WO2023240543A1 - 粘结剂及其制备方法与应用 - Google Patents

粘结剂及其制备方法与应用 Download PDF

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Publication number
WO2023240543A1
WO2023240543A1 PCT/CN2022/099187 CN2022099187W WO2023240543A1 WO 2023240543 A1 WO2023240543 A1 WO 2023240543A1 CN 2022099187 W CN2022099187 W CN 2022099187W WO 2023240543 A1 WO2023240543 A1 WO 2023240543A1
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Prior art keywords
polyvinylidene fluoride
binder
million
preparation
optionally
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Application number
PCT/CN2022/099187
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English (en)
French (fr)
Inventor
段连威
刘会会
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宁德时代新能源科技股份有限公司
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Application filed by 宁德时代新能源科技股份有限公司 filed Critical 宁德时代新能源科技股份有限公司
Priority to CN202280002865.4A priority Critical patent/CN115867625A/zh
Priority to KR1020247005241A priority patent/KR20240034816A/ko
Priority to EP22930171.8A priority patent/EP4321588A1/en
Priority to PCT/CN2022/099187 priority patent/WO2023240543A1/zh
Priority to PCT/CN2023/088512 priority patent/WO2023241201A1/zh
Priority to PCT/CN2023/088502 priority patent/WO2023241200A1/zh
Publication of WO2023240543A1 publication Critical patent/WO2023240543A1/zh

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    • 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
    • C08F14/00—Homopolymers and copolymers 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
    • C08F14/18—Monomers containing fluorine
    • C08F14/22—Vinylidene fluoride
    • 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
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D127/00—Coating compositions based on homopolymers or copolymers 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; Coating compositions based on derivatives of such polymers
    • C09D127/02—Coating compositions based on homopolymers or copolymers 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; Coating compositions based on derivatives of such polymers not modified by chemical after-treatment
    • C09D127/12—Coating compositions based on homopolymers or copolymers 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; Coating compositions based on derivatives of such polymers not modified by chemical after-treatment containing fluorine atoms
    • C09D127/16—Homopolymers or copolymers of 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
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers

Definitions

  • the present application relates to the field of secondary batteries, and more specifically to a binder and its preparation method and application.
  • Secondary batteries such as lithium-ion batteries, often need to add binders to the positive active material layer to improve the bonding force between the active material layer and the current collector, as well as the bonding force between active material particles.
  • Polyvinylidene fluoride is one of the most widely used binder types in lithium-ion batteries. It has strong adhesiveness, is insoluble in the electrolyte, does not react with the electrolyte, is not prone to cracks after repeated charging, and has no obvious adhesive properties. Descending and other advantages. However, in traditional technology, the amount of polyvinylidene fluoride used as a binder often accounts for more than 2.5% of the raw material mass of the active material layer. If the amount of binder is too high, it will occupy the proportion of the active material in the active material layer, often resulting in As a result, the pole pieces are brittle and have poor toughness, and the cycle performance of the battery is reduced.
  • an adhesive and its preparation method and application are provided.
  • a first aspect of the application provides a binder, including polyvinylidene fluoride with a weight average molecular weight of 1.5 to 5 million; optionally, the polyvinylidene fluoride has a weight average molecular weight of 1.8 to 3.2 million.
  • polyvinylidene fluoride with a weight average molecular weight of 1.5 to 5 million as the binder component
  • the content of the binder in the active material layer can be effectively reduced. , thereby avoiding defects such as brittle pole pieces and impaired battery cycle performance caused by excessive amounts of binder in traditional technology. At the same time, it will not reduce the friction between active material layer components and between the active material layer and the current collector. Adhesion.
  • the polydispersity coefficient of the polyvinylidene fluoride is 1.5 to 2.5; optionally, the polydispersity coefficient of the polyvinylidene fluoride is 2 to 2.3.
  • a suitable polydispersity coefficient can make polyvinylidene fluoride with a weight average molecular weight of 1.5 to 5 million better dispersed in the solvent when preparing the cathode slurry, thereby effectively increasing the solid content of the slurry and reducing production costs.
  • the number average molecular weight of the polyvinylidene fluoride is 600,000 to 3 million; optionally, the number average molecular weight of the polyvinylidene fluoride is 1 million to 2 million.
  • the polydispersity coefficient of polyvinylidene fluoride can be made within an appropriate range.
  • the Dv50 particle size of the polyvinylidene fluoride is 50 ⁇ m to 150 ⁇ m; optionally, the Dv50 particle size of the polyvinylidene fluoride is 60 ⁇ m to 100 ⁇ m.
  • Controlling the Dv50 particle size of polyvinylidene fluoride within an appropriate range can enable polyvinylidene fluoride with a weight average molecular weight of 1.5 to 5 million to have appropriate solubility.
  • it can not only avoid large
  • the molecular weight of polyvinylidene fluoride dissolves too slowly, thereby speeding up the preparation of cathode slurry.
  • it also allows the amount of binder to be controlled at a low level without affecting the bonding performance. Excessive negative impact, thus effectively improving the performance damage of pole pieces and batteries caused by high amounts of binders in traditional technologies.
  • the polyvinylidene fluoride has a crystallinity of 38% to 48%; optionally, the polyvinylidene fluoride has a crystallinity of 40% to 45%.
  • the crystallinity of polyvinylidene fluoride also affects its solubility. Therefore, a suitable crystallinity range is also an important factor in keeping the amount of binder at a low level.
  • the viscosity of the binder solution prepared by dissolving polyvinylidene fluoride in N-methylpyrrolidone is 3500 mPa ⁇ s to 5000 mPa ⁇ s, and in the binder solution, the bonding The mass percentage of the agent is 3% to 5%.
  • the binder solution needs to have a certain viscosity to prevent the positive electrode active material and conductive agent and other additives from settling, so that the slurry can be placed more stably.
  • at least 7% mass percentage of binder is required.
  • the amount of binder can be controlled. In the range of 3% to 5%, it provides the possibility for the subsequent binder to have a lower content in the cathode active material layer.
  • a second aspect of the application provides a method for preparing the adhesive described in one or more of the aforementioned embodiments, including the following steps:
  • Controlling the temperature, pressure and time of the polymerization reaction within the appropriate range can make vinylidene fluoride react in the form of homopolymerization, thereby obtaining polyvinylidene fluoride with higher regularity, and the weight average molecular weight of polyvinylidene fluoride can be controlled.
  • a preset range to achieve a low amount of binder in the cathode slurry.
  • the chain transfer agent includes one or more of cyclohexane, isopropyl alcohol, methanol, and acetone.
  • the amount of the chain transfer agent is 1.5% to 3% of the mass of the vinylidene fluoride monomer. Controlling the amount of chain transfer agent within an appropriate range can control the polymer chain length, thereby obtaining a polyvinylidene fluoride product with an appropriate molecular weight range.
  • the polymerization reaction includes the following steps:
  • the materials Before raising the temperature to carry out the polymerization reaction, the materials must be mixed evenly to make the reaction proceed more thoroughly, and the resulting polyvinylidene fluoride polydispersity coefficient, crystallinity and particle size will be more appropriate.
  • the amount of the solvent is 2 to 8 times the mass of the vinylidene fluoride monomer.
  • the dispersant includes one or more of cellulose ether and polyvinyl alcohol; optionally, the cellulose ether includes methyl cellulose ether and carboxyethyl cellulose ether. one or more.
  • the amount of the dispersant is 0.1% to 0.3% of the mass of the vinylidene fluoride monomer.
  • the initiator is an organic peroxide; optionally, the organic peroxide includes tert-amyl peroxypivalate, tert-amyl peroxypivalate, 2-ethyl One or more of peroxydicarbonate, diisopropylperoxydicarbonate and tert-butylperoxypivalate.
  • the amount of the initiator is 0.15% to 1% of the mass of the vinylidene fluoride monomer.
  • the pH adjuster includes one or more of potassium carbonate, potassium bicarbonate, sodium carbonate, sodium bicarbonate, and ammonia.
  • the pH adjuster is used in an amount of 0.05% to 0.2% based on the mass of the vinylidene fluoride monomer.
  • a third aspect of the application provides the use of polyvinylidene fluoride as defined in one or more of the foregoing embodiments in the preparation of adhesives.
  • a fourth aspect of the present application provides a secondary battery, including a positive electrode plate, a separation film and a negative electrode plate, the isolation film being disposed between the positive electrode piece and the negative electrode piece;
  • the positive electrode sheet includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector.
  • the positive active material layer includes the binder described in one or more of the aforementioned embodiments.
  • the mass percentage of the binder in the cathode active material layer is 0.6% to 1.2%; optionally, the mass percentage of the binder is 0.6% to 0.8%. .
  • the amount of binder in the cathode active material layer is often as high as 2.5% or more. When the amount drops to 2% or less, it will significantly affect the adhesion of the particles between the cathode active material layers, or the active material layer and the The adhesiveness between current collectors, and the use of the adhesive in this application can greatly reduce the amount of adhesive to 1.2% and below compared with traditional technology, and does not have a significant impact on the adhesive performance, low adhesive amount The brittleness and cycle performance of the pole piece are effectively improved.
  • a fifth aspect of the present application provides a battery module, including the secondary battery described in one or more of the aforementioned embodiments.
  • a sixth aspect of the application provides a battery pack, including the battery module as claimed in the preceding claims.
  • a seventh aspect of the present application provides an electrical device, including one or more of the secondary battery described in one or more of the aforementioned embodiments, the aforementioned battery module, and the aforementioned battery pack.
  • Figure 1 is a scanning electron microscope image of polyvinylidene fluoride particles according to an embodiment of the present application.
  • Figure 2 is a scanning electron microscope image of polyvinylidene fluoride particles according to an embodiment of the present application.
  • Figure 3 is a scanning electron microscope image of polyvinylidene fluoride particles according to an embodiment of the present application.
  • Figure 4 is a scanning electron microscope image of polyvinylidene fluoride particles according to an embodiment of the present application.
  • Figure 5 is a scanning electron microscope image of Comparative Example 1 of the present application.
  • FIG. 6 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG. 7 is an exploded view of the secondary battery according to the embodiment of the present application shown in FIG. 6 .
  • Figure 8 is a schematic diagram of a battery module according to an embodiment of the present application.
  • Figure 9 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG. 10 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG. 9 .
  • FIG. 11 is a schematic diagram of a power consumption device using a secondary battery as a power source according to an embodiment of the present application.
  • Ranges disclosed herein are defined in terms of lower and upper limits. A given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive of the endpoints, and may be arbitrarily combined, that is, any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, understand that ranges of 60-110 and 80-120 are also expected. 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.
  • the numerical range “a ⁇ b” represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers.
  • the numerical range “0 ⁇ 5" means that all real numbers between "0 ⁇ 5" have been listed in this article, and "0 ⁇ 5" is just an abbreviation of these numerical combinations.
  • a certain parameter is an integer ⁇ 2
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • step (c) means that step (c) may be added to the method in any order.
  • the method may include steps (a), (b) and (c). , may also include steps (a), (c) and (b), may also include steps (c), (a) and (b), etc.
  • condition "A or B” is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists) ; Or both A and B are true (or exist).
  • the binder is an indispensable raw material for preparing the positive active material layer. It provides adhesive force between the raw material particles of the active material layer and between the active material layer and the current collector layer, ensuring that the secondary battery is in good condition. It can operate normally during multiple charging and discharging processes. In order to ensure sufficient bonding force, in traditional technology, it is generally necessary to use a binder with a mass percentage of more than 2.5% of the positive active material layer. However, excessive binder dosage will cause the finished electrode piece to be brittle and prone to cracking during use and processing, affecting the production yield and safety of the battery. Moreover, excessive binder content is also detrimental to battery cycle performance. Therefore, how to reduce the amount of binder in the positive active material layer without negatively affecting its bonding performance is an urgent problem to be solved in the field of secondary batteries.
  • the inventor of the present application has provided a binder through extensive research, which includes polyvinylidene fluoride with a weight average molecular weight of 1.5 to 5 million; optionally, the weight average molecular weight of the polyvinylidene fluoride is 180 ⁇ 3.2 million.
  • the weight average molecular weight of polyvinylidene fluoride can also be, for example, 1.6 million, 1.7 million, 1.8 million, 1.9 million, 2 million, 2.1 million, 2.2 million, 2.3 million, 2.4 million, 2.5 million, 2.6 million, 2.7 million, 2.8 million , 2.9 million, 3 million, 3.1 million, 3.2 million, 3.3 million, 3.4 million, 3.5 million, 3.6 million, 3.7 million, 3.8 million, 3.9 million, 4 million, 4.1 million, 4.2 million, 4.3 million, 4.4 million, 4.5 million 10,000, 4.6 million, 4.7 million, 4.8 million or 4.9 million, or within the range of any two points above.
  • polyvinylidene fluoride with a weight average molecular weight of 1.5 to 5 million as the binder component
  • the content of the binder in the active material layer can be effectively reduced. , thereby avoiding defects such as brittle pole pieces and impaired battery cycle performance caused by excessive amounts of binder in traditional technology. At the same time, it will not reduce the friction between active material layer components and between the active material layer and the current collector. Adhesion.
  • polyvinylidene fluoride has a polydispersity coefficient of 1.5 to 2.5; optionally, polyvinylidene fluoride has a polydispersity coefficient of 2 to 2.3.
  • the polydispersity coefficient of polyvinylidene fluoride can also be, for example, 1.6, 1.7, 1.8, 1.9, 2, 2.1 or 2.2, or it can be within a range consisting of any two points mentioned above.
  • a suitable polydispersity coefficient can make polyvinylidene fluoride with a weight average molecular weight of 1.5 to 5 million better dispersed in the solvent when preparing the cathode slurry, thereby effectively increasing the solid content of the slurry and reducing production costs.
  • the polydispersity coefficient can be tested using methods known in the art, for example, using Waters 2695 Isocratic HPLC gel chromatograph (differential refractive index detector 2141).
  • 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.
  • NMP N-methylpyrrolidone
  • the number average molecular weight of polyvinylidene fluoride is 600,000 to 3 million; optionally, the number average molecular weight of polyvinylidene fluoride is 1 million to 2 million.
  • the number average molecular weight of polyvinylidene fluoride can also be, for example, 700,000, 800,000, 900,000, 1 million, 1.1 million, 1.2 million, 1.3 million, 1.4 million, 1.5 million, 1.6 million, 1.7 million, 1.8 million or 1.9 million. , or within the range consisting of any two point values mentioned above.
  • the polydispersity coefficient of polyvinylidene fluoride can be made within an appropriate range.
  • the Dv50 particle size of polyvinylidene fluoride ranges from 50 ⁇ m to 150 ⁇ m; optionally, the Dv50 particle size of polyvinylidene fluoride ranges from 60 ⁇ m to 100 ⁇ m.
  • the Dv50 particle size of polyvinylidene fluoride can also be, for example, 70 ⁇ m, 80 ⁇ m, 90 ⁇ m, 100 ⁇ m, 110 ⁇ m, 120 ⁇ m, 130 ⁇ m or 140 ⁇ m, or it can be within the range of any two of the above points.
  • Controlling the Dv50 particle size of polyvinylidene fluoride within an appropriate range can enable polyvinylidene fluoride with a weight average molecular weight of 1.5 to 5 million to have appropriate solubility.
  • it can not only avoid large
  • the molecular weight of polyvinylidene fluoride dissolves too slowly, thereby speeding up the preparation of cathode slurry.
  • Dv50 refers to the particle size corresponding to when the cumulative particle size distribution number of particles reaches 50% in the particle size distribution curve. Its physical meaning is that 50% of the particles have a particle size smaller (or larger) than it.
  • Dv50 can be easily measured using a laser particle size analyzer, such as the Mastersizer 2000E laser particle size analyzer of Malvern Instruments Co., Ltd. in the United Kingdom, referring to the GB/T 19077-2016 particle size distribution laser diffraction method.
  • the polyvinylidene fluoride has a crystallinity of 38% to 48%; optionally, the polyvinylidene fluoride has a crystallinity of 40% to 45%.
  • the crystallinity of polyvinylidene fluoride may also be, for example, 39%, 40%, 41%, 42%, 43% or 44%, or it may be within the range of any two of the above points.
  • the crystallinity of polyvinylidene fluoride also affects its solubility. Therefore, a suitable crystallinity range is also an important factor in keeping the amount of binder at a low level.
  • the crystallinity can be tested using methods known in the art.
  • differential scanning calorimetry DSC
  • the viscosity of the binder solution prepared by dissolving polyvinylidene fluoride in N-methylpyrrolidone is 3500 mPa ⁇ s to 5000 mPa ⁇ s, and the mass percentage of the binder in the binder solution is 3% to 5%.
  • the viscosity of the binder solution may also be, for example, 3750 mPa ⁇ s, 4000 mPa ⁇ s, 4250 mPa ⁇ s, 4500 mPa ⁇ s or 4750 mPa ⁇ s, or within a range consisting of any two of the above points.
  • the binder solution When preparing positive electrode slurry, the binder solution needs to have a certain viscosity to prevent the positive electrode active material and conductive agent and other additives from settling, so that the slurry can be placed more stably.
  • a solution viscosity of 3500mPa ⁇ s to 5000mPa ⁇ s at least 7% mass percentage of binder is required.
  • the amount of binder can be controlled. In the range of 3% to 5%, it provides the possibility for the subsequent binder to have a lower content in the cathode active material layer.
  • the viscosity of the binder solution can be tested using methods known in the art.
  • the viscosity of the binder solution can be measured using an Anton Paar rotational rheometer to test the dynamic viscosity of the material.
  • the shear rate is 0.1s -1 ⁇ 100s -1 . Measure 31 points. After fitting, the consistency coefficient can be obtained, which can be characterized. Binder solution viscosity.
  • the second aspect of this application provides a method for preparing the adhesive of one or more of the aforementioned embodiments, including the following steps:
  • non-reactive gas refers to a gas that does not react with reactants in the reaction system.
  • Common non-reactive gases may include, for example, inert gases such as argon and nitrogen.
  • reaction pressure may also be, for example, 6.5MPa, 7MPa or 7.5MPa.
  • the reaction temperature may also be 50°C or 55°C, for example.
  • the polymerization reaction time can also be, for example, 7 h, 8 h or 9 h.
  • Controlling the temperature, pressure and time of the polymerization reaction within the appropriate range can make vinylidene fluoride react in the form of homopolymerization, thereby obtaining polyvinylidene fluoride with higher regularity, and the weight average molecular weight of polyvinylidene fluoride can be controlled.
  • a preset range to achieve a low amount of binder in the cathode slurry.
  • the chain transfer agent includes one or more of cyclohexane, isopropyl alcohol, methanol, and acetone.
  • the amount of chain transfer agent used is 1.5% to 3% by mass of the vinylidene fluoride monomer.
  • the amount of chain transfer agent can also be, for example, 2% or 2.5%. Controlling the dosage of the chain transfer agent within a suitable range can control the polymer chain length, thereby obtaining a polyvinylidene fluoride product with a suitable molecular weight range.
  • the polymerization reaction includes the following steps:
  • the materials Before raising the temperature to carry out the polymerization reaction, the materials must be mixed evenly to make the reaction proceed more thoroughly, and the resulting polyvinylidene fluoride polydispersity coefficient, crystallinity and particle size will be more appropriate.
  • the amount of solvent used is 2 to 8 times the mass of vinylidene fluoride monomer.
  • the amount of solvent used may also be, for example, 3, 4, 5, 6 or 7 times the mass of vinylidene fluoride monomer.
  • Suitable solvents may include, for example, water, preferably deionized water.
  • the dispersant includes one or more of cellulose ether and polyvinyl alcohol; optionally, the cellulose ether includes one or more of methyl cellulose ether and carboxyethyl cellulose ether. kind.
  • the amount of dispersant is 0.1% to 0.3% based on the mass of vinylidene fluoride monomer.
  • the amount of dispersant may also be, for example, 0.2%.
  • the initiator is an organic peroxide; optionally, the organic peroxide includes tert-amyl peroxypivalate, tert-amyl peroxypivalate, 2-ethyl peroxydicarbonate One or more of ester, diisopropyl peroxydicarbonate and tert-butyl peroxypivalate.
  • the amount of initiator used is 0.15% to 1% of the mass of vinylidene fluoride monomer.
  • the amount of initiator can also be, for example, 0.2%, 0.4%, 0.6% or 0.8%.
  • the pH adjusting agent includes one or more of potassium carbonate, potassium bicarbonate, sodium carbonate, sodium bicarbonate, and ammonia.
  • the amount of pH adjuster is 0.05% to 0.2% based on the mass of vinylidene fluoride monomer.
  • the amount of pH adjuster can also be, for example, 0.1% or 0.15%.
  • a third aspect of the application provides the use of polyvinylidene fluoride as defined in one or more of the foregoing embodiments in the preparation of adhesives.
  • a fourth aspect of the present application provides a secondary battery, including a positive electrode plate, a separation film and a negative electrode plate, the isolation film being disposed between the positive electrode piece and the negative electrode piece;
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector.
  • the positive electrode active material layer includes the binder of one or more of the aforementioned embodiments.
  • the mass percentage of the binder in the cathode active material layer is 0.6% to 1.2%; optionally, the mass percentage of the binder is 0.6% to 0.8%.
  • the amount of binder may also be, for example, 0.7%, 0.8%, 0.9%, 1% or 1.1%. In traditional technology, the amount of binder in the cathode active material layer is often as high as 2.5% or more.
  • a fifth aspect of the present application provides a battery module, including the secondary battery of one or more of the aforementioned embodiments.
  • a sixth aspect of the application provides a battery pack, including the battery module as claimed in the preceding claims.
  • a seventh aspect of the present application provides an electrical device, including one or more of the secondary battery of one or more of the aforementioned embodiments, the aforementioned battery module, and the aforementioned battery pack.
  • 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 active material layer disposed on at least one surface of the positive electrode current collector.
  • the positive electrode active material layer contains the binder provided in the first aspect of the present application.
  • the positive electrode current collector has two surfaces opposite in its own thickness direction, and the positive electrode active material layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • the metal foil aluminum foil can be used.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer.
  • the composite current collector can be formed by forming metal materials (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyterephthalate It is formed on substrates such as ethylene glycol ester (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the cathode active material may be a cathode active material known in the art for batteries.
  • the cathode active material may include at least one of the following materials: an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and their respective modified compounds.
  • the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials of batteries can also be used. Only one type of these positive electrode active materials may be used alone, or two or more types may be used in combination.
  • lithium transition metal oxides may include, but are not limited to, lithium cobalt 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 NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (can also be abbreviated to NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (can also be abbreviated to NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (can also be abbreviated to NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (also referred to as NCM811), at least one of lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15),
  • lithium-containing phosphates with an olivine structure can include but are not limited to lithium iron phosphate (such as LiFePO 4 (also referred to as LFP)), composite materials of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), composite materials of lithium manganese phosphate and carbon, manganese phosphate At least one composite material of lithium iron, lithium iron manganese phosphate and carbon.
  • lithium iron phosphate such as LiFePO 4 (also referred to as LFP)
  • composite materials of lithium iron phosphate and carbon such as LiMnPO 4
  • LiMnPO 4 lithium manganese phosphate
  • manganese phosphate At least one composite material of lithium iron, lithium iron manganese phosphate and carbon.
  • the positive active material layer optionally further includes other conventional binders other than the binders provided in the first aspect of the application.
  • the conventional binder may include polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene At least one of vinyl fluoride-hexafluoropropylene copolymer and fluorine-containing acrylate resin.
  • PTFE polytetrafluoroethylene
  • the positive active material layer optionally further includes a conductive agent.
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components in a solvent (such as N -methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode piece can be obtained.
  • a solvent such as N -methylpyrrolidone
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, where the negative electrode film layer includes a negative electrode active material.
  • the negative electrode current collector has two surfaces opposite 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 by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative active materials, conductive agents, binders and any other components in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode piece can be obtained.
  • a solvent such as deionized water
  • the electrolyte plays a role in conducting ions between the positive and negative electrodes.
  • the type of electrolyte in this application can be selected according to needs.
  • the electrolyte can be liquid, gel, or completely solid.
  • the electrolyte is an electrolyte solution.
  • the electrolyte 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 film can be a single-layer film or a multi-layer composite film, with no special restrictions. When the isolation film is a multi-layer composite film, the materials of each layer can be the same or different, and there is no particular limitation.
  • the positive electrode piece, the negative electrode piece and the separator film can be made into an electrode assembly through a winding process or a lamination process.
  • the secondary battery may include an outer packaging.
  • the outer packaging can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag.
  • the material of the soft bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.
  • FIG. 6 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. 8 shows the battery module 4 as an example.
  • a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 .
  • the plurality of secondary batteries 5 can be fixed by fasteners.
  • the battery module 4 may further include a housing having a receiving space in which a plurality of secondary batteries 5 are received.
  • the above-mentioned battery modules can also be assembled into a battery pack.
  • 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 electrical devices may include mobile equipment, electric vehicles, electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.
  • mobile devices can be, for example, mobile phones, laptops, etc.; electric vehicles can be, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc. , but not limited to this.
  • a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.
  • FIG. 11 shows an electrical device 6 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 secondary batteries can be used as the power source.
  • the weight described in the description of the embodiments of this application may be mass units well-known in the field of chemical engineering such as ⁇ g, mg, g, kg, etc. If the manufacturer of the reagents or instruments used is not indicated, they are all conventional products that can be purchased commercially.
  • the relevant parameters of the polyvinylidene fluoride binder prepared in this example are as follows: weight average molecular weight 1.8 million, polydispersity coefficient 2.1, crystallinity 42%, Dv50 particle size 60 ⁇ m;
  • the vinyl binder was dissolved in N-methylpyrrolidone solution to make a solution with a mass concentration of 4wt%, and the measured viscosity of the solution was 3600mPa ⁇ s;
  • step (3) Apply the positive electrode slurry prepared in step (2) to the carbon-coated aluminum foil, bake it at 110°C for 15 minutes, cold press it and cut it into 15mm diameter discs, and then combine them with the metal lithium sheet, isolation film, and electrolytic The liquid is made into a deduction.
  • Example 2 It is basically the same as Example 1, except that the mass percentage content of the polyvinylidene fluoride binder in step (2) is 0.9%, 1%, 1.1%, and 1.2%.
  • step (1) after the polymerization reaction is carried out for 8 hours, 25g of cyclohexane is added to continue the reaction;
  • the relevant parameters of the polyvinylidene fluoride binder prepared in this example are as follows: weight average molecular weight 2.5 million, polydispersity coefficient 2.1, crystallinity 44%, Dv50 particle size 80 ⁇ m; The vinyl binder was dissolved in N-methylpyrrolidone solution to make a solution with a mass concentration of 4 wt%, and the viscosity of the solution was measured to be 4300 mPa ⁇ s.
  • Example 6 It is basically the same as Example 6, except that the mass percentage content of the polyvinylidene fluoride binder in step (2) is 0.9%, 1%, 1.1%, and 1.2%.
  • step (1) after the polymerization reaction is carried out for 10 hours, 20 g of cyclohexane is added to continue the reaction;
  • the relevant parameters of the polyvinylidene fluoride binder prepared in this example are as follows: weight average molecular weight 3.2 million, polydispersity coefficient 2.2, crystallinity 45%, Dv50 particle size 100 ⁇ m; The vinyl binder was dissolved in N-methylpyrrolidone solution to make a solution with a mass concentration of 4 wt%, and the viscosity of the solution was measured to be 4900 mPa ⁇ s.
  • Example 11 It is basically the same as Example 11, except that the mass percentage content of the polyvinylidene fluoride binder in step (2) is 0.9%, 1%, 1.1%, and 1.2%.
  • step (1) after the polymerization reaction was carried out for 12 hours, 15 g of cyclohexane was added to continue the reaction;
  • the relevant parameters of the polyvinylidene fluoride binder prepared in this example are as follows: weight average molecular weight 5 million, polydispersity coefficient 2.2, crystallinity 46%, Dv50 particle size 150 ⁇ m; The vinyl binder was dissolved in N-methylpyrrolidone solution to prepare a solution with a mass concentration of 4 wt%, and the measured viscosity of the solution was 6500 mPa ⁇ s.
  • Example 16 It is basically the same as Example 16, except that the mass percentages of the polyvinylidene fluoride binder in step (2) are 0.6% and 0.7% respectively.
  • step (1) after the polymerization reaction was carried out for 5 hours, 33 g of cyclohexane was added to continue the reaction;
  • the relevant parameters of the polyvinylidene fluoride binder prepared in this example are as follows: weight average molecular weight 1.5 million, polydispersity coefficient 2.18, crystallinity 41.5%, Dv50 particle size 45 ⁇ m;
  • the vinyl binder was dissolved in N-methylpyrrolidone solution to prepare a solution with a mass concentration of 4 wt%, and the viscosity of the solution was measured to be 3000 mPa ⁇ s.
  • Example 19 It is basically the same as Example 19, except that the mass percentage of the polyvinylidene fluoride binder in step (2) is 1.8%.
  • Example 2 It is basically the same as Example 1, except that the temperature of the polymerization reaction in step (1) is 65°C;
  • the relevant parameters of the polyvinylidene fluoride binder prepared in this comparative example are as follows: weight average molecular weight 2 million, polydispersity coefficient 2.4, crystallinity 52%, Dv50 particle size 50 ⁇ m;
  • the vinyl binder was dissolved in N-methylpyrrolidone solution to prepare a solution with a mass concentration of 4 wt%, and the measured viscosity of the solution was 4000 mPa ⁇ s.
  • Example 2 It is basically the same as Example 1, except that the polymerization reaction time in step (1) is 12 h;
  • the relevant parameters of the polyvinylidene fluoride binder prepared in this comparative example are as follows: weight average molecular weight 1.83 million, polydispersity coefficient 2.1, crystallinity 42%, Dv50 particle size 60 ⁇ m;
  • the vinyl binder was dissolved in N-methylpyrrolidone solution to prepare a solution with a mass concentration of 4 wt%, and the viscosity of the solution was measured to be 3700 mPa ⁇ s.
  • Example 1 It is basically the same as Example 1, except that the pressure of the polymerization reaction in step (1) is 9MPa;
  • the relevant parameters of the polyvinylidene fluoride binder prepared in this comparative example are as follows: weight average molecular weight 1.6 million, polydispersity coefficient 2.15, crystallinity 42%, Dv50 particle size 50 ⁇ m; The vinyl binder was dissolved in N-methylpyrrolidone solution to make a solution with a mass concentration of 4 wt%, and the viscosity of the solution was measured to be 2500 mPa ⁇ s.
  • step (2) the polyvinylidene fluoride binder prepared in step (1) is replaced with a commercially available polyvinylidene fluoride with a weight average molecular weight of 800,000 (East Sunshine Co., Ltd. 701A grade produced), so that the mass percentage of polyvinylidene fluoride in the slurry solute is 2.5%.
  • Example 2 It is basically the same as Example 1, except that the temperature of the polymerization reaction in step (1) is 35°C;
  • the relevant parameters of the polyvinylidene fluoride binder prepared in this comparative example are as follows: weight average molecular weight 1.2 million, polydispersity coefficient 1.8, crystallinity 40%, Dv50 particle size 30 ⁇ m;
  • the vinyl binder was dissolved in N-methylpyrrolidone solution to prepare a solution with a mass concentration of 4 wt%, and the measured viscosity of the solution was 450 mPa ⁇ s.
  • step (1) It is basically the same as Example 1, except that the polymerization reaction time in step (1) is 4 hours;
  • the relevant parameters of the polyvinylidene fluoride binder prepared in this comparative example are as follows: weight average molecular weight 1.1 million, polydispersity coefficient 1.9, crystallinity 38%, Dv50 particle size 25 ⁇ m;
  • the vinyl binder was dissolved in N-methylpyrrolidone solution to make a solution with a mass concentration of 4 wt%, and the measured viscosity of the solution was 232 mPa ⁇ s.
  • Example 2 It is basically the same as Example 1, except that the pressure of the polymerization reaction in step (1) is 5MPa;
  • the relevant parameters of the polyvinylidene fluoride binder prepared in this comparative example are as follows: weight average molecular weight 1.4 million, polydispersity coefficient 2.2, crystallinity 41%, Dv50 particle size 40 ⁇ m; The vinyl binder was dissolved in N-methylpyrrolidone solution to make a solution with a mass concentration of 4 wt%, and the viscosity of the solution was measured to be 1800 mPa ⁇ s.
  • the cold-pressed pole pieces are sampled along the transverse direction, which can be 3 samples with an area of 100cm 2 (4cm ⁇ 25cm longitudinally).
  • Pre-fold the 100cm 2 sample folded in half according to the 25cm longitudinal direction
  • fold the pre-folded experimental diaphragm Place it on the plane of the experimental bench.
  • the battery capacity retention rate data is measured after 500 cycles under the above test conditions.
  • the obtained data is the value of P500.
  • Example 17 when the weight average molecular weight of polyvinylidene fluoride reaches 5 million, only 0.6% of the dosage can provide a bonding force of 30.7N/m, and the battery cycle performance is good, but the brittleness of the pole piece is slightly higher, but Still better than the commercially available adhesive (Comparative Example 1). It can be seen that the binder provided by this application can effectively reduce the amount of binder in the positive active material, and provide good electrode piece toughness, adhesion and battery cycle performance.
  • Example 21 Comparing Example 1 and Example 21, although the molecular weights of the two are close, the crystallinity and polydispersity coefficient of the polyvinylidene fluoride prepared by the polymerization reaction in Example 21 are also higher due to the higher reaction temperature, which affects the brittleness of the pole piece and the average roll.
  • the number of pressings is significantly reduced. Therefore, the polymerization reaction temperature is preferably controlled at 45°C to 60°C, so that the crystallinity can be controlled within the appropriate range of 38% to 48%, and the polydispersity coefficient can be controlled at a more preferred range. Within the range of 2 ⁇ 2.3.
  • Comparative Examples 1 to 5, Comparative Examples 6 to 10, Comparative Examples 11 to 15, Comparative Examples 16 to 18, and Comparative Examples 19 to 20 show that as the amount of polyvinylidene fluoride increases, the adhesive force and The cycle performance has increased, but the pole pieces will gradually become brittle, and the average number of rolls will decrease. Especially in Example 20, after the amount of binder is greatly increased to 1.8%, the improvement in cycle performance and adhesive force will become Limited, but the number of rolling times will be significantly reduced.
  • Example 22 Compared with Example 1, in Example 22, the polymerization reaction time is longer. As the monomers continue to be consumed and the pressure decreases, the polymerization conditions are no longer reached. Extending the reaction time cannot continue the polymerization reaction. Therefore, For the sake of energy consumption and efficiency, it is more appropriate to control the reaction time within 10 hours.
  • Example 23 Compared with Example 1, in Example 23, the reaction pressure is higher, the pressure for monomers to enter the reaction solution is higher, and more monomers enter the reaction solution, which can lead to the occurrence of a large-scale polymerization reaction, resulting in the generation of polyvinylidene fluoride. As the amount of ethylene increases, as the monomer decreases, polyvinylidene fluoride lacks the supply of monomers to produce a relatively small molecular weight, which has a certain impact on battery performance.
  • Example 2 Compared with Example 1, in Comparative Example 2, the reaction temperature is lower, the accelerating force of copolymerization is smaller, the polymerization reaction is insufficient, and the prepared molecular weight is smaller, resulting in a significant decrease in the adhesive force and cycle performance at the same addition amount. obvious decline.
  • Example 3 Compared with Example 1, in Comparative Example 3, the polymerization reaction time is shorter, the polymerization reaction cannot continue, and the prepared molecular weight is smaller, which will also cause a decrease in adhesive force and cycle performance.
  • Example 1 Compared with Example 1, in Comparative Example 4, the reaction pressure is smaller, the pressure for the monomers to enter the reaction solution is smaller, the reaction monomers cannot be continuously replenished, which is not conducive to the continuous progress of the polymerization, and the molecular weight of the product is too low. The adhesion requirements cannot be met, and the battery cycle performance is also reduced.

Abstract

本申请公开了一种粘结剂，包括重均分子量为150～500万的聚偏氟乙烯；可选地，聚偏氟乙烯的重均分子量为180～320万。

Description

粘结剂及其制备方法与应用 技术领域
本申请涉及二次电池领域，更具体地涉及一种粘结剂及其制备方法与应用。
背景技术
这里的陈述仅提供与本申请有关的背景信息，而不必然构成现有技术。
二次电池，如锂离子电池的正极活性材料层中，往往均需要添加粘结剂，以提升活性材料层与集流体之间的粘结力，以及活性材料颗粒之间的粘结力。聚偏氟乙烯是锂离子电池中使用最为广泛的粘结剂类型之一，其具有粘结性强、不溶于电解液、不与电解质反应、反复充电后不易产生裂痕且粘结性不产生明显下降等优势。然而，传统技术中，聚偏氟乙烯作为粘结剂的用量往往占据活性材料层原料质量的2.5％以上，粘结剂的用量过高，会挤占活性材料在活性材料层中的占比，往往导致极片较脆、韧性较差，并造成电池的循环性能下降。
发明内容
根据本申请的各种实施例，提供一种粘结剂及其制备方法与应用。
本申请的第一方面，提供了一种粘结剂，包括重均分子量为150～500万的聚偏氟乙烯；可选地，所述聚偏氟乙烯的重均分子量为180～320万。
通过选用重均分子量为150～500万的聚偏氟乙烯作为粘结剂组分，当将该粘结剂用于锂离子电池极片制备时，能够有效降低活性材料层中粘结剂的含量，从而避免传统技术中粘结剂用量过高导致的极片较脆、电池循环性能受损等缺陷，同时，不会降低活性材料层组分之间、以及活性材料层与集流体之间的粘结力。
在一些实施方式中，所述聚偏氟乙烯的多分散系数为1.5～2.5；可选地，所述聚偏氟乙烯的多分散系数为2～2.3。合适的多分散系数能使得制备正极浆料时，重均分子量为150～500万的聚偏氟乙烯在溶剂中的分散性更好，从而能有效提升浆料固含量，降低生产成本。
在一些实施方式中，所述聚偏氟乙烯的数均分子量为60～300万；可选地，所述聚偏氟乙烯的数均分子量为100～200万。通过控制聚偏氟乙烯的数均分子量在一定范围内，能够使得聚偏氟乙烯的多分散系数在合适范围内。
在一些实施方式中，所述聚偏氟乙烯的Dv50粒径为50μm～150μm；可选地，所述聚偏氟乙烯的Dv50粒径为60μm～100μm。将聚偏氟乙烯的Dv50粒径控制在合适范围内，能使得重均分子量为150～500万的聚偏氟乙烯具有合适的溶解度，用于制备锂离子电池正极极片时，不仅可以避免大分子量的聚偏氟乙烯溶解过慢，从而加快制备正极浆料时的速度，最重要的是，还能使得粘结剂的用量可以被控制在较低的水平，且不会对粘结性能造成过大的负面影响，从而有效改善了传统技术中高用量粘结剂带来的极片和电池性能受损的情况。
在一些实施方式中，所述聚偏氟乙烯的结晶度为38％～48％；可选地，所述聚偏氟乙烯的结晶度为40％～45％。聚偏氟乙烯的结晶度同样会对其溶解性造成影响，因此，合适的结晶度范围也是使得粘结剂用量能维持在较低水平的重要因素。
在一些实施方式中，所述聚偏氟乙烯溶于N-甲基吡咯烷酮制得的粘结剂溶液的粘度为3500mPa·s～5000mPa·s，且所述粘结剂溶液中，所述粘结剂的质量百分含量为3％～5％。制备正极浆料时，粘结剂溶液需要具有一定的粘度，才能防止正极活性材料以及导电剂等助剂的沉降，使浆料能较稳定地放置。传统技术中，要达到3500mPa·s～5000mPa·s的溶液粘度，至少需要7％质量百分含量的粘结剂才能实现，而采用本申请的粘结剂，则可以将粘结剂的用量控制在3％～5％范围内，为后续粘结剂在正极活性材料层中能具备较低含量提供了可能性。
本申请的第二方面，提供了前述一种或多种实施方式所述的粘结剂的制备方法，包括以下步骤：
将偏氟乙烯单体在非反应性气体氛围、6MPa～8MPa的反应压力、45℃～60℃的反应温度下进行聚合反应6h～10h；
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。
控制聚合反应的温度、压力以及时间在合适范围内，能使得偏氟乙烯以均聚的形式反应，从而获得规整度更高的聚偏氟乙烯，而且能将聚偏氟乙烯的重均分子量控制在预设范围内，以实现正极浆料中粘结剂的低用量。
在一些实施方式中，所述链转移剂包括环己烷、异丙醇、甲醇以及丙酮中的一种或多种。
在一些实施方式中，所述链转移剂的用量为所述偏氟乙烯单体质量的1.5％～3％。链转移剂的用量控制在合适范围内，能使得聚合物链长可控，从而获得合适分子量范 围的聚偏氟乙烯产物。
在一些实施方式中，所述聚合反应包括以下步骤：
向容器中加入溶剂和分散剂，对所述容器抽真空后充入非反应性气体；
向所述容器中加入引发剂和pH调节剂，调节pH值至6.5～7，然后加入偏氟乙烯单体，使所述容器中的压力达到6MPa～8MPa；
搅拌30min～60min后，升温至45℃～60℃，进行聚合反应。
升温进行聚合反应前，先将物料混合均匀，能使反应进行得更彻底，所得的聚偏氟乙烯多分散系数、结晶度以及粒径更恰当。
在一些实施方式中，所述溶剂的用量为所述偏氟乙烯单体质量的2～8倍。
在一些实施方式中，所述分散剂包括纤维素醚和聚乙烯醇中的一种或多种；可选地，所述纤维素醚包括甲基纤维素醚和羧乙基纤维素醚中的一种或多种。
在一些实施方式中，所述分散剂的用量为所述偏氟乙烯单体质量的0.1％～0.3％。
在一些实施方式中，所述引发剂为有机过氧化物；可选地，所述有机过氧化物包括过氧化新戊酸叔戊酯、过氧化叔戊基新戊酸酯、2-乙基过氧化二碳酸酯、二异丙基过氧化二碳酸酯以及叔丁基过氧化新戊酸酯中的一种或多种。
在一些实施方式中，所述引发剂的用量为所述偏氟乙烯单体质量的0.15％～1％。
在一些实施方式中，所述pH调节剂包括碳酸钾、碳酸氢钾、碳酸钠、碳酸氢钠以及氨水中的一种或多种。
在一些实施方式中，所述pH调节剂的用量为所述偏氟乙烯单体质量的0.05％～0.2％。
本申请的第三方面，提供了前述一种或多种实施方式中所定义的聚偏氟乙烯在制备粘结剂中的应用。
本申请的第四方面，提供了一种二次电池，包括正极极片、隔离膜以及负极极片，所述隔离膜设置于所述正极极片和所述负极极片之间；
所述正极极片包括正极集流体以及设置于所述正极集流体至少一个表面的正极活性材料层，所述正极活性材料层包括前述一种或多种实施方式所述的粘结剂。
在一些实施方式中，所述正极活性材料层中，所述粘结剂的质量百分含量为0.6％～1.2％；可选地，述粘结剂的质量百分含量为0.6％～0.8％。传统技术中，正极活性材料层中粘结剂的用量往往高达2.5％以上，用量下降至2％及以下时，就会明显影响正极活性材料层间颗粒的粘结性，或是活性材料层与集流体之间的粘结性，而采用 本申请中的粘结剂，能较传统技术将粘结剂用量大大降低至1.2％及以下，且不对粘结性能造成明显影响，低粘结剂用量使得极片的脆性和循环性能得到有效改善。
本申请的第五方面，提供了一种电池模块，包括前述一种或多种实施方式所述的二次电池。
本申请的第六方面，提供了一种电池包，包括权利要求前述的电池模块。
本申请的第七方面，提供了一种用电装置，包括前述一种或多种实施方式所述的二次电池、前述的电池模块以及前述的电池包中的一种或多种。
本申请的一个或多个实施例的细节在下面的附图和描述中提出。本申请的其他特征、目的和优点将从说明书、附图以及权利要求书变得明显。
附图说明
为了更好地描述和说明这里公开的那些申请的实施例或示例，可以参考一幅或多幅附图。用于描述附图的附加细节或示例不应当被认为是对所公开的申请、目前描述的实施例或示例以及目前理解的这些申请的最佳模式中的任何一者的范围的限制。
图1为本申请一实施方式的聚偏氟乙烯颗粒的扫描电镜图。
图2为本申请一实施方式的聚偏氟乙烯颗粒的的扫描电镜图。
图3为本申请一实施方式的聚偏氟乙烯颗粒的的扫描电镜图。
图4为本申请一实施方式的聚偏氟乙烯颗粒的的扫描电镜图。
图5为本申请对比例1的扫描电镜图。
图6是本申请一实施方式的二次电池的示意图。
图7是图6所示的本申请一实施方式的二次电池的分解图。
图8是本申请一实施方式的电池模块的示意图。
图9是本申请一实施方式的电池包的示意图。
图10是图9所示的本申请一实施方式的电池包的分解图。
图11是本申请一实施方式的二次电池用作电源的用电装置的示意图。
附图标记说明：
1：电池包；2：上箱体；3：下箱体；4：电池模块；5：二次电池；51：壳体；52：电极组件；53：盖板。
具体实施方式
为了使本申请的目的、技术方案及优点更加清楚明白，以下结合附图及实施例， 对本申请进行进一步详细说明。应当理解，此处描述的具体实施例仅仅用以解释本申请，并不用于限定本申请。
除非另有定义，本文所使用的所有的技术和科学术语与属于本申请的技术领域的技术人员通常理解的含义相同。本文中在本申请的说明书中所使用的术语只是为了描述具体的实施例的目的，不是旨在于限制本申请。本文所使用的术语“和/或”包括一个或多个相关的所列项目的任意的和所有的组合。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60～120和80～110的范围，理解为60～110和80～120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1～3、1～4、1～5、2～3、2～4和2～5。在本申请中，除非有其他说明，数值范围“a～b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0～5”表示本文中已经全部列出了“0～5”之间的全部实数，“0～5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或 B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
一般情况下，粘结剂是制备正极活性材料层不可或缺的原料，它为活性材料层各原料颗粒之间、以及活性材料层与集流体层之间提供粘结力，确保二次电池在多次充放电过程中能正常运行。为了保证足够的粘结力，传统技术中，一般需要采用正极活性材料层质量百分含量2.5％以上的粘结剂。然而，过高的粘结剂用量会导致极片成品脆性大，使用和加工过程中容易开裂，影响电池的生产良品率和使用安全。而且，过高的粘结剂含量也不利于电池的循环性能。因此，如何降低正极活性材料层中粘结剂的用量，且不对其粘结性能造成负面影响，是二次电池领域亟待解决的问题。
基于此，本申请的发明人通过大量研究，提供了一种粘结剂，其包括重均分子量为150～500万的聚偏氟乙烯；可选地，聚偏氟乙烯的重均分子量为180～320万。聚偏氟乙烯的重均分子量例如还可以是160万、170万、180万、190万、200万、210万、220万、230万、240万、250万、260万、270万、280万、290万、300万、310万、320万、330万、340万、350万、360万、370万、380万、390万、400万、410万、420万、430万、440万、450万、460万、470万、480万或490万，或者其在上述任意两个点值组成的范围内。
通过选用重均分子量为150～500万的聚偏氟乙烯作为粘结剂组分，当将该粘结剂用于锂离子电池极片制备时，能够有效降低活性材料层中粘结剂的含量，从而避免传统技术中粘结剂用量过高导致的极片较脆、电池循环性能受损等缺陷，同时，不会降低活性材料层组分之间、以及活性材料层与集流体之间的粘结力。
在一些实施方式中，聚偏氟乙烯的多分散系数为1.5～2.5；可选地，聚偏氟乙烯的多分散系数为2～2.3。聚偏氟乙烯的多分散系数例如还可以是1.6、1.7、1.8、1.9、2、2.1或2.2，或者其在上述任意两个点值组成的范围内。合适的多分散系数能使得制备正极浆料时，重均分子量为150～500万的聚偏氟乙烯在溶剂中的分散性更好，从而能有效提升浆料固含量，降低生产成本。
本申请中，多分散系数的测试可以选用本领域已知的方法进行测试，例如，采用Waters 2695 Isocratic HPLC型凝胶色谱仪(示差折光检测器2141)。以质量分数为3.0％的聚苯乙烯溶液试样做参比，选择匹配的色谱柱(油性：Styragel 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。待示数稳定后获取数据。分别读取重均分子量a和数均分子量b。多分散系数＝a/b。
在一些实施方式中，聚偏氟乙烯的数均分子量为60～300万；可选地，聚偏氟乙烯的数均分子量为100～200万。聚偏氟乙烯的数均分子量例如还可以是70万、80万、90万、100万、110万、120万、130万、140万、150万、160万、170万、180万或190万，或者其在上述任意两个点值组成的范围内。通过控制聚偏氟乙烯的数均分子量在一定范围内，能够使得聚偏氟乙烯的多分散系数在合适范围内。
在一些实施方式中，聚偏氟乙烯的Dv50粒径为50μm～150μm；可选地，聚偏氟乙烯的Dv50粒径为60μm～100μm。聚偏氟乙烯的Dv50粒径例如还可以是70μm、80μm、90μm、100μm、110μm、120μm、130μm或140μm，或者其在上述任意两个点值组成的范围内。将聚偏氟乙烯的Dv50粒径控制在合适范围内，能使得重均分子量为150～500万的聚偏氟乙烯具有合适的溶解度，用于制备锂离子电池正极极片时，不仅可以避免大分子量的聚偏氟乙烯溶解过慢，从而加快制备正极浆料时的速度，最重要的是，还能使得粘结剂的用量可以被控制在较低的水平，且不会对粘结性能造成过大的负面影响，从而有效改善了传统技术中高用量粘结剂带来的极片和电池性能受损的情况。
本申请中，Dv50指：在粒度分布曲线中，颗粒的累计粒度分布数达到50％时所对应的粒径，它的物理意义是粒径小于(或大于)它的颗粒占50％。作为示例，Dv50可以参照GB/T 19077-2016粒度分布激光衍射法，采用激光粒度分析仪方便地测定，如英国马尔文仪器有限公司的Mastersizer 2000E型激光粒度分析仪。
在一些实施方式中，聚偏氟乙烯的结晶度为38％～48％；可选地，聚偏氟乙烯的结晶度为40％～45％。聚偏氟乙烯的结晶度例如还可以是39％、40％、41％、42％、43％或44％，或者其在上述任意两个点值组成的范围内。聚偏氟乙烯的结晶度同样会对其溶解性造成影响，因此，合适的结晶度范围也是使得粘结剂用量能维持在较低水平的重要因素。
本申请中，结晶度的测试可以选用本领域已知的方法进行测试，例如，采用差示扫描量热法(DSC)测定结晶度，DSC能够测定结晶聚合物熔融时放出的热量，此热量是聚合物结晶部分的熔融热ΔHf，聚合物熔融热与其结晶度成正比，因此结晶度θ＝ 聚合物部分结晶熔融热/聚合物100％结晶熔融热×100％，其中聚合物100％结晶熔融热是已知的。
在一些实施方式中，聚偏氟乙烯溶于N-甲基吡咯烷酮制得的粘结剂溶液的粘度为3500mPa·s～5000mPa·s，且粘结剂溶液中，粘结剂的质量百分含量为3％～5％。粘结剂溶液的粘度例如还可以是3750mPa·s、4000mPa·s、4250mPa·s、4500mPa·s或4750mPa·s，或者其在上述任意两个点值组成的范围内。制备正极浆料时，粘结剂溶液需要具有一定的粘度，才能防止正极活性材料以及导电剂等助剂的沉降，使浆料能较稳定地放置。传统技术中，要达到3500mPa·s～5000mPa·s的溶液粘度，至少需要7％质量百分含量的粘结剂才能实现，而采用本申请的粘结剂，则可以将粘结剂的用量控制在3％～5％范围内，为后续粘结剂在正极活性材料层中能具备较低含量提供了可能性。
本申请中，粘结剂溶液的粘度可以采用本领域已知的方法进行测试。作为示例，粘结剂溶液的粘度例如可以采用Anton Paar旋转流变仪测试物料的动态粘度，剪切速率0.1s -1～100s -1，测量31个点，拟合后得到稠度系数，可表征粘结剂溶液粘度。
本申请的第二方面，提供了前述一种或多种实施方式的粘结剂的制备方法，包括以下步骤：
将偏氟乙烯单体在非反应性气体氛围、6MPa～8MPa的反应压力、45℃～60℃的反应温度下进行聚合反应6h～10h；
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。
可以理解，非反应性气体是指不与反应体系中反应物进行反应的气体，常见的非反应性气体例如可以包括氩气等惰性气体以及氮气。
在一些实施方式中，反应压力例如还可以是6.5MPa、7MPa或7.5MPa。
在一些实施方式中，反应温度例如还可以是50℃或55℃。
在一些实施方式中，聚合反应的时间例如还可以是7h、8h或9h。
控制聚合反应的温度、压力以及时间在合适范围内，能使得偏氟乙烯以均聚的形式反应，从而获得规整度更高的聚偏氟乙烯，而且能将聚偏氟乙烯的重均分子量控制在预设范围内，以实现正极浆料中粘结剂的低用量。
在一些实施方式中，链转移剂包括环己烷、异丙醇、甲醇以及丙酮中的一种或多种。
在一些实施方式中，链转移剂的用量为偏氟乙烯单体质量的1.5％～3％，链转移剂 的用量例如还可以是2％或2.5％。链转移剂的用量控制在合适范围内，能使得聚合物链长可控，从而获得合适分子量范围的聚偏氟乙烯产物。
在一些实施方式中，聚合反应包括以下步骤：
向容器中加入溶剂和分散剂，对容器抽真空后充入非反应性气体；
向容器中加入引发剂和pH调节剂，调节pH值至6.5～7，然后加入偏氟乙烯单体，使容器中的压力达到6MPa～8MPa；
搅拌30min～60min后，升温至45℃～60℃，进行聚合反应。
升温进行聚合反应前，先将物料混合均匀，能使反应进行得更彻底，所得的聚偏氟乙烯多分散系数、结晶度以及粒径更恰当。
在一些实施方式中，溶剂的用量为偏氟乙烯单体质量的2～8倍。溶剂的用量例如还可以是偏氟乙烯单体质量的3、4、5、6或7倍。合适的溶剂例如可以包括水，优选地，为去离子水。
在一些实施方式中，分散剂包括纤维素醚和聚乙烯醇中的一种或多种；可选地，纤维素醚包括甲基纤维素醚和羧乙基纤维素醚中的一种或多种。
在一些实施方式中，分散剂的用量为偏氟乙烯单体质量的0.1％～0.3％。分散剂的用量例如还可以是0.2％。
在一些实施方式中，引发剂为有机过氧化物；可选地，有机过氧化物包括过氧化新戊酸叔戊酯、过氧化叔戊基新戊酸酯、2-乙基过氧化二碳酸酯、二异丙基过氧化二碳酸酯以及叔丁基过氧化新戊酸酯中的一种或多种。
在一些实施方式中，引发剂的用量为偏氟乙烯单体质量的0.15％～1％。引发剂的用量例如还可以是0.2％、0.4％、0.6％或0.8％。
在一些实施方式中，pH调节剂包括碳酸钾、碳酸氢钾、碳酸钠、碳酸氢钠以及氨水中的一种或多种。
在一些实施方式中，pH调节剂的用量为偏氟乙烯单体质量的0.05％～0.2％。pH调节剂的用量例如还可以是0.1％或0.15％。
本申请的第三方面，提供了前述一种或多种实施方式中所定义的聚偏氟乙烯在制备粘结剂中的应用。
本申请的第四方面，提供了一种二次电池，包括正极极片、隔离膜以及负极极片，隔离膜设置于正极极片和负极极片之间；
正极极片包括正极集流体以及设置于正极集流体至少一个表面的正极活性材料 层，正极活性材料层包括前述一种或多种实施方式的粘结剂。
在一些实施方式中，正极活性材料层中，粘结剂的质量百分含量为0.6％～1.2％；可选地，述粘结剂的质量百分含量为0.6％～0.8％。粘结剂的用量例如还可以是0.7％、0.8％、0.9％、1％或1.1％。传统技术中，正极活性材料层中粘结剂的用量往往高达2.5％以上，用量下降至2％及以下时，就会明显影响正极活性材料层间颗粒的粘结性，或是活性材料层与集流体之间的粘结性，而采用本申请中的粘结剂，能较传统技术将粘结剂用量大大降低至1.2％及以下，且不对粘结性能造成明显影响，低粘结剂用量使得极片的脆性和循环性能得到有效改善。
本申请的第五方面，提供了一种电池模块，包括前述一种或多种实施方式的二次电池。
本申请的第六方面，提供了一种电池包，包括权利要求前述的电池模块。
本申请的第七方面，提供了一种用电装置，包括前述一种或多种实施方式的二次电池、前述的电池模块以及前述的电池包中的一种或多种。
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。
本申请的一个实施方式中，提供一种二次电池。
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。
正极极片
正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极活性材料层，正极活性材料层中包含本申请第一方面提供的粘结剂。
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，正极活性材料层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，所述正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE) 等的基材)上而形成。
在一些实施方式中，正极活性材料可采用本领域公知的用于电池的正极活性材料。作为示例，正极活性材料可包括以下材料中的至少一种：橄榄石结构的含锂磷酸盐、锂过渡金属氧化物及其各自的改性化合物。但本申请并不限定于这些材料，还可以使用其他可被用作电池正极活性材料的传统材料。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。其中，锂过渡金属氧化物的示例可包括但不限于锂钴氧化物(如LiCoO 2)、锂镍氧化物(如LiNiO 2)、锂锰氧化物(如LiMnO 2、LiMn 2O 4)、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LiNi 1/3Co 1/3Mn 1/3O 2(也可以简称为NCM333)、LiNi 0.5Co 0.2Mn 0.3O 2(也可以简称为NCM523)、LiNi 0.5Co 0.25Mn 0.25O 2(也可以简称为NCM211)、LiNi 0.6Co 0.2Mn 0.2O 2(也可以简称为NCM622)、LiNi 0.8Co 0.1Mn 0.1O 2(也可以简称为NCM811)、锂镍钴铝氧化物(如LiNi 0.85Co 0.15Al 0.05O 2)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LiFePO 4(也可以简称为LFP))、磷酸铁锂与碳的复合材料、磷酸锰锂(如LiMnPO 4)、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料中的至少一种。
在一些实施方式中，正极活性材料层还可选地包括除本申请第一方面提供的粘结剂以外的其他常规粘结剂。作为示例，所述常规粘结剂可以包括聚四氟乙烯(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。
在一些实施方式中，正极活性材料层还可选地包括导电剂。作为示例，所述导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，可以通过以下方式制备正极极片：将上述用于制备正极极片的组分，例如正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，即可得到正极极片。
负极极片
负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极膜层，所述负极膜层包括负极活性材料。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极膜层设置在 负极集流体相对的两个表面中的任意一者或两者上。
在一些实施方式中，所述负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，负极活性材料可采用本领域公知的用于电池的负极活性材料。作为示例，负极活性材料可包括以下材料中的至少一种：人造石墨、天然石墨、软炭、硬炭、硅基材料、锡基材料和钛酸锂等。所述硅基材料可选自单质硅、硅氧化合物、硅碳复合物、硅氮复合物以及硅合金中的至少一种。所述锡基材料可选自单质锡、锡氧化合物以及锡合金中的至少一种。但本申请并不限定于这些材料，还可以使用其他可被用作电池负极活性材料的传统材料。这些负极活性材料可以仅单独使用一种，也可以将两种以上组合使用。
在一些实施方式中，负极膜层还可选地包括粘结剂。所述粘结剂可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的至少一种。
在一些实施方式中，负极膜层还可选地包括导电剂。导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，负极膜层还可选地包括其他助剂，例如增稠剂(如羧甲基纤维素钠(CMC-Na))等。
在一些实施方式中，可以通过以下方式制备负极极片：将上述用于制备负极极片的组分，例如负极活性材料、导电剂、粘结剂和任意其他组分分散于溶剂(例如去离子水)中，形成负极浆料；将负极浆料涂覆在负极集流体上，经烘干、冷压等工序后，即可得到负极极片。
电解质
电解质在正极极片和负极极片之间起到传导离子的作用。本申请对电解质的种类没有具体的限制，可根据需求进行选择。例如，电解质可以是液态的、凝胶态的或全固态的。
在一些实施方式中，所述电解质采用电解液。所述电解液包括电解质盐和溶剂。
在一些实施方式中，电解质盐可选自六氟磷酸锂、四氟硼酸锂、高氯酸锂、六氟砷酸锂、双氟磺酰亚胺锂、双三氟甲磺酰亚胺锂、三氟甲磺酸锂、二氟磷酸锂、二氟草酸硼酸锂、二草酸硼酸锂、二氟二草酸磷酸锂及四氟草酸磷酸锂中的至少一种。
在一些实施方式中，溶剂可选自碳酸亚乙酯、碳酸亚丙酯、碳酸甲乙酯、碳酸二乙酯、碳酸二甲酯、碳酸二丙酯、碳酸甲丙酯、碳酸乙丙酯、碳酸亚丁酯、氟代碳酸亚乙酯、甲酸甲酯、乙酸甲酯、乙酸乙酯、乙酸丙酯、丙酸甲酯、丙酸乙酯、丙酸丙酯、丁酸甲酯、丁酸乙酯、1,4-丁内酯、环丁砜、二甲砜、甲乙砜及二乙砜中的至少一种。
在一些实施方式中，所述电解液还可选地包括添加剂。例如添加剂可以包括负极成膜添加剂、正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温或低温性能的添加剂等。
隔离膜
在一些实施方式中，二次电池中还包括隔离膜。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。
在一些实施方式中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的至少一种。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施方式中，二次电池可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，作为塑料，可列举出聚丙烯、聚对苯二甲酸丁二醇酯以及聚丁二酸丁二醇酯等。
本申请对二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图6是作为一个示例的方形结构的二次电池5。
在一些实施方式中，参照图7，外包装可包括壳体51和盖板53。其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53能够盖设于所述开口，以封闭所述容纳腔。正极极片、负极极 片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔内。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或多个，本领域技术人员可根据具体实际需求进行选择。
在一些实施方式中，二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为一个或多个，具体数量本领域技术人员可根据电池模块的应用和容量进行选择。
图8是作为一个示例的电池模块4。参照图8，在电池模块4中，多个二次电池5可以是沿电池模块4的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个二次电池5进行固定。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个二次电池5容纳于该容纳空间。
在一些实施方式中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以为一个或多个，具体数量本领域技术人员可根据电池包的应用和容量进行选择。
图9和图10是作为一个示例的电池包1。参照图9和图10，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
另外，本申请还提供一种用电装置，所述用电装置包括本申请提供的二次电池、电池模块、或电池包中的至少一种。所述二次电池、电池模块、或电池包可以用作所述用电装置的电源，也可以用作所述用电装置的能量存储单元。所述用电装置可以包括移动设备、电动车辆、电气列车、船舶及卫星、储能系统等，但不限于此。其中，移动设备例如可以是手机、笔记本电脑等；电动车辆例如可以是纯电动车、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，但不限于此。
作为所述用电装置，可以根据其使用需求来选择二次电池、电池模块或电池包。
图11是作为一个示例的用电装置6。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求 轻薄化，可以采用二次电池作为电源。
本申请的一个或多个实施例的细节在下面的附图和描述中提出。本申请的其他特征、目的和优点将从说明书、附图以及权利要求书变得明显。
以下结合具体实施例和对比例对本申请做进一步详细的说明。以下具体实施例中未写明的实验参数，优先参考本申请文件中给出的指引，还可以参考本领域的实验手册或本领域已知的其它实验方法，或者参考厂商推荐的实验条件。可理解，以下实施例所用的仪器和原料较为具体，在其他具体实施例中，可不限于此；本申请说明书实施例中所提到的相关成分的重量不仅仅可以指代各组分的具体含量，也可以表示各组分间重量的比例关系，因此，只要是按照本申请实施例说明书相关组分的含量按比例放大或缩小均在本申请说明书实施例公开的范围之内。具体地，本申请实施例说明书中所述的重量可以是μg、mg、g、kg等化学化工领域公知的质量单位。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
实施例1
(1)聚偏氟乙烯粘结剂的制备：
在10L的高压釜中加入4kg的去离子水和2g的甲基纤维素醚，抽真空并用N 2置换O 2三次，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；聚合反应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；
本实施例中制得的聚偏氟乙烯粘结剂的相关参数如下：重均分子量180万，多分散系数2.1，结晶度42％，Dv50粒径60μm；将本实施例制得的聚偏氟乙烯粘结剂溶于N-甲基吡咯烷酮溶液，制成质量百分浓度为4wt％的溶液，测得溶液粘度为3600mPa·s；
(2)正极浆料的制备：
将3.99kg磷酸铁锂、32.8g步骤(1)中制得的聚偏氟乙烯粘结剂、57.4g的乙炔黑、12.3g分散剂、2.4kg的N-甲基吡咯烷酮(NMP)混合均匀，得到正极浆料；正极浆料的溶质中，聚偏氟乙烯粘结剂的质量百分含量为0.8％；
(3)将步骤(2)中制得的正极浆料刮涂到涂碳铝箔上面，110℃烘烤15min，冷压后裁剪成直径15mm的圆片，再与金属锂片、隔离膜、电解液制作成扣电。
实施例2～5
与实施例1基本相同，区别在于，步骤(2)中聚偏氟乙烯粘结剂的质量百分含量 依次为0.9％、1％、1.1％、1.2％。
实施例6
与实施例1基本相同，区别在于，步骤(1)中，聚合反应进行反应8h后加入25g的环己烷继续反应；
本实施例中制得的聚偏氟乙烯粘结剂的相关参数如下：重均分子量250万，多分散系数2.1，结晶度44％，Dv50粒径80μm；将本实施例制得的聚偏氟乙烯粘结剂溶于N-甲基吡咯烷酮溶液，制成质量百分浓度为4wt％的溶液，测得溶液粘度为4300mPa·s。
实施例7～10
与实施例6基本相同，区别在于，步骤(2)中聚偏氟乙烯粘结剂的质量百分含量依次为0.9％、1％、1.1％、1.2％。
实施例11
与实施例1基本相同，区别在于，步骤(1)中，聚合反应进行反应10h后加入20g的环己烷继续反应；
本实施例中制得的聚偏氟乙烯粘结剂的相关参数如下：重均分子量320万，多分散系数2.2，结晶度45％，Dv50粒径100μm；将本实施例制得的聚偏氟乙烯粘结剂溶于N-甲基吡咯烷酮溶液，制成质量百分浓度为4wt％的溶液，测得溶液粘度为4900mPa·s。
实施例12～15
与实施例11基本相同，区别在于，步骤(2)中聚偏氟乙烯粘结剂的质量百分含量依次为0.9％、1％、1.1％、1.2％。
实施例16
与实施例1基本相同，区别在于，步骤(1)中，聚合反应进行反应12h后加入15g的环己烷继续反应；
本实施例中制得的聚偏氟乙烯粘结剂的相关参数如下：重均分子量500万，多分散系数2.2，结晶度46％，Dv50粒径150μm；将本实施例制得的聚偏氟乙烯粘结剂溶于N-甲基吡咯烷酮溶液，制成质量百分浓度为4wt％的溶液，测得溶液粘度为6500mPa·s。
实施例17～18
与实施例16基本相同，区别在于，步骤(2)中聚偏氟乙烯粘结剂的的质量百分含量依次为0.6％、0.7％。
实施例19
与实施例1基本相同，区别在于，步骤(1)中，聚合反应进行反应5h后加入33g的环己烷继续反应；
本实施例中制得的聚偏氟乙烯粘结剂的相关参数如下：重均分子量150万，多分散系数2.18，结晶度41.5％，Dv50粒径45μm；将本实施例制得的聚偏氟乙烯粘结剂溶于N-甲基吡咯烷酮溶液，制成质量百分浓度为4wt％的溶液，测得溶液粘度为3000mPa·s。
实施例20
与实施例19基本相同，区别在于，步骤(2)中聚偏氟乙烯粘结剂的质量百分含量为1.8％。
实施例21
与实施例1基本相同，区别在于，步骤(1)中的聚合反应的温度为65℃；
本对比例中制得的聚偏氟乙烯粘结剂的相关参数如下：重均分子量200万，多分散系数2.4，结晶度52％，Dv50粒径50μm；将本实施例制得的聚偏氟乙烯粘结剂溶于N-甲基吡咯烷酮溶液，制成质量百分浓度为4wt％的溶液，测得溶液粘度为4000mPa·s。
实施例22
与实施例1基本相同，区别在于，步骤(1)中的聚合反应的时间为12h；
本对比例中制得的聚偏氟乙烯粘结剂的相关参数如下：重均分子量183万，多分散系数2.1，结晶度42％，Dv50粒径60μm；将本实施例制得的聚偏氟乙烯粘结剂溶于N-甲基吡咯烷酮溶液，制成质量百分浓度为4wt％的溶液，测得溶液粘度为3700mPa·s。
实施例23
与实施例1基本相同，区别在于，步骤(1)中的聚合反应的压力为9MPa；
本对比例中制得的聚偏氟乙烯粘结剂的相关参数如下：重均分子量160万，多分散系数2.15，结晶度42％，Dv50粒径50μm；将本实施例制得的聚偏氟乙烯粘结剂溶于N-甲基吡咯烷酮溶液，制成质量百分浓度为4wt％的溶液，测得溶液粘度为2500mPa·s。
对比例1
与实施例1基本相同，区别在于，步骤(2)中将步骤(1)中制得的聚偏氟乙烯粘结剂替换为市售的80万重均分子量的聚偏氟乙烯(东阳光公司生产的701A牌号)，使浆料溶质中聚偏氟乙烯的质量百分含量为2.5％。
对比例2
与实施例1基本相同，区别在于，步骤(1)中的聚合反应的温度为35℃；
本对比例中制得的聚偏氟乙烯粘结剂的相关参数如下：重均分子量120万，多分散系数1.8，结晶度40％，Dv50粒径30μm；将本实施例制得的聚偏氟乙烯粘结剂溶于N-甲基吡咯烷酮溶液，制成质量百分浓度为4wt％的溶液，测得溶液粘度为450mPa·s。
对比例3
与实施例1基本相同，区别在于，步骤(1)中的聚合反应的时间为4h；
本对比例中制得的聚偏氟乙烯粘结剂的相关参数如下：重均分子量110万，多分散系数1.9，结晶度38％，Dv50粒径25μm；将本实施例制得的聚偏氟乙烯粘结剂溶于N-甲基吡咯烷酮溶液，制成质量百分浓度为4wt％的溶液，测得溶液粘度为232mPa·s。
对比例4
与实施例1基本相同，区别在于，步骤(1)中的聚合反应的压力为5MPa；
本对比例中制得的聚偏氟乙烯粘结剂的相关参数如下：重均分子量140万，多分散系数2.2，结晶度41％，Dv50粒径40μm；将本实施例制得的聚偏氟乙烯粘结剂溶于N-甲基吡咯烷酮溶液，制成质量百分浓度为4wt％的溶液，测得溶液粘度为1800mPa·s。
表征测试：
将各实施例和对比例中制得的聚偏氟乙烯粘结剂、极片或扣电电池进行以下表征测试：
(1)将聚偏氟乙烯粘结剂通过扫描电子显微镜扫描，判断形貌并确定粒径；
(2)将极片进行脆性测试，测试步骤如下：
冷压后的极片沿横向方向取样，可以为(4cm×25cm纵向)100cm 2面积的样品样本数3条，将样品100cm 2(按25cm纵向方向对折)预对折，将预对折的实验膜片放置与实验台平面，用2kg的圆筒辊进行辊压1次后，对灯光查看是否有漏光点，有漏光点样品不符合要求，无漏光点记录辊压次数，并对实验样品沿纵向折痕处反折，折痕对光观察，直至出现透光点并记录辊压次数n1。重复上述操作得到第二条、第三条的透光辊压次数n2、n3，计算平均辊压次数＝(n1+n2+n3)/3；
(3)粘结力测试，测试步骤如下：
参考国标《胶粘剂180°剥离强度实验方法》，用刀片截取宽30mm*长度为100-160mm的试样，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；
将宽度与极片等宽，长度大于试样长度80-200mm的纸带插入极片下方，并且用皱纹胶固定；
打开三思拉力机电源(灵敏度为1N)，指示灯亮，调整限位块到合适位置，将钢板未贴极片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。
(4)电池容量保持率测试，测试步骤如下：
将电池以1/3C恒流充电至3.65V，再以3.65V恒定电压充电至电流为0.05C，搁置5min，再以1/3C放电至2.5V，所得容量记为初始容量C0。对上述同一个电池重复以上步骤，并同时记录循环第n次后电池的放电容量Cn，则每次循环后电池容量保持率Pn＝Cn/C0*100％，以P1、P2……P100这100个点值为纵坐标，以对应的循环次数为横坐标，得到电池容量保持率与循环次数的曲线图；
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；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。
以上测试数据列入表1中：
表1
Figure PCTCN2022099187-appb-000001
Figure PCTCN2022099187-appb-000002
分析表1数据，比较实施例1、实施例6、实施例11、实施例16、实施例19可知，随着重均分子量上升，粘结剂的Dv50粒径、粘结力和循环性能总体呈上升趋势，极片平均辊压次数则会逐渐下降。从实施例17可知，当聚偏氟乙烯重均分子量达到500万时，仅0.6％的用量就能提供30.7N/m的粘结力，且电池循环性能良好，不过极片脆性稍高，但仍然优于市售的粘结剂(对比例1)。可见，本申请提供的粘结剂能切实降低正极活性材料中粘结剂的用量，并提供良好的极片韧性、粘结力以及电池循环性能。
比较实施例1和实施例21，虽然两者分子量接近，但实施例21由于反应温度偏高，聚合反应制备聚偏氟乙烯结晶度和多分散系数也偏高，影响极片的脆性，平均辊压次数明显下降，因此，聚合反应温度优选控制在45℃～60℃，从而可以使得结晶度也能控制在38％～48％这一合适的范围，并保持多分散系数能控制在更优选的2～2.3范围内。
比较实施例1～5、比较实施例6～10、比较实施例11～15、比较实施例16～18，比较实施例19～20可知，随着聚偏氟乙烯的用量上升，粘结力和循环性能有所上升，但极片会逐渐变脆，平均辊压次数下降，特别是实施例20中，粘结剂的用量大幅提升至1.8％后，对循环性能和粘结力的提升变得有限，但辊压次数会有明显的下降。
相较于实施例1，实施例22中，聚合反应时间较长，随着单体的持续消耗，压力的降低，已达不到聚合的条件，延长反应时间并不能持续进行聚合反应，因此，出于能耗和效率的考虑，将反应时间控制在10h以内更合适。
相较于实施例1，实施例23中，反应压力较大，单体进入反应液的压力较大，单体进入反应液较多，可导致大范围聚合反应的发生，导致生成的聚偏氟乙烯数量增多， 随着单体的减少，聚偏氟乙烯缺少单体的供给生成的分子量相对较小，对电池性能有一定的影响。
相较于实施例1，对比例2中，反应温度偏低，共聚的促动力较小，聚合反应不充分，制备的分子量偏小，造成同等添加量下粘结力的大幅下降，以及循环性能的明显下降。
相较于实施例1，对比例3中，聚合反应时间较短，聚合反应不能持续进行，制备的分子量偏小，同样会造成粘结力和循环性能的下降。
相较于实施例1，对比例4中，反应压力较小，单体进入反应液的压力较小，反应单体不能持续的补充，不利于聚合的持续进行，制得的产物分子量过低，无法满足对粘结力的要求，且电池循环性能也有所下降。
以上所述实施例的各技术特征可以进行任意的组合，为使描述简洁，未对上述实施例中的各个技术特征所有可能的组合都进行描述，然而，只要这些技术特征的组合不存在矛盾，都应当认为是本说明书记载的范围。
以上所述实施例仅表达了本申请的几种实施方式，其描述较为具体和详细，但并不能因此而理解为对专利范围的限制。应当指出的是，对于本领域的普通技术人员来说，在不脱离本申请构思的前提下，还可以做出若干变形和改进，这些都属于本申请的保护范围。因此，本申请的保护范围应以所附权利要求为准。

Claims (23)

  1. 一种粘结剂，包括重均分子量为150～500万的聚偏氟乙烯；可选地，所述聚偏氟乙烯的重均分子量为180～320万。
  2. 根据权利要求1所述的粘结剂，其特征在于，所述聚偏氟乙烯的多分散系数为1.5～2.5；可选地，所述聚偏氟乙烯的多分散系数为2～2.3。
  3. 根据权利要求1～2任一项所述的粘结剂，其特征在于，所述聚偏氟乙烯的数均分子量为60～300万；可选地，所述聚偏氟乙烯的数均分子量为100～200万。
  4. 根据权利要求1～3任一项所述的粘结剂，其特征在于，所述聚偏氟乙烯的Dv50粒径为50μm～150μm；可选地，所述聚偏氟乙烯的Dv50粒径为60μm～100μm。
  5. 根据权利要求1～4任一项所述的粘结剂，其特征在于，所述聚偏氟乙烯的结晶度为38％～48％；可选地，所述聚偏氟乙烯的结晶度为40％～45％。
  6. 根据权利要求1～5任一项所述的粘结剂，其特征在于，所述聚偏氟乙烯溶于N-甲基吡咯烷酮制得的粘结剂溶液的粘度为3500mPa·s～5000mPa·s，且所述粘结剂溶液中，所述粘结剂的质量百分含量为3％～5％。
  7. 根据权利要求1～6任一项所述的粘结剂的制备方法，包括以下步骤：
    将偏氟乙烯单体在非反应性气体氛围、6MPa～8MPa的反应压力、45℃～60℃的反应温度下进行聚合反应6h～10h；
    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。
  8. 根据权利要求7所述的制备方法，其特征在于，所述链转移剂包括环己烷、异丙醇、甲醇以及丙酮中的一种或多种。
  9. 根据权利要求7～8任一项所述的制备方法，其特征在于，所述链转移剂的用量为所述偏氟乙烯单体质量的1.5％～3％。
  10. 根据权利要求7～9任一项所述的制备方法，其特征在于，所述聚合反应包括以下步骤：
    向容器中加入溶剂和分散剂，对所述容器抽真空后充入非反应性气体；
    向所述容器中加入引发剂和pH调节剂，调节pH值至6.5～7，然后加入偏氟乙烯单体，使所述容器中的压力达到6MPa～8MPa；
    搅拌30min～60min后，升温至45℃～60℃，进行聚合反应。
  11. 根据权利要求10所述的制备方法，其特征在于，所述溶剂的用量为所述偏氟 乙烯单体质量的2～8倍。
  12. 根据权利要求10～11任一项所述的制备方法，其特征在于，所述分散剂包括纤维素醚和聚乙烯醇中的一种或多种；可选地，所述纤维素醚包括甲基纤维素醚和羧乙基纤维素醚中的一种或多种。
  13. 根据权利要求10～12任一项所述的制备方法，其特征在于，所述分散剂的用量为所述偏氟乙烯单体质量的0.1％～0.3％。
  14. 根据权利要求10～13任一项所述的制备方法，其特征在于，所述引发剂为有机过氧化物；可选地，所述有机过氧化物包括过氧化新戊酸叔戊酯、过氧化叔戊基新戊酸酯、2-乙基过氧化二碳酸酯、二异丙基过氧化二碳酸酯以及叔丁基过氧化新戊酸酯中的一种或多种。
  15. 根据权利要求10～14任一项所述的制备方法，其特征在于，所述引发剂的用量为所述偏氟乙烯单体质量的0.15％～1％。
  16. 根据权利要求10～15任一项所述的制备方法，其特征在于，所述pH调节剂包括碳酸钾、碳酸氢钾、碳酸钠、碳酸氢钠以及氨水中的一种或多种。
  17. 根据权利要求10～16任一项所述的制备方法，其特征在于，所述pH调节剂的用量为所述偏氟乙烯单体质量的0.05％～0.2％。
  18. 如权利要求1～6任一项所定义的聚偏氟乙烯在制备粘结剂中的应用。
  19. 一种二次电池，包括正极极片、隔离膜以及负极极片，所述隔离膜设置于所述正极极片和所述负极极片之间；
    所述正极极片包括正极集流体以及设置于所述正极集流体至少一个表面的正极活性材料层，所述正极活性材料层包括权利要求1～6任一项所述的粘结剂。
  20. 根据权利要求19所述的二次电池，其特征在于，所述正极活性材料层中，所述粘结剂的质量百分含量为0.6％～1.2％；可选地，述粘结剂的质量百分含量为0.6％～0.8％。
  21. 一种电池模块，包括权利要求19～20任一项所述的二次电池。
  22. 一种电池包，包括权利要求21所述的电池模块。
  23. 一种用电装置，包括权利要求19～20任一项所述的二次电池、权利要求21所述的电池模块以及权利要求22所述的电池包中的一种或多种。
PCT/CN2022/099187 2022-06-16 2022-06-16 粘结剂及其制备方法与应用 WO2023240543A1 (zh)

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CN103890998A (zh) * 2011-10-21 2014-06-25 帝人株式会社 非水系二次电池用隔膜及非水系二次电池
CN111052449A (zh) * 2017-09-13 2020-04-21 帝人株式会社 非水系二次电池用隔膜及非水系二次电池
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CN103890998A (zh) * 2011-10-21 2014-06-25 帝人株式会社 非水系二次电池用隔膜及非水系二次电池
CN103387633A (zh) * 2012-05-08 2013-11-13 辽宁富朗科技有限公司 一种超高分子量聚偏氟乙烯材料的制备方法
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