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WO2023193166A1 - 电极组件以及包含其的二次电池、电池模块、电池包及用电装置 - Google Patents

电极组件以及包含其的二次电池、电池模块、电池包及用电装置 Download PDF

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WO2023193166A1
WO2023193166A1 PCT/CN2022/085463 CN2022085463W WO2023193166A1 WO 2023193166 A1 WO2023193166 A1 WO 2023193166A1 CN 2022085463 W CN2022085463 W CN 2022085463W WO 2023193166 A1 WO2023193166 A1 WO 2023193166A1
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optionally
negative electrode
electrode assembly
micropores
positive electrode
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PCT/CN2022/085463
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English (en)
French (fr)
Inventor
陈均桄
程丛
裴海乐
张盛武
王星会
李世松
Original Assignee
宁德时代新能源科技股份有限公司
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Priority to PCT/CN2022/085463 priority Critical patent/WO2023193166A1/zh
Priority to KR1020247011668A priority patent/KR20240050479A/ko
Priority to CN202280011837.9A priority patent/CN117203784A/zh
Priority to JP2024516758A priority patent/JP2024533552A/ja
Publication of WO2023193166A1 publication Critical patent/WO2023193166A1/zh
Priority to US18/617,506 priority patent/US20240313224A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • 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
    • 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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
    • H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • 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
    • H01M2004/028—Positive electrodes
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application belongs to the field of battery technology, and specifically relates to an electrode assembly and a secondary battery, a battery module, a battery pack and an electrical device including the electrode assembly.
  • the positive electrode plate is one of the key factors that determine the performance of the secondary battery.
  • the solvent used for the existing positive electrode slurry is usually an oil-based solvent, such as N-methylpyrrolidone (NMP).
  • NMP N-methylpyrrolidone
  • Aqueous cathode slurries using water as solvent have attracted more and more attention from researchers due to their low cost and environmental friendliness.
  • water-based positive electrode sheets have the disadvantages of high moisture content and poor capacity performance, which limits their practical application.
  • the purpose of this application is to provide an electrode assembly and a secondary battery, a battery module, a battery pack and an electrical device containing the same, so that an electrode assembly using a water-based positive electrode plate and a secondary battery, a battery module, a battery pack containing the same are provided.
  • electrical devices have the characteristics of high energy density, good cycle performance, low internal resistance, low cost and environmental friendliness.
  • a first aspect of the present application provides an electrode assembly, including a water-based positive electrode piece and a negative electrode piece, wherein the water-based positive electrode piece includes a positive electrode current collector and a positive electrode film layer located on at least one surface of the positive electrode current collector, so The positive electrode film layer includes a positive electrode active material; the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer located on at least one surface of the negative electrode current collector, the negative electrode film layer includes a negative electrode active material; the water-based positive electrode sheet At least part of the surface is provided with a plurality of first micropores, and satisfies: 0.001% ⁇ (S 12 ⁇ H 12 ⁇ D 1 )/(S 11 ⁇ C 1 ⁇ H 11 ) ⁇ 1%, H 11 ⁇ m represents the water system The thickness of the positive electrode piece, H 12 ⁇ m represents the depth of the first micropores, S 11 m 2 represents the area of the water-based positive electrode piece, S 12 m 2 represents the total area of the plurality of first micro
  • the water-based positive electrode piece satisfies 0.001% ⁇ (S 12 ⁇ H 12 ⁇ D 1 )/(S 11 ⁇ C 1 ⁇ H 11 ) ⁇ 1%
  • the negative electrode piece satisfies 0 ⁇ (S 22 ⁇ H 22 ⁇ D 2 )/(S 21 ⁇ C 2 ⁇ H 21 ) ⁇ 2.5%.
  • the electrode assembly can have low moisture content, high electrolyte infiltration rate and high drying rate. When used in secondary batteries, it can make Secondary batteries have the characteristics of high energy density, good cycle performance, low internal resistance, low cost and environmental friendliness.
  • the electrode assembly can have low surface resistance and good interface properties, thereby enabling a secondary battery using the electrode assembly It has good electrochemical properties, such as high cycle stability, high capacity development and low internal resistance.
  • (S 12 ⁇ H 12 ⁇ D 1 )/(S 11 ⁇ C 1 ⁇ H 11 ) within the above range can also maintain good mechanical properties of the water-based positive electrode piece.
  • the negative electrode piece can not only have a high electrolyte infiltration rate, but also have low surface resistance and good interface properties. Therefore, the secondary battery using the electrode assembly of the present application can have high cycle stability, high capacity performance and low internal resistance.
  • (S 22 ⁇ H 22 ⁇ D 2 )/(S 21 ⁇ C 2 ⁇ H 21 ) within the above range can also enable the negative electrode piece to maintain good mechanical properties.
  • the ratio of the total area of the plurality of first micropores to the area of the water-based positive electrode sheet is within the above range, which enables the water-based positive electrode sheet to have good mechanical properties, and also allows the water-based positive electrode sheet to have appropriate porosity, thereby achieving It is beneficial to the drainage of water and the infiltration of electrolyte. In addition, it can also make the water-based positive electrode plate have suitable electron conduction channels and active ion transmission channels.
  • the ratio of the depth of the first micropores to the thickness of the water-based positive electrode sheet is within the above range, which not only ensures that the water-based positive electrode sheet has a high drying rate and high electrolyte infiltration rate, but also ensures that the water-based positive electrode sheet has good mechanical properties. performance.
  • C 1 is 2.0-3.0, optionally 2.3-2.7.
  • the compacted density of the water-based positive electrode sheets is controlled within an appropriate range, which can bring the positive active material particles in the positive electrode film layer into close contact and increase the positive active material content per unit volume, thereby increasing the energy density of the secondary battery.
  • D 1 is 0.5-1.5, optionally 0.8-1.3.
  • the volume average particle size Dv50 of the positive active material is within the above range, which can shorten the diffusion path of active ions, thereby further improving the energy density, cycle performance and rate performance of the secondary battery.
  • the ratio of the total area of the plurality of second micropores to the area of the negative electrode piece is within the above range, which enables the negative electrode piece to have good mechanical properties, and also allows the negative electrode piece to have appropriate porosity and high capacity, thereby having It is beneficial to improve the electrolyte infiltration rate and capacity development of the electrode assembly. In addition, it can also make the negative electrode plate have suitable electron conduction channels and active ion transmission channels.
  • the ratio of the depth of the second micropores to the thickness of the negative electrode piece is within the above range, which not only ensures that the negative electrode piece has a high electrolyte infiltration rate, but also ensures that the negative electrode piece has good mechanical properties.
  • C 2 is 1.2-2.0, optionally 1.4-1.8.
  • Controlling the compaction density of the negative electrode sheet within an appropriate range can bring the negative active material particles in the negative electrode film layer into close contact and increase the negative active material content per unit volume, thereby increasing the energy density of the secondary battery.
  • D 2 is 12-20, optionally 15-19.
  • the volume average particle size Dv50 of the negative active material is within the above range, which can shorten the diffusion path of active ions, thereby further improving the energy density, cycle performance and rate performance of the secondary battery.
  • the electrode assembly satisfies: 0.1 ⁇ A/B ⁇ 1.0, optionally, 0.25 ⁇ A/B ⁇ 0.50, A represents (S 12 ⁇ H 12 ⁇ D 1 )/(S 11 ⁇ C 1 ⁇ H 11 ), B represents (S 22 ⁇ H 22 ⁇ D 2 )/(S 21 ⁇ C 2 ⁇ H 21 ).
  • A/B within the above range can further increase the electrolyte infiltration rate of the electrode assembly, and is more conducive to the rapid discharge of residual moisture from the electrode assembly during the drying process, thereby enabling the secondary battery to have low impedance and high energy density. and high cycle capacity retention.
  • the electrode assembly satisfies: S 3 /S 22 ⁇ 5%, optionally, 8% ⁇ S 3 /S 22 ⁇ 70%, and S 3 m 2 represents the plurality of first micropores The overlapping area with the plurality of second micropores.
  • the overlapping area of the first micropores on the surface of the water-based positive electrode sheet and the second micropores on the surface of the negative electrode sheet is within the above range, which is conducive to the formation of channels between the first micropores, the second micropores and the micropores in the isolation film. This is conducive to the rapid discharge of residual moisture in the electrode assembly and improves the electrolyte infiltration rate of the electrode assembly. Therefore, when the electrode assembly of the present application is applied to a secondary battery, the secondary battery can have low impedance, high energy density and high cycle capacity retention rate.
  • the morphology of each first micropore is a regular shape or an irregular shape.
  • the morphology of each first micropore includes a circle, a rectangle, or a square.
  • the equivalent diameter of each first micropore is 1 ⁇ m-200 ⁇ m, optionally 50 ⁇ m-180 ⁇ m.
  • the equivalent diameter of the first micropore is within the above range, which can ensure that the water-based positive electrode piece has good mechanical properties while ensuring that the water-based positive electrode piece has low moisture content, high electrolyte infiltration rate and high drying rate. For example, it can make the water-based positive electrode plate have high strength and good flexibility. Therefore, the electrode assembly can have a high electrolyte infiltration rate and good processability, and therefore, the secondary battery using the electrode assembly can also have good electrochemical performance and high productivity.
  • the center distance between adjacent first microholes is 1 mm to 10 mm.
  • the center distance between adjacent first micropores is within the above range, which enables the first micropores to be properly distributed on the surface of the water-based positive electrode piece. As a result, the distribution of the first micropores can be avoided from being too dense, thereby allowing the water-based positive electrode piece to maintain good mechanical properties.
  • the plurality of first micropores are distributed in an array.
  • the morphology of each second micropore is a regular shape or an irregular shape.
  • the morphology of each second micropore includes a circle, a rectangle, or a square.
  • the equivalent diameter of each second micropore is 1 ⁇ m-200 ⁇ m, optionally 50 ⁇ m-150 ⁇ m.
  • the equivalent diameter of the second micropores is within the above range, which enables the negative electrode piece to have good mechanical properties on the premise of ensuring that the negative electrode piece has a high electrolyte infiltration rate. For example, it can make the negative electrode piece have higher electrolyte infiltration rate. Strength and good flexibility. Therefore, the electrode assembly can have a high electrolyte infiltration rate and good processability, and therefore, the secondary battery using the electrode assembly can also have good electrochemical performance and high productivity.
  • the center distance between adjacent second microholes is 1 mm to 10 mm.
  • the center distance between adjacent second micropores is within the above range, which enables the second micropores to be appropriately distributed on the surface of the negative electrode piece. As a result, the distribution of the second micropores can be avoided from being too dense, thereby allowing the negative electrode piece to maintain good mechanical properties.
  • the plurality of second micropores are distributed in an array.
  • the positive electrode film layer further includes one or more of an aqueous adhesive and a conductive agent.
  • the water-based adhesive includes methylcellulose and its salts, xanthan gum and its salts, chitosan and its salts, alginic acid and its salts, polyethylenimine and its salts , polyacrylamide, acrylonitrile-acrylic acid copolymer and its derivatives or mixtures thereof.
  • the water-based adhesive includes a compound mixture of xanthan gum and polyethyleneimine.
  • the mass ratio of the xanthan gum and the polyethyleneimine is 2:1-0.2:2.8.
  • the number average molecular weight of the xanthan gum is 300000-2000000.
  • the number average molecular weight of the polyethyleneimine is 2,000-50,000.
  • the water-based adhesive includes a compound mixture of acrylonitrile-acrylic acid copolymer and polyethyleneimine.
  • the mass ratio of the acrylonitrile-acrylic acid copolymer and the polyethyleneimine is 2:1-0.2:2.8.
  • the number average molecular weight of the acrylonitrile-acrylic acid copolymer is 300000-2000000.
  • the number average molecular weight of the polyethyleneimine is 2,000-70,000.
  • the conductive agent includes one or more of conductive carbon black, superconducting carbon black, conductive graphite, acetylene black, Ketjen black, graphene, and carbon nanotubes.
  • a second aspect of the present application provides a secondary battery, which includes the electrode assembly of the first aspect of the present application.
  • 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 of the present application.
  • a fifth aspect of the present application provides an electrical 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 of the present application.
  • the secondary battery of the present application has low moisture content, high electrolyte infiltration rate and high drying rate.
  • the secondary battery of the present application also has high energy density, good cycle performance, low internal resistance, low cost and environmental friendliness.
  • the battery modules, battery packs and electrical devices 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 cross-sectional view of an embodiment of the water-based positive electrode sheet of the present application.
  • Figure 2 is a schematic cross-sectional view of another embodiment of the water-based positive electrode sheet of the present application.
  • FIG. 3 is a schematic diagram of an embodiment of the secondary battery of the present application.
  • FIG. 4 is an exploded schematic view of the embodiment of the secondary battery of FIG. 3 .
  • FIG. 5 is a schematic diagram of an embodiment of the battery module of the present application.
  • Figure 6 is a schematic diagram of an embodiment of the battery pack of the present application.
  • FIG. 7 is an exploded schematic view of the embodiment of the battery pack shown in FIG. 6 .
  • FIG. 8 is a schematic diagram of an embodiment of a power consumption 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. A given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive of the endpoints, and may be arbitrarily combined, that is, any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, understand that ranges of 60-110 and 80-120 are also expected. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-5.
  • the numerical range “a-b” represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers.
  • the numerical range “0-5" means that all real numbers between "0-5" have been listed in this article, and "0-5" is just an abbreviation of these numerical combinations.
  • a certain parameter is an integer ⁇ 2
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • step (c) means that step (c) may be added to the method in any order.
  • the method may include steps (a), (b) and (c). , may also include steps (a), (c) and (b), may also include steps (c), (a) and (b), etc.
  • condition "A or B” is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists) ; Or both A and B are true (or exist).
  • the term "about” is used to describe and illustrate small variations.
  • the term may refer to a variation range of less than or equal to ⁇ 10% of the stated numerical value.
  • Aqueous cathode slurries using water as solvent have attracted more and more attention from researchers due to their low cost and environmental friendliness.
  • aqueous cathode slurries often use binders with hydrophilic groups, and these hydrophilic groups and solvent water will have a greater impact on the performance of secondary batteries.
  • Water-based cathode sheets prepared using water-based cathode slurries will retain some moisture and are difficult to remove during the drying process. Therefore, when the current water-based cathode sheets are used in secondary batteries, the residual moisture will not only affect the performance of the cathode sheets.
  • the wettability will also cause side reactions with the electrolyte and electrode active materials inside the battery, resulting in increased irreversible loss of active ions, reduced battery energy density, excessive capacity attenuation, and in addition, battery swelling and increased self-discharge.
  • Adjusting the preparation process of the positive electrode sheet such as controlling the solid content of the aqueous positive electrode slurry, and using a process that combines thermal coating, cold pressing and vacuum baking to prepare the positive electrode sheet, although it can effectively accelerate the evaporation of water and reduce the The remaining moisture in the water-based positive electrode sheet will correspondingly increase the preparation cost of the water-based positive electrode sheet and reduce the production capacity of the secondary battery.
  • the inventor designed an electrode assembly based on the structure of the electrode assembly.
  • the electrode assembly can have low moisture content, high electrolyte infiltration rate and high drying rate.
  • the electrode assembly can also have high energy density, Good cycle performance, low internal resistance, low cost and environmentally friendly characteristics.
  • a first aspect of the present application provides an electrode assembly, which includes a water-based positive electrode piece and a negative electrode piece.
  • the aqueous positive electrode sheet includes a positive electrode current collector and a positive electrode film layer located on at least one surface of the positive electrode current collector.
  • the positive electrode film layer includes a positive electrode active material.
  • At least part of the surface of the water-based positive electrode piece is provided with a plurality of first micropores, and satisfies: 0.001% ⁇ (S 12 ⁇ H 12 ⁇ D 1 )/(S 11 ⁇ C 1 ⁇ H 11 ) ⁇ 1%
  • H 11 ⁇ m represents the thickness of the water-based positive electrode sheet
  • H 12 ⁇ m represents the depth of the first micropore
  • S 11 m 2 represents the area of the water-based positive electrode sheet
  • S 12 m 2 represents the plurality of first micropores.
  • the total area of micropores, C 1 g/cc represents the compacted density of the water-based cathode electrode piece, and D 1 ⁇ m represents the volume average particle size Dv50 of the cathode active material.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer located on at least one surface of the negative electrode current collector.
  • the negative electrode film layer includes a negative electrode active material.
  • At least part of the surface of the negative electrode piece is provided with a plurality of second micropores, and satisfies: 0 ⁇ (S 22 ⁇ H 22 ⁇ D 2 )/(S 21 ⁇ C 2 ⁇ H 21 ) ⁇ 2.5%
  • H 21 ⁇ m represents the thickness of the negative electrode piece
  • H 22 ⁇ m represents the depth of the second micropores
  • S 21 m 2 represents the area of the negative electrode piece
  • S 22 m 2 represents the total area of the plurality of second micropores.
  • Area, C 2 g/cc represents the compacted density of the negative electrode piece
  • D 2 ⁇ m represents the volume average particle size Dv50 of the negative active material.
  • the inventor unexpectedly discovered that a plurality of first micropores are provided on at least part of the surface of the aqueous positive electrode piece, and the aqueous positive electrode piece (S 12 ⁇ H 12 ⁇ D
  • the value of 1 )/(S 11 ⁇ C 1 ⁇ H 11 ) within the above range can make it easy to remove the remaining moisture in the aqueous positive electrode piece, thereby improving the interface performance of the electrode assembly and reducing the swelling and self-inflation of the electrode assembly. Risk of discharge and corrosion.
  • the above-mentioned first micropores are provided on the surface of the water-based positive electrode piece.
  • the electrode assembly of the present application when the electrode assembly of the present application is applied to a secondary battery, it can not only reduce the risk of inflation, self-discharge, and corrosion of the secondary battery, but also improve the energy density, cycle performance, and rate performance of the secondary battery.
  • the secondary battery using the electrode assembly of the present application can have good electrochemical performance and high energy density.
  • the water-based positive electrode plate has at least one of the following situations: the plurality of The ratio S 12 /S 11 of the total area of the first micropores to the area of the water-based positive electrode sheet is small, the ratio H 12 /H 11 of the depth of the first micropores to the thickness of the water-based positive electrode sheet is small, and the positive electrode activity
  • the volume average particle size D 1 of the material is small, and the compacted density C 1 of the water-based positive electrode piece is large.
  • the spacing between the particles of the positive active material is very small and the contact is close, resulting in fewer active ion transmission channels, higher internal resistance of the secondary battery, and poor electrolyte infiltration performance, which is not conducive to the performance of the battery capacity.
  • the water-based positive electrode sheet has fewer moisture drainage channels, and the moisture is not easily discharged quickly during the drying process, resulting in a high residual moisture content and a higher risk of bloating, self-discharge, and corrosion in the secondary battery.
  • the negative electrode plate has at least one of the following situations: the plurality of The ratio of the total area of the second micropores to the area of the negative electrode piece is S 22 /S 21. The ratio of the depth of the second micropores to the thickness of the negative electrode piece is H 22 /H 21. The volume of the negative active material is large. The average particle size D 2 is larger and the compacted density C 2 of the negative electrode piece is smaller. As a result, the energy density of the secondary battery drops significantly.
  • the water-based positive electrode piece satisfies 0.001% ⁇ (S 12 ⁇ H 12 ⁇ D 1 )/(S 11 ⁇ C 1 ⁇ H 11 ) ⁇ 1%
  • the negative electrode piece satisfies 0 ⁇ (S 22 ⁇ H 22 ⁇ D 2 )/(S 21 ⁇ C 2 ⁇ H 21 ) ⁇ 2.5%.
  • the electrode assembly can have low moisture content, high electrolyte infiltration rate and high drying rate. When used in secondary batteries, it can make Secondary batteries have the characteristics of high energy density, good cycle performance, low internal resistance, low cost and environmental friendliness.
  • the surfaces of the aqueous positive electrode plate and negative electrode plate are equipped with micropores, so that during the assembly process of the secondary battery, the electrolyte can not only infiltrate the electrode assembly along the horizontal direction of the electrode plate/separator, but also along the electrode.
  • the electrode assembly is infiltrated into a network formed by the micropores of the electrode piece and the micropores of the isolation film in the vertical direction of the electrode piece; secondly, the surface of the water-based positive electrode piece and the negative electrode piece is equipped with micropores, and the remaining moisture in the electrode piece can be dried in the electrode assembly During the process, it is quickly discharged to the outside of the electrode assembly, which can further reduce the moisture content of the electrode assembly; thirdly, after a reasonable combination of the micropores on the surface of the electrode piece, the compaction density of the electrode piece, and the particle size of the active material, it can ensure that the water-based positive electrode piece It has suitable electron conduction channels and active ion transmission channels at the same time as the negative electrode plate.
  • the water-based positive electrode sheet can satisfy: 0.05% ⁇ (S 12 ⁇ H 12 ⁇ D 1 )/(S 11 ⁇ C 1 ⁇ H 11 ) ⁇ 0.5%, 0.05% ⁇ (S 12 ⁇ H 12 ⁇ D 1 )/(S 11 ⁇ C 1 ⁇ H 11 ) ⁇ 0.45%, 0.05% ⁇ (S 12 ⁇ H 12 ⁇ D 1 )/(S 11 ⁇ C 1 ⁇ H 11 ) ⁇ 0.4%, 0.05 % ⁇ (S 12 ⁇ H 12 ⁇ D 1 )/(S 11 ⁇ C 1 ⁇ H 11 ) ⁇ 0.35%, 0.05% ⁇ (S 12 ⁇ H 12 ⁇ D 1 )/(S 11 ⁇ C 1 ⁇ H 11 ) ⁇ 0.3%, 0.05% ⁇ (S 12 ⁇ H 12 ⁇ D 1 )/(S 11 ⁇ C 1 ⁇ H 11 ) ⁇ 0.25%, 0.05% ⁇ (S 12 ⁇ H 12 ⁇ D 1 )/(S 11 ⁇ C 1 ⁇ H 11 ) ⁇ 0.2
  • the inventor found through research that (S 12 ⁇ H 12 ⁇ D 1 )/(S 11 ⁇ C 1 ⁇ H 11 ) within the above range, the moisture in the water-based positive electrode piece can During the drying process of the electrode assembly, it is quickly discharged to the outside of the electrode assembly, thereby further reducing the moisture content of the positive electrode piece and increasing the electrolyte infiltration rate and drying rate of the electrode assembly.
  • the electrode assembly can have low surface resistance and good interface properties, so that the secondary battery using the electrode assembly can have good electrochemical properties, such as high cycle stability, high capacity development and low internal resistance.
  • (S 12 ⁇ H 12 ⁇ D 1 )/(S 11 ⁇ C 1 ⁇ H 11 ) within the above range can also maintain good mechanical properties of the water-based positive electrode piece. Therefore, the positive electrode piece is less likely to be deformed during the assembly and processing of the electrode assembly. Therefore, the electrode assembly can not only maintain good electrochemical performance during processing and assembly, but also have high productivity.
  • the negative electrode plate can satisfy: 0.2% ⁇ (S 22 ⁇ H 22 ⁇ D 2 )/(S 21 ⁇ C 2 ⁇ H 21 ) ⁇ 2.0%, 0.2% ⁇ (S 22 ⁇ H 22 ⁇ D 2 )/(S 21 ⁇ C 2 ⁇ H 21 ) ⁇ 1.8%, 0.2% ⁇ (S 22 ⁇ H 22 ⁇ D 2 )/(S 21 ⁇ C 2 ⁇ H 21 ) ⁇ 1.5%, 0.2% ⁇ (S 22 ⁇ H 22 ⁇ D 2 )/(S 21 ⁇ C 2 ⁇ H 21 ) ⁇ 1.2%, 0.2% ⁇ (S 22 ⁇ H 22 ⁇ D 2 )/(S 21 ⁇ C 2 ⁇ H 21 ) ⁇ 1.0%, 0.2% ⁇ (S 22 ⁇ H 22 ⁇ D 2 )/(S 21 ⁇ C 2 ⁇ H 21 ) ⁇ 0.8%, 0.2% ⁇ (S 22 ⁇ H 22 ⁇ D 2 )/(S 21 ⁇ C 2 ⁇ H 21 ) ⁇ 0.5%,
  • the inventor found through research that (S 22 ⁇ H 22 ⁇ D 2 )/(S 21 ⁇ C 2 ⁇ H 21 ) within the above range, the negative electrode plate can not only have high electrolysis Liquid infiltration rate, low surface resistance and good interface properties. Therefore, the secondary battery using the electrode assembly of the present application can have high cycle stability, high capacity performance and low internal resistance.
  • (S 22 ⁇ H 22 ⁇ D 2 )/(S 21 ⁇ C 2 ⁇ H 21 ) within the above range can also enable the negative electrode piece to maintain good mechanical properties. Therefore, the negative electrode piece is less likely to be deformed during the assembly and processing of the electrode assembly. Therefore, the electrode assembly can not only maintain good electrochemical performance during processing and assembly, but also have high productivity.
  • the ratio of the total area of the plurality of first micropores to the area of the aqueous positive electrode sheet satisfies 0 ⁇ S 12 /S 11 ⁇ 2%.
  • the ratio of the total area of the plurality of first micropores to the area of the water-based positive electrode piece is within the above range, which can enable the water-based positive electrode piece to have good mechanical properties. As a result, the risk of irreversible deformation of the water-based positive electrode piece during processing can be reduced, thereby increasing the productivity of the electrode assembly. If the ratio of the total area of the plurality of first micropores to the area of the water-based positive electrode piece is within the above range, the water-based positive electrode piece can also have appropriate porosity, which is beneficial to water discharge and electrolyte infiltration.
  • the ratio of the total area of the plurality of first micropores to the area of the aqueous positive electrode piece is within the above range, which can also enable the aqueous positive electrode piece to have appropriate electron conduction channels and active ion transmission channels. Therefore, the application of electrode assemblies to secondary batteries can enable the secondary batteries to have high productivity, high cycle stability, high capacity and low internal resistance.
  • the ratio of the depth of the first micropores to the thickness of the aqueous positive electrode sheet satisfies 30% ⁇ H 12 /H 11 ⁇ 100%.
  • the depth of the first micropores may be less than or equal to the thickness of the water-based positive electrode piece.
  • the first micropores may be through holes penetrating the positive electrode piece.
  • the ratio of the depth of the first micropores to the thickness of the water-based positive electrode piece is within the above range, which can not only ensure that the water-based positive electrode piece has a high drying rate and a high electrolyte infiltration rate, It can also ensure that the water-based positive electrode piece has good mechanical properties. Therefore, the electrode assembly of the present application can have good interface properties, low surface resistance and high processing efficiency. When applied to secondary batteries, the secondary batteries can have good cycle performance, good rate performance and high productivity.
  • C 1 g/cc represents the compacted density of the water-based positive electrode piece.
  • C 1 can be 2.0-3.0.
  • C 1 can be about 2.0, about 2.1, about 2.2, about 2.3, about 2.4, About 2.5, about 2.6, about 2.7, about 2.8, about 2.9, about 3.0, or within the range of any of the above values.
  • Ci is optionally 2.3-2.7.
  • the compacted density of the water-based positive electrode sheets is controlled within an appropriate range, which can bring the positive active material particles in the positive electrode film layer into close contact and increase the positive active material content per unit volume, thereby increasing the energy density of the secondary battery.
  • D 1 ⁇ m represents the volume average particle size Dv50 of the cathode active material.
  • D 1 may be 0.5-1.5.
  • D 1 may be about 0.5, about 0.6, about 0.7, about 0.8, about 0.9, about 1.0, about 1.1, about 1.2, about 1.3, about 1.4, about 1.5, or within the range of any of the above values.
  • D 1 is optionally 0.8-1.3.
  • the volume average particle diameter Dv50 of the positive electrode active material is within the above range, which can shorten the diffusion path of active ions. Therefore, when the electrode assembly of the present application is applied to a secondary battery, it can further improve the energy density, cycle performance and rate performance of the secondary battery.
  • the ratio of the total area of the plurality of first micropores to the area of the water-based positive electrode piece is S 12 /S 11
  • the ratio of the depth of the first micropores to the thickness of the water-based positive electrode piece is H 12 /H 11.
  • the compacted density C 1 of the aqueous cathode plate and the volume average particle size D 1 of the cathode active material are within the above range, which can be beneficial to the control of (S 12 ⁇ H 12 ⁇ D 1 )/(S 11 ⁇ C 1 ⁇ H 11 ) is within the scope of this application. Therefore, when the electrode assembly of the present application is applied to a secondary battery, it can not only reduce the risk of inflation, self-discharge, and corrosion of the secondary battery, but also improve the energy density, cycle performance, and rate performance of the secondary battery.
  • the ratio of the total area of the plurality of second micropores to the area of the negative electrode piece can satisfy: 0 ⁇ S 22 /S 21 ⁇ 0.2%.
  • the negative electrode piece when the ratio of the total area of the plurality of second micropores to the area of the negative electrode piece is within the above range, the negative electrode piece can have good mechanical properties. As a result, the risk of irreversible deformation of the negative electrode piece during processing can be reduced, thereby increasing the productivity of the electrode assembly. If the ratio of the total area of the plurality of second micropores to the area of the negative electrode piece is within the above range, the negative electrode piece can also have appropriate porosity and high capacity, thereby helping to improve the electrolyte infiltration rate and capacity of the electrode assembly. play.
  • the ratio of the total area of the plurality of second micropores to the area of the negative electrode piece is within the above range, which can also enable the negative electrode piece to have appropriate electron conduction channels and active ion transmission channels. Therefore, the application of electrode assemblies to secondary batteries can enable the secondary batteries to have high productivity, high cycle stability, high capacity and low internal resistance.
  • the ratio of the depth of the second micropores to the thickness of the negative electrode sheet can satisfy: 30% ⁇ H 22 /H 21 ⁇ 100%, 30% ⁇ H 22 /H 21 ⁇ 90%, 30% ⁇ H 22 /H 21 ⁇ 80%, 30% ⁇ H 22 /H 21 ⁇ 70%, 30% ⁇ H 22 /H 21 ⁇ 60%, 40% ⁇ H 22 /H 21 ⁇ 100%, 40% ⁇ H 22 /H 21 ⁇ 90%, 40% ⁇ H 22 /H 21 ⁇ 80%, 40% ⁇ H 22 /H 21 ⁇ 70%, 40% ⁇ H 22 /H 21 ⁇ 60%, 50% ⁇ H 22 /H 21 ⁇ 100%, 50% ⁇ H 22 /H 21 ⁇ 90%, 50% ⁇ H 22 /H 21 ⁇ 80%, 50% ⁇ H 22 /H 21 ⁇ 70%, 60% ⁇ H 22 /H 21 ⁇ 100%, 60% ⁇ H 22 /H 21 ⁇ 90%, 60% ⁇ H 22 /H 21 ⁇ 80%, 70%
  • the depth of the second micropore may be less than or equal to the thickness of the negative electrode piece.
  • the second micropores may be through holes penetrating the negative electrode piece.
  • the ratio of the depth of the second micropores to the thickness of the negative electrode piece is within the above range, which can not only ensure that the negative electrode piece has a high electrolyte infiltration rate, but also ensure that the negative electrode piece has Good mechanical properties. Therefore, the electrode assembly of the present application can have good interface performance, low surface resistance and high processing efficiency, and can be used in secondary batteries to make the secondary battery have good cycle performance, good rate performance and high productivity.
  • C 2 g/cc represents the compacted density of the negative electrode piece.
  • C 2 can be 1.2-2.0.
  • C 2 can be about 1.2, about 1.3, about 1.4, about 1.5, about 1.6, about 1.7, about 1.8, about 1.9, about 2.0, or within the range of any of the above values.
  • C is optionally 1.4-1.8.
  • Controlling the compaction density of the negative electrode sheet within an appropriate range can bring the negative active material particles in the negative electrode film layer into close contact and increase the negative active material content per unit volume, thereby increasing the energy density of the secondary battery.
  • D 2 ⁇ m represents the volume average particle size Dv50 of the negative active material.
  • D 2 can be 12-20.
  • D 2 can be about 12, about 13, about 14, about 15, about 16, about 17, about 18, about 19, about 20, or within the range of any of the above values.
  • D2 is optionally 15-19.
  • the volume average particle diameter Dv50 of the negative active material is within the above range, which can shorten the diffusion path of active ions. Therefore, when the electrode assembly of the present application is applied to a secondary battery, it can further improve the energy density, cycle performance and rate performance of the secondary battery.
  • the compacted density C 2 of the negative electrode piece and the volume average particle size D 2 of the negative active material are within the above range, which can be beneficial to the control of (S 22 ⁇ H 22 ⁇ D 2 )/(S 21 ⁇ C 2 ⁇ H 21 ) within the scope of this application. Therefore, when the electrode assembly of the present application is used in secondary batteries, the secondary batteries can have good electrochemical performance and high energy density.
  • the electrode assembly can satisfy: 0.10 ⁇ A/B ⁇ 1.0, A represents (S 12 ⁇ H 12 ⁇ D 1 )/(S 11 ⁇ C 1 ⁇ H 11 ), and B represents (S 22 ⁇ H 22 ⁇ D 2 )/(S 21 ⁇ C 2 ⁇ H 21 ).
  • A/B within the above range can give full play to the respective advantages of the water-based positive electrode piece and the negative electrode piece as well as the synergistic effect between the two, thereby further improving the electrode performance.
  • the electrolyte infiltration rate of the component is improved, and it is more conducive to the rapid discharge of residual moisture from the electrode component during the drying process. Therefore, when the electrode assembly of the present application is applied to a secondary battery, the secondary battery can have low impedance, high energy density and high cycle capacity retention rate.
  • the electrode assembly can satisfy: S 3 /S 22 ⁇ 5%, for example, S 3 /S 22 can be about 5%, about 8%, about 10%, about 15%, about 20% , about 25%, about 30%, about 35%, about 40%, about 45%, about 50%, about 55%, about 60%, about 65%, about 70%, about 75%, about 80%, about 85%, about 90%, about 95%, about 100% or within the range of any of the above values.
  • S 3 m 2 represents the overlapping area of the plurality of first micropores and the plurality of second micropores.
  • the electrode assembly can satisfy: 8% ⁇ S 3 /S 22 ⁇ 85%, 8% ⁇ S 3 /S 22 ⁇ 80%, 8% ⁇ S 3 /S 22 ⁇ 75%, 8 % ⁇ S 3 /S 22 ⁇ 70%, 15% ⁇ S 3 /S 22 ⁇ 85%, 15% ⁇ S 3 /S 22 ⁇ 80%, 15% ⁇ S 3 /S 22 ⁇ 75%, 15% ⁇ S 3 /S 22 ⁇ 70%, 25% ⁇ S 3 /S 22 ⁇ 85%, 25% ⁇ S 3 /S 22 ⁇ 80%, 25% ⁇ S 3 /S 22 ⁇ 75%, 25% ⁇ S 3 /S 22 ⁇ 70%, 40% ⁇ S 3 /S 22 ⁇ 85%, 40% ⁇ S 3 /S 22 ⁇ 80%, 40% ⁇ S 3 /S 22 ⁇ 75% or 40% ⁇ S 3 /S 22 ⁇ 70%.
  • the overlapping area of the first micropores on the surface of the water-based positive electrode piece and the second micropores on the surface of the negative electrode piece is within the above range, which is beneficial to the first micropores and the second micropores.
  • the pores and the micropores in the isolation film form channels, which facilitates the rapid discharge of residual moisture in the electrode assembly and increases the electrolyte infiltration rate of the electrode assembly. Therefore, when the electrode assembly of the present application is applied to a secondary battery, the secondary battery can have low impedance, high energy density and high cycle capacity retention rate.
  • the morphology of each first micropore can be the same or different.
  • the morphology of each first micropore may be a regular shape or an irregular shape.
  • the shape of each first micropore may include a circle, a rectangle, or a square.
  • the equivalent diameter of each first micropore may be 1 ⁇ m-200 ⁇ m, for example, may be about 5 ⁇ m, about 10 ⁇ m, about 20 ⁇ m, about 50 ⁇ m, about 80 ⁇ m, about 100 ⁇ m, about 120 ⁇ m, about 150 ⁇ m, about 180 ⁇ m. , about 200 ⁇ m or within the range of any of the above values.
  • the equivalent diameter of each first micropore may be 5 ⁇ m-180 ⁇ m, 10 ⁇ m-180 ⁇ m, 20 ⁇ m-180 ⁇ m, 30 ⁇ m-180 ⁇ m, 50 ⁇ m-180 ⁇ m, 5 ⁇ m-150 ⁇ m, 10 ⁇ m-150 ⁇ m, 20 ⁇ m-150 ⁇ m, 30 ⁇ m. -150 ⁇ m or 50 ⁇ m-150 ⁇ m.
  • the equivalent diameter of each first micropore may be the diameter of a circle having the same area as each first micropore.
  • the equivalent diameter of the first micropore is within the above range, which can ensure that the water-based positive electrode piece has good mechanical properties while ensuring that the water-based positive electrode piece has low moisture content, high electrolyte infiltration rate and high drying rate. For example, it can make the water-based positive electrode plate have high strength and good flexibility. Therefore, the electrode assembly can have a high electrolyte infiltration rate and good processability, and therefore, the secondary battery using the electrode assembly can also have good electrochemical performance and high productivity.
  • the center distance between adjacent first micropores can be 1 mm to 10 mm, for example, it can be about 1 mm, about 2 mm, about 3 mm, about 4 mm, about 5 mm, about 6 mm, about 7 mm, about 8 mm, About 9mm, about 10mm or within the range of any of the above values.
  • the center distance of adjacent first micropores is within the above range, which can enable the first micropores to be properly distributed on the surface of the water-based positive electrode piece. As a result, the distribution of the first micropores can be avoided from being too dense, thereby allowing the water-based positive electrode piece to maintain good mechanical properties.
  • the plurality of first micropores may be distributed in an array.
  • the morphology of each second micropore can be the same or different.
  • the morphology of each second micropore may be a regular shape or an irregular shape.
  • the shape of each second micropore may include a circle, a rectangle, or a square.
  • the equivalent diameter of each second micropore may be 1 ⁇ m-200 ⁇ m, for example, may be about 5 ⁇ m, about 10 ⁇ m, about 20 ⁇ m, about 50 ⁇ m, about 80 ⁇ m, about 100 ⁇ m, about 120 ⁇ m, about 150 ⁇ m, about 180 ⁇ m. , about 200 ⁇ m or within the range of any of the above values.
  • the equivalent diameter of each second micropore may be 5 ⁇ m-180 ⁇ m, 10 ⁇ m-180 ⁇ m, 20 ⁇ m-180 ⁇ m, 30 ⁇ m-180 ⁇ m, 50 ⁇ m-180 ⁇ m, 5 ⁇ m-150 ⁇ m, 10 ⁇ m-150 ⁇ m, 20 ⁇ m-150 ⁇ m, 30 ⁇ m. -150 ⁇ m or 50 ⁇ m-150 ⁇ m.
  • each second micropore may be the diameter of a circle having the same area as each second micropore.
  • the equivalent diameter of the second micropores is within the above range, which enables the negative electrode piece to have good mechanical properties on the premise of ensuring that the negative electrode piece has a high electrolyte infiltration rate. For example, it can make the negative electrode piece have higher electrolyte infiltration rate. Strength and good flexibility. Therefore, the electrode assembly can have a high electrolyte infiltration rate and good processability, and therefore, the secondary battery using the electrode assembly can also have good electrochemical performance and high productivity.
  • the center distance between adjacent second micropores can be 1 mm to 10 mm, for example, it can be about 1 mm, about 2 mm, about 3 mm, about 4 mm, about 5 mm, about 6 mm, about 7 mm, about 8 mm, About 9mm, about 10mm or within the range of any of the above values.
  • the center distance of adjacent second micropores is within the above range, which enables the second micropores to be appropriately distributed on the surface of the negative electrode piece. As a result, the distribution of the second micropores can be avoided from being too dense, thereby allowing the negative electrode piece to maintain good mechanical properties.
  • the plurality of second micropores may be distributed in an array.
  • the positive electrode current collector has two surfaces opposite in its thickness direction, and the positive electrode film layer can be located on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the negative electrode current collector has two surfaces opposite in its thickness direction, and the negative electrode film layer can be located on any one or both of the two opposite surfaces of the negative electrode current collector.
  • FIG. 1 is a schematic cross-sectional view of a partial embodiment of the water-based positive electrode sheet of the present application
  • FIG. 2 is a schematic cross-sectional view of a partial embodiment of the water-based positive electrode sheet of the present application.
  • the positive electrode film layer 102 is disposed on both sides of the positive electrode current collector 101.
  • Figure 1 shows that the ratio of the depth of the first micropores to the thickness of the positive electrode sheet is less than 100%, that is, H 12 is less than H 11 ;
  • Figure 2 shows that the first microhole is a through hole that penetrates the positive electrode piece. At this time, H 12 is equal to H 11 .
  • the arrangement of the second micropores on the surface of the negative electrode piece is similar to that of the water-based positive electrode piece.
  • the type of cathode active material is not specifically limited, and cathode active materials known in the art for secondary batteries can be used.
  • the cathode active material may include one or more of lithium transition metal oxides, olivine-structured lithium-containing phosphates, and their respective modified compounds.
  • the above-mentioned modified compounds of each positive electrode active material may be doping modification, surface coating modification, or both doping and surface coating modification of the positive electrode active material.
  • lithium transition metal oxides may include lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, One or more of lithium nickel cobalt aluminum oxide and their respective modified compounds.
  • the lithium-containing phosphate with an olivine structure may include lithium iron phosphate, a composite of lithium iron phosphate and carbon, a lithium manganese phosphate, a composite of lithium manganese phosphate and carbon, a lithium manganese iron phosphate, a lithium manganese iron phosphate and carbon.
  • the composite materials and their respective modifying compounds One or more of the composite materials and their respective modifying compounds. Only one type of these positive electrode active materials may be used alone, or two or more types may be used in combination.
  • the cathode active material may include one or more of lithium-containing phosphates with an olivine structure and modified compounds thereof.
  • the positive electrode film layer may further include one or more of an aqueous adhesive and a conductive agent.
  • the water-based adhesive can bond the positive active material, conductive agent, etc. to the current collector, enhance the electronic contact between the positive active material and the conductive agent, and between the positive active material and the positive current collector, and stabilize the structure of the positive electrode piece.
  • oil-based adhesives such as polyvinylidene fluoride
  • water-based adhesives are lower in cost, more environmentally friendly, and safer to use.
  • the water-based adhesive may include an aqueous dispersion solution or emulsion with a solid component content of more than 5%.
  • the water-based adhesive may also contain solids that can form a stable dispersion with water with a solid component content of more than 1%.
  • the aqueous adhesive includes soluble polysaccharides and their derivatives, water-soluble or water-dispersed polymers, or mixtures thereof.
  • the water-based adhesive may include methylcellulose and its salts, xanthan gum and its salts, chitosan and its salts, alginic acid and its salts, polyethyleneimine and its salts, polyacrylamide, Acrylonitrile-acrylic acid copolymer and its derivatives or mixtures thereof.
  • the aqueous adhesive may include a compound mixture of xanthan gum and polyethyleneimine.
  • the mass ratio of the xanthan gum and the polyethyleneimine may be 2:1-0.2:2.8.
  • the number average molecular weight of the xanthan gum may be 300,000-2,000,000.
  • the number average molecular weight of the polyethyleneimine may be 2,000-50,000.
  • the aqueous adhesive may include a blend of acrylonitrile-acrylic acid copolymer and polyethyleneimine.
  • the mass ratio of the acrylonitrile-acrylic acid copolymer and the polyethyleneimine may be 2:1-0.2:2.8.
  • the number average molecular weight of the acrylonitrile-acrylic acid copolymer may be 300,000-2,000,000.
  • the number average molecular weight of the polyethyleneimine may be 2,000-70,000.
  • the water-based binder is selected from the above substances and can further enhance the electronic contact between the positive active material and the conductive agent and between the positive active material and the positive current collector, thereby better stabilizing The structure of the positive electrode piece. Therefore, when the electrode assembly of the present application is applied to a secondary battery, the secondary battery can have high cycle stability and low internal resistance.
  • the conductive agent may include conductive carbon black, superconducting carbon black, conductive graphite, acetylene black, Ketjen black, graphite One or more of alkenes and carbon nanotubes.
  • the positive electrode film layer is usually formed by coating the positive electrode slurry on the positive electrode current collector, drying, and cold pressing.
  • the positive electrode slurry is usually formed by dispersing the positive electrode active material, aqueous binder, conductive agent and any other components in deionized water and stirring evenly.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • a metal foil aluminum foil can be used.
  • the composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer.
  • the metal material may include one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys.
  • the polymer material base layer may include polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE) one or more.
  • the negative electrode film layer is usually formed by coating the negative electrode slurry on the negative electrode current collector, drying, and cold pressing.
  • the negative electrode slurry coating is usually formed by dispersing the negative electrode active material, optional conductive agent, optional binder, and other optional additives in a solvent and stirring evenly.
  • the solvent may be N-methylpyrrolidone (NMP) or water, but is not limited thereto.
  • the adhesive used for the negative electrode film layer may include styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (for example, polyacrylic acid PAA, polymethacrylic acid PMAA, polysodium acrylate PAAS ), one or more of polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), carboxymethyl chitosan (CMCS).
  • the conductive agent used for the negative electrode film layer may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • Other optional auxiliaries may include one or more of thickeners (eg, sodium carboxymethyl cellulose CMC), PTC thermistor materials.
  • the type of negative electrode active material is not particularly limited, and negative electrode active materials known in the art for secondary batteries can be used.
  • the negative active material may include one or more of graphite, soft carbon, hard carbon, mesocarbon microspheres, carbon fiber, carbon nanotubes, silicon-based materials, tin-based materials, and lithium titanate.
  • the silicon-based material may include one or more of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitride composite, and silicon alloy materials.
  • the tin-based material may include one or more of elemental tin, tin oxide, and tin alloy materials.
  • the present application is not limited to these materials, and other conventionally known materials that can be used as negative electrode active materials for secondary batteries can also be used. Only one type of these negative electrode active materials may be used alone, or two or more types may be used in combination.
  • the type of negative electrode current collector is not subject to specific restrictions and can be selected according to actual needs.
  • the negative electrode current collector can use metal foil or composite current collector.
  • a metal foil a copper foil can be used as the negative electrode current collector.
  • the composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer.
  • the metal material may be selected from 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 the group consisting of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), poly One or more types of ethylene (PE).
  • PP polypropylene
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE poly One or more types of ethylene
  • the negative electrode sheet does not exclude other additional functional layers in addition to the negative electrode film layer.
  • the negative electrode sheet described in this application may further include a conductive undercoat layer (for example, composed of a conductive agent and an adhesive) disposed between the negative electrode current collector and the negative electrode film layer.
  • the negative electrode sheet described in this application further includes a protective layer covering the surface of the negative electrode film layer.
  • the manner in which the first micropores and the second micropores are implemented is not subject to specific restrictions, and can be achieved by means known in the art.
  • the means of arranging the first microholes and the second microholes on the surface of the pole piece may include any one of laser drilling, mechanical punching, or a combination thereof.
  • the lasers can be staggered up and down, an appropriate drilling array can be set up according to the drilling process requirements, and the appropriate laser energy can be selected according to the required microhole depth.
  • the electrode assembly further includes a separation membrane.
  • the isolation membrane is disposed between the water-based positive electrode piece and the negative electrode piece, and mainly functions to prevent the positive and negative electrodes from short-circuiting, and at the same time, allows active ions to pass through.
  • the material of the isolation film may include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation film may be a single-layer film or a multi-layer composite film. When the isolation film is a multi-layer composite film, the materials of each layer may be the same or different.
  • the water-based positive electrode piece, the isolation film and the negative electrode piece can be made into an electrode assembly through a winding process or a lamination process.
  • the thickness of the membrane layer and the pole piece has a meaning known in the art, and can be tested using methods known in the art.
  • a spiral micrometer is used for measurement.
  • the volume average particle diameter Dv50 of the material is a well-known meaning in the art. It represents the particle diameter corresponding to when the cumulative volume distribution percentage of the material reaches 50%. It can be measured using instruments and methods known in the art. For example, you can refer to the GB/T 19077-2016 particle size distribution laser diffraction method and use a laser particle size analyzer to conveniently measure it, such as the Mastersizer 2000E laser particle size analyzer of Malvern Instruments Co., Ltd. in the United Kingdom.
  • the compacted density of the pole piece is a meaning known in the art, and can be tested using methods known in the art.
  • the compacted density of the pole piece the surface density of the film layer/the thickness of the film layer.
  • the areal density of the film layer is a well-known meaning in the art, and can be tested using methods known in the art. For example, take a single-sided coated and cold-pressed pole piece (if it is a double-sided coated pole piece, you can wipe it first. Remove the film layer on one side), cut it into small discs, and weigh it; then wipe off the film layer of the weighed pole piece, and weigh the current collector.
  • the surface density of the film layer (weight of the small disc - weight of the current collector)/area of the small disc.
  • a second aspect of the present application provides a secondary battery, including the electrode assembly and an electrolyte of the first aspect of the present application.
  • the electrolyte plays a role in conducting active ions between the positive electrode piece and the negative electrode piece.
  • the electrolyte may be selected from at least one of a solid electrolyte and a liquid electrolyte (ie, electrolyte).
  • the electrolyte is an electrolyte solution.
  • the electrolyte includes electrolyte salts and solvents.
  • the electrolyte salt may include selected from the group consisting of lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium perchlorate (LiClO 4 ), lithium hexafluoroarsenate (LiAsF 6 ), Lithium fluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoromethanesulfonyl borate (LiDFOB), lithium dioxalatoborate (LiBOB), One or more of lithium difluorophosphate (LiPO 2 F 2 ), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetraflu
  • LiPF 6 lithium hexafluorophosphate
  • LiBF 4 lithium perchlorate
  • the solvent may include a solvent selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate ( DMC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl 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), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MS
  • additives are optionally included in the electrolyte.
  • additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain properties of the battery, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and battery low-temperature power performance. additives, etc.
  • the secondary battery may include an outer packaging.
  • the outer packaging can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag.
  • the material of the soft bag may be plastic, such as one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), etc.
  • This application has no particular limitation on the shape of the secondary battery, which may be a flat body, a rectangular parallelepiped or other shapes. As shown in FIG. 3 , a secondary battery 5 with a rectangular parallelepiped structure is shown as an example.
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity.
  • the housing 51 has an opening communicating with the accommodation cavity, and the cover plate 53 is used to cover the opening to close the accommodation cavity.
  • the electrode assembly 52 of the first aspect of the embodiment of the present application is packaged in the containing cavity. The electrolyte soaks into the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and can be adjusted according to needs.
  • the electrode assembly can be placed in an outer package, dried and then injected with electrolyte. After vacuum packaging, standing, formation, shaping and other processes, a secondary battery can be obtained.
  • the secondary batteries according to the present application can be assembled into battery modules.
  • the number of secondary batteries contained in the battery module can be multiple. The specific number can be adjusted according to the application and capacity of the battery module.
  • FIG. 5 is a schematic diagram of the battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 .
  • the plurality of secondary batteries 5 can be fixed by fasteners.
  • the battery module 4 may further include a housing having a receiving space in which a plurality of secondary batteries 5 are received.
  • the above-mentioned battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be adjusted according to the application and capacity of the battery pack.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 arranged in the battery box.
  • the battery box includes an upper box 2 and a lower box 3 .
  • the upper box 2 is used to cover the lower box 3 and form a closed space for accommodating the battery module 4 .
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • An embodiment of the present application also provides an electrical device, which includes at least one of a secondary battery, a battery module or a battery pack of the present application.
  • the secondary battery, battery module or battery pack may be used as a power source for the electrical device or as an energy storage unit for the electrical device.
  • the electrical device may be, but is not limited to, mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric Golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.
  • the power-consuming device can select a secondary battery, a battery module or a battery pack according to its usage requirements.
  • FIG. 8 is a schematic diagram of an electrical device as an example.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc.
  • battery packs or battery modules can be used.
  • the power-consuming device may be a mobile phone, a tablet computer, a laptop computer, etc.
  • the electrical device is usually required to be light and thin, and secondary batteries can be used as power sources.
  • the secondary batteries of Examples 1 to 25 and Comparative Examples 4 to 10 were all prepared according to the following methods.
  • the water-based adhesive is a compound of polyacrylonitrile-acrylate copolymer LA-133 (purchased from Sichuan Indile Technology Co., Ltd.) and polyethylene imine. In this compound, LA-133 and polyethylene imine The mass ratio of amine is 1:1.
  • a laser drilling device is used to drill the water-based positive electrode piece, thereby providing a plurality of first micropores on the surface of the water-based positive electrode piece.
  • a laser drilling device is used to drill the negative electrode piece, thereby providing a plurality of second microholes on the surface of the negative electrode piece.
  • the equivalent diameter of the second micropore d 2 ( ⁇ m), the center distance between adjacent second micropores L 2 (mm), the ratio of the total area of the plurality of second micropores to the area of the negative electrode plate S 22 /S 21.
  • the ratio of the depth of the second micropore to the thickness of the negative electrode piece H 22 /H 21 , the compacted density of the negative electrode piece C 2 (g/cc), and the volume average particle size of the negative electrode active material D 2 ( ⁇ m) , (S 22 ⁇ H 22 ⁇ D 2 )/(S 21 ⁇ C 2 ⁇ H 21 ) are shown in Table 1 respectively.
  • the preparation process of the water-based positive electrode sheet, the preparation of the negative electrode sheet, the isolation film, the preparation of the electrolyte, and the preparation of the secondary battery are basically the same as in Example 1. The difference is that no holes are punched on the surface of the water-based positive electrode sheet and the negative electrode sheet. .
  • the preparation process of the water-based positive electrode sheet, the preparation of the negative electrode sheet, the preparation of the isolation film, the electrolyte, and the secondary battery are basically the same as those in Example 1. The difference is that in Comparative Example 2, holes are not drilled on the surface of the negative electrode sheet. In proportion 3, no holes are drilled on the surface of the water-based positive electrode piece.
  • the uncharged batteries obtained in each Example and Comparative Example were allowed to stand for different times before being subjected to the first charging test.
  • the first charging current is set to 0.1C (51.2A)
  • the charging cut-off voltage is set to 3.65V.
  • disassemble the battery in a drying room and observe whether the large surface area of the negative electrode appears off-white after lithium deposition. If a black area is found on the surface, it indicates insufficient infiltration of the electrolyte. If a black area is not exposed on the surface, it indicates that the electrolyte is not fully infiltrated. Completely infiltrate the negative electrode piece and record the shortest time required for the electrolyte to completely infiltrate the negative electrode piece.
  • Electrolyte infiltration time T 1 During the test, a group is set up for every half-hour increase in infiltration time. Each group disassembles three electrode assemblies for judgment. The shortest time required for the three electrode assemblies to simultaneously meet the electrolyte to completely infiltrate the negative electrode piece is used as the electrode assembly. Electrolyte infiltration time T 1 .
  • the batteries obtained in each of the Examples and Comparative Examples without liquid injection after being put into the shell were placed in a vacuum oven for drying performance testing.
  • the oven temperature is set to 105°C, and the water content of the battery is measured every 1 hour.
  • the battery water content is lower than 200ppm (mass concentration), it is deemed to have been dried, and the drying time T 2 is recorded.
  • the charge and discharge voltage is set to 2.5V ⁇ 3.65V
  • the charge and discharge current is set to 1C (512A)
  • the discharge capacity after the first cycle of the secondary battery and the discharge capacity after 300 cycles are read.
  • the average discharge capacity of the three secondary batteries after the first cycle is taken as the initial capacity of the secondary battery.
  • the capacity retention rate of the secondary battery after 300 cycles (discharge capacity after 300 cycles/discharge capacity after the first cycle) ⁇ 100%.
  • the aqueous positive electrode piece and the negative electrode piece meet the conditions defined in this application, and can make the secondary battery have high initial capacity, high electrolyte infiltration rate and high Drying rate, secondary batteries also have high cycle capacity retention and low internal resistance.
  • Comparative Examples 1-3 there are no micropores on the surface of the water-based positive electrode piece and/or the negative electrode piece, the electrolyte infiltration rate and drying rate of the electrode assembly are very small, and more moisture is easy to remain in the electrode assembly. Therefore, the secondary battery using this electrode assembly has high internal resistance and poor cycle performance.
  • Comparative Example 4-5 has micropores on both the surface of the water-based positive electrode piece and the negative electrode piece. However, in the prepared water-based positive electrode piece, (S 12 ⁇ H 12 ⁇ D 1 )/(S 11 ⁇ C 1 ⁇ H 11 ) Less than 0.001%.
  • Comparative Examples 6-7 have micropores on the surface of both the water-based positive electrode piece and the negative electrode piece. However, in the prepared water-based positive electrode piece, (S 12 ⁇ H 12 ⁇ D 1 )/(S 11 ⁇ C 1 ⁇ H 11 ) More than 1%, thus the energy density of the secondary battery is significantly reduced. In Comparative Examples 8-10, micropores are provided on the surfaces of both the water-based positive electrode piece and the negative electrode piece. However, in the prepared negative electrode piece, (S 22 ⁇ H 22 ⁇ D 2 )/(S 21 ⁇ C 2 ⁇ H 21 ) is larger than 2.5%, thereby significantly reducing the energy density of the secondary battery.

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Abstract

提供了一种电极组件（52）以及包含其的二次电池（5）、电池模块（4）、电池包（1）及用电装置。电极组件（52）包括水系正极极片和负极极片，其中，水系正极极片包括正极集流体（101）以及位于正极集流体（101）至少一个表面上的正极膜层（102），正极膜层（102）包括正极活性材料；负极极片包括负极集流体以及位于负极集流体至少一个表面上的负极膜层，负极膜层包括负极活性材料；水系正极极片至少部分表面设有多个第一微孔，并且满足：0.001％≤(S12×H12×D1)/(S11×C1×H11)≤1％，负极极片至少部分表面设有多个第二微孔，并且满足：0＜(S22×H22×D2)/(S21×C2×H21)≤2.5％。

Description

电极组件以及包含其的二次电池、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以及包含其的二次电池、电池模块、电池包及用电装置。
背景技术
近年来，二次电池被广泛应用于水力、火力、风力和太阳能电站等储能电源系统，以及电动工具、电动自行车、电动摩托车、电动汽车、军事装备、航空航天等多个领域。随着二次电池的应用及推广，其成本问题和环境污染问题受到越来越多的关注。正极极片是决定二次电池性能的关键因素之一，用于现有正极浆料的溶剂通常为油系溶剂，例如N-甲基吡咯烷酮(NMP)，但是NMP存在用量高、易挥发、难回收、毒性高且成本高的缺陷，不仅会对环境造成严重污染，而且还会危害人的身体健康。采用水作为溶剂的水系正极浆料由于具有成本低廉且环境友好的特点，受到研究者越来越多的关注。但是，水系正极极片存在水分含量高、容量发挥差的缺陷，由此限制了其实际应用。
发明内容
本申请的目的在于提供一种电极组件以及包含其的二次电池、电池模块、电池包及用电装置，使得采用水系正极极片的电极组件以及包含其的二次电池、电池模块、电池包及用电装置兼具高能量密度、良好的循环性能、低内阻、低成本和环境友好的特点。
本申请第一方面提供一种电极组件，包括水系正极极片和负极极片，其中，所述水系正极极片包括正极集流体以及位于所述正极集流体至少一个表面上的正极膜层，所述正极膜层包括正极活性材料；所述负极极片包括负极集流体以及位于所述负极集流体至少一个表面上的负极膜层，所述负极膜层包括负极活性材料；所述水系正极极片至少部分表面设有多个第一微孔，并且满足：0.001％≤(S 12×H 12×D 1)/(S 11×C 1×H 11)≤1％，H 11μm表示所述水系正极极片的厚度，H 12μm表示所述第一微孔的深度，S 11m 2表示所述水系正极极片的面积，S 12m 2表示所述多个第一微孔的总面积，C 1g/cc表示所述水系正极极片的压实密度，D 1μm表示所述正极活性材料的体积平均粒径Dv50；所述负极极片至少部分表面设有多个第二微孔，并且满足：0＜(S 22×H 22×D 2)/(S 21×C 2×H 21)≤2.5％，H 21μm表示所述负极极片的厚度，H 22μm表示所述第二微孔的深度，S 21m 2表示所述负极极片的面积，S 22m 2表示所述多个第二微孔的总面积，C 2g/cc表示所述负极极片的压实密度，D 2μm表示所述负极活性材料的体积平均粒径Dv50。
本申请的电极组件中，通过使水系正极极片满足0.001％≤(S 12×H 12×D 1)/(S 11×C 1×H 11)≤1％、负极极片满足0＜(S 22×H 22×D 2)/(S 21×C 2×H 21)≤2.5％，电极组件能够具有低水分含量、高电解液浸润速率和高烘干速率，应用于二次电池，能够 使得二次电池兼具高能量密度、良好的循环性能、低内阻、低成本和环境友好的特点。
在本申请任意实施方式中，0.05％≤(S 12×H 12×D 1)/(S 11×C 1×H 11)≤0.5％；可选地，0.15％≤(S 12×H 12×D 1)/(S 11×C 1×H 11)≤0.25％。
(S 12×H 12×D 1)/(S 11×C 1×H 11)在上述范围内，电极组件能够具有低表面阻抗和良好的界面性能，从而能够使得应用该电极组件的二次电池具备良好的电化学性能，例如高循环稳定性、高容量发挥和低内阻。此外，(S 12×H 12×D 1)/(S 11×C 1×H 11)在上述范围内，还能够使得水系正极极片保持良好的机械性能。
在本申请任意实施方式中，0.2％≤(S 22×H 22×D 2)/(S 21×C 2×H 21)≤2.0％；可选地，0.4％≤(S 22×H 22×D 2)/(S 21×C 2×H 21)≤1.0％。
(S 22×H 22×D 2)/(S 21×C 2×H 21)在上述范围内，负极极片不仅能够具有高电解液浸润速率，还能够具有低表面阻抗和良好的界面性能。由此，应用本申请的电极组件的二次电池能够具备高循环稳定性、高容量发挥和低内阻。此外，(S 22×H 22×D 2)/(S 21×C 2×H 21)在上述范围内，还能够使得负极极片保持良好的机械性能。
在本申请任意实施方式中，0＜S 12/S 11≤2％，可选地，0.4％≤S 12/S 11≤0.6％。
多个第一微孔的总面积与水系正极极片的面积之比在上述范围内，能够使得水系正极极片具备良好的机械性能，还能够使得水系正极极片具有合适的孔隙率，从而有利于水分排出和电解液的浸润，此外，还能够使得水系正极极片具有合适的电子导通通道和活性离子传输通道。
在本申请任意实施方式中，30％≤H 12/H 11≤100％，可选地，60％≤H 12/H 11≤100％。
第一微孔的深度与水系正极极片的厚度之比在上述范围内，不仅能够保证水系正极极片具有高烘干速率和高电解液浸润速率，还能够保证水系正极极片具有良好的机械性能。
在本申请任意实施方式中，C 1为2.0-3.0，可选地为2.3-2.7。
水系正极极片的压实密度控制在合适的范围内，能使正极膜层中的正极活性材料颗粒紧密接触，提高单位体积内的正极活性材料含量，由此提高二次电池的能量密度。
在本申请任意实施方式中，D 1为0.5-1.5，可选地为0.8-1.3。
正极活性材料的体积平均粒径Dv50在上述范围内，能够缩短活性离子的扩散路径，从而能够进一步提高二次电池的能量密度、循环性能和倍率性能。
在本申请任意实施方式中，0＜S 22/S 21≤0.2％，可选地，0.04％≤S 22/S 21≤0.06％。
多个第二微孔的总面积与负极极片的面积之比在上述范围内，能够使得负极极片具备良好的机械性能，还能够使得负极极片具有合适的孔隙率和高容量，从而有利于提高电极组件的电解液浸润速率和容量发挥，此外，还能够使得负极极片具有合适的电子导通通道和活性离子传输通道。
在本申请任意实施方式中，30％≤H 22/H 21≤100％，可选地，60％≤H 22/H 21≤100％。
第二微孔的深度与负极极片的厚度之比在上述范围内，不仅能够保证负极极片具有高电解液浸润速率，还能够保证负极极片具有良好的机械性能。
在本申请任意实施方式中，C 2为1.2-2.0，可选地为1.4-1.8。
负极极片的压实密度控制在合适的范围内，能使负极膜层中的负极活性材料颗粒紧密接触，提高单位体积内的负极活性材料含量，由此提高二次电池的能量密度。
在本申请任意实施方式中，D 2为12-20，可选地为15-19。
负极活性材料的体积平均粒径Dv50在上述范围内，能够缩短活性离子的扩散路径，从而能够进一步提高二次电池的能量密度、循环性能和倍率性能。
在本申请任意实施方式中，电极组件满足：0.1≤A/B≤1.0，可选地，0.25≤A/B≤0.50，A表示(S 12×H 12×D 1)/(S 11×C 1×H 11)，B表示(S 22×H 22×D 2)/(S 21×C 2×H 21)。
A/B的值在上述范围内，能够进一步提高电极组件的电解液浸润速率，并且更有利于电极组件在干燥过程中快速排出残留的水分，从而能够使得二次电池具有低阻抗、高能量密度和高循环容量保持率。
在本申请任意实施方式中，电极组件满足：S 3/S 22≥5％，可选地，8％≤S 3/S 22≤70％，S 3m 2表示所述多个第一微孔与所述多个第二微孔的重合面积。
水系正极极片表面的第一微孔与负极极片的表面的第二微孔的重合面积在上述范围内，有利于第一微孔、第二微孔与隔离膜中的微孔形成通道，从而有利于电极组件中残留水分的快速排出、提高电极组件的电解液浸润速率。因此，本申请的电极组件应用于二次电池，能够使得二次电池具有低阻抗、高能量密度和高循环容量保持率。
在本申请任意实施方式中，各第一微孔的形貌为规则形状或不规则形状，可选地，各第一微孔的形貌包括圆形、矩形或正方形。
在本申请任意实施方式中，各第一微孔的等效直径为1μm-200μm，可选地为50μm-180μm。
第一微孔的等效直径在上述范围内，能够在保证水系正极极片具有低水分含量、高电解液浸润速率和高烘干速率的前提下，使得水系正极极片具有良好的机械性能，例如，能够使得水系正极极片具有较高的强度和良好的柔韧性。因此，电极组件能够具有高电解液浸润速率和良好的加工性能，由此，应用该电极组件的二次电池也能够具备良好的电化学性能和高产能。
在本申请任意实施方式中，相邻所述第一微孔的中心距为1mm-10mm。
相邻的第一微孔的中心距在上述范围内，能够使得第一微孔合适地分布于水系正极极片的表面。由此，能够避免第一微孔的分布过于密集，从而使得水系正极极片保持良好的机械性能。
在本申请任意实施方式中，所述多个第一微孔呈阵列分布。
在本申请任意实施方式中，各第二微孔的形貌为规则形状或不规则形状，可选地，各第二微孔的形貌包括圆形、矩形或正方形。
在本申请任意实施方式中，各第二微孔的等效直径为1μm-200μm，可选地为50μm-150μm。
第二微孔的等效直径在上述范围内，能够在保证负极极片具有高电解液浸润速率的前提下，使得负极极片具有良好的机械性能，例如，能够使得负极极片具有较高的强度和良好的柔韧性。因此，电极组件能够具有高电解液浸润速率和良好的加工性能，由此，应用该电极组件的二次电池也能够具备良好的电化学性能和高产能。
在本申请任意实施方式中，相邻所述第二微孔的中心距为1mm-10mm。
相邻的第二微孔的中心距在上述范围内，能够使得第二微孔合适地分布于负极极片的表面。由此，能够避免第二微孔的分布过于密集，从而使得负极极片保持良好的机 械性能。
在本申请任意实施方式中，所述多个第二微孔呈阵列分布。
在本申请任意实施方式中，所述正极膜层还包括水性粘接剂、导电剂中的一种或多种。
在本申请任意实施方式中，所述水性粘接剂包括甲基纤维素及其盐、黄原胶及其盐、壳聚糖及其盐、海藻酸及其盐、聚乙烯亚胺及其盐、聚丙烯酰胺、丙烯腈-丙烯酸共聚物及其衍生物或其混合物。
在本申请任意实施方式中，所述水性粘接剂包括黄原胶和聚乙烯亚胺的复配混合物。可选地，所述黄原胶和所述聚乙烯亚胺的质量比为2:1-0.2:2.8。可选地，所述黄原胶的数均分子量为300000-2000000。可选地，所述聚乙烯亚胺的数均分子量为2000-50000。
在本申请任意实施方式中，所述水性粘接剂包括丙烯腈-丙烯酸共聚物和聚乙烯亚胺的复配混合物。可选地，所述丙烯腈-丙烯酸共聚物和所述聚乙烯亚胺的质量比为2:1-0.2:2.8。可选地，所述丙烯腈-丙烯酸共聚物的数均分子量为300000-2000000。可选地，所述聚乙烯亚胺的数均分子量为2000-70000。
在本申请任意实施方式中，所述导电剂包括导电炭黑、超导炭黑、导电石墨、乙炔黑、科琴黑、石墨烯、碳纳米管中的一种或多种。
本申请第二方面提供一种二次电池，其包括本申请第一方面的电极组件。
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。
本申请的二次电池具有低水分含量、高电解液浸润速率和高烘干速率，本申请的二次电池还兼具高能量密度、良好的循环性能、低内阻、低成本和环境友好的特点。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是本申请的水系正极极片的一实施方式的截面示意图。
图2是本申请的水系正极极片的另一实施方式的截面示意图。
图3是本申请的二次电池的一实施方式的示意图。
图4是图3的二次电池的实施方式的分解示意图。
图5是本申请的电池模块的一实施方式的示意图。
图6是本申请的电池包的一实施方式的示意图。
图7是图6所示的电池包的实施方式的分解示意图。
图8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。
在附图中，附图未必按照实际的比例绘制。其中，附图标记说明如下：101正极集流体，102正极膜层，1电池包，2上箱体，3下箱体，4电池模块，5二次电池，51壳体，52电极组件，53盖板。
具体实施方式
以下，适当地参照附图详细说明具体公开了本申请的电极组件以及包含其的二次电池、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)。
如果没有特别的说明，在本申请中，术语“第一”、“第二”等是用于区别不同对象，而不是用于描述特定顺序或主次关系。
在本申请中，术语“约”用以描述及说明小的变化，当结合数值使用时，术语可指代小于或等于所述数值的±10％的变化范围。
在本文的描述中，除非另有说明，“以上”、“以下”为包含本数。
在本文的描述中，除非另有说明，“多种”、“多个”、“多者”的含义是两种、两个或两者以上。
随着二次电池的应用及推广，其成本问题和环境污染问题受到越来越多的关注。采用水作为溶剂的水系正极浆料由于具有成本低廉且环境友好的特点，受到研究者越来越多的关注。然而，发明人经研究发现，水系正极浆料往往采用具有亲水基团的粘接剂，这些亲水基团和溶剂水会对二次电池的性能产生较大的影响。使用水系正极浆料制备的水系正极极片会残留部分水分且难以在烘干过程中除去，由此，目前的水系正极极片应用于二次电池时，残留的水分不仅会影响正极极片的浸润性能，还会与电池内部的电解质、电极活性材料等发生副反应，导致活性离子不可逆损失增加、电池能量密度降低、容量衰减过快，此外还会导致电池气胀、自放电升高等。
目前，相关技术中多是通过调整正极浆料的配方或者正极极片的制备工艺来降低水系正极极片的水分含量。其中，调整正极浆料的配方，例如，在水系正极浆料中加入无水乙醇，能够在一定程度上降低水系正极极片中残留的水分含量。但是，在水系正极浆料中加入乙醇后，引入的活性基团羟基会影响二次电池的界面性能，例如导致析锂、界面黑斑等现象的发生。由此，不仅降低了二次电池的循环性能，还带来了安全隐患。调整正极极片的制备工艺，例如控制水系正极浆料的固含量，并采用热涂布、冷压碾压和真空烘烤相结合的工艺制备正极极片，虽然能够有效加速水分的挥发、减少水系正极极片中残留的水分，但是会相应地增加水系正极极片的制备成本、降低二次电池的产能。
发明人经深入思考，从电极组件的结构出发，设计了一种电极组件，该电极组件能够具有低水分含量、高电解液浸润速率和高烘干速率，电极组件还能够兼具高能量密度、良好的循环性能、低内阻、低成本和环境友好的特点。
电极组件
本申请第一方面提供一种电极组件，其包括水系正极极片和负极极片。
所述水系正极极片包括正极集流体以及位于所述正极集流体至少一个表面上的正极膜层，所述正极膜层包括正极活性材料。所述水系正极极片至少部分表面设有多个第一微孔，并且满足：0.001％≤(S 12×H 12×D 1)/(S 11×C 1×H 11)≤1％，H 11μm表示所述水系正极极片的厚度，H 12μm表示所述第一微孔的深度，S 11m 2表示所述水系正极极片的面积，S 12m 2表示所述多个第一微孔的总面积，C 1g/cc表示所述水系正极极片的压实密度，D 1μm表示所述正极活性材料的体积平均粒径Dv50。
所述负极极片包括负极集流体以及位于所述负极集流体至少一个表面上的负极膜层，所述负极膜层包括负极活性材料。所述负极极片至少部分表面设有多个第二微孔，并且满足：0＜(S 22×H 22×D 2)/(S 21×C 2×H 21)≤2.5％，H 21μm表示所述负极极片的厚度，H 22μm表示所述第二微孔的深度，S 21m 2表示所述负极极片的面积，S 22m 2表示所述多个第二 微孔的总面积，C 2g/cc表示所述负极极片的压实密度，D 2μm表示所述负极活性材料的体积平均粒径Dv50。
并非意在受限于任何理论或解释，发明人意外地发现，在水系正极极片的至少部分表面设有多个第一微孔，并且使水系正极极片中(S 12×H 12×D 1)/(S 11×C 1×H 11)的值在上述范围内，能够使得水系正极极片中残留的水分易于除去，由此能够改善电极组件的界面性能，降低电极组件气胀、自放电和被腐蚀的风险。此外，在水系正极极片的表面设有上述第一微孔，一方面能够增大正极极片的孔隙率，从而有利于增大电解液的浸润速率，另一方面能够极大地缩短锂离子的扩散距离，从而有效降低锂离子的传质阻力、降低电池内阻。因此，本申请的电极组件应用于二次电池，不仅能够降低二次电池气胀、自放电和被腐蚀的风险，还能够提高二次电池的能量密度、循环性能和倍率性能。
另外，并非意在受限于任何理论或解释，本申请的电极组件中，负极极片的至少部分表面设有多个第二微孔，并且负极极片中(S 22×H 22×D 2)/(S 21×C 2×H 21)的值在上述范围内，不仅能够进一步提高负极极片的锂离子传输能力、增大电解液的浸润速率，还能够有利于正极活性材料的容量发挥。由此，能够使得应用本申请电极组件的二次电池具备良好的电化学性能和高能量密度。
发明人研究发现，(S 12×H 12×D 1)/(S 11×C 1×H 11)小于0.001％时，所述水系正极极片存在下述情形中的至少一者：所述多个第一微孔的总面积与水系正极极片的面积之比S 12/S 11较小、第一微孔的深度与水系正极极片的厚度之比H 12/H 11较小、正极活性材料的体积平均粒径D 1较小、水系正极极片的压实密度C 1较大。由此，正极活性材料颗粒之间的间距很小、接触较紧密，导致活性离子传输通道较少，二次电池的内阻较高、电解液浸润性能较差，不利于电池容量的发挥。此外，水系正极极片的水分排出通道较少，水分不易在烘干过程中快速排出，导致水分残留量较高，二次电池出现气胀、自放电和被腐蚀的风险较高。
发明人研究发现，(S 12×H 12×D 1)/(S 11×C 1×H 11)大于1％时，所述水系正极极片存在下述情形中的至少一者：所述多个第一微孔的总面积与水系正极极片的面积之比S 12/S 11较大、第一微孔的深度与水系正极极片的厚度之比H 12/H 11较大、正极活性材料的体积平均粒径D 1较大、水系正极极片的压实密度C 1较小。由此，二次电池的能量密度下降明显。
发明人研究发现，(S 22×H 22×D 2)/(S 21×C 2×H 21)大于2.5％时，所述负极极片存在下述情形中的至少一者：所述多个第二微孔的总面积与负极极片的面积之比S 22/S 21较大、第二微孔的深度与负极极片的厚度之比H 22/H 21较大、负极活性材料的体积平均粒径D 2较大、负极极片的压实密度C 2较小。由此，二次电池的能量密度下降明显。
本申请的电极组件中，通过使水系正极极片满足0.001％≤(S 12×H 12×D 1)/(S 11×C 1×H 11)≤1％、负极极片满足0＜(S 22×H 22×D 2)/(S 21×C 2×H 21)≤2.5％，电极组件能够具有低水分含量、高电解液浸润速率和高烘干速率，应用于二次电池，能够使得二次电池兼具高能量密度、良好的循环性能、低内阻、低成本和环境友好的特点。
可能的原因包括：首先，水系正极极片和负极极片的表面均设有微孔，使得二次电池组装过程中，电解液不仅能够沿极片/隔膜水平方向浸润电极组件，还能够沿极片垂直方向通过极片微孔以及隔离膜微孔组建的网络浸润电极组件；其次，水系正极极片和负极极片的表面均设有微孔，极片中残留的水分能够在电极组件烘干过程中快速排出至 电极组件外部，由此，能够进一步降低电极组件的水分含量；再次，极片表面微孔、极片压实密度和活性材料颗粒粒径合理搭配后，能够保证水系正极极片和负极极片同时具有合适的电子导通通道和活性离子传输通道。
在一些实施方式中，所述水系正极极片可满足：0.05％≤(S 12×H 12×D 1)/(S 11×C 1×H 11)≤0.5％，0.05％≤(S 12×H 12×D 1)/(S 11×C 1×H 11)≤0.45％，0.05％≤(S 12×H 12×D 1)/(S 11×C 1×H 11)≤0.4％，0.05％≤(S 12×H 12×D 1)/(S 11×C 1×H 11)≤0.35％，0.05％≤(S 12×H 12×D 1)/(S 11×C 1×H 11)≤0.3％，0.05％≤(S 12×H 12×D 1)/(S 11×C 1×H 11)≤0.25％，0.05％≤(S 12×H 12×D 1)/(S 11×C 1×H 11)≤0.2％，0.05％≤(S 12×H 12×D 1)/(S 11×C 1×H 11)≤0.15％，0.1％≤(S 12×H 12×D 1)/(S 11×C 1×H 11)≤0.5％，0.1％≤(S 12×H 12×D 1)/(S 11×C 1×H 11)≤0.45％，0.1％≤(S 12×H 12×D 1)/(S 11×C 1×H 11)≤0.4％，0.1％≤(S 12×H 12×D 1)/(S 11×C 1×H 11)≤0.35％，0.1％≤(S 12×H 12×D 1)/(S 11×C 1×H 11)≤0.3％，0.1％≤(S 12×H 12×D 1)/(S 11×C 1×H 11)≤0.25％，0.1％≤(S 12×H 12×D 1)/(S 11×C 1×H 11)≤0.2％，0.15％≤(S 12×H 12×D 1)/(S 11×C 1×H 11)≤0.5％，0.15％≤(S 12×H 12×D 1)/(S 11×C 1×H 11)≤0.45％，0.15％≤(S 12×H 12×D 1)/(S 11×C 1×H 11)≤0.4％，0.15％≤(S 12×H 12×D 1)/(S 11×C 1×H 11)≤0.35％，0.15％≤(S 12×H 12×D 1)/(S 11×C 1×H 11)≤0.3％，0.15％≤(S 12×H 12×D 1)/(S 11×C 1×H 11)≤0.25％，0.2％≤(S 12×H 12×D 1)/(S 11×C 1×H 11)≤0.5％，0.2％≤(S 12×H 12×D 1)/(S 11×C 1×H 11)≤0.45％，0.2％≤(S 12×H 12×D 1)/(S 11×C 1×H 11)≤0.4％，0.2％≤(S 12×H 12×D 1)/(S 11×C 1×H 11)≤0.35％，0.2％≤(S 12×H 12×D 1)/(S 11×C 1×H 11)≤0.3％，0.25％≤(S 12×H 12×D 1)/(S 11×C 1×H 11)≤0.5％，0.25％≤(S 12×H 12×D 1)/(S 11×C 1×H 11)≤0.45％或0.25％≤(S 12×H 12×D 1)/(S 11×C 1×H 11)≤0.4％。
并非意在受限于任何理论或解释，发明人研究发现，(S 12×H 12×D 1)/(S 11×C 1×H 11)在上述范围内，水系正极极片中的水分能够在电极组件烘干过程中快速排出至电极组件外部，从而能够进一步降低正极极片的水分含量、提高电极组件的电解液浸润速率和烘干速率。由此，电极组件能够具有低表面阻抗和良好的界面性能，从而能够使得应用该电极组件的二次电池具备良好的电化学性能，例如高循环稳定性、高容量发挥和低内阻。此外，(S 12×H 12×D 1)/(S 11×C 1×H 11)在上述范围内，还能够使得水系正极极片保持良好的机械性能。由此，正极极片在电极组件的组装和加工过程中，不易发生形变。因此，电极组件在加工及组装过程中不仅能够保持良好的电化学性能，还能够具有较高的产能。
在一些实施方式中，所述负极极片可满足：0.2％≤(S 22×H 22×D 2)/(S 21×C 2×H 21)≤2.0％，0.2％≤(S 22×H 22×D 2)/(S 21×C 2×H 21)≤1.8％，0.2％≤(S 22×H 22×D 2)/(S 21×C 2×H 21)≤1.5％，0.2％≤(S 22×H 22×D 2)/(S 21×C 2×H 21)≤1.2％，0.2％≤(S 22×H 22×D 2)/(S 21×C 2×H 21)≤1.0％，0.2％≤(S 22×H 22×D 2)/(S 21×C 2×H 21)≤0.8％，0.2％≤(S 22×H 22×D 2)/(S 21×C 2×H 21)≤0.5％，0.3％≤(S 22×H 22×D 2)/(S 21×C 2×H 21)≤2.0％，0.3％≤(S 22×H 22×D 2)/(S 21×C 2×H 21)≤1.8％，0.3％≤(S 22×H 22×D 2)/(S 21×C 2×H 21)≤1.5％，0.3％≤(S 22×H 22×D 2)/(S 21×C 2×H 21)≤1.2％，0.3％≤(S 22×H 22×D 2)/(S 21×C 2×H 21)≤1.0％，0.3％≤(S 22×H 22×D 2)/(S 21×C 2×H 21)≤0.8％，0.3％≤(S 22×H 22×D 2)/(S 21×C 2×H 21)≤0.5％，0.4％≤(S 22×H 22×D 2)/(S 21×C 2×H 21)≤2.0％，0.4％≤(S 22×H 22×D 2)/(S 21×C 2×H 21)≤1.8％，0.4％≤(S 22×H 22×D 2)/(S 21×C 2×H 21)≤1.5％，0.4％≤(S 22×H 22×D 2)/(S 21×C 2×H 21)≤1.2％，0.4％≤(S 22×H 22×D 2)/(S 21×C 2×H 21)≤1.0％，0.4％≤(S 22×H 22×D 2)/(S 21×C 2×H 21)≤0.8％，0.5％≤(S 22×H 22×D 2)/(S 21×C 2×H 21)≤2.0％，0.5％≤(S 22×H 22×D 2)/(S 21×C 2×H 21)≤1.8％，0.5％≤(S 22×H 22×D 2)/(S 21×C 2×H 21)≤1.5％，0.5％≤(S 22×H 22×D 2)/(S 21×C 2×H 21)≤1.2％，0.5％≤(S 22×H 22×D 2)/(S 21×C 2×H 21)≤1.0％或0.5％≤ (S 22×H 22×D 2)/(S 21×C 2×H 21)≤0.8％。
并非意在受限于任何理论或解释，发明人研究发现，(S 22×H 22×D 2)/(S 21×C 2×H 21)在上述范围内，负极极片不仅能够具有高电解液浸润速率，还能够具有低表面阻抗和良好的界面性能。由此，应用本申请的电极组件的二次电池能够具备高循环稳定性、高容量发挥和低内阻。此外，(S 22×H 22×D 2)/(S 21×C 2×H 21)在上述范围内，还能够使得负极极片保持良好的机械性能。由此，负极极片在电极组件的组装和加工过程中，不易发生形变。因此，电极组件在加工及组装过程中不仅能够保持良好的电化学性能，还能够具有较高的产能。
在一些实施方式中，多个第一微孔的总面积与水系正极极片的面积之比满足0＜S 12/S 11≤2％。例如，0.1％≤S 12/S 11≤2％，0.1％≤S 12/S 11≤1.8％，0.1％≤S 12/S 11≤1.5％，0.1％≤S 12/S 11≤1.2％，0.1％≤S 12/S 11≤1％，0.1％≤S 12/S 11≤0.8％，0.1％≤S 12/S 11≤0.6％，0.2％≤S 12/S 11≤2％，0.2％≤S 12/S 11≤1.8％，0.2％≤S 12/S 11≤1.5％，0.2％≤S 12/S 11≤1.2％，0.2％≤S 12/S 11≤1％，0.2％≤S 12/S 11≤0.8％，0.2％≤S 12/S 11≤0.6％，0.3％≤S 12/S 11≤2％，0.3％≤S 12/S 11≤1.8％，0.3％≤S 12/S 11≤1.5％，0.3％≤S 12/S 11≤1.2％，0.3％≤S 12/S 11≤1％，0.3％≤S 12/S 11≤0.8％，0.3％≤S 12/S 11≤0.6％，0.4％≤S 12/S 11≤2％，0.4％≤S 12/S 11≤1.8％，0.4％≤S 12/S 11≤1.5％，0.4％≤S 12/S 11≤1.2％，0.4％≤S 12/S 11≤1％，0.4％≤S 12/S 11≤0.8％，0.4％≤S 12/S 11≤0.6％，0.5％≤S 12/S 11≤2％，0.5％≤S 12/S 11≤1.8％，0.5％≤S 12/S 11≤1.5％，0.5％≤S 12/S 11≤1.2％，0.5％≤S 12/S 11≤1％，0.5％≤S 12/S 11≤0.8％或0.5％≤S 12/S 11≤0.6％。
并非意在受限于任何理论或解释，多个第一微孔的总面积与水系正极极片的面积之比在上述范围内，能够使得水系正极极片具备良好的机械性能。由此，能够降低水系正极极片在加工过程中发生不可逆形变的风险，从而提高电极组件的产能。多个第一微孔的总面积与水系正极极片的面积之比在上述范围内，还能够使得水系正极极片具有合适的孔隙率，从而有利于水分排出和电解液的浸润。此外，多个第一微孔的总面积与水系正极极片的面积之比在上述范围内，还能够使得水系正极极片具有合适的电子导通通道和活性离子传输通道。因此，电极组件应用于二次电池，能够使得二次电池具有高产能、高循环稳定性、高容量发挥和低内阻。
在一些实施方式中，第一微孔的深度与水系正极极片的厚度之比满足30％≤H 12/H 11≤100％。例如，30％≤H 12/H 11≤90％，30％≤H 12/H 11≤80％，30％≤H 12/H 11≤70％，30％≤H 12/H 11≤60％，30％≤H 12/H 11≤50％，30％≤H 12/H 11≤40％，40％≤H 12/H 11≤100％，40％≤H 12/H 11≤90％，40％≤H 12/H 11≤80％，40％≤H 12/H 11≤70％，40％≤H 12/H 11≤60％，40％≤H 12/H 11≤50％，50％≤H 12/H 11≤100％，50％≤H 12/H 11≤90％，50％≤H 12/H 11≤80％，50％≤H 12/H 11≤70％，50％≤H 12/H 11≤60％，60％≤H 12/H 11≤100％，60％≤H 12/H 11≤90％，60％≤H 12/H 11≤80％，60％≤H 12/H 11≤70％，70％≤H 12/H 11≤100％，70％≤H 12/H 11≤90％，70％≤H 12/H 11≤80％，80％≤H 12/H 11≤100％，80％≤H 12/H 11≤90％或90％≤H 12/H 11≤100％。
本申请中，第一微孔的深度可以小于或等于水系正极极片的厚度。当H 12/H 11为100％时，第一微孔可为贯穿正极极片的贯通孔。
并非意在受限于任何理论或解释，第一微孔的深度与水系正极极片的厚度之比在上述范围内，不仅能够保证水系正极极片具有高烘干速率和高电解液浸润速率，还能够保证水系正极极片具有良好的机械性能。因此，本申请的电极组件能够具有良好的界面 性能、低表面阻抗和高加工效率，应用于二次电池，能够使得二次电池具备良好的循环性能、良好的倍率性能和高产能。
C 1g/cc表示水系正极极片的压实密度，在一些实施方式中，C 1可为2.0-3.0，例如，C 1可以为约2.0、约2.1、约2.2、约2.3、约2.4、约2.5、约2.6、约2.7、约2.8、约2.9、约3.0或处于以上任何数值所组成的范围内。在一些实施方式中，C 1可选地为2.3-2.7。
水系正极极片的压实密度控制在合适的范围内，能使正极膜层中的正极活性材料颗粒紧密接触，提高单位体积内的正极活性材料含量，由此提高二次电池的能量密度。
D 1μm表示正极活性材料的体积平均粒径Dv50，在一些实施方式中，D 1可为0.5-1.5，例如，D 1可为约0.5、约0.6、约0.7、约0.8、约0.9、约1.0、约1.1、约1.2、约1.3、约1.4、约1.5或处于以上任何数值所组成的范围内。在一些实施方式中，D 1可选地为0.8-1.3。
正极活性材料的体积平均粒径Dv50在上述范围内，能够缩短活性离子的扩散路径。因此，本申请的电极组件应用于二次电池，能够进一步提高二次电池的能量密度、循环性能和倍率性能。
此外，控制电极组件中，多个第一微孔的总面积与水系正极极片的面积之比S 12/S 11、第一微孔的深度与水系正极极片的厚度之比H 12/H 11、水系正极极片的压实密度C 1、正极活性材料的体积平均粒径D 1在上述范围内，能够有利于调控(S 12×H 12×D 1)/(S 11×C 1×H 11)在本申请的范围内。因此，本申请的电极组件应用于二次电池，不仅能够降低二次电池气胀、自放电和被腐蚀的风险，还能够提高二次电池的能量密度、循环性能和倍率性能。
在一些实施方式中，多个第二微孔的总面积与负极极片的面积之比可满足：0＜S 22/S 21≤0.2％。例如，0.02％≤S 22/S 21≤0.2％，0.02％≤S 22/S 21≤0.18％，0.02％≤S 22/S 21≤0.16％，0.02％≤S 22/S 21≤0.14％，0.02％≤S 22/S 21≤0.12％，0.02％≤S 22/S 21≤0.1％，0.02％≤S 22/S 21≤0.08％，0.02％≤S 22/S 21≤0.06％，0.02％≤S 22/S 21≤0.04％，0.04％≤S 22/S 21≤0.2％，0.04％≤S 22/S 21≤0.18％，0.04％≤S 22/S 21≤0.16％，0.04％≤S 22/S 21≤0.14％，0.04％≤S 22/S 21≤0.12％，0.04％≤S 22/S 21≤0.1％，0.04％≤S 22/S 21≤0.08％，0.04％≤S 22/S 21≤0.06％，0.06％≤S 22/S 21≤0.2％，0.06％≤S 22/S 21≤0.18％，0.06％≤S 22/S 21≤0.16％，0.06％≤S 22/S 21≤0.14％，0.06％≤S 22/S 21≤0.12％，0.06％≤S 22/S 21≤0.1％或0.06％≤S 22/S 21≤0.08％。
并非意在受限于任何理论或解释，多个第二微孔的总面积与负极极片的面积之比在上述范围内，能够使得负极极片具备良好的机械性能。由此，能够降低负极极片在加工过程中发生不可逆形变的风险，从而提高电极组件的产能。多个第二微孔的总面积与负极极片的面积之比在上述范围内，还能够使得负极极片具有合适的孔隙率和高容量，从而有利于提高电极组件的电解液浸润速率和容量发挥。此外，多个第二微孔的总面积与负极极片的面积之比在上述范围内，还能够使得负极极片具有合适的电子导通通道和活性离子传输通道。因此，电极组件应用于二次电池，能够使得二次电池具有高产能、高循环稳定性、高容量发挥和低内阻。
在一些实施方式中，第二微孔的深度与负极极片的厚度之比可满足：30％≤H 22/H 21≤100％，30％≤H 22/H 21≤90％，30％≤H 22/H 21≤80％，30％≤H 22/H 21≤70％，30％≤H 22/H 21≤60％，40％≤H 22/H 21≤100％，40％≤H 22/H 21≤90％，40％≤H 22/H 21≤80％，40％ ≤H 22/H 21≤70％，40％≤H 22/H 21≤60％，50％≤H 22/H 21≤100％，50％≤H 22/H 21≤90％，50％≤H 22/H 21≤80％，50％≤H 22/H 21≤70％，60％≤H 22/H 21≤100％，60％≤H 22/H 21≤90％，60％≤H 22/H 21≤80％，70％≤H 22/H 21≤100％，70％≤H 22/H 21≤90％，70％≤H 22/H 21≤80％，80％≤H 22/H 21≤100％，80％≤H 22/H 21≤90％或90％≤H 22/H 21≤100％。
本申请中，第二微孔的深度可以小于或等于负极极片的厚度。当H 22/H 21为100％时，第二微孔可为贯穿负极极片的贯通孔。
并非意在受限于任何理论或解释，第二微孔的深度与负极极片的厚度之比在上述范围内，不仅能够保证负极极片具有高电解液浸润速率，还能够保证负极极片具有良好的机械性能。因此，本申请的电极组件能够具有良好的界面性能、低表面阻抗和高加工效率，应用于二次电池，能够使得二次电池具备良好的循环性能、良好的倍率性能和高产能。
C 2g/cc表示负极极片的压实密度，在一些实施方式中，C 2可为1.2-2.0，例如，C 2可以为约1.2、约1.3、约1.4、约1.5、约1.6、约1.7、约1.8、约1.9、约2.0或处于以上任何数值所组成的范围内。在一些实施方式中，C 2可选地为1.4-1.8。
负极极片的压实密度控制在合适的范围内，能使负极膜层中的负极活性材料颗粒紧密接触，提高单位体积内的负极活性材料含量，由此提高二次电池的能量密度。
D 2μm表示负极活性材料的体积平均粒径Dv50，在一些实施方式中，D 2可为12-20，例如，D 2可以为约12、约13、约14、约15、约16、约17、约18、约19、约20或处于以上任何数值所组成的范围内。在一些实施方式中，D 2可选地为15-19。
负极活性材料的体积平均粒径Dv50在上述范围内，能够缩短活性离子的扩散路径。因此，本申请的电极组件应用于二次电池，能够进一步提高二次电池的能量密度、循环性能和倍率性能。
此外，控制电极组件中，多个第二微孔的总面积与负极极片的面积之比S 22/S 21、第二微孔的深度与负极极片的厚度之比H 22/H 21、负极极片的压实密度C 2、负极活性材料的体积平均粒径D 2在上述范围内，能够有利于调控(S 22×H 22×D 2)/(S 21×C 2×H 21)在本申请的范围内。因此，本申请的电极组件应用于二次电池，能够使得二次电池具备良好的电化学性能和高能量密度。
在一些实施方式中，所述电极组件可满足：0.10≤A/B≤1.0，A表示(S 12×H 12×D 1)/(S 11×C 1×H 11)，B表示(S 22×H 22×D 2)/(S 21×C 2×H 21)。例如，0.10≤A/B≤0.75，0.10≤A/B≤0.50，0.10≤A/B≤0.50，0.10≤A/B≤0.25，0.15≤A/B≤1.0，0.15≤A/B≤0.75，0.15≤A/B≤0.50，0.15≤A/B≤0.25，0.20≤A/B≤1.0，0.20≤A/B≤0.75，0.20≤A/B≤0.50，0.20≤A/B≤0.25，0.25≤A/B≤1.0，0.25≤A/B≤0.75，0.25≤A/B≤0.50，0.30≤A/B≤1.0，0.30≤A/B≤0.75，0.30≤A/B≤0.50，0.35≤A/B≤1.0，0.35≤A/B≤0.75，0.35≤A/B≤0.50，0.40≤A/B≤1.0，0.40≤A/B≤0.75或0.40≤A/B≤0.50。
并非意在受限于任何理论或解释，A/B的值在上述范围内，能够充分发挥水系正极极片和负极极片各自的优势以及二者之间的协同作用效果，从而能够进一步提高电极组件的电解液浸润速率，并且更有利于电极组件在干燥过程中快速排出残留的水分。因此，本申请的电极组件应用于二次电池，能够使得二次电池具有低阻抗、高能量密度和高循环容量保持率。
在一些实施方式中，所述电极组件可满足：S 3/S 22≥5％，例如，S 3/S 22可以为约5％、约8％、约10％、约15％、约20％、约25％、约30％、约35％、约40％、约45％、约50％、约55％、约60％、约65％、约70％、约75％、约80％、约85％、约90％、约95％、约100％或处于以上任何数值所组成的范围内。其中，S 3m 2表示所述多个第一微孔与所述多个第二微孔的重合面积。
在一些实施方式中，所述电极组件可满足：8％≤S 3/S 22≤85％，8％≤S 3/S 22≤80％，8％≤S 3/S 22≤75％，8％≤S 3/S 22≤70％，15％≤S 3/S 22≤85％，15％≤S 3/S 22≤80％，15％≤S 3/S 22≤75％，15％≤S 3/S 22≤70％，25％≤S 3/S 22≤85％，25％≤S 3/S 22≤80％，25％≤S 3/S 22≤75％，25％≤S 3/S 22≤70％，40％≤S 3/S 22≤85％，40％≤S 3/S 22≤80％，40％≤S 3/S 22≤75％或40％≤S 3/S 22≤70％。
并非意在受限于任何理论或解释，水系正极极片表面的第一微孔与负极极片的表面的第二微孔的重合面积在上述范围内，有利于第一微孔、第二微孔与隔离膜中的微孔形成通道，从而有利于电极组件中残留水分的快速排出、提高电极组件的电解液浸润速率。因此，本申请的电极组件应用于二次电池，能够使得二次电池具有低阻抗、高能量密度和高循环容量保持率。
本申请对第一微孔的形貌不作限定，各第一微孔的形貌可以相同，也可以不同。在一些实施方式中，各第一微孔的形貌可为规则形状或不规则形状。在一些实施方式中，各第一微孔的形貌可包括圆形、矩形或正方形。
在一些实施方式中，各第一微孔的等效直径可为1μm-200μm，例如可以为约5μm、约10μm、约20μm、约50μm、约80μm、约100μm、约120μm、约150μm、约180μm、约200μm或处于以上任何数值所组成的范围内。在一些实施方式中，各第一微孔的等效直径可为5μm-180μm，10μm-180μm，20μm-180μm，30μm-180μm，50μm-180μm，5μm-150μm，10μm-150μm，20μm-150μm，30μm-150μm或50μm-150μm。
各第一微孔的等效直径可以为与各第一微孔具有相等面积的圆所具有的直径。第一微孔的等效直径在上述范围内，能够在保证水系正极极片具有低水分含量、高电解液浸润速率和高烘干速率的前提下，使得水系正极极片具有良好的机械性能，例如，能够使得水系正极极片具有较高的强度和良好的柔韧性。因此，电极组件能够具有高电解液浸润速率和良好的加工性能，由此，应用该电极组件的二次电池也能够具备良好的电化学性能和高产能。
在一些实施方式中，相邻所述第一微孔的中心距可为1mm-10mm，例如可以为约1mm、约2mm、约3mm、约4mm、约5mm、约6mm、约7mm、约8mm、约9mm、约10mm或处于以上任何数值所组成的范围内。
并非意在受限于任何理论或解释，相邻的第一微孔的中心距在上述范围内，能够使得第一微孔合适地分布于水系正极极片的表面。由此，能够避免第一微孔的分布过于密集，从而使得水系正极极片保持良好的机械性能。
本申请对所述多个第一微孔的分布形式不作限定。在一些实施方式中，所述多个第一微孔可呈阵列分布。
本申请对第二微孔的形貌不作限定，各第二微孔的形貌可以相同，也可以不同。在一些实施方式中，各第二微孔的形貌可为规则形状或不规则形状。在一些实施方式中， 各第二微孔的形貌可包括圆形、矩形或正方形。
在一些实施方式中，各第二微孔的等效直径可为1μm-200μm，例如可以为约5μm、约10μm、约20μm、约50μm、约80μm、约100μm、约120μm、约150μm、约180μm、约200μm或处于以上任何数值所组成的范围内。在一些实施方式中，各第二微孔的等效直径可为5μm-180μm，10μm-180μm，20μm-180μm，30μm-180μm，50μm-180μm，5μm-150μm，10μm-150μm，20μm-150μm，30μm-150μm或50μm-150μm。
各第二微孔的等效直径可以为与各第二微孔具有相等面积的圆所具有的直径。第二微孔的等效直径在上述范围内，能够在保证负极极片具有高电解液浸润速率的前提下，使得负极极片具有良好的机械性能，例如，能够使得负极极片具有较高的强度和良好的柔韧性。因此，电极组件能够具有高电解液浸润速率和良好的加工性能，由此，应用该电极组件的二次电池也能够具备良好的电化学性能和高产能。
在一些实施方式中，相邻所述第二微孔的中心距可为1mm-10mm，例如可以为约1mm、约2mm、约3mm、约4mm、约5mm、约6mm、约7mm、约8mm、约9mm、约10mm或处于以上任何数值所组成的范围内。
并非意在受限于任何理论或解释，相邻的第二微孔的中心距在上述范围内，能够使得第二微孔合适地分布于负极极片的表面。由此，能够避免第二微孔的分布过于密集，从而使得负极极片保持良好的机械性能。
本申请对所述多个第二微孔的分布形式不作限定。在一些实施方式中，所述多个第二微孔可呈阵列分布。
在本申请中，所述正极集流体具有在自身厚度方向相对的两个表面，所述正极膜层可以位于所述正极集流体的两个相对表面中的任意一者或两者上。所述负极集流体具有在自身厚度方向相对的两个表面，所述负极膜层可以位于所述负极集流体的两个相对表面中的任意一者或两者上。
需要说明的是，水系正极极片的厚度H 11表示正极集流体和正极膜层的厚度之和，负极极片的厚度H 21表示负极集流体和负极膜层的厚度之和。图1是本申请的水系正极极片局部的一实施方式的截面示意图，图2是本申请的水系正极极片局部的另一实施方式的截面示意图。如图1和图2所示，正极膜层102设置于正极集流体101的两侧，其中，图1表示第一微孔的深度与正极极片的厚度之比小于100％，即H 12小于H 11；图2表示第一微孔为贯穿正极极片的贯通孔，此时H 12等于H 11。在本申请中，负极极片表面第二微孔的设置情况与水系正极极片类似。
本申请的电极组件中，正极活性材料的种类并不受具体的限制，可采用本领域公知的用于二次电池的正极活性材料。在一些实施方式中，所述正极活性材料可以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多种。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。
作为示例，锂过渡金属氧化物可以包括锂钴氧化物、锂镍氧化物、锂锰氧化物、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物、锂镍钴铝氧化物及其各自的改性化合物中的一种或多种。作为示例，橄榄石结构的含锂磷酸盐可以包括磷酸铁锂、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多种。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。
可选地，所述正极活性材料可包括橄榄石结构的含锂磷酸盐及其改性化合物中的一种或多种。
在一些实施方式中，所述正极膜层还可以包括水性粘接剂、导电剂中的一种或多种。水性粘接剂可将正极活性材料、导电剂等粘接于集流体上，增强正极活性材料与导电剂之间以及正极活性材料与正极集流体之间的电子接触、稳定正极极片的结构。水性粘接剂相比于油系粘接剂，例如聚偏氟乙烯等，成本更低、对环境更加友好且使用更安全。
所述水性粘接剂可以包含固体组分含量在5％以上的水分散溶液或乳液。所述水性粘接剂还可以包含可与水形成固体组分含量在1％以上的稳定分散液的固体。在一些实施方式中，所述水性粘接剂包括可溶性多糖类及其衍生物、水溶性或水分散液高分子聚合物或其混合物。例如，所述水性粘接剂可包括甲基纤维素及其盐、黄原胶及其盐、壳聚糖及其盐、海藻酸及其盐、聚乙烯亚胺及其盐、聚丙烯酰胺、丙烯腈-丙烯酸共聚物及其衍生物或其混合物。
在一些实施方式中，所述水性粘接剂可包括黄原胶和聚乙烯亚胺的复配混合物。可选地，所述黄原胶和所述聚乙烯亚胺的质量比可为2:1-0.2:2.8。可选地，所述黄原胶的数均分子量可为300000-2000000。可选地，所述聚乙烯亚胺的数均分子量可为2000-50000。
在一些实施方式中，所述水性粘接剂可包括丙烯腈-丙烯酸共聚物和聚乙烯亚胺的复配混合物。可选地，所述丙烯腈-丙烯酸共聚物和所述聚乙烯亚胺的质量比可为2:1-0.2:2.8。可选地，所述丙烯腈-丙烯酸共聚物的数均分子量可为300000-2000000。可选地，所述聚乙烯亚胺的数均分子量可为2000-70000。
并非意在受限于任何理论或解释，水性粘接剂选自上述物质，能够进一步增强正极活性材料与导电剂之间以及正极活性材料与正极集流体之间的电子接触，从而更好地稳定正极极片的结构。由此，本申请的电极组件应用于二次电池，能够使得二次电池具备高循环稳定性和低内阻。
本申请对用于正极膜层的导电剂的种类没有特别的限制，在一些实施方式中，所述导电剂可包括导电炭黑、超导炭黑、导电石墨、乙炔黑、科琴黑、石墨烯、碳纳米管中的一种或多种。
在本申请的电极组件中，正极膜层通常是将正极浆料涂布在正极集流体上，经干燥、冷压而成的。所述正极浆料通常是将正极活性材料、水性粘接剂、导电剂以及任意的其他组分分散于去离子水中并搅拌均匀而形成的。
在一些实施方式中，所述正极集流体可采用金属箔片或复合集流体。作为金属箔片的示例，可采用铝箔。复合集流体可包括高分子材料基层以及形成于高分子材料基层至少一个表面上的金属材料层。作为示例，金属材料可包括铝、铝合金、镍、镍合金、钛、钛合金、银、银合金中的一种或多种。作为示例，高分子材料基层可包括聚丙烯(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)中的一种或多种。
在本申请的电极组件中，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。负极浆料涂通常是将负极活性材料、可选的导电剂、可选地粘接剂、其他可选的助剂分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)或水，但不限于此。作为示例，用于负极膜层的粘接剂可包括丁苯橡胶(SBR)、水溶性不饱和树脂SR-1B、水系丙烯酸树脂(例如，聚丙烯酸PAA、聚甲基丙烯酸PMAA、聚丙烯酸钠PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、羧甲基壳聚糖(CMCS)中的一种或多种。作为示例，用于负极膜层的导电剂可包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯、碳纳米纤维中一种或多种。其他可选的助剂可包括增稠剂(例如，羧甲基纤维素钠CMC)、PTC热敏电阻材料中的一种或多种。
负极活性材料的种类并不受到具体的限制，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，负极活性材料可包括石墨、软碳、硬碳、中间相碳微球、碳纤维、碳纳米管、硅基材料、锡基材料、钛酸锂中的一种或多种。硅基材料可包括单质硅、硅氧化物、硅碳复合物、硅氮复合物、硅合金材料中的一种或多种。锡基材料可包括单质锡、锡氧化物、锡合金材料中的一种或多种。本申请并不限定于这些材料，还可以使用其他可被用作二次电池负极活性材料的传统公知的材料。这些负极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
负极集流体的种类不受具体的限制，可根据实际需求进行选择。例如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，负极集流体可采用铜箔。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、银合金中的一种或多种。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)中的一种或多种。
另外，本申请的电极组件中，负极极片并不排除除了负极膜层之外的其他附加功能层。例如在一些实施方式中，本申请所述的负极极片还可以包括设置在负极集流体和负极膜层之间的导电底涂层(例如由导电剂和粘接剂组成)。在另外一些实施方式中，本申请所述的负极极片还包括覆盖在负极膜层表面的保护层。
本申请的电极组件中，第一微孔和第二微孔的实现方式不受到具体的限制，可采用本领域公知的手段实现。在一些实施方式中，在极片表面设置第一微孔和第二微孔的手段可以包括激光打孔、机械冲孔中的任意一种方式或其组合。例如采用激光打孔时，可以使激光器上下错开排布，根据打孔工艺方案需求设置合适的打孔阵列，根据所需微孔深度选择合适的激光能量。
在一些实施方式中，所述电极组件还包括隔离膜。所述隔离膜设置在所述水系正极极片和所述负极极片之间，主要起到防止正负极短路的作用，同时可以使活性离子通过。本申请对所述隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
作为示例，所述隔离膜的材质可以包括玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。所述隔离膜可以是单层薄膜，也可以是多层复合薄膜。当所述隔离膜为多层复合薄膜时，各层的材料相同或不同。
在一些实施方式中，所述水系正极极片、所述隔离膜和所述负极极片可通过卷绕工艺或叠片工艺制成电极组件。
在本申请中，膜层和极片的厚度为本领域公知的含义，可采用本领域已知的方法进行测试。例如采用螺旋测微仪进行测定。
在本申请中，材料的体积平均粒径Dv50为本领域公知的含义，其表示材料累计体积分布百分数达到50％时所对应的粒径，可以用本领域公知的仪器及方法进行测定。例如可以参照GB/T 19077-2016粒度分布激光衍射法，采用激光粒度分析仪方便地测定，如英国马尔文仪器有限公司的Mastersizer 2000E型激光粒度分析仪。
在本申请中，极片的压实密度为本领域公知的含义，可采用本领域已知的方法进行测试。极片的压实密度＝膜层的面密度/膜层的厚度。膜层的面密度为本领域公知的含义，可采用本领域已知的方法进行测试，例如取单面涂布且经冷压后的极片(若是双面涂布的极片，可先擦拭掉其中一面的膜层)，冲切成小圆片，称其重量；然后将上述称重后的极片的膜层擦拭掉，称量集流体的重量。膜层的面密度＝(小圆片的重量-集流体的重量)/小圆片的面积。
二次电池
本申请第二方面提供一种二次电池，包括本申请第一方面的电极组件和电解质。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。
在一些实施方式中，电解质采用电解液。电解液包括电解质盐和溶剂。
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。在一些实施方式中，作为示例，电解质盐可包括选自六氟磷酸锂(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)、四氟草酸磷酸锂(LiTFOP)中的一种或多种。
溶剂的种类不受具体的限制，可根据实际需求进行选择。在一些实施方式中，作为示例，溶剂可包括选自碳酸乙烯酯(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)中的一种或多种。
在一些实施方式中，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、改善电池低温功率性能的添加剂等。
在一些实施方式中，二次电池可包括外包装。该外包装可用于封装上述电极组件 及电解质。
在一些实施方式中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，如聚丙烯(PP)、聚对苯二甲酸丁二醇酯(PBT)、聚丁二酸丁二醇酯(PBS)等中的一种或多种。
本申请对二次电池的形状没有特别的限制，其可以是扁平体、长方体或其他形状。如图3是作为一个示例的长方体结构的二次电池5。
在一些实施方式中，如图4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，底板和侧板合围形成容纳腔。壳体51具有与所述容纳腔连通的开口，盖板53用于盖设所述开口，以封闭所述容纳腔。本申请实施方式第一方面的电极组件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多个，可根据需求来调节。
本申请的二次电池的制备方法是公知的。在一些实施方式中，可将电极组件置于外包装中，烘干后注入电解液，经过真空封装、静置、化成、整形等工序，得到二次电池。
电池模块和电池包
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5是作为一个示例的电池模块4的示意图。如图5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。
在一些实施方式中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以根据电池包的应用和容量进行调节。
图6和图7是作为一个示例的电池包1的示意图。如图6和图7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、电池模块或电池包中的至少一种。所述二次电池、电池模块或电池包可以用作所述用电装置的电源，也可以用作所述用电装置的能量存储单元。所述用电装置可以但不限于是移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等。
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8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、和比值都是基于质量计，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至25和对比例4至10的二次电池均按照下述方法制备。
(1)水系正极极片的制备
将正极活性材料磷酸铁锂、导电剂导电碳黑、水性粘接剂按照质量比96:1:3混合均匀，加入适量的去离子水，得到固含量为50％的正极浆料；将正极浆料均匀涂覆于正极集流体表面，烘干后得到双面涂布的水系正极极片。水性粘接剂为聚丙烯腈-丙烯酸酯共聚物LA-133(购自四川茵地乐科技有限公司)与聚乙烯亚胺的复配物，该复配物中，LA-133与聚乙烯亚胺的质量比为1:1。
采用激光打孔装置对水系正极极片进行打孔，从而在水系正极极片表面设置多个第一微孔。第一微孔的等效直径d 1(μm)、相邻第一微孔的中心距L 1(mm)、多个第一微孔的总面积与水系正极极片的面积之比S 12/S 11、第一微孔的深度与水系正极极片的厚度之比H 12/H 11、水系正极极片的压实密度C 1(g/cc)、正极活性材料的体积平均粒径D 1(μm)、(S 12×H 12×D 1)/(S 11×C 1×H 11)分别如表1所示。
(2)负极极片的制备
将负极活性材料人造石墨、导电剂导电碳黑、粘接剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC)按照质量比96.2:1.8:0.8:1.2混合后，加入适量的去离子水，混合均匀得到负极浆料；将负极浆料均匀地涂覆于负极集流体表面，烘干后得到双面涂布的负极极片。
采用激光打孔装置对负极极片进行打孔，从而在负极极片表面设置多个第二微孔。第二微孔的等效直径d 2(μm)、相邻第二微孔的中心距L 2(mm)、多个第二微孔的总面积与负极极片的面积之比S 22/S 21、第二微孔的深度与负极极片的厚度之比H 22/H 21、负极极片的压实密度C 2(g/cc)、负极活性材料的体积平均粒径D 2(μm)、(S 22×H 22×D 2)/(S 21×C 2×H 21)分别如表1所示。
(3)电解液的制备
在氩气气氛手套箱中(H 2O<0.1ppm，O 2<0.1ppm)，将有机溶剂碳酸乙烯酯(EC)和碳酸甲乙酯(EMC)按照体积比3:7混合均匀，加入12.5％LiPF 6溶解于有机溶剂中，搅拌均匀，得到电解液。
(4)隔离膜
以聚丙烯膜作为隔离膜。
(5)二次电池的制备
将水系正极极片、隔离膜、负极极片按照顺序叠好，以使隔离膜处于水系正极极 片与负极极片之间，起到隔离的作用；将叠好的水系正极极片、隔离膜、负极极片卷绕得到电极组件；给电极组件焊接极耳后，将电极组件装入铝壳中，烘烤以除去水分；在铝壳中注入电解液后封口，得到不带电的电池；将不带电的电池依次经过静置、热冷压、化成、整形、容量测试等工序，得到二次电池。
对比例1
水系正极极片的制备、负极极片的制备、隔离膜、电解液的制备、二次电池的制备过程与实施例1基本相同，区别在于：未在水系正极极片及负极极片表面打孔。
对比例2-3
水系正极极片的制备、负极极片的制备、隔离膜、电解液的制备、二次电池的制备过程与实施例1基本相同，区别在于：对比例2未在负极极片表面打孔，对比例3未在水系正极极片表面打孔。
测试部分
(1)电极组件的电解液浸润性能测试
将各实施例及对比例得到的不带电的电池静置不同时间后进行首次充电测试。首次充电的电流设定为0.1C(51.2A)，充电截止电压设定为3.65V。充电结束后在干燥房中拆解电池，观察负极极片大面区域是否呈现锂沉积后的灰白色，如发现表面暴露黑色区域则表明电解液浸润不充分，如表面未暴露黑色区域则表明电解液完全浸润负极极片，记录电解液完全浸润负极极片所需的最短时间。测试时按每增加半小时浸润时间设置一个组别，每个组别拆解三个电极组件进行判定，以三个电极组件同时满足电解液完全浸润负极极片所需要的最短时间作为电极组件的电解液浸润时间T 1。
(2)二次电池的烘干性能测试
将各实施例及对比例得到的入壳后未注液电池放入真空烘箱内进行烘干性能测试。烘箱温度设定为105℃，每隔1h取出测量电池的水含量。电池水含量低于200ppm(质量浓度)时则视为已烘干，记录烘干时间T 2。
(3)二次电池的初始容量以及循环性能测试
使用电池测试仪对二次电池进行充放电测试。其中，充放电电压设定为2.5V～3.65V，充放电电流设定为1C(512A)，读取二次电池首圈循环后的放电容量和循环300圈后的放电容量。
取三个二次电池首圈循环后的放电容量的平均值作为二次电池的初始容量。
二次电池循环300圈后的容量保持率＝(循环300圈后的放电容量/首圈循环后的放电容量)×100％。
(4)二次电池的直流电阻阻抗(DCR)测试
在25℃下，将二次电池以1/3C恒流充电至3.65V，再以3.65V恒压充电至电流为0.05C，静置5min后，记录此时的电压V 1；将二次电池以1/3C恒流放电30s，记录此时的电压V 2，以(V 2-V 1)/(1/3C)表示首圈循环后的内阻。重复以上步骤，并同时记录二次电池循环300圈后的内阻。
各实施例和对比例的参数如表1所示，测试结果如表2所示。
Figure PCTCN2022085463-appb-000001
Figure PCTCN2022085463-appb-000002
表2
Figure PCTCN2022085463-appb-000003
根据表1及表2可知，实施例1-25的电极组件中，水系正极极片及负极极片满足本申请限定的条件，能够使得二次电池具有高初始容量、高电解液浸润速率和高烘干速率，同时二次电池还具有高循环容量保持率和低内阻。
对比例1-3中，水系正极极片和/或负极极片表面未设有微孔，电极组件的电解液浸润速率和烘干速率非常小，且电极组件中易残留较多的水分。由此，应用该电极组件的二次电池的内阻较高且循环性能较差。对比例4-5在水系正极极片和负极极片表面均设置微孔，但是制备的水系正极极片中，(S 12×H 12×D 1)/(S 11×C 1×H 11)小于0.001％，此时，电极组件的电解液浸润速率和烘干速率与对比例1-3相比，略有增加，但改善效果不明显，进而对二次电池循环性能的改善效果也不明显。对比例6-7在水系正极极片和负极极片表面均设置微孔，但是制备的水系正极极片中，(S 12×H 12×D 1)/(S 11×C 1×H 11)大于1％，由此二次电池的能量密度明显下降。对比例8-10在水系正极极片和负极极片表面均设置微孔，但是制备的负极极片中，(S 22×H 22×D 2)/(S 21×C 2×H 21)大于2.5％，由此二次电池的能量密度明显下降。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。

Claims (16)

  1. 一种电极组件，包括水系正极极片和负极极片，其中，
    所述水系正极极片包括正极集流体以及位于所述正极集流体至少一个表面上的正极膜层，所述正极膜层包括正极活性材料；
    所述负极极片包括负极集流体以及位于所述负极集流体至少一个表面上的负极膜层，所述负极膜层包括负极活性材料；
    所述水系正极极片至少部分表面设有多个第一微孔，并且满足：
    0.001％≤(S 12×H 12×D 1)/(S 11×C 1×H 11)≤1％，
    H 11μm表示所述水系正极极片的厚度，H 12μm表示所述第一微孔的深度，S 11m 2表示所述水系正极极片的面积，S 12m 2表示所述多个第一微孔的总面积，C 1g/cc表示所述水系正极极片的压实密度，D 1μm表示所述正极活性材料的体积平均粒径Dv50；
    所述负极极片至少部分表面设有多个第二微孔，并且满足：
    0＜(S 22×H 22×D 2)/(S 21×C 2×H 21)≤2.5％，
    H 21μm表示所述负极极片的厚度，H 22μm表示所述第二微孔的深度，S 21m 2表示所述负极极片的面积，S 22m 2表示所述多个第二微孔的总面积，C 2g/cc表示所述负极极片的压实密度，D 2μm表示所述负极活性材料的体积平均粒径Dv50。
  2. 根据权利要求1所述的电极组件，其中，
    0.05％≤(S 12×H 12×D 1)/(S 11×C 1×H 11)≤0.5％；
    可选地，0.15％≤(S 12×H 12×D 1)/(S 11×C 1×H 11)≤0.25％。
  3. 根据权利要求1所述的电极组件，其中，
    0.2％≤(S 22×H 22×D 2)/(S 21×C 2×H 21)≤2.0％；
    可选地，0.4％≤(S 22×H 22×D 2)/(S 21×C 2×H 21)≤1.0％。
  4. 根据权利要求1或2所述的电极组件，其中，
    0＜S 12/S 11≤2％，可选地，0.4％≤S 12/S 11≤0.6％；和/或，
    30％≤H 12/H 11≤100％，可选地，60％≤H 12/H 11≤100％；和/或，
    C 1为2.0-3.0，可选地为2.3-2.7；和/或，
    D 1为0.5-1.5，可选地为0.8-1.3。
  5. 根据权利要求1或3所述的电极组件，其中，
    0＜S 22/S 21≤0.2％，可选地，0.04％≤S 22/S 21≤0.06％；和/或，
    30％≤H 22/H 21≤100％，可选地，60％≤H 22/H 21≤100％；和/或，
    C 2为1.2-2.0，可选地为1.4-1.8；和/或，
    D 2为12-20，可选地为15-19。
  6. 根据权利要求1-5中任一项所述的电极组件，其中，所述电极组件满足：0.1≤A/B≤1.0，可选地，0.25≤A/B≤0.50，A表示(S 12×H 12×D 1)/(S 11×C 1×H 11)，B表示(S 22×H 22×D 2)/(S 21×C 2×H 21)。
  7. 根据权利要求1-6中任一项所述的电极组件，其中，所述电极组件满足：
    S 3/S 22≥5％，S 3m 2表示所述多个第一微孔与所述多个第二微孔的重合面积，
    可选地，8％≤S 3/S 22≤70％。
  8. 根据权利要求1-7中任一项所述的电极组件，其中，所述第一微孔满足如下条件(1)至(4)中的至少一者，
    (1)各第一微孔的形貌为规则形状或不规则形状，可选地，各第一微孔的形貌包括圆形、矩形或正方形；
    (2)各第一微孔的等效直径为1μm-200μm，可选地为50μm-180μm；
    (3)相邻所述第一微孔的中心距为1mm-10mm；
    (4)所述多个第一微孔呈阵列分布。
  9. 根据权利要求1-8中任一项所述的电极组件，其中，所述第二微孔满足如下条件(1)至(4)中的至少一者，
    (1)各第二微孔的形貌为规则形状或不规则形状，可选地，各第二微孔的形貌包括圆形、矩形或正方形；
    (2)各第二微孔的等效直径为1μm-200μm，可选地为50μm-150μm；
    (3)相邻所述第二微孔的中心距为1mm-10mm；
    (4)所述多个第二微孔呈阵列分布。
  10. 根据权利要求1-9中任一项所述的电极组件，其中，所述正极膜层还包括水性粘接剂、导电剂中的一种或多种，
    可选地，所述水性粘接剂包括甲基纤维素及其盐、黄原胶及其盐、壳聚糖及其盐、海藻酸及其盐、聚乙烯亚胺及其盐、聚丙烯酰胺、丙烯腈-丙烯酸共聚物及其衍生物或其混合物；
    可选地，所述导电剂包括导电炭黑、超导炭黑、导电石墨、乙炔黑、科琴黑、石墨烯、碳纳米管中的一种或多种。
  11. 根据权利要求10所述的电极组件，其中，所述水性粘接剂包括黄原胶和聚乙烯亚胺的复配混合物，
    可选地，所述黄原胶和所述聚乙烯亚胺的质量比为2:1-0.2:2.8，
    可选地，所述黄原胶的数均分子量为300000-2000000，
    可选地，所述聚乙烯亚胺的数均分子量为2000-50000。
  12. 根据权利要求10所述的电极组件，其中，所述水性粘接剂包括丙烯腈-丙烯酸共聚物和聚乙烯亚胺的复配混合物，
    可选地，所述丙烯腈-丙烯酸共聚物和所述聚乙烯亚胺的质量比为2:1-0.2:2.8，
    可选地，所述丙烯腈-丙烯酸共聚物的数均分子量为300000-2000000，
    可选地，所述聚乙烯亚胺的数均分子量为2000-70000。
  13. 一种二次电池，包括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. 一种电池模块，包括根据权利要求13所述的二次电池。
  15. 一种电池包，包括根据权利要求13所述的二次电池、根据权利要求14所述的电池模块中的一种。
  16. 一种用电装置，包括根据权利要求13所述的二次电池、根据权利要求14所述的电池模块、根据权利要求15所述的电池包中的至少一种。
PCT/CN2022/085463 2022-04-07 2022-04-07 电极组件以及包含其的二次电池、电池模块、电池包及用电装置 WO2023193166A1 (zh)

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