WO2024007169A1 - 用于二次电池的粘结剂、负极极片、二次电池、电池模块、电池包和用电装置 - Google Patents

用于二次电池的粘结剂、负极极片、二次电池、电池模块、电池包和用电装置 Download PDF

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WO2024007169A1
WO2024007169A1 PCT/CN2022/103974 CN2022103974W WO2024007169A1 WO 2024007169 A1 WO2024007169 A1 WO 2024007169A1 CN 2022103974 W CN2022103974 W CN 2022103974W WO 2024007169 A1 WO2024007169 A1 WO 2024007169A1
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negative electrode
nitrile rubber
binder
battery
fluoropolymer
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PCT/CN2022/103974
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English (en)
French (fr)
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吴启凡
张明
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宁德时代新能源科技股份有限公司
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Priority to PCT/CN2022/103974 priority Critical patent/WO2024007169A1/zh
Publication of WO2024007169A1 publication Critical patent/WO2024007169A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the field of battery technology, and in particular to a binder for secondary batteries, negative electrode sheets, secondary batteries, battery modules, battery packs and electrical devices.
  • lithium-ion batteries and sodium-ion electromagnetics have been increasingly widely used, including in energy storage power systems such as hydraulic, thermal, wind and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.
  • energy storage power systems such as hydraulic, thermal, wind and solar power stations
  • power tools electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields.
  • lithium-ion battery and sodium-ion battery technology higher requirements have been put forward for their energy density, cycle performance and safety performance.
  • This application was made in view of the above problems, and aims to provide a binder for secondary batteries, negative electrode sheets, secondary batteries, battery modules, battery packs and electrical devices to solve the problem of easy electrode sheets There is a cracking problem.
  • the first aspect of the present application provides a binder for secondary batteries.
  • the binder includes fluoropolymer and nitrile rubber resin. Fluoropolymer and nitrile rubber resin The mass ratio is 1: (0.1-8), wherein the nitrile rubber resin includes one or more of nitrile rubber, hydrogenated nitrile rubber, carboxyl nitrile rubber and vulcanized nitrile rubber.
  • a binder is formed by compounding a fluoropolymer and a nitrile rubber resin, so that the binder is both flexible and can ensure high bonding force of the binder.
  • Such an adhesive can be
  • the binder is used in secondary batteries to effectively prevent the pole pieces from falling off, cracking or breaking, and improves the quality of the pole pieces, thereby further improving the processing performance of the secondary battery.
  • the mass ratio of fluorine-containing polymer and nitrile rubber resin is 1: (0.3-2.5).
  • the fluoropolymer and nitrile rubber resin have a suitable ratio, so that the adhesive has both high flexibility and high bonding force, and the adhesive can The active materials are firmly bonded together and firmly bonded to the current collector. Therefore, the pole piece containing the adhesive of the present application can more effectively prevent the pole piece from falling off, cracking or breaking during the winding or lamination process. .
  • the weight average molecular weight of the nitrile rubber resin is 200,000-800,000, optionally 300,000-600,000.
  • the nitrile rubber resin is a polymer with a relatively large weight average molecular weight.
  • the weight average molecular weight of nitrile rubber resin is greater than 800,000, the intermolecular force increases and the entanglement between macromolecular chains increases.
  • the physical and mechanical properties of nitrile rubber resin such as elongation and elasticity are better. But its processability is poor.
  • the weight average molecular weight of nitrile rubber resin is less than 200,000, the intermolecular force is relatively weakened, the entanglement between macromolecular chains is reduced, and the processability is better, but the elongation and elasticity of nitrile rubber resin are The physical and mechanical properties are poor, manifested by insufficient adhesion.
  • the nitrile rubber resin has the structural formula shown in Formula I
  • the nitrile rubber resin with such a structure has better flexibility and better compatibility with fluoropolymers, so that the adhesive containing the nitrile rubber resin has Better processing performance.
  • the fluoropolymer has a weight average molecular weight of 400,000 to 1,500,000, optionally 700,000 to 1,200,000.
  • the greater the weight average molecular weight of the fluoropolymer the greater the adhesive force.
  • the pole piece containing the adhesive of the present application has stronger peeling strength.
  • the weight average molecular weight of the fluoropolymer is too low, the binder has insufficient adhesion to the active material; when the weight average molecular weight of the fluoropolymer is too high, the binder, active material, and optional conductive agent The slurry formed is easy to gel and is not conducive to subsequent processing.
  • the fluoropolymer is selected from the group consisting of divinylidene fluoride (VDF) homopolymer, copolymer of divinylidene fluoride (VDF) and tetrafluoroethylene (TFE), divinylidene fluoride (VDF), One or more of the copolymers of ethylene (VDF) and hexafluoropropylene (HFP), vinylidene fluoride (VDF) and acrylate copolymers, optionally selected from vinylidene fluoride (VDF) homopolymers or Copolymer of vinylidene fluoride (VDF) and acrylate.
  • VDF divinylidene fluoride
  • VDF tetrafluoroethylene
  • TFE tetrafluoroethylene
  • VDF divinylidene fluoride
  • these specific optional fluoropolymers can impart good bonding properties to the binder and can also provide the binder with good compatibility with the active material and optional conductive agent. It also helps the electrolyte to infiltrate the binder.
  • the viscosity of a 5% weight concentration solution of the binder in N-methylpyrrolidone (NMP) is 300 mPa.s to 3000 mPa.s.
  • a 5% weight concentration solution of the binder in N-methylpyrrolidone (NMP) has a viscosity of 500 mPa.s to 2000 mPa.s, such that the binder has excellent viscosity. While bonding strength, it can also provide good film-forming processing performance. Therefore, the pole piece containing the adhesive of the present application is less likely to fall off, crack or break after winding or hot pressing, which improves the performance of the electrode pole piece. quality, thus improving the reliability and safety of the battery.
  • the second aspect of the application also provides a negative electrode sheet, including a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector.
  • the negative electrode film layer includes: a negative electrode active material and the binder of the first aspect of the application. .
  • applying a binder with good flexibility and high adhesion force to secondary batteries can effectively prevent the negative electrode sheet from falling off, cracking or breaking after being rolled or hot-pressed. phenomenon, improving the quality of the negative electrode piece, thereby further improving the processing performance of the secondary battery, and improving the reliability and safety of the battery.
  • the areal density of the negative electrode sheet is 2 mg/cm 2 to 13 mg/cm 2 , optionally 5 mg/cm 2 to 12 mg/cm 2 , and more optionally 7.5 mg. /cm 2 ⁇ 12 mg/cm 2 .
  • the kinetic performance of the secondary battery and the cycle performance of the secondary battery can be further improved.
  • the mass ratio of the negative active material to the binder is (85% to 97%): (1.5% to 7%).
  • the negative active material and the binder have an appropriate proportion.
  • the binder binds the negative active materials together to form a negative electrode film layer, and firmly bonds the negative electrode film layer to the negative electrode assembly. on the fluid, and can realize the area density of the negative electrode film layer in the negative electrode sheet to reach more than 7.5mg/ cm2 .
  • the negative active material is selected from one or more of soft carbon, hard carbon, artificial graphite, natural graphite, elemental silicon, silicon oxide compounds, and silicon carbon composites.
  • the choice is hard carbon.
  • the third aspect of the application also provides a secondary battery, including the negative electrode plate of the second aspect of the application.
  • the secondary battery is a sodium ion secondary battery.
  • a fourth aspect of the present application provides a battery module including the secondary battery of the third aspect of the present application.
  • a fifth aspect of the present application provides a battery pack, including the battery module of the fourth aspect of the present application.
  • a sixth aspect of the present application provides an electrical device, including at least one selected from the secondary battery of the third aspect of the present application, the battery module of the fourth aspect of the present application, or the battery pack of the fifth aspect of the present application. kind.
  • FIG. 1 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG. 2 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 1 .
  • FIG. 3 is a schematic diagram of a battery module according to an embodiment of the present application.
  • Figure 4 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG. 5 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG. 4 .
  • FIG. 6 is a schematic diagram of a power consumption device using a secondary battery as a power source according to an embodiment of the present application.
  • Ranges disclosed herein are defined in terms of lower and upper limits. A given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive of the endpoints, and may be arbitrarily combined, that is, any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, understand that ranges of 60-110 and 80-120 are also expected. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-5.
  • the numerical range “a-b” represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers.
  • the numerical range “0-5" means that all real numbers between "0-5" have been listed in this article, and "0-5" is just an abbreviation of these numerical combinations.
  • a certain parameter is an integer ⁇ 2
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • step (c) means that step (c) may be added to the method in any order.
  • the method may include steps (a), (b) and (c). , may also include steps (a), (c) and (b), may also include steps (c), (a) and (b), etc.
  • condition "A or B” is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists) ; Or both A and B are true (or exist).
  • lithium-ion batteries and sodium-ion batteries have achieved great development, higher requirements have been put forward for their energy density, cycle performance and safety performance.
  • the negative active material in lithium-ion batteries or sodium-ion batteries is one of the main factors affecting the performance of lithium-ion batteries or sodium-ion batteries.
  • hard carbon materials have the advantages of lower energy storage voltage, higher capacity and good cycle stability. They also have the advantages of rich sources and simple preparation process. They are currently one of the most promising anode active materials. one. Hard carbon materials have a large application market in both lithium-ion batteries and sodium-ion batteries. Especially in sodium-ion batteries, they are currently the most commercially valuable anode active material.
  • hard carbon materials are hard and brittle, which makes the negative electrode film layer containing hard carbon and the negative electrode sheet containing hard carbon have the disadvantage of being hard and brittle, causing the negative electrode sheet to easily fall off, crack, or Breakage, etc., especially for negative electrode sheets with a thick negative electrode film layer.
  • the cracking or fracture of the negative electrode sheet is more serious, and the quality of the negative electrode sheet cannot meet the production requirements.
  • the applicant improved the adhesive and compounded nitrile rubber resin and fluoropolymer to make the adhesive meet the flexibility and adhesive strength required for mass production.
  • the binder is used in secondary batteries to solve the problems of pole piece flexibility and adhesion.
  • alkyl refers to a saturated hydrocarbon group, including both straight-chain and branched-chain structures.
  • C 1 to 18 alkyl represents an alkyl group with 1 to 18 carbon atoms, examples of which include but are not limited to methyl, ethyl, propyl (such as n-propyl, isopropyl), butyl (such as n-butyl , isobutyl, sec-butyl, tert-butyl), pentyl (such as n-pentyl, isopentyl, neopentyl), etc.
  • the first aspect of the application provides a binder for secondary batteries.
  • the binder includes fluoropolymer and nitrile rubber resin.
  • the mass ratio of fluoropolymer to nitrile rubber resin is 1 ⁇ (0.1 ⁇ 8), wherein the nitrile rubber resin includes one or more of nitrile rubber, hydrogenated nitrile rubber, carboxyl nitrile rubber and vulcanized nitrile rubber.
  • binders are used in secondary batteries.
  • active materials and optional conductive agents can be bonded together to form an active material film layer with appropriate cohesive strength, and make such activity
  • the material film layer is firmly bonded to the current collector, and the binder also allows electroactive ions (such as lithium ions and sodium ions) to easily diffuse from the electrolyte into the binder of the active material film layer and can pass through the bonding agent.
  • the agent transfers efficiently to the active material. Therefore, the adhesive has the dual functions of providing mechanical support (providing cohesive strength of the active material film layer and bonding strength to the current collector) and ion transport.
  • the adhesive of the present application includes a combination of fluoropolymer and nitrile rubber resin. The fluoropolymer and nitrile rubber resin are explained separately below.
  • Fluoropolymers mainly include fluororesin, fluororubber, etc., such as polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVDF), which have good heat resistance, cold resistance, electrical insulation, and chemical resistance. and mechanical.
  • fluoropolymers are chemically inert and do not react with electrolytes or active materials when the battery is charged and discharged.
  • Fluoropolymers have high adhesion and stability and can be used as binders.
  • fluoropolymers have high mechanical strength and poor flexibility. That is, when fluoropolymer is used as a binder, the negative electrode piece has good bonding force but poor flexibility, causing the electrode piece to easily break during winding and hot pressing.
  • Fluoropolymers mainly include fluororesins, fluororubbers, etc., such as polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVDF), as well as vinylidene fluoride and other monomers such as tetrafluoroethylene (TFE), hexafluoroethylene Propylene (HFP), or acrylate copolymer, has good heat resistance, cold resistance, electrical insulation, chemical corrosion resistance and mechanical properties. Because of their high chemical inertness, fluoropolymers do not react with electrolyte solutions or active materials when charging and discharging batteries.
  • PTFE polytetrafluoroethylene
  • PVDF polyvinylidene fluoride
  • vinylidene fluoride and other monomers such as tetrafluoroethylene (TFE), hexafluoroethylene Propylene (HFP), or acrylate copolymer
  • fluoropolymers allow active ions of active materials to be transported by diffusion between polymer molecules, and their high It has excellent adhesion and stability and can be used as a binder in secondary batteries, especially in electrode active material layers.
  • the fluorine-containing polymer in the binder of the present application is a typical semi-crystalline polymer, and its crystallinity can be 35% to 78%.
  • the fluorine-containing polymer in the binder of the present application since the polymer molecular chain contains fluorine atoms replacing hydrogen atoms, and fluorine atoms have a larger volume and stronger polarity than hydrogen atoms, This results in an increase in the rigidity of the polymer molecular chain.
  • fluoropolymers will swell with the absorption of the electrolyte solution, causing damage to the active material and current collector due to swelling of the fluoropolymer in the electrolyte solution when only using the fluoropolymer as a binder. Deterioration of adhesion.
  • Nitrile rubber resin includes one or more of nitrile rubber, hydrogenated nitrile rubber, carboxyl nitrile rubber and vulcanized nitrile rubber.
  • Nitrile rubber resin has good oil resistance and contains polarity in its molecules. Nitrile group, therefore, nitrile rubber resin has good flexibility and good compatibility with polar polymer substances.
  • the adhesive formed by nitrile rubber resin has good flexibility.
  • nitrile rubber resin is a non-crystalline amorphous polymer, its molecular chain is soft and the chain segments have high mobility. Nitrile rubber resin therefore exhibits high elastic or rubbery mechanical properties and good flexibility.
  • the adhesive includes a combination of nitrile rubber-based resin and fluoropolymer.
  • nitrile rubber resin according to the present application has good compatibility with fluoropolymers. Without intending to be bound by any theory or explanation, the inventors believe that it is due to the intermolecular interaction between the nitrile rubber resin and the fluoropolymer, such as the hydrogen in the fluoropolymer and the cyano group in the nitrile rubber resin.
  • the binder of the present application since the polymer molecules of the nitrile rubber resin have high flexibility, when they are compatible and blended with the fluoropolymer, they can provide molecular segments for the fluoropolymer. Greater free volume and the ability to reduce the crystallinity of the fluoropolymer, thereby increasing the flexibility of the binder material.
  • the polymer molecules of nitrile rubber resin and fluoropolymer molecules can be fully entangled and hydrogen bonded, the adhesive material can maintain good adhesion.
  • the mass ratio of fluoropolymer to nitrile rubber resin is 1: (0.1-8).
  • the mass ratio of fluoropolymer to nitrile rubber resin is greater than 8, the content of nitrile rubber resin in the binder is higher, which can improve the flexibility of the binder, but the adhesive force of the binder is poor. , the active material cannot be stably bonded to the current collector, and the formed film layer is prone to falling off.
  • the mass ratio of fluoropolymer to nitrile rubber resin is less than 0.1, the fluoropolymer content in the binder is higher, which can improve the bonding strength of the binder, but the flexibility of the binder is poor.
  • a binder is formed by compounding a fluoropolymer and a nitrile rubber resin, so that the binder has flexibility and can ensure the adhesiveness of the binder, and the binder is applied to In secondary batteries, it can effectively prevent the pole pieces from falling off, cracking or breaking, and improve the quality of the pole pieces, thereby further improving the processing performance of secondary batteries.
  • the mass ratio of fluoropolymer to nitrile rubber resin is 1: (0.3-2.5).
  • the mass ratio of fluoropolymer to nitrile rubber resin is 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1: 1. 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2, 1:2.1, 1:2.2, One of 1:2.3.
  • the fluoropolymer and nitrile rubber resin have a suitable ratio, so that the adhesive has both high flexibility and high bonding force, and the adhesive can The active materials are firmly bonded together and firmly bonded to the current collector. Therefore, the pole pieces containing the adhesive of the present application can more effectively prevent the pole pieces from falling off, cracking or breaking during the winding or lamination process.
  • the weight average molecular weight of the nitrile rubber resin is 200,000-800,000.
  • the weight average molecular weight of the nitrile rubber resin is 200,000 to 800,000, and the weight average molecular weight of the nitrile rubber resin is 200,000, 300,000, 400,000, 500,000, 600,000, 700,000, 800,000 or the above. Any other range formed by any two endpoints.
  • the weight average molecular weight of the nitrile rubber resin is 300,000 to 600,000.
  • the weight average molecular weight of the nitrile rubber resin can be measured using conventional methods in the art.
  • the weight average molecular weight of a polymer can be measured using gel permeation chromatography using the Waters E2695 instrument, a technique well known to those skilled in the art.
  • the nitrile rubber resin is a polymer with a relatively large weight average molecular weight.
  • the weight average molecular weight of nitrile rubber resin is greater than 800,000, the intermolecular force increases and the macromolecular chains are difficult to move.
  • the physical and mechanical properties of nitrile rubber resin such as elongation and elasticity are good, but its processability Poor.
  • the weight average molecular weight of nitrile rubber resin is less than 200,000, the intermolecular force is relatively weakened, the macromolecular chains are easy to move, and the processability is good, but the physical and mechanical properties such as elongation and elasticity of nitrile rubber resin are poor. Poor, manifested as insufficient adhesion. Therefore, it is necessary to control the appropriate weight average molecular weight of nitrile rubber resin.
  • the nitrile rubber-based resin has the structural formula shown in Formula I,
  • the nitrile rubber resin is hydrogenated nitrile rubber.
  • x is selected from 1700 to 13000
  • y is selected from 600 to 800
  • z is selected from 0 to 4000.
  • the nitrile rubber resin is a polymer containing cyano groups in its molecular chain structure.
  • x, y and z represent the degree of polymerization of each structural unit, that is, the statistical average of the number of structural units contained in the polymer molecular chain, and do not necessarily mean that the structural units form a block of a certain length.
  • the polarity of nitrile rubber resin increases, but the flexibility of its macromolecular chain decreases, and the adhesiveness further decreases, so it is appropriate to control x, y and z degree of aggregation.
  • the nitrile rubber resin with such a structure has better flexibility and better compatibility with fluoropolymers, so that the adhesive containing the nitrile rubber resin has Better flexibility and processing properties.
  • the fluoropolymer has a weight average molecular weight of 400,000 to 1,500,000.
  • the weight average molecular weight of the fluoropolymer is 400,000 to 1,500,000, and the weight average molecular weight of the fluoropolymer is 400,000, 500,000, 600,000, 700,000, 800,000, 900,000, 1000,000, 1100,000, 1200,000, 1300,000, 1400,000, 1500,000 or any other range consisting of any two of the above endpoints.
  • the fluoropolymer has a weight average molecular weight of 700,000 to 1,200,000.
  • the greater the weight average molecular weight of the fluoropolymer the stronger the bonding performance.
  • the pole piece containing the adhesive of the present application has stronger peeling strength.
  • the weight average molecular weight of the fluoropolymer is too low, the binder has insufficient adhesion to the active material; when the weight average molecular weight of the fluoropolymer is too high, the binder, active material, and optional conductive agent The slurry formed is easy to gel and is not conducive to subsequent processing.
  • the fluoropolymer is selected from the group consisting of divinylidene fluoride (VDF) homopolymer, copolymer of divinylidene fluoride (VDF) and tetrafluoroethylene (TFE), divinylidene fluoride (VDF) and hexafluoroethylene
  • VDF divinylidene fluoride
  • TFE tetrafluoroethylene
  • HFP propylene copolymer
  • VDF vinylidene fluoride
  • acrylate copolymer acrylate copolymer
  • the fluoropolymer is selected from a homopolymer of vinylidene fluoride (VDF) or a copolymer of vinylidene fluoride (VDF) and an acrylate.
  • the fluoropolymer is vinylidene fluoride (VDF) homopolymer.
  • these specific optional fluoropolymers can impart good bonding properties to the binder and can also provide the binder with good compatibility with the active material and optional conductive agent. It also helps the electrolyte to infiltrate the binder.
  • a 5% weight concentration solution of the binder in N-methylpyrrolidone (NMP) has a viscosity of 300 mPa.s to 3000 mPa.s.
  • the viscosity of the binder solution is a meaning known in the art and can be tested using methods known in the art.
  • a Brookfield DV2T viscometer can be used to test the viscosity value at a certain temperature (for example, room temperature 25°C) and humidity (for example, relative humidity RH ⁇ 80%).
  • a 5% weight concentration solution of the binder in N-methylpyrrolidone (NMP) has a viscosity of 300 mPa.s to 3000 mPa.s, such that the binder has excellent viscosity.
  • NMP N-methylpyrrolidone
  • the pole piece containing the adhesive of the present application is less likely to fall off, crack or break after hot pressing or winding, which improves the performance of the pole piece. quality.
  • the second aspect of the application also provides a negative electrode sheet, including a negative electrode current collector and a negative electrode film layer disposed on at least one side of the negative electrode current collector.
  • the negative electrode film layer includes: a negative electrode active material and the binder of the first aspect of the application. .
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector.
  • the negative electrode film layer includes a negative electrode active material and the binder of the first aspect of the present application.
  • the binder bonds the negative active materials together to form a negative electrode film layer, and bonds the negative electrode film layer to the negative electrode current collector.
  • the negative electrode current collector has two opposite surfaces in its own thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base material.
  • the composite current collector can be formed by forming metal materials (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative active material may be a negative active material known in the art for batteries.
  • the negative active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and the like.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon carbon composites, silicon nitrogen composites and silicon alloys.
  • the tin-based material may be selected from at least one of elemental tin, tin oxide compounds and tin alloys.
  • the present application is not limited to these materials, and other traditional materials that can be used as battery negative electrode active materials can also be used. Only one type of these negative electrode active materials may be used alone, or two or more types may be used in combination.
  • applying a flexible and adhesive binder to secondary batteries can effectively prevent the negative electrode sheet from falling off, cracking or breaking after being rolled or hot-pressed.
  • the quality of the negative electrode piece is improved, thereby further improving the processing performance of the secondary battery.
  • the areal density of the negative electrode film layer in the negative electrode sheet ranges from 2 mg/cm 2 to 13 mg/cm 2 .
  • the areal density of the negative electrode film layer has a well-known meaning in the art. It refers to the mass of the negative electrode film layer on one side of the negative electrode current collector per unit area, and can be measured using methods known in the art.
  • the areal density of the negative electrode film layer prepared using the above-mentioned binder can be 2 mg/cm 2 to 13 mg/cm 2 , and the areal density of the negative electrode film layer is 2 mg/cm 2 or 3 mg/cm 2 , 4mg/cm 2 , 5mg/cm 2 , 6mg/cm 2 , 7mg/cm 2 , 8mg/cm 2 , 9mg/cm 2 , 10mg/cm 2 , 11mg/cm 2 , 12mg/cm 2 , 13mg/cm 2 Or within any other range consisting of any two of the above endpoints.
  • the areal density of the negative electrode film layer in the negative electrode piece is 5 mg/cm 2 to 12 mg/cm 2 .
  • the areal density of the negative electrode film layer in the negative electrode piece is 7.5 mg/cm 2 to 12 mg/cm 2 .
  • the area density of the negative electrode film layer in the negative electrode sheet is 7.5 mg/cm 2 to 12 mg/cm 2 , which shows that the more mass per unit area of the negative electrode film layer, the more concentrated the stress will be after hot pressing or winding. If the stress is concentrated, the negative electrode piece is prone to powder falling off or cracking.
  • the binder of this application has both flexibility and adhesiveness, allowing the areal density of the negative electrode film layer in the negative electrode sheet to reach more than 7.5mg/ cm2 , and the phenomenon of powder falling off, cracking or breakage of the negative electrode sheet is significantly reduced. .
  • the kinetic performance of the secondary battery and the cycle performance of the secondary battery can be further improved.
  • the mass ratio of the negative active material to the binder is (85% to 97%): (1.5% to 7%).
  • the mass ratio of the negative active material, the binder and the conductive agent is (85% to 97%): (1.5% to 7%): (0 to 5%).
  • the negative active material and the binder have an appropriate proportion.
  • the binder binds the negative active materials together to form a negative electrode film layer, and firmly bonds the negative electrode film layer to the negative electrode assembly. on the fluid, and can realize the area density of the negative electrode film layer in the negative electrode sheet to reach more than 7.5mg/ cm2 .
  • the mass proportion of the negative active material in the negative electrode film is too small, that is, the mass proportion of the binder is too small, the adhesion of the negative electrode film will be reduced, and the negative electrode film will easily peel, crack or break during processing. And other issues.
  • the conductivity of the negative electrode film layer will decrease, and it will not be able to effectively improve the sodium insertion overpotential or lithium insertion overpotential, and it is easy to form sodium dendrites or lithium dendrites, and the battery cycle Performance degrades.
  • the negative active material is selected from one or more of soft carbon, hard carbon, artificial graphite, natural graphite, elemental silicon, silicon oxide compounds, and silicon carbon composites.
  • the negative active material is hard carbon.
  • Hard carbon has the advantages of lower energy storage voltage, higher capacity and good cycle stability. It also has the advantages of abundant sources and simple preparation process. It is currently one of the most promising anode active materials.
  • hard carbon is hard and brittle, so that the negative electrode film layer containing hard carbon and the negative electrode sheet containing hard carbon have the disadvantage of being hard and brittle, especially when the thickness of the negative electrode film layer is thick, the negative electrode sheet will The phenomenon of powder loss, cracking or breakage after hot pressing or winding is more serious.
  • a flexible and adhesive binder is obtained by compounding fluoropolymer and nitrile rubber resin. The binder binds hard carbon together to form a negative electrode film layer, and binds the negative electrode film to The layer is firmly bonded to the negative electrode current collector, thereby effectively preventing the negative electrode piece containing hard carbon from falling off, cracking or breaking.
  • the negative electrode film layer optionally further includes a conductive agent.
  • the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the negative electrode sheet can be prepared by combining the above-mentioned components for preparing the negative electrode sheet, such as negative active material (such as hard carbon), conductive agent, binder (such as fluoropolymer and Nitrile rubber resin) and any other components are dispersed in a solvent (such as NMP) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, it can be obtained Negative pole piece.
  • negative active material such as hard carbon
  • conductive agent such as fluoropolymer and Nitrile rubber resin
  • binder such as fluoropolymer and Nitrile rubber resin
  • FIG. 1 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG. 2 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 1 .
  • Figure 3 is a schematic diagram of a battery module according to an embodiment of the present application.
  • Figure 4 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG. 5 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG. 4 .
  • FIG. 6 is a schematic diagram of a power consumption device using a secondary battery as a power source according to an embodiment of the present application.
  • the third aspect of the application also provides a secondary battery, including the negative electrode plate of the second aspect of the application.
  • a secondary battery typically includes a positive electrode plate, a negative electrode plate, an electrolyte and a separator.
  • active ions are inserted and detached back and forth between the positive and negative electrodes.
  • the electrolyte plays a role in conducting ions between the positive and negative electrodes.
  • the isolation film is placed between the positive electrode piece and the negative electrode piece. It mainly prevents the positive and negative electrodes from short-circuiting and allows ions to pass through.
  • the secondary battery is a sodium ion secondary battery.
  • the negative electrode plate may be the negative electrode plate of the second aspect of the present application. Therefore, the previous description of the embodiments of the negative electrode plate according to the present application is also applicable to the negative electrode plate in the secondary battery, and the same content will not be described again.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer formed on at least part of the surface of the positive electrode current collector.
  • the positive electrode film layer includes a positive electrode active material, and the positive electrode active material can It includes at least one of sodium transition metal oxide, polyanionic compound and Prussian blue compound.
  • the positive electrode active material can It includes at least one of sodium transition metal oxide, polyanionic compound and Prussian blue compound.
  • this application is not limited to these materials.
  • Other conventionally known materials that can be used as positive electrode active materials for sodium ion batteries can also be used.
  • the transition metals in sodium transition metal oxides, can be Mn, Fe, At least one of Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce.
  • the sodium transition metal oxide is, for example, Na x MO 2 , where M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, 0 ⁇ x ⁇ 1.
  • the polyanionic compound may be a type of compound having sodium ions, transition metal ions, and tetrahedral (YO 4 ) n- anion units.
  • the transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce;
  • Y can be at least one of P, S and Si;
  • n represents (YO 4 ) n -valency.
  • the polyanionic compound may also be a type of compound having sodium ions, transition metal ions, tetrahedral (YO 4 ) n- anion units and halogen anions.
  • the transition metal can be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce;
  • Y can be at least one of P, S and Si, n represents (YO 4 )
  • the halogen can be at least one of F, Cl and Br.
  • the polyanionic compound may also be a type of compound having sodium ions, tetrahedral (YO 4 ) n- anion units, polyhedral units (ZO y ) m+ , and optional halogen anions.
  • Y can be at least one of P, S and Si
  • n represents the valence state of (YO 4 ) n-
  • Z represents a transition metal, which can be Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V , Zr and Ce
  • m represents the valence state of (ZO y ) m+
  • the halogen can be at least one of F, Cl and Br.
  • the polyanionic compounds are NaFePO 4 , Na 3 V 2 (PO4) 3 , NaM'PO 4 F (M' is one or more of V, Fe, Mn and Ni) and Na 3 ( At least one of VO y ) 2 (PO 4 ) 2 F 3-2y (0 ⁇ y ⁇ 1).
  • the Prussian blue compound may be a compound having sodium ions, transition metal ions, and cyanide ions (CN - ).
  • the transition metal may be at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce.
  • the Prussian blue compound is, for example, Na a Me b Me' c (CN) 6 , where Me and Me' are each independently at least one of Ni, Cu, Fe, Mn, Co and Zn, 0 ⁇ a ⁇ 2, 0 ⁇ b ⁇ 1, 0 ⁇ c ⁇ 1.
  • the positive electrode film layer may further include a conductive agent to improve the conductive performance of the positive electrode.
  • a conductive agent to improve the conductive performance of the positive electrode.
  • the conductive agent can be one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphite, graphene and carbon nanofibers.
  • the positive electrode film layer may further include a binder to firmly bond the positive electrode active material and optional conductive agent to the positive electrode current collector.
  • a binder to firmly bond the positive electrode active material and optional conductive agent to the positive electrode current collector.
  • the binder may be at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyacrylic acid (PAA), polyacrylonitrile (PAN), and polyvinyl alcohol (PVA).
  • the positive electrode current collector can be a conductive carbon sheet, metal foil, carbon-coated metal foil, porous metal plate or composite current collector, wherein the conductive carbon material of the conductive carbon sheet can be superconducting carbon, acetylene black, carbon One or more of black, Ketjen black, carbon dots, carbon nanotubes, graphite, graphene and carbon nanofibers, the metal materials of metal foil, carbon-coated metal foil and porous metal plate can be independently selected from At least one of copper, aluminum, nickel and stainless steel.
  • the composite current collector may be a composite current collector formed by a combination of a metal foil material and a polymer base film.
  • the positive electrode current collector is, for example, one or more of copper foil, aluminum foil, nickel foil, stainless steel foil, stainless steel mesh, and carbon-coated aluminum foil. Aluminum foil is preferably used.
  • the above-mentioned positive electrode sheet can be prepared according to conventional methods in the art.
  • the positive electrode active material and optional conductive agent and binder are dispersed in a solvent (such as N-methylpyrrolidone, referred to as NMP) to form a uniform positive electrode slurry, and the positive electrode slurry is coated on the positive electrode current collector , after drying and cold pressing, the positive electrode piece is obtained.
  • a solvent such as N-methylpyrrolidone, referred to as NMP
  • the isolation membrane in the sodium ion battery of the present application can be made of various materials suitable for isolation membranes of electrochemical energy storage devices in the art.
  • it can be made of, but not limited to, polyethylene, polypropylene, polyvinylidene, etc. At least one of vinyl fluoride, aramid, polyethylene terephthalate, polytetrafluoroethylene, polyacrylonitrile, polyimide, polyamide, polyester and natural fiber.
  • the electrolyte plays a role in conducting ions between the positive electrode piece and the negative electrode piece.
  • the type of electrolyte in this application can be selected according to needs.
  • the electrolyte can be liquid, gel, or completely solid.
  • the electrolyte may include an organic solvent and an electrolyte sodium salt.
  • the organic solvent may be ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, propylene carbonate, methyl acetate, ethyl propionate, fluoroethylene carbonate, One or more of diethyl ether, diglyme, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, and methyl tert-butyl ether;
  • the electrolyte sodium salt can be sodium hexafluorophosphate, bis- One or more of sodium fluorosulfonimide, sodium bistrifluoromethanesulfonimide, sodium triflate, sodium tetrafluoroborate, sodium difluorophosphate, sodium perchlorate, and sodium chloride.
  • the solvent may be selected from the group consisting of ethylene carbonate, propylene carbonate, methylethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, Butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate At least one of ester, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • the electrolyte optionally further includes additives.
  • 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 or low-temperature performance, etc.
  • the positive electrode piece, the negative electrode piece, and the separator film can be made into an electrode assembly through a winding process or a lamination process.
  • the secondary battery may include an outer packaging.
  • the outer packaging can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag.
  • the material of the soft bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
  • FIG. 1 shows a square-structured secondary battery 5 as an example.
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity.
  • the housing 51 has an opening communicating with the accommodation cavity, and the cover plate 53 can cover the opening to close the accommodation cavity.
  • the positive electrode piece, the negative electrode piece and the isolation film can be formed into the electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the containing cavity.
  • the electrolyte soaks into the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.
  • secondary batteries can be assembled into battery modules, and the number of secondary batteries contained in the battery module can be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery module.
  • FIG. 3 shows a battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 .
  • the plurality of secondary batteries 5 can be fixed by fasteners.
  • the battery module 4 may further include a housing having a receiving space in which a plurality of secondary batteries 5 are received.
  • the above-mentioned battery modules can also be assembled into a battery pack.
  • the number of battery modules contained in the battery pack can be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery pack.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box.
  • the battery box includes an upper box 2 and a lower box 3 .
  • the upper box 2 can be covered with the lower box 3 and form a closed space for accommodating the battery module 4 .
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • the present application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided by the present application.
  • the secondary battery, battery module, or battery pack may be used as a power source for the electrical device, or may be used as an energy storage unit for the electrical device.
  • the electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, and electric golf carts). , electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited to these.
  • a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.
  • FIG. 6 shows an electrical device as an example.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc.
  • a battery pack or battery module can be used.
  • the device may be a mobile phone, a tablet, a laptop, etc.
  • the device is usually required to be thin and light, and a secondary battery can be used as a power source.
  • the weight average molecular weight of vinylidene fluoride homopolymer is 100W
  • the grease of nitrile rubber has the structural formula shown in the following formula
  • x:y 1:0.5
  • weight average molecular weight of nitrile rubber is 40W.
  • binders obtained in Examples 1 to 13 and Comparative Examples 1 to 10 were used as binders for negative electrode sheets, and negative electrode sheets were prepared as follows.
  • NMP N-methylpyrrolidone
  • the single-sided coated and cold-pressed negative electrode piece (if it is a double-sided coated negative electrode piece, the negative electrode film layer on one side can be wiped off first), is punched into small discs with an area of S 1 , and is called Weight, recorded as M 1 . Then wipe off the negative electrode film layer of the weighed negative electrode piece, weigh the weight of the negative electrode current collector, and record it as M 0 .
  • the area density of the negative electrode film layer (weight M 1 of the negative electrode piece - negative electrode current collector Weight M 0 )/S 1 .
  • the diameter of the rolling needle is R
  • R 2.0mm has cracks
  • Rolling needles are prepared as follows:
  • Example 1 twenty three 12 ⁇ 1 Example 2 twenty two 11 ⁇ 1 Example 3 twenty two 11 ⁇ 1 Example 4 20 10 1 Example 5 twenty one 11 ⁇ 1 Example 6 twenty two 11 ⁇ 1 Example 7 19 10 1 Example 8 20 11 ⁇ 1 Example 9 twenty three 11 ⁇ 1 Example 10 twenty three 12 1 Example 11 19 10 1 Example 12 18 10 ⁇ 1 Example 13 20 11 ⁇ 1 Comparative example 1 28 5 4 Comparative example 2 3 6 ⁇ 1 Comparative example 3 -- 5 -- Comparative example 4 -- 7 -- Comparative example 5 5 6 ⁇ 1 Comparative example 6 25 7 4 Comparative example 7 2 6 ⁇ 1
  • Comparative example 8 18 7 ⁇ 2 Comparative example 9 4 7 ⁇ 1 Comparative example 10 15 7 ⁇ 2
  • Examples 1 to 13 have all achieved good results.
  • the bonding force between the negative electrode diaphragm and the negative electrode current collector is strong, the negative electrode sheet has a high surface density and good flexibility.
  • the obtained negative electrode sheet meet production needs.
  • the binder is formed by compounding fluoropolymer and nitrile rubber resin, so that the binder has both flexibility and high adhesion. When the binder is used in secondary batteries, it can effectively avoid the negative electrode The defects of pole piece cracking can be improved by improving the quality of the negative pole piece, thereby further improving the processing performance of the secondary battery.
  • Comparative Examples 1 and 2 only fluoropolymer is used as the binder, and the flexibility and area density of the negative electrode sheet formed by it is low. If only nitrile rubber resin is used as the binder, the negative electrode sheet formed has a low surface density, and the bonding force between the negative electrode diaphragm and the negative electrode current collector is poor.
  • the mass ratio of fluoropolymer to nitrile rubber resin is an important factor affecting the performance of the negative electrode plate.
  • the mass ratio of fluoropolymer to nitrile rubber resin is greater than 8
  • the content of nitrile rubber resin in the binder is higher, which can improve the flexibility of the binder, but the bonding
  • the adhesive force of the agent is poor, and the active material cannot be stably bonded to the current collector, and the film layer formed is easy to fall off.
  • the mass ratio of fluoropolymer to nitrile rubber resin is less than 0.1, the fluoropolymer content in the binder is higher, which can improve the bonding strength of the binder, but the flexibility of the binder is poor. Defects that will affect the processing performance of subsequent secondary batteries, such as cold-pressed strip breakage, winding breakage, die-cutting powder, etc., will affect the processing performance.
  • the weight average molecular weight of fluoropolymers and nitrile rubber resins also affects the performance of the negative electrode plate. For example, in Comparative Examples 3, 4, 9 and 10, when the weight average molecular weight of the fluoropolymer is too large or too small, the binding force of the binder to the active material is insufficient, and the slurry gel formed does not meet the production requirements. , normal coating cannot be performed. When the weight average molecular weight of the nitrile rubber resin is too small, the bonding force is insufficient; when the weight average molecular weight of the nitrile rubber resin is too large, cracks will appear and the production requirements cannot be met.

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Abstract

一种二次电池的粘结剂、负极极片、二次电池、电池模块、电池包和用电装置。粘结剂包括含氟聚合物和丁腈橡胶类树脂，含氟聚合物与丁腈橡胶类树脂的质量比为1：（0.1~8），其中，丁腈橡胶类树脂包括丁腈橡胶、氢化丁腈橡胶、羧基丁腈橡胶和硫化丁腈橡胶中的一种或几种。通过含氟聚合物与丁腈橡胶类树脂复配形成粘结剂，粘结剂应用于二次电池中，能够有效地避免负极片掉粉、开裂或断裂。

Description

用于二次电池的粘结剂、负极极片、二次电池、电池模块、电池包和用电装置 技术领域
本申请涉及电池技术领域，特别是涉及一种用于二次电池的粘结剂、负极极片、二次电池、电池模块、电池包和用电装置。
背景技术
近年来，以锂离子电池、钠离子电磁为代表的二次电池得到越来越广泛的应用，包括用于水力、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。随着锂离子电池和钠离子电池技术的发展，对二者的能量密度、循环性能和安全性能等也提出了更高的要求。
但是，现有的锂离子电池以及钠离子电池中的电极极片在涂布和卷绕等工序容易出现开裂或断裂等问题，且面密度较高时问题加剧，从而影响锂离子电池和钠离子电池的性能，限制了锂离子电池和钠离子电池的发展。
发明内容
本申请是鉴于上述课题而进行的，旨在提供一种用于二次电池的粘结剂、负极极片、二次电池、电池模块、电池包和用电装置，以解决的电极极片容易出现开裂的问题。
为了达到上述目的，本申请的第一方面提供了一种用于二次电池的粘结剂，粘结剂包括含氟聚合物和丁腈橡胶类树脂，含氟聚合物与丁腈橡胶类树脂的质量比为1∶(0.1～8)，其中，丁腈橡胶类树脂包括丁腈橡胶、氢化丁腈橡胶、羧基丁腈橡胶和硫化丁腈橡胶中的一种或几种。
根据本申请的实施例，通过含氟聚合物与丁腈橡胶类树脂复配形成粘结剂，使得粘结剂既具有柔韧性，又能够保证粘结剂的高粘结力，将这样的粘结剂应用 于二次电池中，能够有效地避免极片掉粉、开裂或断裂，提高极片的质量，从而进一步提高二次电池的加工性能。
在本申请第一方面的任一实施方式中，含氟聚合物与丁腈橡胶类树脂的质量比为1∶(0.3～2.5)。
在这些可选的实施例中，含氟聚合物与丁腈橡胶类树脂具有适宜的配比，使得粘结剂既具有较高的柔韧性，又具有较高的粘结力，粘结剂可将活性材料牢固地粘结在一起并与集流体牢固地粘接，因此包含本申请粘结剂的极片在卷绕或叠片过程中，能够更有效的抑制极片掉粉、开裂或断裂。
在本申请第一方面的任一实施方式中，丁腈橡胶类树脂的重均分子量为200,000～800,000，可选地为300,000～600,000。
在这些可选的实施例中，丁腈橡胶类树脂为聚合物，其重均分子量相对较大。当丁腈橡胶类树脂的重均分子量大于800,000时，其分子间的作用力增加，大分子链之间的缠结增加，丁腈橡胶类树脂的伸长率和弹性等物理机械性能较好，但其加工性较差。当丁腈橡胶类树脂的重均分子量小于200,000时，其分子间的作用力相对减弱，大分子链之间的缠结减少，加工性较好，但是丁腈橡胶类树脂的伸长率和弹性等物理机械性能较差，表现为粘结力不足。
在本申请第一方面的任一实施方式中，丁腈橡胶类树脂具有式I所示的结构式
Figure PCTCN2022103974-appb-000001
其中，R选自H、C 1～18烷基、-COOR 1中的一种或几种，R 1选自H、C 1～18烷基中的一种或几种，x、y和z之间满足x∶y∶z＝1∶(0.36～1)∶(0～0.3)。
在这些可选的实施例中，如此结构的丁腈橡胶类树脂，其具有更佳的柔韧性能，以及与含氟聚合物相容性较好，使得包含丁腈橡胶类树脂的粘结剂具有更佳的加工性能。
在本申请第一方面的任一实施方式中，含氟聚合物的重均分子量为400,000～1,500,000，可选地为700,000～1,200,000。
在这些可选的实施例中，含氟聚合物的重均分子量越大，粘结力越大，应用于二次电池时，包含本申请粘结剂的极片具有较强的剥离强度。当含氟聚合物的重 均分子量过低时，粘结剂对活性材料的粘结力不足；当含氟聚合物的重均分子量过高时，粘结剂、活性材料和可选的导电剂形成的浆料容易凝胶，不利于后续加工。
在本申请第一方面的任一实施方式中，含氟聚合物选自偏氟二乙烯(VDF)均聚物、偏氟二乙烯(VDF)与四氟乙烯(TFE)共聚物、偏氟二乙烯(VDF)与六氟丙烯(HFP)共聚物、偏氟二乙烯(VDF)与丙烯酸酯共聚物中的一种或几种，可选地选自偏氟二乙烯(VDF)均聚物或偏氟二乙烯(VDF)与丙烯酸酯共聚物。
在这些可选的实施例中，这些具体可选的含氟聚合物能够赋予粘结剂良好的粘结性能，还能使粘结剂与活性材料和可选的导电剂具有较好的相容性，也有利于电解液浸润粘结剂。
在本申请第一方面的任一实施方式中，粘结剂在N-甲基吡咯烷酮(NMP)中的5％重量浓度的溶液的粘度为300mPa.s～3000mPa.s。
在这些可选的实施例中，粘结剂在N-甲基吡咯烷酮(NMP)中的5％重量浓度的溶液的粘度为500mPa.s～2000mPa.s，从而使得粘结剂在具有优异的粘结力的同时，还能够提供良好的成膜加工性能，因此包含本申请粘结剂的极片在卷绕或热压后更不容易出现掉粉、开裂或断裂的现象，提高了电极极片的质量，从而提高了电池的可靠性和安全性。
申请的第二方面还提供一种负极极片，包括负极集流体以及设置在负极集流体至少一侧面上的负极膜层，负极膜层包括：负极活性材料和本申请第一方面的粘结剂。
根据本申请的实施例，将具有柔韧性佳和粘结力高的粘结剂应用于二次电池中，能够有效地避免负极极片在卷绕或热压后出现掉粉、开裂或断裂的现象，提高了负极极片的质量，从而进一步提高二次电池的加工性能，并且提高了电池的可靠性和安全性。
在本申请第二方面的任一实施方式中，负极极片的面密度为2mg/cm 2～13mg/cm 2，可地为5mg/cm 2～12mg/cm 2，更可选地为7.5mg/cm 2～12mg/cm 2。
在这些可选的实施例中，当负极膜层的面密度在上述范围内时，可以进一步改善二次电池的动力学性能和二次电池的循环性能。
在本申请第二方面的任一实施方式中，负极活性材料与粘结剂的质量比为 (85％～97％)∶(1.5％～7％)。
在这些可选的实施例中，负极活性材料与粘结剂具有适量的配比，粘结剂将负活性材料粘结在一起形成负极膜层，并将负极膜层牢固地粘接在负极集流体上，并能够实现负极极片中负极膜层的面密度能够达到7.5mg/cm 2以上。
在本申请第二方面的任一实施方式中，负极活性材料选自软碳、硬碳、人造石墨、天然石墨、单质硅、硅氧化合物、硅碳复合物中的一种或几种，可选地为硬碳。
申请的第三方面还提供一种二次电池，包括本申请第二方面的负极极片。
在本申请第三方面的任一实施方式中，二次电池为钠离子二次电池。
本申请的第四方面提供一种电池模块，包括本申请的第三方面的二次电池。
本申请的第五方面提供一种电池包，包括本申请的第四方面的电池模块。
本申请的第六方面提供一种用电装置，包括选自本申请的第三方面的二次电池、本申请的第四方面的电池模块或本申请的第五方面的电池包中的至少一种。
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例，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是本申请一实施方式的二次电池的示意图。
图2是图1所示的本申请一实施方式的二次电池的分解图。
图3是本申请一实施方式的电池模块的示意图。
图4是本申请一实施方式的电池包的示意图。
图5是图4所示的本申请一实施方式的电池包的分解图。
图6是本申请一实施方式的二次电池用作电源的用电装置的示意图。
附图标记说明：
1电池包；2上箱体；3下箱体；4电池模块；5二次电池；51壳体；52电极组件；53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用于二次电池的粘结剂、负极极片、二次电池、电池模块、电池包和用电装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，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)。
随着锂离子电池和钠离子电池都取得了极大的发展，对二者的能量密度、循环性能和安全性能等也提出了更高的要求。其中，锂离子电池或钠离子电池中的负极活性材料是影响锂离子电池或钠离子电池性能的主要因素之一。通常，硬碳材料因其具有较低的储能电压、较高的容量和良好的循环稳定性的优点，还具有来源丰富、制备工艺简单等优势，是目前最具有应用前景的负极活性材料之一。硬碳材料在锂离子电池和钠离子电池上均有很大的应用市场，尤其在钠离子电池中，是目前最具商业化价值的负极活性材料。但是，硬碳材料具有一个明显的特点是颗粒硬脆，从而使得包含硬碳的负极膜层，以及包含硬碳的负极极片均具有硬脆的缺点，导致负极极片易掉粉、开裂或断裂等，特别是负极膜层厚度较厚的负极极片，其在卷绕或叠片过程中，负极极片开裂或断裂更为严重，负极极片的质量无法符合生产要求。
基于申请人发现的上述问题，申请人对粘结剂进行了改进，丁腈橡胶类树脂与含氟聚合物进行复配，使得粘结剂满足量产需求的柔韧性和粘结力，将粘结剂应用于二次电池，能够解决极片柔韧性和粘结力的问题。
术语“烷基”是指饱和烃基，既包括直链结构也包括支链结构。C 1～18烷基表示具有1～18个碳原子的烷基，其实例包括但不限于甲基、乙基、丙基(如正丙基、异丙基)、丁基(如正丁基、异丁基、仲丁基、叔丁基)、戊基(如正戊基、异戊基、新戊基)等。
在本说明书的各处，取代基以组或范围公开。明确地预期这种描述包括这些组和范围的成员的每一个单独的子组合。例如，明确地预期术语“C 1～18”单独地公开C 1、C 2、C 3、C 4、C 5、C 6、C 7、C 8、C 9、C 10、C 11、C 12、C 13、C 14、C 15、C 16、C 17、C 18以及由上述任意两者组成的范围。
粘结剂
本申请的第一方面提供了一种用于二次电池的粘结剂，粘结剂包括含氟聚合物和丁腈橡胶类树脂，含氟聚合物与丁腈橡胶类树脂的质量比为1∶(0.1～8)，其中，丁腈橡胶类树脂包括丁腈橡胶、氢化丁腈橡胶、羧基丁腈橡胶和硫化丁腈橡胶中的一种或几种。
根据本申请的实施例，粘结剂应用于二次电池中，例如可以将活性材料和可选的导电剂粘结在一起以形成具有适当内聚强度的活性材料膜层，并使得这样的活性材料膜层牢固地粘结在集流体上，而且粘结剂还允许电活性离子(例如锂离子和钠离子)从电解液中容易地扩散进入活性材料膜层的粘结剂并可经由粘结剂传递有效地向活性材料迁移。因此，粘合剂具有提供机械支撑(提供活性材料膜层的内聚强度和与集流体的粘结强度)和离子运输的双重功能。本申请的粘结剂包括含氟聚合物和丁腈橡胶类树脂的组合，下面对含氟聚合物和丁腈橡胶类树脂分别解释说明。
含氟聚合物主要包括氟树脂、氟橡胶等，例如聚四氟乙烯(PTFE)或聚偏二氟乙烯(PVDF)，其具有良好的耐热性、耐寒性、电绝缘性、耐化学腐蚀性和机械性。此外，含氟聚合物在电池充放电时，具有化学惰性并且不与电解质或活性材料进行反应，并且含氟聚合物具有较高的粘结力和稳定性，可以作为粘结剂。但是，含氟聚合物机械强度高柔韧性差，即以含氟聚合物为粘结剂时，负极极片的粘结力好但柔韧性差，导致极片在卷绕和热压时易断裂。
含氟聚合物主要包括氟树脂、氟橡胶等，例如聚四氟乙烯(PTFE)或聚偏二氟乙烯(PVDF)，以及偏二氟乙烯与其它单体如四氟乙烯(TFE)、六氟丙烯(HFP)、或丙烯酸酯的共聚物，其具有良好的耐热性、耐寒性、电绝缘性、耐化学腐蚀性和机械性能。含氟聚合物因具有高化学惰性，在电池充放电时不与电解质溶液或活性材料进行反应，而且含氟聚合物允许活性材料的活性离子通过在聚合物分子之间扩散运输，以及其较高的粘结力和稳定性，可以作为用于二次电池、特别是电极活性材料层中的粘结剂。本申请粘结剂中的含氟聚合物是一类典型的半结晶聚合物，其结晶度可以为35％～78％。另一方面，在本申请粘结剂中的含氟聚合物中，由于聚合物分子链包含取代氢原子的氟原子，而氟原子较之氢原子具有更大的体积和更强的极性，从而导致聚合物分子链的刚性增加。因此，发明人发现，当仅单一使用含氟聚合物作为粘结剂时，会导致电极活性材料膜层的脆性较高，特别是包含硬碳材料作为活性材料；这样脆性较高的活性材料膜层在电极片的卷绕或叠片过程中，会发生掉粉、 开裂或断裂等。并非意在受限于任何理论或解释，发明人认为电极活性材料膜层的脆性问题与含氟聚合物粘结剂具有较高的分子链刚性和结晶度相关。此外，含氟聚合物会随电解质溶液的吸收而溶胀，导致当仅单一使用含氟聚合物作为粘结剂时，含氟聚合物由于在电解质溶液中发生溶胀而导致对活性材料与集流体的粘结力劣化。
丁腈橡胶类树脂包括丁腈橡胶、氢化丁腈橡胶、羧基丁腈橡胶和硫化丁腈橡胶中的一种或几种，丁腈橡胶类树脂具有较好的耐油性，其分子内含有极性的腈基，因此，丁腈橡胶类树脂具有较好的柔韧性能，以及对极性高分子物质有良好的相容性，丁腈橡胶类树脂形成的粘结剂具有较好的柔韧性。而且，丁腈橡胶类树脂是非结晶的无定形聚合物，其分子链柔软且链段有较高的活动度。丁腈橡胶类树脂因此表现出高弹态或橡胶态的力学性能，具有良好的柔韧性。
根据本申请的实施例，粘结剂包含丁腈橡胶类树脂和含氟聚合物的组合。发明人发现，根据本申请的丁腈橡胶类树脂与含氟聚合物具有良好的相容性。并非意在受限于任何理论或解释，发明人认为由于丁腈橡胶类树脂和含氟聚合物的分子间的相互作用，如含氟聚合物中的氢与丁腈橡胶类树脂中的氰基之间，以及丁腈橡胶类树脂中的氢(特别是丁腈橡胶类树脂含有诸如羧基的改性官能团时)与含氟聚合物中的氟之间的氢键作用，从而使得根据本申请的丁腈橡胶类树脂与含氟聚合物具有良好的相容性。因此，在本申请的粘结剂中，由于丁腈橡胶类树脂的聚合物分子具有很高的柔性，其与含氟聚合物相容共混时，可以为含氟聚合物的分子链段提供更大的自由体积，而且能够降低含氟聚合物的结晶度，从而提高粘结剂材料的柔韧性。另一方面，由于丁腈橡胶类树脂的聚合物分子与含氟聚合物分子能够充分缠结并存在氢键作用，因此可以使得粘结剂材料保持良好的粘结力。
在一些实施例中，含氟聚合物与丁腈橡胶类树脂的质量比为1∶(0.1～8)。当含氟聚合物与丁腈橡胶类树脂的质量比大于8时，粘结剂中丁腈橡胶类树脂含量较高，可提高粘结剂的柔韧性，但是粘结剂的粘结力较差，无法将活性材料稳定的粘结到集流体上，且形成的膜层容易发生脱落。当含氟聚合物与丁腈橡胶类树脂的质量比小于0.1时，粘结剂中含氟聚合物含量较高，可提高粘结剂的粘结力，但粘结剂的柔韧性较差，会影响后续的二次电池的加工性能，例如冷压断带，卷绕断裂，模切掉粉等影响加工性能的缺陷。因此，将丁腈橡胶类树脂与含氟聚合物进行复配，发挥它 们的优势互补和弥补彼此缺点的协同作用，将粘结剂应用于二次电池，能够解决极片开裂的问题，并提高二次电池的加工性能。
根据本申请的实施例，通过含氟聚合物与丁腈橡胶类树脂复配形成粘结剂，使得粘结剂既具有柔韧性又能够保证粘结剂的粘结性，将粘结剂应用于二次电池中，能够有效地避免极片掉粉、开裂或断裂，提高极片的质量，从而进一步提高二次电池的加工性能。
在一些实施例中，含氟聚合物与丁腈橡胶类树脂的质量比为1∶(0.3～2.5)。
在本实施例中，含氟聚合物与丁腈橡胶类树脂的质量比为1∶0.3、1∶0.4、1∶0.5、1∶0.6、1∶0.7、1∶0.8、1∶0.9、1∶1、1∶1.1、1∶1.2、1∶1.3、1∶1.4、1∶1.5、1∶1.6、1∶1.7、1∶1.8、1∶1.9、1∶2、1∶2.1、1∶2.2、1∶2.3中的一种。
在这些可选的实施例中，含氟聚合物与丁腈橡胶类树脂具有适宜的配比，使得粘结剂既具有较高的柔韧性又具有较高的粘结力，粘结剂可将活性材料牢固地粘结在一起并与集流体牢固地粘接，因此包含本申请粘结剂的极片在卷绕或叠片过程中，能够更有效的抑制极片掉粉、开裂或断裂。
在一些实施例中，丁腈橡胶类树脂的重均分子量为200,000～800,000。
在本申请一些实施例中，丁腈橡胶类树脂的重均分子量为200,000～800,000，丁腈橡胶类树脂的重均分子量为200,000、300,000、400,000、500,000、600,000、700,000、800,000或在由上述的任意两个端点所组成的其它范围内。
可选地，丁腈橡胶类树脂的重均分子量为300,000～600,000。
根据本申请，丁腈橡胶类树脂的重均分子量可以采用本领域的常规方式测量。例如，聚合物的重均分子量可以利用凝胶渗透色谱法进行测量，使用仪器为waters e2695，该技术是本领域技术人员熟知的。
在这些可选的实施例中，丁腈橡胶类树脂为聚合物，其重均分子量相对较大。当丁腈橡胶类树脂的重均分子量大于800,000时，其分子间的作用力增加，大分子链不易移动，丁腈橡胶类树脂的伸长率和弹性等物理机械性能较好，但其加工性较差。当丁腈橡胶类树脂的重均分子量小于200,000时，其分子间的作用力相对减弱，大分子链易于移动，加工性较好，但是丁腈橡胶类树脂的伸长率和弹性等物理机械性能较差，表现为粘结力不足。因此，需要控制丁腈橡胶类树脂适当的重均分子量。
在一些实施例中，丁腈橡胶类树脂具有式I所示的结构式，
Figure PCTCN2022103974-appb-000002
其中，R选自H、C 1～18烷基、-COOR 1中的一种或几种，R 1选自H、C 1～18烷基中的一种或几种，x、y和z之间满足x∶y∶z＝1∶(0.36～1)∶(0～0.3)。
可选地，丁腈橡胶类树脂为氢化丁腈橡胶。
可选地，x和y之间满足x∶y＝1∶(0.36～0.8)。更可选地，x和y之间满足x∶y＝1∶(0.6～0.7)。
在本申请一些实施例中，x选自1700～13000，y选自600～800，z选自0～4000。
在本实施例中，丁腈橡胶类树脂为分子链结构中含有氰基的聚合物。式I中x、y和z表示各结构单元的聚合度，即聚合物分子链中所含结构单元数目的统计平均值，而不必表示所示结构单元形成一定长度的嵌段。其中，丁腈橡胶类树脂中丙烯腈含量的增加，丁腈橡胶类树脂的极性增大，但是其大分子链的柔性下降，而且粘结性也进一步下降，因此控制x、y和z适宜的聚合度。
在这些可选的实施例中，如此结构的丁腈橡胶类树脂，其具有更佳的柔韧性能，以及与含氟聚合物相容性较好，使得包含丁腈橡胶类树脂的粘结剂具有更佳的柔韧性和加工性能。
在一些实施例中，含氟聚合物的重均分子量为400,000～1,500,000。
在本申请一些实施例中，含氟聚合物的重均分子量为400,000～1,500,000，含氟聚合物的重均分子量为400,000、500,000、600,000、700,000、800,000、900,000、1000,000、1100,000、1200,000、1300,000、1400,000、1500,000或在由上述的任意两个端点所组成的其它范围内。
可选地，含氟聚合物的重均分子量为700,000～1,200,000。
在这些可选的实施例中，含氟聚合物的重均分子量越大，粘结性能越强，应用于二次电池时，包含本申请粘结剂的极片具有较强的剥离强度。当含氟聚合物的重均分子量过低时，粘结剂对活性材料的粘结力不足；当含氟聚合物的重均分子量过高时，粘结剂、活性材料和可选的导电剂形成的浆料容易凝胶，不利于后续加工。
在一些实施例中，含氟聚合物选自偏氟二乙烯(VDF)均聚物、偏氟二乙 烯(VDF)与四氟乙烯(TFE)共聚物、偏氟二乙烯(VDF)与六氟丙烯(HFP)共聚物、偏氟二乙烯(VDF)与丙烯酸酯共聚物中的一种或几种。
可选地，含氟聚合物选自偏氟二乙烯(VDF)均聚物或偏氟二乙烯(VDF)与丙烯酸酯共聚物。
更可选地，含氟聚合物为偏氟二乙烯(VDF)均聚物。
在这些可选的实施例中，这些具体可选的含氟聚合物能够赋予粘结剂良好的粘结性能，还能使粘结剂与活性材料和可选的导电剂具有较好的相容性，也有利于电解液浸润粘结剂。
在一些实施例中，粘结剂在N-甲基吡咯烷酮(NMP)中的5％重量浓度的溶液的粘度为300mPa.s～3000mPa.s。
根据本申请，粘结剂溶液的粘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。例如可使用Brookfield DV2T粘度计，在一定温度(例如室温25℃)和湿度(例如相对湿度RH＜80％)下，测试得到粘度值。
在这些可选的实施例中，粘结剂在N-甲基吡咯烷酮(NMP)中的5％重量浓度的溶液的粘度为300mPa.s～3000mPa.s，从而使得粘结剂在具有优异的粘结力的同时，还能够提供良好的成膜加工性能，因此包含本申请粘结剂的极片在热压或卷绕后更不容易出现掉粉、开裂或断裂的现象，提高了极片的质量。
负极极片
申请的第二方面还提供一种负极极片，包括负极集流体以及设置在负极集流体至少一侧面上的负极膜层，负极膜层包括：负极活性材料和本申请第一方面的粘结剂。
在一些实施例中，负极极片包括负极集流体以及设置在负极集流体至少一个表面的负极膜层，负极膜层包括负极活性材料和本申请第一方面的粘结剂。在本实施例中，粘结剂将负活性材料粘结在一起形成负极膜层，并将负极膜层粘接到负极集流体上。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极膜层设置在负极集流体相对的两个表面中的任意一者或两者上。
在一些实施例中，负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔、铝箔。复合集流体可包括高分子材料基层和形成于高分子 材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施例中，负极活性材料可采用本领域公知的用于电池的负极活性材料。作为示例，负极活性材料可包括以下材料中的至少一种：人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂等。所述硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅氮复合物以及硅合金中的至少一种。所述锡基材料可选自单质锡、锡氧化合物以及锡合金中的至少一种。但本申请并不限定于这些材料，还可以使用其他可被用作电池负极活性材料的传统材料。这些负极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
根据本申请的实施例，将具有柔韧性和粘结性的粘结剂应用于二次电池中，能够有效地避免负极极片在卷绕或热压后出现掉粉、开裂或断裂的现象，提高了负极极片的质量，从而进一步提高二次电池的加工性能。
在一些实施例中，负极极片中负极膜层的面密度为2mg/cm 2～13mg/cm 2。
根据本申请，负极膜层的面密度为本领域公知的含义，指的是单位面积上负极集流体单侧的负极膜层质量，可采用本领域已知的方法测定。
在本申请一些实施例中，使用上述粘结剂制得的负极膜层的面密度可以为2mg/cm 2～13mg/cm 2，负极膜层的面密度为2mg/cm 2、3mg/cm 2、4mg/cm 2、5mg/cm 2、6mg/cm 2、7mg/cm 2、8mg/cm 2、9mg/cm 2、10mg/cm 2、11mg/cm 2、12mg/cm 2、13mg/cm 2或在由上述的任意两个端点所组成的其它范围内。
可选地，负极极片中负极膜层的面密度为5mg/cm 2～12mg/cm 2。
更可选地，负极极片中负极膜层的面密度为7.5mg/cm 2～12mg/cm 2。
在本实施例中，负极极片中负极膜层的面密度为7.5mg/cm 2～12mg/cm 2，表明负极膜层单位面积的质量越多，在热压或卷绕后应力越集中，应力集中负极极片则容易出现掉粉或开裂的现象。但是本申请的粘结剂同时具备柔韧性和粘结性，使得负极极片中负极膜层的面密度能够达到7.5mg/cm 2以上，且负极极片掉粉、开裂或断裂的现象明显降低。
在这些可选的实施例中，当负极膜层的面密度在上述范围内时，可以进一 步改善二次电池的动力学性能和二次电池的循环性能。
在一些实施例中，负极活性材料与粘结剂的质量比为(85％～97％)∶(1.5％～7％)。
可选地，负极活性材料、粘结剂和导电剂的质量比为(85％～97％)∶(1.5％～7％)：(0～5％)。
在这些可选的实施例中，负极活性材料与粘结剂具有适量的配比，粘结剂将负活性材料粘结在一起形成负极膜层，并将负极膜层牢固地粘接在负极集流体上，并能够实现负极极片中负极膜层的面密度能够达到7.5mg/cm 2以上。当负极活性材料在负极膜层中的质量占比过多，即粘结剂的质量占比过少，会使得负极膜层粘结性下降，加工过程中易出现负极膜层剥落、开裂或断裂等问题。当负极活性材料在负极膜层中的质量占比过少，会使得负极膜层导电性下降，无法有效改善嵌钠过电势或嵌锂过电势，容易形成钠枝晶或锂枝晶，电池循环性能下降。
在一些实施例中，负极活性材料选自软碳、硬碳、人造石墨、天然石墨、单质硅、硅氧化合物、硅碳复合物中的一种或几种。
可选地，负极活性材料为硬碳。硬碳具有较低的储能电压、较高的容量和良好的循环稳定性的优点，还具有来源丰富、制备工艺简单等优势，是目前最具有应用前景的负极活性材材料之一。但是，硬碳具有硬脆的特点，从而使得包含硬碳的负极膜层，以及包含硬碳的负极极片均具有硬脆的缺点，特别是负极膜层的厚度较厚时，负极极片在热压或卷绕后出现掉粉、开裂或断裂的现象更为严重。然而，本申请通过含氟聚合物与丁腈橡胶类树脂复配，获得具有柔韧性和粘结性的粘结剂，粘结剂将硬碳粘结在一起形成负极膜层，并将负极膜层牢固地粘接在负极集流体上，从而有效防止包含硬碳的负极极片出现掉粉、开裂或断裂的现象。
在一些实施例中，负极膜层还可选地包括导电剂。导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施例中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如负极活性材料(例如硬碳)、导电剂、粘结剂(例如含氟聚合物与丁腈橡胶类树脂)和任意其他组分分散于溶剂(例如NMP)中，形成负极浆料；将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，即可得到负极极片。
另外，以下适当参照附图1至图6，对本申请的二次电池、电池模块、电池 包和用电装置进行说明。图1是本申请一实施方式的二次电池的示意图。图2是图1所示的本申请一实施方式的二次电池的分解图。图3是本申请一实施方式的电池模块的示意图。图4是本申请一实施方式的电池包的示意图。图5是图4所示的本申请一实施方式的电池包的分解图。图6是本申请一实施方式的二次电池用作电源的用电装置的示意图。
申请的第三方面还提供一种二次电池，包括本申请第二方面的负极极片。
通常情况下，二次电池包括正极极片、负极极片、电解质和隔离膜。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。电解质在正极极片和负极极片之间起到传导离子的作用。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使离子通过。
在本申请第三方面的任一实施方式中，二次电池为钠离子二次电池。
在本申请的一些实施例中，负极极片可以是上述本申请第二方面的负极极片。因此，前面对于根据本申请的负极极片的实施例的描述同样适用于二次电池中的负极极片，相同的内容不再赘述。
在本申请的一些实施例中，正极极片包括正极集流体及形成于所述正极集流体的至少部分表面上的正极膜层，所述正极膜层包括正极活性材料，所述正极活性材料可以包括钠过渡金属氧化物、聚阴离子型化合物和普鲁士蓝类化合物中的至少一种。但本申请并不限定于这些材料，还可以使用其他可被用作钠离子电池正极活性材料的传统公知的材料在一些实施例中，钠过渡金属氧化物中，过渡金属可以是Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的至少一种。钠过渡金属氧化物例如为Na xMO 2，其中M为Ti、V、Mn、Co、Ni、Fe、Cr及Cu中的一种或几种，0＜x≤1。
在一些实施例中，聚阴离子型化合物可以是具有钠离子、过渡金属离子及四面体型(YO 4) n-阴离子单元的一类化合物。过渡金属可以是Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的至少一种；Y可以是P、S及Si中的至少一种；n表示(YO 4) n-的价态。
在另一些实施例中，聚阴离子型化合物还可以是具有钠离子、过渡金属离子、四面体型(YO 4) n-阴离子单元及卤素阴离子的一类化合物。过渡金属可以是Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的至少一种；Y可以是P、S及Si中的至少一种，n表示(YO 4) n-的价态；卤素可以是F、Cl及Br中的至少一种。
在又一些实施例中，聚阴离子型化合物还可以是具有钠离子、四面体型(YO 4) n-阴离子单元、多面体单元(ZO y) m+及可选的卤素阴离子的一类化合物。Y可以是P、S及Si中的至少一种，n表示(YO 4) n-的价态；Z表示过渡金属，可以是Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的至少一种，m表示(ZO y) m+的价态；卤素可以是F、Cl及Br中的至少一种。
示例性地，聚阴离子型化合物例如是NaFePO 4、Na 3V 2(PO4) 3、NaM’PO 4F(M’为V、Fe、Mn及Ni中的一种或几种)及Na 3(VO y) 2(PO 4) 2F 3-2y(0≤y≤1)中的至少一种。
在一些实施例中，普鲁士蓝类化合物可以是具有钠离子、过渡金属离子及氰根离子(CN -)的一类化合物。过渡金属可以是Mn、Fe、Ni、Co、Cr、Cu、Ti、Zn、V、Zr及Ce中的至少一种。普鲁士蓝类化合物例如为Na aMe bMe’ c(CN) 6，其中Me及Me’各自独立地为Ni、Cu、Fe、Mn、Co及Zn中的至少一种，0＜a≤2，0＜b＜1，0＜c＜1。
在一些实施例中，正极膜层还可以包括导电剂，以改善正极的导电性能。本申请对导电剂的种类不做具体限制，可以根据实际需求进行选择。作为示例，导电剂可以为超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨、石墨烯及碳纳米纤维中的一种或几种。
在一些实施例中，正极膜层还可以包括粘结剂，以将正极活性材料和可选的导电剂牢固地粘结在正极集流体上。本申请对粘结剂的种类不做具体限制，可以根据实际需求进行选择。作为示例，粘结剂可以为聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、聚丙烯酸(PAA)、聚丙烯腈(PAN)、聚乙烯醇(PVA)的至少一种。
在一些实施例中，正极集流体可以采用导电碳片、金属箔材、涂炭金属箔材、多孔金属板或复合集流体，其中导电碳片的导电碳材质可以为超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨、石墨烯及碳纳米纤维中的一种或几种，金属箔材、涂炭金属箔材和多孔金属板的金属材质各自独立地可以选自铜、铝、镍及不锈钢中的至少一种。复合集流体可以为金属箔材与高分子基膜复合形成的复合集流体。正极集流体例如为铜箔、铝箔、镍箔、不锈钢箔、不锈钢网及涂炭铝箔中的一种或几种，优选采用铝箔。
以按照本领域常规方法制备上述正极极片。通常将正极活性材料及可选的导电剂和粘结剂分散于溶剂(例如N-甲基吡咯烷酮，简称为NMP)中，形成均匀的正极浆料，将正极浆料涂覆在正极集流体上，经烘干、冷压后，得到正极极片。
在一些实施例中，本申请的钠离子电池中的隔离膜可以是本领域各种适用于电化学储能装置隔离膜的材料，例如，可以是包括但不限于聚乙烯、聚丙烯、聚偏氟乙烯、芳纶、聚对苯二甲酸乙二醇酯、聚四氟乙烯、聚丙烯腈、聚酰亚胺，聚酰胺、聚酯和天然纤维中的至少一种。
在本申请的一些实施例中，电解质在正极极片和负极极片之间起到传导离子的作用。本申请对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可以是液态的、凝胶态的或全固态的。
在一些实施例中，电解液可以是包括有机溶剂和电解质钠盐。作为示例，有机溶剂可以是碳酸乙烯酯、碳酸丙烯酯、碳酸二乙酯、碳酸二甲酯、碳酸甲乙酯、碳酸亚丙酯、醋酸甲酯、丙酸乙酯、氟代乙烯碳酸脂、乙醚、二甘醇二甲醚、三乙二醇二甲醚、四乙二醇二甲醚、甲基叔丁基醚中的一种或几种；电解质钠盐可以是六氟磷酸钠、双氟磺酰亚胺钠、双三氟甲烷磺酰亚胺钠、三氟甲磺酸钠、四氟硼酸钠、二氟磷酸钠、高氯酸钠、氯化钠中的一种或几种。
在一些实施例中，溶剂可选自碳酸亚乙酯、碳酸亚丙酯、碳酸甲乙酯、碳酸二乙酯、碳酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸亚丁酯、氟代碳酸亚乙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯、1,4-丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜中的至少一种。
在一些实施例中，所述电解液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、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
在一些实施例中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施例中，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。
在一些实施例中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，作为塑料，可列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图1示出了作为一个示例的方形结构的二次电池5。
在一些实施方式中，参照图2，外包装可包括壳体51和盖板53。其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53能够盖设于所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔内。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或多个，本领域技术人员可根据具体实际需求进行选择。
在一些实施方式中，二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为一个或多个，具体数量本领域技术人员可根据电池模块的应用和容量进行选择。
图3示出了作为一个示例的电池模块4。参照图3，在电池模块4中，多个二次电池5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个二次电池5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个二次电池5容纳于该容纳空间。
在一些实施方式中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以为一个或多个，具体数量本领域技术人员可根据电池包的应用和容量进行选择。
图4和图5示出了作为一个示例的电池包1。参照图4和图5，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
另外，本申请还提供一种用电装置，所述用电装置包括本申请提供的二次电池、电池模块、或电池包中的至少一种。所述二次电池、电池模块、或电池包可以用作所述用电装置的电源，也可以用作所述用电装置的能量存储单元。所述用电装置 可以包括移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等，但不限于此。
作为所述用电装置，可以根据其使用需求来选择二次电池、电池模块或电池包。
图6示出了作为一个示例的用电装置。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用二次电池作为电源。
实施例
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
实施例1
将70g的偏氟二乙烯均聚物与30g的丁腈橡胶混合均匀，获得粘结剂，
其中，偏氟二乙烯均聚物的重均分子量为100W，丁腈橡胶的脂具有下式所示的结构式，
Figure PCTCN2022103974-appb-000003
其中，x∶y＝1∶0.5，丁腈橡胶的重均分子量为40W。
其他实施例2～13与对比例1～10与实施例1粘结剂的获得方法相同或相近。
将实施例1～13和对比例1～10的含氟聚合物和丁腈橡胶类树脂按照下表1进行混合得到粘结剂。
表1实施例1～13与对比例1～10的参数结果
Figure PCTCN2022103974-appb-000004
Figure PCTCN2022103974-appb-000005
Figure PCTCN2022103974-appb-000006
另外，将上述实施例1～13和对比例1～10的得到的粘结剂作为负极极片的粘结剂，分别如下所示制备负极极片。
负极极片的制备
将负极活性材料硬碳、导电剂Super P、粘结剂按质量比95∶0.7∶4.3在适量的N-甲基吡咯烷酮(NMP)中充分搅拌混合，使其形成均匀的负极浆料；将负极浆料涂覆于负极集流体铜箔的表面上形成负极膜层，经干燥、冷压后，得到负极极片。
按照如下的测试方法测试各实施例和对比例的粘结剂的脆性测试、负极极片的柔韧性测试和面密度测试
(1)粘结力
将负极极片裁成长100mm、宽10mm的测试样品。取一条宽度25mm的不锈钢板，贴双面胶(宽度11mm)，将测试样品粘贴在不锈钢板上的双面胶上，用2000g压辊在其表面来回滚压三次(300mm/min)。将测试样品180度弯折，手动将测试样品的负极膜片与集流体剥开25mm，将该测试样品固定在试验机(例如INSTRON 336)上，使剥离面与试验机力线保持一致，试验机以30mm/min连续剥离，得到的剥离力曲线，取平稳断的均值作为剥离力F0，则测试样品中负极膜层与集流体之间的粘结力F＝F0/测试样品的宽度(F的计量单位：N/m)。
(2)面密度
单面涂布且经冷压后的负极极片(若是双面涂布的负极极片，可先擦拭掉其中一面的负极膜层)，冲切成面积为S 1的小圆片，称其重量，记录为M 1。然后将上述称重后的负极极片的负极膜层擦拭掉，称量负极集流体的重量，记录为M 0，负极膜层的面密度＝(负极极片的重量M 1-负极集流体的重量M 0)/S 1。
(3)柔韧性
通过卷针测量负极极片的柔韧性，制备长宽40mm×长度为100mm的负极极片样品，在特制的卷针上进行卷绕，用目测和显微镜结合的方式，观察负极极片裂纹情况，判断柔韧性等级：
卷针的直径为R，
R≤1.0mm时极片不产生裂纹，为柔韧性一级，满足生产需求；
R＝1.0mm有裂纹，R＝2.0mm无裂纹，为柔韧性二级，满足生产需求；
R＝2.0mm有裂纹，R＝3.0mm有裂纹，为柔韧性三级，不满足生产需求；
R＝3.0mm无裂纹，R＝4.0mm有裂纹，为柔韧性四级，不满足生产需求；
卷针的制备方法如下：
将常规直径分别为1.0mm、2.0mm、3.0mm、4.0mm的304不锈钢棒截取60mm，焊接于150mm×300mm的钢板上进行固定即得所述卷针。使用的卷针直径越小而极片又不开裂，表明极片的柔韧性越好，反之，使用的卷针直径越大而极片又裂纹，表明极片的柔韧性越差。
表2实施例1～13与对比例1～10的测试结果
项目 粘结力(N/m) 面密度(mg/cm 2) 柔韧性
实施例1 23 12 ≤1
实施例2 22 11 ≤1
实施例3 22 11 ≤1
实施例4 20 10 1
实施例5 21 11 ≤1
实施例6 22 11 ≤1
实施例7 19 10 1
实施例8 20 11 ≤1
实施例9 23 11 ≤1
实施例10 23 12 1
实施例11 19 10 1
实施例12 18 10 ≤1
实施例13 20 11 ≤1
对比例1 28 5 4
对比例2 3 6 ≤1
对比例3 -- 5 --
对比例4 -- 7 --
对比例5 5 6 ≤1
对比例6 25 7 4
对比例7 2 6 ≤1
对比例8 18 7 ≤2
对比例9 4 7 ≤1
对比例10 15 7 ≤2
根据上述结果可知，实施例1至13，均取得了良好的效果，负极膜片与负极集流体之间粘结力强，负极极片的面密度较高以及柔韧性好，获得的负极极片满足生产需求。通过含氟聚合物与丁腈橡胶类树脂复配形成粘结剂，使得粘结剂既具有柔韧性和较高的粘结性，将粘结剂应用于二次电池中，能够有效地避免负极极片开裂的缺陷，提高负极极片的质量，从而进一步提高二次电池的加工性能。
对比例1和2，单一使用含氟聚合物作为粘结剂，其形成的负极极片柔韧性和面密度均较低。单一使用丁腈橡胶类树脂作为粘结剂，其形成的负极极片的面密度低，且负极膜片与负极集流体之间粘结力差。
另外，含氟聚合物与丁腈橡胶类树脂的质量比是影响负极极极片性能的重要因素。如对比例5和6，当含氟聚合物与丁腈橡胶类树脂的质量比大于8时，粘结剂中丁腈橡胶类树脂含量较高，可提高粘结剂的柔韧性，但是粘结剂的粘结力较差，无法将活性材料稳定的粘结到集流体上，且形成的膜层容易发生脱落。当含氟聚合物与丁腈橡胶类树脂的质量比小于0.1时，粘结剂中含氟聚合物含量较高，可提高粘结剂的粘结力，但粘结剂的柔韧性较差，会影响后续的二次电池的加工性能，例如冷压断带，卷绕断裂，模切掉粉等影响加工性能的缺陷。
含氟聚合物与丁腈橡胶类树脂的重均分子量大小同样影响负极极极片性能。如对比例3、4、9和10，当含氟聚合物的重均分子量过大或过小时，粘结剂对活性材料的粘结力均不足，形成的浆料凝胶，部满足生产要求，无法进行正常涂布。当丁腈橡胶类树脂的重均分子量过小时，粘结力不足；当丁腈橡胶类树脂的重均分子量过大时，出现裂纹，不满足生产需求。
虽然已经参考优选实施例对本申请进行了描述，但在不脱离本申请的范围的情况下，可以对其进行各种改进并且可以用等效物替换其中的部件。尤其是，只要不存在结构冲突，各个实施例中所提到的各项技术特征均可以任意方式组合起来。本申请并不局限于文中公开的特定实施例，而是包括落入权利要求的范围内的所有技术方案。

Claims (16)

  1. 一种用于二次电池的粘结剂，包括含氟聚合物和丁腈橡胶类树脂，所述含氟聚合物与所述丁腈橡胶类树脂的质量比为1∶(0.1～8)，其中，所述丁腈橡胶类树脂包括丁腈橡胶、氢化丁腈橡胶、羧基丁腈橡胶和硫化丁腈橡胶中的一种或几种。
  2. 根据权利要求1所述的粘结剂，其中，所述含氟聚合物与所述丁腈橡胶类树脂的质量比为1∶(0.3～2.5)。
  3. 根据权利要求1或2所述的端盖组件，其中，所述丁腈橡胶类树脂的重均分子量为200,000～800,000，可选地为300,000～600,000
  4. 根据权利要求1至3任一项所述的粘结剂，其中，所述丁腈橡胶类树脂具有式I所示的结构式
    Figure PCTCN2022103974-appb-100001
    其中，R选自H、C 1～18烷基、-COOR 1中的一种或几种，R 1选自H、C 1～18烷基，x、y和z之间满足x∶y∶z＝1∶(0.36～1)∶(0～0.3)。
  5. 根据权利要求1至4所述的粘结剂，其中，所述含氟聚合物的重均分子量为400,000～1,500,000，可选地为700,000～1,200,000。
  6. 根据权利要求1至5任一项所述的粘结剂，其中，所述含氟聚合物选自偏氟二乙烯(VDF)均聚物、偏氟二乙烯(VDF)与四氟乙烯(TFE)共聚物、偏氟二乙烯(VDF)与六氟丙烯(HFP)共聚物、偏氟二乙烯(VDF)与丙烯酸酯共聚物中的一种或几种，可选地选自偏氟二乙烯(VDF)均聚物或偏氟二乙烯(VDF)与丙烯酸酯共聚物。
  7. 根据权利要求1至5任一项所述的粘结剂，其中，所述粘结剂在N-甲基吡咯烷酮(NMP)中的5％重量浓度的溶液的粘度为300mPa.s～3000mPa.s。
  8. 一种负极极片，包括负极集流体以及设置在所述负极集流体至少一侧面上的负极膜层，所述负极膜层包括：
    负极活性材料和权利要求1至7任一项所述的粘结剂。
  9. 根据权利要求8所述的负极极片，其中，所述负极极片的面密度为2mg/cm 2～13mg/cm 2，可选地为5mg/cm 2～12mg/cm 2，更可选地为7.5mg/cm 2～12mg/cm 2。
  10. 根据权利要求8所述的负极极片，其中，所述负极活性材料、所述粘结剂和导电剂的质量比为(85％～97％)∶(1.5％～7％)。
  11. 根据权利要求8所述的负极极片，其中，所述负极活性材料选自软碳、硬碳、人造石墨、天然石墨、单质硅、硅氧化合物、硅碳复合物中的一种或几种，可选地为硬碳。
  12. 一种二次电池，包括权利要求8至11中任一项所述的负极极片。
  13. 根据权利要求12所述的二次电池，所述二次电池为钠离子二次电池。
  14. 一种电池模块，包括权利要求12或13所述的二次电池。
  15. 一种电池包，包括权利要求14所述的电池模块。
  16. 一种用电装置，包括选自权利要求12或13所述的二次电池、权利要求14所述的电池模块、权利要求15所述的电池包中的至少一种。
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JPH0963590A (ja) * 1995-08-28 1997-03-07 Sony Corp 非水電解質二次電池
JP2000106185A (ja) * 1998-09-29 2000-04-11 Hitachi Chem Co Ltd 非水電解質二次電池
KR20160087657A (ko) * 2015-01-14 2016-07-22 주식회사 엘지화학 전극용 슬러리 조성물, 전극 및 이차전지
CN107112500A (zh) * 2014-10-02 2017-08-29 株式会社Lg 化学 包括橡胶类粘合剂的正极活性材料浆料及由其制备的正极
CN107580732A (zh) * 2015-06-12 2018-01-12 株式会社Lg化学 正极材料混合物和包含其的二次电池
CN111542950A (zh) * 2018-02-19 2020-08-14 株式会社Lg化学 正极和包括所述正极的二次电池
CN114388725A (zh) * 2020-10-21 2022-04-22 深圳格林德能源集团有限公司 一种锂离子电池正极极片及其制备方法

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JPH0963590A (ja) * 1995-08-28 1997-03-07 Sony Corp 非水電解質二次電池
JP2000106185A (ja) * 1998-09-29 2000-04-11 Hitachi Chem Co Ltd 非水電解質二次電池
CN107112500A (zh) * 2014-10-02 2017-08-29 株式会社Lg 化学 包括橡胶类粘合剂的正极活性材料浆料及由其制备的正极
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CN114388725A (zh) * 2020-10-21 2022-04-22 深圳格林德能源集团有限公司 一种锂离子电池正极极片及其制备方法

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