WO2023184489A1 - 二次电池、电池模块、电池包和用电装置 - Google Patents

二次电池、电池模块、电池包和用电装置 Download PDF

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WO2023184489A1
WO2023184489A1 PCT/CN2022/084834 CN2022084834W WO2023184489A1 WO 2023184489 A1 WO2023184489 A1 WO 2023184489A1 CN 2022084834 W CN2022084834 W CN 2022084834W WO 2023184489 A1 WO2023184489 A1 WO 2023184489A1
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group
optionally
secondary battery
carbonate
coating layer
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French (fr)
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张立美
陈培培
蒋耀
刘姣
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Contemporary Amperex Technology Co Ltd
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Contemporary Amperex Technology Co Ltd
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Priority to CN202280040020.4A priority Critical patent/CN117425976A/zh
Priority to EP22934325.6A priority patent/EP4386898B1/en
Priority to PCT/CN2022/084834 priority patent/WO2023184489A1/zh
Publication of WO2023184489A1 publication Critical patent/WO2023184489A1/zh
Priority to US18/736,563 priority patent/US12183917B2/en
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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
    • H01M4/13—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
    • 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
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • 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
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0569—Liquid materials characterised by the solvents
    • 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
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—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
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • 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
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B25/00—Phosphorus; Compounds thereof
    • C01B25/16—Oxyacids of phosphorus; Salts thereof
    • C01B25/26—Phosphates
    • C01B25/45—Phosphates containing plural metal, or metal and ammonium
    • 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
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0568—Liquid materials characterised by the solutes
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2300/00—Electrolytes
    • H01M2300/0017—Non-aqueous electrolytes
    • H01M2300/0025—Organic electrolyte
    • H01M2300/0028—Organic electrolyte characterised by the solvent
    • H01M2300/0037—Mixture of solvents
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the technical field of lithium batteries, and in particular to a secondary battery, a battery module, a battery pack and an electrical device.
  • lithium-ion batteries are widely used in energy storage power systems such as hydraulic, thermal, wind and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, Military equipment, aerospace and other fields. Due to the great development of lithium-ion batteries, higher requirements have been put forward for their energy density, cycle performance and safety performance.
  • lithium manganese phosphate cathode active materials Compared with other cathode active materials, lithium manganese phosphate cathode active materials have higher safety and cycle life.
  • the disadvantage of lithium manganese phosphate is poor rate performance. Currently, this is usually solved by coating or doping. One question. However, it is still hoped that the rate performance, cycle performance, high temperature stability, etc. of lithium manganese phosphate cathode active materials can be further improved.
  • This application was made in view of the above problems, and its purpose is to provide a secondary battery, a battery module, a battery pack and a power device to solve the problems of poor rate performance and cycle performance of lithium manganese phosphate secondary batteries.
  • R is selected from one or more of the group consisting of B, Si, N and S;
  • the shell includes a first coating layer that covers the core and a first coating layer that covers the core.
  • a second coating layer of the coating wherein the first coating layer includes pyrophosphate MP 2 O 7 and phosphate XPO 4 , wherein M and X are each independently selected from Li, Fe, Ni, Mg, Co, Cu , one or more from the group consisting of Zn, Ti, Ag, Zr, Nb and Al, the second coating layer includes carbon;
  • the non-aqueous electrolyte solution includes a first additive, and the first additive includes one or more of the group consisting of a compound represented by Formula 1, a compound represented by Formula 2, and a compound represented by Formula 3,
  • R 1 and R 2 each independently represent F, C1 to C6 fluoroalkyl group, C1 to C6 alkyl group, C1 to C6 alkoxy group, C2 to C6 alkenyl group, C2 to C6 alkynyl group, C6 Any one of ⁇ C10 aryl groups, and at least one of R 1 and R 2 represents any one of F or C1 to C6 fluoroalkyl groups;
  • R 3 and R 4 are each independently F, any of a C1-C6 fluoroalkyl group, a C1-C6 alkyl group, a C1-C6 alkoxy group, a C2-C6 alkenyl group, or a C2-C6 alkynyl group.
  • One, and at least one of R 3 and R 4 represents any one of F or C1 to C6 fluoroalkyl;
  • M in each chemical formula independently represents one of alkali metals and alkaline earth metals
  • n 0, 1 or 2.
  • the above limitation on the numerical range of y is not only a limitation on the stoichiometric number of each element as A, but also on the stoichiometric number of 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 of y defined in this application, and y1 , y2...yn and the sum must also fall within this numerical range.
  • the limitation on the numerical range of the R stoichiometric number in this application also has the above meaning.
  • the lithium manganese phosphate cathode active material of the present application has a core-shell structure with two coating layers, in which the core includes Li 1+x Mn 1-y A y P 1-z R z O 4 .
  • the element A doped in the manganese position of lithium manganese phosphate in the core helps to reduce the lattice change rate of lithium manganese phosphate during the lithium deintercalation process, improves the structural stability of the lithium manganese phosphate cathode material, and greatly reduces the dissolution of manganese. And reduce the oxygen activity on the particle surface.
  • the element R doped at the phosphorus site helps change the ease of Mn-O bond length change, thereby reducing the lithium ion migration barrier, promoting lithium ion migration, and improving the rate performance of secondary batteries.
  • the first coating layer of the cathode active material of the present application includes pyrophosphate and phosphate. Since the migration barrier of transition metals in pyrophosphate is high (>1eV), it can effectively inhibit the dissolution of transition metals. Phosphate has excellent ability to conduct lithium ions and can reduce the surface miscellaneous lithium content. In addition, since the second coating layer is a carbon-containing layer, it can effectively improve the conductive properties and desolvation ability of LiMnPO 4 . In addition, the "barrier" function of the second coating layer can further hinder the migration of manganese ions into the electrolyte and reduce the corrosion of the active material by the electrolyte.
  • this application uses specific element doping and surface coating of lithium manganese phosphate to effectively suppress the dissolution of manganese ions during the process of deintercalation of lithium, and at the same time promote the migration of lithium ions, thereby improving the rate performance of the battery core and improving the secondary Cycle performance and high temperature performance of secondary batteries.
  • phosphate additives are introduced into the non-aqueous electrolyte to form Li x F y PO 4 on the surface of the pyrophosphate during the charging process of the lithium ion battery, improving the ion conductivity of the lithium manganese phosphate cathode active material after being coated with pyrophosphate. ability, thereby further improving the capacity development performance and rate performance of the secondary battery including it.
  • R 1 and R 2 each independently represent F, a C1-C3 fluoroalkyl group, a C1-C3 alkyl group, a C1-C3 alkoxy group, a C2-C3 Any one of alkenyl, C2-C3 alkynyl, phenyl, benzyl, and methylphenyl, and at least one of R 1 and R 2 represents F or C1-C3 fluoroalkyl.
  • R 1 and R 2 each independently represents any one of F, C1 to C3 alkyl, C1 to C3 fluoroalkyl, optionally, C1 to C3 fluorine
  • the alkyl group is -CF 3 , -C 2 F 5 , -CH 2 CF 3 or -CF 2 CH 3
  • the C1 to C3 alkyl group is methyl or ethyl.
  • R 3 and R 4 are each independently F, C1-C3 fluoroalkyl group, C1-C3 alkyl group, C1-C3 alkoxy group, C2-C3 alkenyl group , any one of C2 ⁇ C3 alkynyl groups, and at least one of R3 and R4 represents any one of F or C1 ⁇ C3 fluoroalkyl group, optionally, R3 , R4 Each independently represents any one of F or a C1-C3 fluoroalkyl group.
  • M in each chemical formula independently represents one of Li, Na, and K.
  • the first additive used in this application can be arbitrarily selected from each of the above chemical formulas.
  • the first additive includes one or more of the following compounds:
  • the above-mentioned first additive includes any one or more of the following compounds:
  • Each of the above-mentioned first additives has a high efficiency in forming Li x F y PO 4 during the charging process, and therefore more efficiently improves the ion conduction ability of the cathode active material of the present application.
  • the above-mentioned non-aqueous electrolyte further includes a second additive
  • the second additive includes a cyclic carbonate compound containing an unsaturated bond, a halogen-substituted cyclic carbonate compound, a sulfate compound, a sulfite compound, or Various.
  • the above-mentioned second additive can improve the capacity, cycle performance, etc. of the secondary battery according to its own performance. Those skilled in the art can select the corresponding second additive according to actual needs.
  • the content of the first additive is W1% by weight based on the total weight of the non-aqueous electrolyte
  • W1 is 0.01 to 20 (such as 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 1, 2 , 3, 4, 5, 8, 10, 12, 15, 18 or 20), optionally 0.1 to 10 or 0.5 to 5, and/or the content of the second additive is W2% by weight
  • W2 is 0.01 to 20 (e.g. 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 1, 2, 3, 4, 5, 8, 10, 12, 15, 18 or 20), optionally 0.1 to 10 or 0.3 to 5.
  • the above-mentioned content of the first additive not only avoids an increase in the resistance of the positive and negative electrodes caused by too much of the first additive, but also ensures the large capacity and high rate performance of the secondary battery. Therefore, when the mass ratio of the first additive in the non-aqueous electrolyte is within the above range, it can significantly improve the ion conductivity of the positive active material of the present application without deteriorating the impedance of the positive and negative electrodes, thereby further improving the secondary battery. capacity and rate performance.
  • W1/W2 is defined as M, and M is 0.001 to 20 (such as 0.01, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 1, 2, 3, 4, 5, 8, 10, 12 , 15, 18 or 20), optionally 0.1 to 10.
  • W2/W1 is within the above range, the two can work better together to further improve capacity development and cycle performance.
  • the above-mentioned non-aqueous electrolyte also includes an organic solvent.
  • the type of organic solvent is not particularly limited and can be selected according to actual needs.
  • the organic solvent includes cyclic carbonate compounds and chain carbonate compounds.
  • one or more carboxylic acid ester compounds further including dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, ethylene carbonate, Propylene carbonate, butylene carbonate, ⁇ -butyrolactone, methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, butyl propionate, One or more of the group consisting of tetrahydrofuran.
  • the above-mentioned non-aqueous electrolyte solution further includes an electrolyte salt.
  • the electrolyte salt includes LiN(C x F 2x+1 SO 2 )(C y F 2y+1 SO 2 ), Li(FSO 2 ) 2 N, LiCF 3 SO 3 , LiPF 6 , LiBF 4 , LiAsF 6 , LiClO 4 , LiBOB, LiDFOB, LiTFOP, one or more of the group consisting of, x and y represent positive integers, optionally, x and y are each independently 0, 1, 2 or 3, non-aqueous electrolyte
  • the concentration range of the medium electrolyte salt is 0.5M ⁇ 2.5M, and the optional range is 0.8M ⁇ 2M, which can ensure the smooth and rapid migration of Li + in the positive and negative electrodes.
  • the coating amount of the first coating layer is C1% by weight, and C1 is greater than 0 and less than or equal to 7, and can optionally be 4 to 5.6.
  • the coating amount of the first coating layer is within the above range, the elution of manganese ions can be further suppressed and the transport of lithium ions can be further promoted.
  • the coating amount of the first coating layer is too small, the inhibitory effect of pyrophosphate on the dissolution of manganese ions may be insufficient, and the improvement of lithium ion transmission performance is not significant; if If the coating amount of the first coating layer is too large, the coating layer may be too thick, increase the battery impedance, and affect the dynamic performance of the battery.
  • the coating amount of the second coating layer is C2% by weight, and C2 is greater than 0 and less than or equal to 6, optionally 3 to 5.
  • the carbon-containing layer as the second coating layer can function as a "barrier" to avoid direct contact between the positive 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 dynamic performance of the battery.
  • the carbon material has a low gram capacity, when the amount of the second coating layer is too large, the overall gram capacity of the cathode active material may be reduced. Therefore, when the coating amount of the second coating layer is within the above range, the kinetic performance and safety performance of the battery can be further improved without sacrificing the gram capacity of the cathode active material.
  • the relationship between the first additive content W1 and the coating amount C1 of the first coating layer and the coating amount C2 of the second coating layer W1/(C1+C2) is C, and C is 0.001 to 2, optional from 0.01 to 1.
  • C is less than the above range, the first additive will form a small amount of film on the surface of the pyrophosphate, and the further improvement effect on the rate performance of the secondary battery is not significant; when C is greater than the above range, too much of the first additive will cause negative and negative effects.
  • the electrode impedance increases, and the capacity improvement and rate performance improvement effects of the secondary battery are affected.
  • 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 appropriate ratio of pyrophosphate and phosphate is conducive to giving full play to the synergistic effect of the two. And can effectively avoid the following situations: if there is too much pyrophosphate and too little phosphate, it may cause the battery impedance to increase; if there is too much phosphate and too little pyrophosphate, the effect of inhibiting the dissolution of manganese ions is not significant.
  • the interplanar spacing of the phosphate in the first coating layer is 0.345-0.358 nm, and the angle between the crystal directions (111) is 24.25°-26.45°; the pyrophosphate in the first coating layer
  • the interplanar spacing is 0.293-0.326nm, and the angle between the crystal orientation (111) is 26.41°-32.57°.
  • y is selected from any value in the range of 0.1-0.4. By selecting the y value within this range, the gram capacity and rate performance of the first cathode active material 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 from 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 from 1:499 to 1:249.
  • z represents the sum of stoichiometric numbers of P-site doping elements.
  • the crystallinity of the pyrophosphate and the phosphate is each independently 10% to 100%, optionally 50% to 100%.
  • pyrophosphate and phosphate having a certain degree of crystallinity are beneficial to maintaining structural stability of the first coating layer and reducing lattice defects. On the one hand, this is conducive to giving full play to the role of pyrophosphate in hindering the dissolution of manganese ions.
  • A is selected from at least two elements selected from Fe, Ti, V, Ni, Co, and Mg.
  • the Li/Mn anti-site defect concentration of the first cathode active material is 4% or less, optionally 2% or less.
  • the Li/Mn anti-site defect refers to the interchange of positions of Li + and Mn 2+ in the LiMnPO 4 crystal lattice. Since the Li + transport channel is a one-dimensional channel, Mn 2+ is difficult to migrate in the Li + transport channel. Therefore, the anti-site defective Mn 2+ will hinder the transport of Li + . By controlling the Li/Mn antisite defect concentration at a low level, the gram capacity and rate performance of LiMnPO can be improved.
  • the lattice change rate of the positive electrode active material is 6% or less, optionally 4% or less.
  • the lithium deintercalation process of LiMnPO 4 is a two-phase reaction.
  • the interface stress of the two phases is determined by the lattice change rate. The smaller the lattice change rate, the smaller the interface stress and the easier Li + transport. Therefore, reducing the lattice change rate of the core will be beneficial to enhancing the Li + transport capability, thereby improving the rate performance of secondary batteries.
  • the surface oxygen valence state of the first cathode active material is -1.88 or less, optionally -1.98 to -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 its oxidizing property.
  • the first cathode active material of the present application by controlling the surface valence state of oxygen at a low level, the reactivity on the surface of the cathode material can be reduced, and the interface side reactions between the cathode material and the electrolyte can be further reduced, thereby further improving the performance of the second cathode material. Cycle performance and high temperature storage performance of secondary batteries.
  • the positive active material has a compacted density of 2.0 g/cm or more at 3 tons (T), optionally 2.2 g/cm or more.
  • T 3 tons
  • a second aspect of the present application also provides a battery module.
  • the battery module includes a secondary battery, and the secondary battery is any of the above-mentioned secondary batteries of the present application.
  • a third aspect of the present application also provides a battery pack.
  • the battery pack includes a battery module, and the battery module is the above-mentioned battery module of the present application.
  • a fourth aspect of the present application also provides an electrical device, which includes at least one of a secondary battery, a battery module, or a battery pack.
  • a secondary battery which includes at least one of a secondary battery, a battery module, or a battery pack.
  • the above secondary batteries, battery modules, and battery packs are all provided by the present application. Secondary batteries, battery modules, and battery packs.
  • the battery module and battery pack of the present application have higher cycle performance and rate characteristics, and especially the high temperature stability is significantly improved, thereby providing power consumption devices with the secondary battery, battery module or battery pack of the present application.
  • High power cycle stability and high temperature operating stability are particularly preferred.
  • Figure 1 is an XRD spectrum of a cathode active material according to an embodiment of the present application.
  • FIG. 2 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG. 3 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 2 .
  • Figure 4 is a schematic diagram of a battery module according to an embodiment of the present application.
  • Figure 5 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG. 6 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG. 5 .
  • FIG. 7 is a schematic diagram of a power consumption device using a secondary battery as a power source according to an embodiment of the present application.
  • Ranges disclosed herein are defined in terms of lower and upper limits. A given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive of the endpoints, and may be arbitrarily combined, that is, any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, understand that ranges of 60-110 and 80-120 are also expected. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-5.
  • the numerical range “a-b” represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers.
  • the numerical range “0-5" means that all real numbers between "0-5" have been listed in this article, and "0-5" is just an abbreviation of these numerical combinations.
  • a certain parameter is an integer ⁇ 2
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • step (c) means that step (c) may be added to the method in any order.
  • the method may include steps (a), (b) and (c). , may also include steps (a), (c) and (b), may also include steps (c), (a) and (b), etc.
  • condition "A or B” is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists) ; Or both A and B are true (or exist).
  • coating layer refers to a material layer coated on the core.
  • the material layer may completely or partially cover the core.
  • the use of “coating layer” is only for convenience of description and is not intended to limit this article. invention.
  • the term “thickness of the coating layer” refers to the thickness of the material layer coating the core in the radial direction of the 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, elements, halides, and oxides. and hydroxides, etc.
  • the inventor of the present application found in actual operations that manganese ions are relatively seriously eluted from the lithium manganese phosphate cathode active material during the deep charge and discharge process. Although there are attempts in the prior art to coat lithium manganese phosphate with lithium iron phosphate to reduce interface side reactions, this coating cannot prevent the migration of eluted manganese into the electrolyte. The eluted manganese is reduced to metallic manganese after migrating to the negative electrode. The metal manganese produced is equivalent to a "catalyst", which can catalyze the decomposition of the SEI film (solid electrolyte interphase, solid electrolyte interface film) on the surface of the negative electrode.
  • Part of the by-products produced are gases, which can easily cause the battery to expand and affect the safety of the secondary battery. Performance, and the other part is deposited on the surface of the negative electrode, blocking the passage of lithium ions in and out of the negative electrode, causing the impedance of the secondary battery to increase and affecting the dynamic performance of the battery. In addition, in order to replenish the lost SEI film, the electrolyte and active lithium inside the battery are continuously consumed, which has an irreversible impact on the capacity retention rate of the secondary battery.
  • the inventor found that for lithium manganese phosphate cathode active materials, problems such as severe manganese ion dissolution and high surface reactivity may be caused by the Ginger-Taylor effect of Mn 3+ after delithiation and the change in the size of the Li + channel.
  • the inventor modified lithium manganese phosphate to obtain a cathode active material that can significantly reduce the dissolution of manganese ions and reduce the lattice change rate, and thus has good cycle performance, high-temperature storage performance and safety performance.
  • Secondary batteries also known as rechargeable batteries or storage batteries, refer to batteries that can be recharged to activate active materials and continue to be used after the battery is discharged.
  • a secondary battery normally includes a positive electrode plate, a negative electrode plate, a separator and an electrolyte.
  • active ions such as lithium ions
  • the isolation film is placed between the positive electrode piece and the negative electrode piece. It mainly prevents the positive and negative electrodes from short-circuiting and allows active ions to pass through.
  • the electrolyte is between the positive electrode piece and the negative electrode piece and mainly plays the role of conducting active ions.
  • the non-aqueous electrolyte solution includes a first additive, and the first additive includes one or more of the group consisting of a compound represented by Formula 1, a compound represented by Formula 2, and a compound represented by Formula 3,
  • R 1 and R 2 each independently represent F, C1 to C6 fluoroalkyl group, C1 to C6 alkyl group, C1 to C6 alkoxy group, C2 to C6 alkenyl group, C2 to C6 alkynyl group, C6 Any one of ⁇ C10 aryl groups, and at least one of R 1 and R 2 represents any one of F or C1 to C6 fluoroalkyl groups;
  • R 3 and R 4 are each independently F, any of a C1-C6 fluoroalkyl group, a C1-C6 alkyl group, a C1-C6 alkoxy group, a C2-C6 alkenyl group, or a C2-C6 alkynyl group.
  • One, and at least one of R 3 and R 4 represents any one of F or C1 to C6 fluoroalkyl;
  • M in each chemical formula independently represents one of alkali metals and alkaline earth metals
  • n 0, 1 or 2.
  • the positive electrode sheet usually includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector.
  • the positive electrode film layer includes a positive electrode active material.
  • the positive electrode current collector has two surfaces facing each other in its own thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • the metal foil aluminum foil can be used.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer.
  • the composite current collector can be formed by forming metal materials (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the lithium manganese phosphate cathode active material of the present application has a core-shell structure with two coating layers, in which the core includes Li 1+x Mn 1-y A y P 1-z R z O 4 .
  • the element A doped in the manganese position of lithium manganese phosphate in the core helps to reduce the lattice change rate of lithium manganese phosphate during the lithium deintercalation process, improves the structural stability of the lithium manganese phosphate cathode material, greatly reduces the dissolution of manganese and reduces the Oxygen activity on the particle surface.
  • the element R doped at the phosphorus site helps change the ease of Mn-O bond length change, thereby reducing the lithium ion migration barrier, promoting lithium ion migration, and improving the rate performance of secondary batteries.
  • the first coating layer of the cathode active material of the present application includes pyrophosphate and phosphate. Since the migration barrier of transition metals in pyrophosphate is high (>1eV), it can effectively inhibit the dissolution of transition metals. Phosphate has excellent ability to conduct lithium ions and can reduce the surface miscellaneous lithium content. In addition, since the second coating layer is a carbon-containing layer, it can effectively improve the conductive properties and desolvation ability of LiMnPO 4 . In addition, the "barrier" function of the second coating layer can further hinder the migration of manganese ions into the electrolyte and reduce the corrosion of the active material by the electrolyte.
  • this application uses specific element doping and surface coating of lithium manganese phosphate to effectively suppress the dissolution of manganese ions during the process of deintercalation of lithium, and at the same time promote the migration of lithium ions, thereby improving the rate performance of the battery core and improving the secondary Cycle performance and high temperature performance of secondary batteries.
  • phosphate additives are introduced into the non-aqueous electrolyte to form Li x F y PO 4 on the surface of the pyrophosphate during the charging process of the lithium ion battery, improving the ion conductivity of the lithium manganese phosphate cathode active material after being coated with pyrophosphate. ability, thereby further improving the capacity development performance and rate performance of the secondary battery including it.
  • R 1 and R 2 each independently represent F, a C1-C3 fluoroalkyl group, a C1-C3 alkyl group, a C1-C3 alkoxy group, a C2-C3 Any one of alkenyl, C2-C3 alkynyl, phenyl, benzyl, and methylphenyl, and at least one of R 1 and R 2 represents F or C1-C3 fluoroalkyl.
  • R 1 and R 2 each independently represents any one of F, C1 to C3 alkyl, C1 to C3 fluoroalkyl, optionally, C1 to C3 fluorine
  • the alkyl group is -CF 3 , -C 2 F 5 , -CH 2 CF 3 or -CF 2 CH 3
  • the C1 to C3 alkyl group is methyl or ethyl.
  • R 3 and R 4 are each independently F, C1-C3 fluoroalkyl group, C1-C3 alkyl group, C1-C3 alkoxy group, C2-C3 alkenyl group , any one of C2 ⁇ C3 alkynyl groups, and at least one of R3 and R4 represents any one of F or C1 ⁇ C3 fluoroalkyl group, optionally, R3 , R4 Each independently represents any one of F or a C1-C3 fluoroalkyl group.
  • M in each chemical formula independently represents one of Li, Na, and K.
  • the first additive used in this application can be arbitrarily selected from each of the above chemical formulas.
  • the first additive includes one or more of the following compounds:
  • the above-mentioned first additive includes any one or more of the following compounds:
  • Each of the above-mentioned first additives has a high efficiency in forming Li x F y PO 4 during the charging process, and therefore more efficiently improves the ion conduction ability of the cathode active material of the present application.
  • the above-mentioned non-aqueous electrolyte further includes a second additive
  • the second additive includes a cyclic carbonate compound containing an unsaturated bond, a halogen-substituted cyclic carbonate compound, a sulfate compound, a sulfite compound, or Various.
  • the above-mentioned second additive can improve the capacity, cycle performance, etc. of the secondary battery according to its own performance. Those skilled in the art can select the corresponding second additive according to actual needs.
  • the content of the first additive is W1% by weight, W1 is 0.01 to 20, optionally 0.1 to 10 or 0.5 to 5, and/or the second additive is The content is W2% by weight, W2 is 0.01 to 20, optionally 0.1 to 10 or 0.3 to 5.
  • the above-mentioned content of the first additive not only avoids an increase in the resistance of the positive and negative electrodes caused by excessive amounts of the first additive, but also ensures the large capacity and high rate performance of the secondary battery.
  • the mass ratio of the first additive in the non-aqueous electrolyte when the mass ratio of the first additive in the non-aqueous electrolyte is within the above range, it can significantly improve the ion conductivity of the positive active material of the present application without deteriorating the impedance of the positive and negative electrodes, thereby further improving the secondary battery. capacity and rate performance.
  • W1/W2 is defined as M, with M ranging from 0.001 to 20, optionally from 0.1 to 10.
  • W2/W1 is within the above range, the two can work better together to further improve capacity development and cycle performance.
  • the above-mentioned non-aqueous electrolyte also includes an organic solvent.
  • the type of organic solvent is not particularly limited and can be selected according to actual needs.
  • the organic solvent includes cyclic carbonate compounds and chain carbonate compounds.
  • one or more carboxylic acid ester compounds further including dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl ethyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, ethylene carbonate, Propylene carbonate, butylene carbonate, ⁇ -butyrolactone, methyl formate, ethyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, butyl propionate, One or more of the group consisting of tetrahydrofuran.
  • the above-mentioned non-aqueous electrolyte solution further includes an electrolyte salt.
  • the electrolyte salt includes LiN(C x F 2x+1 SO 2 )(C y F 2y+1 SO 2 ), Li(FSO 2 ) 2 N, LiCF 3 SO 3 , LiPF 6 , LiBF 4 , LiAsF 6 , LiClO 4 , LiBOB, LiDFOB, LiTFOP, one or more of the group consisting of, x and y represent positive integers, optionally, x and y are each independently 0, 1, 2 or 3, non-aqueous electrolyte
  • the concentration range of the medium electrolyte salt is 0.5M ⁇ 2.5M, and the optional range is 0.8M ⁇ 2M, which is conducive to the smooth and rapid migration of Li + .
  • the coating amount of the first coating layer is C1% by weight, and C1 is greater than 0 and less than or equal to 7, and can optionally be 4 to 5.6.
  • the coating amount of the first coating layer is within the above range, the elution of manganese ions can be further suppressed and the transport of lithium ions can be further promoted.
  • the coating amount of the first coating layer is too small, the inhibitory effect of pyrophosphate on the dissolution of manganese ions may be insufficient, and the improvement of lithium ion transmission performance is not significant; if If the coating amount of the first coating layer is too large, the coating layer may be too thick, increase the battery impedance, and affect the dynamic performance of the battery.
  • the coating amount of the second coating layer is C2% by weight, and C2 is greater than 0 and less than or equal to 6, optionally 3 to 5.
  • the carbon-containing layer as the second coating layer can function as a "barrier" to avoid direct contact between the positive 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 dynamic performance of the battery.
  • the carbon material has a low gram capacity, when the amount of the second coating layer is too large, the overall gram capacity of the cathode active material may be reduced. Therefore, when the coating amount of the second coating layer is within the above range, the kinetic performance and safety performance of the battery can be further improved without sacrificing the gram capacity of the cathode active material.
  • the relationship between the first additive content W1 and the coating amount C1 of the first coating layer and the coating amount C2 of the second coating layer W1/(C1+C2) is C, and C is 0.001 to 2, optional from 0.01 to 1.
  • C is less than the above range, the first additive will form a small amount of film on the surface of the pyrophosphate, and the further improvement effect on the rate performance of the secondary battery is not significant; when C is greater than the above range, too much of the first additive will cause negative and negative effects.
  • the electrode impedance increases, and the capacity improvement and rate performance improvement effects of the secondary battery are affected.
  • 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 appropriate ratio of pyrophosphate and phosphate is conducive to giving full play to the synergistic effect of the two. And can effectively avoid the following situations: if there is too much pyrophosphate and too little phosphate, it may cause the battery impedance to increase; if there is too much phosphate and too little pyrophosphate, the effect of inhibiting the dissolution of manganese ions is not significant.
  • the interplanar spacing of the phosphate of the first coating layer is 0.345-0.358 nm, and the angle of the crystal direction (111) is 24.25°-26.45°; the first coating layer pyrophosphate
  • the crystal plane spacing of salt is 0.293-0.326nm, and the angle between the crystal directions (111) is 26.41°-32.57°.
  • the angle between the interplanar spacing and the crystal direction (111) of the phosphate and pyrophosphate in the first coating layer is within 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. performance and rate capabilities.
  • the ratio of y to 1-y is 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 1:9 to 1:999, optionally 1:499 to 1:249.
  • y represents the sum of stoichiometric numbers of P-site doping elements.
  • the crystallinity of the pyrophosphate and phosphate salts are each independently from 10% to 100%, optionally from 50% to 100%.
  • pyrophosphate and phosphate having a certain degree of crystallinity are beneficial to maintaining the structural stability of the first coating layer and reducing lattice defects.
  • this is conducive to giving full play to the role of pyrophosphate in hindering the dissolution of manganese ions.
  • it is also conducive to the phosphate reducing the surface miscellaneous lithium content and reducing the valence state of surface oxygen, thereby reducing the interface between the positive electrode active material and the non-aqueous electrolyte. Side reactions, reducing the consumption of non-aqueous electrolyte, and improving the cycle performance and safety performance of secondary batteries.
  • the crystallinity of pyrophosphate and phosphate can be adjusted, for example, by adjusting the process conditions of the sintering process, such as sintering temperature, sintering time, and the like.
  • the crystallinity of pyrophosphate and phosphate can be measured by methods known in the art, such as by X-ray diffraction, density, infrared spectroscopy, differential scanning calorimetry, and nuclear magnetic resonance absorption methods.
  • A is selected from at least two of Fe, Ti, V, Ni, Co and Mg.
  • Doping the manganese site in the lithium manganese phosphate cathode active material with two or more of the above elements at the same time is beneficial to enhancing the doping effect. On the one hand, it further reduces the lattice change rate, thereby inhibiting the dissolution of manganese and reducing the loss of electrolyte and active lithium. consumption, on the other hand, it is also conducive to further reducing surface oxygen activity and reducing interface side reactions between the positive active material and the electrolyte, thereby improving the cycle performance and high-temperature storage performance of the battery.
  • the Li/Mn anti-site defect concentration of the cathode active material is 4% or less, optionally 2% or less.
  • the Li/Mn anti-site defect means that the positions of Li + and Mn 2+ are interchanged in the LiMnPO 4 crystal lattice. Since the Li + transport channel is a one-dimensional channel, Mn 2+ is difficult to migrate in the Li + transport channel. Therefore, the anti-site defective Mn 2+ will hinder the transport of Li + .
  • the anti-site defect concentration can be measured in accordance with JIS K 0131-1996, for example.
  • the lattice change rate of the cathode active material is below 6%, optionally below 4%.
  • the lithium deintercalation process of LiMnPO 4 is a two-phase reaction.
  • the interface stress of the two phases is determined by the lattice change rate. The smaller the lattice change rate, the smaller the interface stress and the easier Li + transport. Therefore, reducing the lattice change rate of the core will be beneficial to enhance the Li + transport capability, thereby improving the rate performance of further secondary batteries.
  • the surface oxygen valence state of the cathode active material is -1.88 or less, optionally -1.98 ⁇ -1.88.
  • the higher the valence state of oxygen in the compound the stronger its ability to obtain electrons, that is, the stronger its oxidizing property.
  • the reactivity on the surface of the cathode material can be reduced, and the interface side reactions between the cathode material and the electrolyte can be reduced, thereby improving the secondary Battery cycle performance and high temperature storage performance.
  • the positive active material has a compacted density of 2.0 g/cm or more at 3 tons (T), optionally 2.2 g/cm or more.
  • the compacted density of the positive active material that is, the greater the weight of the active material per unit volume, the more conducive it will be to increasing the volumetric energy density of the battery.
  • the compacted density can be measured according to GB/T 24533-2009, for example.
  • the positive active material used in the secondary battery of the present application is prepared by the following preparation method, which includes the following steps:
  • a core material including Li 1+x Mn 1-y A y P 1-z R z O 4 ; provide MP 2 O 7 powder and an The powder is added to the XPO 4 suspension containing the source of carbon and mixed, and the cathode active material is obtained through sintering.
  • the step of providing the core material includes the following steps: Step (1): Mix and stir a source of manganese, a source of element A and an acid in a container to obtain manganese salt particles doped with element A; step (2): Mix the manganese salt particles doped with element A with a source of lithium, a source of phosphorus and a source of element R in a solvent to obtain a slurry, and then sinter it under the protection of an inert gas atmosphere to obtain a slurry doped with element A.
  • step (1) is carried out at a temperature of 20-120°C, optionally 25-80°C; and/or the stirring described in step (1) is carried out at 500-700rpm for 60-420 minutes, Optionally 120-360 minutes.
  • the source of the above-mentioned element A is selected from one or more of elemental elements, sulfates, halides, nitrates, organic acid salts, oxides or hydroxides of element A; and/or, elements
  • the source of R is selected from one or more elements, sulfates, halides, nitrates, organic acid salts, oxides or hydroxides of element R, and inorganic acids of element R.
  • MP 2 O 7 powder is prepared by adding a source of element M and a source of phosphorus to a solvent to obtain a mixture, adjusting the pH of the mixture to 4-6, stirring and fully reacting, and then drying , obtained by sintering, wherein M is selected from one or more of Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb or Al.
  • M is selected from one or more of Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb or Al.
  • the optional above-mentioned drying step is drying at 100-300°C, optionally 150-200°C for 4-8 hours; the above-mentioned sintering step is sintering under an inert gas atmosphere at 500-800°C, optionally 650-800°C for 4-8 hours. 10h.
  • the sintering temperature in the above coating step is 500-800°C, and the sintering time is 4-10 hours.
  • the positive electrode film layer may also include other positive electrode active materials known in the art for secondary batteries.
  • the cathode active material may include at least one of the following materials: an olivine-structured lithium-containing phosphate, a 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 for secondary batteries can also be used. Only one type of these positive electrode active materials may be used alone, or two or more types may be used in combination.
  • lithium transition metal oxides may include, but are not limited to, lithium nickel oxide (such as LiNiO 2 ), lithium manganese oxide (such as LiMnO 2 , LiMn 2 O 4 ), lithium nickel cobalt oxide, lithium manganese cobalt oxide , at least one of lithium nickel manganese oxide and its modified compounds.
  • lithium-containing phosphates with an olivine structure may include, but are not limited to, lithium iron phosphate (such as LiFePO 4 (also referred to as LFP)), composites 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, a composite material of lithium manganese iron phosphate, or a composite material of lithium manganese iron phosphate and carbon.
  • lithium iron phosphate such as LiFePO 4 (also referred to as LFP)
  • composites 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, a composite material of lithium manganese iron phosphate, or a composite material of lithium manganese iron phosphate and carbon.
  • the positive electrode film layer optionally further includes a binder.
  • the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene tripolymer. At least one of a meta-copolymer, a tetrafluoroethylene-hexafluoropropylene copolymer and a fluorine-containing acrylate resin.
  • the positive electrode film layer optionally further includes a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components in a solvent (such as N -methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode piece can be obtained.
  • a solvent such as N -methylpyrrolidone
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, where the negative electrode film layer includes a negative electrode active material.
  • the negative electrode current collector has two opposite surfaces in its own thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base material.
  • the composite current collector can be formed by forming metal materials (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative active material may be a negative active material known in the art for batteries.
  • the negative active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and the like.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon carbon composites, silicon nitrogen composites and silicon alloys.
  • the tin-based material may be selected from at least one of elemental tin, tin oxide compounds and tin alloys.
  • the present application is not limited to these materials, and other traditional materials that can be used as battery negative electrode active materials can also be used. Only one type of these negative electrode active materials may be used alone, or two or more types may be used in combination.
  • the negative electrode film layer optionally further includes a binder.
  • the binder may be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), At least one of polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the negative electrode film layer optionally further includes a conductive agent.
  • the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the negative electrode film layer optionally includes other auxiliaries, such as thickeners (such as sodium carboxymethylcellulose (CMC-Na)) and the like.
  • thickeners such as sodium carboxymethylcellulose (CMC-Na)
  • the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative active materials, conductive agents, binders and any other components in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode piece can be obtained.
  • a solvent such as deionized water
  • the secondary battery further includes a separator film.
  • a separator film There is no particular restriction on the type of isolation membrane in this application. Any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be used.
  • the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation film can be a single-layer film or a multi-layer composite film, with no special restrictions. When the isolation film is a multi-layer composite film, the materials of each layer can be the same or different, and there is no particular limitation.
  • the positive electrode piece, the negative electrode piece and the separator film can be made into an electrode assembly through a winding process or a lamination process.
  • the secondary battery may include an outer packaging.
  • the outer packaging can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag.
  • the material of the soft bag can be plastic. Examples of plastics include polypropylene, polybutylene terephthalate, polybutylene succinate, etc.
  • FIG. 2 shows a square-structured secondary battery 5 as an example.
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity.
  • the housing 51 has an opening communicating with the accommodation cavity, and the cover plate 53 can cover the opening to close the accommodation cavity.
  • the positive electrode piece, the negative electrode piece and the isolation film can be formed into the electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the containing cavity.
  • the electrolyte soaks into the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.
  • secondary batteries can be assembled into battery modules, and the number of secondary batteries contained in the battery module can be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery module.
  • FIG. 4 is a battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 .
  • the plurality of secondary batteries 5 can be fixed by fasteners.
  • the battery module 4 may further include a housing having a receiving space in which a plurality of secondary batteries 5 are received.
  • the above-mentioned battery modules can also be assembled into a battery pack.
  • the number of battery modules contained in the battery pack can be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery pack.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box.
  • the battery box includes an upper box 2 and a lower box 3 .
  • the upper box 2 can be covered with the lower box 3 and form a closed space for accommodating the battery module 4 .
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • the present application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided by the present application.
  • the secondary battery, battery module, or battery pack may be used as a power source for the electrical device, or may be used as an energy storage unit for the electrical device.
  • the electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, and electric golf carts). , electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited to these.
  • a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.
  • Fig. 7 is an electrical device as an example.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc.
  • a battery pack or battery module can be used.
  • the first additive is selected from the following compounds:
  • the second additive is selected from the following compounds:
  • the reaction kettle was heated to 80°C and stirred at a rotation speed of 600 rpm for 6 hours until the reaction was terminated (no bubbles were generated) to obtain a manganese oxalate suspension co-doped with Fe, Co, V and S.
  • the suspension was then filtered, and the filter cake was dried at 120° C. and then ground to obtain Fe, Co and V co-doped manganese oxalate dihydrate particles with a median particle size Dv50 of 100 nm.
  • Preparation of Fe, Co, V and S co-doped lithium manganese phosphate combine the manganese oxalate dihydrate particles obtained in the previous step (1793.4g), 369.0g lithium carbonate (calculated as Li 2 CO 3 , the same below), 1.6g Dilute sulfuric acid with a concentration of 60% (calculated as 60% H 2 SO 4 , the same below) and 1148.9g ammonium dihydrogen phosphate (calculated as NH 4 H 2 PO 4 , the same below) were added to 20 liters of deionized water, and the mixture was Stir for 10 hours to mix evenly and obtain a slurry.
  • lithium iron pyrophosphate powder Dissolve 4.77g lithium carbonate, 7.47g ferrous carbonate, 14.84g ammonium dihydrogen phosphate and 1.3g oxalic acid dihydrate in 50ml deionized water. The pH of the mixture was 5, and the reaction mixture was stirred for 2 hours to fully react. The reacted solution was then heated to 80°C and maintained at this temperature for 4 hours to obtain a suspension containing Li 2 FeP 2 O 7. The suspension was filtered, washed with deionized water, and dried at 120°C for 4 hours. , get powder. The powder was sintered at 650° C. in a nitrogen atmosphere for 8 hours, and then naturally cooled to room temperature and then ground to obtain Li 2 FeP 2 O 7 powder.
  • lithium iron phosphate suspension Dissolve 11.1g lithium carbonate, 34.8g ferrous carbonate, 34.5g ammonium dihydrogen phosphate, 1.3g oxalic acid dihydrate and 74.6g sucrose (calculated as C 12 H 22 O 11 , the same below) In 150 ml of deionized water, a mixture was obtained, and then stirred for 6 hours to allow the above mixture to fully react. The reacted solution was then heated to 120°C and maintained at this temperature for 6 hours to obtain a suspension containing LiFePO4 .
  • the double-layer coated lithium manganese phosphate cathode active material prepared above, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) were added to N-methylpyrrolidone (NMP) in a weight ratio of 92:2.5:5.5 ), stir and mix evenly to obtain positive electrode slurry. Then, the positive electrode slurry is evenly coated on the aluminum foil at a density of 0.280g/ 1540.25mm2 , dried, cold pressed, and cut to obtain the positive electrode piece.
  • negative active material artificial graphite artificial graphite, hard carbon, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethylcellulose (CMC-Na) in a weight ratio of 90:5:2:2 : 1 Dissolve in solvent deionized water, stir and mix evenly to prepare negative electrode slurry.
  • the negative electrode slurry is evenly coated on the negative electrode current collector copper foil at a density of 0.117g/1540.25mm 2 , and then dried, cold pressed, and cut to obtain negative electrode pieces.
  • a commercially available PP-PE copolymer microporous film with a thickness of 20 ⁇ m and an average pore diameter of 80 nm was used.
  • the positive electrode piece, isolation film, and negative electrode piece obtained above are stacked in order, so that the isolation film is between the positive and negative electrodes to play an isolation role, and the bare battery core is obtained by winding.
  • the bare battery core is placed in the outer packaging, the above-mentioned electrolyte is injected and packaged to obtain a full battery (hereinafter also referred to as "full battery").
  • the double-layer coated lithium manganese phosphate cathode active material prepared above, PVDF, and acetylene black were added to NMP in a weight ratio of 90:5:5, and stirred in a drying room to form a slurry.
  • the above slurry is coated on aluminum foil, dried and cold pressed to form a positive electrode sheet.
  • the coating amount is 0.2g/cm 2 and the compacted density is 2.0g/cm 3 .
  • Lithium sheets are used as negative electrodes, and the above-mentioned electrolyte is used, together with the above-prepared positive electrode sheets, to assemble into button batteries in a buckle box (hereinafter also referred to as "buckets").
  • the coating amount shown in Table 1 is the same as that in Example 1.
  • the ratio of the coating amount corresponding to -1 is adjusted accordingly, so that the amounts of Li 2 FeP 2 O 7 /LiFePO 4 in Examples 1-2 to 1-6 are 12.6g/37.7g, 15.7g/47.1g, and 18.8 respectively. g/56.5g, 22.0/66.0g and 25.1g/75.4g.
  • the other conditions are the same as in Example 1-1 except that the amount of sucrose used is 37.3g.
  • the amounts of various raw materials are adjusted accordingly according to the coating amounts shown in Table 1 so that the amounts of Li 2 FeP 2 O 7 /LiFePO 4 are 23.6g/39.3g respectively. , 31.4g/31.4g, 39.3g/23.6g and 47.2g/15.7g, the conditions of Examples 1-11 to 1-14 were the same as Example 1-7.
  • Examples 1-15 were the same as Examples 1-14 except that 492.80 g of ZnCO3 was used instead of ferrous carbonate in the preparation process of the co-doped lithium manganese phosphate core.
  • Examples 1-16 used 466.4g NiCO 3 , 5.0g zinc carbonate and 7.2g titanium sulfate instead of ferrous carbonate in the preparation process of the co-doped lithium manganese phosphate core.
  • 455.2g of ferrous carbonate and 8.5g of vanadium dichloride were used in the preparation process of the lithium manganese phosphate core.
  • 455.2g of ferrous carbonate was used in the preparation process of the co-doped lithium manganese phosphate core.
  • 4.9g of vanadium dichloride and 2.5g of magnesium carbonate the conditions of Examples 1-17 to 1-19 were the same as Example 1-7.
  • Examples 1-19 used 369.4g of lithium carbonate and 1.05g of 60% concentrated dilute nitric acid instead of dilute sulfuric acid in the preparation process of the co-doped lithium manganese phosphate core.
  • the conditions of Examples 1-19 to 1-20 were the same as those of Example 1-18, except that 369.7g of lithium carbonate was used and 0.78g of silicic acid was used instead of dilute sulfuric acid.
  • Example 1-21 632.0g manganese carbonate, 463.30g ferrous carbonate, 30.5g vanadium dichloride, 21.0g magnesium carbonate and 0.78g silicic acid were used in the preparation process of the co-doped lithium manganese phosphate core. ;
  • Example 1-22 uses 746.9g manganese carbonate, 289.6g ferrous carbonate, 60.9g vanadium dichloride, 42.1g magnesium carbonate and 0.78g silicic acid in the preparation process of co-doped lithium manganese phosphate core. Except for this, the conditions of Examples 1-21 to 1-22 were the same as those of Example 1-20.
  • Examples 1-23 in the preparation process of the co-doped lithium manganese phosphate core, 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;
  • Examples 1-24 used 862.1g manganese carbonate, 173.8g ferrous carbonate, 1155.1g ammonium dihydrogen phosphate, and 1.86g boric acid (mass fraction 99.5%) in the preparation process of the co-doped lithium manganese phosphate core.
  • the conditions of Examples 1-23 to 1-24 were the same as those of Example 1-22.
  • Example 1-25 uses 370.1g lithium carbonate, 1.56g silicic acid and 1147.7g ammonium dihydrogen phosphate in the preparation process of the co-doped lithium manganese phosphate core, the conditions of Examples 1-25 are the same as those of Examples 1-20 are the same.
  • Examples 1-26, 368.3g lithium carbonate, 4.9g dilute sulfuric acid with a mass fraction of 60%, 919.6g manganese carbonate, 224.8g ferrous carbonate, and 3.7g dichloride were used in the preparation process of the co-doped lithium manganese phosphate core.
  • the conditions of Examples 1-26 were the same as Examples 1-20 except for vanadium, 2.5g magnesium carbonate and 1146.8g ammonium dihydrogen phosphate.
  • Example 1-27 used 367.9g lithium carbonate, 6.5g dilute sulfuric acid with a concentration of 60% and 1145.4g ammonium dihydrogen phosphate in the preparation process of the co-doped lithium manganese phosphate core.
  • the conditions of Example 1-27 Same as Examples 1-20.
  • Examples 1-28 to 1-33 are the same as those of Example 1-20, except that the usage amounts of dilute sulfuric acid with a concentration of 60% are: 8.2g, 9.8g, 11.4g, 13.1g, 14.7g and 16.3g respectively. .
  • the sintering temperature in the powder sintering step is 550°C and the sintering time is 1 hour 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 hours to control the crystallinity of LiFePO 4 to 30%.
  • Other conditions are the same as in Example 1-1 same.
  • the sintering temperature in the powder sintering step is 550°C and the sintering time is 2 hours 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 hours to control the crystallinity of LiFePO 4 to 50%.
  • Other conditions are the same as in Example 1-1 same.
  • the sintering temperature in the powder sintering step is 600°C and the sintering time is 3 hours 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 same.
  • the sintering temperature in the powder sintering step is 650°C and the sintering time is 4 hours to control the crystallinity of Li 2 FeP 2 O 7 to 100%
  • the sintering temperature in the coating sintering step is 700°C and the sintering time is 6 hours to control the crystallinity of LiFePO 4 to 100%.
  • Other conditions are the same as in Example 1-1 same.
  • the heating temperature/stirring time in the reaction kettle of Example 3-1 is 60°C/120 minutes respectively; the heating temperature in the reaction kettle of Example 3-2 The temperature/stirring time is 70°C/120 minutes respectively; the heating temperature/stirring time in the reaction kettle of Example 3-3 is 80°C/120 minutes respectively; the heating temperature/stirring time in the reaction kettle of Example 3-4 is respectively 90°C/120 minutes; the heating temperature/stirring time in the reaction kettle of Example 3-5 is 100°C/120 minutes respectively; the heating temperature/stirring time in the reaction kettle of Example 3-6 is 110°C/120 minutes respectively; The heating temperature/stirring time in the reaction kettle of Example 3-7 is 120°C/120 minutes respectively; the heating temperature/stirring time in the reaction kettle of Example 3-8 is 130°C/120 minutes respectively; the reaction of Example 3-9 The heating temperature/stirring time in the kettle is 100°C/60 minutes respectively;
  • Examples 4-1 to 4-4 except that in the preparation process of lithium iron pyrophosphate (Li 2 FeP 2 O 7 ), the drying temperature/drying time in the drying step are respectively 100°C/4 hours and 150°C/6 hours, 200°C/6 hours and 200°C/6 hours; in the preparation process of lithium iron pyrophosphate (Li 2 FeP 2 O 7 ), the sintering temperature and sintering time in the sintering step are 700°C/6 hours, 700 Except for °C/6 hours, 700°C/6 hours and 600°C/6 hours, other conditions are the same as Examples 1-7.
  • Embodiments 4-5 to 4-7 except that the drying temperature/drying time in the drying step during the coating process are 150°C/6 hours, 150°C/6 hours and 150°C/6 hours respectively; in the coating process
  • the other conditions were the same as Examples 1-12 except that the sintering temperature and sintering time in the sintering step were 600°C/4 hours, 600°C/6 hours, and 800°C/8 hours respectively.
  • Preparation of manganese oxalate Add 1149.3g of manganese carbonate to the reaction kettle, and add 5 liters of deionized water and 1260.6g of oxalic acid dihydrate (calculated as C 2 H 2 O 4 ⁇ 2H 2 O, the same below). Heat the reaction kettle to 80°C and stir at 600 rpm for 6 hours until the reaction is terminated (no bubbles are generated) to obtain a manganese oxalate suspension, then filter the suspension, dry the filter cake at 120°C, and then proceed After grinding, manganese oxalate dihydrate particles with a median particle size Dv50 of 100 nm were obtained.
  • Preparation of carbon-coated lithium manganese phosphate Take 1789.6g of the 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 , the same below) and 31g 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 mix evenly to obtain a slurry. Transfer the slurry to spray drying equipment for spray drying and granulation, set the drying temperature to 250°C, and dry for 4 hours to obtain powder. In a protective atmosphere of nitrogen (90 volume %) + hydrogen (10 volume %), the above powder was sintered at 700° C. for 4 hours to obtain carbon-coated lithium manganese phosphate.
  • Comparative Example 2 Other conditions of Comparative Example 2 were the same as Comparative Example 1 except that 689.5 g of manganese carbonate was used and 463.3 g of additional ferrous carbonate were added.
  • Comparative Example 3 Other conditions of Comparative Example 3 were the same as Comparative Example 1 except that 1148.9 g of ammonium dihydrogen phosphate and 369.0 g of lithium carbonate were used, and 1.6 g of 60% concentration dilute sulfuric acid was additionally added.
  • Comparative Example 4 Except for using 689.5g of manganese carbonate, 1148.9g of ammonium dihydrogen phosphate and 369.0g of lithium carbonate, and additionally adding 463.3g of ferrous carbonate and 1.6g of 60% concentration of dilute sulfuric acid, the other conditions of Comparative Example 4 were the same as those of Comparative Example 4. Same as scale 1.
  • lithium iron pyrophosphate powder Dissolve 9.52g lithium carbonate, 29.9g ferrous carbonate, 29.6g ammonium dihydrogen phosphate and 32.5g oxalic acid dihydrate in 50mL deionized water. The pH of the mixture was 5, and the reaction mixture was stirred for 2 hours to fully react. The reacted solution was then heated to 80°C and maintained at this temperature for 4 hours to obtain a suspension containing Li 2 FeP 2 O 7. The suspension was filtered, washed with deionized water, and dried at 120°C for 4 hours to obtain powder. The powder is sintered at 500°C in a nitrogen atmosphere for 4 hours, and is naturally cooled to room temperature before grinding. The crystallinity of Li 2 FeP 2 O 7 is controlled to 5%. When preparing carbon-coated materials, Li 2 FeP 2 The other conditions of Comparative Example 5 were the same as Comparative Example 4 except that the amount of O 7 was 62.8g.
  • lithium iron phosphate suspension Dissolve 14.7g lithium carbonate, 46.1g ferrous carbonate, 45.8g ammonium dihydrogen phosphate and 50.2g oxalic acid dihydrate in 500mL deionized water, and then stir for 6 hours. The mixture reacted fully. The reacted solution was then heated to 120°C and maintained at this temperature for 6 hours to obtain a suspension containing LiFePO 4 .
  • the sintering temperature in the coating sintering step during the preparation of lithium iron phosphate (LiFePO 4 ) was 600°C.
  • Comparative Example 6 The other conditions of Comparative Example 6 were the same as Comparative Example 4 except that the sintering time was 4h to control the crystallinity of LiFePO 4 to 8%. When preparing carbon-coated materials, the amount of LiFePO 4 was 62.8g.
  • lithium iron pyrophosphate powder Dissolve 2.38g lithium carbonate, 7.5g ferrous carbonate, 7.4g ammonium dihydrogen phosphate and 8.1g oxalic acid dihydrate in 50mL deionized water. The pH of the mixture was 5, and the reaction mixture was stirred for 2 hours to fully react. The reacted solution was then heated to 80°C and maintained at this temperature for 4 hours to obtain a suspension containing Li 2 FeP 2 O 7. The suspension was filtered, washed with deionized water, and dried at 120°C for 4 hours to obtain powder. The powder was sintered at 500° C. in a nitrogen atmosphere for 4 hours, and then naturally cooled to room temperature and then ground to control the crystallinity of Li 2 FeP 2 O 7 to 5%.
  • lithium iron phosphate suspension Dissolve 11.1g lithium carbonate, 34.7g ferrous carbonate, 34.4g ammonium dihydrogen phosphate, 37.7g oxalic acid dihydrate and 37.3g sucrose (calculated as C 12 H 22 O 11 , the same below) in 1500 mL deionized water, and then stirred for 6 hours to fully react the mixture. The reacted solution was then heated to 120°C and maintained at this temperature for 6 hours to obtain a suspension containing LiFePO4 .
  • lithium iron pyrophosphate powder 15.7g was added to the above-mentioned lithium iron phosphate (LiFePO 4 ) and sucrose suspension.
  • the sintering temperature in the coating sintering step was 600°C, and the sintering time was 4 hours to control Except that the crystallinity of LiFePO 4 was 8%, other conditions of Comparative Example 7 were the same as 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 is respectively 80°C/3 hours, 80°C/3 hours, and 80 in Comparative Examples 8-10. °C/3 hours; in the preparation process of lithium iron pyrophosphate (Li 2 FeP 2 O 7 ), the sintering temperature and sintering time in the sintering step are respectively 400°C/3 hours and 400°C/ 3 hours, 350°C/2 hours, the drying temperature/drying time in the drying step during the preparation of lithium iron phosphate (LiFePO 4 ) in Comparative Example 11 is 80°C/3 hours; and in Comparative Examples 8-11 Li
  • the other conditions are the same as in Examples 1-7 except that the dosages of 2 FeP 2 O 7 /LiFePO 4 are 47.2g/15.7g, 15.7g/47.2g, 62.8g/0g, and 0g/62.8g respectively.
  • the button battery prepared above was left to stand for 5 minutes in a constant temperature environment of 25°C, discharged to 2.5V at 0.1C, left to stand for 5 minutes, charged to 4.3V at 0.1C, and then charged at a constant voltage of 4.3V to The current is less than or equal to 0.05mA, let it stand for 5 minutes; then discharge to 2.5V according to 0.1C.
  • the discharge capacity at this time is the initial gram capacity, recorded as D0, the discharge energy is the initial energy, recorded as E0, and the average discharge voltage of the buckle is V That is E0/D0.
  • the above-prepared full cell was stored at 100% state of charge (SOC) at 60°C. Measure the open circuit voltage (OCV) and AC internal resistance (IMP) of the battery cells before, after and during storage to monitor SOC, and measure the volume of the battery cells. The full battery was taken out after every 48 hours of storage, and the open circuit voltage (OCV) and internal resistance (IMP) were tested after leaving it for 1 hour. After cooling to room temperature, the cell volume was measured using the drainage method. The drainage method is to first separately measure the gravity F 1 of the battery cell using a balance that automatically converts units based on the dial data, then completely places the battery core in deionized water (density is known to be 1g/cm 3 ), and measures the battery core at this time.
  • the positive active material sample is prepared into a buckle, and the above buckle is charged at a small rate of 0.05C until the current is reduced to 0.01C. Then take out the positive electrode piece from the battery and soak it in dimethyl carbonate (DMC) for 8 hours. Then it is dried, scraped into powder, and particles with a particle size less than 500nm are screened out. Take a sample and calculate its unit cell volume v1 in the same way as the above-mentioned test of fresh samples, and use (v0-v1)/v0 ⁇ 100% as the lattice change rate (unit cell volume change rate) before and after complete deintercalation of lithium. in the table.
  • DMC dimethyl carbonate
  • the positive electrode active material sample prepared above Take 5 g of the positive electrode active material sample prepared above and prepare a buckle according to the above buckle preparation method. Charge with a small rate of 0.05C until the current is reduced to 0.01C. Then take out the positive electrode piece from the battery and soak it in dimethyl carbonate (DMC) for 8 hours. Then it is dried, scraped into powder, and particles with a particle size less than 500nm are screened out. The obtained particles were measured with electron energy loss spectroscopy (EELS, the instrument model used was Talos F200S) to obtain the energy loss near-edge structure (ELNES), which reflects the density of states and energy level distribution of the element. According to the density of states and energy level distribution, the number of occupied electrons is calculated by integrating the valence band density of states data, thereby deducing the valence state of the charged surface oxygen.
  • EELS electron energy loss spectroscopy
  • the crystallinity is the ratio of the crystalline part scattering to the total scattering intensity.
  • the existence of the first coating layer is conducive to reducing the Li/Mn anti-site defect concentration of the obtained material and the dissolution of Fe and manganese ions after cycling, and improving the battery reduce the charge capacity and improve the safety performance and cycle performance of the battery.
  • the lattice change rate, anti-site defect concentration and Fe and manganese ion dissolution of the resulting material can be significantly reduced, the gram capacity of the battery can be increased, and the safety performance and performance of the battery can be improved. Cycle performance.

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Abstract

本申请提供了二次电池、电池模块、电池包和用电装置。二次电池包括正极极片以及非水电解液，正极活性材料包括内核及包覆所述内核的壳，内核包括Li1+xMn1-yAyP1-zRzO4，壳包括包覆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，第一包覆层包括焦磷酸盐MP2O7和磷酸盐XPO4，第二包覆层包含碳；非水电解液包括第一添加剂，第一添加剂包括式1所示化合物、式2所示化合物、式3所示化合物组成的组中的一种或多种。提高了磷酸锰锂二次电池的倍率性能、循环性能和高温稳定性。

Description

二次电池、电池模块、电池包和用电装置 技术领域
本申请涉及锂电池技术领域，尤其涉及一种二次电池、电池模块、电池包和用电装置。
背景技术
近年来，随着锂离子电池的应用范围越来越广泛，锂离子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。由于锂离子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。
与其他正极活性材料相比，磷酸锰锂正极活性材料具有较高的安全性和循环寿命，但是磷酸锰锂的缺点在于倍率性能较差，目前通常是通过包覆或掺杂等手段来解决这一问题。但仍然希望能够进一步提升磷酸锰锂正极活性材料的倍率性能、循环性能、高温稳定性等。
发明内容
本申请是鉴于上述课题而进行的，其目的在于，提供一种二次电池、电池模块、电池包和用电装置，以解决磷酸锰锂二次电池的倍率性能和循环性能差的问题。
为了达到上述目的，本申请的第一方面提供了一种二次电池，包括正极极片以及非水电解液，其中，正极活性材料包括内核及包覆所述内核的壳，内核包括Li 1+xMn 1-yA yP 1-zR zO 4，其中x＝-0.100～0.100，y＝0.001～0.500，z＝0.001～0.100，A选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge组成的组中的一种或多种，可选为Fe、Ti、V、Ni、Co和Mg组成的组中的一种或多种，R选自B、Si、N和S组成的组中的一种或多种；壳包括包覆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，第一包覆层包括焦磷酸盐MP 2O 7和磷酸盐XPO 4，其中M和X各自独立地选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb和Al组成的组中的一种或多种，第二包覆层包含碳；
非水电解液包括第一添加剂，所述第一添加剂包括式1所示化合物、式2所示化合物、式3所示化合物组成的组中的一种或多种，
Figure PCTCN2022084834-appb-000001
R 1、R 2各自独立地表示F、C1～C6的氟代烷基、C1～C6的烷基、C1～C6的烷氧基、C2～C6的烯基、C2～C6的炔基、C6～C10的芳基中的任意一种，并且R 1、R 2中的至少一者表示F或C1～C6的氟代烷基中的任意一种；
R 3、R 4各自独立地F、C1～C6的氟代烷基、C1～C6的烷基、C1～C6的烷氧基、C2～C6的烯基、C2～C6的炔基中的任意一种，并且R 3、R 4中的至少一者表示F或C1～C6的氟代烷基中的任意一种；
R 5、R 6各自独立地F、C1～C6的氟代烷基、C1～C6的烷基、C1～C6的烷氧基、C2～C6的烯基、C2～C6的炔基、羰基、O -、＝O、- -BF 3、-O -BF 3中的任意一种；
各化学式中的M各自独立地表示碱金属、碱土金属中的一种；
n为0、1或2。
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。
本申请的磷酸锰锂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。所述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锰离子溶出，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，如图1所示，本申请中通过对比LiMnPO 4掺杂前后XRD谱图，可见，本申请的正极活性材料与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。
同时，非水电解液中引入磷酸盐类添加剂，在锂离子电池充电过程中在焦磷酸盐表面形成Li xF yPO 4，改善焦磷酸盐包覆后的磷酸锰锂正极活性材料的导离子能力，从而进一步改善包括其的二次电池的容量发挥性能和倍率性能。
在任意实施方式中，式1中，上述R 1、R 2各自独立地表示F、C1～C3的氟代烷基、C1～C3的烷基、C1～C3的烷氧基、C2～C3的烯基、C2～C3的炔基、苯基、苯甲基、甲基苯基中的任意一种，并且R 1、R 2中的至少一者表示F或C1～C3的氟代烷基中的任意一种，可选地，R 1、R 2各自独立地表示F、C1～C3的烷基、C1～C3的氟代烷基中的任意一种，可选地，C1～C3的氟代烷基为-CF 3、-C 2F 5、-CH 2CF 3或-CF 2CH 3，所述C1～C3的烷基为甲基或乙基。
在任意实施方式中，式2中，R 3、R 4各自独立地F、C1～C3的氟代烷基、C1～C3的烷基、C1～C3的烷氧基、C2～C3的烯基、C2～C3的炔基中的任意一种，并且R 3、R 4中的至少一者表示F或C1～C3的氟代烷基中的任意一种，可选地，R 3、R 4各自独立地表示F或C1～C3的氟代烷基中的任意一种。
在任意实施方式中，式3中，R 5、R 6各自独立地F、C1～C3的氟代烷基、C1～C3的烷基、C1～C3的烷氧基、C2～C6的烯基、C2～C6的炔基、羰基、O-、＝O、--BF 3、-O-BF 3中的任意一种，可选地，所述R 5、R 6各自独立地F、氟代甲基、甲基、O-、＝O、--BF 3、-O-BF 3中的任意一种，且n为0或。
在任意实施方式中，各化学式中的M各自独立地表示Li、Na、K中的一种。
可选地，用于本申请的第一添加剂可以从上述各化学式中进行任意选择，在一些实施方式中，第一添加剂包括如下化合物中的一种或多种：
Figure PCTCN2022084834-appb-000002
Figure PCTCN2022084834-appb-000003
在一些实施例中，上述第一添加剂包括以下化合物中的任意一种或多种：
Figure PCTCN2022084834-appb-000004
上述各第一添加剂在充电过程中形成Li xF yPO 4效率较高，因此，更高效地改善了本申请的正极活性材料的导离子能力。
在一些实施方式中，上述非水电解液还包括第二添加剂，第二添加剂包括含有不饱和键的环状碳酸酯化合物、卤素取代的环状碳酸酯化合物、硫酸酯化合物、亚硫酸酯化合物、磺酸内酯化合物、二磺酸化合物、腈化合物、芳香化合物、异氰酸酯化合物、磷腈化合物、环状酸酐化合物、亚磷酸酯化合物、磷酸酯化合物、硼酸酯化合物组成的组中的一种或多种。上述第二添加剂可以根据自身性能改善二次电池的容量、循环性能等，本领域技术人员可以根据实际需求来选择相应的第二添加剂。
在一些实施方式中，基于非水电解液的总重量，第一添加剂的含量为W1重量％，W1为0.01至20(比如为0.01、0.05、0.1、0.2、0.3、0.4、0.5、1、2、3、4、5、8、10、12、15、18或20)，可选地为0.1至10或0.5至5，和/或第二添加剂的含量为W2重量％，W2为0.01至20(比如为0.01、0.05、0.1、0.2、0.3、0.4、0.5、1、2、3、4、5、8、10、12、15、18或20)，可选地为0.1至10或0.3至5。上述含量的第一添加剂，既避免了第一添加剂过多导致正负极阻抗增 大，保证了二次电池的大容量和高倍率性能。因此第一添加剂在非水电解液中的质量占比处于上述范围时，既能显著改善本申请的正极活性材料的导离子能力，又能不恶化正负极阻抗，进而进一步改善了二次电池容量发挥能力和倍率性能。
在一些实施方式中，W1/W2定义为M，M为0.001至20(比如为0.01、0.05、0.1、0.2、0.3、0.4、0.5、1、2、3、4、5、8、10、12、15、18或20)，可选地0.1至10。当W2/W1处于上述范围时，二者可以发挥更好地协同作用，进一步改善容量发挥和循环性能。
在一些实施方式中，上述非水电解液还包括有机溶剂，有机溶剂的种类没有特别的限制，可根据实际需求进行选择，可选地，有机溶剂包括环状碳酸酯化合物、链状碳酸酯化合物、羧酸酯化合物中的一种或多种，进一步地包括碳酸二甲酯、碳酸二乙酯、碳酸二丙酯、碳酸甲乙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸乙烯酯、碳酸丙烯酯、碳酸丁烯酯、γ-丁内酯、甲酸甲酯、甲酸乙酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丁酯、四氢呋喃组成的组中的一种或多种。
在一些实施方式中，上述非水电解液还包括电解质盐。可选地，电解质盐包括LiN(C xF 2x+1SO 2)(C yF 2y+1SO 2)、Li(FSO 2) 2N、LiCF 3SO 3、LiPF 6、LiBF 4、LiAsF 6、LiClO 4、LiBOB、LiDFOB、LiTFOP组成的组中的一种或几种，x、y表示正整数，可选地，x、y各自独立地为0、1、2或3，非水电解液中电解质盐的浓度范围为0.5M～2.5M，可选为0.8M～2M，可以保证Li +平稳快速的在正负极迁移。
在一些实施方式中，基于内核的重量计，第一包覆层的包覆量为C1重量％，C1大于0且小于等于7，可选为4～5.6。当第一包覆层的包覆量在上述范围内时，能够进一步抑制锰离子溶出，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离子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。
在一些实施方式中，基于内核的重量计，第二包覆层的包覆量为C2重量％，C2大于0且小于等于6，可选为3～5。作为第二包覆层的含碳层一方面可以发挥“屏障”功能，避免正极活性材料与电解液直接接触，从而减少电解液对活性材料的腐蚀，提高电池在高温下的安全性能。另一方面，其具备较强的导电能力，可降低电池内阻，从而改善电池的动力学性能。然而，由于碳材料的克容量较低，因此当第二包覆层的用量过大时，可能会降低正极活性材料整体的克容量。因此，第二包覆层的包覆量在上述范围时，能够在不牺牲正极活性材料克容量的前提下，进一步改善电池的动力学性能和安全性能。
在一些实施方式中，第一添加剂含量W1与第一包覆层的包覆量C1和第二包覆层的包覆量C2的关系式W1/(C1+C2)为C，C为0.001至2，可选为0.01至1。当C小于上述范围，第一添加剂在焦磷酸盐表面成膜量较少，对二次电池 倍率性能的进一步改善效果不显著；当C大于上述范围，过多的第一添加剂又会使正负极阻抗增大，二次电池的容量提升和倍率性能提升效果受到影响。
在一些实施方式中，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，则抑制锰离子溶出的效果不显著。
在任意实施方式中，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，能够更有效地避免包覆层中的杂质相，从而进一步提升材料的克容量，进一步提高二次电池的循环性能和倍率性能。
在任意实施方式中，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％。在该实施方式的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离子溶出的作用，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。
在任意实施方式中，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。
在任意实施方式中，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，进一步减少正极材料与电解液的界面副反应，从而进一步改善二次电池的循环性能和高温储存性能。
在任意实施方式中，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。
本申请的第二方面还提供一种电池模块，该电池模块包括二次电池，该二次电池为本申请的任意一种上述二次电池。
本申请的第三方面还提供一种电池包，该电池包包括电池模块，该电池模块为本申请的上述电池模块。
本申请的第四方面还提供一种用电装置，该用电装置包括二次电池、电池模块或电池包中的至少一种，上述二次电池、电池模块和电池包均为本申请的提供的二次电池、电池模块、电池包。
由此，本申请的电池模块、电池包具有较高的循环性能、倍率特性，尤其是高温稳定性也有明显改善，进而为具有本申请二次电池、电池模块或电池包的用电装置提供了较高的动力循环稳定性和高温运行稳定性。
附图说明
图1是本申请一实施方式的正极活性材料的XRD谱图。
图2是本申请一实施方式的二次电池的示意图。
图3是图2所示的本申请一实施方式的二次电池的分解图。
图4是本申请一实施方式的电池模块的示意图。
图5是本申请一实施方式的电池包的示意图。
图6是图5所示的本申请一实施方式的电池包的分解图。
图7是本申请一实施方式的二次电池用作电源的用电装置的示意图。
附图标记说明：
1电池包；2上箱体；3下箱体；4电池模块；5二次电池；51壳体；52电极组件；53顶盖组件
具体实施方式
以下，适当地参照附图详细说明具体公开了本申请的二次电池、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，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤 (c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
在本文中，术语“包覆层”是指包覆在内核上的物质层，所述物质层可以完全或部分地包覆内核，使用“包覆层”只是为了便于描述，并不意图限制本发明。同样地，术语“包覆层的厚度”是指包覆在内核上的所述物质层在内核径向上的厚度。
在本文中，术语“源”是指作为某种元素的来源的化合物，作为实例，所述“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。
本申请发明人在实际作业中发现：磷酸锰锂正极活性材料在深度充放电过程中，锰离子溶出比较严重。虽然现有技术中有尝试对磷酸锰锂进行磷酸铁锂包覆，从而减少界面副反应，但这种包覆无法阻止溶出的锰向电解液中的迁移。溶出的锰在迁移到负极后，被还原成金属锰。这些产生的金属锰相当于“催化剂”，能够催化负极表面的SEI膜(solid electrolyte interphase，固态电解质界面膜)分解，产生的副产物一部分为气体，容易导致电池发生膨胀，影响二次电池的安全性能，另一部分沉积在负极表面，阻碍锂离子进出负极的通道，造成二次电池的阻抗增加，影响电池的动力学性能。此外，为补充损失的SEI膜，电解液和电池内部的活性锂被不断消耗，给二次电池的容量保持率带来不可逆的影响。
发明人经过大量研究后发现，对于磷酸锰锂正极活性材料，锰离子溶出严重和表面反应活性高等问题可能是由于脱锂后Mn 3+的姜-泰勒效应和Li +通道大小变化引起的。为此，发明人通过对磷酸锰锂进行改性，得到了能够显著降低锰离子溶出和降低晶格变化率，进而具备良好的循环性能、高温存储性能和安全性能的正极活性材料。
[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。
本申请的一个实施方式提供一种二次电池，包括正极极片以及非水电解液，其中，正极活性材料包括内核及包覆所述内核的壳，内核包括Li 1+xMn 1-yA yP 1-zR zO 4，其中x＝-0.100～0.100，例如x可以为0.006、0.004、0.003、0.002、0.001、0、-0.001、-0.003、-0.004、-0.005、-0.006、-0.007、-0.008、-0.009、-0.10；y＝0.001～0.500，例如y可以为0.1、0.2、0.25、0.3、0.35、0.4、0.45；z＝0.001～0.100，例如z可以为0.001、0.002、0.003、0.004、0.005、0.006、0.007、0.008、0.009、0.1；A选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge组成的组中的一种或多种，可选为Fe、Ti、V、Ni、Co和Mg组成的组中的一种或多种，R选自B、Si、N和S组成的组中的一种或多种；壳包括包覆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，第一包覆层包括焦磷酸盐MP 2O 7和磷酸盐XPO 4，其中M和X各自独立地选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb和Al组成的组中的一种或多种，第二包覆层包含碳；
非水电解液包括第一添加剂，所述第一添加剂包括式1所示化合物、式2所示化合物、式3所示化合物组成的组中的一种或多种，
Figure PCTCN2022084834-appb-000005
R 1、R 2各自独立地表示F、C1～C6的氟代烷基、C1～C6的烷基、C1～C6的烷氧基、C2～C6的烯基、C2～C6的炔基、C6～C10的芳基中的任意一种，并且 R 1、R 2中的至少一者表示F或C1～C6的氟代烷基中的任意一种；
R 3、R 4各自独立地F、C1～C6的氟代烷基、C1～C6的烷基、C1～C6的烷氧基、C2～C6的烯基、C2～C6的炔基中的任意一种，并且R 3、R 4中的至少一者表示F或C1～C6的氟代烷基中的任意一种；
R 5、R 6各自独立地F、C1～C6的氟代烷基、C1～C6的烷基、C1～C6的烷氧基、C2～C6的烯基、C2～C6的炔基、羰基、O -、＝O、- -BF 3、-O -BF 3中的任意一种；
各化学式中的M各自独立地表示碱金属、碱土金属中的一种；
n为0、1或2。
正极极片通常包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，正极膜层包括正极活性材料。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极膜层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，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。
本申请的磷酸锰锂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锰离子溶出，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，如图1所示，本申请中通过对比LiMnPO 4掺杂前后XRD谱图，可见，本申请的正极活性材料与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。
同时，非水电解液中引入磷酸盐类添加剂，在锂离子电池充电过程中在焦磷酸盐表面形成Li xF yPO 4，改善焦磷酸盐包覆后的磷酸锰锂正极活性材料的导离子能力，从而进一步改善包括其的二次电池的容量发挥性能和倍率性能。
在任意实施方式中，式1中，上述R 1、R 2各自独立地表示F、C1～C3的氟代烷基、C1～C3的烷基、C1～C3的烷氧基、C2～C3的烯基、C2～C3的炔基、苯基、苯甲基、甲基苯基中的任意一种，并且R 1、R 2中的至少一者表示F或C1～C3的氟代烷基中的任意一种，可选地，R 1、R 2各自独立地表示F、C1～C3的烷基、C1～C3的氟代烷基中的任意一种，可选地，C1～C3的氟代烷基为-CF 3、-C 2F 5、-CH 2CF 3或-CF 2CH 3，所述C1～C3的烷基为甲基或乙基。
在任意实施方式中，式2中，R 3、R 4各自独立地F、C1～C3的氟代烷基、C1～C3的烷基、C1～C3的烷氧基、C2～C3的烯基、C2～C3的炔基中的任意一种，并且R 3、R 4中的至少一者表示F或C1～C3的氟代烷基中的任意一种，可选地，R 3、R 4各自独立地表示F或C1～C3的氟代烷基中的任意一种。
在任意实施方式中，式3中，R 5、R 6各自独立地F、C1～C3的氟代烷基、C1～C3的烷基、C1～C3的烷氧基、C2～C6的烯基、C2～C6的炔基、羰基、O-、＝O、--BF 3、-O-BF 3中的任意一种，可选地，所述R 5、R 6各自独立地F、氟代甲基、甲基、O-、＝O、--BF 3、-O-BF 3中的任意一种，且n为0或。
在任意实施方式中，各化学式中的M各自独立地表示Li、Na、K中的一种。
可选地，用于本申请的第一添加剂可以从上述各化学式中进行任意选择，在一些实施方式中，第一添加剂包括如下化合物中的一种或多种：
Figure PCTCN2022084834-appb-000006
Figure PCTCN2022084834-appb-000007
在一些实施例中，上述第一添加剂包括以下化合物中的任意一种或多种：
Figure PCTCN2022084834-appb-000008
上述各第一添加剂在充电过程中形成Li xF yPO 4效率较高，因此，更高效地改善了本申请的正极活性材料的导离子能力。
在一些实施方式中，上述非水电解液还包括第二添加剂，第二添加剂包括含有不饱和键的环状碳酸酯化合物、卤素取代的环状碳酸酯化合物、硫酸酯化合物、亚硫酸酯化合物、磺酸内酯化合物、二磺酸化合物、腈化合物、芳香化合物、异氰酸酯化合物、磷腈化合物、环状酸酐化合物、亚磷酸酯化合物、磷酸酯化合物、硼酸酯化合物组成的组中的一种或多种。上述第二添加剂可以根据自身性能改善二次电池的容量、循环性能等，本领域技术人员可以根据实际需求来选择相应的第二添加剂。
在一些实施方式中，基于非水电解液的总重量，第一添加剂的含量为W1重量％，W1为0.01至20，可选地为0.1至10或0.5至5，和/或第二添加剂的含量为W2重量％，W2为0.01至20，可选地为0.1至10或0.3至5。上述含量的第一添加剂，既避免了第一添加剂过多导致正负极阻抗增大，保证了二次电池的大容量和高倍率性能。因此第一添加剂在非水电解液中的质量占比处于上述范围时，既能显著改善本申请的正极活性材料的导离子能力，又能不恶化正负极阻抗，进而进一步改善了二次电池容量发挥能力和倍率性能。
在一些实施方式中，W1/W2定义为M，M为0.001至20，可选地0.1至10。当W2/W1处于上述范围时，二者可以发挥更好地协同作用，进一步改善容量发挥和循环性能。
在一些实施方式中，上述非水电解液还包括有机溶剂，有机溶剂的种类没有特别的限制，可根据实际需求进行选择，可选地，有机溶剂包括环状碳酸酯化合物、链状碳酸酯化合物、羧酸酯化合物中的一种或多种，进一步地包括碳酸二甲酯、碳酸二乙酯、碳酸二丙酯、碳酸甲乙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸乙烯酯、碳酸丙烯酯、碳酸丁烯酯、γ-丁内酯、甲酸甲酯、甲酸乙酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丁酯、四氢呋喃组成的组中的一种或多种。
在一些实施方式中，上述非水电解液还包括电解质盐。可选地，电解质盐包括LiN(C xF 2x+1SO 2)(C yF 2y+1SO 2)、Li(FSO 2) 2N、LiCF 3SO 3、LiPF 6、LiBF 4、LiAsF 6、LiClO 4、LiBOB、LiDFOB、LiTFOP组成的组中的一种或几种，x、y表示正整数，可选地，x、y各自独立地为0、1、2或3，非水电解液中电解质盐的浓度范围为0.5M～2.5M，可选为0.8M～2M，有利于Li +平稳快速的迁移。
在一些实施方式中，基于内核的重量计，第一包覆层的包覆量为C1重量％，C1大于0且小于等于7，可选为4～5.6。当第一包覆层的包覆量在上述范围内时，能够进一步抑制锰离子溶出，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离子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。
在一些实施方式中，基于内核的重量计，第二包覆层的包覆量为C2重量％，C2大于0且小于等于6，可选为3～5。作为第二包覆层的含碳层一方面可以发挥“屏障”功能，避免正极活性材料与电解液直接接触，从而减少电解液对活性材料的腐蚀，提高电池在高温下的安全性能。另一方面，其具备较强的导电能力，可降低电池内阻，从而改善电池的动力学性能。然而，由于碳材料的克容量较低，因此当第二包覆层的用量过大时，可能会降低正极活性材料整体的克容量。因此，第二包覆层的包覆量在上述范围时，能够在不牺牲正极活性材料克容量的前提下，进一步改善电池的动力学性能和安全性能。
在一些实施方式中，第一添加剂含量W1与第一包覆层的包覆量C1和第二包覆层的包覆量C2的关系式W1/(C1+C2)为C，C为0.001至2，可选为0.01至1。当C小于上述范围，第一添加剂在焦磷酸盐表面成膜量较少，对二次电池倍率性能的进一步改善效果不显著；当C大于上述范围，过多的第一添加剂又会使正负极阻抗增大，二次电池的容量提升和倍率性能提升效果受到影响。
在一些实施方式中，可选地，第一包覆层中焦磷酸盐和磷酸盐的重量比为1:3至3:1，可选为1:3至1:1。
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，则抑制锰离子溶出的效果不显著。
在一些实施方式中，可选地，第一包覆层的磷酸盐的晶面间距为0.345-0.358nm，晶向(111)的夹角为24.25°-26.45°；第一包覆层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，循环性能和倍率性能。
在一些实施方式中，可选地，在内核中，y与1-y的比值为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，正极活性材料的能量密度和循环性能可进一步提升。
在一些实施方式中，可选地，在内核中，z与1-z的比值为1：9至1：999，可选为1：499至1：249。此处y表示P位掺杂元素的化学计量数之和。在满足 上述条件时，正极活性材料的能量密度和循环性能可进一步提升。
在一些实施方式中，可选地，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％。
在上述实施方式的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离子溶出的作用，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，从而减少正极活性材料与非水电解液的界面副反应，减少对非水电解液的消耗，改善二次电池的循环性能和安全性能。
需要说明的是，在本申请中，焦磷酸盐和磷酸盐的结晶度例如可通过调整烧结过程的工艺条件例如烧结温度、烧结时间等进行调节。焦磷酸盐和磷酸盐的结晶度可通过本领域中已知的方法测量，例如通过X射线衍射法、密度法、红外光谱法、差示扫描量热法和核磁共振吸收方法等方法测量。
在一些实施方式中，可选地，A选自Fe、Ti、V、Ni、Co和Mg中的至少两种。
在磷酸锰锂正极活性材料中的锰位同时掺杂两种以上的上述元素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。
在一些实施方式中，可选地，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。
在上述实施方式的正极活性材料中，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。本申请中，反位缺陷浓度例如可根据JIS K 0131-1996测定。
在一些实施方式中，可选地，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，从而改善进一步二次电池的倍率性能。
在一些实施方式中，可选地，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 在本申请的磷酸锰锂正极活性材料中，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。
在一些实施方式中，可选地，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。
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。
本申请二次电池所用的正极活性材料采用如下制备方法制备而成，该制备方法包括以下步骤：
提供包括Li 1+xMn 1-yA yP 1-zR zO 4的内核材料；提供MP 2O 7粉末和包含碳的源的XPO 4悬浊液，将内核材料、MP 2O 7粉末加入到包含碳的源的XPO 4悬浊液中并混合，经烧结获得正极活性材料。
在一些实施方式中，提供内核材料的步骤包括以下步骤：步骤(1)：将锰的源、元素A的源和酸在容器中混合并搅拌，得到掺杂有元素A的锰盐颗粒；步骤(2)：将掺杂有元素A的锰盐颗粒与锂的源、磷的源和元素R的源在溶剂中混合并得到浆料，在惰性气体气氛保护下烧结后得到掺杂有元素A和元素R的磷酸锰锂，其中，掺杂有元素A和元素R的磷酸锰锂为Li 1+xMn 1-yA yP 1-zR zO 4，其中x＝-0.100-0.100，y＝0.001-0.500，z＝0.001-0.100，A选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种，可选为Fe、Ti、V、Ni、Co和Mg中的一种或多种，R选自B、Si、N和S中的一种或多种。
可选地，上述步骤(1)在20-120℃，可选为25-80℃的温度下进行；和/或，步骤(1)中所述搅拌在500-700rpm下进行60-420分钟，可选地为120-360分钟。
在一些实施例中，上述元素A的源选自元素A的单质、硫酸盐、卤化物、硝酸盐、有机酸盐、氧化物或氢氧化物中的一种或多种；和/或，元素R的源选自元素R的单质、硫酸盐、卤化物、硝酸盐、有机酸盐、氧化物或氢氧化物以及元素R的无机酸中的一种或多种。
在一些实施例中，MP 2O 7粉末通过以下方法制备：将元素M的源和磷的源添加到溶剂中，得到混合物，调节混合物的pH为4-6，搅拌并充分反应，然后经干燥、烧结获得，其中M选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb或Al中的一种或多种。可选上述干燥步骤为在100-300℃、可选150-200℃下干燥4-8h；上述烧结步骤为在500-800℃、可选650-800℃下，在惰性气体气氛下烧结4-10h。
在一些实施例中，上述包覆步骤中的烧结温度为500-800℃，烧结时间为4-10h。
在一些实施方式中，正极膜层还可包含本领域公知的用于二次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二次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。
在一些实施方式中，正极膜层还可选地包括粘结剂。作为示例，粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。
在一些实施方式中，正极膜层还可选地包括导电剂。作为示例，导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，可以通过以下方式制备正极极片：将上述用于制备正极极片的组分，例如正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
[负极极片]
负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，所述负极膜层包括负极活性材料。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极膜层设置在负极集流体相对的两个表面中的任意一者或两者上。
在一些实施方式中，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。
[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能够盖设于所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔内。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或多个，本领域技术人员可根据具体实际需求进行选择。
在一些实施方式中，二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为一个或多个，具体数量本领域技术人员可根据电池模块的应用和容量进行选择。
图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，所述用电装置包括本申请提供的二次电池、电池模块、或电池包中的至少一种。所述二次电池、电池模块、或电池包可以用作所述用电装置的电源，也可以用作所述用电装置的能量存储单元。所述用电装置可以包括移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等，但不限于此。
作为所述用电装置，可以根据其使用需求来选择二次电池、电池模块或电池包。
图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。
其中，第一添加剂选自如下化合物：
化合物1：
Figure PCTCN2022084834-appb-000009
化合物2:
Figure PCTCN2022084834-appb-000010
化合物3：
Figure PCTCN2022084834-appb-000011
化合物4：
Figure PCTCN2022084834-appb-000012
第二添加剂选自如下化合物：
化合物5：
Figure PCTCN2022084834-appb-000013
化合物6：
Figure PCTCN2022084834-appb-000014
化合物7：
Figure PCTCN2022084834-appb-000015
实施例1-1
【双层包覆的磷酸锰锂正极活性材料的制备】
(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MnCO3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。然后过滤所述悬浮液，将滤饼在120℃下烘干，之后进行研磨，得到中值粒径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。将所述浆料转移到喷雾干燥设备中进行喷雾干燥造粒，设定干燥温度为250℃，干燥4小时，得到粉料。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。将所述粉末在650℃、氮气气氛下烧结8小时，并自然冷却至室温后进行研磨，得到Li 2FeP 2O 7粉末。
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。
【正极极片的制备】
将上述制备的双层包覆的磷酸锰锂正极活性材料、导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按重量比为92：2.5：5.5加入到N-甲基吡咯烷酮(NMP)中，搅拌混合均匀，得到正极浆料。然后将正极浆料按0.280g/1540.25mm 2均匀涂覆于铝箔上，经烘干、冷压、分切，得到正极极片。
【负极极片的制备】
将负极活性物质人造石墨、硬碳、导电剂乙炔黑、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC-Na)按照重量比为90：5：2：2：1溶于溶剂去离子水中，搅拌混合均匀后制备成负极浆料。将负极浆料按0.117g/1540.25mm 2均匀涂覆在负极集流体铜箔上，经过烘干、冷压、分切得到负极极片。
【电解液的制备】
在氩气气氛手套箱中(H 2O<0.1ppm，O 2<0.1ppm)，作为有机溶剂，将碳酸亚乙酯(EC)/碳酸甲乙酯(EMC)按照体积比3/7混合均匀，向其中加入化合物1(作为第一添加剂，在电解液中的质量含量为2％)、化合物5(作为第二添加剂，在电解液中的质量含量为1％)、LiPF 6(作为电解质盐，在电解液中的质量含量为1％)，搅拌均匀，得到电解液。
【隔离膜】
使用市售的厚度为20μm、平均孔径为80nm的PP-PE共聚物微孔薄膜(来自卓高电子科技公司，型号20)。
【全电池的制备】
将上述获得的正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正负极中间起到隔离的作用，并卷绕得到裸电芯。将裸电芯置于外包装中，注入上述电解液并封装，得到全电池(下文也称“全电”)。
【扣式电池的制备】
将上述制备的双层包覆的磷酸锰锂正极活性材料、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，采用上述电解液，与上述制备的正极极片一起在扣电箱中组装成扣式电池(下文也称“扣电”)。
实施例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2-1至2-4
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1小时以控制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2小时以控制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2小时以控制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3小时以控制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3小时以控制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4小时以控制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4小时以控制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6小时以控制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4-7
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℃/4小时、150℃/6小时、200℃/6小时和200℃/6小时；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℃/6小时、700℃/6小时、700℃/6小时和600℃/6小时以外，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℃/6小时、150℃/6小时和150℃/6小时；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℃/4小时、600℃/6小时和800℃/8小时以外，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，然后过滤所述悬浮液，将滤饼在120℃下烘干，之后进行研磨，得到中值粒径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。将所述浆料转移到喷雾干燥设备中进行喷雾干燥造粒，设定干燥温度为250℃，干燥4小时，得到粉料。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：将9.52g碳酸锂、29.9g碳酸亚铁、29.6g磷酸二氢铵和32.5g二水合草酸溶于50mL去离子水中。混合物的pH为5，搅拌2小时使反应混合物充分反应。然后将反应后的溶液升温到80℃并保持该温度4小时，得到包含Li 2FeP 2O 7的悬浊液，将悬浊液进行过滤，用去离子水洗涤，并在120℃下干燥4小时，得到粉末。将所述粉末在500℃、氮气 气氛下烧结4小时，并自然冷却至室温后进行研磨，控制Li 2FeP 2O 7的结晶度为5％，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：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4小时，得到粉末。将所述粉末在500℃、氮气气氛下烧结4小时，并自然冷却至室温后进行研磨，控制Li 2FeP 2O 7的结晶度为5％。
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4小时以控制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℃/3小时、80℃/3小时、80℃/3小时；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℃/3小时、400℃/3小时、350℃/2小时，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℃/3小时；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。
上述实施例和对比例的【正极极片的制备】、【负极极片的制备】、【电解液的制备】、【隔离膜】和【电池的制备】均与实施例1-1的工艺相同。
【相关参数测试】
1.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5分钟，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。
2.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5分钟，按照0.1C放电至2.5V，静置5分钟，按照0.1C充电至4.3V，然后在4.3V下恒压充电至电流小于等于0.05mA，静置5分钟；然后按照0.1C放电至2.5V，此时的放电容量为初始克容量，记为D0，放电能量为初始能量，记为E0，扣电平均放电电压V即为E0/D0。
3.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5分钟，记录此时的充电容量为电芯残余容量。
4.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5分钟，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。
5.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°/分钟对样品进行测试，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。
6.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。
7.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。
8.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。
9.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。
10.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。
11.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。
Figure PCTCN2022084834-appb-000016
Figure PCTCN2022084834-appb-000017
Figure PCTCN2022084834-appb-000018
Figure PCTCN2022084834-appb-000019
Figure PCTCN2022084834-appb-000020
Figure PCTCN2022084834-appb-000021
Figure PCTCN2022084834-appb-000022
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和锰离子溶出量，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和锰离子溶出量，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和锰离子溶出量逐渐下降，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和锰离子溶出量逐渐下降，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 PCTCN2022084834-appb-000023
Figure PCTCN2022084834-appb-000024
Figure PCTCN2022084834-appb-000025
Figure PCTCN2022084834-appb-000026
Figure PCTCN2022084834-appb-000027
Figure PCTCN2022084834-appb-000028
Figure PCTCN2022084834-appb-000029
Figure PCTCN2022084834-appb-000030
Figure PCTCN2022084834-appb-000031
Figure PCTCN2022084834-appb-000032
Figure PCTCN2022084834-appb-000033
Figure PCTCN2022084834-appb-000034

Claims (21)

  1. 一种二次电池，包括正极极片以及非水电解液，其中，
    所述正极极片包括正极活性材料，所述正极活性材料包括内核及包覆所述内核的壳，
    所述内核包括Li 1+xMn 1-yA yP 1-zR zO 4，其中x＝-0.100～0.100，y＝0.001～0.500，z＝0.001～0.100，所述A选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge组成的组中的一种或多种，可选为Fe、Ti、V、Ni、Co和Mg组成的组中的一种或多种，所述R选自B、Si、N和S组成的组中的一种或多种；
    所述壳包括包覆所述内核的第一包覆层以及包覆所述第一包覆层的第二包覆层，其中，
    所述第一包覆层包括焦磷酸盐MP 2O 7和磷酸盐XPO 4，其中所述M和X各自独立地选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb和Al组成的组中的一种或多种，
    所述第二包覆层包含碳；
    所述非水电解液包括第一添加剂，所述第一添加剂包括式1所示化合物、式2所示化合物、式3所示化合物组成的组中的一种或多种，
    Figure PCTCN2022084834-appb-100001
    R 1、R 2各自独立地表示F、C1～C6的氟代烷基、C1～C6的烷基、C1～C6的烷氧基、C2～C6的烯基、C2～C6的炔基、C6～C10的芳基中的任意一种，并且R 1、R 2中的至少一者表示F或C1～C6的氟代烷基中的任意一种；
    R 3、R 4各自独立地F、C1～C6的氟代烷基、C1～C6的烷基、C1～C6的烷氧基、C2～C6的烯基、C2～C6的炔基中的任意一种，并且R 3、R 4中的至少一者表示F或C1～C6的氟代烷基中的任意一种；
    R 5、R 6各自独立地F、C1～C6的氟代烷基、C1～C6的烷基、C1～C6的烷氧基、C2～C6的烯基、C2～C6的炔基、羰基、O -、＝O、- -BF 3、-O -BF 3中的任意一种；
    各化学式中的M各自独立地表示碱金属、碱土金属中的一种；
    n为0、1或2。
  2. 根据权利要求1所述的二次电池，其中，
    R 1、R 2各自独立地表示F、C1～C3的氟代烷基、C1～C3的烷基、C1～C3的烷氧基、C2～C3的烯基、C2～C3的炔基、苯基、苯甲基、甲基苯基中的任意一种，并且R 1、R 2中的至少一者表示F或C1～C3的氟代烷基中的任意一种，可选地，R 1、R 2各自独立地表示F、C1～C3的烷基、C1～C3的氟代烷基中的任意一种，可选地，所述C1～C3的氟代烷基为-CF 3、-C 2F 5、-CH 2CF 3或-CF 2CH 3，所述C1～C3的烷基为甲基或乙基；和/或，
    R 3、R 4各自独立地F、C1～C3的氟代烷基、C1～C3的烷基、C1～C3的烷氧基、C2～C3的烯基、C2～C3的炔基中的任意一种，并且R 3、R 4中的至少一者表示F或C1～C3的氟代烷基中的任意一种，可选地，R 3、R 4各自独立地表示F或C1～C3的氟代烷基中的任意一种；和/或，
    R 5、R 6各自独立地F、C1～C3的氟代烷基、C1～C3的烷基、C1～C3的烷氧基、C2～C6的烯基、C2～C6的炔基、羰基、O-、＝O、- -BF 3、-O -BF 3中的任意一种，可选地，所述R5、R6各自独立地F、氟代甲基、甲基、O -、＝O、- -BF 3、-O -BF 3中的任意一种，且n为0或1；和/或
    各化学式中的M各自独立地表示Li、Na、K中的一种。
  3. 根据权利要求1或2所述的二次电池，其中，所述第一添加剂包括如下化合物中的一种或多种：
    Figure PCTCN2022084834-appb-100002
    Figure PCTCN2022084834-appb-100003
    Figure PCTCN2022084834-appb-100004
  4. 根据权利要求1-3中任一项所述的二次电池，其中，所述第一添加剂包括以下化合物中的任意一种或多种：
    Figure PCTCN2022084834-appb-100005
  5. 根据权利要求1-4中任一项所述的二次电池，其中，
    所述非水电解液还包括第二添加剂，所述第二添加剂包括含有不饱和键的环状碳酸酯化合物、卤素取代的环状碳酸酯化合物、硫酸酯化合物、亚硫酸酯化合物、磺酸内酯化合物、二磺酸化合物、腈化合物、芳香化合物、异氰酸酯化合物、磷腈化合物、环状酸酐化合物、亚磷酸酯化合物、磷酸酯化合物、硼酸酯化合物组成的组中的一种或多种。
  6. 根据权利要求5所述的二次电池，其中，基于所述非水电解液的总重量，所述第一添加剂的含量为W1重量％，W1为0.01至20，可选地为0.1至10或0.5至5，和/或所述第二添加剂的含量为W2重量％，W2为0.01至20，可选地为0.1至10或0.3至5，
    可选地，所述W1/W2定义为M，M为0.001至20，可选地0.1至10。
  7. 根据权利要求1-6中任一项所述的二次电池，其中，所述非水电解液还包括有机溶剂和电解质盐，
    可选地，所述有机溶剂包括环状碳酸酯化合物、链状碳酸酯化合物、羧酸酯化合物中的一种或多种，进一步地包括碳酸二甲酯、碳酸二乙酯、碳酸二丙酯、碳酸甲乙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸乙烯酯、碳酸丙烯酯、碳酸丁烯酯、γ-丁内酯、甲酸甲酯、甲酸乙酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丁酯、四氢呋喃组成的组中的一种或多种；和/或，
    可选地，所述电解质盐包括LiN(C xF 2x+1SO 2)(C yF 2y+1SO 2)、Li(FSO 2) 2N、LiCF 3SO 3、LiPF 6、LiBF 4、LiAsF 6、LiClO 4、LiBOB、LiDFOB、LiTFOP组成的组中的一种或几种，x、y表示正整数，可选地，x、y各自独立地为0、1、2或3，所述非水电解液中所述电解质盐的浓度范围为0.5M～2.5M，可选为0.8M～2M。
  8. 根据权利要求1-7中任一项所述的二次电池，其中，
    基于所述内核的重量计，所述第一包覆层的包覆量为C1重量％，C1大于0且小于等于7，可选为4～5.6；和/或，
    基于所述内核的重量计，所述第二包覆层的包覆量为C2重量％，C2大于0且小于等于6，可选为3～5。
  9. 根据权利要求4所述的二次电池，其中，
    基于所述内核的重量计，所述第一包覆层的包覆量为C1重量％，C1大于0且小于等于7，可选为4～5.6；和/或，
    基于所述内核的重量计，所述第二包覆层的包覆量为C2重量％，C2大于0且小于等于6，可选为3～5；
    其中，第一添加剂含量W1与第一包覆层的包覆量C1和第二包覆层的包覆量C2的关系式W1/(C1+C2)为C，C为0.001至2，可可选为0.01至1。
  10. 根据权利要求1-9中任一项所述的二次电池，其中，
    所述第一包覆层中焦磷酸盐和磷酸盐的重量比为1:3至3:1，可选为1:3至1:1。
  11. 根据权利要求1-10中任一项所述的二次电池，其中，
    所述第一包覆层的磷酸盐的晶面间距为0.345-0.358nm，晶向(111)的夹角为24.25°-26.45°；
    所述第一包覆层的焦磷酸盐的晶面间距为0.293-0.326nm，晶向(111)的夹角为26.41°-32.57°。
  12. 根据权利要求1-11中任一项所述的二次电池，其中，
    在所述内核中，y与1-y的比值为1：10至10：1，可选为1：4至1：1；和/或，
    在所述内核中，z与1-z的比值为1：9至1：999，可选为1：499至1：249。
  13. 根据权利要求1-12中任一项所述的二次电池，其中，
    所述焦磷酸盐和磷酸盐的结晶度各自独立地为10％至100％，可选为50％至100％。
  14. 根据权利要求1-13中任一项所述的二次电池，其中，
    所述A选自Fe、Ti、V、Ni、Co和Mg中的至少两种。
  15. 根据权利要求1-14中任一项所述的二次电池，其中，
    所述正极活性材料的Li/Mn反位缺陷浓度为4％以下，可选为2％以下。
  16. 根据权利要求1-14中任一项所述的二次电池，其中，
    所述正极活性材料的晶格变化率为6％以下，可选为4％以下。
  17. 根据权利要求1-16中任一项所述的二次电池，其中，
    所述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。
  18. 根据权利要求1-17中任一项所述的二次电池，其中，
    所述正极活性材料在3吨下的压实密度为2.0g/cm 3以上，可选地为2.2g/cm 3以上。
  19. 一种电池模块，包括权利要求1-18中任一项所述的二次电池。
  20. 一种电池包，包括权利要求19所述的电池模块。
  21. 一种用电装置，包括选自权利要求1-18中任一项所述的二次电池、权利要求19所述的电池模块或权利要求20所述的电池包中的至少一种。
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