WO2023240613A1 - 正极活性材料及制备方法、正极极片、二次电池、电池模块、电池包及用电装置 - Google Patents

正极活性材料及制备方法、正极极片、二次电池、电池模块、电池包及用电装置 Download PDF

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WO2023240613A1
WO2023240613A1 PCT/CN2022/099516 CN2022099516W WO2023240613A1 WO 2023240613 A1 WO2023240613 A1 WO 2023240613A1 CN 2022099516 W CN2022099516 W CN 2022099516W WO 2023240613 A1 WO2023240613 A1 WO 2023240613A1
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optionally
active material
range
core
coating
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PCT/CN2022/099516
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English (en)
French (fr)
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蒋耀
张欣欣
欧阳楚英
徐波
邓斌
袁天赐
王志强
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 to KR1020247001994A priority Critical patent/KR20240024199A/ko
Priority to EP22933866.0A priority patent/EP4318655A1/en
Priority to CN202280082206.6A priority patent/CN118414724A/zh
Priority to JP2024501213A priority patent/JP2024526699A/ja
Priority to PCT/CN2022/099516 priority patent/WO2023240613A1/zh
Priority to KR1020247007998A priority patent/KR20240046889A/ko
Priority to JP2024515538A priority patent/JP2024534988A/ja
Priority to EP22882998.2A priority patent/EP4418363A1/en
Priority to CN202280013384.3A priority patent/CN116964781A/zh
Priority to PCT/CN2022/126838 priority patent/WO2023066394A1/zh
Priority to US18/527,290 priority patent/US20240294392A1/en
Publication of WO2023240613A1 publication Critical patent/WO2023240613A1/zh
Priority to US18/641,410 priority patent/US20240282969A1/en

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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
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    • 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
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    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
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    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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    • 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
    • H01M4/5805—Phosphides
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    • 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
    • H01M4/581—Chalcogenides or intercalation compounds thereof
    • H01M4/5815—Sulfides
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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
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    • 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
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    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the technical field of secondary batteries, and in particular to positive active materials, preparation methods of positive active materials, positive electrode sheets, secondary batteries, battery modules, battery packs and electrical devices.
  • secondary batteries are widely used in energy storage power systems such as hydraulic, thermal, wind and solar power stations, as well as power 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 cathode active material for secondary batteries Li/Mn anti-site defects are prone to occur during the charge and discharge process of lithium manganese phosphate, and manganese dissolution is serious, affecting the gram capacity of the secondary battery and resulting in the safety performance of the secondary battery. and cycle performance deteriorates.
  • This application was made in view of the above-mentioned issues, and its purpose is to provide a positive electrode active material, a preparation method of the positive electrode active material, a positive electrode plate, a secondary battery, a battery module, a battery pack and an electrical device to solve the existing problems.
  • the lithium manganese phosphate cathode active material is prone to Li/Mn anti-site defects during the charge and discharge process, and the manganese dissolution is a serious problem, thereby solving the problems of low capacity, poor safety performance and poor cycle performance of secondary batteries.
  • the first aspect of the present application provides a cathode active material with a core-shell structure, which includes a core and a shell covering the core,
  • the kernel contains Li 1+x Mn 1-y A y P 1-z R z O 4 , where x is any value in the range -0.100-0.100, y is any value in the range 0.001-0.600, and z is 0.001- Any value within the range of 0.100,
  • A is one selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and Ge Or multiple elements, optionally one or more elements selected from Fe, V, Ni, Co and Mg, R is one or more elements selected from B, Si, N and S, optionally Ground is one or more elements selected from Si, N and S;
  • the shell includes a first cladding layer covering the core, a second cladding layer covering the first cladding layer, and a third cladding layer covering the second cladding layer, wherein,
  • the first coating layer includes crystalline pyrophosphate Li a MP 2 O 7 and/or M b (P 2 O 7 ) c , where a is greater than 0 and less than or equal to 2, and b is any in the range of 1-4 Value, c is any value in the range of 1-3, M in crystalline pyrophosphate Li a MP 2 O 7 and M b (P 2 O 7 ) c is each independently selected from Fe, Ni, Mg, Co , one or more elements among Cu, Zn, Ti, Ag, Zr, Nb and Al, optionally selected from Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr and Al one or more elements;
  • the second cladding layer includes crystalline oxide M′ d O e , where d is greater than 0 and less than or equal to 2, e is greater than 0 and less than or equal to 5, and M′ is selected from alkali metals, alkaline earth metals, transition metals, One or more elements from Group IIIA elements, Group IVA elements, lanthanide elements and Sb, optionally selected from 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, One or more elements from Cd, In, Sn, Sb, Te, W, La and Ce, more optionally selected from Mg, Al, Si, Ti, V, Ni, Cu, Zr and W one or more elements;
  • the third cladding layer contains carbon.
  • the inventor of the present application found in actual operations that Li/Mn anti-site defects are easily generated in the lithium manganese phosphate cathode active material during deep charge and discharge processes, and manganese dissolution is relatively serious.
  • the eluted manganese is reduced to metallic manganese after migrating to the negative electrode.
  • the metal manganese produced is equivalent to a "catalyst", which can catalyze the decomposition of the SEI film (solid electrolyte interphase, solid electrolyte interface film) on the surface of the negative electrode.
  • Part of the by-products produced are gases, which can easily cause the battery to expand and affect the safety of the secondary battery.
  • Performance and the other part is deposited on the surface of the negative electrode, blocking the passage of lithium ions in and out of the negative electrode, causing the impedance of the secondary battery to increase and affecting the dynamic performance and cycle performance of the battery.
  • the electrolyte and active lithium inside the battery are continuously consumed, which has an irreversible impact on the capacity retention rate of the secondary battery.
  • crystalline means that the degree of crystallinity is above 50%, that is, between 50% and 100%. Crystallinity less than 50% is called glassy state.
  • the crystallinity of the crystalline pyrophosphate of the present application ranges from 50% to 100%. Pyrophosphate with a certain degree of crystallinity is not only conducive to giving full play to the ability of the pyrophosphate coating to hinder manganese dissolution and reducing interface side reactions, but also enables the pyrophosphate coating and oxide coating to be better. The lattice matching is performed to achieve a tight bond between the cladding layer and the cladding layer.
  • the above limitation on the numerical range of y is not only for each element as A
  • the limitation of the stoichiometry of the element is also the limitation of the sum of the stoichiometry of each element as A.
  • the stoichiometric numbers y1, y2...yn of A1, A2...An each need to fall within the numerical range of y defined in this application, and y1 , y2...yn and the sum must also fall within this numerical range.
  • R is two or more elements
  • the limitation on the numerical range of the R stoichiometric number in this application also has the above meaning.
  • the above-mentioned limitation on the numerical range of b is not only a limitation on the stoichiometric number of each element as M, It is also a limitation on the sum of the stoichiometric numbers of each element as M.
  • M is two or more elements M1, M2...Mn
  • the stoichiometric numbers b1, b2...bn of M1, M2...Mn must each fall within the numerical range of b defined in this application, and b1 The sum of , b2...bn must also fall within this numerical range.
  • M' in the chemical formula M' d O e is two or more elements
  • the limitation on the numerical range of the stoichiometric number d of M' in this application also has the above meaning.
  • the interplanar distance of the crystalline pyrophosphate in the first coating layer ranges from 0.293 to 0.470 nm, and the angle range of the crystal direction (111) ranges from 18.00° to 32.00°;
  • the interplanar spacing range of the crystalline pyrophosphate in the first coating layer is 0.297-0.462nm; and/or,
  • the angle range of the crystal orientation (111) of the crystalline pyrophosphate in the first coating layer is 19.211°-30.846°.
  • the first coating layer in the cathode active material of the present application uses crystalline materials, and their crystal plane spacing and included angle range are within the above range. As a result, the impurity phase in the coating layer can be effectively avoided, thereby increasing the gram capacity of the material and improving the cycle performance and rate performance of the secondary battery.
  • the ratio of y to 1-y is 1:10 to 1:1, optionally 1:4 to 1:1.
  • the cycle performance and rate performance of the secondary battery are further improved.
  • the ratio of z to 1-z is from 1:9 to 1:999, optionally from 1:499 to 1:249. As a result, the cycle performance and rate performance of the secondary battery are further improved.
  • the carbon in the third coating layer is a mixture of SP2 form carbon and SP3 form carbon; optionally, the molar ratio of SP2 form carbon to SP3 form carbon is in the range of 0.07-13 Any value can be selected as any value in the range of 0.1-10, and further can be selected as any value in the range of 2.0-3.0.
  • This application improves the overall performance of the secondary battery by limiting the molar ratio of SP2 form carbon to SP3 form carbon within the above range.
  • 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 preferably greater than 0 and less than or equal to 5.5% by weight. Less than or equal to 2% by weight, based on the weight of the 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 core ;and / or
  • the coating amount of the third coating layer is greater than 0 and less than or equal to 6 wt%, 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 core Weight scale.
  • the coating amount of the three coating layers is preferably within the above range, so that the core can be fully coated without sacrificing the gram capacity of the cathode active material. to further improve the kinetic performance and safety performance of secondary batteries.
  • the thickness of the first cladding layer is 2-10 nm.
  • the thickness of the first coating layer ranges from 2 to 10 nm, the dissolution and migration of transition metal ions can be further reduced and the dynamic performance of the secondary battery can be improved.
  • the thickness of the second cladding layer is 3-15 nm.
  • the thickness of the second coating layer is in the range of 3-15 nm, the surface structure of the second coating layer is stable and the side reaction with the electrolyte is small. Therefore, the interface side reaction can be effectively reduced, thereby improving the high-temperature performance of the secondary battery. .
  • the thickness of the third cladding layer is 5-25 nm.
  • the electrical conductivity of the material can be improved and the compaction density performance of the battery pole piece prepared using the cathode active material can be improved.
  • the manganese element content is in the range of 10% by weight - 35% by weight, optionally in the range of 15% by weight - 30% by weight, and more optionally in the range of 17% by weight - 20% 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 to phosphorus element is in the range of 0.90-1.25, more optionally in the range of 0.95-1.20.
  • the content of manganese element is within the above range, which can effectively improve the structural stability and density of the cathode active material, thereby improving the cycle, storage and compaction density of the secondary battery. performance; and can maintain a certain voltage platform height, thereby improving the energy density of secondary batteries.
  • the content of phosphorus element is within the above range, which can effectively improve the conductivity of the cathode active material and improve the structural stability of the cathode active material.
  • the weight ratio of manganese element to phosphorus element is within the above range, which can reduce the dissolution of transition metals and improve the stability of the cathode active material and the cycle and storage of secondary batteries. performance, and can maintain a certain discharge voltage platform height, thereby improving the energy density of secondary batteries.
  • the lattice change rate of the cathode active material before and after complete deintercalation of lithium is 50% or less, optionally 4% or less, more preferably 3.8% or less, further optionally 2.0% -3.8%.
  • the cathode active material with a core-shell structure of the present application can achieve a lower lattice change rate before and after deintercalation of lithium. Therefore, the use of positive active materials can improve the gram capacity and rate performance of secondary batteries.
  • the Li/Mn anti-site defect concentration of the cathode active material is 5.3% or less, optionally 4% or less, more optionally 2.2% or less, further optionally 1.5%-2.2% .
  • the transport of Li + can be improved, while the gram capacity of the cathode active material and the rate performance of the secondary battery can be improved.
  • the compacted density of the positive active material at 3T is 1.95g/cm or more, optionally 2.2g/cm or more, further optionally 2.2g/cm or more and 2.8 g/cm 3 or less, and further optional, 2.2 g/cm 3 or more and 2.65 g/cm 3 or less. Therefore, by increasing the compaction density, the weight of the positive electrode active material per unit volume increases, which is beneficial to increasing the volumetric energy density of the secondary battery.
  • the surface oxygen valence state of the cathode active material is -1.89 or less, optionally -1.90 to -1.98. Therefore, by limiting the surface oxygen valence state of the positive electrode active material within the above range, the interface side reaction between the positive electrode material and the electrolyte can be reduced, thereby improving the battery cell cycle, high-temperature storage gas production and other performances.
  • a second aspect of this application provides a method for preparing a cathode active material, including the following steps:
  • the core material contains Li 1+x Mn 1-y A y P 1-z R z O 4 , where x is any value in the range of -0.100-0.100, and y is any value in the range of 0.001-0.600 Value, z is any value in the range of 0.001-0.100,
  • A is selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and one or more elements in Ge, optionally one or more elements selected from Fe, V, Ni, Co and Mg
  • R is one or more elements selected from B, Si, N and S or Multiple elements, optionally one or more elements selected from Si, N and S;
  • the first coating step providing a first mixture containing pyrophosphate Li a MP 2 O 7 and/or M b (P 2 O 7 ) c , mixing the core material with the first mixture, drying, and sintering to obtain the first Material covered by the coating layer; where a is greater than 0 and less than or equal to 2, b is any value in the range of 1-4, c is any value in the range of 1-3; pyrophosphate Li a MP 2 O 7 M in and M 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. Optionally is one or more elements selected from Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr and Al;
  • the second coating step providing a second mixture containing the oxide M' d O e , mixing the material covered by the first coating layer with the second mixture, drying, and sintering to obtain a material covered by two layers of coating layer ; wherein, d is greater than 0 and less than or equal to 2, e is greater than 0 and less than or equal to 5, and M′ is selected from alkali metals, alkaline earth metals, transition metals, Group IIIA elements, Group IVA elements, lanthanide elements and Sb
  • M′ is selected from alkali metals, alkaline earth metals, transition metals, Group IIIA elements, Group IVA elements, lanthanide elements and Sb
  • M′ is selected from alkali metals, alkaline earth metals, transition metals, Group IIIA elements, Group IVA elements, lanthanide elements and Sb
  • M′ is selected from alkali metals, alkaline earth metals, transition metals, Group IIIA elements, Group IVA elements, lanthanide elements and S
  • the third coating step providing a third mixture containing a carbon source, mixing the material covered by the two coating layers with the third mixture, drying, and sintering to obtain a positive active material;
  • the positive active material has a core-shell structure, which includes a core and a shell covering the core.
  • the core includes Li 1+x Mn 1-y A y P 1-z R z O 4
  • the shell includes a first layer covering the core.
  • the second cladding layer contains crystalline oxide M′ d O e
  • the third cladding layer contains carbon.
  • this application provides a new type of lithium manganese phosphate core by doping element A at the manganese position and doping element R at the phosphorus position, and sequentially performs three-layer coating on the surface of the core.
  • the cathode active material with a core-shell structure can greatly reduce the generation of Li/Mn anti-site defects, significantly reduce manganese dissolution, reduce the lattice change rate, and increase the compaction density.
  • it can improve the performance of secondary batteries. capacity and improve the cycle performance, high-temperature storage performance and safety performance of secondary batteries.
  • the step of providing the core material includes the following steps:
  • Step (1) Mix a manganese source, a source of element A and an acid to obtain a mixture;
  • Step (2) Mix the mixture obtained in step (1) with a lithium source, a phosphorus source, a source of element R and an optional solvent, and sinter under the protection of an inert gas to obtain Li 1+x Mn 1-y A y Core material of P 1-z R z O 4 .
  • step (1) is performed at 20°C-120°C, optionally 40°C-120°C; and/or, in step (1), by rotating at 400-700 rpm Stir for 1-9h to mix.
  • step (2) mixing is performed at a temperature of 20-120°C, optionally 40-120°C, for 1-10 hours.
  • a first mixture is obtained by mixing a source of element M, a phosphorus source, an acid, an optional lithium source and an optional solvent; and/or,
  • a second mixture is obtained by mixing the source of element M' with a solvent; and/or,
  • a third mixture is obtained by mixing the carbon source and the solvent.
  • the source of element M, the phosphorus source, the acid, the optional lithium source and the optional solvent are mixed at room temperature for 1-5 hours, and then heated to 50 °C-120 °C and keep mixing at this temperature for 2-10 hours.
  • the above mixing is carried out under the condition of pH 3.5-6.5.
  • the source of element M' and the solvent are mixed at room temperature for 1-10 hours, and then heated to 60°C-150°C and maintained at this temperature for 2-10 hours.
  • the source of element A is one selected from the group consisting of elemental elements, carbonates, sulfates, halides, nitrates, organic acid salts, oxides and hydroxides of element A. or more; and/or,
  • the source of element R is one or more selected from the group consisting of inorganic acids, organic acids, sulfates, halides, nitrates, organic acid salts, oxides and hydroxides of element R.
  • sintering in the first coating step, sintering is performed at 650-800°C for 2-8 hours; and/or in the second coating step, sintering is performed at 400-750°C. 6-10 hours; and/or, in the third coating step, sintering is performed at 600-850°C for 6-10 hours.
  • 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 disposed on at least one surface of the positive electrode current collector.
  • the positive electrode film layer includes the positive electrode active material of the first aspect of the present application or is formed by the positive electrode active material of the first aspect of the present application.
  • a fourth aspect of the present application provides a secondary battery, including the positive active material of the first aspect of the present application or the positive active material prepared by the preparation method of the second aspect of the present application or the positive electrode sheet of the third aspect of the present application.
  • a fifth aspect of the present application provides a battery module including the secondary battery of the fourth aspect of the present application.
  • a sixth aspect of the present application provides a battery pack, including the battery module of the fifth aspect of the present application.
  • a seventh aspect of the present application provides an electrical device, including at least one selected from the group consisting of the secondary battery of the fourth aspect of the present application, the battery module of the fifth aspect of the present application, and the battery pack of the sixth aspect of the present application. kind.
  • Figure 1 is a schematic diagram of a positive electrode active material with a three-layer coating structure according to an embodiment of the present application.
  • FIG. 2 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG. 3 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 2 .
  • Figure 4 is a schematic diagram of a battery module according to an embodiment of the present application.
  • Figure 5 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG. 6 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG. 5 .
  • FIG. 7 is a schematic diagram of a power consumption device using a secondary battery as a power source according to an embodiment of the present application.
  • Ranges disclosed herein are defined in terms of lower and upper limits. 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 of the endpoints, and may be arbitrarily combined, that is, 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, understand that ranges of 60-110 and 80-120 are also expected. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then 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" means that all real numbers between "0-5" have been listed in this article, and "0-5" is just an abbreviation of these numerical combinations.
  • a certain parameter is an integer ⁇ 2
  • a method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • step (c) means that step (c) can be added to the method in any order.
  • the method may include steps (a), (b) and (c), and may also include step (a). , (c) and (b), and may also include steps (c), (a) and (b), etc.
  • condition "A or B” is satisfied by any of the following conditions: 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 refers to the material layer coating the core.
  • the material layer can completely or partially cover the core.
  • coating layer is only for convenience of description. It is not intended to limit the invention.
  • the term “thickness of the cladding layer” refers to the thickness of the cladding layer in the radial direction of the core.
  • the term “cladding layer” is defined as above.
  • Secondary batteries also known as rechargeable batteries or storage batteries, refer to batteries that can be recharged to activate active materials and continue to be used after the battery is discharged.
  • a secondary battery normally includes a positive electrode plate, a negative electrode plate, a separator and an electrolyte.
  • active ions such as lithium ions
  • the isolation film is placed between the positive electrode piece and the negative electrode piece. It mainly prevents the positive and negative electrodes from short-circuiting and allows active ions to pass through.
  • the electrolyte is between the positive electrode piece and the negative electrode piece and mainly plays the role of conducting active ions.
  • the present application provides a cathode active material with a core-shell structure, which includes a core and a shell covering the core.
  • the kernel contains Li 1+x Mn 1-y A y P 1-z R z O 4 , where x is any value in the range -0.100-0.100, y is any value in the range 0.001-0.600, and z is 0.001- Any value within the range of 0.100,
  • A is one selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and Ge Or multiple elements, optionally one or more elements selected from Fe, V, Ni, Co and Mg, R is one or more elements selected from B, Si, N and S, optionally Ground is one or more elements selected from Si, N and S;
  • the shell includes a first cladding layer covering the core, a second cladding layer covering the first cladding layer, and a third cladding layer covering the second cladding layer, wherein,
  • the first coating layer includes crystalline pyrophosphate Li a MP 2 O 7 and/or M b (P 2 O 7 ) c , where a is greater than 0 and less than or equal to 2, and b is any in the range of 1-4 Value, c is any value in the range of 1-3, M in crystalline pyrophosphate Li a MP 2 O 7 and M b (P 2 O 7 ) c is each independently selected from Fe, Ni, Mg, Co , one or more elements among Cu, Zn, Ti, Ag, Zr, Nb and Al, optionally selected from Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr and Al one or more elements;
  • the second cladding layer includes crystalline oxide M′ d O e , where d is greater than 0 and less than or equal to 2, e is greater than 0 and less than or equal to 5, and M′ is selected from alkali metals, alkaline earth metals, transition metals, One or more elements from Group IIIA elements, Group IVA elements, lanthanide elements and Sb, optionally selected from 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, One or more elements from Cd, In, Sn, Sb, Te, W, La and Ce, more optionally selected from Mg, Al, Si, Ti, V, Ni, Cu, Zr and W one or more elements;
  • the third cladding layer contains carbon.
  • the cathode active material of the present application can improve the gram capacity, cycle performance and safety performance of the secondary battery. Although the mechanism is not yet clear, it is speculated that the cathode active material of the present application has a core-shell structure.
  • the cathode active material of the present application has a core-shell structure.
  • the element A doped at the manganese position of lithium manganese phosphate also helps to reduce the lattice change rate of lithium manganese phosphate during the process of deintercalating lithium, improves the structural stability of the cathode material, and greatly improves the structural stability of the cathode material.
  • Reduce the dissolution of manganese and reduce the oxygen activity on the particle surface; the element R doped at the phosphorus site also helps to change the ease of Mn-O bond length change, thereby improving electronic conductivity and lowering the lithium ion migration barrier, promoting lithium Ion migration improves the rate performance of secondary batteries.
  • the above limitation on the numerical range of y is not only for each element as The limitation of the stoichiometry of the element A is also the limitation of the sum of the stoichiometry of each element that is A.
  • the stoichiometric numbers y1, y2...yn of A1, A2...An each need to fall within the numerical range of y defined in this application, and y1 , y2...yn and the sum must also fall within this numerical range.
  • R is two or more elements
  • the limitation on the numerical range of the R stoichiometric number in this application also has the above meaning.
  • A is one selected from the group consisting of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and Ge , two, three or four elements
  • Q, D, E and K are each independently selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and A kind of Ge, optionally, at least one of Q, D, E, and K is Fe.
  • one of n1, n2, n3, and n4 is zero, and the rest are not zero; more optionally, two of n1, n2, n3, and n4 are zero, and the rest are not zero; also optionally, Three of n1, n2, n3, and n4 are zero, and the rest are not zero.
  • doping 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 beneficial to uniform distribution of doping elements.
  • the values of x, y, and z are such that the entire core remains electrically neutral.
  • the size of x is affected by the valence sizes of A and R and the sizes of y and z to ensure that the entire system is electrically neutral. If the value of x is too small, the lithium content of the entire core system will be reduced, affecting the gram capacity of the material.
  • the y value will limit the total amount of all doping elements. If y is too small, that is, the doping amount is too small, the doping elements will have no effect. If y exceeds 0.5, the Mn content in the system will be less, affecting the material's properties. voltage platform.
  • the R element is doped at the P position. Since the PO tetrahedron is relatively stable, and an excessive z value will affect the stability of the material, the z value is limited to 0.001-0.100.
  • the entire core system remains electrically neutral, ensuring that there are as few defects and impurities in the cathode active material as possible. If there is an excess of transition metal (such as manganese) in the cathode active material, since the structure of the material system itself is relatively stable, the excess transition metal is likely to precipitate in the form of elemental substances, or form a heterogeneous phase inside the crystal lattice, maintaining the electrical neutrality. Sex can make such impurities as small as possible. In addition, ensuring the electrical neutrality of the system can also generate lithium vacancies in the material in some cases, thereby making the material's dynamic properties better.
  • transition metal such as manganese
  • the inventor of the present application cut out the middle region of the prepared cathode active material particles using a focused ion beam (FIB for short), and analyzed it through a transmission electron microscope (TEM for short) and X-ray energy spectroscopy (EDS for short). Tests were conducted and it was found that each element was evenly distributed and no aggregation occurred.
  • FIB focused ion beam
  • EDS X-ray energy spectroscopy
  • a, b, and c have values such that the crystalline pyrophosphate Li a MP 2 O 7 or M b (P 2 O 7 ) c remains electrically neutral.
  • the values of d and e are such that the crystalline state M′dOe remains electrically neutral.
  • crystalline means that the degree of crystallinity is above 50%, that is, between 50% and 100%. Crystallinity less than 50% is called glassy state.
  • the crystalline pyrophosphate salts of the present application have a crystallinity of 50% to 100%. Pyrophosphate with a certain degree of crystallinity is not only conducive to giving full play to the ability of the pyrophosphate coating to hinder manganese dissolution and reducing interface side reactions, but also enables the pyrophosphate coating and oxide coating to be better The lattice matching is performed to achieve a tighter combination of the cladding layers.
  • the crystallinity of the crystalline pyrophosphate material of the first coating layer of the cathode active material can be tested by conventional technical means in the art, such as by density method, infrared spectroscopy, and differential scanning calorimetry. and nuclear magnetic resonance absorption methods, and can also be tested by, for example, X-ray diffraction.
  • a specific X-ray diffraction method for testing the crystallinity of the first coating layer crystalline pyrophosphate of the cathode active material may include the following steps:
  • the crystallinity is the ratio of the crystalline part scattering to the total scattering intensity.
  • the crystallinity of the pyrophosphate in the coating layer can be adjusted, for example, by adjusting the process conditions of the sintering process, such as sintering temperature, sintering time, and the like.
  • pyrophosphate as the first coating layer can effectively isolate the doped metal ions from the electrolyte.
  • the structure of crystalline pyrophosphate is stable. Therefore, crystalline pyrophosphate coating can effectively inhibit the dissolution of transition metals and improve cycle performance.
  • the bond between the first cladding layer and the core is similar to a heterojunction, and the strength of the bond is limited by the degree of lattice matching.
  • the degree of bonding between the first cladding layer and the core is measured mainly by calculating the mismatch between the lattice constants of the core and the cladding. In this application, after the A and R elements are doped in the core, compared with undoped elements, the matching between the core and the first cladding layer is improved, and the core and the pyrophosphate cladding layer can be closer ground together.
  • Crystalline oxide was selected as the second coating layer, firstly, because it has a high lattice match with the crystalline pyrophosphate of the first coating layer (the mismatch degree is only 3%); secondly, as the third coating layer
  • the crystalline oxide of the second coating layer itself has better stability than pyrophosphate, and coating pyrophosphate with it is beneficial to improving the stability of the material.
  • the structure of the crystalline oxide as the second coating layer is very stable. Therefore, coating with crystalline oxide can effectively reduce the interface side reactions on the surface of the positive electrode active material, thereby improving the high-temperature cycle and performance of the secondary battery. Storage performance.
  • the lattice matching between the second cladding layer and the first cladding layer is similar to the above-mentioned combination between the first cladding layer and the core.
  • the lattice mismatch is less than 5%, the lattice matching is relatively small. Well, the two are easily combined closely.
  • carbon is used as the third layer of coating. Since electrochemical reactions occur when used in secondary batteries, electrons are required to participate. Therefore, in order to increase electron transmission between particles and at different locations on the particles, materials with excellent conductive properties can be used. Carbon coating. Carbon coating can effectively improve the conductive properties and desolvation ability of cathode active materials.
  • Figure 1 is a schematic diagram of an ideal cathode active material with a three-layer coating structure.
  • the innermost circle schematically represents the core, which is the first cladding layer, the second cladding layer, and the third cladding layer from the inside to the outside.
  • This figure represents the ideal state where each layer is completely covered. In practice, each coating layer can be fully covered or partially covered.
  • the interplanar distance of the crystalline pyrophosphate in the first coating layer ranges from 0.293 to 0.470 nm, and the included angle of the crystal orientation (111) ranges from 18.00° to 32.00°;
  • the interplanar spacing range of the crystalline pyrophosphate in the first coating layer is 0.297-0.462nm; and/or,
  • the angle range of the crystal orientation (111) of the crystalline pyrophosphate in the first coating layer is 19.211°-30.846°.
  • the crystalline pyrophosphate in the first coating layer can be characterized by conventional technical means in the art, or can be characterized by, for example, transmission electron microscopy (TEM). Under TEM, the core and cladding layers can be distinguished by testing the interplanar spacing.
  • TEM transmission electron microscopy
  • the specific testing method for the interplanar spacing and included angle of the crystalline pyrophosphate in the first coating layer may include the following steps:
  • Crystalline pyrophosphate within the above-mentioned crystal plane spacing and angle range can more effectively suppress the lattice change rate and Mn dissolution of lithium manganese phosphate during the lithium deintercalation process, thereby improving the high-temperature cycle performance and rate of secondary batteries. performance, cycling stability and high temperature storage performance.
  • 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 element 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 stoichiometric numbers of the P-site doping elements R.
  • the carbon in the third coating layer is a mixture of SP2 form carbon and SP3 form carbon; optionally, the molar ratio of SP2 form carbon to SP3 form carbon is any value in the range of 0.07-13, more It can be any value in the range of 0.1-10, and further can be any value in the range of 2.0-3.0.
  • the molar ratio of SP2 form carbon to SP3 form carbon can 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 overall electrical performance of the secondary battery is improved. Specifically, by using a mixed form of SP2 form carbon and SP3 form carbon and limiting the ratio of SP2 form carbon to SP3 form carbon within a certain range, good conductivity can be achieved while ensuring the passage of lithium ions, so there is It is beneficial to the realization of secondary battery functions and its cycle performance.
  • the mixing ratio of the SP2 form and the SP3 form of the third cladding carbon can be controlled by sintering conditions such as sintering temperature and sintering time.
  • sintering conditions such as sintering temperature and sintering time.
  • sucrose is used as the carbon source to prepare the third coating layer
  • the sucrose is cracked at high temperature and deposited on the second coating layer.
  • both SP3 and SP2 forms will be produced. of carbon coating.
  • the ratio of SP2 form carbon and SP3 form carbon can be controlled by selecting high temperature cracking conditions and sintering conditions.
  • the structure and characteristics of the carbon in the third coating layer can be measured by Raman spectroscopy.
  • the specific test method is as follows: by peak splitting the energy spectrum of the Raman test, Id/Ig is obtained (where Id is the peak of SP3 form carbon Intensity, Ig is the peak intensity of SP2 form carbon), thereby confirming the molar ratio of the two.
  • 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, and more optionally greater than 0 and less than or equal to 2 % by weight, based on weight of 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 core ;and / or
  • the coating amount of the third coating layer is greater than 0 and less than or equal to 6 wt%, 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 core Weight scale.
  • the coating amount of each layer is not zero.
  • the coating amount of the three coating layers is preferably within the above range, so that the core can be fully coated without sacrificing the gram capacity of the cathode active material. Under the premise, the dynamic performance and safety performance of secondary batteries can be further improved.
  • the coating amount is within the above range, the dissolution of the transition metal can be reduced, ensuring the smooth migration of lithium ions, thereby improving the rate performance of the cathode active material.
  • the positive active material can maintain a certain platform voltage and ensure the coating effect.
  • the carbon coating mainly plays the role of enhancing electron transmission between particles.
  • the structure also contains a large amount of amorphous carbon, the density of carbon is low.
  • the coating amount is within the above range. Within, the compaction density of the pole pieces can be guaranteed.
  • the thickness of the first cladding layer is 2-10 nm; and/or
  • the thickness of the second cladding layer is 3-15nm; and/or
  • the thickness of the third cladding layer is 5-25nm.
  • 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 any range of any of the above values.
  • the thickness of the second cladding layer may 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 15nm, or within any range of any of the above values.
  • the thickness of the third cladding layer may 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 values.
  • the thickness of the first coating layer ranges from 2 to 10 nm, it can effectively reduce the dissolution of transition metals and ensure the dynamic performance of the secondary battery.
  • the thickness of the second coating layer is in the range of 3-15 nm, the surface structure of the second coating layer is stable and the side reaction with the electrolyte is small. Therefore, the interface side reaction can be effectively reduced, thereby improving the high-temperature performance of the secondary battery. .
  • the electrical conductivity of the material can be improved and the compaction performance of the battery pole piece prepared using the positive active material can be improved.
  • the thickness test of the coating layer is mainly carried out through 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 slice with a thickness of about 100nm from the middle position or near the middle position of the selected particle, and then Conduct TEM test on the sheet, measure the thickness of the coating layer, measure 3-5 positions, and take the average value.
  • the manganese element content is in the range of 10%-35% by weight, optionally in the range of 15%-30% by weight, more optionally in the range of 17%-20% by weight, based on the weight of the cathode active material.
  • 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, and the weight ratio range of manganese element and phosphorus element is 0.90-1.25, optionally in the range of 0.90-1.25. 0.95-1.20.
  • the content of manganese may correspond to the content of the core.
  • limiting the content of manganese element within the above range can ensure the stability and high density of the positive 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 secondary batteries.
  • 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 weight ratio of manganese to phosphorus content is within the above range, which can effectively reduce the dissolution of transition metal manganese, improve the stability and gram capacity of the positive active material, thereby improving the cycle performance and storage performance of the secondary battery, and at the same time help In order to reduce the impurity phase in the material and maintain the discharge voltage platform height of the material, the energy density of the secondary battery is improved.
  • the measurement of manganese and phosphorus elements can be carried out using conventional technical means in this field.
  • the following method is used to determine the content of manganese and phosphorus: dissolve the material in dilute hydrochloric acid (concentration 10-30%), use ICP to test the content of each element in the solution, and then measure and convert the content of manganese. Get its weight ratio.
  • the lattice change rate of the cathode active material with a core-shell structure before and after complete deintercalation of lithium is 50% or less, optionally 4% or less, more preferably 3.8% or less, further optionally: 2.0%-3.8%.
  • the lithium deintercalation process of lithium manganese phosphate is a two-phase reaction.
  • the interfacial stress of the two phases is determined by the lattice change rate before and after lithium deintercalation.
  • the cathode active material with a core-shell structure of the present application can achieve a lower lattice change rate before and after deintercalation of lithium, so the use of the cathode active material can improve the rate performance of the secondary battery.
  • the lattice change rate can be measured by methods known in the art, such as X-ray diffraction (XRD).
  • the Li/Mn anti-site defect concentration of the cathode active material having a core-shell structure is 5.3% or less, optionally 4% or less, more optionally 2.2% or less, further optionally 1.5%- 2.2%.
  • the Li/Mn anti-site defect in this application refers to the interchange of positions of Li + and Mn 2+ in the LiMnPO 4 crystal lattice.
  • the Li/Mn antisite defect concentration refers to the percentage of Li + exchanged with Mn 2+ to the total amount of Li + .
  • the Li/Mn antisite defect concentration can be tested in accordance with JIS K 0131-1996, for example.
  • the cathode active material with a core-shell structure of the present application can achieve the above-mentioned lower Li/Mn anti-site defect concentration.
  • the inventor of the present application speculates that because Li + and Mn 2+ will exchange positions in the LiMnPO 4 lattice, and the Li + transmission channel is a one-dimensional channel, Mn 2+ is in Li + It will be difficult to migrate in the channel, thus hindering the transport of Li + . Therefore, the cathode active material with a core-shell structure of the present application has a low Li/Mn anti-site defect concentration within the above range. Therefore, it can reduce the Mn 2+ hindrance to the transport of Li + and at the same time improve the performance of the cathode active material. Capacity play and rate performance.
  • the compacted density of the positive active material at 3T is 1.95g/cm 3 or more, optionally 2.2g/cm 3 or more, further optionally 2.2g/cm 3 or more and 2.8g/cm 3
  • further options are 2.2g/ cm3 or more and 2.65g/ cm3 or less.
  • the higher the compaction density the greater the weight of the active material per unit volume. Therefore, increasing the compaction density is beneficial to increasing the volumetric energy density of the battery core.
  • the compacted density can be measured according to GB/T 24533-2009.
  • the surface oxygen valence state of the cathode active material is -1.89 or less, optionally -1.90 to -1.98.
  • the stable valence state of oxygen is originally -2.
  • its surface valence state is below -1.7.
  • the surface oxygen valence state of the cathode active material of the present application is within the above range, which can reduce the interface side reaction between the cathode material and the electrolyte, thereby improving the circulation of the battery core, high-temperature storage gas production and other performances.
  • EELS electron energy loss spectroscopy
  • doping elements it is beneficial to enhance the doping effect. On the one hand, it further reduces the lattice change rate, thereby inhibiting the dissolution of manganese and reducing the consumption of electrolyte and active lithium. On the other hand, it is also beneficial to Further reduce surface oxygen activity and reduce interface side reactions between the positive electrode active material and the electrolyte, thereby improving the cycle performance and high-temperature storage performance of the secondary battery.
  • x is any value within the range of -0.005-0.002, such as -0.004, -0.003, -0.002, -0.001, 0, 0.001, 0.002.
  • y in the core of the cathode active material, y may be, for example, 0.001, 0.002, 0.3, 0.35, 0.4, 0.5.
  • z in the core of the cathode active material, z may be, for example, 0.001, 0.002, 0.003, 0.005, 0.1.
  • d is any value in the range of 1-2.
  • e in the second coating layer of the cathode active material, e is any value in the range of 1-5.
  • This application provides a preparation method of cathode active material, including the following steps:
  • the core material contains Li 1+x Mn 1-y A y P 1-z R z O 4 , where x is any value in the range of -0.100-0.100, and y is any value in the range of 0.001-0.600 Value, z is any value in the range of 0.001-0.100,
  • A is selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and one or more elements in Ge, optionally one or more elements selected from Fe, V, Ni, Co and Mg
  • R is one or more elements selected from B, Si, N and S or Multiple elements, optionally one or more elements selected from Si, N and S;
  • the first coating step providing a first mixture containing pyrophosphate Li a MP 2 O 7 and/or M b (P 2 O 7 ) c , mixing the core material with the first mixture, drying, and sintering to obtain the first Material covered by the coating layer; where a is greater than 0 and less than or equal to 2, b is any value in the range of 1-4, c is any value in the range of 1-3; pyrophosphate Li a MP 2 O 7 M in and M 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. Optionally is one or more elements selected from Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr and Al;
  • the second coating step providing a second mixture containing the oxide M' d O e , mixing the material covered by the first coating layer with the second mixture, drying, and sintering to obtain a material covered by two layers of coating layer ; wherein, d is greater than 0 and less than or equal to 2, e is greater than 0 and less than or equal to 5, and M′ is selected from alkali metals, alkaline earth metals, transition metals, Group IIIA elements, Group IVA elements, lanthanide elements and Sb
  • M′ is selected from alkali metals, alkaline earth metals, transition metals, Group IIIA elements, Group IVA elements, lanthanide elements and Sb
  • M′ is selected from alkali metals, alkaline earth metals, transition metals, Group IIIA elements, Group IVA elements, lanthanide elements and Sb
  • M′ is selected from alkali metals, alkaline earth metals, transition metals, Group IIIA elements, Group IVA elements, lanthanide elements and S
  • the third coating step providing a third mixture containing a carbon source, mixing the material covered by the two coating layers with the third mixture, drying, and sintering to obtain a positive active material;
  • the positive active material has a core-shell structure, which includes a core and a shell covering the core.
  • the core includes Li 1+x Mn 1-y A y P 1-z R z O 4
  • the shell includes a first layer covering the core.
  • the second cladding layer contains crystalline oxide M′ d O e
  • the third cladding layer contains carbon.
  • A, R, M, M′, x, y, z, a, b, c, d, e are as defined above.
  • this application provides a new type of lithium manganese phosphate core by doping element A at the manganese position and doping element R at the phosphorus position, and sequentially performs three-layer coating on the surface of the core.
  • the cathode active material with a core-shell structure can greatly reduce the generation of Li/Mn anti-site defects, significantly reduce manganese dissolution, reduce the lattice change rate, and increase the compaction density.
  • it can improve the performance of secondary batteries. capacity and improve the cycle performance, high-temperature storage performance and safety performance of secondary batteries.
  • the step of providing core material includes the following steps:
  • Step (1) Mix a manganese source, a source of element A and an acid to obtain a mixture;
  • Step (2) Mix the mixture obtained in step (1) with a lithium source, a phosphorus source, a source of element R and an optional solvent, and sinter under the protection of an inert gas to obtain Li 1+x Mn 1-y A y Core material of P 1-z R z O 4 .
  • a and R are as defined above.
  • step (1) is performed at 20°C-120°C, optionally at 40°C-120°C (eg, about 30°C, about 50°C, about 60°C, about 70°C, about 80°C, about 90°C °C, about 100 °C, about 110 °C or about 120 °C); and/or, in step (1), by stirring at 400-700 rpm for 1-9h (optional 3-7h, for example, 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) for mixing.
  • 1-9h optional 3-7h, for example, 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
  • the temperature is 20-120°C, optionally 40-120°C (for example, 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) for 1-10h (for example, 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).
  • 1-10h for example, 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 prepared core and the cathode active material produced therefrom have fewer lattice defects, which is beneficial to inhibiting manganese dissolution and reducing the interaction between the cathode active material and the electrolyte. Interfacial side reactions, thereby improving the cycle performance and safety performance of secondary batteries.
  • step (2) mixing is performed at a pH of 3.5-6, optionally a pH of 4-6, more optionally a pH of 4-5.
  • the pH can be adjusted by methods commonly used in the art, for example, by adding acid or alkali.
  • the mixture obtained in step (1) is filtered, dried, and sand-ground to obtain element A-doped manganese salt particles with a particle size of 50-200 nm, and the element A-doped manganese salt particles are
  • the manganese salt particles are used in step (2) to be mixed with a lithium source, a phosphorus source, a source of element R and an optional solvent.
  • the molar ratio of the mixture or element A-doped manganese salt particles to the lithium source and phosphorus source is 1:0.5-2.1:0.5-2.1, optionally It’s about 1:1:1.
  • step (2) sintering is performed at 600-950°C for 4-10 hours under an inert gas or a mixed atmosphere of inert gas and hydrogen; optionally, the protective atmosphere is 70-90 volume % nitrogen and A mixed gas of 10-30% hydrogen by volume; optionally, 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, 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, and can be improved
  • the crystallinity of the core reduces the generation of impurities, allowing the core to maintain a certain particle size, thereby increasing the gram capacity and compaction density of the positive active material, and improving the overall performance of the secondary battery, including rate performance.
  • the mixed materials in step (2) are dried to obtain powder, and then the powder is sintered to obtain a core containing Li 1+x Mn 1-y A y P 1-z R z O 4 Material.
  • the first mixture is obtained by mixing a source of element M, a phosphorus source, an acid, an optional lithium source, and an optional solvent; and/or,
  • a second mixture is obtained by mixing the source of element M' with a solvent; and/or,
  • a third mixture is obtained by mixing the carbon source and the solvent.
  • the first mixture, the second mixture, and the third mixture may be provided in the form of suspensions.
  • the source of element M, the phosphorus source, the acid, the optional lithium source, and the optional solvent are mixed at room temperature for 1-5 hours (eg, about 1.5 hours, about 2 hours , about 3 hours, about 4 hours, about 4.5 hours or about 5 hours), and then raise the temperature to 50°C-120°C (such as 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 keep mixing at this temperature for 2-10 hours (for example, 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), and the above mixing is performed under the condition that the pH is 3.5-6.5 (for example, 4-6).
  • the source of element M' is mixed with the solvent at room temperature for 1-10 hours (e.g., 1.5 hours, about 2 hours, about 3 hours, about 4 hours, about 4.5 hours, about 5 hours, about 6 hours, about 7 hours, about 8 hours, about 9 hours or about 10 hours), and then raise the temperature to 60°C-150°C (for example, 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 maintain the temperature for mixing for 2-10 hours (for example, 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).
  • 1-10 hours e.g., 1.5 hours, about 2 hours, about 3 hours, about 4 hours, about 4.5 hours, about 5 hours, about 6 hours, about 7 hours, about 8 hours, about 9 hours or about 10 hours
  • 60°C-150°C for example, about
  • the preparation method of the present application has no particular limitation on the source of materials.
  • the source of a certain element may include one of the elements, sulfates, halides, nitrates, organic acid salts, oxides or hydroxides of the element. or more, provided that the source can achieve the purpose of the preparation method of the present application.
  • the source of element A is one or more selected from the group consisting of elemental elements, carbonates, sulfates, halides, nitrates, organic acid salts, oxides and hydroxides of element A; and /or,
  • the source of element R is one or more selected from the group consisting of inorganic acids, organic acids, sulfates, halides, nitrates, organic acid salts, oxides and hydroxides of element R.
  • the source of element M is one or more selected from the group consisting of elemental elements, carbonates, sulfates, halides, nitrates, organic acid salts, oxides and hydroxides of element M.
  • the source of element M' is one or more selected from the group consisting of elemental substances, carbonates, sulfates, halides, nitrates, organic acid salts, oxides and hydroxides of element M' .
  • the addition amounts of the respective sources of elements A, R, M, and M' depend on the target doping amount, and the ratio of the amounts of lithium source, manganese source, and phosphorus source complies with the stoichiometric ratio.
  • the manganese source may be a manganese-containing material known in the art that can be used to prepare lithium manganese phosphate.
  • the manganese source may be one or more selected from the group consisting of elemental manganese, manganese dioxide, manganese phosphate, manganese oxalate, and manganese carbonate.
  • the acid may be one or more selected from organic acids such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, silicic acid, silicic acid, etc., and organic acids such as oxalic acid.
  • the acid is a dilute organic acid with a concentration of 60% by weight or less.
  • the lithium source may be a lithium-containing substance known in the art that can be used to prepare lithium manganese phosphate.
  • the lithium source is one or more selected from lithium carbonate, lithium hydroxide, lithium phosphate, and lithium dihydrogen phosphate.
  • the phosphorus source may be a phosphorus-containing material known in the art that can be used to prepare lithium manganese phosphate.
  • the phosphorus source is one or more selected from diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium phosphate and phosphoric acid.
  • the carbon source is one or more selected from starch, sucrose, glucose, polyvinyl alcohol, polyethylene glycol, and citric acid.
  • 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,
  • sintering is performed at 400-750°C (for example, about 400°C, about 450°C, about 500°C, about 550°C, about 600°C, about 700°C, about 750°C) for 6-10 hours ( For example, about 6 hours, about 7 hours, about 8 hours, about 9 hours, or about 10 hours); and/or,
  • sintering is performed 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, about 9 hours or about 10 hours).
  • drying is performed at 80°C to 200°C, optionally 80°C to 190°C, more optionally 120°C to 180°C, or even
  • the optional drying temperature is 120°C to 170°C
  • the most optional is 120°C to 160°C
  • the drying time is 3-9h
  • the optional 4-8h is the most optional is 5-7h
  • the present application provides a positive electrode sheet, which includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector.
  • the positive electrode film layer includes the aforementioned positive electrode active material or the positive electrode active material prepared by the aforementioned preparation method;
  • the content of the positive electrode active material in the positive electrode film layer is more than 10% by weight, based on the total weight of the positive electrode film layer.
  • the content of the cathode active material in the cathode film layer is 90-99.5% by weight, based on the total weight of the cathode film layer. Ensure that the secondary battery has higher capacity and better cycle performance, high-temperature storage performance and safety performance.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • the metal foil aluminum foil can be used.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer.
  • the composite current collector can be formed by forming metal materials (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the positive electrode film layer may also include other positive electrode active materials known in the art for use in batteries.
  • the cathode active material may include at least one of the following materials: an olivine-structured lithium-containing phosphate and modified compounds thereof.
  • the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials of batteries can also be used. Only one type of these positive electrode active materials may be used alone, or two or more types may be used in combination.
  • lithium-containing phosphates with an olivine structure may include, but are not limited to, lithium iron phosphate (such as LiFePO 4 (also referred to as LFP)), composite materials of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ) , at least one composite material of lithium manganese phosphate and carbon.
  • lithium iron phosphate such as LiFePO 4 (also referred to as LFP)
  • composite materials of lithium iron phosphate and carbon such as LiMnPO 4
  • LiMnPO 4 lithium manganese phosphate
  • the positive electrode film layer optionally further includes a binder.
  • the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene tripolymer. At least one of a meta-copolymer, a tetrafluoroethylene-hexafluoropropylene copolymer and a fluorine-containing acrylate resin.
  • the positive electrode film layer optionally further includes 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 negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector.
  • the negative electrode film layer includes a negative electrode active material.
  • the negative electrode current collector has two opposite surfaces in its own thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base material.
  • the composite current collector can be formed by forming metal materials (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative active material may be a negative active material known in the art for batteries.
  • the negative active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and the like.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon carbon composites, silicon nitrogen composites and silicon alloys.
  • the tin-based material may be selected from at least one of elemental tin, tin oxide compounds and tin alloys.
  • the present application is not limited to these materials, and other traditional materials that can be used as battery negative electrode active materials can also be used. Only one type of these negative electrode active materials may be used alone, or two or more types may be used in combination.
  • the negative electrode film layer optionally further includes a binder.
  • the binder may be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), At least one of polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the negative electrode film layer optionally further includes a conductive agent.
  • the conductive agent may 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 optionally includes other auxiliaries, such as thickeners (such as sodium carboxymethylcellulose (CMC-Na)) and the like.
  • thickeners such as sodium carboxymethylcellulose (CMC-Na)
  • the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative active materials, conductive agents, binders and any other components 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 piece can be obtained.
  • a solvent such as deionized water
  • the electrolyte plays a role in conducting ions between the positive and negative electrodes.
  • the type of electrolyte in this application can be selected according to needs.
  • the electrolyte can be liquid, gel, or completely solid.
  • the electrolyte is liquid and includes an electrolyte salt and a solvent.
  • the electrolyte salt may be selected from the group consisting of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonimide, lithium bistrifluoromethanesulfonimide, trifluoromethane At least one of lithium sulfonate, lithium difluorophosphate, lithium difluoroborate, lithium dioxaloborate, lithium difluorodioxalate phosphate and lithium tetrafluoroxalate phosphate.
  • the solvent may be selected from the group consisting of ethylene carbonate, propylene carbonate, methylethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl 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 optionally also includes additives.
  • additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain properties of the battery, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.
  • the secondary battery further includes a separator film.
  • a separator film There is no particular restriction on the type of isolation membrane in this application. Any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be used.
  • the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation film can be a single-layer film or a multi-layer composite film, with no special restrictions. When the isolation film is a multi-layer composite film, the materials of each layer can be the same or different, and there is no particular limitation.
  • the positive electrode piece, the negative electrode piece and the separator film can be made into an electrode assembly through a winding process or a lamination process.
  • the secondary battery may include an outer packaging.
  • the outer packaging can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • 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 bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
  • FIG. 2 shows a square-structured secondary battery 5 as an example.
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity.
  • the housing 51 has an opening communicating with the accommodation cavity, and the cover plate 53 can cover the opening to close the accommodation cavity.
  • the positive electrode piece, the negative electrode piece and the isolation film can be formed into the electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the containing cavity.
  • the electrolyte soaks into 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.
  • secondary batteries can be assembled into battery modules, and the number of secondary batteries contained in the battery module can be one or more. The specific number can be selected by those skilled in the art according to the application and capacity of the battery module.
  • FIG. 4 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 can be fixed by fasteners.
  • the battery module 4 may further include a housing having a receiving space in which a plurality of secondary batteries 5 are received.
  • the above-mentioned battery modules can also be assembled into a battery pack.
  • the number of battery modules contained in the battery pack can be one or more. Those skilled in the art can select the specific number 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 2 and a lower box 3 .
  • the upper box 2 can be covered with the lower box 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 electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided by the present application.
  • the secondary battery, battery module, or battery pack can be used as a power source for the power-consuming device, or as an energy storage unit of the power-consuming device.
  • Electric devices may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric Trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited to these.
  • secondary batteries, battery modules or battery packs can be selected according to its usage requirements.
  • Fig. 7 is an electrical device as an example.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc.
  • a battery pack or battery module can be used.
  • Step S1 Preparation of Fe, Co, V and S co-doped manganese oxalate
  • Step S2 Preparation of 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
  • Li 2 FeP 2 O 7 solution Dissolve 7.4g lithium carbonate, 11.6g ferrous carbonate, 23.0g ammonium dihydrogen phosphate and 12.6g oxalic acid dihydrate in 500mL deionized water, control the pH to 5, then stir and keep at room temperature The reaction was carried out for 2 hours to obtain a solution, and then the temperature of the solution was raised to 80°C and maintained at this temperature for 4 hours to obtain a first coating layer suspension.
  • Step S4 Coating of the first coating layer
  • step S2 Add 1571.9g of the doped lithium manganese phosphate core material obtained in step S2 to the first coating layer suspension (coating material content is 15.7g) obtained in step S3, stir and mix thoroughly for 6 hours, and mix evenly Finally, it was transferred to an oven at 120°C for drying for 6 hours, and then sintered at 650°C for 6 hours to obtain the pyrophosphate-coated material.
  • Step S5 Preparation of the second coating layer suspension
  • Step S6 Coating of the second coating layer
  • step S4 Add 1586.8g of the pyrophosphate-coated material obtained in step S4 to the second coating layer suspension obtained in step S5 (coating material content is 47.1g), stir and mix thoroughly for 6 hours, and mix evenly Finally, it was transferred to an oven at 120°C for drying 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
  • sucrose aqueous solution Dissolve 37.3g of sucrose in 500g of deionized water, then stir and fully dissolve to obtain a sucrose aqueous solution.
  • Step S8 Coating of the third coating layer
  • step S6 Add 1633.9g of the two-layer coating 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 a 150°C oven to dry for 6 hours, and then sinter at 700°C for 10 hours. A three-layer coated material is obtained.
  • the cathode active materials of Examples 2 to 56 and Comparative Examples 1 to 17 were prepared in a method similar to Example 1. The differences in the preparation of the cathode active materials are shown in Tables 1-6.
  • Comparative Examples 1-2, 4-10 and 12 are not coated with the first layer, so there are no steps S3-S4; Comparative Example 1-11 is not coated with the second layer, so there are no steps S5-S6.
  • the three-layer-coated cathode active material prepared above, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) were added to N-methylpyrrolidone (NMP) in a weight ratio of 97.0:1.2:1.8 , stir and mix evenly to obtain the positive electrode slurry. Then, the positive electrode slurry is evenly coated on the aluminum foil at a density of 0.280g/ 1540.25mm2 , dried, cold pressed, and cut to obtain the positive electrode piece.
  • NMP N-methylpyrrolidone
  • the mass ratio of the negative active material artificial graphite, conductive agent superconducting carbon black (Super-P), binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethylcellulose (CMC-Na) is 95%: Dissolve 1.5%: 1.8%: 1.7% in deionized water, stir thoroughly and mix evenly to obtain a negative electrode slurry with a viscosity of 3000 mPa.s and a solid content of 52%; coat the negative electrode slurry on a 6 ⁇ m negative electrode current collector copper foil , then baked at 100°C for 4 hours to dry, and rolled to obtain a negative electrode piece with a compacted density of 1.75g/cm3.
  • the positive electrode piece, isolation film, and negative electrode piece obtained above are stacked in order, so that the isolation film is between the positive and negative electrodes to play an isolation role, and the bare battery core is obtained by winding.
  • the bare battery core is placed in the outer packaging, the above-mentioned electrolyte is injected and packaged to obtain a full battery (hereinafter also referred to as "full battery").
  • the positive active material sample is prepared into a buckle, and the above buckle is charged at a small rate of 0.05C until the current is reduced to 0.01C. Then take out the positive electrode piece from the battery and soak it in dimethyl carbonate (DMC) for 8 hours. Then it is dried, scraped into powder, and particles with a particle size less than 500nm are screened out. Take a sample and calculate its unit cell volume v1 in the same way as the above-mentioned test of fresh samples, and use (v0-v1)/v0 ⁇ 100% as the lattice change rate (unit cell volume change rate) before and after complete deintercalation of lithium.
  • DMC dimethyl carbonate
  • the fresh full batteries prepared in the above examples and comparative examples were allowed to stand for 5 minutes, and then discharged to 2.5V at 1/3C. Let it stand for 5 minutes, charge at 1/3C to 4.3V, and then charge at a constant voltage of 4.3V until the current is less than or equal to 0.05mA. Let it stand for 5 minutes, and record the charging capacity at this time as C0. Discharge to 2.5V according to 1/3C, let it sit for 5 minutes, then charge to 4.3V according to 3C, let it stand for 5 minutes, record the charging capacity at this time as C1.
  • the 3C charging constant current ratio is C1/C0 ⁇ 100%.
  • the full battery made of the positive electrode active material of each of the above embodiments and comparative examples was discharged to a cut-off voltage of 2.0V using a 0.1C rate. Then disassemble the battery, take out the negative electrode piece, randomly pick 30 discs of unit area (1540.25mm 2 ) on the negative electrode piece, and use Agilent ICP-OES730 to test the inductively coupled plasma emission spectrum (ICP). Calculate the amounts of Fe (if the Mn site of the cathode active material is doped with Fe) and Mn based on the ICP results, and then calculate the dissolution amount of Mn (and Fe doped at the Mn site) after cycles. The test standard is based on EPA-6010D-2014.
  • the cathode active material sample prepared above Take 5 g of the cathode active material sample prepared above and prepare a buckle according to the above preparation method of buckle. Charge with a small rate of 0.05C until the current is reduced to 0.01C. Then take out the positive electrode piece from the battery and soak it in DMC for 8 hours. Then it is dried, scraped into powder, and particles with a particle size less than 500nm are screened out. The obtained particles were measured with electron energy loss spectroscopy (EELS, the instrument model used was Talos F200S) to obtain the energy loss near-edge structure (ELNES), which reflects the density of states and energy level distribution of the element. According to the density of states and energy level distribution, the number of occupied electrons is calculated by integrating the valence band density of states data, thereby deducing the valence state of the charged surface oxygen.
  • EELS electron energy loss spectroscopy
  • Dissolve 5g of the positive active material prepared above in 100ml aqua regia (concentrated hydrochloric acid: concentrated nitric acid 1:3) (concentrated hydrochloric acid concentration ⁇ 37%, concentrated nitric acid concentration ⁇ 65%), and use ICP to test the content of each element of the solution. content, and then measure and convert the content of manganese element or phosphorus element (amount of manganese element or phosphorus element/amount of cathode active material * 100%) to obtain its weight ratio.
  • the button batteries prepared in the above examples and comparative examples were charged to 4.3V at 0.1C, then charged at a constant voltage at 4.3V until the current was less than or equal to 0.05mA, left to stand for 5 minutes, and then charged at 0.1 C is discharged to 2.0V.
  • the discharge capacity at this time is the initial gram capacity, recorded as D0.
  • the full cells prepared in each of the above-described Examples and Comparative Examples were stored at 60° C. at 100% state of charge (SOC). Measure the open circuit voltage (OCV) and AC internal resistance (IMP) of the battery cells before, after and during storage to monitor SOC, and measure the volume of the battery cells. 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 leaving it for 1 hour. After cooling to room temperature, the cell volume was measured using the drainage method.
  • SOC state of charge
  • the drainage method is to first separately measure the gravity F 1 of the battery cell using a balance that automatically converts units based on the dial data, then completely places the battery core in deionized water (density is known to be 1g/cm 3 ), and measures the battery core at this time.
  • the thickness test of the coating layer mainly uses FIB to cut a slice with a thickness of about 100nm from the middle of a single particle of the cathode active material prepared above, and then perform a TEM test on the slice to obtain the original TEM test picture and save the original picture format (xx.dm3) .
  • the thickness of the selected particles was measured at three locations and averaged.
  • This test is performed by Raman spectroscopy. By peak 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 microscopy

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Abstract

本申请提供一种正极活性材料、其制备方法、正极极片、二次电池、电池模块、电池包和用电装置；正极活性材料包括含Li 1+xMn 1-yA yP 1-zR zO 4的内核、包覆内核的含晶态焦磷酸盐Li aMP 2O 7和/或M b(P 2O 7) c的第一包覆层、包覆第一包覆层的含晶态氧化物M' dO e的第二包覆层以及包覆第二包覆层的含碳的第三包覆层。本申请正极活性材料能减少Li/Mn反位缺陷的产生、减少锰溶出并降低晶格变化率，提高二次电池的容量，改善二次电池的循环性能、高温存储性能和安全性能。

Description

正极活性材料及制备方法、正极极片、二次电池、电池模块、电池包及用电装置 技术领域
本申请涉及二次电池技术领域，尤其涉及正极活性材料、正极活性材料的制备方法、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，磷酸锰锂的充放电过程中，容易产生Li/Mn反位缺陷，锰溶出较严重，影响了二次电池的克容量，导致二次电池的安全性能和循环性能变差。
发明内容
本申请是鉴于上述课题而进行的，其目的在于，提供一种正极活性材料、正极活性材料的制备方法、正极极片、二次电池、电池模块、电池包和用电装置，以解决现有的磷酸锰锂正极活性材料在充放电过程中容易产生Li/Mn反位缺陷，锰溶出较严重的问题，从而解决二次电池的容量低、安全性能和循环性能差等问题。
为了达到上述目的，本申请第一方面提供了一种具有核-壳结构的正极活性材料，其包括内核及包覆内核的壳，
内核包含Li 1+xMn 1-yA yP 1-zR zO 4，其中，x为-0.100-0.100范围内的任意数值，y为0.001-0.600范围内的任意数值，z为0.001-0.100范围内的任意数值，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，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；
壳包括包覆内核的第一包覆层、包覆第一包覆层的第二包覆层以及包覆第二包覆层的第三包覆层，其中，
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，a大于0且小于或等于2，b为1-4范围内的任意数值，c为1-3范围内的任意数值，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；
第二包覆层包含晶态氧化物M′ dO e，其中，d大于0且小于或等于2，e大于0且小于或等于5，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；
第三包覆层包含碳。
本申请发明人在实际作业中发现：磷酸锰锂正极活性材料在深度充放电过程中，易产生Li/Mn反位缺陷，锰溶出比较严重。溶出的锰在迁移到负极后，被还原成金属锰。这些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，产生的副产物一部分为气体，容易导致电池发生膨胀，影响二次电池的安全性能，另一部分沉积在负极表面，阻碍锂离子进出负极的通道，造成二次电池的阻抗增加，影响电池的动力学性能和循环性能。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，给二次电池的容量保持率带来不可逆的影响。
由此，本申请人意外地发现：通过在磷酸锰锂的锰位掺杂元素A并在磷位掺杂元素R得到掺杂的磷酸锰锂内核并在内核表面依次进行三层包覆，提供了一种新型的具有核-壳结构的正极活性材料，能够大大减少Li/Mn反位缺陷的产生、显著降低锰溶出并降低晶格变化率、增大压实密度，应用于二次电池中能提高二次电池的容量，改善二次电池的循环性能、高温存储性能和安全性能。其中，第二包覆层中的晶态氧化物具备高的结构稳定性、表面活性低，因此，通过包覆第二包覆层能有效减少界面副反应，从而改善电池的高温循环和高温存储等性能。
本文中，晶态意指结晶度在50％以上，即50％-100％。结晶度小于50％的称为玻璃态。
本申请的晶态焦磷酸盐的结晶度为50％至100％。具备一定结晶度的焦磷酸盐不但有利于充分发挥焦磷酸盐包覆层阻碍锰溶出的能力、减少界面副反应的功能，而且能够使得焦磷酸盐包覆层和氧化物包覆层能够更好的进行晶格匹配，从而能够实现包覆层和包覆层之间紧密的结合。
除非另有说明，否则化学式Li 1+xMn 1-yA yP 1-zR zO 4中，当A为两种以上元素时，上述对于y数值范围的限定不仅是对每种作为A的元素的化学计量数的限定，也是对各个作为A的元素的化学计量数之和的限定。例如当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。
除非另有说明，否则化学式M b(P 2O 7) c中，当M为两种以上元素时，上述对于b数值范围的限定不仅是对每种作为M的元素的化学计量数的限定，也是对各个作为M的元素的化学计量数之和的限定。例如当M为两种以上元素M1、M2……Mn时，M1、M2……Mn各自的化学计量数b1、b2……bn各自均需落入本申请对b限定的数值范围内，且b1、b2……bn之和也需落入该数值范围内。类似地，对 于化学式M′ dO e中M′为两种以上元素的情况，本申请中对M′化学计量数d的数值范围的限定也具有上述含义。
在第一方面的任意实施方式中，第一包覆层中的晶态焦磷酸盐的晶面间距范围为0.293-0.470nm，晶向(111)的夹角范围为18.00°-32.00°；
可选地，所述第一包覆层中的晶态焦磷酸盐的晶面间距范围为0.297-0.462nm；和/或，
可选地，所述第一包覆层中的晶态焦磷酸盐的晶向(111)的夹角范围为19.211°-30.846°。
本申请的正极活性材料中的第一包覆层使用晶态物质，它们的晶面间距和夹角范围在上述范围内。由此，能够有效避免包覆层中的杂质相，从而提升材料的克容量，提升二次电池的循环性能和倍率性能。
在第一方面的任意实施方式中，在内核中，y与1-y的比值为1:10至1:1，可选为1:4至1:1。由此，进一步提升二次电池的循环性能和倍率性能。
在第一方面的任意实施方式中，在内核中，z与1-z的比值为1:9至1:999，可选为1:499至1:249。由此，进一步提升二次电池循环性能和倍率性能。
在第一方面的任意实施方式中，第三包覆层中的碳为SP2形态碳与SP3形态碳的混合物；可选地，SP2形态碳与SP3形态碳的摩尔比为0.07-13范围内的任意数值，更可选为0.1-10范围内的任意数值，进一步可选为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。
在第一方面的任意实施方式中，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％，基于内核的重量计；和/或
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％，基于内核的重量计；和/或
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％，基于内核的重量计。
本申请具有核-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。
在第一方面的任意实施方式中，第一包覆层的厚度为2-10nm。本申请中，当第一包覆层的厚度范围为2-10nm时，能进一步减少过渡金属离子的溶出和迁移，提升二次电池的动力学性能。
在第一方面的任意实施方式中，第二包覆层的厚度为3-15nm。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。
在第一方面的任意实施方式中，第三包覆层的厚度为5-25nm。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实密度性能。
在第一方面的任意实施方式中，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。
本申请的具有核-壳结构的正极活性材料中，锰元素的含量在上述范围内，能有效提高正极活性材料的结构稳定性和密度，从而提升二次电池的循环、存储和压实密度等性能；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。
本申请的具有核-壳结构的正极活性材料中，磷元素的含量在上述范围内，能有效提高正极活性材料的电导率，并且能提高正极活性材料的结构稳定性。
本申请的具有核-壳结构的正极活性材料中，锰元素与磷元素的重量比在上述范围内，能减少过渡金属的溶出，以提高正极活性材料的稳定性和二次电池的循环及存储性能，并且能维持一定的放电电压平台高度，从而提高二次电池的能量密度。
在第一方面的任意实施方式中，正极活性材料在完全脱嵌锂前后的晶格变化率为50％以下，可选为4％以下，更可选为3.8％以下，进一步可选为2.0％-3.8％。
本申请的具有核-壳结构的正极活性材料能够实现较低的脱嵌锂前后的晶格变化率。因此使用正极活性材料能够改善二次电池的克容量和倍率性能。
在第一方面的任意实施方式中，正极活性材料的Li/Mn反位缺陷浓度为5.3％以下，可选为4％以下，更可选为2.2％以下，进一步可选为1.5％-2.2％。通过Li/Mn反位缺陷浓度在上述范围内，能够提升Li +的传输，同时提升正极活性材料的克容量和二次电池的倍率性能。
在第一方面的任意实施方式中，正极活性材料在3T下的压实密度为1.95g/cm 3以上，可选为2.2g/cm 3以上，进一步可选为2.2g/cm 3以上且2.8g/cm 3以下，更进一步可选为2.2g/cm 3以上且2.65g/cm 3以下。由此，提高压实密度，则单位体积的正极活性材料的重量增大，有利于提高二次电池的体积能量密度。
在第一方面的任意实施方式中，正极活性材料的表面氧价态为-1.89以下，可选地为-1.90至-1.98。由此，通过如上将正极活性材料的表面氧价态限定在上述范围内，能够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。
本申请第二方面提供了一种正极活性材料的制备方法，包括以下步骤：
提供内核材料的步骤：内核材料包含Li 1+xMn 1-yA yP 1-zR zO 4，其中x为-0.100-0.100范围内的任意数值，y为0.001-0.600范围内的任意 数值，z为0.001-0.100范围内的任意数值，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，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；
第一包覆步骤：提供包含焦磷酸盐Li aMP 2O 7和/或M 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；其中，a大于0且小于或等于2，b为1-4范围内的任意数值，c为1-3范围内的任意数值；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；
第二包覆步骤：提供包含氧化物M′ dO e的第二混合物，将第一包覆层包覆的材料与第二混合物混合，干燥，烧结，得到两层包覆层包覆的材料；其中，d大于0且小于或等于2，e大于0且小于或等于5，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；
第三包覆步骤：提供包含碳源的第三混合物，将两层包覆层包覆的材料与第三混合物混合，干燥，烧结，得到正极活性材料；
其中，正极活性材料具有核-壳结构，其包括内核及包覆内核的壳，内核包含Li 1+xMn 1-yA yP 1-zR zO 4，壳包括包覆内核的第一包覆层、包覆第一包覆层的第二包覆层以及包覆第二包覆层的第三包覆层，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，第二包覆层包含晶态氧化物M′ dO e，第三包覆层包含碳。
由此，本申请通过在磷酸锰锂的锰位掺杂元素A并在磷位掺杂元素R得到掺杂的磷酸锰锂内核并在内核表面依次进行三层包覆，提供了一种新型的具有核-壳结构的正极活性材料，能够大大减少Li/Mn反位缺陷的产生、显著降低锰溶出并降低晶格变化率、增大压实密度，应用于二次电池中能提高二次电池的容量，改善二次电池的循环性能、高温存储性能和安全性能。
本申请第二方面的任意实施方式中，提供内核材料的步骤包括以下步骤：
步骤(1)：将锰源、元素A的源和酸混合，得到混合物；
步骤(2)：将步骤(1)得到的混合物与锂源、磷源、元素R的源及可选的溶剂混合，在惰性气体保护下烧结，得到包含Li 1+xMn 1-yA yP 1-zR zO 4的内核材料。
本申请第二方面的任意实施方式中，步骤(1)在20℃-120℃、可选为在40℃-120℃下进行；和/或，步骤(1)中，通过以400-700rpm转速搅拌1-9h进行混合。
本申请第二方面的任意实施方式中，步骤(2)中，在20-120℃、可选为40-120℃的温度下混合1-10h。
本申请第二方面的任意实施方式中，
第一包覆步骤中，通过将元素M的源、磷源、酸、任选的锂源和任选的溶剂混合得到第一混合物；和/或，
第二包覆步骤中，通过将元素M′的源与溶剂混合得到第二混合物；和/或，
第三包覆步骤中，通过将碳源与溶剂混合得到第三混合物。
本申请第二方面的任意实施方式中，第一包覆步骤中，元素M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。
本申请第二方面的任意实施方式中，第二包覆步骤中，元素M′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。
本申请第二方面的任意实施方式中，元素A的源为选自元素A的单质、碳酸盐、硫酸盐、卤化物、硝酸盐、有机酸盐、氧化物和氢氧化物中的一种或多种；和/或，
元素R的源为选自元素R的无机酸、有机酸、硫酸盐、卤化物、硝酸盐、有机酸盐、氧化物和氢氧化物中的一种或多种。
本申请第二方面的任意实施方式中，第一包覆步骤中，烧结在650-800℃下进行2-8小时；和/或，第二包覆步骤中，烧结在400-750℃下进行6-10小时；和/或，第三包覆步骤中，烧结在600-850℃下进行6-10小时。
本申请第三方面提供了一种正极极片，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，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制备方法制备的正极活性材料；可选地，正极活性材料在正极膜层中的含量为90-99.5重量％，更可选为95-99.5重量％，基于正极膜层的总重量计。
本申请第四方面提供了一种二次电池，包括本申请第一方面的正极活性材料或者通过本申请第二方面的制备方法制备的正极活性材料或者本申请第三方面的正极极片。
本申请的第五方面提供一种电池模块，包括本申请的第四方面的二次电池。
本申请的第六方面提供一种电池包，包括本申请的第五方面的电池模块。
本申请的第七方面提供一种用电装置，包括选自本申请的第四方面的二次电池、本申请的第五方面的电池模块和本申请的第六方面的电池包中的至少一种。
附图说明
图1是本申请一实施方式的三层包覆结构的正极活性材料的示意图。
图2是本申请一实施方式的二次电池的示意图。
图3是图2所示的本申请一实施方式的二次电池的分解图。
图4是本申请一实施方式的电池模块的示意图。
图5是本申请一实施方式的电池包的示意图。
图6是图5所示的本申请一实施方式的电池包的分解图。
图7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：
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
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、正极活性材料的制备方法、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的，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“某数值以下”、“某数值以上”的范围表示以某数值为上限或下限所限定的范围。
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，方法包括步骤(a)和(b)，表示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，提到方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到方法，例如，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，“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)。
如果没有特别的说明，在本申请中，术语“包覆层”是指包覆在内核上的物质层，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。
如果没有特别的说明，在本申请中，术语“包覆层的厚度”是指包覆层在内核径向上的厚度，“包覆层”的术语定义同上。
[二次电池]
二次电池又称为充电电池或蓄电池，是指在电池放电后可通过充电的方式使活性材料激活而继续使用的电池。
通常情况下，二次电池包括正极极片、负极极片、隔离膜及电解 液。在电池充放电过程中，活性离子(例如锂离子)在正极极片和负极极片之间往返嵌入和脱出。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，同时可以使活性离子通过。电解液在正极极片和负极极片之间，主要起到传导活性离子的作用。
[正极活性材料]
本申请提供了一种具有核-壳结构的正极活性材料，其包括内核及包覆内核的壳，
内核包含Li 1+xMn 1-yA yP 1-zR zO 4，其中，x为-0.100-0.100范围内的任意数值，y为0.001-0.600范围内的任意数值，z为0.001-0.100范围内的任意数值，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，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；
壳包括包覆内核的第一包覆层、包覆第一包覆层的第二包覆层以及包覆第二包覆层的第三包覆层，其中，
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，a大于0且小于或等于2，b为1-4范围内的任意数值，c为1-3范围内的任意数值，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；
第二包覆层包含晶态氧化物M′ dO e，其中，d大于0且小于或等于2，e大于0且小于或等于5，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；
第三包覆层包含碳。
本申请正极活性材料能够提高二次电池的克容量、循环性能和安全性能。虽然机理尚不清楚，但推测是本申请的正极活性材料为核-壳结构，其中通过对磷酸锰锂内核的锰位和磷位分别掺杂元素A和元素R，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；通过对内核包覆包括晶态焦磷酸盐的第一包覆层，能够进一步增大锰的迁移阻力，减少其溶出，并减少表面杂锂含量、减少内核与电解液的接触，从而减少界面副反应、减少产气，提高二次电池的高温存储性能、循环性能和安全性能；通过进一步包覆具有高稳定性的晶态氧化物包覆层，可以使正极活性材料的表面的界面副反应有效降低，进而改善二次电池的高温循环及存储性能；通过再进一步包覆碳层作为第三包覆层，能够进一步提升二次电池的安全性能和动力学性能。此外，在内核中，在磷酸锰锂的锰位掺杂的元素A还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。
除非另有说明，否则在化学式Li 1+xMn 1-yA yP 1-zR zO 4中，当A为两种以上元素时，上述对于y数值范围的限定不仅是对每种作为A的元素的化学计量数的限定，也是对各个作为A的元素的化学计量数之和的限定。例如当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。
在一些实施方式中，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Q 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，Q、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，Q、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。内核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。
在一些实施方式中，x、y和z的值满足以下条件：使整个内核保持电中性。
内核Li 1+xMn 1-yA yP 1-zR zO 4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。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。
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材料中产生锂空位，从而使材料的动力学性能更优异。
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。A元素和R元素掺杂后的磷酸锰锂的XRD图中的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，因此，内核性能的改善主要是来自元素掺杂，而不是杂相导致的。本申请发明人在制备正极活性材料后，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，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。
在一些实施方式中，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。
在一些实施方式中，d和e的值满足以下条件：使晶态M′ dO e保持电中性。
在一些实施方式中，晶态意指结晶度在50％以上，即50％-100％。结晶度小于50％的称为玻璃态。
在一些实施方式中，本申请的晶态焦磷酸盐的结晶度为50％至100％。具备一定结晶度的焦磷酸盐不但有利于充分发挥焦磷酸盐包覆层阻碍锰溶出的能力、减少界面副反应的功能，而且能够使得焦磷酸盐包覆层和氧化物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，正极活性材料的第一包覆层物质晶态焦磷酸盐的结晶度可以通过本领域中常规的技术手段来测试，例如通过密度法、红外光谱法、差示扫描量热法和核磁共振吸收方法测量，也可以通过例如，X射线衍射法来测试。
具体的X射线衍射法测试正极活性材料的第一包覆层晶态焦磷酸盐的结晶度的方法可以包括以下步骤：
取一定量的正极活性材料粉末，通过X射线测得总散射强度，它是整个空间物质的散射强度之和，只与初级射线的强度、正极活性材料粉末化学结构、参加衍射的总电子数即质量多少有关，而与样品的序态无关；然后从衍射图上将结晶散射和非结晶散射分开，结晶度即是结晶部分散射对散射总强度之比。
需要说明的是，在一些实施方式中，包覆层中的焦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。
在一些实施方式中，由于金属离子在焦磷酸盐中难以迁移，因此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。
在一些实施方式中，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。第一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，在内核中掺杂了A和R元素后，与不掺杂元素相比，内核与第一包覆层的匹配度得到改善，内核与焦磷酸盐包覆层之间能够更紧密地结合在一起。
选择晶态氧化物作为第二包覆层，首先，是因为它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％)；其次，作为第二包覆层的晶态氧化物本身的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。作为第二包覆层的晶态氧化物的结构很稳定，因此，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。由于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，以及颗粒上不同位置的电子传输，可以使用具有优异导电性能的碳来进行包覆。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。
图1为理想中的三层包覆结构的正极活性材料的示意图。如图所示，最里面的圆示意表示内核，由内向外依次为第一包覆层、第二包覆层、第三包覆层。该图表示的是每层均完全包覆的理想状态，实践中，每一包覆层可以是完全包覆，也可以是部分包覆。
在一些实施方式中，第一包覆层中的晶态焦磷酸盐的晶面间距范围为0.293-0.470nm，晶向(111)的夹角范围为18.00°-32.00°；
可选地，所述第一包覆层中的晶态焦磷酸盐的晶面间距范围为0.297-0.462nm；和/或，
可选地，所述第一包覆层中的晶态焦磷酸盐的晶向(111)的夹角范围为19.211°-30.846°。
对于第一包覆层中的晶态焦磷酸盐，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。
第一包覆层中的晶态焦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，保存原始图片。
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。
在上述晶面间距和夹角范围内的晶态焦磷酸盐，能够更有效地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性能、倍率性能、循环稳定性和高温储存性能。
在一些实施方式中，在内核中，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，使用正极活性材料的二次电池的能量密度、倍率性能和循环性能可进一步提升。
在一些实施方式中，在内核中，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，使用正极活性材料的二次电池的能量密度、倍率性能和循环性能可进一步提升。
在一些实施方式中，第三包覆层中的碳为SP2形态碳与SP3形态碳的混合物；可选地，SP2形态碳与SP3形态碳的摩尔比为0.07-13范围内的任意数值，更可选为0.1-10范围内的任意数值，进一步可选为2.0-3.0范围内的任意数值。
在一些实施方式中，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。
本申请中，“约”某个数值表示一个范围，表示该数值±10％的范围。
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。
第三包覆层碳的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。
第三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。
在一些实施方式中，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％，基于内核的重量计；和/或
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％，基于内核的重量计；和/或
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％，基于内核的重量计。
本申请中，每一层的包覆量均不为零。
本申请的具有核-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。
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。
在一些实施方式中，第一包覆层的厚度为2-10nm；和/或
第二包覆层的厚度为3-15nm；和/或
第三包覆层的厚度为5-25nm。
在一些实施方式中，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。
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，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。
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。
在一些实施方式中，具有核-壳结构的正极活性材料在完全脱嵌锂前后的晶格变化率为50％以下，可选为4％以下，更可选为3.8％以下，进一步可选为2.0％-3.8％。
磷酸锰锂(LiMnPO 4)的脱嵌锂过程是两相反应。两相的界面应力由脱嵌锂前后的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，减小内核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。本申请的具有核-壳结构的正极活性材料能够实现较低的脱嵌锂前后的晶格变化率，因此使用正极活性材料能够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。
在一些实施方式中，具有核-壳结构的正极活性材料的Li/Mn反位缺陷浓度为5.3％以下，可选为4％以下，更可选为2.2％以下，进一步可选为1.5％-2.2％。
本申请的Li/Mn反位缺陷，指的是LiMnPO 4晶格中，Li +与Mn 2+的位置发生互换。相应地，Li/Mn反位缺陷浓度指的是与Mn 2+发生互换的Li +占Li +总量的百分比。本申请中，Li/Mn反位缺陷浓度例如，可以依据JIS K 0131-1996进行测试。
本申请的具有核-壳结构的正极活性材料能够实现上述较低的Li/Mn反位缺陷浓度。虽然机理尚不十分清楚，但本申请发明人推测，由于LiMnPO 4晶格中，Li +与Mn 2+会发生位置互换，而Li +传输通道 为一维通道，因此Mn 2+在Li +通道中将难以迁移，进而阻碍Li +的传输。由此，本申请的具有核-壳结构的正极活性材料由于Li/Mn反位缺陷浓度较低，在上述范围内，因此，能够降低Mn 2+阻碍Li +的传输，同时提升正极活性材料的克容量发挥和倍率性能。
在一些实施方式中，正极活性材料在3T下的压实密度为1.95g/cm 3以上，可选为2.2g/cm 3以上，进一步可选为2.2g/cm 3以上且2.8g/cm 3以下，更进一步可选为2.2g/cm 3以上且2.65g/cm 3以下。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。
在一些实施方式中，正极活性材料的表面氧价态为-1.89以下，可选地为-1.90至-1.98。
氧的稳定价态本为-2价，价态越接近-2价，其得电子能力越强，即氧化性越强，通常情况下，其表面价态在-1.7以下。本申请正极活性材料的表面氧价态在上述范围内，能够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。
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。
通过在上述范围内对掺杂元素进行选择，有利于增强掺杂效果，一方面进一步减小晶格变化率，从而抑制锰的溶出，减少电解液和活性锂的消耗，另一方面也有利于进一步降低表面氧活性，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高温储存性能。
在一些实施方式中，正极活性材料的内核中，x为-0.005-0.002范围内的任意数值，例如-0.004、-0.003、-0.002、-0.001、0、0.001、0.002。
在一些实施方式中，正极活性材料的内核中，y可以为例如0.001、0.002、0.3、0.35、0.4、0.5。
在一些实施方式中，正极活性材料的内核中，z可以为例如0.001、0.002、0.003、0.005、0.1。
在一些实施方式中，正极活性材料的第二包覆层中，d为1-2范围内的任意数值。
在一些实施方式中，正极活性材料的第二包覆层中，e为1-5范围内的任意数值。
[正极活性材料的制备方法]
本申请提供了一种正极活性材料的制备方法，包括以下步骤：
提供内核材料的步骤：内核材料包含Li 1+xMn 1-yA yP 1-zR zO 4，其中x为-0.100-0.100范围内的任意数值，y为0.001-0.600范围内的任意数值，z为0.001-0.100范围内的任意数值，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，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；
第一包覆步骤：提供包含焦磷酸盐Li aMP 2O 7和/或M 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；其中，a大于0且小于或等于2，b为1-4范围内的任意数值，c为1-3范围内的任意数值；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；
第二包覆步骤：提供包含氧化物M′ dO e的第二混合物，将第一包覆层包覆的材料与第二混合物混合，干燥，烧结，得到两层包覆层包覆的材料；其中，d大于0且小于或等于2，e大于0且小于或等于5，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；
第三包覆步骤：提供包含碳源的第三混合物，将两层包覆层包覆的材料与第三混合物混合，干燥，烧结，得到正极活性材料；
其中，正极活性材料具有核-壳结构，其包括内核及包覆内核的壳，内核包含Li 1+xMn 1-yA yP 1-zR zO 4，壳包括包覆内核的第一包覆层、包覆第一包覆层的第二包覆层以及包覆第二包覆层的第三包覆层，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，第二包覆层包含晶态氧化物M′ dO e，第三包覆层包含碳。A、R、M、M′、x、y、z、a、b、c、d、e的定义如前述。
由此，本申请通过在磷酸锰锂的锰位掺杂元素A并在磷位掺杂元素R得到掺杂的磷酸锰锂内核并在内核表面依次进行三层包覆，提供了一种新型的具有核-壳结构的正极活性材料，能够大大减少Li/Mn反位缺陷的产生、显著降低锰溶出并降低晶格变化率、增大压实密度，应用于二次电池中能提高二次电池的容量，改善二次电池的循环性能、高温存储性能和安全性能。
在一些实施方式中，提供内核材料的步骤包括以下步骤：
步骤(1)：将锰源、元素A的源和酸混合，得到混合物；
步骤(2)：将步骤(1)得到的混合物与锂源、磷源、元素R的源及可选的溶剂混合，在惰性气体保护下烧结，得到包含Li 1+xMn 1-yA yP 1-zR zO 4的内核材料。A和R的定义如前述。
在一些实施方式中，步骤(1)在20℃-120℃、可选为在40℃-120℃(例如约30℃、约50℃、约60℃、约70℃、约80℃、约90℃、约100℃、约110℃或约120℃)下进行；和/或，步骤(1)中，通过以400-700rpm转速搅拌1-9h(可选为3-7h，例如约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)进行混合。
在一些实施方式中，步骤(2)中，在20-120℃、可选为40-120℃(例如约30℃、约50℃、约60℃、约70℃、约80℃、约90℃、约100℃、约110℃或约120℃)的温度下混合1-10h(例如约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)。
当内核颗粒制备过程中的温度和时间处于上述范围内时，制备获得的内核以及由其制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，步骤(2)中，在pH为3.5-6条件下混合，可选地pH为4-6，更可选地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pH，例如可通过添加酸或碱。
在一些可选实施方式中，将步骤(1)获得的混合物过滤，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，将经元素A掺杂的锰盐颗粒用于步骤(2)中与锂源、磷源、元素R的源及可选的溶剂混合。
在一些实施方式中，可选地，在步骤(2)中，混合物或经元素A掺杂的锰盐颗粒与锂源、磷源的摩尔比为1：0.5-2.1：0.5-2.1，可选为约1：1：1。
在一些实施方式中，步骤(2)中，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，保护气氛为70-90体积％氮气和10-30体积％氢气的混合气体；可选地，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，烧结的温度、烧结时间可在上述任意数值的任意范围内，能提高内核的结晶度，减少杂相生成，使内核维持一定的颗粒度，从而提高正极活性材料的克容量、压实密度，提高二次电池的整体性能包括倍率性能。
在一些可选实施方式中，将步骤(2)中混合后的物料干燥得到粉料，然后将粉料烧结得到包含Li 1+xMn 1-yA yP 1-zR zO 4的内核材料。
在一些实施方式中，第一包覆步骤中，通过将元素M的源、磷源、酸、任选的锂源和任选的溶剂混合得到第一混合物；和/或，
第二包覆步骤中，通过将元素M′的源与溶剂混合得到第二混合物；和/或，
第三包覆步骤中，通过将碳源与溶剂混合得到第三混合物。
在一些实施方式中，第一混合物、第二混合物和第三混合物可以悬浊液的形式提供。
在一些实施方式中，第一包覆步骤中，元素M的源、磷源、酸、任选的锂源和任选的溶剂在室温下混合1-5小时(例如约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)，再升温至50℃-120℃(例如55℃、约60℃、约70℃、约80℃、约90℃、约100℃、约110℃或约120℃)并保持该温度混合2-10小时(例如约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)，上述混合均在pH为3.5-6.5(例如4-6)条件下进行。
在一些实施方式中，第二包覆步骤中，元素M′的源与溶剂在室温下混合1-10小时(例如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)，再升温至60℃-150℃(例如约65℃、约70℃、约80℃、约90℃、约100℃、约110℃、约120℃、约130℃、约140℃或约150℃)并保持该温度混合2-10小时(例如约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)。
本申请的制备方法对材料的来源并没有特别的限制，某种元素的来源可包括该元素的单质、硫酸盐、卤化物、硝酸盐、有机酸盐、氧化物或氢氧化物中的一种或多种，前提是该来源可实现本申请制备方法的目的。
在一些实施方式中，元素A的源为选自元素A的单质、碳酸盐、硫酸盐、卤化物、硝酸盐、有机酸盐、氧化物和氢氧化物中的一种或多种；和/或，
元素R的源为选自元素R的无机酸、有机酸、硫酸盐、卤化物、硝酸盐、有机酸盐、氧化物和氢氧化物中的一种或多种。
在一些实施方式中，元素M的源为选自元素M的单质、碳酸盐、硫酸盐、卤化物、硝酸盐、有机酸盐、氧化物和氢氧化物中的一种或多种。
在一些实施方式中，元素M’的源为选自元素M’的单质、碳酸盐、硫酸盐、卤化物、硝酸盐、有机酸盐、氧化物和氢氧化物中的一种或多种。
元素A、R、M、M’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。
本申请中，锰源可为本领域已知的可用于制备磷酸锰锂的含锰物质。作为示例，锰源可为选自单质锰、二氧化锰、磷酸锰、草酸锰、碳酸锰中的一种或多种。
本申请中，酸可为选自盐酸、硫酸、硝酸、磷酸、硅酸、亚硅酸等有机酸和有机酸如草酸中的一种或多种。在一些实施方式中，酸为浓度为60重量％以下的稀的有机酸。
本申请中，锂源可为本领域已知的可用于制备磷酸锰锂的含锂物质。作为示例，锂源为选自碳酸锂、氢氧化锂、磷酸锂、磷酸二氢锂中的一种或多种。
本申请中，磷源可为本领域已知的可用于制备磷酸锰锂的含磷物质。作为示例，磷源为选自磷酸氢二铵、磷酸二氢铵、磷酸铵和磷酸中的一种或多种。
本申请中，作为示例，碳源为选自淀粉、蔗糖、葡萄糖、聚乙烯醇、聚乙二醇、柠檬酸中的一种或多种。
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。
[正极极片]
本申请提供了一种正极极片，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，正极膜层包括前述的正极活性材料或通过前述的制备方法制备的正极活性材料；可选地，正极活性材料在正极膜层中的含量为10重量％以上，基于正极膜层的总重量计。
在一些实施方式中，正极活性材料在正极膜层中的含量为90-99.5重量％，基于正极膜层的总重量计。保证二次电池具有较高的容量和较好的循环性能、高温存储性能和安全性能。
在一些实施方式中，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，正极膜层还可包含本领域公知的用于电池的其它正极活性材料。作为示例，正极活性材料可包括以下材料中的至少一种：橄榄石结构的含锂磷酸盐及其改性化合物。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正极活性材料的传统材料。这些正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。其中，橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂(如LiFePO 4(也可以简称为LFP))、磷酸铁锂与碳的复合材料、 磷酸锰锂(如LiMnPO 4)、磷酸锰锂与碳的复合材料中的至少一种。
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，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，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。
[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，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，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。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。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。作为示例，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。作为示例，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，电解质为液态的，且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，电解液还可选地包括添加剂。作为示例，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2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3，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能够盖设于开口，以封闭容纳腔。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4是作为一个示例的电池模块4。参照图4，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5和图6是作为一个示例的电池包1。参照图5和图6，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，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。二次电池、电池模块、或电池包可以用作用电装置的电源，也可以用作用电装置的能量存储单元。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7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。
[实施例]
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。
本申请实施例涉及的原材料来源如下：
Figure PCTCN2022099516-appb-000001
Figure PCTCN2022099516-appb-000002
正极活性材料及其浆料的制备
实施例1
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至56及对比例1至17
以类似于实施例1的方法制作实施例2至56和对比例1至17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1-6。
其中，对比例1-2、4-10和12未包覆第一层，因此没有步骤S3-S4；对比例1-11未包覆第二层，因此没有步骤S5-S6。
Figure PCTCN2022099516-appb-000003
Figure PCTCN2022099516-appb-000004
Figure PCTCN2022099516-appb-000005
Figure PCTCN2022099516-appb-000006
Figure PCTCN2022099516-appb-000007
Figure PCTCN2022099516-appb-000008
Figure PCTCN2022099516-appb-000009
Figure PCTCN2022099516-appb-000010
Figure PCTCN2022099516-appb-000011
Figure PCTCN2022099516-appb-000012
Figure PCTCN2022099516-appb-000013
Figure PCTCN2022099516-appb-000014
Figure PCTCN2022099516-appb-000015
Figure PCTCN2022099516-appb-000016
Figure PCTCN2022099516-appb-000017
Figure PCTCN2022099516-appb-000018
Figure PCTCN2022099516-appb-000019
Figure PCTCN2022099516-appb-000020
Figure PCTCN2022099516-appb-000021
Figure PCTCN2022099516-appb-000022
Figure PCTCN2022099516-appb-000023
Figure PCTCN2022099516-appb-000024
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”)。
Ⅰ.正极活性材料的性能测试
1.晶格变化率测试方法：
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)。
采用上述的扣电制备方法，将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，并置于碳酸二甲酯(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胞体积v1，将(v0-v1)/v0×100％作为其完全脱嵌锂前后的晶格变化率(晶胞体积变化率)。
2.Li/Mn反位缺陷浓度的测定：
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.压实密度的测定：
取5g的上述制得的正极活性材料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。
4. 3C充电恒流比的测定：
在25℃恒温环境下，将上述各个实施例和对比例制备的新鲜全 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，说明二次电池的倍率性能越好。
5.过渡金属Mn(以及Mn位掺杂的Fe)溶出测试：
将45℃下循环至容量衰减至80％后的上述各个实施例和对比例的正极活性材料所制的全电池采用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.表面氧价态的测定：
取5g上述制得的正极活性材料样品按照上述扣电的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。
7.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。
8.扣式电池初始克容量测量方法：
在2.5-4.3V下，将上述各实施例和对比例制备的扣式电池按照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。
9.全电池60℃存储30天电芯膨胀测试：
在60℃下，存储100％充电状态(SOC)的上述各个实施例和对比例制备的全电池。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，全部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。
10.全电池45℃下循环性能测试：
在45℃的恒温环境下，在2.5-4.3V下，按照1C充电至4.3V，然后在4.3V下恒压充电至电流≤0.05mA，静置5min，然后按照1C放电至2.5V，容量记为D n(n＝0,1,2,……)。重复前述过程，直至容量衰减(fading)到80％，记录此时的重复次数，即为45℃下80％容量保持率对应的循环圈数。
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，即可对不同包覆层的物质及晶态进行识别。
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。
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。
Figure PCTCN2022099516-appb-000025
Figure PCTCN2022099516-appb-000026
Figure PCTCN2022099516-appb-000027
Figure PCTCN2022099516-appb-000028
Figure PCTCN2022099516-appb-000029
Figure PCTCN2022099516-appb-000030
Figure PCTCN2022099516-appb-000031
Figure PCTCN2022099516-appb-000032
Figure PCTCN2022099516-appb-000033
Figure PCTCN2022099516-appb-000034
Figure PCTCN2022099516-appb-000035
Figure PCTCN2022099516-appb-000036
Figure PCTCN2022099516-appb-000037
Figure PCTCN2022099516-appb-000038
Figure PCTCN2022099516-appb-000039

Claims (22)

  1. 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。
  2. 根据权利要求1所述的正极活性材料，其中，在所述内核中， y与1-y的比值为1:10至1:1，可选为1:4至1:1。
  3. 根据权利要求1或2所述的正极活性材料，其中，在所述内核中，z与1-z的比值为1:9至1:999，可选为1:499至1:249。
  4. 根据权利要求1-3中任一项所述的正极活性材料，其中，所述第三包覆层中的碳为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0.07-13范围内的任意数值，更可选为0.1-10范围内的任意数值，进一步可选为2.0-3.0范围内的任意数值。
  5. 根据权利要求1-4中任一项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。
  6. 根据权利要求1-5中任一项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。
  7. 根据权利要求1-6中任一项所述的正极活性材料，其中，
    所述第一包覆层中的晶态焦磷酸盐的晶面间距范围为0.293-0.470nm，晶向(111)的夹角范围为18.00°-32.00°；
    可选地，所述第一包覆层中的晶态焦磷酸盐的晶面间距范围为0.297-0.462nm；和/或，
    可选地，所述第一包覆层中的晶态焦磷酸盐的晶向(111)的夹角范围为19.211°-30.846°。
  8. 根据权利要求1-7中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。
  9. 根据权利要求1-8中任一项所述的正极活性材料，其中，所述正极活性材料在完全脱嵌锂前后的晶格变化率为50％以下，可选为4％以下，更可选为3.8％以下，进一步可选为2.0％-3.8％。
  10. 根据权利要求1-9中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5.3％以下，可选为4％以下，更可选为2.2％以下，进一步可选为1.5％-2.2％。
  11. 根据权利要求1-10中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1.95g/cm 3以上，可选为2.2g/cm 3以上，进一步可选为2.2g/cm 3以上且2.8g/cm 3以下，更进一步可选为2.2g/cm 3以上且2.65g/cm 3以下。
  12. 根据权利要求1-11中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以下，可选地为-1.90至-1.98。
  13. 一种正极活性材料的制备方法，包括以下步骤：
    提供内核材料的步骤：所述内核材料包含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；
    第一包覆步骤：提供包含焦磷酸盐Li aMP 2O 7和/或M 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；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；
    第二包覆步骤：提供包含氧化物M′ dO e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，得到两层包覆层包覆的材料；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；
    第三包覆步骤：提供包含碳源的第三混合物，将所述两层包覆层包覆的材料与第三混合物混合，干燥，烧结，得到正极活性材料；
    其中，所述正极活性材料具有核-壳结构，其包括所述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，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，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，所述第二包覆层包含晶态氧化物M′ dO e，所述第三包覆层包含碳。
  14. 根据权利要求13所述的制备方法，所述提供内核材料的步骤包括以下步骤：
    步骤(1)：将锰源、元素A的源和酸混合，得到混合物；
    步骤(2)：将所述步骤(1)得到的混合物与锂源、磷源、元素R的源及可选的溶剂混合，在惰性气体保护下烧结，得到包含Li 1+xMn 1-yA yP 1-zR zO 4的内核材料；
    可选地，所述步骤(1)在20℃-120℃、更可选为在40℃-120℃下进行；和/或，所述步骤(1)中，通过以400-700rpm转速搅拌1-9h进行混合；
    可选地，所述步骤(2)中，在20-120℃、可选为40-120℃的温度下混合1-10h。
  15. 根据权利要求13或14所述的制备方法，其中，
    所述第一包覆步骤中，通过将元素M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，
    所述第二包覆步骤中，通过将元素M′的源与溶剂混合得到第二混合物；和/或，
    所述第三包覆步骤中，通过将碳源与溶剂混合得到第三混合物；
    可选地，所述第一包覆步骤中，所述元素M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，所述第二包覆步骤中，所述元素M′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。
  16. 根据权利要求13-15中任一项所述的制备方法，其中，
    所述元素A的源为选自元素A的单质、碳酸盐、硫酸盐、卤化 物、硝酸盐、有机酸盐、氧化物和氢氧化物中的一种或多种；和/或，
    所述元素R的源为选自元素R的无机酸、有机酸、硫酸盐、卤化物、硝酸盐、有机酸盐、氧化物和氢氧化物中的一种或多种。
  17. 根据权利要求13-16中任一项所述的制备方法，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。
  18. 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1-12中任一项所述的正极活性材料或通过权利要求13-17中任一项所述的制备方法制备的正极活性材料；可选地，所述正极活性材料在所述正极膜层中的含量为90-99.5重量％，更可选为95-99.5重量％，基于所述正极膜层的总重量计。
  19. 一种二次电池，包括权利要求1-12中任一项所述的正极活性材料或者通过权利要求13-17中任一项所述的制备方法制备的正极活性材料或者权利要求18所述的正极极片。
  20. 一种电池模块，其包括权利要求19所述的二次电池。
  21. 一种电池包，其包括权利要求20所述的电池模块。
  22. 一种用电装置，其包括选自权利要求19所述的二次电池、权利要求20所述的电池模块和权利要求21所述的电池包中的至少一种。
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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102931404A (zh) * 2012-11-12 2013-02-13 复旦大学 磷位硼掺杂磷酸锰锂/碳复合材料及其制备方法
CN104577115A (zh) * 2014-12-26 2015-04-29 青海时代新能源科技有限公司 一种锂离子电池正极材料、其制备方法及应用
CN106816600A (zh) * 2015-11-30 2017-06-09 比亚迪股份有限公司 一种磷酸锰铁锂类材料及其制备方法以及电池浆料和正极与锂电池
US20190020015A1 (en) * 2017-07-14 2019-01-17 Hcm Co., Ltd. Lithium manganese iron phosphate-based particulate for a cathode of a lithium battery, lithium manganese iron phosphate-based powdery material containing the same, and method for manufacturing the powdery material
CN110854360A (zh) * 2018-08-21 2020-02-28 住友大阪水泥股份有限公司 锂离子二次电池用正极材料、锂离子二次电池用电极及锂离子二次电池
CN114256448A (zh) * 2020-09-25 2022-03-29 比亚迪股份有限公司 磷酸锰铁锂复合材料及其制备方法和锂离子电池

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102931404A (zh) * 2012-11-12 2013-02-13 复旦大学 磷位硼掺杂磷酸锰锂/碳复合材料及其制备方法
CN104577115A (zh) * 2014-12-26 2015-04-29 青海时代新能源科技有限公司 一种锂离子电池正极材料、其制备方法及应用
CN106816600A (zh) * 2015-11-30 2017-06-09 比亚迪股份有限公司 一种磷酸锰铁锂类材料及其制备方法以及电池浆料和正极与锂电池
US20190020015A1 (en) * 2017-07-14 2019-01-17 Hcm Co., Ltd. Lithium manganese iron phosphate-based particulate for a cathode of a lithium battery, lithium manganese iron phosphate-based powdery material containing the same, and method for manufacturing the powdery material
CN110854360A (zh) * 2018-08-21 2020-02-28 住友大阪水泥股份有限公司 锂离子二次电池用正极材料、锂离子二次电池用电极及锂离子二次电池
CN114256448A (zh) * 2020-09-25 2022-03-29 比亚迪股份有限公司 磷酸锰铁锂复合材料及其制备方法和锂离子电池

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