WO2023060494A1 - 电极组件、二次电池、电池模块、电池包及用电装置 - Google Patents

电极组件、二次电池、电池模块、电池包及用电装置 Download PDF

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WO2023060494A1
WO2023060494A1 PCT/CN2021/123648 CN2021123648W WO2023060494A1 WO 2023060494 A1 WO2023060494 A1 WO 2023060494A1 CN 2021123648 W CN2021123648 W CN 2021123648W WO 2023060494 A1 WO2023060494 A1 WO 2023060494A1
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Prior art keywords
positive electrode
film layer
negative electrode
positive
satisfies
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PCT/CN2021/123648
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English (en)
French (fr)
Inventor
张涛
何建福
刘倩
孙雪阳
叶永煌
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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 JP2022551417A priority Critical patent/JP7483910B2/ja
Priority to PCT/CN2021/123648 priority patent/WO2023060494A1/zh
Priority to KR1020227029908A priority patent/KR20230054313A/ko
Priority to CN202180091947.6A priority patent/CN116783736A/zh
Priority to EP21930598.4A priority patent/EP4195331A4/en
Priority to US17/933,855 priority patent/US20230112421A1/en
Publication of WO2023060494A1 publication Critical patent/WO2023060494A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • 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
    • H01M10/04—Construction or manufacture in general
    • H01M10/0431—Cells with wound or folded electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/058—Construction or manufacture
    • 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
    • H01M10/058—Construction or manufacture
    • H01M10/0585—Construction or manufacture of accumulators having only flat construction elements, i.e. flat positive electrodes, flat negative electrodes and flat separators
    • 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
    • H01M10/058—Construction or manufacture
    • H01M10/0587—Construction or manufacture of accumulators having only wound construction elements, i.e. wound positive electrodes, wound negative electrodes and wound separators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/04—Processes of manufacture in general
    • H01M4/0402—Methods of deposition of the material
    • H01M4/0404—Methods of deposition of the material by coating on electrode collectors
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/131—Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/139—Processes of manufacture
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/64—Carriers or collectors
    • H01M4/66—Selection of materials
    • H01M4/661—Metal or alloys, e.g. alloy coatings
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/10—Primary casings; Jackets or wrappings
    • H01M50/102—Primary casings; Jackets or wrappings characterised by their shape or physical structure
    • H01M50/105—Pouches or flexible bags
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/10—Primary casings; Jackets or wrappings
    • H01M50/116—Primary casings; Jackets or wrappings characterised by the material
    • H01M50/117—Inorganic material
    • H01M50/119—Metals
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
    • H01M50/46—Separators, membranes or diaphragms characterised by their combination with electrodes
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/50—Current conducting connections for cells or batteries
    • H01M50/543—Terminals
    • H01M50/547—Terminals characterised by the disposition of the terminals on the cells
    • H01M50/55—Terminals characterised by the disposition of the terminals on the cells on the same side of the cell
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/027—Negative electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M2010/4292—Aspects relating to capacity ratio of electrodes/electrolyte or anode/cathode
    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/10—Primary casings; Jackets or wrappings
    • H01M50/102—Primary casings; Jackets or wrappings characterised by their shape or physical structure
    • H01M50/103—Primary casings; Jackets or wrappings characterised by their shape or physical structure prismatic or rectangular
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/10—Primary casings; Jackets or wrappings
    • H01M50/147—Lids or covers
    • H01M50/148—Lids or covers characterised by their shape
    • H01M50/15—Lids or covers characterised by their shape for prismatic or rectangular cells
    • 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
    • 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
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present application belongs to the field of battery technology, and in particular relates to an electrode assembly, a secondary battery, a battery module, a battery pack and an electrical device.
  • the purpose of the present application is to provide an electrode assembly, a secondary battery, a battery module, a battery pack and an electrical device, aiming at greatly prolonging the cycle life of the secondary battery.
  • the first aspect of the present application provides an electrode assembly, which includes a positive pole piece, a negative pole piece, and a separator between the positive pole piece and the negative pole piece, the positive pole piece includes a positive current collector and a The first positive electrode film layer and the second positive electrode film layer on the two opposite surfaces of the positive electrode current collector, and the negative electrode sheet includes the negative electrode current collector and the first negative electrode on the two opposite surfaces of the negative electrode current collector film layer and the second negative electrode film layer; the first positive electrode film layer is located on the side of the positive electrode collector close to the separator and the second negative electrode film layer is located on the side of the negative electrode collector close to the separator One side, or, the first positive electrode film layer is located on the side of the positive electrode collector away from the separator and the second negative electrode film layer is located on the side of the negative electrode collector away from the separator; wherein , the positive pole piece satisfies 0 ⁇ CAP1/CAP2 ⁇ 1, CAP1 represents the capacity of the first positive film layer in Ah, CAP2 represents the capacity of the
  • the capacity stored on both sides of the positive electrode sheet is different.
  • the voltage response speed of the low-capacity positive electrode film layer during charging can be improved.
  • this part of the pre-stored active ions can be gradually released to supplement the consumption of active ions, thereby delaying the capacity decay of the secondary battery and greatly extending the cycle life of the secondary battery.
  • the electrode assembly satisfies 0 ⁇ R 4 /R 3 ⁇ R 2 /R 1 ⁇ 20.
  • the electrode assembly satisfies 0 ⁇ R 4 /R 3 ⁇ R 2 /R 1 ⁇ 20.
  • the positive pole piece satisfies 0.33 ⁇ CAP1/CAP2 ⁇ 1.
  • the positive pole piece satisfies 0.5 ⁇ CAP1/CAP2 ⁇ 1.
  • the positive pole piece satisfies 0.5 ⁇ CAP1/CAP2 ⁇ 0.9.
  • the secondary battery can have a longer cycle life and a high energy density.
  • the resistances of the first positive electrode film layer, the second positive electrode film layer, the first negative electrode film layer and the second negative electrode film layer are respectively within appropriate ranges, the consistency of the positive electrode sheet and the negative electrode sheet is better, which is beneficial to secondary The battery gets a longer cycle life.
  • the first positive electrode film layer includes a first positive electrode active material
  • the second positive electrode film layer includes a second positive electrode active material
  • the positive electrode sheet satisfies one or more of the following (1) to (3).
  • the negative electrode sheet satisfies R 4 /R 3 ⁇ 1, and the electrode assembly satisfies 0 ⁇ R 4 /R 3 ⁇ R 2 /R 1 ⁇ 20.
  • 0 ⁇ R 4 /R 3 -R 2 /R 1 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 5.
  • the negative electrode sheet satisfies R 4 /R 3 ⁇ 1
  • the positive electrode sheet satisfies 0 ⁇ R 2 /R 1 ⁇ 20
  • the electrode assembly satisfies 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 20.
  • 0 ⁇ R 4 /R 3 -R 2 /R 1 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 5.
  • the negative electrode sheet satisfies 1 ⁇ R 4 /R 3 ⁇ 30
  • the positive electrode sheet satisfies 0 ⁇ R 2 /R 1 ⁇ 20
  • the electrode assembly satisfies 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 20.
  • 0 ⁇ R 4 /R 3 -R 2 /R 1 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 5.
  • the negative electrode sheet satisfies 0 ⁇ R 4 /R 3 ⁇ 1
  • the positive electrode sheet satisfies 0 ⁇ R 2 /R 1 ⁇ 1
  • the electrode assembly satisfies 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 1.
  • 0 ⁇ R 4 /R 3 -R 2 /R 1 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 1.
  • 0.1 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 0.9.
  • the negative electrode sheet satisfies 0 ⁇ R 4 /R 3 ⁇ 1
  • the positive electrode sheet satisfies 0.05 ⁇ R 2 /R 1 ⁇ 0.9
  • the electrode assembly satisfies 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 1.
  • 0 ⁇ R 4 /R 3 -R 2 /R 1 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 1.
  • the negative electrode sheet satisfies 0.05 ⁇ R 4 /R 3 ⁇ 0.9
  • the positive electrode sheet satisfies 0.05 ⁇ R 2 /R 1 ⁇ 0.9
  • the electrode assembly satisfies 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 1.
  • 0 ⁇ R 4 /R 3 -R 2 /R 1 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 1.
  • the second aspect of the present application provides a secondary battery, which includes an outer package, an electrolyte, and the electrode assembly according to the first aspect of the present application.
  • the outer package includes a casing and a cover plate, the casing has an accommodating cavity and an opening, the electrode assembly is accommodated in the accommodating cavity, and the cover plate is used to close the opening of the casing.
  • a third aspect of the present application provides a battery module, which includes the secondary battery of the second aspect of the present application.
  • a fourth aspect of the present application provides a battery pack, which includes one of the secondary battery of the second aspect of the present application and the battery module of the third aspect.
  • the fifth aspect of the present application provides an electric device, which includes at least one of the secondary battery of the second aspect of the present application, the battery module of the third aspect, and the battery pack of the fourth aspect.
  • the battery module, battery pack and electric device of the present application include the secondary battery provided by 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 a secondary battery of the present application.
  • FIG. 2 is an exploded schematic diagram of an embodiment of the secondary battery of the present application.
  • Fig. 3 is a schematic structural view of an embodiment of the electrode assembly of the present application.
  • Fig. 4 is a schematic structural view of another embodiment of the electrode assembly of the present application.
  • Fig. 5 is a schematic structural view of another embodiment of the electrode assembly of the present application.
  • Fig. 6 is a schematic structural view of another embodiment of the electrode assembly of the present application.
  • Fig. 7 is a schematic structural view of another embodiment of the electrode assembly of the present application.
  • Fig. 8 is a schematic structural view of another embodiment of the electrode assembly of the present application.
  • Fig. 9 is a schematic structural view of another embodiment of the electrode assembly of the present application.
  • Fig. 10 is a schematic structural view of another embodiment of the electrode assembly of the present application.
  • Fig. 11 is a schematic structural view of another embodiment of the electrode assembly of the present application.
  • Fig. 12 is a schematic structural view of another embodiment of the electrode assembly of the present application.
  • Fig. 13 is a schematic structural view of another embodiment of the electrode assembly of the present application.
  • Fig. 14 is a schematic structural view of another embodiment of the electrode assembly of the present application.
  • Fig. 15 is a schematic structural view of another embodiment of the electrode assembly of the present application.
  • Fig. 16 is a schematic structural view of another embodiment of the electrode assembly of the present application.
  • Fig. 17 is a schematic diagram of an embodiment of the battery module of the present application.
  • Fig. 18 is a schematic diagram of an embodiment of the battery pack of the present application.
  • FIG. 19 is an exploded view of the embodiment of the battery pack shown in FIG. 18 .
  • FIG. 20 is a schematic diagram of an embodiment of an electrical device including the secondary battery of the present application as a power source.
  • ranges disclosed herein are defined in terms of lower and upper limits, and a given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive and may be combined arbitrarily, ie any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are contemplated. Additionally, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, the following ranges are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-5.
  • the numerical range "a-b” represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers.
  • the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article, and "0-5" is only an abbreviated representation of the combination of these values.
  • a certain parameter is an integer ⁇ 2
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed in sequence, and may also include steps (b) and (a) performed in sequence.
  • steps (c) means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c) , may also include steps (a), (c) and (b), may also include steps (c), (a) and (b) and so on.
  • the “comprising” and “comprising” mentioned in this application mean open or closed.
  • the “comprising” and “comprising” may mean that other components not listed may be included or included, or only listed components may be included or included.
  • the term "or” is inclusive unless otherwise stated.
  • the phrase "A or B” means “A, B, or both A and B.” More specifically, the condition "A or B” is satisfied by either of the following: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists) ; or both A and B are true (or exist).
  • FIG. 1 is a schematic diagram of a secondary battery 5 having a square structure as an example.
  • the secondary battery 5 includes an outer package, an electrode assembly and an electrolyte, and the outer package is used to package the electrode assembly and the electrolyte.
  • the outer package of the secondary battery may be a hard case, such as a hard plastic case, aluminum case, steel case, and the like.
  • the outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag.
  • the soft bag can be made of plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), and polybutylene succinate (PBS).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PBS polybutylene succinate
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plates enclose to form an accommodating cavity.
  • the housing 51 has an opening communicating with the receiving chamber, and the cover plate 53 is used to cover the opening to close the receiving chamber.
  • the electrode assembly 52 is packaged in the accommodating cavity, and the electrolyte is infiltrated in 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 requirements.
  • FIG. 3 is a schematic structural view of an embodiment of an electrode assembly according to the present application.
  • the electrode assembly 52 comprises a positive pole piece 10, a negative pole piece 20 and a separator 30, wherein the separator 30 is located between the positive pole piece 10 and the negative pole piece 20, the positive pole piece 10, the negative pole piece 20 and the separator 30 can be formed into an electrode assembly 52 through a winding process or a lamination process.
  • the positive electrode sheet 10 includes a first positive electrode film layer 101 , a second positive electrode film layer 102 and a positive electrode collector 103 , and the first positive electrode film layer 101 and the second positive electrode film layer 102 are located on opposite surfaces of the positive electrode collector 103 .
  • the first positive electrode film layer 101 includes the first positive electrode active material, the first positive electrode conductive agent and the first positive electrode binder
  • the second positive electrode film layer 102 includes the second positive electrode active material, the second positive electrode conductive agent and the second positive electrode binder. agent.
  • the negative electrode sheet 20 includes a first negative electrode film layer 201 , a second negative electrode film layer 202 and a negative electrode collector 203 .
  • the first negative electrode film layer 201 and the second negative electrode film layer 202 are located on opposite surfaces of the negative electrode collector 203 .
  • the first negative electrode film layer 201 includes the first negative electrode active material, the first negative electrode conductive agent and the first negative electrode binder
  • the second negative electrode film layer 202 includes the second negative electrode active material, the second negative electrode conductive agent and the second negative electrode binder. agent.
  • the first positive electrode film layer 101 and the second negative electrode film layer 202 are disposed close to or far from the separator 30 at the same time.
  • the first positive electrode film layer 101 is located on the side of the positive electrode collector 103 close to the separator 30 and the second negative electrode film layer 202 is located on the side of the negative electrode collector 203 close to the separator 30 .
  • the first positive electrode film layer 101 is located on the side of the positive electrode collector 103 away from the separator 30 and the second negative electrode film layer 202 is located on the side of the negative electrode collector 203 away from the separator 30 .
  • the positive electrode sheet 10 satisfies 0 ⁇ CAP1/CAP2 ⁇ 1, CAP1 represents the capacity of the first positive electrode film layer 101 in Ah, and CAP2 represents the second positive electrode film layer in Ah 102 capacity.
  • the electrode assembly 52 satisfies R 4 /R 3 -R 2 /R 1 ⁇ 0, R 1 represents the resistance of the first positive electrode film layer 101 in ⁇ , R 2 represents the resistance of the second positive electrode film layer 102 in ⁇ , R 3 represents the resistance of the first negative electrode film layer 201 in m ⁇ , and R 4 represents the resistance of the second negative electrode film layer 202 in m ⁇ .
  • active ions are extracted from the positive electrode.
  • the rate and quantity of active ions are related to the charging current and charging time of the secondary battery. The larger the charging current and the longer the charging time, the more active ions are extracted, and the extraction capacity The higher the ratio (that is, the ratio of extraction capacity to storage capacity), the higher the positive electrode voltage.
  • the current is evenly distributed on the positive electrode sheet, and the low-capacity positive electrode film layer (the first positive electrode film layer in this application) and the high-capacity positive electrode film layer (the second negative electrode film layer in this application) are carried out simultaneously Active ions are released and the number of active ions released is consistent.
  • the low-capacity positive electrode film layer and the high-capacity positive electrode film layer store different capacities, the low-capacity positive electrode film layer and the high-capacity positive electrode film layer have different proportions of output capacity, and the corresponding voltages are also different.
  • the high-capacity positive electrode film layer has a lower capacity than the lower-capacity positive electrode film layer. Since the low-capacity positive electrode film layer and the high-capacity positive electrode film layer are in parallel structure, the cut-off voltage of the secondary battery will be triggered on the side that reaches the cut-off voltage first.
  • the high-capacity positive electrode film layer can have active ion pre-storage.
  • the low-capacity positive film layer there is a potential difference between the low-capacity positive film layer and the high-capacity positive film layer. Therefore, the active ions pre-stored in the high-capacity positive film layer can gradually be released and dissolved into the electrolyte and transferred to the low-capacity positive film layer, thereby high
  • the high-capacity positive electrode film layer can supplement the active ion consumption of the low-capacity positive electrode film layer, delay the capacity decay of the secondary battery and greatly extend the cycle life of the secondary battery.
  • the double-sided coating design of the conventional positive pole piece is often not timely due to the voltage response in the actual application process, resulting in the positive pole piece being unable to achieve active ion pre-storage, or not having a sufficient amount of active ion pre-storage, which does not significantly improve the cycle life of the secondary battery. It is not possible to make the secondary battery have a longer cycle life.
  • the capacity stored on both sides of the positive electrode sheet is different. By reasonably setting the relationship between the resistance on both sides of the positive electrode sheet and the resistance on both sides of the negative electrode sheet, the voltage response speed of the low-capacity positive electrode film layer during charging can be improved.
  • the electrode assembly 52 does not satisfy R 4 /R 3 -R 2 /R 1 ⁇ 0, the difference in the proportion of the extraction capacity between the low-capacity positive electrode film and the high-capacity positive electrode film is small, and the high-capacity positive electrode film does not have sufficient activity Pre-storage of ions does not significantly improve the cycle life of secondary batteries.
  • the capacity of the positive electrode film layer is a well-known meaning in the art, and can be measured with instruments and methods known in the art. For example, use a blue electric tester for testing.
  • the capacity of the positive electrode film layer can be tested by the following method: the positive electrode film layer on one side of the cold-pressed positive electrode sheet is wiped off to obtain a single-sided coated positive electrode sheet, and the single-sided coated positive electrode sheet is After being punched into small discs with an area of S 0 , they were assembled into button cells in a glove box, charged at a constant current of 0.1 mA to the cut-off voltage of charge, and discharged at a constant current of 0.1 mA to the cut-off voltage of discharge to obtain the discharge capacity CAP0, The capacity of the positive electrode film layer is obtained by the formula CAP0 ⁇ S/S 0 , S 0 is the area of the small disc, and S is the area of the positive electrode film layer.
  • the capacity CAP1 of the first positive electrode film layer can be tested by the following method: after the second positive electrode film layer of the cold-pressed positive electrode sheet is wiped off, it is punched into a small disc with an area of S0 , and the small disc
  • the chips were assembled into a button battery in the glove box, and then charged to the cut-off voltage with a constant current of 0.1mA on the blue battery tester, and then discharged to the cut-off voltage with a constant current of 0.1mA to obtain the discharge capacity CAP0, through the formula CAP0 ⁇ S 1 /S 0 obtains the capacity CAP1 of the first positive electrode film layer, S 0 is the area of the small disc, and S 1 is the area of the first positive electrode film layer.
  • the capacity CAP2 of the second positive film layer can be tested by the following method: after wiping off the first positive film layer of the cold-pressed positive electrode sheet, punching it into small discs with an area of S0 , placing the small discs in gloves Assemble a button battery in the box, then charge it to the charge cut-off voltage with a constant current of 0.1mA on the blue battery tester, and then discharge it to the cut-off voltage with a constant current of 0.1mA to obtain the discharge capacity CAP0, which can be obtained by the formula CAP0 ⁇ S 2 / S 0 obtains the capacity CAP2 of the second positive electrode film layer, S 0 is the area of the small disc, and S 2 is the area of the second positive electrode film layer.
  • the button cell can be assembled in the order of the negative electrode shell, lithium sheet, a drop of electrolyte, separator, a drop of electrolyte, a small disc with an area of S 0 , a gasket, and a shrapnel.
  • the diameter of the button cell may be 14mm.
  • the film layer on one side of the pole piece can be wiped off with water or other solvents.
  • a processor from IEST of Yuanneng Technology Co., Ltd. can be used for testing.
  • film resistance is a well-known meaning in the art, and can be measured with instruments and methods known in the art.
  • a pole piece resistance meter is used for testing (for example, IEST BER1000 pole piece resistance meter, from Yuanneng Technology Co., Ltd.).
  • the resistance of each film layer can be tested by the following method: wipe off the film layer on one side of the cold-pressed pole piece to obtain a single-sided coated pole piece, and place the single-sided coated pole piece parallel to the pole piece. A certain pressure is applied between the two conductive terminals of the resistance meter to obtain the film resistance.
  • the resistance R1 of the first positive electrode film layer can be tested by the following method: wipe off the second positive electrode film layer of the cold-pressed positive electrode sheet, and then place it in parallel between the two conductive terminals of the electrode sheet resistance meter During this period, a certain pressure is applied to fix it, and the resistance R 1 of the first positive electrode film layer is obtained.
  • the resistance R of the second positive electrode film layer can be tested by the following method: wipe off the first positive electrode film layer of the cold-pressed positive electrode sheet, then place it in parallel between the two conductive terminals of the electrode sheet resistance meter, and apply A certain pressure is fixed to obtain the resistance R 2 of the second positive electrode film layer.
  • the resistance R of the first negative film layer can be tested by the following method: the second negative film layer of the cold-pressed negative electrode sheet is wiped off, and then placed in parallel between the two conductive terminals of the electrode sheet resistance meter, and applied A certain pressure is fixed to obtain the resistance R 3 of the first negative electrode film layer.
  • the resistance R of the second negative film layer can be tested by the following method: wipe off the first negative film layer of the cold-pressed negative electrode sheet, and then place it in parallel between the two conductive terminals of the electrode sheet resistance meter, apply A certain pressure is fixed to obtain the resistance R 4 of the second negative electrode film layer.
  • the diameter of the conductive terminal may be 14mm
  • the applied pressure may be 15Mpa-27Mpa
  • the time range for sampling points may be 10s-20s.
  • the pole piece can be cut into a certain area (for example, 10cm ⁇ 10cm) before testing.
  • the film layer on one side of the pole piece can be wiped off with water or other solvents.
  • the pole piece (for example, the positive pole piece or the negative pole piece) can be directly obtained from a freshly prepared cold-pressed pole piece, or obtained from a secondary battery.
  • the exemplary method of obtaining the pole piece from the secondary battery is as follows: the pole piece is disassembled after the secondary battery is fully charged, and the pole piece is soaked in an organic solvent (for example, dimethyl carbonate) for a period of time (for example, 30min), and then take out the pole piece and dry it at a certain temperature and time (for example, 80°C, 6h).
  • an organic solvent for example, dimethyl carbonate
  • the electrode assembly 52 satisfies 0 ⁇ R 4 /R 3 ⁇ R 2 /R 1 ⁇ 20.
  • R 4 /R 3 -R 2 /R 1 >20 the secondary battery will quickly reach the charge cut-off voltage when charging, resulting in a large number of active ions in both the low-capacity positive electrode film and the high-capacity positive electrode film that have not been released, reducing the Energy density of secondary batteries.
  • R 4 /R 3 -R 2 /R 1 is 0, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or any of the above ranges.
  • the electrode assembly 52 satisfies 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 20, 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 15, 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 10, 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 8, 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 5, 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 2, 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 20, 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 15, 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 10, 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 8, 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 5, 0 ⁇ R 4 /R 3 -R 2 /R 1
  • the capacity CAP1 of the first positive electrode film layer 101 is smaller than the capacity CAP2 of the second positive electrode film layer 102 .
  • CAP1/CAP2 is 0.1, 0.2, 0.33, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or any of the ranges above.
  • the secondary battery can have a longer cycle life and a high energy density.
  • the resistance R 1 of the first anode film layer 101 satisfies 0 ⁇ R 1 ⁇ 20 ⁇ .
  • the resistance R 2 of the second anode film layer 102 satisfies 0 ⁇ R 2 ⁇ 20 ⁇ .
  • the resistance R 3 of the first negative electrode film layer 201 satisfies 0m ⁇ R 3 ⁇ 200m ⁇ .
  • the resistance R 4 of the second negative electrode film layer 202 satisfies 0m ⁇ R 4 ⁇ 200m ⁇ .
  • the resistances of the first positive electrode film layer, the second positive electrode film layer, the first negative electrode film layer and the second negative electrode film layer are respectively within appropriate ranges, the consistency of the positive electrode sheet and the negative electrode sheet is better, which is beneficial to secondary The battery gets a longer cycle life.
  • the negative electrode sheet 20 satisfies R 4 /R 3 ⁇ 1
  • the electrode assembly 52 satisfies 0 ⁇ R 4 /R 3 ⁇ R 2 /R 1 ⁇ 20, at this time, the secondary battery has a longer At the same time of cycle life, it also has high energy density.
  • R 4 /R 3 is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30 or any of the above ranges.
  • the negative pole piece 20 satisfies 1 ⁇ R 4 /R 3 ⁇ 30, 1 ⁇ R 4 /R 3 ⁇ 25, 1 ⁇ R 4 /R 3 ⁇ 20, 1 ⁇ R 4 /R 3 ⁇ 15 , 1 ⁇ R 4 /R 3 ⁇ 10, 1 ⁇ R 4 /R 3 ⁇ 8, 1 ⁇ R 4 /R 3 ⁇ 5, 1 ⁇ R 4 /R 3 ⁇ 4, 1 ⁇ R 4 /R 3 ⁇ 3, 1 ⁇ R 4 /R 3 ⁇ 2, 1 ⁇ R 4 /R 3 ⁇ 30, 1 ⁇ R 4 /R 3 ⁇ 25, 1 ⁇ R 4 /R 3 ⁇ 20, 1 ⁇ R 4 /R 3 ⁇ 15, 1 ⁇ R 4 /R 3 ⁇ 10, 1 ⁇ R 4 /R 3 ⁇ 8, 1 ⁇ R 4 /R
  • R 4 /R 3 -R 2 /R 1 is 0, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or any of the above ranges.
  • the electrode assembly 52 satisfies 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 20, 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 15, 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 10, 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 8, 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 5, 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 2, 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 20, 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 15, 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 10, 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 8, 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 5, 0 ⁇ R 4 /R 3 -R 2 /R 1
  • R 2 /R 1 of the first anode film layer 101 and the second anode film layer 102 there is no particular limitation on the resistance ratio R 2 /R 1 of the first anode film layer 101 and the second anode film layer 102 , and R 2 /R 1 may be greater than 1, equal to 1, or less than 1.
  • R2 / R1 is 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 or any of the above ranges.
  • the positive electrode sheet 10 satisfies 0 ⁇ R 2 /R 1 ⁇ 20, 0 ⁇ R 2 /R 1 ⁇ 15, 0 ⁇ R 2 /R 1 ⁇ 10, 0 ⁇ R 2 /R 1 ⁇ 8,0 ⁇ R 2 /R 1 ⁇ 5, 0 ⁇ R 2 /R 1 ⁇ 4, 0 ⁇ R 2 /R 1 ⁇ 3, 0 ⁇ R 2 /R 1 ⁇ 2, or 0 ⁇ R 2 /R 1 ⁇ 1.
  • the negative electrode sheet 20 satisfies R 4 /R 3 ⁇ 1
  • the positive electrode sheet 10 satisfies 0 ⁇ R 2 /R 1 ⁇ 20
  • the electrode assembly 52 satisfies 0 ⁇ R 4 /R 3 ⁇ R 2 /R 1 ⁇ 20
  • the electrode assembly 52 satisfies 0 ⁇ R 4 /R 3 ⁇ R 2 /R 1 ⁇ 20.
  • the electrode assembly 52 satisfies 0 ⁇ R 4 /R 3 ⁇ R 2 /R 1 ⁇ 5.
  • the electrode assembly 52 satisfies 0 ⁇ R 4 /R 3 ⁇ R 2 /R 1 ⁇ 5.
  • the electrode assembly 52 satisfies 0.1 ⁇ R 4 /R 3 ⁇ R 2 /R 1 ⁇ 2.
  • the negative electrode sheet 20 satisfies 1 ⁇ R 4 /R 3 ⁇ 30
  • the positive electrode sheet 10 satisfies 0 ⁇ R 2 /R 1 ⁇ 20
  • the electrode assembly 52 satisfies 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 20.
  • the electrode assembly 52 satisfies 0 ⁇ R 4 /R 3 ⁇ R 2 /R 1 ⁇ 20.
  • the electrode assembly 52 satisfies 0 ⁇ R 4 /R 3 ⁇ R 2 /R 1 ⁇ 5.
  • the electrode assembly 52 satisfies 0 ⁇ R 4 /R 3 ⁇ R 2 /R 1 ⁇ 5.
  • the electrode assembly 52 satisfies 0.1 ⁇ R 4 /R 3 ⁇ R 2 /R 1 ⁇ 2.
  • the negative electrode sheet 20 satisfies 0 ⁇ R 4 /R 3 ⁇ 1
  • the positive electrode sheet 10 satisfies 0 ⁇ R 2 /R 1 ⁇ 1
  • the electrode assembly 52 satisfies 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 1 in this case, the secondary battery has a higher energy density while having a longer cycle life.
  • R 4 /R 3 is 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or any of the above ranges.
  • the negative pole piece 20 satisfies 0 ⁇ R 4 /R 3 ⁇ 0.9, 0 ⁇ R 4 /R 3 ⁇ 0.8, 0 ⁇ R 4 /R 3 ⁇ 0.7, 0 ⁇ R 4 /R 3 ⁇ 0.6, 0.05 ⁇ R 4 /R 3 ⁇ 1, 0.05 ⁇ R 4 /R 3 ⁇ 0.9, 0.05 ⁇ R 4 /R 3 ⁇ 0.8, 0.05 ⁇ R 4 /R 3 ⁇ 0.7 , 0.05 ⁇ R 4 /R 3 ⁇ 0.6,0.1 ⁇ R4 / R3 ⁇ 1 , 0.1 ⁇ R4 /R3 ⁇ 0.9, 0.1 ⁇ R4 /R3 ⁇ 0.8 , 0.1 ⁇ R4 / R3 ⁇ 0.7 , 0.1 ⁇ R4 / R3 ⁇ 0.6,0.2 ⁇ R 4 /R 3 ⁇ 1,
  • R 2 /R 1 is 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or any of the above ranges.
  • the positive pole piece 10 satisfies 0 ⁇ R 2 /R 1 ⁇ 0.9, 0 ⁇ R 2 /R 1 ⁇ 0.8, 0 ⁇ R 2 /R 1 ⁇ 0.7, 0 ⁇ R 2 /R 1 ⁇ 0.6, 0.05 ⁇ R 2 /R 1 ⁇ 1, 0.05 ⁇ R 2 /R 1 ⁇ 0.9, 0.05 ⁇ R 2 /R 1 ⁇ 0.8 , 0.05 ⁇ R 2 /R 1 ⁇ 0.7, 0.05 ⁇ R 2 /R 1 ⁇ 0.6,0.1 ⁇ R 2 /R 1 ⁇ 1, 0.1 ⁇ R 2 /R 1 ⁇ 0.9, 0.1 ⁇ R 2 /R 1 ⁇ 0.8, 0.1 ⁇ R 2 /R 1 ⁇ 0.7, 0.1 ⁇ R 2 / R 1 ⁇ 0.6,0.2 ⁇ R2 / R1 ⁇ 1
  • R 4 /R 3 -R 2 /R 1 is 0, 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or any of the above ranges.
  • the electrode assembly 52 satisfies 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 1, 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 0.9, 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 0.8, 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 0.7, 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 0.6, 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 1, 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 0.9, 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 0.8, 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 0.7
  • the negative electrode sheet 20 satisfies 0 ⁇ R 4 /R 3 ⁇ 1
  • the positive electrode sheet 10 satisfies 0 ⁇ R 2 /R 1 ⁇ 1
  • the electrode assembly 52 satisfies 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 1.
  • the negative electrode sheet 20 satisfies 0 ⁇ R 4 /R 3 ⁇ 1
  • the positive electrode sheet 10 satisfies 0 ⁇ R 2 /R 1 ⁇ 1
  • the electrode assembly 52 satisfies 0.1 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 0.9.
  • the negative electrode sheet 20 satisfies 0 ⁇ R 4 /R 3 ⁇ 1
  • the positive electrode sheet 10 satisfies 0.05 ⁇ R 4 /R 3 ⁇ 0.9
  • the electrode assembly 52 satisfies 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 1.
  • the negative electrode sheet 20 satisfies 0 ⁇ R 4 /R 3 ⁇ 1
  • the positive electrode sheet 10 satisfies 0.05 ⁇ R 4 /R 3 ⁇ 0.9
  • the electrode assembly 52 satisfies 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 1.
  • the negative electrode sheet 20 satisfies 0 ⁇ R 4 /R 3 ⁇ 1
  • the positive electrode sheet 10 satisfies 0.05 ⁇ R 4 /R 3 ⁇ 0.9
  • the electrode assembly 52 satisfies 0.1 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 0.9.
  • the negative electrode sheet 20 satisfies 0.05 ⁇ R 4 /R 3 ⁇ 0.9
  • the positive electrode sheet 10 satisfies 0.05 ⁇ R 4 /R 3 ⁇ 0.9
  • the electrode assembly 52 satisfies 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 1.
  • the negative pole piece 20 satisfies 0.05 ⁇ R 4 /R 3 ⁇ 0.9
  • the positive pole piece 10 satisfies 0.05 ⁇ R 4 /R 3 ⁇ 0.9
  • the electrode assembly 52 satisfies 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 1.
  • the negative electrode sheet 20 satisfies 0.05 ⁇ R 4 /R 3 ⁇ 0.9
  • the positive electrode sheet 10 satisfies 0.05 ⁇ R 4 /R 3 ⁇ 0.9
  • the electrode assembly 52 satisfies 0.1 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 0.8.
  • the capacity CAP1 of the first positive electrode film layer 101 is smaller than the capacity CAP2 of the second positive electrode film layer 102 .
  • the coating weight of the first positive electrode film layer 101 is smaller than the coating weight of the second positive electrode film layer 102 .
  • the gram capacity of the first positive electrode active material is smaller than the gram capacity of the second positive electrode active material.
  • w 1 represents the mass percentage of the first positive electrode active material based on the total mass of the first positive electrode film layer 101
  • w 2 represents the total mass based on the second positive electrode film layer 102
  • the resistance R 2 of the second positive electrode film layer 102 is smaller than the resistance R 1 of the first positive electrode film layer 101 .
  • the surface of the second positive electrode active material has a conductive carbon layer.
  • the surface of the second positive electrode active material has a conductive carbon layer.
  • the resistance R of the second positive electrode film layer 102 can be made smaller than that of the first positive electrode film layer 101. Resistor R 1 .
  • the electrical conductivity of the second positive electrode conductive agent is greater than the electrical conductivity of the first positive electrode conductive agent.
  • w 3 represents the mass percentage of the first positive electrode conductive agent based on the total mass of the first positive electrode film layer 101
  • w 4 represents the total mass based on the second positive electrode film layer 102
  • the mass percent content of the second positive electrode conductive agent is the mass percent content of the second positive electrode conductive agent.
  • w 5 > w 6 w 5 represents the mass percentage of the first positive electrode binder based on the total mass of the first positive electrode film layer 101
  • w 6 represents the total mass based on the second positive electrode film layer 102 , the mass percentage of the second positive electrode binder.
  • the compacted density of the second positive electrode film layer 102 is smaller than the compacted density of the first positive electrode film layer 101 .
  • the second positive electrode film layer 102 includes a second positive electrode body layer 1021 and a second positive electrode conductive carbon layer 1022 , and the second positive electrode conductive carbon layer 1022 is located on two opposite surfaces of the second positive electrode body layer 1021 on at least one of the surfaces.
  • the first positive electrode film layer 101 includes a first positive electrode body layer 1011 and a first positive electrode ceramic layer 1013, and the first positive electrode ceramic layer 1013 is located on the two opposite surfaces of the first positive electrode body layer 1011. on at least one surface.
  • the first anode ceramic layer 1013 includes one or more of alumina ceramics, silicon nitride ceramics, silicon carbide ceramics, and boron nitride ceramics.
  • FIG. 5 shows that the second positive electrode conductive carbon layer 1022 is located on the two opposite surfaces of the second positive electrode body layer 1021, in other embodiments, the second positive electrode conductive carbon layer 1022 can also be located on the second positive electrode body layer 1021. On one of the two opposite surfaces of the two positive electrode body layers 1021 .
  • FIG. 6 shows that the first anode ceramic layer 1013 is located on the opposite surfaces of the first anode body layer 1011, in other embodiments, the first anode ceramic layer 1013 may also be located on opposite sides of the first anode body layer 1011. on one of the two surfaces.
  • the positive electrode sheet 10 can also satisfy the above (9) and (10) at the same time, so that the resistance R 2 of the second positive electrode film layer 102 is smaller than the resistance R 1 of the first positive electrode film layer 101 .
  • the resistance R 2 of the second positive electrode film layer 102 is greater than the resistance R 1 of the first positive electrode film layer 101 .
  • the surface of the first pole active material has a conductive carbon layer.
  • the surface of the first positive electrode active material has a conductive carbon layer, and when the surface of the second positive electrode active material does not have a conductive carbon layer, the resistance R of the second positive electrode film layer 102 can be made greater than that of the first positive electrode film layer 101 Resistor R 1 .
  • the electrical conductivity of the second positive electrode conductive agent is smaller than the electrical conductivity of the first positive electrode conductive agent.
  • the resistance R 2 of the second positive electrode film layer 102 can be made greater than the resistance R 1 of the first positive electrode film layer 101 by making the first positive electrode film layer 101 contain a first positive electrode conductive agent with higher conductivity.
  • the compacted density of the second positive electrode film layer 102 is greater than the compacted density of the first positive electrode film layer 101 .
  • the first positive electrode film layer 101 includes a first positive electrode body layer 1011 and a first positive electrode conductive carbon layer 1012, and the first positive electrode conductive carbon layer 1012 is located on the two opposite surfaces of the first positive electrode body layer 1011 on at least one of the surfaces.
  • the second anode film layer 102 includes a second anode body layer 1021 and a second anode ceramic layer 1023 , and the second anode ceramic layer 1023 is located on the two opposite surfaces of the second anode body layer 1021 on at least one surface.
  • the second anode ceramic layer 1023 includes one or more of alumina ceramics, silicon nitride ceramics, silicon carbide ceramics, and boron nitride ceramics.
  • FIG. 8 shows that the first positive electrode conductive carbon layer 1012 is located on the two opposite surfaces of the first positive electrode body layer 1011, in other embodiments, the first positive electrode conductive carbon layer 1012 can also be located on the second positive electrode body layer 1011. One of the two opposite surfaces of a positive electrode body layer 1011 .
  • FIG. 9 shows that the second anode ceramic layer 1023 is located on two opposite surfaces of the second anode body layer 1021, in other embodiments, the second anode ceramic layer 1023 may also be located on opposite sides of the second anode body layer 1021. on one of the two surfaces.
  • the positive electrode sheet 10 can also satisfy the above (16) and (17) at the same time, so that the resistance R 2 of the second positive electrode film layer 102 is greater than the resistance R 1 of the first positive electrode film layer 101 .
  • the resistance R 4 of the second negative electrode film layer 202 is greater than the resistance R 3 of the first negative electrode film layer 201 .
  • the surface of the first negative electrode active material has a conductive carbon layer.
  • the surface of the first negative electrode active material has a conductive carbon layer, and when the surface of the second negative electrode active material does not have a conductive carbon layer, the resistance R of the second negative electrode film layer 202 can be made greater than that of the first negative electrode film layer 201 Resistor R3 .
  • the conductivity of the first negative electrode conductive agent is greater than the conductivity of the second negative electrode conductive agent.
  • the resistance R 4 of the second negative electrode film layer 202 can be made greater than the resistance R 3 of the first negative electrode film layer 201 by making the first negative electrode film layer 201 contain a first negative electrode conductive agent with higher conductivity.
  • the compacted density of the first negative electrode film layer 201 is smaller than the compacted density of the second negative electrode film layer 202 .
  • the first negative electrode film layer 201 includes a first negative electrode main body layer 2011 and a first negative electrode conductive carbon layer 2012, and the first negative electrode conductive carbon layer 2012 is located on the two opposite surfaces of the first negative electrode main body layer 2011 on at least one of the surfaces.
  • the second negative electrode film layer 202 includes a second negative electrode body layer 2021 and a second negative electrode ceramic layer 2023, and the second negative electrode ceramic layer 2023 is located on the two opposite surfaces of the second negative electrode body layer 2021. on at least one surface.
  • the second negative electrode ceramic layer 2023 includes one or more of alumina ceramics, silicon nitride ceramics, silicon carbide ceramics, and boron nitride ceramics.
  • FIG. 11 shows that the first negative electrode conductive carbon layer 2012 is located on the two opposite surfaces of the first negative electrode body layer 2011, in other embodiments, the first negative electrode conductive carbon layer 2012 can also be located on the second negative electrode body layer 2011. One of the two opposite surfaces of a negative electrode body layer 2011 .
  • FIG. 12 shows that the second negative electrode ceramic layer 2023 is located on two opposite surfaces of the second negative electrode main body layer 2021, in other embodiments, the second negative electrode ceramic layer 2023 may also be located on opposite sides of the second negative electrode main body layer 2021. on one of the two surfaces.
  • the negative electrode sheet 20 can also satisfy the above (f) and (g) at the same time, so that the resistance R 4 of the second negative electrode film layer 202 is greater than the resistance R 3 of the first negative electrode film layer 201 .
  • the resistance R 4 of the second negative electrode film layer 202 is smaller than the resistance R 3 of the first negative electrode film layer 201 .
  • the surface of the second negative electrode active material has a conductive carbon layer.
  • the surface of the first negative electrode active material does not have a conductive carbon layer, when the surface of the second negative electrode active material has a conductive carbon layer, the resistance R of the second negative electrode film layer 202 can be made less than that of the first negative electrode film layer 201 Resistor R3 .
  • the conductivity of the first negative electrode conductive agent is smaller than the conductivity of the second negative electrode conductive agent.
  • the resistance R 4 of the second negative electrode film layer 202 can be made smaller than the resistance R 3 of the first negative electrode film layer 201 .
  • w 9 represents the mass percentage of the first negative electrode binder based on the total mass of the first negative electrode film layer 201
  • w 10 represents the total mass based on the second negative electrode film layer 202 , the mass percentage of the second negative electrode binder.
  • the compacted density of the first negative electrode film layer 201 is greater than the compacted density of the second negative electrode film layer 202 .
  • the second negative electrode film layer 202 includes a second negative electrode body layer 2021 and a second negative electrode conductive carbon layer 2022, and the second negative electrode conductive carbon layer 2022 is located on the opposite surfaces of the second negative electrode body layer 2021 on at least one of the surfaces.
  • the first negative electrode film layer 201 includes a first negative electrode body layer 2011 and a first negative electrode ceramic layer 2013, and the first negative electrode ceramic layer 2013 is located on the two opposite surfaces of the first negative electrode body layer 2011. on at least one surface.
  • the first negative electrode ceramic layer 2013 includes one or more of alumina ceramics, silicon nitride ceramics, silicon carbide ceramics, and boron nitride ceramics.
  • FIG. 14 shows that the second negative electrode conductive carbon layer 2022 is located on the two opposite surfaces of the second negative electrode body layer 2021, in other embodiments, the second negative electrode conductive carbon layer 2022 is located on the second negative electrode body layer 2021.
  • One of the two opposite surfaces of the main body layer 2021 FIG. 15 shows that the first negative electrode ceramic layer 2013 is located on two opposite surfaces of the first negative electrode main body layer 2011, in other embodiments, the first negative electrode ceramic layer 2013 is located on two opposite surfaces of the first negative electrode main body layer 2011. on one of the surfaces.
  • the negative electrode sheet 20 can also satisfy the above (m) and (n) at the same time, so that the resistance R 4 of the second negative electrode film layer 202 is smaller than the resistance R 3 of the first negative electrode film layer 201 .
  • a metal foil or a composite current collector can be used as the positive electrode current collector.
  • the metal foil aluminum foil may be used for the positive electrode current collector.
  • the composite current collector may include a polymer material base and a metal material layer formed on at least one surface of the polymer material base.
  • the metal material may be selected from one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy.
  • the polymer material base layer can be selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), poly Ethylene (PE), etc.
  • the first positive electrode active material and the second positive electrode active material may be positive electrode active materials known in the art for secondary batteries.
  • the first positive electrode active material and the second positive electrode active material each independently include one or more of lithium transition metal oxides, olivine-structured lithium-containing phosphates and their respective modified compounds.
  • lithium transition metal oxides may include, but are not limited to, 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 One or more of lithium nickel cobalt aluminum oxide and its modified compounds.
  • olivine-structured lithium-containing phosphates may include, but are not limited to, lithium iron phosphate, a composite of lithium iron phosphate and carbon, lithium manganese phosphate, a composite of lithium manganese phosphate and carbon, lithium manganese iron phosphate, lithium manganese iron phosphate
  • One or more of the composite materials with carbon and their respective modified compounds is not limited to these materials, and other conventionally known materials that can be used as a secondary battery positive electrode active material may also be used. These positive electrode active materials may be used alone or in combination of two or more.
  • the modification compound of each of the above-mentioned positive electrode active materials may be modified by doping, surface coating, or surface coating while doping.
  • the first positive electrode active material and the second positive electrode active material can also independently include the lithium transition metal oxide shown in formula 1 and the modified compound thereof. one or several.
  • M is selected from Mn, Al, Zr, Zn
  • Mn One or more of , Cu, Cr, Mg, Fe, V, Ti and B, and A is one or more of N, F, S and Cl.
  • the first positive electrode binder and the second positive electrode binder each independently include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene- One or more of propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PTFE polytetrafluoroethylene
  • tetrafluoroethylene-hexafluoropropylene copolymer tetrafluoroethylene-hexafluoropropylene copolymer
  • fluorine-containing acrylate resin fluorine-containing acrylate resin
  • the first positive electrode conductive agent and the second positive electrode conductive agent each independently include superconducting carbon, conductive graphite (such as KS-6), acetylene black, carbon black (such as Super P), Ketjen One or more of black, carbon dots, carbon nanotubes (CNT), graphene, and carbon nanofibers.
  • the first positive electrode film layer and the second positive electrode film layer are 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, the positive electrode conductive agent, the positive electrode binder and any other components in a solvent and stirring them uniformly.
  • the solvent may be N-methylpyrrolidone (NMP), but is not limited thereto.
  • a metal foil or a composite current collector can be used as the negative electrode current collector.
  • the metal foil copper foil can be used.
  • the composite current collector may include a polymer material base and a metal material layer formed on at least one surface of the polymer material base.
  • the metal material may be selected from one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy.
  • the polymer material base layer can be selected from polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), poly Ethylene (PE), etc.
  • the first negative electrode active material and the second negative electrode active material may be negative electrode active materials known in the art for secondary batteries.
  • the first negative electrode active material and the second negative electrode active material each independently include one or more of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate.
  • the silicon-based material can be selected from one or more of elemental silicon, silicon-oxygen compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys.
  • the tin-based material can be selected from one or more of simple tin, tin oxide compounds and tin alloys.
  • 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. These negative electrode active materials may be used alone or in combination of two or more.
  • the first negative electrode binder and the second negative electrode binder each independently include styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide ( One or more of PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • SBR styrene-butadiene rubber
  • PAA polyacrylic acid
  • PAAS sodium polyacrylate
  • PAAS polyacrylamide
  • PAM polyvinyl alcohol
  • SA sodium alginate
  • PMAA polymethacrylic acid
  • CMCS carboxymethyl chitosan
  • the first negative electrode conductive agent and the second negative electrode conductive agent each independently include superconducting carbon, conductive graphite (such as KS-6), acetylene black, carbon black (such as Super P), Ketjen One or more of black, carbon dots, carbon nanotubes (CNT), graphene and carbon nanofibers.
  • the first negative electrode film layer and the second negative electrode film layer may optionally include other additives, such as thickeners (such as sodium carboxymethylcellulose CMC-Na).
  • thickeners such as sodium carboxymethylcellulose CMC-Na
  • the first negative electrode film layer and the second negative electrode film layer are 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, the negative electrode conductive agent, the negative electrode binder and any other components in a solvent and stirring them uniformly.
  • the solvent may be deionized water, but is not limited thereto.
  • the electrolyte plays the role of conducting active ions between the positive pole piece and the negative pole piece.
  • the secondary battery of the present application has no specific limitation on the type of electrolyte, which can be selected according to requirements.
  • the electrolyte may be selected from at least one of solid electrolytes and liquid electrolytes (ie, electrolytic solutions).
  • the electrolyte is an electrolytic solution.
  • the electrolytic solution includes electrolyte salts and solvents.
  • the type of electrolyte salt is not limited, and can be selected according to actual needs.
  • the electrolyte salt may be selected from lithium hexafluorophosphate LiPF 6 , lithium tetrafluoroborate LiBF 4 , lithium perchlorate LiClO 4 , lithium hexafluoroarsenate LiAsF 6 , lithium bisfluorosulfonyl imide LiFSI, bistrifluoromethanesulfonyl Lithium amine LiTFSI, lithium trifluoromethanesulfonate LiTFS, lithium difluorooxalate borate LiDFOB, lithium difluorooxalate borate LiBOB, lithium difluorophosphate LiPO 2 F 2 , lithium difluorooxalate phosphate LiDFOP and lithium tetrafluorooxalate phosphate LiTFOP one or several.
  • the type of solvent is not limited, and can be selected according to actual needs.
  • the solvent may be selected from ethylene carbonate (EC), propylene carbonate (PC), ethylmethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropylene carbonate ester (DPC), methyl propyl carbonate (MPC), ethylene propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate (MA ), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), butyric acid
  • ethyl ester EB
  • 1,4-butyrolactone GBL
  • sulfolane SF
  • MSM dimethyl sulfone
  • the solvent is a non-aqueous solvent.
  • additives are optionally included in the electrolyte.
  • additives can include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain performances of batteries, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and additives that improve battery low-temperature performance. Additives etc.
  • Secondary batteries using electrolytes and some secondary batteries using solid electrolytes also include a separator.
  • the separator is arranged between the positive pole piece and the negative pole piece, which mainly plays the role of preventing the short circuit of the positive and negative poles, and at the same time allows active ions to pass through.
  • the present application has no particular limitation on the type of the isolation membrane, and any known porous structure isolation membrane with good chemical stability and mechanical stability can be selected.
  • the material of the isolation film can be selected from one or more of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation film can be a single-layer film or a multi-layer composite film. When the separator is a multilayer composite film, the materials of each layer may be the same or different.
  • the present application also provides a method for preparing an electrode assembly, the method may include the following steps:
  • CAP1 represents the first positive electrode film in Ah Layer capacity
  • CAP2 represents the capacity of the second positive film layer in Ah
  • R 1 represents the resistance of the first positive film layer in ⁇
  • R 2 represents the resistance of the second positive film layer in ⁇
  • R 3 Represents the resistance of the first negative electrode film layer in m ⁇
  • R 4 represents the resistance of the second negative electrode film layer in m ⁇ .
  • the electrode assembly obtained by the method of the present application can greatly prolong the cycle life of the secondary battery.
  • the positive electrode sheet, the separator, and the negative electrode sheet can be wound or laminated to form an electrode assembly.
  • step S40 optionally, the electrode assemblies satisfying 0.33 ⁇ CAP1/CAP2 ⁇ 1 and 0 ⁇ R 4 /R 3 ⁇ R 2 /R 1 ⁇ 20 are screened out.
  • step S40 optionally, the electrode assemblies satisfying 0.5 ⁇ CAP1/CAP2 ⁇ 1 and 0 ⁇ R 4 /R 3 ⁇ R 2 /R 1 ⁇ 20 are screened out.
  • step S40 optionally, the electrode assemblies satisfying 0.5 ⁇ CAP1/CAP2 ⁇ 0.9 and 0.1 ⁇ R 4 /R 3 ⁇ R 2 /R 1 ⁇ 2 are screened out.
  • the method further includes the following step: S50, screening the electrode assemblies further satisfying 1 ⁇ R 4 /R 3 ⁇ 30 and 0 ⁇ R 2 /R 1 ⁇ 20 at the same time.
  • the method further includes the following step: S50, screening out electrode assemblies that further satisfy 0 ⁇ R 4 /R 3 ⁇ 1 and 0 ⁇ R 2 /R 1 ⁇ 1 at the same time.
  • the secondary battery according to the present application can be assembled into a battery module, and 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. 17 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 may be fixed by fasteners.
  • the battery module 4 may also include a case having a housing space in which a plurality of secondary batteries 5 are accommodated.
  • the above-mentioned battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be 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 disposed in the battery box.
  • the battery box includes an upper box body 2 and a lower box body 3 , the upper box body 2 is used to cover the lower box body 3 and forms a closed space for accommodating the battery module 4 .
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • Embodiments of the present application further provide an electric device, the electric device includes at least one of the secondary battery, the battery module, and the battery pack of the present application.
  • the secondary battery, battery module or battery pack can be used as a power source of the electric device, and can also be used as an energy storage unit of the electric device.
  • the electric device can be, but not limited to, mobile devices (such as mobile phones, notebook computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • the electric device can select a secondary battery, a battery module or a battery pack according to its usage requirements.
  • FIG. 20 is a schematic diagram of an electrical device as an example.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle.
  • a battery pack or a battery module can be used.
  • the electric device may be a mobile phone, a tablet computer, a notebook computer, and the like.
  • the electrical device is usually required to be light and thin, and a secondary battery can be used as a power source.
  • the structure of the secondary battery is shown in FIG. 3 .
  • the positive electrode active material LiNi 0.5 Co 0.2 Mn 0.3 O 2 , the binder PVDF, and the conductive agent Super P in an appropriate amount of solvent NMP at a weight ratio of 96.2:1.1:2.7 to obtain the second positive electrode slurry.
  • the positive electrode slurry is coated on the side of the positive electrode current collector aluminum foil away from the separator.
  • the coating weight ratio of the first positive electrode slurry and the second positive electrode slurry is 0.76:1
  • the first positive electrode slurry is dried and cold-pressed to form the first positive electrode film layer
  • the second positive electrode slurry is dried
  • the second positive film layer is formed after cold pressing.
  • Negative electrode active material has the graphite of conductive carbon layer, conductive agent Super P, thickener CMC-Na, binding agent SBR by weight ratio 97:1:0.5:1.5 in appropriate amount of solvent deionized water and fully stir and mix, obtain the first A negative electrode slurry, the first negative electrode slurry is coated on the side of the negative electrode current collector copper foil away from the separator.
  • Negative electrode active material graphite, conductive agent Super P, thickener CMC-Na, binder SBR are fully stirred and mixed in an appropriate amount of solvent deionized water in a weight ratio of 97:1:0.5:1.5 to obtain the second negative electrode slurry, Coating the second negative electrode slurry on the side of the negative electrode current collector copper foil close to the separator.
  • the coating weights of the first negative electrode slurry and the second negative electrode slurry are the same, the first negative electrode slurry is dried and cold-pressed to form the first negative electrode film layer, and the second negative electrode slurry is dried and cold-pressed to form the second negative electrode slurry. Two negative film layers.
  • a porous polyethylene film was used as the separator.
  • EC ethylene carbonate
  • EMC ethyl methyl carbonate
  • DEC diethyl carbonate
  • a secondary battery is obtained.
  • the formation process is as follows: the secondary battery is charged to 3.0V with a constant current of 0.1C, and then charged to 3.75V with a constant current of 0.2C.
  • the capacity process is as follows: charge the secondary battery with a constant current of 0.33C to 4.4V, and then charge it with a constant voltage to 0.05C; discharge the secondary battery with a constant current of 0.33C to 2.5V, and then charge it with a constant current of 0.33C to 3.65V , and then constant voltage charging to 0.05C.
  • the preparation method of the secondary battery is similar to that of Example 1, except that the compacted density of the first negative electrode film layer is increased.
  • the preparation method of the secondary battery is similar to that of Example 1, except that the relevant parameters in the preparation of the negative electrode sheet are adjusted.
  • the preparation method of the secondary battery is similar to that of Example 1, except that the relevant parameters in the preparation of the negative electrode sheet are adjusted.
  • Negative electrode active material graphite, conductive agent Super P, thickener CMC-Na, binder SBR are fully stirred and mixed in an appropriate amount of solvent deionized water in a weight ratio of 97:1:0.5:1.5 to obtain the first negative electrode slurry,
  • the first negative electrode slurry was coated on the side of the negative electrode collector copper foil away from the separator, and the side of the negative electrode collector away from the separator was also coated with a conductive carbon layer with a thickness of 0.5 ⁇ m.
  • the preparation method of the secondary battery is similar to that of Example 1, except that the relevant parameters in the preparation of the negative electrode sheet are adjusted.
  • Negative electrode active material graphite, conductive agent Super P, thickener CMC-Na, binder SBR are fully stirred and mixed in an appropriate amount of solvent deionized water in a weight ratio of 97:1:0.5:1.5 to obtain the first negative electrode slurry, Coating the first negative electrode slurry on the side of the negative electrode current collector copper foil away from the separator.
  • Negative electrode active material graphite, conductive agent Super P, thickener CMC-Na, binder SBR are fully stirred and mixed in an appropriate amount of solvent deionized water in a weight ratio of 97:1:0.5:1.5 to obtain the second negative electrode slurry,
  • the second negative electrode slurry was coated on the side of the negative electrode current collector copper foil close to the separator, and the side of the negative electrode current collector close to the separator was also coated with an alumina ceramic layer with a thickness of 0.5 ⁇ m.
  • the preparation method of the secondary battery is similar to that of Example 1, except that the relevant parameters in the preparation of the negative electrode sheet are adjusted.
  • Negative electrode active material graphite, conductive agent Super P, thickener CMC-Na, binder SBR are fully stirred and mixed in an appropriate amount of solvent deionized water in a weight ratio of 97:1:0.5:1.5 to obtain the second negative electrode slurry,
  • the second negative electrode slurry was coated on the side of the negative electrode current collector copper foil close to the separator, and the side of the negative electrode current collector close to the separator was also coated with an alumina ceramic layer with a thickness of 0.5 ⁇ m.
  • the preparation method of the secondary battery is similar to that of Example 1, except that the relevant parameters in the preparation of the negative electrode sheet are adjusted.
  • Negative electrode active material graphite, conductive agent Super P, thickener CMC-Na, binder SBR are fully stirred and mixed in an appropriate amount of solvent deionized water in a weight ratio of 97:1:0.5:1.5 to obtain the first negative electrode slurry, Coating the first negative electrode slurry on the side of the negative electrode current collector copper foil away from the separator.
  • Negative electrode active material graphite, conductive agent Super P, thickener CMC-Na, binder SBR are fully stirred and mixed in an appropriate amount of solvent deionized water in a weight ratio of 97:1:0.5:1.5 to obtain the second negative electrode slurry,
  • the second negative electrode slurry was coated on the side of the negative electrode current collector copper foil close to the separator, and the side of the negative electrode current collector close to the separator was also coated with an alumina ceramic layer with a thickness of 1.2 ⁇ m.
  • the preparation method of the secondary battery is similar to that of Example 1, except that the relevant parameters in the preparation of the negative electrode sheet are adjusted.
  • Negative electrode active material graphite, conductive agent Super P, thickener CMC-Na, binder SBR are fully stirred and mixed in an appropriate amount of solvent deionized water in a weight ratio of 97:1:0.5:1.5 to obtain the second negative electrode slurry,
  • the second negative electrode slurry was coated on the side of the negative electrode current collector copper foil close to the separator, and the side of the negative electrode current collector close to the separator was coated with an alumina ceramic layer with a thickness of 1.2 ⁇ m.
  • the preparation method of the secondary battery is similar to that of Example 1, except that the relevant parameters in the preparation of the negative electrode sheet are adjusted.
  • Negative electrode active material graphite, conductive agent Super P, thickener CMC-Na, binder SBR are fully stirred and mixed in an appropriate amount of solvent deionized water in a weight ratio of 97:1:0.5:1.5 to obtain the second negative electrode slurry,
  • the second negative electrode slurry was coated on the side of the negative electrode current collector copper foil close to the separator, and the side of the negative electrode current collector close to the separator was also coated with an alumina ceramic layer with a thickness of 1.5 ⁇ m.
  • the preparation method of the secondary battery is similar to that of Example 1, except that the relevant parameters in the preparation of the negative electrode sheet are adjusted.
  • Negative electrode active material graphite, conductive agent Super P, thickener CMC-Na, binder SBR are fully stirred and mixed in an appropriate amount of solvent deionized water in a weight ratio of 97:1:0.5:1.5 to obtain the second negative electrode slurry,
  • the second negative electrode slurry was coated on the side of the negative electrode current collector copper foil close to the separator, and the side of the negative electrode current collector close to the separator was also coated with an alumina ceramic layer with a thickness of 2 ⁇ m.
  • the preparation method of the secondary battery is similar to that of Example 1, except that the relevant parameters in the preparation of the negative electrode sheet are adjusted.
  • the side of the negative electrode current collector away from the separator is also coated with a conductive carbon layer with a thickness of 2 ⁇ m, and the side of the negative electrode current collector close to the separator is also coated with an alumina ceramic layer with a thickness of 2 ⁇ m.
  • the preparation method of the secondary battery is similar to that of Example 1, except that the relevant parameters in the preparation of the negative electrode sheet are adjusted.
  • a conductive carbon layer with a thickness of 2 ⁇ m is also coated on the side of the negative electrode current collector away from the separator, and an alumina ceramic layer with a thickness of 4 ⁇ m is coated on the side of the negative electrode current collector close to the separator.
  • the preparation method of the secondary battery is similar to that of Example 1, except that the relevant parameters in the preparation of the positive pole piece and the negative pole piece are adjusted.
  • the coating weight ratio of the first positive electrode slurry and the second positive electrode slurry is 0.6:1, and the side of the positive electrode current collector away from the separator is also coated with an alumina ceramic layer with a thickness of 2 ⁇ m.
  • a conductive carbon layer with a thickness of 2 ⁇ m is also coated on the side of the negative electrode collector away from the separator, and an alumina ceramic layer with a thickness of 6 ⁇ m is coated on the side of the negative electrode collector close to the separator.
  • the preparation method of the secondary battery is similar to that of Example 1, except that the relevant parameters in the preparation of the negative electrode sheet are adjusted.
  • a conductive carbon layer with a thickness of 2 ⁇ m is also coated on the side of the negative electrode collector away from the separator, and an alumina ceramic layer with a thickness of 6 ⁇ m is coated on the side of the negative electrode collector close to the separator.
  • the preparation method of the secondary battery is similar to that of Example 1, except that the relevant parameters in the preparation of the positive pole piece and the negative pole piece are adjusted.
  • Negative electrode active material graphite, conductive agent Super P, thickener CMC-Na, binder SBR are fully stirred and mixed in an appropriate amount of solvent deionized water in a weight ratio of 97:1:0.5:1.5 to obtain the first negative electrode slurry, Coating the first negative electrode slurry on the side of the negative electrode current collector copper foil away from the separator.
  • Negative electrode active material graphite, conductive agent Super P, thickener CMC-Na, binder SBR are fully stirred and mixed in an appropriate amount of solvent deionized water in a weight ratio of 97:1:0.5:1.5 to obtain the second negative electrode slurry,
  • the second negative electrode slurry was coated on the side of the negative electrode current collector copper foil close to the separator, and the side of the negative electrode current collector close to the separator was also coated with an alumina ceramic layer with a thickness of 0.5 ⁇ m.
  • the preparation method of the secondary battery is similar to that of Example 1, except that the relevant parameters in the preparation of the negative electrode sheet are adjusted.
  • Negative electrode active material has the graphite of conductive carbon layer, conductive agent Super P, thickener CMC-Na, binding agent SBR by weight ratio 97.1:0.9:0.5:1.5 in appropriate amount of solvent deionized water and fully stir and mix, obtain the first A negative electrode slurry.
  • the preparation method of the secondary battery is similar to that of Example 1, except that the relevant parameters in the preparation of the positive pole piece and the negative pole piece are adjusted.
  • Negative electrode active material has the graphite of conductive carbon layer, conductive agent Super P, thickener CMC-Na, binding agent SBR by weight ratio 97.05:0.95:0.5:1.5 in appropriate amount of solvent deionized water and fully stir and mix, obtain the first A negative electrode slurry.
  • Negative electrode active material has the graphite of conductive carbon layer, conductive agent Super P, thickener CMC-Na, binding agent SBR by weight ratio 97:1:0.5:1.5 in appropriate amount of solvent deionized water and fully stir and mix, obtain the first Two negative electrode slurry.
  • the preparation method of the secondary battery is similar to that of Example 1, except that the relevant parameters in the preparation of the positive pole piece and the negative pole piece are adjusted.
  • Negative electrode active material has the graphite of conductive carbon layer, conductive agent Super P, thickener CMC-Na, binding agent SBR by weight ratio 97:1:0.5:1.5 in appropriate amount of solvent deionized water and fully stir and mix, obtain the first A negative electrode slurry.
  • Negative electrode active material has the graphite of conductive carbon layer, conductive agent Super P, thickener CMC-Na, binding agent SBR by weight ratio 97:1:0.5:1.5 in appropriate amount of solvent deionized water and fully stir and mix, obtain the second Negative slurry.
  • the preparation method of the secondary battery is similar to that of Example 1, except that the relevant parameters in the preparation of the positive pole piece and the negative pole piece are adjusted.
  • the coating weight ratio of the first positive electrode slurry to the second positive electrode slurry was 0.84:1, and the side of the positive electrode current collector close to the separator was also coated with an alumina ceramic layer with a thickness of 2 ⁇ m.
  • Negative electrode active material has the graphite of conductive carbon layer, conductive agent Super P, thickener CMC-Na, binding agent SBR by weight ratio 97.05:0.95:0.5:1.5 in appropriate amount of solvent deionized water and fully stir and mix, obtain the first A negative electrode slurry.
  • Negative electrode active material has the graphite of conductive carbon layer, conductive agent Super P, thickener CMC-Na, binding agent SBR by weight ratio 97:1:0.5:1.5 in appropriate amount of solvent deionized water and fully stir and mix, obtain the first Two negative electrode slurry.
  • the preparation method of the secondary battery is similar to that of Example 1, except that the relevant parameters in the preparation of the positive pole piece and the negative pole piece are adjusted.
  • the coating weight ratio of the first positive electrode slurry and the second positive electrode slurry is 0.84:1, and the side of the positive electrode current collector close to the separator is also coated with an alumina ceramic layer with a thickness of 1 ⁇ m.
  • Negative electrode active material has the graphite of conductive carbon layer, conductive agent Super P, thickener CMC-Na, binding agent SBR by weight ratio 96.95:1.05:0.5:1.5 in appropriate amount of solvent deionized water and fully stir and mix, obtain the first Two negative electrode slurry.
  • the preparation method of the secondary battery is similar to that of Example 1, except that the relevant parameters in the preparation of the positive pole piece and the negative pole piece are adjusted.
  • the positive electrode slurry is coated on the side of the positive electrode current collector aluminum foil close to the separator, and the side of the positive electrode current collector close to the separator is coated with an alumina ceramic layer with a thickness of 1 ⁇ m.
  • the positive electrode slurry is coated on the side of the positive electrode current collector aluminum foil away from the separator.
  • the coating weight ratio of the first positive electrode slurry and the second positive electrode slurry is 0.84:1.
  • Negative electrode active material graphite, conductive agent Super P, thickener CMC-Na, binder SBR are fully stirred and mixed in an appropriate amount of solvent deionized water in a weight ratio of 97:1:0.5:1.5 to obtain the first negative electrode slurry,
  • the first negative electrode slurry was coated on the side of the negative electrode collector copper foil away from the separator, and the side of the negative electrode collector away from the separator was coated with an alumina ceramic layer with a thickness of 0.5 ⁇ m.
  • Negative electrode active material has the graphite of conductive carbon layer, conductive agent Super P, thickener CMC-Na, binding agent SBR by weight ratio 97:1:0.5:1.5 in appropriate amount of solvent deionized water and fully stir and mix, obtain the first Two negative electrode slurry.
  • the preparation method of the secondary battery is similar to that of Example 1, except that the relevant parameters in the preparation of the positive pole piece and the negative pole piece are adjusted.
  • the coating weight ratio of the first positive electrode slurry to the second positive electrode slurry was 0.84:1, and the side of the positive electrode current collector close to the separator was also coated with an alumina ceramic layer with a thickness of 2 ⁇ m.
  • Negative electrode active material has the graphite of conductive carbon layer, conductive agent Super P, thickener CMC-Na, binding agent SBR by weight ratio 97:1:0.5:1.5 in appropriate amount of solvent deionized water and fully stir and mix, obtain the first A negative electrode slurry.
  • Negative electrode active material has the graphite of conductive carbon layer, conductive agent Super P, thickener CMC-Na, binding agent SBR by weight ratio 97:1:0.5:1.5 in appropriate amount of solvent deionized water and fully stir and mix, obtain the first Two negative electrode slurry.
  • the preparation method of the secondary battery is similar to that of Example 1, except that the relevant parameters in the preparation of the positive pole piece and the negative pole piece are adjusted.
  • the coating weights of the first positive electrode slurry and the second positive electrode slurry are the same.
  • Negative electrode active material graphite, conductive agent Super P, thickener CMC-Na, and binder SBR are fully stirred and mixed in an appropriate amount of solvent deionized water in a weight ratio of 97:1:0.5:1.5 to obtain negative electrode slurry;
  • the slurry is coated on both surfaces of the negative electrode current collector copper foil, and after drying and cold pressing, the negative electrode sheet is obtained.
  • the coating weights on both sides of the negative electrode current collector are the same.
  • the preparation method of the secondary battery is similar to that of Comparative Example 1, except that the relevant parameters in the preparation of the negative pole piece are adjusted.
  • the coating weight ratio of the first positive electrode slurry and the second positive electrode slurry was 0.76:1.
  • the preparation method of the secondary battery is similar to that of Example 1, except that the relevant parameters in the preparation of the positive pole piece and the negative pole piece are adjusted.
  • Negative electrode active material has the graphite of conductive carbon layer, conductive agent Super P, thickener CMC-Na, binding agent SBR by weight ratio 96.95:1.05:0.5:1.5 in appropriate amount of solvent deionized water and fully stir and mix, obtain the first Two negative electrode slurry.
  • the capacity CAP1 of the first positive electrode film layer is obtained by the formula CAP0 ⁇ S 1 /S 0 , S 0 is the area of the small disc, and S 1 is the area of the first positive electrode film layer.
  • the capacity CAP2 of the second positive electrode film layer is obtained by the formula CAP0 ⁇ S 2 /S 0 , where S 0 is the area of the small disc, and S 2 is the area of the second positive electrode film layer.
  • Wipe off the second positive electrode film layer of the cold-pressed positive electrode sheet then place it in parallel between the two conductive terminals of the electrode sheet resistance meter, apply a certain pressure to fix it, and obtain the resistance R 1 of the first positive electrode film layer.
  • Wipe off the first positive film layer of the cold-pressed positive electrode plate then place it in parallel between the two conductive terminals of the plate resistance meter, apply a certain pressure to fix it, and obtain the resistance R 2 of the second positive film layer.
  • Wipe off the second negative electrode film layer of the cold-pressed negative electrode sheet then place it in parallel between the two conductive terminals of the electrode sheet resistance meter, apply a certain pressure to fix it, and obtain the resistance R 3 of the first negative electrode film layer.
  • Wipe off the first negative electrode film layer of the cold-pressed negative electrode sheet then place it in parallel between the two conductive terminals of the electrode sheet resistance meter, apply a certain pressure to fix it, and obtain the resistance R 4 of the second negative electrode film layer.
  • the model of the plate resistance meter is IEST BER1000 (from Yuanneng Technology Co., Ltd.), the diameter of the conductive terminal is 14mm, the applied pressure is 15Mpa-27Mpa, and the time range of the sampling point is 10s-20s.
  • Mass energy density (Wh/Kg) of the secondary battery discharge energy Q/mass m of the secondary battery.
  • the secondary battery is subjected to cyclic charge and discharge test according to the above method, and the discharge capacity after each cycle is recorded until the discharge capacity of the secondary battery decays to 80% of the discharge capacity of the first cycle, and the number of cycles at this time is used to characterize the secondary battery.
  • Table 1 and Table 2 show the performance test results of Examples 1-22 and Comparative Examples 1-3.
  • the electrode assembly can satisfy R 4 /R 3 -R 2 /R 1 ⁇ 0, which can delay the capacity of the secondary battery Attenuate and greatly extend the cycle life of secondary batteries. Further, when the electrode assembly satisfies 0 ⁇ R 4 /R 3 -R 2 /R 1 ⁇ 20, the secondary battery can have a greatly extended cycle life and high energy density at the same time.

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Abstract

本申请提供一种电极组件、二次电池、电池模块、电池包及用电装置，所述电极组件包括正极极片、负极极片以及位于所述正极极片和所述负极极片之间的隔离膜，所述正极极片满足0＜CAP1/CAP2＜1，CAP1表示以Ah计的第一正极膜层的容量，CAP2表示以Ah计的第二正极膜层的容量，所述电极组件满足R4/R3-R2/R1≥0，R1表示以Ω计的第一正极膜层的电阻，R2表示以Ω计的第二正极膜层的电阻，R3表示以mΩ计的第一负极膜层的电阻，R4表示以mΩ计的第二负极膜层的电阻。本申请能大幅延长二次电池的循环寿命。

Description

电极组件、二次电池、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，具体涉及一种电极组件、二次电池、电池模块、电池包及用电装置。
背景技术
近年来，随着二次电池在各类电子产品和新能源汽车等产业的应用及推广，其能量密度受到越来越多的关注。在二次电池充放电过程中，活性离子(例如锂离子)在正极极片和负极极片之间往返嵌入和脱出，由于活性材料结构变化、电解液分解、活性材料表面SEI膜的生成和破坏等，活性离子不可避免地被消耗，二次电池容量不断衰减且难以具有更长的循环寿命。
发明内容
本申请的目的在于提供一种电极组件、二次电池、电池模块、电池包及用电装置，旨在大幅延长二次电池的循环寿命。
本申请第一方面提供一种电极组件，其包括正极极片、负极极片以及位于所述正极极片和所述负极极片之间的隔离膜，所述正极极片包括正极集流体以及位于所述正极集流体相对的两个表面上的第一正极膜层和第二正极膜层，所述负极极片包括负极集流体以及位于所述负极集流体相对的两个表面上的第一负极膜层和第二负极膜层；所述第一正极膜层位于所述正极集流体靠近所述隔离膜的一侧并且所述第二负极膜层位于所述负极集流体靠近所述隔离膜的一侧，或，所述第一正极膜层位于所述正极集流体远离所述隔离膜的一侧并且所述第二负极膜层位于所述负极集流体远离所述隔离膜的一侧；其中，所述正极极片满足0＜CAP1/CAP2＜1，CAP1表示以Ah计的第一正极膜层的容量，CAP2表示以Ah计的第二正极膜层的容量，所述电极组件满足R 4/R 3-R 2/R 1≥0，R 1表示以Ω计的第一正极膜层的电阻，R 2表示以Ω计的第二正极膜层的电阻，R 3表示以mΩ计的第一负极膜层的电阻，R 4表示以mΩ计的第二负极膜层的电阻。
在本申请的电极组件中，正极极片两面存储的容量不同，通过合理设置正极极片两面电阻与负极极片两面电阻之间的关系，能够提升充电过程中低容量正极膜层的电压响应速度，增加低容量正极膜层与高容量正极膜层的电位差，从而使高容量正极膜层具有足量的活性离子预存。随着二次电池循环过程进行，这部分预存的活性离子还能逐步释放，以补充活性离子消耗，从而延缓二次电池容量衰减并大幅延长二次电池循环寿命。
在本申请任意实施方式中，电极组件满足0≤R 4/R 3-R 2/R 1≤20。可选地，电极组件满足0＜R 4/R 3-R 2/R 1≤20。可选地，0.1≤R 4/R 3-R 2/R 1≤2。
在本申请任意实施方式中，正极极片满足0.33≤CAP1/CAP2＜1。可选地，正极极 片满足0.5≤CAP1/CAP2＜1。可选地，正极极片满足0.5≤CAP1/CAP2≤0.9。
第一正极膜层的容量CAP1与第二正极膜层的容量CAP2的比值在合适的范围内时，能使二次电池在具有更长循环寿命的同时，还具有高能量密度。
在本申请任意实施方式中，0Ω＜R 1≤20Ω。可选地，0Ω＜R 1≤5Ω。
在本申请任意实施方式中，0Ω＜R 2≤20Ω。可选地，0Ω＜R 2≤5Ω。
在本申请任意实施方式中，0mΩ＜R 3≤200mΩ。可选地，0mΩ＜R 3≤50mΩ。
在本申请任意实施方式中，0mΩ＜R 4≤200mΩ。可选地，0mΩ＜R 4≤50mΩ。
第一正极膜层、第二正极膜层、第一负极膜层和第二负极膜层的电阻分别在合适的范围内时，正极极片和负极极片的一致性更好，有利于二次电池获得更长的循环寿命。
在本申请任意实施方式中，第一正极膜层包括第一正极活性材料，第二正极膜层包括第二正极活性材料，正极极片满足下述(1)～(3)中的一个或几个：(1)第一正极膜层的涂布重量小于第二正极膜层的涂布重量，(2)第一正极活性材料的克容量小于第二正极活性材料的克容量，(3)w 1＜w 2，w 1表示基于第一正极膜层的总质量，第一正极活性材料的质量百分含量，w 2表示基于第二正极膜层的总质量，第二正极活性材料的质量百分含量。
在本申请任意实施方式中，负极极片满足R 4/R 3≥1，且电极组件满足0≤R 4/R 3-R 2/R 1≤20。可选地，0≤R 4/R 3-R 2/R 1≤5。可选地，0.1≤R 4/R 3-R 2/R 1≤2。
在本申请任意实施方式中，负极极片满足R 4/R 3≥1，正极极片满足0＜R 2/R 1≤20，且电极组件满足0≤R 4/R 3-R 2/R 1≤20。可选地，0≤R 4/R 3-R 2/R 1≤5。可选地，0.1≤R 4/R 3-R 2/R 1≤2。
在本申请任意实施方式中，负极极片满足1≤R 4/R 3≤30，正极极片满足0＜R 2/R 1≤20，且电极组件满足0≤R 4/R 3-R 2/R 1≤20。可选地，0≤R 4/R 3-R 2/R 1≤5。可选地，0.1≤R 4/R 3-R 2/R 1≤2。
在本申请任意实施方式中，负极极片满足0＜R 4/R 3＜1，正极极片满足0＜R 2/R 1＜1，且电极组件满足0≤R 4/R 3-R 2/R 1＜1。可选地，0＜R 4/R 3-R 2/R 1＜1。可选地，0.1≤R 4/R 3-R 2/R 1≤0.9。
在本申请任意实施方式中，负极极片满足0＜R 4/R 3＜1，正极极片满足0.05≤R 2/R 1≤0.9，且电极组件满足0≤R 4/R 3-R 2/R 1＜1。可选地，0＜R 4/R 3-R 2/R 1＜1。可选地，0.1≤R 4/R 3-R 2/R 1≤0.9。
在本申请任意实施方式中，负极极片满足0.05≤R 4/R 3≤0.9，正极极片满足0.05≤R 2/R 1≤0.9，且电极组件满足0≤R 4/R 3-R 2/R 1＜1。可选地，0＜R 4/R 3-R 2/R 1＜1。
在本申请任意实施方式中，正极极片满足R 2/R 1＝1，且负极极片满足R 4/R 3＝1。
本申请第二方面提供一种二次电池，其包括外包装、电解质以及根据本申请第一方面的电极组件。
在本申请任意实施方式中，外包装包括壳体和盖板，壳体具有容纳腔和开口，电极组件容纳于容纳腔中，盖板用于封闭壳体的开口。
本申请第三方面提供一种电池模块，其包括本申请第二方面的二次电池。
本申请第四方面提供一种电池包，其包括本申请第二方面的二次电池、第三方面的电池模块中的一种。
本申请第五方面提供一种用电装置，其包括本申请第二方面的二次电池、第三方面的电池模块、第四方面的电池包中的至少一种。
本申请的电池模块、电池包和用电装置包括本申请提供的二次电池，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是本申请的二次电池的一实施方式的分解示意图。
图3是本申请的电极组件的一实施方式的结构示意图。
图4是本申请的电极组件的另一实施方式的结构示意图。
图5是本申请的电极组件的另一实施方式的结构示意图。
图6是本申请的电极组件的另一实施方式的结构示意图。
图7是本申请的电极组件的另一实施方式的结构示意图。
图8是本申请的电极组件的另一实施方式的结构示意图。
图9是本申请的电极组件的另一实施方式的结构示意图。
图10是本申请的电极组件的另一实施方式的结构示意图。
图11是本申请的电极组件的另一实施方式的结构示意图。
图12是本申请的电极组件的另一实施方式的结构示意图。
图13是本申请的电极组件的另一实施方式的结构示意图。
图14是本申请的电极组件的另一实施方式的结构示意图。
图15是本申请的电极组件的另一实施方式的结构示意图。
图16是本申请的电极组件的另一实施方式的结构示意图。
图17是本申请的电池模块的一实施方式的示意图。
图18是本申请的电池包的一实施方式的示意图。
图19是图18所示的电池包的实施方式的分解图。
图20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。
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电极组件、二次电池、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)。
电极组件及二次电池
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。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。图1是作为一个示例的方形结构的二次电池5的示意图。
二次电池5包括外包装、电极组件以及电解质，所述外包装用于封装所述电极组件及所述电解质。在一些实施例中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，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)中的一种或几种。在一些实施例中，如图2所示，外包装可包括壳体51和盖板53。其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53用于盖设所述开口，以封闭所述容纳腔。电极组件52封装于所述容 纳腔，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。
发明人经过大量研究提出了一种具有大幅延长循环寿命的电极组件。图3为根据本申请的电极组件的实施例的结构示意图。如图3所示，电极组件52包括正极极片10、负极极片20和隔离膜30，其中，隔离膜30位于正极极片10和负极极片20之间，正极极片10、负极极片20和隔离膜30可经卷绕工艺或叠片工艺形成电极组件52。
正极极片10包括第一正极膜层101、第二正极膜层102和正极集流体103，第一正极膜层101和第二正极膜层102位于正极集流体103相对的两个表面上。第一正极膜层101包括第一正极活性材料、第一正极导电剂和第一正极粘结剂，第二正极膜层102包括第二正极活性材料、第二正极导电剂和第二正极粘结剂。
负极极片20包括第一负极膜层201、第二负极膜层202和负极集流体203，第一负极膜层201和第二负极膜层202位于负极集流体203相对的两个表面上。第一负极膜层201包括第一负极活性材料、第一负极导电剂和第一负极粘结剂，第二负极膜层202包括第二负极活性材料、第二负极导电剂和第二负极粘结剂。
第一正极膜层101和第二负极膜层202同时靠近或远离隔离膜30设置。如图3所示，在一些实施例中，第一正极膜层101位于正极集流体103靠近隔离膜30的一侧并且第二负极膜层202位于负极集流体203靠近隔离膜30的一侧。如图4所示，在一些实施例中，第一正极膜层101位于正极集流体103远离隔离膜30的一侧并且第二负极膜层202位于负极集流体203远离隔离膜30的一侧。
在本申请的电极组件的实施例中，正极极片10满足0＜CAP1/CAP2＜1，CAP1表示以Ah计的第一正极膜层101的容量，CAP2表示以Ah计的第二正极膜层102的容量。电极组件52满足R 4/R 3-R 2/R 1≥0，R 1表示以Ω计的第一正极膜层101的电阻，R 2表示以Ω计的第二正极膜层102的电阻，R 3表示以mΩ计的第一负极膜层201的电阻，R 4表示以mΩ计的第二负极膜层202的电阻。
二次电池充电过程中，活性离子从正极脱出，活性离子脱出速率和脱出数量与二次电池充电电流和充电时间相关，充电电流越大、充电时间越长，活性离子脱出数量越多，脱出容量占比(即脱出容量与存储容量的比值)越高，正极电压越高。二次电池充电过程中，电流均匀分布在正极极片，低容量正极膜层(本申请中的第一正极膜层)和高容量正极膜层(本申请中的第二负极膜层)同时进行活性离子脱出且活性离子脱出数量一致。但是，由于低容量正极膜层和高容量正极膜层存储的容量不同，因此，低容量正极膜层和高容量正极膜层脱出容量占比不同、对应的电压也不同。同时，高容量正极膜层脱出容量占比较低容量正极膜层低，由于低容量正极膜层和高容量正极膜层为并联结构，二次电池充电截止电压会以先达到截止电压一侧触发，即以低容量正极膜层一侧触发，因此，高容量正极膜层能具有活性离子预存。此外，低容量正极膜层和高容量正极膜层之间存在电位差，因此，高容量正极膜层预存的活性离子还能逐步脱出溶解到电解液并转移至低容量正极膜层中，从而高容量正极膜层能够补充低容量正极膜层活性离子消耗，延缓二次电池容量衰减并大幅延长二次电池循环寿命。
常规正极极片双面涂布设计在实际应用过程中往往由于电压响应不够及时，导致正极极片无法实现活性离子预存，或没有足量的活性离子预存，对二次电池循环寿命提 升不明显，无法使二次电池具有更长的循环寿命。在本申请的电极组件中，正极极片两面存储的容量不同，通过合理设置正极极片两面电阻与负极极片两面电阻之间的关系，能够提升充电过程中低容量正极膜层的电压响应速度，增加低容量正极膜层与高容量正极膜层的电位差，从而使高容量正极膜层具有足量的活性离子预存。随着二次电池循环过程进行，这部分预存的活性离子还能逐步释放，以补充活性离子消耗，从而延缓二次电池容量衰减并大幅延长二次电池循环寿命。
当电极组件52不满足R 4/R 3-R 2/R 1≥0时，低容量正极膜层与高容量正极膜层脱出容量占比差异较小，高容量正极膜层没有足量的活性离子预存，对二次电池循环寿命提升不明显。
在本申请中，正极膜层的容量为本领域公知的含义，可以用本领域已知的仪器及方法进行测定。例如，采用蓝电测试仪进行测试。作为示例，正极膜层的容量可采用如下方法进行测试：将经冷压的正极极片其中一面的正极膜层擦拭掉得到单面涂布的正极极片，将单面涂布的正极极片冲切成面积为S 0的小圆片后，在手套箱中组装成扣式电池，以0.1mA恒流充电至充电截止电压，以0.1mA恒流放电至放电截止电压，得到放电容量CAP0，通过公式CAP0×S/S 0得到该正极膜层的容量，S 0为小圆片的面积，S为该正极膜层的面积。
具体地，第一正极膜层的容量CAP1可采用如下方法进行测试：将经冷压的正极极片的第二正极膜层擦拭掉后冲切成面积为S 0的小圆片，将小圆片在手套箱中组装成扣式电池，之后在蓝电测试仪上以0.1mA恒流充电至充电截止电压，再以0.1mA恒流放电至放电截止电压，得到放电容量CAP0，通过公式CAP0×S 1/S 0得到第一正极膜层的容量CAP1，S 0为小圆片的面积，S 1为第一正极膜层的面积。第二正极膜层的容量CAP2可采用如下方法进行测试：将经冷压的正极极片的第一正极膜层擦拭掉后冲切成面积为S 0的小圆片，将小圆片在手套箱中组装成扣式电池，之后在蓝电测试仪上以0.1mA恒流充电至充电截止电压，再以0.1mA恒流放电至放电截止电压，得到放电容量CAP0，通过公式CAP0×S 2/S 0得到第二正极膜层的容量CAP2，S 0为小圆片的面积，S 2为第二正极膜层的面积。
扣式电池可按照负极壳子、锂片、一滴电解液、隔离膜、一滴电解液、面积S 0的小圆片、垫片、弹片的顺序组装。扣式电池的直径可为14mm。测试时可通过使用水或其他溶剂擦拭掉极片其中一面的膜层。测试时可采用来自元能科技有限公司IEST的冲片机。
在本申请中，膜层电阻为本领域公知的含义，可以用本领域已知的仪器及方法进行测定。例如，采用极片电阻仪进行测试(例如，IEST BER1000型极片电阻仪，来自元能科技有限公司)。作为示例，各膜层电阻可采用如下方法进行测试：将经冷压的极片其中一面的膜层擦拭掉得到单面涂布的极片，将单面涂布的极片平行放置于极片电阻仪的两个导电端子之间，施加一定的压力固定，得到该膜层电阻。
具体地，第一正极膜层的电阻R 1可采用如下方法进行测试：将经冷压的正极极片的第二正极膜层擦拭掉，之后平行放置于极片电阻仪的两个导电端子之间，施加一定的压力固定，得到第一正极膜层的电阻R 1。第二正极膜层的电阻R 2可采用如下方法进行测试：将经冷压的正极极片的第一正极膜层擦拭掉，之后平行放置于极片电阻仪的两个导电端子之间，施加一定的压力固定，得到第二正极膜层的电阻R 2。第一负极膜层的电阻R 3可采用如下方法进行测试：将经冷压的负极极片的第二负极膜层擦拭掉，之后平行放 置于极片电阻仪的两个导电端子之间，施加一定的压力固定，得到第一负极膜层的电阻R 3。第二负极膜层的电阻R 4可采用如下方法进行测试：将经冷压的负极极片的第一负极膜层擦拭掉，之后平行放置于极片电阻仪的两个导电端子之间，施加一定的压力固定，得到第二负极膜层的电阻R 4。
可选地，导电端子的直径可为14mm，施加的压力可为15Mpa～27Mpa，采点的时间范围可为10s～20s。测试时可先将极片分切成一定面积(例如，10cm×10cm)再进行测试。测试时可通过使用水或其他溶剂擦拭掉极片其中一面的膜层。
需要说明的是，测试时极片(例如，正极极片或负极极片)可直接取新鲜制备的经冷压的极片，或从二次电池中获取极片。其中，从二次电池中获取极片的示例性方法如下：将二次电池满放后拆解出极片，将极片浸泡在有机溶剂(例如，碳酸二甲酯)中一段时间(例如，30min)，然后将极片取出并在一定温度和时间下干燥(例如，80℃，6h)。
在一些实施例中，电极组件52满足0≤R 4/R 3-R 2/R 1≤20。当R 4/R 3-R 2/R 1＞20时，二次电池充电时会快速达到充电截止电压，导致低容量正极膜层和高容量正极膜层中均有大量活性离子未脱出，降低二次电池的能量密度。
例如，R 4/R 3-R 2/R 1为0，0.05，0.1，0.2，0.3，0.4，0.5，0.6，0.7，0.8，0.9，1，2，3，4，5，6，7，8，9，10，11，12，13，14，15，16，17，18，19，20或以上任何数值所组成的范围。可选地，电极组件52满足0≤R 4/R 3-R 2/R 1≤20，0≤R 4/R 3-R 2/R 1≤15，0≤R 4/R 3-R 2/R 1≤10，0≤R 4/R 3-R 2/R 1≤8，0≤R 4/R 3-R 2/R 1≤5，0≤R 4/R 3-R 2/R 1≤2，0＜R 4/R 3-R 2/R 1≤20，0＜R 4/R 3-R 2/R 1≤15，0＜R 4/R 3-R 2/R 1≤10，0＜R 4/R 3-R 2/R 1≤8，0＜R 4/R 3-R 2/R 1≤5，0＜R 4/R 3-R 2/R 1≤2，0.1≤R 4/R 3-R 2/R 1≤20，0.1≤R 4/R 3-R 2/R 1≤15，0.1≤R 4/R 3-R 2/R 1≤10，0.1≤R 4/R 3-R 2/R 1≤8，0.1≤R 4/R 3-R 2/R 1≤5，或0.1≤R 4/R 3-R 2/R 1≤2。
在正极极片10中，第一正极膜层101的容量CAP1小于第二正极膜层102的容量CAP2。例如，CAP1/CAP2为0.1，0.2，0.33，0.4，0.5，0.6，0.7，0.8，0.9或以上任何数值所组成的范围。可选地，0＜CAP1/CAP2＜1，0.1≤CAP1/CAP2＜1，0.2≤CAP1/CAP2＜1，0.33≤CAP1/CAP2＜1，0.4≤CAP1/CAP2＜1，0.5≤CAP1/CAP2＜1，0＜CAP1/CAP2≤0.9，0.1≤CAP1/CAP2≤0.9，0.2≤CAP1/CAP2≤0.9，0.33≤CAP1/CAP2≤0.9，0.4≤CAP1/CAP2≤0.9，0.5≤CAP1/CAP2≤0.9，0＜CAP1/CAP2≤0.8，0.1≤CAP1/CAP2≤0.8，0.2≤CAP1/CAP2≤0.8，0.33≤CAP1/CAP2≤0.8，0.4≤CAP1/CAP2≤0.8，或0.5≤CAP1/CAP2≤0.8。
第一正极膜层的容量CAP1与第二正极膜层的容量CAP2的比值在合适的范围内时，能使二次电池在具有更长循环寿命的同时，还具有高能量密度。
在一些实施例中，第一正极膜层101的电阻R 1满足0Ω＜R 1≤20Ω。可选地，0Ω＜R 1≤5Ω。
在一些实施例中，第二正极膜层102的电阻R 2满足0Ω＜R 2≤20Ω。可选地，0Ω＜R 2≤5Ω。
在一些实施例中，第一负极膜层201的电阻R 3满足0mΩ＜R 3≤200mΩ。可选地，0mΩ＜R 3≤50mΩ。
在一些实施例中，第二负极膜层202的电阻R 4满足0mΩ＜R 4≤200mΩ。可选地，0mΩ＜R 4≤50mΩ。
第一正极膜层、第二正极膜层、第一负极膜层和第二负极膜层的电阻分别在合适的范围内时，正极极片和负极极片的一致性更好，有利于二次电池获得更长的循环寿命。
在一些实施例中，负极极片20满足R 4/R 3≥1，且电极组件52满足0≤R 4/R 3-R 2/R 1≤20，此时，二次电池在具有更长循环寿命的同时，还具有高能量密度。
例如，R 4/R 3为1，2，3，4，5，6，7，8，9，10，11，12，13，14，15，16，17，18，19，20，21，22，23，24，25，26，27，28，29，30或以上任何数值所组成的范围。可选地，负极极片20满足1≤R 4/R 3≤30，1≤R 4/R 3≤25，1≤R 4/R 3≤20，1≤R 4/R 3≤15，1≤R 4/R 3≤10，1≤R 4/R 3≤8，1≤R 4/R 3≤5，1≤R 4/R 3≤4，1≤R 4/R 3≤3，1≤R 4/R 3≤2，1＜R 4/R 3≤30，1＜R 4/R 3≤25，1＜R 4/R 3≤20，1＜R 4/R 3≤15，1＜R 4/R 3≤10，1＜R 4/R 3≤8，1＜R 4/R 3≤5，1＜R 4/R 3≤4，1＜R 4/R 3≤3，或1＜R 4/R 3≤2。
例如，R 4/R 3-R 2/R 1为0，0.05，0.1，0.2，0.3，0.4，0.5，0.6，0.7，0.8，0.9，1，2，3，4，5，6，7，8，9，10，11，12，13，14，15，16，17，18，19，20或以上任何数值所组成的范围。可选地，电极组件52满足0≤R 4/R 3-R 2/R 1≤20，0≤R 4/R 3-R 2/R 1≤15，0≤R 4/R 3-R 2/R 1≤10，0≤R 4/R 3-R 2/R 1≤8，0≤R 4/R 3-R 2/R 1≤5，0≤R 4/R 3-R 2/R 1≤2，0＜R 4/R 3-R 2/R 1≤20，0＜R 4/R 3-R 2/R 1≤15，0＜R 4/R 3-R 2/R 1≤10，0＜R 4/R 3-R 2/R 1≤8，0＜R 4/R 3-R 2/R 1≤5，0＜R 4/R 3-R 2/R 1≤2，0.1≤R 4/R 3-R 2/R 1≤20，0.1≤R 4/R 3-R 2/R 1≤15，0.1≤R 4/R 3-R 2/R 1≤10，0.1≤R 4/R 3-R 2/R 1≤8，0.1≤R 4/R 3-R 2/R 1≤5，或0.1≤R 4/R 3-R 2/R 1≤2。
此时对第一正极膜层101与第二正极膜层102的电阻比值R 2/R 1没有特别的限制，R 2/R 1可大于1、等于1、或小于1。例如，R 2/R 1为0.05，0.1，0.2，0.3，0.4，0.5，0.6，0.7，0.8，0.9，1，2，3，4，5，6，7，8，9，10，11，12，13，14，15，16，17，18，19，20或以上任何数值所组成的范围。可选地，正极极片10满足0＜R 2/R 1≤20，0＜R 2/R 1≤15，0＜R 2/R 1≤10，0＜R 2/R 1≤8，0＜R 2/R 1≤5，0＜R 2/R 1≤4，0＜R 2/R 1≤3，0＜R 2/R 1≤2，或0＜R 2/R 1≤1。
例如，负极极片20满足R 4/R 3≥1，正极极片10满足0＜R 2/R 1≤20，且电极组件52满足0≤R 4/R 3-R 2/R 1≤20。可选地，电极组件52满足0＜R 4/R 3-R 2/R 1≤20。可选地，电极组件52满足0≤R 4/R 3-R 2/R 1≤5。可选地，电极组件52满足0＜R 4/R 3-R 2/R 1≤5。可选地，电极组件52满足0.1≤R 4/R 3-R 2/R 1≤2。
例如，负极极片20满足1≤R 4/R 3≤30，正极极片10满足0＜R 2/R 1≤20，且电极组件52满足0≤R 4/R 3-R 2/R 1≤20。可选地，电极组件52满足0＜R 4/R 3-R 2/R 1≤20。可选地，电极组件52满足0≤R 4/R 3-R 2/R 1≤5。可选地，电极组件52满足0＜R 4/R 3-R 2/R 1≤5。可选地，电极组件52满足0.1≤R 4/R 3-R 2/R 1≤2。
在一些实施例中，负极极片20满足0＜R 4/R 3＜1，正极极片10满足0＜R 2/R 1＜1，且电极组件52满足0≤R 4/R 3-R 2/R 1＜1，此时，二次电池在具有更长循环寿命的同时，还具有高能量密度。
例如，R 4/R 3为0.05，0.1，0.2，0.3，0.4，0.5，0.6，0.7，0.8，0.9或以上任何数值所组成的范围。可选地，负极极片20满足0＜R 4/R 3≤0.9，0＜R 4/R 3≤0.8，0＜R 4/R 3≤0.7， 0＜R 4/R 3≤0.6，0.05≤R 4/R 3＜1，0.05≤R 4/R 3≤0.9，0.05≤R 4/R 3≤0.8，0.05≤R 4/R 3≤0.7，0.05≤R 4/R 3≤0.6，0.1≤R 4/R 3＜1，0.1≤R 4/R 3≤0.9，0.1≤R 4/R 3≤0.8，0.1≤R 4/R 3≤0.7，0.1≤R 4/R 3≤0.6，0.2≤R 4/R 3＜1，0.2≤R 4/R 3≤0.9，0.2≤R 4/R 3≤0.8，0.2≤R 4/R 3≤0.7，或0.2≤R 4/R 3≤0.6。
例如，R 2/R 1为0.05，0.1，0.2，0.3，0.4，0.5，0.6，0.7，0.8，0.9或以上任何数值所组成的范围。可选地，正极极片10满足0＜R 2/R 1≤0.9，0＜R 2/R 1≤0.8，0＜R 2/R 1≤0.7，0＜R 2/R 1≤0.6，0.05≤R 2/R 1＜1，0.05≤R 2/R 1≤0.9，0.05≤R 2/R 1≤0.8，0.05≤R 2/R 1≤0.7，0.05≤R 2/R 1≤0.6，0.1≤R 2/R 1＜1，0.1≤R 2/R 1≤0.9，0.1≤R 2/R 1≤0.8，0.1≤R 2/R 1≤0.7，0.1≤R 2/R 1≤0.6，0.2≤R 2/R 1＜1，0.2≤R 2/R 1≤0.9，0.2≤R 2/R 1≤0.8，0.2≤R 2/R 1≤0.7，或0.2≤R 2/R 1≤0.6。
例如，R 4/R 3-R 2/R 1为0，0.05，0.1，0.2，0.3，0.4，0.5，0.6，0.7，0.8，0.9或以上任何数值所组成的范围。可选地，电极组件52满足0≤R 4/R 3-R 2/R 1＜1，0≤R 4/R 3-R 2/R 1≤0.9，0≤R 4/R 3-R 2/R 1≤0.8，0≤R 4/R 3-R 2/R 1≤0.7，0≤R 4/R 3-R 2/R 1≤0.6，0＜R 4/R 3-R 2/R 1＜1，0＜R 4/R 3-R 2/R 1≤0.9，0＜R 4/R 3-R 2/R 1≤0.8，0＜R 4/R 3-R 2/R 1≤0.7，0＜R 4/R 3-R 2/R 1≤0.6，0.05≤R 4/R 3-R 2/R 1＜1，0.05≤R 4/R 3-R 2/R 1≤0.9，0.05≤R 4/R 3-R 2/R 1≤0.8，0.05≤R 4/R 3-R 2/R 1≤0.7，0.05≤R 4/R 3-R 2/R 1≤0.6，0.1≤R 4/R 3-R 2/R 1＜1，0.1≤R 4/R 3-R 2/R 1≤0.9，0.1≤R 4/R 3-R 2/R 1≤0.8，0.1≤R 4/R 3-R 2/R 1≤0.7，0.1≤R 4/R 3-R 2/R 1≤0.6，0.2≤R 4/R 3-R 2/R 1＜1，0.2≤R 4/R 3-R 2/R 1≤0.9，0.2≤R 4/R 3-R 2/R 1≤0.8，0.2≤R 4/R 3-R 2/R 1≤0.7，或0.2≤R 4/R 3-R 2/R 1≤0.6。
例如，负极极片20满足0＜R 4/R 3＜1，正极极片10满足0＜R 2/R 1＜1，电极组件52满足0＜R 4/R 3-R 2/R 1＜1。
例如，负极极片20满足0＜R 4/R 3＜1，正极极片10满足0＜R 2/R 1＜1，电极组件52满足0.1≤R 4/R 3-R 2/R 1≤0.9。
例如，负极极片20满足0＜R 4/R 3＜1，正极极片10满足0.05≤R 4/R 3≤0.9，电极组件52满足0≤R 4/R 3-R 2/R 1＜1。
例如，负极极片20满足0＜R 4/R 3＜1，正极极片10满足0.05≤R 4/R 3≤0.9，电极组件52满足0＜R 4/R 3-R 2/R 1＜1。
例如，负极极片20满足0＜R 4/R 3＜1，正极极片10满足0.05≤R 4/R 3≤0.9，电极组件52满足0.1≤R 4/R 3-R 2/R 1≤0.9。
例如，负极极片20满足0.05≤R 4/R 3≤0.9，正极极片10满足0.05≤R 4/R 3≤0.9，电极组件52满足0≤R 4/R 3-R 2/R 1＜1。
例如，负极极片20满足0.05≤R 4/R 3≤0.9，正极极片10满足0.05≤R 4/R 3≤0.9，电极组件52满足0＜R 4/R 3-R 2/R 1＜1。
例如，负极极片20满足0.05≤R 4/R 3≤0.9，正极极片10满足0.05≤R 4/R 3≤0.9，电极组件52满足0.1≤R 4/R 3-R 2/R 1≤0.8。
在一些实施例中，正极极片10满足R 2/R 1＝1，负极极片20满足R 4/R 3＝1，此时电极组件52满足R 4/R 3-R 2/R 1＝0。
需要说明的是，具有多种理论可行的方式可以调节第一正极膜层101的容量CAP1、以及第二正极膜层102的容量CAP2。在本申请中，列举了其中一些调节方式，应当理解的 是，本说明书中所列举的方式，仅是为了解释本申请，并非为了限定本申请。
作为示例，正极极片10满足下述(1)～(3)中的一个或几个时，第一正极膜层101的容量CAP1小于第二正极膜层102的容量CAP2。
(1)第一正极膜层101的涂布重量小于第二正极膜层102的涂布重量。
(2)所述第一正极活性材料的克容量小于所述第二正极活性材料的克容量。
(3)w 1＜w 2，w 1表示基于第一正极膜层101的总质量，所述第一正极活性材料的质量百分含量，w 2表示基于第二正极膜层102的总质量，所述第二正极活性材料的质量百分含量。
需要说明的是，具有多种理论可行的方式可以调节第一正极膜层101的电阻R 1、第二正极膜层102的电阻R 2、第一负极膜层201的电阻R 3、以及第二负极膜层202的电阻R 4。在本申请中，列举了其中一些调节方式，应当理解的是，本说明书中所列举的方式，仅是为了解释本申请，并非为了限定本申请。
作为示例，正极极片10满足下述(4)～(10)中的一个或几个时，第二正极膜层102的电阻R 2小于第一正极膜层101的电阻R 1。
(4)所述第二正极活性材料的表面具有导电碳层。所述第二正极活性材料的表面具有导电碳层，所述第一正极活性材料的表面不具有导电碳层时，可以使第二正极膜层102的电阻R 2小于第一正极膜层101的电阻R 1。
(5)所述第二正极导电剂的电导率大于所述第一正极导电剂的电导率。通过使第二正极膜层102包含电导率更高的第二正极导电剂，可以使第二正极膜层102的电阻R 2小于第一正极膜层101的电阻R 1。
(6)w 3＜w 4，w 3表示基于第一正极膜层101的总质量，所述第一正极导电剂的质量百分含量，w 4表示基于第二正极膜层102的总质量，所述第二正极导电剂的质量百分含量。
(7)w 5＞w 6，w 5表示基于第一正极膜层101的总质量，所述第一正极粘结剂的质量百分含量，w 6表示基于第二正极膜层102的总质量，所述第二正极粘结剂的质量百分含量。
(8)第二正极膜层102的压实密度小于第一正极膜层101的压实密度。
(9)如图5所示，第二正极膜层102包括第二正极主体层1021和第二正极导电碳层1022，第二正极导电碳层1022位于第二正极主体层1021相对的两个表面其中的至少一个表面上。
(10)如图6所示，第一正极膜层101包括第一正极主体层1011和第一正极陶瓷层1013，第一正极陶瓷层1013位于第一正极主体层1011相对的两个表面其中的至少一个表面上。可选地，第一正极陶瓷层1013包括氧化铝陶瓷、氮化硅陶瓷、碳化硅陶瓷、氮化硼陶瓷中的一种或几种。
可以理解的是，尽管图5示出第二正极导电碳层1022位于第二正极主体层1021相对的两个表面上，但是在其他的实施例中，第二正极导电碳层1022还可以位于第二正极主体层1021相对的两个表面其中一个表面上。尽管图6示出第一正极陶瓷层1013位于第一正极主体层1011相对的两个表面上，但是在其他的实施例中，第一正极陶瓷层1013还可以位于第一正极主体层1011相对的两个表面其中一个表面上。如图7所示，正极极片10还 可以同时满足上述(9)和(10)，以使第二正极膜层102的电阻R 2小于第一正极膜层101的电阻R 1。
作为示例，正极极片10满足下述(11)～(17)中的一个或几个时，第二正极膜层102的电阻R 2大于第一正极膜层101的电阻R 1。
(11)所述第一极活性材料的表面具有导电碳层。所述第一正极活性材料的表面具有导电碳层，所述第二正极活性材料的表面不具有导电碳层时，可以使第二正极膜层102的电阻R 2大于第一正极膜层101的电阻R 1。
(12)所述第二正极导电剂的电导率小于所述第一正极导电剂的电导率。通过使第一正极膜层101包含电导率更高的第一正极导电剂，可以使第二正极膜层102的电阻R 2大于第一正极膜层101的电阻R 1。
(13)w 3＞w 4，w 3表示基于第一正极膜层101的总质量，所述第一正极导电剂的质量百分含量，w 4表示基于第二正极膜层102的总质量，所述第二正极导电剂的质量百分含量。
(14)w 5＜w 6，w 5表示基于第一正极膜层101的总质量，所述第一正极粘结剂的质量百分含量，w 6表示基于第二正极膜层102的总质量，所述第二正极粘结剂的质量百分含量。
(15)第二正极膜层102的压实密度大于第一正极膜层101的压实密度。
(16)如图8所示，第一正极膜层101包括第一正极主体层1011和第一正极导电碳层1012，第一正极导电碳层1012位于第一正极主体层1011相对的两个表面其中的至少一个表面上。
(17)如图9所示，第二正极膜层102包括第二正极主体层1021和第二正极陶瓷层1023，第二正极陶瓷层1023位于第二正极主体层1021相对的两个表面其中的至少一个表面上。可选地，第二正极陶瓷层1023包括氧化铝陶瓷、氮化硅陶瓷、碳化硅陶瓷、氮化硼陶瓷中的一种或几种。
可以理解的是，尽管图8示出第一正极导电碳层1012位于第一正极主体层1011相对的两个表面上，但是在其他的实施例中，第一正极导电碳层1012还可以位于第一正极主体层1011相对的两个表面其中一个表面上。尽管图9示出第二正极陶瓷层1023位于第二正极主体层1021相对的两个表面上，但是在其他的实施例中，第二正极陶瓷层1023还可以位于第二正极主体层1021相对的两个表面其中一个表面上。如图10所示，正极极片10还可以同时满足上述(16)和(17)，以使第二正极膜层102的电阻R 2大于第一正极膜层101的电阻R 1。
作为示例，负极极片20满足下述(a)～(g)中的一个或几个时，第二负极膜层202的电阻R 4大于第一负极膜层201的电阻R 3。
(a)所述第一负极活性材料的表面具有导电碳层。所述第一负极活性材料的表面具有导电碳层，所述第二负极活性材料的表面不具有导电碳层时，可以使第二负极膜层202的电阻R 4大于第一负极膜层201的电阻R 3。
(b)所述第一负极导电剂的电导率大于所述第二负极导电剂的电导率。通过使第一负极膜层201包含电导率更高的第一负极导电剂，可以使第二负极膜层202的电阻R 4大于第一负极膜层201的电阻R 3。
(c)w 7＞w 8，w 7表示基于第一负极膜层201的总质量，所述第一负极导电剂的质量百分含量，w 8表示基于第二负极膜层202的总质量，所述第二负极导电剂的质量百分含量。
(d)w 9＜w 10，w 9表示基于第一负极膜层201的总质量，所述第一负极粘结剂的质量百分含量，w 10表示基于所述第二负极膜层202的总质量，所述第二负极粘结剂的质量百分含量。
(e)第一负极膜层201的压实密度小于第二负极膜层202的压实密度。
(f)如图11所示，第一负极膜层201包括第一负极主体层2011和第一负极导电碳层2012，第一负极导电碳层2012位于第一负极主体层2011相对的两个表面其中的至少一个表面上。
(g)如图12所示，第二负极膜层202包括第二负极主体层2021和第二负极陶瓷层2023，第二负极陶瓷层2023位于第二负极主体层2021相对的两个表面其中的至少一个表面上。可选地，第二负极陶瓷层2023包括氧化铝陶瓷、氮化硅陶瓷、碳化硅陶瓷、氮化硼陶瓷中的一种或几种。
可以理解的是，尽管图11示出第一负极导电碳层2012位于第一负极主体层2011相对的两个表面上，但是在其他的实施例中，第一负极导电碳层2012还可以位于第一负极主体层2011相对的两个表面其中一个表面上。尽管图12示出第二负极陶瓷层2023位于第二负极主体层2021相对的两个表面上，但是在其他的实施例中，第二负极陶瓷层2023还可以位于第二负极主体层2021相对的两个表面其中一个表面上。如图13所示，负极极片20还可以同时满足上述(f)和(g)，以使第二负极膜层202的电阻R 4大于第一负极膜层201的电阻R 3。
作为示例，负极极片20满足下述(h)～(n)中的一个或几个时，第二负极膜层202的电阻R 4小于第一负极膜层201的电阻R 3。
(h)所述第二负极活性材料的表面具有导电碳层。所述第一负极活性材料的表面不具有导电碳层，所述第二负极活性材料的表面具有导电碳层时，可以使第二负极膜层202的电阻R 4小于第一负极膜层201的电阻R 3。
(i)所述第一负极导电剂的电导率小于所述第二负极导电剂的电导率。通过使第二负极膜层202包含电导率更高的第二负极导电剂，可以使第二负极膜层202的电阻R 4小于第一负极膜层201的电阻R 3。
(j)w 7＜w 8，w 7表示基于第一负极膜层201的总质量，所述第一负极导电剂的质量百分含量，w 8表示基于第二负极膜层202的总质量，所述第二负极导电剂的质量百分含量。
(k)w 9＞w 10，w 9表示基于第一负极膜层201的总质量，所述第一负极粘结剂的质量百分含量，w 10表示基于第二负极膜层202的总质量，所述第二负极粘结剂的质量百分含量。
(l)第一负极膜层201的压实密度大于第二负极膜层202的压实密度。
(m)如图14所示，第二负极膜层202包括第二负极主体层2021和第二负极导电碳层2022，第二负极导电碳层2022位于第二负极主体层2021相对的两个表面其中的至少一个表面上。
(n)如图15所示，第一负极膜层201包括第一负极主体层2011和第一负极陶瓷层2013，第一负极陶瓷层2013位于第一负极主体层2011相对的两个表面其中的至少一个表面上。可选地，第一负极陶瓷层2013包括氧化铝陶瓷、氮化硅陶瓷、碳化硅陶瓷、氮化硼陶瓷中的一种或几种。
可以理解的是，尽管图14示出第二负极导电碳层2022位于第二负极主体层2021相对的两个表面上，但是在其他的实施例中，第二负极导电碳层2022位于第二负极主体层2021相对的两个表面其中一个表面上。尽管图15示出第一负极陶瓷层2013位于第一负极主体层2011相对的两个表面上，但是在其他的实施例中，第一负极陶瓷层2013位于第一负极主体层2011相对的两个表面其中一个表面上。如图16所示，负极极片20还可以同时满足上述(m)和(n)，以使第二负极膜层202的电阻R 4小于第一负极膜层201的电阻R 3。
在一些实施例中，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，正极集流体可采用铝箔。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、银合金中的一种或几种。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。
在一些实施例中，第一正极活性材料和第二正极活性材料可采用本领域公知的用于二次电池的正极活性材料。作为示例，第一正极活性材料和第二正极活性材料各地独立地包括锂过渡金属氧化物、橄榄石结构的含锂磷酸盐及其各自的改性化合物中的一种或几种。锂过渡金属氧化物的示例可包括但不限于锂钴氧化物、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改性化合物中的一种或几种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂、磷酸铁锂与碳的复合材料、磷酸锰锂、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料及其各自的改性化合物中的一种或几种。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正极活性材料的传统公知的材料。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
在一些实施例中，上述各正极活性材料的改性化合物可以是对正极活性材料进行掺杂改性、表面包覆改性、或掺杂同时表面包覆改性。
在一些实施例中，为了进一步提高二次电池的能量密度，第一正极活性材料和第二正极活性材料还可以各地独立地包括式1所示的锂过渡金属氧化物及其改性化合物中的一种或几种。
Li aNi bCo cM dO eA f  式1
式1中，0.8≤a≤1.2，0.5≤b＜1，0＜c＜1，0＜d＜1，1≤e≤2，0≤f≤1，M选自Mn、Al、Zr、Zn、Cu、Cr、Mg、Fe、V、Ti及B中的一种或几种，A选自N、F、S及Cl中的一种或几种。
在一些实施例中，作为示例，第一正极粘结剂和第二正极粘结剂各自独立地包括聚偏氟乙烯(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、含氟丙烯酸酯树脂中的一种或几种。
在一些实施例中，作为示例，第一正极导电剂和第二正极导电剂各自独立地包括超导碳、导电石墨(例如KS-6)、乙炔黑、炭黑(例如Super P)、科琴黑、碳点、碳纳米管(CNT)、石墨烯、碳纳米纤维中的一种或几种。
在一些实施例中，第一正极膜层和第二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。正极浆料通常是将正极活性材料、正极导电剂、正极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。
在一些实施例中，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、银合金中的一种或几种。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。
在一些实施例中，第一负极活性材料和第二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，第一负极活性材料和第二负极活性材料各自独立地包括人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料、钛酸锂中的一种或几种。硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅氮复合物以及硅合金中的一种或几种。锡基材料可选自单质锡、锡氧化合物以及锡合金中的一种或几种。但本申请并不限定于这些材料，还可以使用其他可被用作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。
在一些实施例中，作为示例，第一负极粘结剂和第二负极粘结剂各自独立地包括丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的一种或几种。
在一些实施例中，作为示例，第一负极导电剂和第二负极导电剂各自独立地包括超导碳、导电石墨(例如KS-6)、乙炔黑、炭黑(例如Super P)、科琴黑、碳点、碳纳米管(CNT)、石墨烯及碳纳米纤维中的一种或几种。
在一些实施例中，第一负极膜层和第二负极膜层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠CMC-Na)。
在一些实施例中，第一负极膜层和第二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。负极浆料通常是将负极活性材料、负极导电剂、负极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。溶剂可以是去离子水，但不限于此。
[电解质]
电解质在正极极片和负极极片之间起到传导活性离子的作用。本申请的二次电池对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可以选自固态电解质及液态电解质(即电解液)中的至少一种。
在一些实施例中，电解质采用电解液。电解液包括电解质盐和溶剂。
在一些实施例中，电解质盐的种类不受具体的限制，可根据实际需求进行选择。 作为示例，电解质盐可选自六氟磷酸锂LiPF 6、四氟硼酸锂LiBF 4、高氯酸锂LiClO 4、六氟砷酸锂LiAsF 6、双氟磺酰亚胺锂LiFSI、双三氟甲磺酰亚胺锂LiTFSI、三氟甲磺酸锂LiTFS、二氟草酸硼酸锂LiDFOB、二草酸硼酸锂LiBOB、二氟磷酸锂LiPO 2F 2、二氟二草酸磷酸锂LiDFOP及四氟草酸磷酸锂LiTFOP中的一种或几种。
在一些实施例中，溶剂的种类不受具体的限制，可根据实际需求进行选择。作为示例，溶剂可选自碳酸亚乙酯(EC)、碳酸亚丙酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸亚丁酯(BC)、氟代碳酸亚乙酯(FEC)、甲酸甲酯(MF)、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)、丙酸丙酯(PP)、丁酸甲酯(MB)、丁酸乙酯(EB)、1,4-丁内酯(GBL)、环丁砜(SF)、二甲砜(MSM)、甲乙砜(EMS)及二乙砜(ESE)中的一种或几种。
在一些实施例中，溶剂为非水溶剂。
在一些实施例中，电解液中还可选地包括添加剂。例如添加剂可以包括负极成膜添加剂，也可以包括正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温性能的添加剂、改善电池低温性能的添加剂等。
[隔离膜]
采用电解液的二次电池、以及一些采用固态电解质的二次电池中，还包括隔离膜。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使活性离子通过。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施例中，隔离膜的材质可以选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的一种或几种。隔离膜可以是单层薄膜，也可以是多层复合薄膜。隔离膜为多层复合薄膜时，各层的材料可相同或不同。
[电极组件制备方法]
本申请还提供一种用于制备电极组件的方法，所述方法可包括如下步骤：
S10，将第一正极活性材料、第一正极导电剂、第一正极粘结剂分散于溶剂中并搅拌均匀形成第一正极浆料，将第二正极活性材料、第二正极导电剂、第二正极粘结剂分散于溶剂中并搅拌均匀形成第二正极浆料，将第一正极浆料和第二正极浆料分别涂布在正极集流体相对的两个表面上，经干燥、冷压得到正极极片，其中，第一正极浆料和第二正极浆料分别形成第一正极膜层和第二正极膜层；
S20，将第一负极活性材料、第一负极导电剂、第一负极粘结剂分散于溶剂中并搅拌均匀形成第一负极浆料，将第二负极活性材料、第二负极导电剂、第二负极粘结剂分散于溶剂中并搅拌均匀形成第二负极浆料，将第一负极浆料和第二负极浆料分别涂布在负极集流体相对的两个表面上，经干燥、冷压得到负极极片，其中第一负极浆料和第二负极浆料分别形成第一负极膜层和第二负极膜层；
S30，将正极极片、隔离膜和负极极片组装成电极组件，其中，第一正极膜层位于正极集流体靠近隔离膜的一侧并且第二负极膜层位于负极集流体靠近隔离膜的一侧， 或，第一正极膜层位于正极集流体远离所述隔离膜的一侧并且第二负极膜层位于负极集流体远离隔离膜的一侧；
S40，对电极组件进行检测，从中筛选出同时满足0＜CAP1/CAP2＜1和R 4/R 3-R 2/R 1≥0的电极组件，其中，CAP1表示以Ah计的第一正极膜层的容量，CAP2表示以Ah计的第二正极膜层的容量，R 1表示以Ω计的第一正极膜层的电阻，R 2表示以Ω计的第二正极膜层的电阻，R 3表示以mΩ计的第一负极膜层的电阻，R 4表示以mΩ计的第二负极膜层的电阻。
通过本申请的方法得到的电极组件，均能大幅延长二次电池的循环寿命。
在一些实施例中，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。
在一些实施例中，在步骤S40中，可选地，筛选出同时满足0.33≤CAP1/CAP2＜1和0≤R 4/R 3-R 2/R 1≤20的电极组件。
在一些实施例中，在步骤S40中，可选地，筛选出同时满足0.5≤CAP1/CAP2＜1和0＜R 4/R 3-R 2/R 1≤20的电极组件。
在一些实施例中，在步骤S40中，可选地，筛选出同时满足0.5≤CAP1/CAP2≤0.9和0.1≤R 4/R 3-R 2/R 1≤2的电极组件。
在一些实施例中，所述方法还包括如下步骤：S50，筛选出进一步同时满足1≤R 4/R 3≤30和0＜R 2/R 1≤20的电极组件。
在一些实施例中，所述方法还包括如下步骤：S50，筛选出进一步同时满足0＜R 4/R 3＜1和0＜R 2/R 1＜1的电极组件。
在一些实施例中，所述方法还包括如下步骤：S50，筛选出进一步同时满足R 4/R 3＝1和R 2/R 1＝1的电极组件。
电池模块及电池包
在本申请的一些实施例中，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17是作为一个示例的电池模块4的示意图。如图17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。
在本申请的一些实施例中，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18和图19是作为一个示例的电池包1的示意图。如图18和图19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
本申请的实施方式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、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20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。
实施例1
二次电池的结构如图3所示。
正极极片的制备
将正极活性材料LiNi 0.5Co 0.2Mn 0.3O 2、粘结剂PVDF、导电剂Super P按重量比96.2:1.1:2.7在适量的溶剂NMP中充分搅拌混合，得到第一正极浆料，将第一正极浆料涂布在正极集流体铝箔靠近隔离膜的一侧。
将正极活性材料LiNi 0.5Co 0.2Mn 0.3O 2、粘结剂PVDF、导电剂Super P按重量比96.2:1.1:2.7在适量的溶剂NMP中充分搅拌混合，得到第二正极浆料，将第二正极浆料涂布在正极集流体铝箔远离隔离膜的一侧。
其中，第一正极浆料和第二正极浆料的涂布重量之比为0.76:1，第一正极浆料经干燥、冷压后形成第一正极膜层，第二正极浆料经干燥、冷压后形成第二正极膜层。
负极极片的制备
将负极活性材料具有导电碳层的石墨、导电剂Super P、增稠剂CMC-Na、粘结剂SBR按重量比97:1:0.5:1.5在适量的溶剂去离子水中充分搅拌混合，得到第一负极浆料，将第一负极浆料涂布在负极集流体铜箔远离隔离膜的一侧。
将负极活性材料石墨、导电剂Super P、增稠剂CMC-Na、粘结剂SBR按重量比97:1:0.5:1.5在适量的溶剂去离子水中充分搅拌混合，得到第二负极浆料，将第二负极浆料涂布在负极集流体铜箔靠近隔离膜的一侧。
其中，第一负极浆料和第二负极浆料的涂布重量相同，第一负极浆料经干燥、冷压后形成第一负极膜层，第二负极浆料经干燥、冷压后形成第二负极膜层。
隔离膜
采用多孔聚乙烯膜作为隔离膜。
电解液的制备
将碳酸乙烯酯(EC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)按体积比1:1:1混合，得到有机溶剂；将LiPF 6均匀溶解在上述有机溶剂中得到电解液，其中，LiPF 6的浓度为1mol/L。
二次电池的制备
将上述制备的正极极片、隔离膜、负极极片按顺序堆叠并卷绕，得到电极组件；将电极组件放入外包装中，加入上述电解液，经封装、静置、化成、容量等工序后，得到二次电池。化成工艺如下：将二次电池以0.1C恒流充电至3.0V，再以0.2C恒流充电至3.75V。容量工艺如下：将二次电池以0.33C恒流充电至4.4V，再恒压充电至0.05C；将二次电池以0.33C恒流放电至2.5V，再以0.33C恒流充电至3.65V，再恒压充电至0.05C。
实施例2
二次电池的制备方法与实施例1类似，不同之处在于：增加了第一负极膜层的压实密度。
实施例3
二次电池的制备方法与实施例1类似，不同之处在于：调整了负极极片制备中的相关参数。
将负极活性材料石墨、导电剂Super P、增稠剂CMC-Na、粘结剂SBR按重量比96.6:1.4:0.5:1.5在适量的溶剂去离子水中充分搅拌混合，得到第一负极浆料。
实施例4
二次电池的制备方法与实施例1类似，不同之处在于：调整了负极极片制备中的相关参数。
将负极活性材料石墨、导电剂Super P、增稠剂CMC-Na、粘结剂SBR按重量比97:1:0.5:1.5在适量的溶剂去离子水中充分搅拌混合，得到第一负极浆料，将第一负极浆料涂布在负极集流体铜箔远离隔离膜的一侧，且负极集流体远离隔离膜的一侧还涂布有厚度为0.5μm的导电碳层。
实施例5
二次电池的制备方法与实施例1类似，不同之处在于：调整了负极极片制备中的相关参数。
将负极活性材料石墨、导电剂Super P、增稠剂CMC-Na、粘结剂SBR按重量比97:1:0.5:1.5在适量的溶剂去离子水中充分搅拌混合，得到第一负极浆料，将第一负极浆料涂布在负极集流体铜箔远离隔离膜的一侧。
将负极活性材料石墨、导电剂Super P、增稠剂CMC-Na、粘结剂SBR按重量比97:1:0.5:1.5在适量的溶剂去离子水中充分搅拌混合，得到第二负极浆料，将第二负极浆料涂布在负极集流体铜箔靠近隔离膜的一侧，且负极集流体靠近隔离膜的一侧还涂布有厚度为0.5μm的氧化铝陶瓷层。
实施例6
二次电池的制备方法与实施例1类似，不同之处在于：调整了负极极片制备中的相关参数。
将负极活性材料石墨、导电剂Super P、增稠剂CMC-Na、粘结剂SBR按重量比97:1:0.5:1.5在适量的溶剂去离子水中充分搅拌混合，得到第二负极浆料，将第二负极浆料 涂布在负极集流体铜箔靠近隔离膜的一侧，且负极集流体靠近隔离膜的一侧还涂布有厚度为0.5μm的氧化铝陶瓷层。
实施例7
二次电池的制备方法与实施例1类似，不同之处在于：调整了负极极片制备中的相关参数。
将负极活性材料石墨、导电剂Super P、增稠剂CMC-Na、粘结剂SBR按重量比97:1:0.5:1.5在适量的溶剂去离子水中充分搅拌混合，得到第一负极浆料，将第一负极浆料涂布在负极集流体铜箔远离隔离膜的一侧。
将负极活性材料石墨、导电剂Super P、增稠剂CMC-Na、粘结剂SBR按重量比97:1:0.5:1.5在适量的溶剂去离子水中充分搅拌混合，得到第二负极浆料，将第二负极浆料涂布在负极集流体铜箔靠近隔离膜的一侧，且负极集流体靠近隔离膜的一侧还涂布有厚度为1.2μm的氧化铝陶瓷层。
实施例8
二次电池的制备方法与实施例1类似，不同之处在于：调整了负极极片制备中的相关参数。
将负极活性材料石墨、导电剂Super P、增稠剂CMC-Na、粘结剂SBR按重量比97:1:0.5:1.5在适量的溶剂去离子水中充分搅拌混合，得到第二负极浆料，将第二负极浆料涂布在负极集流体铜箔靠近隔离膜的一侧，且负极集流体靠近隔离膜的一侧涂布有厚度为1.2μm的氧化铝陶瓷层。
实施例9
二次电池的制备方法与实施例1类似，不同之处在于：调整了负极极片制备中的相关参数。
将负极活性材料石墨、导电剂Super P、增稠剂CMC-Na、粘结剂SBR按重量比96.6:1.4:0.5:1.5在适量的溶剂去离子水中充分搅拌混合，得到第一负极浆料。
将负极活性材料石墨、导电剂Super P、增稠剂CMC-Na、粘结剂SBR按重量比97:1:0.5:1.5在适量的溶剂去离子水中充分搅拌混合，得到第二负极浆料，将第二负极浆料涂布在负极集流体铜箔靠近隔离膜的一侧，且负极集流体靠近隔离膜的一侧还涂布有厚度为1.5μm的氧化铝陶瓷层。
实施例10
二次电池的制备方法与实施例1类似，不同之处在于：调整了负极极片制备中的相关参数。
将负极活性材料石墨、导电剂Super P、增稠剂CMC-Na、粘结剂SBR按重量比97:1:0.5:1.5在适量的溶剂去离子水中充分搅拌混合，得到第二负极浆料，将第二负极浆料涂布在负极集流体铜箔靠近隔离膜的一侧，且负极集流体靠近隔离膜的一侧还涂布有厚度为2μm的氧化铝陶瓷层。
实施例11
二次电池的制备方法与实施例1类似，不同之处在于：调整了负极极片制备中的相关参数。
负极集流体远离隔离膜的一侧还涂布有厚度为2μm的导电碳层，负极集流体靠近 隔离膜的一侧还涂布有厚度为2μm的氧化铝陶瓷层。
实施例12
二次电池的制备方法与实施例1类似，不同之处在于：调整了负极极片制备中的相关参数。
负极集流体远离隔离膜的一侧还涂布有厚度为2μm的导电碳层，负极集流体靠近隔离膜的一侧还涂布有厚度为4μm的氧化铝陶瓷层。
实施例13
二次电池的制备方法与实施例1类似，不同之处在于：调整了正极极片和负极极片制备中的相关参数。
第一正极浆料和第二正极浆料的涂布重量之比为0.6:1，且正极集流体远离隔离膜的一侧还涂布有厚度为2μm的氧化铝陶瓷层。
负极集流体远离隔离膜的一侧还涂布有厚度为2μm的导电碳层，负极集流体靠近隔离膜的一侧还涂布有厚度为6μm的氧化铝陶瓷层。
实施例14
二次电池的制备方法与实施例1类似，不同之处在于：调整了负极极片制备中的相关参数。
负极集流体远离隔离膜的一侧还涂布有厚度为2μm的导电碳层，负极集流体靠近隔离膜的一侧还涂布有厚度为6μm的氧化铝陶瓷层。
实施例15
二次电池的制备方法与实施例1类似，不同之处在于：调整了正极极片和负极极片制备中的相关参数。
将正极活性材料LiNi 0.5Co 0.2Mn 0.3O 2、粘结剂PVDF、导电剂Super P按重量比96.2:1.2:2.6在适量的溶剂NMP中充分搅拌混合，得到第一正极浆料。将正极活性材料LiNi 0.5Co 0.2Mn 0.3O 2、粘结剂PVDF、导电剂Super P按重量比96.2:1.1:2.7在适量的溶剂NMP中充分搅拌混合，得到第二正极浆料。第一正极浆料和第二正极浆料的涂布重量之比为0.84:1。
将负极活性材料石墨、导电剂Super P、增稠剂CMC-Na、粘结剂SBR按重量比97:1:0.5:1.5在适量的溶剂去离子水中充分搅拌混合，得到第一负极浆料，将第一负极浆料涂布在负极集流体铜箔远离隔离膜的一侧。
将负极活性材料石墨、导电剂Super P、增稠剂CMC-Na、粘结剂SBR按重量比97:1:0.5:1.5在适量的溶剂去离子水中充分搅拌混合，得到第二负极浆料，将第二负极浆料涂布在负极集流体铜箔靠近隔离膜的一侧，且负极集流体靠近隔离膜的一侧还涂布有厚度为0.5μm的氧化铝陶瓷层。
实施例16
二次电池的制备方法与实施例1类似，不同之处在于：调整了负极极片制备中的相关参数。
将负极活性材料具有导电碳层的石墨、导电剂Super P、增稠剂CMC-Na、粘结剂SBR按重量比97.1:0.9:0.5:1.5在适量的溶剂去离子水中充分搅拌混合，得到第一负极浆料。
实施例17
二次电池的制备方法与实施例1类似，不同之处在于：调整了正极极片和负极极片制备中的相关参数。
将正极活性材料LiNi 0.5Co 0.2Mn 0.3O 2、粘结剂PVDF、导电剂Super P按重量比96.2:1.2:2.6在适量的溶剂NMP中充分搅拌混合，得到第一正极浆料。将正极活性材料LiNi 0.5Co 0.2Mn 0.3O 2、粘结剂PVDF、导电剂Super P按重量比96.2:1.1:2.7在适量的溶剂NMP中充分搅拌混合，得到第二正极浆料。第一正极浆料和第二正极浆料的涂布重量之比为0.84:1。
将负极活性材料具有导电碳层的石墨、导电剂Super P、增稠剂CMC-Na、粘结剂SBR按重量比97.05:0.95:0.5:1.5在适量的溶剂去离子水中充分搅拌混合，得到第一负极浆料。将负极活性材料具有导电碳层的石墨、导电剂Super P、增稠剂CMC-Na、粘结剂SBR按重量比97:1:0.5:1.5在适量的溶剂去离子水中充分搅拌混合，得到第二负极浆料。
实施例18
二次电池的制备方法与实施例1类似，不同之处在于：调整了正极极片和负极极片制备中的相关参数。
将正极活性材料LiNi 0.5Co 0.2Mn 0.3O 2、粘结剂PVDF、导电剂Super P按重量比96.2:1.2:2.6在适量的溶剂NMP中充分搅拌混合，得到第一正极浆料。将正极活性材料LiNi 0.5Co 0.2Mn 0.3O 2、粘结剂PVDF、导电剂Super P按重量比96.2:1.1:2.7在适量的溶剂NMP中充分搅拌混合，得到第二正极浆料。第一正极浆料和第二正极浆料的涂布重量之比为0.84:1。
将负极活性材料具有导电碳层的石墨、导电剂Super P、增稠剂CMC-Na、粘结剂SBR按重量比97:1:0.5:1.5在适量的溶剂去离子水中充分搅拌混合，得到第一负极浆料。负极活性材料具有导电碳层的石墨、导电剂Super P、增稠剂CMC-Na、粘结剂SBR按重量比97:1:0.5:1.5在适量的溶剂去离子水中充分搅拌混合，得到第二负极浆料。
实施例19
二次电池的制备方法与实施例1类似，不同之处在于：调整了正极极片和负极极片制备中的相关参数。
第一正极浆料和第二正极浆料的涂布重量之比为0.84:1，且正极集流体靠近隔离膜的一侧还涂布有厚度为2μm的氧化铝陶瓷层。
将负极活性材料具有导电碳层的石墨、导电剂Super P、增稠剂CMC-Na、粘结剂SBR按重量比97.05:0.95:0.5:1.5在适量的溶剂去离子水中充分搅拌混合，得到第一负极浆料。
将负极活性材料具有导电碳层的石墨、导电剂Super P、增稠剂CMC-Na、粘结剂SBR按重量比97:1:0.5:1.5在适量的溶剂去离子水中充分搅拌混合，得到第二负极浆料。
实施例20
二次电池的制备方法与实施例1类似，不同之处在于：调整了正极极片和负极极片制备中的相关参数。
第一正极浆料和第二正极浆料的涂布重量之比为0.84:1，且正极集流体靠近隔离膜的一侧还涂布有厚度为1μm的氧化铝陶瓷层。
将负极活性材料石墨、导电剂Super P、增稠剂CMC-Na、粘结剂SBR按重量比 97:1:0.5:1.5在适量的溶剂去离子水中充分搅拌混合，得到第一负极浆料。将负极活性材料具有导电碳层的石墨、导电剂Super P、增稠剂CMC-Na、粘结剂SBR按重量比96.95:1.05:0.5:1.5在适量的溶剂去离子水中充分搅拌混合，得到第二负极浆料。
实施例21
二次电池的制备方法与实施例1类似，不同之处在于：调整了正极极片和负极极片制备中的相关参数。
将正极活性材料LiNi 0.5Co 0.2Mn 0.3O 2、粘结剂PVDF、导电剂Super P按重量比96.2:1.1:2.7在适量的溶剂NMP中充分搅拌混合，得到第一正极浆料，将第一正极浆料涂布在正极集流体铝箔靠近隔离膜的一侧，且正极集流体靠近隔离膜的一侧涂布有厚度为1μm的氧化铝陶瓷层。将正极活性材料LiNi 0.5Co 0.2Mn 0.3O 2、粘结剂PVDF、导电剂Super P按重量比96.2:1.3:2.5在适量的溶剂NMP中充分搅拌混合，得到第二正极浆料，将第二正极浆料涂布在正极集流体铝箔远离隔离膜的一侧。第一正极浆料和第二正极浆料的涂布重量之比为0.84:1。
将负极活性材料石墨、导电剂Super P、增稠剂CMC-Na、粘结剂SBR按重量比97:1:0.5:1.5在适量的溶剂去离子水中充分搅拌混合，得到第一负极浆料，将第一负极浆料涂布在负极集流体铜箔远离隔离膜的一侧，且负极集流体远离隔离膜的一侧涂布有厚度为0.5μm的氧化铝陶瓷层。将负极活性材料具有导电碳层的石墨、导电剂Super P、增稠剂CMC-Na、粘结剂SBR按重量比97:1:0.5:1.5在适量的溶剂去离子水中充分搅拌混合，得到第二负极浆料。
实施例22
二次电池的制备方法与实施例1类似，不同之处在于：调整了正极极片和负极极片制备中的相关参数。
第一正极浆料和第二正极浆料的涂布重量之比为0.84:1，且正极集流体靠近隔离膜的一侧还涂布有厚度为2μm的氧化铝陶瓷层。
将负极活性材料具有导电碳层的石墨、导电剂Super P、增稠剂CMC-Na、粘结剂SBR按重量比97:1:0.5:1.5在适量的溶剂去离子水中充分搅拌混合，得到第一负极浆料。将负极活性材料具有导电碳层的石墨、导电剂Super P、增稠剂CMC-Na、粘结剂SBR按重量比97:1:0.5:1.5在适量的溶剂去离子水中充分搅拌混合，得到第二负极浆料。
对比例1
二次电池的制备方法与实施例1类似，不同之处在于：调整了正极极片和负极极片制备中的相关参数。
第一正极浆料和第二正极浆料的涂布重量相同。
将负极活性材料石墨、导电剂Super P、增稠剂CMC-Na、粘结剂SBR按重量比97:1:0.5:1.5在适量的溶剂去离子水中充分搅拌混合，得到负极浆料；将负极浆料涂布在负极集流体铜箔的两个表面上，经干燥、冷压后，得到负极极片。其中，负极集流体两侧的涂布重量相同。
对比例2
二次电池的制备方法与对比例1类似，不同之处在于：调整了负极极片制备中的相关参数。
第一正极浆料和第二正极浆料的涂布重量之比为0.76:1。
对比例3
二次电池的制备方法与实施例1类似，不同之处在于：调整了正极极片和负极极片制备中的相关参数。
将正极活性材料LiNi 0.5Co 0.2Mn 0.3O 2、粘结剂PVDF、导电剂Super P按重量比96.2:1.2:2.6在适量的溶剂NMP中充分搅拌混合，得到第一正极浆料。将正极活性材料LiNi 0.5Co 0.2Mn 0.3O 2、粘结剂PVDF、导电剂Super P按重量比96.2:1.1:2.7在适量的溶剂NMP中充分搅拌混合，得到第二正极浆料。第一正极浆料和第二正极浆料的涂布重量之比为0.84:1。
将负极活性材料石墨、导电剂Super P、增稠剂CMC-Na、粘结剂SBR按重量比97:1:0.5:1.5在适量的溶剂去离子水中充分搅拌混合，得到第一负极浆料。将负极活性材料具有导电碳层的石墨、导电剂Super P、增稠剂CMC-Na、粘结剂SBR按重量比96.95:1.05:0.5:1.5在适量的溶剂去离子水中充分搅拌混合，得到第二负极浆料。
性能测试部分
(1)正极膜层的容量测试
将经冷压的正极极片的第二正极膜层擦拭掉后冲切成直径为14mm的小圆片，将小圆片在手套箱中组装成扣式电池，之后在蓝电测试仪上以0.1mA恒流充电至充电截止电压，再以0.1mA恒流放电至放电截止电压，得到放电容量CAP0。通过公式CAP0×S 1/S 0得到第一正极膜层的容量CAP1，S 0为小圆片的面积，S 1为第一正极膜层的面积。
将经冷压的正极极片的第一正极膜层擦拭掉后冲切成直径为14mm的小圆片，将小圆片在手套箱中组装成扣式电池，之后在蓝电测试仪上以0.1mA恒流充电至充电截止电压，再以0.1mA恒流放电至放电截止电压，得到放电容量CAP0。通过公式CAP0×S 2/S 0得到第二正极膜层的容量CAP2，S 0为小圆片的面积，S 2为第二正极膜层的面积。
(2)各膜层的电阻测试
将经冷压的正极极片的第二正极膜层擦拭掉，之后平行放置于极片电阻仪的两个导电端子之间，施加一定的压力固定，得到第一正极膜层的电阻R 1。将经冷压的正极极片的第一正极膜层擦拭掉，之后平行放置于极片电阻仪的两个导电端子之间，施加一定的压力固定，得到第二正极膜层的电阻R 2。将经冷压的负极极片的第二负极膜层擦拭掉，之后平行放置于极片电阻仪的两个导电端子之间，施加一定的压力固定，得到第一负极膜层的电阻R 3。将经冷压的负极极片的第一负极膜层擦拭掉，之后平行放置于极片电阻仪的两个导电端子之间，施加一定的压力固定，得到第二负极膜层的电阻R 4。
极片电阻仪的型号为IEST BER1000(来自元能科技有限公司)，导电端子的直径为14mm，施加的压力为15Mpa～27Mpa，采点的时间范围为10s～20s。
(3)质量能量密度测试
在25℃下，将二次电池以0.33C恒流充电至4.4V，继续恒压充电至电流为0.05C；将二次电池静置5min后，以0.33C恒流放电至2.5V，得到放电能量Q。
二次电池的质量能量密度(Wh/Kg)＝放电能量Q/二次电池的质量m。
(4)循环性能测试
在25℃下，将二次电池以0.5C恒流充电至4.4V，继续恒压充电至电流为0.05C， 此时二次电池为满充状态，记录此时的充电容量，即为第1圈充电容量；将二次电池静置5min后，以0.5C恒流放电至2.5V，此为一个循环充放电过程，记录此时的放电容量，即为第1圈放电容量。将二次电池按照上述方法进行循环充放电测试，记录每圈循环后的放电容量，直至二次电池的放电容量衰减为第1圈放电容量的80％，用此时的循环圈数表征二次电池在0.5C倍率条件下的循环性能。二次电池的循环圈数越高，循环性能越好。
表1和表2给出实施例1-22和对比例1-3的性能测试结果。
表1
Figure PCTCN2021123648-appb-000001
表2
Figure PCTCN2021123648-appb-000002
Figure PCTCN2021123648-appb-000003
从表2测试结果可知，通过合理设置正极极片两面电阻与负极极片两面电阻之间的关系，使电极组件满足R 4/R 3-R 2/R 1≥0，能够延缓二次电池容量衰减并大幅延长二次电池循环寿命。进一步地，当电极组件满足0≤R 4/R 3-R 2/R 1≤20时，二次电池能同时具有大幅延长的循环寿命和高能量密度。
以上所述，仅为本申请的具体实施方式，但本申请的保护范围并不局限于此，任何熟悉本技术领域的技术人员在本申请揭露的技术范围内，可轻易想到各种等效的修改或替换，这些修改或替换都应涵盖在本申请的保护范围之内。因此，本申请的保护范围应以权利要求的保护范围为准。

Claims (17)

  1. 一种电极组件，包括：
    正极极片，所述正极极片包括正极集流体以及位于所述正极集流体相对的两个表面上的第一正极膜层和第二正极膜层；
    负极极片，所述负极极片包括负极集流体以及位于所述负极集流体相对的两个表面上的第一负极膜层和第二负极膜层；
    位于所述正极极片和所述负极极片之间的隔离膜，其中，所述第一正极膜层位于所述正极集流体靠近所述隔离膜的一侧并且所述第二负极膜层位于所述负极集流体靠近所述隔离膜的一侧，或，所述第一正极膜层位于所述正极集流体远离所述隔离膜的一侧并且所述第二负极膜层位于所述负极集流体远离所述隔离膜的一侧，
    其中，
    所述正极极片满足0＜CAP1/CAP2＜1，CAP1表示以Ah计的第一正极膜层的容量，CAP2表示以Ah计的第二正极膜层的容量，
    所述电极组件满足R 4/R 3-R 2/R 1≥0，R 1表示以Ω计的第一正极膜层的电阻，R 2表示以Ω计的第二正极膜层的电阻，R 3表示以mΩ计的第一负极膜层的电阻，R 4表示以mΩ计的第二负极膜层的电阻。
  2. 根据权利要求1所述的电极组件，其中，所述电极组件满足
    0≤R 4/R 3-R 2/R 1≤20，
    可选地，0＜R 4/R 3-R 2/R 1≤20，
    可选地，0.1≤R 4/R 3-R 2/R 1≤2。
  3. 根据权利要求1或2所述的电极组件，其中，所述正极极片满足
    0.33≤CAP1/CAP2＜1，
    可选地，0.5≤CAP1/CAP2＜1，
    可选地，0.5≤CAP1/CAP2≤0.9。
  4. 根据权利要求1-3中任一项所述的电极组件，其中，
    0Ω＜R 1≤20Ω，可选地，0Ω＜R 1≤5Ω；和/或，
    0Ω＜R 2≤20Ω，可选地，0Ω＜R 2≤5Ω；和/或，
    0mΩ＜R 3≤200mΩ，可选地，0mΩ＜R 3≤50mΩ；和/或，
    0mΩ＜R 4≤200mΩ，可选地，0mΩ＜R 4≤50mΩ。
  5. 根据权利要求1-4中任一项所述的电极组件，其中，所述第一正极膜层包括第一正极活性材料，所述第二正极膜层包括第二正极活性材料，所述正极极片满足下述(1)～(3)中的一个或几个：
    (1)所述第一正极膜层的涂布重量小于所述第二正极膜层的涂布重量，
    (2)所述第一正极活性材料的克容量小于所述第二正极活性材料的克容量，
    (3)w 1＜w 2，w 1表示基于所述第一正极膜层的总质量，所述第一正极活性材料的质量百分含量，w 2表示基于所述第二正极膜层的总质量，所述第二正极活性材料的质量百分含量。
  6. 根据权利要求1-5中任一项所述的电极组件，其中，所述负极极片满足R 4/R 3≥1，且 所述电极组件满足0≤R 4/R 3-R 2/R 1≤20，
    可选地，0≤R 4/R 3-R 2/R 1≤5，
    可选地，0.1≤R 4/R 3-R 2/R 1≤2。
  7. 根据权利要求6所述的电极组件，其中，
    所述正极极片满足0＜R 2/R 1≤20。
  8. 根据权利要求6所述的电极组件，其中，
    所述负极极片满足1≤R 4/R 3≤30，且
    所述正极极片满足0＜R 2/R 1≤20。
  9. 根据权利要求1-5中任一项所述的电极组件，其中，所述负极极片满足0＜R 4/R 3＜1，所述正极极片满足0＜R 2/R 1＜1，且所述电极组件满足0≤R 4/R 3-R 2/R 1＜1，
    可选地，0＜R 4/R 3-R 2/R 1＜1，
    可选地，0.1≤R 4/R 3-R 2/R 1≤0.9。
  10. 根据权利要求9所述的电极组件，其中，
    所述负极极片满足0＜R 4/R 3＜1，且
    所述正极极片满足0.05≤R 2/R 1≤0.9。
  11. 根据权利要求9所述的电极组件，其中，
    所述负极极片满足0.05≤R 4/R 3≤0.9，且
    所述正极极片满足0.05≤R 2/R 1≤0.9。
  12. 根据权利要求1-5中任一项所述的电极组件，其中，所述正极极片满足R 2/R 1＝1，且所述负极极片满足R 4/R 3＝1。
  13. 一种二次电池，包括外包装、电解质以及根据权利要求1-12中任一项所述的电极组件。
  14. 根据权利要求13所述的二次电池，其中，所述外包装包括壳体和盖板，所述壳体具有容纳腔和开口，所述电极组件容纳于所述容纳腔中，所述盖板用于封闭所述壳体的开口。
  15. 一种电池模块，包括根据权利要求13或14所述的二次电池。
  16. 一种电池包，包括根据权利要求13或14所述的二次电池、根据权利要求15所述的电池模块中的一种。
  17. 一种用电装置，包括根据权利要求13或14所述的二次电池、根据权利要求15所述的电池模块、根据权利要求16所述的电池包中的至少一种。
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