WO2023164926A1 - 一种正极极片、二次电池、电池模块、电池包和用电装置 - Google Patents

一种正极极片、二次电池、电池模块、电池包和用电装置 Download PDF

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WO2023164926A1
WO2023164926A1 PCT/CN2022/079269 CN2022079269W WO2023164926A1 WO 2023164926 A1 WO2023164926 A1 WO 2023164926A1 CN 2022079269 W CN2022079269 W CN 2022079269W WO 2023164926 A1 WO2023164926 A1 WO 2023164926A1
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positive electrode
active material
electrode active
layer
battery
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PCT/CN2022/079269
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English (en)
French (fr)
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周翔
刘江
李白清
蒋耀
刘晓梅
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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 CN202280017104.6A priority Critical patent/CN116998032A/zh
Priority to PCT/CN2022/079269 priority patent/WO2023164926A1/zh
Priority to EP22919279.4A priority patent/EP4270575A1/en
Priority to US18/211,591 priority patent/US11888154B2/en
Publication of WO2023164926A1 publication Critical patent/WO2023164926A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—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
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the technical field of secondary batteries, in particular to a positive pole piece, a secondary battery, a battery module, a battery pack and an electrical device.
  • lithium manganese iron phosphate is used as the main material and mixed with ternary materials such as nickel cobalt lithium manganate, nickel cobalt aluminum oxide or lithium cobalt oxide to make secondary batteries.
  • ternary materials such as nickel cobalt lithium manganate, nickel cobalt aluminum oxide or lithium cobalt oxide to make secondary batteries.
  • the present application is made in view of the above-mentioned problems, and its purpose is to provide a positive electrode sheet, a secondary battery, a battery module, a battery pack, and an electrical device to solve the energy problem of secondary batteries made of existing positive active materials.
  • the first aspect of the present application provides a positive electrode sheet, including a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector; the positive electrode film layer is a single-layer structure or a multi-layer structure ;
  • the positive electrode film layer is a single-layer structure, at least one positive electrode film layer contains the first positive electrode active material and the second positive electrode active material with a core-shell structure; and/or, when the positive electrode film layer is a multilayer structure, At least one of the at least one positive electrode film layer contains a first positive electrode active material with a core-shell structure and a second positive electrode active material;
  • the first positive electrode active material includes an inner core, a first coating layer covering the inner core, and a coating The second cladding layer of the first cladding layer; wherein the inner core contains Li 1+x Mn 1-y A y P 1-z R z O 4 , and the first cladding layer contains pyrophosphate MP 2 O 7 and phosphoric acid
  • the transition metal can be greatly reduced. Dissolution and reduce the oxygen activity on the particle surface, promote the migration of lithium ions, improve the electrical conductivity and desolvation performance of the material, improve the rate performance of the battery, improve the cycle performance and high temperature performance of the secondary battery, and reduce the electrolyte on the activity Corrosion of materials.
  • the advantages of the two materials complement each other, which improves the energy density of the secondary battery, and at the same time makes the battery have excellent rate performance, kinetic performance, and cycle performance. , low temperature performance and safety.
  • the particles of the first positive electrode active material are evenly coated on the surface of the second positive electrode active material, so that the crystal lattice of the second positive electrode active material is relatively independent and the skeleton is stable, and it is not easy to collapse during the charging and discharging process of the secondary battery, which further improves the cycle of the battery
  • the coating layer formed by the first positive electrode active material provides elastic strain force for external force impact or shearing, effectively solving the safety problem of the second positive electrode active material.
  • the second aspect of the present application also provides a positive electrode sheet, including a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector; at least one positive electrode film layer is a multilayer structure, any of which has a multilayer structure
  • the positive electrode film layer respectively includes a first positive electrode active material and a second positive electrode active material with a core-shell structure in different layers;
  • the first positive electrode active material includes an inner core, a first coating layer covering the inner core, and a first coating layer
  • the second cladding layer of the cladding layer wherein the inner core contains Li 1+x Mn 1-y A y P 1-z R z O 4 , and the first cladding layer contains pyrophosphate MP 2 O 7 and phosphate XPO 4 ,
  • the second coating layer contains carbon elements; wherein, A is selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb
  • the first positive electrode active material can greatly reduce the dissolution of transition metals and reduce the oxygen activity on the particle surface, promote the migration of lithium ions, improve the conductivity and desolvation performance, improve the rate performance of the battery, and improve the cycle of the secondary battery. performance and high temperature performance while reducing electrolyte corrosion on active materials.
  • the first positive electrode active material and the second positive electrode active material are used in combination.
  • the advantages of the two materials are complementary, which improves the energy density of the secondary battery, and at the same time makes the battery have excellent rate performance, kinetic performance, cycle performance and low-temperature performance, and the first positive electrode active material provides elastic strain force for external impact or shearing, which effectively solves the safety problem of the second positive electrode active material.
  • the third aspect of the present application also provides a positive electrode sheet, including a positive electrode current collector and a positive electrode film layer A and a positive electrode film layer B respectively arranged on the two surfaces of the positive electrode current collector; the positive electrode film layer A and the positive electrode film layer B Each independently has a single-layer structure or a multilayer structure; at least one layer of the positive electrode film layer A contains the first positive electrode active material with a core-shell structure, and at the same time, at least one layer of the positive electrode film layer B contains the second positive electrode active material.
  • the first positive electrode active material comprises an inner core, a first cladding layer covering the inner core, and a second cladding layer covering the first cladding layer; wherein the inner core comprises Li 1+x Mn 1-y A y P 1 -z R z O 4 , the first cladding layer contains pyrophosphate MP 2 O 7 and phosphate XPO 4 , and the second cladding layer contains carbon elements; wherein, A is selected from Zn, Al, Na, K, Mg, One or more elements of Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and Ge; R is selected from one or more of B, Si, N and S x is selected from -0.100-0.100; y is selected from 0.001-0.500; z is selected from 0.001-0.100; M and X are independently selected from Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, One or more elements in Zr, Nb and Al; the second positive
  • the first positive electrode active material can greatly reduce the dissolution of transition metals and reduce the oxygen activity on the particle surface, promote the migration of lithium ions, improve the conductivity and desolvation performance, improve the rate performance of the battery, and improve the cycle of the secondary battery. performance and high temperature performance while reducing electrolyte corrosion on active materials.
  • the first positive electrode active material and the second positive electrode active material are used in combination.
  • the advantages of the two materials are complementary, which improves the energy density of the secondary battery, and at the same time makes the battery have excellent rate performance, kinetic performance, cycle performance and low-temperature performance, and the first positive electrode active material provides elastic strain force for external impact or shearing, which effectively solves the safety problem of the second positive electrode active material.
  • the above-mentioned limitation on the numerical range of y is not only a limitation on the stoichiometric number of each element as A, but also a limitation on each element as A.
  • Limitation of the sum of stoichiometric numbers For example, when A is two or more elements A1, A2...An, the stoichiometric numbers y1, y2...yn of A1, A2...An each need to fall within the numerical range defined by the application for y, and y1 The sum of , y2 ... yn also needs to fall within this value range.
  • the limitation of the numerical range of the stoichiometric number of R in this application also has the above meaning.
  • the mass ratio of the first active material to the second active material is 1:7-7:1, optionally 1:4-4:1.
  • the secondary battery has both excellent rate performance and cycle performance, it has high energy density, excellent kinetic performance and low temperature performance, reduces interface side reactions, and improves the safety of the secondary battery.
  • A in the first positive electrode active material, A is selected from one or more elements selected from Zn, Fe, Ti, V, Ni, Co and Mg; and/or, A is at least two elements selected from Fe, Ti, V, Ni, Co and Mg.
  • x is selected from any value within the range of -0.100-0.006. By selecting the value of x within this range, the kinetic performance of the first positive electrode active material can be further improved.
  • y is selected from any value within the range of 0.1-0.4. By selecting the value of y within this range, the gram capacity and rate performance of the first positive electrode active material can be further improved.
  • M and X are independently selected from one or more elements of Li and Fe.
  • the ratio of y to 1-y is selected from 1:10 to 10:1, optionally 1:4 to 1:1.
  • y represents the sum of stoichiometric numbers of Mn-site doping elements.
  • the ratio of z to 1-z is selected from 1:999 to 1:9, optionally 1:499 to 1:249.
  • z represents the sum of the stoichiometric numbers of the P-site doping elements.
  • the interplanar spacing of the phosphate in the first cladding layer is 0.345-0.358 nm, and the included angle of the crystal direction (111) is 24.25 °-26.45°; the interplanar spacing of the pyrophosphate in the first cladding layer is 0.293-0.326nm, and the included angle of the crystal direction (111) is 26.41°-32.57°.
  • the interplanar spacing of phosphate and pyrophosphate in the first coating layer and the included angle of the crystal direction (111) are in the above range, the impurity phase in the coating layer can be effectively avoided, thereby increasing the gram capacity of the material and improving Cycle performance and rate performance of secondary batteries.
  • the coating amount of the first coating layer is greater than 0% by weight and less than or equal to 7% by weight, and may be 4-5.6% by weight , a kernel-based weight meter.
  • the coating amount of the first coating layer is within the above range, manganese dissolution can be further suppressed, and at the same time, the transport of lithium ions can be further promoted. And it can effectively avoid the following situation: if the coating amount of the first coating layer is too small, it may cause insufficient inhibition of pyrophosphate on manganese dissolution, and the improvement of lithium ion transport performance is not significant; If the coating amount of the first coating layer is too large, the coating layer may be too thick, which increases the battery impedance and affects the kinetic performance of the battery.
  • the weight ratio of pyrophosphate and phosphate in the first coating layer is 1:3 to 3:1, optionally 1: 3 to 1:1.
  • the proper ratio of pyrophosphate and phosphate is conducive to giving full play to the synergistic effect of the two. And it can effectively avoid the following situations: if there is too much pyrophosphate and too little phosphate, it may lead to an increase in battery impedance; if there is too much phosphate and too little pyrophosphate, the effect of inhibiting the dissolution of manganese is not significant.
  • the crystallinity of pyrophosphate and phosphate is independently 10% to 100%, optionally 50% to 100%.
  • pyrophosphate and phosphate with a certain degree of crystallinity are beneficial to keep the structure of the first coating layer stable and reduce lattice defects. On the one hand, this is beneficial to give full play to the role of pyrophosphate in hindering the dissolution of manganese. On the other hand, it is also beneficial to phosphate to reduce the content of lithium on the surface and the valence state of oxygen on the surface, thereby reducing the interface side reactions between the positive electrode material and the electrolyte, and reducing the The consumption of the electrolyte improves the cycle performance and safety performance of the secondary battery.
  • the coating amount of the second coating layer is greater than 0% by weight and less than or equal to 6% by weight, optionally 3-5% by weight , a kernel-based weight meter.
  • the carbon-containing layer as the second coating layer can play a "barrier" function to avoid direct contact between the first positive electrode active material and the electrolyte, thereby reducing the corrosion of the active material by the electrolyte and improving the safety performance of the battery at high temperatures.
  • it has strong electrical conductivity, which can reduce the internal resistance of the battery, thereby improving the kinetic performance of the secondary battery.
  • the gram capacity of the carbon material is low, when the amount of the second coating layer is too large, the gram capacity of the entire positive electrode active material may be reduced. Therefore, when the coating amount of the second coating layer is in the above range, the kinetic performance and safety performance of the secondary battery can be further improved without sacrificing the gram capacity of the positive electrode active material.
  • the Li/Mn antisite defect concentration of the first positive electrode active material is less than 4%, optionally less than 2%.
  • the Li/Mn antisite defect means that in the LiMnPO 4 lattice, the positions of Li + and Mn 2+ are exchanged. Since the Li + transport channel is a one-dimensional channel, Mn 2+ is difficult to migrate in the Li + transport channel, so the Mn 2+ with antisite defects will hinder the transport of Li + .
  • the gram capacity and rate performance of LiMnPO4 can be improved by controlling the Li/Mn antisite defect concentration at a low level.
  • the lattice change rate of the first positive electrode active material is less than 6%, optionally less than 4%.
  • the lithium-deintercalation process of LiMnPO 4 is a two-phase reaction.
  • the interfacial stress of the two phases is determined by the lattice change rate. The smaller the lattice change rate, the smaller the interfacial stress and the easier Li + transport. Therefore, reducing the lattice change rate of the inner core will be beneficial to enhance the Li + transport ability, thereby improving the rate performance of secondary batteries.
  • the surface oxygen valence state of the first positive electrode active material is less than -1.88, optionally -1.98 ⁇ -1.88. This is because the higher the valence state of oxygen in the compound, the stronger its ability to obtain electrons, that is, the stronger the oxidation.
  • the first positive electrode active material of the present application by controlling the surface valence state of oxygen at a lower level, the reactivity of the surface of the positive electrode material can be reduced, and the interface side reaction between the positive electrode material and the electrolyte can be reduced, thereby improving the secondary battery. Excellent cycle performance and high temperature storage performance.
  • the compacted density of the first positive electrode active material at 3 tons (T) is above 2.0 g/cm 3 , optionally above 2.2 g/cm 3 .
  • the sum of the mass of the first positive electrode active material and the second positive electrode active material accounts for 88%-98.7% of the mass of the positive electrode sheet. Further ensure that the secondary battery has excellent rate performance, kinetic performance, cycle performance and low temperature performance, and has a higher energy density.
  • a fourth aspect of the present application provides a secondary battery, including the positive electrode sheet according to any one of the first aspect to 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.
  • the seventh aspect of the present application provides an electric device, including at least one selected from 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.
  • FIG. 1 is a schematic diagram of a first positive electrode active material having a core-shell 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 one embodiment of the present application shown in FIG. 2 .
  • FIG. 4 is a schematic diagram of a battery module according to an embodiment of the present application.
  • FIG. 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 one embodiment of the present application shown in FIG. 5 .
  • FIG. 7 is a schematic diagram of an electrical device in which a secondary battery is used as a power source according to an embodiment of the present application.
  • Fig. 8 is a schematic diagram of the structure of the battery made of the positive pole piece P1 of the present application.
  • FIG. 9 is a schematic diagram of the structure of the battery made of the positive pole piece P2 of the present application.
  • Fig. 10 is a schematic diagram of the structure of the battery made of the positive pole piece P3 of the present application.
  • Fig. 11 is a schematic diagram of the structure of the battery made of the positive pole piece P8 of the present application.
  • FIG. 12 is a schematic diagram of the structure of a battery made of the positive pole piece P10 of the present application.
  • Fig. 13 is a schematic diagram of the structure of the battery made of the positive pole piece P11 of the present application.
  • FIG. 14 is a schematic diagram of the structure of the battery made of the positive pole piece P12 of the present application.
  • Fig. 15 is a schematic diagram of the structure of the battery made of the positive pole piece P17 of the present application.
  • Fig. 16 is a schematic diagram of the structure of the battery made of the positive pole piece P18 of the present application.
  • Fig. 17 is a schematic diagram of the battery structure made of the positive electrode sheet P23 of the present application.
  • Fig. 18 is a schematic diagram of the battery structure made of the positive electrode sheet P24 of the present application.
  • Fig. 19 is a schematic diagram of the battery structure made of the positive electrode sheet P26 of the present application.
  • Fig. 20 is a schematic diagram of the battery structure made of the positive pole piece P27 of the present application.
  • ranges disclosed herein are defined in terms of lower and upper limits, and a given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive and may be combined arbitrarily, ie any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are contemplated. Additionally, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, the following ranges are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-5.
  • the numerical range "a-b” represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers.
  • the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article, and "0-5" is only an abbreviated representation of the combination of these values.
  • a certain parameter is an integer ⁇ 2
  • a method comprising steps (a) and (b) means that the method may comprise steps (a) and (b) performed sequentially, and may also comprise steps (b) and (a) performed sequentially.
  • the method may also include step (c) means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), and may also include step (a) , (c) and (b), may also include steps (c), (a) and (b) and the like.
  • the term "or” is inclusive unless otherwise stated.
  • the phrase "A or B” means “A, B, or both A and B.” More specifically, the condition "A or B” is satisfied by either of the following: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists) ; or both A and B are true (or exist).
  • the median particle size Dv 50 refers to the particle size corresponding to when the cumulative volume distribution percentage of the positive electrode active material reaches 50%.
  • the median diameter Dv 50 of the positive electrode active material can be measured by laser diffraction particle size analysis. For example, with reference to the standard GB/T 19077-2016, a laser particle size analyzer (such as Malvern Master Size 3000) is used for measurement.
  • coating layer refers to a material layer coated on the inner core, and the material layer can completely or partially cover the inner core, and the use of “coating layer” is only for ease of description. It is not intended to limit the invention.
  • thickness of the coating layer refers to the thickness of the material layer coating the inner core in the radial direction of the inner core.
  • source refers to a compound that is the source of a certain element.
  • types of “source” include but are not limited to carbonates, sulfates, nitrates, elemental, Halides, oxides and hydroxides etc.
  • Secondary batteries also known as rechargeable batteries or accumulators, refer to batteries that can be activated by charging the active materials and continue to be used after the battery is discharged.
  • a secondary battery typically includes a positive pole piece, a negative pole piece, a separator, and an electrolyte.
  • active ions such as lithium ions
  • the separator is arranged between the positive pole piece and the negative pole piece, which mainly plays a role in preventing the short circuit of the positive and negative poles, and at the same time allows active ions to pass through.
  • the electrolyte is between the positive pole piece and the negative pole piece, and mainly plays the role of conducting active ions.
  • the embodiment of the first aspect of the present application provides a positive electrode sheet, including a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector; the positive electrode film layer is a single-layer structure or a multi-layer structure; when the positive electrode When the film layer is a single-layer structure, at least one positive electrode film layer contains the first positive electrode active material and the second positive electrode active material with a core-shell structure; and/or, when the positive electrode film layer is a multilayer structure, at least one positive electrode At least one layer of the film layer contains a first positive electrode active material and a second positive electrode active material with a core-shell structure; the first positive electrode active material includes an inner core, a first cladding layer covering the inner core, and a first cladding layer covering the inner core.
  • the second cladding layer of the cladding layer wherein the inner core contains Li 1+x Mn 1-y A y P 1-z R z O 4 , and the first cladding layer contains pyrophosphate MP 2 O 7 and phosphate XPO 4 , the second cladding layer contains carbon elements; wherein, A is selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and Ge One or more elements in; R is selected from one or more elements in B, Si, N and S; x is selected from any value in the range of -0.100-0.100; y is selected from any value in the range of 0.001-0.500 Any numerical value; z is selected from any numerical value within the range of 0.001-0.100; M and X are independently selected from one of Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb and Al or A plurality of elements; the second positive electrode active material
  • the positive electrode film layer is a single-layer structure or a multi-layer structure
  • the two positive electrode film layers are each independently a single-layer structure or a multi-layer structure
  • “when "When the positive electrode film layer is a single-layer structure” refers to when one or two positive electrode film layers are a single-layer structure
  • “when the positive electrode film layer is a multilayer structure” refers to when one or two positive electrode film layers are a multilayer structure.
  • the first positive electrode active material of the present application has a core-shell structure with two cladding layers, wherein the inner core includes Li 1+x Mn 1-y A y P 1-z R z O 4 .
  • the element A doped at the manganese position of lithium manganese phosphate in the inner core helps to reduce the lattice change rate of lithium manganese phosphate during lithium deintercalation, improves the structural stability of lithium manganese phosphate cathode material, greatly reduces the dissolution of manganese and reduces the Oxygen activity on particle surfaces.
  • the element R doped at the phosphorus site helps to change the difficulty of the change of the Mn-O bond length, thereby reducing the migration barrier of lithium ions, promoting the migration of lithium ions, and improving the rate performance of the secondary battery.
  • the first coating layer of the first cathode active material of the present application includes pyrophosphate and phosphate. Due to the high migration barrier (>1eV) of transition metals in pyrophosphate, the dissolution of transition metals can be effectively inhibited. Phosphate has an excellent ability to conduct lithium ions, and can reduce the content of lithium impurities on the surface.
  • the second cladding layer is a carbon-containing layer, it can effectively improve the electrical conductivity and desolvation ability of LiMnPO 4 .
  • the "barrier" effect of the second cladding layer can further hinder the migration of manganese ions into the electrolyte and reduce the corrosion of the active materials by the electrolyte. Therefore, the first positive electrode active material of the present application can effectively suppress the dissolution of Mn in the process of lithium intercalation and deintercalation by performing specific element doping and surface coating on lithium manganese phosphate, and at the same time promote the migration of lithium ions, thereby improving the rate of the battery cell Performance, improve the cycle performance and high temperature performance of the secondary battery.
  • the first positive electrode active material of the present application is basically consistent with the positions of the main characteristic peaks before doping with LiMnPO , indicating that the doped lithium manganese phosphate positive electrode active material has no impurity phase, and the improvement of secondary battery performance mainly comes from Elemental doping, not impurity phases.
  • the advantages of the two materials complement each other, which improves the energy density of the secondary battery, and at the same time makes the battery have excellent rate performance, kinetic performance, and cycle performance. , low temperature performance and safety.
  • the particles of the first positive electrode active material are evenly coated on the surface of the second positive electrode active material, so that the crystal lattice of the second positive electrode active material is relatively independent and the skeleton is stable, and it is not easy to collapse during the charging and discharging process of the secondary battery, which further improves the cycle of the battery
  • the coating layer formed by the first positive electrode active material provides elastic strain force for external force impact or shearing, effectively solving the safety problem of the second positive electrode active material.
  • the positive electrode film layer C and the positive electrode film layer D are respectively arranged on the two surfaces of the positive electrode current collector, the positive electrode film layer C is a multilayer structure, and the positive electrode film layer D is a single layer structure , at least one layer of the positive electrode film layer C contains the first positive electrode active material and the second positive electrode active material; optionally, the positive electrode film layer D contains one or both of the first positive electrode active material and the second positive electrode active material Optionally, the remaining layers in the positive electrode film layer C include the first positive electrode active material or the second positive electrode active material.
  • the positive electrode film layer C and the positive electrode film layer D are respectively arranged on the two surfaces of the positive electrode current collector, the positive electrode film layer C is a multilayer structure, and the positive electrode film layer D is a single layer structure , the positive electrode film layer D contains both the first positive electrode active material and the second positive electrode active material; optionally, any layer in the positive electrode film layer C contains the first positive electrode active material or the second positive electrode active material.
  • a positive electrode film layer is respectively arranged on both surfaces of the positive electrode current collector, each positive electrode film layer has a multilayer structure, and at least one layer of each positive electrode film layer is simultaneously Contains the first positive electrode active material and the second positive electrode active material; optionally, the remaining layers in the positive electrode film layer contain the first positive electrode active material or the second positive electrode active material.
  • the embodiment of the second aspect of the present application provides a positive electrode sheet, including a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector; at least one positive electrode film layer is a multi-layer structure, any The positive electrode film layer of the layer structure comprises a first positive electrode active material and a second positive electrode active material with a core-shell structure in different layers; the first positive electrode active material includes an inner core, a first coating layer covering the inner core, and a coating The second cladding layer of the first cladding layer; wherein the inner core contains Li 1+x Mn 1-y A y P 1-z R z O 4 , and the first cladding layer contains pyrophosphate MP 2 O 7 and phosphoric acid Salt XPO 4 , the second coating layer contains carbon elements; wherein, A is selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, One or more elements in Nb and Ge;
  • the first positive electrode active material of the present application can greatly reduce the dissolution of transition metals and reduce the oxygen activity on the particle surface, promote the migration of lithium ions, improve the conductivity and desolvation performance, improve the rate performance of the battery, and improve the cycle of the secondary battery performance and high temperature performance while reducing electrolyte corrosion on active materials.
  • the first positive electrode active material and the second positive electrode active material are used in combination.
  • the advantages of the two materials are complementary, which improves the energy density of the secondary battery, and at the same time makes the battery have excellent rate performance, kinetic performance, cycle performance and low-temperature performance, and the first positive electrode active material provides elastic strain force for external impact or shearing, which effectively solves the safety problem of the second positive electrode active material.
  • a positive electrode film layer is respectively arranged on the two surfaces of the positive electrode current collector, each positive electrode film layer is a multi-layer structure, and two adjacent layers in each positive electrode film layer respectively contain the first positive electrode active material and the second positive electrode active material.
  • the positive electrode film layer E and the positive electrode film layer F are respectively arranged on the two surfaces of the positive electrode current collector, the positive electrode film layer E has a multilayer structure, and the positive electrode film layer F has a single layer structure , two adjacent layers in the positive electrode film layer E comprise the first positive electrode active material and the second positive electrode active material respectively; optionally, the remaining layers in the positive electrode film layer E and the positive electrode film layer F comprise the first positive electrode active material or the second positive electrode active material Two cathode active materials.
  • the embodiment of the third aspect of the present application provides a positive electrode sheet, including a positive electrode current collector and a positive electrode film layer A and a positive electrode film layer B respectively arranged on the two surfaces of the positive electrode current collector; the positive electrode film layer A and the positive electrode film Layers B are each independently a single-layer structure or a multilayer structure; at least one layer of the positive electrode film layer A contains the first positive electrode active material with a core-shell structure, and at the same time, at least one layer of the positive electrode film layer B contains the second Positive electrode active material; the first positive electrode active material includes an inner core, a first cladding layer covering the inner core, and a second cladding layer covering the first cladding layer; wherein the inner core includes Li 1+x Mn 1-y A y P 1-z R z O 4 , the first cladding layer contains pyrophosphate MP 2 O 7 and phosphate XPO 4 , and the second cladding layer contains carbon elements; wherein, A is selected from Zn, Al, Na, K,
  • the first positive electrode active material of the present application can greatly reduce the dissolution of transition metals and reduce the oxygen activity on the particle surface, promote the migration of lithium ions, improve the conductivity and desolvation performance, improve the rate performance of the battery, and improve the cycle of the secondary battery performance and high temperature performance while reducing electrolyte corrosion on active materials.
  • the first positive electrode active material and the second positive electrode active material are used in combination.
  • the advantages of the two materials are complementary, which improves the energy density of the secondary battery, and at the same time makes the battery have excellent rate performance, kinetic performance, cycle performance and low-temperature performance, and the first positive electrode active material provides elastic strain force for external impact or shearing, which effectively solves the safety problem of the second positive electrode active material.
  • the above-mentioned limitation on the numerical range of y is not only a limitation on the stoichiometric number of each element as A, but also a limitation on each element as A.
  • Limitation of the sum of stoichiometric numbers For example, when A is two or more elements A1, A2...An, the stoichiometric numbers y1, y2...yn of A1, A2...An each need to fall within the numerical range defined by the application for y, and y1 The sum of , y2 ... yn also needs to fall within this value range.
  • the limitation of the numerical range of the stoichiometric number of R in this application also has the above meaning.
  • the first positive electrode active material with a core-shell structure of the present application includes an inner core 11, a first cladding layer 12 covering the inner core 11, and a second cladding layer covering the first cladding layer 12 13, wherein the inner core 11 includes Li 1+x Mn 1-y A y P 1-z R z O 4 .
  • the element A doped at the manganese position of lithium manganese phosphate in the inner core 11 helps to reduce the lattice change rate of lithium manganese phosphate during lithium deintercalation, improves the structural stability of lithium manganese phosphate cathode material, and greatly reduces the Dissolves and reduces oxygen activity on particle surfaces.
  • the element R doped at the phosphorus site helps to change the difficulty of the change of the Mn-O bond length, thereby reducing the migration barrier of lithium ions, promoting the migration of lithium ions, and improving the rate performance of the secondary battery.
  • Li 1+x Mn 1-y A y P 1-z R z O 4 maintains electrical neutrality throughout.
  • the mass ratio of the first active material to the second active material is 1:7-7:1, optionally 1:4-4:1, further optionally 1:3-3:1, such as 1:7, 1:5, 1:3, 1:2, 3:5, 1:1, 5:3, 2:1, 3:1, 5:1, 7:1.
  • A in the first positive electrode active material, is selected from one or more elements selected from Zn, Fe, Ti, V, Ni, Co and Mg; and/or , A is at least two elements selected from Fe, Ti, V, Ni, Co and Mg.
  • x is selected from any value in the range of -0.100-0.006. By selecting the value of x within this range, the kinetic performance of the first positive electrode active material can be further improved.
  • y is selected from any value in the range of 0.1-0.4. By selecting the value of y within this range, the gram capacity of the first positive electrode active material and the rate performance of the secondary battery can be further improved.
  • M and X are independently selected from one or more elements selected from Li and Fe.
  • the ratio of y to 1-y is selected from 1:10 to 10:1, optionally 1:4 to 1:1.
  • y represents the sum of stoichiometric numbers of Mn-site doping elements.
  • the ratio of z to 1-z is selected from 1:999 to 1:9, optionally 1:499 to 1:249.
  • z represents the sum of the stoichiometric numbers of the P-site doping elements.
  • the interplanar spacing of the phosphate in the first cladding layer is 0.345-0.358 nm, and the included angle of the crystal direction (111) is 24.25°-26.45°; the interplanar spacing of the pyrophosphate in the first cladding layer is 0.293-0.326nm, and the included angle of the crystal direction (111) is 26.41°-32.57°.
  • the interplanar spacing of phosphate and pyrophosphate in the first coating layer and the included angle of the crystal direction (111) are in the above range, the impurity phase in the coating layer can be effectively avoided, thereby increasing the gram capacity of the material and improving Cycle performance and rate performance of secondary batteries.
  • the coating amount of the first coating layer is greater than 0% by weight and less than or equal to 7% by weight, and may be 4-5.6% by weight %, based on the weight of the core.
  • the coating amount of the first coating layer is within the above range, manganese dissolution can be further suppressed, and at the same time, the transport of lithium ions can be further promoted. And it can effectively avoid the following situation: if the coating amount of the first coating layer is too small, it may cause insufficient inhibition of pyrophosphate on manganese dissolution, and the improvement of lithium ion transport performance is not significant; If the coating amount of the first coating layer is too large, it may cause the coating layer to be too thick, increase the battery impedance, and affect the kinetic performance of the secondary battery.
  • the weight ratio of pyrophosphate to phosphate in the first coating layer is 1:3 to 3:1, optionally 1 :3 to 1:1.
  • the proper ratio of pyrophosphate and phosphate is conducive to giving full play to the synergistic effect of the two. And it can effectively avoid the following situations: if there is too much pyrophosphate and too little phosphate, it may lead to an increase in battery impedance; if there is too much phosphate and too little pyrophosphate, the effect of inhibiting the dissolution of manganese is not significant.
  • the crystallinity of pyrophosphate and phosphate is independently 10% to 100%, optionally 50% to 100%.
  • pyrophosphate and phosphate with a certain degree of crystallinity are beneficial to keep the structure of the first coating layer stable and reduce lattice defects. On the one hand, this is beneficial to give full play to the role of pyrophosphate in hindering the dissolution of manganese.
  • the coating amount of the second coating layer is greater than 0% by weight and less than or equal to 6% by weight, optionally 3-5% by weight %, based on the weight of the core.
  • the carbon-containing layer as the second coating layer can play a "barrier" function to avoid direct contact between the first positive electrode active material and the electrolyte, thereby reducing the corrosion of the active material by the electrolyte and improving the safety of the secondary battery at high temperatures performance.
  • it has strong conductivity, which can reduce the internal resistance of the secondary battery, thereby improving the kinetic performance of the secondary battery.
  • the gram capacity of the carbon material is low, when the amount of the second coating layer is too large, the gram capacity of the entire positive electrode active material may be reduced. Therefore, when the coating amount of the second coating layer is in the above range, the kinetic performance and safety performance of the secondary battery can be further improved without sacrificing the gram capacity of the positive electrode active material.
  • the Li/Mn antisite defect concentration of the first positive electrode active material is less than 4%, optionally less than 2%.
  • the Li/Mn antisite defect means that in the LiMnPO 4 lattice, the positions of Li + and Mn 2+ are exchanged. Since the Li + transport channel is a one-dimensional channel, Mn 2+ is difficult to migrate in the Li + transport channel, so the Mn 2+ with antisite defects will hinder the transport of Li + .
  • the antisite defect concentration can be measured according to JIS K 0131-1996, for example.
  • the lattice change rate of the first positive electrode active material is less than 6%, optionally less than 4%.
  • the lithium-deintercalation process of LiMnPO 4 is a two-phase reaction.
  • the interfacial stress of the two phases is determined by the lattice change rate. The smaller the lattice change rate, the smaller the interfacial stress and the easier Li + transport. Therefore, reducing the lattice change rate of the inner core will be beneficial to enhance the Li + transport ability, thereby improving the rate performance of secondary batteries.
  • the surface oxygen valence state of the first positive electrode active material is less than -1.88, optionally -1.98 ⁇ -1.88. This is because the higher the valence state of oxygen in the compound, the stronger its ability to obtain electrons, that is, the stronger the oxidation.
  • the first positive electrode active material of the present application by controlling the surface valence state of oxygen at a lower level, the reactivity of the surface of the positive electrode material can be reduced, and the interface side reaction between the positive electrode material and the electrolyte can be reduced, thereby improving the secondary battery. Excellent cycle performance and high temperature storage performance.
  • the first positive electrode active material has a compacted density at 3 tons (T) of 2.0 g/cm 3 or more, optionally 2.2 g/cm 3 or more.
  • T 3 tons
  • the compacted density can be measured according to GB/T 24533-2009, for example.
  • the sum of the mass of the first positive electrode active material and the second positive electrode active material accounts for 88%-98.7% of the mass of the positive electrode sheet. Further ensure that the secondary battery has excellent rate performance, kinetic performance, cycle performance and low temperature performance, and has high energy density.
  • the ratio of a, ( 1-ab) and b in LiNiaCobMn(1-ab) O2 is 5:2:3 or 3:1 :1 or 8:1:1; and/or, the ratio of a, b and (1-ab) in LiNi a Co b Mn (1-ab) O 2 is 5:2:3 or 3:1:1 Or 8:1:1.
  • the energy density of the secondary battery can be further increased.
  • the positive electrode current collector can be a metal foil or a composite current collector.
  • aluminum foil can be used as the metal foil.
  • the composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base.
  • the composite current collector can be formed by forming metal materials (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyethylene terephthalic acid It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene glycol ester
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the positive electrode film layer may further include other positive electrode active materials known in the art for batteries.
  • the positive active material may include at least one of the following materials: olivine-structured lithium-containing phosphate, lithium transition metal oxide, and their respective modified compounds.
  • the present application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials of batteries can also be used. These positive electrode active materials may be used alone or in combination of two or more.
  • lithium transition metal oxides may include, but are not limited to, lithium nickel oxides (such as LiNiO 2 ), lithium manganese oxides (such as LiMnO 2 , LiMn 2 O 4 ), lithium nickel cobalt oxides, lithium manganese cobalt oxides , at least one of lithium nickel manganese oxide and modified compounds thereof.
  • olivine-structured lithium-containing phosphates may include, but are not limited to, lithium iron phosphate (such as LiFePO 4 (also abbreviated as LFP)), composite materials of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), phosphoric acid At least one of a composite material of lithium manganese and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.
  • lithium iron phosphate such as LiFePO 4 (also abbreviated as LFP)
  • composite materials of lithium iron phosphate and carbon such as LiMnPO 4
  • LiMnPO 4 lithium manganese phosphate
  • phosphoric acid At least one of a composite material of lithium manganese and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.
  • the positive electrode film layer may further optionally include a binder.
  • the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene At least one of meta-copolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • the positive electrode film layer may further optionally include a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer arranged on at least one surface of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material.
  • the negative electrode current collector has two opposing surfaces in its own thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposing surfaces of the negative electrode current collector.
  • a metal foil or a composite current collector can be used as the negative electrode current collector.
  • copper foil can be used as the metal foil.
  • the composite current collector may include a base layer of polymer material and a metal layer formed on at least one surface of the base material of polymer material.
  • Composite current collectors can be formed by metal materials (copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyethylene terephthalic acid It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • the negative electrode active material can be a negative electrode active material known in the art for batteries.
  • the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material, lithium titanate, and the like.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon-oxygen compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys.
  • the tin-based material can be selected from at least one of simple tin, tin oxide and tin alloy.
  • the present application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials of batteries can also be used. These negative electrode active materials may be used alone or in combination of two or more.
  • the negative electrode film layer may further optionally include a binder.
  • the binder 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 may also optionally include 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 may optionally include other additives, such as thickeners (such as sodium carboxymethylcellulose (CMC-Na)) and the like.
  • thickeners such as sodium carboxymethylcellulose (CMC-Na)
  • CMC-Na sodium carboxymethylcellulose
  • the negative electrode sheet can be prepared in the following manner: the above-mentioned components used to prepare the negative electrode sheet, such as negative electrode active material, conductive agent, binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.
  • a solvent such as deionized water
  • the electrolyte plays the role of conducting ions between the positive pole piece and the negative pole piece.
  • the present application has no specific limitation on the type of electrolyte, which can be selected according to requirements.
  • electrolytes can be liquid, gel or all solid.
  • the electrolyte is liquid and includes an electrolyte salt and a solvent.
  • the electrolyte salt may be selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, trifluoromethane At least one of lithium sulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium difluorooxalate borate, lithium difluorodifluorooxalatephosphate and lithium tetrafluorooxalatephosphate.
  • the solvent may be selected from ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, Butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate At least one of ester, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • the electrolyte also optionally includes additives.
  • the additives may include negative film-forming additives, positive film-forming additives, and additives that can improve certain performances of the battery, such as additives that improve battery overcharge performance, additives that improve high-temperature or low-temperature performance of the battery, and the like.
  • a separator is further included in the secondary battery.
  • the present application has no particular limitation on the type of the isolation membrane, and any known porous structure isolation membrane with good chemical stability and mechanical stability can be selected.
  • the material of the isolation film can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the separator can be a single-layer film or a multi-layer composite film, without any particular limitation. When the separator is a multilayer composite film, the materials of each layer may be the same or different, and there is no particular limitation.
  • the positive pole piece, the negative pole piece and the separator can be made into an electrode assembly through a winding process or a lamination process.
  • the secondary battery may include an outer package.
  • the outer package can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the secondary battery may be a hard case, such as a hard plastic case, aluminum case, steel case, and the like.
  • the outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag.
  • the material of the soft case may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
  • FIG. 2 shows a square-shaped 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 a side plate connected to the bottom plate, and the bottom plate and the side plates enclose to form an accommodating cavity.
  • the housing 51 has an opening communicating with the accommodating cavity, and the cover plate 53 can cover the opening to close the accommodating cavity.
  • the positive pole piece, the negative pole piece and the separator can be formed into an electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the containing chamber. Electrolyte is infiltrated in the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.
  • the secondary battery can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.
  • FIG. 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 may be fixed by fasteners.
  • the battery module 4 may also include a case having a housing space in which a plurality of secondary batteries 5 are accommodated.
  • the above-mentioned battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3 , the upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery module 4 .
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • the present application also provides an electric device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application.
  • a secondary battery, a battery module, or a battery pack can be used as a power source of a power consumption device, and can also be used as an energy storage unit of the power consumption device.
  • Electric devices can 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 not limited thereto.
  • secondary batteries, battery modules, or battery packs can be selected according to their usage requirements.
  • FIG. 7 is an example of an electrical device.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • a battery pack or a battery module may be used.
  • the reactor was heated to 80° C. and stirred at 600 rpm for 6 hours until the reaction was terminated (no bubbles were generated), and a Fe, Co, V and S co-doped manganese oxalate suspension was obtained. Then filter the suspension, dry the filter cake at 120° C., and then grind to obtain Fe, Co and V co-doped manganese oxalate dihydrate particles with a median diameter Dv50 of 100 nm.
  • lithium iron pyrophosphate powder 4.77 g of lithium carbonate, 7.47 g of ferrous carbonate, 14.84 g of ammonium dihydrogen phosphate and 1.3 g of oxalic acid dihydrate were dissolved in 50 ml of deionized water. The pH of the mixture was 5, and the reaction mixture was stirred for 2 hours to fully react. Then the temperature of the reacted solution was raised to 80°C and maintained at this temperature for 4 hours to obtain a suspension containing Li 2 FeP 2 O 7 , which was filtered, washed with deionized water, and dried at 120°C for 4 hours , to obtain powder. The powder was sintered at 650° C. under a nitrogen atmosphere for 8 hours, cooled naturally to room temperature, and then ground to obtain Li 2 FeP 2 O 7 powder.
  • lithium iron phosphate suspension dissolve 11.1g of lithium carbonate, 34.8g of ferrous carbonate, 34.5g of ammonium dihydrogen phosphate, 1.3g of oxalic acid dihydrate and 74.6g of sucrose (calculated as C 12 H 22 O 11 , the same below) The mixture was obtained in 150 ml of deionized water, and then stirred for 6 hours to fully react the above mixture. The reacted solution was then warmed up to 120 °C and kept at this temperature for 6 hours to obtain a suspension containing LiFePO4 .
  • Examples 1-15 were the same as those of Examples 1-14.
  • Example 1-16 Except that in Example 1-16, 466.4g of NiCO 3 , 5.0g of zinc carbonate and 7.2g of titanium sulfate were used instead of ferrous carbonate during the preparation of the co-doped lithium manganese phosphate core, and in co-doping
  • the ferrous carbonate of 455.2g and the vanadium dichloride of 8.5g are used in the preparation process of the lithium manganese phosphate inner core, and the ferrous carbonate of 455.2g is used in the preparation process of the co-doped lithium manganese phosphate inner core in embodiment 1-18 , 4.9g of vanadium dichloride and 2.5g of magnesium carbonate, the conditions of Examples 1-17 to 1-19 are the same as in Example 1-7.
  • embodiment 1-19 uses the lithium carbonate of 369.4g in the preparation process of co-doped lithium manganese phosphate inner core, and replaces dilute sulfuric acid with the dilute nitric acid of 60% concentration of 1.05g
  • embodiment 1-20 is in co-doped
  • the conditions of Examples 1-19 to 1-20 are the same as those of Example 1-18, except that 369.7 g of lithium carbonate and 0.78 g of silicic acid are used instead of dilute sulfuric acid during the preparation of the lithium manganese phosphate inner core.
  • Examples 1-21 632.0g of manganese carbonate, 463.30g of ferrous carbonate, 30.5g of vanadium dichloride, 21.0g of magnesium carbonate and 0.78g of silicate were used in the preparation process of the co-doped lithium manganese phosphate core.
  • Embodiment 1-22 uses 746.9g manganese carbonate, 289.6g ferrous carbonate, 60.9g of vanadium dichloride, 42.1g of magnesium carbonate and 0.78g of silicate in the preparation process of co-doped lithium manganese phosphate core
  • the conditions of Examples 1-21 to 1-22 are the same as those of Example 1-20.
  • embodiment 1-23 uses 804.6g manganese carbonate, 231.7g ferrous carbonate, 1156.2g ammonium dihydrogen phosphate, 1.2g boric acid (mass fraction 99.5%) and 370.8 g lithium carbonate; embodiment 1-24 uses 862.1g manganese carbonate, 173.8g ferrous carbonate, 1155.1g ammonium dihydrogen phosphate, boric acid (mass fraction 99.5% of 1.86g) in the preparation process of co-doped lithium manganese phosphate core ) and 371.6g lithium carbonate, the conditions of embodiment 1-23 to 1-24 are identical with embodiment 1-22.
  • Example 1-25 uses 370.1g of lithium carbonate, 1.56g of silicic acid and 1147.7g of ammonium dihydrogen phosphate in the preparation process of the co-doped lithium manganese phosphate core, the conditions of Example 1-25 are the same as those of Example 1-20 are the same.
  • embodiment 1-26 uses 368.3g lithium carbonate, 4.9g mass fraction to be 60% dilute sulfuric acid, 919.6g manganese carbonate, 224.8g ferrous carbonate, 3.7g dichloro Except the ammonium dihydrogen phosphate of vanadium, 2.5g magnesium carbonate and 1146.8g, the condition of embodiment 1-26 is identical with embodiment 1-20.
  • Example 1-27 uses 367.9g of lithium carbonate, 6.5g concentration of 60% dilute sulfuric acid and 1145.4g of ammonium dihydrogen phosphate in the preparation process of the co-doped lithium manganese phosphate core, the conditions of Example 1-27 Same as Example 1-20.
  • embodiment 1-28 to 1-33 uses 1034.5g manganese carbonate, 108.9g ferrous carbonate, 3.7g vanadium dichloride and 2.5g magnesium carbonate in the preparation process of co-doped lithium manganese phosphate inner core, the use of lithium carbonate
  • the amounts are: 367.6g, 367.2g, 366.8g, 366.4g, 366.0g, and 332.4g
  • the amounts of ammonium dihydrogen phosphate are: 1144.5g, 1143.4g, 1142.2g, 1141.1g, 1139.9g, and 1138.8g
  • Concentration is that the consumption of the dilute sulfuric acid of 60% is respectively: except 8.2g, 9.8g, 11.4g, 13.1g, 14.7g and 16.3g, the conditions of embodiment 1-28 to 1-33 are identical with embodiment 1-20 .
  • Lithium nickel cobalt manganese oxide LiNi 0.5 Co 0.2 Mn 0.3 O 2 was used as the positive electrode active material.
  • Example 1-1 and Example 1-34 were mixed according to a mass ratio of 1:1.
  • Lithium nickel cobalt manganese oxide LiNi 0.33 Co 0.33 Mn 0.34 O 2 was used as the positive electrode active material.
  • Lithium nickel cobalt manganese oxide LiNi 0.8 Co 0.1 Mn 0.1 O 2 was used as the positive electrode active material.
  • Lithium cobaltate LiCoO2 as the cathode active material.
  • Example 1 The positive electrode active materials of Example 1 and Examples 1-36 were mixed according to a mass ratio of 1:1 as the positive electrode active material.
  • Example 1-1 and Example 1-37 were mixed according to a mass ratio of 1:1 as the positive electrode active material.
  • Example 1-1 and Example 1-38 were mixed according to a mass ratio of 1:1 as the positive electrode active material.
  • Example 1-1 and Example 1-39 were mixed according to a mass ratio of 1:1 as the positive electrode active material.
  • Example 1-1 and Example 1-40 were mixed according to a mass ratio of 1:1 as the positive electrode active material.
  • Example 1-1 and Example 1-41 were mixed according to a mass ratio of 1:1 as the positive electrode active material.
  • the sintering temperature in the powder sintering step is 550°C, and the sintering time is 1h to control the crystallinity of Li 2 FeP 2 O 7 to 30%.
  • the sintering temperature in the coating sintering step is 650° C., and the sintering time is 2 h to control the crystallinity of LiFePO 4 to 30%.
  • Other conditions are the same as in Example 1-1.
  • the sintering temperature in the powder sintering step is 550°C, and the sintering time is 2h to control the crystallinity of Li 2 FeP 2 O 7 to 50%.
  • the sintering temperature in the coating sintering step is 650° C., and the sintering time is 3 h to control the crystallinity of LiFePO 4 to 50%.
  • Other conditions are the same as in Example 1-1.
  • the sintering temperature in the powder sintering step is 600°C, and the sintering time is 3h to control the crystallinity of Li 2 FeP 2 O 7 to 70%.
  • the sintering temperature in the coating sintering step is 650° C., and the sintering time is 4 hours to control the crystallinity of LiFePO 4 to 70%.
  • Other conditions are the same as in Example 1-1.
  • the sintering temperature in the powder sintering step is 650°C, and the sintering time is 4h to control the crystallinity of Li 2 FeP 2 O 7 to 100%.
  • the sintering temperature in the coating sintering step was 700°C, and the sintering time was 6h to control the crystallinity of LiFePO 4 to 100%, other conditions were the same as in Example 1-1.
  • the heating temperature/stirring time in the reactor of Example 3-1 was respectively 60°C/120 minutes; the heating in the reactor of Example 3-2 Temperature/stirring time is respectively 70 °C/120 minutes; The heating temperature/stirring time in embodiment 3-3 reactor is respectively 80 °C/120 minutes; The heating temperature/stirring time in embodiment 3-4 reactor is respectively 90°C/120 minutes; the heating temperature/stirring time in the reactor of Example 3-5 was 100°C/120 minutes respectively; the heating temperature/stirring time in the reactor of Example 3-6 was 110°C/120 minutes respectively; The heating temperature/stirring time in the reactor of embodiment 3-7 is respectively 120 °C/120 minutes; The heating temperature/stirring time in the reactor of embodiment 3-8 is respectively 130 °C/120 minutes; Embodiment 3-9 reaction The heating temperature/stirring time in the kettle is respectively 100 DEG C/60 minutes; The heating temperature/stir
  • Embodiment 4-1 to 4-4 are identical to Embodiment 4-1 to 4-4:
  • the drying temperature/drying time in the drying step are 100°C/4h, 150°C/6h, 200°C/6h and 200°C/6h respectively;
  • the sintering temperature and sintering time in the sintering step are 700°C/6h, 700°C/6h, 700°C/6h and 600°C/6h, respectively, Other conditions are the same as in Example 1-7.
  • Embodiment 4-5 to 4-7 are identical to Embodiment 4-5 to 4-7:
  • drying temperature/drying time in the drying step during the cladding process were 150°C/6h, 150°C/6h and 150°C/6h respectively;
  • sintering temperature and sintering time in the sintering step during the cladding process were respectively Except for 600°C/4h, 600°C/6h and 800°C/8h, the other conditions are the same as in Examples 1-12.
  • Preparation of carbon-coated lithium manganese phosphate take 1789.6g of manganese oxalate dihydrate particles obtained above, 369.4g of lithium carbonate (calculated as Li 2 CO 3 , the same below), 1150.1g of ammonium dihydrogen phosphate (calculated as NH 4 H 2 PO 4 meter, the same below) and 31 g of sucrose (calculated as C 12 H 22 O 11 , the same below) were added to 20 liters of deionized water, and the mixture was stirred for 10 hours to make it evenly mixed to obtain a slurry.
  • lithium carbonate calculated as Li 2 CO 3 , the same below
  • 1150.1g of ammonium dihydrogen phosphate calculated as NH 4 H 2 PO 4 meter, the same below
  • sucrose calculated as C 12 H 22 O 11 , the same below
  • Comparative Example 2 Except for using 689.5g of manganese carbonate and additionally adding 463.3g of ferrous carbonate, other conditions of Comparative Example 2 were the same as those of Comparative Example 1.
  • lithium iron pyrophosphate powder when preparing lithium iron pyrophosphate powder, dissolve 9.52g of lithium carbonate, 29.9g of ferrous carbonate, 29.6g of ammonium dihydrogen phosphate and 32.5g of oxalic acid dihydrate in 50ml of deionized water. The pH of the mixture was 5, and the reaction mixture was stirred for 2 hours to fully react. Then the temperature of the reacted solution was raised to 80°C and maintained at this temperature for 4 hours to obtain a suspension containing Li 2 FeP 2 O 7 , which was filtered, washed with deionized water, and dried at 120°C for 4 hours , to obtain powder.
  • the powder was sintered at 500°C for 4 hours under a nitrogen atmosphere, and then ground after naturally cooling to room temperature.
  • the crystallinity of Li 2 FeP 2 O 7 was controlled to be 5%.
  • Li 2 FeP 2 O 7 The consumption of is 62.8g, other conditions of comparative example 5 are identical with comparative example 4.
  • lithium iron phosphate suspension dissolve 14.7g lithium carbonate, 46.1g ferrous carbonate, 45.8g ammonium dihydrogen phosphate and 50.2g dihydrate oxalic acid in 500ml deionized water, then stir for 6 hours Allow the mixture to fully react.
  • the reacted solution is heated to 120°C and maintained at this temperature for 6 hours to obtain a suspension containing LiFePO 4 , and the sintering temperature in the coating sintering step during the preparation of lithium iron phosphate (LiFePO 4 ) is 600°C ,
  • the sintering time is 4h to control the crystallinity of LiFePO 4 to be 8%, when preparing the carbon-coated material, the amount of LiFePO 4 is 62.8g, the other conditions of Comparative Example 6 are the same as Comparative Example 4.
  • lithium iron pyrophosphate powder 2.38 g of lithium carbonate, 7.5 g of ferrous carbonate, 7.4 g of ammonium dihydrogen phosphate and 8.1 g of oxalic acid dihydrate were dissolved in 50 ml of deionized water. The pH of the mixture was 5, and the reaction mixture was stirred for 2 hours to fully react. Then the temperature of the reacted solution was raised to 80°C and maintained at this temperature for 4 hours to obtain a suspension containing Li 2 FeP 2 O 7 , which was filtered, washed with deionized water, and dried at 120°C for 4 hours , to obtain powder. The powder was sintered at 500° C. under a nitrogen atmosphere for 4 hours, cooled naturally to room temperature, and then ground to control the crystallinity of Li 2 FeP 2 O 7 to 5%.
  • lithium iron phosphate suspension 11.1g of lithium carbonate, 34.7g of ferrous carbonate, 34.4g of ammonium dihydrogen phosphate, 37.7g of oxalic acid dihydrate and 37.3g of sucrose (calculated as C 12 H 22 O 11 , the same below) were dissolved in 1500 ml of deionized water, then stirred for 6 hours to fully react the mixture. The reacted solution was then warmed up to 120 °C and kept at this temperature for 6 hours to obtain a suspension containing LiFePO4 .
  • the sintering temperature in the coating sintering step is 600 ° C, and the sintering time is 4 hours to control the LiFePO 4 Except that the crystallinity of 4 was 8%, the other conditions of Comparative Example 7 were the same as those of Comparative Example 4, and amorphous lithium iron pyrophosphate, amorphous lithium iron phosphate, and carbon-coated positive electrode active materials were obtained.
  • the drying temperature/drying time in the drying step was 80°C/3h, 80°C/3h, 80°C/ 3h;
  • the sintering temperature and sintering time in the sintering step were 400°C/3h, 400°C/3h, and 350°C in Comparative Examples 8-10, respectively.
  • LiFePO 4 lithium iron phosphate
  • Comparative Example 11 the drying temperature/drying time in the drying step during the preparation of lithium iron phosphate (LiFePO 4 ) in Comparative Example 11 was 80°C/3h; and Li 2 FeP 2 O 7 /LiFePO in Comparative Examples 8-11 Except that the dosage of 4 is 47.2g/15.7g, 15.7g/47.2g, 62.8g/0g, 0g/62.8g respectively, other conditions are the same as in Examples 1-7.
  • the positive electrode active material prepared above, the conductive agent superconducting carbon black (Super-P), and the binder polyvinylidene fluoride (PVDF) were added to N-methylpyrrolidone (NMP) in a weight ratio of 92:2.5:5.5 , stirring and mixing uniformly to obtain a slurry of positive electrode active materials with a solid content of 60% w/w.
  • Example 1-1 The slurry of the positive electrode active material in Example 1-1 was evenly coated on both sides of the current collector aluminum foil with a coating amount of 0.019g/cm 2 , vacuum-dried at a high temperature of 100-120°C for 14h, and compacted by a roller press to obtain Positive pole piece P1.
  • the slurry of the positive electrode active material of Example 1-34 is evenly coated on both sides of the current collector aluminum foil with a coating amount of 0.019g/cm 2 , vacuum-dried at a high temperature of 100-120°C for 14h, and compacted by a roller press to obtain Positive pole piece P2.
  • the slurry of the positive electrode active material of Example 1-1 is evenly coated on one side of the aluminum foil with a coating amount of 0.019g/cm
  • the coating amount is evenly coated on the other side of the aluminum foil, vacuum-dried at a high temperature of 100-120° C. for 14 hours, and compacted by a roller press to obtain the positive electrode sheet P3.
  • the slurry of the positive electrode active material of Example 1-35 was uniformly coated on both sides of the aluminum foil of the current collector at a coating amount of 0.019 g/cm 2 , and the other was the same as that of Example 5-3 to obtain the positive electrode sheet P4.
  • the slurry of the positive electrode active material of Example 1-1 is evenly coated on one side of the aluminum foil with a coating amount of 0.019g/cm
  • the slurry of the positive electrode active material of Example 1-35 is coated with a coating amount of 0.019g/cm 2
  • the coating amount was uniformly coated on the other side of the aluminum foil, and the others were the same as in Example 5-3 to obtain the positive electrode sheet P5.
  • the slurry of embodiment 1-34 positive electrode active material is evenly coated on one side of the aluminum foil with the coating amount of 0.019g/cm The coating amount was uniformly coated on the other side of the aluminum foil, and the others were the same as in Example 5-3 to obtain the positive electrode sheet P6.
  • Both sides of the aluminum foil are sequentially coated with the slurry of the positive electrode active material of Example 1-1 and the slurry of the positive electrode active material of Example 1-34, and the coating amount of each layer of slurry is 0.010g/cm 2 , and then, Vacuum drying at a high temperature of 100-120° C. for 14 hours, and compaction by a roller press to obtain the positive electrode sheet P7.
  • Both sides of the aluminum foil are sequentially coated with the slurry of the positive electrode active material of Example 1-34 and the slurry of the positive electrode active material of Example 1-1, and the coating amount of each layer of slurry is 0.010g/cm 2 , and other Example 5-7 is the same, and the positive pole piece P8 is obtained.
  • Both sides of the aluminum foil are sequentially coated with the slurry of the positive electrode active material of Example 1-1 and the slurry of the positive electrode active material of Example 1-35, and the coating amount of each layer of slurry is 0.010g/cm 2 , and other Example 5-7 is the same, and the positive pole piece P9 is obtained.
  • Both sides of the aluminum foil are sequentially coated with the slurry of the positive electrode active material of Example 1-35 and the slurry of the positive electrode active material of Example 1-1, and the coating amount of each layer of slurry is 0.010g/cm 2 , and other Example 5-7 is the same, and the positive electrode sheet P10 is obtained.
  • Both sides of the aluminum foil are sequentially coated with the slurry of the positive electrode active material of Example 1-34 and the slurry of the positive electrode active material of Example 1-35, and the coating amount of each layer of slurry is 0.010g/cm 2 , and other Example 5-7 is the same, and the positive pole piece P11 is obtained.
  • Both sides of the aluminum foil are sequentially coated with the slurry of the positive electrode active material of Example 1-35 and the slurry of the positive electrode active material of Example 1-34, and the coating amount of each layer of slurry is 0.010g/cm 2 , and other Example 5-7 is the same, and the positive pole piece P12 is obtained.
  • the slurry of the positive electrode active material of Example 1-1 and the slurry of the positive electrode active material of Example 1-34 are coated successively, and the coating amount of each layer of slurry is 0.010g/cm 2 , on the aluminum foil
  • the surface B of the sample is uniformly coated with the slurry of the positive electrode active material of Example 1-1, and the coating amount of the slurry is 0.020g/cm 2 , and then dried in vacuum at a high temperature of 100-120°C for 14 hours, and compacted by a roller press to obtain Positive pole piece P13.
  • the slurry of the positive electrode active material of Example 1-1 and the slurry of the positive electrode active material of Example 1-34 are coated successively, and the coating amount of each layer of slurry is 0.010g/cm 2 , on the aluminum foil
  • the slurry of the positive electrode active material of Example 1-34 was evenly coated on the surface B of the sample, and the coating amount of the slurry was 0.020 g/cm 2 .
  • Others were the same as in Example 5-13 to obtain the positive electrode sheet P14.
  • the slurry of the positive electrode active material of Example 1-1 and the slurry of the positive electrode active material of Example 1-34 are coated successively, and the coating amount of each layer of slurry is 0.010g/cm 2 , on the aluminum foil
  • the slurry of the positive electrode active material of Example 1-35 was evenly coated on the surface B of the surface of , and the coating amount of the slurry was 0.020 g/cm 2 .
  • Others were the same as in Example 5-13 to obtain the positive electrode sheet P15.
  • the slurry of the positive electrode active material of Example 1-34 and the slurry of the positive electrode active material of Example 1-1 are coated successively, and the coating amount of each layer of slurry is 0.010g/cm 2 , on the aluminum foil
  • the slurry of the positive electrode active material of Example 1-1 was uniformly coated on the B side of the sample, and the coating amount of the slurry was 0.020 g/cm 2 .
  • Others were the same as in Example 5-13 to obtain the positive electrode sheet P16.
  • the slurry of the positive electrode active material of Example 1-34 and the slurry of the positive electrode active material of Example 1-1 are coated successively, and the coating amount of each layer of slurry is 0.010g/cm 2 , on the aluminum foil
  • the slurry of the positive electrode active material of Example 1-34 was uniformly coated on the B side of the sample, and the coating amount of the slurry was 0.020 g/cm 2 .
  • Others were the same as in Example 5-13 to obtain the positive electrode sheet P17.
  • the slurry of the positive electrode active material of Example 1-34 and the slurry of the positive electrode active material of Example 1-1 are coated successively, and the coating amount of each layer of slurry is 0.010g/cm 2 , on the aluminum foil
  • the slurry of the positive electrode active material of Example 1-35 was evenly coated on the B side of the sample, and the coating amount of the slurry was 0.020 g/cm 2 .
  • Others were the same as in Example 5-13 to obtain the positive electrode sheet P18.
  • the slurry of the positive electrode active material of Example 1-1 and the slurry of the positive electrode active material of Example 1-35 are sequentially coated, and the coating amount of each layer of slurry is 0.010g/cm 2 , on the aluminum foil
  • the slurry of the positive electrode active material of Example 1-1 was uniformly coated on the B side of the sample, and the coating amount of the slurry was 0.020 g/cm 2 .
  • Others were the same as in Example 5-13 to obtain the positive electrode sheet P19.
  • the slurry of the positive electrode active material of Example 1-1 and the slurry of the positive electrode active material of Example 1-35 are sequentially coated, and the coating amount of each layer of slurry is 0.010g/cm 2 , on the aluminum foil
  • the slurry of the positive electrode active material of Example 1-34 was uniformly coated on the B side of the sample, and the coating amount of the slurry was 0.020 g/cm 2 .
  • Others were the same as in Example 5-13 to obtain the positive electrode sheet P20.
  • the slurry of the positive electrode active material of Example 1-1 and the slurry of the positive electrode active material of Example 1-35 are sequentially coated, and the coating amount of each layer of slurry is 0.010g/cm 2 , on the aluminum foil
  • the slurry of the positive electrode active material of Example 1-35 was evenly coated on the B side of the sample, and the coating amount of the slurry was 0.020 g/cm 2 .
  • Others were the same as in Example 5-13 to obtain the positive electrode sheet P21.
  • the slurry of the positive electrode active material of Example 1-35 and the slurry of the positive electrode active material of Example 1-1 are coated successively, and the coating amount of each layer of slurry is 0.010g/cm 2 , on the aluminum foil
  • the slurry of the positive electrode active material of Example 1-1 was evenly coated on the B side of the sample, and the coating amount of the slurry was 0.020 g/cm 2 .
  • Others were the same as in Example 5-13 to obtain the positive electrode sheet P22.
  • the slurry of the positive electrode active material of Example 1-35 and the slurry of the positive electrode active material of Example 1-1 are coated successively, and the coating amount of each layer of slurry is 0.010g/cm 2 , on the aluminum foil
  • the slurry of the positive electrode active material of Example 1-34 was evenly coated on the B side of the sample, and the coating amount of the slurry was 0.020 g/cm 2 .
  • Others were the same as in Example 5-13 to obtain the positive electrode sheet P23.
  • the slurry of the positive electrode active material of Example 1-35 and the slurry of the positive electrode active material of Example 1-1 are coated successively, and the coating amount of each layer of slurry is 0.010g/cm 2 , on the aluminum foil
  • the slurry of the positive electrode active material of Example 1-35 was uniformly coated on the B side of the sample, and the coating amount of the slurry was 0.020 g/cm 2 .
  • Others were the same as in Example 5-13 to obtain the positive electrode sheet P24.
  • the slurry of the positive electrode active material of Example 1-34 and the slurry of the positive electrode active material of Example 1-35 are coated successively, and the coating amount of each layer of slurry is 0.010g/cm 2 , on the aluminum foil
  • the slurry of the positive electrode active material of Example 1-1 was evenly coated on the B side of the sample, and the coating amount of the slurry was 0.020 g/cm 2 .
  • Others were the same as in Example 5-13 to obtain the positive electrode sheet P25.
  • the slurry of the positive electrode active material of Example 1-34 and the slurry of the positive electrode active material of Example 1-35 are coated successively, and the coating amount of each layer of slurry is 0.010g/cm 2 , on the aluminum foil
  • the slurry of the positive electrode active material of Example 1-34 was uniformly coated on the B side of the sample, and the coating amount of the slurry was 0.020 g/cm 2 .
  • Others were the same as in Example 5-13 to obtain the positive electrode sheet P26.
  • the slurry of the positive electrode active material of Example 1-34 and the slurry of the positive electrode active material of Example 1-35 are coated successively, and the coating amount of each layer of slurry is 0.010g/cm 2 , on the aluminum foil
  • the slurry of the positive electrode active material of Example 1-35 was uniformly coated on the B side of the sample, and the coating amount of the slurry was 0.020 g/cm 2 .
  • Others were the same as in Example 5-13 to obtain the positive electrode sheet P27.
  • the slurry of the positive electrode active material of Example 1-35 and the slurry of the positive electrode active material of Example 1-34 are coated successively, and the coating amount of each layer of slurry is 0.010g/cm 2 , on the aluminum foil
  • the slurry of the positive electrode active material of Example 1-1 was uniformly coated on the B side of the sample, and the coating amount of the slurry was 0.020 g/cm 2 .
  • Others were the same as in Example 5-13 to obtain the positive electrode sheet P28.
  • the slurry of the positive electrode active material of Example 1-35 and the slurry of the positive electrode active material of Example 1-34 are coated successively, and the coating amount of each layer of slurry is 0.010g/cm 2 , on the aluminum foil
  • the slurry of the positive electrode active material of Example 1-34 was evenly coated on the B side of the sample, and the coating amount of the slurry was 0.020 g/cm 2 .
  • Others were the same as in Example 5-13 to obtain the positive electrode sheet P29.
  • the slurry of the positive electrode active material of Example 1-35 and the slurry of the positive electrode active material of Example 1-34 are coated successively, and the coating amount of each layer of slurry is 0.010g/cm 2 , on the aluminum foil
  • the slurry of the positive electrode active material of Example 1-35 was evenly coated on the B side of the sample, and the coating amount of the slurry was 0.020 g/cm 2 .
  • Others were the same as in Example 5-13 to obtain the positive electrode sheet P30.
  • the slurry of the positive electrode active material of Example 1-36 is evenly coated on both sides of the current collector aluminum foil with a coating amount of 0.019g/cm 2 , vacuum-dried at a high temperature of 100-120°C for 14h, and compacted by a roller press to obtain Positive pole piece P31.
  • the slurry of the positive electrode active material in Example 1-37 was evenly coated on both sides of the aluminum foil of the current collector with a coating amount of 0.019g/cm 2 , dried in vacuum at a high temperature of 100-120°C for 14h, and compacted by a roller press to obtain Positive pole piece P32.
  • the slurry of the positive electrode active material in Example 1-38 is evenly coated on both sides of the current collector aluminum foil with a coating amount of 0.019g/cm 2 , vacuum-dried at a high temperature of 100-120°C for 14h, and compacted by a roller press to obtain Positive pole piece P33.
  • the slurry of the positive electrode active material in Example 1-39 is evenly coated on both sides of the current collector aluminum foil with a coating amount of 0.019g/cm 2 , vacuum-dried at a high temperature of 100-120°C for 14h, and compacted by a roller press to obtain Positive pole piece P34.
  • the slurry of the positive electrode active material of Example 1-40 is evenly coated on both sides of the current collector aluminum foil with a coating amount of 0.019g/cm 2 , vacuum-dried at a high temperature of 100-120°C for 14h, and compacted by a roller press to obtain Positive pole piece P35.
  • the slurry of the positive electrode active material of Example 1-41 is evenly coated on both sides of the current collector aluminum foil with a coating amount of 0.019g/cm 2 , vacuum-dried at a high temperature of 100-120°C for 14h, and compacted by a roller press to obtain Positive pole piece P36.
  • Example 1-42 The slurry of the positive electrode active material in Example 1-42 was evenly coated on both sides of the aluminum foil of the current collector with a coating amount of 0.019g/cm 2 , and the others were the same as in Example 5-3 to obtain the positive electrode sheet P37.
  • the slurry of the positive electrode active material of Example 1-43 was uniformly coated on both sides of the aluminum foil of the current collector with a coating amount of 0.019g/cm 2 , and the others were the same as in Example 5-3 to obtain the positive electrode sheet P38.
  • the slurry of the positive electrode active material of Example 1-44 was evenly coated on both sides of the aluminum foil of the current collector with a coating amount of 0.019 g/cm 2 , and the other was the same as that of Example 5-3 to obtain the positive electrode sheet P39.
  • the slurry of the positive electrode active material of Example 1-45 was uniformly coated on both sides of the aluminum foil of the current collector at a coating amount of 0.019 g/cm 2 , and the others were the same as in Example 5-3 to obtain the positive electrode sheet P40.
  • the slurry of the positive electrode active material of Example 1-46 was uniformly coated on both sides of the aluminum foil of the current collector with a coating amount of 0.019 g/cm 2 , and the other was the same as that of Example 5-3 to obtain the positive electrode sheet P41.
  • the slurry of the positive electrode active material of Example 1-47 was evenly coated on both sides of the aluminum foil of the current collector with a coating amount of 0.019 g/cm 2 , and the other was the same as that of Example 5-3 to obtain the positive electrode sheet P42.
  • the first layer refers to the layer in contact with the surface of the aluminum foil
  • the second layer refers to the layer provided on the first layer
  • the first positive electrode active material is the positive electrode active material prepared in Example 1-1, and the second positive electrode active material is Example 1-34, Example 1-36, Example 1-37, Example 1- 38.
  • Negative electrode active material artificial graphite, conductive agent superconducting carbon black (Super-P), binder styrene-butadiene rubber (SBR), thickener carboxymethylcellulose sodium (CMC-Na) are 95% according to mass ratio: 1.5%: 1.8%: 1.7% was dissolved in deionized water, and after fully stirring and mixing, a negative electrode slurry with a viscosity of 3000mPa.s and a solid content of 52% was obtained; the negative electrode slurry was coated on a 6 ⁇ m negative electrode current collector copper foil , and then baked at 100° C. for 4 hours to dry, and rolled to obtain a negative electrode sheet with a compacted density of 1.75 g/cm 3 .
  • Ethylene carbonate, dimethyl carbonate and 1,2-propylene glycol carbonate were mixed in a volume ratio of 1:1:1, and then LiPF 6 was uniformly dissolved in the above solution to obtain an electrolyte solution.
  • the concentration of LiPF 6 is 1 mol/L.
  • the bare battery core is formed by winding method, and the aluminum tab and copper tab are respectively punched out to obtain the bare battery core; Weld the copper and copper lugs of two bare cells, aluminum and aluminum tabs to the top cover of the battery, wrap and insulate the bare cells, put the bare cells into the aluminum shell, and connect the top cover to the aluminum shell Welding to form a dry cell, baking the dry cell to remove water, injecting electrolyte, forming and aging the battery, and correspondingly obtaining a full battery.
  • the battery structure made of the positive pole pieces P1, P2, P3, P8, P10, P11, P12, P17, P18, P23, P24, P26, and P27 is shown in Figure 8-20.
  • a lithium sheet is used as the negative electrode, and a solution of 1 mol/L LiPF 6 in ethylene carbonate (EC) + diethyl carbonate (DEC) + dimethyl carbonate (DMC) with a volume ratio of 1:1:1 is used as the electrolysis liquid, and assembled into a button battery (hereinafter also referred to as "button battery") in a button box together with the above-mentioned positive pole piece prepared.
  • EC ethylene carbonate
  • DEC diethyl carbonate
  • DMC dimethyl carbonate
  • a spherical aberration electron microscope (ACSTEM) was used to characterize the internal microstructure and surface structure of the positive electrode active material with high spatial resolution, combined with three-dimensional reconstruction technology to obtain the chemical formula of the core of the positive electrode active material and the composition of the first and second coating layers.
  • the button battery prepared above at a constant temperature of 25°C, let it stand for 5 minutes, discharge it at 0.1C to 2.5V, let it stand for 5 minutes, charge it at 0.1C to 4.3V, and then charge it at a constant voltage at 4.3V until the current is less than Equal to 0.05mA, let stand for 5 minutes; then discharge to 2.5V according to 0.1C, the discharge capacity at this time is the initial gram capacity, denoted as D0, the discharge energy is the initial energy, denoted as E0, and the average discharge voltage V after charging is E0 /D0.
  • the above-fabricated full cells were stored at 60°C at 100% state of charge (SOC).
  • SOC state of charge
  • the open circuit voltage (OCV) and AC internal resistance (IMP) of the cell are measured before, after and during storage to monitor the SOC, and the volume of the cell is measured.
  • the full battery was taken out after every 48 hours of storage, and the open circuit voltage (OCV) and internal resistance (IMP) were tested after standing for 1 hour, and the cell volume was measured by the drainage method after cooling to room temperature.
  • the batteries of all the examples kept the SOC above 99% during the experiment until the end of storage.
  • the anode active material sample was prepared as a button charge using the above button charge preparation method, and the above button charge was charged at a small rate of 0.05C until the current was reduced to 0.01C. Then take out the positive pole piece in the button battery, and soak in dimethyl carbonate (DMC) for 8 hours. Then dry, scrape the powder, and screen out the particles whose particle size is less than 500nm. Take a sample and calculate its unit cell volume v1 in the same way as the above-mentioned test fresh sample, and use (v0-v1)/v0 ⁇ 100% as the lattice change rate (unit cell volume change rate) before and after it completely deintercalates lithium. in the table.
  • DMC dimethyl carbonate
  • the Li/Mn antisite defect concentration is obtained. Specifically, import the XRD results tested in the "Measurement Method of Lattice Change Rate” into the General Structural Analysis System (GSAS) software, and automatically obtain the refined results, which include the occupancy of different atoms. By reading the refined As a result, the Li/Mn antisite defect concentration is obtained.
  • GSAS General Structural Analysis System
  • the full battery was discharged to a cut-off voltage of 2.0V at a rate of 0.1C after being cycled at 45°C until the capacity decayed to 80%. Then the battery was disassembled, and the negative pole piece was taken out. On the negative pole piece, 30 discs with a unit area (1540.25mm 2 ) were randomly selected, and the inductively coupled plasma emission spectrum (ICP) was tested with Agilent ICP-OES730. According to the ICP results, the amounts of Fe (if the Mn site of the positive electrode active material is doped with Fe) and Mn are calculated, so as to calculate the dissolution amount of Mn (and Fe doped at the Mn site) after cycling.
  • the test standard is based on EPA-6010D-2014.
  • the positive electrode active material sample prepared above Take 5 g of the positive electrode active material sample prepared above to prepare a button electrode according to the above button electrode preparation method. Charge the button with a small rate of 0.05C until the current decreases to 0.01C. Then take out the positive pole piece in the button battery, and soak in dimethyl carbonate (DMC) for 8 hours. Then dry, scrape the powder, and screen out the particles whose particle size is less than 500nm. The obtained particles were measured by electron energy loss spectroscopy (EELS, the instrument model used was Talos F200S), and the energy loss near-edge structure (ELNES) was obtained, which reflected the density of states and energy level distribution of the elements. According to the density of states and energy level distribution, the number of occupied electrons is calculated by integrating the data of the valence band density of states, so as to calculate the valence state of the charged surface oxygen.
  • DMC dimethyl carbonate
  • the positive electrode active material powder prepared above Take 5g of the positive electrode active material powder prepared above, and measure the total scattering intensity by X-rays, which is the sum of the scattering intensity of the entire space material, and is only related to the intensity of the primary ray, the chemical structure, and the total number of electrons participating in the diffraction, that is, the mass. It is related, but not related to the order state of the sample; then the crystalline scattering and the non-crystalline scattering are separated from the diffraction pattern, and the degree of crystallinity is the ratio of the crystalline partial scattering to the total scattering intensity.
  • the existence of the first cladding layer is beneficial to reduce the Li/Mn antisite defect concentration of the obtained material and the amount of Fe and Mn dissolved after cycling, and improve the battery performance. Reduce battery capacity and improve battery safety and cycle performance.
  • the lattice change rate, antisite defect concentration and Fe and Mn dissolution amount of the obtained material can be significantly reduced, the gram capacity of the battery can be increased, and the safety performance and cycle of the battery can be improved. performance.
  • the secondary battery prepared by adopting the positive pole piece P1-P42 is tested as follows:
  • the secondary battery using the positive pole piece P3-P30, P37-P42 has higher energy density, higher room temperature rate charge capacity retention rate and low temperature discharge capacity retention rate, and Successfully passed the furnace temperature experiment and acupuncture test.
  • the secondary battery using the positive pole piece P2 failed the furnace temperature test and the acupuncture test, and a fire occurred during the test, and the secondary battery using the positive pole piece P3-P30 failed.
  • the cycle life of the secondary battery is longer than that of the secondary battery using the positive pole piece P2.
  • the secondary battery using the positive pole piece P31-P36 failed to pass the furnace temperature test and the acupuncture test, and a fire occurred during the test; the positive pole piece P37-P42 contained The first positive electrode active material and the second positive electrode active material, and the positive electrode sheets P31-P36 contain an equivalent amount of the corresponding second positive electrode active material.
  • the cycle life of the secondary battery using a single positive electrode sheet containing the second positive electrode active material is longer than that of the secondary battery using a single positive electrode sheet containing the second positive electrode active material.
  • the secondary battery made of the positive electrode sheet of the present application has higher energy density, higher cell rate performance, better kinetic performance and low temperature performance, longer cycle life, and higher safety.
  • the present application is not limited to the above-mentioned embodiments.
  • the above-mentioned embodiments are merely examples, and within the scope of the technical solutions of the present application, embodiments that have substantially the same configuration as the technical idea and exert the same effects are included in the technical scope of the present application.
  • various modifications conceivable by those skilled in the art are added to the embodiments, and other forms constructed by combining some components in the embodiments are also included in the scope of the present application. .

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Abstract

本申请提供一种正极极片、二次电池、电池模块、电池包和用电装置；正极极片包括正极集流体和设置在其至少一个表面的具有单层或多层结构正极膜层；当正极膜层为单层结构时，至少一个正极膜层同时包含第一正极活性材料和第二正极活性材料；和/或，当正极膜层为多层结构时，至少一个正极膜层的至少一层中同时包含第一正极活性材料和第二正极活性材料；第一正极活性材料包括含Li1+xMn1-yAyP1-zRzO4的内核、包覆内核的含焦磷酸盐MP2O7和磷酸盐XPO4的第一包覆层以及包覆第一包覆层的含碳元素的第二包覆层。本申请正极极片所制二次电池的能量密度高，电芯倍率性能高，动力学性能和低温性能好，循环性能好，安全性高。

Description

一种正极极片、二次电池、电池模块、电池包和用电装置 技术领域
本申请涉及二次电池技术领域，尤其涉及一种正极极片、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。以现有的磷酸锰铁锂作为主材，与三元材料镍钴锰酸锂、镍钴铝酸锂或钴酸锂等混掺后制作二次电池，这种技术虽然结合了磷酸锰铁锂与三元材料的各自优势，但磷酸锰铁锂使得电池的动力学性能较差、电芯倍率性能较低，不能满足动力电池需求。
发明内容
本申请是鉴于上述课题而进行的，其目的在于，提供一种正极极片、二次电池、电池模块、电池包和用电装置，以解决采用现有正极活性材料所制二次电池的能量密度低、电芯倍率性能低、动力学性能差、低温性能差、循环寿命短、安全性低的问题。
为了达到上述目的，本申请的第一方面提供了一种正极极片，包括正极集流体和设置在正极集流体的至少一个表面上的正极膜层；正极膜层为单层结构或多层结构；当正极膜层为单层结构时，至少一个正极膜层同时包含具有核-壳结构的第一正极活性材料和第二正极活性材料；和/或，当正极膜层为多层结构时，至少一个正极膜层的至少一层中同时包含具有核-壳结构的第一正极活性材料和第二正极活 性材料；第一正极活性材料包括内核、包覆内核的第一包覆层以及包覆第一包覆层的第二包覆层；其中，内核包含Li 1+xMn 1-yA yP 1-zR zO 4，第一包覆层包含焦磷酸盐MP 2O 7和磷酸盐XPO 4，第二包覆层包含碳元素；其中，A选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素；R选自B、Si、N和S中的一种或多种元素；x选自-0.100-0.100范围内的任意数值；y选自0.001-0.500范围内的任意数值；z选自0.001-0.100范围内的任意数值；M和X独立地选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb和Al中的一种或多种元素；第二正极活性材料选自LiNi aCo bMn (1-a-b)O 2、LiNi aCo bAl (1-a-b)O 2和LiCoO 2中的一种或多种；其中，a独立地选自0.3-0.9范围内的任意数值(可选为0.33-0.8)，a与b之和独立地选自0.3-0.9范围内的任意数值(可选为0.66-0.9)。
由此，本申请人意外地发现：通过在化合物LiMnPO 4的Mn位和P位同时以特定量掺杂特定元素并在化合物表面进行两层包覆获得第一正极活性材料，能够大大减少过渡金属的溶出并降低颗粒表面的氧活性，促进锂离子的迁移，提高材料的导电性能和去溶剂化性能，改善电池的倍率性能，提高二次电池的循环性能和高温性能，同时减少电解液对活性材料的腐蚀。
本申请通过将第一正极活性材料和第二正极活性材料混合使用，两种材料的优势互补，提升了二次电池的能量密度，同时使电池兼具优良的倍率性能、动力学性能、循环性能、低温性能和安全性。第一正极活性材料的颗粒均匀包覆在第二正极活性材料表面，使第二正极活性材料的晶格相对独立、骨架稳定，在二次电池充放电过程中不易坍塌，进一步提高了电池的循环寿命；并且，第一正极活性材料形成的包覆层为外力撞击或剪切提供了弹性应变力，有效解决了第二正极活性材料的安全性问题。
本申请的第二方面还提供一种正极极片，包括正极集流体和设置在正极集流体的至少一个表面上的正极膜层；至少一个正极膜层为多层结构，任一具有多层结构的正极膜层在不同层中分别包含具有核-壳结构的第一正极活性材料和第二正极活性材料；第一正极活性材料 包括内核、包覆内核的第一包覆层以及包覆第一包覆层的第二包覆层；其中，内核包含Li 1+xMn 1-yA yP 1-zR zO 4，第一包覆层包含焦磷酸盐MP 2O 7和磷酸盐XPO 4，第二包覆层包含碳元素；其中，A选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素；R选自B、Si、N和S中的一种或多种元素；x选自-0.100-0.100；y选自0.001-0.500；z选自0.001-0.100；M和X独立地选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb和Al中的一种或多种元素；第二正极活性材料选自LiNi aCo bMn (1-a-b)O 2、LiNi aCo bAl (1-a-b)O 2和LiCoO 2中的一种或多种；其中，a独立地选自0.3-0.9范围内的任意数值(可选为0.33-0.8)，a与b之和独立地选自0.3-0.9范围内的任意数值(可选为0.66-0.9)；可选地，任一具有多层结构的正极膜层在相邻层中分别包含第一正极活性材料和第二正极活性材料。
由此，第一正极活性材料能够大大减少过渡金属的溶出并降低颗粒表面的氧活性，促进锂离子的迁移，提高导电性能和去溶剂化性能，改善电池的倍率性能，提高二次电池的循环性能和高温性能，同时减少电解液对活性材料的腐蚀。
本申请将第一正极活性材料和第二正极活性材料组合使用，两种材料的优势互补，提升了二次电池的能量密度，同时使电池兼具优良的倍率性能、动力学性能、循环性能和低温性能，并且，第一正极活性材料为外力撞击或剪切提供了弹性应变力，有效解决了第二正极活性材料的安全性问题。
本申请的第三方面还提供一种正极极片，包括正极集流体和分别设置在正极集流体的两个表面上的正极膜层A和正极膜层B；正极膜层A和正极膜层B各自独立地为单层结构或多层结构；正极膜层A的至少一层中包含具有核-壳结构的第一正极活性材料，同时，正极膜层B的至少一层中包含第二正极活性材料；第一正极活性材料包括内核、包覆内核的第一包覆层以及包覆第一包覆层的第二包覆层；其中，内核包含Li 1+xMn 1-yA yP 1-zR zO 4，第一包覆层包含焦磷酸盐MP 2O 7和磷酸盐XPO 4，第二包覆层包含碳元素；其中，A选自Zn、Al、Na、 K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素；R选自B、Si、N和S中的一种或多种元素；x选自-0.100-0.100；y选自0.001-0.500；z选自0.001-0.100；M和X独立地选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb和Al中的一种或多种元素；第二正极活性材料选自LiNi aCo bMn (1-a-b)O 2、LiNi aCo bAl (1-a-b)O 2和LiCoO 2中的一种或多种；其中，a独立地选自0.3-0.9范围内的任意数值(可选为0.33-0.8)，a与b之和独立地选自0.3-0.9范围内的任意数值(可选为0.66-0.9)。
由此，第一正极活性材料能够大大减少过渡金属的溶出并降低颗粒表面的氧活性，促进锂离子的迁移，提高导电性能和去溶剂化性能，改善电池的倍率性能，提高二次电池的循环性能和高温性能，同时减少电解液对活性材料的腐蚀。
本申请将第一正极活性材料和第二正极活性材料组合使用，两种材料的优势互补，提升了二次电池的能量密度，同时使电池兼具优良的倍率性能、动力学性能、循环性能和低温性能，并且，第一正极活性材料为外力撞击或剪切提供了弹性应变力，有效解决了第二正极活性材料的安全性问题。
除非另有说明，否则上述化学式中，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。
在第一方面至第三方面的任意实施方式中，第一活性材料与第二活性材料的质量比为1:7-7:1，可选为1:4-4:1。以保证二次电池兼具优良的倍率性能和循环性能，具有较高的能量密度、优良的动力学性能和低温性能，减少界面副反应，提高二次电池的安全性。
在第一方面至第三方面的任意实施方式中，第一正极活性材料中， A选自Zn、Fe、Ti、V、Ni、Co和Mg中的一种或多种元素；和/或，A选自Fe、Ti、V、Ni、Co和Mg中的至少两种元素。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，从而改善电池的循环性能和高温储存性能。
在第一方面至第三方面的任意实施方式中，x选自-0.100-0.006范围内的任意数值。通过在该范围内对x值进行选择，能进一步提升第一正极活性材料的动力学性能。
在第一方面至第三方面的任意实施方式中，y选自0.1-0.4范围内的任意数值。通过在该范围内对y值进行选择，能进一步提升第一正极活性材料的克容量和倍率性能。
在第一方面至第三方面的任意实施方式中，M和X独立地选自Li和Fe中的一种或多种元素。
在第一方面至第三方面的任意实施方式中，y与1-y的比值选自1:10至10:1，可选为1:4至1:1。此处y表示Mn位掺杂元素的化学计量数之和。在满足上述条件时，正极极片所制二次电池的能量密度和循环性能可进一步提升。
在第一方面至第三方面的任意实施方式中，z与1-z的比值选自1:999至1:9，可选为1:499至1:249。此处z表示P位掺杂元素的化学计量数之和。在满足上述条件时，正极极片所制二次电池的能量密度和循环性能可进一步提升。
在第一方面至第三方面的任意实施方式中，第一正极活性材料中，第一包覆层中的磷酸盐的晶面间距为0.345-0.358nm，晶向(111)的夹角为24.25°-26.45°；第一包覆层中的焦磷酸盐的晶面间距为0.293-0.326nm，晶向(111)的夹角为26.41°-32.57°。
当第一包覆层中磷酸盐和焦磷酸盐的晶面间距和晶向(111)的夹角在上述范围时，能够有效避免包覆层中的杂质相，从而提升材料的克容量，提高二次电池的循环性能和倍率性能。
在第一方面至第三方面的任意实施方式中，第一正极活性材料中， 第一包覆层的包覆量为大于0重量％且小于等于7重量％，可选为4-5.6重量％，基于内核的重量计。
当第一包覆层的包覆量在上述范围内时，能够进一步抑制锰溶出，同时进一步促进锂离子的传输。并能够有效避免以下情况：若第一包覆层的包覆量过小，则可能会导致焦磷酸盐对锰溶出的抑制作用不充分，同时对锂离子传输性能的改善也不显著；若第一包覆层的包覆量过大，则可能会导致包覆层过厚，增大电池阻抗，影响电池的动力学性能。
在第一方面至第三方面的任意实施方式中，第一正极活性材料中，第一包覆层中焦磷酸盐和磷酸盐的重量比为1:3至3:1，可选为1:3至1:1。
焦磷酸盐和磷酸盐的合适配比有利于充分发挥二者的协同作用。并能够有效避免以下情况：如果焦磷酸盐过多而磷酸盐过少，则可能导致电池阻抗增大；如果磷酸盐过多而焦磷酸盐过少，则抑制锰溶出的效果不显著。
在第一方面至第三方面的任意实施方式中，第一正极活性材料中，焦磷酸盐和磷酸盐的结晶度各自独立地为10％至100％，可选为50％至100％。
在本申请磷酸锰锂正极活性材料的第一包覆层中，具备一定结晶度的焦磷酸盐和磷酸盐有利于保持第一包覆层的结构稳定，减少晶格缺陷。这一方面有利于充分发挥焦磷酸盐阻碍锰溶出的作用，另一方面也有利于磷酸盐减少表面杂锂含量、降低表面氧的价态，从而减少正极材料与电解液的界面副反应，减少对电解液的消耗，改善二次电池的循环性能和安全性能。
在第一方面至第三方面的任意实施方式中，第一正极活性材料中，第二包覆层的包覆量为大于0重量％且小于等于6重量％，可选为3-5重量％，基于内核的重量计。
作为第二包覆层的含碳层一方面可以发挥“屏障”功能，避免第一正极活性材料与电解液直接接触，从而减少电解液对活性材料的腐蚀，提高电池在高温下的安全性能。另一方面，其具备较强的导电能力， 可降低电池内阻，从而改善二次电池的动力学性能。然而，由于碳材料的克容量较低，因此当第二包覆层的用量过大时，可能会降低正极活性材料整体的克容量。因此，第二包覆层的包覆量在上述范围时，能够在不牺牲正极活性材料克容量的前提下，进一步改善二次电池的动力学性能和安全性能。
在第一方面至第三方面的任意实施方式中，第一正极活性材料的Li/Mn反位缺陷浓度为4％以下，可选为2％以下。在本申请的第一正极活性材料中，Li/Mn反位缺陷是指LiMnPO 4晶格中，Li +和Mn 2+的位置发生互换。由于Li +传输通道为一维通道，Mn 2+在Li +传输通道中难以迁移，因此，反位缺陷的Mn 2+会阻碍Li +的传输。通过将Li/Mn反位缺陷浓度控制在低水平，能够改善LiMnPO 4的克容量和倍率性能。
在第一方面至第三方面的任意实施方式中，第一正极活性材料的晶格变化率为6％以下，可选为4％以下。LiMnPO 4的脱嵌锂过程是两相反应。两相的界面应力由晶格变化率大小决定，晶格变化率越小，界面应力越小，Li +传输越容易。因此，减小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。
在第一方面至第三方面的任意实施方式中，第一正极活性材料的表面氧价态为-1.88以下，可选地为-1.98～-1.88。这是由于氧在化合物中的价态越高，其得电子能力越强，即氧化性越强。而在本申请的第一正极活性材料中，通过将氧的表面价态控制在较低水平，可降低正极材料表面的反应活性，减少正极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。
在第一方面至第三方面的任意实施方式中，第一正极活性材料在3吨(T)下的压实密度为2.0g/cm 3以上，可选地为2.2g/cm 3以上。第一正极活性材料的压实密度越高，即单位体积活性物质的重量越大，将更有利于提升二次电池的体积能量密度。
在第一方面至第三方面的任意实施方式中，第一正极活性材料和第二正极活性材料的质量之和占正极极片的质量的88％-98.7％。进一步保证二次电池具有优良的倍率性能、动力学性能、循环性能和低温 性能，具有较高的能量密度。
本申请的第四方面提供一种二次电池，包括本申请第一方面至第三方面中任一的正极极片。
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为本申请一实施方式的具有核-壳结构的第一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。
图8是本申请正极极片P1所制电池结构的示意图。
图9是本申请正极极片P2所制电池结构的示意图。
图10是本申请正极极片P3所制电池结构的示意图。
图11是本申请正极极片P8所制电池结构的示意图。
图12是本申请正极极片P10所制电池结构的示意图。
图13是本申请正极极片P11所制电池结构的示意图。
图14是本申请正极极片P12所制电池结构的示意图。
图15是本申请正极极片P17所制电池结构的示意图。
图16是本申请正极极片P18所制电池结构的示意图。
图17是本申请正极极片P23所制电池结构的示意图。
图18是本申请正极极片P24所制电池结构的示意图。
图19是本申请正极极片P26所制电池结构的示意图。
图20是本申请正极极片P27所制电池结构的示意图。
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；11内核；12第一包覆层；13第二包覆层。
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极片、二次电池、电池模块、电池包和用电装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
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，中值粒径Dv 50是指，正极活性材料累计体积分布百分数达到50％时所对应的粒径。在本申请中，正极活性材料的中值粒径Dv 50可采用激光衍射粒度分析法测定。例如参照标准GB/T 19077-2016，使用激光粒度分析仪(例如Malvern Master Size 3000)进行测定。
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。同样地，术语“包覆层的厚度”是指包覆在内核上的物质层在内核径向上的厚度。
如果没有特别的说明，在本申请中，术语“源”是指作为某种元素的来源的化合物，作为实例，“源”的种类包括但不限于碳酸盐、硫酸盐、硝酸盐、单质、卤化物、氧化物和氢氧化物等。
[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。
[正极极片]
本申请第一个方面的实施方式提供一种正极极片，包括正极集流体和设置在正极集流体的至少一个表面上的正极膜层；正极膜层为单层结构或多层结构；当正极膜层为单层结构时，至少一个正极膜层同时包含具有核-壳结构的第一正极活性材料和第二正极活性材料；和/或，当正极膜层为多层结构时，至少一个正极膜层的至少一层中同时包含具有核-壳结构的第一正极活性材料和第二正极活性材料；第一正极活性材料包括内核、包覆内核的第一包覆层以及包覆第一包覆层的第二包覆层；其中，内核包含Li 1+xMn 1-yA yP 1-zR zO 4，第一包覆层包含焦磷酸盐MP 2O 7和磷酸盐XPO 4，第二包覆层包含碳元素；其中，A选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素；R选自B、Si、N和S中的一种或多种元素；x选自-0.100-0.100范围内的任意数值；y选自0.001-0.500范围内的任意数值；z选自0.001-0.100范围内的任意数值；M和X独立地选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb和Al中的一种或多种元素；第二正极活性材料选自LiNi aCo bMn (1-a-b)O 2、LiNi aCo bAl (1-a-b)O 2和LiCoO 2中的一种或多种；其中，a独立地选自0.3-0.9范围内的任意数值(可选为0.33-0.8，例如0.5)，a与b之和独立地选自0.3-0.9范围内的任意数值(可选为0.66-0.9，例如0.7)。
需要说明的是：当正极极片包括两个正极膜层时，“正极膜层为单层结构或多层结构”指两个正极膜层各自独立地为单层结构或多层结构；“当正极膜层为单层结构时”指一个或两个正极膜层为单层结构时；“当正极膜层为多层结构时”指一个或两个正极膜层为多层结构时。
本申请的第一正极活性材料为具有两层包覆层的核-壳结构，其中内核包括Li 1+xMn 1-yA yP 1-zR zO 4。内核在磷酸锰锂的锰位掺杂的元素A有助于减小脱嵌锂过程中磷酸锰锂的晶格变化率，提高磷酸锰锂正极材料的结构稳定性，大大减少锰的溶出并降低颗粒表面的氧活性。在磷位掺杂的元素R有助于改变Mn-O键长变化的难易程度，从而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。本申请的第一正极活性材料的第一包覆层包括焦磷酸盐和磷酸盐。由于过渡金属在焦磷酸盐中的迁移势垒较高(>1eV)，能够有效抑制过渡金属的溶出。而磷酸盐具有优异的导锂离子的能力，并可减少表面杂锂含量。另外，由于第二包覆层为含碳层，因而能够有效改善LiMnPO 4的导电性能和去溶剂化能力。此外，第二包覆层的“屏障”作用可以进一步阻碍锰离子迁移到电解液中，并减少电解液对活性材料的腐蚀。因此，本申请第一正极活性材料通过对磷酸锰锂进行特定的元素掺杂和表面包覆，能够有效抑制脱嵌锂过程中的Mn溶出，同时促进锂离子的迁移，从而改善电芯的倍率性能，提高二次电池的循环性能和高温性能。需要指出的是，本申请的第一正极活性材料与LiMnPO 4掺杂前的主要特征峰的位置基本一致，说明掺杂的磷酸锰锂正极活性材料没有杂质相，二次电池性能的改善主要来自元素掺杂，而不是杂质相导致的。
本申请通过将第一正极活性材料和第二正极活性材料混合使用，两种材料的优势互补，提升了二次电池的能量密度，同时使电池兼具优良的倍率性能、动力学性能、循环性能、低温性能和安全性。第一正极活性材料的颗粒均匀包覆在第二正极活性材料表面，使第二正极活性材料的晶格相对独立、骨架稳定，在二次电池充放电过程中不易坍塌，进一步提高了电池的循环寿命；并且，第一正极活性材料形成的包覆层为外力撞击或剪切提供了弹性应变力，有效解决了第二正极 活性材料的安全性问题。
在第一个方面的一些实施方式中，在正极集流体的两个表面上分别设置有正极膜层C和正极膜层D，正极膜层C为多层结构，正极膜层D为单层结构，正极膜层C中的至少一层同时包含第一正极活性材料和第二正极活性材料；可选地，正极膜层D包含第一正极活性材料和第二正极活性材料中的一种或两种；可选地，正极膜层C中的其余层包含第一正极活性材料或第二正极活性材料。
在第一个方面的一些实施方式中，在正极集流体的两个表面上分别设置有正极膜层C和正极膜层D，正极膜层C为多层结构，正极膜层D为单层结构，正极膜层D同时包含第一正极活性材料和第二正极活性材料；可选地，正极膜层C中的任一层包含第一正极活性材料或第二正极活性材料。
在第一个方面的一些实施方式中，在正极集流体的两个表面上分别设置有一个正极膜层，每个正极膜层都为多层结构，每个正极膜层中的至少一层同时包含第一正极活性材料和第二正极活性材料；可选地，正极膜层中的其余层包含第一正极活性材料或第二正极活性材料。
本申请第二个方面的实施方式提供一种正极极片，包括正极集流体和设置在正极集流体的至少一个表面上的正极膜层；至少一个正极膜层为多层结构，任一具有多层结构的正极膜层在不同层中分别包含具有核-壳结构的第一正极活性材料和第二正极活性材料；第一正极活性材料包括内核、包覆内核的第一包覆层以及包覆第一包覆层的第二包覆层；其中，内核包含Li 1+xMn 1-yA yP 1-zR zO 4，第一包覆层包含焦磷酸盐MP 2O 7和磷酸盐XPO 4，第二包覆层包含碳元素；其中，A选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素；R选自B、Si、N和S中的一种或多种元素；x选自-0.100-0.100；y选自0.001-0.500；z选自0.001-0.100；M和X独立地选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb和Al中的一种或多种元素；第二正极活性材料选自LiNi aCo bMn (1-a-b)O 2、LiNi aCo bAl (1-a-b)O 2和LiCoO 2中的一种或多种；其中，a独立地选自0.3-0.9范围内的任意数值(可选为0.33-0.8，例如 0.5)，a与b之和独立地选自0.3-0.9范围内的任意数值(可选为0.66-0.9，例如0.7)；可选地，任一具有多层结构的正极膜层在相邻层中分别包含第一正极活性材料和第二正极活性材料。
本申请的第一正极活性材料能够大大减少过渡金属的溶出并降低颗粒表面的氧活性，促进锂离子的迁移，提高导电性能和去溶剂化性能，改善电池的倍率性能，提高二次电池的循环性能和高温性能，同时减少电解液对活性材料的腐蚀。本申请将第一正极活性材料和第二正极活性材料组合使用，两种材料的优势互补，提升了二次电池的能量密度，同时使电池兼具优良的倍率性能、动力学性能、循环性能和低温性能，并且，第一正极活性材料为外力撞击或剪切提供了弹性应变力，有效解决了第二正极活性材料的安全性问题。
在第二个方面的一些实施方式中，在正极集流体的两个表面上分别设置有一个正极膜层，每个正极膜层都为多层结构，每个正极膜层中的相邻两层分别包含第一正极活性材料和第二正极活性材料。
在第二个方面的一些实施方式中，在正极集流体的两个表面上分别设置有正极膜层E和正极膜层F，正极膜层E为多层结构，正极膜层F为单层结构，正极膜层E中的相邻两层分别包含第一正极活性材料和第二正极活性材料；可选地，正极膜层E中的其余层和正极膜层F包含第一正极活性材料或第二正极活性材料。
本申请第三个方面的实施方式提供一种正极极片，包括正极集流体和分别设置在正极集流体的两个表面上的正极膜层A和正极膜层B；正极膜层A和正极膜层B各自独立地为单层结构或多层结构；正极膜层A的至少一层中包含具有核-壳结构的第一正极活性材料，同时，正极膜层B的至少一层中包含第二正极活性材料；第一正极活性材料包括内核、包覆内核的第一包覆层以及包覆第一包覆层的第二包覆层；其中，内核包含Li 1+xMn 1-yA yP 1-zR zO 4，第一包覆层包含焦磷酸盐MP 2O 7和磷酸盐XPO 4，第二包覆层包含碳元素；其中，A选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素；R选自B、Si、N和S中的一种或多种元素；x选自-0.100-0.100；y选自0.001-0.500；z选自0.001-0.100； M和X独立地选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb和Al中的一种或多种元素；第二正极活性材料选自LiNi aCo bMn (1-a-b)O 2、LiNi aCo bAl (1-a-b)O 2和LiCoO 2中的一种或多种；其中，a独立地选自0.3-0.9范围内的任意数值(可选为0.33-0.8，例如0.5)，a与b之和独立地选自0.3-0.9范围内的任意数值(可选为0.66-0.9，例如0.7)。
本申请的第一正极活性材料能够大大减少过渡金属的溶出并降低颗粒表面的氧活性，促进锂离子的迁移，提高导电性能和去溶剂化性能，改善电池的倍率性能，提高二次电池的循环性能和高温性能，同时减少电解液对活性材料的腐蚀。本申请将第一正极活性材料和第二正极活性材料组合使用，两种材料的优势互补，提升了二次电池的能量密度，同时使电池兼具优良的倍率性能、动力学性能、循环性能和低温性能，并且，第一正极活性材料为外力撞击或剪切提供了弹性应变力，有效解决了第二正极活性材料的安全性问题。
除非另有说明，否则上述化学式中，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。
如图1所示，本申请的具有核-壳结构的第一正极活性材料包括内核11、包覆内核11的第一包覆层12以及包覆第一包覆层12的第二包覆层13，其中内核11包括Li 1+xMn 1-yA yP 1-zR zO 4。所述内核11在磷酸锰锂的锰位掺杂的元素A有助于减小脱嵌锂过程中磷酸锰锂的晶格变化率，提高磷酸锰锂正极材料的结构稳定性，大大减少锰的溶出并降低颗粒表面的氧活性。在磷位掺杂的元素R有助于改变Mn-O键长变化的难易程度，从而降低锂离子迁移势垒，促进锂离子迁移，提高二次电池的倍率性能。
在第一个至第三个方面的一些实施方式中，Li 1+xMn 1-yA yP 1-zR zO 4整个保持电中性。
在第一个至第三个方面的一些实施方式中，第一活性材料与第二活性材料的质量比为1:7-7:1，可选为1:4-4:1，进一步可选为1:3-3:1，例如1:7、1:5、1:3、1:2、3:5、1:1、5:3、2:1、3:1、5:1、7:1。以保证二次电池兼具优良的倍率性能、优良的循环性能和高温稳定性、较高的能量密度、优良的动力学性能和低温性能，减少界面副反应，提高二次电池的安全性。
在第一个至第三个方面的一些实施方式中，第一正极活性材料中，A选自Zn、Fe、Ti、V、Ni、Co和Mg中的一种或多种元素；和/或，A选自Fe、Ti、V、Ni、Co和Mg中的至少两种元素。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。
在第一个至第三个方面的一些实施方式中，x选自-0.100-0.006范围内的任意数值。通过在该范围内对x值进行选择，能进一步提升第一正极活性材料的动力学性能。
在第一个至第三个方面的一些实施方式中，y选自0.1-0.4范围内的任意数值。通过在该范围内对y值进行选择，能进一步提升第一正极活性材料的克容量和二次电池的倍率性能。
在第一个至第三个方面的一些实施方式中，M和X独立地选自Li和Fe中的一种或多种元素。
在第一个至第三个方面的一些实施方式中，y与1-y的比值选自1:10至10:1，可选为1:4至1:1。此处y表示Mn位掺杂元素的化学计量数之和。在满足上述条件时，正极极片所制二次电池的能量密度和循环性能进一步提升。
在第一个至第三个方面的一些实施方式中，z与1-z的比值选自1:999至1:9，可选为1:499至1:249。此处z表示P位掺杂元素的化 学计量数之和。在满足上述条件时，正极极片所制二次电池的能量密度和循环性能可进一步提升。
在第一个至第三个方面的一些实施方式中，第一正极活性材料中，第一包覆层中的磷酸盐的晶面间距为0.345-0.358nm，晶向(111)的夹角为24.25°-26.45°；第一包覆层中的焦磷酸盐的晶面间距为0.293-0.326nm，晶向(111)的夹角为26.41°-32.57°。
当第一包覆层中磷酸盐和焦磷酸盐的晶面间距和晶向(111)的夹角在上述范围时，能够有效避免包覆层中的杂质相，从而提升材料的克容量，提高二次电池的循环性能和倍率性能。
在第一个至第三个方面的一些实施方式中，第一正极活性材料中，第一包覆层的包覆量为大于0重量％且小于等于7重量％，可选为4-5.6重量％，基于内核的重量计。
当第一包覆层的包覆量在上述范围内时，能够进一步抑制锰溶出，同时进一步促进锂离子的传输。并能够有效避免以下情况：若第一包覆层的包覆量过小，则可能会导致焦磷酸盐对锰溶出的抑制作用不充分，同时对锂离子传输性能的改善也不显著；若第一包覆层的包覆量过大，则可能会导致包覆层过厚，增大电池阻抗，影响二次电池的动力学性能。
在第一个至第三个方面的一些实施方式中，第一正极活性材料中，第一包覆层中焦磷酸盐和磷酸盐的重量比为1:3至3:1，可选为1:3至1:1。
焦磷酸盐和磷酸盐的合适配比有利于充分发挥二者的协同作用。并能够有效避免以下情况：如果焦磷酸盐过多而磷酸盐过少，则可能导致电池阻抗增大；如果磷酸盐过多而焦磷酸盐过少，则抑制锰溶出的效果不显著。
在第一个至第三个方面的一些实施方式中，第一正极活性材料中，焦磷酸盐和磷酸盐的结晶度各自独立地为10％至100％，可选为50％至100％。在本申请磷酸锰锂正极活性材料的第一包覆层中，具备一定结晶度的焦磷酸盐和磷酸盐有利于保持第一包覆层的结构稳定，减少晶格缺陷。这一方面有利于充分发挥焦磷酸盐阻碍锰溶出的作用， 另一方面也有利于磷酸盐减少表面杂锂含量、降低表面氧的价态，从而减少正极材料与电解液的界面副反应，减少对电解液的消耗，改善二次电池的循环性能和安全性能。
在第一个至第三个方面的一些实施方式中，第一正极活性材料中，第二包覆层的包覆量为大于0重量％且小于等于6重量％，可选为3-5重量％，基于内核的重量计。
作为第二包覆层的含碳层一方面可以发挥“屏障”功能，避免第一正极活性材料与电解液直接接触，从而减少电解液对活性材料的腐蚀，提高二次电池在高温下的安全性能。另一方面，其具备较强的导电能力，可降低二次电池的内阻，从而改善二次电池的动力学性能。然而，由于碳材料的克容量较低，因此当第二包覆层的用量过大时，可能会降低正极活性材料整体的克容量。因此，第二包覆层的包覆量在上述范围时，能够在不牺牲正极活性材料克容量的前提下，进一步改善二次电池的动力学性能和安全性能。
在第一个至第三个方面的一些实施方式中，第一正极活性材料的Li/Mn反位缺陷浓度为4％以下，可选为2％以下。在本申请的第一正极活性材料中，Li/Mn反位缺陷是指LiMnPO 4晶格中，Li +和Mn 2+的位置发生互换。由于Li +传输通道为一维通道，Mn 2+在Li +传输通道中难以迁移，因此，反位缺陷的Mn 2+会阻碍Li +的传输。通过将Li/Mn反位缺陷浓度控制在低水平，能够改善LiMnPO 4的克容量和二次电池的倍率性能。本申请中，反位缺陷浓度例如可根据JIS K 0131-1996测定。
在第一个至第三个方面的一些实施方式中，第一正极活性材料的晶格变化率为6％以下，可选为4％以下。LiMnPO 4的脱嵌锂过程是两相反应。两相的界面应力由晶格变化率大小决定，晶格变化率越小，界面应力越小，Li +传输越容易。因此，减小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。
在第一个至第三个方面的一些实施方式中，第一正极活性材料的表面氧价态为-1.88以下，可选地为-1.98～-1.88。这是由于氧在化合物中的价态越高，其得电子能力越强，即氧化性越强。而在本申请的 第一正极活性材料中，通过将氧的表面价态控制在较低水平，可降低正极材料表面的反应活性，减少正极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。
在第一个至第三个方面的一些实施方式中，第一正极活性材料在3吨(T)下的压实密度为2.0g/cm 3以上，可选地为2.2g/cm 3以上。第一正极活性材料的压实密度越高，即单位体积活性物质的重量越大，将更有利于提升二次电池的体积能量密度。本申请中，压实密度例如可根据GB/T 24533-2009测定。
在第一个至第三个方面的一些实施方式中，第一正极活性材料和第二正极活性材料的质量之和占正极极片的质量的88％-98.7％。进一步保证二次电池具有优良的倍率性能、动力学性能、循环性能和低温性能，具有较高的能量密度。
在第一个至第三个方面的一些实施方式中，LiNi aCo bMn (1-a-b)O 2中的a、(1-a-b)和b的比值为5:2:3或3:1:1或8:1:1；和/或，LiNi aCo bMn (1-a-b)O 2中的a、b和(1-a-b)的比值为5:2:3或3:1:1或8:1:1。由此能进一步提升二次电池的能量密度。
在第一个至第三个方面的一些实施方式中，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。
在第一个至第三个方面的一些实施方式中，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、锂过渡金属氧化物及其各自的改性化合物。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，锂过渡金属氧化物的示例可包括但不限于锂镍氧化物(如LiNiO 2)、锂 锰氧化物(如LiMnO 2、LiMn 2O 4)、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物及其改性化合物等中的至少一种。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、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料中的至少一种。
在第一个至第三个方面的一些实施方式中，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。
在第一个至第三个方面的一些实施方式中，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。本发明实施例中各成分的含量，如果没有特别说明，均以不含结晶水的质量计。
本申请制备例及实施例涉及的原材料来源如下：
名称 化学式 厂家 规格
碳酸锰 MnCO 3 山东西亚化学工业有限公司 1Kg
碳酸锂 Li 2CO 3 山东西亚化学工业有限公司 1Kg
碳酸镁 MgCO 3 山东西亚化学工业有限公司 1Kg
碳酸锌 ZnCO 3 武汉鑫儒化工有限公司 25Kg
碳酸亚铁 FeCO 3 西安兰之光精细材料有限公司 1Kg
硫酸镍 NiCO 3 山东西亚化学工业有限公司 1Kg
硫酸钛 Ti(SO 4) 2 山东西亚化学工业有限公司 1Kg
硫酸钴 CoSO 4 厦门志信化学有限公司 500g
二氯化钒 VCl 2 上海金锦乐实业有限公司 1Kg
二水合草酸 C 2H 2O 4·2H 2O 上海金锦乐实业有限公司 1Kg
磷酸二氢铵 NH 4H 2PO 4 上海澄绍生物科技有限公司 500g
蔗糖 C 12H 22O 11 上海源叶生物科技有限公司 100g
硫酸 H 2SO 4 深圳海思安生物技术有限公司 质量分数60％
硝酸 HNO 3 安徽凌天精细化工有限公司 质量分数60％
亚硅酸 H 2SiO 3 上海源叶生物科技有限公司 100g
硼酸 H 3BO 3 常州市启迪化工有限公司 1Kg
实施例1-1
(1)共掺杂磷酸锰锂内核的制备
制备Fe、Co和V共掺杂的草酸锰：将689.5g碳酸锰(以MnCO 3计，下同)、455.2g碳酸亚铁(以FeCO 3计，下同)、4.6g硫酸钴(以CoSO 4计，下同)和4.9g二氯化钒(以VCl 2计，下同)在混料机中充分混合6小时。将混合物转移至反应釜中，并加入5升去离子水和1260.6g二水合草酸(以C 2H 2O 4.2H 2O计，下同)。将反应釜加热至80℃，以600rpm的转速搅拌6小时，直至反应终止(无气泡产生)，得到Fe、Co、V和S共掺杂的草酸锰悬浮液。然后过滤悬浮液，将滤饼在120℃下烘干，之后进行研磨，得到中值粒径Dv50为100nm的Fe、Co和V共掺杂的二水草酸锰颗粒。
制备Fe、Co、V和S共掺杂的磷酸锰锂：将前一步骤获得的二水草酸锰颗粒(1793.4g)、369.0g碳酸锂(以Li 2CO 3计，下同)，1.6g浓度为60％的稀硫酸(以60％H 2SO 4计，下同)和1148.9g磷酸二氢铵(以NH 4H 2PO 4计，下同)加入到20升去离子水中，将混合物搅拌10小时使其混合均匀，得到浆料。将浆料转移到喷雾干燥设备中进行喷雾干燥造粒，设定干燥温度为250℃，干燥4小时，得到粉料。在氮气(90体积％)+氢气(10体积％)保护气氛中，将上述粉料在700℃下烧结4小时，得到1572.1g的Fe、Co、V和S共掺杂的磷酸锰锂。
(2)焦磷酸铁锂和磷酸铁锂的制备
制备焦磷酸铁锂粉末：将4.77g碳酸锂、7.47g碳酸亚铁、14.84g磷酸二氢铵和1.3g二水合草酸溶于50ml去离子水中。混合物的pH为5，搅拌2小时使反应混合物充分反应。然后将反应后的溶液升温到80℃并保持该温度4小时，得到包含Li 2FeP 2O 7的悬浊液，将悬浊液进行过滤，用去离子水洗涤，并在120℃下干燥4h，得到粉末。将粉末在650℃、氮气气氛下烧结8小时，并自然冷却至室温后进行研磨，得到Li 2FeP 2O 7粉末。
制备磷酸铁锂悬浊液：将11.1g碳酸锂、34.8g碳酸亚铁、34.5g 磷酸二氢铵、1.3g二水合草酸和74.6g蔗糖(以C 12H 22O 11计，下同)溶于150ml去离子水中，得到混合物，然后搅拌6小时使上述混合物充分反应。然后将反应后的溶液升温到120℃并保持该温度6小时，得到包含LiFePO 4的悬浊液。
(3)包覆
将1572.1g上述Fe、Co、V和S共掺杂的磷酸锰锂与15.72g上述焦磷酸铁锂(Li 2FeP 2O 7)粉末加入到上一步骤制备获得的磷酸铁锂(LiFePO 4)悬浊液中，搅拌混合均匀后转入真空烘箱中在150℃下干燥6小时。然后通过砂磨分散所得产物。在分散后，将所得产物在氮气气氛中、在700℃下烧结6小时，得到目标产物双层包覆的磷酸锰锂。
实施例1-2至1-6
在共掺杂磷酸锰锂内核的制备过程中，除不使用二氯化钒和硫酸钴、使用463.4g的碳酸亚铁，1.6g的60％浓度的稀硫酸，1148.9g的磷酸二氢铵和369.0g碳酸锂以外，实施例1-2至1-6中磷酸锰锂内核的制备条件与实施例1-1相同。
此外，在焦磷酸铁锂和磷酸铁锂的制备过程以及包覆第一包覆层和第二包覆层的过程中，除所使用的原料按照表1中所示包覆量与实施例1-1对应的包覆量的比值对应调整，以使实施例1-2至1-6中Li 2FeP 2O 7/LiFePO 4的用量分别为12.6g/37.7g、15.7g/47.1g、18.8g/56.5g、22.0/66.0g和25.1g/75.4g，实施例1-2至1-6中蔗糖的用量为37.3g以外，其他条件与实施例1-1相同。
实施例1-7至1-10
除蔗糖的用量分别为74.6g、149.1g、186.4g和223.7g以使作为第二包覆层的碳层的对应包覆量分别为31.4g、62.9g、78.6g和94.3g以外，实施例1-7至1-10的条件与实施例1-3相同。
实施例1-11至1-14
除在焦磷酸铁锂和磷酸铁锂的制备过程中按照表1中所示包覆量对应调整各种原料的用量以使Li 2FeP 2O 7/LiFePO 4的用量分别为23.6g/39.3g、31.4g/31.4g、39.3g/23.6g和47.2g/15.7g以外，实施例1-11至1-14的条件与实施例1-7相同。
实施例1-15
除在共掺杂磷酸锰锂内核的制备过程中使用492.80g ZnCO 3代替碳酸亚铁以外，实施例1-15的条件与实施例1-14相同。
实施例1-16至1-18
除实施例1-16在共掺杂磷酸锰锂内核的制备过程中使用466.4g的NiCO 3、5.0g的碳酸锌和7.2g的硫酸钛代替碳酸亚铁，实施例1-17在共掺杂的磷酸锰锂内核的制备过程中使用455.2g的碳酸亚铁和8.5g的二氯化钒，实施例1-18在共掺杂的磷酸锰锂内核的制备过程中使用455.2g的碳酸亚铁、4.9g的二氯化钒和2.5g的碳酸镁以外，实施例1-17至1-19的条件与实施例1-7相同。
实施例1-19至1-20
除实施例1-19在共掺杂磷酸锰锂内核的制备过程中使用369.4g的碳酸锂、和以1.05g的60％浓度的稀硝酸代替稀硫酸，实施例1-20在共掺杂的磷酸锰锂内核的制备过程中使用369.7g的碳酸锂、和以0.78g的亚硅酸代替稀硫酸以外，实施例1-19至1-20的条件与实施例1-18相同。
实施例1-21至1-22
除实施例1-21在共掺杂磷酸锰锂内核的制备过程中使用632.0g碳酸锰、463.30g碳酸亚铁、30.5g的二氯化钒、21.0g的碳酸镁和0.78g的亚硅酸；实施例1-22在共掺杂磷酸锰锂内核的制备过程中使用746.9g碳酸锰、289.6g碳酸亚铁、60.9g的二氯化钒、42.1g的碳酸镁和0.78g的亚硅酸以外，实施例1-21至1-22的条件与实施例1-20相 同。
实施例1-23至1-24
除实施例1-23在共掺杂磷酸锰锂内核的制备过程中使用804.6g碳酸锰、231.7g碳酸亚铁、1156.2g的磷酸二氢铵、1.2g的硼酸(质量分数99.5％)和370.8g碳酸锂；实施例1-24在共掺杂磷酸锰锂内核的制备过程中使用862.1g碳酸锰、173.8g碳酸亚铁、1155.1g的磷酸二氢铵、1.86g的硼酸(质量分数99.5％)和371.6g碳酸锂以外，实施例1-23至1-24的条件与实施例1-22相同。
实施例1-25
除实施例1-25在共掺杂磷酸锰锂内核的制备过程中使用370.1g碳酸锂、1.56g的亚硅酸和1147.7g的磷酸二氢铵以外，实施例1-25的条件与实施例1-20相同。
实施例1-26
除实施例1-26在共掺杂磷酸锰锂内核的制备过程中使用368.3g碳酸锂、4.9g质量分数为60％的稀硫酸、919.6g碳酸锰、224.8g碳酸亚铁、3.7g二氯化钒、2.5g碳酸镁和1146.8g的磷酸二氢铵以外，实施例1-26的条件与实施例1-20相同。
实施例1-27
除实施例1-27在共掺杂磷酸锰锂内核的制备过程中使用367.9g碳酸锂、6.5g浓度为60％的稀硫酸和1145.4g的磷酸二氢铵以外，实施例1-27的条件与实施例1-20相同。
实施例1-28至1-33
除实施例1-28至1-33在共掺杂磷酸锰锂内核的制备过程中使用1034.5g碳酸锰、108.9g碳酸亚铁、3.7g二氯化钒和2.5g碳酸镁，碳酸锂的使用量分别为：367.6g、367.2g、366.8g、366.4g、366.0g和 332.4g，磷酸二氢铵的使用量分别为：1144.5g、1143.4g、1142.2g、1141.1g、1139.9g和1138.8g，浓度为60％的稀硫酸的使用量分别为：8.2g、9.8g、11.4g、13.1g、14.7g和16.3g以外，实施例1-28至1-33的条件与实施例1-20相同。
实施例1-34
镍钴锰酸锂LiNi 0.5Co 0.2Mn 0.3O 2作为正极活性材料。
实施例1-35
将实施例1-1和实施例1-34的正极活性材料按照质量比1:1混合。
实施例1-36
镍钴锰酸锂LiNi 0.33Co 0.33Mn 0.34O 2作为正极活性材料。
实施例1-37
镍钴锰酸锂LiNi 0.8Co 0.1Mn 0.1O 2作为正极活性材料。
实施例1-38
镍钴铝酸锂LiNi 0.33Co 0.33Al 0.34O 2作为正极活性材料。
实施例1-39
镍钴铝酸锂LiNi 0.5Co 0.2Al 0.3O 2作为正极活性材料。
实施例1-40
镍钴铝酸锂LiNi 0.8Co 0.1Al 0.1O 2作为正极活性材料。
实施例1-41
钴酸锂LiCoO 2作为正极活性材料。
实施例1-42
将实施例1和实施例1-36的正极活性材料按照质量比1:1混合作为正极活性材料。
实施例1-43
将实施例1-1和实施例1-37的正极活性材料按照质量比1:1混合作为正极活性材料。
实施例1-44
将实施例1-1和实施例1-38的正极活性材料按照质量比1:1混合作为正极活性材料。
实施例1-45
将实施例1-1和实施例1-39的正极活性材料按照质量比1:1混合作为正极活性材料。
实施例1-46
将实施例1-1和实施例1-40的正极活性材料按照质量比1:1混合作为正极活性材料。
实施例1-47
将实施例1-1和实施例1-41的正极活性材料按照质量比1:1混合作为正极活性材料。
实施例2-1
除在焦磷酸铁锂(Li 2FeP 2O 7)的制备过程中在粉末烧结步骤中的烧结温度为550℃，烧结时间为1h以控制Li 2FeP 2O 7的结晶度为30％，在磷酸铁锂(LiFePO 4)的制备过程中在包覆烧结步骤中的烧结温度为650℃，烧结时间为2h以控制LiFePO 4的结晶度为30％以外，其他条件与实施例1-1相同。
实施例2-2
除在焦磷酸铁锂(Li 2FeP 2O 7)的制备过程中在粉末烧结步骤中的烧结温度为550℃，烧结时间为2h以控制Li 2FeP 2O 7的结晶度为50％，在磷酸铁锂(LiFePO 4)的制备过程中在包覆烧结步骤中的烧结温度为650℃，烧结时间为3h以控制LiFePO 4的结晶度为50％以外，其他条件与实施例1-1相同。
实施例2-3
除在焦磷酸铁锂(Li 2FeP 2O 7)的制备过程中在粉末烧结步骤中的烧结温度为600℃，烧结时间为3h以控制Li 2FeP 2O 7的结晶度为70％，在磷酸铁锂(LiFePO 4)的制备过程中在包覆烧结步骤中的烧结温度为650℃，烧结时间为4h以控制LiFePO 4的结晶度为70％以外，其他条件与实施例1-1相同。
实施例2-4
除在焦磷酸铁锂(Li 2FeP 2O 7)的制备过程中在粉末烧结步骤中的烧结温度为650℃，烧结时间为4h以控制Li 2FeP 2O 7的结晶度为100％，在磷酸铁锂(LiFePO 4)的制备过程中在包覆烧结步骤中的烧结温度为700℃，烧结时间为6h以控制LiFePO 4的结晶度为100％以外，其他条件与实施例1-1相同。
实施例3-1至3-12
除制备Fe、Co和V共掺杂的草酸锰颗粒的过程中，实施例3-1反应釜内的加热温度/搅拌时间分别为60℃/120分钟；实施例3-2反应釜内的加热温度/搅拌时间分别为70℃/120分钟；实施例3-3反应釜内的加热温度/搅拌时间分别为80℃/120分钟；实施例3-4反应釜内的加热温度/搅拌时间分别为90℃/120分钟；实施例3-5反应釜内的加热温度/搅拌时间分别为100℃/120分钟；实施例3-6反应釜内的加热温度/搅拌时间分别为110℃/120分钟；实施例3-7反应釜内的加热温度/搅拌时间分别为120℃/120分钟；实施例3-8反应釜内的加热 温度/搅拌时间分别为130℃/120分钟；实施例3-9反应釜内的加热温度/搅拌时间分别为100℃/60分钟；实施例3-10反应釜内的加热温度/搅拌时间分别为100℃/90分钟；实施例3-11反应釜内的加热温度/搅拌时间分别为100℃/150分钟；实施例3-12反应釜内的加热温度/搅拌时间分别为100℃/180分钟以外，实施例3-1至3-12的其他条件与实施例1-1相同。
实施例4-1至4-4：
除在焦磷酸铁锂(Li 2FeP 2O 7)的制备过程中在干燥步骤中的干燥温度/干燥时间分别为100℃/4h、150℃/6h、200℃/6h和200℃/6h；在焦磷酸铁锂(Li 2FeP 2O 7)的制备过程中在烧结步骤中的烧结温度和烧结时间分别为700℃/6h、700℃/6h、700℃/6h和600℃/6h以外，其它条件与实例1-7相同。
实施例4-5至4-7：
除在包覆过程中在干燥步骤中的干燥温度/干燥时间分别为150℃/6h、150℃/6h和150℃/6h；在包覆过程中在烧结步骤中的烧结温度和烧结时间分别为600℃/4h、600℃/6h和800℃/8h以外，其它条件与实例1-12相同。
对比例1
制备草酸锰：将1149.3g碳酸锰加至反应釜中，并加入5升去离子水和1260.6g二水合草酸(以C 2H 2O 4·2H 2O计，下同)。将反应釜加热至80℃，以600rpm的转速搅拌6小时，直至反应终止(无气泡产生)，得到草酸锰悬浮液，然后过滤悬浮液，将滤饼在120℃下烘干，之后进行研磨，得到中值粒径Dv50为100nm的二水草酸锰颗粒。
制备碳包覆的磷酸锰锂：取1789.6g上述获得的二水草酸锰颗粒、369.4g碳酸锂(以Li 2CO 3计，下同)，1150.1g磷酸二氢铵(以NH 4H 2PO 4计，下同)和31g蔗糖(以C 12H 22O 11计，下同)加入到20升去离子水中，将混合物搅拌10小时使其混合均匀，得到浆料。将浆料转移 到喷雾干燥设备中进行喷雾干燥造粒，设定干燥温度为250℃，干燥4小时，得到粉料。在氮气(90体积％)+氢气(10体积％)保护气氛中，将上述粉料在700℃下烧结4小时，得到碳包覆的磷酸锰锂。
对比例2
除使用689.5g的碳酸锰和额外添加463.3g的碳酸亚铁以外，对比例2的其他条件与对比例1相同。
对比例3
除使用1148.9g的磷酸二氢铵和369.0g碳酸锂，并额外添加1.6g的60％浓度的稀硫酸以外，对比例3的其他条件与对比例1相同。
对比例4
除使用689.5g的碳酸锰、1148.9g的磷酸二氢铵和369.0g碳酸锂，并额外添加463.3g的碳酸亚铁、1.6g的60％浓度的稀硫酸以外，对比例4的其他条件与对比例1相同。
对比例5
除额外增加以下步骤：制备焦磷酸铁锂粉末时，将9.52g碳酸锂、29.9g碳酸亚铁、29.6g磷酸二氢铵和32.5g二水合草酸溶于50ml去离子水中。混合物的pH为5，搅拌2小时使反应混合物充分反应。然后将反应后的溶液升温到80℃并保持该温度4小时，得到包含Li 2FeP 2O 7的悬浊液，将悬浊液进行过滤，用去离子水洗涤，并在120℃下干燥4h，得到粉末。将粉末在500℃、氮气气氛下烧结4小时，并自然冷却至室温后进行研磨，控制Li 2FeP 2O 7的结晶度为5％，制备碳包覆的材料时，Li 2FeP 2O 7的用量为62.8g以外，对比例5的其它条件与对比例4相同。
对比例6
除额外增加以下步骤：制备磷酸铁锂悬浊液时，将14.7g碳酸锂、 46.1g碳酸亚铁、45.8g磷酸二氢铵和50.2g二水合草酸溶于500ml去离子水中，然后搅拌6小时使混合物充分反应。然后将反应后的溶液升温到120℃并保持该温度6小时，得到包含LiFePO 4的悬浊液，在磷酸铁锂(LiFePO 4)的制备过程中在包覆烧结步骤中的烧结温度为600℃，烧结时间为4h以控制LiFePO 4的结晶度为8％以外，制备碳包覆的材料时，LiFePO 4的用量为62.8g以外，对比例6的其它条件与对比例4相同。
对比例7
制备焦磷酸铁锂粉末：将2.38g碳酸锂、7.5g碳酸亚铁、7.4g磷酸二氢铵和8.1g二水合草酸溶于50ml去离子水中。混合物的pH为5，搅拌2小时使反应混合物充分反应。然后将反应后的溶液升温到80℃并保持该温度4小时，得到包含Li 2FeP 2O 7的悬浊液，将悬浊液进行过滤，用去离子水洗涤，并在120℃下干燥4h，得到粉末。将粉末在500℃、氮气气氛下烧结4小时，并自然冷却至室温后进行研磨，控制Li 2FeP 2O 7的结晶度为5％。
制备磷酸铁锂悬浊液：将11.1g碳酸锂、34.7g碳酸亚铁、34.4g磷酸二氢铵、37.7g二水合草酸和37.3g蔗糖(以C 12H 22O 11计，下同)溶于1500ml去离子水中，然后搅拌6小时使混合物充分反应。然后将反应后的溶液升温到120℃并保持该温度6小时，得到包含LiFePO 4的悬浊液。
将得到的焦磷酸铁锂粉末15.7g，加入上述磷酸铁锂(LiFePO 4)和蔗糖悬浊液中，制备过程中在包覆烧结步骤中的烧结温度为600℃，烧结时间为4h以控制LiFePO 4的结晶度为8％以外，对比例7的其它条件与对比例4相同，得到非晶态焦磷酸铁锂、非晶态磷酸铁锂、碳包覆的正极活性材料。
对比例8-11
除在焦磷酸铁锂(Li 2FeP 2O 7)的制备过程中在干燥步骤中的干燥温度/干燥时间在对比例8-10中分别为80℃/3h、80℃/3h、80℃/3h； 在焦磷酸铁锂(Li 2FeP 2O 7)的制备过程中在烧结步骤中的烧结温度和烧结时间在对比例8-10中分别为400℃/3h、400℃/3h、350℃/2h；对比例11在磷酸铁锂(LiFePO 4)的制备过程中在干燥步骤中的干燥温度/干燥时间为80℃/3h；以及在对比例8-11中Li 2FeP 2O 7/LiFePO 4的用量分别为47.2g/15.7g、15.7g/47.2g、62.8g/0g、0g/62.8g以外，其他条件与实施例1-7相同。
将上述制备的正极活性材料、导电剂超导炭黑(Super-P)、粘结剂聚偏二氟乙烯(PVDF)按重量比为92：2.5：5.5加入到N-甲基吡咯烷酮(NMP)中，搅拌混合均匀，得到固含量为60％w/w的正极活性材料的浆料。
正极极片的制备
实施例5-1
将实施例1-1正极活性材料的浆料以0.019g/cm 2的涂布量均匀涂在集流体铝箔的两面，在100～120℃的高温下真空干燥14h，辊压机压实，得到正极极片P1。
实施例5-2
将实施例1-34正极活性材料的浆料以0.019g/cm 2的涂布量均匀涂在集流体铝箔的两面，在100～120℃的高温下真空干燥14h，辊压机压实，得到正极极片P2。
实施例5-3
将实施例1-1正极活性材料的浆料以0.019g/cm 2的涂布量均匀涂布在铝箔的一面上，将实施例1-34正极活性材料的浆料以0.019g/cm 2的涂布量均匀涂布在铝箔的另一面上，在100～120℃的高温下真空干燥14h，辊压机压实，得到正极极片P3。
实施例5-4
将实施例1-35正极活性材料的浆料以0.019g/cm 2的涂布量均匀涂在集流体铝箔的两面，其他与实施例5-3相同，得到正极极片P4。
实施例5-5
将实施例1-1正极活性材料的浆料以0.019g/cm 2的涂布量均匀涂布在铝箔的一面上，将实施例1-35正极活性材料的浆料以0.019g/cm 2的涂布量均匀涂布在铝箔的另一面上，其他与实施例5-3相同，得到正极极片P5。
实施例5-6
将实施例1-34正极活性材料的浆料以0.019g/cm 2的涂布量均匀涂布在铝箔的一面上，将实施例1-35正极活性材料的浆料以0.019g/cm 2的涂布量均匀涂布在铝箔的另一面上，其他与实施例5-3相同，得到正极极片P6。
实施例5-7
在铝箔的两面均依次涂布实施例1-1正极活性材料的浆料和实施例1-34正极活性材料的浆料，每层浆料的涂布量均为0.010g/cm 2，然后，在100～120℃高温真空干燥14h，辊压机压实，得到正极极片P7。
实施例5-8
在铝箔的两面均依次涂布实施例1-34正极活性材料的浆料和实施例1-1正极活性材料的浆料，每层浆料的涂布量均为0.010g/cm 2，其他与实施例5-7相同，得到正极极片P8。
实施例5-9
在铝箔的两面均依次涂布实施例1-1正极活性材料的浆料和实施例1-35正极活性材料的浆料，每层浆料的涂布量均为0.010g/cm 2，其他与实施例5-7相同，得到正极极片P9。
实施例5-10
在铝箔的两面均依次涂布实施例1-35正极活性材料的浆料和实施例1-1正极活性材料的浆料，每层浆料的涂布量均为0.010g/cm 2，其他与实施例5-7相同，得到正极极片P10。
实施例5-11
在铝箔的两面均依次涂布实施例1-34正极活性材料的浆料和实施例1-35正极活性材料的浆料，每层浆料的涂布量均为0.010g/cm 2，其他与实施例5-7相同，得到正极极片P11。
实施例5-12
在铝箔的两面均依次涂布实施例1-35正极活性材料的浆料和实施例1-34正极活性材料的浆料，每层浆料的涂布量均为0.010g/cm 2，其他与实施例5-7相同，得到正极极片P12。
实施例5-13
在铝箔的A面依次涂布实施例1-1正极活性材料的浆料和实施例1-34正极活性材料的浆料，每层浆料的涂布量均为0.010g/cm 2，在铝箔的B面均匀涂布实施例1-1正极活性材料的浆料，浆料的涂布量为0.020g/cm 2，然后，在100～120℃高温真空干燥14h，辊压机压实，得到正极极片P13。
实施例5-14
在铝箔的A面依次涂布实施例1-1正极活性材料的浆料和实施例1-34正极活性材料的浆料，每层浆料的涂布量均为0.010g/cm 2，在铝箔的B面均匀涂布实施例1-34正极活性材料的浆料，浆料的涂布量为0.020g/cm 2，其他与实施例5-13相同，得到正极极片P14。
实施例5-15
在铝箔的A面依次涂布实施例1-1正极活性材料的浆料和实施例1-34正极活性材料的浆料，每层浆料的涂布量均为0.010g/cm 2，在铝箔的B面均匀涂布实施例1-35正极活性材料的浆料，浆料的涂布量为0.020g/cm 2，其他与实施例5-13相同，得到正极极片P15。
实施例5-16
在铝箔的A面依次涂布实施例1-34正极活性材料的浆料和实施例1-1正极活性材料的浆料，每层浆料的涂布量均为0.010g/cm 2，在铝箔的B面均匀涂布实施例1-1正极活性材料的浆料，浆料的涂布量为0.020g/cm 2，其他与实施例5-13相同，得到正极极片P16。
实施例5-17
在铝箔的A面依次涂布实施例1-34正极活性材料的浆料和实施例1-1正极活性材料的浆料，每层浆料的涂布量均为0.010g/cm 2，在铝箔的B面均匀涂布实施例1-34正极活性材料的浆料，浆料的涂布量为0.020g/cm 2，其他与实施例5-13相同，得到正极极片P17。
实施例5-18
在铝箔的A面依次涂布实施例1-34正极活性材料的浆料和实施例1-1正极活性材料的浆料，每层浆料的涂布量均为0.010g/cm 2，在铝箔的B面均匀涂布实施例1-35正极活性材料的浆料，浆料的涂布量为0.020g/cm 2，其他与实施例5-13相同，得到正极极片P18。
实施例5-19
在铝箔的A面依次涂布实施例1-1正极活性材料的浆料和实施例1-35正极活性材料的浆料，每层浆料的涂布量均为0.010g/cm 2，在铝箔的B面均匀涂布实施例1-1正极活性材料的浆料，浆料的涂布量为0.020g/cm 2，其他与实施例5-13相同，得到正极极片P19。
实施例5-20
在铝箔的A面依次涂布实施例1-1正极活性材料的浆料和实施例1-35正极活性材料的浆料，每层浆料的涂布量均为0.010g/cm 2，在铝箔的B面均匀涂布实施例1-34正极活性材料的浆料，浆料的涂布量为0.020g/cm 2，其他与实施例5-13相同，得到正极极片P20。
实施例5-21
在铝箔的A面依次涂布实施例1-1正极活性材料的浆料和实施例1-35正极活性材料的浆料，每层浆料的涂布量均为0.010g/cm 2，在铝箔的B面均匀涂布实施例1-35正极活性材料的浆料，浆料的涂布量为0.020g/cm 2，其他与实施例5-13相同，得到正极极片P21。
实施例5-22
在铝箔的A面依次涂布实施例1-35正极活性材料的浆料和实施例1-1正极活性材料的浆料，每层浆料的涂布量均为0.010g/cm 2，在铝箔的B面均匀涂布实施例1-1正极活性材料的浆料，浆料的涂布量为0.020g/cm 2，其他与实施例5-13相同，得到正极极片P22。
实施例5-23
在铝箔的A面依次涂布实施例1-35正极活性材料的浆料和实施例1-1正极活性材料的浆料，每层浆料的涂布量均为0.010g/cm 2，在铝箔的B面均匀涂布实施例1-34正极活性材料的浆料，浆料的涂布量为0.020g/cm 2，其他与实施例5-13相同，得到正极极片P23。
实施例5-24
在铝箔的A面依次涂布实施例1-35正极活性材料的浆料和实施例1-1正极活性材料的浆料，每层浆料的涂布量均为0.010g/cm 2，在铝箔的B面均匀涂布实施例1-35正极活性材料的浆料，浆料的涂布量为0.020g/cm 2，其他与实施例5-13相同，得到正极极片P24。
实施例5-25
在铝箔的A面依次涂布实施例1-34正极活性材料的浆料和实施例1-35正极活性材料的浆料，每层浆料的涂布量均为0.010g/cm 2，在铝箔的B面均匀涂布实施例1-1正极活性材料的浆料，浆料的涂布量为0.020g/cm 2，其他与实施例5-13相同，得到正极极片P25。
实施例5-26
在铝箔的A面依次涂布实施例1-34正极活性材料的浆料和实施例1-35正极活性材料的浆料，每层浆料的涂布量均为0.010g/cm 2，在铝箔的B面均匀涂布实施例1-34正极活性材料的浆料，浆料的涂布量为0.020g/cm 2，其他与实施例5-13相同，得到正极极片P26。
实施例5-27
在铝箔的A面依次涂布实施例1-34正极活性材料的浆料和实施例1-35正极活性材料的浆料，每层浆料的涂布量均为0.010g/cm 2，在铝箔的B面均匀涂布实施例1-35正极活性材料的浆料，浆料的涂布量为0.020g/cm 2，其他与实施例5-13相同，得到正极极片P27。
实施例5-28
在铝箔的A面依次涂布实施例1-35正极活性材料的浆料和实施例1-34正极活性材料的浆料，每层浆料的涂布量均为0.010g/cm 2，在铝箔的B面均匀涂布实施例1-1正极活性材料的浆料，浆料的涂布量为0.020g/cm 2，其他与实施例5-13相同，得到正极极片P28。
实施例5-29
在铝箔的A面依次涂布实施例1-35正极活性材料的浆料和实施例1-34正极活性材料的浆料，每层浆料的涂布量均为0.010g/cm 2，在铝箔的B面均匀涂布实施例1-34正极活性材料的浆料，浆料的涂布量为0.020g/cm 2，其他与实施例5-13相同，得到正极极片P29。
实施例5-30
在铝箔的A面依次涂布实施例1-35正极活性材料的浆料和实施例1-34正极活性材料的浆料，每层浆料的涂布量均为0.010g/cm 2，在铝箔的B面均匀涂布实施例1-35正极活性材料的浆料，浆料的涂布量为0.020g/cm 2，其他与实施例5-13相同，得到正极极片P30。
实施例5-31
将实施例1-36正极活性材料的浆料以0.019g/cm 2的涂布量均匀涂在集流体铝箔的两面，在100～120℃的高温下真空干燥14h，辊压机压实，得到正极极片P31。
实施例5-32
将实施例1-37正极活性材料的浆料以0.019g/cm 2的涂布量均匀涂在集流体铝箔的两面，在100～120℃的高温下真空干燥14h，辊压机压实，得到正极极片P32。
实施例5-33
将实施例1-38正极活性材料的浆料以0.019g/cm 2的涂布量均匀涂在集流体铝箔的两面，在100～120℃的高温下真空干燥14h，辊压机压实，得到正极极片P33。
实施例5-34
将实施例1-39正极活性材料的浆料以0.019g/cm 2的涂布量均匀涂在集流体铝箔的两面，在100～120℃的高温下真空干燥14h，辊压机压实，得到正极极片P34。
实施例5-35
将实施例1-40正极活性材料的浆料以0.019g/cm 2的涂布量均匀涂在集流体铝箔的两面，在100～120℃的高温下真空干燥14h，辊压机压实，得到正极极片P35。
实施例5-36
将实施例1-41正极活性材料的浆料以0.019g/cm 2的涂布量均匀涂在集流体铝箔的两面，在100～120℃的高温下真空干燥14h，辊压机压实，得到正极极片P36。
实施例5-37
将实施例1-42正极活性材料的浆料以0.019g/cm 2的涂布量均匀涂在集流体铝箔的两面，其他与实施例5-3相同，得到正极极片P37。
实施例5-38
将实施例1-43正极活性材料的浆料以0.019g/cm 2的涂布量均匀涂在集流体铝箔的两面，其他与实施例5-3相同，得到正极极片P38。
实施例5-39
将实施例1-44正极活性材料的浆料以0.019g/cm 2的涂布量均匀涂在集流体铝箔的两面，其他与实施例5-3相同，得到正极极片P39。
实施例5-40
将实施例1-45正极活性材料的浆料以0.019g/cm 2的涂布量均匀涂在集流体铝箔的两面，其他与实施例5-3相同，得到正极极片P40。
实施例5-41
将实施例1-46正极活性材料的浆料以0.019g/cm 2的涂布量均匀涂在集流体铝箔的两面，其他与实施例5-3相同，得到正极极片P41。
实施例5-42
将实施例1-47正极活性材料的浆料以0.019g/cm 2的涂布量均匀涂在集流体铝箔的两面，其他与实施例5-3相同，得到正极极片P42。
以上各正极极片的参数见表1。
表1 正极极片的参数
Figure PCTCN2022079269-appb-000001
Figure PCTCN2022079269-appb-000002
Figure PCTCN2022079269-appb-000003
Figure PCTCN2022079269-appb-000004
Figure PCTCN2022079269-appb-000005
“*”：第1层指与铝箔表面接触的一层，第2层指设置在第1层上的一层。
“#”：第一正极活性材料为实施例1-1制得的正极活性材料，第二正极活性材料为实施例1-34、实施例1-36、实施例1-37、实施例1-38、实施例1-39、实施例1-40或实施例1-41的正极活性材料。
负极极片的制备
将负极活性材料人造石墨、导电剂超导炭黑(Super-P)、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC-Na)按照质量比为95％：1.5％：1.8％：1.7％溶于去离子水中，充分搅拌混合均匀后，得到粘度3000mPa.s、固含52％的负极浆料；将负极浆料涂覆在6μm的负极集流体铜箔上，之后在100℃烘烤4小时以烘干，辊压，得到压实密度为1.75g/cm 3的负极极片。
隔离膜
采用聚丙烯膜。
电解液的制备
将碳酸乙烯酯、碳酸二甲酯和1,2-丙二醇碳酸酯按体积比1:1:1 混合，然后将LiPF 6均匀溶解在上述溶液中，得到电解液。该电解液中，LiPF 6的浓度为1mol/L。
全电池的制备
采用上述的正极极片，按照负极极片、隔膜、正极极片的顺序，采用卷绕法形成裸电芯，分别冲切出铝极耳和铜极耳，得到裸电芯；通过转接片将两个裸电芯铜与铜极耳，铝与铝极耳一起焊接到电池顶盖上，对裸电芯进行包裹绝缘后，将裸电芯装入铝壳中，将顶盖与铝壳焊接形成干电芯，对干电芯进行烘烤除水后注入电解液，对电池进行化成和老化，相应地得到全电池。其中，正极极片P1、P2、P3、P8、P10、P11、P12、P17、P18、P23、P24、P26、P27所制的电池结构如图8-20所示。
扣式电池的制备
将上述制备的正极活性材料、PVDF、乙炔黑以90：5：5的重量比加入至NMP中，在干燥房中搅拌制成浆料。在铝箔上涂覆上述浆料，干燥、冷压制成正极极片。涂覆量为0.2g/cm 2，压实密度为2.0g/cm 3。
采用锂片作为负极，采用1mol/L的LiPF 6在体积比1：1：1的碳酸亚乙酯(EC)+碳酸二乙酯(DEC)+碳酸二甲酯(DMC)中的溶液作为电解液，与上述制备的正极极片一起在扣电箱中组装成扣式电池(下文也称“扣电”)。
正极活性材料的性质测试
1.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第一、二包覆层的组成。
2.扣式电池初始克容量测试：
在2.5～4.3V下，将上述制得的扣式电池按照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。
3.扣电平均放电电压(V)测试：
将上述制得的扣式电池在25℃恒温环境下，静置5min，按照0.1C放电至2.5V，静置5min，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2.5V，此时的放电容量为初始克容量，记为D0，放电能量为初始能量，记为E0，扣电平均放电电压V即为E0/D0。
4.全电池60℃胀气测试：
在60℃下，存储100％充电状态(SOC)的上述制得的全电池。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。
另外，测量电芯残余容量。在2.5～4.3V下，将全电池按照1C充电至4.3V，然后在4.3V下恒压充电至电流小于等于0.05mA。静置5min，记录此时的充电容量为电芯残余容量。
5.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，将上述制得的全电池按 照1C充电至4.3V，然后在4.3V下恒压充电至电流小于等于0.05mA。静置5min，然后按照1C放电至2.5V，记录此时的放电容量为D0。重复前述充放电循环，直至放电容量降低到D0的80％。记录此时电池经过的循环圈数。
6.晶格变化率测试：
在25℃恒温环境下，将上述制得的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)。
采用上述扣电制备方法，将所述正极活性材料样品制备成扣电，并对上述扣电以0.05C小倍率进行充电，直至电流减小至0.01C。然后将扣电中的正极极片取出，并置于碳酸二甲酯(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)示于表中。
7.Li/Mn反位缺陷浓度测试：
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。
8.过渡金属溶出测试：
将45℃下循环至容量衰减至80％后的全电池采用0.1C倍率进行放电至截止电压2.0V。然后将电池拆开，取出负极极片，在负极极片上随机取30个单位面积(1540.25mm 2)的圆片，用Agilent  ICP-OES730测试电感耦合等离子体发射光谱(ICP)。根据ICP结果计算其中Fe(如果正极活性材料的Mn位掺杂有Fe的话)和Mn的量，从而计算循环后Mn(以及Mn位掺杂的Fe)的溶出量。测试标准依据EPA-6010D-2014。
9.表面氧价态测试：
取5g上述制得的正极活性材料样品按照上述扣电制备方法制备成扣电。对扣电采用0.05C小倍率进行充电，直至电流减小至0.01C。然后将扣电中的正极极片取出，并置于碳酸二甲酯(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。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。
10.压实密度测量：
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，用于测试的容器的面积为1540.25mm 2)，通过ρ＝m/v，计算出压实密度。
11.X射线衍射法测试焦磷酸盐和磷酸盐的结晶度
取5g上述制得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、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与散射总强度之比。
12.晶面间距和夹角
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。
以上的结果见表2-5。
Figure PCTCN2022079269-appb-000006
Figure PCTCN2022079269-appb-000007
Figure PCTCN2022079269-appb-000008
Figure PCTCN2022079269-appb-000009
Figure PCTCN2022079269-appb-000010
Figure PCTCN2022079269-appb-000011
综合实施例1-1至1-33以及对比例1-4可知，第一包覆层的存在有利于降低所得材料的Li/Mn反位缺陷浓度和循环后Fe和Mn溶出量，提高电池的扣电克容量，并改善电池的安全性能和循环性能。当在Mn位和磷位分别掺杂其他元素时，可显著降低所得材料的晶格变化率、反位缺陷浓度和Fe和Mn溶出量，提高电池的克容量，并改善电池的安全性能和循环性能。
综合实施例1-1至1-6可知，随着第一包覆层的量从3.2％增加至6.4％，所得材料的Li/Mn反位缺陷浓度逐渐下降，循环后Fe和Mn溶出量逐渐下降，对应电池的安全性能和45℃下的循环性能也得到改善，但扣电克容量略有下降。可选地，当第一包覆层的总量为4-5.6重量％时，对应电池的综合性能最佳。
综合实施例1-3以及实施例1-7至1-10可知，随着第二包覆层的量从1％增加至6％，所得材料的Li/Mn反位缺陷浓度逐渐下降，循环后Fe和Mn溶出量逐渐下降，对应电池的安全性能和45℃下的循环性能也得到改善，但扣电克容量却略有下降。可选地，当第二包覆层的总量为3-5重量％时，对应电池的综合性能最佳。
综合实施例1-11至1-15以及对比例5-6可知，当第一包覆层中同时存在Li 2FeP 2O 7和LiFePO 4、特别是Li 2FeP 2O 7和LiFePO 4的重量比为1：3至3：1，并且尤其是1：3至1：1时，对电池性能的改善更加明显。
Figure PCTCN2022079269-appb-000012
Figure PCTCN2022079269-appb-000013
Figure PCTCN2022079269-appb-000014
Figure PCTCN2022079269-appb-000015
电池测试
采用正极极片P1-P42制备的二次电池进行如下测试：
(1)按照国标GB 38031-2020“电动汽车用动力蓄电池安全要求”中的方法测定二次电池的能量密度和炉温实验结果；
(2)针刺测试：将二次电池充满至100％SOC，用Φ8mm钢针以25mm/2的速度刺穿电芯，观察1h，如未发生起火，则通过测试；
(3)按照国标GBT31486-2015“电动汽车用动力蓄电池电性能要求及试验方法”测定二次电池的室温1C倍率充电容量保持率以及低温放电容量保持率，获得电芯动力学性能数据；
(4)按照国标GBT31484-2015“电动汽车用动力蓄电池循环寿命要求及试验方法”测定二次电池的循环寿命数据；
上述结果见表6。
表6 电池测试的结果
Figure PCTCN2022079269-appb-000016
Figure PCTCN2022079269-appb-000017
Figure PCTCN2022079269-appb-000018
Figure PCTCN2022079269-appb-000019
根据上述结果可知：
与采用正极极片P1的二次电池相比，采用正极极片P3-P30、P37-P42的二次电池的能量密度更高、室温倍率充电容量保持率和低温放电容量保持率更高，并且顺利通过炉温实验和针刺测试。相较于采用正极极片P3-P30的二次电池，采用正极极片P2的二次电池没能通过炉温实验和针刺测试，测试过程中发生起火，采用正极极片P3-P30的二次电池比采用正极极片P2的二次电池的循环寿命更长。相较于采用正极极片P37-P42的二次电池，采用正极极片P31-P36的二次电池没能通过炉温实验和针刺测试，测试过程中发生起火；正极极片P37-P42包含第一正极活性材料和第二正极活性材料，正极极片P31-P36包含等量的与之对应的第二正极活性材料，可知，采用包含第一正极活性材料和第二正极活性材料的正极极片的二次电池比采用单一包含第二正极活性材料的正极极片的二次电池的循环寿命更长。
以上说明，本申请正极极片所制二次电池的能量密度更高，电芯倍率性能更高，动力学性能和低温性能更好，循环寿命更长，同时安全性更高。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。

Claims (19)

  1. 一种正极极片，包括正极集流体和设置在所述正极集流体的至少一个表面上的正极膜层；所述正极膜层为单层结构或多层结构；当所述正极膜层为单层结构时，至少一个所述正极膜层同时包含具有核-壳结构的第一正极活性材料和第二正极活性材料；和/或，当所述正极膜层为多层结构时，至少一个所述正极膜层的至少一层中同时包含具有核-壳结构的第一正极活性材料和第二正极活性材料；
    所述第一正极活性材料包括内核、包覆所述内核的第一包覆层以及包覆所述第一包覆层的第二包覆层；其中，所述内核包含Li 1+xMn 1-yA yP 1-zR zO 4，所述第一包覆层包含焦磷酸盐MP 2O 7和磷酸盐XPO 4，所述第二包覆层包含碳元素；
    其中，
    A选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素；
    R选自B、Si、N和S中的一种或多种元素；
    x选自-0.100-0.100范围内的任意数值；
    y选自0.001-0.500范围内的任意数值；
    z选自0.001-0.100范围内的任意数值；
    M和X独立地选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb和Al中的一种或多种元素；
    所述第二正极活性材料选自LiNi aCo bMn (1-a-b)O 2、LiNi aCo bAl (1-a-b)O 2和LiCoO 2中的一种或多种；其中，a独立地选自0.3-0.9范围内的任意数值(可选为0.33-0.8)，a与b之和独立地选自0.3-0.9范围内的任意数值(可选为0.66-0.9)。
  2. 一种正极极片，包括正极集流体和设置在所述正极集流体的至少一个表面上的正极膜层；至少一个所述正极膜层为多层结构，任一具有多层结构的正极膜层在不同层中分别包含具有核-壳结构的第 一正极活性材料和第二正极活性材料；
    所述第一正极活性材料包括内核、包覆所述内核的第一包覆层以及包覆所述第一包覆层的第二包覆层；其中，所述内核包含Li 1+xMn 1-yA yP 1-zR zO 4，所述第一包覆层包含焦磷酸盐MP 2O 7和磷酸盐XPO 4，所述第二包覆层包含碳元素；
    其中，
    A选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素；
    R选自B、Si、N和S中的一种或多种元素；
    x选自-0.100-0.100；
    y选自0.001-0.500；
    z选自0.001-0.100；
    M和X独立地选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb和Al中的一种或多种元素；
    所述第二正极活性材料选自LiNi aCo bMn (1-a-b)O 2、LiNi aCo bAl (1-a-b)O 2和LiCoO 2中的一种或多种；其中，a独立地选自0.3-0.9范围内的任意数值(可选为0.33-0.8)，a与b之和独立地选自0.3-0.9范围内的任意数值(可选为0.66-0.9)；
    可选地，任一具有多层结构的所述正极膜层在相邻层中分别包含所述第一正极活性材料和所述第二正极活性材料。
  3. 一种正极极片，包括正极集流体和分别设置在所述正极集流体的两个表面上的正极膜层A和正极膜层B；所述正极膜层A和所述正极膜层B各自独立地为单层结构或多层结构；所述正极膜层A的至少一层中包含具有核-壳结构的第一正极活性材料，同时，所述正极膜层B的至少一层中包含第二正极活性材料；
    所述第一正极活性材料包括内核、包覆所述内核的第一包覆层以及包覆所述第一包覆层的第二包覆层；其中，所述内核包含Li 1+xMn 1-yA yP 1-zR zO 4，所述第一包覆层包含焦磷酸盐MP 2O 7和磷酸盐XPO 4，所述第二包覆层包含碳元素；
    其中，
    A选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种元素；
    R选自B、Si、N和S中的一种或多种元素；
    x选自-0.100-0.100；
    y选自0.001-0.500；
    z选自0.001-0.100；
    M和X独立地选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb和Al中的一种或多种元素；
    所述第二正极活性材料选自LiNi aCo bMn (1-a-b)O 2、LiNi aCo bAl (1-a-b)O 2和LiCoO 2中的一种或多种；其中，a独立地选自0.3-0.9范围内的任意数值(可选为0.33-0.8)，a与b之和独立地选自0.3-0.9范围内的任意数值(可选为0.66-0.9)。
  4. 根据权利要求1至3中任一项所述的正极极片，其中，所述第一活性材料与所述第二活性材料的质量比为1:7-7:1，可选为1:4-4:1。
  5. 根据权利要求1至4中任一项所述的正极极片，其中，所述第一正极活性材料中，
    A选自Zn、Fe、Ti、V、Ni、Co和Mg中的一种或多种元素；和/或，
    A选自Fe、Ti、V、Ni、Co和Mg中的至少两种元素；和/或，
    x选自-0.100-0.006范围内的任意数值；和/或，
    y选自0.1-0.4范围内的任意数值；和/或，
    M和X独立地选自Li和Fe中的一种或多种元素；和/或，
    y与1-y的比值选自1:10至10:1，可选为1:4至1:1；和/或，
    z与1-z的比值选自1:999至1:9，可选为1:499至1:249。
  6. 根据权利要求1至5中任一项所述的正极极片，其中，所述第一正极活性材料中，所述第一包覆层中的磷酸盐的晶面间距为 0.345-0.358nm，晶向(111)的夹角为24.25°-26.45°；所述第一包覆层中的焦磷酸盐的晶面间距为0.293-0.326nm，晶向(111)的夹角为26.41°-32.57°。
  7. 根据权利要求1至6中任一项所述的正极极片，其中，所述第一正极活性材料中，所述第一包覆层的包覆量为大于0重量％且小于等于7重量％，可选为4-5.6重量％，基于所述内核的重量计。
  8. 根据权利要求1至7中任一项所述的正极极片，其中，所述第一正极活性材料中，所述第一包覆层中焦磷酸盐和磷酸盐的重量比为1:3至3:1，可选为1:3至1:1。
  9. 根据权利要求1至8中任一项所述的正极极片，其中，所述第一正极活性材料中，所述焦磷酸盐和磷酸盐的结晶度各自独立地为10％至100％，可选为50％至100％。
  10. 根据权利要求1至9中任一项所述的正极极片，其中，所述第一正极活性材料中，所述第二包覆层的包覆量为大于0重量％且小于等于6重量％，可选为3-5重量％，基于所述内核的重量计。
  11. 根据权利要求1至10中任一项所述的正极极片，其中，所述第一正极活性材料的Li/Mn反位缺陷浓度为4％以下，可选为2％以下。
  12. 根据权利要求1至11中任一项所述的正极极片，其中，所述第一正极活性材料的晶格变化率为6％以下，可选为4％以下。
  13. 根据权利要求1至12中任一项所述的正极极片，其中，所述第一正极活性材料的表面氧价态为-1.88以下，可选地为-1.98～-1.88。
  14. 根据权利要求1至13中任一项所述的正极极片，其中，所述第一正极活性材料在3吨(T)下的压实密度为2.0g/cm 3以上，可选地为2.2g/cm 3以上。
  15. 根据权利要求1至14中任一项所述的正极极片，其中，所述第一正极活性材料和所述第二正极活性材料的质量之和占所述正极极片的质量的88％-98.7％。
  16. 一种二次电池，包括权利要求1至15中任一项所述的正极极片。
  17. 一种电池模块，包括权利要求16所述的二次电池。
  18. 一种电池包，包括权利要求17所述的电池模块。
  19. 一种用电装置，包括选自权利要求16所述的二次电池、权利要求17所述的电池模块和权利要求18所述的电池包中的至少一种。
PCT/CN2022/079269 2022-03-04 2022-03-04 一种正极极片、二次电池、电池模块、电池包和用电装置 WO2023164926A1 (zh)

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