WO2024045505A1 - Binder composition, positive electrode slurry, secondary battery, battery module, battery pack, and electric device - Google Patents

Binder composition, positive electrode slurry, secondary battery, battery module, battery pack, and electric device Download PDF

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Publication number
WO2024045505A1
WO2024045505A1 PCT/CN2023/076249 CN2023076249W WO2024045505A1 WO 2024045505 A1 WO2024045505 A1 WO 2024045505A1 CN 2023076249 W CN2023076249 W CN 2023076249W WO 2024045505 A1 WO2024045505 A1 WO 2024045505A1
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polymer
positive electrode
binder
battery
average molecular
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PCT/CN2023/076249
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French (fr)
Chinese (zh)
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李�诚
曾子鹏
刘会会
王景明
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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 WO2024045505A1 publication Critical patent/WO2024045505A1/en

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
    • C08F114/00—Homopolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen
    • C08F114/18—Monomers containing fluorine
    • C08F114/22—Vinylidene fluoride
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • 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
    • 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
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • 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 a positive electrode slurry and a preparation method thereof, secondary batteries, battery modules, battery packs and electrical devices.
  • 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.
  • energy storage power systems such as hydraulic, thermal, wind and solar power stations
  • electric tools such as electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace.
  • secondary batteries As the application scope of secondary batteries becomes more and more extensive, people have also put forward higher requirements for the energy density, cycle performance and safety performance of secondary batteries.
  • the binder composition includes a dispersant and a binder.
  • the dispersant includes a first compound with a weight average molecular weight of 0.5 million to 150.000.
  • Polymers, binders including weight average molecular weight of 700,000 to 110 The second polymer has a weight average molecular weight of 1.3 million to 3 million, and the first polymer, the second polymer and the third polymer are all polymers containing structural units represented by formula I,
  • R 1 and R 2 are each independently selected from hydrogen, fluorine, chlorine or trifluoromethyl.
  • the binder composition provided by this application uses a first polymer with a weight average molecular weight of 0.5 million to 150.000 as a dispersant, which improves the dispersibility and processability of the cathode slurry and significantly reduces the electrode film layer resistance and Improve battery cycle performance.
  • the cathode slurry provided by this application uses a second polymer and a third polymer with different weight average molecular weights as a binder.
  • the addition amount of the binder is The electrode piece can have good adhesion under relatively few conditions, which helps to reduce the amount of binder in the electrode piece, improve the loading capacity of the positive active material of the electrode piece and the energy density of the battery; and, the second polymer and The combined use of the third polymer also improves the crystallinity of the binder and increases the flexibility of the pole piece.
  • the first polymer, the second polymer and the third polymer are all halogenated hydrocarbon polymers, each independently selected from polytetrafluoroethylene, polyvinylidene fluoride, One or more of vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene, and polychlorotrifluoroethylene.
  • the polymer has stable chemical properties, excellent electrical properties, and good mechanical properties, which is beneficial to the preparation of a film layer with appropriate flexibility and hardness.
  • the particles of the first polymer have a median diameter Dv50 of 0.5 ⁇ m to 5 ⁇ m.
  • the particle size of the first polymer particles within a suitable range is beneficial to dissolution in the positive electrode slurry solvent, such as N-methylpyrrolidone, and reduces the processing difficulty of the glue solution.
  • the first polymer is dissolved in N-methylpyrrolidone to prepare a first glue liquid. Based on the total mass of the first glue liquid, when the mass content of the first polymer is 7 %, the viscosity of the first glue liquid is 20-180 mPa ⁇ s.
  • the viscosity of the first polymer within an appropriate range helps to wet and depolymerize the cathode active material powder particles, reduce the agglomeration of the cathode active material and block the filter, and improve the positive electrode active material.
  • the dispersion performance of the electrode slurry improves the solid content of the cathode slurry and the uniformity of the electrode sheet coating, thereby increasing the energy density of the battery.
  • the particles of the second polymer have a median diameter Dv50 of 15 to 25 ⁇ m.
  • the particle size of the second polymer particles within a suitable range is beneficial to its dissolution in the positive electrode slurry solvent, such as N-methylpyrrolidone, reducing the processing difficulty of the glue solution and improving the processing efficiency.
  • the second polymer is dissolved in N-methylpyrrolidone to prepare a second glue liquid. Based on the total mass of the second glue liquid, when the mass content of the second polymer is 7 %, the viscosity of the second glue liquid is 2500-4000 mPa ⁇ s.
  • the viscosity of the second polymer within an appropriate range can reduce the orderliness of the third polymer molecules and reduce the crystallinity of the third polymer molecules.
  • the particles of the third polymer have a median diameter Dv50 of 30 ⁇ m to 100 ⁇ m.
  • the particle size of the third polymer particles is within a suitable range, which is beneficial to its dissolution in the positive electrode slurry solvent, reduces the processing difficulty of the glue solution, and improves the processing efficiency of the electrode piece.
  • the third polymer is dissolved in N-methylpyrrolidone to prepare a third glue liquid. Based on the total mass of the third glue liquid, when the mass content of the third polymer is 4 %, the viscosity of the third glue liquid is 1500-5000 mPa ⁇ s.
  • the viscosity of the third polymer is within a suitable range, and the binder has good bonding properties.
  • the electrode piece can have excellent bonding force, which helps to increase the loading capacity of the positive active material and the battery. Energy Density.
  • the third polymer has a polydispersity coefficient of 2 to 2.3.
  • the third polymer has a polydispersity coefficient of 2.1 to 2.2.
  • the polydispersity coefficient of the third polymer within the above range helps to maintain the stability of the viscosity of the third polymer, thereby improving the stability of pole piece production.
  • the mass ratio of the second polymer and the third polymer is 1:9 to 8:2.
  • the mass ratio of the second polymer to the third polymer is within the above range, it can be ensured that the pole piece has improved flexibility while having good adhesion.
  • the binder has a crystallinity of 25% to 44%.
  • the crystallinity of the binder within a suitable range can improve the flexibility of the pole piece, which is beneficial to the processing of secondary batteries and reduces the safety hazards of secondary batteries.
  • the melting enthalpy of the binder is 25 J/g to 45 J/g.
  • the melting enthalpy of the binder is within a suitable range, the crystallinity of the binder can be moderate, so that the pole piece has both excellent flexibility and adhesive force.
  • a second aspect of the present application provides a cathode slurry, which includes a cathode active material, a conductive agent, and a binder composition in any embodiment.
  • the mass content of the dispersant is 0.05% to 1%, based on the total mass of solid matter of the positive electrode slurry.
  • the mass content of the dispersant within a suitable range can improve the dispersion of the cathode slurry and has no or minimal impact on the bonding performance of the binder.
  • the mass content of the binder is 0.6% to 1.2%, based on the total mass of solid matter of the positive electrode slurry.
  • the mass content of the binder within an appropriate range can ensure that the electrode piece has good adhesion, avoid direct contact between the positive active material and the electrolyte, reduce the occurrence of side reactions, and reduce the safety hazards of secondary batteries; at the same time, the adhesive
  • the addition of the binder is relatively low, which helps to reduce the film resistance of the electrode sheet, increase the loading capacity of the positive active material and increase the energy density of the battery.
  • the positive active material is a lithium-containing transition metal oxide, which may be lithium iron phosphate or lithium nickel cobalt manganese oxide, or their doping modified materials, conductive carbon coating modifications At least one of a conductive metal-coated modified material or a conductive polymer-coated modified material.
  • a lithium-containing transition metal oxide which may be lithium iron phosphate or lithium nickel cobalt manganese oxide, or their doping modified materials, conductive carbon coating modifications At least one of a conductive metal-coated modified material or a conductive polymer-coated modified material.
  • a third aspect of the present application provides a preparation method of cathode slurry, which preparation method includes the following steps:
  • Step 1 Mix the positive active material, conductive agent and binder evenly; the binder includes a second polymer with a weight average molecular weight of 700,000 to 1.1 million and a third polymer with a weight average molecular weight of 1.3 million to 3 million. polymer,
  • Step 2 Add a dispersant and stir to obtain a positive electrode slurry.
  • the dispersant includes a first polymer with a weight average molecular weight of 0.5 million to 150.000.
  • the first polymer and the third polymer are The second polymer and the third polymer are both prepared by polymerizing at least one monomer represented by Formula II under polymerizable conditions,
  • R 1 and R 2 are each independently selected from one or more types of hydrogen, fluorine, chlorine, and trifluoromethyl.
  • the binder By adding the binder first and then the dispersant, it is beneficial to achieve full mixing, adhesion/coating between the positive electrode active material, conductive agent and high molecular weight binder. By adding the dispersant later, the positive electrode activity can be effectively avoided. The sedimentation of substances and high molecular weight binders is conducive to simultaneously improving the dispersion and stability of the cathode slurry.
  • the method of preparing the first polymer includes the following steps:
  • At least one monomer represented by formula II a first initiator and a first solvent, perform a polymerization reaction at normal pressure and a reaction temperature of 55°C to 80°C for 2 hours to 8 hours, stop the reaction, separate solid and liquid, and retain solid phase to obtain the first polymer.
  • the preparation method of the first polymer has low raw material cost and mild reaction conditions, which is conducive to mass production of the dispersant.
  • the preparation method of the third polymer includes the following steps:
  • the monomer represented by formula II causes the reaction pressure to reach 6MPa ⁇ 8MPa, increase the temperature to 35°C ⁇ 60°C to perform the polymerization reaction for 6 hours ⁇ 10 hours;
  • the raw materials are easy to obtain and the reaction conditions are safe and controllable, which is conducive to the expanded production of the third polymer.
  • a fourth aspect of the present application provides a secondary battery, including a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte.
  • 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 is prepared from the positive electrode slurry described in any one of the second aspects of the application.
  • the fifth aspect of the present application provides a battery module, including the fourth aspect of the present application. of secondary batteries.
  • a sixth aspect of the present application provides a battery pack, including the battery module of the fifth aspect of the present application.
  • a seventh aspect of the present application provides an electrical device, including at least one selected from the secondary battery of the fourth aspect of the present application, the battery module of the fifth aspect of the present application, or the battery pack of the sixth aspect of the present application. kind.
  • FIG. 1 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG. 2 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 1 .
  • FIG. 3 is a schematic diagram of a battery module according to an embodiment of the present application.
  • Figure 4 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG. 5 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG. 4 .
  • FIG. 6 is a schematic diagram of a power consumption device using a secondary battery as a power source according to an embodiment of the present application.
  • range disclosed in this application is defined in the form of a lower limit and an upper limit.
  • the given range is defined by selecting a lower limit and an upper limit.
  • the selected lower limit and upper limit Determine the boundaries of a special 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.
  • the numerical range “a ⁇ b” represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers.
  • the numerical range “0 ⁇ 5" means that all real numbers between "0 ⁇ 5" have been listed in this article, and "0 ⁇ 5" is just an abbreviation of these numerical combinations.
  • a certain parameter is an integer ⁇ 2
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • step (c) means that step (c) may be added to the method in any order.
  • the method may include steps (a), (b) and (c). , may also include steps (a), (c) and (b), may also include steps (c), (a) and (b), etc.
  • condition "A or B” is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).
  • binders such as PVDF
  • Traditional binders such as PVDF, often require a high content (more than 2%) to meet the bonding strength requirements of the pole pieces, which limits the increase in active material loading in the pole pieces and is not conducive to the improvement of battery energy density.
  • a high amount of binder can easily cause the film layer at the corner of the innermost cathode to be broken due to insufficient tensile strength, resulting in light transmission of the pole piece, thereby causing the brittleness of the pole piece. (or brittle fracture) problem, reducing the safety and cycle performance of the battery.
  • the traditional binder has poor compatibility with the new generation of cathode active materials, the prepared slurry has poor dispersion and stability, and the cathode active materials in the pole piece are unevenly distributed, which limits the improvement of battery performance.
  • this application proposes a cathode slurry, which includes a cathode active material, a conductive agent, a dispersant and a binder.
  • the dispersant includes a third cathode slurry with a weight average molecular weight of 0.5 million to 150.000.
  • a polymer, the binder includes a second polymer with a weight average molecular weight of 700,000 to 1.1 million and a third polymer with a weight average molecular weight of 1.3 million to 3 million, the first polymer, the third polymer
  • Both the second polymer and the third polymer are polymers containing structural units represented by formula I,
  • R 1 and R 2 are each independently selected from hydrogen, fluorine, chlorine or trifluoromethyl.
  • positive electrode also refers to the "cathode” in a battery.
  • negative electrode also refers to the "anode” in a battery.
  • the term "dispersant” refers to a chemical compound, polymer or mixture that promotes uniform dispersion of material particles in a colloidal solution or colloidal dispersion.
  • binder refers to a chemical compound, polymer or mixture that tightly connects a solid object to another solid object.
  • binder also refers to the chemical compound, polymer or mixture that tightly connects the solid substances in the battery slurry into one body.
  • weight average molecular weight refers to the use of different molecular weights in the polymer. The sum of the weight fractions of molecules multiplied by their corresponding molecular weights.
  • 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 on the other hand also includes derivatives of aggregates of macromolecules formed by polymerization reactions which are obtainable by reaction, for example addition or substitution, of functional groups in said macromolecules and which may be chemically homogeneous or chemically A non-homogeneous compound or mixture.
  • the dispersant is used in battery cathode slurry to improve the dispersibility of the cathode slurry. In some embodiments, the dispersant can also be used in battery negative electrode slurry to improve the dispersibility of the negative electrode slurry.
  • the weight average molecular weight of the first polymer is 0.5 million to 150.000, the intermolecular force is relatively small, the adhesion and wetting properties are good, and the positive electrode in the positive electrode slurry can be well adhered.
  • Active materials prevent/reduce aggregation between positive electrode active materials; the first polymer is dispersed or suspended in the solvent (or dispersion medium) of the positive electrode slurry through electrostatic repulsion or steric hindrance, thereby making the positive electrode slurry
  • the dispersion of the material is significantly improved, and it does not settle after being placed for a certain period of time, which improves the stability of the positive electrode slurry and helps to increase the solid content of the slurry and the coating rate of the pole piece; the positive active material is evenly distributed in the pole piece The distribution is conducive to improving the electron conduction efficiency of the pole piece, reducing the film resistance of the battery pole piece, and improving the battery cycle performance.
  • the binder includes a second polymer with a weight average molecular weight of 700,000 to 1.1 million and a third polymer with a weight average molecular weight of 1.3 million to 3 million.
  • the third polymer has a high viscosity.
  • a small amount of the third polymer can be added to make the pole piece have good bonding force.
  • the outer film layer of the prepared pole piece is easily cracked due to insufficient plastic deformation stress of the binder during the hot pressing process of the battery.
  • the crack fracture refers to the fact that during the processing of the pole piece, the solid matter in the slurry is processed into a film layer that adheres to the current collector, and the pole piece (or bare cell) is formed by the innermost 1 to 2 turns of the cathode corner during hot pressing and shaping. Cracks are prone to occur, causing light transmission in the pole piece. The cracks and fractures of the pole piece cause the pole piece to lose powder and expose fresh aluminum foil. As the cycle proceeds, the electrolyte will decompose to produce hydrofluoric acid. Hydrofluoric acid will corrode the aluminum foil and reduce the electrochemical performance and cycle of the battery. performance.
  • current collector refers to any conductive substrate capable of conducting current to an electrode during discharge or charging of a secondary battery.
  • film layer refers to the coating formed after the positive electrode or negative electrode slurry is coated and dried.
  • the weight average molecular weight of the third polymer is greater than 3 million, although the increase in the viscosity of the binder will further reduce the amount of binder added, it will also aggravate the problem of uneven dispersion of the positive active material and affect the dispersion of the slurry. properties and stability, and ultimately lead to an increase in the resistance of the pole piece film and a decrease in battery cycle performance.
  • the weight average molecular weight of the third polymer is lower than 1.3 million, the viscosity of the binder decreases. Although the dispersion of the slurry is improved, the adhesive force of the pole piece is also reduced. In order to improve the binding force of the electrode piece, it is necessary to increase the amount of the third polymer and/or the second polymer. Increasing the amount of binder will reduce the loading of the positive active material in the electrode piece, thereby affecting the energy density of the battery.
  • the second polymer can be inserted into the regular chain segments of the third polymer molecule to reduce the orderliness of the molecular structure of the third polymer and reduce the crystallinity of the binder. This increases the plastic deformation stress of the film layer enough to prevent cracks and fractures during the hot pressing treatment of the pole piece, improves the flexibility of the pole piece, is conducive to improving the processability of the pole piece and reducing fracture (or brittle fracture) caused by cracks in the pole piece. ) brings potential battery safety hazards.
  • the resistance of the electrode sheet film layer will also increase and the battery cycle performance will decrease due to the increase in binder viscosity.
  • the difference in chain length between the second polymer molecule and the third polymer molecule is reduced.
  • the spatial structure of the third polymer molecule is not sufficient to accommodate the long chain of the second polymer molecule. After the two are mixed, The orderliness of the spatial structure of the third polymer molecule cannot be reduced, nor can the crystallinity of the binder be reduced.
  • the amount of the second polymer and/or the third polymer needs to be increased. It is beneficial to increase the loading capacity of the positive electrode active material in the pole piece; in addition, because the difference in molecular chain length of the second polymer and the third polymer is too large, the molecular chain of the second polymer cannot match the molecular chain of the third polymer. Effective physical entanglement/cross-linking is formed, which has a smaller impact on the crystallinity of the third polymer and cannot improve the plastic strain stress of the film layer and the flexibility of the pole piece.
  • a second polymer and a third polymer with a specific weight average molecular weight especially a second polymer with a weight average molecular weight of 700,000 to 1.1 million and a second polymer with a weight average molecular weight of 1.3 million to 3 million.
  • the combined use of the third polymer can reduce the amount of binder used in the existing technology.
  • the electrode piece can have good bonding force, which helps to improve the positive electrode activity in the electrode piece. Material loading capacity and battery energy density.
  • the combination of the second polymer and the third polymer also improves the crystallinity of the binder and increases the flexibility of the pole piece.
  • the first polymer, second polymer, and/or third polymer are soluble in oily solvents. In some embodiments, the first polymer, second polymer, and/or third polymer are soluble in an aqueous solvent.
  • oily solvents include dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, acetone, and dimethyl carbonate.
  • aqueous solvents include, but are not limited to, water.
  • the first polymer, the second polymer and the third polymer are all halogenated hydrocarbon polymers, each independently selected from polytetrafluoroethylene, polyvinylidene fluoride, One or more of a copolymer of vinylidene fluoride and hexafluoropropylene, a copolymer of vinylidene fluoride and tetrafluoroethylene, a copolymer of vinylidene fluoride and chlorotrifluoroethylene, and polychlorotrifluoroethylene.
  • halogenated hydrocarbon polymer refers to a polymer of halogen-substituted unsaturated hydrocarbons.
  • halogen refers to elements of the halogen family including fluorine, chlorine, bromine, and iodine.
  • the polymer has the characteristics of stable chemical properties and excellent electrical properties, and usually has little or very little swelling in the electrolyte of the battery. At the same time, the polymer has good mechanical properties, which is conducive to the preparation of a film layer with appropriate flexibility and hardness.
  • the particles of the first polymer have a median diameter Dv50 of 0.5 ⁇ m to 5 ⁇ m.
  • the median diameter Dv50 of the particles of the first polymer is 0.5 ⁇ 4.5 ⁇ m, 0.5 ⁇ 4 ⁇ m, 0.5 ⁇ 3.5 ⁇ m, 0.5 ⁇ 3 ⁇ m, 0.5 ⁇ 2.5 ⁇ m, 0.8 ⁇ 5 ⁇ m, 1 ⁇ 4 ⁇ m, 2 ⁇ 5 ⁇ m, or 2 ⁇ 4 ⁇ m.
  • the particle size of the first polymer within a suitable range is beneficial to dissolution in the positive electrode slurry solvent, such as N-methylpyrrolidone, and reduces the processing difficulty of the glue solution.
  • the term “median particle size Dv50” refers to the particle size corresponding to when the cumulative particle size distribution percentage of the measured sample reaches 50%. Its physical meaning is that the particle size is smaller than (or larger than) Yu) Its particles account for 50%.
  • the first polymer is dissolved in N-methylpyrrolidone to prepare a first glue solution. Based on the total mass of the first glue solution, when the mass content of the first polymer is 7 %, the viscosity of the first glue liquid is 20-180 mPa ⁇ s.
  • the first polymer is dissolved in N-methylpyrrolidone to prepare a first glue solution.
  • the viscosity of the first glue liquid is 30-180 mPa ⁇ s, 50-180 mPa ⁇ s, 20-160 mPa ⁇ s, 20-150 mPa ⁇ s, 30-120 mPa ⁇ s or 20-50 mPa ⁇ s.
  • the viscosity of the first polymer When the viscosity of the first polymer is higher than 180 mPa ⁇ s (mass content is 7%), its wettability with the positive active material is reduced, which is not conducive to dispersing the slurry; the first polymer with a viscosity within a suitable range has It helps to moisten and depolymerize the positive active material powder particles, reduce the agglomeration of positive active materials and filter clogging, improve the dispersion performance of the positive slurry, increase the solid content of the positive slurry and the uniformity of the pole piece coating, This in turn increases the energy density of the battery.
  • the particles of the second polymer have a median diameter Dv50 of 15 to 25 ⁇ m. In some embodiments, the particles of the second polymer have a median diameter Dv50 of 15 to 23 ⁇ m, 15 to 20 ⁇ m, 18 to 25 ⁇ m, or 20 to 25 ⁇ m.
  • the particle size of the second polymer within a suitable range is beneficial to its dissolution in the positive electrode slurry solvent, such as N-methylpyrrolidone, reducing the processing difficulty of the glue solution and improving the processing efficiency.
  • the second polymer is dissolved in N-methylpyrrolidone to prepare a second glue liquid. Based on the total mass of the second glue liquid, when the mass content of the second polymer is 7 %, the viscosity of the second glue liquid is 2500-4000 mPa ⁇ s.
  • the second polymer is dissolved in N-methylpyrrolidone to prepare a second glue liquid.
  • the viscosity of the second glue liquid is 2800 ⁇ 4000mPa ⁇ s, 3000 ⁇ 4000mPa ⁇ s, 3200 ⁇ 4000mPa ⁇ s, 3500 ⁇ 4000mPa ⁇ s, 2800 ⁇ 3800mPa ⁇ s or 2800 ⁇ 3500mPa ⁇ s.
  • the viscosity of the second polymer is higher than 4000mPa ⁇ s (mass content is 7%)
  • the The increase in intra-molecule or intermolecular forces is not conducive to the free swing of the second polymer molecular chain in the cathode slurry solvent, thereby affecting the physical cross-linking with the third polymer molecular chain; when the viscosity of the second polymer is lower than At 2800mPa ⁇ s, the adhesive performance of the adhesive will decrease.
  • the amount of adhesive added needs to be increased. This will increase the electrode piece film resistance and cause damage to the battery cycle performance. It is also not conducive to increasing the loading capacity of the positive active material in the pole piece.
  • the viscosity of the second polymer When the viscosity of the second polymer is within a suitable range, its molecular chains can overcome intramolecular or intermolecular forces to physically cross-link/entangle with the molecular chains of the third polymer, reducing the orderliness and stability of the third polymer molecules. Crystal regularity improves the flexibility of the binder.
  • the particles of the third polymer have a median diameter Dv50 of 30 ⁇ m to 100 ⁇ m. In some embodiments, the particles of the third polymer have a median diameter Dv50 of 30 ⁇ m to 80 ⁇ m, 30 ⁇ m to 60 ⁇ m, 40 ⁇ m to 80 ⁇ m, 50 ⁇ m to 80 ⁇ m, or 60 ⁇ m to 80 ⁇ m.
  • the third polymer has a high viscosity and usually has a low dissolution rate in the cathode slurry solvent, such as N-methylpyrrolidone.
  • the particle size of the third polymer within a suitable range is beneficial to reducing the processing difficulty of the glue and improving the electrode performance. chip processing efficiency.
  • the third polymer is dissolved in N-methylpyrrolidone to prepare a third glue liquid. Based on the total mass of the third glue liquid, when the mass content of the third polymer is 4 %, the viscosity of the third glue liquid is 1500-5000 mPa ⁇ s.
  • the third polymer is dissolved in N-methylpyrrolidone to prepare a third glue liquid.
  • the viscosity of the third glue liquid is 1700 ⁇ 4800mPa ⁇ s, 1700 ⁇ 4500mPa ⁇ s, 1700 ⁇ 4300mPa ⁇ s, 1700 ⁇ 4000mPa ⁇ s, 1700 ⁇ 3600mPa ⁇ s, 1700 ⁇ 3500mPa ⁇ s, 2000 ⁇ 4800mPa ⁇ s, 2500 ⁇ 4800mPa ⁇ s or 3600 ⁇ 4800mPa ⁇ s.
  • the viscosity of the third polymer is higher than 4800 mPa ⁇ s (mass content is 4%)
  • the bonding performance is improved, the dispersion of the cathode slurry will be further deteriorated and the cathode active material in the slurry will be unevenly distributed. It not only affects the processing performance of the pole piece, but also causes cracks, particle scratches, pinholes and other defects on the surface of the pole piece.
  • the viscosity of the third polymer is lower than 1700 mPa ⁇ s, the bonding performance of the binder is significantly reduced, and the solid matter in the slurry If the bonding force between the electrodes is insufficient, or the bonding force with the current collector is insufficient, cracking or demoulding defects may occur, seriously endangering the safety of the battery using the electrode piece.
  • the viscosity of the third polymer is within a suitable range, and the binder has good bonding properties. When the addition amount is low, the electrode piece can have excellent bonding force, which helps to increase the loading capacity of the positive active material and the battery. Energy Density.
  • the third polymer has a polydispersity coefficient of 2 to 2.3.
  • the third polymer has a polydispersity coefficient of 2.1 to 2.2.
  • the polydispersity coefficient of the third polymer within the above range helps to maintain the stability of the viscosity of the third polymer, thereby improving the stability of pole piece production.
  • the mass content of the dispersant is 0.05% to 1%, based on the total mass of solid matter of the cathode slurry.
  • the mass content of the dispersant is 0.1% to 1%, 0.2% to 1%, 0.3% to 1%, 0.4% to 1%, 0.6% to 1%, 0.05% to 0.8%, 0.05% to 0.6%, or 0.1% to 0.6%, based on the total mass of solid matter of the positive electrode slurry.
  • the mass content of the dispersant is less than 0.05%, because the content of the dispersant is too low, it cannot fully coat or adhere to the cathode active material in the cathode slurry, which is not conducive to the dispersion of the cathode active material and the cathode slurry powder
  • the body is prone to agglomeration, clogging of filters, etc., which affects the stability of the positive electrode slurry and the processability of the pole piece, resulting in an increase in film resistance.
  • the mass content of the dispersant is higher than 1%, because the content of the dispersant is too high, the bonding performance of the binder is reduced, and the binding force between the conductive agent and the positive electrode active material is reduced, that is, the adhesion of the pole piece is reduced.
  • the junction force is small, and it is easy to demoulding during processing or the positive active material diffuses into the negative electrode during long-term recycling of the battery, causing great safety risks.
  • the mass content of the dispersant within a suitable range can improve the dispersion of the cathode slurry and has no or minimal impact on the bonding performance of the binder.
  • the mass content of the binder is 0.6% to 1.2%, based on the total mass of solid matter of the cathode slurry.
  • the mass content of the binder is 0.7% to 1.2%, 0.8% to 1.2%, 0.9% to 1.2%, 1% to 1.2%, 0.6% to 1.1%, 0.6% to 1.0% , 0.6% to 0.9% or 0.6% to 0.8%, based on the total mass of solid matter of the positive electrode slurry count.
  • the mass content of the binder is higher than 1.2%, although the bonding force of the electrode piece will be significantly improved, the viscosity of the positive electrode slurry will be too high, resulting in uneven distribution of the positive electrode active material in the slurry, affecting the positive electrode slurry.
  • the dispersion and the quality of the pole piece increase the film layer resistance of the pole piece and reduce the battery cycle performance.
  • the mass content of the binder is less than 0.6%, the bonding performance of the binder decreases, resulting in insufficient bonding force of the electrode piece. Demolding is prone to occur during processing or the positive active material of the battery during long-term recycling. Diffusion to the negative electrode, causing great safety hazards.
  • the mass content of the binder within an appropriate range can ensure that the electrode piece has good adhesion, avoid direct contact between the positive active material and the electrolyte, reduce the occurrence of side reactions, and reduce the safety hazards of secondary batteries; at the same time, the adhesive
  • the addition of the binder is relatively low, which helps to reduce the film resistance of the electrode sheet, increase the loading capacity of the positive active material and increase the energy density of the battery.
  • the mass ratio of the second polymer to the third polymer is 1:9 ⁇ 8:2, or 0.1 ⁇ 4:1.
  • the mass ratio of the second polymer to the third polymer is 0.1 ⁇ 4:1, 0.25 ⁇ 4:1, 0.5 ⁇ 4:1, 1 ⁇ 4:1, 1.5 ⁇ 4:1, 2 ⁇ 4:1, 2.5 ⁇ 4:1 or 3 ⁇ 4:1.
  • the mass ratio of the second polymer to the third polymer is within the above range, it can be ensured that the pole piece has improved flexibility while having good adhesion.
  • the binder has a crystallinity of 25% to 44%.
  • the crystallinity of the binder is 25% to 42%, 25% to 40%, 25% to 38%, 25% to 35%, 25% to 32%, 25% to 30% , 28% to 42%, 30% to 42%, or 35% to 42%.
  • the crystallinity of the binder When the crystallinity of the binder is lower than 25%, the bonding force between the solid substances in the pole piece film layer or the bonding force of the film layer is insufficient, and demolding may easily occur during battery processing, or the battery may During long-term recycling, the positive active material diffuses into the negative electrode, causing great safety hazards.
  • the crystallinity of the binder is higher than 44%, the plastic strain stress of the film layer during the hot pressing treatment of the bare battery core is insufficient, and cracks and fractures are prone to occur.
  • the crystallinity of the binder is within a suitable range, which can improve the flexibility of the electrode piece while maintaining a suitable hardness, which is beneficial to the processing of secondary batteries and reduces the safety hazards of secondary batteries.
  • the melting enthalpy of the binder ranges from 25 J/g to 45 J/g.
  • the melting enthalpy of the binder is 28J/g ⁇ 45J/g, 30J/g ⁇ 45J/g, 32J/g ⁇ 45J/g, 35J/g ⁇ 45J/g, 28J/g ⁇ 43J/g, 28J/g ⁇ 40J/g, 28J/g ⁇ 38J/g, 28J/g ⁇ 35J/g, or 28J/g ⁇ 33J/g.
  • the melting enthalpy of the binder is within a suitable range, the crystallinity of the binder can be moderate, so that the pole piece has both excellent flexibility and adhesive force.
  • the cathode active material is a lithium-containing transition metal oxide.
  • the positive active material is lithium iron phosphate or lithium nickel cobalt manganese oxide, or their doping modified materials, or their conductive carbon coating modification materials, conductive metal coating modification materials Or at least one of the conductive polymer coating modified materials.
  • This application also provides a preparation method of cathode slurry, which preparation method includes the following steps:
  • Step 1 Mix the positive active material, conductive agent and binder evenly; the binder includes a second polymer with a weight average molecular weight of 700,000 to 1.1 million and a third polymer with a weight average molecular weight of 1.3 million to 3 million. polymer,
  • Step 2 Add a dispersant and stir to obtain a positive electrode slurry.
  • the dispersant includes a first polymer with a weight average molecular weight of 0.5 million to 150.000.
  • the first polymer, the second polymer and the The third polymers are all prepared by polymerizing at least one monomer represented by formula II under polymerizable conditions,
  • R 1 and R 2 are each independently selected from hydrogen, fluorine, chlorine or trifluoromethyl.
  • the binder By adding the binder first and then the dispersant, it is beneficial to achieve full mixing, adhesion/coating between the positive electrode active material, conductive agent and high molecular weight binder. By adding the dispersant later, the positive electrode activity can be effectively avoided. The sedimentation of substances and high molecular weight binders is conducive to simultaneously improving the dispersion and stability of the cathode slurry.
  • R 1 and R 2 are both hydrogen. In some embodiments, R 1 and R 2 are both fluorine. In some embodiments, R 1 is hydrogen and R 2 is trifluoromethyl. In some embodiments, R 1 is trifluoromethyl and R 2 is hydrogen.
  • the preparation method of the first polymer includes the following steps:
  • At least one monomer represented by formula II a first initiator and a first solvent, perform a polymerization reaction at normal pressure and a reaction temperature of 55°C to 80°C for 2 hours to 8 hours, stop the reaction, separate solid and liquid, and retain solid phase to obtain the first polymer.
  • the preparation method of the first polymer includes the following steps:
  • At least one monomer represented by Formula II a first initiator and a first solvent, perform the polymerization reaction in a non-reactive gas atmosphere, normal pressure, and a reaction temperature of 55°C to 80°C for 2 hours to 8 hours, and then stop the reaction. , solid-liquid separation, retaining the solid phase, and obtaining the first polymer.
  • non-reactive gas refers to a gas that does not participate in the polymerization reaction.
  • exemplary non-reactive gases include any or a combination of argon, helium, and nitrogen.
  • normal pressure refers to a standard atmospheric pressure, which is 101KPa.
  • the reaction temperature is 60°C to 80°C, 65°C to 80°C, 70°C to 80°C, or 66°C to 80°C, 68°C to 80°C, 73°C ⁇ 80°C, 64°C ⁇ 75°C or 55°C ⁇ 73°C.
  • the reaction time is 2 hours to 4 hours, 2 hours to 3 hours, 2 hours to 6 hours, 3 hours to 8 hours, 3 hours to 6 hours, 4 hours to 8 hours, 4 hours to 6 hours, 6 hours to 8 hours.
  • the preparation method of the first polymer further includes the following steps:
  • initiator refers to a substance that initiates the polymerization of monomers during a polymerization reaction.
  • exemplary initiators include 2-ethyl peroxydicarbonate, tert-butyl peroxypivalate, and tert-amyl peroxypivalate.
  • pH adjuster refers to a substance that changes the pH of a solution or dispersion medium, including increasing the acidity or increasing the alkalinity.
  • exemplary pH adjusting agents include sodium bicarbonate, sodium carbonate and sodium hydroxide.
  • dispersing aid refers to substances that can promote the uniform dispersion of monomers in the medium during synthesis reactions.
  • exemplary dispersing aids include carboxyethyl cellulose ether and methyl cellulose ether.
  • the first solvent is water, which is beneficial to reducing harm to the environment.
  • the pH value is adjusted to 6.5-7, such as 6.5, 6.8 or 7.
  • the stirring time is 30 minutes to 55 minutes, 30 minutes to 50 minutes, 30 minutes to 45 minutes, 35 minutes to 60 minutes, 40 minutes to 60 minutes or 45 minutes. ⁇ 60 minutes.
  • the prepared first polymer (or dispersant) has a lower weight average molecular weight and viscosity, has good adhesion with the cathode active material, and significantly improves the dispersion and stability of the slurry. sex.
  • the preparation method of the first polymer has low raw material cost and mild reaction conditions, which is conducive to mass production of the dispersant.
  • the preparation method of the third polymer includes the following steps:
  • the monomer represented by formula II causes the reaction pressure to reach 6MPa ⁇ 8MPa, increase the temperature to 35°C ⁇ 60°C to perform polymerization reaction 6 hours to 10 hours;
  • the preparation method of the third polymer is performed under a non-reactive gas atmosphere.
  • the initiator has the same meaning as the initiator in the preparation method of the first polymer.
  • the first initiator and the second initiator are the same chemical substance. In some embodiments, the first initiator and the second initiator are different chemicals.
  • the second initiator is tert-butyl peroxypivalate.
  • chain transfer agent refers to a chemical substance that generates free radicals that react with raw material molecules to form a product and another free radical, allowing the reaction to continue.
  • Chain transfer agents can be used to control the chain length of polymers, that is, to control the degree of polymerization of polymers, or the viscosity of the polymer.
  • An exemplary chain transfer agent is cyclohexane.
  • the monomer represented by Formula II is charged into the reaction vessel until the reaction pressure reaches 6MPa to 7MPa or 7MPa to 8MPa.
  • the reaction temperature of the third polymer is 37°C to 60°C, 40°C to 60°C, 43°C to 60°C, 45°C to 60°C, 50°C to 60°C, 35°C to 55°C °C, 35°C ⁇ 50°C or 35°C ⁇ 45°C.
  • the reaction time of the third polymer is 6 hours to 9 hours, 6 hours to 8 hours, 6 hours to 7 hours, 7 hours to 10 hours, 8 hours to 10 hours, 9 hours to 10 hours hours hours or 8 to 9 hours.
  • the preparation of the third polymer includes the following steps:
  • the meaning of the dispersion aid is the same as the meaning of the dispersion assistant in the preparation method of the first polymer.
  • the first dispersion aid and the second dispersion aid are the same chemical substance.
  • the first dispersing aid and the second dispersing aid are different chemicals.
  • the second dispersion aid is methylcellulose ether.
  • the pH adjuster has the same meaning as the pH adjuster in the preparation method of the first polymer.
  • the first pH adjusting agent and the second pH adjusting agent are the same chemical substance.
  • the first pH adjusting agent and the second pH adjusting agent are different chemicals.
  • the pH value is adjusted to 6.5-7, such as 6.5, 6.8 or 7.
  • the second solvent is water, which is beneficial to reducing harm to the environment.
  • the stirring time is 30 minutes to 55 minutes, 30 minutes to 50 minutes, 30 minutes to 45 minutes, 35 minutes to 60 minutes, 40 minutes to 60 minutes or 45 minutes to 60 minutes.
  • the raw materials are easy to obtain and the reaction conditions are safe and controllable, which is conducive to the expanded production of the third polymer.
  • the third polymer prepared by this method has relatively high molecular weight and viscosity, and adding a small amount when preparing the battery slurry can make the electrode piece have good adhesive force.
  • a secondary battery is provided.
  • a secondary battery typically includes a positive electrode plate, a negative electrode plate, an electrolyte and a separator.
  • active ions are inserted and detached back and forth between the positive and negative electrodes.
  • the electrolyte plays a role in conducting ions between the positive and negative electrodes.
  • the isolation film is placed between the positive electrode piece and the negative electrode piece. It mainly prevents the positive and negative electrodes from short-circuiting and allows ions to pass through.
  • the 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.
  • 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.
  • Composite current collectors 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 use in batteries.
  • the cathode active material may include at least one of the following materials: olivine-structured lithium-containing phosphates, lithium transition metal oxides, 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 oxides (such as LiCoO 2 ), lithium nickel oxides (such as LiNiO 2 ), lithium manganese oxides (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 (also referred to as 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 At least one of 0.8 Co 0.1 Mn 0.1 O 2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as Li Li
  • the olivine structure contains Examples of lithium phosphates may include, but are not limited to, lithium iron phosphate (such as LiFePO 4 (also referred to as LFP)), composites of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), lithium manganese phosphate and carbon. At least one of composite materials, lithium iron manganese phosphate, and composite materials of lithium iron manganese phosphate and carbon.
  • lithium iron phosphate such as LiFePO 4 (also referred to as LFP)
  • composites of lithium iron phosphate and carbon such as LiMnPO 4
  • LiMnPO 4 lithium manganese phosphate and carbon.
  • At least one of composite materials, lithium iron manganese phosphate, and composite materials of lithium iron manganese phosphate and carbon At least one of composite materials, lithium iron manganese phosphate, and composite materials of lithium iron manganese phosphate and carbon.
  • the positive electrode film layer optionally further includes a binder.
  • the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene At least one of ethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • 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 plate includes a negative electrode current collector and is disposed on at least one surface of the negative electrode current collector.
  • the negative electrode film layer on 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 It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative active material may be a negative active material known in the art for batteries.
  • the negative active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, and the like.
  • the silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon carbon composites, silicon nitrogen composites and silicon alloys.
  • the tin-based material may be selected from at least one of elemental tin, tin oxide compounds and tin alloys.
  • the present application is not limited to these materials, and other traditional materials that can be used as battery negative electrode active materials can also be used. Only one type of these negative electrode active materials may be used alone, or two or more types may be used in combination.
  • 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 in the following manner: adding the above The components used to prepare the negative electrode sheet, such as negative active materials, conductive agents, binders and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode On the current collector, 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 solution 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 membrane can be a single layer
  • the film may also be a multi-layer composite film and is not particularly limited. 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 may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
  • FIG. 1 shows a square-structured secondary battery 5 as an example.
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity.
  • the housing 51 has an opening communicating with the accommodation cavity, and the cover plate 53 can cover the opening to close the accommodation cavity.
  • the positive electrode piece, the negative electrode piece and the isolation film can be formed into the electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the containing cavity.
  • the electrolyte soaks into the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.
  • secondary batteries can be assembled into battery modules, and the number of secondary batteries contained in the battery module can be one or more. Those skilled in the art can select the specific number according to the application and capacity of the battery module.
  • FIG. 3 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.
  • the present application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided by the present application.
  • the secondary battery, battery module, or battery pack may be used as a power source for the electrical device, or may be used as an energy storage unit for the electrical device.
  • the electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, and electric golf carts). , electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited to these.
  • a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.
  • FIG. 6 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.
  • the second PVDF polymer with a weight average molecular weight of 700,000 and the third polymer of Example 1 were respectively dissolved in N-methylpyrrolidone (NMP) solution to form a 10% glue solution. Mass ratio mixing.
  • the PVDF with a weight average molecular weight of 700,000 is the HSV900 model of Arkema France Co., Ltd.
  • Example 2 the mass ratio of the PVDF binder with a weight average molecular weight of 700,000 and the third polymer prepared in Example 1 was adjusted.
  • the specific parameters are shown in Table 1.
  • the second PVDF polymer with a weight average molecular weight of 700,000 and the third polymer of Example 10 were respectively dissolved in N-methylpyrrolidone (NMP) solution to prepare a 10% glue solution, and then mixed with 4:6 Mass ratio mixing.
  • NMP N-methylpyrrolidone
  • Example 10 Other steps are the same as in Example 10, the only difference is that the third polymer in Example 10 is replaced with the third polymer prepared in Example 11, see Table 1 for details.
  • Example 10 Other steps are the same as those in Example 10. The only difference is that the third polymer in Example 10 is replaced with the third polymer prepared in Example 12. See Table 1 for details.
  • the second PVDF polymer with a weight average molecular weight of 1.1 million and the third polymer of Example 1 were respectively dissolved in N-methylpyrrolidone (NMP) solution to form a 10% glue solution. Mass ratio mixing. Among them, the PVDF with a weight average molecular weight of 1.1 million is model 5130 of Solvay (Shanghai) Co., Ltd.
  • the positive electrode active material lithium iron phosphate, conductive agent carbon black, binder and dispersant were added to the binder glue prepared in Example 10 according to the weight ratio of 94.8:4:0.8:0.4 and mixed evenly to obtain a positive electrode slurry.
  • Material add N-methylpyrrolidone (NMP), adjust its solid content to 58%.
  • NMP N-methylpyrrolidone
  • the positive electrode slurry is evenly coated on both surfaces of the aluminum foil positive electrode current collector, and then dried to obtain a film layer; it is then cold pressed and cut to obtain the positive electrode sheet.
  • SBR binder styrene-butadiene rubber
  • CMC thickener sodium carboxymethylcellulose
  • Example 14 Stack the positive electrode sheet, isolation film, and negative electrode sheet prepared in Example 14 in order so that the isolation film is between the positive and negative electrode sheets to play an isolation role, then wind up to obtain a bare battery core, and weld the bare battery core The tabs are removed, and the bare battery core is put into an aluminum case, baked at 80°C to remove water, and then electrolyte is injected and sealed to obtain an uncharged battery. The uncharged battery was then subjected to processes such as standing, hot and cold pressing, formation, shaping, and capacity testing to obtain the lithium-ion battery product of Example 14.
  • Example 15 the amount of positive electrode slurry binder was adjusted, and other steps were the same as in Example 14. See Table 3 for details.
  • Example 19 the weight average molecular weight of the added dispersant is adjusted, and other steps are the same. Example 16.
  • Example 19 the weight average molecular weight of the first polymer in the dispersant is 0.5 million, and the preparation method is as follows:
  • Example 20 the weight average molecular weight of the first polymer in the dispersant is 20,000, and the preparation method is as follows:
  • Example 21 the weight average molecular weight of the first polymer in the dispersant is 80,000, and the preparation method is as follows:
  • the weight average molecular weight of the first polymer in the dispersant in Example 22 is 150,000, and the preparation method is as follows:
  • Example 23 the content of the dispersant was adjusted, and other methods were the same as in Example 21. See Table 3 for specific parameters.
  • Example 27 the ratio of the second polymer and the third polymer in the binder was adjusted. Other methods were the same as in Example 21. The specific parameters are shown in Table 3.
  • Example 31 the weight average molecular weight of the third polymer in the binder was adjusted to 2.5 million, and the mass content of the binder was adjusted. Other methods were the same as in Example 14. The specific parameters are shown in Table 3.
  • Example 36 the weight average molecular weight of the third polymer in the binder was adjusted to 3 million, and the mass content of the binder was adjusted. Other methods were the same as in Example 14. The specific parameters are shown in Table 3.
  • Example 39 the weight average molecular weight of the third polymer in the binder was adjusted to 1.3 million. Other methods were the same as in Example 14. The specific parameters are shown in Table 3.
  • the preparation method of the secondary battery in Example 40 is similar to the preparation method of the secondary battery in Example 14, with the following differences:
  • the positive active material lithium nickel cobalt manganese oxide NCM, the conductive agent carbon black, the binder and the dispersant are added to the glue prepared in Example 13 according to the weight ratio of 94.6:4:1.0:0.4 and mixed evenly. , obtain the positive electrode slurry, add N-methylpyrrolidone (NMP), and adjust its solid content to 58%.
  • NMP N-methylpyrrolidone
  • the positive electrode slurry is evenly coated on both surfaces of the aluminum foil positive electrode current collector, and then dried to obtain a film layer; it is then cold pressed and cut to obtain the positive electrode sheet.
  • Example 41 the weight average molecular weight of the dispersant was adjusted, and other methods were the same as in Example 40.
  • the specific parameters are shown in Table 3.
  • Example 43 the type of the third polymer was adjusted, and other methods were the same as in Example 16. Other parameters are shown in Table 3.
  • Example 43 the third polymer is polytetrafluoroethylene, and its preparation method is:
  • Example 44 the third polymer is a copolymer of vinylidene fluoride and hexafluoropropylene (PVDF-HFP), and its preparation method is:
  • Example 45 the dispersant uses polychlorotrifluoroethylene with a weight average molecular weight of 10,000, and its preparation method is:
  • Example 46 the dispersant uses PVDF-HFP (vinylidene fluoride-hexafluoropropylene) polymer with a weight average molecular weight of 10,000, and its preparation method is:
  • Example 47 The preparation methods of the dispersants in Examples 47 and 48 are basically similar to those in Example 22, except that the comonomers are substituted with tetrafluoroethylene and chlorotrifluoroethylene respectively.
  • Example 49 a vinylidene fluoride-chlorotrifluoroethylene copolymer with a weight average molecular weight of 700,000 was used as the second polymer, and in Example 50, a vinylidene fluoride-hexafluoropropylene copolymer with a weight average molecular weight of 700,000 was used as the second polymer. as the second polymer.
  • the binder only contains a third polymer with a weight average molecular weight of 2.5 million.
  • Comparative Example 2 the binder only contains a second polymer with a weight average molecular weight of 700,000. In Comparative Example 3, the binder only contains a third polymer with a weight average molecular weight of 2.5 million.
  • the agent contains only the second polymer with a weight average molecular weight of 1.1 million material, other methods are the same as Example 1, and the specific parameters are shown in Table 1.
  • Comparative Examples 4 to 6 the binder only contains the second polymer, and in Comparative Examples 7 to 10, the binder only contains the third polymer.
  • Other methods are the same as in Example 14. See Table 3 for specific parameters.
  • the performance test results of the binders prepared in Examples 1 to 13 and Comparative Examples 1 to 3 are shown in Table 1, and the performance test results of the polymers in Examples 1 to 50 and Comparative Examples 1 to 10 are shown in Table 2 As shown, the performance test results of the pole pieces and batteries prepared in Examples 1 to 50 and Comparative Examples 1 to 10 are shown in Table 3, and the test methods are as follows:
  • the first polymer, the second polymer and the third polymer are respectively dissolved in N-methylpyrrolidone (NMP) solvent, wherein the first polymer and the second polymer are configured with a glue solution with a solid content of 7%,
  • the third polymer is configured with a glue solution with a solid content of 4%.
  • Instrument model Shanghai Fangrui NDJ-5S, rotor: 61# (0-500mPa ⁇ s ), 62# (500-2500mPa ⁇ s), 63# (2500-10000mPa ⁇ s), 64# (10000-50000mPa ⁇ s), rotation speed: 12r/min, test temperature: 25°C, test time is 5min, wait The indicator reads data stably.
  • the first polymer and the second polymer in Examples 1-14 were respectively dissolved in N-methylpyrrolidone (NMP) solution to form a 10% glue solution, and then the adhesive according to Examples 1-14 was Weigh the glue solution of the first polymer and the second polymer at a mass ratio of the two and mix them, then place the evenly dispersed mixed solution into a glue film preparation container, dry it at 100°C for 2 days, and then Cut the film into 2 ⁇ 2cm pieces and place them in an aluminum dry pot, shake them flat, cover the crucible lid, and raise the temperature under a nitrogen atmosphere with a purge gas of 50mL/min and a protective gas of 70mL/min.
  • the rate is 10°C/min
  • the test temperature range is -100°C ⁇ 400°C
  • DSC differential scanning calorimeter
  • the battery capacity retention rate data corresponding to Example 14 in Table 3 is the data measured after 500 cycles under the above test conditions, that is, the value of P500.
  • the test procedures of Comparative Example 4 and other examples are the same as above;
  • Lithium nickel cobalt manganese oxide NCM system Taking Example 40 as an example, at 25°C, charge the battery corresponding to Example 40 with a constant current of 1/3C to 4.4V, and then charge with a constant voltage of 4.4V until the current is 0.05C, leave it aside for 5 minutes, and then discharge to 2.8V at 1/3C. The resulting capacity is recorded as the initial capacity C0. Other test steps are the same as for the lithium iron phosphate system.
  • a second polymer with a weight average molecular weight of 700,000 and The third polymer with a weight average molecular weight of 2.5 million is used to prepare a binder in a mass ratio of 1:9 to 9:1, as opposed to using only a third polymer with a weight average molecular weight of 2.5 million as the binder.
  • Ratio 1 the addition of the second polymer reduces the melting enthalpy and crystallinity of the binder and improves the flexibility of the binder.
  • Example 13 a second polymer with a weight average molecular weight of 1.1 million, a median particle diameter Dv50 of 25 ⁇ m, and a viscosity of 2500 mPa ⁇ s and a third polymer with a weight average molecular weight of 2.5 million were used in a mass ratio of 4:6.
  • the binder was prepared within the range. Compared with Comparative Example 3, which only used the second polymer with a weight average molecular weight of 1.1 million as the binder, it showed that the binder was reduced after mixing the second polymer and the third polymer. The melting enthalpy and crystallinity improve the flexibility of the binder.
  • the binder uses a weight average molecular weight of 700,000
  • the weight average molecular weight of the second polymer is 1.8 million (median particle size Dv50 is 60 ⁇ m, viscosity is 3600 mPa ⁇ s), 2.5 million (median particle size Dv50 is 80 ⁇ m, viscosity is 4300 mPa ⁇ s), 3 million (median value
  • the third polymer with particle size Dv50 of 100 ⁇ m and viscosity of 4800 mPa ⁇ s), 1.3 million (median particle size Dv50 of 30 ⁇ m and viscosity of 1700 mPa ⁇ s), and 1.8 million (PTFE/PVDF-HFP) was prepared, and only used Compared with Comparative Examples 7 to 10 of secondary batteries prepared from a third polymer with a weight average molecular weight of 1.8 million, the film layer resistance was reduced, and the average number of rolls of the pole pieces and the capacity retention rate after 500 cycles were significantly improved; compared with Compared with Comparative Example 5,
  • Combining the data in Table 1 shows that mixing the second polymer and the third polymer within a set proportion range can reduce the crystallinity of the binder and improve its flexibility, thereby improving the flexibility of the pole piece; at the same time, the addition of dispersant The dispersion of the slurry can be further improved, and the processability of the pole piece is significantly improved, which is beneficial to improving the uniformity of slurry coating and reducing the resistance of the pole piece, thereby improving the battery cycle performance.
  • the combined use of the second polymer and the third polymer allows the pole piece membrane layer to maintain excellent adhesion on the basis of good processability. force to ensure the cycle safety of secondary batteries.
  • the weight average molecular weights used were 0.5 million (median particle diameter Dv50: 0.5 ⁇ m, viscosity: 20 mPa ⁇ s) and 10,000 (median particle diameter Dv50: 0.8 ⁇ m, Viscosity is 30mPa ⁇ s), 20,000 (median particle diameter Dv50 is 1 ⁇ m, viscosity is 50mPa ⁇ s), 80,000 (median particle diameter Dv50 is 2 ⁇ m, viscosity is 120mPa ⁇ s), 150,000 (median particle diameter Dv50 is 2 ⁇ m, viscosity is 120mPa ⁇ s)
  • a secondary battery was prepared using a dispersant and a binder with a Dv50 of 4 ⁇ m and a viscosity of 180 mPa ⁇ s).
  • the binder used a second polymer with a weight average molecular weight of 700,000 and a weight average molecular weight of 1.8 million with a median particle diameter.
  • a third polymer with a Dv50 of 60 ⁇ m and a viscosity of 3600 mPa ⁇ s, a second polymer with a weight average molecular weight of 1.1 million, and a third polymer with a weight average molecular weight of 2.5 million were prepared.
  • Comparative Examples 5 to 6, and Comparative Examples 8 to 9 the film resistance of the secondary batteries in Examples 19 to 22, and Examples 40 to 42 was reduced, and the average number of rolls of the pole pieces was And the capacity retention rate is significantly improved after 500 cycles.
  • Combining the data in Table 1 shows that mixing the second polymer and the third polymer can reduce the crystallinity of the binder and improve its flexibility, which is beneficial to improving the flexibility of the pole piece; and the dispersion with a weight average molecular weight of less than 150,000
  • the agent helps to improve the dispersion of the slurry and make the slurry evenly coated, thereby reducing the electrode resistance and improving the battery cycle performance.
  • Examples 23 to 26 a dispersant and a binder with a weight average molecular weight of 80,000 and a mass content of 0.05% to 1.00% were used to prepare secondary batteries.
  • the binders used a second dispersant with a weight average molecular weight of 700,000. polymer and a third polymer with a weight average molecular weight of 1.8 million was prepared.
  • the electrode sheet resistance of the secondary batteries in Examples 23 to 26 was significantly reduced, but the adhesive force was not significantly reduced, indicating that the dispersant within this range helps to improve
  • the stability and processability of the positive electrode slurry improves the uniformity of the slurry distribution and reduces the resistance of the electrode piece without significantly reducing the adhesive force of the electrode piece.
  • Examples 27 to 30 a dispersant and a binder with a weight average molecular weight of 80,000 were used to prepare secondary batteries.
  • the binders used a mass ratio of 1:9 to 8:2 and a binder with a weight average molecular weight of 700,000.
  • a second polymer and a third polymer having a weight average molecular weight of 1.8 million were prepared.
  • the electrode sheet film resistance of the secondary batteries in Examples 27 to 30 was significantly reduced, and the average number of rolling of the electrode sheets was also significantly improved, while still maintaining good adhesion and Capacity retention rate after 500 cycles.
  • the combination of the second polymer and the third polymer is beneficial to improving the crystallinity and flexibility of the binder, thereby improving the flexibility of the pole piece and ensuring that the pole piece has good adhesion; while the addition of the dispersant improves the slurry
  • the dispersion and stability of the material improve the film resistance and battery cycle performance.
  • Example 26 a dispersant with a mass content of 1% and a binder with a mass content of 1% was used to prepare a secondary battery.
  • Comparative Example 4 a second polymer with a mass content of 2.5% was used to prepare a secondary battery.
  • the total amount of additives added in Example 26 is less than that of Comparative Example 4, but the film resistance of the pole piece of the secondary battery in Example 26 is significantly reduced, and the average number of rolls of the pole piece and the capacity retention rate after 500 cycles are also significantly improved. While still maintaining good adhesion. This is beneficial to reducing the impedance increase rate of the battery and improving the cycle performance of the battery, and also helps to increase the compaction density of the pole pieces and increase the energy density of the battery.

Abstract

The present application provides a binder composition, a positive electrode slurry, a secondary battery, a battery module, a battery pack, and an electric device. The binder composition comprises a dispersant and a binder. The dispersant comprises a first polymer having a weight-average molecular weight of 5,000-150,000. The binder comprises a second polymer having a weight-average molecular weight of 700,000 to 1,100,000 and a third polymer having a weight-average molecular weight of 1,300,000 to 3,000,000. The first polymer, the second polymer, and the third polymer are all polymers containing a structural unit as represented by formula I. The binder composition can make electrode sheets have good bonding force with a relatively small amount of addition, thereby facilitating reducing the usage amounts of binders in electrode sheets and improving the loading capacity of positive electrode active materials in electrode sheets and the energy density of batteries; moreover, the binder composition can improve the dispersion and processability of positive electrode slurries, significantly reduce the film resistance of electrode sheets and improve the battery cycle performance, and improve the flexibility of electrode sheets.

Description

粘结剂组合物、正极浆料、二次电池、电池模块、电池包和用电装置Binder composition, positive electrode slurry, secondary battery, battery module, battery pack and electrical device
交叉引用cross reference
本申请引用于2022年8月30日递交的名称为“正极浆料及其制备方法、二次电池、电池模块、电池包和用电装置”的第202211052015.3号中国专利申请，其通过引用被全部并入本申请。This application cites Chinese patent application No. 202211052015.3 titled "Cathode Slurry and Preparation Method, Secondary Battery, Battery Module, Battery Pack and Electrical Device" submitted on August 30, 2022, which is fully incorporated by reference. incorporated into this application.
技术领域Technical field
本申请涉及二次电池技术领域，尤其涉及一种正极浆料及其制备方法、二次电池、电池模块、电池包和用电装置。The present application relates to the technical field of secondary batteries, and in particular to a positive electrode slurry and a preparation method thereof, secondary batteries, battery modules, battery packs and electrical devices.
背景技术Background technique
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。随着二次电池的应用范围越来越广泛，人们对二次电池的能量密度、循环性能和安全性能等也提出了更高的要求。In recent years, 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. As the application scope of secondary batteries becomes more and more extensive, people have also put forward higher requirements for the energy density, cycle performance and safety performance of secondary batteries.
传统粘结剂往往需要较高的含量才能满足极片粘结力的需求，这限制了极片中活性物质负载量的提升，不利于电池能量密度的提升。而且，高的粘结剂用量在提升极片压实密度的同时会引发极片脆性问题，降低电池的安全性和循环性能。如何降低极片中粘结剂用量并且改善极片脆性问题成为目前亟需解决的问题。Traditional binders often require a higher content to meet the bonding strength requirements of the pole pieces, which limits the increase in active material loading in the pole pieces and is not conducive to the improvement of battery energy density. Moreover, high binder dosage will not only increase the compaction density of the electrode pieces, but also cause the problem of brittleness of the electrode pieces, reducing the safety and cycle performance of the battery. How to reduce the amount of binder in the pole pieces and improve the brittleness of the pole pieces has become an urgent problem that needs to be solved.
发明内容Contents of the invention
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组合物，粘结剂组合物包含分散剂和粘结剂，分散剂包括重均分子量为0.5万～15万的第一聚合物，粘结剂包括重均分子量为70万～110 万的第二聚合物和重均分子量为130万～300万的第三聚合物，第一聚合物、第二聚合物和第三聚合物均为含有式I所示结构单元的聚合物，
This application was made in view of the above problems, and its purpose is to provide a binder composition. The binder composition includes a dispersant and a binder. The dispersant includes a first compound with a weight average molecular weight of 0.5 million to 150.000. Polymers, binders including weight average molecular weight of 700,000 to 110 The second polymer has a weight average molecular weight of 1.3 million to 3 million, and the first polymer, the second polymer and the third polymer are all polymers containing structural units represented by formula I,
其中，R1、R2各自独立地选自氢、氟、氯或三氟甲基。Wherein, R 1 and R 2 are each independently selected from hydrogen, fluorine, chlorine or trifluoromethyl.
本申请提供的粘结剂组合物中使用了重均分子量为0.5万～15万的第一聚合物为分散剂，提高了正极浆料的分散性和加工性，显著降低极片膜层电阻和提高电池循环性能。本申请提供的正极浆料中联用了不同重均分子量的第二聚合物和第三聚合物作为粘结剂，与现有技术中常用的粘结剂相比，该粘结剂在添加量相对较少的条件下即可使极片具有良好粘结力，有助于降低极片中粘结剂的用量，提高极片正极活性物质负载量和电池能量密度；并且，第二聚合物和第三聚合物的联用还改善了粘结剂的结晶性，提高了极片的柔性。The binder composition provided by this application uses a first polymer with a weight average molecular weight of 0.5 million to 150.000 as a dispersant, which improves the dispersibility and processability of the cathode slurry and significantly reduces the electrode film layer resistance and Improve battery cycle performance. The cathode slurry provided by this application uses a second polymer and a third polymer with different weight average molecular weights as a binder. Compared with the binders commonly used in the prior art, the addition amount of the binder is The electrode piece can have good adhesion under relatively few conditions, which helps to reduce the amount of binder in the electrode piece, improve the loading capacity of the positive active material of the electrode piece and the energy density of the battery; and, the second polymer and The combined use of the third polymer also improves the crystallinity of the binder and increases the flexibility of the pole piece.
在任意实施方式中，所述第一聚合物、所述第二聚合物和所述第三聚合物均为卤代烃聚合物，各自独立地选自聚四氟乙烯、聚偏二氟乙烯、偏二氟乙烯-六氟丙烯共聚物、偏二氟乙烯-三氟氯乙烯、聚三氟氯乙烯中的一种或多种。In any embodiment, the first polymer, the second polymer and the third polymer are all halogenated hydrocarbon polymers, each independently selected from polytetrafluoroethylene, polyvinylidene fluoride, One or more of vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene, and polychlorotrifluoroethylene.
所述聚合物具有稳定的化学性能和优良的电性能，并具有很好的机械性能，有利于制备兼具适当柔性和硬度的膜层。The polymer has stable chemical properties, excellent electrical properties, and good mechanical properties, which is beneficial to the preparation of a film layer with appropriate flexibility and hardness.
在任意实施方式中，所述第一聚合物的颗粒的中值粒径Dv50为0.5μm～5μm。In any embodiment, the particles of the first polymer have a median diameter Dv50 of 0.5 μm to 5 μm.
第一聚合物的颗粒的粒径在合适范围内有利于在正极浆料溶剂，例如N-甲基吡咯烷酮中的溶解，降低胶液的加工难度。The particle size of the first polymer particles within a suitable range is beneficial to dissolution in the positive electrode slurry solvent, such as N-methylpyrrolidone, and reduces the processing difficulty of the glue solution.
在任意实施方式中，所述第一聚合物溶于N-甲基吡咯烷酮制得第一胶液，基于所述第一胶液的总质量计，当所述第一聚合物的质量含量为7％时，所述第一胶液的粘度为20～180mPa·s。In any embodiment, the first polymer is dissolved in N-methylpyrrolidone to prepare a first glue liquid. Based on the total mass of the first glue liquid, when the mass content of the first polymer is 7 %, the viscosity of the first glue liquid is 20-180 mPa·s.
第一聚合物的粘度在合适范围内有助于正极活性物质粉体颗粒的润湿和解聚，减少正极活性物质团聚、堵塞滤网等现象，改善正 极浆料的分散性能，提高正极浆料的固含量和极片涂布的均匀性，进而提升电池的能量密度。The viscosity of the first polymer within an appropriate range helps to wet and depolymerize the cathode active material powder particles, reduce the agglomeration of the cathode active material and block the filter, and improve the positive electrode active material. The dispersion performance of the electrode slurry improves the solid content of the cathode slurry and the uniformity of the electrode sheet coating, thereby increasing the energy density of the battery.
在任意实施方式中，所述第二聚合物的颗粒的中值粒径Dv50为15～25μm。In any embodiment, the particles of the second polymer have a median diameter Dv50 of 15 to 25 μm.
第二聚合物的颗粒的粒径在合适范围内有利于其在正极浆料溶剂，例如N-甲基吡咯烷酮中的溶解，降低胶液的加工难度，提高加工效率。The particle size of the second polymer particles within a suitable range is beneficial to its dissolution in the positive electrode slurry solvent, such as N-methylpyrrolidone, reducing the processing difficulty of the glue solution and improving the processing efficiency.
在任意实施方式中，所述第二聚合物溶于N-甲基吡咯烷酮制得第二胶液，基于所述第二胶液的总质量计，当所述第二聚合物的质量含量为7％时，所述第二胶液的粘度为2500～4000mPa·s。In any embodiment, the second polymer is dissolved in N-methylpyrrolidone to prepare a second glue liquid. Based on the total mass of the second glue liquid, when the mass content of the second polymer is 7 %, the viscosity of the second glue liquid is 2500-4000 mPa·s.
第二聚合物的粘度在合适范围内可以降低第三聚合物分子的排列有序性，降低第三聚合物分子的结晶性。The viscosity of the second polymer within an appropriate range can reduce the orderliness of the third polymer molecules and reduce the crystallinity of the third polymer molecules.
在任意实施方式中，所述第三聚合物的颗粒的中值粒径Dv50为30μm～100μm。In any embodiment, the particles of the third polymer have a median diameter Dv50 of 30 μm to 100 μm.
第三聚合物的颗粒的粒径在合适范围内有利于其在正极浆料溶剂中的溶解，降低胶液的加工难度，提高极片的加工效率。The particle size of the third polymer particles is within a suitable range, which is beneficial to its dissolution in the positive electrode slurry solvent, reduces the processing difficulty of the glue solution, and improves the processing efficiency of the electrode piece.
在任意实施方式中，所述第三聚合物溶于N-甲基吡咯烷酮制得第三胶液，基于所述第三胶液的总质量计，当所述第三聚合物的质量含量为4％时，所述第三胶液的粘度为1500～5000mPa·s。In any embodiment, the third polymer is dissolved in N-methylpyrrolidone to prepare a third glue liquid. Based on the total mass of the third glue liquid, when the mass content of the third polymer is 4 %, the viscosity of the third glue liquid is 1500-5000 mPa·s.
第三聚合物的粘度在合适范围内，粘结剂具有良好的粘结性能，添加量较低时即可使极片具有优良的粘结力，有助于提高正极活性物质的负载量和电池能量密度。The viscosity of the third polymer is within a suitable range, and the binder has good bonding properties. When the addition amount is low, the electrode piece can have excellent bonding force, which helps to increase the loading capacity of the positive active material and the battery. Energy Density.
在任意实施方式中，所述第三聚合物的多分散系数为2～2.3。In any embodiment, the third polymer has a polydispersity coefficient of 2 to 2.3.
在任意实施方式中，所述第三聚合物的多分散系数为2.1～2.2。In any embodiment, the third polymer has a polydispersity coefficient of 2.1 to 2.2.
第三聚合物的多分散系数在上述范围内有助于维持第三聚合物粘度的稳定，从而提高极片生产的稳定性。The polydispersity coefficient of the third polymer within the above range helps to maintain the stability of the viscosity of the third polymer, thereby improving the stability of pole piece production.
在任意实施方式中，在所述粘结剂中，所述第二聚合物和所述第三聚合物的质量比为1:9～8:2。In any embodiment, in the binder, the mass ratio of the second polymer and the third polymer is 1:9 to 8:2.
所述第二聚合物和所述第三聚合物的质量比在上述范围内时，可以确保极片在具有良好粘结力的前提下还具有提高的柔性。 When the mass ratio of the second polymer to the third polymer is within the above range, it can be ensured that the pole piece has improved flexibility while having good adhesion.
在任意实施方式中，所述粘结剂的结晶度为25％～44％。In any embodiment, the binder has a crystallinity of 25% to 44%.
粘结剂的结晶度在合适范围内可以使极片的柔性提高，有利于二次电池加工和降低二次电池的安全隐患。The crystallinity of the binder within a suitable range can improve the flexibility of the pole piece, which is beneficial to the processing of secondary batteries and reduces the safety hazards of secondary batteries.
在任意实施方式中，所述粘结剂的熔融焓为25J/g～45J/g。In any embodiment, the melting enthalpy of the binder is 25 J/g to 45 J/g.
所述粘结剂的熔融焓在合适范围内可以使粘结剂的结晶性适中，使极片兼具优异的柔性和粘结力。If the melting enthalpy of the binder is within a suitable range, the crystallinity of the binder can be moderate, so that the pole piece has both excellent flexibility and adhesive force.
本申请的第二方面提供一种正极浆料，正极浆料中包括正极活性物质，导电剂以及任意实施方式的粘结剂组合物。A second aspect of the present application provides a cathode slurry, which includes a cathode active material, a conductive agent, and a binder composition in any embodiment.
在任意实施方式中，所述分散剂的质量含量为0.05％～1％，基于所述正极浆料的固体物质的总质量计。In any embodiment, the mass content of the dispersant is 0.05% to 1%, based on the total mass of solid matter of the positive electrode slurry.
分散剂的质量含量在合适范围内可以改善正极浆料的分散性，并对粘结剂的粘接性能无影响或影响极小。The mass content of the dispersant within a suitable range can improve the dispersion of the cathode slurry and has no or minimal impact on the bonding performance of the binder.
在任意实施方式中，所述粘结剂的质量含量为0.6％～1.2％，基于所述正极浆料的固体物质的总质量计。In any embodiment, the mass content of the binder is 0.6% to 1.2%, based on the total mass of solid matter of the positive electrode slurry.
粘结剂的质量含量在合适范围内可以确保极片具有良好的粘结力，避免正极活性物质与电解液的直接接触，减少副反应的发生，降低二次电池的安全隐患；同时，该粘结剂的添加量相对较低，有助于减小极片膜层电阻，提高正极活性物质的负载量和提高电池的能量密度。The mass content of the binder within an appropriate range can ensure that the electrode piece has good adhesion, avoid direct contact between the positive active material and the electrolyte, reduce the occurrence of side reactions, and reduce the safety hazards of secondary batteries; at the same time, the adhesive The addition of the binder is relatively low, which helps to reduce the film resistance of the electrode sheet, increase the loading capacity of the positive active material and increase the energy density of the battery.
在任意实施方式中，所述正极活性物质为含锂的过渡金属氧化物，可选为磷酸铁锂或锂镍钴锰氧化物，或它们的掺杂改性材料、、导电碳包覆改性材料、导电金属包覆改性材料或导电聚合物包覆改性材料中的至少一种。In any embodiment, the positive active material is a lithium-containing transition metal oxide, which may be lithium iron phosphate or lithium nickel cobalt manganese oxide, or their doping modified materials, conductive carbon coating modifications At least one of a conductive metal-coated modified material or a conductive polymer-coated modified material.
本申请的第三方面提供一种正极浆料的制备方法，所述制备方法包括以下步骤：A third aspect of the present application provides a preparation method of cathode slurry, which preparation method includes the following steps:
步骤1：将正极活性物质、导电剂和粘结剂混合均匀；所述粘结剂包括重均分子量为70万～110万的第二聚合物和重均分子量为130万～300万的第三聚合物，Step 1: Mix the positive active material, conductive agent and binder evenly; the binder includes a second polymer with a weight average molecular weight of 700,000 to 1.1 million and a third polymer with a weight average molecular weight of 1.3 million to 3 million. polymer,
步骤2：加入分散剂进行搅拌，得到正极浆料，所述分散剂包括重均分子量为0.5万～15万的第一聚合物，所述第一聚合物、所述第 二聚合物和所述第三聚合物均为至少一种式II所示单体在可聚合条件下聚合制备而得，
Step 2: Add a dispersant and stir to obtain a positive electrode slurry. The dispersant includes a first polymer with a weight average molecular weight of 0.5 million to 150.000. The first polymer and the third polymer are The second polymer and the third polymer are both prepared by polymerizing at least one monomer represented by Formula II under polymerizable conditions,
其中，R1、R2各自独立地选自氢、氟、氯、三氟甲基中的一种或多种。Among them, R 1 and R 2 are each independently selected from one or more types of hydrogen, fluorine, chlorine, and trifluoromethyl.
通过先加入粘结剂再加入分散剂的方式有利于实现正极活性物质、导电剂和高分子量的粘结剂之间的充分混合、粘附/包覆，通过后加入分散剂可以有效避免正极活性物质和高分子量的粘结剂的沉降，有利于同时提高正极浆料的分散性和稳定性。By adding the binder first and then the dispersant, it is beneficial to achieve full mixing, adhesion/coating between the positive electrode active material, conductive agent and high molecular weight binder. By adding the dispersant later, the positive electrode activity can be effectively avoided. The sedimentation of substances and high molecular weight binders is conducive to simultaneously improving the dispersion and stability of the cathode slurry.
在任意实施方式中，所述第一聚合物的制备方法包括以下步骤：In any embodiment, the method of preparing the first polymer includes the following steps:
提供至少一种式II所示单体、第一引发剂和第一溶剂，在常压、55℃～80℃的反应温度下进行聚合反应2小时～8小时，停止反应，固液分离，保留固相，得到所述第一聚合物。Provide at least one monomer represented by formula II, a first initiator and a first solvent, perform a polymerization reaction at normal pressure and a reaction temperature of 55°C to 80°C for 2 hours to 8 hours, stop the reaction, separate solid and liquid, and retain solid phase to obtain the first polymer.
第一聚合物的该制备方法原材料成本低，反应条件温和，有利于分散剂的量产。The preparation method of the first polymer has low raw material cost and mild reaction conditions, which is conducive to mass production of the dispersant.
在任意实施方式中，所述第三聚合物的制备方法包括以下步骤：In any embodiment, the preparation method of the third polymer includes the following steps:
提供至少一种式II所示单体、第二引发剂和第二溶剂，当式II所示单体使得反应压力达到6MPa～8MPa，升高温度至35℃～60℃进行聚合反应6小时～10小时；Provide at least one monomer represented by formula II, a second initiator and a second solvent. When the monomer represented by formula II causes the reaction pressure to reach 6MPa~8MPa, increase the temperature to 35℃~60℃ to perform the polymerization reaction for 6 hours~ 10 hours;
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，得到所述第三聚合物。Add a chain transfer agent, wait until the pressure in the reaction system drops to 2MPa to 2.5MPa, stop the reaction, separate the solid and liquid, retain the solid phase, and obtain the third polymer.
在第三聚合物的制备方法中，原料容易获取，反应条件安全可控，有利于第三聚合物的扩大生产。In the preparation method of the third polymer, the raw materials are easy to obtain and the reaction conditions are safe and controllable, which is conducive to the expanded production of the third polymer.
本申请的第四方面提供一种二次电池，包括正极极片、隔离膜、负极极片以及电解液，所述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，所述正极膜层由本申请的第二方面中任一项所述的正极浆料制备的。A fourth aspect of the present application provides a secondary battery, including a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte. 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 is prepared from the positive electrode slurry described in any one of the second aspects of the application.
本申请的第五方面提供一种电池模块，包括本申请的第四方面 的二次电池。The fifth aspect of the present application provides a battery module, including the fourth aspect of the present application. of secondary batteries.
本申请的第六方面提供一种电池包，包括本申请的第五方面的电池模块。A sixth aspect of the present application provides a battery pack, including the battery module of the fifth aspect of the present application.
本申请的第七方面提供一种用电装置，包括选自本申请的第四方面的二次电池、本申请的第五方面的电池模块或本申请的第六方面的电池包中的至少一种。A seventh aspect of the present application provides an electrical device, including at least one selected from the secondary battery of the fourth aspect of the present application, the battery module of the fifth aspect of the present application, or the battery pack of the sixth aspect of the present application. kind.
附图说明Description of drawings
图1是本申请一实施方式的二次电池的示意图。FIG. 1 is a schematic diagram of a secondary battery according to an embodiment of the present application.
图2是图1所示的本申请一实施方式的二次电池的分解图。FIG. 2 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 1 .
图3是本申请一实施方式的电池模块的示意图。Figure 3 is a schematic diagram of a battery module according to an embodiment of the present application.
图4是本申请一实施方式的电池包的示意图。Figure 4 is a schematic diagram of a battery pack according to an embodiment of the present application.
图5是图4所示的本申请一实施方式的电池包的分解图。FIG. 5 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG. 4 .
图6是本申请一实施方式的二次电池用作电源的用电装置的示意图。FIG. 6 is a schematic diagram of a power consumption device using a secondary battery as a power source according to an embodiment of the present application.
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。Explanation of reference symbols:
1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 secondary battery; 51 shell; 52 electrode assembly; 53 cover.
具体实施方式Detailed ways
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物质及其制造方法、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。Embodiments specifically disclosing the positive electrode active material and its manufacturing method, the positive electrode tab, the secondary battery, the battery module, the battery pack, and the electrical device of the present application will be described in detail below with appropriate reference to the drawings. However, unnecessary detailed explanations may be omitted. For example, detailed descriptions of well-known matters may be omitted, or descriptions of substantially the same structure may be repeated. This is to prevent the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application, and are not intended to limit the subject matter described in the claims.
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。The "range" disclosed in this application is defined in the form of a lower limit and an upper limit. The given range is defined by selecting a lower limit and an upper limit. The selected lower limit and upper limit Determine the boundaries of a special 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. Additionally, 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 to 3, 1 to 4, 1 to 5, 2 to 3, 2~4 and 2~5. In this application, unless otherwise stated, 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. For example, 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. In addition, when stating that a certain parameter is an integer ≥ 2, it is equivalent to disclosing that the parameter is an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.
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。If there is no special description, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.
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。If there is no special description, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions.
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。If there is no special instructions, all steps of the present application can be performed sequentially or randomly, and are preferably performed sequentially. For example, 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. For example, mentioning that the method may also include step (c) means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c). , may also include steps (a), (c) and (b), may also include steps (c), (a) and (b), etc.
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。If there is no special explanation, the words "include" and "include" mentioned in this application represent open expressions, which may also be closed expressions. For example, "comprising" and "comprising" may mean that other components not listed may also be included or included, or only the listed components may be included or included.
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)。In this application, the term "or" is inclusive unless otherwise specified. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, 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).
传统粘结剂，如PVDF往往需要较高的含量(2％以上)才能满足极片粘结力的需求，这限制了极片中活性物质负载量的提升，不利于电池能量密度的提升。而且，在电池加工热压整形处理时，高的粘结剂用量容易使得最内圈阴极拐角处的膜层因抗张力不足被绷断，导致极片发生透光现象，从而引发极片的脆性(或脆断)问题，降低电池的安全性和循环性能。再者，传统粘结剂与新一代正极活性物质相容性差，制备的浆料分散性和稳定性较差，极片中的正极活性物质分布不均匀，限制了电池性能的提高。Traditional binders, such as PVDF, often require a high content (more than 2%) to meet the bonding strength requirements of the pole pieces, which limits the increase in active material loading in the pole pieces and is not conducive to the improvement of battery energy density. Moreover, during battery processing and hot-pressing shaping, a high amount of binder can easily cause the film layer at the corner of the innermost cathode to be broken due to insufficient tensile strength, resulting in light transmission of the pole piece, thereby causing the brittleness of the pole piece. (or brittle fracture) problem, reducing the safety and cycle performance of the battery. Furthermore, the traditional binder has poor compatibility with the new generation of cathode active materials, the prepared slurry has poor dispersion and stability, and the cathode active materials in the pole piece are unevenly distributed, which limits the improvement of battery performance.
[正极浆料][Cathode slurry]
基于此，本申请提出了一种正极浆料，所述正极浆料中包括正极活性物质，导电剂，分散剂以及粘结剂，所述分散剂包括重均分子量为0.5万～15万的第一聚合物，所述粘结剂包括重均分子量为70万～110万的第二聚合物和重均分子量为130万～300万的第三聚合物，所述第一聚合物、所述第二聚合物和所述第三聚合物均为含有式I所示结构单元的聚合物，
Based on this, this application proposes a cathode slurry, which includes a cathode active material, a conductive agent, a dispersant and a binder. The dispersant includes a third cathode slurry with a weight average molecular weight of 0.5 million to 150.000. A polymer, the binder includes a second polymer with a weight average molecular weight of 700,000 to 1.1 million and a third polymer with a weight average molecular weight of 1.3 million to 3 million, the first polymer, the third polymer Both the second polymer and the third polymer are polymers containing structural units represented by formula I,
其中，R1、R2各自独立地选自氢、氟、氯或三氟甲基。Wherein, R 1 and R 2 are each independently selected from hydrogen, fluorine, chlorine or trifluoromethyl.
在本文中，术语“正极”也指电池中的“阴极”。术语“负极”也指电池中的“阳极”。In this article, the term "positive electrode" also refers to the "cathode" in a battery. The term "negative electrode" also refers to the "anode" in a battery.
本文中，术语“分散剂”是指促使物料颗粒均匀分散于胶体溶液或胶体分散液的化学化合物、聚合物或混合物。In this article, the term "dispersant" refers to a chemical compound, polymer or mixture that promotes uniform dispersion of material particles in a colloidal solution or colloidal dispersion.
本文中，术语“粘结剂”是指使固体物体与另一固体物体紧密连接为一体的化学化合物、聚合物或混合物。在极片制备过程中，术语“粘结剂”也指使电池浆料中固体物质紧密连接为一体的化学化合物、聚合物或混合物。As used herein, the term "binder" refers to a chemical compound, polymer or mixture that tightly connects a solid object to another solid object. In the electrode plate preparation process, the term "binder" also refers to the chemical compound, polymer or mixture that tightly connects the solid substances in the battery slurry into one body.
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。In this article, the term "weight average molecular weight" refers to the use of different molecular weights in the polymer. The sum of the weight fractions of molecules multiplied by their corresponding molecular weights.
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或混合物。In this context, the term "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 on the other hand also includes derivatives of aggregates of macromolecules formed by polymerization reactions which are obtainable by reaction, for example addition or substitution, of functional groups in said macromolecules and which may be chemically homogeneous or chemically A non-homogeneous compound or mixture.
在一些实施方式中，所述分散剂用于电池正极浆料，提高正极浆料的分散性。在一些实施方式中，所述分散剂还可以用于电池负极浆料，提高负极浆料的分散性。In some embodiments, the dispersant is used in battery cathode slurry to improve the dispersibility of the cathode slurry. In some embodiments, the dispersant can also be used in battery negative electrode slurry to improve the dispersibility of the negative electrode slurry.
不受任何理论的约束，第一聚合物的重均分子量为0.5万～15万时，分子间作用力比较小，粘附力和浸润性能良好，可以很好地粘附正极浆料中的正极活性物质，防止/减少正极活性物质之间聚集；第一聚合物在正极浆料的溶剂(或分散介质)中，通过静电排斥或空间位阻作用，分散或悬浮于溶剂中，进而使得正极浆料的分散性显著提高，在一定时间内放置不沉降，改善了正极浆料的稳定性，有助于提高浆料的固含量和极片的涂布速率；正极活性物质质在极片中均匀分布有利于提高极片的电子传导效率和降低电池极片膜层电阻，提高电池循环性能。Without being bound by any theory, when the weight average molecular weight of the first polymer is 0.5 million to 150.000, the intermolecular force is relatively small, the adhesion and wetting properties are good, and the positive electrode in the positive electrode slurry can be well adhered. Active materials prevent/reduce aggregation between positive electrode active materials; the first polymer is dispersed or suspended in the solvent (or dispersion medium) of the positive electrode slurry through electrostatic repulsion or steric hindrance, thereby making the positive electrode slurry The dispersion of the material is significantly improved, and it does not settle after being placed for a certain period of time, which improves the stability of the positive electrode slurry and helps to increase the solid content of the slurry and the coating rate of the pole piece; the positive active material is evenly distributed in the pole piece The distribution is conducive to improving the electron conduction efficiency of the pole piece, reducing the film resistance of the battery pole piece, and improving the battery cycle performance.
本申请中，所述粘结剂包括重均分子量为70万～110万的第二聚合物和重均分子量为130万～300万的第三聚合物。所述第三聚合物具有较高的粘度，使用第三聚合物作为粘结剂时，添加少量即可使极片具有良好的粘结力。然而，由于第三聚合物的结晶性较高，单独作为粘结剂使用时，制备的极片在电池热压处理时外侧膜层由于粘结剂的塑性变形应力不足而极易产生裂纹断裂。所述裂纹断裂是指在极片加工过程中，浆料中固体物质经处理成为膜层附着在集流上，极片(或裸电芯)在热压整形时最内1～2圈阴极拐角处容易产生裂纹，导致极片发生透光现象。极片的裂纹断裂导致极片在掉粉的同时裸露出新鲜的铝箔。随着循环的进行，电解液会分解产生氢氟酸，氢氟酸对铝箔起腐蚀作用，会降低电池的电化学表现和循环 性能。In this application, the binder includes a second polymer with a weight average molecular weight of 700,000 to 1.1 million and a third polymer with a weight average molecular weight of 1.3 million to 3 million. The third polymer has a high viscosity. When using the third polymer as a binder, a small amount of the third polymer can be added to make the pole piece have good bonding force. However, due to the high crystallinity of the third polymer, when used alone as a binder, the outer film layer of the prepared pole piece is easily cracked due to insufficient plastic deformation stress of the binder during the hot pressing process of the battery. The crack fracture refers to the fact that during the processing of the pole piece, the solid matter in the slurry is processed into a film layer that adheres to the current collector, and the pole piece (or bare cell) is formed by the innermost 1 to 2 turns of the cathode corner during hot pressing and shaping. Cracks are prone to occur, causing light transmission in the pole piece. The cracks and fractures of the pole piece cause the pole piece to lose powder and expose fresh aluminum foil. As the cycle proceeds, the electrolyte will decompose to produce hydrofluoric acid. Hydrofluoric acid will corrode the aluminum foil and reduce the electrochemical performance and cycle of the battery. performance.
在本文中，术语“集流体”是指在二次电池的放电或充电期间能够传导电流至电极的任何导电基底。As used herein, the term "current collector" refers to any conductive substrate capable of conducting current to an electrode during discharge or charging of a secondary battery.
术语“膜层”是指正极或负极浆料涂布干燥后形成的涂层。The term "film layer" refers to the coating formed after the positive electrode or negative electrode slurry is coated and dried.
当第三聚合物的重均分子量大于300万时，虽然粘结剂的粘度提高会进一步降低粘结剂的添加量，但同时也加剧了正极活性物质分散不均匀的问题，影响浆料的分散性和稳定性，并最终导致极片膜层电阻增高和电池循环性能降低。当第三聚合物的重均分子量低于130万时，粘结剂的粘度降低，虽然改善了浆料的分散性，但同时降低了极片的粘结力。为了提高极片的粘结力需要增加第三聚合物和/或第二聚合物的用量，粘结剂用量的提高会降低极片中正极活性物质负载量，进而影响电池能量密度。When the weight average molecular weight of the third polymer is greater than 3 million, although the increase in the viscosity of the binder will further reduce the amount of binder added, it will also aggravate the problem of uneven dispersion of the positive active material and affect the dispersion of the slurry. properties and stability, and ultimately lead to an increase in the resistance of the pole piece film and a decrease in battery cycle performance. When the weight average molecular weight of the third polymer is lower than 1.3 million, the viscosity of the binder decreases. Although the dispersion of the slurry is improved, the adhesive force of the pole piece is also reduced. In order to improve the binding force of the electrode piece, it is necessary to increase the amount of the third polymer and/or the second polymer. Increasing the amount of binder will reduce the loading of the positive active material in the electrode piece, thereby affecting the energy density of the battery.
不受任何理论的约束，本申请中，第二聚合物可以***第三聚合物分子有规则的链段中，使第三聚合物分子结构的有序性降低而降低粘结剂的结晶度，从而提高膜层的塑性变形应力并足以在极片热压处理时不产生裂纹断裂，改善了极片的柔性，有利于提高极片的加工性和降低由极片裂纹引发的断裂(或脆断)带来的电池安全隐患。Without being bound by any theory, in this application, the second polymer can be inserted into the regular chain segments of the third polymer molecule to reduce the orderliness of the molecular structure of the third polymer and reduce the crystallinity of the binder. This increases the plastic deformation stress of the film layer enough to prevent cracks and fractures during the hot pressing treatment of the pole piece, improves the flexibility of the pole piece, is conducive to improving the processability of the pole piece and reducing fracture (or brittle fracture) caused by cracks in the pole piece. ) brings potential battery safety hazards.
当第二聚合物的重均分子量大于110万时，同样会由于粘结剂粘度的提高导致极片膜层电阻增高和电池循环性能降低。另外，由于第二聚合物分子链长的增加，与第三聚合物分子链长的差异减小，第三聚合物分子的空间结构不足以容纳第二聚合物分子的长链，二者混合后无法降低第三聚合物分子空间结构的有序性，也无法降低粘结剂的结晶性。当第二聚合物的重均分子量小于70万时，由于粘结剂的粘度降低，为使极片具有良好的粘结力，需要提高第二聚合物和/或第三聚合物的用量，不利于提高极片中正极活性物质负载量；另外，由于第二聚合物分子链长和第三聚合物分子链长的差异过大，第二聚合物的分子链无法与第三聚合物的分子链形成有效的物理缠绕/交联，对第三聚合物的结晶性影响变小，无法提高膜层的塑性应变力和极片的柔性。 When the weight average molecular weight of the second polymer is greater than 1.1 million, the resistance of the electrode sheet film layer will also increase and the battery cycle performance will decrease due to the increase in binder viscosity. In addition, due to the increase in the chain length of the second polymer molecule, the difference in chain length between the second polymer molecule and the third polymer molecule is reduced. The spatial structure of the third polymer molecule is not sufficient to accommodate the long chain of the second polymer molecule. After the two are mixed, The orderliness of the spatial structure of the third polymer molecule cannot be reduced, nor can the crystallinity of the binder be reduced. When the weight average molecular weight of the second polymer is less than 700,000, due to the reduced viscosity of the binder, in order to ensure that the pole piece has good adhesive force, the amount of the second polymer and/or the third polymer needs to be increased. It is beneficial to increase the loading capacity of the positive electrode active material in the pole piece; in addition, because the difference in molecular chain length of the second polymer and the third polymer is too large, the molecular chain of the second polymer cannot match the molecular chain of the third polymer. Effective physical entanglement/cross-linking is formed, which has a smaller impact on the crystallinity of the third polymer and cannot improve the plastic strain stress of the film layer and the flexibility of the pole piece.
本申请中，通过特定重均分子量的第二聚合物和第三聚合物的联用，特别是重均分子量为70万～110万的第二聚合物和重均分子量为130万～300万的第三聚合物的联用，可以降低现有技术中粘结剂的用量，在粘结剂为低添加量时即可使极片具有良好的粘结力，有助于提高极片中正极活性物质的负载量和电池能量密度。同时，第二聚合物和第三聚合物的联用还改善了粘结剂的结晶性，提高了极片的柔性。In this application, through the combined use of a second polymer and a third polymer with a specific weight average molecular weight, especially a second polymer with a weight average molecular weight of 700,000 to 1.1 million and a second polymer with a weight average molecular weight of 1.3 million to 3 million. The combined use of the third polymer can reduce the amount of binder used in the existing technology. When the binder is added at a low amount, the electrode piece can have good bonding force, which helps to improve the positive electrode activity in the electrode piece. Material loading capacity and battery energy density. At the same time, the combination of the second polymer and the third polymer also improves the crystallinity of the binder and increases the flexibility of the pole piece.
在一些实施方式中，第一聚合物、第二聚合物和/或第三聚合物能够溶解于油性溶剂。在一些实施例中，第一聚合物、第二聚合物和/或第三聚合物能够溶解于水性溶剂中。示例性的油性溶剂包括二甲基乙酰胺、N，N-二甲基甲酰胺、N-甲基吡咯烷酮、丙酮和碳酸二甲酯。水性溶剂的示例包括但不限于水。In some embodiments, the first polymer, second polymer, and/or third polymer are soluble in oily solvents. In some embodiments, the first polymer, second polymer, and/or third polymer are soluble in an aqueous solvent. Exemplary oily solvents include dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, acetone, and dimethyl carbonate. Examples of aqueous solvents include, but are not limited to, water.
在一些实施方式中，所述第一聚合物、所述第二聚合物和所述第三聚合物均为卤代烃聚合物，各自独立地选自聚四氟乙烯、聚偏二氟乙烯、偏二氟乙烯和六氟丙烯的共聚物、偏二氟乙烯和四氟乙烯的共聚物、偏二氟乙烯和三氟氯乙烯的共聚物、聚三氟氯乙烯中的一种或多种。In some embodiments, the first polymer, the second polymer and the third polymer are all halogenated hydrocarbon polymers, each independently selected from polytetrafluoroethylene, polyvinylidene fluoride, One or more of a copolymer of vinylidene fluoride and hexafluoropropylene, a copolymer of vinylidene fluoride and tetrafluoroethylene, a copolymer of vinylidene fluoride and chlorotrifluoroethylene, and polychlorotrifluoroethylene.
在本文中，术语“卤代烃聚合物”是指卤素取代的不饱和烃的聚合物。术语“卤素”指包括氟、氯、溴、碘的卤族元素。As used herein, the term "halogenated hydrocarbon polymer" refers to a polymer of halogen-substituted unsaturated hydrocarbons. The term "halogen" refers to elements of the halogen family including fluorine, chlorine, bromine, and iodine.
所述聚合物具有化学性能稳定和电性能优良的特点，在电池的电解液中通常较小或极少发生溶胀。同时，所述聚合物具有很好的机械性能，有利于制备兼具适当柔性和硬度的膜层。The polymer has the characteristics of stable chemical properties and excellent electrical properties, and usually has little or very little swelling in the electrolyte of the battery. At the same time, the polymer has good mechanical properties, which is conducive to the preparation of a film layer with appropriate flexibility and hardness.
在一些实施方式中，所述第一聚合物的颗粒的中值粒径Dv50为0.5μm～5μm。在一些实施方式中，所述第一聚合物的颗粒的中值粒径Dv50为0.5～4.5μm，0.5～4μm，0.5～3.5μm，0.5～3μm，0.5～2.5μm，0.8～5μm，1～4μm，2～5μm，或者为2～4μm。In some embodiments, the particles of the first polymer have a median diameter Dv50 of 0.5 μm to 5 μm. In some embodiments, the median diameter Dv50 of the particles of the first polymer is 0.5~4.5 μm, 0.5~4 μm, 0.5~3.5 μm, 0.5~3 μm, 0.5~2.5 μm, 0.8~5 μm, 1~ 4μm, 2～5μm, or 2～4μm.
第一聚合物的颗粒粒径在合适范围内有利于在正极浆料溶剂，例如N-甲基吡咯烷酮中的溶解，降低胶液的加工难度。The particle size of the first polymer within a suitable range is beneficial to dissolution in the positive electrode slurry solvent, such as N-methylpyrrolidone, and reduces the processing difficulty of the glue solution.
在本文中，术语“中值粒径Dv50”是指测量样品的累计粒度分布百分数达到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％。In this article, the term "median particle size Dv50" refers to the particle size corresponding to when the cumulative particle size distribution percentage of the measured sample reaches 50%. Its physical meaning is that the particle size is smaller than (or larger than) Yu) Its particles account for 50%.
在一些实施方式中，所述第一聚合物溶于N-甲基吡咯烷酮制得第一胶液，基于所述第一胶液的总质量计，当所述第一聚合物的质量含量为7％时，所述第一胶液的粘度为20～180mPa·s。In some embodiments, the first polymer is dissolved in N-methylpyrrolidone to prepare a first glue solution. Based on the total mass of the first glue solution, when the mass content of the first polymer is 7 %, the viscosity of the first glue liquid is 20-180 mPa·s.
在一些实施方式中，所述第一聚合物溶于N-甲基吡咯烷酮制得第一胶液，基于所述第一胶液的总质量计，当所述第一聚合物的质量含量为7％时，所述第一胶液的粘度为30～180mPa·s，50～180mPa·s，20～160mPa·s，20～150mPa·s，30～120mPa·s或者20～50mPa·s。In some embodiments, the first polymer is dissolved in N-methylpyrrolidone to prepare a first glue solution. Based on the total mass of the first glue solution, when the mass content of the first polymer is 7 %, the viscosity of the first glue liquid is 30-180 mPa·s, 50-180 mPa·s, 20-160 mPa·s, 20-150 mPa·s, 30-120 mPa·s or 20-50 mPa·s.
当第一聚合物的粘度高于180mPa·s(质量含量为7％)时，其与正极活性物质的浸润性有所降低，不利于分散浆料；粘度在合适范围内的第一聚合物有助于正极活性物质粉体颗粒的润湿和解聚，减少正极活性物质团聚、堵塞滤网等现象，改善正极浆料的分散性能，提高正极浆料的固含量和极片涂布的均匀性，进而提升电池的能量密度。When the viscosity of the first polymer is higher than 180 mPa·s (mass content is 7%), its wettability with the positive active material is reduced, which is not conducive to dispersing the slurry; the first polymer with a viscosity within a suitable range has It helps to moisten and depolymerize the positive active material powder particles, reduce the agglomeration of positive active materials and filter clogging, improve the dispersion performance of the positive slurry, increase the solid content of the positive slurry and the uniformity of the pole piece coating, This in turn increases the energy density of the battery.
在一些实施方式中，所述第二聚合物的颗粒的中值粒径Dv50为15～25μm。在一些实施方式中，所述第二聚合物的颗粒的中值粒径Dv50为15～23μm，15～20μm，18～25μm或者20～25μm。In some embodiments, the particles of the second polymer have a median diameter Dv50 of 15 to 25 μm. In some embodiments, the particles of the second polymer have a median diameter Dv50 of 15 to 23 μm, 15 to 20 μm, 18 to 25 μm, or 20 to 25 μm.
第二聚合物的颗粒粒径在合适范围内有利于其在正极浆料溶剂，例如N-甲基吡咯烷酮中的溶解，降低胶液的加工难度，提高加工效率。The particle size of the second polymer within a suitable range is beneficial to its dissolution in the positive electrode slurry solvent, such as N-methylpyrrolidone, reducing the processing difficulty of the glue solution and improving the processing efficiency.
在一些实施方式中，所述第二聚合物溶于N-甲基吡咯烷酮制得第二胶液，基于所述第二胶液的总质量计，当所述第二聚合物的质量含量为7％时，所述第二胶液的粘度为2500～4000mPa·s。In some embodiments, the second polymer is dissolved in N-methylpyrrolidone to prepare a second glue liquid. Based on the total mass of the second glue liquid, when the mass content of the second polymer is 7 %, the viscosity of the second glue liquid is 2500-4000 mPa·s.
在一些实施方式中，所述第二聚合物溶于N-甲基吡咯烷酮制得第二胶液，基于所述第二胶液的总质量计，当所述第二聚合物的质量含量为7％时，所述第二胶液的粘度为2800～4000mPa·s，3000～4000mPa·s，3200～4000mPa·s，3500～4000mPa·s，2800～3800mPa·s或者，2800～3500mPa·s。In some embodiments, the second polymer is dissolved in N-methylpyrrolidone to prepare a second glue liquid. Based on the total mass of the second glue liquid, when the mass content of the second polymer is 7 %, the viscosity of the second glue liquid is 2800~4000mPa·s, 3000~4000mPa·s, 3200~4000mPa·s, 3500~4000mPa·s, 2800~3800mPa·s or 2800~3500mPa·s.
当第二聚合物的粘度高于4000mPa·s(质量含量为7％)时，分 子内或分子间作用力增加，不利于第二聚合物分子链在正极浆料溶剂中的自由摆动，进而影响与第三聚合物分子链的物理交联；当第二聚合物的粘度低于2800mPa·s时会导致粘结剂的粘接性能下降，为使极片具有良好的粘结力需要提高粘结剂的添加量，这会提高极片膜层电阻并导致电池循环性能受损，也不利于提高极片中正极活性物质的负载量。第二聚合物的粘度在合适范围内时，其分子链可以克服分子内或分子间作用力与第三聚合物的分子链进行物理交联/缠绕，降低第三聚合物分子的有序性和结晶规整性，提高粘结剂的柔韧性。When the viscosity of the second polymer is higher than 4000mPa·s (mass content is 7%), the The increase in intra-molecule or intermolecular forces is not conducive to the free swing of the second polymer molecular chain in the cathode slurry solvent, thereby affecting the physical cross-linking with the third polymer molecular chain; when the viscosity of the second polymer is lower than At 2800mPa·s, the adhesive performance of the adhesive will decrease. In order to make the electrode piece have good adhesive force, the amount of adhesive added needs to be increased. This will increase the electrode piece film resistance and cause damage to the battery cycle performance. It is also not conducive to increasing the loading capacity of the positive active material in the pole piece. When the viscosity of the second polymer is within a suitable range, its molecular chains can overcome intramolecular or intermolecular forces to physically cross-link/entangle with the molecular chains of the third polymer, reducing the orderliness and stability of the third polymer molecules. Crystal regularity improves the flexibility of the binder.
在一些实施方式中，所述第三聚合物的颗粒的中值粒径Dv50为30μm～100μm。在一些实施方式中，所述第三聚合物的颗粒的中值粒径Dv50为30μm～80μm，30μm～60μm，40μm～80μm，50μm～80μm，或者60μm～80μm。In some embodiments, the particles of the third polymer have a median diameter Dv50 of 30 μm to 100 μm. In some embodiments, the particles of the third polymer have a median diameter Dv50 of 30 μm to 80 μm, 30 μm to 60 μm, 40 μm to 80 μm, 50 μm to 80 μm, or 60 μm to 80 μm.
第三聚合物粘度较高，通常在正极浆料溶剂，例如N-甲基吡咯烷酮中的溶解速率低，第三聚合物的颗粒粒径在合适范围内有利于降低胶液的加工难度，提高极片的加工效率。The third polymer has a high viscosity and usually has a low dissolution rate in the cathode slurry solvent, such as N-methylpyrrolidone. The particle size of the third polymer within a suitable range is beneficial to reducing the processing difficulty of the glue and improving the electrode performance. chip processing efficiency.
在一些实施方式中，所述第三聚合物溶于N-甲基吡咯烷酮制得第三胶液，基于所述第三胶液的总质量计，当所述第三聚合物的质量含量为4％时，所述第三胶液的粘度为1500～5000mPa·s。In some embodiments, the third polymer is dissolved in N-methylpyrrolidone to prepare a third glue liquid. Based on the total mass of the third glue liquid, when the mass content of the third polymer is 4 %, the viscosity of the third glue liquid is 1500-5000 mPa·s.
在一些实施方式中，所述第三聚合物溶于N-甲基吡咯烷酮制得第三胶液，基于所述第三胶液的总质量计，当所述第三聚合物的质量含量为4％时，所述第三胶液的粘度为1700～4800mPa·s，1700～4500mPa·s，1700～4300mPa·s，1700～4000mPa·s，1700～3600mPa·s，1700～3500mPa·s，2000～4800mPa·s，2500～4800mPa·s或者3600～4800mPa·s。In some embodiments, the third polymer is dissolved in N-methylpyrrolidone to prepare a third glue liquid. Based on the total mass of the third glue liquid, when the mass content of the third polymer is 4 %, the viscosity of the third glue liquid is 1700~4800mPa·s, 1700~4500mPa·s, 1700~4300mPa·s, 1700~4000mPa·s, 1700~3600mPa·s, 1700~3500mPa·s, 2000~ 4800mPa·s, 2500～4800mPa·s or 3600～4800mPa·s.
当所述第三聚合物的粘度高于4800mPa·s(质量含量为4％)时，虽然粘接性能提高，但会导致正极浆料的分散性进一步劣化，浆料中正极活性物质分布不均匀不仅影响极片的加工性能，还会导致极片表面出现开裂、颗粒划痕、针孔等缺陷。当第三聚合物的粘度低于1700mPa·s时，粘结剂的粘结性能明显降低，浆料中固体物质之 间的结合力不足，或与集流体的粘结力不足，容易出现开裂或脱模的缺陷，严重危害使用该极片的电池的安全性。第三聚合物的粘度在合适范围内，粘结剂具有良好的粘结性能，添加量较低时即可使极片具有优良的粘结力，有助于提高正极活性物质的负载量和电池能量密度。When the viscosity of the third polymer is higher than 4800 mPa·s (mass content is 4%), although the bonding performance is improved, the dispersion of the cathode slurry will be further deteriorated and the cathode active material in the slurry will be unevenly distributed. It not only affects the processing performance of the pole piece, but also causes cracks, particle scratches, pinholes and other defects on the surface of the pole piece. When the viscosity of the third polymer is lower than 1700 mPa·s, the bonding performance of the binder is significantly reduced, and the solid matter in the slurry If the bonding force between the electrodes is insufficient, or the bonding force with the current collector is insufficient, cracking or demoulding defects may occur, seriously endangering the safety of the battery using the electrode piece. The viscosity of the third polymer is within a suitable range, and the binder has good bonding properties. When the addition amount is low, the electrode piece can have excellent bonding force, which helps to increase the loading capacity of the positive active material and the battery. Energy Density.
在一些实施方式中，所述第三聚合物的多分散系数为2～2.3。In some embodiments, the third polymer has a polydispersity coefficient of 2 to 2.3.
在一些实施方式中，所述第三聚合物的多分散系数为2.1～2.2。In some embodiments, the third polymer has a polydispersity coefficient of 2.1 to 2.2.
第三聚合物的多分散系数在上述范围内有助于维持第三聚合物粘度的稳定，从而提高极片生产的稳定性。The polydispersity coefficient of the third polymer within the above range helps to maintain the stability of the viscosity of the third polymer, thereby improving the stability of pole piece production.
在一些实施方式中，所述分散剂的质量含量为0.05％～1％，基于所述正极浆料的固体物质的总质量计。In some embodiments, the mass content of the dispersant is 0.05% to 1%, based on the total mass of solid matter of the cathode slurry.
在一些实施方式中，所述分散剂的质量含量为0.1％～1％，0.2％～1％，0.3％～1％，0.4％～1％，0.6％～1％，0.05％～0.8％，0.05％～0.6％，或者0.1％～0.6％，基于所述正极浆料的固体物质的总质量计。In some embodiments, the mass content of the dispersant is 0.1% to 1%, 0.2% to 1%, 0.3% to 1%, 0.4% to 1%, 0.6% to 1%, 0.05% to 0.8%, 0.05% to 0.6%, or 0.1% to 0.6%, based on the total mass of solid matter of the positive electrode slurry.
当所述分散剂的质量含量低于0.05％时，由于分散剂的含量过低，无法充分包覆或附着于正极浆料中的正极活性物质，不利于正极活性物质的分散，正极浆料粉体容易产生团聚、堵塞滤网等现象，影响正极浆料的稳定性和极片的加工性，导致膜层电阻增高。当所述分散剂的的质量含量高于1％时，由于分散剂的含量过高，降低了粘结剂的粘结性能，导电剂和正极活性物质的结合力降低，即，极片的粘结力小，容易在加工过程中出现脱模现象或者电池在长期循环使用过程中正极活性物质扩散到负极，造成极大的安全隐患。分散剂的质量含量在合适范围内可以改善正极浆料的分散性，并对粘结剂的粘接性能无影响或影响极小。When the mass content of the dispersant is less than 0.05%, because the content of the dispersant is too low, it cannot fully coat or adhere to the cathode active material in the cathode slurry, which is not conducive to the dispersion of the cathode active material and the cathode slurry powder The body is prone to agglomeration, clogging of filters, etc., which affects the stability of the positive electrode slurry and the processability of the pole piece, resulting in an increase in film resistance. When the mass content of the dispersant is higher than 1%, because the content of the dispersant is too high, the bonding performance of the binder is reduced, and the binding force between the conductive agent and the positive electrode active material is reduced, that is, the adhesion of the pole piece is reduced. The junction force is small, and it is easy to demoulding during processing or the positive active material diffuses into the negative electrode during long-term recycling of the battery, causing great safety risks. The mass content of the dispersant within a suitable range can improve the dispersion of the cathode slurry and has no or minimal impact on the bonding performance of the binder.
在一些实施方式中，所述粘结剂的质量含量为0.6％～1.2％，基于所述正极浆料的固体物质的总质量计。In some embodiments, the mass content of the binder is 0.6% to 1.2%, based on the total mass of solid matter of the cathode slurry.
在一些实施方式中，所述粘结剂的质量含量为0.7％～1.2％，0.8％～1.2％，0.9％～1.2％，1％～1.2％，0.6％～1.1％，0.6％～1.0％，0.6％～0.9％或者0.6％～0.8％，基于所述正极浆料的固体物质的总质量 计。In some embodiments, the mass content of the binder is 0.7% to 1.2%, 0.8% to 1.2%, 0.9% to 1.2%, 1% to 1.2%, 0.6% to 1.1%, 0.6% to 1.0% , 0.6% to 0.9% or 0.6% to 0.8%, based on the total mass of solid matter of the positive electrode slurry count.
当所述粘结剂的质量含量高于1.2％时，虽然极片的粘结力会显著提高，但由于正极浆料的粘度过高导致浆料中正极活性物质分布不均匀，影响正极浆料的分散性和极片的质量，提高了极片膜层电阻和降低了电池循环性能。当粘结剂的质量含量低于0.6％时，粘结剂的粘接性能下降致使极片的粘结力不足，在加工过程中容易出现脱模现象或者电池在长期循环使用过程中正极活性物质扩散到负极，造成极大的安全隐患。粘结剂的质量含量在合适范围内可以确保极片具有良好的粘结力，避免正极活性物质与电解液的直接接触，减少副反应的发生，降低二次电池的安全隐患；同时，该粘结剂的添加量相对较低，有助于减小极片膜层电阻，提高正极活性物质的负载量和提高电池的能量密度。When the mass content of the binder is higher than 1.2%, although the bonding force of the electrode piece will be significantly improved, the viscosity of the positive electrode slurry will be too high, resulting in uneven distribution of the positive electrode active material in the slurry, affecting the positive electrode slurry. The dispersion and the quality of the pole piece increase the film layer resistance of the pole piece and reduce the battery cycle performance. When the mass content of the binder is less than 0.6%, the bonding performance of the binder decreases, resulting in insufficient bonding force of the electrode piece. Demolding is prone to occur during processing or the positive active material of the battery during long-term recycling. Diffusion to the negative electrode, causing great safety hazards. The mass content of the binder within an appropriate range can ensure that the electrode piece has good adhesion, avoid direct contact between the positive active material and the electrolyte, reduce the occurrence of side reactions, and reduce the safety hazards of secondary batteries; at the same time, the adhesive The addition of the binder is relatively low, which helps to reduce the film resistance of the electrode sheet, increase the loading capacity of the positive active material and increase the energy density of the battery.
在一些实施方式中，在所述粘结剂中，所述第二聚合物和所述第三聚合物的质量比为1:9～8:2，或者0.1～4:1。In some embodiments, in the binder, the mass ratio of the second polymer to the third polymer is 1:9˜8:2, or 0.1˜4:1.
在一些实施方式中，在所述粘结剂中，所述第二聚合物和所述第三聚合物的质量比为0.1～4:1，0.25～4:1，0.5～4:1，1～4:1，1.5～4:1，2～4:1，2.5～4:1或者3～4:1，。In some embodiments, in the binder, the mass ratio of the second polymer to the third polymer is 0.1~4:1, 0.25~4:1, 0.5~4:1, 1 ~4:1, 1.5~4:1, 2~4:1, 2.5~4:1 or 3~4:1.
所述第二聚合物和所述第三聚合物的质量比在上述范围内时，可以确保极片在具有良好粘结力的前提下还具有提高的柔性。When the mass ratio of the second polymer to the third polymer is within the above range, it can be ensured that the pole piece has improved flexibility while having good adhesion.
在一些实施方式中，所述粘结剂的结晶度为25％～44％。In some embodiments, the binder has a crystallinity of 25% to 44%.
在一些实施方式中，所述粘结剂的结晶度为25％～42％，25％～40％，25％～38％，25％～35％，25％～32％，25％～30％，28％～42％，30％～42％，或者35％～42％。In some embodiments, the crystallinity of the binder is 25% to 42%, 25% to 40%, 25% to 38%, 25% to 35%, 25% to 32%, 25% to 30% , 28% to 42%, 30% to 42%, or 35% to 42%.
当所述粘结剂的结晶度低于25％时，极片膜层中固体物质之间的结合力或膜层的粘结力不足，容易在电池加工过程中出现脱模现象，或者电池在长期循环使用过程中正极活性物质扩散到负极，造成极大的安全隐患。当粘结剂的结晶度高于44％时，膜层在裸电芯热压处理时的塑性应变力不足，容易产生裂纹断裂。所述粘结剂的结晶度在合适的范围内，可以使极片柔性提高的同时兼具适宜的硬度，有利于二次电池加工和降低二次电池的安全隐患。 When the crystallinity of the binder is lower than 25%, the bonding force between the solid substances in the pole piece film layer or the bonding force of the film layer is insufficient, and demolding may easily occur during battery processing, or the battery may During long-term recycling, the positive active material diffuses into the negative electrode, causing great safety hazards. When the crystallinity of the binder is higher than 44%, the plastic strain stress of the film layer during the hot pressing treatment of the bare battery core is insufficient, and cracks and fractures are prone to occur. The crystallinity of the binder is within a suitable range, which can improve the flexibility of the electrode piece while maintaining a suitable hardness, which is beneficial to the processing of secondary batteries and reduces the safety hazards of secondary batteries.
在一些实施方式中，所述粘结剂的熔融焓为25J/g～45J/g。In some embodiments, the melting enthalpy of the binder ranges from 25 J/g to 45 J/g.
在一些实施方式中，所述粘结剂的熔融焓为28J/g～45J/g，30J/g～45J/g，32J/g～45J/g，35J/g～45J/g，28J/g～43J/g，28J/g～40J/g，28J/g～38J/g，28J/g～35J/g，或者28J/g～33J/g。In some embodiments, the melting enthalpy of the binder is 28J/g～45J/g, 30J/g～45J/g, 32J/g～45J/g, 35J/g～45J/g, 28J/g ~43J/g, 28J/g~40J/g, 28J/g~38J/g, 28J/g~35J/g, or 28J/g~33J/g.
所述粘结剂的熔融焓在合适范围内可以使粘结剂的结晶性适中，使极片兼具优异的柔性和粘结力。If the melting enthalpy of the binder is within a suitable range, the crystallinity of the binder can be moderate, so that the pole piece has both excellent flexibility and adhesive force.
在一些实施方式中，所述正极活性物质为含锂的过渡金属氧化物。In some embodiments, the cathode active material is a lithium-containing transition metal oxide.
在一些实施方式中，所述正极活性物质为磷酸铁锂或锂镍钴锰氧化物，或它们的掺杂改性材料、或它们的导电碳包覆改性材料、导电金属包覆改性材料或导电聚合物包覆改性材料中的至少一种。In some embodiments, the positive active material is lithium iron phosphate or lithium nickel cobalt manganese oxide, or their doping modified materials, or their conductive carbon coating modification materials, conductive metal coating modification materials Or at least one of the conductive polymer coating modified materials.
本申请还提供了一种正极浆料的制备方法，所述制备方法包括以下步骤：This application also provides a preparation method of cathode slurry, which preparation method includes the following steps:
步骤1：将正极活性物质、导电剂和粘结剂混合均匀；所述粘结剂包括重均分子量为70万～110万的第二聚合物和重均分子量为130万～300万的第三聚合物，Step 1: Mix the positive active material, conductive agent and binder evenly; the binder includes a second polymer with a weight average molecular weight of 700,000 to 1.1 million and a third polymer with a weight average molecular weight of 1.3 million to 3 million. polymer,
步骤2：加入分散剂进行搅拌，得到正极浆料，所述分散剂包括重均分子量为0.5万～15万的第一聚合物，所述第一聚合物、所述第二聚合物和所述第三聚合物均为至少一种式II所示单体在可聚合条件下聚合制备而得，
Step 2: Add a dispersant and stir to obtain a positive electrode slurry. The dispersant includes a first polymer with a weight average molecular weight of 0.5 million to 150.000. The first polymer, the second polymer and the The third polymers are all prepared by polymerizing at least one monomer represented by formula II under polymerizable conditions,
其中，R1、R2各自独立地选自氢、氟、氯或三氟甲基。Wherein, R 1 and R 2 are each independently selected from hydrogen, fluorine, chlorine or trifluoromethyl.
通过先加入粘结剂再加入分散剂的方式有利于实现正极活性物质、导电剂和高分子量的粘结剂之间的充分混合、粘附/包覆，通过后加入分散剂可以有效避免正极活性物质和高分子量粘结剂的沉降，有利于同时提高正极浆料的分散性和稳定性。By adding the binder first and then the dispersant, it is beneficial to achieve full mixing, adhesion/coating between the positive electrode active material, conductive agent and high molecular weight binder. By adding the dispersant later, the positive electrode activity can be effectively avoided. The sedimentation of substances and high molecular weight binders is conducive to simultaneously improving the dispersion and stability of the cathode slurry.
在一些实施方式中，所述R1、R2均为氢。在一些实施方式中，所述R1、R2均为氟。在一些实施方式中，R1为氢、R2为三氟甲基。 在一些实施方式中，R1为三氟甲基、R2为氢。In some embodiments, R 1 and R 2 are both hydrogen. In some embodiments, R 1 and R 2 are both fluorine. In some embodiments, R 1 is hydrogen and R 2 is trifluoromethyl. In some embodiments, R 1 is trifluoromethyl and R 2 is hydrogen.
在一些实施方式中，所述第一聚合物的制备方法包括以下步骤：In some embodiments, the preparation method of the first polymer includes the following steps:
提供至少一种式II所示单体、第一引发剂和第一溶剂，在常压、55℃～80℃的反应温度下进行聚合反应2小时～8小时，停止反应，固液分离，保留固相，得到第一聚合物。Provide at least one monomer represented by formula II, a first initiator and a first solvent, perform a polymerization reaction at normal pressure and a reaction temperature of 55°C to 80°C for 2 hours to 8 hours, stop the reaction, separate solid and liquid, and retain solid phase to obtain the first polymer.
在一些实施方式中，所述第一聚合物的制备方法包括以下步骤：In some embodiments, the preparation method of the first polymer includes the following steps:
提供至少一种式II所示单体、第一引发剂和第一溶剂，在非反应性气体氛围、常压、55℃～80℃的反应温度下进行聚合反应2小时～8小时，停止反应，固液分离，保留固相，得到第一聚合物。Provide at least one monomer represented by Formula II, a first initiator and a first solvent, perform the polymerization reaction in a non-reactive gas atmosphere, normal pressure, and a reaction temperature of 55°C to 80°C for 2 hours to 8 hours, and then stop the reaction. , solid-liquid separation, retaining the solid phase, and obtaining the first polymer.
术语“非反应性气体”是指不会参与聚合反应的气体，示例性的非反应性气体包括氩气、氦气和氮气中的任意或组合。The term "non-reactive gas" refers to a gas that does not participate in the polymerization reaction. Exemplary non-reactive gases include any or a combination of argon, helium, and nitrogen.
术语“常压”指一个标准大气压，即101KPa。The term "normal pressure" refers to a standard atmospheric pressure, which is 101KPa.
在一些实施方式中，第一聚合物的制备方法中，所述反应温度为60℃～80℃，65℃～80℃，70℃～80℃或者66℃～80℃，68℃～80℃，73℃～80℃，64℃～75℃或者55℃～73℃。In some embodiments, in the preparation method of the first polymer, the reaction temperature is 60°C to 80°C, 65°C to 80°C, 70°C to 80°C, or 66°C to 80°C, 68°C to 80°C, 73℃～80℃, 64℃～75℃ or 55℃～73℃.
在一些实施方式中，第一聚合物的制备方法中，所述反应时间为2小时～4小时、2小时～3小时、2小时～6小时、3小时～8小时、3小时～6小时、4小时～8小时、4小时～6小时、6小时～8小时。In some embodiments, in the preparation method of the first polymer, the reaction time is 2 hours to 4 hours, 2 hours to 3 hours, 2 hours to 6 hours, 3 hours to 8 hours, 3 hours to 6 hours, 4 hours to 8 hours, 4 hours to 6 hours, 6 hours to 8 hours.
在一些实施方式中，第一聚合物的制备方法还包括以下步骤：In some embodiments, the preparation method of the first polymer further includes the following steps:
向容器中加入第一溶剂和第一分散助剂，向所述容器充入非反应性气体；Add the first solvent and the first dispersion aid to the container, and fill the container with a non-reactive gas;
向所述容器中加入第一引发剂和第一pH调节剂，调节pH值，然后加入式II所示单体，搅拌0.5小时～1小时后，升温至55℃～80℃，进行聚合反应2小时～8小时。Add the first initiator and the first pH regulator to the container to adjust the pH value, then add the monomer represented by formula II, stir for 0.5 to 1 hour, then raise the temperature to 55°C to 80°C to perform polymerization reaction 2 hours to 8 hours.
术语“引发剂”是指在聚合反应中，能引发单体进行聚合反应的物质。示例性引发剂如2-乙基过氧化二碳酸酯，叔丁基过氧化新戊酸酯、过氧化叔戊基新戊酸酯。The term "initiator" refers to a substance that initiates the polymerization of monomers during a polymerization reaction. Exemplary initiators include 2-ethyl peroxydicarbonate, tert-butyl peroxypivalate, and tert-amyl peroxypivalate.
术语“pH调节剂”是指可以改变溶液或分散介质酸碱度的物质，包括提高酸度或提高碱度。示例性的pH调节剂如碳酸氢钠，碳酸钠和氢氧化钠。 The term "pH adjuster" refers to a substance that changes the pH of a solution or dispersion medium, including increasing the acidity or increasing the alkalinity. Exemplary pH adjusting agents include sodium bicarbonate, sodium carbonate and sodium hydroxide.
术语“分散助剂”是指在合成反应中能够促进单体均匀分散于介质中的物质。示例性的分散助剂包括羧乙基纤维素醚和甲基纤维素醚。The term "dispersion aid" refers to substances that can promote the uniform dispersion of monomers in the medium during synthesis reactions. Exemplary dispersing aids include carboxyethyl cellulose ether and methyl cellulose ether.
在一些实施方式中，第一聚合物的制备方法中，所述第一溶剂为水，有利于降低对环境的危害。In some embodiments, in the method for preparing the first polymer, the first solvent is water, which is beneficial to reducing harm to the environment.
在一些实施方式中，第一聚合物的制备方法中，调节pH值至6.5～7，例如6.5，6.8或7。In some embodiments, in the preparation method of the first polymer, the pH value is adjusted to 6.5-7, such as 6.5, 6.8 or 7.
在一些实施方式中，第一聚合物的制备方法中，搅拌时间为30分钟～55分钟，30分钟～50分钟，30分钟～45分钟，35分钟～60分钟，40分钟～60分钟或者45分钟～60分钟。In some embodiments, in the preparation method of the first polymer, the stirring time is 30 minutes to 55 minutes, 30 minutes to 50 minutes, 30 minutes to 45 minutes, 35 minutes to 60 minutes, 40 minutes to 60 minutes or 45 minutes. ~60 minutes.
第一聚合物的制备方法中，制备的第一聚合物(或分散剂)具有较低的重均分子量和粘度，与正极活性物质具有良好的粘附作用，显著提高浆料的分散性和稳定性。第一聚合物的该制备方法原材料成本低，反应条件温和，有利于分散剂的量产。In the preparation method of the first polymer, the prepared first polymer (or dispersant) has a lower weight average molecular weight and viscosity, has good adhesion with the cathode active material, and significantly improves the dispersion and stability of the slurry. sex. The preparation method of the first polymer has low raw material cost and mild reaction conditions, which is conducive to mass production of the dispersant.
在一些实施方式中，所述第三聚合物的制备方法包括以下步骤：In some embodiments, the preparation method of the third polymer includes the following steps:
提供至少一种式II所示单体、第二引发剂和第二溶剂，当式II所示单体使得反应压力达到6MPa～8MPa时，升高温度至35℃～60℃，进行聚合反应6小时～10小时；Provide at least one monomer represented by formula II, a second initiator and a second solvent. When the monomer represented by formula II causes the reaction pressure to reach 6MPa~8MPa, increase the temperature to 35°C~60°C to perform polymerization reaction 6 hours to 10 hours;
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，得到第三聚合物。Add a chain transfer agent, wait until the pressure in the reaction system drops to 2MPa ~ 2.5MPa, stop the reaction, separate the solid and liquid, retain the solid phase, and obtain the third polymer.
在一些实施方式中，所述第三聚合物的制备方法在非反应性气体氛围下进行。In some embodiments, the preparation method of the third polymer is performed under a non-reactive gas atmosphere.
第三聚合物的制备方法中，所述引发剂的含义与第一聚合物制备方法中引发剂的含义相同。在一些实施方式中，第一引发剂和第二引发剂为同一种化学物质。在一些实施方式中，第一引发剂和第二引发剂为不同的化学物质。In the preparation method of the third polymer, the initiator has the same meaning as the initiator in the preparation method of the first polymer. In some embodiments, the first initiator and the second initiator are the same chemical substance. In some embodiments, the first initiator and the second initiator are different chemicals.
在一些实施方式中，所述第二引发剂为叔丁基过氧化新戊酸酯。In some embodiments, the second initiator is tert-butyl peroxypivalate.
术语“链转移剂”指能够产生自由基，该自由基与原料分子作用后生成产物和另一个自由基，使反应能持续进行的化学物质。链转移剂可以用于控制聚合物的链长度，亦即控制聚合物的聚合度， 或聚合物的粘度。示例性的链转移剂如环己烷。The term "chain transfer agent" refers to a chemical substance that generates free radicals that react with raw material molecules to form a product and another free radical, allowing the reaction to continue. Chain transfer agents can be used to control the chain length of polymers, that is, to control the degree of polymerization of polymers, or the viscosity of the polymer. An exemplary chain transfer agent is cyclohexane.
在一些实施方式中，第三聚合物的制备方法中，向反应容器中充入式II所示单体至反应压力达到6MPa～7MPa或7MPa～8MPa。In some embodiments, in the preparation method of the third polymer, the monomer represented by Formula II is charged into the reaction vessel until the reaction pressure reaches 6MPa to 7MPa or 7MPa to 8MPa.
在一些实施方式中，所述第三聚合物的反应温度为37℃～60℃，40℃～60℃，43℃～60℃，45℃～60℃，50℃～60℃，35℃～55℃，35℃～50℃或者35℃～45℃。In some embodiments, the reaction temperature of the third polymer is 37°C to 60°C, 40°C to 60°C, 43°C to 60°C, 45°C to 60°C, 50°C to 60°C, 35°C to 55°C ℃, 35℃～50℃ or 35℃～45℃.
在一些实施方式中，所述第三聚合物的反应时间为6小时～9小时，6小时～8小时，6小时～7小时，7小时～10小时，8小时～10小时，9小时～10小时或者8小时～9小时。In some embodiments, the reaction time of the third polymer is 6 hours to 9 hours, 6 hours to 8 hours, 6 hours to 7 hours, 7 hours to 10 hours, 8 hours to 10 hours, 9 hours to 10 hours hours or 8 to 9 hours.
在一些实施方式中，所述第三聚合物的制备包括以下步骤：In some embodiments, the preparation of the third polymer includes the following steps:
向容器中加入第二溶剂和第二分散助剂，向所述容器充入非反应性气体；向所述容器中加入第二引发剂和第二pH调节剂，调节pH值，然后加入式II所示单体至反应压力6MPa～8MPa，搅拌0.5小时～1小时后，升温至35℃～60℃，进行聚合反应6小时～10小时；Add a second solvent and a second dispersion aid to the container, fill the container with non-reactive gas; add a second initiator and a second pH adjuster to the container, adjust the pH value, and then add Formula II Bring the indicated monomer to a reaction pressure of 6MPa to 8MPa, stir for 0.5 to 1 hour, then raise the temperature to 35°C to 60°C, and perform polymerization reaction for 6 to 10 hours;
加入链转移剂，继续反应至反应体系中压力降至2MPa～2.5MPa，停止反应，固液分离，保留固相。Add the chain transfer agent and continue the reaction 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.
第三聚合物的制备方法中，所述分散助剂的含义与第一聚合物制备方法中分散助剂的含义相同。在一些实施方式中，第一分散助剂和第二分散助剂为同一种化学物质。在一些实施方式中，第一分散助剂和第二分散助剂为不同的化学物质。在一些实施方式中，所述第二分散助剂为甲基纤维素醚。In the preparation method of the third polymer, the meaning of the dispersion aid is the same as the meaning of the dispersion assistant in the preparation method of the first polymer. In some embodiments, the first dispersion aid and the second dispersion aid are the same chemical substance. In some embodiments, the first dispersing aid and the second dispersing aid are different chemicals. In some embodiments, the second dispersion aid is methylcellulose ether.
第三聚合物的制备方法中，所述pH调节剂的含义与第一聚合物制备方法中pH调节剂的含义相同。在一些实施方式中，第一pH调节剂和第二pH调节剂为同一种化学物质。在一些实施方式中，第一pH调节剂和第二pH调节剂为不同的化学物质。In the preparation method of the third polymer, the pH adjuster has the same meaning as the pH adjuster in the preparation method of the first polymer. In some embodiments, the first pH adjusting agent and the second pH adjusting agent are the same chemical substance. In some embodiments, the first pH adjusting agent and the second pH adjusting agent are different chemicals.
在一些实施方式中，第三聚合物的制备方法中，调节pH值至6.5～7，例如6.5，6.8或7。In some embodiments, in the preparation method of the third polymer, the pH value is adjusted to 6.5-7, such as 6.5, 6.8 or 7.
在一些实施方式中，所述第三聚合物的制备方法中，所述第二溶剂为水，有利于降低对环境的危害。In some embodiments, in the preparation method of the third polymer, the second solvent is water, which is beneficial to reducing harm to the environment.
在一些实施方式中，第三聚合物的制备方法中，搅拌时间为30 分钟～55分钟，30分钟～50分钟，30分钟～45分钟，35分钟～60分钟，40分钟～60分钟或者45分钟～60分钟。In some embodiments, in the preparation method of the third polymer, the stirring time is 30 minutes to 55 minutes, 30 minutes to 50 minutes, 30 minutes to 45 minutes, 35 minutes to 60 minutes, 40 minutes to 60 minutes or 45 minutes to 60 minutes.
第三聚合物的制备方法中，原料容易获取，反应条件安全可控，有利于第三聚合物的扩大生产。通过该方法制备的第三聚合物具有较高的分子量和粘度，在制备电池浆料时添加少量即可使极片具有良好的粘结力。In the preparation method of the third polymer, the raw materials are easy to obtain and the reaction conditions are safe and controllable, which is conducive to the expanded production of the third polymer. The third polymer prepared by this method has relatively high molecular weight and viscosity, and adding a small amount when preparing the battery slurry can make the electrode piece have good adhesive force.
另外，以下适当参照附图对本申请的二次电池、电池模块、电池包和用电装置进行说明。In addition, the secondary battery, battery module, battery pack and electric device of the present application will be described below with appropriate reference to the drawings.
本申请的一个实施方式中，提供一种二次电池。In one embodiment of the present application, a secondary battery is provided.
通常情况下，二次电池包括正极极片、负极极片、电解质和隔离膜。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。电解质在正极极片和负极极片之间起到传导离子的作用。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的作用，同时可以使离子通过。Typically, a secondary battery includes a positive electrode plate, a negative electrode plate, an electrolyte and a separator. During the charging and discharging process of the battery, active ions are inserted and detached back and forth between the positive and negative electrodes. The electrolyte plays a role in conducting ions between the positive and negative electrodes. The isolation film is placed between the positive electrode piece and the negative electrode piece. It mainly prevents the positive and negative electrodes from short-circuiting and allows ions to pass through.
[正极极片][Positive pole piece]
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物质。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.
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。As an example, 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.
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。In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, as 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. Composite current collectors 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.).
在一些实施方式中，正极活性物质可采用本领域公知的用于电池的正极活性物质。作为示例，正极活性物质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物质的传统材料。这些正极活性物质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。In some embodiments, the cathode active material may be a cathode active material known in the art for use in batteries. As an example, the cathode active material may include at least one of the following materials: olivine-structured lithium-containing phosphates, lithium transition metal oxides, and their respective modified compounds. However, 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. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO 2 ), lithium nickel oxides (such as LiNiO 2 ), lithium manganese oxides (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 (also referred to as 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 At least one of 0.8 Co 0.1 Mn 0.1 O 2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O 2 ) and its modified compounds. The olivine structure contains Examples of lithium phosphates may include, but are not limited to, lithium iron phosphate (such as LiFePO 4 (also referred to as LFP)), composites of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), lithium manganese phosphate and carbon. At least one of composite materials, lithium iron manganese phosphate, and composite materials of lithium iron manganese phosphate and carbon.
在一些实施方式中，正极膜层还可选地包括粘结剂。作为示例，所述粘结剂可以包括聚偏氟乙烯(PVDF)、聚四氟乙烯(PTFE)、偏氟乙烯-四氟乙烯-丙烯三元共聚物、偏氟乙烯-六氟丙烯-四氟乙烯三元共聚物、四氟乙烯-六氟丙烯共聚物及含氟丙烯酸酯树脂中的至少一种。In some embodiments, the positive electrode film layer optionally further includes a binder. As examples, the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene At least one of ethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
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。In some embodiments, the positive electrode film layer optionally further includes a conductive agent. As an example, 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.
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，例如正极活性物质、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。In some embodiments, 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.
[负极极片][Negative pole piece]
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。The negative electrode plate includes a negative electrode current collector and is disposed on at least one surface of the negative electrode current collector. The negative electrode film layer on the negative electrode film layer includes a negative electrode active material.
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。As an example, 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.
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。In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, copper 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 material. The composite current collector can be formed by forming metal materials (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
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。In some embodiments, the negative active material may be a negative active material known in the art for batteries. As an example, 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. However, 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.
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。In some embodiments, 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).
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。In some embodiments, 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.
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。In some embodiments, the negative electrode film layer optionally includes other auxiliaries, such as thickeners (such as sodium carboxymethylcellulose (CMC-Na)) and the like.
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。In some embodiments, the negative electrode sheet can be prepared in the following manner: adding the above The components used to prepare the negative electrode sheet, such as negative active materials, conductive agents, binders and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode On the current collector, after drying, cold pressing and other processes, the negative electrode piece can be obtained.
[电解质][electrolyte]
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。The electrolyte plays a role in conducting ions between the positive and negative electrodes. There is no specific restriction on the type of electrolyte in this application, and it can be selected according to needs. For example, the electrolyte can be liquid, gel, or completely solid.
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。In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes electrolyte salts and solvents.
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。In some embodiments, 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.
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。In some embodiments, 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.
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。In some embodiments, the electrolyte optionally further includes additives. For example, 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.
[隔离膜][Isolation film]
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。In some embodiments, the secondary battery further includes 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.
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。In some embodiments, 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 membrane can be a single layer The film may also be a multi-layer composite film and is not particularly limited. 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.
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。In some embodiments, 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.
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。In some embodiments, the secondary battery may include an outer packaging. The outer packaging can be used to package the above-mentioned electrode assembly and electrolyte.
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。In some embodiments, the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag. The material of the soft bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图1是作为一个示例的方形结构的二次电池5。This application has no particular limitation on the shape of the secondary battery, which can be cylindrical, square or any other shape. For example, FIG. 1 shows a square-structured secondary battery 5 as an example.
在一些实施方式中，参照图2，外包装可包括壳体51和盖板53。其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53能够盖设于所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔内。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或多个，本领域技术人员可根据具体实际需求进行选择。In some embodiments, referring to FIG. 2 , 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.
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。In some embodiments, 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.
图3是作为一个示例的电池模块4。参照图3，在电池模块4中，多个二次电池5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个二次电池5进行固定。Figure 3 is a battery module 4 as an example. Referring to FIG. 3 , in the battery module 4 , a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 . Of course, it can also be arranged in any other way. Furthermore, the plurality of secondary batteries 5 can be fixed by fasteners.
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。 Optionally, the battery module 4 may further include a housing having a receiving space in which a plurality of secondary batteries 5 are received.
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。In some embodiments, 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.
图4和图5是作为一个示例的电池包1。参照图4和图5，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。Figures 4 and 5 show the battery pack 1 as an example. Referring to FIGS. 4 and 5 , 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.
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。In addition, the present application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided by the present application. The secondary battery, battery module, or battery pack may be used as a power source for the electrical device, or may be used as an energy storage unit for the electrical device. The electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, and electric golf carts). , electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited to these.
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。As the power-consuming device, a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.
图6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。Figure 6 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. In order to meet the high power and high energy density requirements of the secondary battery for the electrical device, a battery pack or battery module can be used.
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。As another example, 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.
实施例Example
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。 Hereinafter, examples of the present application will be described. The embodiments described below are illustrative and are only used to explain the present application and are not to be construed as limitations of the present application. If specific techniques or conditions are not specified in the examples, the techniques or conditions described in literature in the field or product instructions will be followed. If the manufacturer of the reagents or instruments used is not indicated, they are all conventional products that can be purchased commercially.
实施例1Example 1
1)第三聚合物的制备1) Preparation of the third polymer
在10L的高压釜中加入4kg的去离子水和0.2g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碳酸氢钠，并充入1Kg的偏氟乙烯单体，使压力达到7Mpa，混合搅拌30min，升温到45℃，进行聚合反应；反应8h后加入25g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、干燥即得到聚偏氟乙烯粘结剂。Add 4kg of deionized water and 0.2g of methylcellulose ether to a 10L autoclave, evacuate and replace O2 with N 2 three times, then add 5g of tert-butylperoxypivalate and 2g of sodium bicarbonate again, And fill in 1Kg of vinylidene fluoride monomer to bring the pressure to 7Mpa, mix and stir for 30 minutes, raise the temperature to 45°C, and proceed with the polymerization reaction; after 8 hours of reaction, add 25g of cyclohexane to continue the reaction. When the pressure in the reactor drops to 2MPa Stop the reaction; centrifuge the reaction system and collect the solid phase, wash and dry to obtain the polyvinylidene fluoride binder.
2)粘结剂的制备2) Preparation of adhesive
将重均分子量为70万的PVDF第二聚合物和实施例1的第三聚合物分别溶于N-甲基吡咯烷酮(NMP)溶液中，配置成10％的胶液，再以1:9的质量比混合。其中，重均分子量70万的PVDF为阿科玛法国有限公司的HSV900型号。The second PVDF polymer with a weight average molecular weight of 700,000 and the third polymer of Example 1 were respectively dissolved in N-methylpyrrolidone (NMP) solution to form a 10% glue solution. Mass ratio mixing. Among them, the PVDF with a weight average molecular weight of 700,000 is the HSV900 model of Arkema France Co., Ltd.
实施例2～实施例9调节重均分子量为70万的PVDF粘结剂和实施例1中制备的第三聚合物的质量比，具体参数见表1。In Examples 2 to 9, the mass ratio of the PVDF binder with a weight average molecular weight of 700,000 and the third polymer prepared in Example 1 was adjusted. The specific parameters are shown in Table 1.
实施例10Example 10
1)第三聚合物的制备1) Preparation of the third polymer
在10L的高压釜中加入4kg的去离子水和0.2g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1Kg的偏氟乙烯，单体使压力达到7Mpa，混合搅拌30min，升温到45℃，进行聚合反应；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、干燥即得到聚偏氟乙烯粘结剂。Add 4kg of deionized water and 0.2g of methylcellulose ether to a 10L autoclave, evacuate and replace O2 with N 2 three times, then add 5g of tert-butyl peroxypivalate and 2g of sodium bicarbonate again , and fill in 1Kg of vinylidene fluoride, the monomer pressure reaches 7Mpa, mix and stir for 30 minutes, raise the temperature to 45°C, and perform the polymerization reaction; after 6 hours of reaction, add 30g of cyclohexane to continue the reaction, when the pressure in the reactor drops to 2MPa Stop the reaction; centrifuge the reaction system and collect the solid phase, wash and dry to obtain the polyvinylidene fluoride binder.
2)粘结剂的制备2) Preparation of adhesive
将重均分子量为70万的PVDF第二聚合物和实施例10的第三聚合物分别溶于N-甲基吡咯烷酮(NMP)溶液中，配置成10％的胶液，再以4:6的质量比混合。The second PVDF polymer with a weight average molecular weight of 700,000 and the third polymer of Example 10 were respectively dissolved in N-methylpyrrolidone (NMP) solution to prepare a 10% glue solution, and then mixed with 4:6 Mass ratio mixing.
实施例11Example 11
1)第三聚合物的制备 1) Preparation of the third polymer
在10L的高压釜中加入4kg的去离子水和0.2g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1Kg的偏氟乙烯，单体使压力达到7Mpa，混合搅拌30min，升温到45℃，进行聚合反应；反应9h后加入20g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、干燥即得到聚偏氟乙烯粘结剂。Add 4kg of deionized water and 0.2g of methylcellulose ether to a 10L autoclave, evacuate and replace O2 with N 2 three times, then add 5g of tert-butyl peroxypivalate and 2g of sodium bicarbonate again , and fill in 1Kg of vinylidene fluoride, the monomer pressure reaches 7Mpa, mix and stir for 30 minutes, raise the temperature to 45°C, and perform the polymerization reaction; after 9 hours of reaction, add 20g of cyclohexane to continue the reaction, when the pressure in the reactor drops to 2MPa Stop the reaction; centrifuge the reaction system and collect the solid phase, wash and dry to obtain the polyvinylidene fluoride binder.
2)粘结剂的制备2) Preparation of adhesive
其他步骤与实施例10相同，区别仅在于将实施例10的第三聚合物替换为实施例11制备的第三聚合物，具体参见表1。Other steps are the same as in Example 10, the only difference is that the third polymer in Example 10 is replaced with the third polymer prepared in Example 11, see Table 1 for details.
实施例12Example 12
1)第三聚合物的制备1) Preparation of the third polymer
在10L的高压釜中加入4kg的去离子水和0.2g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1Kg的偏氟乙烯，单体使压力达到7Mpa，混合搅拌30min，升温到37℃，进行聚合反应；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、干燥即得到聚偏氟乙烯粘结剂。Add 4kg of deionized water and 0.2g of methylcellulose ether to a 10L autoclave, evacuate and replace O2 with N 2 three times, then add 5g of tert-butyl peroxypivalate and 2g of sodium bicarbonate again , and fill in 1Kg of vinylidene fluoride, the monomer pressure reaches 7Mpa, mix and stir for 30 minutes, raise the temperature to 37°C, and perform the polymerization reaction; after 6 hours of reaction, add 30g of cyclohexane to continue the reaction, when the pressure in the reactor drops to 2MPa Stop the reaction; centrifuge the reaction system and collect the solid phase, wash and dry to obtain the polyvinylidene fluoride binder.
2)粘结剂的制备2) Preparation of adhesive
其他步骤与实施例10相同，区别仅在于将实施例10的第三聚合物替换为实施例12制备的第三聚合物，具体参见表1。Other steps are the same as those in Example 10. The only difference is that the third polymer in Example 10 is replaced with the third polymer prepared in Example 12. See Table 1 for details.
实施例13Example 13
将重均分子量为110万的PVDF第二聚合物和实施例1的第三聚合物分别溶于N-甲基吡咯烷酮(NMP)溶液中，配置成10％的胶液，再以4:6的质量比混合。其中，重均分子量110万的PVDF为苏威(上海)有限公司的5130型号。The second PVDF polymer with a weight average molecular weight of 1.1 million and the third polymer of Example 1 were respectively dissolved in N-methylpyrrolidone (NMP) solution to form a 10% glue solution. Mass ratio mixing. Among them, the PVDF with a weight average molecular weight of 1.1 million is model 5130 of Solvay (Shanghai) Co., Ltd.
实施例14Example 14
1)分散剂的制备1) Preparation of dispersant
在1L的四口烧瓶加入0.4kg的去离子水和0.2g的羧乙基纤维素醚，通入氮气去除溶液中溶解的氧，再次加入1g 2-乙基过氧化二碳酸酯和0.1g的碳酸氢钠，并充入0.1Kg的偏氟乙烯混合搅拌30min， 升温到68℃，进行聚合反应3h；聚合溶液经蒸馏、洗涤、分离、干燥、粉碎即得到聚偏氟乙烯分散剂。Add 0.4kg of deionized water and 0.2g of carboxyethyl cellulose ether to a 1L four-necked flask, add nitrogen gas to remove dissolved oxygen in the solution, and then add 1g of 2-ethylperoxydicarbonate and 0.1g of sodium bicarbonate, and add 0.1Kg of vinylidene fluoride, mix and stir for 30 minutes. Raise the temperature to 68°C and carry out the polymerization reaction for 3 hours; the polymerization solution is distilled, washed, separated, dried and pulverized to obtain the polyvinylidene fluoride dispersant.
2)正极极片的制备2) Preparation of positive electrode pieces
将正极活性物质磷酸铁锂、导电剂碳黑、粘结剂和分散剂按照94.8:4:0.8:0.4的重量比，加入实施例10中制备的粘结剂的胶液混合均匀，得到正极浆料，加入N-甲基吡咯烷酮(NMP)，调节其固含量为58％。将正极浆料均匀涂覆在铝箔正极集流体的两个表面上，然后干燥，得到膜层；之后经过冷压、分切，得到正极极片。The positive electrode active material lithium iron phosphate, conductive agent carbon black, binder and dispersant were added to the binder glue prepared in Example 10 according to the weight ratio of 94.8:4:0.8:0.4 and mixed evenly to obtain a positive electrode slurry. Material, add N-methylpyrrolidone (NMP), adjust its solid content to 58%. The positive electrode slurry is evenly coated on both surfaces of the aluminum foil positive electrode current collector, and then dried to obtain a film layer; it is then cold pressed and cut to obtain the positive electrode sheet.
3)负极极片的制备3) Preparation of negative electrode piece
将负极活性材料人造石墨、导电剂碳黑、粘结剂丁苯橡胶(SBR)、增稠剂羟甲基纤维素钠(CMC)按照重量比为96.2：0.8：0.8：1.2溶于溶剂去离子水中，混合均匀后制备成负极浆料；将负极浆料多次均匀涂覆在负极集流体铜箔的两个表面上，经过烘干、冷压、分切得到负极极片。Dissolve the negative active material artificial graphite, conductive agent carbon black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethylcellulose (CMC) in the solvent and deionize according to the weight ratio of 96.2:0.8:0.8:1.2 In water, mix evenly and prepare a negative electrode slurry; apply the negative electrode slurry multiple times evenly on both surfaces of the negative electrode current collector copper foil, dry, cold press, and cut to obtain negative electrode sheets.
4)隔离膜4) Isolation film
以聚丙烯膜作为隔离膜。Use polypropylene film as the isolation film.
5)电解液的制备5) Preparation of electrolyte
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)和碳酸甲乙酯(EMC)按照体积比3/7混合均匀，将LiPF6锂盐溶解于有机溶剂中配置成12.5％溶液，得到电解液。In an argon atmosphere glove box (H 2 O <0.1ppm, O 2 <0.1ppm), mix the organic solvents ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of 3/7, and add LiPF 6 Lithium salt is dissolved in an organic solvent to form a 12.5% solution to obtain an electrolyte.
6)电池的制备6) Preparation of battery
将实施例14制备的正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正、负极片之间起到隔离的作用，然后卷绕得到裸电芯，给裸电芯焊接极耳，并将裸电芯装入铝壳中，并在80℃下烘烤除水，随即注入电解液并封口，得到不带电的电池。不带电的电池再依次经过静置、热冷压、化成、整形、容量测试等工序，获得实施例14的锂离子电池产品。Stack the positive electrode sheet, isolation film, and negative electrode sheet prepared in Example 14 in order so that the isolation film is between the positive and negative electrode sheets to play an isolation role, then wind up to obtain a bare battery core, and weld the bare battery core The tabs are removed, and the bare battery core is put into an aluminum case, baked at 80°C to remove water, and then electrolyte is injected and sealed to obtain an uncharged battery. The uncharged battery was then subjected to processes such as standing, hot and cold pressing, formation, shaping, and capacity testing to obtain the lithium-ion battery product of Example 14.
实施例15～实施例18调节正极浆料粘结剂的用量，其他步骤与实施例14相同，具体参见表3。In Examples 15 to 18, the amount of positive electrode slurry binder was adjusted, and other steps were the same as in Example 14. See Table 3 for details.
实施例19～22中调节加入的分散剂的重均分子量，其他步骤同 实施例16。In Examples 19 to 22, the weight average molecular weight of the added dispersant is adjusted, and other steps are the same. Example 16.
实施例19中分散剂中第一聚合物的重均分子量为0.5万，制备方法如下：In Example 19, the weight average molecular weight of the first polymer in the dispersant is 0.5 million, and the preparation method is as follows:
在1L的四口烧瓶中加入0.4kg的去离子水和0.2g的羧乙基纤维素醚，通入氮气去除溶液中溶解的氧再次加入1.2g 2-乙基过氧化二碳酸酯和0.1g的碳酸氢钠，并充入0.1Kg的偏氟乙烯，混合搅拌30min，升温到73℃，进行聚合反应2h；聚合溶液经蒸馏、洗涤、分离、干燥、粉碎即得。Add 0.4kg of deionized water and 0.2g of carboxyethyl cellulose ether to a 1L four-necked flask, pass in nitrogen to remove the dissolved oxygen in the solution, and then add 1.2g of 2-ethyl peroxydicarbonate and 0.1g. of sodium bicarbonate, and add 0.1Kg of vinylidene fluoride, mix and stir for 30 minutes, raise the temperature to 73°C, and perform polymerization reaction for 2 hours; the polymerization solution is obtained by distilling, washing, separating, drying, and pulverizing.
实施例20中分散剂中第一聚合物的重均分子量为2万，制备方法如下：In Example 20, the weight average molecular weight of the first polymer in the dispersant is 20,000, and the preparation method is as follows:
在1L的四口烧瓶中加入0.4kg的去离子水和0.2g的羧乙基纤维素醚，通入氮气去除溶液中溶解的氧再次加入0.9g 2-乙基过氧化二碳酸酯和0.1g的碳酸氢钠，并充入0.1Kg的偏氟乙烯，混合搅拌30min，升温到66℃，进行聚合反应4h；聚合溶液经蒸馏、洗涤、分离、干燥、粉碎即得。Add 0.4kg of deionized water and 0.2g of carboxyethyl cellulose ether to a 1L four-necked flask, pass in nitrogen to remove the dissolved oxygen in the solution, and then add 0.9g of 2-ethylperoxydicarbonate and 0.1g of sodium bicarbonate, and add 0.1Kg of vinylidene fluoride, mix and stir for 30 minutes, raise the temperature to 66°C, and perform polymerization reaction for 4 hours; the polymerization solution is obtained by distilling, washing, separating, drying, and pulverizing.
实施例21中分散剂中第一聚合物的重均分子量为8万，制备方法如下：In Example 21, the weight average molecular weight of the first polymer in the dispersant is 80,000, and the preparation method is as follows:
在1L的四口烧瓶中加入0.4kg的去离子水和0.2g的羧乙基纤维素醚，通入氮气去除溶液中溶解的氧再次加入0.9g 2-乙基过氧化二碳酸酯和0.1g的碳酸氢钠，并充入0.1Kg的偏氟乙烯，混合搅拌30min，升温到64℃，进行聚合反应6h；聚合溶液经蒸馏、洗涤、分离、干燥、粉碎即得。Add 0.4kg of deionized water and 0.2g of carboxyethyl cellulose ether to a 1L four-necked flask, pass in nitrogen to remove the dissolved oxygen in the solution, and then add 0.9g of 2-ethylperoxydicarbonate and 0.1g of sodium bicarbonate, and add 0.1Kg of vinylidene fluoride, mix and stir for 30 minutes, raise the temperature to 64°C, and perform a polymerization reaction for 6 hours; the polymerization solution is obtained by distilling, washing, separating, drying, and pulverizing.
实施例22中分散剂中第一聚合物的重均分子量为15万，制备方法如下：The weight average molecular weight of the first polymer in the dispersant in Example 22 is 150,000, and the preparation method is as follows:
在1L的四口烧瓶中加入0.4kg的去离子水和0.2g的羧乙基纤维素醚，通入氮气去除溶液中溶解的氧再次加入0.7g 2-乙基过氧化二碳酸酯和0.1g的碳酸氢钠，并充入0.1Kg的偏氟乙烯，混合搅拌30min，升温到60℃，进行聚合反应8h；聚合溶液经蒸馏、洗涤、分离、干燥、粉碎即得。Add 0.4kg of deionized water and 0.2g of carboxyethyl cellulose ether to a 1L four-necked flask, pass in nitrogen to remove the dissolved oxygen in the solution, and then add 0.7g of 2-ethylperoxydicarbonate and 0.1g of sodium bicarbonate, and add 0.1Kg of vinylidene fluoride, mix and stir for 30 minutes, raise the temperature to 60°C, and perform polymerization reaction for 8 hours; the polymerization solution is obtained by distilling, washing, separating, drying, and pulverizing.
实施例23～26中调整了分散剂的含量，其他方法同实施例21， 具体参数见表3。In Examples 23 to 26, the content of the dispersant was adjusted, and other methods were the same as in Example 21. See Table 3 for specific parameters.
实施例27～30中调整了粘结剂中第二聚合物和第三聚合物的比例，其他方法同实施例21，具体参数见表3。In Examples 27 to 30, the ratio of the second polymer and the third polymer in the binder was adjusted. Other methods were the same as in Example 21. The specific parameters are shown in Table 3.
实施例31～35中调整了粘结剂中第三聚合物的重均分子量为250万，并调整了粘结剂的质量含量，其他方法同实施例14，具体参数见表3。In Examples 31 to 35, the weight average molecular weight of the third polymer in the binder was adjusted to 2.5 million, and the mass content of the binder was adjusted. Other methods were the same as in Example 14. The specific parameters are shown in Table 3.
实施例36～38中调整了粘结剂中第三聚合物的重均分子量为300万，并调整了粘结剂的质量含量，其他方法同实施例14，具体参数见表3。In Examples 36 to 38, the weight average molecular weight of the third polymer in the binder was adjusted to 3 million, and the mass content of the binder was adjusted. Other methods were the same as in Example 14. The specific parameters are shown in Table 3.
实施例39中调整了粘结剂中第三聚合物的重均分子量为130万，其他方法同实施例14，具体参数见表3。In Example 39, the weight average molecular weight of the third polymer in the binder was adjusted to 1.3 million. Other methods were the same as in Example 14. The specific parameters are shown in Table 3.
实施例40中二次电池的制备方法和实施例14中二次电池的制备方法相似，区别在于：The preparation method of the secondary battery in Example 40 is similar to the preparation method of the secondary battery in Example 14, with the following differences:
2)正极极片的制备2) Preparation of positive electrode pieces
将正极活性物质锂镍钴锰氧化物NCM、导电剂碳黑、粘结剂和分散剂按照94.6:4:1.0:0.4的重量比，加入实施例13中制备的粘结剂的胶液混合均匀，得到正极浆料，加入N-甲基吡咯烷酮(NMP)，调节其固含量为58％。将正极浆料均匀涂覆在铝箔正极集流体的两个表面上，然后干燥，得到膜层；之后经过冷压、分切，得到正极极片。The positive active material lithium nickel cobalt manganese oxide NCM, the conductive agent carbon black, the binder and the dispersant are added to the glue prepared in Example 13 according to the weight ratio of 94.6:4:1.0:0.4 and mixed evenly. , obtain the positive electrode slurry, add N-methylpyrrolidone (NMP), and adjust its solid content to 58%. The positive electrode slurry is evenly coated on both surfaces of the aluminum foil positive electrode current collector, and then dried to obtain a film layer; it is then cold pressed and cut to obtain the positive electrode sheet.
实施例41～42中调整了分散剂的重均分子量，其他方法同实施例40，具体参数见表3。In Examples 41 to 42, the weight average molecular weight of the dispersant was adjusted, and other methods were the same as in Example 40. The specific parameters are shown in Table 3.
实施例43～44中调整了第三聚合物的种类，其他方法与实施例16相同，其他参数见表3。In Examples 43 to 44, the type of the third polymer was adjusted, and other methods were the same as in Example 16. Other parameters are shown in Table 3.
实施例43中第三聚合物为聚四氟乙烯，其制备方法为：In Example 43, the third polymer is polytetrafluoroethylene, and its preparation method is:
在10L的高压釜中加入4kg的去离子水和0.2g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1Kg的四氟乙烯，单体使压力达到7Mpa，混合搅拌30min，升温到45℃，进行聚合反应；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。Add 4kg of deionized water and 0.2g of methylcellulose ether to a 10L autoclave, evacuate and replace O2 with N 2 three times, then add 5g of tert-butyl peroxypivalate and 2g of sodium bicarbonate again , and fill in 1Kg of tetrafluoroethylene, the monomer pressure reaches 7Mpa, mix and stir for 30 minutes, raise the temperature to 45°C, and perform the polymerization reaction; after 6 hours of reaction, add 30g of cyclohexane to continue the reaction, when the pressure in the reactor drops to 2MPa to stop the reaction; to react After the system is centrifuged, the solid phase is collected, washed and dried.
实施例44中第三聚合物为偏二氟乙烯和六氟丙烯的共聚物(PVDF-HFP)，其制备方法为：In Example 44, the third polymer is a copolymer of vinylidene fluoride and hexafluoropropylene (PVDF-HFP), and its preparation method is:
在10L的高压釜中加入4kg的去离子水和0.2g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0.8Kg的偏氟乙烯和0.2Kg的六氟丙烯，单体使压力达到7Mpa，混合搅拌30min，升温到44℃，进行聚合反应；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。Add 4kg of deionized water and 0.2g of methylcellulose ether to a 10L autoclave, evacuate and replace O2 with N 2 three times, then add 5g of tert-butyl peroxypivalate and 2g of sodium bicarbonate again , and fill in 0.8Kg of vinylidene fluoride and 0.2Kg of hexafluoropropylene, the monomer pressure reaches 7Mpa, mix and stir for 30 minutes, raise the temperature to 44°C, and perform the polymerization reaction; after 6 hours of reaction, add 30g of cyclohexane to continue the reaction. Stop the reaction when the pressure in the reaction kettle drops to 2MPa; centrifuge the reaction system and collect the solid phase, wash and dry it.
实施例45中，分散剂使用重均分子量1万的聚三氟氯乙烯，其制备方法为：In Example 45, the dispersant uses polychlorotrifluoroethylene with a weight average molecular weight of 10,000, and its preparation method is:
在1L的四口烧瓶中加入0.4kg的去离子水和0.2g的羧乙基纤维素醚，通入氮气去除溶液中溶解的氧，再次加入1.0g过氧化叔戊基新戊酸酯和0.1g的碳酸钾，充入0.1Kg的三氟氯乙烯，混合搅拌30min，升温到68℃，进行聚合反应3h；聚合溶液经蒸馏、洗涤、分离、干燥、粉碎即得到聚三氟氯乙烯。Add 0.4kg of deionized water and 0.2g of carboxyethyl cellulose ether to a 1L four-necked flask, add nitrogen gas to remove dissolved oxygen in the solution, and then add 1.0g of tert-amyl peroxide pivalate and 0.1 g of potassium carbonate, add 0.1Kg of chlorotrifluoroethylene, mix and stir for 30 minutes, raise the temperature to 68°C, and perform a polymerization reaction for 3 hours; the polymerization solution is distilled, washed, separated, dried, and pulverized to obtain polychlorotrifluoroethylene.
实施例46中，分散剂使用重均分子量1万的PVDF-HFP(偏氟乙烯-六氟丙烯)聚合物，其制备方法为：In Example 46, the dispersant uses PVDF-HFP (vinylidene fluoride-hexafluoropropylene) polymer with a weight average molecular weight of 10,000, and its preparation method is:
在1L的四口烧瓶中加入0.4kg的去离子水和0.2g的羧乙基纤维素醚，通入氮气去除溶液中溶解的氧，再次加入1.0g过氧化叔戊基新戊酸酯和0.1g的碳酸钾，充入0.8Kg的偏氟乙烯、0.2Kg六氟丙烯，混合搅拌30min，升温到68℃，进行聚合反应4h；聚合溶液经蒸馏、洗涤、分离、干燥、粉碎即得到聚偏氟乙烯-六氟丙烯。Add 0.4kg of deionized water and 0.2g of carboxyethyl cellulose ether to a 1L four-necked flask, add nitrogen gas to remove dissolved oxygen in the solution, and then add 1.0g of tert-amyl peroxide pivalate and 0.1 g of potassium carbonate, add 0.8Kg of vinylidene fluoride and 0.2Kg of hexafluoropropylene, mix and stir for 30 minutes, raise the temperature to 68°C, and perform a polymerization reaction for 4 hours; the polymerization solution is distilled, washed, separated, dried, and pulverized to obtain polyvinylidene fluoride. Fluoroethylene-hexafluoropropylene.
实施例47和48中分散剂的制备方法与实施例22基本相似，区别在于将共聚单体分别换位四氟乙烯和三氟氯乙烯。实施例49中以重均分子量为70万的偏二氟乙烯-三氟氯乙烯共聚物作为第二聚合物，实施例50中以重均分子量为70万的偏二氟乙烯-六氟丙烯共聚物作为第二聚合物。对比例1中粘结剂中仅包含重均分子量为250万的第三聚合物，对比例2中粘结剂中仅包含重均分子量为70万的第二聚合物，对比例3中粘结剂中仅包含重均分子量为110万的第二聚合 物，其他方法同实施例1，具体参数见表1。The preparation methods of the dispersants in Examples 47 and 48 are basically similar to those in Example 22, except that the comonomers are substituted with tetrafluoroethylene and chlorotrifluoroethylene respectively. In Example 49, a vinylidene fluoride-chlorotrifluoroethylene copolymer with a weight average molecular weight of 700,000 was used as the second polymer, and in Example 50, a vinylidene fluoride-hexafluoropropylene copolymer with a weight average molecular weight of 700,000 was used as the second polymer. as the second polymer. In Comparative Example 1, the binder only contains a third polymer with a weight average molecular weight of 2.5 million. In Comparative Example 2, the binder only contains a second polymer with a weight average molecular weight of 700,000. In Comparative Example 3, the binder only contains a third polymer with a weight average molecular weight of 2.5 million. The agent contains only the second polymer with a weight average molecular weight of 1.1 million material, other methods are the same as Example 1, and the specific parameters are shown in Table 1.
对比例4～6中粘结剂中仅包含第二聚合物，对比例7～10中粘结剂中仅包含第三聚合物，其他方法同实施例14，具体参数见表3。In Comparative Examples 4 to 6, the binder only contains the second polymer, and in Comparative Examples 7 to 10, the binder only contains the third polymer. Other methods are the same as in Example 14. See Table 3 for specific parameters.
对实施例1～13和对比例1～3中制备的粘结剂的性能测试结果如表1所示，实施例1～50和对比例1～10中的聚合物的性能测试结果如表2所示，实施例1～50和对比例1～10中制备的极片和电池的性能测试结果如表3所示，测试方法如下：The performance test results of the binders prepared in Examples 1 to 13 and Comparative Examples 1 to 3 are shown in Table 1, and the performance test results of the polymers in Examples 1 to 50 and Comparative Examples 1 to 10 are shown in Table 2 As shown, the performance test results of the pole pieces and batteries prepared in Examples 1 to 50 and Comparative Examples 1 to 10 are shown in Table 3, and the test methods are as follows:
性能测定Performance Measurement
1、重均分子量和多分散系数的测试方法1. Testing methods for weight average molecular weight and polydispersity coefficient
采用Waters 2695 Isocratic HPLC型凝胶色谱仪(示差折光检测器2141)。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 HT5 DMF7.8*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。待示数稳定后获取重均分子量和多分散系数的检测数据。Waters 2695 Isocratic HPLC gel chromatograph (differential refractive index detector 2141) was used. Use a polystyrene solution sample with a mass fraction of 3.0% as a reference and select a matching chromatographic column (oil: Styragel HT5 DMF7.8*300mm+Styragel HT4). Use purified N-methylpyrrolidone (NMP) solvent to prepare 3.0% adhesive glue solution, and let the prepared solution stand for one day for later use. When testing, first draw in tetrahydrofuran with a syringe, rinse, and repeat several times. Then draw 5 ml of the test solution, remove the air from the syringe, and dry the needle tip. Finally, slowly inject the sample solution into the injection port. After the display is stable, obtain the detection data of weight average molecular weight and polydispersity coefficient.
2、中值粒径Dv50的测试方法2. Test method for median particle size Dv50
参照GB/T 19077-2016粒度分布激光衍射法，采用激光粒度分析仪英国马尔文Mastersizer 2000E测定。Referring to the GB/T 19077-2016 particle size distribution laser diffraction method, it was measured using a laser particle size analyzer Malvern Mastersizer 2000E in the United Kingdom.
3、粘度测试3. Viscosity test
将第一聚合物、第二聚合物和第三聚合物分别溶解于N-甲基吡咯烷酮(NMP)溶剂中，其中，第一聚合物和第二聚合物配置固含量为7％的胶液，第三聚合物配置固含量为4％的胶液。选取合适的转子，固定好粘度计转子，将胶液放置于粘度计转子下方，浆料恰好淹没转子的刻度线，仪器型号：上海方瑞NDJ-5S，转子：61#(0-500mPa·s)、62#(500-2500mPa·s)、63#(2500-10000mPa·s)、64#(10000-50000mPa·s)，转速：12r/min，测试温度：25℃，测试时间为5min，待示数稳定读取数据。The first polymer, the second polymer and the third polymer are respectively dissolved in N-methylpyrrolidone (NMP) solvent, wherein the first polymer and the second polymer are configured with a glue solution with a solid content of 7%, The third polymer is configured with a glue solution with a solid content of 4%. Select the appropriate rotor, fix the viscometer rotor, place the glue under the viscometer rotor, and the slurry just submerges the scale line of the rotor. Instrument model: Shanghai Fangrui NDJ-5S, rotor: 61# (0-500mPa·s ), 62# (500-2500mPa·s), 63# (2500-10000mPa·s), 64# (10000-50000mPa·s), rotation speed: 12r/min, test temperature: 25℃, test time is 5min, wait The indicator reads data stably.
4、结晶度及熔融焓的测试方法 4. Test methods for crystallinity and melting enthalpy
将实施例1-14中的第一聚合物和第二聚合物分别溶于N-甲基吡咯烷酮(NMP)溶液中，配置成10％的胶液，再按照实施例1-14的粘结剂中第一聚合物和第二聚合物的质量比称量二者的胶液并进行混合，随后将搅拌分散均匀的混合液置于胶膜制备容器中，在100℃下烘干2天，接着将胶膜切成2×2cm的小块置于铝制干锅中，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。The first polymer and the second polymer in Examples 1-14 were respectively dissolved in N-methylpyrrolidone (NMP) solution to form a 10% glue solution, and then the adhesive according to Examples 1-14 was Weigh the glue solution of the first polymer and the second polymer at a mass ratio of the two and mix them, then place the evenly dispersed mixed solution into a glue film preparation container, dry it at 100°C for 2 days, and then Cut the film into 2×2cm pieces and place them in an aluminum dry pot, shake them flat, cover the crucible lid, and raise the temperature under a nitrogen atmosphere with a purge gas of 50mL/min and a protective gas of 70mL/min. The rate is 10℃/min, the test temperature range is -100℃~400℃, and the differential scanning calorimeter (DSC) of the American TA Instrument model Discovery 250 is used to test and eliminate thermal history.
此测试将会得到胶膜的DSC/(Mw/mg)随温度变化曲线，并进行积分，峰面积即为胶膜的熔融焓ΔH(J/g)，按照下式计算：
胶膜结晶度＝ΔH/(ΔHm100％)*100％This test will obtain the DSC/(Mw/mg) curve of the film with temperature and integrate it. The peak area is the melting enthalpy ΔH (J/g) of the film, calculated according to the following formula:
Film crystallinity = ΔH/(ΔHm100%)*100%
其中，ΔHm100％为PVDF的标准熔融焓(晶态熔化热)，ΔHm100％＝104.7J/g。Among them, ΔHm100% is the standard melting enthalpy of PVDF (crystalline fusion heat), ΔHm100%=104.7J/g.
5、正极膜层电阻的测定：5. Determination of positive electrode film resistance:
在正极极片左、中、右处裁剪烘干后的正极浆料(膜层)，裁剪为3mm直径的小圆片。开启元能科技极片电阻仪电源，将置于极片电阻仪“探头”合适位置，点击“开始”按钮，待示数稳定，读取即可。每个小圆片测试两个位置，最后计算六次测量的平均值，即为该极片的膜层电阻。Cut the dried positive electrode slurry (film layer) on the left, middle and right sides of the positive electrode piece into small discs with a diameter of 3mm. Turn on the power of Yuaneng Technology's pole piece resistance meter, place it in the appropriate position of the "probe" of the pole piece resistance meter, click the "Start" button, and wait until the reading is stable, then read it. Each small disc is tested at two positions, and finally the average of the six measurements is calculated, which is the film resistance of the pole piece.
6、极片脆性的测试方法6. Test method for pole piece brittleness
将制备的正极极片裁剪为20×100mm尺寸的测试试样，备用。将极片弯曲对折固定好，使用2kg重的圆筒辊进行辊压一次后，查看极片对折处是否透光漏金属；若无透光漏金属，再将极片反过来对折固定住，再次辊压一次，查看极片对折处是否透光漏金属，重复以上步骤，直至极片对折处透光漏金属为止并记录透光辊压次数。取三个样品进行测试，取平均值。Cut the prepared positive electrode piece into a test sample with a size of 20×100mm and set it aside. Bend the pole piece in half and fix it. Use a 2kg cylindrical roller to roll it once. Check whether there is light transmission and metal leakage at the folded part of the pole piece. If there is no light transmission and metal leakage, fold the pole piece in half and fix it again. Roll once to check whether light is transmitted and metal is leaking from the folded part of the pole piece. Repeat the above steps until light is transmitted and metal is leaked from the folded part of the pole piece and record the number of light-transmitting rolling operations. Take three samples for testing and take the average.
7、粘结力的测试方法7. Testing method for adhesion
参考国标GBT 2790-1995《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： Referring to the national standard GBT 2790-1995 "Test Method for 180° Peel Strength of Adhesives", the bonding force testing process of the examples and comparative examples of this application is as follows:
用刀片截取宽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贴在双面胶上，测试面朝下，后用压辊沿同一个方向滚压三次。Use a blade to cut out a pole piece sample with a width of 30mm and a length of 100-160mm, and stick the special double-sided tape on the steel plate with a width of 20mm and a length of 90-150mm. Paste the pole piece sample intercepted earlier on the double-sided tape with the test side facing down, and then roll it three times in the same direction with a pressure roller.
将宽度与极片试样等宽，长度为250mm的纸带***极片集流体下方，并且用皱纹胶固定。Insert a paper tape with the same width as the pole piece sample and a length of 250 mm under the pole piece current collector, and fix it with wrinkle glue.
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力强度。Turn on the power of the Sansi tensile machine (sensitivity is 1N), the indicator light is on, adjust the limit block to the appropriate position, and fix the end of the steel plate that is not attached to the pole piece sample with the lower clamp. Fold the paper tape upward and fix it with the upper clamp. Use the "up" and "down" buttons on the manual controller attached to the tensile machine to adjust the position of the upper clamp, then test and read the value. Divide the force of the pole piece when the force is balanced by the width of the tape as the bonding force of the pole piece per unit length to characterize the strength of the bonding force between the positive electrode film layer and the current collector.
8、电池容量保持率的测试方法8. Test method for battery capacity retention rate
磷酸铁锂体系：以实施例14为例，电池容量保持率测试过程如下：在25℃下，将实施例14对应的电池，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为：
Pn＝Cn/C0*100％Lithium iron phosphate system: Taking Example 14 as an example, the battery capacity retention test process is as follows: at 25°C, charge the battery corresponding to Example 14 with a constant current of 1/3C to 3.65V, and then charge it with a constant voltage of 3.65V Charge until the current is 0.05C, leave it for 5 minutes, and then discharge to 2.5V at 1/3C. The resulting capacity is recorded as the initial capacity C0. Repeat the above steps for the same battery and record the discharge capacity Cn of the battery after the nth cycle. Then the battery capacity retention rate after each cycle is:
Pn＝Cn/C0*100%
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100次循环对应n＝100。表3中实施例14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。对比例4以及其他实施例的测试过程同上；During this test, the first cycle corresponds to n=1, the second cycle corresponds to n=2, and the 100th cycle corresponds to n=100. The battery capacity retention rate data corresponding to Example 14 in Table 3 is the data measured after 500 cycles under the above test conditions, that is, the value of P500. The test procedures of Comparative Example 4 and other examples are the same as above;
锂镍钴锰氧化物NCM体系：以实施例40为例，在25℃下，将实施例40对应的电池，以1/3C恒流充电至4.4V，再以4.4V恒定电压充电至电流为0.05C，搁置5min，再以1/3C放电至2.8V，所得容量记为初始容量C0。其他测试步骤同磷酸铁锂体系。Lithium nickel cobalt manganese oxide NCM system: Taking Example 40 as an example, at 25°C, charge the battery corresponding to Example 40 with a constant current of 1/3C to 4.4V, and then charge with a constant voltage of 4.4V until the current is 0.05C, leave it aside for 5 minutes, and then discharge to 2.8V at 1/3C. The resulting capacity is recorded as the initial capacity C0. Other test steps are the same as for the lithium iron phosphate system.
上述实施例1～50和对比例1～10的参数和检测结果见下表1、表2和表3。 The parameters and test results of the above-mentioned Examples 1 to 50 and Comparative Examples 1 to 10 are shown in Table 1, Table 2 and Table 3 below.
表1粘结剂的组成参数及检测结果
Table 1 Composition parameters and test results of adhesives
表2聚合物的表征结果
Table 2 Characterization results of polymers
表3极片和电池制备参数及性能测试结果

Table 3 Electrode and battery preparation parameters and performance test results

根据上述结果可知，实施例3～实施例8、实施例10～实施例12中使用重均分子量为70万、中值粒径Dv50为15μm、粘度为4000mPa·s的第二聚合物和重均分子量为130万～300万、多分散系数为2.05～2.2的第三聚合物制备粘结剂，与仅使用重均分子量为70万的第二聚合物做粘结剂的对比例2相比，实施例3～实施例8、实施例10～实施例12的熔融焓和结晶度下降，表明由第二聚合物和第三聚合物混合后改善了粘结剂的柔韧性。From the above results, it can be seen that in Examples 3 to 8 and 10 to 12, a second polymer with a weight average molecular weight of 700,000, a median particle diameter Dv50 of 15 μm, and a viscosity of 4000 mPa·s was used. A third polymer with a molecular weight of 1.3 million to 3 million and a polydispersity coefficient of 2.05 to 2.2 was used to prepare a binder. Compared with Comparative Example 2, which only used a second polymer with a weight average molecular weight of 700,000 as a binder, The melting enthalpy and crystallinity of Examples 3 to 8 and Examples 10 to 12 decreased, indicating that the flexibility of the binder was improved after mixing the second polymer and the third polymer.
实施例1～实施例9中使用重均分子量为70万的第二聚合物和 重均分子量为250万的第三聚合物在质量比为1:9～9:1的范围内制备粘结剂，与仅使用重均分子量为250万的第三聚合物做粘结剂的对比例1相比，第二聚合物的添加降低了粘结剂的熔融焓和结晶度，提高了粘结剂的柔韧性。In Examples 1 to 9, a second polymer with a weight average molecular weight of 700,000 and The third polymer with a weight average molecular weight of 2.5 million is used to prepare a binder in a mass ratio of 1:9 to 9:1, as opposed to using only a third polymer with a weight average molecular weight of 2.5 million as the binder. Compared with Ratio 1, the addition of the second polymer reduces the melting enthalpy and crystallinity of the binder and improves the flexibility of the binder.
实施例13中使用重均分子量为110万、中值粒径Dv50为25μm、粘度为2500mPa·s的第二聚合物和重均分子量为250万的第三聚合物在质量比为4:6的范围内制备粘结剂，与仅使用重均分子量为110万的第二聚合物做粘结剂的对比例3相比，表明由第二聚合物和第三聚合物混合后降低了粘结剂的熔融焓和结晶度，提高了粘结剂的柔韧性。In Example 13, a second polymer with a weight average molecular weight of 1.1 million, a median particle diameter Dv50 of 25 μm, and a viscosity of 2500 mPa·s and a third polymer with a weight average molecular weight of 2.5 million were used in a mass ratio of 4:6. The binder was prepared within the range. Compared with Comparative Example 3, which only used the second polymer with a weight average molecular weight of 1.1 million as the binder, it showed that the binder was reduced after mixing the second polymer and the third polymer. The melting enthalpy and crystallinity improve the flexibility of the binder.
实施例14～实施例18、实施例31～实施例35、实施例36～实施例38、实施例39和实施例43～实施例44中使用质量含量为0.40％的重均分子量为1万的分散剂和质量含量分别为0.80％～1.2％、0.60％～0.8％、0.80％～1.2％、0.80％、1.00％的粘结剂制备二次电池，粘结剂使用重均分子量为70万的第二聚合物和重均分子量为180万(中值粒径Dv50为60μm、粘度为3600mPa·s)、250万(中值粒径Dv50为80μm、粘度为4300mPa·s)、300万(中值粒径Dv50为100μm、粘度为4800mPa·s)、130万(中值粒径Dv50为30μm、粘度为1700mPa·s)、180万(PTFE/PVDF-HFP)的第三聚合物制备，与仅使用重均分子量为180万的第三聚合物制备二次电池的对比例7～对比例10相比，膜层电阻降低，并且，极片平均辊压次数和循环500次容量保持率明显提高；与仅使用重均分子量为70万的第二聚合物制备二次电池的对比例5相比，实施例14～实施例18的膜层电阻降低，极片平均辊压次数、粘结力和循环500次容量保持率明显提高。结合表1中数据表明，第二聚合物和第三聚合物在设定比例范围内混合可以降低粘结剂的结晶性和提高其柔韧性，从而提高极片的柔性；同时，分散剂的添加可以进一步提高浆料的分散性，极片加工性明显提高，有利于改善浆料涂布的均匀性和降低极片电阻，从而提高电池循环性能。第二聚合物和第三聚合物的联合使用，可以使极片膜层在具有良好加工性的基础上，还保持有优良的粘结 力，保证二次电池的循环安全性。In Examples 14 to 18, 31 to 35, 36 to 38, 39 and 43 to 44, a weight average molecular weight of 10,000 was used with a mass content of 0.40%. Dispersants and binders with mass contents of 0.80% to 1.2%, 0.60% to 0.8%, 0.80% to 1.2%, 0.80%, and 1.00% are used to prepare secondary batteries. The binder uses a weight average molecular weight of 700,000 The weight average molecular weight of the second polymer is 1.8 million (median particle size Dv50 is 60 μm, viscosity is 3600 mPa·s), 2.5 million (median particle size Dv50 is 80 μm, viscosity is 4300 mPa·s), 3 million (median value The third polymer with particle size Dv50 of 100 μm and viscosity of 4800 mPa·s), 1.3 million (median particle size Dv50 of 30 μm and viscosity of 1700 mPa·s), and 1.8 million (PTFE/PVDF-HFP) was prepared, and only used Compared with Comparative Examples 7 to 10 of secondary batteries prepared from a third polymer with a weight average molecular weight of 1.8 million, the film layer resistance was reduced, and the average number of rolls of the pole pieces and the capacity retention rate after 500 cycles were significantly improved; compared with Compared with Comparative Example 5, which only uses the second polymer with a weight average molecular weight of 700,000 to prepare a secondary battery, the film layer resistance of Examples 14 to 18 is reduced, and the average number of rolling times, adhesive force and cycle of the pole piece are 500 The secondary capacity retention rate is significantly improved. Combining the data in Table 1 shows that mixing the second polymer and the third polymer within a set proportion range can reduce the crystallinity of the binder and improve its flexibility, thereby improving the flexibility of the pole piece; at the same time, the addition of dispersant The dispersion of the slurry can be further improved, and the processability of the pole piece is significantly improved, which is beneficial to improving the uniformity of slurry coating and reducing the resistance of the pole piece, thereby improving the battery cycle performance. The combined use of the second polymer and the third polymer allows the pole piece membrane layer to maintain excellent adhesion on the basis of good processability. force to ensure the cycle safety of secondary batteries.
实施例19～实施例22、实施例40～42中使用重均分子量为0.5万(中值粒径Dv50为0.5μm、粘度为20mPa·s)、1万(中值粒径Dv50为0.8μm、粘度为30mPa·s)、2万(中值粒径Dv50为1μm、粘度为50mPa·s)、8万(中值粒径Dv50为2μm、粘度为120mPa·s)、15万(中值粒径Dv50为4μm、粘度为180mPa·s)的分散剂和粘结剂制备二次电池，粘结剂分别使用重均分子量为70万的第二聚合物和重均分子量为180万、中值粒径Dv50为60μm、粘度为3600mPa·s的第三聚合物、重均分子量为110万的第二聚合物和重均分子量为250万的第三聚合物制备。与对比例5～对比例6、对比例8～对比例9相比，实施例19～实施例22、实施例40～42中二次电池的膜层电阻降低，并且，极片平均辊压次数和循环500次容量保持率明显提高。结合表1中数据表明，第二聚合物和第三聚合物混合后可以降低粘结剂的结晶性和提高其柔韧性，有利于提高极片的柔性；而重均分子量为15万以下的分散剂有助于改善浆料的分散性，使浆料涂布均匀，进而降低了极片电阻和提高了电池循环性能。In Examples 19 to 22 and 40 to 42, the weight average molecular weights used were 0.5 million (median particle diameter Dv50: 0.5 μm, viscosity: 20 mPa·s) and 10,000 (median particle diameter Dv50: 0.8 μm, Viscosity is 30mPa·s), 20,000 (median particle diameter Dv50 is 1μm, viscosity is 50mPa·s), 80,000 (median particle diameter Dv50 is 2μm, viscosity is 120mPa·s), 150,000 (median particle diameter Dv50 is 2μm, viscosity is 120mPa·s) A secondary battery was prepared using a dispersant and a binder with a Dv50 of 4 μm and a viscosity of 180 mPa·s). The binder used a second polymer with a weight average molecular weight of 700,000 and a weight average molecular weight of 1.8 million with a median particle diameter. A third polymer with a Dv50 of 60 μm and a viscosity of 3600 mPa·s, a second polymer with a weight average molecular weight of 1.1 million, and a third polymer with a weight average molecular weight of 2.5 million were prepared. Compared with Comparative Examples 5 to 6, and Comparative Examples 8 to 9, the film resistance of the secondary batteries in Examples 19 to 22, and Examples 40 to 42 was reduced, and the average number of rolls of the pole pieces was And the capacity retention rate is significantly improved after 500 cycles. Combining the data in Table 1 shows that mixing the second polymer and the third polymer can reduce the crystallinity of the binder and improve its flexibility, which is beneficial to improving the flexibility of the pole piece; and the dispersion with a weight average molecular weight of less than 150,000 The agent helps to improve the dispersion of the slurry and make the slurry evenly coated, thereby reducing the electrode resistance and improving the battery cycle performance.
实施例23～实施例26中使用质量含量为0.05％～1.00％的重均分子量为8万的分散剂和粘结剂制备二次电池，粘结剂分别使用重均分子量为70万的第二聚合物和重均分子量为180万的第三聚合物制备。与对比例5和对比例8相比，实施例23～实施例26中二次电池的极片膜层电阻明显降低，而粘结力没有大幅降低，表明此范围内的分散剂有助于提高正极浆料的稳定性和加工性，提高浆料分布的均匀性和降低极片电阻，同时不会大幅度降低极片的粘结力。In Examples 23 to 26, a dispersant and a binder with a weight average molecular weight of 80,000 and a mass content of 0.05% to 1.00% were used to prepare secondary batteries. The binders used a second dispersant with a weight average molecular weight of 700,000. polymer and a third polymer with a weight average molecular weight of 1.8 million was prepared. Compared with Comparative Example 5 and Comparative Example 8, the electrode sheet resistance of the secondary batteries in Examples 23 to 26 was significantly reduced, but the adhesive force was not significantly reduced, indicating that the dispersant within this range helps to improve The stability and processability of the positive electrode slurry improves the uniformity of the slurry distribution and reduces the resistance of the electrode piece without significantly reducing the adhesive force of the electrode piece.
实施例27～实施例30中使用重均分子量为8万的分散剂和粘结剂制备二次电池，粘结剂分别使用质量比为1:9～8:2的重均分子量为70万的第二聚合物和重均分子量为180万的第三聚合物制备。与对比例5和对比例8相比，实施例27～实施例30中二次电池的极片膜层电阻明显降低，极片平均辊压次数也有显著改善，同时依旧保持良好的粘结力和循环500次容量保持率。表明由此范围内的第 二聚合物和第三聚合物联用有利于改善粘结剂的结晶性和柔韧性，进而提高了极片的柔性，并保证极片具有良好的粘结力；而分散剂的加入提高了浆料的分散性和稳定性，改善了膜层电阻和电池循环性能。In Examples 27 to 30, a dispersant and a binder with a weight average molecular weight of 80,000 were used to prepare secondary batteries. The binders used a mass ratio of 1:9 to 8:2 and a binder with a weight average molecular weight of 700,000. A second polymer and a third polymer having a weight average molecular weight of 1.8 million were prepared. Compared with Comparative Example 5 and Comparative Example 8, the electrode sheet film resistance of the secondary batteries in Examples 27 to 30 was significantly reduced, and the average number of rolling of the electrode sheets was also significantly improved, while still maintaining good adhesion and Capacity retention rate after 500 cycles. Indicates the number within this range The combination of the second polymer and the third polymer is beneficial to improving the crystallinity and flexibility of the binder, thereby improving the flexibility of the pole piece and ensuring that the pole piece has good adhesion; while the addition of the dispersant improves the slurry The dispersion and stability of the material improve the film resistance and battery cycle performance.
实施例26中使用了质量含量为1％的分散剂和质量含量为1％的粘结剂制备二次电池，对比例4中使用质量含量为2.5％的第二聚合物制备二次电池，虽然实施例26中添加的助剂的总量小于对比例4，但是实施例26中二次电池的极片膜层电阻明显降低，极片平均辊压次数和循环500次容量保持率也有显著改善，同时依旧保持良好的粘结力。这有利于降低电池的阻抗增加倍率和提高电池的循环性能，并有助于提高极片的压实密度和提高电池的能量密度。In Example 26, a dispersant with a mass content of 1% and a binder with a mass content of 1% was used to prepare a secondary battery. In Comparative Example 4, a second polymer with a mass content of 2.5% was used to prepare a secondary battery. Although The total amount of additives added in Example 26 is less than that of Comparative Example 4, but the film resistance of the pole piece of the secondary battery in Example 26 is significantly reduced, and the average number of rolls of the pole piece and the capacity retention rate after 500 cycles are also significantly improved. While still maintaining good adhesion. This is beneficial to reducing the impedance increase rate of the battery and improving the cycle performance of the battery, and also helps to increase the compaction density of the pole pieces and increase the energy density of the battery.
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。 It should be noted that the present application is not limited to the above-described embodiment. The above-mentioned embodiments are only examples. Within the scope of the technical solution of the present application, embodiments that have substantially the same structure as the technical idea and exert the same functions and effects are included in the technical scope of the present application. In addition, within the scope that does not deviate from the gist of the present application, various modifications to the embodiments that can be thought of by those skilled in the art, and other forms constructed by combining some of the constituent elements in the embodiments are also included in the scope of the present application. .

Claims (24)

  1. 一种粘结剂组合物，其特征在于，所述粘结剂组合物包含分散剂和粘结剂，所述分散剂包括重均分子量为0.5万～15万的第一聚合物，所述粘结剂包括重均分子量为70万～110万的第二聚合物和重均分子量为130万～300万的第三聚合物，所述第一聚合物、所述第二聚合物和所述第三聚合物均为含有式I所示结构单元的聚合物，
    A binder composition, characterized in that the binder composition includes a dispersant and a binder, the dispersant includes a first polymer with a weight average molecular weight of 0.5 million to 150,000, and the binder The binding agent includes a second polymer with a weight average molecular weight of 700,000 to 1.1 million and a third polymer with a weight average molecular weight of 1.3 million to 3 million. The first polymer, the second polymer and the third polymer The three polymers are all polymers containing the structural units shown in formula I,
    其中，R1、R2各自独立地选自氢、氟、氯或三氟甲基。Wherein, R 1 and R 2 are each independently selected from hydrogen, fluorine, chlorine or trifluoromethyl.
  2. 根据权利要求1所述的粘结剂组合物，其特征在于，所述第一聚合物、所述第二聚合物和所述第三聚合物各自独立地选自聚四氟乙烯、聚偏二氟乙烯、偏二氟乙烯-六氟丙烯共聚物、偏二氟乙烯-三氟氯乙烯、聚三氟氯乙烯中的一种或多种。The adhesive composition according to claim 1, wherein the first polymer, the second polymer and the third polymer are each independently selected from polytetrafluoroethylene, polyvinylidene One or more of vinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-chlorotrifluoroethylene, and polychlorotrifluoroethylene.
  3. 根据权利要求1或2所述的粘结剂组合物，其特征在于，所述第一聚合物的颗粒的中值粒径Dv50为0.5μm～5μm。The adhesive composition according to claim 1 or 2, characterized in that the median particle diameter Dv50 of the particles of the first polymer is 0.5 μm to 5 μm.
  4. 根据权利要求1至3中任一项所述的粘结剂组合物，其特征在于，所述第一聚合物溶于N-甲基吡咯烷酮制得第一胶液，基于所述第一胶液的总质量计，当所述第一聚合物的质量含量为7％时，所述第一胶液的粘度为20～180mPa·s。The adhesive composition according to any one of claims 1 to 3, characterized in that the first polymer is dissolved in N-methylpyrrolidone to prepare a first glue liquid, based on the first glue liquid Based on the total mass, when the mass content of the first polymer is 7%, the viscosity of the first glue liquid is 20-180 mPa·s.
  5. 根据权利要求1至4中任一项所述的粘结剂组合物，其特征在于，所述第二聚合物的颗粒的中值粒径Dv50为15～25μm。The adhesive composition according to any one of claims 1 to 4, wherein the particles of the second polymer have a median diameter Dv50 of 15 to 25 μm.
  6. 根据权利要求1至5中任一项所述的粘结剂组合物，其特征 在于，所述第二聚合物溶于N-甲基吡咯烷酮制得第二胶液，基于所述第二胶液的总质量计，当所述第二聚合物的质量含量为7％时，所述第二胶液的粘度为2500～4000mPa·s。The adhesive composition according to any one of claims 1 to 5, characterized by The second polymer is dissolved in N-methylpyrrolidone to prepare a second glue liquid. Based on the total mass of the second glue liquid, when the mass content of the second polymer is 7%, the The viscosity of the second glue liquid is 2500-4000 mPa·s.
  7. 根据权利要求1至6中任一项所述的粘结剂组合物，其特征在于，所述第三聚合物的颗粒的中值粒径Dv50为30μm～100μm。The adhesive composition according to any one of claims 1 to 6, wherein the particles of the third polymer have a median diameter Dv50 of 30 μm to 100 μm.
  8. 根据权利要求1至7中任一项所述的粘结剂组合物，其特征在于，所述第三聚合物溶于N-甲基吡咯烷酮制得第三胶液，基于所述第三胶液的总质量计，当所述第三聚合物的质量含量为4％时，所述第三胶液的粘度为1500～5000mPa·s。The adhesive composition according to any one of claims 1 to 7, characterized in that the third polymer is dissolved in N-methylpyrrolidone to prepare a third glue liquid, based on the third glue liquid Based on the total mass, when the mass content of the third polymer is 4%, the viscosity of the third glue liquid is 1500-5000 mPa·s.
  9. 根据权利要求1至8中任一项所述的粘结剂组合物，其特征在于，所述第三聚合物的多分散系数为2～2.3。The adhesive composition according to any one of claims 1 to 8, wherein the third polymer has a polydispersity coefficient of 2 to 2.3.
  10. 根据权利要求1至9中任一项所述的粘结剂组合物，其特征在于，所述第二聚合物和所述第三聚合物的质量比为1:9～8:2。The adhesive composition according to any one of claims 1 to 9, characterized in that the mass ratio of the second polymer and the third polymer is 1:9 to 8:2.
  11. 根据权利要求1至10中任一项所述的粘结剂组合物，其特征在于，所述粘结剂的结晶度为25％～44％。The adhesive composition according to any one of claims 1 to 10, characterized in that the crystallinity of the adhesive is 25% to 44%.
  12. 根据权利要求1至11中任一项所述的粘结剂组合物，其特征在于，所述粘结剂的熔融焓为25J/g～45J/g。The adhesive composition according to any one of claims 1 to 11, wherein the melting enthalpy of the adhesive is 25 J/g to 45 J/g.
  13. 一种正极浆料，其特征在于，所述正极浆料中包括正极活性物质，导电剂以及权利要求1至12中任一项所述的粘结剂组合物。A positive electrode slurry, characterized in that the positive electrode slurry includes a positive electrode active material, a conductive agent and the binder composition according to any one of claims 1 to 12.
  14. 根据权利要求13所述的正极浆料，其特征在于，所述分散剂的质量含量为0.05％～1％，基于所述正极浆料的固体物质的总质量计。 The positive electrode slurry according to claim 13, wherein the mass content of the dispersant is 0.05% to 1%, based on the total mass of solid matter in the positive electrode slurry.
  15. 根据权利要求13或14所述的正极浆料，其特征在于，所述粘结剂的质量含量为0.6％～1.2％，基于所述正极浆料的固体物质的总质量计。The positive electrode slurry according to claim 13 or 14, wherein the mass content of the binder is 0.6% to 1.2%, based on the total mass of solid matter of the positive electrode slurry.
  16. 根据权利要求13至15中任一项所述的正极浆料，其特征在于，所述正极活性物质为含锂的过渡金属氧化物。The positive electrode slurry according to any one of claims 13 to 15, wherein the positive electrode active material is a lithium-containing transition metal oxide.
  17. 根据权利要求13至16中任一项所述的正极浆料，其特征在于，所述含锂的过渡金属氧化物为磷酸铁锂或锂镍钴锰氧化物，或它们的掺杂改性材料、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。The cathode slurry according to any one of claims 13 to 16, wherein the lithium-containing transition metal oxide is lithium iron phosphate or lithium nickel cobalt manganese oxide, or their doping modified materials. , at least one of conductive carbon-coated modified materials, conductive metal-coated modified materials, and conductive polymer-coated modified materials.
  18. 一种正极浆料的制备方法，其特征在于，所述制备方法包括以下步骤：A preparation method of positive electrode slurry, characterized in that the preparation method includes the following steps:
    步骤1：将正极活性物质、导电剂和粘结剂混合均匀；所述粘结剂包括重均分子量为70万～110万的第二聚合物和重均分子量为130万～300万的第三聚合物，Step 1: Mix the positive active material, conductive agent and binder evenly; the binder includes a second polymer with a weight average molecular weight of 700,000 to 1.1 million and a third polymer with a weight average molecular weight of 1.3 million to 3 million. polymer,
    步骤2：加入分散剂进行搅拌，得到正极浆料，所述分散剂包括重均分子量为0.5万～15万的第一聚合物，所述第一聚合物、所述第二聚合物和所述第三聚合物均为至少一种式II所示单体在可聚合条件下聚合制备而得，
    Step 2: Add a dispersant and stir to obtain a positive electrode slurry. The dispersant includes a first polymer with a weight average molecular weight of 0.5 million to 150.000. The first polymer, the second polymer and the The third polymers are all prepared by polymerizing at least one monomer represented by formula II under polymerizable conditions,
    其中，R1、R2各自独立地选自氢、氟、氯或三氟甲基。Wherein, R 1 and R 2 are each independently selected from hydrogen, fluorine, chlorine or trifluoromethyl.
  19. 根据权利要求18所述的制备方法，所述第一聚合物的制备方法包括以下步骤： The preparation method according to claim 18, the preparation method of the first polymer includes the following steps:
    提供至少一种式II所示单体、第一引发剂和第一溶剂，在常压、55℃～80℃的反应温度下进行聚合反应2小时～8小时，停止反应，固液分离，保留固相，得到所述第一聚合物。Provide at least one monomer represented by formula II, a first initiator and a first solvent, perform a polymerization reaction at normal pressure and a reaction temperature of 55°C to 80°C for 2 hours to 8 hours, stop the reaction, separate solid and liquid, and retain solid phase to obtain the first polymer.
  20. 根据权利要求18或19所述的制备方法，所述第三聚合物的制备方法包括以下步骤：The preparation method according to claim 18 or 19, the preparation method of the third polymer includes the following steps:
    提供至少一种式II所示单体、第二引发剂和第二溶剂，当式II所示单体使得反应压力达到6MPa～8MPa时，升高温度至35℃～60℃，进行聚合反应6小时～10小时；Provide at least one monomer represented by formula II, a second initiator and a second solvent. When the monomer represented by formula II causes the reaction pressure to reach 6MPa~8MPa, increase the temperature to 35°C~60°C to perform polymerization reaction 6 hours to 10 hours;
    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，得到所述第三聚合物。Add a chain transfer agent, wait until the pressure in the reaction system drops to 2MPa to 2.5MPa, stop the reaction, separate the solid and liquid, retain the solid phase, and obtain the third polymer.
  21. 一种二次电池，其特征在于，包括正极极片、隔离膜、负极极片以及电解液，所述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，所述正极膜层由权利要求1～12中任一项所述的正极浆料或权利要求13～20中任一项所述的制备方法制备的正极浆料制备而得。A secondary battery, characterized in that it includes a positive electrode sheet, a separator, a negative electrode sheet and an electrolyte, 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 is prepared from the positive electrode slurry according to any one of claims 1 to 12 or the positive electrode slurry prepared by the preparation method according to any one of claims 13 to 20.
  22. 一种电池模块，其特征在于，包括权利要求21所述的二次电池。A battery module comprising the secondary battery according to claim 21.
  23. 一种电池包，其特征在于，包括权利要求22所述的电池模块。A battery pack, characterized by comprising the battery module according to claim 22.
  24. 一种用电装置，其特征在于，包括选自权利要求21所述的二次电池、权利要求22所述的电池模块或权利要求23所述的电池包中的至少一种。 An electric device, characterized in that it includes at least one selected from the group consisting of the secondary battery according to claim 21, the battery module according to claim 22, or the battery pack according to claim 23.
PCT/CN2023/076249 2022-08-30 2023-02-15 Binder composition, positive electrode slurry, secondary battery, battery module, battery pack, and electric device WO2024045505A1 (en)

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