mg中的一种或多种，所述R选自B、Si、N和S中的一种或多种；所述壳包括包覆所述内核的第一包覆层以及包覆所述第一包覆层的第二包覆层，其中，所述第一包覆层包括焦磷酸盐MP 2O 7和磷酸盐XPO 4，其中所述M和X各自独立地 选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb或Al中的一种或多种；所述第二包覆层包含碳。
在本申请的另一方面，提出了所述提供内核材料方法，该方法包括以下步骤：步骤(1)：将锰源、元素B的源和酸在溶剂中溶解并搅拌，生成掺杂元素B的锰盐的悬浊液，将悬浊液过滤并烘干滤饼，得到掺杂了元素B的锰盐；步骤(2)：将锂源、磷源、元素A的源、元素C的源和元素D的源、溶剂和由步骤(1)获得的掺杂了元素B的锰盐加入反应容器中研磨并混合，得到浆料；步骤(3)：将由步骤(2)获得的浆料转移到喷雾干燥设备中进行喷雾干燥造粒，得到颗粒；步骤(4)：将由步骤(3)获得的颗粒进行烧结，得到内核Li mA xMn 1-yB yP 1-zC zO 4-nD n。在本申请的任意实施方式中，元素A的源选自元素A的单质、氧化物、磷酸盐、草酸盐、碳酸盐和硫酸盐中的至少一种，元素B的源选自元素B的单质、氧化物、磷酸盐、草酸盐、碳酸盐和硫酸盐中的至少一种，元素C的源选自元素C的硫酸盐、硼酸盐、硝酸盐和硅酸盐中的至少一种，元素D的源选自元素D的单质和铵盐中的至少一种。通过选择各掺杂元素的源，能够提高掺杂元素分布的均匀性，从而改善正极活性材料的性能。
在本申请的另一方面，提出了一种正极活性材料，内核及包覆所述内核的壳，所述内核包括三元材料、 dLi 2MnO 3·(1-d)LiMO 2以及LiMPO 4中的至少一种，0＜d＜1，所述M包括选自Fe、Ni、Co、Mn中的一种或多种，所述壳含有结晶态无机物，所述结晶态无机物使用X射线衍射测量的主峰的半高全宽为0-3°，所述结晶态无机物包括选自金属氧化物以及无机盐中的一种或多种。
所述壳包括所述金属氧化物以及所述无机盐中的至少之一，以及碳。由此，可以改善正极活性材料的导电性以及循环性能和倍率性能。
所述内核包括LiMPO 4且M包括Mn和非Mn元素，所述非Mn元素满足以下条件的至少之一：所述非Mn元素的离子半径为a，锰元素的离子半径为b，|a-b|/b不大于10％；所述非Mn元素的化合价变价电压为U，2V<U<5.5V；所述非Mn元素和O形成的化学键的化学活性不小于P-O键的化学活性；所述非Mn元素的最高化合价不大于6。
本申请通过以上非Mn元素的掺杂方案，可以至少实现以下效果之一：
1)减小材料的晶格变化率，以减小晶界处两相间的晶格常数差异，减小界面应力，增强Li+在界面处的传输能力，从而提升正极活性材料的倍率性能；
2)促进材料容量的发挥，提高电池容量；
3)使得键长的变化速率更快，降低材料的小极化子迁移势垒，从而提升电子电导率；
4)降低材料表面氧的活性，从而抑制Mn溶出和减少正极活性材料与电解液的界面副反应；
5)减小了材料中反位缺陷浓度，提高材料的动力学性能和克容量；
6)改变颗粒的形貌，从而提升压实密度。
本申请通过对掺杂的非Mn元素的掺杂位点以及元素种类、含量进行调控，可至少获得以下有益效果的至少之一：提升材料的正极活性材料的导电率以及容量，并在一定程度上改进甚至克服其稳定性以及循环性能差的劣势。具体地，在Mn位以及P位中的至少之一，特别是Mn位进行非Mn元素的掺杂，可以降低正极活性材料的晶格变化率，改善界面性能，降低与电解液的界面副反应并提升容量。Li位以及O位掺杂非Mn元素可辅助提升该正极活性材料的性能，例如，也可以减小晶格变化率，降低电解液和正极活性材料的界面副反应，降低反位缺陷浓度，提升抗电解液酸腐蚀性能，进而可以辅助提升材料的动力学性能和克容量，并且通过对上述非Mn掺杂元素的调控，还可改善颗粒形貌从而提升压实密度。总的来说，该正极活性材料可以相对于相关技术的可应用于高电压体系的磷酸锰锂等材料，具有显著的循环性能和/或高温稳定性的提升，以及较大的克容量和较大的压实密度。
在任意实施方式中，所述非Mn元素包括第一掺杂元素和第二掺杂元素中的一种或两种，所述第一掺杂元素为锰位掺杂，所述第二掺杂元素为磷位掺杂。第一掺杂元素和第二掺杂元素不仅可有效减少锰溶出，进而减少迁移到负极的锰离子，减少因SEI膜分解而消耗的电解液，提高二次电池的循环性能和安全性能，还能够促进Mn-O键调整，降低锂离子迁移势垒，促进锂离子迁移，提高二次电池的倍率性能。
在任意实施方式中，所述第一掺杂元素满足以下条件的至少之一：所述第一掺杂元素的离子半径为a，锰元素的离子半径为b，|a-b|/b不大于10％；所述第一掺杂元素的化合价变价电压为U，2V<U<5.5V。由此，能够进一步降低该正极活性材料的晶格变化率。
在任意实施方式中，所述第二掺杂元素满足以下条件的至少之一：所述第二掺杂元素和O形成的化学键的化学活性不小于P-O键的化学活性；所述第二掺杂元素的最高化合价不大于6。由此，可提高Mn-O键的变化速率，改善该正极活性材料的小极化子迁移势垒，提升电子电导率。另外，第二元素的掺杂还能够减小材料中的反位缺陷浓度，提高材料的动力学性能和克容量，还可以改变材料形貌，从而提升材料的压实密度。
在任意实施方式中，该正极活性材料含有至少两种所述第一掺杂元素。
在任意实施方式中，所述第一掺杂元素包括选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素。
在任意实施方式中，所述第一掺杂元素包括选自Fe、Ti、V、Ni、Co和Mg中的至少两种。由此，通过掺杂上述范围内的两种或更多种金属，因而在锰位掺杂有利于增强掺杂效果，进一步降低表面氧活性，从而抑制锰的溶出。另外，多个元素的掺杂能够增加元素 间的协同作用，例如在提高电池容量的同时，减少材料的晶格变化率，增强电池的动力学性能。优选的，第一掺杂元素包括Fe元素和三价元素，三价元素占正极活性材料的摩尔比为0.001-0.05。
在任意实施方式中，所述第二掺杂元素包括选自B(硼)、S、Si和N中的一种或多种元素。
在任意实施方式中，该正极活性材料包括Li 1+xMn 1-yA yP 1-zR zO 4，x为在-0.100-0.100范围内的任意数值，y为在0.001-0.500范围内的任意数值，z为在0.001-0.100范围内的任意数值，所述A包括选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素，所述R包括选自B(硼)、S、Si和N中的一种或多种元素。锰位掺杂的元素A选自上述元素有助于减小该材料在脱嵌锂过程中磷酸锰锂的晶格变化率，提高磷酸锰锂正极材料的结构稳定性，大大减少锰的溶出并降低颗粒表面的氧活性；在磷位掺杂的元素R选自上述元素还有助于改变Mn-O键长变化的难易程度，从而改善电子电导并降低锂离子迁移势垒，促进锂离子迁移，提高二次电池的倍率性能。如果x的值过小，会导致整个内核体系的含锂量降低，影响材料的克容量发挥。y值会限制所有掺杂元素的总量，如果y过小，即掺杂量过少，掺杂元素起不到作用，如果y超过0.5，会导致体系中的Mn含量较少，影响材料的电压平台。所述R元素掺杂在P的位置，由于P-O四面体较稳定，z值过大会影响材料的稳定性。因此，当x、y和z选自上述范围时，正极活性材料可以具有更好的性能。
在任意实施方式中，该正极活性材料包括Li 1+xC mMn 1-yA yP 1-zR zO 4-nD n，其中，所述C包括选自Zn、Al、Na、K、Mg、Nb、Mo和W中的一种或多种元素，所述A包括选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Mg、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素，所述R包括选自B(硼)、S、Si和N中的一种或多种元素，所述D包括选自S、F、Cl和Br中的一种或多种元素，x为在-0.100-0.100范围内的任意数值，y为在0.001-0.500范围内的任意数值，z为在0.001-0.100范围内的任意数值，n为在0.001至0.1范围内的任意数值，m为在0.9至1.1范围内的任意数值。通过在化合物的Li位、Mn位、P位和O位同时以特定量掺杂特定的元素，能够获得明显改善的倍率性能，同时显著减少了Mn与Mn位掺杂元素的溶出，获得了显著改善的循环性能和/或高温稳定性，并且材料的克容量和压实密度也可以得到提高。
在任意实施方式中，y与1-y的比值为1：10至1：1，可选为1：4至1：1。由此，正极活性材料的能量密度和循环性能可进一步提升。
在任意实施方式中，(1+x):m在9到1100范围内，可选地在190-998范围内。由此，正极活性材料的能量密度和循环性能可进一步提升。
在任意实施方式中，z与1-z的比值为1：9至1：999，可选为1：499至1：249。由此，进一步提升利用该正极活性材料的二次电池的循环性能和倍率性能。
在任意实施方式中，所述C、R和D各自独立地为上述各自范围内的任一种元素，并且所述A为其范围内的至少两种元素；可选地，所述C为选自Mg和Nb中的任一种元素，和/或，所述A为选自Fe、Ti、V、Co和Mg中的至少两种元素，可选地为Fe与选自Ti、V、Co和Mg中的一种以上元素，和/或，所述R为S，和/或，所述D为F。由此，能够进一步改善二次电池的倍率性能、克容量和/或高温性能。
在任意实施方式中，所述x选自0.001至0.005的范围；和/或，所述y选自0.01至0.5的范围，可选地选自0.25至0.5的范围；和/或，所述z选自0.001至0.005的范围；和/或，所述n选自0.001至0.005的范围。由此，能够进一步提升材料的克容量和倍率性能和/或动力学性能，和/或进一步提升电池的倍率性能和/或电池的高温性能。
在任意实施方式中，所述正极活性材料的晶格变化率为8％以下，可选地为4％以下，可选为3.8％以下，更可选为2.0-3.8％。由此，能够改善电芯的克容量和倍率性能。
在任意实施方式中，所述正极活性材料的Li/Mn反位缺陷浓度为4％以下，可选为2.2％以下，更可选为1.5-2.2％，更可选为2％以下，更可选地为0.5％以下。通过Li/Mn反位缺陷浓度在上述范围内，能够避免Mn 2+阻碍Li +的传输，同时提升正极活性材料的克容量和倍率性能。
在任意实施方式中，所述正极活性材料的表面氧价态为-1.89～-1.98，可选地为-1.90至-1.98，更可选地为-1.90以下，更可选地为-1.82以下。由此，能够增加高活性表面的表面能，减少高活性表面的比例。减轻正极材料与电解液的界面副反应，从而改善电芯的循环，高温存储产气等性能，进而能够改善电芯的循环性能和高温稳定性。
在任意实施方式中，所述正极活性材料在3T下的压实密度为2.0g/cm 3以上，可选地为2.2g/cm 3以上，可选地为2.2g/cm 3以上且2.8g/cm 3以下。由此，能够提高电芯的体积能量密度。
在任意实施方式中，所述结晶态无机物包括焦磷酸盐QP 2O 7和磷酸盐XPO 4，所述金属氧化物包括Q’ eO f，其中所述Q和X各自独立地选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb或Al中的一种或多种；可选地所述Q包括Li以及选自Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb或Al中的一种或多种；Q’为选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb和Al中的一种或多种元素、可选地为选自Li、Fe和Zr中的一种或多种元素，所述M′为选自碱金属、碱土金属、过渡金属、第IIIA族元素、第IVA族元素、镧系元素和Sb中的一种或多种元素、可选地为选自Li、Be、B、Na、Mg、Al、Si、P、K、Ca、Sc、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Ga、Ge、As、Se、Sr、Y、Zr、Nb、 Mo、Tc、Ru、Rh、Pd、Ag、Cd、In、Sn、Sb、Te、W、La和Ce中的一种或多种元素、更可选地为选自Mg、Al、Si、Zn、Zr和Sn中的一种或多种元素，所述e大于0且小于或等于2，所述f大于0且小于或等于5。
在任意实施方式中，所述焦磷酸盐包括Li aQP 2O 7和/或Q b(P 2O 7) c，其中，0≤a≤2，1≤b≤4，1≤c≤6，所述a、b和c的值满足以下条件：使所述Li aQP 2O 7或Q b(P 2O 7) c保持电中性，所述Li aQP 2O 7和Q b(P 2O 7) c中的Q各自独立地为选自Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb或Al中的一种或多种元素。
所述磷酸盐的晶面间距为0.244-0.425nm，可选地为0.345-0.358nm，晶向(111)的夹角为20.00°-37.00°，可选地为24.25°-26.45°；所述焦磷酸盐的晶面间距为0.293-0.470nm，可选地为0.293-0.326nm，晶向(111)的夹角为18-32.57°，可选地为18-32°，可选地为19.211°-30.846°，更可选地为26.41°-32.57°。晶态物质的晶面间距和夹角范围在上述范围内，能够有效避免包覆层中的杂质相，从而提升材料的克容量，循环性能和倍率性能，由此能够更有效地降低脱嵌锂过程中正极活性材料的晶格变化率和锰离子溶出量，从而提升电池的高温循环性能和高温存储性能。
在任意实施方式中，所述壳含有包覆碳层，所述结晶态无机物位于所述内核和所述包覆碳层之间，所述包覆碳层的碳为SP2形态碳与SP3形态碳的混合物，可选地，所述SP2形态碳与SP3形态碳的摩尔比为在0.07-13范围内的任意数值，可选地为在0.1-10范围内的任意数值，可选为在2.0-3.0范围内的任意数值。本申请通过将SP2形态碳与SP3形态碳的摩尔比限制在上述范围内，提升了二次电池的综合性能。通过使用SP2形态碳和SP3形态碳的混合形态并将SP2形态碳和SP3形态碳的比例限制在一定范围内，能够避免以下情况：如果包覆层中的碳都是无定形SP3形态，则导电性差；如果都是石墨化的SP2形态，则虽然导电性良好，但是锂离子通路少，不利于锂的脱嵌。另外，将SP2形态碳与SP3形态碳的摩尔比限制在上述范围内，既能实现良好的导电性，又能保证锂离子的通路，因此有利于二次电池功能的实现及其循环性能。
在任意实施方式中，所述壳包括包覆所述内核的第一包覆层以及包覆所述第一包覆层的第二包覆层，其中，所述第一包覆层包括焦磷酸盐QP 2O 7和磷酸盐XPO 4，所述第二包覆层为包覆碳层。
在任意实施方式中，所述第一包覆层的包覆量大于0重量％且小于等于7重量％，可选为4-5.6重量％，基于所述内核的重量计。
在任意实施方式中，所述第一包覆层中焦磷酸盐和磷酸盐的重量比为1:3至3:1，可选为1:3至1:1。
在任意实施方式中，所述第二包覆层的包覆量为大于0重量％且小于等于6重量％， 可选为3-5重量％，基于所述内核的重量计。
在任意实施方式中，所述第一包覆层的包覆量大于0重量％且小于等于7重量％，可选为4-5.6重量％，基于所述内核的重量计。当第一包覆层的包覆量在上述范围内时，能够有效发挥第一包覆层的功能，同时不会由于包覆层过厚而影响二次电池的动力学性能。
在任意实施方式中，所述第一包覆层中焦磷酸盐和磷酸盐的重量比为1:3至3:1，可选为1:3至1:1。由此，通过焦磷酸盐和磷酸盐在合适的重量比范围，既可有效阻碍锰溶出，又可有效减少表面杂锂含量，减少界面副反应，从而提高二次电池的高温存储性能、安全性能和循环性能。
在任意实施方式中，所述焦磷酸盐和磷酸盐的结晶度各自独立地为10％至100％，可选为50％至100％。由此具备上述范围的结晶度的焦磷酸盐和磷酸盐有利于充分发挥焦磷酸盐阻碍锰溶出和磷酸盐减少表面杂锂含量、减少界面副反应的功能。具备一定结晶度的焦磷酸盐和磷酸盐不但有利于充分发挥焦磷酸盐包覆层阻碍锰溶出和磷酸盐包覆层优异的导锂离子的能力、减少界面副反应的功能，而且能够使得焦磷酸盐包覆层和磷酸盐包覆层能够更好的进行晶格匹配，从而能够实现包覆层更紧密的结合。
在任意实施方式中，所述第二包覆层的包覆量为大于0重量％且小于等于6重量％，可选为3-5重量％，基于所述内核的重量计。
在任意实施方式中，所述壳包括包覆所述内核的第一包覆层以及包覆所述第一包覆层的第二包覆层，其中，所述第一包覆层包括晶态的焦磷酸盐QP 2O 7和金属氧化物Q’ eO f，所述第二包覆层为包覆碳层。
在任意实施方式中，所述第一包覆层的包覆量大于0重量％且小于或等于7重量％，可选为4-5.6重量％，基于所述内核的重量计。
在任意实施方式中，所述第一包覆层中焦磷酸盐和氧化物的重量比为1:3至3:1，可选为1:3至1:1。
在任意实施方式中，所述第二包覆层的包覆量为大于0重量％且小于或等于6重量％，可选为3-5重量％，基于所述内核的重量计。
在任意实施方式中，所述壳包括包覆所述内核的第一包覆层、包覆所述第一包覆层的第二包覆层和包覆所述第二包覆层的第三包覆层，所述第一包覆层包含晶态焦磷酸盐，所述第二包覆层包含金属氧化物Q’ eO f，所述晶态焦磷酸盐包括Li aQP 2O 7和/或Q b(P 2O 7) c，其中，所述a大于0且小于或等于2，所述b为1-4范围内的任意数值，所述c为1-3范围内的任意数值；所述第三包覆层包含碳。
在任意实施方式中，所述第一包覆层的包覆量为大于0且小于或等于6重量％，可选为大于0且小于或等于5.5重量％，更可选为大于0且小于或等于2重量％，基于所述内核 的重量计；和/或所述第二包覆层的包覆量为大于0且小于或等于6重量％，可选为大于0且小于或等于5.5重量％，更可选为2重量％-4重量％，基于所述内核的重量计；和/或所述第三包覆层的包覆量为大于0且小于或等于6重量％，可选为大于0且小于或等于5.5重量％，更可选为大于0且小于或等于2重量％，基于所述内核的重量计。
在任意实施方式中，其中，所述第一包覆层的厚度为2-10nm；和/或所述第二包覆层的厚度为3-15nm；和/或所述第三包覆层的厚度为5-25nm。
在任意实施方式中，基于正极活性材料的重量计，锰元素含量在10重量％-35重量％范围内，可选在15重量％-30重量％范围内，更可选在17重量％-20重量％范围内，磷元素的含量在12重量％-25重量％范围内，可选在15重量％-20重量％范围内；可选地，锰元素和磷元素的重量比在0.90-1.25范围内，更可选为0.95-1.20范围内。锰元素的含量在上述范围内，能够有效避免若锰元素含量过大可能会引起的材料结构稳定性变差、密度下降等问题，从而提升二次电池的循环、存储和压实密度等性能；且能够避免若锰元含量过小可能会导致的电压平台低等问题，从而提升二次电池的能量密度。
在任意实施方式中，所述正极活性材料包括包覆所述内核的第一包覆层、包覆所述第一包覆层的第二包覆层以及包覆所述第二包覆层的第三包覆层，其中，所述第一包覆层包括晶态焦磷酸盐Li aQP 2O 7和/或Q b(P 2O 7) c，所述第二包覆层包括晶态磷酸盐XPO 4，所述第三包覆层为碳。
在任意实施方式中，所述第一包覆层的包覆量为大于0且小于或等于6重量％，可选为大于0且小于或等于5.5重量％，更可选为大于0且小于或等于2重量％，基于所述内核的重量计；和/或所述第二包覆层的包覆量为大于0且小于或等于6重量％，可选为大于0且小于或等于5.5重量％，更可选为2-4重量％，基于所述内核的重量计；和/或所述第三包覆层的包覆量为大于0且小于或等于6重量％，可选为大于0且小于或等于5.5重量％，更可选为大于0且小于或等于2重量％，基于所述内核的重量计。
在任意实施方式中，所述第一包覆层的厚度为1-10nm；和/或所述第二包覆层的厚度为2-15nm；和/或所述第三包覆层的厚度为2-25nm。
在任意实施方式中，其中，基于正极活性材料的重量计，锰元素含量在10重量％-35重量％范围内，可选在15重量％-30重量％范围内，更可选在17重量％-20重量％范围内，磷元素的含量在12重量％-25重量％范围内，可选在15重量％-20重量％范围内，锰元素和磷元素的重量比范围为0.90-1.25，可选为0.95-1.20。
在本申请的另一方面，提出了一种制备正极活性材料的方法。其包括形成内核，以及在所述内核的至少表面形成壳的步骤，所述内核包括三元材料、 dLi 2MnO 3·(1-d)LiMO 2以及LiMPO 4中的至少一种，0＜d＜1，所述M包括选自Fe、Ni、Co、Mn中的一种或多种， 所述壳含有结晶态无机物，所述结晶态无机物使用X射线衍射测量的主峰的半高全宽为0-3°，所述结晶态无机物包括选自金属氧化物以及无机盐中的一种或多种。
在任意实施方式中，所述非Mn元素包括第一和第二掺杂元素，所述方法包括：将锰源、所述锰位元素的掺杂剂和酸混合，得到具有所述第一掺杂元素的锰盐颗粒；将所述具有第一掺杂元素的锰盐颗粒与锂源、磷源和所述第二掺杂元素的掺杂剂在溶剂中混合并得到浆料，在惰性气体气氛保护下烧结后得到具有所述掺杂元素M的所述磷酸锰锂化合物。
在任意实施方式中，元素C的源选自元素C的单质、氧化物、磷酸盐、草酸盐、碳酸盐和硫酸盐中的至少一种，元素A的源选自元素A的单质、氧化物、磷酸盐、草酸盐、碳酸盐、硫酸盐氯化盐、硝酸盐、有机酸盐、氢氧化物、卤化物中的至少一种，元素R的源选自元素R的硫酸盐、硼酸盐、硝酸盐和硅酸盐、有机酸、卤化物、有机酸盐、氧化物、氢氧化物中的至少一种，元素D的源选自元素D的单质和铵盐中的至少一种。
在任意实施方式中，得到具有第一掺杂元素的锰盐颗粒满足以下条件的至少之一：在20-120℃、可选为40-120℃、可选地为60-120℃、更可选地为25-80℃的温度下将锰源、所述锰位元素和酸混合；和/或所述混合在搅拌下进行，所述搅拌在200-800rpm下，可选地400-700rpm下，更可选地500-700rpm进行1-9h，可选地为3-7h，更可选地为可选地为2-6h。
在任意实施方式中，将所述具有第一掺杂元素的锰盐颗粒与锂源、磷源和所述第二掺杂元素的掺杂剂在溶剂中混合是在20-120℃、可选为40-120℃的温度下进行1-10h。制备获得的内核以及由其制得的正极活性材料结晶度更高，晶格缺陷较少，有利于抑制锰溶出，减少正极活性材料与电解液的界面副反应，从而改善二次电池的循环性能和安全性能。
在任意实施方式中，按照化学式Li 1+xC xMn 1-yA yP 1-zR zO 4-nD n形成LiMPO 4，将所述具有第一掺杂元素的锰盐颗粒与锂源、磷源和所述第二掺杂元素的掺杂剂在溶剂中研磨并混合进行8-15小时。
在任意实施方式中，所述壳包括包覆所述内核的第一包覆层和包覆所述第一包覆层的第二包覆层，所述第一包覆层含有所述焦磷酸盐QP 2O 7和所述磷酸盐XPO 4，所述第二包覆层包含碳，所述方法包括：提供QP 2O 7粉末和包含碳的源的XPO 4悬浊液，将所述内核、QP 2O 7粉末加入到包含碳的源的XPO 4悬浊液中并混合，经烧结获得正极活性材料。
在任意实施方式中，所述提供QP 2O 7粉末包括：将元素Q的源和磷的源添加到溶剂中，得到混合物，调节混合物的pH为4-6，搅拌并充分反应，然后经干燥、烧结获得，且所述提供QP 2O 7粉末满足以下条件的至少之一：所述干燥为在100-300℃、可选150-200℃下干燥4-8h；所述烧结为在500-800℃、可选650-800℃下，在惰性气体气氛下烧结4-10h。
在任意实施方式中，形成所述包覆层的烧结温度为500-800℃，烧结时间为4-10h。
在任意实施方式中，形成所述壳包括：分别提供Li aQP 2O 7和/或Q b(P 2O 7) c以及XPO 4悬浊液，将所述内核加入所述悬浊液中并混合，经烧结获得正极活性材料。
在任意实施方式中，形成所述壳包括：将元素Q的源、磷源和酸以及任选地锂源，溶于溶剂中，得到第一包覆层悬浊液；将所述内核与所述第一包覆层悬浊液混合并烧结，得到第一包覆层包覆的材料；将元素X的源、磷源和酸溶于溶剂中，得到第二包覆层悬浊液；将所述第一包覆层包覆的材料与所述第二包覆层悬浊液混合并烧结，得到两层包覆层包覆的材料；将碳源溶于溶剂中溶解得到第三包覆层溶液；将所述两层包覆层包覆的材料加入所述第三包覆层溶液中，混合干燥并烧结得到所述正极活性材料。
在任意实施方式中，形成所述第一包覆层包覆的材料时，控制溶解有元素Q的源、磷源和酸以及任选地锂源的溶液pH为3.5-6.5，搅拌并反应1-5h，将所述溶液升温至50-120℃并保持2-10h，和/或，所述烧结在650-800℃下进行2-6小时。
在任意实施方式中，形成所述两层包覆层包覆的材料时，将元素X的源、磷源和酸溶于溶剂后，搅拌并反应1-10h，将所述溶液升温至60-150℃并保持2-10h，和/或，烧结在500-700℃下进行6-10小时。
在任意实施方式中，形成所述第三包覆步骤中的烧结在700-800℃下进行6-10小时。
在任意实施方式中，所述壳包括包覆所述内核的第一包覆层、包覆所述第一包覆层的第二包覆层，其中，所述第一包覆层包括晶态焦磷酸盐QP 2O 7和所述金属氧化物Q’ eO f，所述第二包覆层包括碳，形成所述壳包括：提供包含晶态焦磷酸盐QP 2O 7的粉末和包含碳源及氧化物Q’ eO f的悬浊液，将所述内核、包含晶态焦磷酸盐QP 2O 7的粉末和包含碳源及氧化物Q’ eO f的悬浊液混合，烧结，获得正极活性材料。
在任意实施方式中，所述壳包括包覆所述内核的第一包覆层、包覆所述第一包覆层的第二包覆层，以及包覆所述第二包覆层的第三包覆层，其中，所述第一包覆层包括晶态焦磷酸盐QP 2O 7，所述第二包覆层包括所述金属氧化物Q’ eO f，所述第三包覆层包括碳，形成所述壳包括：提供包含焦磷酸盐Li aQP 2O 7和/或Q b(P 2O 7) c的第一混合物，将内核材料与第一混合物混合，干燥，烧结，得到第一包覆层包覆的材料；提供包含所述金属氧化物Q’ eO f的第二混合物，将所述第一包覆层包覆的材料与第二混合物混合，干燥，烧结，得到第二包覆层包覆的材料；提供包含碳源的第三混合物，将所述第二包覆层包覆的材料与第三混合物混合，干燥，烧结，得到所述正极活性材料。
在任意实施方式中，形成所述第一包覆层时将元素Q的源、磷源、酸、任选的锂源和任选的溶剂混合得到所述第一混合物；和/或，形成所述第二包覆层时将元素Q′的源与溶剂混合得到第二混合物；和/或，形成所述第三包覆层时将碳源与溶剂混合得到第三混合物；可选地，形成所述第一包覆层时，所述元素Q的源、磷源、酸、任选的锂源和任选的溶剂 在室温下混合1-5h，再升温至50℃-120℃并保持该温度混合2-10h，上述混合均在pH为3.5-6.5条件下进行；可选地，形成所述第二包覆层时，所述元素Q′的源与溶剂在室温下混合1-10h，再升温至60℃-150℃并保持该温度混合2-10h。
在任意实施方式中，所述第一包覆步骤中，所述烧结在650-800℃下进行2-8小时；和/或，所述第二包覆步骤中，所述烧结在400-750℃下进行6-10小时；和/或，所述第三包覆步骤中，所述烧结在600-850℃下进行6-10小时。
在任意实施方式中，所述壳包括包覆所述内核的第一包覆层、包覆所述第一包覆层的第二包覆层，其中，所述第一包覆层包括晶态焦磷酸盐QP 2O 7和所述金属氧化物Q’ eO f，所述第二包覆层包括碳，形成所述壳包括：提供包含晶态焦磷酸盐QP 2O 7的粉末和包含碳源及氧化物Q’ eO f的悬浊液，将所述内核、包含晶态焦磷酸盐QP 2O 7的粉末和包含碳源及氧化物Q’ eO f的悬浊液混合，烧结，获得正极活性材料。
在任意实施方式中，所述壳包括包覆所述内核的第一包覆层、包覆所述第一包覆层的第二包覆层，以及包覆所述第二包覆层的第三包覆层，其中，所述第一包覆层包括晶态焦磷酸盐QP 2O 7，所述第二包覆层包括所述金属氧化物Q’ eO f，所述第三包覆层包括碳，形成所述壳包括：提供包含焦磷酸盐Li aQP 2O 7和/或Q b(P 2O 7) c的第一混合物，将内核材料与第一混合物混合，干燥，烧结，得到第一包覆层包覆的材料；提供包含所述金属氧化物Q’ eO f的第二混合物，将所述第一包覆层包覆的材料与第二混合物混合，干燥，烧结，得到第二包覆层包覆的材料；提供包含碳源的第三混合物，将所述第二包覆层包覆的材料与第三混合物混合，干燥，烧结，得到所述正极活性材料。
在任意实施方式中，形成所述第一包覆层时将元素Q的源、磷源、酸、任选的锂源和任选的溶剂混合得到所述第一混合物；和/或，形成所述第二包覆层时将元素Q′的源与溶剂混合得到第二混合物；和/或，形成所述第三包覆层时将碳源与溶剂混合得到第三混合物；可选地，形成所述第一包覆层时，所述元素Q的源、磷源、酸、任选的锂源和任选的溶剂在室温下混合1-5h，再升温至50℃-120℃并保持该温度混合2-10h，上述混合均在pH为3.5-6.5条件下进行；可选地，形成所述第二包覆层时，所述元素Q′的源与溶剂在室温下混合1-10h，再升温至60℃-150℃并保持该温度混合2-10h。
在任意实施方式中，所述第一包覆步骤中，所述烧结在650-800℃下进行2-8小时；和/或，所述第二包覆步骤中，所述烧结在400-750℃下进行6-10小时；和/或，所述第三包覆步骤中，所述烧结在600-850℃下进行6-10小时。
由此，通过控制掺杂时的反应温度、搅拌速率和混合时间，能够使掺杂元素均匀分布，并且烧结后材料的结晶度更高，从而可提升材料的克容量和倍率性能等。
在本申请的又一方面，本申请提出了一种二次电池，其中，包括前面所述的正极活性 材料或通过前面所述的方法制备的正极活性材料或前面所述的正极极片。
在本申请的又一方面，本申请提出了一种电池模块，其中，包括前面所述的二次电池。
在本申请的又一方面，本申请提出了一种电池包，其中，包括前面所述的电池模块。
在本申请的又一方面，本申请提出了一种用电装置，其中，包括选自前面所述的二次电池、电池模块或电池包中的至少一种。
附图说明
图1为未掺杂的LiMnPO4和实施例2制备的正极活性材料的X射线衍射图谱(XRD)图。
图2为实施例2制备的正极活性材料的X射线能量色散谱(EDS)图。
图3为本申请所述的具有核-壳结构的正极活性材料的示意图。
图4为本申请一实施方式的具有核壳结构的正极活性材料的示意图。
图5是本申请一实施方式的二次电池的示意图。
图6是图5所示的本申请一实施方式的二次电池的分解图。
图7是本申请一实施方式的电池模块的示意图。
图8是本申请一实施方式的电池包的示意图。
图9是8所示的本申请一实施方式的电池包的分解图。
图10是本申请一实施方式的二次电池用作电源的用电装置的示意图。
附图标记说明：
11内核；12第一包覆层；13第二包覆层；14第三包覆层；1电池包；2上箱体；3下箱体；4电池模块；5二次电池；51壳体；52电极组件；53顶盖组件
具体实施方式
下面详细描述本申请的实施例，所述实施例的示例在附图中示出，其中自始至终相同或类似的标号表示相同或类似的元件或具有相同或类似功能的元件。下面通过参考附图描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。
需要说明的是，在本申请的各个方面中所描述的特征和效果可以互相适用，在此不再赘述。
以下，适当地参照附图详细说明具体公开了本申请的正极活性材料及其制造方法、正极极片、二次电池、电池模块、电池包和用电装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人 员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。本申请中，“约”某个数值表示一个范围，表示该数值±10％的范围。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
需要说明的是，在本文中，术语“包覆层”、“包覆”是指包覆在磷酸锰锂等内核材料上的物质层，所述物质层可以完全或部分地包覆内核，使用“包覆层”只是为了便于描述，并不意图限制本发明。另外，每一层包覆层可以是完全包覆，也可以是部分包覆。同样地，术语“包覆层的厚度”是指包覆在内核上的所述物质层在内核径向上的厚度。
在本申请的一个方面，本申请提出了一种正极活性材料，其具有内核及包覆所述内 核的壳，所述内核包括三元材料、 dLi 2MnO 3·(1-d)LiMO 2以及LiMPO 4中的至少一种，0＜d＜1，所述M包括选自Fe、Ni、Co、Mn中的一种或多种，所述壳含有结晶态无机物，所述结晶态无机物使用X射线衍射测量的主峰的半高全宽为0-3°，所述结晶态无机物包括选自金属氧化物以及无机盐中的一种或多种。结晶态的物质晶格结构稳定，对Mn等容易溶出的活泼金属离子有更好的截留作用。
本申请的发明人发现，目前用于锂离子二次电池的正极活性材料为了提高电池性能，如提高容量，改善倍率性能、循环性能等考虑，常在三元正极活性材料，或是可能应用于高电压体系的LiMPO 4，如LiMnPO 4、LiNiPO 4、LiCoPO 4，或是富Li锰基正极活性材料等材料中添加掺杂元素。上述掺杂元素可替换上述材料中的活性过渡金属等位点，从而起到提升材料的电池性能的作用。另一方面，磷酸铁锂等材料中可能添加有Mn元素，但是上述活性过渡金属等元素的添加或是掺杂，容易导致该材料在深度充放电的过程中造成Mn离子等活性金属的溶出。溶出的活性金属元素一方面会进一步向电解液迁移，在负极还原后造成类似催化剂的效应，导致负极表面SEI膜(solid electrolyte interphase，固态电解质界面膜)溶解。另一方面，上述金属元素的溶出也将导致正积极活性材料容量的损失，且溶出后正极活性材料的晶格产生缺陷，导致循环性能差等问题。因此，有必要基于上述含有活性金属元素的正极材料进行改进以缓解甚至解决上述问题。发明人发现，X射线衍射测量的主峰具有上述半高全宽的晶态无机物具有较好的截留溶出活性金属离子的能力，且晶态无机物和前述的内核材料可以较好的结合，具有稳定的结合力，不容易在使用过程中发生可的剥离的问题，且可以通过较为简便的方法实现面积恰当、均匀性较好的包覆层。
具体地，以磷酸锰锂正极活性材料为例，本申请发明人在实际作业中发现，目前现有的磷酸锰锂正极活性材料在深度充放电过程中，锰离子溶出比较严重。虽然现有技术中有尝试对磷酸锰锂进行磷酸铁锂包覆，从而减少界面副反应，但这种包覆无法阻止溶出的锰离子继续向电解液中迁移。溶出的锰离子在迁移到负极后，被还原成金属锰。这样产生的金属锰相当于“催化剂”，能够催化负极表面的SEI膜(solid electrolyte interphase，固态电解质界面膜)分解，产生副产物；所述副产物的一部分为气体，因此导致会二次电池发生膨胀，影响二次电池的安全性能；另外，所述副产物的另一部分沉积在负极表面，会阻碍锂离子进出负极的通道，造成二次电池阻抗增加，从而影响二次电池的动力学性能。此外，为补充损失的SEI膜，电解液和电池内部的活性锂被不断消耗，会给二次电池容量保持率带来不可逆的影响。通过对磷酸锰锂进行改性以及对磷酸锰锂的多层包覆，能够得到一种新型的具有核-壳结构的正极活性材料，所述正极活性材料能够实现显著降低的锰离子溶出以及降低的晶格变化率，其用于二次电池中，能够改善电池的循环性能、倍率性能、安全性能并且提高电池的容量。
在本申请的一些实施方式中，内核包括LiMPO 4且M包括Mn和非Mn元素，所述非Mn元素满足以下条件的至少之一：所述非Mn元素的离子半径为a，锰元素的离子半径为b，|a-b|/b不大于10％；所述非Mn元素的化合价变价电压为U，2V<U<5.5V；所述非Mn元素和O形成的化学键的化学活性不小于P-O键的化学活性；所述非Mn元素的最高化合价不大于6。
作为锂离子二次电池的正极活性材料，磷酸锰锂、磷酸铁锂或是磷酸镍锂等未来可应用于高电压体系的化合物具有较低的成本以及较好的应用前景。但以磷酸锰锂为例，其与其他正极活性材料相比的缺点在于倍率性能较差，目前通常是通过包覆或掺杂等手段来解决这一问题。但仍然希望能够进一步提升磷酸锰锂正极活性材料的倍率性能、循环性能、高温稳定性等。
本申请的发明人反复研究了在磷酸锰锂的Li位、Mn位、P位和O位用各种元素进行掺杂时产生的影响，发现可以通过控制掺杂位点和具体的元素、掺杂量，改善正极活性材料的克容量、倍率性能以及循环性能等。
具体地，选择适当的Mn位掺杂元素，可改善该材料在脱嵌锂过程中磷酸锰锂的晶格变化率，提高正极材料的结构稳定性，大大减少锰的溶出，并降低颗粒表面的氧活性，进而可以提高材料的克容量，并降低该材料在使用过程中和电解液的界面副反应，进而提升材料的循环性能等。更具体地，选择离子半径和Mn元素相似的元素为Mn位掺杂元素，或是选择化合价可变价范围在Mn的化合价变价范围内的元素进行掺杂，可控制掺杂元素和O的键长与Mn-O键键长的变化量，从而有利于稳定掺杂后的正极材料晶格结构。此外，还可以在Mn位引入起到支撑晶格作用的空位元素，如该元素的化合价大于或等于Li与Mn的化合价之和，从而相当于在活泼的、容易溶出的Mn位引入了无法和Li结合的空位点，进而可以对晶格起到支撑的作用。
又例如，选择适当的P位掺杂元素，可助于改变Mn-O键长变化的难易程度，从而改善电子电导并降低锂离子迁移势垒，促进锂离子迁移，提高二次电池的倍率性能。具体地，P-O键自身的四面体结构相对稳固，使得Mn-O键长变化难度大，造成材料整体锂离子迁移势垒较高，而适当的P位掺杂元素可以改善P-O键四面体的坚固程度，从而促进材料的倍率性能改善。具体地，可以选择和O形成的化学键的化学活性不小于P-O键的化学活性的元素在P位进行掺杂，从而可以改善Mn-O键长变化的难易程度。在本申请中，如无特殊说明，“和O形成的化学键的化学活性不小于P-O键的化学活性”，可以通过本领域技术人员所公知的确定化学键活性的测试方式进行确定。例如，可以通过检测键能，或是参考用于打破该化学键的氧化、还原试剂的电化学电位等方式确定。或者，可选择化合价态不显著地高于P，例如低于6的元素在P位进行 掺杂，从而有利于降低Mn和P元素的排斥作用，也可改善材料的克容量、倍率性能等。
类似地，在Li位进行恰当的元素掺杂，也可改善材料晶格变化率，并保持材料的电池容量。
O位掺杂元素可有助于改善材料和电解液的界面副反应，降低界面活性，从而有利于提升该正极活性材料的循环性能等。此外，还可以通过在O为进行掺杂，提升材料抗HF等酸腐蚀的性能，进而有利于提升材料的循环性能和寿命。
在一些实施方式中，上述位点掺杂的非Mn元素可包括第一掺杂元素和第二掺杂元素中的一种或两种，所述第一掺杂元素为锰位掺杂，所述第二掺杂元素为磷位掺杂。第一掺杂元素满足以下条件的至少之一：第一掺杂元素的离子半径为a，锰元素的离子半径为b，|a-b|/b不大于10％；所述第一掺杂元素的化合价变价电压为U，2V<U<5.5V。第二掺杂元素满足以下条件的至少之一：所述第二掺杂元素和O形成的化学键的化学活性不小于P-O键的化学活性；所述掺杂元素M第二掺杂元素的最高化合价不大于6。在一些实施方式中，该正极活性材料还可以同时含有两种第一掺杂元素。
在一些实施方式中，可在上述位置中的Mn位以及P位同时进行掺杂。由此，不仅可有效减少锰溶出，进而减少迁移到负极的锰离子，减少因SEI膜分解而消耗的电解液，提高二次电池的循环性能和安全性能，还能够促进Mn-O键调整，降低锂离子迁移势垒，促进锂离子迁移，提高二次电池的倍率性能。
在本申请的另一些实施方式中，通过在上述四个位置同时以特定量掺杂特定的元素，能够获得明显改善的倍率性能，改善的循环性能和/或高温稳定性，由此获得了改进的磷酸锰锂正极活性材料。
本申请的正极活性材料例如可用于锂离子二次电池中。
第一掺杂元素包括选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素。第一掺杂元素包括选自Fe、Ti、V、Ni、Co和Mg中的至少两种。第二掺杂元素包括选自B(硼)、S、Si和N中的一种或多种元素。
上述掺杂元素应使得体系保持电中性，能够保证正极活性材料中的缺陷和杂相尽量少。如果正极活性材料中存在过量的过渡金属(例如锰)，由于该材料体系本身结构较稳定，那么多余的过渡金属很可能会以单质的形式析出，或在晶格内部形成杂相，保持电中性可使这样的杂相尽量少。另外，保证体系电中性还可以在部分情况下使材料中产生锂空位，从而使材料的动力学性能更优异。
下面，以磷酸锰锂材料为例，详述本申请提出的正极活性材料的具体参数，以及能够获得上述有益效果的原理：
本申请发明人在实际作业中发现，目前现有的磷酸锰锂正极活性材料在深度充放电过程中，锰溶出比较严重。发明人在进行大量研究后发现，通过对磷酸锰锂进行改性能够得到一种新型的正极活性材料，所述正极活性材料能够实现显著降低的锰溶出以及降低的晶格变化率，其用于二次电池中，能够改善电池的循环性能、倍率性能、安全性能并且提高电池的容量。例如，通过在化合物LiMnPO 4的Li位、Mn位、P位和O位同时以特定量掺杂特定的元素，能够获得改善的倍率性能，同时减少了Mn与Mn位掺杂元素的溶出，获得了改善的循环性能和/或高温稳定性，并且正极活性材料的克容量和压实密度也可以得到提高。另外，整个内核体系保持电中性，能够保证正极活性材料中的缺陷和杂相尽量少。如果正极活性材料中存在过量的过渡金属(例如锰)，由于该材料体系本身结构较稳定，那么多余的过渡金属很可能会以单质的形式析出，或在晶格内部形成杂相，保持电中性可使这样的杂相尽量少。另外，保证体系电中性还可以在部分情况下使正极活性材料中产生锂空位，从而使正极活性材料的动力学性能更优异。
在一些实施方式中，上述正极活性材料可以具有化学式为Li 1+xMn 1-yA yP 1-zR zO 4的化合物，其中x为在-0.100-0.100范围内的任意数值，y为在0.001-0.500范围内的任意数值，z为在0.001-0.100范围内的任意数值，所述A包括选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素，所述R包括选自B(硼)、S、Si和N中的一种或多种元素。其中，所述x、y和z的值满足以下条件：使整个化合物保持电中性。
在另一些实施方式中，上述正极活性材料可以具有化学式为Li 1+xC mMn 1-yA yP 1-zR zO 4-nD n的化合物，其中，所述C包括选自Zn、Al、Na、K、Mg、Nb、Mo和W中的一种或多种元素，所述A包括选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Mg、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素，所述R包括选自B(硼)、S、Si和N中的一种或多种元素，所述D包括选自S、F、Cl和Br中的一种或多种元素，x为在0.100-0.100范围内的任意数值，y为在0.001-0.500范围内的任意数值，z为在0.001-0.100范围内的任意数值，n为在0.001至0.1范围内的任意数值，m为在0.9至1.1范围内的任意数值。类似地，上述x、y、z和m的值满足以下条件：使整个化合物保持电中性。
除非另有说明，否则上述内核的化学式中，当某掺杂位点具有两种以上元素时，上述对于x、y、z或m数值范围的限定不仅是对每种作为该位点的元素的化学计量数的限定，也是对各个作为该位点的元素的化学计量数之和的限定。例如，当具有化学式为Li 1+xMn 1-yA yP 1-zR zO 4的化合物时，当A为两种以上元素A1、A2……An时，A1、A2……An各自的化学计量数y1、y2……yn各自均需落入本申请对y限定的数值范围内，且y1、 y2……yn之和也需落入该数值范围内。类似地，对于R为两种以上元素的情况，本申请中对R化学计量数的数值范围的限定也具有上述含义。
在一个可选的实施方式中，当A为选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge中的一种、两种、三种或四种元素时，A y为G n1D n2E n3K n4，其中n1+n2+n3+n4＝y，且n1、n2、n3、n4均为正数且不同时为零，G、D、E、K各自独立地为选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge的一种，可选地，G、D、E、K中至少一个为Fe。可选地，n1、n2、n3、n4之一为零，其余不为零；更可选地，n1、n2、n3、n4中的两个为零，其余不为零；还可选地，n1、n2、n3、n4中的三个为零，其余不为零。Li 1+xMn 1-yA yP 1-zR zO 4中，在锰位掺杂一种、两种、三种或四种上述A元素是有利的，可选地，掺杂一种、两种或三种上述A元素；此外，在磷位掺杂一种或两种R元素是有利的，这样有利于使掺杂元素均匀分布。
例如具体地，Mn位可同时具有Fe和V掺杂。
在一些实施方式中，在Li 1+xMn 1-yA yP 1-zR zO 4中，y与1-y的比值为1：10至1：1，可选为1：4至1：1。此处y表示Mn位掺杂元素A的化学计量数之和。在满足上述条件时，使用所述正极活性材料的二次电池的能量密度和循环性能可进一步提升。在一些实施方式中，z与1-z的比值为1：9至1：999，可选为1：499至1：249。此处z表示P位掺杂元素R的化学计量数之和。在满足上述条件时，使用所述正极活性材料的二次电池的能量密度和循环性能可进一步提升。
在本申请的另一些实施方式中，正极活性材料可含有Li 1+xC mMn 1-yA yP 1-zR zO 4-nD n。其中，x的大小受A和R的价态大小以及y和z的大小的影响，以保证整个体系呈现电中性。如果x的值过小，会导致整个内核体系的含锂量降低，影响材料的克容量发挥。y值会限制所有掺杂元素的总量，如果y过小，即掺杂量过少，掺杂元素起不到作用，如果y超过0.5，会导致体系中的Mn含量较少，影响材料的电压平台。所述R元素掺杂在P的位置，由于P-O四面体较稳定，而z值过大会影响材料的稳定性，因此将z值限定为0.001-0.100。更具体地，x为在0.100-0.100范围内的任意数值，y为在0.001-0.500范围内的任意数值，z为在0.001-0.100范围内的任意数值，n为在0.001至0.1范围内的任意数值，m为在0.9至1.1范围内的任意数值。例如，所述1+x选自0.9至1.1的范围，例如为0.97、0.977、0.984、0.988、0.99、0.991、0.992、0.993、0.994、0.995、0.996、0.997、0.998、1.01，所述x选自0.001至0.1的范围，例如为0.001、0.005，所述y选自0.001至0.5的范围，例如为0.001、0.005、0.02、0.05、0.1、0.15、0.2、0.25、0.3、0.34、0.345、0.349、0.35、0.4，所述z选自0.001至0.1的范围，例如为0.001、0.005、0.08、0.1，所述n 选自0.001至0.1的范围，例如为0.001、0.005、0.08、0.1，并且所述正极活性材料为电中性的。
如前所述，本申请的正极活性材料通过在化合物LiMnPO 4等中进行元素掺杂而获得，不希望囿于理论，现认为磷酸锰锂的性能提升与减小脱嵌锂过程中磷酸锰锂的晶格变化率和降低表面活性有关。减小晶格变化率可减小晶界处两相间的晶格常数差异，减小界面应力，增强Li +在界面处的传输能力，从而提升正极活性材料的倍率性能。而表面活性高容易导致界面副反应严重，加剧产气、电解液消耗和破坏界面，从而影响电池的循环等性能。本申请中，通过Li和Mn位掺杂减小了晶格变化率。Mn位掺杂还有效降低表面活性，从而抑制Mn溶出和正极活性材料与电解液的界面副反应。P位掺杂使Mn-O键长的变化速率更快，降低材料的小极化子迁移势垒，从而有利于电子电导率。O位掺杂对减小界面副反应有良好的作用。P位和O位的掺杂还对反位缺陷的Mn溶出及动力学性能产生影响。因此，掺杂减小了材料中反位缺陷浓度，提高材料的动力学性能和克容量，还可以改变颗粒的形貌，从而提升压实密度。本申请人意外地发现：通过在化合物LiMnPO 4的Li位、Mn位、P位和O位同时以特定量掺杂特定的元素，能够获得明显改善的倍率性能，同时显著减少了Mn与Mn位掺杂元素的溶出，获得了显著改善的循环性能和/或高温稳定性，并且材料的克容量和压实密度也可以得到提高。
通过在上述范围内对Li位掺杂元素进行选择，能够进一步减小脱锂过程中的晶格变化率，从而进一步改善电池的倍率性能。通过在上述范围内对Mn位掺杂元素进行选择，能够进一步提高电子电导率并进一步减小晶格变化率，从而提升电池的倍率性能和克容量。通过在上述范围内对P位掺杂元素进行选择，能够进一步改善电池的倍率性能。通过在上述范围内对O位掺杂元素进行选择，能够进一步减轻界面的副反应，提升电池的高温性能。
在一些实施方式中，所述x选自0.001至0.005的范围；和/或，所述y选自0.01至0.5的范围，可选地选自0.25至0.5的范围；和/或，所述z选自0.001至0.005的范围；和/或，所述n选自0.001至0.005的范围。通过在上述范围内对y值进行选择，能够进一步提升材料的克容量和倍率性能。通过在上述范围内对x值进行选择，能够进一步提升材料的动力学性能。通过在上述范围内对z值进行选择，能够进一步提升二次电池的倍率性能。通过在上述范围内对n值进行选择，能够进一步提升二次电池的高温性能。
在一些实施方式中，具有4个位点均掺杂有非Mn元素的所述正极活性材料满足：(1-y):y在1至4范围内，可选地在1.5至3范围内，且(1+x):m在9到1100范围内， 可选地在190-998范围内。此处y表示Mn位掺杂元素的化学计量数之和。在满足上述条件时，正极活性材料的能量密度和循环性能可进一步提升。
在一些实施方式中，该正极活性材料可以具有Li 1+xMn 1-yA yP 1-zR zO 4和Li 1+xC mMn 1-yA yP 1-zR zO 4-nD n中的至少之一。其中，y与1-y的比值为1：10至1：1，可选为1：4至1：1。z与1-z的比值为1：9至1：999，可选为1：499至1：249。C、R和D各自独立地为上述各自范围内的任一种元素，并且所述A为其范围内的至少两种元素；可选地，所述C为选自Mg和Nb中的任一种元素，和/或，所述A为选自Fe、Ti、V、Co和Mg中的至少两种元素，可选地为Fe与选自Ti、V、Co和Mg中的一种以上元素，和/或，所述R为S，和/或，所述D为F。其中，x选自0.001至0.005的范围；和/或，所述y选自0.01至0.5的范围，可选地选自0.25至0.5的范围；和/或，所述z选自0.001至0.005的范围；和/或，所述n选自0.001至0.005的范围。上述参数在无特殊说明的前提下，可自由进行组合，在此不再一一列举他们组合的情况。
在一些实施方式中，所述正极活性材料的晶格变化率为8％以下，可选地，晶格变化率为4％以下。通过降低晶格变化率，能够使得Li离子传输更容易，即Li离子在材料中的迁移能力更强，有利于改善二次电池的倍率性能。晶格变化率可通过本领域中已知的方法，例如X射线衍射图谱(XRD)测得。LiMnPO 4的脱嵌锂过程是两相反应。两相的界面应力由晶格变化率大小决定，晶格变化率越小，界面应力越小，Li +传输越容易。因此，减小掺杂LiMnPO 4的晶格变化率将有利于增强Li+的传输能力，从而改善二次电池的倍率性能。
在一些实施方式中，可选地，所述正极活性材料的扣电平均放电电压为3.5V以上，放电克容量在140mAh/g以上；可选为平均放电电压3.6V以上，放电克容量在145mAh/g以上。
尽管未掺杂的LiMnPO 4的平均放电电压在4.0V以上，但它的放电克容量较低，通常小于120mAh/g，因此，能量密度较低；通过掺杂调整晶格变化率，可使其放电克容量大幅提升，在平均放电电压微降的情况下，整体能量密度有明显升高。
在一些实施方式中，所述正极活性材料的Li/Mn反位缺陷浓度为2％以下，可选地，Li/Mn反位缺陷浓度为0.5％以下。所谓Li/Mn反位缺陷，指的是LiMnPO4晶格中，Li +与Mn 2+的位置发生互换。Li/Mn反位缺陷浓度指的是正极活性材料中与Mn 2+发生互换的Li +占Li +总量的百分比。反位缺陷的Mn 2+会阻碍Li +的传输，通过降低Li/Mn反位缺陷浓度，有利于提高正极活性材料的克容量和倍率性能。Li/Mn反位缺陷浓度可通过本领域中已知的方法，例如XRD测得。
在一些实施方式中，所述正极活性材料的表面氧价态为-1.82以下，可选地为 -1.89～-1.98。通过降低表面氧价态，能够减轻正极活性材料与电解液的界面副反应，从而改善二次电池的循环性能和高温稳定性。表面氧价态可通过本领域中已知的方法测量，例如通过电子能量损失谱(EELS)测量。
在一些实施方式中，所述正极活性材料在3T(吨)下的压实密度为2.0g/cm3以上，可选地为2.2g/cm3以上。压实密度越高，单位体积活性材料的重量越大，因此提高压实密度有利于提高电芯的体积能量密度。压实密度可依据GB/T 24533-2009测量。
本申请制备的内核的平均粒径范围为50-500nm，Dv50为200-300nm。内核的一次颗粒大小均在50-500nm的范围内，Dv50为200-300nm。如果所述内核平均粒径过大(超过500nm)，则使用该材料的电池的克容量发挥会受到影响；如果所述内核平均粒径过小，则其比表面积较大，容易团聚，难以实现均匀包覆。
通过工艺控制(例如，对各种源的材料进行充分混合、研磨)，能够保证各元素在晶格中均匀分布，不出现聚集的情况。本申请发明人在制备本申请所述的正极活性材料后，通过聚焦离子束(简称FIB)切取已制备好的正极活性材料颗粒的中间区域(内核区域)，通过透射电子显微镜(简称TEM)以及X射线能谱分析(简称EDS)进行测试发现，各元素分布均匀，未出现聚集。同时，本申请的正极活性材料内核与LiMnPO 4掺杂前的主要特征峰的位置基本一致，说明掺杂的磷酸锰锂正极活性材料内核没有杂质相，电池性能的改善主要来自元素掺杂，而不是杂质相导致的。
在一些实施方式中，所述正极活性材料具有核-壳结构，其中壳含有晶态无机物和金属氧化物中的至少之一。具体地，所述结晶态无机物包括焦磷酸盐QP 2O 7和磷酸盐XPO 4，所述金属氧化物包括Q’ eO f。其中所述Q和X各自独立地选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb或Al中的一种或多种；可选地所述Q包括Li以及选自Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb或Al中的一种或多种；Q’为选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb和Al中的一种或多种元素、可选地为选自Li、Fe和Zr中的一种或多种元素，所述M′为选自碱金属、碱土金属、过渡金属、第IIIA族元素、第IVA族元素、镧系元素和Sb中的一种或多种元素、可选地为选自Li、Be、B、Na、Mg、Al、Si、P、K、Ca、Sc、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Ga、Ge、As、Se、Sr、Y、Zr、Nb、Mo、Tc、Ru、Rh、Pd、Ag、Cd、In、Sn、Sb、Te、W、La和Ce中的一种或多种元素、更可选地为选自Mg、Al、Si、Zn、Zr和Sn中的一种或多种元素，所述e大于0且小于或等于2，所述f大于0且小于或等于5。
在一些实施方式中，焦磷酸盐包括Li aQP 2O 7和/或Q b(P 2O 7) c，其中，0≤a≤2，1≤b≤4，1≤c≤6，所述a、b和c的值满足以下条件：使所述Li aQP 2O 7或Q b(P 2O 7) c保持电中性，所述Li aQP 2O 7和Q b(P 2O 7) c中的Q各自独立地为选自Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、 Zr、Nb或Al中的一种或多种元素。
发明人发现，由于金属离子在焦磷酸盐中难以迁移，因此焦磷酸盐作为包覆层可以将掺杂金属离子与电解液进行有效隔离。且晶态焦磷酸盐的结构稳定，因此，晶态焦磷酸盐包覆能够有效抑制过渡金属的溶出，改善循环性能。晶态的磷酸盐和晶态焦磷酸盐的晶格匹配度较高(失配度仅为3％)，稳定性好具有优异导锂离子的能力，，用其包覆内核可提高正极活性材料的稳定性，电解液的界面副反应可得到有效降低，从而改善电池的高温循环及存储性能。类似地，氧化物也可以起到稳定活泼掺杂金属溶出的作用，且氧化物容易合成，成本较低，在一些实施方式中，氧化物和焦磷酸盐等晶态无机物的合适配比有利于充分发挥二者的协同作用，能够进一步抑制锰溶出，同时维持二次电池具备较低的阻抗。
在一些实施方式中，焦磷酸盐和磷酸盐的结晶度各自独立地为10％至100％，可选为50％至100％。发明人发现，晶态的上述无机盐可以更好地和内核结合，并提高截留溶出的Mn等活泼金属离子的能力。具体地，磷酸盐的晶面间距为0.244-0.425nm，可选地为0.345-0.358nm，晶向(111)的夹角为20.00°-37.00°，可选地为24.25°-26.45°；所述焦磷酸盐的晶面间距为0.293-0.470nm，可选地为0.293-0.326nm，晶向(111)的夹角为18-32.57°，可选地为19.211°-30.846°，更可选地为26.41°-32.57°。具备一定结晶度的焦磷酸盐和磷酸盐不但有利于充分发挥焦磷酸盐包覆层阻碍锰离子溶出和磷酸盐包覆层优异的导锂离子的能力、减少界面副反应的功能，而且能够使得焦磷酸盐包覆层和磷酸盐包覆层能够更好的进行晶格匹配，从而能够实现包覆层更紧密的结合。
在一些实施方式中，壳中所具有的包覆层中的无机盐均使用晶态物质。具体地，对于包覆层中的晶态焦磷酸盐和晶态磷酸盐，可通过本领域中常规的技术手段进行表征，也可以例如借助透射电镜(TEM)进行表征。在TEM下，通过测试晶面间距可以区分内核和包覆层。包覆层中的晶态焦磷酸盐和晶态磷酸盐的晶面间距和夹角的具体测试方法可以包括以下步骤：取一定量的经包覆的正极活性材料样品粉末于试管中，并在试管中注入溶剂如酒精，然后进行充分搅拌分散，然后用干净的一次性塑料吸管取适量上述溶液滴加在300目铜网上，此时，部分粉末将在铜网上残留，将铜网连带样品转移至TEM样品腔中进行测试，得到TEM测试原始图片；将上述TEM测试所得原始图片在衍射仪软件中打开，并进行傅里叶变换得到衍射花样，量取衍射花样中衍射光斑到中心位置的距离，即可得到晶面间距，夹角根据布拉格方程进行计算得到。
晶态焦磷酸盐的晶面间距范围和晶态磷酸盐的存在差异，可通过晶面间距的数值直接进行判断。在前述的晶面间距和夹角范围内的晶态焦磷酸盐和晶态磷酸盐，能够更有效地降低脱嵌锂过程中正极活性材料的晶格变化率和锰离子溶出量，从而提升电 池的高温循环性能和高温存储性能。
在一些实施方式中，包覆层还可含有碳。碳材料具有好的电子导电性，在二次电池中应用时发生的是电化学反应，需要有电子的参与，因此，为了增加颗粒与颗粒之间的电子传输，以及颗粒不同位置的电子传输，可以使用具有优异导电性能的碳来对正极活性材料进行包覆。因此，碳包覆可有效改善正极活性材料的导电性能和去溶剂化能力。
例如，在本申请的一些实施方式中，内包覆层的碳为SP2形态碳与SP3形态碳的混合物，可选地，所述SP2形态碳与SP3形态碳的摩尔比为在0.1-10范围内的任意数值，可选为在2.0-3.0范围内的任意数值。具体地，SP2形态碳与SP3形态碳的摩尔比可为约0.1、约0.2、约03、约0.4、约0.5、约0.6、约0.7、约0.8、约0.9、约1、约2、约3、约4、约5、约6、约7、约8、约9或约10，或在上述任意值的任意范围内。
通过选择碳包覆层中碳的形态，从而提升二次电池的综合电性能。具体来说，通过使用SP2形态碳和SP3形态碳的混合形态并将SP2形态碳和SP3形态碳的比例限制在一定范围内，能够避免以下情况：如果包覆层中的碳都是无定形SP3形态，则导电性差；如果都是石墨化的SP2形态，则虽然导电性良好，但是锂离子通路少，不利于锂的脱嵌。另外，将SP2形态碳与SP3形态碳的摩尔比限制在上述范围内，既能实现良好的导电性，又能保证锂离子的通路，因此有利于二次电池功能的实现及其循环性能。
包覆层碳的SP2形态和SP3形态的混合比可以通过烧结条件例如烧结温度和烧结时间来控制。例如，在使用蔗糖作为碳源制备第三包覆层的情况下，使蔗糖在高温下进行裂解后，在第二包覆层上沉积同时在高温作用下，会产生既有SP3形态也有SP2形态的碳包覆层。SP2形态碳和SP3形态碳的比例可以通过选择高温裂解条件和烧结条件来调控。
包覆层碳的结构和特征可通过拉曼(Raman)光谱进行测定，具体测试方法如下：通过对Raman测试的能谱进行分峰，得到Id/Ig(其中Id为SP3形态碳的峰强度，Ig为SP2形态碳的峰强度)，从而确认两者的摩尔比。
在本申请的一些实施方式中，壳包括无机包覆层以及碳包覆层，所述无机包覆层靠近所述内核设置，无机包覆层具有前述的磷酸盐以及焦磷酸盐、金属氧化物中的至少之一。例如，在本申请中，磷酸盐和焦磷酸盐是否位于同一个包覆层中，二者之中谁更靠近内核设置均不受特别限制，本领域技术人员可以根据实际情况进行选择。例如，可令磷酸盐和焦磷酸盐形成一个无机盐包覆层，无机盐包覆层的外侧可进一步具有碳层。或者焦磷酸盐 以及焦磷酸盐均单独形成独立的包覆层，二者中的一个靠近内核设置，另一个包覆靠近内核设置的晶态无机盐包覆层，最外侧再设置碳层。又或者，该核壳结构可以仅含有一个由磷酸盐或者焦磷酸盐构成的无机盐包覆层，外侧再设置碳层。
无机包覆层与核之间的结合类似于异质结，其结合的牢固程度受晶格匹配程度的限制。晶格失配在5％以下时，晶格匹配较好，两者容易结合紧密。紧密的结合能够保证在后续的循环过程中，包覆层不会脱落，有利于保证材料的长期稳定性。包覆层与核之间的结合程度的衡量主要通过计算核与包覆各晶格常数的失配度来进行。本申请中，在所述内核中掺杂了元素后，特别是Mn位以及P位掺杂元素之后，与不掺杂元素相比，所述内核与包覆层的匹配度得到改善，内核与晶态无机盐包覆层之间能够更紧密地结合在一起。
在本申请的一些实施方式中，壳包括第一包覆层、第二包覆层和第三包覆层，第一包覆层包覆内核，并包括晶态焦磷酸盐。第二包覆层包括晶态磷酸盐并包覆第一包覆层，第三包覆层为碳。焦磷酸盐作为第一包覆层可以将掺杂金属离子与电解液进行有效隔离。晶态焦磷酸盐的结构稳定，因此，晶态焦磷酸盐包覆能够有效抑制过渡金属的溶出，改善循环性能。晶态磷酸盐作为第二包覆层与第一层包覆物晶态焦磷酸盐的晶格匹配度较高(失配度仅为3％)，且稳定性好于焦磷酸盐并具有优异导锂离子的能力，有利于提高正极活性材料的稳定性，降低正极活性材料和电解液的界面副反应。第三包覆层可以提高正极活性材料的电子导电性，碳包覆还可有效改善正极活性材料的导电性能和去溶剂化能力。
在上述实施方式中，第一包覆层的包覆量为大于0且小于或等于6重量％，可选为大于0且小于或等于5.5重量％，更可选为大于0且小于或等于2重量％，基于所述内核的重量计。在一些实施方式中，所述第二包覆层的包覆量为大于0且小于或等于6重量％，可选为大于0且小于或等于5.5重量％，更可选为2-4重量％，基于所述内核的重量计。在一些实施方式中，所述第三包覆层的包覆量为大于0且小于或等于6重量％，可选为大于0且小于或等于5.5重量％，更可选为大于0且小于或等于2重量％，基于所述内核的重量计。本申请中，每一层的包覆量均不为零。
本申请所述的具有核-壳结构的正极活性材料中，三层包覆层的包覆量优选在上述范围内，由此能够对所述内核进行充分包覆，并同时在不牺牲正极活性材料克容量的前提下，进一步改善电池的动力学性能、循环性能和安全性能。
对于第一包覆层而言，通过包覆量在上述范围内，则能够有效避免以下情况：包覆量过少则意味着包覆层厚度较薄，可能无法有效阻碍过渡金属的迁移；包覆量过大则意味着包覆层过厚，会影响Li+的迁移，进而影响正极活性材料的倍率性能。对于第二包覆层而言，通过包覆量在上述范围内，则能够有效避免以下情况：包覆量过多，可能会影响正极活性材料整体的平台电压；包覆量过少，可能无法实现足够的包覆效果。对于第三包覆层 而言，碳包覆主要起到增强颗粒间的电子传输的作用，然而由于结构中还含有大量的无定形碳，因此碳的密度较低，因此，如果包覆量过大，会影响极片的压实密度。
在一些实施方式中，所述第一包覆层的厚度为1-10nm。在一些实施方式中，所述第二包覆层的厚度为2-15nm。在一些实施方式中，所述第三包覆层的厚度为2-25nm。在一些实施方式中，所述第一包覆层的厚度可为约2nm、约3nm、约4nm、约5nm、约6nm、约7nm、约8nm、约9nm或约10nm，或在上述任意数值的任意范围内。在一些实施方式中，所述第二包覆层的厚度可为约2nm、约3nm、约4nm、约5nm、约6nm、约7nm、约8nm、约9nm、约10nm、约11nm、约12nm、约13nm、约14nm、约15nm，或在上述任意数值的任意范围内。在一些实施方式中，所述第三层包覆层的厚度可为约2nm、约3nm、约4nm、约5nm、约6nm、约7nm、约8nm、约9nm、约10nm、约11nm、约12nm、约13nm、约14nm、约15nm、约16nm、约17nm、约18nm、约19nm、约20nm、约21nm、约22nm、约23nm、约24nm或约25nm，或在上述任意数值的任意范围内。
当所述第一包覆层的厚度范围为1-10nm时，能够避免过厚时可能产生的对正极活性材料的动力学性能的不利影响，且能够避免过薄时可能无法有效阻碍过渡金属离子的迁移的问题。当所述第二包覆层的厚度在2-15nm范围内时，所述第二包覆层的表面结构稳定，与电解液的副反应小，因此能够有效减轻界面副反应，从而提升电池的高温循环性能和高温存储性能。当所述第三包覆层的厚度范围为2-25nm时，能够提升正极活性材料的电导率并且提升使用所述正极活性材料制备的正极极片的压实密度。包覆层的厚度大小测试主要通过FIB进行，具体方法可以包括以下步骤：从待测正极活性材料粉末中随机选取单个颗粒，从所选颗粒中间位置或中间位置附近切取100nm左右厚度的薄片，然后对薄片进行TEM测试，量取包覆层的厚度，测量3-5个位置，取平均值。
在一些实施方式中，基于正极活性材料的重量计，锰元素含量在10重量％-35重量％范围内，可选在15重量％-30重量％范围内，更可选在17重量％-20重量％范围内。在一些实施方式中，基于正极活性材料的重量计，磷元素的含量在12重量％-25重量％范围内，可选在15重量％-20重量％范围内。在一些实施方式中，锰元素和磷元素的重量比范围为0.90-1.25，可选为0.95-1.20。在本申请中，在仅正极活性材料的内核中含有锰的情况下，锰的含量可与内核的含量相对应。
将所述磷元素的含量限制在上述范围内，能够有效避免以下情况：若磷元素的含量过大，可能会导致P-O的共价性过强而影响小极化子导电，从而影响正极活性材料的电导率；若磷元素的含量过小，可能会使所述内核、所述第一包覆层中的焦磷酸盐和/或所述第二包覆层中的磷酸盐晶格结构的稳定性下降，从而影响正极活性材料整体的稳定性。锰与磷含量重量比大小对电池的性能具有以下影响：该重量比过大，意味着锰元素过多，锰离子溶 出增加，影响正极活性材料的稳定性和克容量发挥，进而影响电池的循环性能及存储性能；该重量比过小，意味着磷元素过多，则容易形成杂相，会使正极活性材料的放电电压平台下降，从而使电池的能量密度降低。锰元素和磷元素的测量可采用本领域中常规的技术手段进行。特别地，采用以下方法测定锰元素和磷元素的含量：将正极活性材料在稀盐酸中(浓度10-30％)溶解，利用ICP测试溶液各元素的含量，然后对锰元素的含量进行测量和换算，得到其重量占比。
在本申请的另一些实施方式中，无机包覆层含有包覆所述内核的第一包覆层以及包覆所述第一包覆层的第二包覆层，其中，所述第一包覆层包括焦磷酸盐QP 2O 7和磷酸盐XPO 4，所述第二包覆层为包覆碳层。其中，焦磷酸盐QP 2O 7和磷酸盐XPO 4的化学组成和结晶情况与前述实施方式相似，在此不再赘述。
具体地，在这些实施方式中，所述第一包覆层的包覆量为大于0重量％且小于等于7重量％，可选为4-5.6重量％，基于所述内核的重量计。可选地，第一包覆层中焦磷酸盐和磷酸盐的重量比为1:3至3:1，可选为1:3至1:1。可选地，第二包覆层的包覆量为大于0重量％且小于等于6重量％，可选为3-5重量％，基于所述内核的重量计。每一层的包覆量均不为零。当所述第一包覆层的包覆量在上述范围内时，能够进一步抑制锰溶出，同时进一步促进锂离子的传输。并能够有效避免以下情况：若第一包覆层的包覆量过小，则可能会导致焦磷酸盐对锰溶出的抑制作用不充分，同时对锂离子传输性能的改善也不显著；若第一包覆层的包覆量过大，则可能会导致包覆层过厚，增大电池阻抗，影响电池的动力学性能。焦磷酸盐和磷酸盐的合适配比有利于充分发挥二者的协同作用。并能够有效避免以下情况：如果焦磷酸盐过多而磷酸盐过少，则可能导致电池阻抗增大；如果磷酸盐过多而焦磷酸盐过少，则抑制锰溶出的效果不显著。
在本申请磷酸锰锂正极活性材料的第一包覆层中，具备一定结晶度的焦磷酸盐和磷酸盐有利于保持第一包覆层的结构稳定，减少晶格缺陷。这一方面有利于充分发挥焦磷酸盐阻碍锰溶出的作用，另一方面也有利于磷酸盐减少表面杂锂含量、降低表面氧的价态，从而减少正极材料与电解液的界面副反应，减少对电解液的消耗，改善电池的循环性能和安全性能。
在一些实施方式中，可选地，第一包覆层的磷酸盐的晶面间距为0.345-0.358nm，晶向(111)的夹角为24.25°-26.45°，可选地第一包覆层的焦磷酸盐的晶面间距为0.293-0.326nm，晶向(111)的夹角为26.41°-32.57°。当第一包覆层中磷酸盐和焦磷酸盐的晶面间距和晶向(111)的夹角在上述范围时，能够有效避免包覆层中的杂质相，从而提升正极活性材料的克容量、循环性能和倍率性能。类似地，焦磷酸盐和磷酸盐的结晶度例如可通过调整烧结过程的工艺条件例如烧结温度、烧结时间等进行调节。焦磷酸盐和磷酸盐的结晶度可通过 本领域中已知的方法测量，例如通过X射线衍射法、密度法、红外光谱法、差示扫描量热法和核磁共振吸收方法等方法测量。
作为第二包覆层的含碳层一方面可以发挥“屏障”功能，避免正极活性材料与电解液直接接触，从而减少电解液对活性材料的腐蚀，提高电池在高温下的安全性能。另一方面，其具备较强的导电能力，可降低电池内阻，从而改善电池的动力学性能。然而，由于碳材料的克容量较低，因此当第二包覆层的用量过大时，可能会降低正极活性材料整体的克容量。因此，第二包覆层的包覆量在上述范围时，能够在不牺牲正极活性材料克容量的前提下，进一步改善电池的动力学性能和安全性能。
在另一些实施方式中，该正极活性材料的壳还可具有第一包覆层和第二包覆层，第一包覆层包括晶态的焦磷酸盐QP 2O 7和金属氧化物Q’ eO f，所述第二包覆层为包覆碳层。关于焦磷酸盐QP 2O 7和金属氧化物Q’ eO f的具体组成，前面已经进行了详细的描述，在此不再赘述。
如图3所示出的，第一包覆层12包括晶态焦磷酸盐和晶态氧化物；由于过渡金属在焦磷酸盐中的迁移势垒较高(>1eV)，能够有效抑制过渡金属的溶出；晶态氧化物具备高的结构稳定性，并且表面活性低，因此，通过晶态氧化物包覆能有效减轻界面副反应，从而改善电池的高温循环和高温存储等性能。另外，由于第二包覆层13为含碳层，因而能够有效改善内核11的导电性能和去溶剂化能力。此外，第二包覆层13的“屏障”作用可以进一步阻碍锰离子迁移到电解液中，并减少电解液对活性材料的腐蚀。因此，以内核为磷酸锂锰为例，本申请正极活性材料通过对磷酸锰锂进行特定的元素掺杂和表面包覆，能够减少Li/Mn反位缺陷的产生，有效抑制脱嵌锂过程中的Mn溶出，同时促进锂离子的迁移，从而改善电芯的倍率性能，提高二次电池的循环性能、高温性能和安全性能。
此处需要特别说明的是，图3中所示出的是本申请所提出的正极活性材料的结构示意图，并不限于前述的实施方式中。本申请中只要具有两层包覆层的正极活性材料，均可具有附图3所示出的结构。其中，包覆层(如图中所示出的12以及13)可实现对内层结构的完全包覆或部分包覆，包覆量或是面积可以为内层结构的100％、90％、80％、70％、60％、50％等。
在上述实施方式中，第一包覆层中焦磷酸盐的晶面间距为0.293-0.326nm，晶向(111)的夹角为26.41°-32.57°；可选地，所述第一包覆层中焦磷酸盐的晶面间距为0.300-0.310nm(例如0.303nm)；和/或，可选地，所述第一包覆层中焦磷酸盐的晶向(111)的夹角为29.00°-30.00°(例如29.496°)。当第一包覆层中焦磷酸盐的晶面间距和晶向(111)的夹角在上述范围时，能够有效避免包覆层中的杂质相，从而提升材料的克容量，提高二次电池的循环性能和倍率性能。
第一包覆层的包覆量大于0重量％且小于或等于7重量％，可选为4-5.6重量％，基于内核的重量计。当第一包覆层的包覆量在上述范围内时，能够进一步抑制锰溶出，同时进一步促进锂离子的传输，维持二次电池具备低阻抗，改善二次电池的动力学性能。在一些实施方式中，第一包覆层中焦磷酸盐和氧化物的重量比为1:3至3:1，可选为1:3至1:1。焦磷酸盐和氧化物的合适配比有利于充分发挥二者的协同作用，能够进一步抑制锰溶出，同时维持二次电池具备较低的阻抗。所述第二包覆层的包覆量为大于0重量％且小于或等于6重量％，可选为3-5重量％，基于所述内核的重量计。碳包覆层的性能以及优点与前述的实施方式中类似，在此不再赘述。
在上述实施方式中，第一包覆层的厚度为1-100nm。由此，过渡金属在第一包覆层中的迁移势垒较高，可有效减少过渡金属的溶出。其中的氧化物具有较高稳定性，可以有效减轻界面副反应，从而提升材料的高温稳定性。在一些实施方式中，第二包覆层的厚度为1-100nm。在一些实施方式中，第一包覆层中焦磷酸盐的结晶度为10％至100％，可选为50％至100％。在本申请磷酸锰锂正极活性材料的第一包覆层中，具备一定结晶度的焦磷酸盐有利于保持第一包覆层的结构稳定，减少晶格缺陷。这一方面有利于充分发挥焦磷酸盐阻碍锰溶出的作用，另一方面也有利于减少表面杂锂含量、降低表面氧的价态，从而减少正极材料与电解液的界面副反应，减少对电解液的消耗，改善二次电池的循环性能和安全性能。
在本申请的又一些实施方式中，壳还可以包括包覆所述内核的第一包覆层、包覆所述第一包覆层的第二包覆层和包覆所述第二包覆层的第三包覆层，类似地，此时该正极活性材料可具有如图4所示出的结构。所述第一包覆层12包含晶态焦磷酸盐，所述第二包覆层13包含金属氧化物Q’ eO f，所述晶态焦磷酸盐包括Li aQP 2O 7和/或Q b(P 2O 7) c，其中，所述a大于0且小于或等于2，所述b为1-4范围内的任意数值，所述c为1-3范围内的任意数值；所述第三包覆层13包含碳。关于晶态焦磷酸盐包括Li aQP 2O 7和/或Q b(P 2O 7) c以及金属氧化物Q’ eO f的具体组成，前面已经进行了详细的描述，在此不再赘述。
类似地，第一包覆层与核之间的结合类似于异质结，其结合的牢固程度受晶格匹配程度的限制。晶态氧化物作为第二包覆层与第一层包覆物晶态焦磷酸盐的晶格匹配度较高(失配度仅为3％)且稳定性好于焦磷酸盐，用其包覆焦磷酸盐有利于提高材料的稳定性。使用晶态氧化物进行包覆能够使正极活性材料的表面的界面副反应得到有效降低，从而改善二次电池的高温循环及存储性能。第二包覆层和第一包覆层之间的晶格匹配方式等，与上述第一包覆层和核之间的结合情况相似，晶格失配在5％以下时，晶格匹配较好，两者容易结合紧密。碳作为第三层包覆的主要原因是碳层的电子导电性较好。
在一些实施方式中，所述第一包覆层的包覆量为大于0且小于或等于6重量％，可选 为大于0且小于或等于5.5重量％，更可选为大于0且小于或等于2重量％，基于所述内核的重量计；和/或所述第二包覆层的包覆量为大于0且小于或等于6重量％，可选为大于0且小于或等于5.5重量％，更可选为2重量％-4重量％，基于所述内核的重量计；和/或所述第三包覆层的包覆量为大于0且小于或等于6重量％，可选为大于0且小于或等于5.5重量％，更可选为大于0且小于或等于2重量％，基于所述内核的重量计。每一层的包覆量均不为零。三层包覆层的包覆量优选在上述范围内，由此能够对内核进行充分包覆，并同时在不牺牲正极活性材料克容量的前提下，进一步改善二次电池的动力学性能和安全性能。具体地，对于第一包覆层而言，通过包覆量在上述范围内，能减少过渡金属的溶出，保证锂离子的顺利迁移，从而提高正极活性材料的倍率性能。对于第二包覆层而言，通过包覆量在上述范围内，能使正极活性材料维持一定的平台电压，并保证包覆效果。对于第三包覆层而言，碳包覆主要起到增强颗粒间的电子传输的作用，然而由于结构中还含有大量的无定形碳，因此碳的密度较低，通过包覆量在上述范围内，能保证极片的压实密度。
在上述实施方式中，所述第一包覆层的厚度为2-10nm；和/或所述第二包覆层的厚度为3-15nm；和/或所述第三包覆层的厚度为5-25nm。第一包覆层的厚度可为约2nm、约3nm、约4nm、约5nm、约6nm、约7nm、约8nm、约9nm或约10nm，或在上述任意数值的任意范围内。在一些实施方式中，第二包覆层的厚度可为约3nm、约4nm、约5nm、约6nm、约7nm、约8nm、约9nm、约10nm、约11nm、约12nm、约13nm、约14nm、约15nm，或在上述任意数值的任意范围内。在一些实施方式中，第三层包覆层的厚度可为约约5nm、约6nm、约7nm、约8nm、约9nm、约10nm、约11nm、约12nm、约13nm、约14nm、约15nm、约16nm、约17nm、约18nm、约19nm、约20nm、约21nm、约22nm、约23nm、约24nm或约25nm，或在上述任意数值的任意范围内。当第一包覆层的厚度范围为2-10nm时，能有效减少过渡金属的溶出，并保证二次电池的动力学性能。当第二包覆层的厚度在3-15nm范围内时，第二包覆层的表面结构稳定，与电解液的副反应小，因此能够有效减轻界面副反应，从而提升二次电池的高温性能。当第三包覆层的厚度范围为5-25nm时，能够提升材料的电导性能并且改善使用正极活性材料制备的电池极片的压密性能。类似地，包覆层的厚度大小测试主要通过FIB进行。
在上述实施方式中，基于正极活性材料的重量计，锰元素含量在10重量％-35重量％范围内，可选在15重量％-30重量％范围内，更可选在17重量％-20重量％范围内，磷元素的含量在12重量％-25重量％范围内，可选在15重量％-20重量％范围内；可选地，锰元素和磷元素的重量比在0.90-1.25范围内，更可选为0.95-1.20范围内。在本申请中，在仅正极活性材料的内核中含有锰的情况下，锰的含量可与内核的含量相对应。在本申请中，将锰元素的含量限制在上述范围内，能保证正极活性材料的稳定性和密度较高，从而提升 二次电池的循环、存储和压密等性能，并且能维持一定的电压平台高度，从而提升二次电池的能量密度。本申请中，将磷元素的含量限制在上述范围内，能有效提高材料的电导率，并且提升材料整体的稳定性。本申请中，锰与磷含量重量比在上述范围内，能有效减少过渡金属锰等元素的溶出，提高正极活性材料的稳定性和克容量，进而提升二次电池的循环性能及存储性能，同时有助于减少材料中杂相，维持材料的放电电压平台高度，从而使二次电池的能量密度提高。
在本申请的一些实施方式中，所述正极活性材料包括包覆所述内核的第一包覆层、包覆所述第一包覆层的第二包覆层以及包覆所述第二包覆层的第三包覆层，其中，所述第一包覆层包括晶态焦磷酸盐Li aQP 2O 7和/或Q b(P 2O 7) c，所述第二包覆层包括晶态磷酸盐XPO 4，所述第三包覆层为碳。
类似地，在该实施方式中，第一包覆层的包覆量为大于0且小于或等于6重量％，可选为大于0且小于或等于5.5重量％，更可选为大于0且小于或等于2重量％，基于所述内核的重量计；和/或所述第二包覆层的包覆量为大于0且小于或等于6重量％，可选为大于0且小于或等于5.5重量％，更可选为2-4重量％，基于所述内核的重量计；和/或所述第三包覆层的包覆量为大于0且小于或等于6重量％，可选为大于0且小于或等于5.5重量％，更可选为大于0且小于或等于2重量％，基于所述内核的重量计。第一包覆层的厚度为1-10nm；和/或所述第二包覆层的厚度为2-15nm；和/或所述第三包覆层的厚度为2-25nm。
基于正极活性材料的重量计，锰元素含量在10重量％-35重量％范围内，可选在15重量％-30重量％范围内，更可选在17重量％-20重量％范围内，磷元素的含量在12重量％-25重量％范围内，可选在15重量％-20重量％范围内，锰元素和磷元素的重量比范围为0.90-1.25，可选为0.95-1.20。
关于上述厚度、磷含量、锰含量、包覆层含量等参数的效果以及实现该效果的原理，前面已经进行了详细的描述，在此不再赘述。
在一些实施方式中，正极活性材料的一次颗粒的平均粒径范围为50-500nm，体积中值粒径Dv50在200-300nm范围内。由于颗粒会发生团聚，因此实际测得团聚后的二次颗粒大小可能为500-40000nm。正极活性材料颗粒的大小会影响材料的加工和极片的压实密度性能。通过选择一次颗粒的平均粒径在上述范围内，从而能够避免以下情况：所述正极活性材料的一次颗粒的平均粒径太小，可能会引起颗粒团聚，分散困难，并且需要较多的粘结剂，导致极片脆性较差；所述正极活性材料的一次颗粒的平均粒径太大，可能会使颗粒间的空隙较大，压实密度降低。通过上述方案，能够有效抑制脱嵌锂过程中磷酸锰锂的晶格变化率和Mn溶出，从而提升二次电池的高温循环稳定性和高温储存性能。
本申请的第二方面涉及一种制备本申请第一方面的正极活性材料的方法。该方法 其包括形成内核，以及在所述内核的至少表面形成壳的步骤，所述内核包括三元材料、 dLi 2MnO 3·(1-d)LiMO 2以及LiMPO 4中的至少一种，0＜d＜1，所述M包括选自Fe、Ni、Co、Mn中的一种或多种，所述壳含有结晶态无机物，所述结晶态无机物使用X射线衍射测量的主峰的半高全宽为0-3°，所述结晶态无机物包括选自金属氧化物以及无机盐中的一种或多种。
关于内核以及壳中各包覆层的结构以及含量，前面已经进行了详细的说明，在此不再赘述。下面，以内核含有LiMPO 4且M包括Mn和非Mn元素的情况为例，详述该方法的各个步骤：
具体地，该方法包括形成LiMPO 4化合物的操作，其中LiMPO 4化合物可具有前述的LiMPO 4化合物的全部特征以及优点，在此不再赘述。简单来说，所述M包括Mn，以及非Mn元素，所述非Mn元素满足以下条件的至少之一：所述非Mn元素的离子半径为a，锰元素的离子半径为b，|a-b|/b不大于10％；所述非Mn元素的化合价可变价范围不大于Mn元素的化合价可变价范围；所述非Mn元素和O形成的化学键的化学活性不小于P-O键的化学活性；所述非Mn元素的最高化合价不大于6。
在一些实施方式中，所述非Mn元素包括第一和第二掺杂元素，所述方法包括：将锰源、所述锰位元素的掺杂剂和酸混合，得到具有第一掺杂元素的锰盐颗粒；将所述具有所述第一掺杂元素的锰盐颗粒与锂源、磷源和所述第二掺杂元素的掺杂剂在溶剂中混合并得到浆料，在惰性气体气氛保护下烧结后得到所述LiMPO 4化合物。关于第一掺杂元素和第二掺杂元素的种类，前面已经进行了详细的描述，在此不再赘述。在一些实施方式中，第一掺杂元素包括选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素，所述第二掺杂元素包括选自B(硼)、S、Si和N中的一种或多种元素。
在一些实施方式中，按照化学式Li 1+xMn 1-yA yP 1-zR zO 4形成所述LiMPO 4化合物，在另一些实施方式中，按照化学式Li 1+xC mMn 1-yA yP 1-zR zO 4-nD n形成所述LiMPO 4化合物。关于各取代位点的元素及其选择原则、有益效果，以及原子比范围，前面已经进行了详细的描述，在此不再赘述。其中，元素C的源选自元素C的单质、氧化物、磷酸盐、草酸盐、碳酸盐和硫酸盐中的至少一种，元素A的源选自元素A的单质、氧化物、磷酸盐、草酸盐、碳酸盐、硫酸盐氯化盐、硝酸盐、有机酸盐、氢氧化物、卤化物中的至少一种，元素R的源选自元素R的硫酸盐、硼酸盐、硝酸盐和硅酸盐、有机酸、卤化物、有机酸盐、氧化物、氢氧化物中的至少一种，元素D的源选自元素D的单质和铵盐中的至少一种。
在一些实施方式中，所述酸选自盐酸、硫酸、硝酸、磷酸、有机酸如草酸等中的一种或多种，例如可为草酸。在一些实施方式中，所述酸为浓度为60重量％以下的稀 酸。在一些实施方式中，所述锰源可为本领域已知的可用于制备磷酸锰锂的含锰物质，例如所述锰源可选自单质锰、二氧化锰、磷酸锰、草酸锰、碳酸锰中的一种或它们的组合。在一些实施方式中，所述锂源可为本领域已知的可用于制备磷酸锰锂的含锂物质，例如所述锂源可选自碳酸锂、氢氧化锂、磷酸锂、磷酸二氢锂中的一种或它们的组合。在一些实施方式中，所述磷源可为本领域已知的可用于制备磷酸锰锂的含磷物质，例如所述磷源可选自磷酸氢二铵、磷酸二氢铵、磷酸铵和磷酸中的一种或它们的组合。各位点掺杂元素各自的源的加入量取决于目标掺杂量，锂源、锰源和磷源的用量之比符合化学计量比。
在一些实施方式中，得到具有第一掺杂元素的锰盐颗粒满足以下条件的至少之一：在20-120℃、可选为40-120℃、可选地为60-120℃、更可选地为25-80℃的温度下将锰源、所述锰位元素和酸混合；和/或所述混合在搅拌下进行，所述搅拌在200-800rpm下，可选地400-700rpm下，更可选地500-700rpm进行1-9h，可选地为3-7h，更可选地为可选地为2-6h。
在一些实施方式中，正极活性物质可以具有第一掺杂元素和第二掺杂元素。该方法可以将所述具有第一掺杂元素的锰盐颗粒与锂源、磷源和所述第二掺杂元素的掺杂剂在溶剂中研磨并混合进行8-15小时。例如，将所述具有第一掺杂元素的锰盐颗粒与锂源、磷源和所述第二掺杂元素的掺杂剂在溶剂中混合是在20-120℃、可选为40-120℃的温度下进行1-10h。
具体地，该方法可按照化学式Li 1+xC xMn 1-yA yP 1-zR zO 4-nD n形成LiMPO 4化合物。更具体地，可将所述具有第一掺杂元素的锰盐颗粒与锂源、磷源和所述第二掺杂元素的掺杂剂在溶剂中研磨并混合进行8-15小时。例如，可将锰源、元素A的源和酸在溶剂中溶解生成掺杂元素A的锰盐的悬浊液，将所述悬浊液过滤并烘干得到掺杂了元素A的锰盐；将锂源、磷源、元素C的源、元素R的源和元素D的源、溶剂和所述掺杂了元素A的锰盐加溶剂混合，得到浆料；将所述浆料进行喷雾干燥造粒，得到颗粒；将所述颗粒进行烧结，得到所述正极活性材料。烧结可以是在600-900℃的温度范围内进行6-14小时。
通过控制掺杂时的反应温度、搅拌速率和混合时间，能够使掺杂元素均匀分布，并且烧结后材料的结晶度更高，从而可提升材料的克容量和倍率性能等。
在一些具体地实施方式中，形成内核的操作可以包括以下步骤：(1)将锰源、元素B的源和酸在溶剂中溶解并搅拌，生成掺杂元素B的锰盐的悬浊液，将悬浊液过滤并烘干滤饼，得到掺杂了元素B的锰盐；(2)将锂源、磷源、元素A的源、元素C的源和元素D的源、溶剂和由步骤(1)获得的掺杂了元素B的锰盐加入反应容器中研磨并混合，得到浆料；(3)将由步骤(2)获得的浆料转移到喷雾干燥设备中进行 喷雾干燥造粒，得到颗粒；(4)将由步骤(3)获得的颗粒进行烧结。
在一些实施方式中，步骤(1)和步骤(2)中所述溶剂各自独立地可为本领域技术人员在锰盐和磷酸锰锂的制备中常规使用的溶剂，例如其可各自独立地选自乙醇、水(例如去离子水)中的至少一种等。
在一些实施方式中，步骤(1)的搅拌在60-120℃范围内的温度下进行。在一些实施方式中，步骤(1)的搅拌通过在200-800rpm，或300-800rpm，或400-800rpm的搅拌速率下进行。在一些实施方式中，步骤(1)的搅拌进行6-12小时。在一些实施方式中，步骤(2)的研磨并混合进行8-15小时。
通过控制掺杂时的反应温度、搅拌速率和混合时间，能够使掺杂元素均匀分布，并且烧结后材料的结晶度更高，从而可提升材料的克容量和倍率性能等。
在一些实施方式中，在步骤(1)中烘干滤饼之前可对滤饼进行洗涤。在一些实施方式中，步骤(1)中的烘干可通过本领域技术人员已知的方式和已知的条件进行，例如，烘干温度可在120-300℃范围内。可选地，可在烘干后将滤饼研磨成颗粒，例如研磨至颗粒的中值粒径Dv50在50-200nm范围内。其中，中值粒径Dv50是指，所述正极活性材料累计体积分布百分数达到50％时所对应的粒径。在本申请中，正极活性材料的中值粒径Dv50可采用激光衍射粒度分析法测定。例如参照标准GB/T 19077-2016，使用激光粒度分析仪(例如Malvern Master Size 3000)进行测定。
在一些实施方式中，在步骤(2)中还向反应容器中加入碳源一起进行研磨并混合。由此，所述方法可获得表面包覆有碳的正极活性材料。可选地，所述碳源包括淀粉、蔗糖、葡萄糖、聚乙烯醇、聚乙二醇、柠檬酸中的一种或几种的组合。所述碳源的用量相对于所述锂源的用量通常在摩尔比0.1％-5％的范围内。所述研磨可通过本领域已知的适合的研磨方式进行，例如可通过砂磨进行。
步骤(3)的喷雾干燥的温度和时间可为本领域中进行喷雾干燥时常规的温度和时间，例如，在100-300℃下，进行1-6小时。
在一些实施方式中，所述烧结在600-900℃的温度范围内进行6-14小时。通过控制烧结温度和时间，能够控制材料的结晶度，降低正极活性材料的循环后Mn与Mn位掺杂元素的溶出量，从而改善电池的高温稳定性和循环性能。在一些实施方式中，所述烧结在保护气氛下进行，所述保护气氛可为氮气、惰性气体、氢气或其混合物。
在另一些实施方式中，该正极活性材料的内核可以仅具有Mn位以及P位掺杂元素。所述提供正极活性材料的步骤可包括：步骤(1)：将锰源、元素A的掺杂剂和酸在容器中混合并搅拌，得到掺杂有元素A的锰盐颗粒；步骤(2)：将所述掺杂有元素A的锰盐颗粒与锂源、磷源和元素R的掺杂剂在溶剂中混合并得到浆料，在惰性 气体气氛保护下烧结后得到掺杂有元素A和元素R的内核。在一些可选实施方式中，在所述锰源、所述元素A的掺杂剂与所述酸在溶剂中反应得到掺杂有元素A的锰盐悬浮液后，将所述悬浮液过滤，烘干，并进行砂磨以得到粒径为50-200nm的经元素A掺杂的锰盐颗粒。在一些可选实施方式中，将步骤(2)中的浆料进行干燥得到粉料，然后将粉料烧结得到掺杂有元素A和元素R的正极活性物质。
在一些实施方式中，所述步骤(1)在20-120℃、可选为40-120℃的温度下进行混合；和/或所述步骤(1)中所述搅拌在400-700rpm下进行1-9h，可选地为3-7h。可选地，所述步骤(1)中的反应温度可在约30℃、约50℃、约60℃、约70℃、约80℃、约90℃、约100℃、约110℃或约120℃进行；所述步骤(1)中所述搅拌进行约2小时、约3小时、约4小时、约5小时、约6小时、约7小时、约8小时或约9小时；可选地，所述步骤(1)中的反应温度、搅拌时间可在上述任意数值的任意范围内。
在一些实施方式中，所述步骤(2)在20-120℃、可选为40-120℃的温度下进行混合1-12h。可选地，所述步骤(2)中的反应温度可在约30℃、约50℃、约60℃、约70℃、约80℃、约90℃、约100℃、约110℃或约120℃进行；所述步骤(2)中所述混合进行约2小时、约3小时、约4小时、约5小时、约6小时、约7小时、约8小时、约9小时、约10小时、约11小时或约12小时；可选地，所述步骤(2)中的反应温度、混合时间可在上述任意数值的任意范围内。
当正极活性颗粒制备过程中的温度和时间处于上述范围内时，制备获得的正极活性材料的晶格缺陷较少，有利于抑制锰溶出，减少正极活性材料与电解液的界面副反应，从而改善二次电池的循环性能和安全性能。
在一些实施方式中，可选地，在制备A元素和R元素掺杂的稀酸锰颗粒的过程中，控制溶液pH为3.5-6，可选地，控制溶液pH为4-6，更可选地，控制溶液pH为4-5。需要说明的是，在本申请中可通过本领域通常使用的方法调节所得混合物的pH，例如可通过添加酸或碱。在一些实施方式中，可选地，在步骤(2)中，所述锰盐颗粒与锂源、磷源的摩尔比为1：0.5-2.1：0.5-2.1，更可选地，所述掺杂有元素A的锰盐颗粒与锂源、磷源的摩尔比为约1：1：1。
在一些实施方式中，可选地，制备A元素和R元素掺杂的磷酸锰锂过程中的烧结条件为：在惰性气体或惰性气体与氢气混合气氛下在600-950℃下烧结4-10小时；可选地，所述烧结可在约650℃、约700℃、约750℃、约800℃、约850℃或约900℃下烧结约2小时、约3小时、约4小时、约5小时、约6小时、约7小时、约8小时、约9小时或约10小时；可选地，所述烧结的温度、烧结时间可在上述任意数值的任意范围内。在制备A元素和R元素掺杂的磷酸锰锂过程中，烧结温度过低以及烧结时间 过短时，会导致材料内核的结晶度较低，会影响整体的性能发挥，而烧结温度过高时，材料内核中容易出现杂相，从而影响整体的性能发挥；烧结时间过长时，材料内核颗粒长的较大，从而影响克容量发挥，压实密度和倍率性能等。在一些可选实施方式中，可选地，保护气氛为70-90体积％氮气和10-30体积％氢气的混合气体。
在一些实施方式中，具有上述化学组成的颗粒可作为内核，该方法还包括形成包覆所述内核的壳的步骤。
具体地，包覆的步骤可以包括形成碳包覆层的步骤，可选地，所述碳源包括淀粉、蔗糖、葡萄糖、聚乙烯醇、聚乙二醇、柠檬酸中的一种或几种的组合。所述碳源的用量相对于所述锂源的用量通常在摩尔比0.1％-5％的范围内。所述研磨可通过本领域已知的适合的研磨方式进行，例如可通过砂磨进行。
在形成碳层之前，该方法还包括形成前述的无机包覆层的步骤。
以包覆层包括第一包覆层和包覆所述第一包覆层的第二包覆层，所述第一包覆层含有焦磷酸盐QP 2O 7和磷酸盐XPO 4，第二包覆层含碳为例，所述方法包括：提供QP 2O 7粉末和包含碳的源的XPO 4悬浊液，将所述磷酸锰锂氧化物、QP 2O 7粉末加入到包含碳的源的XPO 4悬浊液中并混合，经烧结获得正极活性材料。
其中，所述QP 2O 7粉末是市售产品，或者可选地所述提供QP 2O 7粉末包括：将元素Q的源和磷的源添加到溶剂中，得到混合物，调节混合物的pH为4-6，搅拌并充分反应，然后经干燥、烧结获得，且所述提供QP 2O 7粉末满足以下条件的至少之一：所述干燥为在100-300℃、可选150-200℃下干燥4-8h；所述烧结为在500-800℃、可选650-800℃下，在惰性气体气氛下烧结4-10h。例如，具体地，形成所述包覆层的烧结温度为500-800℃，烧结时间为4-10h。
在一些实施方式中，可选地，所述包含碳的源的XPO 4悬浊液是市售可得的，或者可选地，通过以下方法来制备：将锂的源、X的源、磷的源和碳的源在溶剂中混合均匀，然后将反应混合物升温至60-120℃保持2-8小时即可获得包含碳的源的XPO 4悬浊液。可选地，在制备包含碳的源的XPO 4悬浊液的过程中，调节所述混合物的pH为4-6。
在一些实施方式中，可选地，本申请双层包覆的磷酸锰锂正极活性材料的一次颗粒的中值粒径Dv50为50-2000nm。
在另一些实施方式中，包覆层包括包覆所述LiMPO 4化合物的第一包覆层、包覆所述第一包覆层的第二包覆层以及包覆所述第二包覆层的第三包覆层，其中，所述第一包覆层包括晶态焦磷酸盐Li aQP 2O 7和/或Q b(P 2O 7) c，其中，0≤a≤2，1≤b≤4，1≤c≤6，所述a、b和c的值满足以下条件：使所述晶态焦磷酸盐Li aQP 2O 7或Q b(P 2O 7) c保持电中性，所述晶态焦磷酸盐Li aQP 2O 7和Q b(P 2O 7) c中的Q各自独立地为选自Fe、Ni、Mg、Co、Cu、Zn、Ti、 Ag、Zr、Nb或Al中的一种或多种元素；所述第二包覆层包括晶态磷酸盐XPO 4，其中，所述X为选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb或Al中的一种或多种元素；所述第三包覆层为碳。
具体地，在第一包覆步骤中，控制溶解有元素Q的源、磷源和酸以及任选地锂源的溶液pH为3.5-6.5，然后搅拌并反应1-5h，然后将所述溶液升温至50-120℃，并保持该温度2-10h，和/或，烧结在650-800℃下进行2-6小时。可选地，在第一包覆步骤中，所述反应充分进行。可选地，在第一包覆步骤中，所述反应进行约1.5小时、约2小时、约3小时、约4小时、约4.5小时或约5小时。可选地，第一包覆步骤中，所述反应的反应时间可在上述任意数值的任意范围内。可选地，在第一包覆步骤中，控制溶液pH为4-6。可选地，在第一包覆步骤中，将所述溶液升温至约55℃、约60℃、约70℃、约80℃、约90℃、约100℃、约110℃或约120℃，并在该温度下保持约2小时、约3小时、约4小时、约5小时、约6小时、约7小时、约8小时、约9小时或约10小时；可选地，第一包覆步骤中，所述升温的温度和保持时间可在上述任意数值的任意范围内。可选地，在所述第一包覆步骤中，所述烧结可在约650℃、约700℃、约750℃、或约800℃下烧结约2小时、约3小时、约4小时、约5小时或约6小时；可选地，所述烧结的温度、烧结时间可在上述任意数值的任意范围内。
在所述第一包覆步骤中，通过将烧结温度和时间控制在以上范围内，可以避免以下情况：当所述第一包覆步骤中的烧结温度过低以及烧结时间过短时，会导致第一包覆层的结晶度低，非晶态物质较多，这样会导致抑制金属溶出的效果下降，从而影响二次电池的循环性能和高温存储性能；而烧结温度过高时，会导致第一包覆层出现杂相，也会影响到其抑制金属溶出的效果，从而影响二次电池的循环和高温存储性能等；烧结时间过长时，会使第一包覆层的厚度增加，影响Li+的迁移，从而影响材料的克容量发挥和倍率性能等。
在一些实施方式中，所述第二包覆步骤中，将元素X的源、磷源和酸溶于溶剂后，搅拌并反应1-10h，然后将所述溶液升温至60-150℃，并保持该温度2-10h，和/或，烧结在500-700℃下进行6-10小时。可选地，在第二包覆步骤中，所述反应充分进行。可选地，在第二包覆步骤中，所述反应进行约1.5小时、约2小时、约3小时、约4小时、约4.5小时、约5小时、约6小时、约7小时、约8小时、约9小时或约10小时。可选地，第二包覆步骤中，所述反应的反应时间可在上述任意数值的任意范围内。可选地，在第二包覆步骤中，将所述溶液升温至约65℃、约70℃、约80℃、约90℃、约100℃、约110℃、约120℃、约130℃、约140℃或约150℃，并在该温度下保持约2小时、约3小时、约4小时、约5小时、约6小时、约7小时、约8小时、约9小时或约10小时；可选地，第二包覆步骤中，所述升温的温度和保持时间可在上述任意数值的任意范围内。
在所述提供内核材料的步骤和所述第一包覆步骤和所述第二包覆步骤中，在烧结之前，即，在发生化学反应的内核材料的制备中，以及在第一包覆层悬浮液和第二包覆层悬浮液的制备中，通过如上所述选择适当的反应温度和反应时间，从而能够避免以下情况：反应温度过低时，则反应无法发生或反应速率较慢；温度过高时，产物分解或形成杂相；反应时间过长时，产物粒径较大，可能会增加后续工艺的时间和难度；反应时间过短时，则反应不完全，获得的产物较少。
可选地，在第二包覆步骤中，所述烧结可在约550℃、约600℃或约700℃下烧结约6小时、约7小时、约8小时、约9小时或约10小时；可选地，所述烧结的温度、烧结时间可在上述任意数值的任意范围内。在所述第二包覆步骤中，通过将烧结温度和时间控制在以上范围内，可以避免以下情况：当所述第二包覆步骤中的烧结温度过低以及烧结时间过短时，会导致第二包覆层的结晶度低，非晶态较多，降低材料表面反应活性的性能下降，从而影响二次电池的循环和高温存储性能等；而烧结温度过高时，会导致第二包覆层出现杂相，也会影响到其降低材料表面反应活性的效果，从而影响二次电池的循环和高温存储性能等；烧结时间过长时，会使第二包覆层的厚度增加，影响材料的电压平台，从而使材料的能量密度下降等。
在一些实施方式中，所述第三包覆步骤中的烧结在700-800℃下进行6-10小时。可选地，在第三包覆步骤中，所述烧结可在约700℃、约750℃或约800℃下烧结约6小时、约7小时、约8小时、约9小时或约10小时；可选地，所述烧结的温度、烧结时间可在上述任意数值的任意范围内。在所述第三包覆步骤中，通过将烧结温度和时间控制在以上范围内，可以避免以下情况：当所述第三包覆步骤中的烧结温度过低时，会导致第三包覆层的石墨化程度下降，影响其导电性，从而影响材料的克容量发挥；烧结温度过高时，会造成第三包覆层的石墨化程度过高，影响Li+的传输，从而影响材料的克容量发挥等；烧结时间过短时，会导致包覆层过薄，影响其导电性，从而影响材料的克容量发挥；烧结时间过长时，会导致包覆层过厚，影响材料的压实密度等。
在上述第一包覆步骤、第二包覆步骤、第三包覆步骤中，所述干燥均在100℃至200℃、可选为110℃至190℃、更可选为120℃至180℃、甚至更可选为120℃至170℃、最可选为120℃至160℃的干燥温度下进行，干燥时间为3-9h、可选为4-8h，更可选为5-7h，最可选为约6h。
当前述的正极活性材料的壳包括包覆所述内核的第一包覆层、包覆所述第一包覆层的第二包覆层，其中，所述第一包覆层包括晶态焦磷酸盐QP 2O 7和所述金属氧化物Q’ eO f，所述第二包覆层包括碳，形成所述壳包括：提供包含晶态焦磷酸盐QP 2O 7的粉末和包含碳源及氧化物Q’ eO f的悬浊液，将所述内核、包含晶态焦磷酸盐QP 2O 7的粉末和包含碳源及 氧化物Q’ eO f的悬浊液混合，烧结，获得正极活性材料。氧化物Q’ eO f的悬浊液可以是通过市购获取的金属氧化物以及包括但不限于蔗糖等碳源的原料混合在溶剂中形成的悬浊液。
或者，前述的正极活性材料的壳包括包覆所述内核的第一包覆层、包覆所述第一包覆层的第二包覆层，以及包覆所述第二包覆层的第三包覆层，其中，所述第一包覆层包括晶态焦磷酸盐QP 2O 7，所述第二包覆层包括所述金属氧化物Q’ eO f，所述第三包覆层包括碳，形成所述壳包括：提供包含焦磷酸盐Li aQP 2O 7和/或Q b(P 2O 7) c的第一混合物，将内核材料与第一混合物混合，干燥，烧结，得到第一包覆层包覆的材料；提供包含所述金属氧化物Q’ eO f的第二混合物，将所述第一包覆层包覆的材料与第二混合物混合，干燥，烧结，得到第二包覆层包覆的材料；提供包含碳源的第三混合物，将所述第二包覆层包覆的材料与第三混合物混合，干燥，烧结，得到所述正极活性材料。
例如，形成含有见氧化物的包覆层时，所述第一包覆层时将元素Q的源、磷源、酸、任选的锂源和任选的溶剂混合得到所述第一混合物；和/或，形成所述第二包覆层时将元素Q′的源与溶剂混合得到第二混合物；和/或，形成所述第三包覆层时将碳源与溶剂混合得到第三混合物；可选地，形成所述第一包覆层时，所述元素Q的源、磷源、酸、任选的锂源和任选的溶剂在室温下混合1-5h，再升温至50℃-120℃并保持该温度混合2-10h，上述混合均在pH为3.5-6.5条件下进行；可选地，形成所述第二包覆层时，所述元素Q′的源与溶剂在室温下混合1-10h，再升温至60℃-150℃并保持该温度混合2-10h。
当壳结构具有三层结构并含有金属氧化物时，形成所述第一包覆步骤中，所述烧结在650-800℃下进行2-8小时；和/或，所述第二包覆步骤中，所述烧结在400-750℃下进行6-10小时；和/或，所述第三包覆步骤中，所述烧结在600-850℃下进行6-10小时。例如，在一些实施方式中，第一包覆步骤中，烧结在650-800℃(例如约650℃、约700℃、约750℃或约800℃)下进行2-8小时(约2小时、约3小时、约4小时、约5小时、约6小时、约8小时)；和/或，第二包覆步骤中，烧结在400-750℃(例如约400℃、约450℃、约500℃、约550℃、约600℃、约700℃、约750℃)下进行6-10小时(例如约6小时、约7小时、约8小时、约9小时或约10小时)；和/或，第三包覆步骤中，烧结在600-850℃(例如约600℃、约650℃、约700℃、约750℃、约800℃、约850℃)下进行6-10小时(例如约6小时、约7小时、约8小时、约9小时或约10小时)。
在上述第一包覆步骤、第二包覆步骤、第三包覆步骤中，干燥均在80℃至200℃、可选为80℃至190℃、更可选为120℃至180℃、甚至更可选为120℃至170℃、最可选为120℃至160℃的干燥温度下进行，干燥时间为3-9h、可选为4-8h，更可选为5-7h，最可选为约6h。
本申请的第三方面提供一种正极极片，其包括正极集流体以及设置在正极集流体 至少一个表面的正极膜层，所述正极膜层包括本申请第一方面的正极活性材料或通过本申请第二方面的方法制备的正极活性材料，并且所述正极活性材料在所述正极膜层中的含量为10重量％以上，基于所述正极膜层的总重量计。
在一些实施方式中，所述正极活性材料在所述正极膜层中的含量为95-99.5重量％，基于所述正极膜层的总重量计。
本申请的第四方面提供一种二次电池，其包括本申请第一方面的正极活性材料或通过本申请第二方面的方法制备的正极活性材料或本申请第三方面的正极极片。
通常情况下，二次电池包括正极极片、负极极片、电解质和隔离膜。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。电解质在正极极片和负极极片之间起到传导离子的作用。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使离子通过。
以下适当参照附图对本申请的二次电池、电池模块、电池包和用电装置进行说明。
[正极极片]
正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，所述正极膜层包括本申请第一方面的正极活性材料。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极膜层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，所述正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，正极膜层还可选地包括粘结剂。作为示例，所述粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。
在一些实施方式中，正极膜层还可选地包括导电剂。作为示例，所述导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，可以通过以下方式制备正极极片：将上述用于制备正极极片的组分，例如正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N- 甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
[负极极片]
负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，所述负极膜层包括负极活性材料。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极膜层设置在负极集流体相对的两个表面中的任意一者或两者上。
在一些实施方式中，所述负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，负极活性材料可采用本领域公知的用于电池的负极活性材料。作为示例，负极活性材料可包括以下材料中的至少一种：人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂等。所述硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅氮复合物以及硅合金中的至少一种。所述锡基材料可选自单质锡、锡氧化合物以及锡合金中的至少一种。但本申请并不限定于这些材料，还可以使用其他可被用作电池负极活性材料的传统材料。这些负极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
在一些实施方式中，负极膜层还可选地包括粘结剂。所述粘结剂可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。
在一些实施方式中，负极膜层还可选地包括导电剂。导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，负极膜层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。
在一些实施方式中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如负极活性材料、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成负极浆料；将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，即可得到负极极片。
[电解质]
电解质在正极极片和负极极片之间起到传导离子的作用。本申请对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可以是液态的、凝胶态的或全固态的。
在一些实施方式中，所述电解质采用电解液。所述电解液包括电解质盐和溶剂。
在一些实施方式中，电解质盐可选自六氟磷酸锂、四氟硼酸锂、高氯酸锂、六氟砷酸锂、双氟磺酰亚胺锂、双三氟甲磺酰亚胺锂、三氟甲磺酸锂、二氟磷酸锂、二氟草酸硼酸锂、二草酸硼酸锂、二氟二草酸磷酸锂及四氟草酸磷酸锂中的至少一种。
在一些实施方式中，溶剂可选自碳酸亚乙酯、碳酸亚丙酯、碳酸甲乙酯、碳酸二乙酯、碳酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸亚丁酯、氟代碳酸亚乙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯、1,4-丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜中的至少一种。
在一些实施方式中，所述电解液还可选地包括添加剂。例如添加剂可以包括负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
[隔离膜]
在一些实施方式中，二次电池中还包括隔离膜。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施方式中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施方式中，二次电池可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，作为塑料，可列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图5是作为一个示例的方形结构的二次电池5。
在一些实施方式中，参照图6，外包装可包括壳体51和盖板53。其中，壳体51 可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53能够盖设于所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔内。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或多个，本领域技术人员可根据具体实际需求进行选择。
在一些实施方式中，二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为一个或多个，具体数量本领域技术人员可根据电池模块的应用和容量进行选择。
图7是作为一个示例的电池模块4。参照图7，在电池模块4中，多个二次电池5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个二次电池5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个二次电池5容纳于该容纳空间。
在一些实施方式中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以为一个或多个，具体数量本领域技术人员可根据电池包的应用和容量进行选择。
图8和图9是作为一个示例的电池包1。参照图8和图9，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
另外，本申请还提供一种用电装置，所述用电装置包括本申请提供的二次电池、电池模块、或电池包中的至少一种。所述二次电池、电池模块、或电池包可以用作所述用电装置的电源，也可以用作所述用电装置的能量存储单元。所述用电装置可以包括移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等，但不限于此。
作为所述用电装置，可以根据其使用需求来选择二次电池、电池模块或电池包。
图10是作为一个示例的用电装置。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用二次电池作为电源。
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
一、正极活性材料性质及电池性能测试方法
1.晶格变化率测量方法
在25℃恒温环境下，将正极活性材料样品置于XRD(型号为Bruker D8 Discover)中，采用1°/min对样品进行测试，并对测试数据进行整理分析，参照标准PDF卡片，计算出此时的晶格常数a0、b0、c0和v0(a0,b0和c0表示晶胞各个方面上的长度大小，v0表示晶胞体积，可通过XRD精修结果直接获取)。
采用上述实施例中扣电制备方法，将所述正极活性材料样品制备成扣电，并对上述扣电以0.05C小倍率进行充电，直至电流减小至0.01C。然后将扣电中的正极极片取出，并置于DMC中浸泡8小时。然后烘干，刮粉，并筛选出其中粒径小于500nm的颗粒。取样并按照与上述测试新鲜样品同样的方式计算出其晶格常数v1，将(v0-v1)/v0×100％作为其完全脱嵌锂前后的晶格变化率示于表中。
2.Li/Mn反位缺陷浓度测量方法
将“晶格变化率测量方法”中测试的XRD结果与标准晶体的PDF(Powder Diffraction File)卡片对比，得出Li/Mn反位缺陷浓度。具体而言，将“晶格变化率测量方法”中测试的XRD结果导入通用结构分析系统(GSAS)软件中，自动获得精修结果，其中包含了不同原子的占位情况，通过读取精修结果获得Li/Mn反位缺陷浓度。
3.表面氧价态测量方法
取5g正极活性材料样品按照上述实施例中所述扣电制备方法制备成扣电。对扣电采用0.05C小倍率进行充电，直至电流减小至0.01C。然后将扣电中的正极极片取出，并置于DMC中浸泡8小时。然后烘干，刮粉，并筛选出其中粒径小于500nm的颗粒。将所得颗粒用电子能量损失谱(EELS，所用仪器型号为Talos F200S)进行测量，获取能量损失近边结构(ELNES)，其反映元素的态密度和能级分布情况。根据态密度和能级分布，通过对价带态密度数据进行积分，算出占据的电子数，从而推算出充电后的表面氧的价态。
4.压实密度测量方法
取5g的粉末放于压实专用模具(美国CARVER模具，型号13mm)中,然后将模具放在压实密度仪器上。施加3T的压力，在设备上读出压力下粉末的厚度(卸压后的厚度)， 通过ρ＝m/v，计算出压实密度。其中使用的面积值为标准的小图片面积1540.25mm 2。
5.循环后Mn(以及Mn位掺杂的Fe)溶出量测量方法
将45℃下循环至容量衰减至80％后的全电池采用0.1C倍率进行放电至截止电压2.0V。然后将电池拆开，取出负极极片，在负极极片上随机取30个单位面积(1540.25mm 2)的圆片，用Agilent ICP-OES730测试电感耦合等离子体发射光谱(ICP)。根据ICP结果计算其中Fe(如果正极活性材料的Mn位掺杂有Fe的话)和Mn的量，从而计算循环后Mn(以及Mn位掺杂的Fe)的溶出量。测试标准依据EPA-6010D-2014。
6.扣式电池初始克容量测量方法
在2.5～4.3V下，将扣式电池按照0.1C充电至4.3V，然后在4.3V下恒压充电至电流小于等于0.05mA，静置5min，然后按照0.1C放电至2.0V，此时的放电容量为初始克容量，记为D0。
7.3C充电恒流比测量方法
在25℃恒温环境下，将新鲜全电池静置5min，按照1/3C放电至2.5V。静置5min，按照1/3C充电至4.3V，然后在4.3V下恒压充电至电流小于等于0.05mA。静置5min，记录此时的充电容量为C0。按照1/3C放电至2.5V，静置5min，再按照3C充电至4.3V，静置5min，记录此时的充电容量为C1。3C充电恒流比即为C1/C0×100％。3C充电恒流比越高，说明电池的倍率性能越好。
8.全电池45℃循环性能测试
在45℃的恒温环境下，在2.5～4.3V下，将全电池按照1C充电至4.3V，然后在4.3V下恒压充电至电流小于等于0.05mA。静置5min，然后按照1C放电至2.5V，记录此时的放电容量为D0。重复前述充放电循环，直至放电容量降低到D0的80％。记录此时电池经过的循环圈数。
9.全电池60℃胀气测试
在60℃下，存储100％充电状态(SOC)的全电池。在存储前后及过程中测量电芯的开路电压(OCV)和交流内阻(IMP)以监控SOC，并测量电芯的体积。其中在每存储48h后取出全电池，静置1h后测试开路电压(OCV)、内阻(IMP)，并在冷却至室温后用排水法测量电芯体积。排水法即先用表盘数据自动进行单位转换的天平单独测量电芯的重力F 1，然后将电芯完全置于去离子水(密度已知为1g/cm 3)中，测量此时的电芯的重力F 2，电芯受到的浮力F 浮即为F 1-F 2，然后根据阿基米德原理F 浮＝ρ×g×V 排，计算得到电芯体积V＝(F 1-F 2)/(ρ×g)。
由OCV、IMP测试结果来看，本实验过程中直至存储结束，实施例的电池始终保持 99％以上的SOC。
存储30天后，测量电芯体积，并计算相对于存储前的电芯体积，存储后的电芯体积增加的百分比。
另外，测量电芯残余容量。在2.5～4.3V下，将全电池按照1C充电至4.3V，然后在4.3V下恒压充电至电流小于等于0.05mA。静置5min，记录此时的充电容量为电芯残余容量。
10.正极活性材料中锰元素和磷元素的测量
将5g上述制得的正极活性材料在100ml逆王水(浓盐酸：浓硝酸＝1：3)中(浓盐酸浓度～37％，浓硝酸浓度～65％)溶解，利用ICP测试溶液各元素的含量，然后对锰元素或磷元素的含量进行测量和换算(锰元素或磷元素的量/正极活性材料的量*100％)，得到其重量占比。
11.晶面间距和夹角测试
取1g上述制得的各正极活性材料粉末于50mL的试管中，并在试管中注入10mL质量分数为75％的酒精，然后进行充分搅拌分散30分钟，然后用干净的一次性塑料吸管取适量上述溶液滴加在300目铜网上，此时，部分粉末将在铜网上残留，将铜网连带样品转移至TEM(Talos F200s G2)样品腔中进行测试，得到TEM测试原始图片，保存原始图片格式(xx.dm3)。将上述TEM测试所得原始图片在DigitalMicrograph软件中打开，并进行傅里叶变换(点击操作后由软件自动完成)得到衍射花样，量取衍射花样中衍射光斑到中心位置的距离，即可得到晶面间距，夹角根据布拉格方程进行计算得到。通过得到的晶面间距和相应夹角数据，与其标准值比对，即可对包覆层的不同物质进行识别。
12.包覆层厚度测试
包覆层的厚度大小测试主要通过FIB从上述制得的正极活性材料单个颗粒中间切取100nm左右厚度的薄片，然后对薄片进行TEM测试，得到TEM测试原始图片，保存原始图片格式(xx.dm3)。
将上述TEM测试所得原始图片在DigitalMicrograph软件中打开，通过晶格间距和夹角信息，识别出包覆层，量取包覆层的厚度。
对所选颗粒测量三个位置处的厚度，取平均值。
13.第三层包覆层碳中SP2形态和SP3形态摩尔比的测定
本测试通过拉曼(Raman)光谱进行。通过对Raman测试的能谱进行分峰，得到Id/Ig，其中Id为SP3形态碳的峰强度，Ig为SP2形态碳的峰强度，从而确认两者的摩尔比。
14.内核化学式及不同包覆层组成的测定
采用球差电镜仪(ACSTEM)对正极活性材料内部微观结构和表面结构进行高空间分 辨率表征，结合三维重构技术得到正极活性材料的内核化学式及不同包覆层的组成。
二、正极材料以及二次电池的制备
实施例1
(1)正极活性材料的制备
S1：制备掺杂的草酸锰
将1.3mol的MnSO 4﹒H 2O、0.7mol的FeSO 4﹒H 2O在混料机中充分混合6小时。将混合物转移至反应釜中，并加入10L去离子水和2mol二水合草酸(以草酸计)。将反应釜加热至80℃，以600rpm的转速搅拌6小时，反应终止(无气泡产生)，得到Fe掺杂的草酸锰悬浮液。然后过滤所述悬浮液，将滤饼在120℃下烘干，之后进行研磨，得到中值粒径Dv 50为100nm左右的Fe掺杂的草酸锰颗粒。
S2：制备共掺杂磷酸锰锂内核
取1mol上述草酸锰颗粒、0.497mol碳酸锂、0.001mol的Mo(SO 4) 3、含有0.999mol磷酸的浓度为85％的磷酸水溶液、0.001mol的H 4SiO 4和0.0005mol的NH 4HF 2加入到20L去离子水中。将混合物转入砂磨机中充分研磨搅拌10小时，得到浆料。将所述浆料转移到喷雾干燥设备中进行喷雾干燥造粒，设定干燥温度为250℃，干燥4小时，得到颗粒。在氮气(90体积％)+氢气(10体积％)保护气氛中，将上述粉料在700℃下烧结10小时，得到Li 0.994Mo 0.001Mn 0.65Fe 0.35P 0.999Si 0.001O 3.999F 0.001，即共掺杂磷酸锰锂内核。
S3：第一包覆层悬浊液的制备
制备Li 2FeP 2O 7溶液，将7.4g碳酸锂，11.6g碳酸亚铁，23.0g磷酸二氢铵和12.6g二水合草酸溶于500mL去离子水中，控制pH为5，然后搅拌并在室温下反应2小时得到溶液，之后将该溶液升温到80℃并保持此温度4小时，得到第一包覆层悬浊液。
S4：第一包覆层的包覆
取10mol(约1574g)按照步骤S2工艺获得的共掺杂磷酸锰锂内核材料加入到步骤S3中获得的第一包覆层悬浊液(第一包覆层物质含量为15.7g)中，充分搅拌混合6小时，混合均匀后，转入120℃烘箱中干燥6小时，然后在650℃下烧结6小时得到焦磷酸盐包覆后的材料。
S5：第二包覆层悬浊液的制备
将3.7g碳酸锂、11.6g碳酸亚铁、11.5g磷酸二氢铵和12.6g二水合草酸溶于1500mL去离子水中，然后搅拌并反应6小时得到溶液，之后将该溶液升温到120℃并保持此温度6小时，得到第二包覆层悬浊液。
S6：第二包覆层的包覆
将步骤S4中获得的焦磷酸盐包覆后的材料加入到步骤S5中得到的第二包覆层悬浊液(第二包覆层物质含量为47.1g)中，充分搅拌混合6小时，混合均匀后，转入120℃烘箱中干燥6小时，然后700℃烧结8小时得到两层包覆后的材料。
S7：第三包覆层水溶液的制备
将37.3g蔗糖溶于500g去离子水中，然后搅拌并充分溶解，得到蔗糖水溶液。
S8：第三包覆层的包覆
将步骤S6中获得的两层包覆的材料加入到步骤S7中得到的蔗糖溶液中，一同搅拌混 合6小时，混合均匀后，转入150℃烘箱中干燥6小时，然后在700℃下烧结10小时得到三层包覆后的材料。
(2)正极极片的制备
将上述制备的三层包覆后的正极活性材料、导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按重量比为97.0:1.2:1.8加入到N-甲基吡咯烷酮(NMP)中，搅拌混合均匀，得到正极浆料。然后将正极浆料按0.280g/1540.25mm 2均匀涂覆于铝箔上，经烘干、冷压、分切，得到正极极片。
(3)负极极片的制备
将负极活性材料人造石墨、硬碳、导电剂乙炔黑、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC)按照重量比为90:5:2:2:1溶于溶剂去离子水中，搅拌混合均匀后制备成负极浆料。将负极浆料按0.117g/1540.25mm 2均匀涂覆在负极集流体铜箔上，经过烘干、冷压、分切，得到负极极片。
(4)电解液的制备
在氩气气氛手套箱中(H 2O<0.1ppm，O 2<0.1ppm)，将有机溶剂碳酸乙烯酯(EC)/碳酸甲乙酯(EMC)按照体积比3/7混合均匀，加入12.5重量％(基于碳酸乙烯酯/碳酸甲乙酯溶剂的重量计)LiPF 6溶解于上述有机溶剂中，搅拌均匀，得到电解液。
(5)隔离膜的制备
使用市售的厚度为20μm、平均孔径为80nm的PP-PE共聚物微孔薄膜(来自卓高电子科技公司，型号20)。
(6)全电池的制备
将上述获得的正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正负极中间起到隔离的作用，并卷绕得到电极组件。将电极组件置于外包装中，注入上述电解液并封装，得到全电池(下文也称“全电”)。
(7)扣式电池的制备
将上述制备的三层包覆后的正极活性材料、聚偏二氟乙烯(PVDF)、乙炔黑以90:5:5的重量比加入至N-甲基吡咯烷酮(NMP)中，在干燥房中搅拌制成浆料。在铝箔上涂覆上述浆料，干燥、冷压制成正极极片。涂覆量为0.2g/cm 2，压实密度为2.0g/cm 3。
采用锂片作为负极，采用1mol/L的LiPF 6在体积比1:1:1的碳酸乙烯酯(EC)、碳酸二乙酯(DEC)和碳酸二甲酯(DMC)中的溶液为电解液，与上述制备的正极极片一起在扣电箱中组装成扣式电池(下文也称“扣电”)。
实施例2
除了在步骤S1和步骤S2中，将FeSO 4﹒H 2O的量改为0.68mol，将Li 2CO 3的量改为0.4885mol，将Mo(SO 4) 3换成MgSO 4，将H 4SiO 4换成HNO 3，在步骤S1制备掺杂的草酸锰时还加入0.02mol的Ti(SO 4) 2之外，其他条件与实施例1相同。
实施例3
除了在步骤S1和步骤S2中，将Li 2CO 3的量改为0.496mol，将Mo(SO 4) 3换成W(SO 4) 3，将H 4SiO 4换成H 2SO 4之外，其他条件与实施例1相同。
实施例4
除了在步骤S1和步骤S2中，将Li 2CO 3的量改为0.4985mol，将0.001mol的Mo(SO 4) 3 换成0.0005mol的Al 2(SO 4) 3，将NH 4HF 2换成NH 4HCl 2之外，其他条件与实施例1相同。
实施例5
除了在步骤S1和步骤S2中，将FeSO 4﹒H 2O的量改为0.69mol，将Li 2CO 3的量改为0.4965mol，将0.001mol的Mo(SO 4) 3换成0.0005mol的Nb 2(SO 4) 5，将H 4SiO 4换成H 2SO 4，在步骤S1制备掺杂的草酸锰时还加入0.01mol的VCl 2之外，其他条件与实施例1相同。
实施例6
除了在步骤S1和步骤S2中，将FeSO 4﹒H 2O的量改为0.68mol，将Li 2CO 3的量改为0.4965mol，将0.001mol的Mo(SO 4) 3换成0.0005mol的Nb 2(SO 4) 5，将H 4SiO 4换成H 2SO 4，在步骤S1制备掺杂的草酸锰时还加入0.01mol的VCl 2和0.01mol的MgSO 4之外，其他条件与实施例1相同。
实施例7
除了在步骤S1和步骤S2中，将MgSO 4换成CoSO 4之外，其他条件与实施例6相同。
实施例8
除了在步骤S1和步骤S2中，将MgSO 4换成NiSO 4之外，其他条件与实施例6相同。
实施例9
除了在步骤S1和步骤S2中，将FeSO 4﹒H 2O的量改为0.698mol，将Li 2CO 3的量改为0.4955mol，将0.001mol的Mo(SO 4) 3换成0.0005mol的Nb 2(SO 4) 5，将H 4SiO 4换成H 2SO 4，将NH 4HF 2换成NH 4HCl 2，在步骤S1制备掺杂的草酸锰时还加入0.002mol的Ti(SO 4) 2之外，其他条件与实施例1相同。
实施例10
除了在步骤S1和步骤S2中，将FeSO 4﹒H 2O的量改为0.68mol，将Li 2CO 3的量改为0.4975mol，将0.001mol的Mo(SO 4) 3换成0.0005mol的Nb 2(SO 4) 5，将NH 4HF 2换成NH 4HBr 2，在步骤S1制备掺杂的草酸锰时还加入0.01mol的VCl 2和0.01mol的MgSO 4之外，其他条件与实施例1相同。
实施例11
除了在步骤S1和步骤S2中，将FeSO 4﹒H 2O的量改为0.69mol，将Li 2CO 3的量改为0.499mol，将Mo(SO 4) 3换成MgSO 4，将NH 4HF 2换成NH 4HBr 2，在步骤S1制备掺杂的草酸锰时还加入0.01mol的VCl 2之外，其他条件与实施例1相同。
实施例12
除了在步骤S1和步骤S2中，将MnSO 4﹒H 2O的量改为1.36mol，将FeSO 4﹒H 2O的量改为0.6mol，将Li 2CO 3的量改为0.4985mol，将Mo(SO 4) 3换成MgSO 4，将H 4SiO 4换成HNO 3，在步骤S1制备掺杂的草酸锰时还加入0.04mol的VCl 2之外，其他条件与实施例1相同。
实施例13
除了在步骤S1和步骤S2中，将MnSO 4﹒H 2O的量改为1.16mol，将FeSO 4﹒H 2O的量改为0.8mol之外，其他条件与实施例12相同。
实施例14
除了在步骤S1和步骤S2中，将MnSO 4﹒H 2O的量改为1.3mol，将VCl 2的量改为0.1mol之外，其他条件与实施例12相同。
实施例15
除了在步骤S1和步骤S2中，将MnSO 4﹒H 2O的量改为1.2mol，将Li 2CO 3的量改为0.494mol，将0.001mol的Mo(SO 4) 3换成0.005mol的MgSO 4，将H 4SiO 4换成H 2SO 4，在步骤S1制备掺杂的草酸锰时还加入0.1mol的VCl 2之外，其他条件与实施例1相同。
实施例16
除了在步骤S1和步骤S2中，将MnSO 4﹒H 2O的量改为1.2mol，将Li 2CO 3的量改为0.467mol，将0.001mol的Mo(SO 4) 3换成0.005mol的MgSO 4，将0.001mol的H 4SiO 4换成0.005mol的H 2SO 4，将1.175mol浓度为85％的磷酸换成1.171mol浓度为85％的磷酸，在步骤S1制备掺杂的草酸锰时还加入0.1mol的VCl 2之外，其他条件与实施例1相同。
实施例17
除了在步骤S1和步骤S2中，将MnSO 4﹒H 2O的量改为1.2mol，将Li 2CO 3的量改为0.492mol，将0.001mol的Mo(SO 4) 3换成0.005mol的MgSO 4，将H 4SiO 4换成H 2SO 4，将0NH 4HF 2的量改为0.0025mol，在步骤S1制备掺杂的草酸锰时还加入0.1mol的VCl 2之外，其他条件与实施例1相同。
实施例18
除了在步骤S1和步骤S2中，将FeSO 4﹒H 2O的量改为0.5mol，将Li 2CO 3的量改为0.492mol，将0.001mol的Mo(SO 4) 3换成0.005mol的MgSO 4，将H 4SiO 4换成H 2SO 4，将NH 4HF 2的量改为0.0025mol，在步骤S1制备掺杂的草酸锰时还加入0.1mol的VCl 2和0.1mol的CoSO 4之外，其他条件与实施例1相同。
实施例19
除了在步骤S1和步骤S2中，将FeSO 4﹒H 2O的量改为0.4mol，将CoSO 4的量改为0.2mol之外，其他条件与实施例18相同。
实施例20
除了在步骤S1和步骤S2中，将MnSO 4﹒H 2O的量改为1.5mol，将FeSO 4﹒H 2O的量改为0.1mol，将CoSO 4的量改为0.3mol之外，其他条件与实施例18相同。
实施例21
除了在步骤S1和步骤S2中，将CoSO 4换成NiSO 4之外，其他条件与实施例18相同。
实施例22
除了在步骤S1和步骤S2中，将MnSO 4﹒H 2O的量改为1.5mol，将FeSO 4﹒H 2O的量改为0.2mol，将0.1mol的CoSO 4换成0.2mol的NiSO 4之外，其他条件与实施例18相同。
实施例23
除了在步骤S1和步骤S2中，将MnSO 4﹒H 2O的量改为1.4mol，将FeSO 4﹒H 2O的量改为0.3mol，将CoSO 4的量改为0.2mol之外，其他条件与实施例18相同。
实施例24
除了在步骤S1和步骤S2中，将MnSO 4﹒H 2O的量改为1.2mol，将FeSO 4﹒H 2O的量改为0.5mol，将CoSO 4的量改为0.2mol之外，其他条件与实施例18相同。
实施例25
除了在步骤S1和步骤S2中，将MnSO 4﹒H 2O的量改为1.0mol，将FeSO 4﹒H 2O的量改为0.7mol，将CoSO 4的量改为0.2mol之外，其他条件与实施例18相同。
实施例26
除了在步骤S1和步骤S2中，将MnSO 4﹒H 2O的量改为1.4mol，将FeSO 4﹒H 2O的量改为0.3mol，将Li 2CO 3的量改为0.4825mol，将0.001mol的Mo(SO 4) 3换成0.005mol的MgSO 4，将H 4SiO 4的量改为0.1mol，将磷酸的量改为0.9mol，将NH 4HF 2的量改为0.04mol，在步骤S1制备掺杂的草酸锰时还加入0.1mol的VCl 2和0.2mol的CoSO 4之外，其他条件与实施例1相同。
实施例27
除了在步骤S1和步骤S2中，将MnSO 4﹒H 2O的量改为1.4mol，将FeSO 4﹒H 2O的量改为0.3mol，将Li 2CO 3的量改为0.485mol，将0.001mol的Mo(SO 4) 3换成0.005mol的MgSO 4，将H 4SiO 4的量改为0.08mol，将磷酸的量改为0.92mol，将NH 4HF 2的量改为0.05mol，在步骤S1制备掺杂的草酸锰时还加入0.1mol的VCl 2和0.2mol的CoSO 4之外，其他条件与实施例1相同。
实施例28至44
除了在步骤S3至步骤S6中，选择不同的第一包覆层物质或第二包覆层物质进行包覆之外，其他条件与实施例1相同。各包覆层物质的制备方法参见表1和表2。
实施例45至59
除了在步骤S4、步骤S6、步骤S8中，将所使用的各包覆层物质按照表8中所示包覆量对应调整各种原料的用量之外，其他条件与实施例1相同。
实施例60
除了在步骤S4中，将粉末烧结步骤中的烧结温度调整为550℃，烧结时间调整为1小时以控制Li 2FeP 2O 7的结晶度为30％，在步骤S5中将包覆烧结温度调整为650℃，烧结时间调整为2小时以控制LiFePO 4的结晶度为30％之外，其他条件与实施例1相同。
实施例61
除了在步骤S4中，将粉末烧结步骤中的烧结温度调整为550℃，烧结时间调整为2小时以控制Li 2FeP 2O 7的结晶度为50％，在步骤S5中将包覆烧结温度调整为650℃，烧结时间调整为3小时以控制LiFePO 4的结晶度为50％之外，其他条件与实施例1相同。
实施例62
除了在步骤S4中，将粉末烧结步骤中的烧结温度调整为600℃，烧结时间调整为3小时以控制Li 2FeP 2O 7的结晶度为70％，在步骤S5中将包覆烧结温度调整为650℃，烧结时间调整为4小时以控制LiFePO 4的结晶度为70％之外，其他条件与实施例1相同。
对比例1
除了改变正极活性材料的制备步骤，其他条件与实施例1相同。
制备草酸锰：将1mol的MnSO 4﹒H 2O加至反应釜中，并加入10L去离子水和1mol二水合草酸(以草酸计)。将反应釜加热至80℃，以600rpm的转速搅拌6小时,反应终止(无气泡产生)，得到草酸锰悬浮液。然后过滤所述悬浮液，将滤饼在120℃下烘干，之后进行研磨，得到中值粒径Dv 50为50-200nm的草酸锰颗粒。
制备正极活性材料：取1mol上述草酸锰颗粒、0.5mol碳酸锂、含有1mol磷酸的浓度为85％的磷酸水溶液和0.01mol蔗糖加入到20L去离子水中。将混合物转入砂磨机中充分研磨搅拌10小时，得到浆料。将所述浆料转移到喷雾干燥设备中进行喷雾干燥造粒，设 定干燥温度为250℃，干燥4小时，得到颗粒。在氮气(90体积％)+氢气(10体积％)保护气氛中，将上述粉料在700℃下烧结10小时，得到碳包覆的LiMnPO 4。
对比例2
除了在对比例1中，将1mol的MnSO 4﹒H 2O换成0.85mol的MnSO 4﹒H 2O和0.15mol的FeSO 4﹒H 2O，并加入到混料机中充分混合6小时之后再加入反应釜之外，其他条件与对比例1相同。
对比例3
除了改变正极活性材料的制备步骤，其他条件与实施例1相同。
制备掺杂的草酸锰：将1.9mol的MnSO 4﹒H 2O、0.1mol的ZnSO 4在混料机中充分混合6小时。将混合物转移至反应釜中，并加入10L去离子水和2mol二水合草酸(以草酸计)。将反应釜加热至80℃，以600rpm的转速搅拌6小时，反应终止(无气泡产生)，得到Fe掺杂的草酸锰悬浮液。然后过滤所述悬浮液，将滤饼在120℃下烘干，之后进行研磨，得到中值粒径Dv 50为100nm左右的Fe掺杂的草酸锰颗粒。
制备正极活性材料：取1mol上述草酸锰颗粒、0.495mol碳酸锂、0.005mol的MgSO 4、含有1mol磷酸的浓度为85％的磷酸水溶液和0.01mol蔗糖加入到20L去离子水中。将混合物转入砂磨机中充分研磨搅拌10小时，得到浆料。将所述浆料转移到喷雾干燥设备中进行喷雾干燥造粒，设定干燥温度为250℃，干燥4小时，得到颗粒。在氮气(90体积％)+氢气(10体积％)保护气氛中，将上述粉料在700℃下烧结10小时，得到碳包覆的Li 0.990Mg 0.005Mn 0.95Zn 0.05PO 4。
对比例4
除了改变正极活性材料的制备步骤，其他条件与实施例1相同。
制备掺杂的草酸锰：将1.2mol的MnSO 4﹒H 2O、0.8mol的FeSO 4﹒H 2O在混料机中充分混合6小时。将混合物转移至反应釜中，并加入10L去离子水和2mol二水合草酸(以草酸计)。将反应釜加热至80℃，以600rpm的转速搅拌6小时，反应终止(无气泡产生)，得到Fe掺杂的草酸锰悬浮液。然后过滤所述悬浮液，将滤饼在120℃下烘干，之后进行研磨，得到中值粒径Dv 50为100nm左右的Fe掺杂的草酸锰颗粒。
制备正极活性材料：取1mol上述草酸锰颗粒、0.45mol碳酸锂、0.005的Nb 2(SO 4) 5、含有1mol磷酸的浓度为85％的磷酸水溶液、0.025mol的NH 4HF 2和0.01mol蔗糖加入到20L去离子水中。将混合物转入砂磨机中充分研磨搅拌10小时，得到浆料。将所述浆料转移到喷雾干燥设备中进行喷雾干燥造粒，设定干燥温度为250℃，干燥4小时，得到颗粒。在氮气(90体积％)+氢气(10体积％)保护气氛中，将上述粉料在700℃下烧结10小时，得到碳包覆的Li 0.90Nb 0.01Mn 0.6Fe 0.4PO 3.95F 0.05。
对比例5
除了改变正极活性材料的制备步骤，其他条件与实施例1相同。
制备掺杂的草酸锰：将1.4mol的MnSO 4﹒H 2O、0.6mol的FeSO 4﹒H 2O在混料机中充分混合6小时。将混合物转移至反应釜中，并加入10L去离子水和2mol二水合草酸(以草酸计)。将反应釜加热至80℃，以600rpm的转速搅拌6小时，反应终止(无气泡产生)，得到Fe掺杂的草酸锰悬浮液。然后过滤所述悬浮液，将滤饼在120℃下烘干，之后进行研磨，得到中值粒径Dv 50为100nm左右的Fe掺杂的草酸锰颗粒。
制备正极活性材料：取1mol上述草酸锰颗粒、0.38mol碳酸锂、0.12mol的MgSO 4、含有0.999mol磷酸的浓度为85％的磷酸水溶液、0.001mol的H 4SiO 4、0.0005mol的NH 4HF 2和0.01mol蔗糖加入到20L去离子水中。将混合物转入砂磨机中充分研磨搅拌10小时，得到浆料。将所述浆料转移到喷雾干燥设备中进行喷雾干燥造粒，设定干燥温度为250℃，干燥4小时，得到颗粒。在氮气(90体积％)+氢气(10体积％)保护气氛中，将上述粉料在700℃下烧结10小时，得到碳包覆的Li 0.76Mg 0.12Mn 0.7Fe 0.3P 0.999Si 0.001O 3.999F 0.001。
对比例6
除了改变正极活性材料的制备步骤，其他条件与实施例1相同。
制备掺杂的草酸锰：将0.8mol的MnSO 4﹒H 2O、1.2mol的ZnSO 4在混料机中充分混合6小时。将混合物转移至反应釜中，并加入10L去离子水和2mol二水合草酸(以草酸计)。将反应釜加热至80℃，以600rpm的转速搅拌6小时，反应终止(无气泡产生)，得到Fe掺杂的草酸锰悬浮液。然后过滤所述悬浮液，将滤饼在120℃下烘干，之后进行研磨，得到中值粒径Dv 50为100nm左右的Fe掺杂的草酸锰颗粒。
制备正极活性材料：取1mol上述草酸锰颗粒、0.499mol碳酸锂、0.001mol的MgSO 4、含有0.999mol磷酸的浓度为85％的磷酸水溶液、0.001mol的H 4SiO 4、0.0005mol的NH 4HF 2和0.01mol蔗糖加入到20L去离子水中。将混合物转入砂磨机中充分研磨搅拌10小时，得到浆料。将所述浆料转移到喷雾干燥设备中进行喷雾干燥造粒，设定干燥温度为250℃，干燥4小时，得到颗粒。在氮气(90体积％)+氢气(10体积％)保护气氛中，将上述粉料在700℃下烧结10小时，得到碳包覆的Li 0.998Mg 0.001Mn 0.4Zn 0.6P 0.999Si 0.001O 3.999F 0.001。
对比例7
除了改变正极活性材料的制备步骤，其他条件与实施例1相同。
制备掺杂的草酸锰：将1.4mol的MnSO 4﹒H 2O、0.6mol的FeSO 4﹒H 2O在混料机中充分混合6小时。将混合物转移至反应釜中，并加入10L去离子水和2mol二水合草酸(以草酸计)。将反应釜加热至80℃，以600rpm的转速搅拌6小时，反应终止(无气泡产生)，得到Fe掺杂的草酸锰悬浮液。然后过滤所述悬浮液，将滤饼在120℃下烘干，之后进行研磨，得到中值粒径Dv 50为100nm左右的Fe掺杂的草酸锰颗粒。
制备正极活性材料：取1mol上述草酸锰颗粒、0.534mol碳酸锂、0.001mol的MgSO 4、含有0.88mol磷酸的浓度为85％的磷酸水溶液、0.12mol的H 4SiO 4、0.025mol的NH 4HF 2和0.01mol蔗糖加入到20L去离子水中。将混合物转入砂磨机中充分研磨搅拌10小时，得到浆料。将所述浆料转移到喷雾干燥设备中进行喷雾干燥造粒，设定干燥温度为250℃，干燥4小时，得到颗粒。在氮气(90体积％)+氢气(10体积％)保护气氛中，将上述粉料在700℃下烧结10小时，得到碳包覆的Li 1.068Mg 0.001Mn 0.7Fe 0.3P 0.88Si 0.12O 3.95F 0.05。
对比例8
除了改变正极活性材料的制备步骤，其他条件与实施例1相同。
制备掺杂的草酸锰：将1.2mol的MnSO 4﹒H 2O、0.8mol的FeSO 4﹒H 2O在混料机中充分混合6小时。将混合物转移至反应釜中，并加入10L去离子水和2mol二水合草酸(以草酸计)。将反应釜加热至80℃，以600rpm的转速搅拌6小时，反应终止(无气泡产生)，得到Fe掺杂的草酸锰悬浮液。然后过滤所述悬浮液，将滤饼在120℃下烘干，之后进行研磨，得到中值粒径Dv 50为100nm左右的Fe掺杂的草酸锰颗粒。
制备正极活性材料：取1mol上述草酸锰颗粒、0.474mol碳酸锂、0.001mol的MgSO 4、含有0.93mol磷酸的浓度为85％的磷酸水溶液、0.07mol的H 4SiO 4、0.06mol的NH 4HF 2和0.01mol蔗糖加入到20L去离子水中。将混合物转入砂磨机中充分研磨搅拌10小时，得到浆料。将所述浆料转移到喷雾干燥设备中进行喷雾干燥造粒，设定干燥温度为250℃，干燥4小时，得到颗粒。在氮气(90体积％)+氢气(10体积％)保护气氛中，将上述粉料在700℃下烧结10小时，得到碳包覆的Li 0.948Mg 0.001Mn 0.6Fe 0.4P 0.93Si 0.07O 3.88F 0.12。
对比例9
除了改变正极活性材料的制备步骤，其他条件与实施例1相同。
制备掺杂的草酸锰：将1.3mol的MnSO 4﹒H 2O、0.7mol的FeSO 4﹒H 2O在混料机中充分混合6小时。将混合物转移至反应釜中，并加入10L去离子水和2mol二水合草酸(以草酸计)。将反应釜加热至80℃，以600rpm的转速搅拌6小时，反应终止(无气泡产生)，得到Fe掺杂的草酸锰悬浮液。然后过滤所述悬浮液，将滤饼在120℃下烘干，之后进行研磨，得到中值粒径Dv 50为100nm左右的Fe掺杂的草酸锰颗粒。
制备正极活性材料：取1mol上述草酸锰颗粒、0.497mol碳酸锂、0.001mol的Mo(SO 4) 3、含有0.999mol磷酸的浓度为85％的磷酸水溶液、0.001mol的H 4SiO 4、0.0005mol的NH 4HF 2和0.01mol蔗糖加入到20L去离子水中。将混合物转入砂磨机中充分研磨搅拌10小时，得到浆料。将所述浆料转移到喷雾干燥设备中进行喷雾干燥造粒，设定干燥温度为250℃，干燥4小时，得到颗粒。在氮气(90体积％)+氢气(10体积％)保护气氛中，将上述粉料在700℃下烧结10小时，得到碳包覆的Li 0.994Mo 0.001Mn 0.65Fe 0.35P 0.999Si 0.001O 3.999F 0.001。
对比例10
除了改变步骤S4以及不执行步骤S5和S6之外，其他条件与实施例1相同。
S4：第一包覆层的包覆
取10mol(约1574g)按照步骤S2工艺获得的共掺杂磷酸锰锂内核材料加入到步骤S3中获得的第一包覆层悬浊液(第一包覆层物质含量为62.8g)中，充分搅拌混合6小时，混合均匀后，转入120℃烘箱中干燥6小时，然后在500℃下烧结4小时，以控制Li 2FeP 2O 7的结晶度为5％，得到非晶态Li 2FeP 2O 7包覆后的材料。
对比例11
除了改变步骤S6以及不执行步骤S3和S4之外，其他条件与实施例1相同。
S6：第二包覆层的包覆
取10mol(约1574g)按照步骤S2工艺获得的共掺杂磷酸锰锂内核材料加入到步骤S5中得到的第二包覆层悬浊液(第二包覆层物质含量为62.8g)中，充分搅拌混合6小时，混合均匀后，转入120℃烘箱中干燥6小时，然后在600℃下烧结4小时，以控制LiFePO 4的结晶度为8％，得到非晶态LiFePO 4包覆的材料。
对比例12
除了改变步骤S4和步骤S6之外，其他条件与实施例1相同。
S4：第一包覆层的包覆
取10mol(约1574g)按照步骤S2工艺获得的共掺杂磷酸锰锂内核材料加入到步骤S3中获得的第一包覆层悬浊液(第一包覆层物质含量为15.7g)中，充分搅拌混合6小时，混合均匀后，转入120℃烘箱中干燥6小时，然后在500℃下烧结4小时，以控制Li 2FeP 2O 7 的结晶度为5％，得到非晶态Li 2FeP 2O 7包覆后的材料。
S6：第二包覆层的包覆
将步骤S4中获得的非晶态Li 2FeP 2O 7包覆后的材料加入到步骤S5中得到的第二包覆层悬浊液(第二包覆层物质含量为47.1g)中，充分搅拌混合6小时，混合均匀后，转入120℃烘箱中干燥6小时，然后在600℃下烧结4小时，以控制LiFePO 4的结晶度为8％，得到非晶态Li 2FeP 2O 7和非晶态LiFePO 4包覆后的材料。
表1
Figure PCTCN2022126838-appb-000001
表2
Figure PCTCN2022126838-appb-000002
Figure PCTCN2022126838-appb-000003
表3示出对比例1至12的正极活性材料组成。
表4示出对比例1至12的正极活性材料、正极极片、扣电或全电按照上述性能测试方法测得的性能数据。
表5示出实施例1-44的正极活性材料组成。
表6示出实施例1-44的正极活性材料、正极极片、扣电或全电按照上述性能测试方法测得的性能数据。
表3
Figure PCTCN2022126838-appb-000004
Figure PCTCN2022126838-appb-000005
表4
Figure PCTCN2022126838-appb-000006
表5
Figure PCTCN2022126838-appb-000007
Figure PCTCN2022126838-appb-000008
Figure PCTCN2022126838-appb-000009
表6
Figure PCTCN2022126838-appb-000010
Figure PCTCN2022126838-appb-000011
Figure PCTCN2022126838-appb-000012
由表4和表6可知，本申请通过对磷酸锰锂的Li位、Mn位、P位和O位同时以特定量掺杂特定的元素进行改性以及对磷酸锰锂进行多层包覆，由此得到的正极活性材料实现了更小的晶格变化率、更小的Li/Mn反位缺陷浓度、更大的压实密度、更接近于-2价的表面氧价态、更少的循环后Mn和Fe溶出量，从而本申请的电池具有更好的性能，例如具有更高的容量、更好的高温存储性能和高温循环性能。
图7示出未掺杂的LiMnPO 4和实施例2制备的正极活性材料内核的X射线衍射图谱(XRD)图。由图中可以看出，实施例2的正极活性材料内核的XRD图中主要特征峰位置与未掺杂的LiMnPO 4的一致，说明掺杂过程没有引入杂质相，性能的改善主要是来自元素掺杂，而不是杂相导致的。图8示出实施例2制备的正极活性材料内核的X射线能量色散谱(EDS)图。图中点状分布的为各掺杂元素。由图中可以看出实施例2制备的正极活性材料内核中，元素掺杂均匀。
从实施例12-27中还可以看出，在其他元素相同的情况下，(1-y):y在1至4范围内且m:x在9到1100范围内，可选地，(1-y):y在1.5至3范围内且m:x在190至998范围内时，能够进一步提升电池的能量密度和循环性能。
表7示出实施例32至44的第一包覆层物质和第二包覆层物质的晶面间距和夹角。
表7
Figure PCTCN2022126838-appb-000013
由表7可知，本申请第一包覆层和第二包覆层的晶面间距和夹角均在本申请所述范围内，并且结合表6可知，采用这些第一包覆层和第二包覆层时同样获得了具有良好性能的正极活性材料并实现了良好的电池性能结果。
表8示出实施例45至59的正极活性材料组成。
表9示出实施例45至59的正极活性材料、正极极片、扣电或全电按照上述性能测试方法测得的性能数据。
表8
Figure PCTCN2022126838-appb-000014
表9
Figure PCTCN2022126838-appb-000015
Figure PCTCN2022126838-appb-000016
由表9可知，包覆层的包覆量在合适的范围内时，可以进一步改善正极活性材料以及电池的性能。
表10示出实施例60至62的正极活性材料、正极极片、扣电或全电按照上述性能测试方法测得的性能数据。
表10
Figure PCTCN2022126838-appb-000017
由表10可以看出，随着焦磷酸盐和磷酸盐的结晶度逐渐增加，对应正极活性材料的晶格变化率、Li/Mn反位缺陷浓度以及循环后Fe和Mn溶出量逐渐下降，电池的容量逐渐增加，高温循环性能和高温存储性能也逐渐改善。
下面详述内核为Li 1+xC mMn 1-yA yP 1-zR zO 4-nD n，壳包括第一包覆层(焦磷酸盐和磷酸盐)，第二包覆层包含碳的情况下的具体实施例：
实施例1-A
(1)正极活性材料的制备
S1：制备掺杂的草酸锰
各项参数同实施例1的S1步骤。
S2：制备共掺杂磷酸锰锂内核
各项参数同实施例1的S2步骤，得到Li 0.994Mo 0.001Mn 0.65Fe 0.35P 0.999Si 0.001O 3.999F 0.001，即共掺杂磷酸锰锂内核。
S3：制备焦磷酸铁锂粉末
将4.77g碳酸锂、7.47g碳酸亚铁、14.84g磷酸二氢铵和1.3g二水合草酸溶于50mL去离子水中。混合物的pH为5，搅拌2小时使反应混合物充分反应。然后将反应后的溶液升温到80℃并保持该温度4小时，得到包含Li 2FeP 2O 7的悬浊液，将悬浊液进行过滤，用去离子水洗涤，并在120℃下干燥4小时，得到粉末。将所述粉末在650℃、氮气气氛下烧结8小时，并自然冷却至室温后进行研磨，得到Li 2FeP 2O 7粉末。
S4：制备磷酸铁锂悬浊液
将11.1g碳酸锂、34.8g碳酸亚铁、34.5g磷酸二氢铵、1.3g二水合草酸和37.3g蔗糖(以C 12H 22O 11计，下同)溶于150mL去离子水中，得到混合物，然后搅拌6小时使上述混合物充分反应。然后将反应后的溶液升温到120℃并保持该温度6小时，得到包含蔗糖和LiFePO 4的悬浊液。
S5：包覆
取10mol(约1570g)按照步骤S2工艺获得的共掺杂的磷酸锰锂内核与15.7g步骤S3获得的Li 2FeP 2O 7粉末加入到步骤S4获得的LiFePO 4悬浊液(包含37.3g蔗糖和47.2g的LiFePO 4)中，搅拌混合均匀后转入真空烘箱中在150℃下干燥6小时。然后通过砂磨分散所得产物。在分散后，将所得产物在氮气气氛中、在700℃下烧结6小时，得到正极活性材料。
(2)正极极片的制备
将上述正极活性材料、导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按重量比为92:2.5:5.5加入到N-甲基吡咯烷酮(NMP)中，搅拌混合均匀，得到正极浆料。然后将正极浆料按0.280g/1540.25mm 2均匀涂覆于铝箔上，经烘干、冷压、分切，得到正极极片。
(3)负极极片的制备
各项参数同实施例1的负极极片制备。
(4)电解液的制备
各项参数同实施例1的电解液。
(5)隔离膜
各项参数同实施例1的隔离膜。
(6)全电池以及扣式电池的制备
各项参数同实施例1，获取全电池(下文也称“全电”)、扣式电池(下文也称“扣电”)。
实施例2-A
除了在步骤S1和步骤S2中，将FeSO 4﹒H 2O的量改为0.68mol，将Li 2CO 3的量改为0.4885mol，将Mo(SO 4) 3换成MgSO 4，将H 4SiO 4换成HNO 3，在步骤S1制备掺杂的草酸锰时还加入0.02mol的Ti(SO 4) 2之外，其他条件与实施例1-A相同。
实施例3-A
除了在步骤S1和步骤S2中，将Li 2CO 3的量改为0.496mol，将Mo(SO 4) 3换成W(SO 4) 3，将H 4SiO 4换成H 2SO 4之外，其他条件与实施例1-A相同。
实施例4-A
除了在步骤S1和步骤S2中，将Li 2CO 3的量改为0.4985mol，将0.001mol的Mo(SO 4) 3换成0.0005mol的Al 2(SO 4) 3，将NH 4HF 2换成NH 4HCl 2之外，其他条件与实施例1-A相同。
实施例5-A
除了在步骤S1和步骤S2中，将FeSO 4﹒H 2O的量改为0.69mol，将Li 2CO 3的量改为0.4965mol，将0.001mol的Mo(SO 4) 3换成0.0005mol的Nb 2(SO 4) 5，将H 4SiO 4换成H 2SO 4，在步骤S1制备掺杂的草酸锰时还加入0.01mol的VCl 2之外，其他条件与实施例1-A相同。
实施例6-A
除了在步骤S1和步骤S2中，将FeSO 4﹒H 2O的量改为0.68mol，将Li 2CO 3的量改为0.4965mol，将0.001mol的Mo(SO 4) 3换成0.0005mol的Nb 2(SO 4) 5，将H 4SiO 4换成H 2SO 4，在步骤S1制备掺杂的草酸锰时还加入0.01mol的VCl 2和0.01mol的MgSO 4之外，其他条件与实施例1-A相同。
实施例7-A
除了在步骤S1和步骤S2中，将MgSO 4换成CoSO 4之外，其他条件与实施例6-A相同。
实施例8-A
除了在步骤S1和步骤S2中，将MgSO 4换成NiSO 4之外，其他条件与实施例6-A相同。
实施例9-A
除了在步骤S1和步骤S2中，将FeSO 4﹒H 2O的量改为0.698mol，将Li 2CO 3的量改为0.4955mol，将0.001mol的Mo(SO 4) 3换成0.0005mol的Nb 2(SO 4) 5，将H 4SiO 4换成H 2SO 4，将NH 4HF 2换成NH 4HCl 2，在步骤S1制备掺杂的草酸锰时还加入0.002mol的Ti(SO 4) 2之外，其他条件与实施例1-A相同。
实施例10-A
除了在步骤S1和步骤S2中，将FeSO 4﹒H 2O的量改为0.68mol，将Li 2CO 3的量改为0.4975mol，将0.001mol的Mo(SO 4) 3换成0.0005mol的Nb 2(SO 4) 5，将NH 4HF 2换成NH 4HBr 2，在步骤S1制备掺杂的草酸锰时还加入0.01mol的VCl 2和0.01mol的MgSO 4之外，其他条件与实施例1-A相同。
实施例11-A
除了在步骤S1和步骤S2中，将FeSO 4﹒H 2O的量改为0.69mol，将Li 2CO 3的量改为0.499mol，将Mo(SO 4) 3换成MgSO 4，将NH 4HF 2换成NH 4HBr 2，在步骤S1制备掺杂的草酸锰时还加入0.01mol的VCl 2之外，其他条件与实施例1-A相同。
实施例12-A
除了在步骤S1和步骤S2中，将MnSO 4﹒H 2O的量改为1.36mol，将FeSO 4﹒H 2O的量改为0.6mol，将Li 2CO 3的量改为0.4985mol，将Mo(SO 4) 3换成MgSO 4，将H 4SiO 4换成HNO 3，在步骤S1制备掺杂的草酸锰时还加入0.04mol的VCl 2之外，其他条件与实施例1-A相同。
实施例13-A
除了在步骤S1和步骤S2中，将MnSO 4﹒H 2O的量改为1.16mol，将FeSO 4﹒H 2O的量改为0.8mol之外，其他条件与实施例12-A相同。
实施例14-A
除了在步骤S1和步骤S2中，将MnSO 4﹒H 2O的量改为1.3mol，将VCl 2的量改为0.1mol之外，其他条件与实施例12-A相同。
实施例15-A
除了在步骤S1和步骤S2中，将MnSO 4﹒H 2O的量改为1.2mol，将Li 2CO 3的量改为0.494mol，将0.001mol的Mo(SO 4) 3换成0.005mol的MgSO 4，将H 4SiO 4换成H 2SO 4，在步骤S1制备掺杂的草酸锰时还加入0.1mol的VCl 2之外，其他条件与实施例1-A相同。
实施例16-A
除了在步骤S1和步骤S2中，将MnSO 4﹒H 2O的量改为1.2mol，将Li 2CO 3的量改为0.467mol，将0.001mol的Mo(SO 4) 3换成0.005mol的MgSO 4，将0.001mol的H 4SiO 4换成0.005mol的H 2SO 4，将1.175mol浓度为85％的磷酸换成1.171mol浓度为85％的磷酸，在步骤S1制备掺杂的草酸锰时还加入0.1mol的VCl 2之外，其他条件与实施例1-A相同。
实施例17-A
除了在步骤S1和步骤S2中，将MnSO 4﹒H 2O的量改为1.2mol，将Li 2CO 3的量改为0.492mol，将0.001mol的Mo(SO 4) 3换成0.005mol的MgSO 4，将H 4SiO 4换成H 2SO 4，将0NH 4HF 2的量改为0.0025mol，在步骤S1制备掺杂的草酸锰时还加入0.1mol的VCl 2之外，其他条件与实施例1-A相同。
实施例18-A
除了在步骤S1和步骤S2中，将FeSO 4﹒H 2O的量改为0.5mol，将Li 2CO 3的量改为0.492mol，将0.001mol的Mo(SO 4) 3换成0.005mol的MgSO 4，将H 4SiO 4换成H 2SO 4，将NH 4HF 2的量改为0.0025mol，在步骤S1制备掺杂的草酸锰时还加入0.1mol的VCl 2和0.1mol的CoSO 4之外，其他条件与实施例1-A相同。
实施例19-A
除了在步骤S1和步骤S2中，将FeSO 4﹒H 2O的量改为0.4mol，将CoSO 4的量改为0.2mol之外，其他条件与实施例18-A相同。
实施例20-A
除了在步骤S1和步骤S2中，将MnSO 4﹒H 2O的量改为1.5mol，将FeSO 4﹒H 2O的量改为0.1mol，将CoSO 4的量改为0.3mol之外，其他条件与实施例18-A相同。
实施例21-A
除了在步骤S1和步骤S2中，将CoSO 4换成NiSO 4之外，其他条件与实施例18相同。
实施例22-A
除了在步骤S1和步骤S2中，将MnSO 4﹒H 2O的量改为1.5mol，将FeSO 4﹒H 2O的量改为0.2mol，将0.1mol的CoSO 4换成0.2mol的NiSO 4之外，其他条件与实施例18-A相同。
实施例23-A
除了在步骤S1和步骤S2中，将MnSO 4﹒H 2O的量改为1.4mol，将FeSO 4﹒H 2O的量改为0.3mol，将CoSO 4的量改为0.2mol之外，其他条件与实施例18-A相同。
实施例24-A
除了在步骤S1和步骤S2中，将MnSO 4﹒H 2O的量改为1.2mol，将FeSO 4﹒H 2O的量改为0.5mol，将CoSO 4的量改为0.2mol之外，其他条件与实施例18-A相同。
实施例25-A
除了在步骤S1和步骤S2中，将MnSO 4﹒H 2O的量改为1.0mol，将FeSO 4﹒H 2O的量改为0.7mol，将CoSO 4的量改为0.2mol之外，其他条件与实施例18-A相同。
实施例26-A
除了在步骤S1和步骤S2中，将MnSO 4﹒H 2O的量改为1.4mol，将FeSO 4﹒H 2O的量改为0.3mol，将Li 2CO 3的量改为0.4825mol，将0.001mol的Mo(SO 4) 3换成0.005mol的MgSO 4，将H 4SiO 4的量改为0.1mol，将磷酸的量改为0.9mol，将NH 4HF 2的量改为0.04mol，在步骤S1制备掺杂的草酸锰时还加入0.1mol的VCl 2和0.2mol的CoSO 4之外，其他条件与实施例1-A相同。
实施例27-A
除了在步骤S1和步骤S2中，将MnSO 4﹒H 2O的量改为1.4mol，将FeSO 4﹒H 2O的量改为0.3mol，将Li 2CO 3的量改为0.485mol，将0.001mol的Mo(SO 4) 3换成0.005mol的MgSO 4，将H 4SiO 4的量改为0.08mol，将磷酸的量改为0.92mol，将NH 4HF 2的量改为0.05mol，在步骤S1制备掺杂的草酸锰时还加入0.1mol的VCl 2和0.2mol的CoSO 4之外，其他条件与实施例1-A相同。
实施例28-A至32-A
除了在步骤S3和步骤S4中，将所使用的原料按照表5中所示包覆量对应调整各种原料的用量以使实施例28至32中Li 2FeP 2O 7/LiFePO 4的用量分别为12.6g/37.7g、14.1g/42.4g、18.8g/56.5g、22.0/66.0g和25.1g/75.4g之外，其他条件与实施例1-A相同。
实施例33-A至36-A
除了在步骤S4中，将蔗糖的用量分别调整为74.6g、149.1g、186.4g和223.7g以使作为第二包覆层的碳层的对应包覆量分别为31.4g、62.9g、78.6g和94.3g之外，其他条件与实施例1-A相同。
实施例37-A至40-A
除了在步骤S3和步骤S4中，将所使用的原料按照表5中所示包覆量对应调整各种原料的用量以使实施例37至40中Li 2FeP 2O 7/LiFePO 4的用量分别为23.6g/39.3g、31.4g/31.4g、39.3g/23.6g和47.2g/15.7g之外，其他条件与实施例1-A相同。
实施例41-A
除了在步骤S4中，将粉末烧结步骤中的烧结温度调整为550℃，烧结时间调整为1小时以控制Li 2FeP 2O 7的结晶度为30％，在步骤S5中将包覆烧结温度调整为650℃，烧结时间调整为2小时以控制LiFePO 4的结晶度为30％之外，其他条件与实施例1-A相同。
实施例42-A
除了在步骤S4中，将粉末烧结步骤中的烧结温度调整为550℃，烧结时间调整为2小时以控制Li 2FeP 2O 7的结晶度为50％，在步骤S5中将包覆烧结温度调整为650℃，烧结时间调整为3小时以控制LiFePO 4的结晶度为50％之外，其他条件与实施例1-A相同。
实施例43-A
除了在步骤S4中，将粉末烧结步骤中的烧结温度调整为600℃，烧结时间调整为3小时以控制Li 2FeP 2O 7的结晶度为70％，在步骤S5中将包覆烧结温度调整为650℃，烧结时间调整为4小时以控制LiFePO 4的结晶度为70％之外，其他条件与实施例1-A相同。
实施例44-A至57-A
除了改变步骤S1制备掺杂的草酸锰时的搅拌转速、加热温度，以及步骤S2制备共掺杂磷酸锰锂内核时在砂磨机中研磨搅拌的时间、烧结温度和烧结时间，其他条件与实施例1-A相同，具体如下表8-A所示。
实施例58-A至61-A
除了将步骤S3制备焦磷酸铁锂粉末时的干燥温度/干燥时间分别调整为100℃/4h、150℃/6h、200℃/6h和200℃/6h，烧结温度和烧结时间分别调整为700℃/6h、700℃/6h、700℃/6h和600℃/6h之外，其他条件与实施例1-A相同。
实施例62-A至64-A
除了将步骤S5包覆时的干燥温度/干燥时间分别调整为150℃/6h、150℃/6h和150℃/6h，烧结温度和烧结时间分别调整为680℃/4h、750℃/6h和800℃/8h之外，其他条件与实施例38-A相同。
对比例(1-A)～对比例(9-A)的制备同前述的对比例1-9，在此不再赘述。
对比例10-A
除了改变步骤S3和步骤S5以及不执行步骤S4之外，其他条件与实施例1-A相同。
S3：制备焦磷酸铁锂粉末
将9.52g碳酸锂、29.9g碳酸亚铁、29.6g磷酸二氢铵和32.5g二水合草酸溶于50mL去离子水中。混合物的pH为5，搅拌2小时使反应混合物充分反应。然后将反应后的溶液升温到80℃并保持该温度4小时，得到包含Li 2FeP 2O 7的悬浊液，将悬浊液进行过滤，用去离子水洗涤，并在120℃下干燥4小时，得到粉末。将所述粉末在500℃、氮气气氛下烧结4小时，并自然冷却至室温后进行研磨，控制Li 2FeP 2O 7的结晶度为5％。
S5：包覆
取10mol(约1570g)按照步骤S2工艺获得的共掺杂的磷酸锰锂内核、62.8g步骤S3获得的Li 2FeP 2O 7粉末和37.3g蔗糖在500mL去离子水中搅拌混合均匀后转入真空烘箱中在150℃下干燥6小时。然后通过砂磨分散所得产物。在分散后，将所得产物在氮气气氛中、在700℃下烧结6小时，得到非晶态焦磷酸铁锂、碳包覆的正极活性材料。
对比例11-A
除了改变步骤S4和步骤S5以及不执行步骤S3之外，其他条件与实施例1-A相同。
S4：制备磷酸铁锂悬浊液
将14.7g碳酸锂、46.1g碳酸亚铁、45.8g磷酸二氢铵和50.2g二水合草酸和37.3g蔗糖溶于500mL去离子水中，得到混合物，然后搅拌6小时使上述混合物充分反应。然后将反 应后的溶液升温到120℃并保持该温度6小时，得到包含LiFePO 4的悬浊液。
S5：包覆
取10mol(约1570g)按照步骤S2工艺获得的共掺杂的磷酸锰锂内核加入到步骤S4获得的LiFePO 4悬浊液(包含37.3g蔗糖和62.8g的LiFePO 4)中，搅拌混合均匀后转入真空烘箱中在150℃下干燥6小时。然后通过砂磨分散所得产物。在分散后，将所得产物在氮气气氛中、在600℃下烧结4小时，得到非晶态磷酸铁锂、碳包覆的正极活性材料。
对比例12-A
除了改变步骤S3至步骤S5之外，其他条件与实施例1-A相同。
S3：制备焦磷酸铁锂粉末
将2.38g碳酸锂、7.5g碳酸亚铁、7.4g磷酸二氢铵和8.1g二水合草酸溶于50mL去离子水中。混合物的pH为5，搅拌2小时使反应混合物充分反应。然后将反应后的溶液升温到80℃并保持该温度4小时，得到包含Li 2FeP 2O 7的悬浊液，将悬浊液进行过滤，用去离子水洗涤，并在120℃下干燥4小时，得到粉末。将所述粉末在500℃、氮气气氛下烧结4小时，并自然冷却至室温后进行研磨，控制Li 2FeP 2O 7的结晶度为5％。
S4：制备磷酸铁锂悬浊液
将11.1g碳酸锂、34.8g碳酸亚铁、34.5g磷酸二氢铵、37.7g二水合草酸和37.3g蔗糖溶于1500mL去离子水中，得到混合物，然后搅拌6小时使上述混合物充分反应。然后将反应后的溶液升温到120℃并保持该温度6小时，得到包含LiFePO 4的悬浊液。
S5：包覆
取10mol(约1570g)按照步骤S2工艺获得的共掺杂的磷酸锰锂内核与15.7g步骤S3获得的Li 2FeP 2O 7粉末加入到步骤S4获得的LiFePO 4悬浊液(包含37.3g蔗糖和47.2g的LiFePO 4)中，搅拌混合均匀后转入真空烘箱中在150℃下干燥6小时。然后通过砂磨分散所得产物。在分散后，将所得产物在氮气气氛中、在600℃下烧结4小时以控制LiFePO 4的结晶度为8％，得到非晶态焦磷酸铁锂、非晶态磷酸铁锂、碳包覆的正极活性材料。
对上述实施例以及对比例进行性能测试，其余测试参数同实施例1，扣电平均放电电压(V)测试参数如下：
将上述制得的扣式电池在25℃恒温环境下，静置5分钟，按照0.1C放电至2.5V，静置5分钟，按照0.1C充电至4.3V，然后在4.3V下恒压充电至电流小于等于0.05mA，静置5分钟；然后按照0.1C放电至2.5V，此时的放电容量为初始克容量，记为D0，放电能量为初始能量，记为E0，扣电平均放电电压V即为E0/D0。
表1-A示出实施例1-A至11-A、对比例1-A至12-A的正极活性材料组成。
表2-A示出实施例1-A至11-A、对比例1-A至12-A的正极活性材料、正极极片、扣电或全电按照上述性能测试方法测得的性能数据。
表1-A
Figure PCTCN2022126838-appb-000018
Figure PCTCN2022126838-appb-000019
Figure PCTCN2022126838-appb-000020
表2-A
Figure PCTCN2022126838-appb-000021
Figure PCTCN2022126838-appb-000022
由表2-A可知，本申请通过对磷酸锰锂的Li位、Mn位、P位和O位同时以特定量掺杂特定的元素进行改性以及对磷酸锰锂进行多层包覆，由此得到的正极活性材料实现了更小的晶格变化率、更小的Li/Mn反位缺陷浓度、更大的压实密度、更接近于-2价的表面氧价态、更少的循环后Fe和Mn溶出量，从而本申请的电池具有更好的性能，例如具有更高的容量、更好的高温存储性能和高温循环性能。
表3-A示出实施例12-A至27-A的正极活性材料组成。
表4-A示出实施例12-A至27-A的正极活性材料、正极极片、扣电或全电按照上述性能测试方法测得的性能数据。
表3-A
Figure PCTCN2022126838-appb-000023
Figure PCTCN2022126838-appb-000024
表4-A
Figure PCTCN2022126838-appb-000025
由表4-A可知，在其他元素相同的情况下，(1-y):y在1至4范围内且a:x在9到1100范围内，可选地，(1-y):y在1.5至3范围内且a:x在190至998范围内时，能够进一步提升电池的能量密度和循环性能。
表5-A示出实施例28-A至40-A的正极活性材料组成。
表6-A示出实施例28-A至40-A的正极活性材料、正极极片、扣电或全电按照上述性能测试方法测得的性能数据。
表5-A
Figure PCTCN2022126838-appb-000026
表6-A
Figure PCTCN2022126838-appb-000027
Figure PCTCN2022126838-appb-000028
综合实施例1-A以及实施例28-A至32-A可知，随着第一包覆层的量从3.2％增加至6.4％，所得正极活性材料的Li/Mn反位缺陷浓度逐渐下降，循环后Fe和Mn溶出量逐渐下降，对应电池的安全性能和循环性能也得到改善，但克容量略有下降。可选地，当第一包覆层的总量为4-5.6重量％时，对应电池的综合性能最佳。
综合实施例1-A以及实施例33-A至36-A可知，随着第二包覆层的量从1％增加至6％，所得正极活性材料的Li/Mn反位缺陷浓度逐渐下降，循环后Fe和Mn溶出量逐渐下降，对应电池的安全性能和循环性能也得到改善，但克容量却略有下降。可选地，当第二包覆层的总量为3-5重量％时，对应电池的综合性能最佳。
综合实施例1-A以及实施例37-A至40-A可知，当第一包覆层中同时存在Li 2FeP 2O 7和LiFePO 4、特别是Li 2FeP 2O 7和LiFePO 4的重量比为1:3至3:1，并且尤其是1:3至1:1时，对电池性能的改善更加明显。
表7-A示出实施例1-A、41-A至43-A的正极活性材料、正极极片、扣电或全电按照上述性能测试方法测得的性能数据。
表7-A
Figure PCTCN2022126838-appb-000029
由表7可知，随着第一包覆层中焦磷酸盐和磷酸盐的结晶度逐渐增加，对应正极活性材料的晶格变化率、Li/Mn反位缺陷浓度以及循环后Fe和Mn溶出量逐渐下降，电池的容量逐渐增加，安全性能和循环性能也逐渐改善。
实施例44-A至57-A除了改变步骤S1制备掺杂的草酸锰时的搅拌转速、加热温度，以及步骤S2制备共掺杂磷酸锰锂内核时在砂磨机中研磨搅拌的时间、烧结温度和烧结时间，其他条件与实施例1-A相同，具体如下表8-A所示。表9-A示出实施例44-A至57-A的正极活性材料、正极极片、扣电或全电按照上述性能测试方法测得的性能数据。
表8-A
Figure PCTCN2022126838-appb-000030
Figure PCTCN2022126838-appb-000031
表9-A
Figure PCTCN2022126838-appb-000032
Figure PCTCN2022126838-appb-000033
从表9-A中可以看出，通过调整步骤S1制备掺杂的草酸锰时的搅拌转速、加热温度，以及步骤S2制备共掺杂磷酸锰锂内核时在砂磨机中研磨搅拌的时间、烧结温度和烧结时间等参数，可以进一步改善正极活性材料以及电池的性能。
实施例58-A至61-A除了改变步骤S3制备焦磷酸铁锂粉末时的干燥温度、干燥时间、烧结温度和烧结时间之外，其他条件与实施例1-A相同，具体如下表10-A所示。表11-A示出实施例58-A至61-A的正极活性材料、正极极片、扣电或全电按照上述性能测试方法测得的性能数据。
实施例62-A至64-A除了改变步骤S5包覆时的干燥温度、干燥时间、烧结温度和烧结时间之外，其他条件与实施例38相同，具体如下表12-A所示。表13-A示出实施例62-A至64-A的正极活性材料、正极极片、扣电或全电按照上述性能测试方法测得的性能数据。
表10-A
Figure PCTCN2022126838-appb-000034
表11-A
Figure PCTCN2022126838-appb-000035
Figure PCTCN2022126838-appb-000036
表12-A
Figure PCTCN2022126838-appb-000037
表13-A
Figure PCTCN2022126838-appb-000038
Figure PCTCN2022126838-appb-000039
由表1-A 1和13-A可知，通过调节步骤S3至S5中的干燥温度、干燥时间、烧结温度、烧结时间等参数，可以进一步改善正极活性材料以及电池的性能。
下面，详述内核为Li 1+xMn 1-yA yP 1-zR zO 4，壳包括第一包覆层包括晶态的焦磷酸盐QP 2O 7和金属氧化物Q’ eO f，第二包覆层为包覆碳层的实施例的制备以及性能测试：
制备例及实施例涉及的原材料来源如下：
名称 化学式 厂家 规格
碳酸锰 MnCO 3 山东西亚化学工业有限公司 1Kg
碳酸锂 Li 2CO 3 山东西亚化学工业有限公司 1Kg
碳酸镁 MgCO 3 山东西亚化学工业有限公司 1Kg
碳酸锌 ZnCO 3 武汉鑫儒化工有限公司 25Kg
碳酸亚铁 FeCO 3 西安兰之光精细材料有限公司 1Kg
硫酸镍 NiCO 3 山东西亚化学工业有限公司 1Kg
硫酸钛 Ti(SO 4) 2 山东西亚化学工业有限公司 1Kg
硫酸钴 CoSO 4 厦门志信化学有限公司 500g
二氯化钒 VCl 2 上海金锦乐实业有限公司 1Kg
二水合草酸 C 2H 2O 4 ●2H 2O 上海金锦乐实业有限公司 1Kg
磷酸二氢铵 NH 4H 2PO 4 上海澄绍生物科技有限公司 500g
蔗糖 C 12H 22O 11 上海源叶生物科技有限公司 100g
硫酸 H 2SO 4 深圳海思安生物技术有限公司 质量分数60％
硝酸 HNO 3 安徽凌天精细化工有限公司 质量分数60％
硝酸 HNO 3 安徽凌天精细化工有限公司 质量分数85％
亚硅酸 H 2SiO 3 上海源叶生物科技有限公司 100g
硼酸 H 3BO 3 常州市启迪化工有限公司 1Kg
三氧化二铝 Al2O3 河北冠朗生物科技有限公司 25Kg
氧化镁 MgO 河北冠朗生物科技有限公司 25Kg
二氧化锆 ZrO2 清选晟熠生物科技有限公司 1Kg
氧化铜 CuO 河北冠朗生物科技有限公司 25Kg
二氧化硅 SiO2 河北冠朗生物科技有限公司 25Kg
三氧化钨 WO3 河北冠朗生物科技有限公司 25Kg
二氧化钛 TiO2 上海源叶生物科技有限公司 500g
五氧化二钒 V2O5 上海金锦乐实业有限公司 1Kg
氧化镍 NiO 湖北万得化工有限公司 25Kg
实施例1-1
(1)共掺杂磷酸锰锂内核的制备
制备Fe、Co和V共掺杂的草酸锰：将689.5g碳酸锰(以MnCO 3计，下同)、455.2g碳酸亚铁(以FeCO 3计，下同)、4.6g硫酸钴(以CoSO 4计，下同)和4.9g二氯化钒(以VCl 2计，下同)在混料机中充分混合6小时。将混合物转移至反应釜中，并加入5升去离子水和1260.6g二水合草酸(以C 2H 2O 4.2H 2O计，下同)。将反应釜加热至80℃，以600rpm的转速搅拌6小时，直至反应终止(无气泡产生)，得到Fe、Co和V共掺杂的草酸锰悬浮液。然后过滤悬浮液，将滤饼在120℃下烘干，之后进行研磨，得到中值粒径Dv50为100nm的Fe、Co和V共掺杂的二水草酸锰颗粒。
制备Fe、Co、V和S共掺杂的磷酸锰锂：将前一步骤获得的二水草酸锰颗粒(1793.4g)、369.0g碳酸锂(以Li 2CO 3计，下同)，1.6g浓度为60％的稀硫酸(以60％H 2SO 4计，下同)和1148.9g磷酸二氢铵(以NH 4H 2PO 4计，下同)加入到20升去离子水中，将混合物搅拌10小时使其混合均匀，得到浆料。将浆料转移到喷雾干燥设备中进行喷雾干燥造粒，设定干燥温度为250℃，干燥4小时，得到粉料。在氮气(90体积％)+氢气(10体积％)保护气氛中，将上述粉料在700℃下烧结4小时，得到1572.1g的Fe、Co、V和S共掺杂的磷酸锰锂。
(2)焦磷酸铁锂和包含三氧化二铝和蔗糖的悬浊液的制备
制备焦磷酸铁锂粉末：将4.77g碳酸锂、7.47g碳酸亚铁、14.84g磷酸二氢铵和1.3g二水合草酸溶于50ml去离子水中。混合物的pH为5，搅拌2小时使 反应混合物充分反应。然后将反应后的溶液升温到80℃并保持该温度4小时，得到包含Li 2FeP 2O 7的悬浊液，将悬浊液进行过滤，用去离子水洗涤，并在120℃下干燥4h，得到粉末。将粉末在650℃、氮气气氛下烧结8小时，并自然冷却至室温后进行研磨，得到Li 2FeP 2O 7粉末。
制备包含三氧化二铝和蔗糖的悬浊液：将47.1g纳米Al 2O 3(粒径约20nm)和74.6g蔗糖(以C 12H 22O 11计，下同)溶于1500ml去离子水中，然后搅拌6小时使上述混合物充分混合。然后将得到的溶液升温到120℃并保持该温度6小时，得到包含三氧化二铝和蔗糖的悬浊液。
(3)包覆
将1572.1g上述Fe、Co、V和S共掺杂的磷酸锰锂与15.72g上述焦磷酸铁锂(Li 2FeP 2O 7)粉末加入到上一步骤制备获得的包含三氧化二铝和蔗糖的悬浊液中，搅拌混合均匀后转入真空烘箱中在150℃下干燥6小时。然后通过砂磨分散所得产物。在分散后，将所得产物在氮气气氛中、在700℃下烧结6小时，得到目标产物双层包覆的磷酸锰锂。
实施例1-2至1-6
在共掺杂磷酸锰锂内核的制备过程中，除不使用二氯化钒和硫酸钴、使用463.4g的碳酸亚铁，1.6g的60％浓度的稀硫酸，1148.9g的磷酸二氢铵和369.0g碳酸锂以外，实施例1-2至1-6中磷酸锰锂内核的制备条件与实施例1-1相同。
此外，在焦磷酸铁锂和包含三氧化二铝和蔗糖的悬浊液的制备过程以及包覆第一包覆层和第二包覆层的过程中，除所使用的原料按照表1中所示包覆量与实施例1-1对应的包覆量的比值对应调整，以使实施例1-2至1-6中Li 2FeP 2O 7/Al 2O 3的用量分别为12.6g/37.68g、15.7g/47.1g、18.8g/56.52g、22.0/65.94g和25.1g/75.36g，实施例1-2至1-6中蔗糖的用量为37.3g以外，其他条件与实施例1-1相同。
实施例1-7至1-10
除蔗糖的用量分别为74.6g、149.1g、186.4g和223.7g以使作为第二包覆层的碳层的对应包覆量分别为31.4g、62.9g、78.6g和94.3g以外，实施例1-7至1-10的条件与实施例1-3相同。
实施例1-11至1-14
除在焦磷酸铁锂和包含三氧化二铝和蔗糖的悬浊液的制备过程中，按照表1 中所示包覆量对应调整各种原料的用量以使Li 2FeP 2O 7/Al 2O 3的用量分别为23.6g/39.25g、31.4g/31.4g、39.3g/23.55g和47.2g/15.7g以外，实施例1-11至1-14的条件与实施例1-7相同。
实施例1-15
除在共掺杂磷酸锰锂内核的制备过程中使用492.80g ZnCO 3代替碳酸亚铁以外，实施例1-15的条件与实施例1-14相同。
实施例1-16至1-18
除实施例1-16在共掺杂磷酸锰锂内核的制备过程中使用466.4g的NiCO 3、5.0g的碳酸锌和7.2g的硫酸钛代替碳酸亚铁，实施例1-17在共掺杂的磷酸锰锂内核的制备过程中使用455.2g的碳酸亚铁和8.5g的二氯化钒，实施例1-18在共掺杂的磷酸锰锂内核的制备过程中使用455.2g的碳酸亚铁、4.9g的二氯化钒和2.5g的碳酸镁以外，实施例1-16至1-18的条件与实施例1-7相同。
实施例1-19至1-20
除实施例1-19在共掺杂磷酸锰锂内核的制备过程中使用369.4g的碳酸锂、和以1.05g的60％浓度的稀硝酸代替稀硫酸，实施例1-20在共掺杂的磷酸锰锂内核的制备过程中使用369.7g的碳酸锂、和以0.78g的亚硅酸代替稀硫酸以外，实施例1-19至1-20的条件与实施例1-18相同
实施例1-21至1-22
除实施例1-21在共掺杂磷酸锰锂内核的制备过程中使用632.0g碳酸锰、463.30g碳酸亚铁、30.5g的二氯化钒、21.0g的碳酸镁和0.78g的亚硅酸；实施例1-22在共掺杂磷酸锰锂内核的制备过程中使用746.9g碳酸锰、289.6g碳酸亚铁、60.9g的二氯化钒、42.1g的碳酸镁和0.78g的亚硅酸以外，实施例1-21至1-22的条件与实施例1-20相同。
实施例1-23至1-24
除实施例1-23在共掺杂磷酸锰锂内核的制备过程中使用804.6g碳酸锰、231.7g碳酸亚铁、1156.2g的磷酸二氢铵、1.2g的硼酸(质量分数99.5％)和370.8g碳酸锂；实施例1-24在共掺杂磷酸锰锂内核的制备过程中使用862.1g碳酸锰、173.8g碳酸亚铁、1155.1g的磷酸二氢铵、1.86g的硼酸(质量分数99.5％)和371.6g碳酸锂以外，实施例1-23至1-24的条件与实施例1-22相同。
实施例1-25
除实施例1-25在共掺杂磷酸锰锂内核的制备过程中使用370.1g碳酸锂、1.56g的亚硅酸和1147.7g的磷酸二氢铵以外，实施例1-25的条件与实施例1-20相同。
实施例1-26
除实施例1-26在共掺杂磷酸锰锂内核的制备过程中使用368.3g碳酸锂、4.9g质量分数为60％的稀硫酸、919.6g碳酸锰、224.8g碳酸亚铁、3.7g二氯化钒、2.5g碳酸镁和1146.8g的磷酸二氢铵以外，实施例1-26的条件与实施例1-20相同。
实施例1-27
除实施例1-27在共掺杂磷酸锰锂内核的制备过程中使用367.9g碳酸锂、6.5g浓度为60％的稀硫酸和1145.4g的磷酸二氢铵以外，实施例1-27的条件与实施例1-20相同。
实施例1-28至1-33
除实施例1-28至1-33在共掺杂磷酸锰锂内核的制备过程中使用1034.5g碳酸锰、108.9g碳酸亚铁、3.7g二氯化钒和2.5g碳酸镁，碳酸锂的使用量分别为：367.6g、367.2g、366.8g、366.4g、366.0g和332.4g，磷酸二氢铵的使用量分别为：1144.5g、1143.4g、1142.2g、1141.1g、1139.9g和1138.8g，浓度为60％的稀硫酸的使用量分别为：8.2g、9.8g、11.4g、13.1g、14.7g和16.3g以外，实施例1-28至1-33的条件与实施例1-20相同。
实施例1-34至实施例1-38、实施例1-43
除了在焦磷酸铁锂和包含氧化物和蔗糖的悬浊液的制备过程以及包覆第一包覆层和第二包覆层的过程中，所使用的原料按照表1中所示包覆量与实施例1-1对应的包覆量的比值对应调整，以使实施例1-34中Li 2FeP 2O 7/MgO的用量分别为15.72g/47.1g、实施例1-35中Li 2FeP 2O 7/ZrO 2的用量分别为15.72g/47.1g、实施例1-36中Li 2FeP 2O 7/ZnO的用量分别为15.72g/47.1g、实施例1-37中Li 2FeP 2O 7/SnO 2的用量分别为15.72g/47.1g、实施例1-38中Li 2FeP 2O 7/SiO 2的用量分别为15.72g/47.1g，实施例1-43中Li 2FeP 2O 7/V 2O 5的用量分别为15.72g/47.1g，其他条件与实施例1-1相同。
实施例1-39至实施例1-41
1)实施例1-39中，内核Li 1.1Mn 0.6Fe 0.393Mg 0.007P 0.9Si 0.1O 4的制备。
制备Fe和Mg共掺杂的草酸锰：将689.5g碳酸锰(以MnCO 3计，下同)、455.2g碳酸亚铁(以FeCO 3计，下同)和5.90g碳酸镁(以MgCO 3计，下同)在混料机中充分混合6小时。将混合物转移至反应釜中，并加入5升去离子水和1260.6g二水合草酸(以C 2H 2O 4.2H 2O计，下同)。将反应釜加热至80℃，以600rpm的转速搅拌6小时，直至反应终止(无气泡产生)，得到Fe和Mg共掺杂的草酸锰悬浮液。然后过滤悬浮液，将滤饼在120℃下烘干，之后进行研磨，得到中值粒径Dv50为100nm的Fe和Mg共掺杂的二水草酸锰颗粒。
制备Fe、Mg和Si共掺杂的磷酸锰锂：将前一步骤获得的二水草酸锰颗粒(1791.3g)、406.3g碳酸锂(以Li 2CO 3计，下同)，7.8g亚硅酸(以H 2SiO 3计，下同)和1035.0g磷酸二氢铵(以NH 4H 2PO 4计，下同)加入到20升去离子水中，将混合物搅拌10小时使其混合均匀，得到浆料。将浆料转移到喷雾干燥设备中进行喷雾干燥造粒，设定干燥温度为250℃，干燥4小时，得到粉料。在氮气(90体积％)+氢气(10体积％)保护气氛中，将上述粉料在700℃下烧结4小时，得到1574.0g的Fe、Mg和Si共掺杂的磷酸锰锂。
2)实施例1-40中，内核LiMn 0.999Fe 0.001P 0.995N 0.005O 4的制备。
制备Fe掺杂的草酸锰：将1148.0g碳酸锰(以MnCO 3计，下同)和11.58g碳酸亚铁(以FeCO 3计，下同)在混料机中充分混合6小时。将混合物转移至反应釜中，并加入5升去离子水和1260.6g二水合草酸(以C 2H 2O 4.2H 2O计，下同)。将反应釜加热至80℃，以600rpm的转速搅拌6小时，直至反应终止(无气泡产生)，得到Fe掺杂的草酸锰悬浮液。然后过滤悬浮液，将滤饼在120℃下烘干，之后进行研磨，得到中值粒径Dv50为100nm的Fe掺杂的二水草酸锰颗粒。
制备Fe和N共掺杂的磷酸锰锂：将前一步骤获得的二水草酸锰颗粒(1789.9g)、369.4g碳酸锂(以Li 2CO 3计，下同)，5.25g稀硝酸(以60％HNO 3计，下同)和1144.3g磷酸二氢铵(以NH 4H 2PO 4计，下同)加入到20升去离子水中，将混合物搅拌10小时使其混合均匀，得到浆料。将浆料转移到喷雾干燥设备中进行喷雾干燥造粒，设定干燥温度为250℃，干燥4小时，得到粉料。在氮气(90体积％)+氢气(10体积％)保护气氛中，将上述粉料在700℃下烧结4小时，得到1567.7g的Fe和N共掺杂的磷酸锰锂。
3)实施例1-41中，内核LiMn 0.50Fe 0.50P 0.995N 0.005O 4的制备。
制备Fe掺杂的草酸锰：将574.7g碳酸锰(以MnCO 3计，下同)和579.27g碳酸亚铁(以FeCO 3计，下同)在混料机中充分混合6小时。将混合物转移至反应釜中，并加入5升去离子水和1260.6g二水合草酸(以C 2H 2O 4.2H 2O计，下同)。将反应釜加热至80℃，以600rpm的转速搅拌6小时，直至反应终止(无气泡产生)，得到Fe掺杂的草酸锰悬浮液。然后过滤悬浮液，将滤饼在120℃下烘干，之后进行研磨，得到中值粒径Dv50为100nm的Fe掺杂的二水草酸锰颗粒。
制备Fe和N共掺杂的磷酸锰锂：将前一步骤获得的二水草酸锰颗粒(1794.4g)、369.4g碳酸锂(以Li 2CO 3计，下同)，5.25g稀硝酸(以60％HNO 3计，下同)和1144.3g磷酸二氢铵(以NH 4H 2PO 4计，下同)加入到20升去离子水中，将混合物搅拌10小时使其混合均匀，得到浆料。将浆料转移到喷雾干燥设备中进行喷雾干燥造粒，设定干燥温度为250℃，干燥4小时，得到粉料。在氮气(90体积％)+氢气(10体积％)保护气氛中，将上述粉料在700℃下烧结4小时，得到1572.2g的Fe和N共掺杂的磷酸锰锂。
实施例1-39至实施例1-41的其他条件参照实施例1-1。
实施例1-42
在焦磷酸锆的制备过程中，将123.2g二氧化锆(以ZrO 2计，下同)和230.6g磷酸(以85％H 3PO 4计，下同)充分混合。将其加热到350℃，同时不断搅拌2小时使反应混合物充分反应。然后将反应后的溶液在350℃保持4小时，得到包含ZrP 2O 7的粘稠的糊状物，最终变成固体物，并用去离子水进行洗涤，将所得产物在装有乙醇的球磨机中进行研磨4h，并将所得产物在红外灯下进行烘干，得到ZrP 2O 7粉末。
实施例1-44
在焦磷酸银的制备过程中，将463.4g氧化银(以Ag 2O计，下同)和230.6g磷酸(以85％H 3PO 4计，下同)充分混合。将其加热到450℃，同时不断搅拌2小时使反应混合物充分反应。然后将反应后的溶液在450℃保持4小时，得到包含Ag 4P 2O 7的粘稠的糊状物，最终变成固体物，并用去离子水进行洗涤，将所得产物在装有乙醇的球磨机中进行研磨4h，并将所得产物在红外灯下进行烘干，得到Ag 4P 2O 7粉末。
实施例1-45
除内核制备过程中使用1044.6g的碳酸锰、1138.5g的磷酸二氢铵和369.4g碳酸锂，并额外添加105.4g的碳酸亚铁、10.5g稀硝酸(以60％HNO 3计，下同)以外，其实与实施例1-1相同。
实施例1-46
除内核制备过程中使用104.5g的碳酸锰、1138.5g的磷酸二氢铵和371.3g碳酸锂，并额外添加1052.8g的碳酸亚铁、5.25g稀硝酸(以60％HNO 3计，下同)以外，其它与实施例1-1相同。
实施例1-47
除在焦磷酸铁锂和包含三氧化二铝和蔗糖的悬浊液的制备过程中，按照表1中所示包覆量对应调整各种原料的用量以使Li 2FeP 2O 7/Al 2O 3的用量分别为62.9g/47.1g以外，实施例1-47的其它条件与实施例1-1相同。
实施例1-48
除蔗糖的用量为111.9g以使作为第二包覆层的碳层的对应包覆量为47.1g以外，其余操作与实施例1-1相同。
实施例1-49
除内核制备过程中使用1034.3g的碳酸锰、1138.5g的磷酸二氢铵和371.3g碳酸锂，并额外添加115.8g的碳酸亚铁、5.25g稀硝酸(以60％HNO 3计，下同)以外，其它与实施例1-1相同。
实施例1-50
除内核制备过程中使用1091.8g的碳酸锰、1138.5g的磷酸二氢铵和371.3g碳酸锂，并额外添加57.9g的碳酸亚铁、5.25g稀硝酸(以60％HNO 3计，下同)以外，其它与实施例1-1相同。
实施例1-51
除内核制备过程中使用804.5g的碳酸锰、1138.5g的磷酸二氢铵和371.3g碳酸锂，并额外添加347.4g的碳酸亚铁、5.25g稀硝酸(以60％HNO 3计，下同)，蔗糖的用量为111.9g，对应的碳的包覆量为47.1g以外，其它与实施例1-1相同。
实施例1-52
除使用747.0g的碳酸锰、1138.5g的磷酸二氢铵和371.3g碳酸锂，并额外添加405.3g的碳酸亚铁、5.25g稀硝酸(以60％HNO 3计，下同)，蔗糖的用量为111.9g，对应的碳的包覆量为47.1g以外，其它与实施例1-1相同。
实施例2-1
除在焦磷酸铁锂(Li 2FeP 2O 7)的制备过程中在粉末烧结步骤中的烧结温度为550℃，烧结时间为1h以控制Li 2FeP 2O 7的结晶度为30％，在Al 2O 3的制备过程中在包覆烧结步骤中的烧结温度为650℃，烧结时间为2h以控制Al 2O 3的结晶度为100％以外，其他条件与实施例1-1相同。
实施例2-2
除在焦磷酸铁锂(Li 2FeP 2O 7)的制备过程中在粉末烧结步骤中的烧结温度为550℃，烧结时间为2h以控制Li 2FeP 2O 7的结晶度为50％，在Al 2O 3的制备过程中在包覆烧结步骤中的烧结温度为650℃，烧结时间为3h以控制Al 2O 3的结晶度为100％以外，其他条件与实施例1-1相同。
实施例2-3
除在焦磷酸铁锂(Li 2FeP 2O 7)的制备过程中在粉末烧结步骤中的烧结温度为600℃，烧结时间为3h以控制Li 2FeP 2O 7的结晶度为70％，在Al 2O 3的制备过程中在包覆烧结步骤中的烧结温度为650℃，烧结时间为4h以控制Al 2O 3的结晶度为100％以外，其他条件与实施例1-1相同。
实施例2-4
除在焦磷酸铁锂(Li 2FeP 2O 7)的制备过程中在粉末烧结步骤中的烧结温度为650℃，烧结时间为4h以控制Li 2FeP 2O 7的结晶度为10％，在Al 2O 3的制备过程中在包覆烧结步骤中的烧结温度为500℃，烧结时间为6h以控制Al 2O 3的结晶度为100％以外，其他条件与实施例1-1相同。
实施例3-1至3-12
除制备Fe、Co和V共掺杂的草酸锰颗粒的过程中，实施例3-1反应釜内的加热温度/搅拌时间分别为60℃/120分钟；实施例3-2反应釜内的加热温度/搅拌时间分别为70℃/120分钟；实施例3-3反应釜内的加热温度/搅拌时间分别为80℃/120分钟；实施例3-4反应釜内的加热温度/搅拌时间分别为90℃/120分钟；实施例3-5反应釜内的加热温度/搅拌时间分别为100℃/120分钟；实施例3-6反应釜内的加热温度/搅拌时间分别为110℃/120分钟；实施例3-7反应釜内的加热温度/搅拌时间分别为120℃/120分钟；实施例3-8反应釜内的加热温度/搅拌时间分别为130℃/120分钟；实施例3-9反应釜内的加热温度/搅拌时间分别为100℃/60分钟；实施例3-10反应釜内的加热温度/搅拌时间分别为100℃/90分钟； 实施例3-11反应釜内的加热温度/搅拌时间分别为100℃/150分钟；实施例3-12反应釜内的加热温度/搅拌时间分别为100℃/180分钟以外，实施例3-1至3-12的其他条件与实施例1-1相同。
实施例4-1至4-4：
除在焦磷酸铁锂(Li 2FeP 2O 7)的制备过程中在干燥步骤中的干燥温度/干燥时间分别为100℃/4h、150℃/6h、200℃/6h和200℃/6h；在焦磷酸铁锂(Li 2FeP 2O 7)的制备过程中在烧结步骤中的烧结温度和烧结时间分别为700℃/6h、700℃/6h、700℃/6h和600℃/6h以外，其它条件与实例1-7相同。
实施例4-5至4-7：
除在包覆过程中在干燥步骤中的干燥温度/干燥时间分别为150℃/6h、150℃/6h和150℃/6h；在包覆过程中在烧结步骤中的烧结温度和烧结时间分别为600℃/4h、600℃/6h和800℃/8h以外，其它条件与实例1-12相同。
对比例1-1
制备草酸锰：将1149.3g碳酸锰加至反应釜中，并加入5升去离子水和1260.6g二水合草酸(以C 2H 2O 4·2H 2O计，下同)。将反应釜加热至80℃，以600rpm的转速搅拌6小时，直至反应终止(无气泡产生)，得到草酸锰悬浮液，然后过滤悬浮液，将滤饼在120℃下烘干，之后进行研磨，得到中值粒径Dv50为100nm的二水草酸锰颗粒。
制备碳包覆的磷酸锰锂：取1789.6g上述获得的二水草酸锰颗粒、369.4g碳酸锂(以Li 2CO 3计，下同)，1150.1g磷酸二氢铵(以NH 4H 2PO 4计，下同)和31g蔗糖(以C 12H 22O 11计，下同)加入到20升去离子水中，将混合物搅拌10小时使其混合均匀，得到浆料。将浆料转移到喷雾干燥设备中进行喷雾干燥造粒，设定干燥温度为250℃，干燥4小时，得到粉料。在氮气(90体积％)+氢气(10体积％)保护气氛中，将上述粉料在700℃下烧结4小时，得到碳包覆的磷酸锰锂。
对比例1-2
除使用689.5g的碳酸锰和额外添加463.3g的碳酸亚铁以外，对比例2的其他条件与对比例1-1相同。
对比例1-3
除使用1148.9g的磷酸二氢铵和369.0g碳酸锂，并额外添加1.6g的60％浓 度的稀硫酸以外，对比例3的其他条件与对比例1-1相同。
对比例1-4
除使用689.5g的碳酸锰、1148.9g的磷酸二氢铵和369.0g碳酸锂，并额外添加463.3g的碳酸亚铁、1.6g的60％浓度的稀硫酸以外，其他条件与对比例1-1相同。
对比例1-5
除额外增加以下步骤：制备焦磷酸铁锂粉末时，将9.52g碳酸锂、29.9g碳酸亚铁、29.6g磷酸二氢铵和32.5g二水合草酸溶于50ml去离子水中。混合物的pH为5，搅拌2小时使反应混合物充分反应。然后将反应后的溶液升温到80℃并保持该温度4小时，得到包含Li 2FeP 2O 7的悬浊液，将悬浊液进行过滤，用去离子水洗涤，并在120℃下干燥4h，得到粉末。将粉末在500℃、氮气气氛下烧结4小时，并自然冷却至室温后进行研磨，控制Li 2FeP 2O 7的结晶度为5％，制备碳包覆的材料时，Li 2FeP 2O 7的用量为62.8g以外其它条件与对比例1-4相同。
对比例1-6
除额外增加以下步骤：将62.92g纳米Al 2O 3(粒径约20nm)和37.4g蔗糖(以C 12H 22O 11计，下同)溶于1500ml去离子水中，然后搅拌6小时使混合物充分反应。然后将反应后的溶液升温到120℃并保持该温度6小时，得到包含三氧化二铝和蔗糖的悬浊液。其他条件与对比例1-4相同。
对比例1-7
制备非晶态焦磷酸铁锂粉末：将2.38g碳酸锂、7.5g碳酸亚铁、7.4g磷酸二氢铵和8.1g二水合草酸溶于50ml去离子水中。混合物的pH为5，搅拌2小时使反应混合物充分反应。然后将反应后的溶液升温到80℃并保持该温度4小时，得到包含Li 2FeP 2O 7的悬浊液，将悬浊液进行过滤，用去离子水洗涤，并在120℃下干燥4h，得到粉末。将粉末在500℃、氮气气氛下烧结4小时，并自然冷却至室温后进行研磨，控制Li 2FeP 2O 7的结晶度为5％。
制备包含三氧化二铝和蔗糖的悬浊液：将47.19g纳米Al 2O 3(粒径约20nm)和37.4g蔗糖(以C 12H 22O 11计，下同)溶于1500ml去离子水中，然后搅拌6小时使混合物充分反应。然后将反应后的溶液升温到120℃并保持该温度6小时，得到包含三氧化二铝和蔗糖的悬浊液。
将1573.0g内核、15.73g焦磷酸铁锂粉末，加入上述悬浊液中，制备过程中 在包覆烧结步骤中的烧结温度为600℃，烧结时间为4h以控制LiFePO 4的结晶度为8％以外，对比例7的其它条件与对比例4相同，得到非晶态焦磷酸铁锂、非晶态氧化铝、碳包覆的正极活性材料。
对比例1-8至1-11
除在焦磷酸铁锂(Li 2FeP 2O 7)的制备过程中在干燥步骤中的干燥温度/干燥时间在对比例1-8至1-10中分别为80℃/3h、80℃/3h、80℃/3h；在包覆过程中在烧结步骤中的烧结温度和烧结时间在对比例8-10中分别为400℃/3h、400℃/3h、350℃/2h；对比例1-11在包覆过程中在干燥步骤中的干燥温度/干燥时间为80℃/3h；在对比例8-9中Li 2FeP 2O 7/Al 2O 3的重量比分别为1:3、1:1；在对比例10中仅采用Li 2FeP 2O 7；在对比例1-11中仅采用Al 2O 3以外，其他条件与实施例1-1至1-7相同。
正极极片的制备
各项参数同实施例1-A，得到正极极片。
负极极片的制备
将负极活性材料人造石墨、导电剂超导炭黑(Super-P)、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC-Na)按照质量比为95％：1.5％：1.8％：1.7％溶于去离子水中，充分搅拌混合均匀后，得到粘度3000mPa.s、固含52％的负极浆料；将负极浆料涂覆在6μm的负极集流体铜箔上，之后在100℃烘烤4小时以烘干，辊压，得到压实密度为1.75g/cm 3的负极极片。
隔离膜
采用聚丙烯膜。
电解液的制备
将碳酸乙烯酯、碳酸二甲酯和1,2-丙二醇碳酸酯按体积比1:1:1混合，然后将LiPF 6均匀溶解在上述溶液中，得到电解液。该电解液中，LiPF 6的浓度为1mol/L。
全电池的制备
将上述获得的正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正负极中间起到隔离的作用，并卷绕得到裸电芯。将裸电芯置于外包装中，注入上述电解液并封装，得到全电池(下文也称“全电”)。
扣式电池的制备
各项参数同实施例1-A，在扣电箱中组装成扣式电池(下文也称“扣电”)。
以上的结果见表1-4。
表1-1实施例1-1至1-52以及对比例1-1至1-7的性能测试结果
Figure PCTCN2022126838-appb-000040
Figure PCTCN2022126838-appb-000041
Figure PCTCN2022126838-appb-000042
Figure PCTCN2022126838-appb-000043
Figure PCTCN2022126838-appb-000044
Figure PCTCN2022126838-appb-000045
Figure PCTCN2022126838-appb-000046
Figure PCTCN2022126838-appb-000047
Figure PCTCN2022126838-appb-000048
Figure PCTCN2022126838-appb-000049
Figure PCTCN2022126838-appb-000050
Figure PCTCN2022126838-appb-000051
Figure PCTCN2022126838-appb-000052
Figure PCTCN2022126838-appb-000053
Figure PCTCN2022126838-appb-000054
Figure PCTCN2022126838-appb-000055
综合实施例1-1至1-52以及对比例1-1至1-4可知，第一包覆层的存在有利于降低所得材料的Li/Mn反位缺陷浓度和循环后Fe和Mn溶出量，提高电池的扣电克容量和压实密度，并改善电池的安全性能和循环性能。当在Mn位和磷位分别掺杂其他元素时，可显著降低所得材料的晶格变化率、反位缺陷浓度和Fe和Mn溶出量，提高电池的克容量和压实密度，并改善电池的安全性能和循环性能。
综合实施例1-2至1-6可知，随着第一包覆层的量从3.2％增加至6.4％，所得材料的Li/Mn反位缺陷浓度逐渐下降，循环后Fe和Mn溶出量逐渐下降，对应电池的安全性能和45℃下的循环性能也得到改善，但扣电克容量略有下降。可选地，当第一包覆层的总量为4-5.6重量％时，对应电池的综合性能最佳。
综合实施例1-3以及实施例1-7至1-10可知，随着第二包覆层的量从1％增加至6％，所得材料的循环后Fe和Mn溶出量逐渐下降，对应电池的安全性能和45℃下的循环性能也得到改善，但扣电克容量却略有下降。可选地，当第二包覆层的总量为3-5重量％时，对应电池的综合性能最佳。
综合实施例1-11至1-15以及对比例1-5和1-6可知，当第一包覆层中同时存在Li 2FeP 2O 7和Al 2O 3、特别是Li 2FeP 2O 7和Al 2O 3的重量比为1：3至3：1，并且尤其是1：3至1：1时，对电池性能的改善更加明显。
表2-1实施例1-1、实施例2-1至2-4的性能测试结果
Figure PCTCN2022126838-appb-000056
由表2-1可以看出，随着第一包覆层中焦磷酸盐的结晶度逐渐增加，对应材料的晶格变化率、Li/Mn反位缺陷浓度以及Fe和Mn溶出量逐渐下降，电池的扣电容量逐渐增加，安全性能和循环性能也逐渐改善。
表3-1实施例3-1至3-12的性能测试结果
Figure PCTCN2022126838-appb-000057
Figure PCTCN2022126838-appb-000058
由表3-1可以看出，通过调整草酸锰颗粒制备过程中在反应釜内的反应温度和反应时间，可以进一步改善本申请正极材料的各项性能。例如，在反应温度从60℃逐渐增大至130℃的过程中，晶格变化率、Li/Mn反位缺陷浓度先减小后增 大，对应的循环后金属溶出量、安全性能也呈现出类似的规律，而扣电容量和循环性能随着温度升高先增大后减小。控制反应温度不变，调整反应时间，也可呈现出类似的规律。
表4-1实施例4-1至4-7以及对比例1-8至1-11的性能测试结果
Figure PCTCN2022126838-appb-000059
Figure PCTCN2022126838-appb-000060
从表4-1中可以看出，在通过本申请的方法制备焦磷酸铁锂时，通过调节制备过程中的干燥温度/时间和烧结温度/时间，可以改善所得材料的性能，从而改善电池性能；在包覆过程中，通过调节干燥温度/时间和烧结温度/时间，可以改善所得材料的性能，从而改善电池性能。从对比例1-8至1-11可以看出，当焦磷酸铁锂制备过程中的干燥温度低于100℃或烧结步骤的温度低于400℃时，将无法获得本申请所希望制得的Li 2FeP 2O 7，从而无法改善材料性能以及二次电池的性能。
下面详述内核为Li 1+xMn 1-yA yP 1-zR zO 4，壳包括所述第一包覆层包含晶态焦磷酸盐，第二包覆层包含金属氧化物Q’ eO f，第三包覆层包含碳的实施例的制备以及性能测试，其中如无特殊说明，所涉及的试剂来源同实施例1-1至1-52的实际来源：
实施例1-B
步骤S1：制备Fe、Co、V和S共掺杂的草酸锰
将689.6g碳酸锰、455.27g碳酸亚铁、4.65g硫酸钴、4.87g二氯化钒加入混料机中充分混合6h。然后将得到的混合物转入反应釜中，并加入5L去离子水和1260.6g二水合草酸，加热至80℃，以500rpm的转速充分搅拌6h，混合均匀，直至反应终止无气泡产生，得到Fe、Co、和V共掺杂的草酸锰悬浮液。然后将悬浮液过滤，在120℃下烘干，再进行砂磨，得到粒径为100nm的草酸锰颗粒。
步骤S2：制备内核Li 0.997Mn 0.60Fe 0.393V 0.004Co 0.003P 0.997S 0.003O 4
取(1)中制备的草酸锰1793.1g以及368.3g碳酸锂、1146.6g磷酸二氢铵和4.9g稀硫酸，将它们加入到20L去离子水中，充分搅拌，在80℃下均匀混合反应10h，得到浆料。将浆料转入喷雾干燥设备中进行喷雾干燥造粒，在250℃的温度下进行干燥，得到粉料。在保护气氛(90％氮气和10％氢气)中，在700℃下将粉料在辊道窑中进行烧结4h，得到内核材料。采用电感耦合等离子体发射光谱(ICP)对内核材料进行元素含量检测，得到内核化学式为上述所示。
步骤S3：第一包覆层悬浊液的制备
制备Li 2FeP 2O 7溶液：将7.4g碳酸锂，11.6g碳酸亚铁，23.0g磷酸二氢铵和12.6g二水合草酸溶于500mL去离子水中，控制pH为5，然后搅拌并在室温下反应2h得到溶液，之后将该溶液升温到80℃并保持此温度4h，得到第一包覆层悬浊液。
步骤S4：第一包覆层的包覆
将步骤S2中获得的掺杂后的1571.9g磷酸锰锂内核材料加入到步骤S3中获得的第一包覆层悬浊液(包覆物质含量为15.7g)中，充分搅拌混合6h，混合均匀后，转入120℃烘箱中干燥6h，然后在650℃下烧结6h得到焦磷酸盐包覆后的材料。
步骤S5：第二包覆层悬浊液的制备
将47.1g纳米级Al 2O 3(粒径约20nm)溶于1500mL去离子水中，搅拌2h，得到第二包覆层悬浊液。
步骤S6：第二包覆层的包覆
将步骤S4中获得的1586.8g的焦磷酸盐包覆后的材料加入到步骤S5中得到的第二包覆层悬浊液(包覆物质含量为47.1g)中，充分搅拌混合6h，混合均匀后，转入120℃烘箱中干燥6h，然后700℃烧结8h得到两层包覆后的材料。
步骤S7：第三包覆层水溶液的制备
将37.3g蔗糖溶于500g去离子水中，然后搅拌并充分溶解，得到蔗糖水溶液。
步骤S8：第三包覆层的包覆
将步骤S6中获得的两层包覆的材料1633.9g加入到步骤S7中得到的蔗糖溶液中，一同搅拌混合6h，混合均匀后，转入150℃烘箱中干燥6h，然后在700℃下烧结10h得到三层包覆后的材料。
实施例2-B至62-B及对比例1-B至11-B
以类似于实施例1-B的方法制作实施例2-B至62-B和对比例1-B至11-B的正极活性材料，正极活性材料的制备中的不同之处参见表1-B至6-B。
其中，对比例1-B至2-B、4-B至10-B和实施例58B未包覆第一层，因此没有步骤S3-S4；对比例1-B至10-B以及实施例57-B未包覆第二层，因此没有步骤S5-S6。
表1-B：制备Fe、Co、V和S共掺杂的草酸锰和制备内核(步骤S1-S2)
Figure PCTCN2022126838-appb-000061
Figure PCTCN2022126838-appb-000062
Figure PCTCN2022126838-appb-000063
Figure PCTCN2022126838-appb-000064
Figure PCTCN2022126838-appb-000065
Figure PCTCN2022126838-appb-000066
Figure PCTCN2022126838-appb-000067
表2-B：第一包覆层悬浊液的制备(步骤S3)
Figure PCTCN2022126838-appb-000068
Figure PCTCN2022126838-appb-000069
表3-B：第一包覆层的包覆(步骤S4)
Figure PCTCN2022126838-appb-000070
Figure PCTCN2022126838-appb-000071
Figure PCTCN2022126838-appb-000072
Figure PCTCN2022126838-appb-000073
Figure PCTCN2022126838-appb-000074
表4-B：第二包覆层悬浊液的制备(步骤S5)
Figure PCTCN2022126838-appb-000075
Figure PCTCN2022126838-appb-000076
Figure PCTCN2022126838-appb-000077
表5-B：第二包覆层的包覆(步骤S6)
Figure PCTCN2022126838-appb-000078
Figure PCTCN2022126838-appb-000079
Figure PCTCN2022126838-appb-000080
Figure PCTCN2022126838-appb-000081
Figure PCTCN2022126838-appb-000082
表6-B：第三层包覆层的包覆(步骤S8)
Figure PCTCN2022126838-appb-000083
Figure PCTCN2022126838-appb-000084
Figure PCTCN2022126838-appb-000085
Figure PCTCN2022126838-appb-000086
Figure PCTCN2022126838-appb-000087
正极极片的制备
各项参数同实施例1。
负极极片的制备、隔离膜和电解液
各项参数同实施例1-1。
全电池的制备
将上述获得的正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正负极中间起到隔离的作用，并卷绕得到裸电芯。将裸电芯置于外包装中，注入上述电解液并封装，得到全电池(下文也称“全电”)。
扣式电池的制备
将上述的正极极片与负极、电解液一起在扣电箱中组装成扣式电池。
实施例和对比例的正极活性材料的性能测试结果参见下面的表格。 表7-B：正极活性材料的粉料性能及电池性能
Figure PCTCN2022126838-appb-000088
Figure PCTCN2022126838-appb-000089
Figure PCTCN2022126838-appb-000090
Figure PCTCN2022126838-appb-000091
Figure PCTCN2022126838-appb-000092
Figure PCTCN2022126838-appb-000093
表8-B：第一包覆层中的晶态焦磷酸盐的晶面间距和晶向(111)夹角
Figure PCTCN2022126838-appb-000094
由表7-B、8-B可见，与对比例相比，本申请实施例实现了更小的晶格变化率、更小的Li/Mn反位缺陷浓度、更大的压实密度、更接近于-2价的表面氧价态、更少的循环后Mn和Fe溶出量以及更好的电池性能，例如更高的扣电容量、更好的高温存储性能、更高的安全性和更好的循环性能。
表9-B：正极活性材料每一层的厚度以及锰元素和磷元素的重量比
Figure PCTCN2022126838-appb-000095
Figure PCTCN2022126838-appb-000096
Figure PCTCN2022126838-appb-000097
由表9-B可以看出，通过对磷酸锰铁锂(含锰量35％，含磷量约20％)的锰位和磷位进行掺杂以及三层包覆，正极活性材料中的锰元素含量以及锰元素与磷元素的重量含量比明显降低；此外，将实施例1-B至14-B与对比例3-B、对比例4-B、实施例58-B相比，结合表7-B可知，正极活性材料中锰元素和磷元素的降低会导致锰铁溶出量降低并且其制备的二次电池的电池性能提升。
Ⅱ.考察包覆层烧结方法对对正极活性材料性能的影响
下表中的实施例和对比例的电池制备类似于实施例1-B，不同之处使用下表中的方法参数。结果参见下表10-B。
表10-B：步骤S4、S6和S8对正极活性材料性能的影响
Figure PCTCN2022126838-appb-000098
Figure PCTCN2022126838-appb-000099
由以上内容可以看出，当步骤S4烧结温度范围为650-800℃且烧结时间为2-6小时、步骤S6烧结温度为400-600℃且烧结时间为6-10小时、步骤S8烧结温度为700-800℃且烧结时间为6-10小时时，能够实现更小的晶格变化率、更小的Li/Mn反位缺陷浓度、更少的锰元素和铁元素的溶出量、更好的3C充电恒流比、更大的电池容量、更好的电池循环性能、更好的高温存储稳定性。
此外，与实施例II-16(步骤S4的烧结温度为750℃，烧结时间为4.5小时)相比，实施例II-1(步骤S4的烧结温度为750℃时且烧结时间为4h时)实现了更好的正极活性材料性能和电池性能，这表明当步骤S4的烧结温度为750℃或大于750℃时，需要控制烧结时间小于4.5小时。
Ⅲ.考察内核制备中反应温度和反应时间对正极活性材料性能的影响
下表中的实施例的正极活性材料和电池制备类似于实施例1-B，正极活性材料制备中的不同之处参见下表中的方法参数。结果同样参见下表。
表11-B：内核制备中反应温度和反应时间对正极活性材料性能的影响
Figure PCTCN2022126838-appb-000100
Figure PCTCN2022126838-appb-000101
由表11-B可以看出，当步骤S1中的反应温度范围为60-120℃、反应时间为2-9小时且步骤S2中的反应温度范围为40-120℃、反应时间为1-10小时时，正极活性材料粉料性能(晶格变化率、Li/Mn反位缺陷浓度、表面氧价态、压实密度)和所制备的电池性能(电容量、高温循环性能、高温存储性能)均表现优异。
下面详述内核为Li 1+xC mMn 1-yA yP 1-zR zO 4-nD n，壳包括的所述第一包覆层包含晶态焦磷酸盐和金属氧化物Q’ eO f，第二包覆层包含碳的正极活性材料的制备以及性能测试：
实施例1C-1
步骤S1：制备掺杂的草酸锰
各项参数同实施例1的掺杂草酸锰的制备。
步骤S2：制备包含Li 0.994Mo 0.001Mn 0.65Fe 0.35P 0.999Si 0.001O 3.999F 0.001的内核
取1mol Fe掺杂的草酸锰颗粒、0.497mol碳酸锂、0.001mol的Mo(SO 4) 3、含有0.999mol磷酸的浓度85％的磷酸水溶液、0.001mol的H 4SiO 4、0.0005mol的NH 4HF 2和0.005mol蔗糖加入到20L去离子水中，将混合物转入砂磨机中充分研磨搅拌10小时，得到浆料；将浆料转移到喷雾干燥设备中进行喷雾干燥造粒，设定干燥温度为250℃，干燥4小时，得到颗粒；在氮气(90％v/v)+氢气(10％v/v)保护气氛中，将颗粒在700℃下烧结10小时，得到内核材料。采用电感耦合等离子体发射光谱(ICP)对内核材料进行元素含量检测，得到内核化学式为上述所示。
步骤S3：制备焦磷酸铁锂粉末
将4.77g碳酸锂、7.47g碳酸亚铁、14.84g磷酸二氢铵和1.3g二水合草酸溶于50ml去离子水中。混合物的pH为5，搅拌2小时使反应混合物充分反应。然后将反应后的溶液升温到80℃并保持该温度4小时，得到包含Li 2FeP 2O 7的悬浊液，将悬浊液进行过滤，用去离子水洗涤，并在120℃下干燥4h，得到粉末。将粉末在650℃、氮气气氛下烧结8小时，并自然冷却至室温后进行研磨，得到Li 2FeP 2O 7粉末。
步骤S4：制备包含三氧化二铝和蔗糖的悬浊液
将4.71g纳米级Al 2O 3(粒径约20nm)和3.73g蔗糖(以C 12H 22O 11计，下 同)加入150ml去离子水中，搅拌6小时充分混合，然后将混合物升温至120℃并保持该温度6小时，得到包含三氧化二铝和蔗糖的悬浊液。
步骤S5：两层包覆层的制备
将157.21g上述内核与1.57g上述焦磷酸铁锂(Li 2FeP 2O 7)粉末加入到上一步骤制备获得的包含三氧化二铝和蔗糖的悬浊液中，搅拌混合均匀后转入真空烘箱中在150℃下干燥6小时，然后通过砂磨分散所得产物，分散后将产物在氮气气氛中于700℃下烧结6小时，得到双层包覆的磷酸锰锂。
实施例1C-2至1C-59及对比例1C至12C
以类似于实施例1C-1的方法制作实施例1C-2至1C-59和对比例1C至12C的正极活性材料，正极活性材料的制备中的不同之处参见表1C至4C。
其中，对比例1C至9C不涉及步骤S3-S5；对比例10C不涉及步骤S4；对比例11C不涉及步骤S3。
表1C：制备掺杂的草酸锰和制备内核(步骤S1-S2)
Figure PCTCN2022126838-appb-000102
Figure PCTCN2022126838-appb-000103
Figure PCTCN2022126838-appb-000104
Figure PCTCN2022126838-appb-000105
Figure PCTCN2022126838-appb-000106
Figure PCTCN2022126838-appb-000107
Figure PCTCN2022126838-appb-000108
Figure PCTCN2022126838-appb-000109
表2C：仅制备焦磷酸盐粉末(步骤S3)
Figure PCTCN2022126838-appb-000110
表3C：制备包含氧化物和蔗糖的悬浊液(步骤S4)
Figure PCTCN2022126838-appb-000111
Figure PCTCN2022126838-appb-000112
Figure PCTCN2022126838-appb-000113
表4C：制备两层包覆层(步骤S5)
Figure PCTCN2022126838-appb-000114
Figure PCTCN2022126838-appb-000115
Figure PCTCN2022126838-appb-000116
Figure PCTCN2022126838-appb-000117
Figure PCTCN2022126838-appb-000118
Figure PCTCN2022126838-appb-000119
Figure PCTCN2022126838-appb-000120
Figure PCTCN2022126838-appb-000121
Figure PCTCN2022126838-appb-000122
实施例2C-1
除在制备焦磷酸铁锂(Li 2FeP 2O 7)粉末的步骤S3中，在粉末烧结步骤中的烧结温度为550℃，烧结时间为1h以控制Li 2FeP 2O 7的结晶度为30％，其他条件与实施例1C-1相同。
实施例2C-2
除在制备焦磷酸铁锂(Li 2FeP 2O 7)粉末的步骤S3中，在粉末烧结步骤中的烧结温度为550℃，烧结时间为2h以控制Li 2FeP 2O 7的结晶度为50％，其他条件与实施例1C-1相同。
实施例2C-3
除在制备焦磷酸铁锂(Li 2FeP 2O 7)粉末的步骤S3中，在粉末烧结步骤中的烧结温度为600℃，烧结时间为3h以控制Li 2FeP 2O 7的结晶度为70％，其他条件与实施例1C-1相同。
实施例2C-4
除在制备焦磷酸铁锂(Li 2FeP 2O 7)粉末的步骤S3中，在粉末烧结步骤中的烧结温度为500℃以控制Li 2FeP 2O 7的结晶度为10％，其他条件与实施例1C-1相同。
正极极片的制备
将上述制备的双层包覆的磷酸锰锂正极活性材料、导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按重量比为92：2.5：5.5加入到N-甲基吡咯烷酮(NMP)中，搅拌混合均匀，得到正极浆料。然后将正极浆料按0.280g/1540.25mm 2均匀涂覆于铝箔上，经烘干、冷压、分切，得到正极极片。
负极极片的制备
将负极活性材料人造石墨、导电剂超导炭黑(Super-P)、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC-Na)按照质量比为95％：1.5％：1.8％：1.7％溶于去离子水中，充分搅拌混合均匀后，得到粘度3000mPa.s、固含52％的负极浆料；将负极浆料涂覆在6μm的负极集流体铜箔上，之后在100℃烘烤4小时以烘干，辊压，得到压实密度为1.75g/cm 3的负极极片。
隔离膜
采用聚丙烯膜。
电解液的制备
将碳酸乙烯酯、碳酸二甲酯和1,2-丙二醇碳酸酯按体积比1:1:1混合，然后将LiPF 6均匀溶解在上述溶液中，得到电解液。该电解液中，LiPF 6的浓度为1mol/L。
全电池的制备
将上述获得的正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正负极中间起到隔离的作用，并卷绕得到裸电芯。将裸电芯置于外包装中，注入上述电解液并封装，得到全电池(下文也称“全电”)。
扣式电池的制备
将上述制备的正极活性材料、PVDF、乙炔黑以90：5：5的重量比加入至NMP中，在干燥房中搅拌制成浆料。在铝箔上涂覆上述浆料，干燥、冷压制成正极极片。涂覆量为0.2g/cm 2，压实密度为2.0g/cm 3。
采用锂片作为负极，采用1mol/L的LiPF 6在体积比1：1：1的碳酸亚乙酯(EC)+碳酸二乙酯(DEC)+碳酸二甲酯(DMC)中的溶液作为电解液，与上述制备的正极极片一起在扣电箱中组装成扣式电池。
表5C：实施例1C-1至1C-59以及对比例1C至12C的性能测试结果
Figure PCTCN2022126838-appb-000123
Figure PCTCN2022126838-appb-000124
Figure PCTCN2022126838-appb-000125
Figure PCTCN2022126838-appb-000126
Figure PCTCN2022126838-appb-000127
Figure PCTCN2022126838-appb-000128
Figure PCTCN2022126838-appb-000129
Figure PCTCN2022126838-appb-000130
Figure PCTCN2022126838-appb-000131
Figure PCTCN2022126838-appb-000132
综合实施例1C-1至1C-59以及对比例1C至9C可知，第一包覆层的存在有利于降低所得材料的Li/Mn反位缺陷浓度和循环后Fe和Mn溶出量，提高电池的扣电克容量，并改善电池的高温存储性能、安全性能和循环性能。当在Li位、Mn位、磷位和氧位分别掺杂其他元素时，可显著降低所得材料的晶格变化率、反位缺陷浓度和Fe和Mn溶出量，提高电池的克容量和压实密度，并改善电池的高温存储性能、安全性能和循环性能。
综合实施例1C-33至1C-36可知，随着第一包覆层的量从3.2％增加至6.4％，所得材料的循环后Fe和Mn溶出量逐渐下降，对应电池的高温存储性能、安全性能和45℃下的循环性能也得到改善，但扣电克容量略有下降。可选地，当第一包覆层的总量为4-6.4重量％时，对应电池的综合性能最佳。
综合实施例1C-1以及实施例1C-37至1C-40可知，随着第二包覆层的量从1％增加至6％，所得材料的循环后Fe和Mn溶出量逐渐下降，对应电池的高温存储性能、安全性能和45℃下的循环性能也得到改善，但扣电克容量却略有下降。可选地，当第二包覆层的总量为3-5重量％时，对应电池的综合性能最佳。
综合实施例1C-1、实施例1C-41至1C-44可知，当第一包覆层中同时存在Li 2FeP 2O 7和Al 2O 3、特别是Li 2FeP 2O 7和Al 2O 3的重量比为1：3至3：1时，对电池性能的改善明显。
表6C：实施例1C-1、实施例2C-1至2C-4的性能测试结果
Figure PCTCN2022126838-appb-000133
由表6C可以看出，随着第一包覆层中焦磷酸盐的结晶度逐渐增加，对应材料的晶格变化率、Li/Mn反位缺陷浓度以及Fe和Mn溶出量逐渐下降，电池的扣电容量逐渐增加，安全性能和循环性能也逐渐改善。
表7C：步骤S1-S2采用不同参数的性能测试结果
Figure PCTCN2022126838-appb-000134
Figure PCTCN2022126838-appb-000135
由表7C可以看出，通过调整内核制备过程中反应釜内的搅拌转速、反应温度、研磨时间以及烧结温度和时间，可以进一步改善本申请正极材料的各项性能。 表8C：步骤S3采用不同参数的性能测试结果
Figure PCTCN2022126838-appb-000136
表9C：步骤S5采用不同参数的性能测试结果
Figure PCTCN2022126838-appb-000137
从表8C、9C中可以看出，在通过本申请的方法制备焦磷酸铁锂时，通过调节制备过程中的干燥温度/时间和烧结温度/时间，可以改善所得材料的性能，从而改善电池性能；在包覆过程中，通过调节干燥温度/时间和烧结温度/时间，可以改善所得材料的性能，从而改善电池性能。
下面详述内核为Li 1+xC mMn 1-yA yP 1-zR zO 4-nD n，壳包括第一包覆层(晶态焦磷酸盐)、第二包覆层(金属氧化物Q’ eO f)和第三包覆层(碳)的正极活性材料的制备以及性能测试：
实施例1D
步骤S1：制备掺杂的草酸锰
各项操作同实施例1。
步骤S2：制备包含Li 0.994Mo 0.001Mn 0.65Fe 0.35P 0.999Si 0.001O 3.999F 0.001的内核
各项操作同实施例1C-1的步骤S2。
步骤S3：第一包覆层悬浊液的制备
制备Li 2FeP 2O 7溶液：将7.4g碳酸锂，11.6g碳酸亚铁，23.0g磷酸二氢铵和12.6g二水合草酸溶于500mL去离子水中，控制pH为5，然后搅拌并在室温下反应2h得到溶液，之后将该溶液升温到80℃并保持此温度4h，得到第一包覆层悬浊液。
步骤S4：第一包覆层的包覆
将步骤S2中获得的掺杂后的157.2g磷酸锰锂内核材料加入到步骤S3中获得的第一包覆层悬浊液(包覆物质含量为1.572g)中，充分搅拌混合6h，混合均匀后，转入120℃烘箱中干燥6h，然后在650℃下烧结6h得到焦磷酸盐包覆后的材料。
步骤S5：第二包覆层悬浊液的制备
将4.71g纳米Al 2O 3(粒径约20nm)溶于1500mL去离子水中，搅拌2h，得到第二包覆层悬浊液。
步骤S6：第二包覆层的包覆
将步骤S4中获得的158.772g的焦磷酸盐包覆后的材料加入到步骤S5中得到的第二包覆层悬浊液(包覆物质含量为4.71g)中，充分搅拌混合6h，混合均匀后，转入120℃烘箱中干燥6h，然后700℃烧结8h得到两层包覆后的材料。
步骤S7：第三包覆层水溶液的制备
将37.3g蔗糖溶于500g去离子水中，然后搅拌并充分溶解，得到蔗糖水溶液。
步骤S8：第三包覆层的包覆
将步骤S6中获得的两层包覆的材料1633.9g加入到步骤S7中得到的蔗糖溶液中，一同搅拌混合6h，混合均匀后，转入150℃烘箱中干燥6h，然后在700℃下烧结10h得到三层包覆后的材料。
实施例2D至89D及对比例1D至12D
以类似于实施例1D的方法制作实施例2D至89D和对比例1D至12D的正极活性材料，正极活性材料的制备中的不同之处参见表1D至6D。
其中，对比例1D-9D和对比例11D未包覆第一层，因此没有步骤S3-S4；对比例1D-10D未包覆第二层，因此没有步骤S5-S6。
表1D：制备掺杂的草酸锰和制备内核(步骤S1-S2)
Figure PCTCN2022126838-appb-000138
Figure PCTCN2022126838-appb-000139
Figure PCTCN2022126838-appb-000140
Figure PCTCN2022126838-appb-000141
Figure PCTCN2022126838-appb-000142
Figure PCTCN2022126838-appb-000143
Figure PCTCN2022126838-appb-000144
Figure PCTCN2022126838-appb-000145
Figure PCTCN2022126838-appb-000146
Figure PCTCN2022126838-appb-000147
Figure PCTCN2022126838-appb-000148
Figure PCTCN2022126838-appb-000149
Figure PCTCN2022126838-appb-000150
表2D：第一包覆层悬浊液的制备(步骤S3)
Figure PCTCN2022126838-appb-000151
Figure PCTCN2022126838-appb-000152
*当第一包覆层包覆物质的量成倍增加或减少时，第一包覆层悬浊液的原料用量相应地成倍增加或减少。
表3D：第一包覆层的包覆(步骤S4)
Figure PCTCN2022126838-appb-000153
Figure PCTCN2022126838-appb-000154
表4D：第二包覆层悬浊液的制备(步骤S5)
Figure PCTCN2022126838-appb-000155
*当第二包覆层包覆物质的量成倍增加或减少时，第二包覆层悬浊液的原料用量相应地成倍增加或减少(但去离子水用量不变)。
表5D：第二包覆层的包覆(步骤S6)
Figure PCTCN2022126838-appb-000156
Figure PCTCN2022126838-appb-000157
Figure PCTCN2022126838-appb-000158
表6D：第三层包覆层的包覆(步骤S8)
Figure PCTCN2022126838-appb-000159
Figure PCTCN2022126838-appb-000160
Figure PCTCN2022126838-appb-000161
正极极片的制备
将上述制备的三层包覆后的正极活性材料、导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按重量比为97.0：1.2：1.8加入到N-甲基吡咯烷酮(NMP)中，搅拌混合均匀，得到正极浆料。然后将正极浆料按0.280g/1540.25mm 2均匀涂覆于铝箔上，经烘干、冷压、分切，得到正极极片。
负极极片的制备
将负极活性材料人造石墨、导电剂超导炭黑(Super-P)、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC-Na)按照质量比为95％：1.5％：1.8％：1.7％溶于去离子水中，充分搅拌混合均匀后，得到粘度3000mPa.s、固含52％的负极浆料；将负极浆料涂覆在6μm的负极集流体铜箔上，之后在100℃烘烤4小时以烘干，辊压，得到压实密度为1.75g/cm3的负极极片。
隔离膜
采用聚丙烯膜。
电解液的制备
将碳酸乙烯酯、碳酸二甲酯和1,2-丙二醇碳酸酯按体积比1:1:1混合，然后将LiPF 6均匀溶解在上述溶液中，得到电解液。该电解液中，LiPF 6的浓度为1mol/L。
全电池的制备
将上述获得的正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正负极中间起到隔离的作用，并卷绕得到裸电芯。将裸电芯置于外包装中，注入上述电解液并封装，得到全电池(下文也称“全电”)。
扣式电池的制备
将上述的正极极片与负极、电解液一起在扣电箱中组装成扣式电池(下文也称“扣电”)。
表7D：正极活性材料的粉料性能及电池性能
Figure PCTCN2022126838-appb-000162
Figure PCTCN2022126838-appb-000163
Figure PCTCN2022126838-appb-000164
Figure PCTCN2022126838-appb-000165
Figure PCTCN2022126838-appb-000166
Figure PCTCN2022126838-appb-000167
Figure PCTCN2022126838-appb-000168
Figure PCTCN2022126838-appb-000169
Figure PCTCN2022126838-appb-000170
Figure PCTCN2022126838-appb-000171
Figure PCTCN2022126838-appb-000172
Figure PCTCN2022126838-appb-000173
Figure PCTCN2022126838-appb-000174
Figure PCTCN2022126838-appb-000175
Figure PCTCN2022126838-appb-000176
Figure PCTCN2022126838-appb-000177
表8D：第一包覆层中焦磷酸盐的晶面间距和晶向夹角参数
Figure PCTCN2022126838-appb-000178
Figure PCTCN2022126838-appb-000179
Figure PCTCN2022126838-appb-000180
Figure PCTCN2022126838-appb-000181
Figure PCTCN2022126838-appb-000182
由表7D-8D可知，与对比例相比，实施例实现了更小的晶格变化率、更小的Li/Mn反位缺陷浓度、更大的压实密度、更接近于-2价的表面氧价态、更少的循环后Mn和Fe溶出量以及更好的电池性能，例如更高的扣电容量、更好的高温存储性能、更高的安全性和更好的循环性能。
表9D：正极活性材料的性能测试结果(其中的实施例29D-44D的第一包覆层、第二包覆层和第三包覆层与实施例1D的相同)
Figure PCTCN2022126838-appb-000183
Figure PCTCN2022126838-appb-000184
Figure PCTCN2022126838-appb-000185
Figure PCTCN2022126838-appb-000186
由表9D可知，本申请通过对磷酸锰铁锂的Li位、锰位、磷位和O位进行全掺杂以及三层包覆，实现了更小的晶格变化率、更小的Li/Mn反位缺陷浓度、更大的压实密度、更接近于-2价的表面氧价态、更少的循环后Mn和Fe溶出量以及更好的电池性能，例如更高的扣电容量、更好的高温存储性能、更高的安全性和更好的循环性能。
表10D：制备的正极活性材料的性能测试结果
Figure PCTCN2022126838-appb-000187
Figure PCTCN2022126838-appb-000188
由表10D可知，随着正极活性材料中焦磷酸盐结晶度的升高，压实密度逐渐增大，3C充电恒流比增大，循环后Mn和Fe溶出量降低，扣点容量升高，高温存储性能、安全性能和循环性能提升。
以上详细描述了本申请的优选实施方式，但是，本申请并不限于上述实施方式中的具体细节，在本申请的技术构思范围内，可以对本申请的技术方案进行多种简单变型，这些简单变型均属于本申请的保护范围。
另外需要说明的是，在上述具体实施方式中所描述的各个具体技术特征，在不矛盾的情况下，可以通过任何合适的方式进行组合。
此外，本申请的各种不同的实施方式之间也可以进行任意组合，只要其不违背本申请的思想，其同样应当视为本申请所公开的内容。
在本申请的描述中，需要理解的是，术语“上”、“下”、“前”、“后”、“顶”、“底”、“内”、“外”等指示的方位或位置关系为基于附图所示的方位或位置关系，仅是为了便于描述本申请和简化描述，而不是指示或暗示所指的装置或元件必须具有特定的方位、以特定的方位构造和操作，因此不能理解为对本申请的限制。

Claims (80)

  1. 一种正极活性材料，其具有内核及包覆所述内核的壳，
    所述内核包括三元材料、 dLi 2MnO 3·(1-d)LiMO 2以及LiMPO 4中的至少一种，0＜d＜1，所述M包括选自Fe、Ni、Co、Mn中的一种或多种，
    所述壳含有结晶态无机物，所述结晶态无机物使用X射线衍射测量的主峰的半高全宽为0-3°，所述结晶态无机物包括选自金属氧化物以及无机盐中的一种或多种。
  2. 根据权利要求1所述的正极活性材料，其中，所述壳包括所述金属氧化物以及所述无机盐中的至少之一，以及碳。
  3. 根据权利要求1或2所述的正极活性材料，其中，所述内核包括LiMPO 4且M包括Mn和非Mn元素，所述非Mn元素满足以下条件的至少之一：
    所述非Mn元素的离子半径为a，锰元素的离子半径为b，|a-b|/b不大于10％；
    所述非Mn元素的化合价变价电压为U，2V<U<5.5V；
    所述非Mn元素和O形成的化学键的化学活性不小于P-O键的化学活性；
    所述非Mn元素的最高化合价不大于6。
  4. 根据权利要求3所述的正极活性材料，其中，所述非Mn元素包括第一掺杂元素和第二掺杂元素中的一种或两种，所述第一掺杂元素为锰位掺杂，所述第二掺杂元素为磷位掺杂。
  5. 根据权利要求4所述的正极活性材料，其中，所述第一掺杂元素满足以下条件的至少之一：
    所述第一掺杂元素的离子半径为a，锰元素的离子半径为b，|a-b|/b不大于10％；
    所述第一掺杂元素的化合价变价电压为U，2V<U<5.5V。
  6. 根据权利要求4所述的正极活性材料，其中，所述第二掺杂元素满足以下条件的至少之一：
    所述第二掺杂元素和氧的化学键的化学活性不小于P-O键的化学活性；
    所述第二掺杂元素的最高化合价不大于6。
  7. 根据权利要求4-6任一项所述的正极活性材料，其中，含有至少两种所述第一掺杂元素。
  8. 根据权利要求4-7任一项所述的正极活性材料，其中，所述第一掺杂元素包括选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素。
  9. 根据权利要求8所述的正极活性材料，其中，所述第一掺杂元素包括选自Fe、Ti、 V、Ni、Co和Mg中的至少两种。
  10. 根据权利要求4-9任一项所述的正极活性材料，其中，所述第二掺杂元素包括选自B(硼)、S、Si和N中的一种或多种元素。
  11. 根据权利要求1-10任一项所述的正极活性材料，其中，所述内核具有化学式为Li 1+xMn 1-yA yP 1-zR zO 4的化合物，x为在-0.100-0.100范围内的任意数值，y为在0.001-0.500范围内的任意数值，z为在0.001-0.100范围内的任意数值，所述A包括选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素，
    所述R包括选自B(硼)、S、Si和N中的一种或多种元素。
  12. 根据权利要求1-10任一项所述的正极活性材料，其中，内核具有化学式为Li 1+xC mMn 1-yA yP 1-zR zO 4-nD n的化合物，
    其中，所述C包括选自Zn、Al、Na、K、Mg、Nb、Mo和W中的一种或多种元素，
    所述A包括选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Mg、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素，
    所述R包括选自B(硼)、S、Si和N中的一种或多种元素，
    所述D包括选自S、F、Cl和Br中的一种或多种元素，
    x为在0.100-0.100范围内的任意数值，y为在0.001-0.500范围内的任意数值，z为在0.001-0.100范围内的任意数值，n为在0.001至0.1范围内的任意数值，m为在0.9至1.1范围内的任意数值。
  13. 根据权利要求11或12所述的正极活性材料，其中，y与1-y的比值为1：10至1：1，可选为1：4至1：1。
  14. 根据权利要求11或12所述的正极活性材料，其中，z与1-z的比值为1：9至1：999，可选为1：499至1：249。
  15. 根据权利要求11或12所述的正极活性材料，其中，所述C、R和D各自独立地为上述各自范围内的任一种元素，并且所述A为其范围内的至少两种元素；
    可选地，
    所述C为选自Mg和Nb中的任一种元素，和/或，
    所述A为选自Fe、Ti、V、Co和Mg中的至少两种元素，可选地为Fe与选自Ti、V、Co和Mg中的一种以上元素，和/或，
    所述R为S，和/或，
    所述D为F。
  16. 根据权利要求11或12所述的正极活性材料，其中，所述x选自0.001至0.005的范围；和/或，所述y选自0.01至0.5的范围，可选地选自0.25至0.5的范围；和/或，所述 z选自0.001至0.005的范围；和/或，所述n选自0.001至0.005的范围。
  17. 根据权利要求1-16任一项所述的正极活性材料，其中，所述正极活性材料的晶格变化率为8％以下，可选地为4％以下，可选为3.8％以下，更可选为2.0-3.8％。
  18. 根据权利要求1-17任一项所述的正极活性材料，其中，所述正极活性材料的Li/Mn反位缺陷浓度为4％以下，可选为2.2％以下，更可选为1.5-2.2％，更可选为2％以下，更可选地为0.5％以下。
  19. 根据权利要求1-18任一项所述的正极活性材料，其中，所述正极活性材料的表面氧价态为-1.89～-1.98，可选地为-1.90至-1.98，更可选地为-1.90以下，更可选地为-1.82以下。
  20. 根据权利要求1-19任一项所述的正极活性材料，其中，所述正极活性材料在3T下的压实密度为2.0g/cm 3以上，可选地为2.2g/cm 3以上，可选地为2.2g/cm 3以上且2.8g/cm 3以下。
  21. 根据权利要求1-20任一项所述的正极活性材料，其中，所述结晶态无机物包括焦磷酸盐QP 2O 7和磷酸盐XPO 4，所述金属氧化物包括Q’ eO f，
    其中所述Q和X各自独立地选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb或Al中的一种或多种；可选地所述Q包括Li以及选自Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb或Al中的一种或多种；
    Q’为选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb和Al中的一种或多种元素、可选地为选自Li、Fe和Zr中的一种或多种元素，所述M′为选自碱金属、碱土金属、过渡金属、第IIIA族元素、第IVA族元素、镧系元素和Sb中的一种或多种元素、可选地为选自Li、Be、B、Na、Mg、Al、Si、P、K、Ca、Sc、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Ga、Ge、As、Se、Sr、Y、Zr、Nb、Mo、Tc、Ru、Rh、Pd、Ag、Cd、In、Sn、Sb、Te、W、La和Ce中的一种或多种元素、更可选地为选自Mg、Al、Si、Zn、Zr和Sn中的一种或多种元素，所述e大于0且小于或等于2，所述f大于0且小于或等于5。
  22. 根据权利要求21所述的正极材料，其中，所述焦磷酸盐包括Li aQP 2O 7和/或Q b(P 2O 7) c，其中，0≤a≤2，1≤b≤4，1≤c≤6，所述a、b和c的值满足以下条件：使所述Li aQP 2O 7或Q b(P 2O 7) c保持电中性，所述Li aQP 2O 7和Q b(P 2O 7) c中的Q各自独立地为选自Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb或Al中的一种或多种元素。
  23. 根据权利要求21或22所述的正极材料，其中，所述磷酸盐的晶面间距为0.244-0.425nm，可选地为0.345-0.358nm，晶向(111)的夹角为20.00°-37.00°，可选地为24.25°-26.45°；所述焦磷酸盐的晶面间距为0.293-0.470nm，可选地为0.293-0.326nm，晶向(111)的夹角为18-32.57°，可选地为19.211°-30.846°，更可选地为26.41°-32.57°。
  24. 根据权利要求21-23中任一项所述的正极活性材料，其中，
    所述焦磷酸盐和磷酸盐的结晶度各自独立地为10％至100％，可选为50％至100％。
  25. 根据权利要求21-24任一项所述的正极活性材料，其中，所述壳含有包覆碳层，所述结晶态无机物位于所述内核和所述包覆碳层之间，所述包覆碳层的碳为SP2形态碳与SP3形态碳的混合物，可选地，所述SP2形态碳与SP3形态碳的摩尔比为在0.07-13范围内的任意数值，可选地为在0.1-10范围内的任意数值，可选为在2.0-3.0范围内的任意数值。
  26. 根据权利要求21-25任一项所述的正极活性材料，其中，所述壳包括包覆所述内核的第一包覆层以及包覆所述第一包覆层的第二包覆层，
    其中，所述第一包覆层包括焦磷酸盐QP 2O 7和磷酸盐XPO 4，所述第二包覆层为包覆碳层。
  27. 根据权利要求26所述的正极活性材料，其中，所述第一包覆层的包覆量大于0重量％且小于等于7重量％，可选为4-5.6重量％，基于所述内核的重量计。
  28. 根据权利要求26或27中任一项所述的正极活性材料，其中，
    所述第一包覆层中焦磷酸盐和磷酸盐的重量比为1:3至3:1，可选为1:3至1:1。
  29. 根据权利要求26-28中任一项所述的正极活性材料，其中，
    所述第二包覆层的包覆量为大于0重量％且小于等于6重量％，可选为3-5重量％，基于所述内核的重量计。
  30. 根据权利要求21-25任一项所述的正极活性材料，其中，所述壳包括包覆所述内核的第一包覆层以及包覆所述第一包覆层的第二包覆层，
    其中，所述第一包覆层包括晶态的焦磷酸盐QP 2O 7和金属氧化物Q’ eO f，所述第二包覆层为包覆碳层。
  31. 根据权利要求30所述的正极活性材料，其中，所述第一包覆层的包覆量大于0重量％且小于或等于7重量％，可选为4-5.6重量％，基于所述内核的重量计。
  32. 根据权利要求30或31所述的正极活性材料，其中，所述第一包覆层中焦磷酸盐和氧化物的重量比为1:3至3:1，可选为1:3至1:1。
  33. 根据权利要求30-32中任一项所述的正极活性材料，其中，所述第二包覆层的包覆量为大于0重量％且小于或等于6重量％，可选为3-5重量％，基于所述内核的重量计。
  34. 根据权利要求21-25任一项所述的正极材料，其特征在于，所述壳包括包覆所述内核的第一包覆层、包覆所述第一包覆层的第二包覆层和包覆所述第二包覆层的第三包覆层，
    所述第一包覆层包含晶态焦磷酸盐，
    所述第二包覆层包含金属氧化物Q’ eO f，
    所述晶态焦磷酸盐包括Li aQP 2O 7和/或Q b(P 2O 7) c，其中，所述a大于0且小于或等于2，所述b为1-4范围内的任意数值，所述c为1-3范围内的任意数值；
    所述第三包覆层包含碳。
  35. 根据权利要求34所述的正极活性材料，其中，所述第一包覆层的包覆量为大于0且小于或等于6重量％，可选为大于0且小于或等于5.5重量％，更可选为大于0且小于或等于2重量％，基于所述内核的重量计；和/或
    所述第二包覆层的包覆量为大于0且小于或等于6重量％，可选为大于0且小于或等于5.5重量％，更可选为2重量％-4重量％，基于所述内核的重量计；和/或
    所述第三包覆层的包覆量为大于0且小于或等于6重量％，可选为大于0且小于或等于5.5重量％，更可选为大于0且小于或等于2重量％，基于所述内核的重量计。
  36. 根据权利要求根据权利要求34或35所述的正极活性材料，其中，
    所述第一包覆层的厚度为2-10nm；和/或
    所述第二包覆层的厚度为3-15nm；和/或
    所述第三包覆层的厚度为5-25nm。
  37. 根据权利要求34-36任一项所述的正极活性材料，其中，基于正极活性材料的重量计，
    锰元素含量在10重量％-35重量％范围内，可选在15重量％-30重量％范围内，更可选在17重量％-20重量％范围内，
    磷元素的含量在12重量％-25重量％范围内，可选在15重量％-20重量％范围内；
    可选地，锰元素和磷元素的重量比在0.90-1.25范围内，更可选为0.95-1.20范围内。
  38. 根据权利要求21所述的正极活性材料，其中，所述正极活性材料包括包覆所述内核的第一包覆层、包覆所述第一包覆层的第二包覆层以及包覆所述第二包覆层的第三包覆层，其中，
    所述第一包覆层包括晶态焦磷酸盐Li aQP 2O 7和/或Q b(P 2O 7) c，
    所述第二包覆层包括晶态磷酸盐XPO 4，
    所述第三包覆层为碳。
  39. 根据权利要求38所述的正极活性材料，其中，所述第一包覆层的包覆量为大于0且小于或等于6重量％，可选为大于0且小于或等于5.5重量％，更可选为大于0且小于或等于2重量％，基于所述内核的重量计；和/或
    所述第二包覆层的包覆量为大于0且小于或等于6重量％，可选为大于0且小于或等于5.5重量％，更可选为2-4重量％，基于所述内核的重量计；和/或
    所述第三包覆层的包覆量为大于0且小于或等于6重量％，可选为大于0且小于或等于5.5重量％，更可选为大于0且小于或等于2重量％，基于所述内核的重量计。
  40. 根据权利要求38或39所述的具有核-壳结构的正极活性材料，其中，所述第一包 覆层的厚度为1-10nm；和/或
    所述第二包覆层的厚度为2-15nm；和/或
    所述第三包覆层的厚度为2-25nm。
  41. 根据权利要求38-40中任一项所述的具有核-壳结构的正极活性材料，其中，
    基于正极活性材料的重量计，锰元素含量在10重量％-35重量％范围内，可选在15重量％-30重量％范围内，更可选在17重量％-20重量％范围内，磷元素的含量在12重量％-25重量％范围内，可选在15重量％-20重量％范围内，锰元素和磷元素的重量比范围为0.90-1.25，可选为0.95-1.20。
  42. 一种制备正极活性材料的方法，其包括形成内核，以及在所述内核的至少表面形成壳的步骤，
    所述内核包括三元材料、 dLi 2MnO 3·(1-d)LiMO 2以及LiMPO 4中的至少一种，0＜d＜1，所述M包括选自Fe、Ni、Co、Mn中的一种或多种，
    所述壳含有结晶态无机物，所述结晶态无机物使用X射线衍射测量的主峰的半高全宽为0-3°，所述结晶态无机物包括选自金属氧化物以及无机盐中的一种或多种。
  43. 根据权利要求42所述的方法，其中，所述内核包括LiMPO 4且M包括Mn和非Mn元素，所述非Mn元素满足以下条件的至少之一，所述方法包括在锰源、锂源、磷源和含有所述非Mn元素的掺杂剂混合并烧结，
    所述非Mn元素满足以下条件的至少之一：
    所述非Mn元素的离子半径为a，锰元素的离子半径为b，|a-b|/b不大于10％；
    所述非Mn元素的化合价变价电压为U，2V<U<5.5V；
    所述非Mn元素和O形成的化学键的化学活性不小于P-O键的化学活性；
    所述非Mn元素的最高化合价不大于6。
  44. 根据权利要求43所述的方法，其中，所述非Mn元素包括第一掺杂元素和第二掺杂元素中的一种或两种，所述第一掺杂元素为锰位掺杂，所述第二掺杂元素为磷位掺杂，
    所述第一掺杂元素满足以下条件的至少之一：所述掺杂元素的离子半径为a，锰元素的离子半径为b，|a-b|/b不大于10％；以及所述掺杂元素的化合价变价电压为U，2V<U<5.5V；
    所述第二掺杂元素满足以下条件的至少之一：所述第二掺杂元素和氧的化学键的化学活性不小于P-O键的化学活性；以及所述第二掺杂元素的最高化合价不大于6。
  45. 根据权利要求44所述的方法，所述非Mn元素包括第一和第二掺杂元素，所述方法包括：
    将锰源、所述锰位元素的掺杂剂和酸混合，得到具有所述第一掺杂元素的锰盐颗粒；
    将所述具有第一掺杂元素的锰盐颗粒与锂源、磷源和所述第二掺杂元素的掺杂剂在溶 剂中混合并得到浆料，在惰性气体气氛保护下烧结后得到具有所述掺杂元素M的所述磷酸锰锂化合物。
  46. 根据权利要求44或45所述的方法，其中，所述第一掺杂元素包括选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素，所述第二掺杂元素包括选自B(硼)、S、Si和N中的一种或多种元素。
  47. 根据权利要求42-46任一项所述的方法，其中，所述方法包括：
    按照化学式Li 1+xMn 1-yA yP 1-zR zO 4形成LiMPO 4，x为在-0.100-0.100范围内的任意数值，y为在0.001-0.500范围内的任意数值，z为在0.001-0.100范围内的任意数值，所述A包括选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素，
    所述R包括选自B(硼)、S、Si和N中的一种或多种元素。
  48. 根据权利要求42-46任一项所述的方法，其中，所述方法包括：
    按照化学式Li 1+xC mMn 1-yA yP 1-zR zO 4-nD n形成LiMPO 4，其中，所述C包括选自Zn、Al、Na、K、Mg、Nb、Mo和W中的一种或多种元素，
    所述A包括选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Mg、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素，
    所述R包括选自B(硼)、S、Si和N中的一种或多种元素，
    所述D包括选自S、F、Cl和Br中的一种或多种元素，
    x为在0.100-0.100范围内的任意数值，y为在0.001-0.500范围内的任意数值，z为在0.001-0.100范围内的任意数值，n为在0.001至0.1范围内的任意数值，m为在0.9至1.1范围内的任意数值。
  49. 根据权利要求47或48所述的方法，其中，元素C的源选自元素C的单质、氧化物、磷酸盐、草酸盐、碳酸盐和硫酸盐中的至少一种，元素A的源选自元素A的单质、氧化物、磷酸盐、草酸盐、碳酸盐、硫酸盐氯化盐、硝酸盐、有机酸盐、氢氧化物、卤化物中的至少一种，元素R的源选自元素R的硫酸盐、硼酸盐、硝酸盐和硅酸盐、有机酸、卤化物、有机酸盐、氧化物、氢氧化物中的至少一种，元素D的源选自元素D的单质和铵盐中的至少一种。
  50. 根据权利要求45所述的方法，得到具有第一掺杂元素的锰盐颗粒满足以下条件的至少之一：
    在20-120℃、可选为40-120℃、可选地为60-120℃、更可选地为25-80℃的温度下将锰源、所述锰位元素和酸混合；和/或
    所述混合在搅拌下进行，所述搅拌在200-800rpm下，可选地400-700rpm下，更可选 地500-700rpm进行1-9h，可选地为3-7h，更可选地为可选地为2-6h。
  51. 根据权利要求45所述的方法，其中，将所述具有第一掺杂元素的锰盐颗粒与锂源、磷源和所述第二掺杂元素的掺杂剂在溶剂中混合是在20-120℃、可选为40-120℃的温度下进行1-10h。
  52. 根据权利要求45所述的方法，其中，按照化学式Li 1+xC xMn 1-yA yP 1-zR zO 4-nD n形成LiMPO 4，将所述具有第一掺杂元素的锰盐颗粒与锂源、磷源和所述第二掺杂元素的掺杂剂在溶剂中研磨并混合进行8-15小时。
  53. 根据权利要求42-52中任一项所述的方法，其中，所述无机盐包括所述结晶态无机物包括焦磷酸盐QP 2O 7和磷酸盐XPO 4中的至少之一，所述金属氧化物包括Q’ eO f，
    其中所述Q和X各自独立地选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb或Al中的一种或多种；可选地所述Q包括Li以及选自Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb或Al中的一种或多种；
    Q’为选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb和Al中的一种或多种元素、可选地为选自Li、Fe和Zr中的一种或多种元素，所述M′为选自碱金属、碱土金属、过渡金属、第IIIA族元素、第IVA族元素、镧系元素和Sb中的一种或多种元素、可选地为选自Li、Be、B、Na、Mg、Al、Si、P、K、Ca、Sc、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Ga、Ge、As、Se、Sr、Y、Zr、Nb、Mo、Tc、Ru、Rh、Pd、Ag、Cd、In、Sn、Sb、Te、W、La和Ce中的一种或多种元素、更可选地为选自Mg、Al、Si、Zn、Zr和Sn中的一种或多种元素，所述e大于0且小于或等于2，所述f大于0且小于或等于5；
    可选地，所述焦磷酸盐包括Li aQP 2O 7和/或Q b(P 2O 7) c，其中，0≤a≤2，1≤b≤4，1≤c≤6，所述a、b和c的值满足以下条件：使所述Li aQP 2O 7或Q b(P 2O 7) c保持电中性，所述Li aQP 2O 7和Q b(P 2O 7) c中的Q各自独立地为选自Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb或Al中的一种或多种元素。
  54. 根据权利要求53所述的方法，其中，所述壳包括包覆所述内核的第一包覆层和包覆所述第一包覆层的第二包覆层，所述第一包覆层含有所述焦磷酸盐QP 2O 7和所述磷酸盐XPO 4，所述第二包覆层包含碳，所述方法包括：
    提供QP 2O 7粉末和包含碳的源的XPO 4悬浊液，将所述内核、QP 2O 7粉末加入到包含碳的源的XPO 4悬浊液中并混合，经烧结获得正极活性材料。
  55. 根据权利要求54所述的方法，其中，所述提供QP 2O 7粉末包括：
    将元素Q的源和磷的源添加到溶剂中，得到混合物，调节混合物的pH为4-6，搅拌并充分反应，然后经干燥、烧结获得，且所述提供QP 2O 7粉末满足以下条件的至少之一：
    所述干燥为在100-300℃、可选150-200℃下干燥4-8h；
    所述烧结为在500-800℃、可选650-800℃下，在惰性气体气氛下烧结4-10h。
  56. 根据权利要求54所述的方法，其中，形成所述包覆层的烧结温度为500-800℃，烧结时间为4-10h。
  57. 根据权利要求53所述的方法，其中，所述壳包括包覆所述内核的第一包覆层、包覆所述第一包覆层的第二包覆层以及包覆所述第二包覆层的第三包覆层，其中，
    所述第一包覆层包括晶态焦磷酸盐Li aQP 2O 7和/或Q b(P 2O 7) c，
    所述第二包覆层包括晶态磷酸盐XPO 4，
    所述第三包覆层为碳。
  58. 根据权利要求57所述的方法，其中，形成所述壳包括：分别提供Li aQP 2O 7和/或Q b(P 2O 7) c以及XPO 4悬浊液，将所述内核加入所述悬浊液中并混合，经烧结获得正极活性材料。
  59. 根据权利要求58所述的方法，形成所述壳包括：
    将元素Q的源、磷源和酸以及任选地锂源，溶于溶剂中，得到第一包覆层悬浊液；将所述内核与所述第一包覆层悬浊液混合并烧结，得到第一包覆层包覆的材料；
    将元素X的源、磷源和酸溶于溶剂中，得到第二包覆层悬浊液；将所述第一包覆层包覆的材料与所述第二包覆层悬浊液混合并烧结，得到两层包覆层包覆的材料；
    将碳源溶于溶剂中溶解得到第三包覆层溶液；将所述两层包覆层包覆的材料加入所述第三包覆层溶液中，混合干燥并烧结得到所述正极活性材料。
  60. 根据权利要求59所述的方法，其中，形成所述第一包覆层包覆的材料时，控制溶解有元素Q的源、磷源和酸以及任选地锂源的溶液pH为3.5-6.5，搅拌并反应1-5h，将所述溶液升温至50-120℃并保持2-10h，和/或，
    所述烧结在650-800℃下进行2-6小时。
  61. 根据权利要求59所述的方法，其中，形成所述两层包覆层包覆的材料时，将元素X的源、磷源和酸溶于溶剂后，搅拌并反应1-10h，将所述溶液升温至60-150℃并保持2-10h，和/或，
    烧结在500-700℃下进行6-10小时。
  62. 根据权利要求53所述的方法，其中，所述壳包括包覆所述内核的第一包覆层、包覆所述第一包覆层的第二包覆层，其中，所述第一包覆层包括晶态焦磷酸盐QP 2O 7和所述金属氧化物Q’ eO f，所述第二包覆层包括碳，形成所述壳包括：
    提供包含晶态焦磷酸盐QP 2O 7的粉末和包含碳源及氧化物Q’ eO f的悬浊液，将所述内核、包含晶态焦磷酸盐QP 2O 7的粉末和包含碳源及氧化物Q’ eO f的悬浊液混合，烧结，获得正极活性材料。
  63. 根据权利要求53所述的方法，其中，所述壳包括包覆所述内核的第一包覆层、包覆所述第一包覆层的第二包覆层，以及包覆所述第二包覆层的第三包覆层，其中，所述第一包覆层包括晶态焦磷酸盐QP 2O 7，所述第二包覆层包括所述金属氧化物Q’ eO f，所述第三包覆层包括碳，形成所述壳包括：提供包含焦磷酸盐Li aQP 2O 7和/或Q b(P 2O 7) c的第一混合物，将内核材料与第一混合物混合，干燥，烧结，得到第一包覆层包覆的材料；
    提供包含所述金属氧化物Q’ eO f的第二混合物，将所述第一包覆层包覆的材料与第二混合物混合，干燥，烧结，得到第二包覆层包覆的材料；
    提供包含碳源的第三混合物，将所述第二包覆层包覆的材料与第三混合物混合，干燥，烧结，得到所述正极活性材料。
  64. 根据权利要求63所述的方法，其中，
    形成所述第一包覆层时将元素Q的源、磷源、酸、任选的锂源和任选的溶剂混合得到所述第一混合物；和/或，
    形成所述第二包覆层时将元素Q′的源与溶剂混合得到第二混合物；和/或，
    形成所述第三包覆层时将碳源与溶剂混合得到第三混合物；
    可选地，形成所述第一包覆层时，所述元素Q的源、磷源、酸、任选的锂源和任选的溶剂在室温下混合1-5h，再升温至50℃-120℃并保持该温度混合2-10h，上述混合均在pH为3.5-6.5条件下进行；
    可选地，形成所述第二包覆层时，所述元素Q′的源与溶剂在室温下混合1-10h，再升温至60℃-150℃并保持该温度混合2-10h。
  65. 根据权利要求63或64所述的方法，其中，
    所述第一包覆步骤中，所述烧结在650-800℃下进行2-8小时；和/或，
    所述第二包覆步骤中，所述烧结在400-750℃下进行6-10小时；和/或，
    所述第三包覆步骤中，所述烧结在600-850℃下进行6-10小时。
  66. 一种具有核-壳结构的正极活性材料，包括内核及包覆所述内核的壳，其中，
    所述内核的化学式为Li mA xMn 1-yB yP 1-zC zO 4-nD n，所述A包括选自Zn、Al、Na、K、Mg、Nb、Mo和W中的一种或多种元素，所述B包括选自Ti、V、Zr、Fe、Ni、Mg、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素，所述C包括选自B(硼)、S、Si和N中的一种或多种元素，所述D包括选自S、F、Cl和Br中的一种或多种元素，所述m选自0.9至1.1的范围，所述x选自0.001至0.1的范围，所述y选自0.001至0.5的范围，所述z选自0.001至0.1的范围，所述n选自0.001至0.1的范围，并且所述内核为电中性的；
    所述壳包括包覆所述内核的第一包覆层、包覆所述第一包覆层的第二包覆层以及包覆所述第二包覆层的第三包覆层，其中，
    所述第一包覆层包括晶态焦磷酸盐Li aMP 2O 7和/或M b(P 2O 7) c，0≤a≤2，1≤b≤4，1≤c≤6，所述a、b和c的值满足以下条件：使晶态焦磷酸盐Li aMP 2O 7或M b(P 2O 7) c保持电中性， 所述晶态焦磷酸盐Li aMP 2O 7和M b(P 2O 7) c中的M各自独立地为选自Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb和Al中的一种或多种元素，
    所述第二包覆层包括晶态磷酸盐XPO 4，所述X为选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb和Al中的一种或多种元素；
    所述第三包覆层为碳。
  67. 一种具有核-壳结构的正极活性材料，包括内核及包覆所述内核的壳，其中，
    所述内核的化学式为Li aA xMn 1-yB yP 1-zC zO 4-nD n，所述A包括选自Zn、Al、Na、K、Mg、Nb、Mo和W中的一种或多种元素，所述B包括选自Ti、V、Zr、Fe、Ni、Mg、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素，所述C包括选自B(硼)、S、Si和N中的一种或多种元素，所述D包括选自S、F、Cl和Br中的一种或多种元素，所述a选自0.9至1.1的范围，所述x选自0.001至0.1的范围，所述y选自0.001至0.5的范围，所述z选自0.001至0.1的范围，所述n选自0.001至0.1的范围，并且所述内核为电中性的；
    所述壳包括包覆所述内核的第一包覆层以及包覆所述第一包覆层的第二包覆层，其中，
    所述第一包覆层包括焦磷酸盐MP 2O 7和磷酸盐XPO 4，所述M和X各自独立地选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb和Al中的一种或多种；
    所述第二包覆层包含碳。
  68. 一种具有核-壳结构的正极活性材料，其包括内核及包覆所述内核的壳，
    所述内核包含Li 1+xMn 1-yA yP 1-zR zO 4，其中，所述x为-0.100～0.100范围内的任意数值，所述y为0.001～0.500范围内的任意数值，所述z为0.001～0.100范围内的任意数值，所述A为选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素、可选地为选自Zn、Fe、Ti、V、Ni、Co和Mg中的一种或多种元素，所述R为选自B、Si、N和S中的一种或多种元素；
    所述壳包括包覆所述内核的第一包覆层以及包覆所述第一包覆层的第二包覆层；
    其中，所述第一包覆层包含晶态焦磷酸盐M aP 2O 7和晶态氧化物M′ bO c，其中，所述a大于0且小于或等于4，所述b大于0且小于或等于2，所述c大于0且小于或等于5，所述M为选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb和Al中的一种或多种元素、可选地为选自Li、Fe和Zr中的一种或多种元素，所述M′为选自碱金属、碱土金属、过渡金属、第IIIA族元素、第IVA族元素、镧系元素和Sb中的一种或多种元素、可选地为选自Li、Be、B、Na、Mg、Al、Si、P、K、Ca、Sc、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Ga、Ge、As、Se、Sr、Y、Zr、Nb、Mo、Tc、Ru、Rh、Pd、Ag、Cd、In、Sn、Sb、Te、W、La和Ce中的一种或多种元素、更可选地为选自Mg、Al、Si、Zn、Zr和Sn中的一种或多种元素；
    所述第二包覆层包含碳。
  69. 一种具有核-壳结构的正极活性材料，其包括内核及包覆所述内核的壳，
    所述内核包含Li 1+xMn 1-yA yP 1-zR zO 4，其中，所述x为-0.100-0.100范围内的任意数值，所述y为0.001-0.600范围内的任意数值，所述z为0.001-0.100范围内的任意数值，所述A为选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素、可选地为选自Fe、V、Ni、Co和Mg中一种或多种元素，所述R为选自B、Si、N和S中的一种或多种元素、可选地为选自Si、N和S中的一种或多种元素；
    所述壳包括包覆所述内核的第一包覆层、包覆所述第一包覆层的第二包覆层以及包覆所述第二包覆层的第三包覆层，其中，
    所述第一包覆层包含晶态焦磷酸盐Li aMP 2O 7和/或M b(P 2O 7) c，其中，所述a大于0且小于或等于2，所述b为1-4范围内的任意数值，所述c为1-3范围内的任意数值，所述晶态焦磷酸盐Li aMP 2O 7和M b(P 2O 7) c中的M各自独立地为选自Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb和Al中的一种或多种元素、可选地为选自Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr和Al中的一种或多种元素；
    所述第二包覆层包含晶态氧化物M′ dO e，其中，所述d大于0且小于或等于2，所述e大于0且小于或等于5，所述M′为选自碱金属、碱土金属、过渡金属、第IIIA族元素、第IVA族元素、镧系元素和Sb中的一种或多种元素，可选地为选自Li、Be、B、Na、Mg、Al、Si、P、S、K、Ca、Sc、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Ga、Ge、As、Se、Sr、Y、Zr、Nb、Mo、Tc、Ru、Rh、Pd、Ag、Cd、In、Sn、Sb、Te、W、La和Ce中的一种或多种元素，更可选地为选自Mg、Al、Si、Ti、V、Ni、Cu、Zr和W中的一种或多种元素；
    所述第三包覆层包含碳。
  70. 一种具有核-壳结构的正极活性材料，其包括内核及包覆所述内核的壳，
    所述内核包含Li mA xMn 1-yB yP 1-zC zO 4-nD n，其中，所述m选自0.5-1.2范围内的任意数值、可选地为选自0.9-1.1范围内的任意数值，所述x选自0.001-0.5范围内的任意数值、可选地为选自0.001-0.1范围内的任意数值，所述y选自0.001-0.5范围内的任意数值，所述z选自0.001-0.2范围内的任意数值、可选地为选自0.001-0.1范围内的任意数值，所述n选自0.001-0.5范围内的任意数值、可选地为选自0.001-0.1范围内的任意数值，所述A为选自Zn、Al、Na、K、Mg、Nb、Mo和W中的一种或多种元素、可选地为选自Al、Mg、Nb、Mo和W中的一种或多种元素，所述B为选自Ti、V、Zr、Fe、Ni、Mg、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素、可选地为选自Ti、V、Fe、Ni、Mg和Co中的一种或多种元素，所述C为选自B、S、Si和N中的一种或多种元素、可选地为选自S、Si和N中的一种或多种元素，所述D为选自S、F、Cl和Br中的一种或多种元素、可选地为选自F、 Cl和Br中的一种或多种元素；
    所述壳包括包覆所述内核的第一包覆层以及包覆所述第一包覆层的第二包覆层；
    其中，所述第一包覆层包含晶态焦磷酸盐M aP 2O 7和氧化物M′ bO c，其中，所述a大于0且小于或等于4、可选地为大于0且小于或等于3，所述b大于0且小于或等于2，所述c大于0且小于或等于5，所述M为选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb和Al中的一种或多种元素、可选地为选自Li和Fe中的一种或多种元素，所述M′为选自碱金属、碱土金属、过渡金属、第IIIA族元素、第IVA族元素、镧系元素和Sb中的一种或多种元素、可选地为选自Li、Be、B、Na、Mg、Al、Si、P、K、Ca、Sc、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Ga、Ge、As、Se、Sr、Y、Zr、Nb、Mo、Tc、Ru、Rh、Pd、Ag、Cd、In、Sn、Sb、Te、W、La和Ce中的一种或多种元素、更可选地为选自Mg、Al、V、Cu、Zn、Zr和W中的一种或多种元素；
    所述第二包覆层包含碳。
  71. 一种具有核-壳结构的正极活性材料，其包括内核及包覆所述内核的壳，
    所述内核包含Li mA xMn 1-yB yP 1-zC zO 4-nD n，其中，所述m选自0.9-1.1范围内的任意数值，所述x选自0.001-0.1范围内的任意数值，所述y选自0.001-0.6范围内的任意数值、可选地为选自0.001-0.5范围内的任意数值，所述z选自0.001-0.1范围内的任意数值，所述n选自0.001-0.1范围内的任意数值，所述A为选自Zn、Al、Na、K、Mg、Nb、Mo和W中的一种或多种元素、可选地为选自Al、Mg、Nb、Mo和W中的一种或多种元素，所述B为选自Ti、V、Zr、Fe、Ni、Mg、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素、可选地为选自Ti、V、Fe、Ni、Mg和Co中的一种或多种元素，所述C为选自B、S、Si和N中的一种或多种元素、可选地为选自S、Si和N中的一种或多种元素，所述D为选自S、F、Cl和Br中的一种或多种元素、可选地为选自F、Cl和Br中的一种或多种元素；
    所述壳包括包覆所述内核的第一包覆层、包覆所述第一包覆层的第二包覆层以及包覆所述第二包覆层的第三包覆层，其中，
    所述第一包覆层包含晶态焦磷酸盐Li aMP 2O 7和/或M b(P 2O 7) c，其中，所述a大于0且小于或等于2，所述b为1-4范围内的任意数值，所述c为1-3范围内的任意数值，所述晶态焦磷酸盐Li aMP 2O 7和M b(P 2O 7) c中的M各自独立地为选自Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb和Al中的一种或多种元素，可选地为选自Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr和Al中的一种或多种元素；
    所述第二包覆层包含氧化物M′ dO e，其中，所述d大于0且小于或等于2，所述e大于0且小于或等于5，所述M′为选自碱金属、碱土金属、过渡金属、第IIIA族元素、第IVA 族元素、镧系元素和Sb中的一种或多种元素，可选地为选自Li、Be、B、Na、Mg、Al、Si、P、S、K、Ca、Sc、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn、Ga、Ge、As、Se、Sr、Y、Zr、Nb、Mo、Tc、Ru、Rh、Pd、Ag、Cd、In、Sn、Sb、Te、W、La和Ce中的一种或多种元素，更可选地为选自Mg、Al、Ca、Ti、V、Co、Ni、Cu、Zn和Zr中的一种或多种元素；
    所述第三包覆层包含碳。
  72. 一种正极活性材料，其具有化学式Li aA xMn 1-yB yP 1-zC zO 4-nD n，其中，所述A包括选自Zn、Al、Na、K、Mg、Nb、Mo和W中的一种或多种元素，所述B包括选自Ti、V、Zr、Fe、Ni、Mg、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素，所述C包括选自B(硼)、S、Si和N中的一种或多种元素，所述D包括选自S、F、Cl和Br中的一种或多种元素，所述a选自0.9至1.1的范围，所述x选自0.001至0.1的范围，所述y选自0.001至0.5的范围，所述z选自0.001至0.1的范围，所述n选自0.001至0.1的范围，并且所述正极活性材料为电中性的。
  73. 一种具有核-壳结构的正极活性材料，其包括内核及包覆所述内核的壳，所述内核的化学式为Li 1+xMn 1-yA yP 1-zR zO 4，其中x为在-0.100-0.100范围内的任意数值，y为在0.001-0.500范围内的任意数值，z为在0.001-0.100范围内的任意数值，所述A为选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素，可选为Fe、Ti、V、Ni、Co和Mg中一种或多种元素，所述R为选自B、Si、N和S中的一种或多种元素，可选地，所述R为选自B、Si、N和S中的一种元素；所述x、y和z的值满足以下条件：使整个内核保持电中性；所述壳包括包覆所述内核的第一包覆层、包覆所述第一包覆层的第二包覆层以及包覆所述第二包覆层的第三包覆层，其中，所述第一包覆层包括晶态焦磷酸盐Li aMP 2O 7和/或M b(P 2O 7) c，其中，0≤a≤2，1≤b≤4，1≤c≤6，所述a、b和c的值满足以下条件：使晶态焦磷酸盐Li aMP 2O 7或M b(P 2O 7) c保持电中性，所述晶态焦磷酸盐Li aMP 2O 7和M b(P 2O 7) c中的M各自独立地为选自Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb或Al中的一种或多种元素，所述第二包覆层包括晶态磷酸盐XPO 4，其中，所述X为选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb或Al中的一种或多种元素；所述第三包覆层为碳。
  74. 一种具有核-壳结构的正极活性材料，其包括内核及包覆所述内核的壳，所述内核包括Li 1+xMn 1-yA yP 1-zR zO 4，其中x＝-0.100～0.100，y＝0.001～0.500，z＝0.001～0.100，所述A选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、 Co、Ga、Sn、Sb、Nb和Ge中的一种或多种，可选为Fe、Ti、V、Ni、Co和Mg中的一种或多种，所述R选自B、Si、N和S中的一种或多种；所述壳包括包覆所述内核的第一包覆层以及包覆所述第一包覆层的第二包覆层，其中，所述第一包覆层包括焦磷酸盐MP 2O 7和磷酸盐XPO 4，其中所述M和X各自独立地选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb或Al中的一种或多种；所述第二包覆层包含碳。
  75. 一种正极极片，其包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，所述正极膜层包括权利要求1-41、66-74中任一项所述的正极活性材料或通过权利要求42-65中任一项所述的方法制备的正极活性材料。
  76. 根据权利要求75所述的正极极片，其中，所述正极活性材料在所述正极膜层中的含量为10重量％以上，可选地，95-99.5重量％，基于所述正极膜层的总重量计。
  77. 一种二次电池，其中，包括权利要求1-41、66-74中任一项所述的正极活性材料或通过权利要求42-65中任一项所述的方法制备的正极活性材料或权利要求75或76所述的正极极片。
  78. 一种电池模块，其中，包括权利要求77所述的二次电池。
  79. 一种电池包，其中，包括权利要求77所述的二次电池或权利要求78所述的电池模块。
  80. 一种用电装置，其中，包括选自权利要求77所述的二次电池、权利要求78所述的电池模块或权利要求79所述的电池包中的至少一种。
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