WO2023206427A1 - 二次电池以及包含其的电池模块、电池包及用电装置 - Google Patents

二次电池以及包含其的电池模块、电池包及用电装置 Download PDF

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WO2023206427A1
WO2023206427A1 PCT/CN2022/090476 CN2022090476W WO2023206427A1 WO 2023206427 A1 WO2023206427 A1 WO 2023206427A1 CN 2022090476 W CN2022090476 W CN 2022090476W WO 2023206427 A1 WO2023206427 A1 WO 2023206427A1
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group
monovalent
optionally
alkyl
trivalent
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PCT/CN2022/090476
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English (en)
French (fr)
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张立美
邹海林
陈培培
刘姣
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宁德时代新能源科技股份有限公司
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Priority to PCT/CN2022/090476 priority Critical patent/WO2023206427A1/zh
Priority to CN202280013152.8A priority patent/CN116848690A/zh
Publication of WO2023206427A1 publication Critical patent/WO2023206427A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • 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 belongs to the field of battery technology, and specifically relates to a secondary battery, a battery module, a battery pack and an electrical device containing the same.
  • lithium manganese phosphate has become one of the most popular cathode active materials due to its advantages of high capacity, good safety performance and rich sources of raw materials.
  • lithium manganese phosphate is prone to manganese ions dissolving during charging, resulting in rapid capacity attenuation. Restricting its commercialization process.
  • the purpose of this application is to provide a secondary battery and a battery module, a battery pack and a power device containing the same, aiming to make the secondary battery have both high energy density and good rate performance, cycle performance and storage performance. and safety performance.
  • a first aspect of the application provides a secondary battery, including a positive electrode plate and a non-aqueous electrolyte, wherein,
  • the positive electrode sheet includes a positive active material with a core-shell structure, and the positive active material includes a core and a shell covering the core,
  • the core includes Li 1+x Mn 1-y A y P 1-z R z O 4 , x is -0.100 to 0.100, y is 0.001 to 0.500, z is 0.001 to 0.100, and the A is selected from Zn, Al , one or more of Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and Ge, optionally Fe, Ti, V, Ni , one or more of Co and Mg, the R is selected from one or more of B, Si, N and S;
  • the shell includes a first cladding layer covering the core and a second cladding layer covering the first cladding layer, wherein,
  • the first coating layer includes pyrophosphate MP 2 O 7 and phosphate XPO 4 , and the M and X are each independently selected from Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr , one or more of Nb and Al,
  • the second cladding layer includes carbon
  • the non-aqueous electrolyte solution includes a first additive, and the first additive includes one or more compounds represented by Formula 1-A to Formula 1-D,
  • R 1 represents a hydrogen atom or at least one of the group consisting of the following groups: hydroxyl, C1 to C18 monovalent alkyl, C1 to C18 monovalent alkoxy, C2 to C18 monovalent alkoxyalkyl, C3 ⁇ C18 monovalent cycloalkyl group, C2 ⁇ C18 monovalent oxyheterocycloalkyl group, C6 ⁇ C18 monovalent aryl group, C7 ⁇ C18 monovalent arylalkyl group, C7 ⁇ C18 monovalent alkylaryl group, C6 ⁇ C18 Monovalent aryloxy group, C7 ⁇ C18 monovalent aryloxyalkyl group, C12 ⁇ C18 monovalent aryl ether group, C2 ⁇ C18 monovalent heteroaryl group, C3 ⁇ C18 monovalent heteroarylalkyl group, C3 ⁇ C18 monovalent alkyl heteroaryl and C1 ⁇ C18 monovalent silyl;
  • R 2 to R 21 each independently represent a hydrogen atom or at least one of the group consisting of the following groups: C1 to C18 monovalent alkyl group, C2 to C18 monovalent alkoxyalkyl group, C3 to C18 monovalent ring Alkyl, C2 ⁇ C18 monovalent oxygen heterocycloalkyl, C6 ⁇ C18 monovalent aryl, C7 ⁇ C18 monovalent arylalkyl, C7 ⁇ C18 monovalent alkylaryl, C7 ⁇ C18 monovalent aryloxy Alkyl group, C12 ⁇ C18 monovalent aryl ether group, C2 ⁇ C18 monovalent heteroaryl group, C3 ⁇ C18 monovalent heteroarylalkyl group, C3 ⁇ C18 monovalent alkyl heteroaryl group and C1 ⁇ C18 monovalent silane group, and when R 2 and R 3 are both hydrogen atoms, R 1 is not a hydroxyl group;
  • R 2 and R 3 can also be bonded to each other to form a ring structure
  • R 4 and R 5 can also be bonded to each other to form a ring structure
  • R 6 and R 7 can also be bonded to each other to form a ring structure
  • R 8 and R 9 can also be bonded to each other to form a ring structure.
  • R 10 and R 11 can also bond to each other to form a ring structure
  • R 12 and R 13 can also bond to each other to form a ring structure
  • R 14 and R 15 can also bond to each other to form a ring structure
  • R 16 and R 17 can also be bonded to each other to form a ring structure
  • R 18 and R 19 can also be bonded to each other to form a ring structure
  • R 20 and R 21 can also be bonded to each other to form a ring structure;
  • L 1 represents an oxygen atom or at least one of the group consisting of the following groups: C1 ⁇ C18 divalent alkyl group, C1 ⁇ C18 oxa divalent alkyl group, C6 ⁇ C18 divalent cycloalkyl group, C6 ⁇ C18 divalent alkyl group Oxygen heterocycloalkyl group, C6 ⁇ C18 divalent aryl group, C7 ⁇ C18 divalent arylalkyl group, C7 ⁇ C18 divalent alkyl aryl group, C6 ⁇ C18 divalent aryloxy group, C7 ⁇ C18 divalent aryloxy group Aryloxyalkyl, C12 ⁇ C18 divalent aryl ether group, C2 ⁇ C18 divalent heteroaryl, C3 ⁇ C18 divalent heteroarylalkyl and C3 ⁇ C18 divalent alkylheteroaryl;
  • L 2 represents at least one of the following groups: C1 to C18 trivalent alkyl, C1 to C18 oxa trivalent alkyl, C6 to C18 trivalent cycloalkyl, C6 to C18 trivalent oxa Cycloalkyl, C6 ⁇ C18 trivalent aryl, C7 ⁇ C18 trivalent arylalkyl, C7 ⁇ C18 trivalent alkyl aryl, C6 ⁇ C18 trivalent aryloxy, C7 ⁇ C18 trivalent aryloxy Alkyl group, C12 ⁇ C18 trivalent aryl ether group, C3 ⁇ C18 trivalent heteroaryl group, C3 ⁇ C18 trivalent heteroaryl alkyl group and C3 ⁇ C18 trivalent alkyl heteroaryl group;
  • L 3 represents at least one of the group consisting of the following groups: C1 to C18 tetravalent alkyl, C1 to C18 oxa tetravalent alkyl, C6 to C18 tetravalent cycloalkyl, C6 to C18 tetravalent oxa Cycloalkyl, C6 ⁇ C18 tetravalent aryl, C7 ⁇ C18 tetravalent arylalkyl, C7 ⁇ C18 tetravalent alkyl aryl, C7 ⁇ C18 tetravalent aryloxyalkyl, C12 ⁇ C18 tetravalent aryl Ether group, C4 ⁇ C18 tetravalent heteroaryl group, C4 ⁇ C18 tetravalent heteroarylalkyl group and C4 ⁇ C18 tetravalent alkylheteroaryl group.
  • this application can effectively reduce the dissolution of manganese ions during the process of deintercalating lithium, and at the same time promote the migration of lithium ions, thereby improving the rate performance, cycle performance, and Storage performance and security performance.
  • the non-aqueous electrolyte contains the first additive shown in Formula 1-A to Formula 1-D, it can form a dense and stable interface film on the surface of the positive electrode active material during the charging process of the secondary battery, reducing the The dissolution of the first coating layer reduces the dissolution of manganese ions, while reducing the catalytic oxidation of the second coating layer under high voltage, reducing the consumption of non-aqueous electrolyte and active lithium ions. Therefore, the secondary battery of the present application can simultaneously have high energy density and good rate performance, cycle performance, storage performance and safety performance.
  • R 2 and R 3 are bonded to each other to form a ring structure.
  • At least one of R 1 to R 3 represents a C3 to C18 monovalent cycloalkyl group, a C2 to C18 monovalent oxygen heterocycloalkyl group, a C6 to C18 monovalent aryl group, a C7 to C18 monovalent arylalkyl group, C7 ⁇ C18 monovalent alkylaryl group, C7 ⁇ C18 monovalent aryloxyalkyl group, C12 ⁇ C18 monovalent aryl ether group, C2 ⁇ C18 monovalent heteroaryl group, C3 ⁇ C18 monovalent heteroarylalkyl group or C3 to C18 monovalent alkyl heteroaryl group.
  • R 1 to R 3 each independently represent a C6 to C18 monovalent aryl group, a C7 to C18 monovalent arylalkyl group, a C7 to C18 monovalent alkyl aryl group, or a C7 to C18 monovalent aryloxy group.
  • R 1 to R 3 represent the above substituents, it helps to form an interface film containing cross-linked macromolecular polymer on the surface of the cathode active material, further reducing the dissolution of the first coating layer and reducing the catalysis of the second coating layer. Oxidation reduces the dissolution of manganese ions and the consumption of non-aqueous electrolyte and active lithium ions, thereby further enhancing the improvement effect on the cycle performance and storage performance of secondary batteries.
  • At least one group of R 4 and R 5 , R 6 and R 7 are bonded to each other to form a ring structure.
  • L 1 represents an oxygen atom
  • R 4 to R 7 each independently represent a C6 to C18 monovalent aryl group, a C7 to C18 monovalent arylalkyl group, or a C7 to C18 monovalent alkyl group.
  • At least one group of R 8 and R 9 , R 10 and R 11 , R 12 and R 13 are bonded to each other to form a ring structure.
  • L 2 represents a C6-C18 trivalent aryl group, a C7-C18 trivalent arylalkyl group, a C7-C18 trivalent alkyl aryl group, a C6-C18 trivalent aryloxy group, C7 ⁇ C18 trivalent aryloxyalkyl, C12 ⁇ C18 trivalent aryl ether group, C3 ⁇ C18 trivalent heteroaryl, C3 ⁇ C18 trivalent heteroarylalkyl or C3 ⁇ C18 trivalent alkyl heteroaryl base.
  • At least one group of R 14 and R 15 , R 16 and R 17 , R 18 and R 19 , R 20 and R 21 are bonded to each other to form a ring structure.
  • L 3 represents a C6 to C18 tetravalent aryl group, a C7 to C18 tetravalent arylalkyl group, a C7 to C18 tetravalent aryloxyalkyl group, or a C7 to C18 tetravalent aryloxyalkyl group.
  • group C12 ⁇ C18 tetravalent aryl ether group, C4 ⁇ C18 tetravalent heteroaryl group, C4 ⁇ C18 tetravalent heteroarylalkyl group or C4 ⁇ C18 tetravalent alkylheteroaryl group.
  • the first additive includes at least one of the following compounds:
  • the inventor found that using at least one of the above-mentioned compounds H1 to H36 as the first additive can form a denser and more stable interface film on the surface of the cathode active material, which helps to further reduce the first coating layer
  • the dissolution and reduction of the catalytic oxidation of the second coating layer further reduce the dissolution of manganese ions and the consumption of non-aqueous electrolyte and active lithium ions, thereby further enhancing the improvement effect on the cycle performance and storage performance of the secondary battery.
  • the first additive includes at least one of H1 to H10, H13 to H15, and H31 to H33. More optionally, the first additive includes at least one of H1 to H8, H32 to H33. .
  • These first additives help to form an interface film containing cross-linked macromolecular polymers on the surface of the cathode active material, further reducing the dissolution of the first coating layer and reducing the catalytic oxidation of the second coating layer, thereby further reducing manganese ions. Dissolution and consumption of non-aqueous electrolyte and active lithium ions can further enhance the improvement effect on the cycle performance and storage performance of secondary batteries.
  • the non-aqueous electrolyte further includes a second additive
  • the second additive includes sultone, cyclic sulfate, lithium difluorophosphate, lithium difluorodioxalate phosphate, lithium difluorodioxalate, One or more of lithium fluoxalate and borate.
  • the non-aqueous electrolyte solution contains both the first additive and the second additive, it helps to significantly improve the cycle performance and storage performance of the secondary battery, and at the same time improves the capacity development and rate performance of the secondary battery.
  • the sultone includes at least one of the compounds represented by Formula 2-A,
  • p1 represents 1, 2 or 3
  • p2 represents 1 or 2
  • p3 represents 1 or 2
  • R 22 each independently represents a hydrogen atom, a halogen atom, a carboxylate group, a sulfonate group, a C1 to C6 monovalent alkyl group, a C1 to C6 monovalent haloalkyl group, a C1 to C6 monovalent alkoxy group, or a C1 to C6 A chain structure or a cyclic structure formed by one or more of monovalent haloalkoxy groups, C2-C6 monovalent alkenyl groups bonded to each other through single bonds.
  • R 22 represents a cyclic structure, it is bonded through a single bond.
  • R 23 each independently represents a hydrogen atom, a halogen atom, a carboxylate group, a sulfonate group, a C1 to C6 monovalent alkyl group, a C1 to C6 monovalent haloalkyl group, a C1 to C6 monovalent alkoxy group, and a C1 to C6 A chain structure or a cyclic structure formed by one or more of monovalent haloalkoxy groups, C2-C6 monovalent alkenyl groups bonded to each other through single bonds.
  • R 23 represents a cyclic structure, it is bonded through a single bond.
  • R 24 represents a carbonyl group or C(Y 1 ) 2
  • Y 1 independently represents a hydrogen atom, a halogen atom, a carboxylate group, a sulfonate group, a C1 to C6 monovalent alkyl group, a C1 to C6 monovalent haloalkyl group, One or a combination of C1 ⁇ C6 monovalent alkoxy group, C1 ⁇ C6 monovalent haloalkoxy group, C2 ⁇ C6 monovalent alkenyl group, C6 ⁇ C12 monovalent aryl group,
  • R 22 and R 23 may also be bonded to each other to form a ring structure.
  • the sultone includes at least one of the following compounds:
  • the cyclic sulfate ester includes at least one of the compounds represented by Formula 2-B,
  • q1 means 1, 2 or 3
  • q2 means 1 or 2
  • q3 means 1 or 2
  • R 25 each independently represents a hydrogen atom, a halogen atom, a carbonyl oxygen atom, a carboxylic acid ester group, a sulfate ester group, a C1 to C6 monovalent alkyl group, a C1 to C6 monovalent haloalkyl group, a C1 to C6 monovalent alkoxy group, A chain structure or a cyclic structure formed by one or more of C1 to C6 monovalent haloalkoxy groups, C2 to C6 monovalent alkenyl groups bonded to each other through single bonds.
  • R 25 represents a cyclic structure, by Single bonded to the polycyclic ring of formula 2-B or sharing one carbon atom with the polycyclic ring of formula 2-B to form a spirocyclic compound,
  • R 26 independently represents a hydrogen atom, a halogen atom, a carboxylic acid ester group, a sulfate ester group, a C1 to C6 monovalent alkyl group, a C1 to C6 monovalent haloalkyl group, a C1 to C6 monovalent alkoxy group, a C1 to C6 monovalent alkoxy group, and a C1 to C6 monovalent alkoxy group.
  • R 26 represents a cyclic structure, it is bonded through a single bond.
  • R 25 and R 26 may also be bonded to each other to form a ring structure.
  • the cyclic sulfate ester includes at least one of the following compounds:
  • the content of the first additive is W1% by weight
  • W1 is 0.01 to 20, optionally 0.1 to 10, more optionally 0.3 to 5, based on the non-aqueous electrolyte solution Total weight.
  • the content of the second additive is W2% by weight
  • W2 is 0.01 to 20, optionally 0.1 to 10, more optionally 0.3 to 5, based on the non-aqueous electrolyte solution Total weight.
  • the coating amount of the first coating layer is C1 weight %, where C1 is greater than 0 and less than or equal to 7, optionally 4 to 5.6, based on the weight of the core. Therefore, the function of the first coating layer can be effectively exerted, and at the same time, the dynamic performance of the secondary battery will not be affected due to an excessive thickness of the coating layer.
  • the coating amount of the second coating layer is C2 weight %, where C2 is greater than 0 and less than or equal to 6, optionally 3 to 5, based on the weight of the core. Therefore, the presence of the second coating layer can avoid direct contact between the positive electrode active material and the electrolyte, reduce the erosion of the positive electrode active material by the electrolyte, and improve the conductivity of the positive electrode active material. When the coating amount of the second layer is within the above range, the gram capacity of the cathode active material can be effectively increased.
  • W1/W2 is 0.01 to 20, optionally 0.01 to 10. This can further enhance the improvement effect on the cycle performance and storage performance of the secondary battery, while improving the capacity and rate performance of the secondary battery.
  • (W1+W2)/(C1+C2) is 0.001 to 2, optionally 0.01 to 1. This can significantly enhance the improvement effect on the cycle performance and storage performance of the secondary battery, while improving the capacity and rate performance of the secondary battery.
  • the non-aqueous electrolyte further includes a third additive
  • the third additive includes a cyclic carbonate compound containing an unsaturated bond, a halogen-substituted cyclic carbonate compound, a nitrile compound, One or more of phosphazene compounds, aromatic hydrocarbons and halogenated aromatic hydrocarbon compounds, isocyanate compounds, acid anhydride compounds, phosphite compounds, phosphate ester compounds, sulfite compounds, and methylene disulfonate compounds.
  • the third additive helps to form a denser and more stable interface film on the surface of the positive electrode and/or negative electrode active material, thereby helping to further improve at least one of the cycle performance, storage performance, and rate performance of the secondary battery.
  • the ratio of y to 1-y is 1:10 to 10:1, optionally 1:4 to 1:1.
  • the energy density and cycle performance of secondary batteries can be further improved.
  • the ratio of z to 1-z is 1:9 to 1:999, optionally 1:499 to 1:249.
  • the energy density and cycle performance of secondary batteries can be further improved.
  • the A is selected from at least two of Fe, Ti, V, Ni, Co and Mg. Therefore, since A is two or more metals within the above range, doping at the manganese site is beneficial to enhancing the doping effect, further reducing surface oxygen activity and inhibiting the dissolution of manganese ions.
  • the interplanar spacing of the phosphate of the first coating layer is 0.345-0.358 nm, and the angle between the crystal directions (111) is 24.25°-26.45°.
  • the interplanar spacing of the pyrophosphate of the first coating layer is 0.293-0.326 nm, and the angle between the crystal directions (111) is 26.41°-32.57°.
  • the weight ratio of pyrophosphate and phosphate in the first coating layer is 1:3 to 3:1, optionally 1:3 to 1:1. Therefore, by using pyrophosphate and phosphate in a suitable weight ratio range, it can not only effectively hinder the dissolution of manganese ions, but also effectively reduce the surface miscellaneous lithium content and reduce interface side reactions, thereby improving the rate performance and cycle performance of the secondary battery. , storage performance and security performance.
  • the crystallinity of the pyrophosphate and phosphate is each independently from 10% to 100%, optionally from 50% to 100%. Therefore, pyrophosphate and phosphate having a crystallinity in the above range are conducive to giving full play to the role of pyrophosphate in hindering the elution of manganese ions and phosphate in reducing the surface miscellaneous lithium content and reducing interface side reactions.
  • the Li/Mn anti-site defect concentration of the cathode active material is 4% or less, optionally 2% or less. As a result, the gram capacity and rate performance of the cathode active material can be improved.
  • the lattice change rate of the cathode active material is 6% or less, optionally 4% or less. This can improve the rate performance of the secondary battery.
  • the surface oxygen valence state of the cathode active material is -1.88 or less, optionally -1.98 to -1.88.
  • the cycle performance and storage performance of the secondary battery can be improved.
  • the compacted density of the positive active material at 3 tons is 2.0g/cm or more, optionally 2.2g/cm or more. This is beneficial to improving the volumetric energy density of the secondary battery.
  • the specific surface area of the cathode active material is Bm 2 /g, and B is 7 to 18, optionally 10 to 15. At this time, it can be ensured that the positive electrode plate has a high ability to absorb lithium ions, and at the same time, the secondary battery has good rate performance, cycle performance and storage performance.
  • a second aspect of the present application provides a battery module, including the secondary battery of the first aspect of the present application.
  • a third aspect of this application provides a battery pack, including the battery module of the second aspect of this application.
  • a fourth aspect of the present application provides an electrical device, including at least one selected from the secondary battery of the first aspect of the present application, the battery module of the second aspect of the present application, or the battery pack of the third aspect of the present application.
  • the battery module, battery pack, and electrical device of the present application include the secondary battery of the present application, and thus have at least the same advantages as the secondary battery.
  • FIG. 1 is a schematic diagram of an embodiment of the secondary battery of the present application.
  • FIG. 2 is an exploded schematic view of the embodiment of the secondary battery of FIG. 1 .
  • FIG. 3 is a schematic diagram of an embodiment of the battery module of the present application.
  • FIG. 4 is a schematic diagram of an embodiment of the battery pack of the present application.
  • FIG. 5 is an exploded schematic view of the embodiment of the battery pack shown in FIG. 4 .
  • FIG. 6 is a schematic diagram of an embodiment of a power consumption device including the secondary battery of the present application as a power source.
  • Figure 7 is a comparison chart between the XRD spectrum of the positive active material core prepared in Example 1-1 and the standard XRD spectrum of lithium manganese phosphate (00-033-0804).
  • 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).
  • the median particle size Dv50 refers to the particle size corresponding to when the cumulative volume distribution percentage of the material reaches 50%.
  • the median particle diameter Dv50 of the material can be determined using laser diffraction particle size analysis. For example, refer to the standard GB/T 19077-2016 and use a laser particle size analyzer (such as Malvern Master Size 3000) for measurement.
  • 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.
  • each coating layer can be completely covered or partially covered.
  • 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.
  • aryl refers to a closed aromatic ring or ring system.
  • the "aryl” structure may be a single ring, a polycyclic ring, a fused ring, etc.
  • aryl groups include, but are not limited to, phenyl, naphthyl, anthracenyl, phenanthrenyl, diphenyl, terphenyl, tetraphenyl, triphenylene, pyrenyl, Base, perylene group, indenyl, benzophenanthyl, fluorenyl, 9,9-dimethylfluorenyl, spirodifluorenyl.
  • heteroaryl means an aryl group in which one or more atoms in the ring are elements other than carbon.
  • heteroaryl groups include, but are not limited to, pyrrolyl, furyl, thienyl, indolyl, benzofuryl, benzothienyl, dibenzofuran, dibenzothiophene, carbazolyl, indenocarbazole base, indolocarbazolyl, pyridyl, pyrimidinyl, pyrazinyl, pyridazinyl, triazinyl, oxazolyl, isoxazolyl, thiazolyl, isothiazolyl.
  • Heteroatoms in heteroaryl groups may include N, O, S, Si, etc. The number of heteroatoms in the heteroaryl group may be one or multiple, and the multiple heteroatoms may be the same or different.
  • a substituent when a substituent represents a group of certain groups, it includes groups in which these groups are bonded with a single bond.
  • the substituent when the substituent represents "at least one of a group consisting of a hydroxyl group, a C1 to C18 monovalent alkyl group, and a C6 to C18 monovalent aryl group", the substituent separately discloses the hydroxyl group and the C1 to C18 monovalent alkyl group.
  • C6 ⁇ C18 monovalent aryl group hydroxyl-substituted C1 ⁇ C18 monovalent alkyl group, hydroxyl-substituted C6 ⁇ C18 monovalent aryl group and C1 ⁇ C18 monovalent alkyl substituted C6 ⁇ C18 monovalent aryl group.
  • each substituent when each substituent represents "monovalent”, it refers to the group formed by removing one H atom from the molecule; when each substituent represents “bivalent”, it refers to the group formed by removing two H atoms from the molecule.
  • the formed group when each substituent represents “trivalent”, refers to the group formed by removing three H atoms from the molecule; when each substituent represents “tetravalent”, it refers to the group formed by removing four H atoms from the molecule.
  • C1-C6 alkyl is expressly contemplated to separately disclose C1, C2, C3, C4, C5, C6, C1-C6, C1-C5, C1-C4, C1-C3, C1-C2, C2 ⁇ C6, C2 ⁇ C5, C2 ⁇ C4, C2 ⁇ C3, C3 ⁇ C6, C3 ⁇ C5, C3 ⁇ C4, C4 ⁇ C6, C4 ⁇ C5 and C5 ⁇ C6 alkyl.
  • 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 ions into the non-aqueous electrolyte. The eluted manganese ions are 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 secondary battery to expand and affect the secondary battery.
  • 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 secondary battery.
  • the non-aqueous electrolyte and the active lithium ions inside the battery are continuously consumed, which has an irreversible impact on the capacity retention rate of the secondary battery.
  • the inventor designed a secondary battery based on the positive electrode and non-aqueous electrolyte, which can simultaneously have high energy density and good rate performance, cycle performance, storage performance and safety performance. .
  • a first aspect of the present application provides a secondary battery.
  • 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 includes an electrode assembly and a non-aqueous electrolyte.
  • the electrode assembly includes a positive electrode piece, a negative electrode piece and a separator, and the separator is disposed between the positive electrode piece and the negative electrode piece.
  • the non-aqueous electrolyte plays a role in conducting lithium ions between the positive electrode piece and the negative electrode piece.
  • the positive electrode sheet used in the secondary battery of the present application at least includes a positive active material with a core-shell structure.
  • the positive active material includes a core and a shell covering the core.
  • the core includes Li 1+x Mn 1-y A y P 1-z R z O 4 , x is -0.100 to 0.100, y is 0.001 to 0.500, z is 0.001 to 0.100, and the A is selected from Zn, Al , one or more of Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and Ge, optionally Fe, Ti, V, Ni , one or more of Co and Mg, and the R is selected from one or more of B, Si, N and S.
  • the shell includes a first coating layer coating the core and a second coating layer coating the first coating layer, wherein the first coating layer includes pyrophosphate MP 2 O 7 and Phosphate XPO 4 , the M and X are each independently selected from one or more of Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb and Al; the second The cladding contains carbon.
  • 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 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 obtained a positive electrode active material that can significantly reduce the dissolution of manganese ions and reduce the lattice change rate by doping and modifying lithium manganese phosphate and coating the lithium manganese phosphate with multiple layers.
  • the lithium manganese phosphate cathode active material of the present application has a core-shell structure with a double coating layer, 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 active material, and greatly reduces the number of manganese ions. dissolution 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 reduce the dissolution of transition metal ions. Phosphate has excellent ability to conduct lithium ions and can reduce the surface miscellaneous lithium content.
  • the second coating layer of the cathode active material of the present application is a carbon-containing layer, which can effectively improve the conductive properties and desolvation ability of LiMnPO 4 .
  • the "barrier" function of the second coating layer can further hinder the migration of manganese ions into the non-aqueous electrolyte and reduce the erosion of the positive electrode active material by the non-aqueous electrolyte.
  • this application can effectively reduce the dissolution of manganese ions during the process of deintercalating lithium, and at the same time promote the migration of lithium ions, thereby improving the rate performance and cycle performance of secondary batteries. performance, storage performance and security performance.
  • the core of the cathode active material in this application is basically consistent with the position of the main characteristic peak of LiMnPO 4 before doping, indicating that the doped lithium manganese phosphate cathode active material core has no impurity phase, and the improvement in secondary battery performance mainly comes from It is caused by elemental doping rather than impurity phases.
  • x is -0.100 to 0.100.
  • x can be 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, -0.100.
  • y ranges from 0.001 to 0.500, for example, y can be 0.1, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45.
  • z ranges from 0.001 to 0.100, for example, z can be 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.100.
  • 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 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 reducing the dissolution of manganese ions, reducing the amount of non-aqueous electrolyte and On the other hand, the consumption of active lithium ions is also conducive to further reducing surface oxygen activity and reducing interface side reactions between the positive electrode active material and the non-aqueous electrolyte, thereby improving the cycle performance and high-temperature storage performance of the secondary battery.
  • the interplanar spacing of the phosphate of the first coating layer is 0.345-0.358 nm, and the angle between the crystal directions (111) is 24.25°-26.45°.
  • the interplanar spacing of the pyrophosphate of the first coating layer is 0.293-0.326 nm, and the included angle of the crystal direction (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 reduced, thereby increasing the gram capacity of the cathode active material. , cycle performance and rate performance.
  • 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. It can not only effectively hinder the dissolution of manganese ions, but also effectively reduce the surface miscellaneous lithium content and reduce interface side reactions, thereby improving the rate performance of the secondary battery. , cycle performance and safety performance. 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 reducing the dissolution of manganese ions is not significant.
  • the crystallinity of the pyrophosphate and phosphate salts each independently ranges from 10% to 100%, optionally from 50% to 100%.
  • pyrophosphate and phosphate with 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 storage 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.
  • the coating amount of the first coating layer is C1 weight %, where C1 is greater than 0 and less than or equal to 7, optionally 4 to 5.6, based on the weight of the core.
  • the coating amount of the first coating layer is within the above range, the dissolution of manganese ions can be further reduced and the transport of lithium ions can be further promoted. And can effectively avoid the following situations: if 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 secondary battery.
  • the coating amount of the second coating layer is C2% by weight, where C2 is greater than 0 and less than or equal to 6, optionally 3 to 5, based on the weight of the core.
  • the carbon-containing layer as the second coating layer can function as a "barrier" to avoid direct contact between the positive electrode active material and the non-aqueous electrolyte, thereby reducing the erosion of the positive electrode active material by the non-aqueous electrolyte and improving the performance of the secondary battery at high temperatures. lower safety performance.
  • it has strong electrical conductivity, which can reduce the internal resistance of the battery, thereby improving the dynamic performance of the secondary 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 secondary battery can be further improved without sacrificing the gram capacity of the cathode active material.
  • the Li/Mn anti-site defect concentration of the cathode active material is 4% or less, optionally 2% or less.
  • the Li/Mn antisite defect refers to the interchange of positions of Li + and Mn 2+ in the LiMnPO 4 lattice.
  • the Li/Mn anti-site defect concentration refers to the percentage of Li + exchanged with Mn 2+ in the positive active material to the total amount of Li + . 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 cathode active material of the present application by controlling the Li/Mn anti-site defect concentration at a low level, the gram capacity and rate performance of the cathode active material can be improved.
  • 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 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 average discharge voltage of the cathode active material is more than 3.5V, and the discharge capacity is more than 140mAh/g; optionally, the average discharge voltage is more than 3.6V, and the discharge capacity is more than 145mAh. /g or above.
  • the average discharge voltage of undoped LiMnPO 4 is above 4.0V, its discharge gram capacity is low, usually less than 120mAh/g. Therefore, the energy density of the secondary battery is low; the lattice change rate is adjusted by doping , which can greatly increase its discharge capacity and significantly increase the overall energy density of the secondary battery while the average discharge voltage drops slightly.
  • the surface oxygen valence state of the cathode active material is -1.88 or less, optionally -1.98 to -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 active material can be reduced, and the interface side reactions between the cathode active material and the non-aqueous electrolyte can be reduced. Thereby improving the cycle performance and high-temperature storage performance of secondary batteries.
  • the compacted density of the cathode active material at 3 tons (T) is 2.0 g/cm 3 or more, optionally 2.2 g/cm 3 or more.
  • the compacted density of the positive electrode active material that is, the greater the weight of the positive electrode active material per unit volume, will be more conducive to increasing the volumetric energy density of the secondary battery.
  • the compacted density can be measured according to GB/T 24533-2009, for example.
  • the specific surface area of the cathode active material is Bm 2 /g, and B is 7 to 18, optionally 10 to 15.
  • the specific surface area of the cathode active material is higher, and the lithium ion conduction ability of the cathode plate will be improved, which in turn can improve the capacity and rate performance of the secondary battery.
  • the specific surface area of the positive active material should not be too high, which may increase the contact area between the positive active material and the non-aqueous electrolyte, thereby increasing interface side reactions and affecting the cycle performance and storage performance of the secondary battery.
  • the specific surface area of the positive electrode active material has a meaning known in the art and can be measured using instruments and methods known in the art.
  • the nitrogen adsorption specific surface area analysis method can be used for testing, and the BET (Brunauer Emmett Teller) method can be used to calculate it.
  • the testing instrument can be the Tri-Star 3020 specific surface area pore size analysis tester from the American Micromeritics company.
  • the present application also provides a method for preparing a cathode active material, which includes the following steps of providing a core material and a coating step.
  • the core includes Li 1+x Mn 1-y A y P 1-z R z O 4 , x is -0.100 to 0.100, y is 0.001 to 0.500, z is 0.001 to 0.100, the A is selected from one or more of Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb, Nb and Ge, optionally Fe , one or more of Ti, V, Ni, Co and Mg, and the R is selected from one or more of B, Si, N and S.
  • Coating step Provide MP 2 O 7 powder and an XPO 4 suspension containing a carbon source, add the core material and MP 2 O 7 powder to the XPO 4 suspension containing a carbon source, and mix.
  • the cathode active material is obtained by sintering, and the M and X are each independently selected from one or more of Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr, Nb and Al.
  • the positive active material has a core-shell structure, which includes an inner core and a shell covering the inner core.
  • the shell includes a first coating layer covering the inner core and a first coating layer covering the inner core.
  • the second coating layer includes pyrophosphate MP 2 O 7 and phosphate XPO 4 , and the second coating layer includes carbon.
  • the preparation method of the present application has no special restrictions on the source of materials.
  • the core material in the preparation method of the present application can be commercially available, or can be prepared by the method of the present application.
  • the core material is prepared by the method described below.
  • the step of providing core material includes the following steps (1) and (2).
  • Step (1) Mix and stir the source of manganese, the source of element A and the 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 doping.
  • a source of lithium a source of lithium
  • a source of phosphorus a source of element R
  • 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 doping.
  • the lithium manganese phosphate doped with element A and element R is Li 1+x Mn 1-y A y P 1-z R z O 4 , x is -0.100 to 0.100, y is 0.001 to 0.500, z is 0.001 to 0.100, and the A is selected from Zn, Al, Na, K, Mg, Mo, W, Ti, V, Zr, Fe, Ni, Co, Ga, Sn, Sb , one or more of Nb and Ge, optionally one or more of Fe, Ti, V, Ni, Co and Mg, the R is selected from one or more of B, Si, N and S or more.
  • step (1) is performed at a temperature of 20-120°C, optionally 25-80°C.
  • the stirring in step (1) is performed at 500-700 rpm for 60-420 minutes, optionally 120-360 minutes.
  • the doping elements can be evenly distributed, reduce lattice defects, reduce manganese ion dissolution, and reduce interface side reactions between the cathode active material and the non-aqueous electrolyte, thereby improving the The gram capacity and rate performance of the cathode active material, etc.
  • the source of a certain element may include one or more of the elements, sulfates, halides, nitrates, organic acid salts, oxides or hydroxides, provided that It is this source that can achieve the purpose of the preparation method of the present application.
  • the source of element A is selected from one or more of elemental elements, sulfates, halides, nitrates, organic acid salts, oxides or hydroxides of element A.
  • the source of the element R is selected from one or more elements, sulfates, halides, nitrates, organic acid salts, oxides or hydroxides of the element R, and inorganic acids of the element R.
  • the inorganic acid of element R is selected from one or more of phosphoric acid, nitric acid, boric acid, silicic acid, and orthosilicic acid.
  • the source of manganese is one or more selected from the group consisting of elemental manganese, manganese dioxide, manganese phosphate, manganese oxalate, and manganese carbonate.
  • element A is iron, and optionally, in step (1), the source of iron is one or more selected from the group consisting of ferrous carbonate, ferric hydroxide, and ferrous sulfate.
  • the acid is selected from one or more of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, organic acids such as oxalic acid, etc., optionally oxalic acid.
  • the acid is a dilute acid with a concentration of 60% by weight or less.
  • the source of lithium is one or more selected from the group consisting of lithium carbonate, lithium hydroxide, lithium phosphate, and lithium dihydrogen phosphate.
  • the source of phosphorus is one or more selected from the group consisting of diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium phosphate and phosphoric acid.
  • the solvent used in the preparation method described in this application is a solvent commonly used in the art.
  • the solvents in the preparation method of the present application can be independently selected from at least one of ethanol and water (such as deionized water).
  • the pH of the solution is controlled to be 4-6. It should be noted that in this application, the pH of the resulting mixture can be adjusted by methods commonly used in the art, for example, by adding acid or alkali.
  • step (2) the molar ratio of the manganese salt particles doped with element A to the source of lithium and the source of phosphorus is 1:(0.5-2.1):(0.5 -2.1).
  • the sintering conditions are: sintering at 600-800°C for 4-10 hours under the protection of an inert gas or a mixed atmosphere of inert gas and hydrogen.
  • the crystallinity of the material after sintering is higher, which can improve the gram capacity and rate performance of the cathode active material.
  • the mixture of inert gas and hydrogen is nitrogen (70-90 volume%) + hydrogen (10-30 volume%).
  • the MP 2 O 7 powder is a commercially available product, or alternatively, the MP 2 O 7 powder is prepared by adding a source of element M and a source of phosphorus to In the solvent, a mixture is obtained, adjust the pH of the mixture to 4-6, stir and fully react, and then obtain it by drying and sintering, where M is selected from Li, Fe, Ni, Mg, Co, Cu, Zn, Ti, Ag, Zr , one or more of Nb and Al.
  • the drying step is drying at 100-300°C, optionally 150-200°C for 4-8 hours.
  • the sintering step is sintering at 500-800°C, optionally 650-800°C, in an inert gas atmosphere for 4-10 hours.
  • the XPO suspension comprising a source of carbon is commercially available, or alternatively, is prepared by combining a source of lithium, a source of X, phosphorus The source and the carbon source are mixed evenly in the solvent, and then the reaction mixture is heated to 60-120°C and maintained for 2-8 hours to obtain an XPO 4 suspension containing the carbon source.
  • the pH of the mixture is adjusted to 4-6.
  • the source of carbon is an organic carbon source
  • the organic carbon source is selected from one or more of starch, sucrose, glucose, polyvinyl alcohol, polyethylene glycol, and citric acid.
  • the mass ratio of the A element and R element-doped lithium manganese phosphate (core), MP 2 O 7 powder and XPO 4 suspension containing the source of carbon is 1 :(0.001-0.05):(0.001-0.05).
  • the sintering temperature in the coating step is 500-800°C, and the sintering time is 4-10 hours.
  • the median particle diameter Dv50 of the primary particles of the double-layer-coated lithium manganese phosphate cathode active material of the present application is 50-2000 nm.
  • the positive electrode sheet of the present application may include 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 current collector has two surfaces opposite in its thickness direction, and the positive electrode film layer A layer is provided on any one or both of two opposing surfaces of the positive electrode current collector.
  • the positive electrode film layer includes the positive electrode active material as described above in this application.
  • the content of the cathode active material in the cathode film layer is more than 10% by weight, based on the total weight of the cathode film layer. More optionally, the content of the cathode active material in the cathode film layer is 90-99.5% by weight, based on the total weight of the cathode film layer.
  • the content of the cathode active material is within the above range, it is beneficial to give full play to the advantages of the cathode active material of the present application.
  • the positive electrode film layer does not exclude other positive electrode active materials in addition to the above-mentioned positive electrode active materials provided in this application.
  • the positive electrode film layer may also include layered lithium transition metal oxide and its at least one of the modified compounds.
  • the other cathode active materials may include lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide , at least one of lithium nickel cobalt aluminum oxide and their respective modified compounds.
  • the positive electrode film layer optionally further includes a positive electrode conductive agent.
  • a positive electrode conductive agent includes superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, and graphene. , at least one of carbon nanofibers.
  • the positive electrode film layer optionally further includes a positive electrode binder.
  • a positive electrode binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene -At least one of propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • a metal foil aluminum foil can be used.
  • the composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer.
  • the metal material may be selected from at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy.
  • the polymer material base layer can be selected from the group consisting of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), poly Ethylene (PE), etc.
  • the positive electrode film layer is usually formed by coating the positive electrode slurry on the positive electrode current collector, drying, and cold pressing.
  • the positive electrode slurry is usually formed by dispersing the positive electrode active material, optional conductive agent, optional binder and any other components in a solvent and stirring evenly.
  • the solvent may be N-methylpyrrolidone (NMP), but is not limited thereto.
  • 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 and including a negative electrode active material.
  • the negative electrode current collector has two surfaces opposite in its 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 active material may be a negative active material known in the art for secondary batteries.
  • the negative active material includes but is not limited to at least one of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate.
  • the silicon-based material may include at least one of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitride composite, and silicon alloy material.
  • the tin-based material may include at least one of elemental tin, tin oxide, and tin alloy materials.
  • the present application is not limited to these materials, and other conventionally known materials that can be used as negative electrode active materials for secondary batteries 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 negative electrode conductive agent.
  • a negative electrode conductive agent may include superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphite At least one of alkenes and carbon nanofibers.
  • the negative electrode film layer optionally further includes a negative electrode binder.
  • a negative electrode binder may include styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (for example, At least one of polyacrylic acid PAA, polymethacrylic acid PMAA, polyacrylic acid sodium PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), carboxymethyl chitosan (CMCS) kind.
  • SBR styrene-butadiene rubber
  • SR-1B water-soluble unsaturated resin
  • acrylic resin for example, At least one of polyacrylic acid PAA, polymethacrylic acid PMAA, polyacrylic acid sodium PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), carboxymethyl chitosan (CMCS) kind.
  • the negative electrode film layer optionally further includes other additives.
  • other auxiliaries may include thickeners, such as sodium carboxymethylcellulose (CMC), PTC thermistor materials, and the like.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • the metal foil copper foil can be used.
  • the composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer.
  • the metal material may be selected from at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy.
  • the polymer material base layer can be selected from the group consisting of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), poly Ethylene (PE), etc.
  • the negative electrode film layer is usually formed by coating the negative electrode slurry on the negative electrode current collector, drying, and cold pressing.
  • the negative electrode slurry is usually formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional additives in a solvent and stirring evenly.
  • the solvent may be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.
  • the negative electrode plate does not exclude other additional functional layers in addition to the negative electrode film layer.
  • the negative electrode sheet described in the present application further includes a conductive undercoat layer (for example, made of Conductive agent and adhesive).
  • the negative electrode sheet described in this application further includes a protective layer covering the surface of the negative electrode film layer.
  • isolation membrane there is no particular restriction on the type of isolation membrane in this application, and any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be used.
  • the material of the isolation membrane may include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation film may be a single-layer film or a multi-layer composite film. When the isolation film is a multi-layer composite film, the materials of each layer may be the same or different.
  • the positive electrode piece, the isolation film and the negative electrode piece can be made into an electrode assembly through a winding process or a lamination process.
  • Secondary batteries include non-aqueous electrolyte, which is a bridge for the passage of lithium ions in the secondary battery. It plays the role of transporting lithium ions between the positive and negative electrodes in the secondary battery, and plays a critical role in the capacity, cycle performance, and performance of the secondary battery. Storage performance, rate performance and safety performance all play a vital role.
  • the most widely used non-aqueous electrolyte system currently commercially is a mixed carbonate solution of lithium hexafluorophosphate.
  • lithium hexafluorophosphate has poor thermal stability in high temperature environments and will decompose to form PF 5 at higher temperatures.
  • PF 5 has strong Lewis acidity and will interact with the lone pair of electrons on the oxygen atoms in the organic solvent molecules to decompose the organic solvent.
  • PF 5 is highly sensitive to trace amounts of moisture in the non-aqueous electrolyte. Water will generate HF, thereby increasing the acidity of the non-aqueous electrolyte, which will easily destroy the coating layer on the surface of the positive electrode active material.
  • the carbon in the second coating layer will catalyze the oxidative decomposition of the non-aqueous electrolyte under high voltage, further increasing the irreversible consumption of active lithium ions.
  • the inventor further conducted a lot of research and cleverly added the first additive shown in the following formula 1-A to formula 1-D in the non-aqueous electrolyte, which can reduce the dissolution of the first coating layer and reduce the dissolution of the second coating layer.
  • the catalytic oxidation effect of the coating can significantly improve the cycle performance and storage performance of the secondary battery.
  • the non-aqueous electrolyte solution of the present application includes at least a first additive, and the first additive includes one or more compounds represented by Formula 1-A to Formula 1-D.
  • R 1 represents a hydrogen atom or at least one of the group consisting of the following groups: hydroxyl, C1 to C18 monovalent alkyl, C1 to C18 monovalent alkoxy, C2 to C18 monovalent alkoxyalkyl, C3 ⁇ C18 monovalent cycloalkyl group, C2 ⁇ C18 monovalent oxyheterocycloalkyl group, C6 ⁇ C18 monovalent aryl group, C7 ⁇ C18 monovalent arylalkyl group, C7 ⁇ C18 monovalent alkylaryl group, C6 ⁇ C18 Monovalent aryloxy group, C7 ⁇ C18 monovalent aryloxyalkyl group, C12 ⁇ C18 monovalent aryl ether group, C2 ⁇ C18 monovalent heteroaryl group, C3 ⁇ C18 monovalent heteroarylalkyl group, C3 ⁇ C18 monovalent alkyl heteroaryl group and C1 ⁇ C18 monovalent silyl group.
  • R 2 to R 21 each independently represent a hydrogen atom or at least one of the group consisting of the following groups: C1 to C18 monovalent alkyl group, C2 to C18 monovalent alkoxyalkyl group, C3 to C18 monovalent ring Alkyl, C2 ⁇ C18 monovalent oxygen heterocycloalkyl, C6 ⁇ C18 monovalent aryl, C7 ⁇ C18 monovalent arylalkyl, C7 ⁇ C18 monovalent alkylaryl, C7 ⁇ C18 monovalent aryloxy Alkyl group, C12 ⁇ C18 monovalent aryl ether group, C2 ⁇ C18 monovalent heteroaryl group, C3 ⁇ C18 monovalent heteroarylalkyl group, C3 ⁇ C18 monovalent alkyl heteroaryl group and C1 ⁇ C18 monovalent silane base.
  • R 1 is not a hydroxyl group.
  • R 2 and R 3 can also be bonded to each other to form a ring structure
  • R 4 and R 5 can also be bonded to each other to form a ring structure
  • R 6 and R 7 can also be bonded to each other to form a ring structure
  • R 8 and R 9 can also be bonded to each other to form a ring structure.
  • R 10 and R 11 can also bond to each other to form a ring structure
  • R 12 and R 13 can also bond to each other to form a ring structure
  • R 14 and R 15 can also bond to each other to form a ring structure
  • R 16 and R 17 can also be bonded to each other to form a ring structure
  • R 18 and R 19 can also be bonded to each other to form a ring structure
  • R 20 and R 21 can also be bonded to each other to form a ring structure.
  • L 1 represents an oxygen atom or at least one of the group consisting of the following groups: C1 ⁇ C18 divalent alkyl group, C1 ⁇ C18 oxa divalent alkyl group, C6 ⁇ C18 divalent cycloalkyl group, C6 ⁇ C18 divalent alkyl group Oxygen heterocycloalkyl group, C6 ⁇ C18 divalent aryl group, C7 ⁇ C18 divalent arylalkyl group, C7 ⁇ C18 divalent alkyl aryl group, C6 ⁇ C18 divalent aryloxy group, C7 ⁇ C18 divalent aryloxy group Aryloxyalkyl group, C12-C18 divalent aryl ether group, C2-C18 divalent heteroaryl group, C3-C18 divalent heteroarylalkyl group and C3-C18 divalent alkylheteroaryl group.
  • L 2 represents at least one of the following groups: C1 to C18 trivalent alkyl, C1 to C18 oxa trivalent alkyl, C6 to C18 trivalent cycloalkyl, C6 to C18 trivalent oxa Cycloalkyl, C6 ⁇ C18 trivalent aryl, C7 ⁇ C18 trivalent arylalkyl, C7 ⁇ C18 trivalent alkyl aryl, C6 ⁇ C18 trivalent aryloxy, C7 ⁇ C18 trivalent aryloxy Alkyl group, C12 ⁇ C18 trivalent aryl ether group, C3 ⁇ C18 trivalent heteroaryl group, C3 ⁇ C18 trivalent heteroaryl alkyl group and C3 ⁇ C18 trivalent alkyl heteroaryl group.
  • L 3 represents at least one of the group consisting of the following groups: C1 to C18 tetravalent alkyl, C1 to C18 oxa tetravalent alkyl, C6 to C18 tetravalent cycloalkyl, C6 to C18 tetravalent oxa Cycloalkyl, C6 ⁇ C18 tetravalent aryl, C7 ⁇ C18 tetravalent arylalkyl, C7 ⁇ C18 tetravalent alkyl aryl, C7 ⁇ C18 tetravalent aryloxyalkyl, C12 ⁇ C18 tetravalent aryl Ether group, C4 ⁇ C18 tetravalent heteroaryl group, C4 ⁇ C18 tetravalent heteroarylalkyl group and C4 ⁇ C18 tetravalent alkylheteroaryl group.
  • the non-aqueous electrolyte contains the first additive shown in Formula 1-A to Formula 1-D, it can form a dense and stable interface film on the surface of the positive electrode active material during the charging process of the secondary battery, reducing the The dissolution of the first coating layer reduces the dissolution of manganese ions, while reducing the catalytic oxidation of the second coating layer under high voltage, reducing the consumption of non-aqueous electrolyte and active lithium ions, which can significantly improve the cycle of secondary batteries. Performance and storage performance, in particular, can significantly improve the cycle performance and storage performance of secondary batteries under high temperature and high voltage.
  • the first additive includes one or more compounds represented by Formula 1-A to Formula 1-D. Specifically, in some embodiments, the first additive includes one or more of the compounds represented by Formula 1-A; in some embodiments, the first additive includes one or more of the compounds represented by Formula 1-B. One or more of; in some embodiments, the first additive includes one or more of the compounds represented by Formula 1-C; in some embodiments, the first additive includes Formula 1-D One or more of the compounds shown; in some embodiments, the first additive simultaneously includes any two, three or four of the compounds shown in Formula 1-A to Formula 1-D.
  • R 2 and R 3 are bonded to each other to form a ring structure. More optionally, R 2 and R 3 are bonded to each other to form a ring structure of five or more members.
  • R 1 to R 3 represents a C3 to C18 monovalent cycloalkyl group, a C2 to C18 monovalent oxygen heterocycloalkyl group, a C6 to C18 monovalent aryl group, C7 ⁇ C18 monovalent arylalkyl group, C7 ⁇ C18 monovalent alkylaryl group, C7 ⁇ C18 monovalent aryloxyalkyl group, C12 ⁇ C18 monovalent aryl ether group, C2 ⁇ C18 monovalent heteroaryl group, C3 ⁇ C18 monovalent heteroarylalkyl group or C3 ⁇ C18 monovalent alkylheteroaryl group.
  • R 1 to R 3 each independently represent a C3 to C18 monovalent cycloalkyl group, a C2 to C18 monovalent oxygen heterocycloalkyl group, a C6 to C18 monovalent aryl group, or a C7 to C18 monovalent aryl alkyl group.
  • R 1 to R 3 each independently represent a C6 to C18 monovalent aryl group, a C7 to C18 monovalent aryl alkyl group, a C7 to C18 monovalent alkyl aryl group, and a C7 to C18 monovalent aryl oxygen group.
  • R 1 to R 3 represent the above substituents, it helps to form an interface film containing cross-linked macromolecular polymer on the surface of the cathode active material, further reducing the dissolution of the first coating layer and reducing the catalysis of the second coating layer. Oxidation reduces the dissolution of manganese ions and the consumption of non-aqueous electrolyte and active lithium ions, thereby further enhancing the improvement effect on the cycle performance and storage performance of secondary batteries.
  • the compound represented by Formula 1-A includes at least one of the following compounds:
  • the compound represented by Formula 1-A includes at least one of H1 to H10 and H13 to H15. More optionally, the compound represented by Formula 1-A includes at least one of H1 to H10. Further optionally, the compound represented by Formula 1-A includes at least one of H1 to H8.
  • R 4 to R 7 all represent hydrogen atoms
  • L 1 represents a C6 to C18 divalent cycloalkyl group, a C6 to C18 divalent oxygen heterocycloalkyl group, or a C6 to C18 divalent aromatic group.
  • group C7 ⁇ C18 divalent arylalkyl group, C7 ⁇ C18 divalent alkylaryl group, C6 ⁇ C18 divalent aryloxy group, C7 ⁇ C18 divalent aryloxyalkyl group, C12 ⁇ C18 divalent aryl group Ether group, C2 ⁇ C18 divalent heteroaryl group, C3 ⁇ C18 divalent heteroarylalkyl group or C3 ⁇ C18 divalent alkylheteroaryl group.
  • R 4 to R 7 all represent hydrogen atoms
  • L 1 represents a C6 to C18 divalent aryl group, a C7 to C18 divalent arylalkyl group, a C7 to C18 divalent alkylaryl group, or a C6 to C18 divalent aryl alkyl group.
  • R 4 to R 7 all represent hydrogen atoms
  • L 1 represents a divalent phenyl group, a divalent diphenyl group, a divalent terphenyl group, a divalent tetraphenyl group, a divalent naphthyl group, a divalent naphthyl group, Valent anthracene base, divalent phenanthrene base, divalent pyrene base or divalent fluorenyl base.
  • At least one group of R 4 and R 5 , R 6 and R 7 are bonded to each other to form a ring structure.
  • R 4 and R 5 are bonded to each other to form a ring structure
  • R 6 and R 7 are bonded to each other to form a ring structure
  • R 4 and R 5 are bonded to each other to form a ring structure
  • R 6 and R 7 are bonded to each other to form a ring structure.
  • R 4 to R 7 are the same and none are hydrogen atoms.
  • L 1 represents an oxygen atom
  • R 4 to R 7 independently represent a C3 to C18 monovalent cycloalkyl group, a C2 to C18 monovalent oxygen heterocycloalkyl group, and a C6 to C18 monovalent oxygen heterocycloalkyl group.
  • L 1 represents an oxygen atom
  • R 4 to R 7 independently represent a C6 to C18 monovalent aryl group, a C7 to C18 monovalent arylalkyl group, a C7 to C18 monovalent alkylaryl group, and a C7 ⁇ C18 monovalent aryloxyalkyl group, C12 ⁇ C18 monovalent aryl ether group, C2 ⁇ C18 monovalent heteroaryl group, C3 ⁇ C18 monovalent heteroarylalkyl group or C3 ⁇ C18 monovalent alkylheteroaryl group .
  • the compound represented by Formula 1-B includes at least one of the following compounds:
  • the compound represented by Formula 1-B includes at least one of H31 to H33. More optionally, the compound represented by Formula 1-B includes at least one of H32 to H33.
  • At least one group of R 8 and R 9 , R 10 and R 11 , R 12 and R 13 are bonded to each other to form a ring structure.
  • R 8 and R 9 are bonded to each other to form a ring structure
  • R 10 and R 11 are bonded to each other to form a ring structure
  • R 12 and R 13 are bonded to each other to form a ring structure
  • R 8 and R 9 , R 10 and Any two or three groups of R 11 , R 12 and R 13 are bonded to each other to form a ring structure.
  • R 8 to R 13 independently represent C1 to C18 monovalent alkyl, C2 to C18 monovalent alkoxyalkyl, C3 to C18 monovalent cycloalkyl, C2 to C18 Monovalent oxygen heterocycloalkyl group, C6 ⁇ C18 monovalent aryl group, C7 ⁇ C18 monovalent arylalkyl group, C7 ⁇ C18 monovalent alkyl aryl group, C7 ⁇ C18 monovalent aryloxyalkyl group, C12 ⁇ C18 monovalent aryl ether group, C2 to C18 monovalent heteroaryl group, C3 to C18 monovalent heteroarylalkyl group or C3 to C18 monovalent alkyl heteroaryl group.
  • L 2 represents a C6 to C18 trivalent cycloalkyl group, a C6 to C18 trivalent oxyheterocycloalkyl group, a C6 to C18 trivalent aryl group, or a C7 to C18 trivalent arylalkyl group.
  • L 2 represents a C6 ⁇ C18 trivalent aryl group, a C7 ⁇ C18 trivalent arylalkyl group, a C7 ⁇ C18 trivalent alkyl aryl group, a C6 ⁇ C18 trivalent aryloxy group, a C7 ⁇ C18 trivalent aryloxy group.
  • L 2 represents a trivalent phenyl group, a trivalent phenylalkyl group, or a trivalent alkylphenyl group.
  • the compound represented by Formula 1-C includes at least one of the following compounds:
  • At least one group of R 14 and R 15 , R 16 and R 17 , R 18 and R 19 , R 20 and R 21 are bonded to each other to form a ring structure.
  • R 14 and R 15 are bonded to each other to form a ring structure
  • R 16 and R 17 are bonded to each other to form a ring structure
  • R 18 and R 19 are bonded to each other to form a ring structure
  • R 20 and R 21 are bonded to each other to form a ring structure.
  • Ring structure, or any two, three or four groups of R 14 and R 15 , R 16 and R 17 , R 18 and R 19 , R 20 and R 21 are bonded to each other to form a ring structure.
  • R 14 to R 21 independently represent C1 to C18 monovalent alkyl, C2 to C18 monovalent alkoxyalkyl, C3 to C18 monovalent cycloalkyl, C2 to C18 Monovalent oxygen heterocycloalkyl group, C6 ⁇ C18 monovalent aryl group, C7 ⁇ C18 monovalent arylalkyl group, C7 ⁇ C18 monovalent alkyl aryl group, C7 ⁇ C18 monovalent aryloxyalkyl group, C12 ⁇ C18 monovalent aryl ether group, C2 to C18 monovalent heteroaryl group, C3 to C18 monovalent heteroarylalkyl group or C3 to C18 monovalent alkyl heteroaryl group.
  • L 3 represents a C6 to C18 tetravalent cycloalkyl group, a C6 to C18 tetravalent oxaheterocycloalkyl group, a C6 to C18 tetravalent aryl group, or a C7 to C18 tetravalent arylalkyl group.
  • C7 ⁇ C18 tetravalent alkyl aryl group C7 ⁇ C18 tetravalent aryloxyalkyl group, C12 ⁇ C18 tetravalent aryl ether group, C4 ⁇ C18 tetravalent heteroaryl group, C4 ⁇ C18 tetravalent heteroaryl alkyl group base or C4 ⁇ C18 tetravalent alkylheteroaryl group.
  • L 3 represents C6 ⁇ C18 tetravalent aryl group, C7 ⁇ C18 tetravalent arylalkyl group, C7 ⁇ C18 tetravalent alkyl aryl group, C7 ⁇ C18 tetravalent aryloxyalkyl group, C12 ⁇ C18 tetravalent aryl ether group, C4 ⁇ C18 tetravalent heteroaryl group, C4 ⁇ C18 tetravalent heteroarylalkyl group or C4 ⁇ C18 tetravalent alkylheteroaryl group.
  • L 3 represents a tetravalent phenyl group, a tetravalent diphenyl group, a tetravalent terphenyl group or a tetravalent tetravalent tetraphenyl group.
  • the compounds represented by formula 1-D include the following compounds:
  • the inventor found that using at least one of the above-mentioned compounds H1 to H36 as the first additive can form a denser and more stable interface film on the surface of the cathode active material, which helps to further reduce the first coating layer
  • the dissolution and reduction of the catalytic oxidation of the second coating layer further reduce the dissolution of manganese ions and the consumption of non-aqueous electrolyte and active lithium ions, thereby further enhancing the improvement effect on the cycle performance and storage performance of the secondary battery.
  • the first additive includes at least one of H1 to H10, H13 to H15, and H31 to H33. More optionally, the first additive includes at least one of H1 to H10 and H32 to H33. Further optionally, the first additive includes at least one of H1 to H8 and H32 to H33.
  • These first additives help to form an interface film containing cross-linked macromolecular polymers on the surface of the cathode active material, further reducing the dissolution of the first coating layer and reducing the catalytic oxidation of the second coating layer, thereby further reducing manganese ions. Dissolution and consumption of non-aqueous electrolyte and active lithium ions can further enhance the improvement effect on the cycle performance and storage performance of secondary batteries.
  • the inventor also found that when the non-aqueous electrolyte contains too much first additive, the positive electrode interface resistance increases significantly, thereby affecting the capacity development and rate performance of the secondary battery. Therefore, the content of the first additive in the non-aqueous electrolyte solution should not be too high.
  • the content of the first additive is W1% by weight, and W1 is 0.01 to 20, optionally 0.1 to 10, more optionally 0.3 to 5, based on the total weight of the non-aqueous electrolyte. .
  • the content of the first additive When the content of the first additive is within an appropriate range, it can reduce the dissolution of the first coating layer and the catalytic oxidation of the second coating layer without deteriorating the cathode interface impedance, thereby significantly improving the cycle of the secondary battery. performance and storage performance without affecting the capacity and rate performance of the secondary battery.
  • the non-aqueous electrolyte further includes a second additive
  • the second additive includes sultone, cyclic sulfate, lithium difluorophosphate (LiPO 2 F 2 ), difluorodioxalophosphate One or more of lithium (LiDODFP) and lithium difluorooxalate borate (LiDFOB).
  • the second additive helps to form a low-resistance interface film on the surface of the positive electrode active material.
  • the second additive can also form a dense and stable interface film on the surface of the negative electrode active material, reducing the direct contact between the negative electrode active material and the non-aqueous electrolyte. , Reduce negative electrode interface side reactions. Therefore, when the non-aqueous electrolyte solution contains both the first additive and the second additive, it helps to significantly improve the cycle performance and storage performance of the secondary battery, and at the same time improves the capacity development and rate performance of the secondary battery.
  • the sultone includes at least one of the compounds represented by Formula 2-A,
  • p1 represents 1, 2 or 3
  • p2 represents 1 or 2
  • p3 represents 1 or 2.
  • the cyclic structure may be a cyclic sulfonate ester group, a cyclic carboxylate ester group, or an oxeterocycloalkyl group. More optionally, the cyclic structure is a four-membered ring, a five-membered ring or a six-membered ring structure.
  • R 22 represents a cyclic structure, it is bonded to the polycyclic ring of Formula 2-A through a single bond or shares one carbon atom with the polycyclic ring of Formula 2-A to form a spirocyclic compound.
  • the cyclic structure may be a cyclic sulfonate ester group, a cyclic carboxylate ester group, or an oxeterocycloalkyl group. More optionally, the cyclic structure is a four-membered ring, a five-membered ring or a six-membered ring structure.
  • R 23 represents a cyclic structure, it is bonded to the polycyclic ring of Formula 2-A through a single bond or shares one carbon atom with the polycyclic ring of Formula 2-A to form a spirocyclic compound.
  • R 22 and R 23 may also be bonded to each other to form a ring structure.
  • the sultone includes at least one of the following compounds:
  • the cyclic sulfate ester includes at least one of the compounds represented by Formula 2-B,
  • q1 means 1, 2 or 3
  • q2 means 1 or 2
  • q3 means 1 or 2.
  • the cyclic structure may be a cyclic sulfate ester group, a cyclic carboxylate ester group, or an oxeterocycloalkyl group. More optionally, the cyclic structure is a four-membered ring, a five-membered ring or a six-membered ring structure.
  • R 25 represents a cyclic structure, it is bonded to the polycyclic ring of Formula 2-B through a single bond or shares one carbon atom with the polycyclic ring of Formula 2-B to form a spirocyclic compound.
  • the cyclic structure may be a cyclic sulfate ester group, a cyclic carboxylate ester group, or an oxeterocycloalkyl group. More optionally, the cyclic structure is a four-membered ring, a five-membered ring or a six-membered ring structure.
  • R 26 represents a cyclic structure, it is bonded to the polycyclic ring of Formula 2-B through a single bond or shares one carbon atom with the polycyclic ring of Formula 2-B to form a spirocyclic compound.
  • R 25 and R 26 may also be bonded to each other to form a ring structure.
  • the cyclic sulfate ester includes at least one of the following compounds:
  • the inventor also found that when the non-aqueous electrolyte contains too much second additive, the positive electrode interface impedance increases instead of decreasing, thus affecting the capacity development and rate performance of the secondary battery. Therefore, the content of the second additive in the non-aqueous electrolyte should not be too high.
  • the content of the second additive is W2% by weight, and W2 is 0.01 to 20, optionally 0.1 to 10, more optionally 0.3 to 5, based on the total weight of the non-aqueous electrolyte. .
  • the content of the second additive is within an appropriate range, the capacity performance and rate performance of the secondary battery can be effectively improved.
  • W1/W2 is 0.01 to 20.
  • W1/W2 is 0.01 to 10, 0.1 to 10, 0.1 to 8, 0.1 to 5, 0.2 to 5, 0.5 to 5 or 1 to 5.
  • the synergistic effect between the two can be better exerted, which helps to form a dense, stable and low-resistance interface film on the surface of the cathode active material, further reducing the first package
  • the dissolution of the coating layer and the reduction of the catalytic oxidation effect of the second coating layer further reduce the dissolution of manganese ions and the consumption of non-aqueous electrolyte and active lithium ions, thereby further enhancing the improvement effect on the cycle performance and storage performance of the secondary battery. , while improving the capacity and rate performance of secondary batteries.
  • the second additive cannot effectively reduce the positive electrode interface impedance, which may affect the capacity and rate performance of the secondary battery; when W1/W2 is small, the first additive cannot be significantly reduced
  • the dissolution of the coating layer and the reduction of the catalytic oxidation effect of the second coating layer may not significantly improve the cycle performance and storage performance of the secondary battery.
  • the coating amount of the first coating layer is C1% by weight
  • the coating amount of the second coating layer is C2% by weight
  • the content of the first additive is W1% by weight
  • the content of the first coating layer is C1% by weight.
  • the content W2 weight % of the two additives satisfies: (W1+W2)/(C1+C2) from 0.001 to 2.
  • (W1+W2)/(C1+C2) is 0.01 to 2, 0.01 to 1.5, 0.01 to 1, 0.1 to 1, 0.14 to 1, 0.18 to 1 or 0.22 to 1.
  • the liquid injection coefficient Q0g/Ah of the secondary battery satisfies Q0 from 2.5 to 4.0.
  • the content of the first additive is W1%
  • the content of the second additive is W2%
  • the initial capacity of the secondary battery is D0mAh/g
  • the injection coefficient of the secondary battery is Q0g/Ah.
  • the specific surface area B m 2 /g of the cathode active material satisfies [(W1%+W2%) ⁇ D0 ⁇ Q0]/B and is 0.005 to 10, optionally 0.01 to 5.
  • [(W1%+W2%) ⁇ D0 ⁇ Q0]/B is within a suitable range, it can significantly enhance the improvement effect on the cycle performance and storage performance of the secondary battery, while improving the capacity and rate performance of the secondary battery.
  • the initial capacity D0mAh/g of the secondary battery can be obtained by the following method: in a constant temperature environment of 25°C, charge the secondary battery to the upper limit cut-off voltage at 0.33C, then charge at a constant voltage until the current is less than or equal to 0.05mA, and let it stand for 5 minutes. , and then discharge to the discharge cut-off voltage at 0.33C.
  • the ratio of the discharge capacity at this time to the mass of the positive active material is the initial capacity of the secondary battery D0mAh/g.
  • the charge and discharge cut-off voltage of the secondary battery can be 2.5V ⁇ 4.3V.
  • the non-aqueous electrolyte further includes a third additive, which includes a cyclic carbonate compound containing an unsaturated bond, a halogen-substituted cyclic carbonate compound, a nitrile compound, and a phosphazene compound. , one or more of aromatic hydrocarbons and halogenated aromatic hydrocarbon compounds, isocyanate compounds, acid anhydride compounds, phosphite compounds, phosphate ester compounds, sulfite compounds, and methylene disulfonate compounds.
  • the third additive helps to form a denser surface on the surface of the positive electrode and/or negative electrode active material. and a stable interface film, thereby helping to further improve at least one of the cycle performance, storage performance, and rate performance of the secondary battery.
  • the content of the third additive is W3% by weight, and W3 is below 10, optionally 0.1 to 10, more optionally 0.5 to 5, based on the total weight of the non-aqueous electrolyte.
  • the third additive can be selected from the following specific substances in any ratio.
  • the cyclic carbonate compound containing a carbon-carbon unsaturated bond may include one or more compounds represented by Formula 3-1.
  • R 27 represents a C1-C6 alkylene group substituted by an alkenyl or alkynyl group on the branch chain, or a substituted or unsubstituted C2-C6 linear alkenylene group, wherein the substituent is selected from halogen atoms, C1-C6 alkyl groups, One or more types of C2 to C6 alkenyl groups.
  • the cyclic carbonate compound containing a carbon-carbon unsaturated bond may include, but is not limited to, one or more of the following compounds.
  • the halogen-substituted cyclic carbonate compound may include one or more compounds represented by Formula 3-2.
  • R 28 represents a halogen-substituted C1-C6 alkylene group or a halogen-substituted C2-C6 alkenylene group.
  • halogen-substituted cyclic carbonate compounds may include, but are not limited to, fluoroethylene carbonate (FEC), fluoropropylene carbonate (FPC), trifluoropropylene carbonate (TFPC), trans or cis -One or more of -4,5-difluoro-1,3-dioxolane-2-one (hereinafter both are collectively referred to as DFEC).
  • FEC fluoroethylene carbonate
  • FPC fluoropropylene carbonate
  • TFPC trifluoropropylene carbonate
  • the nitrile compound may be a dinitrile or trinitrile compound.
  • the nitrile compound may include one or more of the compounds represented by Formula 3-3 and Formula 3-4.
  • R 29 represents a substituted or unsubstituted C1 to C12 alkylene group, a substituted or unsubstituted C1 to C12 oxaalkylene group, a substituted or unsubstituted C2 to C12 alkenylene group, or a substituted or unsubstituted C2 to C12 alkylene group.
  • R 30 to R 32 each independently represent a substituted or unsubstituted C0 ⁇ C12 alkylene group, a substituted or unsubstituted C1 ⁇ C12 oxaalkylene group, a substituted or unsubstituted C2 ⁇ C12 alkenylene group, Substituted or unsubstituted C2-C12 alkynylene group, wherein the substituent is selected from one or more types of halogen atoms, nitrile groups, C1-C6 alkyl groups, C2-C6 alkenyl groups, and C1-C6 alkoxy groups.
  • the nitrile compound may include ethanedonitrile, malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile, suberonitrile, azelonitrile, sebaconitrile, undecane dinitrile, Dodecane dinitrile, tetramethylsuccinonitrile, methylglutaronitrile, butenedonitrile, 2-pentenedonitrile, hex-2-enedonitrile, hex-3-enedonitrile, oct-4- One or more of enedonitrile, oct-4-ynediconitrile, 1,2,3-propanetricarbonitrile, 1,3,5-pentanetricarbonitrile, and 1,3,6-hexanetricarbonitrile.
  • the phosphazene compound may be a cyclic phosphazene compound.
  • the cyclic phosphazene compound may include one of methoxypentafluorocyclotriphosphazene, ethoxypentafluorocyclotriphosphazene, phenoxypentafluorocyclotriphosphazene, and ethoxyheptafluorocyclotetraphosphazene or more.
  • the cyclic phosphazene compound may include one or more of methoxypentafluorocyclotriphosphazene, ethoxypentafluorocyclotriphosphazene, and phenoxypentafluorocyclotriphosphazene.
  • the cyclic phosphazene compound may include methoxypentafluorocyclotriphosphazene, ethoxypentafluorocyclotriphosphazene, or combinations thereof.
  • Aromatic hydrocarbons and halogenated aromatic hydrocarbon compounds may include cyclohexylbenzene, fluorocyclohexylbenzene compounds (such as 1-fluoro-2-cyclohexylbenzene, 1-fluoro-3-cyclohexylbenzene, 1-fluoro-4-cyclohexylbenzene Benzene), tert-butylbenzene, tert-amylbenzene, 1-fluoro-4-tert-butylbenzene, biphenyl, terphenyl (ortho, meta, para), diphenyl ether, fluorobenzene , difluorobenzene (ortho, meta, para), anisole, 2,4-difluoroanisole, partially hydrogenated terphenyl (such as 1,2-dicyclohexylbenzene, 2-benzene One or more of bicyclohexyl, 1,2-diphenylcyclohexane, o-cycl
  • aromatic hydrocarbons and halogenated aromatic hydrocarbon compounds may include biphenyl, terphenyl (ortho, meta, para), fluorobenzene, cyclohexylbenzene, tert-butylbenzene, and tert-amylbenzene. of one or more.
  • aromatic hydrocarbons and halogenated aromatic hydrocarbon compounds may include one or more of biphenyl, o-terphenyl, fluorobenzene, cyclohexylbenzene, and tert-amylbenzene.
  • Isocyanate compounds may include methyl isocyanate, ethyl isocyanate, butyl isocyanate, phenyl isocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, octamethylene diisocyanate, 1,4-phenylene diisocyanate , one or more of 2-isocyanatoethyl acrylate and 2-isocyanatoethyl methacrylate.
  • the isocyanate compound may include one or more of hexamethylene diisocyanate, octamethylene diisocyanate, 2-isocyanatoethyl acrylate, and 2-isocyanatoethyl methacrylate.
  • the acid anhydride compound may be a chain acid anhydride or a cyclic acid anhydride.
  • the acid anhydride compound may include one or more of acetic anhydride, propionic anhydride, succinic anhydride, maleic anhydride, 2-allylsuccinic anhydride, glutaric anhydride, itaconic anhydride, and 3-sulfo-propionic anhydride.
  • the acid anhydride compound may include one or more of succinic anhydride, maleic anhydride, and 2-allylsuccinic anhydride.
  • the anhydride compound may include succinic anhydride, 2-allylsuccinic anhydride, or combinations thereof.
  • the phosphite compound may be a silane phosphite compound, which may specifically include one or more of the compounds represented by Formula 3-5.
  • R 33 to R 41 each independently represent a halogen-substituted or unsubstituted C1-C6 alkane. base.
  • the silane phosphite compound may include, but is not limited to, one or more of the following compounds.
  • the phosphate ester compound may be a silane phosphate ester compound, which may specifically include one or more compounds represented by Formula 3-6.
  • R 42 to R 50 each independently represent a halogen-substituted or unsubstituted C1-C6 alkyl group. .
  • the silane phosphate compound may include, but is not limited to, one or more of the following compounds.
  • the sulfite compound may be a cyclic sulfite compound, and may specifically include one or more of the compounds represented by formulas 3-7.
  • R 51 represents a substituted or unsubstituted C1-C6 alkylene group, a substituted or unsubstituted C2-C6 alkenylene group, wherein the substituent is selected from one of halogen atoms, C1-C3 alkyl groups, and C2-C4 alkenyl groups.
  • R 51 represents a substituted or unsubstituted C1-C6 alkylene group, a substituted or unsubstituted C2-C6 alkenylene group, wherein the substituent is selected from one of halogen atoms, C1-C3 alkyl groups, and C2-C4 alkenyl groups.
  • the sulfite compound may include one or more of vinyl sulfite (ES), propylene sulfite (PS), and butylene sulfite (BS).
  • ES vinyl sulfite
  • PS propylene sulfite
  • BS butylene sulfite
  • the methylene disulfonate compound may include one or more of the compounds represented by formulas 3-8.
  • R 52 to R 55 each independently represent a hydrogen atom, a halogen atom, a substituted or unsubstituted C1-C10 alkyl group, a substituted or unsubstituted C2-C10 alkenyl group, wherein the substituent is selected from a halogen atom, a C1-C3 alkyl group One or more of C2-C4 alkenyl groups.
  • the methylene disulfonate compound may include, but is not limited to, one or more of the following compounds.
  • the third additive may include one or more of vinylene carbonate (VC), vinyl ethylene carbonate (VEC), and fluoroethylene carbonate (FEC).
  • VC vinylene carbonate
  • VEC vinyl ethylene carbonate
  • FEC fluoroethylene carbonate
  • the non-aqueous electrolyte solution also includes lithium salt and organic solvent.
  • This application has no special restrictions on the types of the lithium salt and the organic solvent, and can be selected according to actual needs.
  • the organic solvent may include one or more of chain carbonate, cyclic carbonate, and carboxylic acid ester.
  • this application has no specific restrictions on the types of the chain carbonate, the cyclic carbonate, and the carboxylic acid ester, and they can be selected according to actual needs.
  • the organic solvent includes dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethyl methyl carbonate (EMC), methyl propyl carbonate (MPC), carbonic acid Ethylene carbonate (EPC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), ⁇ -butyrolactone (GBL), methyl formate (MF), ethyl formate ( EF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), methyl propionate (PP), tetrahydrofuran ( THF) one or more.
  • DMC dimethyl carbonate
  • DEC diethyl carbonate
  • DPC dipropyl carbonate
  • EMC ethyl methyl carbonate
  • MPC methyl propyl carbonate
  • EPC methyl propy
  • the lithium salt may include LiN(C m F 2m+1 SO 2 )(C n F 2n+1 SO 2 ), LiPF 6 , LiBF 4 , LiBOB, LiAsF 6 , Li(FSO 2 ) 2 N, One or more of LiCF 3 SO 3 and LiClO 4 , m and n are both natural numbers.
  • the non-aqueous electrolyte includes the above-mentioned lithium salt, it helps to form a dense, stable and low-resistance interfacial film on the surface of the positive electrode and/or negative electrode active material, effectively improving the cycle performance, storage performance, and rate performance of the secondary battery. At least one.
  • the dielectric constant of cyclic carbonate is high, which is beneficial to the dissociation of lithium salt.
  • the content of the cyclic carbonate may be above 20% by weight, optionally 20% to 80% by weight, more optionally 20% to 50% by weight, based on the organic solvent. Total weight.
  • the cyclic carbonate includes one or more of ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC).
  • the dielectric constant of chain carbonate is small and its ability to dissociate lithium salt is weak. However, it has low viscosity and good fluidity, which can increase the migration rate of lithium ions.
  • the content of the chain carbonate may be above 10% by weight, optionally from 10% to 80% by weight, based on the total weight of the organic solvent.
  • the chain carbonate includes dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethyl methyl carbonate (EMC), and methylpropyl carbonate (MPC) , one or more of ethyl propyl carbonate (EPC).
  • Carboxylic acid esters have the advantages of low viscosity and high dielectric constant, and can improve the conductivity of non-aqueous electrolytes.
  • the content of the carboxylic acid ester may be from 0 to 70% by weight, optionally from 0 to 60% by weight, based on the total weight of the organic solvent.
  • the carboxylic acid esters include methyl formate (MF), ethyl formate (EF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate ( One or more of MP), ethyl propionate (EP), and methyl propionate (PP).
  • the content of lithium salt may be 6% to 39% by weight, optionally 10% to 31% by weight, more optionally 11% to 24% by weight, further optionally 12% to 20% by weight, based on the total weight of the non-aqueous electrolyte solution.
  • the non-aqueous electrolyte solution of the present application can be prepared according to conventional methods in this field.
  • the additive, the organic solvent, the lithium salt, etc. can be mixed uniformly to obtain a non-aqueous electrolyte solution.
  • the order of adding each material is not particularly limited.
  • the additive, the lithium salt, etc. can be added to the organic solvent and mixed evenly to obtain a non-aqueous electrolyte.
  • each component and its content in the non-aqueous electrolyte solution can be measured according to conventional methods in this field.
  • it can be measured by gas chromatography-mass spectrometry (GC-MS), ion chromatography (IC), liquid chromatography (LC), nuclear magnetic resonance spectroscopy (NMR), or the like.
  • GC-MS gas chromatography-mass spectrometry
  • IC ion chromatography
  • LC liquid chromatography
  • NMR nuclear magnetic resonance spectroscopy
  • non-aqueous electrolyte solution of the present application can also be obtained from secondary batteries.
  • An exemplary method of obtaining non-aqueous electrolyte from a secondary battery includes the following steps: centrifuge the secondary battery after discharging it to the discharge cut-off voltage, and then take an appropriate amount of the centrifuged liquid for testing.
  • the secondary battery may include an outer packaging.
  • the outer packaging can be used to package the above-mentioned electrode assembly and non-aqueous 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 soft bag may be made of plastic, such as at least one of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), and the like.
  • This application has no particular limitation on the shape of the secondary battery, which can be cylindrical, square or any other shape. As shown in FIG. 1 , a square-structured secondary battery 5 is shown 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 to form a receiving cavity.
  • the housing 51 has an opening communicating with the accommodation cavity, and the cover plate 53 is used to 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 non-aqueous electrolyte soaks into the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or several, and can be adjusted according to needs.
  • the positive electrode sheet, the separator, the negative electrode sheet and the non-aqueous electrolyte may be assembled to form a secondary battery.
  • the positive electrode sheet, isolation film, and negative electrode sheet can be formed into an electrode assembly through a winding process or a lamination process.
  • the electrode assembly is placed in an outer package, dried, and then injected with non-aqueous electrolyte. After vacuum packaging, static Through processes such as placement, formation, and shaping, secondary batteries are obtained.
  • the secondary batteries according to the present application can be assembled into a battery module.
  • the number of secondary batteries contained in the battery module can be multiple, and the specific number can be adjusted according to the application and capacity of the battery module.
  • FIG. 3 is a schematic diagram of the 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, and the number of battery modules contained in the battery pack can be adjusted 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 arranged in the battery box.
  • the battery box includes an upper box 2 and a lower box 3 .
  • the upper box 2 is used to cover 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 of the present application.
  • the secondary battery, battery module or battery pack may be used as a power source for the electrical device or as an energy storage unit for the electrical device.
  • the electrical device may be, but is not limited to, mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric Golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • the power-consuming device can select a secondary battery, a battery module or a battery pack according to its usage requirements.
  • FIG. 6 is a schematic diagram of 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.
  • battery packs or battery modules can be used.
  • the power-consuming device may be a mobile phone, a tablet computer, a laptop computer, etc.
  • the electrical device is usually required to be light and thin, and secondary batteries can be used as power sources.
  • 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 to obtain 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.
  • 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 electrode assembly is obtained by winding.
  • the electrode assembly is placed in an outer package, and the above-mentioned non-aqueous electrolyte is injected and packaged to obtain a full battery (hereinafter also referred to as "full battery").
  • the injection coefficient of the full battery is 3.5g/Ah.
  • 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 together with the positive electrode sheets and non-aqueous electrolyte prepared above, they are assembled into button batteries (hereinafter also referred to as "charge batteries”) in a buckle box.
  • 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 zinc carbonate was used instead of ferrous carbonate in the preparation process of the co-doped lithium manganese phosphate core.
  • Examples 1-16 used 466.4g of nickel carbonate, 5.0g of zinc carbonate and 7.2g of 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 1-16 to 1-18 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. .
  • Examples 2-1 to 2-3 except for the preparation process of the positive active material, the preparation of the positive electrode sheet, the preparation of the negative electrode sheet, the preparation of the non-aqueous electrolyte, the preparation of the separator and the preparation of the battery are all the same as in Example 1 -1 has the same process.
  • 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.
  • Example 1- 1 The preparation process of non-aqueous electrolyte solution is detailed in Table 2.
  • Comparative Examples 1 to 8 were the same as those in Example 1-1 except for the preparation process of the positive active material and the non-aqueous electrolyte.
  • the preparation process of non-aqueous electrolyte solution is detailed in Table 2.
  • 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 4 hours 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.
  • ACSTEM Spherical aberration electron microscopy
  • 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 batteries in all embodiments always maintained an SOC of more than 99% during this test until the end of storage.
  • the full battery prepared above was charged to 4.3V at 1C, and then charged at a constant voltage of 4.3V until the current was less than or equal to 0.05mA. Let it stand for 5 minutes, then discharge it to 2.5V according to 1C, and record the discharge capacity at this time as D0. Repeat the aforementioned charge and discharge cycles until the discharge capacity is reduced to 80% of D0. Record the number of cycles the battery has gone through 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.
  • Table 1 shows the positive electrode active material compositions of Examples 1-1 to 1-33 and Comparative Examples 1 to 8.
  • Table 2 shows the non-aqueous electrolyte preparation processes of Examples 1-1 to 1-33, Examples 2-1 to 2-3, Examples 3-1 to 3-32, and Comparative Examples 1 to 8.
  • Table 3 shows the performance data of the positive active materials, positive electrode sheets, buckled power or full power of Examples 1-1 to 1-33 and Comparative Examples 1 to 8 measured according to the above performance testing method.
  • Table 4 shows the performance data measured according to the above performance testing method for the positive active materials, positive electrode sheets, buckled electricity or full electricity of Examples 2-1 to 2-3.
  • the existence of the first coating layer is beneficial to reducing the Li/Mn anti-site defect concentration of the obtained material and the amount of Fe and Mn dissolution after cycling, and improving the performance of the battery.
  • gram capacity and improve the cycle performance and storage performance of the battery.
  • the lattice change rate, anti-site defect concentration and Fe and Mn dissolution of the resulting material can be significantly reduced, the gram capacity of the battery can be increased, and the cycle performance and storage of the battery can be improved. performance.
  • the presence of the first additive in the non-aqueous electrolyte is beneficial to reducing the dissolution of the first coating layer and reducing the catalytic oxidation of the second coating layer, thereby further improving the cycle performance and storage performance of the battery.
  • Figure 7 is a comparison chart between the XRD spectrum of the positive active material core prepared in Example 1-1 and the standard XRD spectrum of lithium manganese phosphate (00-033-0804).
  • the core of the positive active material of the present application is basically consistent with the position of the main characteristic peak before lithium manganese phosphate doping, indicating that the core of the positive active material of the present application has no impurity phase, and the improvement of battery performance mainly comes from element doping. , rather than caused by impurity phases.
  • Table 5 shows the performance data of Examples 3-1 to 3-20 measured according to the above performance test method with the battery turned off or fully powered.
  • Table 6 shows the performance data of Examples 3-21 to 3-32 measured according to the above performance test method with the battery turned off or fully powered.
  • Example 1-1 Based on Example 1-1 and Examples 3-1 to 3-10, it can be seen that different types of first additives have slightly different effects on improving battery performance.
  • Example 3-1 and Examples 3-11 to 3-20 it can be seen that when the non-aqueous electrolyte also contains an appropriate amount of the second additive and/or the third additive, it can help to further increase the gram capacity and rate of the battery. performance, cycle performance and storage performance.
  • the coating amount of the first coating layer is C1% by weight
  • the coating amount of the second coating layer is C2% by weight
  • the content of the first additive is W1
  • the content of weight % and the second additive W2 weight % satisfies: W1/W2 is 0.01 to 20, optionally 0.01 to 10; and/or, (W1+W2)/(C1+C2) is 0.001 to 2, optional When it is 0.01 to 1, it helps to further improve the gram capacity, rate performance, cycle performance and storage performance of the battery.

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Abstract

本申请提供一种二次电池以及包含其的电池模块、电池包及用电装置。所述二次电池包括正极极片以及非水电解液，其中，所述正极极片包括具有核-壳结构的正极活性材料，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Li1+xMn1-yAyP1-zRzO4，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；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-A至式1-D所示化合物中的一种或多种。本申请能使二次电池同时兼具较高的能量密度以及良好的倍率性能、循环性能、存储性能和安全性能。

Description

二次电池以及包含其的电池模块、电池包及用电装置 技术领域
本申请属于电池技术领域，具体涉及一种二次电池以及包含其的电池模块、电池包及用电装置。
背景技术
近年来，二次电池被广泛应用于水力、火力、风力和太阳能电站等储能电源***，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。随着二次电池的应用及推广，其安全性能受到越来越多的关注。磷酸锰锂由于具有容量高、安全性能好及原材料来源丰富等优势成为了目前最受关注的正极活性材料之一，然而磷酸锰锂在充电时容易发生锰离子溶出，导致容量迅速衰减，由此制约了其商业化进程。
发明内容
本申请的目的在于提供一种二次电池以及包含其的电池模块、电池包及用电装置，旨在使二次电池同时兼具较高的能量密度以及良好的倍率性能、循环性能、存储性能和安全性能。
本申请第一方面提供一种二次电池，包括正极极片以及非水电解液，其中，
所述正极极片包括具有核-壳结构的正极活性材料，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，x为-0.100至0.100，y为0.001至0.500，z为0.001至0.100，所述A选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种，可选为Fe、Ti、V、Ni、Co和Mg中的一种或多种，所述R选自B、Si、N和S中的一种或多种；
所述壳包括包覆所述内核的第一包覆层以及包覆所述第一包覆层的第二包覆层，其中，
所述第一包覆层包括焦磷酸盐MP 2O 7和磷酸盐XPO 4，所述M和X各自独立地选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb和Al中的一种或多种，
所述第二包覆层包含碳；
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-A至式1-D所示化合物中的一种或多种，
Figure PCTCN2022090476-appb-000001
R 1表示氢原子或由以下基团组成的组中的至少一种：羟基、C1～C18一价烷基、C1～C18一价烷氧基、C2～C18一价烷氧基烷基、C3～C18一价环烷基、C2～C18一价氧杂环烷基、C6～C18一价芳基、C7～C18一价芳基烷基、C7～C18一价烷基芳基、C6～C18一价芳基氧基、C7～C18一价芳基氧基烷基、C12～C18一价芳醚基、C2～C18一价杂芳基、C3～C18一价杂芳基烷基、C3～C18一价烷基杂芳基和C1～C18一价硅烷基；
R 2至R 21分别独立地表示氢原子或由以下基团组成的组中的至少一种：C1～C18一价烷基、C2～C18一价烷氧基烷基、C3～C18一价环烷基、C2～C18一价氧杂环烷基、C6～C18一价芳基、C7～C18一价芳基烷基、C7～C18一价烷基芳基、C7～C18一价芳基氧基烷基、C12～C18一价芳醚基、C2～C18一价杂芳基、C3～C18一价杂芳基烷基、C3～C18一价烷基杂芳基和C1～C18一价硅烷基，并且R 2和R 3均为氢原子时，R 1不为羟基；
R 2和R 3还可以相互键合形成环结构，R 4和R 5还可以相互键合形成环结构，R 6和R 7还可以相互键合形成环结构，R 8和R 9还可以相互键合形成环结构，R 10和R 11还可以相互键合形成环结构，R 12和R 13还可以相互键合形成环结构，R 14和R 15还可以相互键合形成环结构，R 16和R 17还可以相互键合形成环结构，R 18和R 19还可以相互键合形成环结构，R 20和R 21还可以相互键合形成环结构；
L 1表示氧原子或由以下基团组成的组中的至少一种：C1～C18二价烷基、C1～C18氧杂二价烷基、C6～C18二价环烷基、C6～C18二价氧杂环烷基、C6～C18二价芳基、C7～C18二价芳基烷基、C7～C18二价烷基芳基、C6～C18二价芳基氧基、C7～C18二价芳基氧基烷 基、C12～C18二价芳醚基、C2～C18二价杂芳基、C3～C18二价杂芳基烷基和C3～C18二价烷基杂芳基；
L 2表示由以下基团组成的组中的至少一种：C1～C18三价烷基、C1～C18氧杂三价烷基、C6～C18三价环烷基、C6～C18三价氧杂环烷基、C6～C18三价芳基、C7～C18三价芳基烷基、C7～C18三价烷基芳基、C6～C18三价芳基氧基、C7～C18三价芳基氧基烷基、C12～C18三价芳醚基、C3～C18三价杂芳基、C3～C18三价杂芳基烷基和C3～C18三价烷基杂芳基；
L 3表示由以下基团组成的组中的至少一种：C1～C18四价烷基、C1～C18氧杂四价烷基、C6～C18四价环烷基、C6～C18四价氧杂环烷基、C6～C18四价芳基、C7～C18四价芳基烷基、C7～C18四价烷基芳基、C7～C18四价芳基氧基烷基、C12～C18四价芳醚基、C4～C18四价杂芳基、C4～C18四价杂芳基烷基和C4～C18四价烷基杂芳基。
本申请通过对磷酸锰锂进行特定的元素掺杂和表面包覆，能够有效减少脱嵌锂过程中的锰离子溶出，同时促进锂离子的迁移，从而改善二次电池的倍率性能、循环性能、存储性能和安全性能。当非水电解液含有上述式1-A至式1-D所示的第一添加剂后，其能够在二次电池充电过程中在正极活性材料表面形成一层致密且稳定的界面膜，减少第一包覆层的溶解，减少锰离子溶出，同时降低第二包覆层在高电压下的催化氧化作用，减少非水电解液和活性锂离子的消耗。因此，本申请的二次电池能够同时兼具较高的能量密度以及良好的倍率性能、循环性能、存储性能和安全性能。
在本申请的任意实施方式中，R 2和R 3相互键合形成环结构。
在本申请的任意实施方式中，R 1至R 3中的至少一者表示C3～C18一价环烷基、C2～C18一价氧杂环烷基、C6～C18一价芳基、C7～C18一价芳基烷基、C7～C18一价烷基芳基、C7～C18一价芳基氧基烷基、C12～C18一价芳醚基、C2～C18一价杂芳基、C3～C18一价杂芳基烷基或C3～C18一价烷基杂芳基。可选地，R 1至R 3分别独立地表示C6～C18一价芳基、C7～C18一价芳基烷基、C7～C18一价烷基芳基、C7～C18一价芳基氧基烷基、C12～C18一价芳醚基、C2～C18一价杂芳基、C3～C18一价杂芳基烷基或C3～C18一价烷基杂芳基。
当R 1至R 3表示上述取代基时，有助于在正极活性材料表面形成包含交联大分子聚合物的界面膜，进一步减少第一包覆层的溶解和降低第二包覆层的催化氧化作用，减少锰离子溶出以及非水电解液和活性锂离子的消耗，从而能够进一步增强对二次电池循环性能和存储性能的改善效果。
在本申请的任意实施方式中，R 4和R 5、R 6和R 7中的至少一组相互键合形成环结构。
在本申请的任意实施方式中，L 1表示氧原子，并且R 4至R 7分别独立地表示C6～C18一价芳基、C7～C18一价芳基烷基、C7～C18一价烷基芳基、C7～C18一价芳基氧基烷基、C12～C18一价芳醚基、C2～C18一价杂芳基、C3～C18一价杂芳基烷基或C3～C18一价烷基杂芳基。
在本申请的任意实施方式中，R 8和R 9、R 10和R 11、R 12和R 13中的至少一组相互键合形成环结构。
在本申请的任意实施方式中，L 2表示C6～C18三价芳基、C7～C18三价芳基烷基、C7～C18三价烷基芳基、C6～C18三价芳基氧基、C7～C18三价芳基氧基烷基、C12～C18三价芳醚基、C3～C18三价杂芳基、C3～C18三价杂芳基烷基或C3～C18三价烷基杂芳基。
在本申请的任意实施方式中，R 14和R 15、R 16和R 17、R 18和R 19、R 20和R 21中的至少一组相互键合形成环结构。
在本申请的任意实施方式中，L 3表示C6～C18四价芳基、C7～C18四价芳基烷基、C7～C18四价烷基芳基、C7～C18四价芳基氧基烷基、C12～C18四价芳醚基、C4～C18四价杂芳基、C4～C18四价杂芳基烷基或C4～C18四价烷基杂芳基。
在本申请的任意实施方式中，所述第一添加剂包括如下化合物中的至少一种：
Figure PCTCN2022090476-appb-000002
Figure PCTCN2022090476-appb-000003
发明人在研究过程中发现，以上述化合物H1至H36中的至少一种作为第一添加剂，能够在正极活性材料表面形成更为致密且稳定的界面膜，有助于进一步减少第一包覆层 的溶解和降低第二包覆层的催化氧化作用，从而进一步减少锰离子溶出以及非水电解液和活性锂离子的消耗，由此能够进一步增强对二次电池循环性能和存储性能的改善效果。
可选地，所述第一添加剂包括H1至H10、H13至H15、H31至H33中的至少一种，更可选地，所述第一添加剂包括H1至H8、H32至H33中的至少一种。这些第一添加剂有助于在正极活性材料表面形成包含交联大分子聚合物的界面膜，进一步减少第一包覆层的溶解和降低第二包覆层的催化氧化作用，从而进一步减少锰离子溶出以及非水电解液和活性锂离子的消耗，由此能够进一步增强对二次电池循环性能和存储性能的改善效果。
在本申请的任意实施方式中，所述非水电解液还包括第二添加剂，所述第二添加剂包括磺酸内酯、环状硫酸酯、二氟磷酸锂、二氟二草酸磷酸锂、二氟草酸硼酸锂中的一种或多种。当非水电解液中同时含有第一添加剂和第二添加剂时，有助于明显改善二次电池的循环性能和存储性能，同时提升二次电池的容量发挥和倍率性能。
在本申请的任意实施方式中，所述磺酸内酯包括式2-A所示化合物中的至少一种，
Figure PCTCN2022090476-appb-000004
p1表示1、2或3，p2表示1或2，p3表示1或2，
R 22分别独立地表示氢原子、卤原子、羧酸酯基、磺酸酯基、C1～C6一价烷基、C1～C6一价卤代烷基、C1～C6一价烷氧基、C1～C6一价卤代烷氧基、C2～C6一价烯基中的一种或其中的多种通过单键相互键合形成的链状结构或环状结构，R 22表示环状结构时，通过单键键合至式2-A的多元环或与式2-A的多元环共享一个碳原子形成螺环化合物，
R 23分别独立地表示氢原子、卤原子、羧酸酯基、磺酸酯基、C1～C6一价烷基、C1～C6一价卤代烷基、C1～C6一价烷氧基、C1～C6一价卤代烷氧基、C2～C6一价烯基中的一种或其中的多种通过单键相互键合形成的链状结构或环状结构，R 23表示环状结构时，通过单键键合至式2-A的多元环或与式2-A的多元环共享一个碳原子形成螺环化合物，
R 24表示羰基或C(Y 1) 2，Y 1分别独立地表示氢原子、卤原子、羧酸酯基、磺酸酯基、C1～C6一价烷基、C1～C6一价卤代烷基、C1～C6一价烷氧基、C1～C6一价卤代烷氧基、C2～C6一价烯基、C6～C12一价芳基中的一种或其组合，
R 22和R 23还可以相互键合形成环结构。
可选地，所述磺酸内酯包括如下化合物中的至少一种：
Figure PCTCN2022090476-appb-000005
Figure PCTCN2022090476-appb-000006
在本申请的任意实施方式中，所述环状硫酸酯包括式2-B所示化合物中的至少一种，
Figure PCTCN2022090476-appb-000007
q1表示1、2或3，q2表示1或2，q3表示1或2，
R 25分别独立地表示氢原子、卤原子、羰基氧原子、羧酸酯基、硫酸酯基、C1～C6一价烷基、C1～C6一价卤代烷基、C1～C6一价烷氧基、C1～C6一价卤代烷氧基、C2～C6一价烯基中的一种或其中的多种通过单键相互键合形成的链状结构或环状结构，R 25表示环状结构时，通过单键键合至式2-B的多元环或与式2-B的多元环共享一个碳原子形成螺环化合物，
R 26分别独立地表示氢原子、卤原子、羧酸酯基、硫酸酯基、C1～C6一价烷基、C1～C6一价卤代烷基、C1～C6一价烷氧基、C1～C6一价卤代烷氧基、C2～C6一价烯基中的一种或其中的多种通过单键相互键合形成的链状结构或环状结构，R 26表示环状结构时，通过单键键合至式2-B的多元环或与式2-B的多元环共享一个碳原子形成螺环化合物，
R 25和R 26还可以相互键合形成环结构。
可选地，所述环状硫酸酯包括如下化合物中的至少一种：
Figure PCTCN2022090476-appb-000008
在本申请的任意实施方式中，所述第一添加剂的含量为W1重量％，W1为0.01至20，可选为0.1至10，更可选为0.3至5，基于所述非水电解液的总重量计。由此，既能减少第一包覆层的溶解、降低第二包覆层的催化氧化作用，又不恶化正极界面阻抗，进而能够明显改善二次电池的循环性能和存储性能，同时不影响二次电池的容量发挥和倍率性能。
在本申请的任意实施方式中，所述第二添加剂的含量为W2重量％，W2为0.01至20，可选为0.1至10，更可选为0.3至5，基于所述非水电解液的总重量计。由此，能够有效地改善二次电池的容量发挥和倍率性能。
在本申请的任意实施方式中，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至5.6，基于所述内核的重量计。由此，能够有效发挥第一包覆层的功能，同时不会由于包覆层过厚而影响二次电池的动力学性能。
在本申请的任意实施方式中，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至5，基于所述内核的重量计。由此，第二包覆层的存在能够避免正极活性材料与电解液直接接触，减少电解液对正极活性材料的侵蚀，并提高正极活性材料的导电能力。当第二层包覆量在上述范围内时，能够有效提升正极活性材料的克容量。
在本申请的任意实施方式中，W1/W2为0.01至20，可选为0.01至10。由此能够进一步增强对二次电池循环性能和存储性能的改善效果，同时提升二次电池的容量发挥和倍率性能。
在本申请的任意实施方式中，(W1+W2)/(C1+C2)为0.001至2，可选为0.01至1。由此能够明显增强对二次电池循环性能和存储性能的改善效果，同时提升二次电池的容量发挥和倍率性能。
在本申请的任意实施方式中，所述非水电解液还包括第三添加剂，所述第三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、腈化合物、磷腈化合物、芳香烃及卤代芳香烃化合物、异氰酸酯化合物、酸酐化合物、亚磷酸酯化合物、磷酸酯化合物、亚硫酸酯化合物、二磺酸亚甲酯化合物中的一种或多种。第三添加剂有助于在正极和/或负极活性材料表面形成更为致密且稳定的界面膜，从而有助于进一步提升二次电池的循环性能、存储性能、倍率性能中的至少一者。
在本申请的任意实施方式中，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。由此，二次电池的能量密度和循环性能可进一步提升。
在本申请的任意实施方式中，在所述内核中，z与1-z的比值为1:9至1:999，可选为1:499至1:249。由此，二次电池的能量密度和循环性能可进一步提升。
在本申请的任意实施方式中，所述A选自Fe、Ti、V、Ni、Co和Mg中的至少两种。由此，通过所述A为上述范围内的两种或更多种金属，因而在锰位掺杂有利于增强掺杂效果，进一步降低表面氧活性和抑制锰离子的溶出。
在本申请的任意实施方式中，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°。由此，进一步提升二次电池的循环性能和倍率性能。
在本申请的任意实施方式中，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°。由此，进一步提升二次电池的循环性能和倍率性能。
在本申请的任意实施方式中，所述第一包覆层中焦磷酸盐和磷酸盐的重量比为1:3至3:1，可选为1:3至1:1。由此，通过焦磷酸盐和磷酸盐在合适的重量比范围，既可有效阻碍锰离子溶出，又可有效减少表面杂锂含量，减少界面副反应，从而提高二次电池的倍率性能、循环性能、存储性能和安全性能。
在本申请的任意实施方式中，所述焦磷酸盐和磷酸盐的结晶度各自独立地为10％至100％，可选为50％至100％。由此具备上述范围的结晶度的焦磷酸盐和磷酸盐有利于充分发挥焦磷酸盐阻碍锰离子溶出和磷酸盐减少表面杂锂含量、减少界面副反应的作用。
在本申请的任意实施方式中，所述正极活性材料的Li/Mn反位缺陷浓度为4％以下，可选为2％以下。由此，能够提升正极活性材料的克容量和倍率性能。
在本申请的任意实施方式中，所述正极活性材料的晶格变化率为6％以下，可选为4％以下。由此，能够改善二次电池的倍率性能。
在本申请的任意实施方式中，所述正极活性材料的表面氧价态为-1.88以下，可选为-1.98至-1.88。由此，能够改善二次电池的循环性能和存储性能。
在本申请的任意实施方式中，所述正极活性材料在3吨下的压实密度为2.0g/cm 3以上，可选为2.2g/cm 3以上。由此，有利于提升二次电池的体积能量密度。
在本申请的任意实施方式中，所述正极活性材料的比表面积为Bm 2/g，B为7至18，可选为10至15。此时，能够保证正极极片具有较高的到锂离子能力，同时二次电池具有良好的倍率性能、循环性能和存储性能。
本申请第二方面提供一种电池模块，包括本申请第一方面的二次电池。
本申请第三方面提供一种电池包，包括本申请第二方面的电池模块。
本申请第四方面提供一种用电装置，包括选自本申请第一方面的二次电池、本申请第二方面的电池模块或本申请第三方面的电池包中的至少一种。
本申请的电池模块、电池包、用电装置包括本申请的二次电池，因而至少具有与所述二次电池相同的优势。
附图说明
为了更清楚地说明本申请实施例的技术方案，下面将对本申请实施例中所需要使用的附图作简单地介绍。显而易见地，下面所描述的附图仅仅是本申请的一些实施方式，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据附图获得其他的附图。
图1是本申请的二次电池的一实施方式的示意图。
图2是图1的二次电池的实施方式的分解示意图。
图3是本申请的电池模块的一实施方式的示意图。
图4是本申请的电池包的一实施方式的示意图。
图5是图4所示的电池包的实施方式的分解示意图。
图6是包含本申请的二次电池作为电源的用电装置的一实施方式的示意图。
图7是实施例1-1制备的正极活性材料内核的XRD谱图与磷酸锰锂XRD标准谱图(00-033-0804)的对比图。
在附图中，附图未必按照实际的比例绘制。附图标记说明如下：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盖板。
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以及包含其的电池模块、电池包及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，并且这样的技术方案应被认为包含在本申请的公开内容中。
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，并且这样的技术方案应被认为包含在本申请的公开内容中。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
需要说明的是，在本文中，中值粒径Dv50是指材料累计体积分布百分数达到50％时所对应的粒径。在本申请中，材料的中值粒径Dv50可采用激光衍射粒度分析法测定。例如参照标准GB/T 19077-2016，使用激光粒度分析仪(例如Malvern Master Size 3000)进行测定。
在本文中，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。另外，每一层包覆层可以是完全包覆，也可以是部分包覆。
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。
在本文中，术语“芳基”是指闭合的芳族环或环体系。在未明确指出时，“芳基”结构可以是单环、多环或稠环等。芳基的实例包括但不限于苯基、萘基、蒽基、菲基、二联苯基、三联苯基、四联苯基、三亚苯基、芘基、
Figure PCTCN2022090476-appb-000009
基、苝基、茚基、苯并菲基、芴基、9,9-二甲基芴基、螺二芴基。
在本文中，术语“杂芳基”是指芳基的环中的一个或多个原子是除碳以外的元素。杂芳基的实例包括但不限于吡咯基、呋喃基、噻吩基、吲哚基、苯并呋喃基、苯并噻吩基、二苯并呋喃、二苯并噻吩、咔唑基、茚并咔唑基、吲哚并咔唑基、吡啶基、嘧啶基、吡嗪基、哒嗪基、三嗪基、噁唑基、异噁唑基、噻唑基、异噻唑基。杂芳基中的杂原子可以包括N、O、S、Si等。杂芳基中杂原子的数目可以为一个，也可以为多个，并且所述多个杂原子可以相同也可以不同。
在本文中，当取代基表示某些基团组成的组时，包括这些基团以单键键合而形成的基团。例如，当取代基表示“由羟基、C1～C18一价烷基、C6～C18一价芳基组成的组成中的至少一种时”，取代基单独公开了羟基、C1～C18一价烷基、C6～C18一价芳基、羟基取代的C1～C18一价烷基、羟基取代的C6～C18一价芳基和C1～C18一价烷基取代的C6～C18一价芳基。
在本文中，当各取代基表示“一价”时，是指分子中去掉一个H原子而形成的基团，当各取代基表示“二价”时，是指分子中去掉两个H原子而形成的基团，当各取代基表示“三价”时，是指分子中去掉三个H原子而形成的基团，当各取代基表示“四价”时，是指分子中去掉四个H原子而形成的基团。
在本说明书的各处，化合物的取代基以组或范围公开。明确地预期这种描述包括这些组和范围的成员的每一个单独的子组合。例如，明确地预期术语“C1～C6烷基”单独地公开C1、C2、C3、C4、C5、C6、C1～C6、C1～C5、C1～C4、C1～C3、C1～C2、C2～C6、C2～C5、C2～C4、C2～C3、C3～C6、C3～C5、C3～C4、C4～C6、C4～C5和C5～C6烷基。
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离子向非水电解液中的迁移。溶出的锰离子在迁移到负极后，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，容易导致二次电池发生膨胀，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，影响二次电池的动力学性能。此外，为补充损失的SEI膜，非水电解液和电池内部的活性锂离子被不断消耗，给二次电池的容量保持率带来不可逆的影响。
发明人经深入思考，从正极和非水电解液出发，设计了一种二次电池，该二次电池能够同时兼具较高的能量密度以及良好的倍率性能、循环性能、存储性能和安全性能。
具体地，本申请第一方面提供了一种二次电池。
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，二次电池包括电极组件和非水电解液，所述电极组件包括正极极片、负极极片和隔离膜，并且所述隔离膜设置在所述正极极片和所述负极极片之间，主要起到防止正负极短路的作用，同时可以使锂离子通过。所述非水电解液在所述正极极片和所述负极极片之间起到传导锂离子的作用。
[正极极片]
本申请的二次电池中采用的正极极片至少包括具有核-壳结构的正极活性材料，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，x为-0.100至0.100，y为0.001至0.500，z为0.001至0.100，所述A选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种，可选为Fe、Ti、V、Ni、Co和Mg中的一种或多种，所述R选自B、Si、N和S中的一种或多种。所述壳包括包覆所述内核的第一包覆层以及包覆所述第一包覆层的第二包覆层，其中，所述第一包覆层包括焦磷酸盐MP 2O 7和磷酸盐XPO 4，所述M和X各自独立地选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb和Al中的一种或多种；所述第二包覆层包含碳。
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。
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掺杂改性以及对磷酸锰锂进行多层包覆，得到了能够显著降低锰离子溶出和降低晶格变化率的正极活性材料。
本申请的磷酸锰锂正极活性材料为具有双层包覆层的核-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，提高磷酸锰锂正极活性材料的结构稳定性，大大减少锰离子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)，能够有效减少过渡金属离子的溶出。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。
本申请的正极活性材料的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非水电解液中，并减少非水电解液对正极活性材料的侵蚀。
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，能够有效减少脱嵌锂过程中的锰离子溶出，同时促进锂离子的迁移，从而改善二次电池的倍率性能、循环性能、存储性能和安全性能。
需要指出的是，本申请的正极活性材料内核与LiMnPO 4掺杂前的主要特征峰的位置基本一致，说明掺杂的磷酸锰锂正极活性材料内核没有杂质相，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。
在所述内核中，x为-0.100至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、-0.100。
在所述内核中，y为0.001至0.500，例如y可以为0.1、0.2、0.25、0.3、0.35、0.4、0.45。
在所述内核中，z为0.001至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、0.100。
在一些实施方式中，可选地，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。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，二次电池的能量密度和循环性能可进一步提升。
在一些实施方式中，可选地，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。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，二次电池的能量密度和循环性能可进一步提升。
在一些实施方式中，可选地，所述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，从而减少锰离子的溶出，减少非水电解液和活性锂离子的消耗，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非水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存储性能。
在一些实施方式中，可选地，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°。
在一些实施方式中，可选地，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°。
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，能够有效减少包覆层中的杂质相，从而提升正极活性材料的克容量、循环性能和倍率性能。
在一些实施方式中，可选地，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。
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，既可有效阻碍锰离子溶出，又可有效减少表面杂锂含量，减少界面副反应，从而提高二次电池的倍率性能、循环性能和安全性能。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，则减少锰离子溶出的效果不显著。
在一些实施方式中，可选地，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％。
在本申请磷酸锰锂正极活性材料的第一包覆层中，具备一定结晶度的焦磷酸盐和磷酸盐有利于保持第一包覆层的结构稳定，减少晶格缺陷。这一方面有利于充分发挥焦磷酸盐阻碍锰离子溶出的作用，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存储性能。
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，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至5.6，基于所述内核的重量计。
当所述第一包覆层的包覆量在上述范围内时，能够进一步减少锰离子溶出，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，影响二次电池的动力学性能。
在一些实施方式中，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至5，基于所述内核的重量计。
作为第二包覆层的含碳层一方面可以发挥“屏障”功能，避免正极活性材料与非水电解液直接接触，从而减少非水电解液对正极活性材料的侵蚀，提高二次电池在高温下的安全性能。另一方面，其具备较强的导电能力，可降低电池内阻，从而改善二次电池的动力学性能。然而，由于碳材料的克容量较低，因此当第二包覆层的用量过大时，可能会降低正极活性材料整体的克容量。因此，第二包覆层的包覆量在上述范围时，能够在不牺牲正极活性材料克容量的前提下，进一步改善二次电池的动力学性能和安全性能。
在一些实施方式中，可选地，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。
Li/Mn反位缺陷是指LiMnPO 4晶格中，Li +和Mn 2+的位置发生互换。Li/Mn反位缺陷浓度指的是正极活性材料中与Mn 2+发生互换的Li +占Li +总量的百分比。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。在本申请的正极活性材料中，通过将Li/Mn反位缺陷浓度控制在低水平，能够提升正极活性材料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，所述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。
在一些实施方式中，可选地，所述正极活性材料的扣电平均放电电压为3.5V以上，放电克容量在140mAh/g以上；可选为平均放电电压3.6V以上，放电克容量在145mAh/g以上。
尽管未掺杂的LiMnPO 4的平均放电电压在4.0V以上，但它的放电克容量较低，通常小于120mAh/g，因此，二次电池的能量密度较低；通过掺杂调整晶格变化率，可使其放电克容量大幅提升，在平均放电电压微降的情况下，二次电池整体能量密度有明显升高。
在一些实施方式中，可选地，所述正极活性材料的表面氧价态为-1.88以下，可选为-1.98至-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，可降低正极活性材料表面的反应活性，减少正极活性材料与非水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存储性能。
在一些实施方式中，可选地，所述正极活性材料在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，即单位体积正极活性材料的重量越大，将更有利于提升二次电池的体积能量密度。本申请中，压实密度例如可根据GB/T 24533-2009测定。
在一些实施方式中，可选地，所述正极活性材料的比表面积为Bm 2/g，B为7至18，可选为10至15。
正极活性材料的比表面积较高，正极极片的导锂离子能力会提高，进而能够提升二次电池的容量发挥和倍率性能。但是，正极活性材料的比表面积也不宜过高，由此可能增加正极活性材料与非水电解液的接触面积，进而增加界面副反应，影响二次电池的循环性能和存储性能。通过将正极活性材料的比表面积控制在合适的范围内，能够保证正极极片具有较高的到锂离子能力，同时二次电池具有良好的倍率性能、循环性能和存储性能。正极活性材料的比表面积为本领域公知的含义，可以用本领域公知的仪器及方法进行测定。例如可以根据GB/T 19587-2017，采用氮气吸附比表面积分析方法进行测试，并用BET(Brunauer Emmett Teller)法计算得出。测试仪器可采用美国Micromeritics公司的Tri-Star 3020型比表面积孔径分析测试仪。
本申请还提供一种正极活性材料的制备方法，其包括以下提供内核材料的步骤和包覆步骤。
提供内核材料的步骤：所述内核包括Li 1+xMn 1-yA yP 1-zR zO 4，x为-0.100至0.100，y为0.001至0.500，z为0.001至0.100，所述A选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种，可选为Fe、Ti、V、Ni、Co和Mg中的一种或多种，所述R选自B、Si、N和S中的一种或多种。
包覆步骤：提供MP 2O 7粉末和包含碳的源的XPO 4悬浊液，将所述内核材料、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，所述M和X各自独立地选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb和Al中的一种或多种。 其中，所述正极活性材料具有核-壳结构，其包括内核及包覆所述内核的壳，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，所述第一包覆层包括焦磷酸盐MP 2O 7和磷酸盐XPO 4，所述第二包覆层包含碳。
本申请的制备方法对材料的来源没有特别的限制。可选地，本申请制备方法中的内核材料可以是市售获得的，也可以是通过本申请的方法制备获得的。可选地，所述内核材料通过下文中所述方法制备获得。
在一些实施方式中，可选地，提供内核材料的步骤包括以下步骤(1)和步骤(2)。
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)：将所述掺杂有元素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，所述掺杂有元素A和元素R的磷酸锰锂为Li 1+xMn 1-yA yP 1-zR zO 4，x为-0.100至0.100，y为0.001至0.500，z为0.001至0.100，所述A选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种，可选为Fe、Ti、V、Ni、Co和Mg中的一种或多种，所述R选自B、Si、N和S中的一种或多种。
可选地，所述步骤(1)在20-120℃，可选为25-80℃的温度下进行。所述步骤(1)中所述搅拌在500-700rpm下进行60-420分钟，可选地为120-360分钟。
通过控制掺杂时的反应温度、搅拌速率和混合时间，能够使掺杂元素均匀分布，减少晶格缺陷，减少锰离子溶出，减少正极活性材料与非水电解液的界面副反应，从而可提升正极活性材料的克容量和倍率性能等。
需要说明的是，在本申请中，某种元素的来源可包括该元素的单质、硫酸盐、卤化物、硝酸盐、有机酸盐、氧化物或氢氧化物中的一种或多种，前提是该来源可实现本申请制备方法的目的。作为示例，所述元素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。作为示例，所述元素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。可选地，元素R的无机酸选自磷酸、硝酸、硼酸、亚硅酸、原硅酸中的一种或多种。
可选地，在步骤(1)中，锰的源为选自单质锰、二氧化锰、磷酸锰、草酸锰、碳酸锰中的一种或多种。
可选地，元素A为铁，并且可选地，在步骤(1)中，铁的源为选自碳酸亚铁、氢氧化铁、硫酸亚铁中的一种或多种。
可选地，在步骤(1)中，所述酸选自盐酸、硫酸、硝酸、磷酸、有机酸如草酸等中的一种或多种，可选为草酸。在一些实施方式中，所述酸为浓度为60重量％以下的稀酸。
可选地，在步骤(2)中，锂的源为选自碳酸锂、氢氧化锂、磷酸锂、磷酸二氢锂中的一种或多种。
可选地，在步骤(2)中，磷的源为选自磷酸氢二铵、磷酸二氢铵、磷酸铵和磷酸中的一种或多种。
在一些实施方式中，可选地，本申请所述制备方法中使用的溶剂为本领域通常使用的溶剂。例如，本申请制备方法中的溶剂可各自独立地选自乙醇、水(例如去离子水)中的至少一种。
在一些实施方式中，可选地，在制备A元素掺杂的锰盐颗粒的过程中，控制溶液pH为4-6。需要说明的是，在本申请中可通过本领域通常使用的方法调节所得混合物的pH，例如可通过添加酸或碱。
在一些实施方式中，可选地，在步骤(2)中，所述掺杂有元素A的锰盐颗粒与锂的源、磷的源的摩尔比为1:(0.5-2.1):(0.5-2.1)。
在一些实施方式中，可选地，在步骤(2)中，烧结条件为：在惰性气体或惰性气体与氢气混合气氛保护下在600-800℃下烧结4-10小时。由此，烧结后材料的结晶度更高，从而可提升正极活性材料的克容量和倍率性能等。
可选地，惰性气体与氢气混合物为氮气(70-90体积％)+氢气(10-30体积％)。
在一些实施方式中，可选地，所述MP 2O 7粉末是市售产品，或者可选地，所述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和Al中的一种或多种。
可选地，在MP 2O 7粉末的制备过程中，所述干燥步骤为在100-300℃、可选150-200℃下干燥4-8小时。
可选地，在MP 2O 7粉末的制备过程中，所述烧结步骤为在500-800℃、可选650-800℃下，在惰性气体气氛下烧结4-10小时。
在一些实施方式中，可选地，所述包含碳的源的XPO 4悬浊液是市售可得的，或者可选地，通过以下方法来制备：将锂的源、X的源、磷的源和碳的源在溶剂中混合均匀，然后将反应混合物升温至60-120℃保持2-8小时即可获得包含碳的源的XPO 4悬浊液。可选地，在制备包含碳的源的XPO 4悬浊液的过程中，调节所述混合物的pH为4-6。
可选地，碳的源为有机碳源，并且所述有机碳源选自淀粉、蔗糖、葡萄糖、聚乙烯醇、聚乙二醇、柠檬酸中的一种或多种。
在一些实施方式中，在包覆步骤中，所述A元素和R元素掺杂的磷酸锰锂(内核)、MP 2O 7粉末和包含碳的源的XPO 4悬浊液的质量比为1:(0.001-0.05):(0.001-0.05)。
在一些实施方式中，可选地，所述包覆步骤中的烧结温度为500-800℃，烧结时间为4-10小时。
在一些实施方式中，可选地，本申请双层包覆的磷酸锰锂正极活性材料的一次颗粒的中值粒径Dv50为50-2000nm。
本申请的正极极片可以包括正极集流体以及设置在所述正极集流体至少一个表面的正极膜层，具体地，所述正极集流体具有在自身厚度方向相对的两个表面，所述正极膜层设置于所述正极集流体的两个相对表面中的任意一者或两者上。所述正极膜层包括本申请如上所述的正极活性材料。
在一些实施方式中，可选地，所述正极活性材料在所述正极膜层中的含量为10重量％以上，基于所述正极膜层的总重量计。更可选地，所述正极活性材料在所述正极膜层中的含量为90-99.5重量％，基于所述正极膜层的总重量计。
当所述正极活性材料的含量在上述范围内时，有利于充分发挥本申请正极活性材料的优势。
所述正极膜层并不排除除了本申请提供的上述正极活性材料之外的其他正极活性材料，例如，在一些实施方式中，所述正极膜层还可以包括层状锂过渡金属氧化物及其改性化合物中的至少一种。作为示例，所述其他正极活性材料可包括锂钴氧化物、锂镍氧化物、锂锰氧化物、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物、锂镍钴铝氧化物及其各自的改性化合物中的至少一种。
在一些实施方式中，所述正极膜层还可选地包括正极导电剂。本申请对所述正极导电剂的种类没有特别的限制，作为示例，所述正极导电剂包括超导碳、导电石墨、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯、碳纳米纤维中的至少一种。
在一些实施方式中，所述正极膜层还可选地包括正极粘结剂。本申请对所述正极粘结剂的种类没有特别的限制，作为示例，所述正极粘结剂可包括聚偏氟乙烯(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、含氟丙烯酸酯类树脂中的至少一种。
在一些实施方式中，所述正极集流体可采用金属箔片或复合集流体。作为金属箔片的示例，可采用铝箔。复合集流体可包括高分子材料基层以及形成于高分子材料基层至少一个表面上的金属材料层。作为示例，金属材料可选自铝、铝合金、镍、镍合金、钛、钛合金、银、银合金中的至少一种。作为示例，高分子材料基层可选自聚丙烯(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。
所述正极膜层通常是将正极浆料涂布在正极集流体上，经干燥、冷压而成的。所述正极浆料通常是将正极活性材料、可选的导电剂、可选的粘结剂以及任意的其他组分分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)，但不限于此。
[负极极片]
在一些实施方式中，所述负极极片包括负极集流体以及设置在所述负极集流体至少一个表面且包括负极活性材料的负极膜层。例如，所述负极集流体具有在自身厚度方向相对的两个表面，所述负极膜层设置在所述负极集流体的两个相对表面中的任意一者或两者上。
所述负极活性材料可采用本领域公知的用于二次电池的负极活性材料。作为示例，所述负极活性材料包括但不限于天然石墨、人造石墨、软炭、硬炭、硅基材料、锡基材料、钛酸锂中的至少一种。所述硅基材料可包括单质硅、硅氧化物、硅碳复合物、硅氮复合物、硅合金材料中的至少一种。所述锡基材料可包括单质锡、锡氧化物、锡合金材料中的至少一种。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负极活性材料的传统公知的材料。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，所述负极膜层还可选地包括负极导电剂。本申请对所述负极导电剂的种类没有特别的限制，作为示例，所述负极导电剂可包括超导碳、导电石墨、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯、碳纳米纤维中的至少一种。
在一些实施方式中，所述负极膜层还可选地包括负极粘结剂。本申请对所述负极粘 结剂的种类没有特别的限制，作为示例，所述负极粘结剂可包括丁苯橡胶(SBR)、水溶性不饱和树脂SR-1B、水性丙烯酸类树脂(例如，聚丙烯酸PAA、聚甲基丙烯酸PMAA、聚丙烯酸钠PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、羧甲基壳聚糖(CMCS)中的至少一种。
在一些实施方式中，所述负极膜层还可选地包括其他助剂。作为示例，其他助剂可包括增稠剂，例如，羧甲基纤维素钠(CMC)、PTC热敏电阻材料等。
在一些实施方式中，所述负极集流体可采用金属箔片或复合集流体。作为金属箔片的示例，可采用铜箔。复合集流体可包括高分子材料基层以及形成于高分子材料基层至少一个表面上的金属材料层。作为示例，金属材料可选自铜、铜合金、镍、镍合金、钛、钛合金、银、银合金中的至少一种。作为示例，高分子材料基层可选自聚丙烯(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。
所述负极膜层通常是将负极浆料涂布在负极集流体上，经干燥、冷压而成的。所述负极浆料通常是将负极活性材料、可选的导电剂、可选地粘结剂、其他可选的助剂分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)或去离子水，但不限于此。
所述负极极片并不排除除了所述负极膜层之外的其他附加功能层。例如在某些实施例中，本申请所述的负极极片还包括夹在所述负极集流体和所述负极膜层之间、设置于所述负极集流体表面的导电底涂层(例如由导电剂和粘结剂组成)。在另外一些实施例中，本申请所述的负极极片还包括覆盖在所述负极膜层表面的保护层。
[隔离膜]
本申请对所述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，所述隔离膜的材质可以包括玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。所述隔离膜可以是单层薄膜，也可以是多层复合薄膜。当所述隔离膜为多层复合薄膜时，各层的材料相同或不同。
在一些实施方式中，所述正极极片、所述隔离膜和所述负极极片可通过卷绕工艺或叠片工艺制成电极组件。
[非水电解液]
二次电池包括非水电解液，其是二次电池中锂离子通行的桥梁，在二次电池中承担着正负极之间输送锂离子的作用，对二次电池的容量发挥、循环性能、存储性能、倍率性能及安全性能等都起着至关重要的作用。
目前商业化应用最广的非水电解液体系为六氟磷酸锂的混合碳酸酯溶液，但是，六氟磷酸锂在高温环境下的热稳定性较差，其在较高温度下会分解生成PF 5。PF 5具有较强的路易斯酸性，会与有机溶剂分子中氧原子上的孤对电子作用而使有机溶剂分解；此外，PF 5对于非水电解液中微量的水分具有较高的敏感性，遇水会产生HF，从而增加非水电解液的酸度，进而容易破坏正极活性材料表面的包覆层，特别地，容易破坏上述包括焦磷酸盐和磷酸盐的第一包覆层，加速锰离子溶出，影响二次电池的循环性能和存储性能。 此外，第二包覆层中的碳在高电压下会催化非水电解液氧化分解，进一步增加活性锂离子的不可逆消耗。
发明人进一步进行了大量研究，巧妙地在非水电解液中加入了如下式1-A至式1-D所示的第一添加剂，其能够减少第一包覆层的溶解和降低第二包覆层的催化氧化作用，从而能够明显改善二次电池的循环性能和存储性能。
具体地，本申请的非水电解液至少包括第一添加剂，所述第一添加剂包括式1-A至式1-D所示化合物中的一种或多种。
Figure PCTCN2022090476-appb-000010
R 1表示氢原子或由以下基团组成的组中的至少一种：羟基、C1～C18一价烷基、C1～C18一价烷氧基、C2～C18一价烷氧基烷基、C3～C18一价环烷基、C2～C18一价氧杂环烷基、C6～C18一价芳基、C7～C18一价芳基烷基、C7～C18一价烷基芳基、C6～C18一价芳基氧基、C7～C18一价芳基氧基烷基、C12～C18一价芳醚基、C2～C18一价杂芳基、C3～C18一价杂芳基烷基、C3～C18一价烷基杂芳基和C1～C18一价硅烷基。
R 2至R 21分别独立地表示氢原子或由以下基团组成的组中的至少一种：C1～C18一价烷基、C2～C18一价烷氧基烷基、C3～C18一价环烷基、C2～C18一价氧杂环烷基、C6～C18一价芳基、C7～C18一价芳基烷基、C7～C18一价烷基芳基、C7～C18一价芳基氧基烷基、C12～C18一价芳醚基、C2～C18一价杂芳基、C3～C18一价杂芳基烷基、C3～C18一价烷基杂芳基和C1～C18一价硅烷基。
R 2和R 3均为氢原子时，R 1不为羟基。
R 2和R 3还可以相互键合形成环结构，R 4和R 5还可以相互键合形成环结构，R 6和R 7还可以相互键合形成环结构，R 8和R 9还可以相互键合形成环结构，R 10和R 11还可以相互键合形成环结构，R 12和R 13还可以相互键合形成环结构，R 14和R 15还可以相互键合形成环结构，R 16和R 17还可以相互键合形成环结构，R 18和R 19还可以相互键合形成环结构，R 20和R 21还可以相互键合形成环结构。
L 1表示氧原子或由以下基团组成的组中的至少一种：C1～C18二价烷基、C1～C18氧杂二价烷基、C6～C18二价环烷基、C6～C18二价氧杂环烷基、C6～C18二价芳基、C7～C18二价芳基烷基、C7～C18二价烷基芳基、C6～C18二价芳基氧基、C7～C18二价芳基氧基烷基、C12～C18二价芳醚基、C2～C18二价杂芳基、C3～C18二价杂芳基烷基和C3～C18二价烷基杂芳基。
L 2表示由以下基团组成的组中的至少一种：C1～C18三价烷基、C1～C18氧杂三价烷基、C6～C18三价环烷基、C6～C18三价氧杂环烷基、C6～C18三价芳基、C7～C18三价芳基烷基、C7～C18三价烷基芳基、C6～C18三价芳基氧基、C7～C18三价芳基氧基烷基、C12～C18三价芳醚基、C3～C18三价杂芳基、C3～C18三价杂芳基烷基和C3～C18三价烷基杂芳基。
L 3表示由以下基团组成的组中的至少一种：C1～C18四价烷基、C1～C18氧杂四价烷基、C6～C18四价环烷基、C6～C18四价氧杂环烷基、C6～C18四价芳基、C7～C18四价芳基烷基、C7～C18四价烷基芳基、C7～C18四价芳基氧基烷基、C12～C18四价芳醚基、C4～C18四价杂芳基、C4～C18四价杂芳基烷基和C4～C18四价烷基杂芳基。
当非水电解液含有上述式1-A至式1-D所示的第一添加剂后，其能够在二次电池充电过程中在正极活性材料表面形成一层致密且稳定的界面膜，减少第一包覆层的溶解，减少锰离子溶出，同时降低第二包覆层在高电压下的催化氧化作用，减少非水电解液和活性锂离子的消耗，由此能够明显提升二次电池的循环性能和存储性能，特别地，能够明显提升二次电池高温高电压下的循环性能和存储性能。
所述第一添加剂包括式1-A至式1-D所示化合物中的一种或多种。具体地，在一些实施方式中，所述第一添加剂包括式1-A所示化合物中的一种或多种；在一些实施方式中，所述第一添加剂包括式1-B所示化合物中的一种或多种；在一些实施方式中，所述第一添加剂包括式1-C所示化合物中的一种或多种；在一些实施方式中，所述第一添加剂包括式1-D所示化合物中的一种或多种；在一些实施方式中，所述第一添加剂同时包括式1-A至式1-D所示化合物中的任意两种、三种或四种。
在一些实施方式中，可选地，R 2和R 3相互键合形成环结构。更可选地，R 2和R 3相互键合形成五元以上的环结构。
在一些实施方式中，可选地，R 1至R 3中的至少一者表示C3～C18一价环烷基、C2～C18一价氧杂环烷基、C6～C18一价芳基、C7～C18一价芳基烷基、C7～C18一价烷基芳基、C7～C18一价芳基氧基烷基、C12～C18一价芳醚基、C2～C18一价杂芳基、C3～C18一价杂芳基烷基或C3～C18一价烷基杂芳基。更可选地，R 1至R 3分别独立地表示C3～C18一价环烷基、C2～C18一价氧杂环烷基、C6～C18一价芳基、C7～C18一价芳基烷基、C7～C18一价烷基芳基、C7～C18一价芳基氧基烷基、C12～C18一价芳醚基、C2～C18一价杂芳基、C3～C18一价杂芳基烷基或C3～C18一价烷基杂芳基。进一步可选地，R 1至R 3分 别独立地表示C6～C18一价芳基、C7～C18一价芳基烷基、C7～C18一价烷基芳基、C7～C18一价芳基氧基烷基、C12～C18一价芳醚基、C2～C18一价杂芳基、C3～C18一价杂芳基烷基或C3～C18一价烷基杂芳基。
当R 1至R 3表示上述取代基时，有助于在正极活性材料表面形成包含交联大分子聚合物的界面膜，进一步减少第一包覆层的溶解和降低第二包覆层的催化氧化作用，减少锰离子溶出以及非水电解液和活性锂离子的消耗，从而能够进一步增强对二次电池循环性能和存储性能的改善效果。
作为示例，所述式1-A所示化合物包括如下化合物中的至少一种：
Figure PCTCN2022090476-appb-000011
Figure PCTCN2022090476-appb-000012
可选地，所述式1-A所示化合物包括H1至H10、H13至H15中的至少一种。更可选地，所述式1-A所示化合物包括H1至H10中的至少一种。进一步可选地，所述式1-A所示化合物包括H1至H8中的至少一种。
在一些实施方式中，可选地，R 4至R 7均表示氢原子，并且L 1表示C6～C18二价环烷基、C6～C18二价氧杂环烷基、C6～C18二价芳基、C7～C18二价芳基烷基、C7～C18二价烷基芳基、C6～C18二价芳基氧基、C7～C18二价芳基氧基烷基、C12～C18二价芳醚基、C2～C18二价杂芳基、C3～C18二价杂芳基烷基或C3～C18二价烷基杂芳基。更可选地，R 4至R 7均表示氢原子，并且L 1表示C6～C18二价芳基、C7～C18二价芳基烷基、C7～C18二价烷基芳基、C6～C18二价芳基氧基、C7～C18二价芳基氧基烷基、C12～C18二价芳醚基、C2～C18二价杂芳基、C3～C18二价杂芳基烷基或C3～C18二价烷基杂芳基。进一步可选地，R 4至R 7均表示氢原子，并且L 1表示二价苯基、二价二联苯基、二价三联苯基、二价四联苯基、二价萘基、二价蒽基、二价菲基、二价芘基或二价芴基。
在一些实施方式中，R 4和R 5、R 6和R 7中的至少一组相互键合形成环结构。例如，R 4和R 5相互键合形成环结构，或者R 6和R 7相互键合形成环结构，或者，R 4和R 5相互键合形成环结构并且R 6和R 7相互键合形成环结构。
在一些实施方式中，可选地，R 4至R 7相同且均不为氢原子。
在一些实施方式中，可选地，L 1表示氧原子，并且R 4至R 7分别独立地表示C3～C18一价环烷基、C2～C18一价氧杂环烷基、C6～C18一价芳基、C7～C18一价芳基烷基、C7～C18一价烷基芳基、C7～C18一价芳基氧基烷基、C12～C18一价芳醚基、C2～C18一价杂芳基、C3～C18一价杂芳基烷基或C3～C18一价烷基杂芳基。更可选地，L 1表示氧原子，并且R 4至R 7分别独立地表示C6～C18一价芳基、C7～C18一价芳基烷基、C7～C18一价烷基芳基、C7～C18一价芳基氧基烷基、C12～C18一价芳醚基、C2～C18一价杂芳基、C3～C18一价杂芳基烷基或C3～C18一价烷基杂芳基。
作为示例，所述式1-B所示化合物包括如下化合物中的至少一种：
Figure PCTCN2022090476-appb-000013
可选地，所述式1-B所示化合物包括H31至H33中的至少一种。更可选地，所述式1-B所示化合物包括H32至H33中的至少一种。
在一些实施方式中，可选地，R 8和R 9、R 10和R 11、R 12和R 13中的至少一组相互键合形成环结构。例如，R 8和R 9相互键合形成环结构，或者R 10和R 11相互键合形成环结构，或者R 12和R 13相互键合形成环结构，或者R 8和R 9、R 10和R 11、R 12和R 13中的任意两组或三组相互键合形成环结构。
在一些实施方式中，可选地，R 8至R 13分别独立地表示C1～C18一价烷基、C2～C18一价烷氧基烷基、C3～C18一价环烷基、C2～C18一价氧杂环烷基、C6～C18一价芳基、C7～C18一价芳基烷基、C7～C18一价烷基芳基、C7～C18一价芳基氧基烷基、C12～C18一价芳醚基、C2～C18一价杂芳基、C3～C18一价杂芳基烷基或C3～C18一价烷基杂芳基。
在一些实施方式中，可选地，L 2表示C6～C18三价环烷基、C6～C18三价氧杂环烷基、C6～C18三价芳基、C7～C18三价芳基烷基、C7～C18三价烷基芳基、C6～C18三价芳基氧基、C7～C18三价芳基氧基烷基、C12～C18三价芳醚基、C3～C18三价杂芳基、C3～C18三价杂芳基烷基或C3～C18三价烷基杂芳基。更可选地，L 2表示C6～C18三价芳基、C7～C18三价芳基烷基、C7～C18三价烷基芳基、C6～C18三价芳基氧基、C7～C18三价芳基氧基烷基、C12～C18三价芳醚基、C3～C18三价杂芳基、C3～C18三价杂芳基烷基或C3～C18三价烷基杂芳基。进一步可选地，L 2表示三价苯基、三价苯基烷基、三价烷基苯基。
作为示例，所述式1-C所示化合物包括如下化合物中的至少一种：
Figure PCTCN2022090476-appb-000014
一些实施方式中，可选地，R 14和R 15、R 16和R 17、R 18和R 19、R 20和R 21中的至少一组相互键合形成环结构。例如，R 14和R 15相互键合形成环结构，或者R 16和R 17相互键合形成环结构，或者R 18和R 19相互键合形成环结构，或者R 20和R 21相互键合形成环结构，或者R 14和R 15、R 16和R 17、R 18和R 19、R 20和R 21中的任意两组、三组或四组相互键合形成环结构。
在一些实施方式中，可选地，R 14至R 21分别独立地表示C1～C18一价烷基、C2～C18一价烷氧基烷基、C3～C18一价环烷基、C2～C18一价氧杂环烷基、C6～C18一价芳基、C7～C18一价芳基烷基、C7～C18一价烷基芳基、C7～C18一价芳基氧基烷基、C12～C18一价芳醚基、C2～C18一价杂芳基、C3～C18一价杂芳基烷基或C3～C18一价烷基杂芳基。
在一些实施方式中，可选地，L 3表示C6～C18四价环烷基、C6～C18四价氧杂环烷基、C6～C18四价芳基、C7～C18四价芳基烷基、C7～C18四价烷基芳基、C7～C18四价芳基氧基烷基、C12～C18四价芳醚基、C4～C18四价杂芳基、C4～C18四价杂芳基烷基或C4～C18四价烷基杂芳基。更可选地，L 3表示C6～C18四价芳基、C7～C18四价芳基烷基、C7～C18四价烷基芳基、C7～C18四价芳基氧基烷基、C12～C18四价芳醚基、C4～C18四价杂芳基、C4～C18四价杂芳基烷基或C4～C18四价烷基杂芳基。进一步可选地，L 3表示四价苯基、四价二联苯基、四价三联苯基或四价四联苯基。
作为示例，所述式1-D所示化合物包括如下化合物：
Figure PCTCN2022090476-appb-000015
发明人在研究过程中发现，以上述化合物H1至H36中的至少一种作为第一添加剂，能够在正极活性材料表面形成更为致密且稳定的界面膜，有助于进一步减少第一包覆层的溶解和降低第二包覆层的催化氧化作用，从而进一步减少锰离子溶出以及非水电解液和活性锂离子的消耗，由此能够进一步增强对二次电池循环性能和存储性能的改善效果。
可选地，所述第一添加剂包括H1至H10、H13至H15、H31至H33中的至少一种。更可选地，所述第一添加剂包括H1至H10、H32至H33中的至少一种。进一步可选地，所述第一添加剂包括H1至H8、H32至H33中的至少一种。这些第一添加剂有助于在正极活性材料表面形成包含交联大分子聚合物的界面膜，进一步减少第一包覆层的溶解和降低第二包覆层的催化氧化作用，从而进一步减少锰离子溶出以及非水电解液和活性锂离子的消耗，由此能够进一步增强对二次电池循环性能和存储性能的改善效果。
发明人在研究过程中还发现，当非水电解液含有过多的第一添加剂时，正极界面阻抗明显增加，由此影响二次电池的容量发挥和倍率性能。因此，第一添加剂在非水电解液中的含量不宜过高。在一些实施方式中，所述第一添加剂的含量为W1重量％，W1为0.01至20，可选为0.1至10，更可选为0.3至5，基于所述非水电解液的总重量计。当第一添加剂含量在合适的范围内时，既能减少第一包覆层的溶解、降低第二包覆层的催化氧化作用，又不恶化正极界面阻抗，进而能够明显改善二次电池的循环性能和存储性能，同时不影响二次电池的容量发挥和倍率性能。
在一些实施方式中，所述非水电解液还包括第二添加剂，所述第二添加剂包括磺酸内酯、环状硫酸酯、二氟磷酸锂(LiPO 2F 2)、二氟二草酸磷酸锂(LiDODFP)、二氟草酸硼酸锂(LiDFOB)中的一种或多种。
第二添加剂有助于在正极活性材料表面形成低阻抗的界面膜，此外，第二添加剂还可以在负极活性材料表面形成致密且稳定的界面膜，减少负极活性材料与非水电解液的直接接触，减少负极界面副反应。由此，当非水电解液中同时含有第一添加剂和第二添加剂时，有助于明显改善二次电池的循环性能和存储性能，同时提升二次电池的容量发挥和倍率性能。
在一些实施方式中，所述磺酸内酯包括式2-A所示化合物中的至少一种，
Figure PCTCN2022090476-appb-000016
p1表示1、2或3，p2表示1或2，p3表示1或2。
R 22分别独立地表示氢原子、卤原子、羧酸酯基(-C(＝O)-O-)、磺酸酯基(-S(＝O)2-O-)、C1～C6一价烷基、C1～C6一价卤代烷基、C1～C6一价烷氧基、C1～C6一价卤代烷氧基、C2～C6一价烯基中的一种或其中的多种通过单键相互键合形成的链状结构或环状结构。可选地，所述环状结构可为环状磺酸酯基、环状羧酸酯基、氧杂环烷基。更可选地，所述环状结构为四元环、五元环或六元环结构。
R 22表示环状结构时，通过单键键合至式2-A的多元环或与式2-A的多元环共享一个碳原子形成螺环化合物。
R 23分别独立地表示氢原子、卤原子、羧酸酯基(-C(＝O)-O-)、磺酸酯基(-S(＝O)2-O-)、C1～C6一价烷基、C1～C6一价卤代烷基、C1～C6一价烷氧基、C1～C6一价卤代烷氧基、C2～C6一价烯基中的一种或其中的多种通过单键相互键合形成的链状结构或环状结构。可选地，所述环状结构可为环状磺酸酯基、环状羧酸酯基、氧杂环烷基。更可选地，所述环状结构为四元环、五元环或六元环结构。
R 23表示环状结构时，通过单键键合至式2-A的多元环或与式2-A的多元环共享一个碳原子形成螺环化合物。
R 24表示羰基(C＝O)或C(Y 1) 2，Y 1分别独立地表示氢原子、卤原子、羧酸酯基(-CO-O-)、磺酸酯基(-S(＝O)2-O-)、C1～C6一价烷基、C1～C6一价卤代烷基、C1～C6一价烷氧基、C1～C6一价卤代烷氧基、C2～C6一价烯基、C6～C12一价芳基中的一种或其组合。
R 22和R 23还可以相互键合形成环结构。
可选地，所述磺酸内酯包括如下化合物中的至少一种：
Figure PCTCN2022090476-appb-000017
在一些实施方式中，所述环状硫酸酯包括式2-B所示化合物中的至少一种，
Figure PCTCN2022090476-appb-000018
q1表示1、2或3，q2表示1或2，q3表示1或2。
R 25分别独立地表示氢原子、卤原子、羰基氧原子、羧酸酯基(-C(＝O)-O-)、硫酸酯基(-O-S(＝O)2-O-)、C1～C6一价烷基、C1～C6一价卤代烷基、C1～C6一价烷氧基、C1～C6一价卤代烷氧基、C2～C6一价烯基中的一种或其中的多种通过单键相互键合形成的链状结构或环状结构。可选地，所述环状结构可为环状硫酸酯基、环状羧酸酯基、氧杂环烷基。更可选地，所述环状结构为四元环、五元环或六元环结构。
R 25表示环状结构时，通过单键键合至式2-B的多元环或与式2-B的多元环共享一个碳原子形成螺环化合物。
R 26分别独立地表示氢原子、卤原子、羧酸酯基(-C(＝O)-O-)、硫酸酯基(-O-S(＝O)2-O-)、C1～C6一价烷基、C1～C6一价卤代烷基、C1～C6一价烷氧基、C1～C6一价卤代烷氧基、C2～C6一价烯基中的一种或其中的多种通过单键相互键合形成的链状结构或环状结构。可选地，所述环状结构可为环状硫酸酯基、环状羧酸酯基、氧杂环烷基。更可选地，所述环状结构为四元环、五元环或六元环结构。
R 26表示环状结构时，通过单键键合至式2-B的多元环或与式2-B的多元环共享一个碳原子形成螺环化合物。
R 25和R 26还可以相互键合形成环结构。
可选地，所述环状硫酸酯包括如下化合物中的至少一种：
Figure PCTCN2022090476-appb-000019
发明人在研究过程中还发现，当非水电解液含有过多的第二添加剂时，正极界面阻抗不降反增，由此影响二次电池的容量发挥和倍率性能。因此，第二添加剂在非水电解液中的含量不宜过高。在一些实施方式中，所述第二添加剂的含量为W2重量％，W2为0.01至20，可选为0.1至10，更可选为0.3至5，基于所述非水电解液的总重量计。当第二添加剂含量在合适的范围内时，能够有效地改善二次电池的容量发挥和倍率性能。
发明人在研究过程中还发现，所述第一添加剂的含量W1重量％和所述第二添加剂的含量W2重量％的比值也会影响二次电池的电化学性能。在一些实施方式中，W1/W2为0.01至20。可选地，W1/W2为0.01至10，0.1至10，0.1至8，0.1至5，0.2至5，0.5至5或1至5。W1/W2在合适的范围内时，能够更好地发挥二者之间的协同作用效果，有助于在正极活性材料表面形成一层致密、稳定且低阻抗的界面膜，进一步减少第一包覆层的溶解和降低第二包覆层的催化氧化作用，进一步减少锰离子溶出以及非水电解液和活性锂离子的消耗，由此能够进一步增强对二次电池循环性能和存储性能的改善效果，同时提升二次电池的容量发挥和倍率性能。并能够有效避免以下情况：W1/W2较大时，第二添加剂不能有效降低正极界面阻抗，由此可能影响二次电池的容量发挥和倍率性能；W1/W2较小时，不能明显减少第一包覆层的溶解和降低第二包覆层的催化氧化作用，由此对二次电池循环性能和存储性能的改善效果可能不明显。
在一些实施方式中，所述第一包覆层的包覆量C1重量％、所述第二包覆层的包覆量C2重量％、所述第一添加剂的含量W1重量％和所述第二添加剂的含量W2重量％满足：(W1+W2)/(C1+C2)为0.001至2。可选地，(W1+W2)/(C1+C2)为0.01至2，0.01至1.5，0.01至1，0.1至1，0.14至1，0.18至1或0.22至1。(W1+W2)/(C1+C2)在合适的范围内时，能够明显增强对二次电池循环性能和存储性能的改善效果，同时提升二次电池的容量发挥和倍率性能。并能够有效避免以下情况：(W1+W2)/(C1+C2)较小时，没有足够的第一添加剂和第二添加剂在正极活性材料表面成膜，由此不能明显减少第一包覆层的溶解和降低第二包覆层的催化氧化作用，从而对二次电池循环性能和存储性能的改善效果不明显；(W1+W2)/(C1+C2)较大时，正极界面阻抗增加，影响二次电池的容量发挥和倍率性能。
在一些实施方式中，二次电池的注液系数Q0g/Ah满足Q0为2.5至4.0。
在一些实施方式中，所述第一添加剂的含量W1％、所述第二添加剂的含量W2％、所述二次电池的初始容量D0mAh/g、所述二次电池的注液系数Q0g/Ah和所述正极活性材料的比表面积B m 2/g满足[(W1％+W2％)×D0×Q0]/B为0.005至10，可选为0.01至5。 [(W1％+W2％)×D0×Q0]/B在合适的范围内时，能够明显增强对二次电池循环性能和存储性能的改善效果，同时提升二次电池的容量发挥和倍率性能。并能够有效避免以下情况：[(W1％+W2％)×D0×Q0]/B较小时，没有足够的第一添加剂和第二添加剂在正极活性材料表面成膜，由此不能明显减少第一包覆层的溶解和降低第二包覆层的催化氧化作用，从而对二次电池循环性能和存储性能的改善效果不明显；[(W1％+W2％)×D0×Q0]/B较大时，正极界面阻抗增加，影响二次电池的容量发挥和倍率性能。
二次电池的初始容量D0mAh/g可以通过如下方法得到：在25℃恒温环境下，将二次电池按照0.33C充电至上限截止电压，然后恒压充电至电流小于等于0.05mA，静置5分钟，然后按照0.33C放电至放电截止电压，此时的放电容量与正极活性材料质量的比值即为二次电池的初始容量D0mAh/g。在本申请的测试方法中，二次电池的充放电截止电压可为2.5V～4.3V。
在一些实施方式中，所述非水电解液还包括第三添加剂，所述第三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、腈化合物、磷腈化合物、芳香烃及卤代芳香烃化合物、异氰酸酯化合物、酸酐化合物、亚磷酸酯化合物、磷酸酯化合物、亚硫酸酯化合物、二磺酸亚甲酯化合物中的一种或多种。当非水电解液同时含有第一添加剂和第三添加剂，或者同时含有第一添加剂、第二添加剂和第三添加剂时，第三添加剂有助于在正极和/或负极活性材料表面形成更为致密且稳定的界面膜，从而有助于进一步提升二次电池的循环性能、存储性能、倍率性能中的至少一者。在一些实施方式中，所述第三添加剂的含量为W3重量％，W3在10以下，可选为0.1至10，更可选为0.5至5，基于所述非水电解液的总重量计。
本申请对第三添加剂的种类没有特别的限制，只要不有损本申请的主旨即可，例如，第三添加剂可以以任意的比率从下述具体物质中进行选择。
(a)含有碳碳不饱和键的环状碳酸酯化合物
含有碳碳不饱和键的环状碳酸酯化合物可包括式3-1所示的化合物中的一种或多种。R 27表示支链上有烯基或炔基取代的C1～C6亚烷基、取代或未取代的C2～C6直链亚烯基，其中，取代基选自卤素原子、C1～C6烷基、C2～C6烯基中的一种或多种。
Figure PCTCN2022090476-appb-000020
可选地，含有碳碳不饱和键的环状碳酸酯化合物可包括但不限于如下化合物中的一种或多种。
Figure PCTCN2022090476-appb-000021
(b)卤素取代的环状碳酸酯化合物
卤素取代的环状碳酸酯化合物可包括式3-2所示的化合物中的一种或多种。R 28表示卤素取代的C1～C6亚烷基、卤素取代的C2～C6亚烯基。
Figure PCTCN2022090476-appb-000022
可选地，卤素取代的环状碳酸酯化合物可包括但不限于氟代碳酸乙烯酯(FEC)、氟代碳酸丙烯酯(FPC)、三氟代碳酸丙烯酯(TFPC)、反式或顺式-4,5-二氟-1,3-二氧杂环戊烷-2-酮(以下将两者统称为DFEC)中的一种或多种。
(c)腈化合物
腈化合物可为二腈或三腈化合物。可选地，腈化合物可包括式3-3和式3-4所示的化合物中的一种或多种。R 29表示取代或未取代的C1～C12亚烷基、取代或未取代的C1～C12氧杂亚烷基、取代或未取代的C2～C12亚烯基、取代或未取代的C2～C12亚炔基，R 30至R 32分别独立地表示取代或未取代的C0～C12亚烷基、取代或未取代的C1～C12氧杂亚烷基、取代或未取代的C2～C12亚烯基、取代或未取代的C2～C12亚炔基，其中，取代基选自卤素原子、腈基、C1～C6烷基、C2～C6烯基、C1～C6烷氧基中的一种或多种。
Figure PCTCN2022090476-appb-000023
可选地，腈化合物可包括乙二腈、丙二腈、丁二腈、戊二腈、己二腈、庚二腈、辛二腈、壬二腈、癸二腈、十一烷二腈、十二烷二腈、四甲基琥珀腈、甲基戊二腈、丁烯二腈、2-戊烯二腈、己-2-烯二腈、己-3-烯二腈、辛-4-烯二腈、辛-4-炔二腈、1,2,3-丙三甲腈、1,3,5-戊三甲腈、1,3,6-己烷三腈中的一种或几种。
(d)磷腈化合物
磷腈化合物可为环状磷腈化合物。环状磷腈化合物可包括甲氧基五氟环三磷腈、乙氧基五氟环三磷腈、苯氧基五氟环三磷腈、乙氧基七氟环四磷腈中的一种或多种。可选地，环状磷腈化合物可包括甲氧基五氟环三磷腈、乙氧基五氟环三磷腈、苯氧基五氟环三磷腈中的一种或多种。进一步可选地，环状磷腈化合物可包括甲氧基五氟环三磷腈、乙氧基五氟环三磷腈或其组合。
(e)芳香烃及卤代芳香烃化合物
芳香烃及卤代芳香烃化合物可包括环己基苯、氟代环己基苯化合物(例如1-氟-2-环己基苯、1-氟-3-环己基苯、1-氟-4-环己基苯)、叔丁基苯、叔戊基苯、1-氟-4-叔丁基苯、联苯、三联苯(邻位体、间位体、对位体)、二苯基醚、氟苯、二氟苯(邻位体、间位体、对位体)、茴香醚、2,4-二氟茴香醚、三联苯的部分氢化物(例如1,2-二环己基苯、2-苯基双环己基、1,2-二苯基环己烷、邻环己基联苯)中的一种或多种。可选地，芳香烃及卤代芳香烃化合物可包括联苯、三联苯(邻位体、间位体、对位体)、氟苯、环己基 苯、叔丁基苯、叔戊基苯中的一种或多种。进一步可选地，芳香烃及卤代芳香烃化合物可包括联苯、邻三联苯、氟苯、环己基苯、叔戊基苯中的一种或多种。
(f)异氰酸酯化合物
异氰酸酯化合物可包括甲基异氰酸酯、乙基异氰酸酯、丁基异氰酸酯、苯基异氰酸酯、四亚甲基二异氰酸酯、六亚甲基二异氰酸酯、八亚甲基二异氰酸酯、1,4-亚苯基二异氰酸酯、丙烯酸2-异氰酸根合乙酯、甲基丙烯酸2-异氰酸根合乙酯中的一种或多种。可选地，异氰酸酯化合物可包括六亚甲基二异氰酸酯、八亚甲基二异氰酸酯、丙烯酸2-异氰酸根合乙酯、甲基丙烯酸2-异氰酸根合乙酯中的一种或多种。
(g)酸酐化合物
酸酐化合物可为链状酸酐或环状酸酐。具体地，酸酐化合物可包括乙酸酐、丙酸酐、琥珀酸酐、马来酸酐、2-烯丙基琥珀酸酐、戊二酸酐、衣康酸酐、3-磺基-丙酸酐中的一种或多种。可选地，酸酐化合物可包括琥珀酸酐、马来酸酐、2-烯丙基琥珀酸酐中的一种或多种。进一步可选地，酸酐化合物可包括琥珀酸酐、2-烯丙基琥珀酸酐或其组合。
(h)亚磷酸酯化合物
亚磷酸酯化合物可为硅烷亚磷酸酯化合物，具体可包括式3-5所示的化合物中的一种或多种，R 33至R 41分别独立地表示卤素取代或未取代的C1～C6烷基。
Figure PCTCN2022090476-appb-000024
可选地，硅烷亚磷酸酯化合物可包括但不限于如下化合物中的一种或多种。
Figure PCTCN2022090476-appb-000025
(i)磷酸酯化合物
磷酸酯化合物可为硅烷磷酸酯化合物，具体可包括式式3-6所示的化合物中的一种或多种，R 42至R 50分别独立地表示卤素取代或未取代的C1～C6烷基。
Figure PCTCN2022090476-appb-000026
可选地，硅烷磷酸酯化合物可包括但不限于如下化合物中的一种或多种。
Figure PCTCN2022090476-appb-000027
(j)亚硫酸酯化合物
亚硫酸酯化合物可为环状亚硫酸酯化合物，具体可包括式3-7所示的化合物中的一种或多种。R 51表示取代或未取代的C1～C6亚烷基、取代或未取代的C2～C6亚烯基，其中，取代基选自卤素原子、C1～C3烷基、C2～C4烯基中的一种或多种。
Figure PCTCN2022090476-appb-000028
可选地，亚硫酸酯化合物可包括亚硫酸乙烯酯(ES)、亚硫酸丙烯酯(PS)、亚硫酸丁烯酯(BS)中的一种或多种。
(k)二磺酸亚甲酯化合物
二磺酸亚甲酯化合物可包括式3-8所示的化合物中的一种或多种。R 52至R 55分别独立地表示氢原子、卤素原子、取代或未取代的C1～C10烷基、取代或未取代的C2～C10烯基，其中，取代基选自卤素原子、C1～C3烷基、C2～C4烯基中的一种或多种。
Figure PCTCN2022090476-appb-000029
可选地，二磺酸亚甲酯化合物可包括但不限于如下化合物中的一种或多种。
Figure PCTCN2022090476-appb-000030
在一些实施方式中，可选地，所述第三添加剂可包括碳酸亚乙烯酯(VC)、乙烯基碳酸乙烯酯(VEC)、氟代碳酸乙烯酯(FEC)中的一种或多种。这些第三添加剂为电化学还原型添加剂，其还原电位比有机溶剂高，因此可在负极活性材料表面优先发生电化学还原形成性能优良的界面膜，降低有机溶剂对界面膜的破坏程度，进而采用其的二次电池能具有更好的电化学性能和安全性能。
所述非水电解液还包括锂盐和有机溶剂。本申请对所述锂盐和所述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。
作为示例，所述有机溶剂可以包括链状碳酸酯、环状碳酸酯、羧酸酯中的一种或多种。其中，本申请对所述链状碳酸酯、所述环状碳酸酯、所述羧酸酯的种类没有具体的限制，可根据实际需求进行选择。可选地，所述有机溶剂包括碳酸二甲酯(DMC)、碳酸二乙酯(DEC)、碳酸二丙酯(DPC)、碳酸甲乙酯(EMC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸亚乙酯(EC)、碳酸亚丙酯(PC)、碳酸亚丁酯(BC)、γ-丁内酯(GBL)、甲酸甲酯(MF)、甲酸乙酯(EF)、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(PA)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸甲酯(PP)、四氢呋喃(THF)中的一种或多种。
作为示例，所述锂盐可包括LiN(C mF 2m+1SO 2)(C nF 2n+1SO 2)、LiPF 6、LiBF 4、LiBOB、LiAsF 6、Li(FSO 2) 2N、LiCF 3SO 3以及LiClO 4中的一种或多种，m、n均为自然数。当非水电解液包括上述锂盐时，有助于在正极和/或负极活性材料表面形成致密、稳定且低阻抗的界面膜，有效提高二次电池的循环性能、存储性能、倍率性能中的至少一者。
环状碳酸酯的介电常数较高，有利于锂盐的解离。在一些实施方式中，所述环状碳酸酯的含量可以在20％重量以上，可选为20重量％至80重量％，更可选为20重量％至50重量％，基于所述有机溶剂的总重量计。可选地，所述环状碳酸酯包括碳酸亚乙酯(EC)、碳酸亚丙酯(PC)、碳酸亚丁酯(BC)中的一种或多种。
链状碳酸酯的介电常数较小，解离锂盐的能力较弱，但粘度小、流动性好，可以增锂离子的迁移速率。在一些实施方式中，所述链状碳酸酯的含量可以在10重量％以上，可选为10重量％至80重量％，基于所述有机溶剂的总重量计。可选地，所述链状碳酸酯包括碳酸二甲酯(DMC)、碳酸二乙酯(DEC)、碳酸二丙酯(DPC)、碳酸甲乙酯(EMC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)中的一种或多种。
羧酸酯具有低粘度、高介电常数的优点，可以提升非水电解液的电导率。在一些实施方式中，所述羧酸酯的含量可以0重量％至70重量％，可选为0重量％至60重量％，基于所述有机溶剂的总重量计。可选地，所述羧酸酯包括甲酸甲酯(MF)、甲酸乙酯(EF)、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(PA)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸甲酯(PP)中的一种或多种。
锂盐的含量增加，可迁移锂离子总数增加，但同时非水电解液粘度也增加，锂离子迁移速率反而减慢。因此，锂盐的含量会出现一个最佳值。在一些实施方式中，所述锂盐的含量可以为6重量％至39重量％，可选为10重量％至31重量％，更可选为11重量％至24重量％，进一步可选地为12重量％至20重量％，基于所述非水电解液的总重量计。
本申请的非水电解液可以按照本领域常规的方法制备。例如，可以将所述添加剂、所述有机溶剂、所述锂盐等混合均匀，得到非水电解液。各物料的添加顺序并没有特别的限制，例如，可以将所述添加剂、所述锂盐等加入到所述有机溶剂中混合均匀，得到非水电解液。
在本申请中，所述非水电解液中的各组分及其含量可以按照本领域常规的方法测定。例如，可以通过气相色谱-质谱联用法(GC-MS)、离子色谱法(IC)、液相色谱法(LC)、核磁共振波谱法(NMR)等进行测定。
需要说明的是，本申请的非水电解液也可以从二次电池中获取。从二次电池中获取非水电解液的一个示例性方法包括如下步骤：将二次电池放电至放电截止电压后进行离 心处理，之后取适量离心处理得到的液体进行测试。
[外包装]
在一些实施方式中，所述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非水电解液。
在一些实施方式中，所述二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。所述二次电池的外包装也可以是软包，例如袋式软包。所述软包的材质可以是塑料，如聚丙烯(PP)、聚对苯二甲酸丁二醇酯(PBT)、聚丁二酸丁二醇酯(PBS)等中的至少一种。
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。如图1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，如图2所示，外包装可包括壳体51和盖板53。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用于盖设所述开口，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。非水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几个，可根据需求来调节。
本申请的二次电池的制备方法是公知的。在一些实施方式中，可将正极极片、隔离膜、负极极片和非水电解液组装形成二次电池。作为示例，可将正极极片、隔离膜、负极极片经卷绕工艺或叠片工艺形成电极组件，将电极组件置于外包装中，烘干后注入非水电解液，经过真空封装、静置、化成、整形等工序，得到二次电池。
电池模块
在一些实施方式中，根据本申请的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多个，具体数量可根据电池模块的应用和容量来调节。
图3是作为一个示例的电池模块4的示意图。如图3所示，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。
电池包
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根据电池包的应用和容量进行调节。
图4和图5是作为一个示例的电池包1的示意图。如图4和图5所示，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用于盖设下箱体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。
用电装置
本申请还提供一种用电装置，所述用电装置包括本申请的二次电池、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。所述用电装置可以但不限于是移动设备(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***等。
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6是作为一个示例的用电装置的示意图。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高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的用电装置可以是手机、平板电脑、笔记本电脑等。该用电装置通常要求轻薄化，可以采用二次电池作为电源。
实施例
下述实施例更具体地描述了本申请公开的内容，这些实施例仅仅用于阐述性说明，因为在本申请公开内容的范围内进行各种修改和变化对本领域技术人员来说是明显的。除非另有声明，以下实施例中所报道的所有份、百分比、和比值都是基于重量计，而且实施例中使用的所有试剂都可商购获得或是按照常规方法进行合成获得，并且可直接使用而无需进一步处理，以及实施例中使用的仪器均可商购获得。
本申请实施例涉及的原材料来源如下：
名称 化学式 厂家 规格
碳酸锰 MnCO 3 山东西亚化学工业有限公司 1Kg
碳酸锂 Li 2CO 3 山东西亚化学工业有限公司 1Kg
碳酸镁 MgCO 3 山东西亚化学工业有限公司 1Kg
碳酸锌 ZnCO 3 武汉鑫儒化工有限公司 25Kg
碳酸亚铁 FeCO 3 西安兰之光精细材料有限公司 1Kg
硫酸镍 NiCO 3 山东西亚化学工业有限公司 1Kg
硫酸钛 Ti(SO 4) 2 山东西亚化学工业有限公司 1Kg
硫酸钴 CoSO 4 厦门志信化学有限公司 500g
二氯化钒 VCl 2 上海金锦乐实业有限公司 1Kg
二水合草酸 C 2H 2O 4·2H 2O 上海金锦乐实业有限公司 1Kg
磷酸二氢铵 NH 4H 2PO 4 上海澄绍生物科技有限公司 500g
蔗糖 C 12H 22O 11 上海源叶生物科技有限公司 100g
硫酸 H 2SO 4 深圳海思安生物技术有限公司 质量分数60％
硝酸 HNO 3 安徽凌天精细化工有限公司 质量分数60％
亚硅酸 H 2SiO 3 上海源叶生物科技有限公司 100g
硼酸 H 3BO 3 常州市启迪化工有限公司 1Kg
实施例1-1
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MnCO 3计，下同)、455.2g碳酸亚铁(以FeCO 3计，下同)、4.6g硫酸钴(以CoSO 4计，下同)和4.9g二氯化钒(以VCl 2计，下同)在混料机中充分混合6小时。将混合物转移至反应釜中，并加入5升去离子水和1260.6g二水合草酸(以C 2H 2O 4.2H 2O计，下同)。将反应釜加热至80℃，以600rpm的转速搅拌6小时，直至反应终止(无气泡产生)，得到Fe、Co、V和S共掺杂的草酸锰悬浮液。然后过滤所述悬浮液，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4小时，得到粉末。将所述粉末在650℃、氮气气氛下烧结8小时，并自然冷却至室温后进行研磨，得到Li 2FeP 2O 7粉末。
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
将负极活性材料人造石墨、硬碳、导电剂乙炔黑、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC)按照重量比为90:5:2:2:1溶于溶剂去离子水中，搅拌混合均匀后制备成负极浆料。将负极浆料按0.117g/1540.25mm 2均匀涂覆在负极集流体铜箔上，经过烘干、冷压、分切得到负极极片。
非水电解液的制备
在氩气气氛手套箱中(H 2O<0.1ppm，O 2<0.1ppm)，将碳酸亚乙酯(EC)、碳酸二乙酯(DEC)和碳酸二甲酯(DMC)按照体积比1:1:1混合均匀作为有机溶剂，之后加入12.5重量％(基于所述非水电解液的总重量计)LiPF 6和1重量％(基于所述非水电解液的总重量计)化合物H3溶解于上述有机溶剂中，搅拌均匀，得到非水电解液。
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，并卷绕得到电极组件。将电极组件置于外包装中，注入上述非水电解液并封装，得到全电池(下文也称“全电”)。全电池的注液系数为3.5g/Ah。
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，与上述制备的正极极片和非水电解液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1-33除正极活性材料的制备工艺外，正极极片的制备、负极极片的制备、非水电解液的制备、隔离膜的制备和电池的制备均与实施例1-1的工艺相同。
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碳酸锌代替碳酸亚铁以外，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的碳酸镍、5.0g的碳酸锌和7.2g的硫酸钛代替碳酸亚铁，实施例1-17在共掺杂的磷酸锰锂内核的制备过程中使用455.2g的碳酸亚铁和8.5g的二氯化钒，实施例1-18在共掺杂的磷酸锰锂内核的制备过程中使用455.2g的碳酸亚铁、4.9g的二氯化钒和2.5g的碳酸镁以外，实施例1-16至1-18的条件与实施例1-7相同。
实施例1-19至1-20
除实施例1-19在共掺杂磷酸锰锂内核的制备过程中使用369.4g的碳酸锂、和以1.05g的60％浓度的稀硝酸代替稀硫酸，实施例1-20在共掺杂的磷酸锰锂内核的制备过程中使用369.7g的碳酸锂、和以0.78g的亚硅酸代替稀硫酸以外，实施例1-19至1-20的条件与实施例1-18相同。
实施例1-21至1-22
除实施例1-21在共掺杂磷酸锰锂内核的制备过程中使用632.0g碳酸锰、463.30g碳酸亚铁、30.5g的二氯化钒、21.0g的碳酸镁和0.78g的亚硅酸；实施例1-22在共掺杂磷酸锰锂内核的制备过程中使用746.9g碳酸锰、289.6g碳酸亚铁、60.9g的二氯化钒、42.1g的碳酸镁和0.78g的亚硅酸以外，实施例1-21至1-22的条件与实施例1-20相同。
实施例1-23至1-24
除实施例1-23在共掺杂磷酸锰锂内核的制备过程中使用804.6g碳酸锰、231.7g碳酸亚铁、1156.2g的磷酸二氢铵、1.2g的硼酸(质量分数99.5％)和370.8g碳酸锂；实施例1-24在共掺杂磷酸锰锂内核的制备过程中使用862.1g碳酸锰、173.8g碳酸亚铁、1155.1g的磷酸二氢铵、1.86g的硼酸(质量分数99.5％)和371.6g碳酸锂以外，实施例1-23至1-24的条件与实施例1-22相同。
实施例1-25
除实施例1-25在共掺杂磷酸锰锂内核的制备过程中使用370.1g碳酸锂、1.56g的亚硅酸和1147.7g的磷酸二氢铵以外，实施例1-25的条件与实施例1-20相同。
实施例1-26
除实施例1-26在共掺杂磷酸锰锂内核的制备过程中使用368.3g碳酸锂、4.9g质量分数为60％的稀硫酸、919.6g碳酸锰、224.8g碳酸亚铁、3.7g二氯化钒、2.5g碳酸镁和1146.8g的磷酸二氢铵以外，实施例1-26的条件与实施例1-20相同。
实施例1-27
除实施例1-27在共掺杂磷酸锰锂内核的制备过程中使用367.9g碳酸锂、6.5g浓度为60％的稀硫酸和1145.4g的磷酸二氢铵以外，实施例1-27的条件与实施例1-20相同。
实施例1-28至1-33
除实施例1-28至1-33在共掺杂磷酸锰锂内核的制备过程中使用1034.5g碳酸锰、108.9g碳酸亚铁、3.7g二氯化钒和2.5g碳酸镁，碳酸锂的使用量分别为：367.6g、367.2g、366.8g、366.4g、366.0g和332.4g，磷酸二氢铵的使用量分别为：1144.5g、1143.4g、1142.2g、1141.1g、1139.9g和1138.8g，浓度为60％的稀硫酸的使用量分别为：8.2g、9.8g、11.4g、13.1g、14.7g和16.3g以外，实施例1-28至1-33的条件与实施例1-20相同。
实施例2-1至2-3除正极活性材料的制备工艺外，正极极片的制备、负极极片的制备、非水电解液的制备、隔离膜的制备和电池的制备均与实施例1-1的工艺相同。
实施例2-1
除在焦磷酸铁锂(Li 2FeP 2O 7)的制备过程中在粉末烧结步骤中的烧结温度为550℃，烧结时间为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3-1至3-32除非水电解液的制备工艺外，正极活性材料的制备、正极极片的制备、负极极片的制备、隔离膜的制备和电池的制备均与实施例1-1的工艺相同。非水电解液的制备工艺详见表2。
对比例1至8除正极活性材料和非水电解液的制备工艺外，正极极片的制备、负极极片的制备、隔离膜的制备和电池的制备均与实施例1-1的工艺相同。非水电解液的制备工艺详见表2。
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。
非水电解液的制备：在氩气气氛手套箱中(H 2O<0.1ppm，O 2<0.1ppm)，将碳酸亚乙酯(EC)、碳酸二乙酯(DEC)和碳酸二甲酯(DMC)按照体积比1:1:1混合均匀作为有机溶剂，之后加入12.5重量％(基于所述非水电解液的总重量计)LiPF 6溶解于上述有机溶剂中，搅拌均匀，得到非水电解液。
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4小时以控制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
除非水电解液中未加入化合物H3外，其他条件与实施例1-3相同。
相关参数测试
1.内核化学式及不同包覆层组成的测定：
采用球差电镜仪(ACSTEM)对正极活性材料内部微观结构和表面结构进行高空间分辨率表征，结合三维重构技术得到正极活性材料的内核化学式及第一、第二包覆层的组成。
2.扣式电池初始克容量测试：
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。
3.扣电平均放电电压(V)测试：
将上述制得的扣式电池在25℃恒温环境下，静置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。
4.全电池60℃胀气测试：
在60℃下，存储100％充电状态(SOC)的上述制得的全电池。在存储前后及过程中测量电池的开路电压(OCV)和交流内阻(IMP)以监控SOC，并测量电池的体积。其中在每存储48小时后取出全电池，静置1小时后测试开路电压(OCV)、内阻(IMP)，并在冷却至室温后用排水法测量电池体积。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池的重力F 1，然后将电池完全置于去离子水(密度已知为1g/cm 3)中，测量此时的电池的重力F 2，电池受到的浮力F 浮即为F 1-F 2，然后根据阿基米德原理F 浮＝ρ×g×V 排，计算得到电池体积V＝(F 1-F 2)/(ρ×g)。
由OCV、IMP测试结果来看，本测试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，测量电池体积，并计算相对于存储前的电池体积，存储后的电池体积增加的百分比。
5.全电池45℃下循环性能测试：
在45℃的恒温环境下，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。
6.晶格变化率测量方法：
在25℃恒温环境下，将上述制得的正极活性材料样品置于X射线衍射仪(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表示晶胞各个方向上的长度大小，v0表示晶胞体积，可通过XRD精修结果直接获取)。
采用上述扣电制备方法，将所述正极活性材料样品制备成扣电，并对上述扣电以0.05C小倍率进行充电，直至电流减小至0.01C。然后将扣电中的正极极片取出，并置于碳酸二甲酯(DMC)中浸泡8小时。然后烘干，刮粉，并筛选出其中粒径小于500nm的颗粒。取样并按照与上述测试新鲜样品同样的方式计算出其晶胞体积v1，将(v0-v1)/v0×100％作为其完全脱嵌锂前后的晶格变化率(晶胞体积变化率)示于表中。
7.Li/Mn反位缺陷浓度测试：
将“晶格变化率测量方法”中测试的XRD结果与标准晶体的PDF(Powder Diffraction File)卡片对比，得出Li/Mn反位缺陷浓度。具体而言，将“晶格变化率测量方法”中测试的XRD结果导入通用结构分析***(GSAS)软件中，自动获得精修结果，其中包含了不同原子的占位情况，通过读取精修结果获得Li/Mn反位缺陷浓度。
8.过渡金属溶出测试：
将45℃下循环至容量衰减至80％后的全电池采用0.1C倍率进行放电至截止电压2.0V。然后将电池拆开，取出负极极片，在负极极片上随机取30个单位面积(1540.25mm 2)的圆片，用Agilent ICP-OES730测试电感耦合等离子体发射光谱(ICP)。根据ICP结果计算其中Fe(如果正极活性材料的Mn位掺杂有Fe的话)和Mn的量，从而计算循环后Mn(以及Mn位掺杂的Fe)的溶出量。测试标准依据EPA-6010D-2014。
9.表面氧价态测试：
取5g上述制得的正极活性材料样品按照上述扣电制备方法制备成扣电。对扣电采用0.05C小倍率进行充电，直至电流减小至0.01C。然后将扣电中的正极极片取出，并置于碳酸二甲酯(DMC)中浸泡8小时。然后烘干，刮粉，并筛选出其中粒径小于500nm的颗粒。将所得颗粒用电子能量损失谱(EELS，所用仪器型号为Talos F200S)进行测量，获取能量损失近边结构(ELNES)，其反映元素的态密度和能级分布情况。根据态密度和能级分布，通过对价带态密度数据进行积分，算出占据的电子数，从而推算出充电后的表面氧的价态。
10.压实密度测量：
取5g的上述制得的正极活性材料粉末放于压实专用模具(美国CARVER模具，型号13mm)中，然后将模具放在压实密度仪器上。施加3T(吨)的压力，在设备上读出压力下粉末的厚度(卸压后的厚度，用于测试的容器的面积为1540.25mm 2)，通过ρ＝m/v，计算出压实密度。
11.比表面积测量：
取5g的上述制得的正极活性材料粉末，采用美国Micromeritics公司的Tri-Star 3020型比表面积孔径分析测试仪进行测试，并用BET(Brunauer Emmett Teller)法计算得到比表面积。测试标准依据GB/T 19587-2017。
12.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。
13.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。
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。
表1示出实施例1-1至1-33、对比例1至8的正极活性材料组成。
表1
Figure PCTCN2022090476-appb-000031
Figure PCTCN2022090476-appb-000032
表2示出实施例1-1至1-33、实施例2-1至2-3、实施例3-1至3-32、对比例1至8的的非水电解液制备工艺。
表2
Figure PCTCN2022090476-appb-000033
Figure PCTCN2022090476-appb-000034
Figure PCTCN2022090476-appb-000035
Figure PCTCN2022090476-appb-000036
表3示出实施例1-1至1-33、对比例1至8的正极活性材料、正极极片、扣电或全电按照上述性能测试方法测得的性能数据。
表4示出实施例2-1至2-3的正极活性材料、正极极片、扣电或全电按照上述性能测试方法测得的性能数据。
Figure PCTCN2022090476-appb-000037
Figure PCTCN2022090476-appb-000038
综合实施例1-1至1-33以及对比例1至8可知，第一包覆层的存在有利于降低所得材料的Li/Mn反位缺陷浓度和循环后Fe和Mn溶出量，提高电池的克容量，并改善电池的循环性能和存储性能。当在Mn位和磷位分别掺杂其他元素时，可显著降低所得材料的晶格变化率、反位缺陷浓度和Fe和Mn溶出量，提高电池的克容量，并改善电池的循环性能和存储性能。非水电解液中第一添加剂的存在有利于减少第一包覆层的溶解和降低第二包覆层的催化氧化作用，从而进一步提升电池的循环性能和存储性能。
综合实施例1-2至1-6可知，随着第一包覆层的量从3.2％增加至6.4％，所得材料的Li/Mn反位缺陷浓度逐渐下降，循环后Fe和Mn溶出量逐渐下降，对应电池的安全性能和45℃下的循环性能也得到改善，但克容量略有下降。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％，所得材料循环后Fe和Mn溶出量逐渐下降，对应电池的安全性能和45℃下的循环性能也得到改善，但克容量却略有下降。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。
图7是实施例1-1制备的正极活性材料内核的XRD谱图与磷酸锰锂XRD标准谱图(00-033-0804)的对比图。如图7所示，本申请的正极活性材料内核与磷酸锰锂掺杂前的主要特征峰的位置基本一致，说明本申请的正极活性材料内核没有杂质相，电池性能的改善主要来自元素掺杂，而不是杂质相导致的。
由表3可以看出，随着第一包覆层中焦磷酸盐和磷酸盐的结晶度逐渐增加，对应材料的晶格变化率、Li/Mn反位缺陷浓度和Fe和Mn溶出量逐渐下降，电池的克容量逐渐增加，安全性能和循环性能也逐渐改善。
实施例3-1至3-32除非水电解液的制备工艺与实施例1-1不同外，其他条件均与实施例1-1相同。
表5示出实施例3-1至3-20的扣电或全电按照上述性能测试方法测得的性能数据。
表6示出实施例3-21至3-32的扣电或全电按照上述性能测试方法测得的性能数据。
Figure PCTCN2022090476-appb-000039
Figure PCTCN2022090476-appb-000040
综合实施例1-1和实施例3-1至3-10可知，第一添加剂的种类不同，对电池性能的改善效果略有差异。
综合实施例3-1和实施例3-11至3-20可知，当非水电解液中还含有适量的第二添加剂和/或第三添加剂时，有助于进一步提升电池的克容量、倍率性能、循环性能和存储性能。
综合实施例3-11和实施例3-21至3-32可知，第一包覆层的包覆量C1重量％、第二包覆层的包覆量C2重量％、第一添加剂的含量W1重量％和第二添加剂的含量W2重量％满足：W1/W2为0.01至20，可选为0.01至10；和/或，(W1+W2)/(C1+C2)为0.001至2，可选为0.01至1时，有助于进一步提升电池的克容量、倍率性能、循环性能和存储性能。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。

Claims (14)

  1. 一种二次电池，包括正极极片以及非水电解液，其中，
    所述正极极片包括具有核-壳结构的正极活性材料，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，x为-0.100至0.100，y为0.001至0.500，z为0.001至0.100，所述A选自Zn、Al、Na、K、Mg、Mo、W、Ti、V、Zr、Fe、Ni、Co、Ga、Sn、Sb、Nb和Ge中的一种或多种，可选为Fe、Ti、V、Ni、Co和Mg中的一种或多种，所述R选自B、Si、N和S中的一种或多种；
    所述壳包括包覆所述内核的第一包覆层以及包覆所述第一包覆层的第二包覆层，其中，
    所述第一包覆层包括焦磷酸盐MP 2O 7和磷酸盐XPO 4，所述M和X各自独立地选自Li、Fe、Ni、Mg、Co、Cu、Zn、Ti、Ag、Zr、Nb和Al中的一种或多种，
    所述第二包覆层包含碳；
    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-A至式1-D所示化合物中的一种或多种，
    Figure PCTCN2022090476-appb-100001
    R 1表示氢原子或由以下基团组成的组中的至少一种：羟基、C1～C18一价烷基、C1～C18一价烷氧基、C2～C18一价烷氧基烷基、C3～C18一价环烷基、C2～C18一价氧杂环烷基、C6～C18一价芳基、C7～C18一价芳基烷基、C7～C18一价烷基芳基、C6～C18一价芳基氧基、C7～C18一价芳基氧基烷基、C12～C18一价芳醚基、C2～C18一价杂芳基、C3～C18一价杂芳基烷基、C3～C18一价烷基杂芳基和C1～C18一价硅烷基；
    R 2至R 21分别独立地表示氢原子或由以下基团组成的组中的至少一种：C1～C18一价烷基、C2～C18一价烷氧基烷基、C3～C18一价环烷基、C2～C18一价氧杂环烷基、C6～C18一价芳基、C7～C18一价芳基烷基、C7～C18一价烷基芳基、C7～C18一价芳基氧基烷基、C12～C18一价芳醚基、C2～C18一价杂芳基、C3～C18一价杂芳基烷基、C3～C18一价烷基杂芳基和C1～C18一价硅烷基，并且R 2和R 3均为氢原子时，R 1不为羟基；
    R 2和R 3还可以相互键合形成环结构，R 4和R 5还可以相互键合形成环结构，R 6和R 7还可以相互键合形成环结构，R 8和R 9还可以相互键合形成环结构，R 10和R 11还可以相互键合形成环结构，R 12和R 13还可以相互键合形成环结构，R 14和R 15还可以相互键合形成环结构，R 16和R 17还可以相互键合形成环结构，R 18和R 19还可以相互键合形成环结构，R 20和R 21还可以相互键合形成环结构；
    L 1表示氧原子或由以下基团组成的组中的至少一种：C1～C18二价烷基、C1～C18氧杂二价烷基、C6～C18二价环烷基、C6～C18二价氧杂环烷基、C6～C18二价芳基、C7～C18二价芳基烷基、C7～C18二价烷基芳基、C6～C18二价芳基氧基、C7～C18二价芳基氧基烷基、C12～C18二价芳醚基、C2～C18二价杂芳基、C3～C18二价杂芳基烷基和C3～C18二价烷基杂芳基；
    L 2表示由以下基团组成的组中的至少一种：C1～C18三价烷基、C1～C18氧杂三价烷基、C6～C18三价环烷基、C6～C18三价氧杂环烷基、C6～C18三价芳基、C7～C18三价芳基烷基、C7～C18三价烷基芳基、C6～C18三价芳基氧基、C7～C18三价芳基氧基烷基、C12～C18三价芳醚基、C3～C18三价杂芳基、C3～C18三价杂芳基烷基和C3～C18三价烷基杂芳基；
    L 3表示由以下基团组成的组中的至少一种：C1～C18四价烷基、C1～C18氧杂四价烷基、C6～C18四价环烷基、C6～C18四价氧杂环烷基、C6～C18四价芳基、C7～C18四价芳基烷基、C7～C18四价烷基芳基、C7～C18四价芳基氧基烷基、C12～C18四价芳醚基、C4～C18四价杂芳基、C4～C18四价杂芳基烷基和C4～C18四价烷基杂芳基。
  2. 根据权利要求1所述的二次电池，其中，所述第一添加剂满足如下条件(1)至(9)中的至少一者：
    (1)R 2和R 3相互键合形成环结构；
    (2)R 1至R 3中的至少一者表示C3～C18一价环烷基、C2～C18一价氧杂环烷基、C6～C18一价芳基、C7～C18一价芳基烷基、C7～C18一价烷基芳基、C7～C18一价芳基氧基烷基、C12～C18一价芳醚基、C2～C18一价杂芳基、C3～C18一价杂芳基烷基或C3～C18一价烷基杂芳基；
    (3)R 1至R 3分别独立地表示C6～C18一价芳基、C7～C18一价芳基烷基、C7～C18一价烷基芳基、C7～C18一价芳基氧基烷基、C12～C18一价芳醚基、C2～C18一价杂芳基、C3～C18一价杂芳基烷基或C3～C18一价烷基杂芳基；
    (4)R 4和R 5、R 6和R 7中的至少一组相互键合形成环结构；
    (5)L 1表示氧原子，并且R 4至R 7分别独立地表示C6～C18一价芳基、C7～C18一价芳基烷基、C7～C18一价烷基芳基、C7～C18一价芳基氧基烷基、C12～C18一价芳醚基、C2～C18一价杂芳基、C3～C18一价杂芳基烷基或C3～C18一价烷基杂芳基；
    (6)R 8和R 9、R 10和R 11、R 12和R 13中的至少一组相互键合形成环结构；
    (7)L 2表示C6～C18三价芳基、C7～C18三价芳基烷基、C7～C18三价烷基芳基、C6～C18三价芳基氧基、C7～C18三价芳基氧基烷基、C12～C18三价芳醚基、C3～C18三价杂芳基、C3～C18三价杂芳基烷基或C3～C18三价烷基杂芳基；
    (8)R 14和R 15、R 16和R 17、R 18和R 19、R 20和R 21中的至少一组相互键合形成环结构；
    (9)L 3表示C6～C18四价芳基、C7～C18四价芳基烷基、C7～C18四价烷基芳基、C7～C18四价芳基氧基烷基、C12～C18四价芳醚基、C4～C18四价杂芳基、C4～C18四价杂芳基烷基或C4～C18四价烷基杂芳基。
  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至少一种：
    Figure PCTCN2022090476-appb-100002
    Figure PCTCN2022090476-appb-100003
    可选地，所述第一添加剂包括H1至H10、H13至H15、H31至H33中的至少一种，
    更可选地，所述第一添加剂包括H1至H8、H32至H33中的至少一种。
  4. 根据权利要求1-3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磺酸内酯、环状硫酸酯、二氟磷酸锂、二氟二草酸磷酸锂、二氟草酸硼酸锂中的一种或多种。
  5. 根据权利要求4所述的二次电池，其中，
    所述磺酸内酯包括式2-A所示化合物中的至少一种，
    Figure PCTCN2022090476-appb-100004
    p1表示1、2或3，p2表示1或2，p3表示1或2，
    R 22分别独立地表示氢原子、卤原子、羧酸酯基、磺酸酯基、C1～C6一价烷基、C1～C6一价卤代烷基、C1～C6一价烷氧基、C1～C6一价卤代烷氧基、C2～C6一价烯基中的一种或其中的多种通过单键相互键合形成的链状结构或环状结构，R 22表示环状结构时，通过单键键合至式2-A的多元环或与式2-A的多元环共享一个碳原子形成螺环化合物，
    R 23分别独立地表示氢原子、卤原子、羧酸酯基、磺酸酯基、C1～C6一价烷基、C1～C6一价卤代烷基、C1～C6一价烷氧基、C1～C6一价卤代烷氧基、C2～C6一价烯基中的一种或其中的多种通过单键相互键合形成的链状结构或环状结构，R 23表示环状结构时，通过单键键合至式2-A的多元环或与式2-A的多元环共享一个碳原子形成螺环化合物，
    R 24表示羰基或C(Y 1) 2，Y 1分别独立地表示氢原子、卤原子、羧酸酯基、磺酸酯基、C1～C6一价烷基、C1～C6一价卤代烷基、C1～C6一价烷氧基、C1～C6一价卤代烷氧基、C2～C6一价烯基、C6～C12一价芳基中的一种或其组合，
    R 22和R 23还可以相互键合形成环结构，
    可选地，所述磺酸内酯包括如下化合物中的至少一种：
    Figure PCTCN2022090476-appb-100005
    Figure PCTCN2022090476-appb-100006
    和/或，
    所述环状硫酸酯包括式2-B所示化合物中的至少一种，
    Figure PCTCN2022090476-appb-100007
    q1表示1、2或3，q2表示1或2，q3表示1或2，
    R 25分别独立地表示氢原子、卤原子、羰基氧原子、羧酸酯基、硫酸酯基、C1～C6一价烷基、C1～C6一价卤代烷基、C1～C6一价烷氧基、C1～C6一价卤代烷氧基、C2～C6一价烯基中的一种或其中的多种通过单键相互键合形成的链状结构或环状结构，R 25表示环状结构时，通过单键键合至式2-B的多元环或与式2-B的多元环共享一个碳原子形成螺环化合物，
    R 26分别独立地表示氢原子、卤原子、羧酸酯基、硫酸酯基、C1～C6一价烷基、C1～C6一价卤代烷基、C1～C6一价烷氧基、C1～C6一价卤代烷氧基、C2～C6一价烯基中的一种或其中的多种通过单键相互键合形成的链状结构或环状结构，R 26表示环状结构时，通过单键键合至式2-B的多元环或与式2-B的多元环共享一个碳原子形成螺环化合物，
    R 25和R 26还可以相互键合形成环结构，
    可选地，所述环状硫酸酯包括如下化合物中的至少一种：
    Figure PCTCN2022090476-appb-100008
  6. 根据权利要求1-5中任一项所述的二次电池，其中，
    所述第一添加剂的含量为W1重量％，W1为0.01至20，可选为0.1至10，更可选为 0.3至5，基于所述非水电解液的总重量计；和/或，
    所述第二添加剂的含量为W2重量％，W2为0.01至20，可选为0.1至10，更可选为0.3至5，基于所述非水电解液的总重量计；和/或，
    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至5.6，基于所述内核的重量计；和/或，
    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至5，基于所述内核的重量计。
  7. 根据权利要求6所述的二次电池，其中，
    W1/W2为0.01至20，可选为0.01至10；和/或，
    (W1+W2)/(C1+C2)为0.001至2，可选为0.01至1。
  8. 根据权利要求1-7中任一项所述的二次电池，其中，所述非水电解液还包括第三添加剂，所述第三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、腈化合物、磷腈化合物、芳香烃及卤代芳香烃化合物、异氰酸酯化合物、酸酐化合物、亚磷酸酯化合物、磷酸酯化合物、亚硫酸酯化合物、二磺酸亚甲酯化合物中的一种或多种。
  9. 根据权利要求1-8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；和/或，
    所述A选自Fe、Ti、V、Ni、Co和Mg中的至少两种。
  10. 根据权利要求1-9中任一项所述的二次电池，其中，所述第一包覆层满足如下条件(1)至(4)中的至少一者：
    (1)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°；
    (2)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°；
    (3)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；
    (4)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％。
  11. 根据权利要求1-10中任一项所述的二次电池，其中，所述正极活性材料满足如下条件(1)至(5)中的至少一者：
    (1)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；
    (2)所述正极活性材料的晶格变化率为6％以下，可选为4％以下；
    (3)所述正极活性材料的表面氧价态为-1.88以下，可选为-1.98至-1.88；
    (4)所述正极活性材料在3吨下的压实密度为2.0g/cm 3以上，可选为2.2g/cm 3以上；
    (5)所述正极活性材料的比表面积为B m 2/g，B为7至18，可选为10至15。
  12. 一种电池模块，包括权利要求1-11中任一项所述的二次电池。
  13. 一种电池包，包括权利要求12所述的电池模块。
  14. 一种用电装置，包括选自权利要求1-11中任一项所述的二次电池、权利要求12所述的电池模块或权利要求13所述的电池包中的至少一种。
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