WO2024045506A1 - 粘结剂、制备方法、正极极片、二次电池及用电装置 - Google Patents

粘结剂、制备方法、正极极片、二次电池及用电装置 Download PDF

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Publication number
WO2024045506A1
WO2024045506A1 PCT/CN2023/076261 CN2023076261W WO2024045506A1 WO 2024045506 A1 WO2024045506 A1 WO 2024045506A1 CN 2023076261 W CN2023076261 W CN 2023076261W WO 2024045506 A1 WO2024045506 A1 WO 2024045506A1
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Prior art keywords
polymer
binder
positive electrode
formula
vinylidene fluoride
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PCT/CN2023/076261
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English (en)
French (fr)
Inventor
段连威
孙成栋
刘会会
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宁德时代新能源科技股份有限公司
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Publication of WO2024045506A1 publication Critical patent/WO2024045506A1/zh

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Classifications

    • 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
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • H01M4/621—Binders
    • H01M4/622—Binders being polymers
    • H01M4/623—Binders being polymers fluorinated polymers
    • 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 relates to the technical field of secondary batteries, and in particular to an adhesive, a preparation method, a positive electrode sheet, a secondary battery, a battery module, a battery pack and an electrical device.
  • secondary batteries have been widely used in energy storage power systems such as hydraulic, thermal, wind and solar power stations, as well as in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. With the popularization of secondary battery applications, higher requirements have been placed on its cycle performance and service life.
  • Binders are commonly used materials in secondary batteries and are in great demand for battery pole pieces, separators, packaging, etc.
  • the existing adhesive requires a large amount of addition to ensure that the pole pieces have sufficient adhesion.
  • the adhesive cannot maintain sufficient flexibility during the cycle, making the pole pieces prone to brittle fracture, which in turn causes safety issues. Therefore, existing adhesives still need to be improved.
  • This application was made in view of the above problems, and its purpose is to provide a binder that can make the pole piece have excellent bonding force at a low addition amount, and at the same time, the binder can improve the polarity.
  • the flexibility of the sheet improves the cycle performance of the battery.
  • the present application provides a binder, which is a polymer containing structural units as shown in Formula I and Formula II,
  • R 1 is selected from one or more types of fluorine, chlorine, and trifluoromethyl, and the weight average molecular weight of the polymer is 1.8 million to 5 million.
  • This binder can ensure sufficient adhesion of the pole piece at a low addition amount, and can further improve the flexibility of the pole piece and reduce the probability of brittle fracture of the pole piece, thus improving the safety and cycle performance of the battery.
  • the mass fraction of the structural unit represented by Formula II is 0.5% to 15%, based on the total mass of the polymer.
  • the binder can make the pole piece have both excellent flexibility and good adhesion at a low addition amount, allowing the battery to maintain good performance during cycling. capacity performance.
  • the polymer has a polydispersity of 2 to 2.3.
  • the polydispersity coefficient of the polymer is 2.1 to 2.2.
  • Controlling the polydispersity coefficient of the polymer within an appropriate range can improve the flexibility of the pole piece and enable the pole piece to have good adhesion.
  • the polymer has a Dv50 particle size of 50 ⁇ m to 160 ⁇ m, optionally, the polymer has a Dv50 particle size of 50 ⁇ m to 100 ⁇ m.
  • Controlling the Dv50 particle size of the polymer within an appropriate range can improve the flexibility of the pole piece and enable the pole piece to have good adhesion.
  • the polymer has a crystallinity of 34% to 42%, optionally, the polymer has a crystallinity of 35% to 40%.
  • Controlling the crystallinity of the polymer within an appropriate range can improve the flexibility of the pole piece and enable the pole piece to have good adhesion.
  • the viscosity of the glue containing 4% mass content of the polymer prepared by dissolving the polymer in N-methylpyrrolidone is 2400 mPa ⁇ s to 5000 mPa ⁇ s.
  • the viscosity of the glue containing 4% mass content of the polymer prepared by dissolving the polymer in N-methylpyrrolidone is 2500 mPa ⁇ s to 4000 mPa ⁇ s.
  • the polymer is a vinylidene fluoride-chlorotrifluoroethylene copolymer, a vinylidene fluoride-chlorotrifluoroethylene-tetrafluoroethylene copolymer, a vinylidene fluoride-chlorotrifluoroethylene-hexafluoropropylene copolymer, Vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene-tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer or vinylidene fluoride-hexafluoropropylene One or more copolymers.
  • a second aspect of the application also provides a method for preparing an adhesive, including the following steps:
  • the monomer represented by formula III and the monomer represented by formula IV are polymerized to prepare a polymer;
  • R 2 is selected from one or more types of fluorine, chlorine, and trifluoromethyl, and the weight average molecular weight of the polymer is 1.8 million to 5 million.
  • the preparation method of the binder is simple, environmentally friendly, and conducive to industrial production. At the same time, the binder prepared by this method makes the pole piece have excellent flexibility and good adhesion, and the battery has a high level of cycle retention.
  • the mass content of the monomer represented by Formula IV is 0.5% to 15%, based on the total mass of the monomers of Formula III and Formula IV.
  • the pole piece When the mass fraction of the monomer represented by Formula IV is within an appropriate range, the pole piece has both excellent flexibility and good adhesion, allowing the battery to maintain a high cycle capacity during cycling.
  • the monomer represented by Formula IV is one or more of chlorotrifluoroethylene, tetrafluoroethylene, and hexafluoropropylene.
  • the above-mentioned raw materials are simple and easy to obtain, which can significantly reduce production costs and increase output.
  • the monomers represented by formula III and formula IV are reacted in a non-reactive gas atmosphere, a reaction pressure of 6MPa to 8MPa, and a reaction temperature of 45°C to 60°C for 6 to 12 hours; chain transfer is added Agent, wait until the pressure in the reaction system drops to 2MPa ⁇ 2.5MPa, stop the reaction, separate the solid and liquid, and retain the solid phase.
  • the preparation method further includes the following steps: adding a solvent and a dispersant to the container, evacuating the container and then filling it with a non-reactive gas; adding an initiator and a pH regulator to the container, and adjusting The pH value reaches 6.5-7, and then the monomers shown in Formula III and Formula IV are added to bring the pressure in the container to 6MPa-8MPa; after stirring for 30-60 minutes, the temperature is raised to 45°C-60°C to proceed with polymerization. reaction.
  • Controlling the reaction pressure, reaction pressure, and reaction temperature of the polymerization reaction within a suitable range can control the weight average molecular weight of the polymer, so that the electrode piece has both excellent flexibility and good adhesion, and the battery has high cycle capacity retention. Rate.
  • a third aspect of the present application provides a positive electrode sheet, including a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector.
  • the positive electrode film layer includes a positive electrode active material, a conductive agent, and a binder in any embodiment.
  • the adhesive prepared by the preparation method in any embodiment.
  • the positive electrode sheet has both excellent flexibility and good adhesion.
  • the mass fraction of the binder is 0.8% to 1%, based on the total mass of the positive electrode film layer.
  • Controlling the mass fraction of the binder within an appropriate range enables the pole piece to have both excellent flexibility and adhesion, allowing the battery to have a high cycle capacity retention rate during cycling.
  • the positive active material is a lithium-containing transition metal oxide.
  • the positive active material is at least one of lithium iron phosphate and its modified materials, lithium nickel cobalt manganese oxide and its modified materials, and the modified materials are obtained by doping and coating with conductive carbon. It is prepared by one or more modification methods of , conductive metal coating, and conductive polymer coating.
  • the fourth aspect of the present application provides a method for preparing a positive electrode sheet, including the following steps: First stage: prepare the positive active material, the conductive agent and the binder in any embodiment or by the preparation method in any embodiment Mix the binder and perform the first stirring; the second stage: add the solvent and perform the second stirring; the third stage: add the dispersant and perform the third stirring to obtain a slurry, and control the viscosity of the slurry to be between 8000 and 15000 mPa ⁇ s; The fourth stage: Coat the slurry on the positive electrode current collector to obtain the positive electrode piece.
  • the preparation method is simple and convenient for industrial production.
  • the stirring revolution speed is 25 rpm
  • Stirring time is 30 minutes.
  • the stirring revolution speed is 25 rpm
  • the stirring rotation speed is 800-1000 rpm
  • the stirring time is 50-80 minutes.
  • the stirring rotation speed is 1200-1500 rpm, and the stirring time is 50-70 minutes.
  • a secondary battery including an electrode assembly and an electrolyte.
  • the electrode assembly includes a separator, a negative electrode sheet, and the positive electrode sheet of the third aspect of the present application.
  • a battery module including the secondary battery of the fifth aspect of the present application.
  • a battery pack is provided, including the battery module of the sixth aspect of the present application.
  • an electrical device including at least one of the secondary battery of the fifth aspect of the present application, the battery module of the sixth aspect, or the battery pack of the seventh aspect of the present application.
  • Figure 1 is the bonding force-displacement diagram of Example 1 and Comparative Example 4;
  • Figure 2 is a graph showing the battery capacity retention rate and the number of cycles in Example 1 and Comparative Example 4;
  • Figure 3 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • Figure 4 is an exploded view of the secondary battery according to an embodiment of the present application shown in Figure 3;
  • FIG. 5 is a schematic diagram of a battery module according to an embodiment of the present application.
  • Figure 6 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG 7 is an exploded view of the battery pack according to an embodiment of the present application shown in Figure 6;
  • FIG. 8 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.
  • the method may also include step (c), indicating that step (c) may be added to the method in any order.
  • the method may include the 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).
  • Polyvinylidene fluoride is currently one of the most widely used binder types in secondary batteries.
  • the viscosity of traditional polyvinylidene fluoride is low, and a large amount of addition is often required to ensure effective bonding of active materials, thereby enabling the pole pieces to achieve effective bonding force.
  • the increase in the amount of traditional polyvinylidene fluoride will, on the one hand, reduce the load of active materials in the pole pieces, affecting the improvement of battery power performance. On the other hand, it will reduce the flexibility of the pole pieces, making the pole pieces prone to brittle fracture, making it difficult to meet the requirements of the requirements. Battery cycle performance and safety performance requirements.
  • this application proposes a binder, which is a polymer containing structural units represented by Formula I and Formula II,
  • R 1 is selected from one or more types of fluorine, chlorine, and trifluoromethyl, and the weight average molecular weight of the polymer is 1.8 million to 5 million.
  • binder refers to a chemical compound, polymer or mixture that forms a colloidal solution or colloidal dispersion in a dispersion medium.
  • polymer includes on the one hand an assembly of macromolecules that are chemically homogeneous but differ in degree of polymerization, molar mass and chain length, prepared by polymerization reactions.
  • the term also includes such aggregates of macromolecules formed by polymerization reactions Derivatives, that is, compounds that can be obtained through the reaction of functional groups in the above macromolecules, such as addition or substitution, and can be chemically homogeneous or chemically heterogeneous.
  • weight average molecular weight refers to the sum of the weight fractions of molecules of different molecular weights in the polymer multiplied by their corresponding molecular weights.
  • the dispersion medium of the binder is an oily solvent.
  • the oily solvent include but are not limited to dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, acetone, dicarbonate Methyl ester, ethyl cellulose, polycarbonate. That is, the binder is dissolved in the oily solvent.
  • a binder is used to fix the electrode active material and/or conductive agent in place and adhere them to the conductive metal component to form an electrode.
  • the binder serves as a positive electrode binder and is used to bind the positive electrode active material and/or conductive agent to form an electrode.
  • the binder serves as a negative electrode binder and is used to bind the negative electrode active material and/or conductive agent to form an electrode.
  • fluoro refers to the -F group.
  • chlorine refers to the -Cl group.
  • trifluoromethyl refers to the -CF 3 group.
  • the binder is a halogenated hydrocarbon copolymer, which can be selected from the group consisting of vinylidene fluoride-chlorotrifluoroethylene copolymer, vinylidene fluoride-chlorotrifluoroethylene-tetrafluoroethylene copolymer, vinylidene fluoride-trifluoroethylene copolymer.
  • Chlorofluoroethylene-hexafluoropropylene copolymer vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene-tetrafluoroethylene-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene One or more of copolymers and vinylidene fluoride-hexafluoropropylene copolymers.
  • the fluorine element contained in the polymer forms hydrogen bonds with the hydroxyl groups or/and carboxyl groups on the surface of the active material and the current collector surface, which can improve the adhesion of the pole piece.
  • Polymers with a weight average molecular weight of 1.8 million to 5 million can improve the adhesion of the pole pieces at low addition amounts.
  • the structural unit represented by formula II in the polymer can introduce disordered units into the crystallization region of the periodically arranged chain segments formed by the structural unit represented by formula I, thereby reducing the crystallinity of the polymer and increasing the mobility of the chain segments.
  • the polymer contains the structural unit shown in formula II, which can reduce the content of the structural unit shown in formula I, reduce the crystallization caused by the polymerization of the structural unit shown in formula I, and further improve the Pole piece flexibility.
  • This binder can ensure sufficient adhesion of the pole piece at a low addition amount, and can further improve the flexibility of the pole piece, reduce the probability of brittle fracture of the pole piece, thereby improving the safety and cycle performance of the battery. .
  • the weight average molecular weight of the polymer can be tested using methods known in the art, such as gel chromatography, such as Waters 2695 Isocratic HPLC gel chromatograph (differential refractive index detector 2141 )carry out testing.
  • the test method is to use a polystyrene solution sample with a mass fraction of 3.0% as a reference and select a matching chromatographic column (oil: Styragel HT5DMF7.8*300mm+Styragel HT4).
  • NMP N-methylpyrrolidone
  • the mass fraction of the structural unit represented by Formula II is 0.5% to 15%, based on the total mass of the polymer.
  • the mass fraction of the structural unit represented by Formula II can be 0.5% to 1%, 0.5% to 2%, 0.5% to 3%, 0.5% to 4%, 0.5% to 5%, 0.5% ⁇ 6%, 0.5% ⁇ 7%, 0.5% ⁇ 8%, 0.5% ⁇ 9%, 0.5% ⁇ 10%, 0.5% ⁇ 11%, 0.5% ⁇ 12%, 0.5% ⁇ 13%, 0.5% ⁇ 14 %1% ⁇ 2%, 1% ⁇ 3%, 1% ⁇ 4%, 1% ⁇ 5%, 1% ⁇ 6%, 1% ⁇ 7%, 1% ⁇ 8%, 1% ⁇ 9%, 1 % ⁇ 10%, 1% ⁇ 11%, 1% ⁇ 12%, 1% ⁇ 13%, 1% ⁇ 14%, 1% ⁇ 15%, 2% ⁇ 3%, 2% ⁇ 4%, 2% ⁇ 5%, 2% to 6%, 2% to 7%, 2% to 8%, 2% to 9%, 2% to 10%, 2% to 1
  • the pole piece can have both excellent flexibility and good adhesion with a low amount of binder, which can improve the battery's performance during cycling. capacity retention rate.
  • the polymer has a polydispersity coefficient of 2 to 2.3. In some embodiments, the polydispersity coefficient of the polymer is any one of 2 to 2.1, 2 to 2.2, 2 to 2.3, 2.1 to 2.2, and 2.1 to 2.3.
  • polydispersity coefficient refers to the ratio of the weight average molecular weight of the polymer to the number average molecular weight of the polymer.
  • number average molecular weight refers to the sum of the mole fractions of molecules of different molecular weights in the polymer multiplied by their corresponding molecular weights.
  • the polydispersity coefficient of the polymer is within a suitable range, the polymer has suitable ordering, and the binder has excellent dispersion, which can improve the flexibility of the pole piece and enable the pole piece to have good adhesion.
  • a suitable polydispersity coefficient of the polymer can reduce the difficulty of the polymer preparation process and improve the product quality.
  • a suitable polydispersity coefficient can effectively increase the solid content of the slurry and reduce production costs.
  • the polydispersity coefficient can be tested using methods known in the art, such as gel chromatography, such as Waters 2695 Isocratic HPLC gel chromatograph (differential refractive index detector 2141).
  • gel chromatography such as Waters 2695 Isocratic HPLC gel chromatograph (differential refractive index detector 2141).
  • a polystyrene solution sample with a mass fraction of 3.0% is used as a reference to select a matching chromatographic column (oil: Styragel HT5DMF7.8*300mm+Styragel HT4).
  • NMP N-methylpyrrolidone
  • the polymer has a Dv50 particle size of 50 ⁇ m to 160 ⁇ m.
  • the Dv50 particle size of the polymer can be selected from 50 ⁇ m to 60 ⁇ m, 60 ⁇ m to 70 ⁇ m, 70 ⁇ m to 80 ⁇ m, 80 ⁇ m to 90 ⁇ m, 90 ⁇ m to 100 ⁇ m, 100 ⁇ m to 110 ⁇ m, 110 ⁇ m to 120 ⁇ m, 120 ⁇ m to 130 ⁇ m, and 130 ⁇ m to 140 ⁇ m. medium any kind.
  • Dv50 particle size refers to the particle size corresponding to when the cumulative particle size distribution number of particles reaches 50% in the particle size distribution curve. Its physical meaning is that particles with a particle size smaller (or larger) than it account for 50%. %.
  • Controlling the Dv50 particle size of the polymer within an appropriate range can improve the solubility of the binder, improve the flexibility of the pole piece, and make the pole piece have better adhesion.
  • the Dv50 particle size of the polymer in a suitable range can also enable the dosage of the binder to be controlled at a low level without excessive negative impact on the bonding performance, thereby effectively improving the high dosage in traditional technology.
  • the binder causes damage to the pole piece and battery performance.
  • the Dv50 particle size of the polymer can be tested using methods known in the art. For example, referring to the GB/T 19077-2016 particle size distribution laser diffraction method, use a 50ml beaker to weigh 0.1g ⁇ 0.13g of polymer. polymer powder, then weigh 5g of absolute ethanol, add it to the beaker containing the polymer powder, put in a stirrer with a length of about 2.5mm, and seal it with plastic wrap. Put the sample into an ultrasonic machine for 5 minutes, transfer to a magnetic stirrer and stir at a speed of 500 rpm for more than 20 minutes. Use a laser particle size analyzer for measurement, such as the Mastersizer 2000E laser particle size analyzer of Malvern Instruments Co., Ltd. in the UK. test.
  • the polymer has a crystallinity of 34% to 42%.
  • the crystallinity of the polymer can be selected from 34% to 36%, 35% to 37%, 36% to 38%, 38% to 40%, 40% to 42%, 39% to 40%, Any one of 40% to 41%, 41% to 42%, and 35% to 40%.
  • crystallity refers to the proportion of crystalline areas in a polymer. There are some areas with stable and regularly arranged molecules in the structure. The area where the molecules are regularly and closely arranged is called a crystalline area.
  • Appropriate crystallinity makes the polymer chain segments have excellent mobility and improves the flexibility of the pole piece.
  • appropriate crystallinity makes the polymer have excellent solubility, increases the speed of the pulping process, and improves production efficiency.
  • Appropriate crystallinity enables the polymer molecular chains to have excellent regularity and close packing, improving the chemical stability and thermal stability of the binder.
  • the pole piece By controlling the crystallinity of the polymer within an appropriate range so that the amount of binder is at a low level, the pole piece can have both excellent flexibility and good adhesion, which in turn helps to increase the loading capacity of active materials and Battery cycle performance.
  • the crystallinity can be tested using methods known in the art, such as differential scanning thermal analysis.
  • 0.5g of polymer is placed in an aluminum dry pot, shaken flat, and the crucible lid is covered. Under a nitrogen atmosphere, with a purge gas of 50 ml/min and a protective gas of 70 ml/min, the heating rate is The temperature is 10°C per minute, and the test temperature range is -100°C to 400°C.
  • a differential scanning calorimeter (DSC) of the American TA Instrument model Discovery 250 is used to test and eliminate thermal history.
  • the viscosity of the glue containing 4% polymer, prepared by dissolving the polymer in N-methylpyrrolidone is 2400 mPa ⁇ s to 5000 mPa ⁇ s.
  • the viscosity of the glue containing a polymer with a mass content of 4%, prepared by dissolving the polymer in N-methylpyrrolidone is 2400mPa ⁇ s ⁇ 3000mPa ⁇ s, 3000mPa ⁇ s ⁇ 3300mPa ⁇ s, 3300mPa ⁇ s ⁇ 3500mPa ⁇ s, 3500mPa ⁇ s ⁇ 3800mPa ⁇ s, 3800mPa ⁇ s ⁇ 4000mPa ⁇ s, 4000mPa ⁇ s ⁇ 4200mPa ⁇ s, 4200mPa ⁇ s ⁇ 4600mPa ⁇ s, 4600mPa ⁇ s ⁇ 4750mPa ⁇ s, 3100mPa ⁇ s Any one of ⁇ 3400mPa ⁇ s, 3400mPa ⁇ s ⁇ 3800mPa ⁇ s, 3800mPa ⁇ s ⁇ 4600mPa ⁇ s, 2500mPa ⁇ s ⁇ 4000mPa ⁇ s.
  • the polymer is dissolved in N-methylpyrrolidone to prepare a substance containing
  • the viscosity of the glue solution with a polymer content of 4% is 24000mPa ⁇ s ⁇ 4000mPa ⁇ s.
  • the viscosity of the glue containing a polymer with a mass content of 4%, prepared by dissolving the polymer in N-methylpyrrolidone can be selected from 2400mPa ⁇ s to 3000mPa ⁇ s, 3000mPa ⁇ s to 3300mPa ⁇ s.
  • the polymer glue liquid has a suitable viscosity so that the binder containing the polymer has a suitable viscosity.
  • the binder has a suitable viscosity so that the binder can be effective during the preparation of the cathode slurry. Dispersed in the solvent, it improves the performance of the binder, increases the speed of the pulping process, and improves the processing performance of the binder; on the other hand, the binder has a suitable viscosity so that the pole piece has excellent bonding agent.
  • the binder when preparing the positive electrode slurry, the binder needs to have a certain viscosity to prevent the positive electrode active materials and conductive agents and other additives from settling, so that the slurry can be placed more stably.
  • a binder with a mass content of at least 7% is required, based on the total mass of the glue.
  • it can Controlling the amount of binder at 4% provides support for reducing the content of binder in the positive electrode film layer.
  • the viscosity of the binder can be tested using methods known in the art, such as the rotational viscometer test method.
  • use a 500ml beaker to weigh 14g of polymer and 336g of N-methylpyrrolidone (NMP) respectively use a Lichen high-speed grinder to stir and disperse, with a rotation speed of 800 rpm, a stirring time of 120 minutes, and ultrasonic vibration for 30 minutes to remove bubbles.
  • NMP N-methylpyrrolidone
  • the Lichen Technology NDJ-5S rotational viscometer for testing.
  • Test the viscosity at a rotor speed of 12 rpm, 6 Read the viscosity data after a few minutes.
  • a method for preparing an adhesive including the following steps:
  • the monomer represented by formula III and the monomer represented by formula IV are polymerized to prepare a polymer;
  • R 2 is selected from one or more types of fluorine, chlorine, and trifluoromethyl, and the weight average molecular weight of the polymer is 1.8 million to 5 million.
  • the preparation method of the binder is simple, environmentally friendly, and conducive to industrial production. At the same time, the binder prepared by this method makes the pole piece have excellent flexibility and good adhesion, and the battery has a good cycle retention rate.
  • the mass fraction of the monomer represented by Formula IV is 0.5% to 15%, based on the total mass of the monomer represented by Formula III and the monomer represented by Formula IV.
  • the mass fraction of the monomer represented by Formula IV can be 0.5% to 1%, 0.5% to 2%, 0.5% to 3%, 0.5% to 4%, 0.5% to 5%, 0.5% ⁇ 6%, 0.5% ⁇ 7%, 0.5% ⁇ 8%, 0.5% ⁇ 9%, 0.5% ⁇ 10%, 0.5% ⁇ 11%, 0.5% ⁇ 12%, 0.5% ⁇ 13%, 0.5% ⁇ 14 %1% ⁇ 2%, 1% ⁇ 3%, 1% ⁇ 4%, 1% ⁇ 5%, 1% ⁇ 6%, 1% ⁇ 7%, 1% ⁇ 8%, 1% ⁇ 9%, 1 % ⁇ 10%, 1% ⁇ 11%, 1% ⁇ 12%, 1% ⁇ 13%, 1% ⁇ 14%, 1% ⁇ 15%, 2% ⁇ 3%, 2% ⁇ 4%, 2% ⁇ 5%, 2% to 6%, 2% to 7%, 2% to 8%, 2% to
  • the binder When the mass fraction of the monomer represented by Formula IV is within an appropriate range, the binder enables the pole piece to have both excellent flexibility and good adhesion, and the battery can maintain a high cycle capacity retention rate during cycling.
  • the monomer represented by Formula III is one or more of chlorotrifluoroethylene, tetrafluoroethylene, and hexafluoropropylene.
  • the monomer represented by Formula IV is chlorotrifluoroethylene, tetrafluoroethylene, hexafluoropropylene, chlorotrifluoroethylene and tetrafluoroethylene, chlorotrifluoroethylene, tetrafluoroethylene and hexafluoropropylene, trifluoroethylene, Chlorofluoroethylene and hexafluoropropylene, tetrafluoroethylene and hexafluoropropylene.
  • the above-mentioned raw materials are simple and easy to obtain, which can significantly reduce production costs and increase output.
  • the monomer represented by formula III and the monomer represented by formula IV are reacted in a non-reactive gas atmosphere, a reaction pressure of 6MPa to 8MPa, and a reaction temperature of 45°C to 60°C for 6 hours to 12 Hour;
  • non-reactive gas refers to a gas that does not react with the reactants in the reaction system.
  • Common non-reactive gases are inert gases such as argon and nitrogen.
  • the reaction pressure is one of 6MPa ⁇ 6.5MPa, 6.5MPa ⁇ 7MPa, 7MPa ⁇ 7.5MPa, 7.5MPa ⁇ 8MPa, 6MPa ⁇ 7MPa, 7MPa ⁇ 8MPa.
  • the reaction temperature is one of 45°C to 50°C, 50°C to 55°C, 55°C to 60°C, 45°C to 55°C, and 50°C to 60°C.
  • the polymerization reaction time is 6 hours to 7 hours, 7 hours to 8 hours, 8 hours to 9 hours, 9 hours to 10 hours, 10 hours to 11 hours, 11 hours to 12 hours, 6 hours to One of 8 hours, 6 hours to 10 hours.
  • the pressure of the polymerization reaction is high, and the pressure for the monomers to enter the reaction solution is high. More monomers enter the reaction solution, which can lead to the occurrence of a large-scale polymerization reaction, resulting in an increase in the number of generated polymers and a large polydispersity coefficient. With the reduction of monomers, the polymer lacks the supply of monomers, resulting in a relatively small weight average molecular weight of the generated polymer, which affects the adhesion of the pole pieces and the battery cycle capacity retention rate.
  • the pressure of the polymerization reaction is small, and the pressure for the monomers to enter the reaction solution is small.
  • the reaction monomers cannot be continuously replenished, which is not conducive to the continued progress of the polymerization.
  • the weight average molecular weight of the polymer produced is too low and cannot meet the requirements for adhesive force. requirements, and the battery cycle performance has also declined.
  • the polymerization reaction temperature is too low, the copolymerization driving force is small, the polymerization reaction does not occur sufficiently, and the weight average molecular weight of the prepared polymer is too small, resulting in a significant decrease in adhesive force and a significant decrease in cycle performance.
  • the polymerization reaction temperature is too high, which can lead to the occurrence of a wide range of polymerization reactions, resulting in an increase in the number of polymers produced.
  • the polymer With the reduction of monomers, the polymer lacks the supply of monomers, resulting in a relatively small weight average molecular weight of the produced polymers. , affecting the adhesion of the pole pieces and the battery cycle capacity retention rate.
  • the polymerization reaction time is short, the polymerization reaction cannot continue, and the weight average molecular weight of the prepared polymer is small, which will also cause a decrease in adhesion and cycle performance.
  • the polymerization reaction time is long. As the monomers continue to be consumed and the pressure decreases, the conditions for the polymerization reaction to occur are no longer reached. Extending the reaction time will not allow the polymerization reaction to continue and reduce production efficiency.
  • Controlling the reaction pressure, reaction temperature, and reaction time of the polymerization reaction within the appropriate range can control the weight average molecular weight of the polymer, so that the electrode piece has excellent adhesion, and the battery has better cycle capacity maintenance during the cycle. Rate.
  • the chain transfer agent includes one or more of cyclohexane, isopropyl alcohol, methanol, and acetone.
  • the amount of chain transfer agent used is 1.5% to 3% of the total mass of the monomer represented by formula III and the monomer represented by formula IV.
  • the amount of chain transfer agent used can also be, for example, 2% or 2.5%. . Controlling the amount of chain transfer agent within a suitable range can control the polymer chain length, thereby obtaining a polymer with a suitable weight average molecular weight range.
  • the polymerization reaction includes the following steps:
  • the materials Before raising the temperature to carry out the polymerization reaction, the materials should be mixed evenly first, so that the reaction can proceed more thoroughly, and the polydispersity coefficient, crystallinity and particle size of the prepared polymer will be more suitable.
  • the amount of solvent used is 2 to 8 times the total mass of the monomer represented by formula III and the monomer represented by formula IV.
  • the amount of solvent used may also be, for example, 3, 4, 5, 6 or 7 times the total mass of the monomer represented by formula III and the monomer represented by formula IV.
  • the solvent is an aqueous solvent.
  • the dispersant includes one or more of cellulose ether and polyvinyl alcohol; optionally, the cellulose ether includes one or more of methyl cellulose ether and carboxyethyl cellulose ether. kind.
  • the amount of dispersant is 0.1% to 0.3% of the total mass of the monomer represented by formula III and the monomer represented by formula IV.
  • the amount of dispersant used may also be, for example, 0.2% of the total mass of the monomer represented by formula III and the monomer represented by formula IV.
  • the initiator is an organic peroxide; optionally, the organic peroxide includes tert-amyl peroxypivalate, tert-amyl peroxypivalate, 2-ethyl peroxydicarbonate One or more of ester, diisopropyl peroxydicarbonate and tert-butyl peroxypivalate.
  • the amount of initiator used is 0.15% to 1% of the total mass of the monomer represented by Formula III and the monomer represented by Formula IV.
  • the amount of initiator used may also be, for example, 0.2%, 0.4%, 0.6% or 0.8% of the total mass of the monomer represented by formula III and the monomer represented by formula IV.
  • the pH adjusting agent includes one or more of potassium carbonate, potassium bicarbonate, sodium carbonate, sodium bicarbonate, and ammonia.
  • the amount of pH adjuster is 0.05% to 0.2% of the total mass of the monomer represented by formula III and the monomer represented by formula IV.
  • the amount of pH adjuster used may also be, for example, 0.1% or 0.15% of the total mass of the monomer represented by Formula III and the monomer represented by Formula IV.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector.
  • the positive electrode film layer includes a positive electrode active material, a conductive agent and a binder in some embodiments or prepared by a preparation method in some embodiments. Binder.
  • the positive electrode sheet has both excellent flexibility and good adhesion.
  • the mass fraction of the binder is 0.8% to 1%, based on the total mass of the positive electrode film layer. In some embodiments, the mass fraction of the binder is 0.8% to 0.85%, 0.8% to 0.9%, 0.8% to 0.95%, 0.8% to 1%, 0.85% to 0.9%, 0.85% to 0.95%, 0.85 % ⁇ 1%, 0.9% ⁇ 0.95%, 0.9% ⁇ 1%, 0.95% ⁇ 1%.
  • the mass fraction of the binder in a suitable range ensures that the surface of the positive electrode active material has a suitable binder coating layer, so that the binder can bond the conductive agent and the positive electrode active material together, and the binder is tightly bound to the positive electrode active material. Material and conductive agent surface, the pole piece is not easy to remove powder during the cycle, which improves the cycle performance of the battery. In addition, the appropriate mass fraction of the binder makes the pole piece have excellent flexibility.
  • Controlling the mass fraction of the binder within an appropriate range enables the pole piece to have both excellent flexibility and good adhesion, allowing the battery to have good cycle capacity retention during cycling.
  • the cathode active material is a lithium-containing transition metal oxide.
  • the positive active material is lithium iron phosphate, lithium nickel cobalt manganese oxide, a doped modified material of lithium iron phosphate, a doped modified material of lithium nickel cobalt manganese oxide, or conductive carbon packages thereof. At least one of coating modified materials, conductive metal coating modified materials, and conductive polymer coating modified materials.
  • a method for preparing a positive electrode sheet including the following steps: first stage: preparing the positive active material, the conductive agent and the binder in any embodiment or by the preparation method in any embodiment Mix the binder and perform the first stirring; the second stage: add the solvent and perform the second stirring; the third stage: add the dispersant and perform the third stirring to obtain a slurry, and control the viscosity of the slurry to be between 8000mpa ⁇ s ⁇ 15000mpa ⁇ s; The fourth stage: Coat the slurry on the positive electrode current collector to obtain the positive electrode piece.
  • the preparation method is simple and convenient for industrial production. Through the above preparation method, the settlement of the high molecular weight binder of the present application in the slurry can be reduced, which is beneficial to improving the quality of the slurry and the uniformity of the pole pieces.
  • the stirring revolution speed is 25 rpm and the stirring time is 30 minutes.
  • the stirring revolution speed is 25 rpm
  • the stirring rotation speed is 800 to 1000 rpm
  • the stirring time is 50 to 80 minutes.
  • the stirring rotation speed is 1200-1500 minutes, and the stirring time is 50-70 minutes.
  • the dispersant added in the third stirring includes cellulose compounds, polyalkylene oxide, polyvinyl alcohol, polyvinylpyrrolidone (PVP), polyvinyl acetal, polyvinyl ether, polyvinyl sulfonic acid, Polyvinyl chloride (PVC), polyvinylidene fluoride, chitosan, starch, amylose, polyacrylamide, poly-N-isopropylacrylamide, poly-N,N-dimethylpropylene Amide, polyethyleneimine, polyethylene oxide, poly(2-methoxyethoxyethylene), poly(acrylamide-co-diallyldimethylammonium chloride), acrylonitrile/butadiene/ Styrene (ABS) polymer, acrylonitrile/styrene/acrylate (ASA) polymer, blends of acrylonitrile/styrene/acrylate (ASA) polymer and propylene carbonate, styrene/acrylonitrile
  • ABS
  • the positive electrode current collector has two surfaces facing each other in its own thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • the metal foil aluminum foil can be used.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer.
  • the composite current collector can be formed by forming metal materials (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the cathode active material may be a cathode active material known in the art for batteries.
  • the cathode active material may include at least one of the following materials: an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and their respective modified compounds.
  • the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials of batteries can also be used. Only one type of these positive electrode active materials may be used alone, or two or more types may be used in combination.
  • lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO 2 ), lithium nickel oxide (such as LiNiO 2 ), lithium manganese oxide (such as LiMnO 2 , LiMn 2 O 4 ), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1/ 3 Co 1/3 Mn 1/3 O 2 (can also be abbreviated to NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (can also be abbreviated to NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (can also be abbreviated to NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (can also be abbreviated to NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (can also be abbreviated to NCM 811 ), lithium nickel cobalt aluminum oxide (such as Li
  • lithium-containing phosphates with an olivine structure may include but are not limited to lithium iron phosphate (such as LiFePO 4 (also referred to as LFP)), iron phosphate At least one of a composite material of lithium and carbon, a composite material of lithium manganese phosphate (such as LiMnPO 4 ), a composite material of lithium manganese phosphate and carbon, a composite material of lithium iron manganese phosphate, or a composite material of lithium iron manganese phosphate and carbon.
  • lithium iron phosphate such as LiFePO 4 (also referred to as LFP)
  • iron phosphate At least one of a composite material of lithium and carbon, a composite material of lithium manganese phosphate (such as LiMnPO 4 ), a composite material of lithium manganese phosphate and carbon, a composite material of lithium iron manganese phosphate, or a composite material of lithium iron manganese phosphate and carbon.
  • the positive electrode film layer optionally further includes a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components in a solvent (such as N -methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode piece can be obtained.
  • a solvent such as N -methylpyrrolidone
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, where the negative electrode film layer includes a negative electrode active material.
  • the negative electrode current collector has two opposite surfaces in its own thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.
  • the negative electrode current collector may be a metal foil or a composite current collector.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base material.
  • the composite current collector can be formed by forming metal materials (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyterephthalate Ethylene glycol ester (PET), polybutylene terephthalate (PBT), polyphenylene It is formed on base materials such as ethylene (PS) and polyethylene (PE).
  • PP polypropylene
  • PET polyterephthalate Ethylene glycol ester
  • PBT polybutylene terephthalate
  • base materials such as ethylene (PS) and polyethylene (PE).
  • the negative active material may be a negative active material known in the art for batteries.
  • the negative active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and the like.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon carbon composites, silicon nitrogen composites and silicon alloys.
  • the tin-based material may be selected from at least one of elemental tin, tin oxide compounds and tin alloys.
  • the present application is not limited to these materials, and other traditional materials that can be used as battery negative electrode active materials can also be used. Only one type of these negative electrode active materials may be used alone, or two or more types may be used in combination.
  • the negative electrode film layer optionally further includes a binder.
  • the binder can be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), polysodium acrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), poly At least one of methacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the negative electrode film layer optionally further includes a conductive agent.
  • the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the negative electrode film layer optionally includes other auxiliaries, such as thickeners (such as sodium carboxymethylcellulose (CMC-Na)) and the like.
  • thickeners such as sodium carboxymethylcellulose (CMC-Na)
  • the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative active materials, conductive agents, binders and any other components in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode piece can be obtained.
  • a solvent such as deionized water
  • the electrolyte plays a role in conducting ions between the positive and negative electrodes.
  • the type of electrolyte in this application can be selected according to needs.
  • the electrolyte can be liquid, gel, or completely solid.
  • the electrolyte is an electrolyte solution.
  • the electrolyte includes Electrolyte salts and solvents.
  • the electrolyte salt may be selected from the group consisting of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonimide, lithium bistrifluoromethanesulfonimide, trifluoromethane At least one of lithium sulfonate, lithium difluorophosphate, lithium difluoroborate, lithium dioxaloborate, lithium difluorodioxalate phosphate and lithium tetrafluoroxalate phosphate.
  • 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 secondary battery further includes a separator film.
  • a separator film There is no particular restriction on the type of isolation membrane in this application. Any well-known porous structure isolation membrane with good chemical stability and mechanical stability can be used.
  • the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.
  • the isolation film can be a single-layer film or a multi-layer composite film, with no special restrictions. When the isolation film is a multi-layer composite film, the materials of each layer can be the same or different, and there is no particular limitation.
  • the positive electrode piece, the negative electrode piece and the separator film can be made into an electrode assembly through a winding process or a lamination process.
  • the secondary battery may include an outer packaging.
  • the outer packaging can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag.
  • the material of the soft bag can be plastic. Examples of plastics include polypropylene, polypropylene and polypropylene. Butylene phthalate and polybutylene succinate, etc.
  • FIG. 3 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. 5 is a battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 .
  • the plurality of secondary batteries 5 can be fixed by fasteners.
  • the battery module 4 may further include a housing having a receiving space in which a plurality of secondary batteries 5 are received.
  • the above-mentioned battery modules can also be assembled into a battery pack.
  • the number of battery modules contained in the battery pack can be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery pack.
  • the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box.
  • the battery box includes an upper box 2 and a lower box 3 .
  • the upper box 2 can be covered with the lower box 3 and form a closed space for accommodating the battery module 4 .
  • Multiple battery modules 4 can be arranged in the battery box in any manner.
  • this application also provides an electrical device, the electrical device includes the application's At least one of a secondary battery, a battery module, or a battery pack is provided.
  • 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.
  • Figure 8 is an electrical device as an example.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc.
  • a battery pack or battery module can be used.
  • the 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.
  • NMP N-methylpyrrolidone
  • the viscosity is high, add NMP solution to reduce it to the above viscosity range, then stir for 30 minutes at a revolution speed of 25 r/min and a rotation speed of 1250 r/min to obtain the positive electrode slurry.
  • the prepared cathode slurry is scraped onto the carbon-coated aluminum foil with a scraping weight of 500mg/(1540mm 2 ) on one side, baked at 110°C for 15 minutes, cold pressed until the compacted density is 2.7g/cm 3 and then cut into diameters of 15mm. The disc is obtained, and the positive electrode piece is obtained.
  • Metal lithium sheets are used as negative electrode sheets.
  • Example 1 The positive electrode sheet, negative electrode sheet, separator and electrolyte in Example 1 were assembled into a button battery in a buck box.
  • Example 2 It is basically the same as Example 1, except that the polymerization reaction time is adjusted to 8h, 10h, 11h, 11.5h, and 12h respectively, and the mass of cyclohexane is adjusted to 25g, 20g, 18.5g, 16.5g, and 15g, respectively.
  • the specific parameters are shown in Table 1.
  • Example 1 Basically the same as Example 1, the difference is that the total amount of vinylidene fluoride and chlorotrifluoroethylene monomers added is kept unchanged, and the mass fraction of chlorotrifluoroethylene is adjusted. Based on the total amount of vinylidene fluoride and chlorotrifluoroethylene monomers, Mass meter, the specific parameters are shown in Table 1.
  • Example 2 It is basically the same as Example 1, except that the mass fraction of the vinylidene fluoride-chlorotrifluoroethylene copolymer binder is adjusted, based on the total mass of the positive electrode film layer.
  • the specific parameters are as shown in Table 1.
  • Example 2 Basically the same as Example 1, except that 0.06kg chlorotrifluoroethylene was replaced with 0.03kg chlorotrifluoroethylene and 0.03kg tetrafluoroethylene, 0.02kg chlorotrifluoroethylene, 0.02kg tetrafluoroethylene and 0.02kg hexafluoroethylene, respectively.
  • Acrylic Basically the same as Example 1, except that 0.06kg chlorotrifluoroethylene was replaced with 0.03kg chlorotrifluoroethylene and 0.03kg tetrafluoroethylene, 0.02kg chlorotrifluoroethylene, 0.02kg tetrafluoroethylene and 0.02kg hexafluoroethylene, respectively.
  • Acrylic Basically the same as Example 1, except that 0.06kg chlorotrifluoroethylene was replaced with 0.03kg chlorotrifluoroethylene and 0.03kg tetrafluoroethylene, 0.02kg chlorotrifluoroethylene, 0.02kg tetrafluoroethylene and 0.02kg hexafluoroethylene, respectively.
  • Example 3 Basically the same as Example 3, the difference is that 0.06kg chlorotrifluoroethylene is replaced with 0.03kg chlorotrifluoroethylene and 0.03kg tetrafluoroethylene, 0.02kg chlorotrifluoroethylene, 0.02kg tetrafluoroethylene and 0.02kg hexafluoroethylene Acrylic.
  • Example 12 Basically the same as Example 12, except that 0.06kg chlorotrifluoroethylene was replaced with 0.03kg chlorotrifluoroethylene and 0.03kg tetrafluoroethylene, 0.02kg chlorotrifluoroethylene, 0.02kg tetrafluoroethylene and 0.02kg hexafluoroethylene, respectively.
  • Acrylic Basically the same as Example 12, except that 0.06kg chlorotrifluoroethylene was replaced with 0.03kg chlorotrifluoroethylene and 0.03kg tetrafluoroethylene, 0.02kg chlorotrifluoroethylene, 0.02kg tetrafluoroethylene and 0.02kg hexafluoroethylene, respectively.
  • Acrylic Basically the same as Example 12, except that 0.06kg chlorotrifluoroethylene was replaced with 0.03kg chlorotrifluoroethylene and 0.03kg tetrafluoroethylene, 0.02kg chlorotrifluoroethylene, 0.02kg tetrafluoroethylene and 0.02kg hexafluoroethylene, respectively.
  • Example 2 It is basically the same as Example 1, except that 0.06 kg of chlorotrifluoroethylene is replaced with 0.06 kg of tetrafluoroethylene and 0.06 kg of hexafluoropropylene.
  • Example 1 Basically the same as Example 1, the reaction pressure of the polymerization reaction was adjusted to 5MPa, the reaction temperature was adjusted to 38°C, the reaction time was adjusted to 3h, and the mass of cyclohexane was adjusted to 42g.
  • the specific parameters are shown in Table 1.
  • Example 1 Basically the same as Example 1, the difference is that the polymerization temperature is adjusted to 35°C, the mass of cyclohexane is adjusted to 40g, and the polymerized monomer is only 1kg vinylidene fluoride monomer.
  • the polymerization temperature is adjusted to 35°C
  • the mass of cyclohexane is adjusted to 40g
  • the polymerized monomer is only 1kg vinylidene fluoride monomer.
  • Example 2 It is basically the same as Example 1, except that the reaction time of the polymerization reaction is adjusted to 5 h, the mass of cyclohexane is adjusted to 36 g, and the polymerized monomer is only 1 kg of vinylidene fluoride.
  • the specific parameters are as shown in Table 1.
  • the binder is polyvinylidene fluoride, purchased from Dongyangguang Company, model number 701A, and the mass fraction of the binder is adjusted to 2.5%, based on the total mass of the positive electrode film layer, specifically The parameters are shown in Table 1.
  • Example 1 It is basically the same as Example 1, except that the polymerized monomer is only 1 kg of vinylidene fluoride, and the specific parameters are as shown in Table 1.
  • Example 3 Basically the same as Example 3, the polymerized monomer is only 1kg vinylidene fluoride, and the specific parameters are shown in Table 1.
  • Example 12 Basically the same as Example 12, the polymerized monomer is only 1kg vinylidene fluoride, and the specific parameters are shown in Table 1.
  • the cold-pressed pole pieces are sampled along the transverse direction.
  • the number of samples can be 4cm in transverse width, 25cm in longitudinal length, and 100cm2 in area. Fold the sample in half in the longitudinal direction of 25cm and place the pre-folded pattern.
  • a paper tape with the same width as the pole piece sample and a length of 250 mm is fixed on the pole piece current collector and fixed with wrinkle glue.
  • Figure 2 is a graph showing the battery capacity retention rate and the number of cycles of Example 1 and Comparative Example 4.
  • the battery capacity retention rate data corresponding to Examples 1 to 20 or Comparative Examples 1 to 7 in Table 1 is the data measured after 500 cycles under the above test conditions, that is, the value of P500.
  • Figure 1 is a bonding force-displacement diagram between Example 1 and Comparative Example 4. It can be seen from the figure that at the same displacement, the bonding force of Example 1 is significantly higher than that of Comparative Example 4, indicating that under When the amount of binder added is low, the binder of the vinylidene fluoride-chlorotrifluoroethylene copolymer enables the pole piece to have excellent bonding force.
  • Figure 2 is a graph showing the battery capacity retention rate and the number of cycles of Example 1 and Comparative Example 4. It can be seen from the figure that after the battery has been cycled 500 times, the cycle capacity retention rate of Example 1 is significantly higher than that of Comparative Example 4.
  • the vinylidene fluoride-chlorotrifluoroethylene copolymer binder can improve the cycle capacity retention rate of the battery during cycling and effectively improve the high-amount binder used in traditional technology. This may cause damage to the pole piece and battery performance.
  • the binders in Examples 1 to 22 all contain polymers.
  • the polymers contain structural units derived from vinylidene fluoride, and also contain structures derived from chlorotrifluoroethylene, tetrafluoroethylene, and hexafluoropropylene. Any one of the units, and the weight average molecular weight of the polymer is 1.8 million to 5 million.
  • Ethylene-hexafluoropropylene copolymer or vinylidene fluoride-tetrafluoroethylene copolymer or vinylidene fluoride-hexafluoropropylene copolymer binder gives the pole piece excellent flexibility and adhesion, which can improve the battery's performance during cycling.
  • the medium capacity retention rate effectively improves the damage to the pole piece and battery performance caused by the high amount of binder in traditional technology.
  • Example 10 From the comparison of Example 1, Examples 7 to 9 and Example 10, it can be seen that when the mass fraction of chlorotrifluoroethylene in the vinylidene fluoride-chlorotrifluoroethylene copolymer is 0.5% to 15%, based on the vinylidene fluoride-trifluoroethylene copolymer, Based on the total mass of the vinyl chloride copolymer, this binder enables the pole piece to have both excellent flexibility and good adhesion, allowing the battery to maintain good capacity performance during cycling.
  • the vinylidene fluoride-chlorotrifluoroethylene copolymer binder with a polydispersity coefficient of 2.1 to 2.2 can improve the flexibility of the pole piece and enable the battery to have good adhesive force.
  • Example 1 From the comparison of Example 1, Example 2 and Examples 3 to 6, from the comparison of Example 1 and Example 9 to Examples 7 to 8 and Example 10, it can be seen that when the crystallization of vinylidene fluoride-chlorotrifluoroethylene copolymer With a strength of 35% to 40%, the adhesive can improve the flexibility of the pole piece and provide the battery with good adhesion.

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Abstract

本申请提供了一种粘结剂、制备方法、正极极片、二次电池及用电装置。该粘结剂为含有如式I、式II所示的结构单元的聚合物，其中，R1选自氟、氯、三氟甲基中的一种或多种，该聚合物的重均分子量为180万～500万。该粘结剂在低添加量下就能够保证极片具有足够的粘结力，同时可以进一步提升极片的柔性，降低极片发生脆断的概率，从而提高电池的安全性和循环性能。

Description

粘结剂、制备方法、正极极片、二次电池及用电装置
交叉引用
本申请引用于2022年8月30日递交的名称为“粘结剂、制备方法、正极极片、二次电池及用电装置”的第202211046282.X号中国专利申请，其通过引用被全部并入本申请。
技术领域
本申请涉及二次电池技术领域，尤其涉及一种粘结剂、制备方法、正极极片、二次电池、电池模块、电池包及用电装置。
背景技术
近年来，二次电池广泛应用于水力、火力、风力和太阳能电站等储能电源***，以及电动工具、电动自行车、电动摩托车、电动汽车、军事装备、航空航天等多个领域。随着二次电池应用的普及，对其循环性能、使用寿命等也提出了更高的要求。
粘结剂是二次电池中的常用材料，在电池的极片、隔离膜、封装处等均有很大需求。但是现有的粘结剂需要大量添加才能够保证极片具有足够的粘结力，同时在循环过程中粘结剂无法保持足够的柔性，使得极片容易发生脆断，进而引发安全问题。因此，现有的粘结剂仍有待改进。
发明内容
本申请是鉴于上述课题而进行的，其目的在于，提供一种粘结剂，该粘结剂在低添加量下就可以使得极片具有优异的粘结力，同时该粘结剂能够提高极片的柔韧性，进而提高电池的循环性能。
为了达到上述目的，本申请提供了一种粘结剂，该粘结剂为含有如式I、式II所示的结构单元的聚合物，
其中，R1选自氟、氯、三氟甲基中的一种或多种，该聚合物的重均分子量为180万～500万。
该粘结剂在低添加量下就能够保证极片具有足够的粘结力，同时可以进一步提升极片的柔性，降低极片发生脆断的概率，从而提高电池的安全性和循环性能。
在任意实施方式中，式II所示的结构单元的质量分数为0.5％～15％，基于聚合物总质量计。
式II所示的结构单元的质量分数在合适范围内时，粘结剂在低添加量下就能使得极片兼具优异的柔韧性和良好的粘结力，使得电池在循环过程中保持良好的容量性能。
在任意实施方式中，聚合物的多分散系数为2～2.3。可选地，聚合物的多分散系数为2.1～2.2。
控制聚合物的多分散系数在合适范围内，可以提高极片的柔韧性，并且使得极片具有良好的粘结力。
在任意实施方式中，聚合物的Dv50粒径为50μm～160μm，可选地，聚合物的Dv50粒径为50μm～100μm。
控制聚合物的Dv50粒径在合适范围内，可以提高极片的柔韧性，并且使得极片具有良好的粘结力。
在任意实施方式中，聚合物的结晶度为34％～42％，可选地，聚合物的结晶度为35％～40％。
控制聚合物的结晶度在合适范围内，可以提高极片的柔韧性，并且使得极片具有良好的粘结力。
在任意实施方式中，聚合物溶于N-甲基吡咯烷酮制得的含有质量含量为4％的所述聚合物的胶液的粘度为2400mPa·s～5000mPa·s。可选地，聚合物溶于N-甲基吡咯烷酮制得的含有质量含量为4％的所述聚合物的胶液的粘度为2500mPa·s～4000mPa·s。
控制聚合物的胶液粘度在合适范围内，使得粘结剂用量在较低 水平时就能够保证极片具备良好的粘结性能。
在任意实施方式中，聚合物为偏氟乙烯-三氟氯乙烯共聚物、偏氟乙烯-三氟氯乙烯-四氟乙烯共聚物、偏氟乙烯-三氟氯乙烯-六氟丙烯共聚物、偏氟乙烯-四氟乙烯-六氟丙烯共聚物、偏氟乙烯-三氟氯乙烯-四氟乙烯-六氟丙烯共聚物、偏氟乙烯-四氟乙烯共聚物或偏氟乙烯-六氟丙烯共聚物中的一种或多种。
本申请的第二方面还提供一种粘结剂的制备方法，包括以下步骤：
在可聚合条件下，将式III所示的单体和式Ⅳ所示的单体进行聚合反应制备聚合物；
其中，R2选自氟、氯、三氟甲基中的一种或多种，聚合物的重均分子量为180万～500万。
该粘结剂的制备方法简单，对环境友好，利于工业化生产。同时该方法制备的粘结剂，使得极片兼具优异的柔韧性和良好的粘结力，电池具有高水平的循环保持率。
在任意实施方式中，式Ⅳ所示的单体的质量含量为0.5％～15％，基于式III和式Ⅳ单体的总质量计。
式Ⅳ所示的单体的质量分数在合适范围内时，极片兼具优异的柔韧性和良好的粘结力，使得电池在循环过程中能够保持高的循环容量。
在任意实施方式中，式Ⅳ所示的单体为三氟氯乙烯、四氟乙烯、六氟丙烯中的一种或多种。
上述原材料简单易得，能够大幅度降低生产成本，提高产量。
在任意实施方式中，将式III和式Ⅳ所示的单体在非反应性气体氛围、6MPa～8MPa的反应压力、45℃～60℃的反应温度下反应6小时～12小时；加入链转移剂，待反应体系中压力降至2MPa～2.5MPa，停止反应，固液分离，保留固相。
在任意实施方式中，制备方法还包括以下步骤：向容器中加入溶剂和分散剂，对所述容器抽真空后充入非反应性气体；向所述容器中加入引发剂和pH调节剂，调节pH值至6.5～7，然后加入式III和式Ⅳ所示的单体，使所述容器中的压力达到6MPa～8MPa；搅拌30分钟～60分钟后，升温至45℃～60℃，进行聚合反应。
控制聚合反应的反应压力、反应压力、反应温度在合适的范围内，可以控制聚合物的重均分子量，使得极片兼具优异的柔韧性和良好的粘结力，电池具有高的循环容量保持率。
本申请的第三方面提供一种正极极片，包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，正极膜层包括正极活性材料、导电剂和任意实施方式中的粘结剂或任意实施方式中的制备方法制备的粘结剂。
该正极极片兼具优异的柔韧性和良好的粘结力。
在任意实施方式中，粘结剂的质量分数为0.8％～1％，基于正极膜层的总质量计。
控制粘结剂的质量分数在合适的范围内，使得极片兼具优异的柔韧性和粘结力，使得电池在循环过程中具有高的循环容量保持率。
在任意实施方式中，正极活性材料为含锂的过渡金属氧化物。
在任意实施方式中，正极活性材料为磷酸铁锂及其改性材料、锂镍钴锰氧化物及其改性材料中的至少一种，所述改性材料是通过掺杂、导电碳包覆、导电金属包覆、导电聚合物包覆中的一种或多种改性方式制备的。
本申请的第四方面提供一种正极极片的制备方法，包括如下步骤：第一阶段：将正极活性材料、导电剂和任意实施例中的粘结剂或如任意实施例中的制备方法制备的粘结剂混合，进行第一搅拌；第二阶段：加入溶剂进行第二搅拌；第三阶段：加入分散剂进行第三搅拌，得到浆料，控制浆料粘度为在8000～15000mPa·s；第四阶段：在正极集流体上涂布浆料，得到正极极片。
该制备方法简单，利于工业生产。
在任意实施方式中，第一搅拌中，搅拌公转速度为25转/分钟， 搅拌时间为30分钟。
在任意实施方式中，第二搅拌中，搅拌公转速度为25转/分钟，搅拌自转速度800～1000转/分钟，搅拌时间为50～80分钟。
在任意实施方式中，第三搅拌中，搅拌自转速度1200～1500转/分钟，搅拌时间为50～70分钟。
在本申请的第五方面，提供一种二次电池，包括电极组件和电解液，所述电极组件包括隔离膜、负极极片和本申请第三方面的正极极片。
在本申请的第六方面，提供一种电池模块，包括本申请第五方面的二次电池。
在本申请的第七方面，提供一种电池包，包括本申请第六方面的电池模块。
在本申请的第八方面，提供一种用电装置，包括本申请第五方面的二次电池、第六方面的电池模块或第七方面的电池包中的至少一种。
附图说明
图1为实施例1和对比例4的粘结力-位移图；
图2为实施例1和对比例4的电池容量保持率与循环次数的曲线图；
图3是本申请一实施方式的二次电池的示意图；
图4是图3所示的本申请一实施方式的二次电池的分解图；
图5是本申请一实施方式的电池模块的示意图；
图6是本申请一实施方式的电池包的示意图；
图7是图6所示的本申请一实施方式的电池包的分解图；
图8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正极活性材料及其制造方法、正极极片、二次电池、电池模块、电池包和电学装置的实施方式。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)。
聚偏氟乙烯是目前二次电池中使用最为广泛的粘结剂种类之一。然而，传统聚偏氟乙烯的粘度低，往往需要大量添加才能保证活性物质的有效粘结，从而使得极片达到有效的粘结力。然而传统聚偏氟乙烯用量的提高一方面会降低活性材料在极片中的负载量，影响电池功率性能的提升，一方面会降低极片的柔性，使得极片易于发生脆断，难以满足对于电池循环性能和安全性能的要求。
[粘结剂]
基于此，本申请提出了一种粘结剂，该粘结剂为含有式I、式II所示的结构单元的聚合物，
其中，R1选自氟、氯、三氟甲基中的一种或多种，该聚合物的重均分子量为180万～500万。
在本文中，术语“粘结剂”是指在分散介质中形成胶体溶液或胶体分散液的化学化合物、聚合物或混合物。
在本文中，术语“聚合物”一方面包括通过聚合反应制备的化学上均一的、但在聚合度、摩尔质量和链长方面不同的大分子的集合体。该术语另一方面也包括由聚合反应形成的这样的大分子集合体 的衍生物，即可以通过上述大分子中的官能团的反应，例如加成或取代获得的并且可以是化学上均一的或化学上不均一的化合物。
在本文中，术语“重均分子量”是指聚合物中用不同分子量的分子所占的重量分数与其对应的分子量乘积的总和。
在一些实施方式中，粘结剂的分散介质是油性溶剂，油性溶剂的示例包括但不限于二甲基乙酰胺、N，N-二甲基甲酰胺、N-甲基吡咯烷酮、丙酮、碳酸二甲酯、乙基纤维素、聚碳酸酯。即，粘结剂溶解于油性溶剂中。
在一些实施方式中，粘结剂用于将电极活性物质及/或导电剂固定在合适位置并将它们粘附在导电金属部件以形成电极。
在一些实施方式中，粘结剂作为正极粘结剂，用于粘结正极活性材料及/或导电剂以形成电极。
在一些实施方式中，粘结剂作为负极粘结剂，用于粘结负极活性材料及/或导电剂以形成电极。
在本文中，术语“氟”指的是-F基团。
在本文中，术语“氯”指的是-Cl基团。
在本文中，术语“三氟甲基”指的是-CF3基团。
在一些实施方式中，粘结剂为卤代烃共聚物，可选自偏氟乙烯-三氟氯乙烯共聚物、偏氟乙烯-三氟氯乙烯-四氟乙烯共聚物、偏氟乙烯-三氟氯乙烯-六氟丙烯共聚物、偏氟乙烯-四氟乙烯-六氟丙烯共聚物、偏氟乙烯-三氟氯乙烯-四氟乙烯-六氟丙烯共聚物、偏氟乙烯-四氟乙烯共聚物、偏氟乙烯-六氟丙烯共聚物中的一种或多种。
聚合物含有的氟元素与活性材料表面及集流体表面的羟基或/和羧基形成氢键作用，能够提高极片的粘结力。重均分子量为180万～500万的聚合物能够在低添加量下提高极片的粘结力。聚合物中式Ⅱ所示的结构单元，能够在式Ⅰ所示的结构单元形成的周期排列的链段的结晶区中引入无序单元，进而降低聚合物的结晶度，增加链段的可移动性，提高了极片的柔韧性，同时聚合物中包含式Ⅱ所示的结构单元，能够降低式Ⅰ所示的结构单元的含量，减少式Ⅰ所示的结构单元聚合导致的结晶，进而进一步提高极片的柔韧性。
该粘结剂在较低的添加量下就能够保证极片具有足够的粘结力，同时可以进一步改善极片的柔性，降低极片发生脆断的概率，从而提高电池的安全性和循环性能。
在本申请中，聚合物的重均分子量的测试可以选用本领域已知的方法进行测试，例如采用凝胶色谱法进行测试，如采用Waters 2695 Isocratic HPLC型凝胶色谱仪(示差折光检测器2141)进行测试。在一些实施方式中，测试方法为以质量分数为3.0％的聚苯乙烯溶液试样做参比，选择匹配的色谱柱(油性：Styragel HT5DMF7.8*300mm+Styragel HT4)。用纯化后的N-甲基吡咯烷酮(NMP)溶剂配置3.0％的聚合物胶液，配置好的溶液静置一天，备用。测试时，先用注射器吸取四氢呋喃，进行冲洗，重复几次。然后吸取5ml实验溶液，排除注射器中的空气，将针尖擦干。最后将试样溶液缓缓注入进样口。待示数稳定后获取数据，读取重均分子量。
在一些实施方式中，式II所示的结构单元的质量分数为0.5％～15％，基于聚合物总质量计。在一些实施方式中，式II所示的结构单元的质量分数可以为0.5％～1％，0.5％～2％，0.5％～3％，0.5％～4％，0.5％～5％，0.5％～6％，0.5％～7％，0.5％～8％，0.5％～9％，0.5％～10％，0.5％～11％，0.5％～12％，0.5％～13％，0.5％～14％1％～2％，1％～3％，1％～4％，1％～5％，1％～6％，1％～7％，1％～8％，1％～9％，1％～10％，1％～11％，1％～12％，1％～13％，1％～14％，1％～15％，2％～3％，2％～4％，2％～5％，2％～6％，2％～7％，2％～8％，2％～9％，2％～10％，2％～11％，2％～12％，2％～13％，2％～14％，2％～15％，3％～4％，3％～5％，3％～6％，3％～7％，3％～8％，3％～9％，3％～10％，3％～11％，3％～12％，3％～13％，3％～14％，3％～15％，4％～5％，4％～6％，4％～7％，4％～8％，4％～9％，4％～10％，4％～11％，4％～12％，4％～13％，4％～14％，4％～15％，5％～6％，5％～7％，5％～8％，5％～9％，5％～10％，5％～11％，5％～12％，5％～13％，5％～14％，5％～15％，6％～7％，6％～8％，6％～9％，6％～10％，6％～11％，6％～12％，6％～13％，6％～14％，6％～15％，7％～8％， 7％～9％，7％～10％，7％～11％，7％～12％，7％～13％，7％～14％，7％～15％，8％～9％，8％～10％，8％～11％，8％～12％，8％～13％，8％～14％，8％～15％，9％～10％，9％～11％，9％～12％，9％～13％，9％～14％，9％～15％，10％～11％，10％～12％，10％～13％，10％～14％，10％～15％，11％～12％，11％～13％，11％～14％，11％～15％，12％～13％，12％～14％，12％～15％，13％～14％，13％～15％，14％～15％中的任意一种。
式II所示的结构单元的质量分数在合适范围内时，使得极片在粘结剂低添加量的情况下就能兼具优异的柔韧性和良好的粘结力，能够提升电池在循环过程中的容量保持率。
在一些实施方式中，聚合物的多分散系数为2～2.3。在一些实施方式中，聚合物的多分散系数为2～2.1、2～2.2、2～2.3、2.1～2.2、2.1～2.3中的任意一种。
在本文书，术语“多分散系数”指聚合物的重均分子量与聚合物的数均分子量的比值。
在本文中，术语“数均分子量”是指聚合物中用不同分子量的分子所占的摩尔分数与其对应的分子量乘积的总和。
聚合物的多分散系数在合适范围内，聚合物具有合适的有序性，粘结剂具有优异的分散性，可以提高极片的柔韧性，并使得极片具有良好的粘结力。另外合适的聚合物的多分散系数，可以降低聚合物的制备工艺难度，提高产品的优率，同时合适的多分散系数还能有效提升浆料固含量，降低生产成本。
本申请中，多分散系数的测试可以选用本领域已知的方法进行测试，例如采用凝胶色谱法进行测试，如采用Waters 2695 Isocratic HPLC型凝胶色谱仪(示差折光检测器2141)进行测试。在一些实施方式中，以质量分数为3.0％的聚苯乙烯溶液试样做参比，选择匹配的色谱柱(油性：Styragel HT5DMF7.8*300mm+Styragel HT4)。用纯化后的N-甲基吡咯烷酮(NMP)溶剂配置3.0％的聚合物胶液，配置好的溶液静置一天，备用。测试时，先用注射器吸取四氢呋喃，进行冲洗，重复几次。然后吸取5ml实验溶液，排除注射器中的空 气，将针尖擦干。最后将试样溶液缓缓注入进样口。待示数稳定后获取数据。分别读取重均分子量a和数均分子量b。多分散系数＝a/b。
在一些实施方式中，聚合物的Dv50粒径为50μm～160μm。在一些实施方式中，聚合物的Dv50粒径可选为50μm～60μm、60μm～70μm、70μm～80μm、80μm～90μm、90μm～100μm、100μm～110μm、110μm～120μm、120μm～130μm、130μm～140μm、140μm～150μm、150μm～160μm、50μm～70μm、70μm～90μm、90μm～110μm、110μm～130μm、130μm～150μm、60μm～80μm、80μm～100μm、60μm～140μm、50μm～100μm中的任意一种。
在本文中，术语“Dv50粒径”指在粒度分布曲线中，颗粒的累计粒度分布数达到50％时所对应的粒径，它的物理意义是粒径小于(或大于)它的颗粒占50％。
控制聚合物的Dv50粒径在合适范围内，可以提高粘结剂的溶解性，提高极片的柔韧性，并使得极片具有较好粘结力。同时合适范围的聚合物的Dv50粒径，还能使得粘结剂的用量可以被控制在较低的水平，且不会对粘结性能造成过大的负面影响，从而有效改善了传统技术中高用量粘结剂带来的极片和电池性能受损的情况。
本申请中，聚合物的Dv50粒径的测试可以选用本领域已知的方法进行测试，例如，参照GB/T 19077-2016粒度分布激光衍射法，用50ml烧杯称量0.1g～0.13g的聚合物粉料，再称取5g无水乙醇，加入到装有聚合物粉料的烧杯中，放入长度约2.5mm的搅拌子，并用保鲜膜密封。将样品放入超声机超声5分钟，转移到磁力搅拌机用500转/分钟的速度搅拌20分钟以上，采用激光粒度分析仪进行测定，如英国马尔文仪器有限公司的Mastersizer 2000E型激光粒度分析仪进行测试。
在一些实施方式中，聚合物的结晶度为34％～42％。
在一些实施方式中，聚合物的结晶度可选为34％～36％、35％～37％、36％～38％、38％～40％、40％～42％、39％～40％、40％～41％、41％～42％、35％～40％中的任意一种。
在本文中，术语“结晶度”指聚合物中结晶区域所占的比例，微 观结构中存在一些具有稳定规整排列的分子的区域，分子有规则紧密排列的区域称为结晶区域。
合适的结晶度使得聚合物链段的具有优异的可移动性，改善极片的柔韧性，另外合适的结晶度使得聚合物具有优异的溶解性，提高制浆过程的速度，提高生产效率，同时合适的结晶度使得聚合物分子链具有优异的规整密堆积程度，提高粘结剂的化学稳定性和热稳定性。
控制聚合物的结晶度在合适范围内，使得粘结剂用量在较低水平时，极片就能兼具优异的柔韧性和良好的粘结力，进而有助于提高活性物质的负载量和电池的循环性能。
本申请中，结晶度的测试可以选用本领域已知的方法进行测试，如采用差式扫描热分析法进行测试。示例性地，将0.5g聚合物置于铝制干锅中，抖平，盖上坩埚盖子，在氮气气氛下，以50毫升/分钟的吹扫气，以70毫升/分钟的保护气，升温速率为每分钟10℃，测试温度范围-100℃～400℃，利用美国TA仪器型号为Discovery 250的差示扫描量热仪(DSC)进行测试并消除热历史。
此测试将会得到聚合物的DSC/(Mw/mg)随温度变化曲线，并进行积分，峰面积即为聚合物的熔融焓ΔH(J/g)，聚合物结晶度＝(ΔH/ΔHm)×100％，其中ΔHm为聚偏氟乙烯的标准熔融焓(晶态熔化热)，ΔHm＝104.7J/g。
在一些实施方式中，聚合物溶于N-甲基吡咯烷酮制得的含有质量含量为4％的聚合物的胶液的粘度为2400mPa·s～5000mPa·s。
在一些实施方式中，聚合物溶于N-甲基吡咯烷酮制得的含有质量含量为4％的聚合物的胶液的粘度为2400mPa·s～3000mPa·s、3000mPa·s～3300mPa·s、3300mPa·s～3500mPa·s、3500mPa·s～3800mPa·s、3800mPa·s～4000mPa·s、4000mPa·s～4200mPa·s、4200mPa·s～4600mPa·s、4600mPa·s～4750mPa·s、3100mPa·s～3400mPa·s、3400mPa·s～3800mPa·s、3800mPa·s～4600mPa·s、2500mPa·s～4000mPa·s中的任意一种。
在一些实施方式中，聚合物溶于N-甲基吡咯烷酮制得的含有质 量含量为4％的聚合物的胶液的粘度为24000mPa·s～4000mPa·s。在一些实施方式中，聚合物溶于N-甲基吡咯烷酮制得的含有质量含量为4％的聚合物的胶液的粘度可选为2400mPa·s～3000mPa·s、3000mPa·s～3300mPa·s、3300mPa·s～3500mPa·s、3500mPa·s～3800mPa·s、3800mPa·s～4000mPa·s、3100mPa·s～3400mPa·s、3400mPa·s～3800mPa·s、2500mPa·s～4000mPa·s中的任意一种。
聚合物胶液具有合适的粘度，使得包含该聚合物的粘结剂具有合适的粘度，一方面，粘结剂具有合适的粘度，使得在制备正极浆料的过程中，粘结剂可以有效的分散于溶剂中，提高粘结剂的使用性能，同时还能提高制浆过程的速度，提高粘结剂的加工性能；另一方面，粘结剂具有合适的粘度使得极片具有优异的粘结剂。
另外制备正极浆料时，粘结剂需要具有一定的粘度，才能防止正极活性材料以及导电剂等助剂的沉降，使浆料能较稳定地放置。传统技术中，要达到2500mPa·s～5000mPa·s的胶液粘度，至少需要含有质量含量为7％的粘结剂，基于胶液的总质量计，而采用本申请的粘结剂，则可以将粘结剂的用量控制在4％，为降低粘结剂在正极膜层中的含量提供了支持。
控制粘结剂溶液的粘度在合适范围内，使得极片在粘结剂低添加量的情况下就能兼具优异的柔韧性和良好的粘结性能。
本申请中，粘结剂的粘度可以采用本领域已知的方法进行测试，如旋转粘度计测试法。作为示例，用500ml烧杯分别称取14g聚合物和336g N-甲基吡咯烷酮(NMP)，使用力辰高速研磨机搅拌分散，转速800转/分钟，搅拌时间120分钟后超声震荡30分钟去除气泡。在室温下，使用力辰科技NDJ-5S旋转粘度计进行测试，选用3号转子***胶液，保证转子液面标志和胶液液面相平，以12转/分钟的转子转速测试粘度，6分钟后读取粘度数据即可。
本申请的一个实施方式中，提供一种粘结剂的制备方法，包括以下步骤：
在可聚合条件下，将式III所示的单体和式Ⅳ所示的单体进行聚合反应制备聚合物；
其中，R2选自氟、氯、三氟甲基中的一种或多种，聚合物的重均分子量为180万～500万。
该粘结剂的制备方法简单，对环境友好，利于工业化生产。同时该方法制备的粘结剂，使得极片兼具优异的柔韧性和良好的粘结力，电池具有较好的循环保持率。
在一些实施方式中，式Ⅳ所示的单体的质量分数0.5％～15％，基于式III所示的单体和式Ⅳ所示的单体总质量计。在一些实施方式中，式Ⅳ所示的单体的质量分数可以为0.5％～1％，0.5％～2％，0.5％～3％，0.5％～4％，0.5％～5％，0.5％～6％，0.5％～7％，0.5％～8％，0.5％～9％，0.5％～10％，0.5％～11％，0.5％～12％，0.5％～13％，0.5％～14％1％～2％，1％～3％，1％～4％，1％～5％，1％～6％，1％～7％，1％～8％，1％～9％，1％～10％，1％～11％，1％～12％，1％～13％，1％～14％，1％～15％，2％～3％，2％～4％，2％～5％，2％～6％，2％～7％，2％～8％，2％～9％，2％～10％，2％～11％，2％～12％，2％～13％，2％～14％，2％～15％，3％～4％，3％～5％，3％～6％，3％～7％，3％～8％，3％～9％，3％～10％，3％～11％，3％～12％，3％～13％，3％～14％，3％～15％，4％～5％，4％～6％，4％～7％，4％～8％，4％～9％，4％～10％，4％～11％，4％～12％，4％～13％，4％～14％，4％～15％，5％～6％，5％～7％，5％～8％，5％～9％，5％～10％，5％～11％，5％～12％，5％～13％，5％～14％，5％～15％，6％～7％，6％～8％，6％～9％，6％～10％，6％～11％，6％～12％，6％～13％，6％～14％，6％～15％，7％～8％，7％～9％，7％～10％，7％～11％，7％～12％，7％～13％，7％～14％，7％～15％，8％～9％，8％～10％，8％～11％，8％～12％，8％～13％，8％～14％，8％～15％，9％～10％，9％～11％，9％～12％，9％～13％，9％～14％，9％～15％，10％～11％，10％～12％，10％～13％，10％～14％，10％～15％，11％～12％，11％～13％，11％～14％，11％～15％，12％～13％，12％～14％，12％～15％，13％～14％，13％～15％，14％～15％ 中的任意一种。
式Ⅳ所示的单体的质量分数在合适范围内时，粘结剂使得极片兼具优异的柔韧性和良好的粘结力，并且电池在循环过程中能够保持高的循环容量保持率。
在一些实施方式中，式III所示的单体为三氟氯乙烯、四氟乙烯、六氟丙烯中的一种或多种。在一些实施方式中，式Ⅳ所示的单体为三氟氯乙烯、四氟乙烯、六氟丙烯、三氟氯乙烯和四氟乙烯、三氟氯乙烯和四氟乙烯和六氟丙烯、三氟氯乙烯和六氟丙烯、四氟乙烯和六氟丙烯。
上述原材料简单易得，能够大幅度降低生产成本，提高产量。
在一些实施方式中，将式III所示的单体和式Ⅳ所示的单体在非反应性气体氛围、6MPa～8MPa的反应压力、45℃～60℃的反应温度下反应6小时～12小时；
加入链转移剂，待反应体系中压力降至2MPa～2.5MPa，停止反应，固液分离，保留固相。
本文中，术语“非反应性气体”指不与反应体系中反应物进行反应的气体，常见的非反应性气体为氩气等惰性气体以及氮气。
在一些实施方式中，反应压力为6MPa～6.5MPa、6.5MPa～7MPa、7MPa～7.5MPa、7.5MPa～8MPa、6MPa～7MPa、7MPa～8MPa中的一种。
在一些实施方式中，反应温度为45℃～50℃、50℃～55℃、55℃～60℃、45℃～55℃、50℃～60℃中的一种。
在一些实施方式中，聚合反应的时间为6小时～7小时、7小时～8小时、8小时～9小时、9小时～10小时、10小时～11小时、11小时～12小时、6小时～8小时、6小时～10小时中的一种。
聚合反应压力较大，单体进入反应溶液的压力较大，单体进入反应溶液中较多，可导致大范围聚合反应的发生，导致生成的聚合物数量增多，多分散系数大，随着单体的减少，聚合物缺少单体的供给，导致生成的聚合物的重均分子量相对较小，影响极片的粘结力和电池循环容量保持率。
聚合反应压力较小，单体进入反应溶液的压力较小，反应单体不能持续的补充，不利于聚合的持续进行，制得的聚合物的重均分子量过低，无法满足对粘结力的要求，且电池循环性能也有所下降。
聚合反应温度偏低，共聚的促动力较小，聚合反应发生的不充分，制备的聚合物的重均分子量偏小，造成粘结力的大幅下降，以及循环性能的明显下降。
聚合反应温度偏高，可导致大范围聚合反应的发生，导致生成的聚合物数量增多，随着单体的减少，聚合物缺少单体的供给，导致生成的聚合物的重均分子量相对较小，影响极片的粘结力和电池循环容量保持率。
聚合反应时间较短，聚合反应不能持续进行，制备的聚合物的重均分子量偏小，同样会造成粘结力和循环性能的下降。
聚合反应时间较长，随着单体的持续消耗，压力的降低，已达不到聚合反应可以发生的条件，延长反应时间并不能持续进行聚合反应，降低生产效率。
控制聚合反应的反应压力、反应温度、反应时间在合适的范围内，可以控制聚合物的重均分子量，使得极片具有优异的粘结力，使得电池在循环过程中具有较好的循环容量保持率。
在一些实施方式中，链转移剂包括环己烷、异丙醇、甲醇以及丙酮中的一种或多种。
在一些实施方式中，链转移剂的用量为式III所示的单体和式Ⅳ所示的单体总质量的1.5％～3％，链转移剂的用量例如还可以是2％或2.5％。链转移剂的用量控制在合适范围内，能使得聚合物链长可控，从而获得合适的重均分子量范围的聚合物。
在一些实施方式中，聚合反应包括以下步骤：
向容器中加入溶剂和分散剂，对容器抽真空后充入非反应性气体；
向容器中加入引发剂和pH调节剂，调节pH值至6.5～7，然后加入式III所示的单体和式Ⅳ所示的单体，
使容器中的压力达到6MPa～8MPa；
搅拌30分钟～60分钟后，升温至45℃～60℃，进行聚合反应。
升温进行聚合反应前，先将物料混合均匀，能使反应进行得更彻底，制备的聚合物的多分散系数、结晶度以及粒径更合适。
在一些实施方式中，溶剂的用量为式III所示的单体和式Ⅳ所示的单体总质量的2～8倍。溶剂的用量例如还可以是式III所示的单体和式Ⅳ所示的单体总质量的3、4、5、6或7倍。在一些实施方式中，溶剂为水溶剂。
在一些实施方式中，分散剂包括纤维素醚和聚乙烯醇中的一种或多种；可选地，纤维素醚包括甲基纤维素醚和羧乙基纤维素醚中的一种或多种。
在一些实施方式中，分散剂的用量为式III所示的单体和式Ⅳ所示的单体总质量的0.1％～0.3％。分散剂的用量例如还可以是式III所示的单体和式Ⅳ所示单体的总质量的0.2％。
在一些实施方式中，引发剂为有机过氧化物；可选地，有机过氧化物包括过氧化新戊酸叔戊酯、过氧化叔戊基新戊酸酯、2-乙基过氧化二碳酸酯、二异丙基过氧化二碳酸酯以及叔丁基过氧化新戊酸酯中的一种或多种。
在一些实施方式中，引发剂的用量为式III所示的单体和式Ⅳ所示的单体总质量的0.15％～1％。引发剂的用量例如还可以是式III所示的单体和式Ⅳ所示的单体总质量的0.2％、0.4％、0.6％或0.8％。
在一些实施方式中，pH调节剂包括碳酸钾、碳酸氢钾、碳酸钠、碳酸氢钠以及氨水中的一种或多种。
在一些实施方式中，pH调节剂的用量为式III所示的单体和式Ⅳ所示的单体总质量的0.05％～0.2％。pH调节剂的用量例如还可以是式III所示的单体和式Ⅳ所示的单体总质量的0.1％或0.15％。
[正极极片]
正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，正极膜层包括正极活性材料、导电剂和一些实施方式中的粘结剂或一些实施方式中的制备方法制备的粘结剂。
该正极极片兼具优异的柔韧性和良好的粘结力。
在一些实施方式中，粘结剂的质量分数为0.8％～1％，基于正极膜层的总质量计。在一些实施方式中，粘结剂的质量分数为0.8％～0.85％、0.8％～0.9％、0.8％～0.95％、0.8％～1％、0.85％～0.9％、0.85％～0.95％、0.85％～1％、0.9％～0.95％、0.9％～1％、0.95％～1％。
合适范围的粘结剂的质量分数，使得正极活性材料表面具有合适的粘结剂包覆层，使得粘结剂能够将导电剂和正极活性材料粘结到一起，粘结剂紧密结合在正极活性材料和导电剂表面，极片在循环过程中不易脱粉，提高电池的循环性能，另外合适的质量分数的粘结剂使得极片具有优异的柔韧性。
控制粘结剂的质量分数在合适的范围内，使得极片兼具优异的柔韧性和良好的粘结力，使得电池在循环过程中具有良好的循环容量保持率。
在一些实施方式中，正极活性材料为含锂的过渡金属氧化物。在一些实施方式中，正极活性材料为磷酸铁锂、锂镍钴锰氧化物、磷酸铁锂的掺杂改性材料、锂镍钴锰氧化物的掺杂改性材料、或它们的导电碳包覆改性材料、导电金属包覆改性材料、导电聚合物包覆改性材料中的至少一种。
在一些实施方式中，提供一种正极极片的制备方法，包括如下步骤：第一阶段：将正极活性材料、导电剂和任意实施方式中的粘结剂或如任意实施方式中的制备方法制备的粘结剂混合，进行第一搅拌；第二阶段：加入溶剂进行第二搅拌；第三阶段：加入分散剂进行第三搅拌，得到浆料，控制浆料粘度为在8000mpa·s～15000mpa·s；第四阶段：在正极集流体上涂布浆料，得到正极极片。
该制备方法简单，利于工业生产。通过上述制备方法可以减少本申请的高分子量粘结剂在浆料中的沉降，有利于提高浆料品质和极片的均匀度。
在一些实施方式中，第一搅拌中，搅拌公转速度为25转/分钟，搅拌时间为30分钟。
在一些实施方式中，第二搅拌中，搅拌公转速度为25转/分钟， 搅拌自转速度800～1000转/分钟，搅拌时间为50～80分钟。
在一些实施方式中，第三搅拌中，搅拌自转速度1200～1500分钟，搅拌时间为50～70分钟。
在一些实施方式中，第三搅拌中加入的分散剂包括纤维素化合物、聚环氧烷、聚乙烯醇、聚乙烯吡咯烷酮(PVP)、聚乙烯醇缩醛、聚乙烯醚、聚乙烯磺酸、聚氯乙烯(PVC)、聚偏二氟乙烯、壳聚糖、淀粉、直链淀粉(amylose)、聚丙烯酰胺、聚-N-异丙基丙烯酰胺、聚-N,N-二甲基丙烯酰胺、聚乙烯亚胺、聚氧化乙烯、聚(2-甲氧基乙氧基乙烯)、聚(丙烯酰胺-共-二烯丙基二甲基氯化铵)、丙烯腈/丁二烯/苯乙烯(ABS)聚合物、丙烯腈/苯乙烯/丙烯酸酯(ASA)聚合物、丙烯腈/苯乙烯/丙烯酸酯(ASA)聚合物与碳酸丙烯酯的共混物、苯乙烯/丙烯腈(SAN)共聚物、或甲基丙烯酸甲酯/丙烯腈/丁二烯/苯乙烯(MABS)聚合物中的一种或多种。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极膜层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，所述正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，正极活性材料可采用本领域公知的用于电池的正极活性材料。作为示例，正极活性材料可包括以下材料中的至少一种：橄榄石结构的含锂磷酸盐、锂过渡金属氧化物及其各自的改性化合物。但本申请并不限定于这些材料，还可以使用其他可被用作电池正极活性材料的传统材料。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。其中，锂过渡金属氧化物的示例可包括但不限于锂钴氧化物(如LiCoO2)、锂镍氧化物 (如LiNiO2)、锂锰氧化物(如LiMnO2、LiMn2O4)、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(如LiNi1/3Co1/3Mn1/3O2(也可以简称为NCM333)、LiNi0.5Co0.2Mn0.3O2(也可以简称为NCM523)、LiNi0.5Co0.25Mn0.25O2(也可以简称为NCM211)、LiNi0.6Co0.2Mn0.2O2(也可以简称为NCM622)、LiNi0.8Co0.1Mn0.1O2(也可以简称为NCM811)、锂镍钴铝氧化物(如LiNi0.85Co0.15Al0.05O2)及其改性化合物等中的至少一种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂(如LiFePO4(也可以简称为LFP))、磷酸铁锂与碳的复合材料、磷酸锰锂(如LiMnPO4)、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料中的至少一种。
在一些实施方式中，正极膜层还可选地包括导电剂。作为示例，所述导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，可以通过以下方式制备正极极片：将上述用于制备正极极片的组分，例如正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
[负极极片]
负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，所述负极膜层包括负极活性材料。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极膜层设置在负极集流体相对的两个表面中的任意一者或两者上。
在一些实施方式中，所述负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯 乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，负极活性材料可采用本领域公知的用于电池的负极活性材料。作为示例，负极活性材料可包括以下材料中的至少一种：人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂等。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。
在一些实施方式中，负极膜层还可选地包括粘结剂。所述粘结剂可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。
在一些实施方式中，负极膜层还可选地包括导电剂。导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，负极膜层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。
在一些实施方式中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如负极活性材料、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成负极浆料；将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，即可得到负极极片。
[电解质]
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。
在一些实施方式中，所述电解质采用电解液。所述电解液包括 电解质盐和溶剂。
在一些实施方式中，电解质盐可选自六氟磷酸锂、四氟硼酸锂、高氯酸锂、六氟砷酸锂、双氟磺酰亚胺锂、双三氟甲磺酰亚胺锂、三氟甲磺酸锂、二氟磷酸锂、二氟草酸硼酸锂、二草酸硼酸锂、二氟二草酸磷酸锂及四氟草酸磷酸锂中的至少一种。
在一些实施方式中，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。
在一些实施方式中，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。
[隔离膜]
在一些实施方式中，二次电池中还包括隔离膜。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施方式中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施方式中，二次电池可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，作为塑料，可列举出聚丙烯、聚对 苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图3是作为一个示例的方形结构的二次电池5。
在一些实施方式中，参照图4，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5是作为一个示例的电池模块4。参照图5，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6和图7是作为一个示例的电池包1。参照图6和图7，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***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8是作为一个示例的用电装置。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
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
1)粘结剂的制备
在10L的高压釜中加入4kg的去离子水和2g的甲基纤维素醚，抽真空并用N2置换O2三次，再次加入5g叔丁基过氧化新戊酸酯和2g的碳酸氢钠，并充入0.94kg的偏氟乙烯和0.06kg三氟氯乙烯，使体系压力达到7MPa，混合搅拌30min，升温到45℃，反应6h后加入30g的环己烷继续反应，当反应釜内压力降到2MPa时停止反应。将反应体系离心后收集固相，洗涤、干燥即得到偏氟乙烯-三氟氯乙烯聚合物。
2)正极极片的制备
将3990g磷酸铁锂，40.8g的偏氟乙烯-三氟氯乙烯共聚物粘结剂，49.4g的乙炔黑在行星式搅拌罐中，公转转速25r/min，搅拌30min，其中粘结剂的质量分数为1％，基于正极膜层的总质量计；
在搅拌罐中加入2.4kg的N-甲基吡咯烷酮(NMP)溶液，公转速度25r/min，自转速度900r/min，搅拌70min；
在搅拌罐中加入12.3g聚乙烯吡咯烷酮分散剂，以公转速度25r/min，自转速度1250r/min，搅拌60min；
搅拌结束，测试浆料粘度，粘度控制在8000～15000mpa·s。
如粘度偏高，添加NMP溶液使之降低到上述粘度区间后按照公转速度25r/min，自转速度1250r/min，搅拌30min，得到正极浆料。将制得的正极浆料刮涂到涂碳铝箔上面，刮涂重量单面500mg/(1540mm2)，110℃烘烤15min，冷压到压密密度为2.7g/cm3后裁剪成直径15mm的圆片，即得到正极极片。
3)负极极片
以金属锂片作为负极极片。
4)隔离膜
以聚丙烯膜作为隔离膜。
5)电解液的制备
在氩气气氛手套箱中(H2O<0.1ppm，O2<0.1ppm)，将有机溶剂碳酸乙烯酯(EC)/碳酸甲乙酯(EMC)按照体积比3/7混合均匀，加入LiPF6锂盐溶解于有机溶剂中，搅拌均匀，配置1M LiPF6EC/EMC溶液得到电解液。
6)电池的制备
将实施例1中的正极极片、负极极片、隔离膜和电解液在扣电箱中组装成扣式电池。
实施例2～6
与实施例1基本相同，区别在于，分别将聚合反应时间调整为8h、10h、11h、11.5h、12h，并且分别将环己烷的质量调整为25g、20g、18.5g、16.5g、15g，具体参数如表1所示。
实施例7～10
与实施例1基本相同，区别在于，保持加入的偏氟乙烯和三氟氯乙烯单体总量不变，调整三氟氯乙烯的质量分数，基于偏氟乙烯和三氟氯乙烯单体的总质量计，具体参数如表1所示。
实施例11～14
与实施例1基本相同，区别在于，调整了偏氟乙烯-三氟氯乙烯共聚物粘结剂的质量分数，基于正极膜层的总质量计，具体参数如表1所示。
实施例15～16
与实施例1基本相同，区别在于，将0.06kg三氟氯乙烯分别替换成0.03kg三氟氯乙烯和0.03kg四氟乙烯，0.02kg三氟氯乙烯、0.02kg四氟乙烯和0.02kg六氟丙烯。
实施例17～18
与实施例3基本相同，区别在于，将0.06kg三氟氯乙烯分别替换成0.03kg三氟氯乙烯和0.03kg四氟乙烯，0.02kg三氟氯乙烯、0.02kg四氟乙烯和0.02kg六氟丙烯。
实施例19～20
与实施例12基本相同，区别在于，将0.06kg三氟氯乙烯分别替换成0.03kg三氟氯乙烯和0.03kg四氟乙烯，0.02kg三氟氯乙烯、0.02kg四氟乙烯和0.02kg六氟丙烯。
实施例21～22
与实施例1基本相同，区别在于，将0.06kg三氟氯乙烯分别替换成0.06kg四氟乙烯，0.06kg六氟丙烯。
对比例1
与实施例1基本相同，将聚合反应的反应压力调整为5MPa，反应温度调整为38℃，反应时间调整为3h，环己烷的质量调整为42g，具体参数如表1所示。
对比例2
与实施例1基本相同，区别在于，将聚合温度调整为35℃，环己烷的质量调整为40g，聚合单体只有1kg偏氟乙烯单体，具体参 数如表1所示。
对比例3
与实施例1基本相同，区别在于，将聚合反应的反应时间调整为5h，环己烷的质量调整为36g，聚合单体只有1kg偏氟乙烯，具体参数如表1所示。
对比例4
与实施例1基本相同，该粘结剂为聚偏氟乙烯，购买于东阳光公司，型号为701A牌号，并调整粘结剂的质量分数为2.5％，基于正极膜层的总质量计，具体参数如表1所示。
对比例5
与实施例1基本相同，区别在于，聚合单体只有1kg偏氟乙烯，具体参数如表1所示。
对比例6
与实施例3基本相同，聚合单体只有1kg偏氟乙烯，具体参数如表1所示。
对比例7
与实施例12基本相同，聚合单体只有1kg偏氟乙烯，具体参数如表1所示。
二、性能测试
1、粘结剂性质测试
1)重均分子量测试
采用Waters 2695 Isocratic HPLC型凝胶色谱仪(示差折光检测器2141)。以质量分数为3.0％的聚苯乙烯溶液试样做参比，选择匹配的色谱柱(油性：Styragel HT5DMF7.8*300mm+Styragel HT4)。用纯化后的N-甲基吡咯烷酮(NMP)溶剂配置3.0％的粘结剂胶液，配置好的溶液静置一天，备用。测试时，先用注射器吸取四氢呋喃，进行冲洗，重复几次。然后吸取5ml实验溶液，排除注射器中的空气，将针尖擦干。最后将试样溶液缓缓注入进样口。待示数稳定后获取数据，读取重均分子量。
2)多分散系数测试
采用Waters 2695 Isocratic HPLC型凝胶色谱仪(示差折光检测器2141)。以质量分数为3.0％的聚苯乙烯溶液试样做参比，选择匹配的色谱柱(油性：Styragel HT5DMF7.8*300mm+Styragel HT4)。用纯化后的N-甲基吡咯烷酮(NMP)溶剂配置3.0％的粘结剂胶液，配置好的溶液静置一天，备用。测试时，先用注射器吸取四氢呋喃，进行冲洗，重复几次。然后吸取5ml实验溶液，排除注射器中的空气，将针尖擦干。最后将试样溶液缓缓注入进样口。待示数稳定后获取数据。分别读取重均分子量a和数均分子量b。多分散系数＝a/b。
3)Dv50测试
参照GB/T 19077-2016粒度分布激光衍射法，用50ml烧杯称量0.1g～0.13g的粘结剂粉料，在称取5g无水乙醇，加入到装有粘结剂粉料的烧杯中，放入长度约2.5mm的搅拌子，并用保鲜膜密封。将样品放入超声机超声5min，转移到磁力搅拌机用500r/min的速度搅拌20min以上，每批次产品抽取2个样品测试取平均值。采用激光粒度分析仪进行测定，如英国马尔文仪器有限公司的Mastersizer2000E型激光粒度分析仪进行测试。
4)结晶度测试
将0.5g粘结剂置于铝制干锅中，抖平，盖上坩埚盖子，在氮气气氛下，以50ml/min的吹扫气，以70ml/min的保护气，升温速率为10℃/min，测试温度范围-100℃～400℃，利用美国TA仪器型号为Discovery 250的差示扫描量热仪(DSC)进行测试并消除热历史。
此测试将会得到粘结剂的DSC/(Mw/mg)随温度变化曲线，并进行积分，峰面积即为粘结剂的熔融焓ΔH(J/g)，粘结剂结晶度＝ΔH/(ΔHm100％)*100％，其中ΔHm100％为聚偏氟乙烯的标准熔融焓(晶态熔化热)，ΔHm100％＝104.7J/g。
5)粘结剂粘度测试
用500ml烧杯分别称取14g聚合物和336g N-甲基吡咯烷酮(NMP)，使用力辰高速研磨机搅拌分散，转速800r/min，搅拌时间120min后超声震荡30min去除气泡。在室温下，使用力辰科技NDJ-5S旋转粘度计进行测试，选用3号转子***胶液，保证转子液面标 志和胶液液面相平，以12r/min的转子转速测试粘度，6min后读取粘度数据即可。
2、极片性能测试
1)平均辊压次数测试
冷压后的极片沿横向方向取样，可以为横向宽度为4cm，纵向长度为25cm，面积为100cm2的样品样本数3条，将样品按25cm纵向方向对折预对折，将预对折的式样放置与实验台平面，用2kg的圆筒辊进行辊压1次后，对灯光查看是否有漏光点，有漏光点样品不符合要求，无漏光点记录辊压次数，并对实验样品沿纵向折痕处反折，折痕对光观察，直至出现透光点并记录辊压次数n1。重复上述操作得到第二条、第三条的透光辊压次数n2、n3，计算平均辊压次数＝(n1+n2+n3)/3。
2)粘结力测试
参考GB-T2790-1995国标《胶粘剂180°剥离强度实验方法》，本申请实施例和对比例的粘结力测试过程如下：
用刀片截取宽度为30mm，长度为100-160mm的极片试样，将专用双面胶贴于钢板上，胶带宽度20mm，长度90-150mm。将前面截取的极片试样的正极膜层面贴在双面胶上，后用2kg压辊沿同一个方向滚压三次。
将宽度与极片试样等宽，长度为250mm的纸带固定于极片集流体上，并且用皱纹胶固定。
打开三思拉力机电源(灵敏度为1N)，指示灯亮，调整限位块到合适位置，将钢板未贴极片试样的一端用下夹具固定。将纸带向上翻折，用上夹具固定，利用拉力机附带的手动控制器上的“上行”和“下行”按钮调整上夹具的位置。然后进行测试并读取数值。将极片受力平衡时的力除以胶带的宽度作为单位长度的极片的粘结力，以表征正极膜层与集流体之间的粘结强度，得到如附图1所示的实施例1和对比例4的粘结力-位移图。
3、电池性能测试
1)电池容量保持率测试
电池容量保持率测试过程如下：在25℃下，将扣式电池以1/3C恒流充电至3.65V，再以3.65V恒定电压充电至电流为0.05C，搁置5min，再以1/3C放电至2.5V，所得容量记为初始容量C0。对上述同一个电池重复以上步骤，并同时记录循环第n次后电池的放电容量Cn，则每次循环后电池容量保持率Pn＝(Cn/C0)×100％，以P1、P2……P500这500个点值为纵坐标，以对应的循环次数为横坐标，得到电池容量保持率与循环次数的曲线图。附图2所示的实施例1和对比例4的电池容量保持率与循环次数的曲线图。
该测试过程中，第一次循环对应n＝1、第二次循环对应n＝2、……第500次循环对应n＝500。表1中实施例1～20或对比例1～7对应的电池容量保持率数据是在上述测试条件下循环500次之后测得的数据，即P500的值。
上述实施例1～20和对比例1～7中得到粘结剂、极片和电池进行性能测试结果如表1所示。
三、各实施例、对比例测试结果分析
按照上述方法分别制备各实施例和对比例的电池，并测量各项性能参数，结果见下表1。
表1实施例1～22和对比例1～7的参数与性能测试表


图1为实施例1与对比例4的粘结力-位移图，从图中可以看出，在相同位移时，实施例1的粘结力明显高于对比例4的粘结力，表明在粘结剂添加量较低的情况下，该偏氟乙烯-三氟氯乙烯共聚物的粘结剂使得极片具有优异的粘结力。图2为实施例1与对比例4的电池容量保持率与循环次数的曲线图，从图中可以看出，在电池循环500次后，实施例1的循环容量保持率明显高于对比例4，表明在粘结剂添加量较低的情况下，该偏氟乙烯-三氟氯乙烯共聚物粘结剂能够提高电池在循环过程中的循环容量保持率，有效改善传统技术中高用量粘结剂带来的极片和电池性能受损的情况。
根据上述结果可知，实施例1～22中的粘结剂均包含聚合物，聚合物包含衍生自偏氟乙烯的结构单元，还包含衍生自三氟氯乙烯、四氟乙烯、六氟丙烯的结构单元中的任意一种，且该聚合物的重均分子量为180万～500万。从实施例1～10、实施例15～18、实施例21～22和对比例1的对比，从实施例12、实施例19、实施例20和对 比例2～3的对比可知，以该重均分子量180万～500万的聚合物作为粘结剂能够在低添加量下使得极片兼具优异的粘结力和柔性，进而提高电池在循环过程中的容量保持率。
从实施例1、实施例6～10、实施例15～16、实施例21～22和对比例5的对比，从实施例3、实施例17～18和对比例6的对比，从实施例12、实施例19～20和对比例7的对比可知，高分子量粘结剂中共聚单体的引入能够在不明显降低极片粘结力的情况下，提高极片的柔韧性，减少在卷绕和热压工序中出现断裂或漏光风险，提高电池的安全性能。
实施例1～22与对比例4相比，在粘结剂添加量较低的情况下，重均分子量为150万～500万的偏氟乙烯-三氟氯乙烯共聚物或偏氟乙烯-三氟氯乙烯-四氟乙烯共聚物或偏氟乙烯-三氟氯乙烯-四氟乙烯-六氟丙烯共聚物或偏氟乙烯-三氟氯乙烯-六氟丙烯共聚物或偏氟乙烯-四氟乙烯-六氟丙烯共聚物或偏氟乙烯-四氟乙烯共聚物或偏氟乙烯-六氟丙烯共聚物粘结剂使得极片具有优异的柔韧性和粘结力，进而能够提高电池在循环过程中的容量保持率，有效改善了传统技术中高用量粘结剂带来的极片和电池性能受损的情况。
从实施例1、实施例7～9和实施例10对比可知，当偏氟乙烯-三氟氯乙烯共聚物中的三氟氯乙烯的质量分数0.5％～15％，基于偏氟乙烯-三氟氯乙烯共聚物总质量计时，该粘结剂使得极片兼具优异的柔韧性和良好的粘结力，使得电池在循环过程中保持良好的容量性能。
从实施例1～22中可知，多分散系数为2～2.3的偏氟乙烯-三氟氯乙烯共聚物或偏氟乙烯-三氟氯乙烯-四氟乙烯共聚物或偏氟乙烯-三氟氯乙烯-四氟乙烯-六氟丙烯共聚物或偏氟乙烯-三氟氯乙烯-六氟丙烯共聚物或偏氟乙烯-四氟乙烯-六氟丙烯共聚物或偏氟乙烯-四氟乙烯共聚物或偏氟乙烯-六氟丙烯共聚物粘结剂可以提高极片的柔韧性，并且使得电池具有良好的粘结力。从实施例1～6中可知，多分散系数为2.1～2.2的偏氟乙烯-三氟氯乙烯共聚物粘结剂可以提高极片的柔韧性，并且使得电池具有良好的粘结力。
从实施例1～22中得知，Dv50粒径为50μm～160μm的偏氟乙烯 -三氟氯乙烯共聚物或偏氟乙烯-三氟氯乙烯-四氟乙烯共聚物或偏氟乙烯-三氟氯乙烯-四氟乙烯-六氟丙烯共聚物或偏氟乙烯-三氟氯乙烯-六氟丙烯共聚物或偏氟乙烯-四氟乙烯-六氟丙烯共聚物或偏氟乙烯-四氟乙烯共聚物或偏氟乙烯-六氟丙烯共聚物粘结剂可以提高极片的柔韧性，并且使得电池具有良好的粘结力。从实施例1～3和实施例4～6对比可知，当偏氟乙烯-三氟氯乙烯共聚物的Dv50粒径为50μm～100μm，极片的柔韧性可以进一步提高。
从实施例1～22中得知，结晶度为34％～42％的偏氟乙烯-三氟氯乙烯共聚物或偏氟乙烯-三氟氯乙烯-四氟乙烯共聚物或偏氟乙烯-三氟氯乙烯-四氟乙烯-六氟丙烯共聚物或偏氟乙烯-三氟氯乙烯-六氟丙烯共聚物或偏氟乙烯-四氟乙烯-六氟丙烯共聚物或偏氟乙烯-四氟乙烯共聚物或偏氟乙烯-六氟丙烯共聚物粘结剂可以提高极片的柔韧性，并且使得电池具有良好的粘结力。从实施例1、实施例2和实施例3～6对比，从实施例1、实施例9和实施例7～8、实施例10对比可知，当偏氟乙烯-三氟氯乙烯共聚物的结晶度为35％～40％，该粘结剂可以提高极片的柔韧性，并且使得电池具有良好的粘结力。
从实施例1～22中得知，当偏氟乙烯-三氟氯乙烯共聚物或偏氟乙烯-三氟氯乙烯-四氟乙烯共聚物或偏氟乙烯-三氟氯乙烯-四氟乙烯-六氟丙烯共聚物或偏氟乙烯-三氟氯乙烯-六氟丙烯共聚物或偏氟乙烯-四氟乙烯-六氟丙烯共聚物或偏氟乙烯-四氟乙烯共聚物或偏氟乙烯-六氟丙烯共聚物粘结剂溶于N-甲基吡咯烷酮制得的质量含量为4％的粘结剂溶液的粘度为2400mPa·s～5000mPa·s。该粘结剂在低添加量下，就具有足够的粘度，进而能够保证极片在粘结剂低添加的情况下就具有足够的粘结力。
从实施例1、7～9和实施例10对比、实施例1～4和实施例5～6可知，当偏氟乙烯-三氟氯乙烯共聚物溶于N-甲基吡咯烷酮制得的粘结剂溶液的粘度为2500mPa·s～4000mPa·s，且该粘结剂溶液中，粘结剂的质量百分含量为4％。该粘结剂在低添加量下即具有足够的粘度，能够保证极片在粘结剂低添加量下的粘结力。
从实施例1～6和对比例1对比可知，当偏氟乙烯与三氟氯乙烯 的聚合反应的反应压力为6MPa～8MPa，反应温度是45℃～60℃，反应时间为6h～12h，制备的偏氟乙烯-三氟氯乙烯共聚物的分子量为180万～500万，该粘结剂可以使得极片兼具优异的柔韧性和粘结力，能够提高电池在循环过程中的容量保持率。
从实施6、实施例12～13和实施例11、实施例14对比可知，当偏氟乙烯-三氟氯乙烯共聚物的粘结剂的质量分数为0.8％～1％，基于正极膜层的总质量计时，该粘结剂可以使得极片兼具优异的柔韧性和粘结力。
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 (20)

  1. 一种粘结剂，其特征在于，所述粘结剂为含有如式I、式II所示的结构单元的聚合物，
    其中，R1选自氟、氯、三氟甲基中的一种或多种，所述聚合物的重均分子量为180万～500万。
  2. 根据权利要求1所述的粘结剂，其特征在于，所述式II所示的结构单元的质量分数0.5％～15％，基于所述聚合物的总质量计。
  3. 根据权利要求1所述的粘结剂，其特征在于，所述聚合物的多分散系数为2～2.3。
  4. 根据权利要求1至3中任一项所述的粘结剂，其特征在于，所述聚合物的Dv50粒径为50μm～160μm。
  5. 根据权利要求1至3中任一项所述的粘结剂，其特征在于，所述聚合物的结晶度为34％～42％。
  6. 根据权利要求1至3中任一项所述的粘结剂，其特征在于，所述聚合物溶于N-甲基吡咯烷酮制得的含有质量含量为4％的所述聚合物的胶液的粘度为2400mPa·s～5000mPa·s。
  7. 根据权利要求1至3中任一项所述的粘结剂，其特征在于，所述聚合物为偏氟乙烯-三氟氯乙烯共聚物、偏氟乙烯-三氟氯乙烯-四氟乙烯共聚物、偏氟乙烯-三氟氯乙烯-六氟丙烯共聚物、偏氟乙烯-四氟乙烯-六氟丙烯共聚物、偏氟乙烯-三氟氯乙烯-四氟乙烯-六氟丙烯共聚物、偏氟乙烯-四氟乙烯共聚物、偏氟乙烯-六氟丙烯共聚物中的一种或多种。
  8. 一种粘结剂的制备方法，其特征在于，包括以下步骤：
    在可聚合条件下，将式III所示的单体和式Ⅳ所示的单体进行聚合反应制备聚合物；
    其中，R2选自氟、氯、三氟甲基中的一种或多种，所述聚合物的重均分子量为180万～500万。
  9. 根据权利要求8所述的制备方法，其特征在于，所述式Ⅳ所示单体的质量含量为0.5％～15％，基于所述式III和式Ⅳ所示单体的总质量计。
  10. 根据权利要求8所述的制备方法，其特征在于，所述式Ⅳ所示单体为三氟氯乙烯、四氟乙烯、六氟丙烯中的一种或多种。
  11. 根据权利要求8至10中任一项所述的制备方法，其特征在于，所述聚合反应包括以下步骤：
    将式III和式Ⅳ所示的单体在非反应性气体氛围、6MPa～8MPa的反应压力、45℃～60℃的反应温度下反应6小时～12小时；
    加入链转移剂，待反应体系中压力降至2MPa～2.5MPa，停止反应，固液分离，保留固相。
  12. 根据权利要求8至10中任一项所述的制备方法，其特征在于，所述制备方法还包括以下步骤：
    向容器中加入溶剂和分散剂，对所述容器抽真空后充入非反应性气体；
    向所述容器中加入引发剂和pH调节剂，调节pH值至6.5～7，然后加入式III和式Ⅳ所示的单体，使所述容器中的压力达到6MPa～8MPa；
    搅拌30分钟～60分钟后，升温至45℃～60℃，进行聚合反应。
  13. 一种正极极片，包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，所述正极膜层包括正极活性材料、导电剂和权利要求1至7中任一项所述的粘结剂或如权利要求8至12中任一项所述的制备方法制备的粘结剂。
  14. 根据权利要求13所述的正极极片，其特征在于，所述粘结剂的质量分数为0.8％～1％，基于所述正极膜层的总质量计。
  15. 根据权利要求13或14所述的正极极片，其特征在于，所述正极活性材料为含锂的过渡金属氧化物。
  16. 根据权利要求13或14所述的正极极片，其特征在于，所述正极活性材料为磷酸铁锂及其改性材料、锂镍钴锰氧化物及其改性材料中的至少一种，所述改性材料是通过掺杂、导电碳包覆、导电金属包覆、导电聚合物包覆中的一种或多种改性方式制备的。
  17. 一种二次电池，其特征在于，包括电极组件和电解液，所述电极组件包括隔离膜、负极极片和如权利要求13至16中任一项所述的正极极片。
  18. 一种电池模块，其特征在于，包括权利要求17所述的二次电池。
  19. 一种电池包，其特征在于，包括权利要求18所述的电池模块。
  20. 一种用电装置，其特征在于，包括选自权利要求17所述的二次电池、权利要求18所述的电池模块或权利要求19所述的电池包中的至少一种。
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Publication number Priority date Publication date Assignee Title
CN117638068A (zh) * 2022-08-30 2024-03-01 宁德时代新能源科技股份有限公司 粘结剂、制备方法、正极浆料、二次电池、电池模块、电池包及用电装置
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Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103891001A (zh) * 2011-10-21 2014-06-25 帝人株式会社 非水系二次电池用隔膜及非水系二次电池
CN104285320A (zh) * 2012-05-21 2015-01-14 大金工业株式会社 电极合剂
CN105754027A (zh) * 2014-12-15 2016-07-13 浙江蓝天环保高科技股份有限公司 一种偏氟乙烯聚合物、其制备方法及应用
CN105794019A (zh) * 2013-12-06 2016-07-20 大金工业株式会社 二次电池用隔膜和二次电池
WO2017082259A1 (ja) * 2015-11-11 2017-05-18 帝人株式会社 非水系二次電池用セパレータ及び非水系二次電池
WO2022114044A1 (ja) * 2020-11-30 2022-06-02 株式会社クレハ フッ化ビニリデン共重合体組成物およびその製造方法、ポリマー分散液、非水電解質二次電池用電極、非水電解質二次電池用電解質層、ならびに非水電解質二次電池
CN115133034A (zh) * 2022-08-30 2022-09-30 宁德时代新能源科技股份有限公司 粘结剂、制备方法、正极极片、二次电池及用电装置

Family Cites Families (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP4253051B2 (ja) * 1997-12-26 2009-04-08 株式会社クレハ 非水系電池用電極合剤および非水系電池
JP4226704B2 (ja) * 1998-11-05 2009-02-18 株式会社クレハ 非水系電気化学素子電極用バインダー溶液、電極合剤、電極および電気化学素子
FR2812294B1 (fr) * 2000-07-31 2003-01-17 Solvay Polymeres du fluorure de vinylidene, procede pour les fabriquer et utilisation de ceux-ci
JP2006059771A (ja) * 2004-08-24 2006-03-02 Sanyo Electric Co Ltd 非水電解質電池
CN104497190B (zh) * 2014-12-29 2016-09-21 浙江孚诺林化工新材料有限公司 一种用于锂离子电池电极材料粘结剂的偏氟乙烯聚合物的制备方法
WO2016148304A1 (ja) * 2015-03-18 2016-09-22 日本ゼオン株式会社 二次電池正極バインダー組成物、二次電池正極用スラリー組成物、二次電池用正極および二次電池
CN106674412B (zh) * 2016-12-26 2018-12-18 山东华夏神舟新材料有限公司 一种1,1-二氟乙烯类聚合物及其制备方法
WO2018169789A1 (en) * 2017-03-13 2018-09-20 Arkema Inc. Polymer binder
JP6959751B2 (ja) * 2017-03-31 2021-11-05 株式会社クレハ フッ化ビニリデン共重合体粒子及びその利用
JP7060986B2 (ja) * 2018-03-15 2022-04-27 株式会社クレハ バインダー組成物、非水電解質二次電池用電極を製造するための合剤、非水電解質二次電池用の電極および非水電解質二次電池
CN112159493B (zh) * 2020-08-26 2022-05-13 浙江衢州巨塑化工有限公司 一种锂电池粘结剂用共聚型pvdf树脂的制备方法
WO2022124253A1 (ja) * 2020-12-07 2022-06-16 ダイキン工業株式会社 共重合体、結着剤、成形品および共重合体の製造方法

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103891001A (zh) * 2011-10-21 2014-06-25 帝人株式会社 非水系二次电池用隔膜及非水系二次电池
CN104285320A (zh) * 2012-05-21 2015-01-14 大金工业株式会社 电极合剂
CN105794019A (zh) * 2013-12-06 2016-07-20 大金工业株式会社 二次电池用隔膜和二次电池
CN105754027A (zh) * 2014-12-15 2016-07-13 浙江蓝天环保高科技股份有限公司 一种偏氟乙烯聚合物、其制备方法及应用
WO2017082259A1 (ja) * 2015-11-11 2017-05-18 帝人株式会社 非水系二次電池用セパレータ及び非水系二次電池
WO2022114044A1 (ja) * 2020-11-30 2022-06-02 株式会社クレハ フッ化ビニリデン共重合体組成物およびその製造方法、ポリマー分散液、非水電解質二次電池用電極、非水電解質二次電池用電解質層、ならびに非水電解質二次電池
CN115133034A (zh) * 2022-08-30 2022-09-30 宁德时代新能源科技股份有限公司 粘结剂、制备方法、正极极片、二次电池及用电装置

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