WO2024092813A1 - 含氟聚合物、导电浆料、正极极片、二次电池、用电装置 - Google Patents

含氟聚合物、导电浆料、正极极片、二次电池、用电装置 Download PDF

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WO2024092813A1
WO2024092813A1 PCT/CN2022/130117 CN2022130117W WO2024092813A1 WO 2024092813 A1 WO2024092813 A1 WO 2024092813A1 CN 2022130117 W CN2022130117 W CN 2022130117W WO 2024092813 A1 WO2024092813 A1 WO 2024092813A1
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formula
fluorine
monomer represented
positive electrode
conductive paste
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PCT/CN2022/130117
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English (en)
French (fr)
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冯伟
刘会会
欧阳楚英
孙成栋
张帅
左欢欢
张文帅
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宁德时代新能源科技股份有限公司
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Priority to PCT/CN2022/130117 priority Critical patent/WO2024092813A1/zh
Publication of WO2024092813A1 publication Critical patent/WO2024092813A1/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
    • C08F214/00—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
    • C08F214/18—Monomers containing fluorine
    • 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
    • C08F214/00—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
    • C08F214/18—Monomers containing fluorine
    • C08F214/22—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
    • C08F220/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and only one being terminated by only one carboxyl radical or a salt, anhydride ester, amide, imide or nitrile thereof
    • C08F220/02—Monocarboxylic acids having less than ten carbon atoms; Derivatives thereof
    • C08F220/04—Acids; Metal salts or ammonium salts thereof
    • C08F220/06—Acrylic acid; Methacrylic acid; Metal salts or ammonium salts thereof
    • 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 invention relates to the technical field of secondary batteries, and in particular to a fluorine-containing polymer, a conductive slurry, a positive electrode sheet, a secondary battery, and an electrical device.
  • the active materials of secondary batteries have poor electrical conductivity, which can easily lead to problems such as large internal resistance, poor rate performance and cycle performance during battery manufacturing. Therefore, it is necessary to add conductive agents to improve the conductivity of the active materials and thus improve the overall performance of the battery.
  • the existing conductive agents generally have a large specific surface area, and are prone to agglomeration under the action of van der Waals forces, which affects their conductivity. At the same time, they can easily lead to uneven distribution of the positive electrode sheets, affecting the performance of the active materials. Therefore, it is urgent to solve this technical problem.
  • the present application is made in view of the above-mentioned problems, and its purpose is to provide a fluorine-containing polymer and a conductive paste containing the fluorine-containing polymer to improve the dispersibility of the conductive agent and thus optimize the performance of the battery.
  • the first aspect of the present application provides a fluorine-containing polymer, comprising a structural unit derived from a monomer represented by formula I and a structural unit derived from a monomer represented by formula II,
  • R 1 , R 2 , and R 3 are each independently selected from one or more of hydrogen, fluorine, chlorine, and fluorine-substituted C 1-3 alkyl;
  • R 4 and R 5 are each independently selected from one or more of hydrogen, substituted or unsubstituted C 1-5 alkyl;
  • R 6 is selected from one or more of aromatic-substituted C 1-5 alkyl, and substituted or substituted aromatic.
  • the fluorine-containing polymer provided in the present application can reduce the viscosity of the conductive slurry, improve the filterability of the conductive slurry, and the slurry will not gel after standing for 60 days, thereby improving the anti-gelling and storage properties of the conductive slurry, and improving the processability and stability of the conductive slurry, so that the conductive slurry can meet the production requirements of the conductive slurry without the need for additional dispersant, thereby further reducing the diaphragm resistance of the electrode and the DC impedance of the battery.
  • R 1 in Formula I is fluorine
  • R 2 and R 3 are each independently selected from one or more of hydrogen, fluorine, chlorine, and trifluoromethyl.
  • the molar content of the structural unit derived from the monomer represented by formula I is 50% to 70%, based on the total molar number of all structural units in the fluorine-containing polymer.
  • the viscosity of the conductive paste and the adhesion of the electrode sheet can be taken into account, thereby comprehensively improving the processing performance and use performance of the conductive paste.
  • the molar content of the structural unit derived from the monomer represented by formula II is 30% to 50%, based on the total molar number of all structural units in the fluorine-containing polymer.
  • the viscosity of the conductive paste and the adhesion of the electrode sheet can be taken into account, thereby comprehensively improving the processing performance and use performance of the conductive paste.
  • the weight average molecular weight of the fluorinated polymer is 100,000 to 140,000.
  • the viscosity of the conductive paste and the adhesion of the electrode can be taken into account, thereby comprehensively improving the processing performance and use performance of the conductive paste.
  • the monomer represented by formula I is selected from one or more of vinyl fluoride, vinylidene fluoride, tetrafluoroethylene, chlorotrifluoroethylene, and hexafluoropropylene.
  • the monomer represented by formula II is selected from one or more of 2-benzyl acrylic acid, 2-(4-isobutylbenzyl) acrylic acid, 2-methylene-4-phenylbutyric acid, and 2-(1-phenylethyl) acrylic acid.
  • the second aspect of the present application provides a method for preparing a fluorine-containing polymer, comprising the following steps:
  • At least one monomer represented by formula I and at least one monomer represented by formula II are polymerized,
  • R 1 , R 2 , and R 3 are each independently selected from one or more of hydrogen, fluorine, chlorine, and fluorine-substituted C 1-3 alkyl;
  • R 4 and R 5 are each independently selected from one or more of hydrogen, substituted or unsubstituted C 1-5 alkyl;
  • R 6 is selected from one or more of aromatic-substituted C 1-5 alkyl, and substituted or substituted aromatic.
  • the fluorinated polymer prepared by this method can reduce the viscosity of the conductive slurry, improve the filterability of the conductive slurry, prevent the slurry from gelling after standing for 60 days, improve the anti-gelling and storage properties of the conductive slurry, significantly broaden the process window of the conductive slurry, and improve the processability of the conductive slurry, so that the conductive slurry can meet the production needs of the conductive slurry without adding a dispersant, thereby further reducing the diaphragm resistance of the electrode and the DC impedance of the battery.
  • R 1 in Formula I is fluorine
  • R 2 and R 3 are each independently selected from one or more of hydrogen, fluorine, chlorine, and trifluoromethyl.
  • the molar content of the monomer represented by formula I is 50% to 70%, based on the total molar number of the monomer represented by formula I and the monomer represented by formula II.
  • the molar content of the monomer represented by formula II is 30% to 50%, based on the total molar number of the monomer represented by formula I and the monomer represented by formula II.
  • the polymerization reaction includes a first stage polymerization and a second stage polymerization
  • First stage polymerization adding an initiator, an emulsifier, at least one monomer represented by formula I and an aqueous medium into a reaction vessel to carry out first stage polymerization, and continuously feeding the monomer represented by formula I in the first stage polymerization;
  • Second stage polymerization After a period of reaction, at least one monomer represented by formula II is added into the reaction vessel for second stage polymerization, and the monomer represented by formula I is continuously introduced into the second stage polymerization.
  • the method provided in the present application first continuously feeds the monomer shown in formula I to form a fluorine-containing segment, so that the fluorine-containing polymer has high thermal stability; then the monomer shown in formula II is introduced to reduce the contact between the fluorine-containing segment and the external environment, effectively alleviating the gel phenomenon caused by the fluorine element.
  • the fluorine-containing polymer prepared by this method can effectively improve the stability of the conductive slurry, improve the anti-sedimentation property of the slurry, improve the adhesion of the pole piece, reduce the diaphragm resistance of the pole piece and the DC internal resistance of the battery, and improve the dynamic performance of the battery.
  • the monomer shown in formula II when the monomer shown in formula II is introduced into the reaction vessel for the second stage of polymerization reaction, the monomer shown in formula I is continuously introduced into the reaction vessel, which helps to improve the compatibility of the segment generated by the first stage of polymerization reaction with the segment generated by the second stage of polymerization reaction, and improve the stability of the fluorine-containing polymer.
  • the mass of the monomer of formula I introduced in the first stage polymerization is 80% to 85% of the total mass of the monomer of formula I supplied in the polymerization reaction, and the mass of the monomer of formula I introduced in the second stage polymerization is 15% to 20% of the total mass of the monomer of formula I supplied in the polymerization reaction.
  • the mass percentage of the initiator is 0.5% to 1.4%, based on the total mass of the monomer represented by formula I and the monomer represented by formula II.
  • the mass percentage of the emulsifier is 0.1% to 0.4%, based on the total mass of the monomer represented by formula I and the monomer represented by formula II.
  • the mass percentage of the aqueous medium provided in the first stage polymerization is 400% to 600%, based on the total mass of the monomer represented by formula I and the monomer represented by formula II.
  • reaction pressure of the first stage polymerization and the second stage polymerization are both 6.0 MPa to 9.0 MPa, and the reaction temperature is 80° C. to 120° C.
  • the emulsifier is an alkali metal perfluorooctanoate.
  • the initiator is one or both of N,N-dimethylbenzylamine and N-methylamphetamine.
  • the third aspect of the present application provides use of the fluorine-containing polymer of the first aspect in a secondary battery.
  • a conductive paste comprising a conductive agent, a solvent and the fluorine-containing polymer described in the first aspect.
  • the conductive slurry provided in the present application can improve the dispersibility of the conductive agent in the positive electrode slurry, enhance the conductive effect of the conductive agent in the electrode sheet, and thereby effectively reduce the conductive agent content in the electrode sheet, which is beneficial to further increase the loading amount of the positive electrode active material in the electrode sheet and improve the battery power performance.
  • the mass fraction of the conductive agent is 10.0% to 15.0%, based on the total mass of the conductive paste.
  • the mass fraction of the conductive agent is controlled within a suitable range, based on the total mass of the conductive paste.
  • a paste with a suitable viscosity can make the electrode sheet have good adhesion, and comprehensively improve the processing performance and use performance of the paste.
  • the mass fraction of the fluorine-containing polymer is 0.5% to 2.5%, based on the total mass of the conductive paste.
  • the mass fraction of the fluorine-containing polymer is controlled within a suitable range, based on the total mass of the conductive paste.
  • the paste has a suitable viscosity, so that the electrode has good adhesion, and the processing performance and use performance of the paste are comprehensively improved.
  • the solid content of the conductive paste is 10.5% to 17.5%, and the viscosity of the conductive paste is 300 mPa ⁇ s to 900 mPa ⁇ s.
  • the solid content is 10.5% to 17.5%, and the viscosity is 300mPa ⁇ s to 900mPa ⁇ s. It can be directly mixed and stirred with active materials and binders to prepare positive electrode slurry without adding additional additives, which is beneficial to improving production efficiency and reducing production costs.
  • the fifth aspect of the present application provides a positive electrode plate, including a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes a positive electrode active material, a conductive agent and a binder, and the conductive agent is a deposit of the conductive slurry of the fourth aspect.
  • the conductive agent in the positive electrode plates disclosed in the present application exists in the form of conductive slurry deposits in the positive electrode plates, so that the positive electrode plates can have low membrane resistance when a low amount of conductive agent is added, which provides the possibility of further increasing the loading amount of positive electrode active materials in the plates.
  • the film resistance of the positive electrode sheet is lower than 0.2 ⁇ .
  • the bonding force per unit length between the positive electrode film layer and the positive electrode current collector is not less than 14 N/m.
  • the sixth aspect of the present application provides a secondary battery, comprising a separator, a negative electrode plate, an electrolyte and the positive electrode plate described in the fifth aspect.
  • the secondary battery comprises at least one of a lithium ion battery, a sodium ion battery, a magnesium ion battery and a potassium ion battery.
  • a seventh aspect of the present application provides a battery module, comprising the secondary battery of the sixth aspect of the present application.
  • An eighth aspect of the present application provides a battery pack, comprising the secondary battery of the sixth aspect of the present application or the battery module of the seventh aspect of the present application.
  • the ninth aspect of the present application provides an electrical device comprising at least one selected from the secondary battery of the sixth aspect of the present application, the battery module of the seventh aspect of the present application, and the battery pack of the eighth aspect of the present application.
  • FIG1 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG2 is an exploded view of the secondary battery according to one embodiment of the present application shown in FIG1 ;
  • FIG3 is a schematic diagram of a battery module according to an embodiment of the present application.
  • FIG4 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG5 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG4 ;
  • FIG. 6 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.
  • range disclosed in the present application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range.
  • the range defined in this way can be inclusive or exclusive of end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60-120 and 80-110 is listed for a specific parameter, it is understood that the range of 60-110 and 80-120 is also expected.
  • the numerical range "a-b" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers.
  • the numerical range "0-5" represents that all real numbers between "0-5" have been fully listed herein, and "0-5" is just the abbreviation of these numerical combinations.
  • a parameter is expressed as an integer ⁇ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • the method may further include step (c), which means that step (c) may be added to the method in any order.
  • the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.
  • the “include” and “comprising” mentioned in this application represent open-ended or closed-ended expressions.
  • the “include” and “comprising” may represent that other components not listed may also be included or only the listed components may be included or only the listed components may be included.
  • the term "or” is inclusive.
  • the phrase “A or B” means “A, B, or both A and B”. More specifically, any of the following conditions satisfies the condition "A or B”: 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 active materials of secondary batteries have poor electrical conductivity, and are prone to problems such as large internal resistance, poor rate performance and cycle performance during the battery manufacturing process. Therefore, it is necessary to add a conductive agent to improve the conductivity of the active materials, thereby improving the overall performance of the battery.
  • the existing conductive agents generally have a large specific surface area, and are very easy to agglomerate under the action of van der Waals forces, affecting their conductive effect. The applicant found that preparing the conductive agent into a conductive slurry first, and then mixing it with the active material and/or binder to prepare a slurry helps to slow down the agglomeration of the conductive agent during the slurry mixing process.
  • a dispersant needs to be added to the conductive slurry to improve the dispersibility and stability of the conductive slurry.
  • the addition of a dispersant to the conductive slurry will affect the electrochemical performance, cycle performance and batch stability of the battery, and it is also easy for the dispersant to be incompatible with the positive electrode slurry system.
  • the present application has developed a fluorine-containing polymer, which makes the conductive slurry have a suitable viscosity and excellent filterability, improves the anti-gel and storage properties of the conductive slurry, significantly broadens the process window of the conductive slurry, and improves the processability of the conductive slurry.
  • a fluorine-containing polymer comprising a structural unit derived from a monomer shown in formula I and a structural unit derived from a monomer shown in formula II,
  • R 1 , R 2 , and R 3 are each independently selected from one or more of hydrogen, fluorine, chlorine, and fluorine-substituted C 1-3 alkyl;
  • R 4 and R 5 are each independently selected from one or more of hydrogen, substituted or unsubstituted C 1-5 alkyl;
  • R 6 is selected from one or more of aromatic-substituted C 1-5 alkyl, and substituted or substituted aromatic.
  • fluorine-containing polymer refers to a polymer containing fluorine in its structural units.
  • polymer includes, on the one hand, a collection of macromolecules that are chemically uniform but differ in degree of polymerization, molar mass and chain length, prepared by polymerization.
  • the term also includes, on the other hand, derivatives of such a collection of macromolecules formed by polymerization, i.e. products that can be obtained by reaction of functional groups in the above-mentioned macromolecules, such as addition or substitution, and can be chemically uniform or chemically inhomogeneous.
  • C 1-3 alkyl refers to a straight or branched hydrocarbon chain radical consisting solely of carbon and hydrogen atoms, with no unsaturation present in the radical, having from one to three carbon atoms, and attached to the rest of the molecule by a single bond.
  • fluorine-substituted C 1-3 alkyl group refers to a C 1-3 alkyl group in which at least one hydrogen atom is substituted by a fluorine atom.
  • C 1-5 alkyl refers to a straight or branched hydrocarbon chain radical consisting solely of carbon and hydrogen atoms, with no unsaturation present in the radical, having from one to five carbon atoms, and attached to the rest of the molecule by a single bond.
  • substituted means that at least one hydrogen atom of the compound or chemical moiety is replaced by another chemical moiety with a substituent, wherein the substituent is independently selected from: hydroxyl, thiol, amino, cyano, nitro, aldehyde, halogen atom, alkenyl, alkynyl, aryl, heteroaryl, C 1-6 alkyl, C 1-6 alkoxy.
  • aryl refers to an aromatic ring system in which at least one ring is aromatic, including, but not limited to, phenyl, biphenyl, indanyl, 1-naphthyl, 2-naphthyl, and tetrahydronaphthyl.
  • process window refers to the process range that can ensure product quality, including but not limited to temperature range, pressure range, storage time length, etc. It can be understood that the wider the process window, the lower the requirement for process accuracy.
  • R 6 is a C 1-5 alkyl substituted with an aromatic group, wherein the aromatic group is a substituted or unsubstituted aromatic group.
  • the monomer represented by formula I is selected from one or more of vinyl fluoride, vinylidene fluoride, tetrafluoroethylene, chlorotrifluoroethylene, and hexafluoropropylene.
  • the monomer represented by formula II is selected from one or more of 2-benzyl acrylic acid, 2-(4-isobutylbenzyl) acrylic acid, 2-methylene-4-phenylbutyric acid, and 2-(1-phenylethyl) acrylic acid.
  • the polymer comprises one or more structural units derived from the monomers shown in formula I. In some embodiments, the polymer comprises one or more structural units derived from the monomers shown in formula II. In some embodiments, the polymer includes but is not limited to vinylidene fluoride-2-benzyl acrylic acid copolymer, vinylidene fluoride-2-(4-isobutylbenzyl) acrylic acid copolymer, vinylidene fluoride-2-methylene-4-phenylbutyric acid copolymer, vinylidene fluoride-2-(1-phenylethyl) acrylic acid copolymer, fluorinated vinyl-2-benzyl acrylic acid copolymer, tetrafluoroethylene-2-benzyl acrylic acid copolymer, tetrafluoroethylene-2-(4-isobutylbenzyl) acrylic acid copolymer, vinylidene fluoride-trifluorochloroethylene-2-benzyl acrylic acid copolymer.
  • the fluorine element in the structural unit derived from the monomer shown in formula I can form a hydrogen bond with the hydroxyl group or/and the carboxyl group on the surface of the current collector.
  • the carboxyl group contained in the structural unit derived from the monomer shown in formula II can form a hydrogen bond with the hydroxyl group or/and the carboxyl group on the surface of the current collector.
  • the two work together to make the positive electrode sheet have better adhesion.
  • the structural unit derived from the monomer shown in formula II can effectively reduce the fluorine content of the fluorine-containing polymer and improve the slurry gel phenomenon caused by the fluorine element.
  • the structural unit derived from the monomer shown in formula II can further increase the steric hindrance of the fluorine-containing polymer, reduce the aggregation of the fluorine-containing unit, play a role in reducing the viscosity of the slurry, alleviate the gel of the slurry, and effectively improve the filterability of the slurry.
  • the aromatic group contained in the structural unit derived from the monomer shown in formula II has similar elements and structures to the conductive agent, and can improve the stability of the conductive slurry through interaction with the conductive agent, and improve the anti-sedimentation property of the conductive slurry.
  • the fluorine-containing polymer provided in the present application can reduce the viscosity of the conductive slurry, improve the filterability of the conductive slurry, make the slurry less likely to gel during storage, improve the anti-gelling and storage properties of the conductive slurry, significantly broaden the process window of the conductive slurry, and improve the processability of the conductive slurry, so that the conductive slurry can meet the production requirements of the conductive slurry without adding a dispersant, thereby further reducing the diaphragm resistance of the electrode and the DC impedance of the battery.
  • R 1 in Formula I is fluorine
  • R 2 and R 3 are each independently selected from one or more of hydrogen, fluorine, chlorine, and trifluoromethyl.
  • the molar content of the structural unit derived from the monomer shown in formula I is 50% to 70%, based on the total molar number of all structural units in the fluoropolymer. In some embodiments, the molar content of the structural unit derived from the monomer shown in formula I can be any one of 50%, 60%, and 70%, based on the total molar number of all structural units in the fluoropolymer.
  • the molar content of the structural unit derived from the monomer represented by Formula I is controlled within a suitable range so that the conductive paste has a suitable viscosity, which can take into account both the viscosity of the conductive paste and the adhesion of the electrode sheet, thereby comprehensively improving the processing performance and use performance of the conductive paste.
  • the molar content of the structural unit derived from the monomer shown in formula II is 30% to 50%, based on the total molar number of all structural units in the fluoropolymer. In some embodiments, the molar content of the structural unit derived from the monomer shown in formula II can be any one of 30%, 40%, and 50%, based on the total molar number of all structural units in the fluoropolymer.
  • the molar content of the structural unit derived from the monomer represented by Formula II is controlled within a suitable range so that the conductive paste has a suitable viscosity, which can take into account both the viscosity of the conductive paste and the adhesion of the electrode sheet, thereby comprehensively improving the processing performance and use performance of the conductive paste.
  • the weight average molecular weight of the fluorine-containing polymer is 100,000 to 140,000. In some embodiments, the weight average molecular weight of the fluorine-containing polymer can be selected from any one of 100,000, 110,000, 120,000, 130,000, and 140,000.
  • weight average molecular weight refers to the sum of the products of the weight fractions of molecules with different molecular weights in a polymer and their corresponding molecular weights.
  • the weight average molecular weight of the polymer can be tested by methods known in the art, such as gel chromatography, such as Waters 2695 Isocratic HPLC gel chromatograph (differential refractive index detector 2141).
  • the test method is to use a polystyrene solution sample with a mass fraction of 3.0% as a reference and select a matching chromatographic column (oily: Styragel HT5DMF7.8 ⁇ 300mm+Styragel HT4).
  • NMP N-methylpyrrolidone
  • Controlling the weight average molecular weight of the fluorinated polymer within a suitable range allows the slurry to have a suitable viscosity, which is beneficial to the subsequent preparation of the positive electrode slurry.
  • the fluorinated polymer with a suitable weight average molecular weight is conducive to the formation of a three-dimensional network bonding structure, which makes the electrode sheet have good bonding force. It can take into account the viscosity of the conductive slurry and the bonding properties of the electrode sheet, and comprehensively improve the processing performance and use performance of the conductive slurry.
  • a method for preparing a fluorine-containing polymer comprising the following steps:
  • At least one monomer represented by formula I and at least one monomer represented by formula II are polymerized,
  • R 1 , R 2 , and R 3 are each independently selected from one or more of hydrogen, fluorine, chlorine, and fluorine-substituted C 1-3 alkyl;
  • R 4 and R 5 are each independently selected from one or more of hydrogen, substituted or unsubstituted C 1-5 alkyl;
  • R 6 is selected from one or more of aromatic-substituted C 1-5 alkyl, and substituted or substituted aromatic.
  • the fluorinated polymer prepared by this method can reduce the viscosity of the conductive paste, improve the filterability of the conductive paste, make the paste less likely to gel during storage, improve the anti-gelling and storage properties of the conductive paste, significantly broaden the process window of the conductive paste, and improve the processability of the conductive paste, so that the conductive paste can meet the production needs of the conductive paste without adding a dispersant.
  • R 1 is fluorine
  • R 2 and R 3 are each independently selected from one or more of hydrogen, fluorine, chlorine, and trifluoromethyl.
  • the molar content of the monomer represented by formula I is 50% to 70%, based on the total molar number of the monomer represented by formula I and the monomer represented by formula II.
  • the molar content of the monomer represented by formula II is 30% to 50%, based on the total molar number of the monomer represented by formula I and the monomer represented by formula II.
  • the polymerization reaction includes a first stage polymerization and a second stage polymerization
  • First stage polymerization adding an initiator, an emulsifier, at least one monomer represented by formula I and an aqueous medium into a reaction vessel to carry out first stage polymerization, and continuously feeding the monomer represented by formula I in the first stage polymerization;
  • Second stage polymerization After a period of reaction, at least one monomer represented by formula II is added into the reaction vessel for second stage polymerization, and the monomer represented by formula I is continuously introduced into the second stage polymerization.
  • the method provided in the present application forms a fluorine-containing segment by first continuously feeding the monomer shown in formula I, so that the fluorine-containing polymer has high thermal stability; and then the monomer shown in formula II is introduced to reduce the contact between the fluorine-containing segment and the external environment, effectively alleviating the gel phenomenon caused by the fluorine element.
  • the fluorine-containing polymer prepared by this method can effectively improve the stability of the conductive slurry, improve the anti-sedimentation property of the slurry, improve the adhesion of the pole piece, reduce the diaphragm resistance of the pole piece and the DC internal resistance of the battery, and improve the dynamic performance of the battery.
  • the monomer shown in formula II when the monomer shown in formula II is fed into the reaction vessel for the second stage of polymerization, the monomer shown in formula I is continuously fed into the reaction vessel, which helps to improve the compatibility of the segment generated by the first stage of polymerization and the segment generated by the second stage of polymerization, and improve the stability of the fluorine-containing polymer.
  • the mass of the monomer of formula I introduced in the first stage polymerization is 80% to 85% of the total mass of the monomer of formula I supplied in the polymerization reaction, and the mass of the monomer of formula I introduced in the second stage polymerization reaction is 15% to 20% of the total mass of the monomer of formula I supplied in the polymerization reaction.
  • the mass percentage of the initiator is 0.5% to 1.4%, based on the total mass of the monomer represented by formula I and the monomer represented by formula II.
  • the mass percentage of the emulsifier is 0.1% to 0.4%, based on the total mass of the monomer represented by formula I and the monomer represented by formula II.
  • the mass percentage of the aqueous medium provided in the first stage polymerization is 400% to 600%, based on the total mass of the monomer represented by formula I and the monomer represented by formula II.
  • reaction pressure of the first stage polymerization and the second stage polymerization are both 6.0 MPa to 9.0 MPa, and the reaction temperature is 80° C. to 120° C.
  • the emulsifier is an alkali metal perfluorooctanoate.
  • the initiator is one or both of N,N-dimethylbenzylamine and N-methylamphetamine.
  • the secondary battery includes at least one of a lithium ion battery, a sodium ion battery, a magnesium ion battery, and a potassium ion battery.
  • a conductive paste comprising a conductive agent, a solvent, and a fluorine-containing polymer in any embodiment.
  • the solvent is an aqueous solvent, such as deionized water.
  • the solvent is an oily solvent
  • examples of the oily solvent include, but are not limited to, dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, acetone, dimethyl carbonate, ethyl cellulose, and polycarbonate.
  • the conductive slurry provided by the present application can improve the dispersibility of the conductive agent in the positive electrode slurry, improve the conductive effect of the conductive agent in the electrode sheet, and thus effectively reduce the content of the conductive agent in the electrode sheet, which is conducive to further increasing the load of the electrode sheet and improving the battery power performance.
  • the fluorinated polymer in the conductive slurry can play the role of a binder and a dispersant at the same time, and there is no need to add other dispersants to the conductive slurry, which is conducive to further increasing the load of active substances in the electrode sheet and the bonding force of the electrode sheet.
  • the mass fraction of the conductive agent is 10.0% to 15.0%, based on the total mass of the conductive paste. In some embodiments, the mass fraction of the conductive agent can be any one of 10%, 11%, 12%, 13%, 14%, and 15%.
  • the mass fraction of the conductive agent is controlled within a suitable range, based on the total mass of the conductive paste.
  • the paste has a suitable viscosity, and the electrode has good adhesion, which comprehensively improves the processing performance and use performance of the paste.
  • the mass fraction of the fluorine-containing polymer is 0.5% to 2.5%, based on the total mass of the conductive paste. In some embodiments, the mass fraction of the fluorine-containing polymer can be any one of 0.5%, 1.0%, 1.5%, 2.0%, and 2.5%.
  • the mass fraction of the fluorinated polymer is controlled within a suitable range, based on the total mass of the conductive slurry.
  • the slurry has a suitable viscosity, which is beneficial to the subsequent preparation of the positive electrode slurry, while making the electrode sheet have good adhesion, and comprehensively improving the processing performance and use performance of the slurry.
  • the solid content of the conductive paste is 10.5% to 17.5%, and the viscosity of the conductive paste is 300 mPa ⁇ s to 900 mPa ⁇ s.
  • the viscosity of the conductive paste may be any one of 400mPa ⁇ s to 900mPa ⁇ s, 400mPa ⁇ s to 800mPa ⁇ s, 400mPa ⁇ s to 750mPa ⁇ s, 400mPa ⁇ s to 600mPa ⁇ s, 450mPa ⁇ s to 800mPa ⁇ s, 450mPa ⁇ s to 750mPa ⁇ s, 450mPa ⁇ s to 650mPa ⁇ s, and 500mPa ⁇ s to 750mPa ⁇ s.
  • the conductive paste with a solid content of 10.5% to 17.5% and a viscosity of 300 mPa ⁇ s to 900 mPa ⁇ s can be directly mixed and stirred with the active material and the binder to prepare the positive electrode paste. There is no need to add additional additives to the conductive paste, which is beneficial to improving production efficiency and reducing production costs.
  • a positive electrode plate comprising a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, wherein the positive electrode film layer comprises a positive electrode active material, a conductive agent and a binder, wherein the conductive agent is a deposit of a conductive slurry in any embodiment.
  • binder refers to a chemical compound, polymer or mixture that forms a colloidal solution or colloidal dispersion in a dispersion medium.
  • the conductive agent in the positive electrode plates disclosed in the present application exists in the form of conductive slurry deposits in the positive electrode plates, so that the positive electrode plates can have low membrane resistance when a low amount of conductive agent is added, which provides the possibility of further increasing the loading amount of positive electrode active materials in the plates.
  • the film resistance of the positive electrode sheet is lower than 0.2 ⁇ .
  • the bonding force per unit length between the positive electrode film layer and the positive electrode current collector is not less than 14 N/m.
  • the positive electrode current collector has two surfaces opposite to each other in its 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 may be used.
  • the composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base.
  • the composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the positive electrode active material may be a positive electrode active material for a battery known in the art.
  • the positive electrode 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 for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more.
  • lithium transition metal oxides may include, but are not limited to , lithium cobalt oxide (such as LiCoO2 ), lithium nickel oxide (such as LiNiO2 ), lithium manganese oxide (such as LiMnO2 , LiMn2O4 ), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi1 / 3Co1 / 3Mn1 / 3O2 (also referred to as NCM333 ), LiNi0.5Co0.2Mn0.3O2 (also referred to as NCM523 ) , LiNi0.5Co0.25Mn0.25O2 (also referred to as NCM211 ) , LiNi0.6Co0.2Mn0.2O2 (also referred to as NCM622 ), LiNi0.8Co0.1Mn0.1O2 (also referred to as NCM811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05
  • lithium-containing phosphates with an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO 4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon.
  • lithium iron phosphate such as LiFePO 4 (also referred to as LFP)
  • LiMnPO 4 lithium manganese phosphate
  • LiMnPO 4 lithium manganese phosphate
  • LiMnPO 4 lithium manganese phosphate and carbon
  • the positive electrode film layer may also optionally include a binder.
  • the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • PTFE polytetrafluoroethylene
  • vinylidene fluoride-tetrafluoroethylene-propylene terpolymer vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer
  • the positive electrode film layer may further include a conductive agent, which may include, for example, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • a conductive agent which may include, for example, 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 in the following manner: the above-mentioned components for preparing the positive electrode sheet, such as the fluorine-containing polymer, the conductive agent, and the solvent are first stirred to prepare a conductive slurry, and the positive electrode active material, the binder and any other components are dispersed in the conductive slurry to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.
  • the above-mentioned components for preparing the positive electrode sheet such as the fluorine-containing polymer, the conductive agent, and the solvent are first stirred to prepare a conductive slurry, and the positive electrode active material, the binder and any other components are dispersed in the conductive slurry to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.
  • 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, wherein the negative electrode film layer includes a negative electrode active material.
  • the negative electrode current collector has two surfaces opposite to each other in its 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 metal foil copper foil may 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 substrate.
  • the composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • PP polypropylene
  • PET polyethylene terephthalate
  • PBT polybutylene terephthalate
  • PS polystyrene
  • PE polyethylene
  • the negative electrode active material may be a negative electrode active material for a battery known in the art.
  • the negative electrode 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, etc.
  • 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 negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.
  • the negative electrode film layer may further include a binder.
  • the binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • a conductive agent which 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 may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).
  • a thickener eg, sodium carboxymethyl cellulose (CMC-Na)
  • the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder 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 collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.
  • a solvent such as deionized water
  • the electrolyte plays the role of conducting ions between the positive electrode and the negative electrode.
  • the present application has no specific restrictions on the type of electrolyte, which can be selected according to needs.
  • the electrolyte can be liquid, gel or all-solid.
  • the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.
  • the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.
  • the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.
  • the electrolyte may further include additives, such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.
  • additives such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.
  • the secondary battery further includes a separator.
  • the present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.
  • 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 film or a multi-layer composite film, without particular limitation.
  • the materials of each layer can be the same or different, without particular limitation.
  • the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.
  • the secondary battery may include an outer package, which may be used to encapsulate the electrode assembly and the 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 package, such as a bag-type soft package.
  • the material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.
  • FIG1 is a secondary battery 5 of a square structure as an example.
  • the outer package may include a shell 51 and a cover plate 53.
  • the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity.
  • the shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity.
  • the positive electrode sheet, the negative electrode sheet and the isolation film can form an electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is encapsulated in the receiving cavity.
  • the electrolyte is infiltrated in 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 may be assembled into a battery module.
  • the number of secondary batteries contained in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.
  • FIG3 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. Of course, they may also be arranged in any other manner. Further, the plurality of secondary batteries 5 may be fixed by fasteners.
  • the battery module 4 may further include a housing having a housing space, and the plurality of secondary batteries 5 are housed in the housing space.
  • the battery modules described above may also be assembled into a battery pack.
  • the battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.
  • FIG4 and FIG5 are battery packs 1 as an example.
  • 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 body 2 and a lower box body 3, and the upper box body 2 can be covered on the lower box body 3 to form a closed space for accommodating the battery modules 4.
  • the plurality of 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 in the present application.
  • the secondary battery, battery module, or battery pack can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device.
  • the electrical 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, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto.
  • a secondary battery, a battery module or a battery pack may be selected according to its usage requirements.
  • Fig. 6 is an example of an electric device.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.
  • a battery pack or a battery module may be used.
  • a device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be thin and light, and a secondary battery may be used as a power source.
  • the reactor was evacuated and filled with nitrogen, and the operation was repeated until the oxygen concentration in the reactor was less than 100 ppm;
  • the temperature in the kettle was raised to 100°C to start the reaction, and vinylidene fluoride monomer was continuously introduced during the reaction to maintain the reaction pressure in the kettle constant;
  • the reaction product is condensed, washed, separated, dried and crushed to obtain a vinylidene fluoride-2-benzyl acrylic acid copolymer.
  • the active material artificial graphite, the conductive agent carbon black, the binder styrene-butadiene rubber (SBR), and the thickener sodium hydroxymethyl cellulose (CMC) are dissolved in the solvent deionized water in a weight ratio of 96.2:0.8:0.8:1.2, and the negative electrode slurry is prepared after being evenly mixed; the negative electrode slurry is evenly coated on the negative electrode collector copper foil once or multiple times, and the negative electrode sheet is obtained after drying, cold pressing, and slitting.
  • Polypropylene film is used as the isolation film.
  • the positive electrode sheet, the separator, and the negative electrode sheet of Example 1 are stacked in order, so that the separator is between the positive and negative electrode sheets to play an isolating role, and then wound to obtain a bare cell, and the bare cell is welded with a pole ear, and the bare cell is placed in an aluminum shell, and baked at 80°C to remove water, and then the electrolyte is injected and sealed to obtain an uncharged battery.
  • the uncharged battery is then subjected to the processes of static, hot and cold pressing, formation, shaping, and capacity testing in sequence to obtain the lithium-ion battery product of Example 1.
  • Example 2 the molar ratio of each monomer in the fluorine-containing polymer was adjusted, and other parameters were kept consistent with those in Example 1. The specific parameters are shown in Tables 1 and 2.
  • Example 6 the polymerization temperature for preparing the fluorinated polymer and the mass of the initiator N,N-dimethylbenzylamine were adjusted so that the fluorinated polymer had different weight average molecular weights. Other parameters were kept consistent with those in Example 1. Specific parameters are shown in Tables 1 and 2.
  • Example 6 the polymerization reaction temperature was adjusted to 95° C., and the mass of N,N-dimethylbenzylamine was adjusted to 51.3 g;
  • Example 7 the mass of N,N-dimethylbenzylamine was adjusted to 56.7 g;
  • Example 8 the mass of N,N-dimethylbenzylamine was adjusted to 59.4 g;
  • Example 9 the polymerization reaction temperature was adjusted to 95° C., and the mass of N,N-dimethylbenzylamine was adjusted to 48.6 g.
  • Example 10 the mass fraction of the fluorine-containing polymer in the conductive paste was adjusted, and other parameters were kept consistent with those in Example 1. The specific parameters are shown in Tables 1 and 2.
  • Example 14 to 17 the mass fraction of the conductive agent in the conductive primer slurry was adjusted, and other parameters remained the same as in Example 1. The specific parameters are shown in Tables 1 and 2.
  • Example 18 2-benzyl acrylic acid monomer is replaced by 2-(4-isobutylbenzyl) acrylic acid monomer, and other parameters are the same as in Example 1. For specific parameters, see Tables 1 and 2.
  • the fluorine-containing polymer is a vinylidene fluoride-2-benzyl acrylic acid copolymer prepared by a conventional method, and its synthesis method is:
  • the reactor was evacuated and filled with nitrogen, and the operation was repeated until the oxygen concentration in the reactor was less than 100 ppm;
  • the temperature in the kettle was raised to 100°C to start the reaction, and vinylidene fluoride monomer was continuously introduced during the reaction to maintain the reaction pressure in the kettle constant;
  • Comparative Example 1 a vinylidene fluoride polymer was used as the fluorine-containing polymer.
  • Comparative Example 3 is substantially the same as Example 1, except that the conductive paste containing the fluorine-containing polymer is replaced with a conductive paste containing a dispersant.
  • the specific preparation method is as follows:
  • Comparative Example 4 is basically the same as Example 1, except that conductive carbon black is used instead of conductive paste to directly prepare the positive electrode plate.
  • Comparative Example 5 is substantially the same as Comparative Example 4, except that the mass content of the conductive carbon black is adjusted to 2.0%, based on the total mass of the positive electrode film layer.
  • a Waters 2695 Isocratic HPLC gel chromatograph (differential refractive index detector 2141) was used.
  • a polystyrene solution sample with a mass fraction of 3.0% was used as a reference, and a matching chromatographic column (oily: Styragel HT5 DMF 7.8 ⁇ 300 mm + Styragel HT4) was selected.
  • a 3.0% fluoropolymer solution was prepared with purified N-methylpyrrolidone (NMP) solvent, and the prepared solution was allowed to stand for one day for use. During the test, tetrahydrofuran was first drawn with a syringe and rinsed, and repeated several times.
  • NMP N-methylpyrrolidone
  • Instrument model Shanghai Fangrui NDJ-5S, rotor is 62#, the speed is 30 rpm, and the viscosity range of the slurry can be measured from 0 to 1000mPa ⁇ s; rotor is 63#, the speed is 30 rpm, and the viscosity range of the slurry can be measured from 0 to 2000mPa ⁇ s), the test temperature is 25°C, the test time is 5 minutes, and the data is read after the display is stable.
  • the solid content is (M2-M0)/(M1-M0);
  • the solid content of the upper and lower conductive pastes was measured in the same way after standing for 24 hours, and the solid content of the lower conductive paste minus the solid content of the upper conductive paste was taken as the difference in the upper/lower solid content after the conductive paste was allowed to stand for 24 hours.
  • No gel The slurry flows naturally and continuously, and the slurry flows on the surface of the steel ruler without lumps.
  • the adhesion test process of the embodiments and comparative examples of the present application is as follows: Use a blade to intercept a sample with a width of 30mm and a length of 100-160mm, and stick the special double-sided tape on the steel plate, the tape width is 20mm, and the length is 90-150mm. Stick the positive electrode film layer of the electrode sample intercepted earlier on the double-sided tape, and then roll it three times in the same direction with a 2kg roller. Fix a paper tape with a width equal to the electrode and a length of 250mm on the electrode collector and fix it with wrinkled glue.
  • the indicator light is on, adjust the limit block to the appropriate position, and fix the end of the steel plate without the electrode with the lower clamp. Fold the paper tape upwards and fix it with the upper clamp, and 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, the tensile speed is 50mm/min. The force when the electrode is under force balance divided by the width of the tape is taken as the bonding force of the electrode per unit length to characterize the bonding strength between the positive electrode film layer and the current collector.
  • the secondary battery was charged to 4.2V at a constant current rate of 1/3C, and then charged to a current of 0.05C at a constant voltage of 4.2V, and left for 5 minutes. Then, it was discharged at a rate of 1/3C for 90 minutes, the electrode assembly was adjusted to 50% SOC, and left for 60 minutes, and then discharged at a rate of 4C for 30S, and the 50% SOC discharge DCR was obtained according to the test data.
  • Examples 1 to 19 disclose a fluorine-containing polymer, and the fluorine-containing polymers all contain a structural unit derived from vinylidene fluoride and a structural unit derived from 2-benzyl acrylic acid or 2-(4-isobutylbenzyl) acrylic acid.
  • Comparison of Examples 1 to 5 and Example 19 with Comparative Example 1 shows that, compared with conventional polyvinylidene fluoride, the fluorinated polymer provided in the present application can reduce the viscosity of the conductive paste, improve the filterability of the conductive paste, and make the conductive paste less likely to gel during storage, thereby improving the anti-gelling and storage properties of the conductive paste. Due to the improvement in the dispersion performance of the conductive paste, the diaphragm resistance of the electrode and the DC impedance of the battery are further reduced.
  • Example 1 Comparison of Example 1 with Comparative Example 2 shows that, compared with the vinylidene fluoride-acrylic acid copolymer, the vinylidene fluoride-2-benzyl acrylic acid copolymer disclosed in the present application can improve the anti-sedimentation property of the conductive paste and improve the adhesion of the electrode.
  • the mass content of the structural unit derived from vinylidene fluoride is 50% to 70%, which is based on the mass of the fluorine-containing polymer, and can take into account both the viscosity of the conductive paste and the adhesion of the electrode, thereby comprehensively improving the processing performance and use performance of the conductive paste.
  • the weight average molecular weight of the fluorine-containing polymer is 100,000-140,000, which can take into account the viscosity of the conductive paste and the adhesion of the electrode, and comprehensively improve the processing performance and use performance of the conductive paste.
  • Example 19 From the comparison between Example 1 and Example 19, it can be seen that compared with the vinylidene fluoride-2-benzyl acrylic acid copolymer prepared by the traditional method, the vinylidene fluoride-2-benzyl acrylic acid copolymer disclosed in the present application can improve the anti-sedimentation property of the conductive slurry, improve the adhesion of the electrode sheet, reduce the diaphragm resistance of the electrode sheet and the DC internal resistance of the battery, and improve the dynamic performance of the battery.
  • the conductive pastes in Examples 1 to 19 all include conductive carbon black, N-methylpyrrolidone and vinylidene fluoride-2-benzyl acrylic acid copolymer or vinylidene fluoride-2-(4-isobutylbenzyl) acrylic acid copolymer.
  • the fluorine-containing polymer disclosed in the present application can reduce the viscosity of the conductive slurry, which is beneficial to the subsequent coating process.
  • it can improve the filterability of the conductive slurry, significantly alleviate the gelation of the conductive slurry during storage, improve the anti-gelation and storage properties of the conductive slurry, and at the same time improve the adhesion of the electrode sheet, reduce the membrane resistance of the electrode sheet, and reduce the DC internal resistance of the battery, thereby improving the dynamic performance of the battery.
  • Comparison of Examples 1, 10-11 and 12-13 shows that the mass fraction of the fluorine-containing polymer is 0.5%-2.5% based on the total mass of the conductive paste.
  • the paste has a suitable viscosity and makes the electrode sheet have good adhesion, which comprehensively improves the processing performance and use performance of the paste.
  • Example 14-15 and Example 16-17 shows that the mass fraction of the conductive agent is 10.0%-15.0%, based on the total mass of the conductive paste.
  • the paste has a suitable viscosity and makes the electrode sheet have good adhesion, which comprehensively improves the processing performance and use performance of the paste.
  • the solid content of the conductive paste is 10.5% to 17.5%, and the viscosity of the conductive paste is 300 mPa ⁇ s to 900 mPa ⁇ s.
  • the conductive paste prepared from the fluorinated polymer does not require the addition of additional dispersants or thickeners to improve processing performance, which helps to improve production efficiency and optimize production processes.
  • the positive electrode sheets in Examples 1 to 19 all include a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes a positive electrode active material, a conductive agent and a binder, wherein the conductive agent is a deposit of a conductive slurry.
  • the positive electrode plates of the present application contain a conductive agent in the form of a deposit of conductive slurry, which is beneficial to improving the adhesion of the positive electrode plates, reducing the diaphragm resistance of the plates and the DC internal resistance of the battery, and improving the dynamic performance of the battery.
  • the positive electrode plates disclosed in the present application contain a conductive agent in the form of a sediment of a conductive slurry, which can effectively reduce the content of the conductive agent that needs to be added to the positive electrode plates, and is beneficial to improving the energy density of the battery.
  • the bonding force per unit length between the positive electrode film layer and the positive electrode current collector is not less than 14 N/m, and the positive electrode sheet can meet actual usage requirements.

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Abstract

一种含氟聚合物、导电浆料、正极极片、二次电池、用电装置。含氟聚合物包含衍生自式I所示单体的结构单元和衍生自式II所示单体的结构单元，其中，R 1、R 2、R 3各自独立地选自氢、氟、氯、氟取代的C 1-3烷基中的一种或多种，R 4、R 5选自氢、取代或未取代的C 1-5烷基，R 6选自芳香基取代的C 1-5烷基、取代或未取代的芳香基中的一种或多种。含氟聚合物可以提高导电浆料的过滤性，提高导电浆料的抗凝胶性和存储性，显著拓宽了导电浆料的工艺窗口，改善了导电浆料的可加工性。

Description

含氟聚合物、导电浆料、正极极片、二次电池、用电装置 技术领域
本申请涉及二次电池技术领域，尤其涉及一种含氟聚合物、导电浆料、正极极片、二次电池、用电装置
背景技术
二次电池的活性材料由于本身导电性差，在电池制作过程中容易出现内阻大、倍率性能和循环性能不佳等问题，因此需要通过添加导电剂来提高活性材料的导电性，进而提升电池的综合性能。然而现有的导电剂比表面积一般较大，在范德华力的作用下，极易发生团聚，影响其导电效果，同时容易导致正极极片分布不均匀，影响活性材料性能的发挥。因此，亟需解决该技术问题。
发明内容
本申请是鉴于上述课题而进行的，其目的在于，提供一种含氟聚合物及包含该含氟聚合物的导电浆料，以提高导电剂的分散性，进而优化电池的性能。
本申请的第一方面提供了一种含氟聚合物，包含衍生自式I所示单体的结构单元和衍生自式II所示单体的结构单元，
Figure PCTCN2022130117-appb-000001
其中，R 1、R 2、R 3各自独立地选自氢、氟、氯、氟取代的C 1-3烷基中的一种或多种，R 4、R 5各自独立地选自氢、取代或未取代的C 1-5烷基中的一种或多种，R 6选自芳香基取代的C 1-5烷基、取代或取代的芳香基中的一种或多种。
本申请提供的含氟聚合物能够降低导电浆料的粘度，提高导电浆料的过滤性，且浆料在静置60天后不发生凝胶，提高导电浆料的 抗凝胶性和存储性，改善了导电浆料的可加工性和稳定性，使得导电浆料在无需额外添加分散剂的情况下就能够满足导电浆料的生产需求，从而进一步降低极片的膜片电阻和电池的直流阻抗。
在任意实施方式中，所述式I中的R 1为氟，R 2、R 3各自独立地选自氢、氟、氯、三氟甲基中的一种或多种。
在任意实施方式中，衍生自式I所示单体的结构单元的摩尔含量为50％～70％，基于所述含氟聚合物中所有结构单元的总摩尔数计。
控制衍生自式I所示单体的结构单元的摩尔含量在合适范围内，可以兼顾导电浆料的粘度和极片的粘结性，综合改善导电浆料的加工性能和使用性能。
在任意实施方式中，衍生自式II所示单体的结构单元的摩尔含量为30％～50％，基于所述含氟聚合物中所有结构单元的总摩尔数计。
控制衍生自式II所示单体的结构单元的摩尔含量在合适范围内，可以兼顾导电浆料的粘度和极片的粘结性，综合改善导电浆料的加工性能和使用性能。
在任意实施方式中，含氟聚合物的重均分子量为10万～14万。
控制含氟聚合物的重均分子量在合适范围内，可以兼顾导电浆料的粘度和极片的粘结性，综合改善导电浆料的加工性能和使用性能。
在任意实施方式中，所述式I所示单体选自氟乙烯、偏二氟乙烯、四氟乙烯、三氟氯乙烯、六氟丙烯中的一种或多种。
在任意实施方式中，式II所示单体选自2-苄基丙烯酸、2-(4-异丁基苄基)丙烯酸、2-亚甲基-4-苯基丁酸、2-(1-苯基乙基)丙烯酸的一种或多种。
本申请的第二方面提供一种含氟聚合物的制备方法，包括以下步骤：
在可聚合条件下，将至少一种式I所示单体和至少一种式II所示单体进行聚合反应，
Figure PCTCN2022130117-appb-000002
其中，R 1、R 2、R 3各自独立地选自氢、氟、氯、氟取代的C 1-3烷基中的一种或多种，R 4、R 5各自独立地选自氢、取代或未取代的C 1-5烷基中的一种或多种，R 6选自芳香基取代的C 1-5烷基、取代或取代的芳香基中的一种或多种。
该方法制备出的含氟聚合物相比于传统粘结剂能够降低导电浆料的粘度，提高导电浆料的过滤性，使得浆料在静置60天后不发生凝胶，提高导电浆料的抗凝胶性和存储性，显著拓宽了导电浆料的工艺窗口，改善了导电浆料的可加工性，使得导电浆料在无需添加分散剂的情况下就能够满足导电浆料的生产需求，从而进一步降低极片的膜片电阻和电池的直流阻抗。
在任意实施方式中，所述式I中的R 1为氟，R 2、R 3各自独立地选自氢、氟、氯、三氟甲基中的一种或多种。
在任意实施方式中，所述式I所示单体的摩尔含量为50％～70％，基于式I所示单体和式II所示单体的总摩尔数计。
在任意实施方式中，所述式II所示单体的摩尔含量为30％～50％，基于式I所示单体和式II所示单体的总摩尔数计。
在任意实施方式中，所述聚合反应包括第一段聚合和第二段聚合，
第一段聚合：向反应容器内加入引发剂、乳化剂、至少一种式I所示单体以及水性介质进行第一段聚合，在所述第一段聚合中连续送入式I所示单体；
第二段聚合：反应一段时间后，向反应容器内加入至少一种式II所示单体进行第二段聚合，在所述第二段聚合中连续送入式I所示单体。
本申请提供的方法通过首先连续送入式I所示单体形成含氟链段，使得含氟聚合物具有高的热稳定性；再通入式II所示单体以减少含氟链段与外界环境的接触，有效缓解氟元素导致的凝胶现象。该方 法制备出的含氟聚合物相比于通过将单体全部通入反应容器同时聚合制备的含氟聚合物可以有效提高导电浆料的稳定性，提高浆料的抗沉降性，提高极片的粘结性，降低极片的膜片电阻和电池的直流内阻，提高电池的动力学性能。另外在向反应容器内送入式II所示单体进行第二段聚合反应时，继续向反应容器内送入式I所示单体，有助于提高第一段聚合反应生成的链段与第二段聚合反应生成的链段的相容性，提高含氟聚合物的稳定性。
在任意实施方式中，第一段聚合中通入的式I所示单体的质量为聚合反应中所供给的式I所示单体的总质量的80％～85％，所述第二段聚合中通入的式I所示单体的质量为聚合反应中所供给的式I所示单体的总质量的15％～20％。
在任意实施方式中，引发剂的质量百分比为0.5％～1.4％，基于所述式I所示单体和式II所示单体的总质量计。
在任意实施方式中，所述乳化剂的质量百分比为0.1％～0.4％，基于所述式I所示单体和式II所示单体的总质量计。
在任意实施方式中，第一段聚合中提供的水性介质的质量百分比为400％～600％，基于所述式I所示单体和式II所示单体的总质量计。
在任意实施方式中，所述第一段聚合和第二段聚合的反应压力均为6.0MPa～9.0MPa，反应温度为80℃～120℃。
在任意实施方式中，乳化剂为全氟辛酸碱金属盐。
在任意实施方式中，引发剂为N,N二甲基苄胺、N-甲基苯丙胺中的一种或两种。
本申请的第三方面，提供第一方面的含氟聚合物在二次电池中的应用。
本申请的第四方面，提供一种导电浆料，包括导电剂、溶剂和第一方面所述的含氟聚合物。
相比于现有技术中在正极浆料制备过程中直接加入导电剂，本申请提供的导电浆料能够提高导电剂在正极浆料中的分散性，提升 导电剂在极片中的导电效果，进而有效降低极片中的导电剂含量，有利于进一步增加极片中正极活性物质的负载量，提升电池功率性能。
在任意实施方式中，导电剂的质量分数为10.0％～15.0％，基于所述导电浆料的总质量计。
控制导电剂的质量分数在合适范围内，基于导电浆料的总质量计。具有合适粘度的浆料可以使得极片具有良好的粘结性，综合改善浆料的加工性能和使用性能。
在任意实施方式中，所述含氟聚合物的质量分数为0.5％～2.5％，基于所述导电浆料的总质量计。
控制含氟聚合物的质量分数在合适范围内，基于导电浆料的总质量计。浆料具有适宜的粘度，使得极片具有良好的粘结性，综合改善浆料的加工性能和使用性能。
在任意实施方式中，所述导电浆料的固含量为10.5％～17.5％，且所述导电浆料的粘度为300mPa·s～900mPa·s。
固含量为10.5％～17.5％，粘度为300mPa·s～900mPa·s，可以直接与活性材料、粘结剂进行混合搅拌制备正极浆料，无需增加额外的助剂，利于提高生产效率、降低生产成本。
本申请的第五方面提供一种正极极片，包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，所述正极膜层包括正极活性材料、导电剂和粘结剂，所述导电剂为第四方面的导电浆料的沉积物。
相比于现有技术中直接加入导电剂粉体制备的正极极片，本申请公开的正极极片中的导电剂以导电浆料沉积物的形式存在于正极极片中，使得正极极片在导电剂低添加量的情况下，就能具有低的膜片电阻，为进一步提高极片中正极活性物质的负载量提供了可能。
在任意实施方式中，基于所述正极膜层的总质量计，所述导电剂质量含量为0.5％～0.8％时，所述正极极片的膜片电阻低于0.2Ω。
在任意实施方式中，正极膜层与所述正极集流体间单位长度的 粘结力不小于14N/m。
本申请的第六方面提供一种二次电池，包括隔离膜、负极极片、电解质和第五方面所述的正极极片。可选地，所述二次电池包括锂离子电池、钠离子电池、镁离子电池、钾离子电池中的至少一种。
本申请的第七方面提供一种电池模块，包括本申请的第六方面的二次电池。
本申请的第八方面提供一种电池包，包括本申请第六方面的二次电池或本申请的第七方面的电池模块。
本申请的第九方面提供一种用电装置，包括选自本申请的第六方面的二次电池、本申请的第七方面的电池模块、本申请的第八方面的电池包中的至少一种。
附图说明
图1是本申请一实施方式的二次电池的示意图；
图2是图1所示的本申请一实施方式的二次电池的分解图；
图3是本申请一实施方式的电池模块的示意图；
图4是本申请一实施方式的电池包的示意图；
图5是图4所示的本申请一实施方式的电池包的分解图；
图6是本申请一实施方式的二次电池用作电源的用电装置的示意图。
附图标记说明：
1电池包；2上箱体；3下箱体；4电池模块；5二次电池；51壳体；52电极组件；53盖板。
具体实施方式
以下，适当地参照附图详细说明具体公开了本申请的粘结剂、制备方法、电极、电池及用电装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不 必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-5。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。
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)。
二次电池的活性材料由于本身导电性差，在电池制作过程中容易出现内阻大、倍率性能和循环性能不佳等问题，因此需要通过添加导电剂来提高活性材料的导电性，进而提升电池的综合性能。然而现有的导电剂比表面积一般较大，在范德华力的作用下，极易发生团聚，影响其导电效果。申请人发现将导电剂先制备成导电浆料，再与活性材料和/或粘结剂混合制备浆料有助于减缓导电剂在合浆过程中的团聚，然而导电浆料中需要加入分散剂以提高导电浆料的分散性和稳定性。导电浆料中分散剂的加入会影响电池的电化学性能、循环性能和批次稳定性，也容易出现分散剂与正极浆料体系不相容的情况。基于上述技术问题，本申请开发出一种含氟聚合物，使得导电浆料具有合适的粘度和优异的过滤性，提高导电浆料的抗凝胶性和存储性，显著拓宽了导电浆料的工艺窗口，改善了导电浆料的可加工性。
[含氟聚合物]
基于此，本申请提出了一种含氟聚合物，包含衍生自式I所示单体的结构单元和衍生自式II所示单体的结构单元，
Figure PCTCN2022130117-appb-000003
其中，R 1、R 2、R 3各自独立地选自氢、氟、氯、氟取代的C 1-3烷基中的一种或多种，R 4、R 5各自独立地选自氢、取代或未取代的C 1-5烷基中的一种或多种，R 6选自芳香基取代的C 1-5烷基、取代或取代的芳香基中的一种或多种。
在本文中，术语“含氟聚合物”是指结构单元中包含氟元素的聚合物。
在本文中，术语“聚合物”一方面包括通过聚合反应制备的化学上均一的、但在聚合度、摩尔质量和链长方面不同的大分子的集合体。该术语另一方面也包括由聚合反应形成的这样的大分子集合体的衍生物，即可以通过上述大分子中的官能团的反应，例如加成或取代获得的并且可以是化学上均一的或化学上不均一的产物。
在本文中，术语“C 1-3烷基”是指仅由碳和氢原子组成的直链或支链烃链基团，基团中不存在不饱和，具有从一至三个碳原子，并且通过单键附接到分子的其余部分。
在本文中，术语“氟取代的C 1-3烷基”是指至少一个氢原子被氟原子取代的C 1-3烷基。
在本文中，术语“C 1-5烷基”是指仅由碳和氢原子组成的直链或支链烃链基团，基团中不存在不饱和，具有从一至五个碳原子，并且通过单键附接到分子的其余部分。
在本文中，术语“取代的”是指该化合物或化学部分的至少一个氢原子被另一种化学部分被取代基取代，其中的取代基各自独立地选自：羟基、巯基、氨基、氰基、硝基、醛基、卤素原子、烯基、炔基、芳基、杂芳基、C 1-6烷基、C 1-6烷氧基。
在本文中，术语“芳香基”是指至少一个环为芳族的芳族环系统，其包括但不限于苯基、联苯基、茚满基、1-萘基、2-萘基和四氢萘基。
在本文中，术语“工艺窗口”指能够保证产品质量的工艺区间，包括但不限于温度区间、压力区间、存储时间长度等，可以理解的是工艺窗口越宽，对工艺精度的需求越低。
在一些实施方式中，R 6为芳香基取代的C 1-5烷基，其中芳香基为取代或未取代的芳香基。
在一些实施方式中，所述式I所示单体选自氟乙烯、偏二氟乙烯、四氟乙烯、三氟氯乙烯、六氟丙烯中的一种或多种。
在一些实施方式中，式II所示单体选自2-苄基丙烯酸、2-(4-异丁基苄基)丙烯酸、2-亚甲基-4-苯基丁酸、2-(1-苯基乙基)丙烯酸的一种或多种。
在一些实施方式中，聚合物包含一种或多种衍生自式I所示单体的结构单元。在一些实施方式中，聚合物包含一种或多种衍生自式II所示单体的结构单元。在一些实施方式中，聚合物包括但不限于偏二氟乙烯-2-苄基丙烯酸共聚物、偏二氟乙烯-2-(4-异丁基苄基)丙烯酸共聚物、偏二氟乙烯-2-亚甲基-4-苯基丁酸共聚物、偏二氟乙烯-2-(1-苯基乙基)丙烯酸共聚物、氟乙烯-2-苄基丙烯酸共聚物、四氟乙烯-2-苄基丙烯酸共聚物、四氟乙烯-2-(4-异丁基苄基)丙烯酸共聚物、偏二氟乙烯-三氟氯乙烯-2-苄基丙烯酸共聚物。
衍生自式I所示单体的结构单元中的氟元素与集流体表面的羟基或/和羧基能够形成氢键作用，另外衍生自式II所示单体的结构单元含有的羧基与集流体表面的羟基或/和羧基能够形成氢键作用，两者共同作用使得正极极片具有较好的粘结力。另衍生自式II所示单体的结构单元能够有效降低含氟聚合物的氟含量，改善氟元素导致的浆料凝胶现象。而且衍生自式II所示单体的结构单元能够进一步增加含氟聚合物的空间位阻，减少含氟单元的聚集，起到降低浆料粘度，缓解浆料凝胶的作用，有效改善浆料的过滤性。同时衍生自式II所示单体的结构单元含有的芳香基与导电剂具有相似的元素和结构，可以通过与导电剂的相互作用提高导电浆料的稳定性，提高导电浆料的抗沉降性。
本申请提供的含氟聚合物相比于传统的聚偏二氟乙烯粘结剂，能够降低导电浆料的粘度，提高导电浆料的过滤性，使得浆料在储存过程中不易发生凝胶，提高导电浆料的抗凝胶性和存储性，显著拓宽了导电浆料的工艺窗口，改善了导电浆料的可加工性，使得导电浆料在无需添加分散剂的情况下就能够满足导电浆料的生产需求，从而进一步降低极片的膜片电阻和电池的直流阻抗。
在一些实施方式中，式I中的R 1为氟，R 2、R 3各自独立地选自 氢、氟、氯、三氟甲基中的一种或多种。
在一些实施方式中，衍生自式I所示单体的结构单元的摩尔含量为50％～70％，基于所述含氟聚合物中所有结构单元的总摩尔数计。在一些实施方式中，衍生自式I所示单体的结构单元的摩尔含量可选为50％、60％、70％中的任意一种，基于所述含氟聚合物中所有结构单元的总摩尔数计。
控制衍生自式I所示单体的结构单元的摩尔含量在合适范围内，使得导电浆料具有合适的粘度，可以兼顾导电浆料的粘度和极片的粘结性，综合改善导电浆料的加工性能和使用性能。
在一些实施方式中，衍生自式II所示单体的结构单元的摩尔含量为30％～50％，基于所述含氟聚合物中所有结构单元的总摩尔数计。在一些实施方式中，衍生自式II所示单体的结构单元的摩尔含量可选为30％、40％、50％中的任意一种，基于所述含氟聚合物中所有结构单元的总摩尔数计。
控制衍生自式II所示单体的结构单元的摩尔含量在合适范围内，使得导电浆料具有合适的粘度，可以兼顾导电浆料的粘度和极片的粘结性，综合改善导电浆料的加工性能和使用性能。
在一些实施方式中，含氟聚合物的重均分子量为10万～14万。在一些实施方式中，含氟聚合物的重均分子量可选为10万、11万、12万、13万、14万中的任意一种。
在本文中，术语“重均分子量”是指聚合物中用不同分子量的分子所占的重量分数与其对应的分子量乘积的总和。
在本申请中，聚合物的重均分子量的测试可以选用本领域已知的方法进行测试，例如采用凝胶色谱法进行测试，如采用Waters 2695 Isocratic HPLC型凝胶色谱仪(示差折光检测器2141)进行测试。在一些实施方式中，测试方法为以质量分数为3.0％的聚苯乙烯溶液试样做参比，选择匹配的色谱柱(油性：Styragel HT5DMF7.8×300mm+Styragel HT4)。用纯化后的N-甲基吡咯烷酮(NMP)溶剂配置3.0％的含氟聚合物胶液，配置好的溶液静置一天，备用。测 试时，先用注射器吸取四氢呋喃，进行冲洗，重复几次。然后吸取5ml实验溶液，排除注射器中的空气，将针尖擦干。最后将试样溶液缓缓注入进样口。待示数稳定后获取数据，读取重均分子量。
控制含氟聚合物的重均分子量在合适范围内，使得浆料具有合适的粘度，利于后续制备正极浆料的工作，同时合适重均分子量的含氟聚合物利于形成三维网状粘结结构，使得极片具有良好的粘结力，可以兼顾导电浆料的粘度和极片的粘结性，综合改善导电浆料的加工性能和使用性能。
本申请的一个实施方式中，提供一种含氟聚合物的制备方法，包括以下步骤：
在可聚合条件下，将至少一种式I所示单体和至少一种式II所示单体进行聚合反应，
Figure PCTCN2022130117-appb-000004
其中，R 1、R 2、R 3各自独立地选自氢、氟、氯、氟取代的C 1-3烷基中的一种或多种，R 4、R 5各自独立地选自氢、取代或未取代的C 1-5烷基中的一种或多种，R 6选自芳香基取代的C 1-5烷基、取代或取代的芳香基中的一种或多种。
该方法制备出的含氟聚合物相比于传统粘结剂能够降低导电浆料的粘度，提高导电浆料的过滤性，使得浆料在储存过程中不易发生凝胶，提高导电浆料的抗凝胶性和存储性，显著拓宽了导电浆料的工艺窗口，改善了导电浆料的可加工性，使得导电浆料在无需添加分散剂的情况下就能够满足导电浆料的生产需求。
在一些实施方式中，式I中R 1为氟，R 2、R 3各自独立地选自氢、氟、氯、三氟甲基中的一种或多种。
在一些实施方式中，所述式I所示单体的摩尔含量为50％～70％，基于式I所示单体和式II所示单体的总摩尔数计。
在一些实施方式中，所述式II所示单体的摩尔含量为30％～50％，基于式I所示单体和式II所示单体的总摩尔数计。
在一些实施方式中，所述聚合反应包括第一段聚合和第二段聚合，
第一段聚合：向反应容器内加入引发剂、乳化剂、至少一种式I所示单体以及水性介质进行第一段聚合，在所述第一段聚合中连续送入式I所示单体；
第二段聚合：反应一段时间后，向反应容器内加入至少一种式II所示单体进行第二段聚合，在所述第二段聚合中连续送入式I所示单体。
本申请提供的方法通过首先连续送入式I所示单体形成含氟链段，使得含氟聚合物具有高的热稳定性；再通入式II所示单体以减少含氟链段与外界环境的接触，有效缓解氟元素导致的凝胶现象。该方法制备出的含氟聚合物相比于通过将单体全部通入反应容器同时聚合制备的含氟聚合物可以有效提高导电浆料的稳定性，提高浆料的抗沉降性，提高极片的粘结性，降低极片的膜片电阻和电池的直流内阻，提高电池的动力学性能。另外在向反应容器内送入式II所示单体进行第二段聚合反应时，继续向反应容器内送入式I所示单体，有助于提高第一段聚合反应生成的链段与第二段聚合反应生成的链段的相容性，提高含氟聚合物的稳定性。
在一些实施方式中，第一段聚合中通入的式I所示单体的质量为聚合反应中所供给的式I所示单体的总质量的80％～85％，所述第二段聚合反应中通入的式I所示单体的质量为聚合反应中所供给的式I所示单体的总质量的15％～20％。
在一些实施方式中，引发剂的质量百分比为0.5％～1.4％，基于所述式I所示单体和式II所示单体的总质量计。
在一些实施方式中，所述乳化剂的质量百分比为0.1％～0.4％，基于所述式I所示单体和式II所示单体的总质量计。
在一些实施方式中，第一段聚合中提供的水性介质的质量百分比为400％～600％，基于所述式I所示单体和式II所示单体的总质量计。
在一些实施方式中，所述第一段聚合和第二段聚合的反应压力均为6.0MPa～9.0MPa，反应温度为80℃～120℃。
在一些实施方式中，乳化剂为全氟辛酸碱金属盐。
在一些实施方式中，引发剂为N,N二甲基苄胺、N-甲基苯丙胺中的一种或两种。
本申请的一个实施方式中，提供一种任意实施方式中的含氟聚合物在二次电池中的应用，可选地，二次电池包括锂离子电池、钠离子电池、镁离子电池、钾离子电池中的至少一种。
[导电浆料]
本申请的一个实施方式中，提供一种导电浆料，包括导电剂、溶剂和任意实施方式中的含氟聚合物。
在一些实施方式中，溶剂是水性溶剂，如去离子水。
在一些实施方式中，溶剂是油性溶剂，油性溶剂的示例包括但不限于二甲基乙酰胺、N，N-二甲基甲酰胺、N-甲基吡咯烷酮、丙酮、碳酸二甲酯、乙基纤维素、聚碳酸酯。
相比于现有技术中在正极浆料制备过程中直接加入导电剂，本申请提供的导电浆料能够提高导电剂在正极浆料中的分散性，提升导电剂在极片中的导电效果，进而有效降低极片中的导电剂含量，有利于进一步增加极片的负载量，提升电池功率性能。而且导电浆料中的含氟聚合物可以同时发挥粘结剂和分散剂的作用，无需在导电浆料中额外添加其他分散剂，有利于进一步提高极片中活性物质的负载量以及极片的粘结力。
在一些实施方式中，导电剂的质量分数为10.0％～15.0％，基于所述导电浆料的总质量计。在一些实施方式中，导电剂的质量分数可选为10％、11％、12％、13％、14％、15％中的任意一种。
控制导电剂的质量分数在合适范围内，基于导电浆料的总质量计。浆料具有合适的粘度，并使得极片具有良好的粘结性，综合改善浆料的加工性能和使用性能。
在一些实施方式中，所述含氟聚合物的质量分数为0.5％～2.5％， 基于所述导电浆料的总质量计。在一些实施方式中，含氟聚合物的质量分数可选为0.5％、1.0％、1.5％、2.0％、2.5％中的任意一种。
控制含氟聚合物的质量分数在合适范围内，基于导电浆料的总质量计。浆料具有适宜的粘度，有利于后续的正极浆料的制备工作，同时使得极片具有良好的粘结性，综合改善浆料的加工性能和使用性能。
在一些实施方式中，所述导电浆料的固含量为10.5％～17.5％，且所述导电浆料的粘度为300mPa·s～900mPa·s。
在一些实施方式中，导电浆料的粘度可选为400mPa·s～900mPa·s、400mPa·s～800mPa·s、400mPa·s～750mPa·s、400mPa·s～600mPa·s、450mPa·s～800mPa·s、450mPa·s～750mPa·s、450mPa·s～650mPa·s、500mPa·s～750mPa·s中的任意一种。
固含量为10.5％～17.5％，粘度为300mPa·s～900mPa·s的导电浆料可以直接与活性材料、粘结剂进行混合搅拌制备正极浆料，无需在导电浆料中添加额外的助剂，利于提高生产效率、降低生产成本。
[正极极片]
本申请的一些实施方式中提供一种正极极片，包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，所述正极膜层包括正极活性材料、导电剂和粘结剂，所述导电剂为任意实施方式中的导电浆料的沉积物。
在本文中，术语“粘结剂”是指在分散介质中形成胶体溶液或胶体分散液的化学化合物、聚合物或混合物。
相比于现有技术中直接加入导电剂粉体制备的正极极片，本申请公开的正极极片中的导电剂以导电浆料沉积物的形式存在于正极极片中，使得正极极片在导电剂低添加量的情况下，就能具有低的膜片电阻，为进一步提高极片中正极活性物质的负载量提供了可能。
在一些实施方式中，基于所述正极膜层的总质量剂，所述导电剂质量含量为0.5％～0.8％时，所述正极极片的膜片电阻低于0.2Ω。
在一些实施方式中，正极膜层与所述正极集流体间单位长度的 粘结力不小于14N/m。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极膜层设置在正极集流体相对的两个表面的其中任意一者或两者上。
在一些实施方式中，所述正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
在一些实施方式中，正极活性材料可采用本领域公知的用于电池的正极活性材料。作为示例，正极活性材料可包括以下材料中的至少一种：橄榄石结构的含锂磷酸盐、锂过渡金属氧化物及其各自的改性化合物。但本申请并不限定于这些材料，还可以使用其他可被用作电池正极活性材料的传统材料。这些正极活性材料可以仅单独使用一种，也可以将两种以上组合使用。其中，锂过渡金属氧化物的示例可包括但不限于锂钴氧化物(如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NCM 333)、LiNi 0.5Co 0.2Mn 0.3O 2(也可以简称为NCM 523)、LiNi 0.5Co 0.25Mn 0.25O 2(也可以简称为NCM 211)、LiNi 0.6Co 0.2Mn 0.2O 2(也可以简称为NCM 622)、LiNi 0.8Co 0.1Mn 0.1O 2(也可以简称为NCM 811)、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。
在一些实施方式中，正极膜层还可选地包括导电剂。作为示例，所述导电剂可以包括超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的至少一种。
在一些实施方式中，可以通过以下方式制备正极极片：将上述用于制备正极极片的组分，例如先将含氟聚合物、导电剂、溶剂搅拌制备导电浆料，将正极活性材料、粘结剂和任意其他的组分分散于导电浆料中，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1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2，外包装可包括壳体51和盖板53。其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53能够盖设于所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔内。电解液浸润于电极组件52中。二次电池5所含电极组件52的数量可以为一个或多个，本领域技术人员可根据具体实际需求进行选择。
在一些实施方式中，二次电池可以组装成电池模块，电池模块所含二次电池的数量可以为一个或多个，具体数量本领域技术人员可根据电池模块的应用和容量进行选择。
图3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。
可选地，电池模块4还可以包括具有容纳空间的外壳，多个二次电池5容纳于该容纳空间。
在一些实施方式中，上述电池模块还可以组装成电池包，电池包所含电池模块的数量可以为一个或多个，具体数量本领域技术人员可根据电池包的应用和容量进行选择。
图4和图5是作为一个示例的电池包1。参照图5和图6，在电池包1中可以包括电池箱和设置于电池箱中的多个电池模块4。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳电池模块4的封闭空间。多个电池模块4可以按照任意的方式排布于电池箱中。
另外，本申请还提供一种用电装置，所述用电装置包括本申请提供的二次电池、电池模块、或电池包中的至少一种。所述二次电池、电池模块、或电池包可以用作所述用电装置的电源，也可以用 作所述用电装置的能量存储单元。所述用电装置可以包括移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等，但不限于此。
作为所述用电装置，可以根据其使用需求来选择二次电池、电池模块或电池包。
图6是作为一个示例的用电装置。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
作为另一个示例的装置可以是手机、平板电脑、笔记本电脑等。该装置通常要求轻薄化，可以采用二次电池作为电源。
实施例
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
一、制备方法
实施例1
1)含氟聚合物的制备
将22.6kg的去离子水(电导率小于等于2μs/cm)、11.3g的全氟辛酸钠盐、40.7g的N,N二甲基苄胺，依次加入50L反应釜内，关闭反应釜；
釜内抽真空，充氮气，重复操作至反应釜内氧气浓度小于100ppm；
向反应釜内通入偏二氟乙烯单体至釜内压力8.0MPa；
釜内升温至100℃开始反应，反应过程中不断通入偏二氟乙烯单 体维持釜内反应压力不变；
在通入16.8mol偏二氟乙烯单体后，向反应釜内加入20mol的2-苄基丙烯酸，维持反应压力8.0MPa和温度100℃，向反应釜内通入剩余3.2mol的偏二氟乙烯单体，继续反应2小时；
反应完成时釜内压力将至0.2MPa，回收未反应的偏氟乙烯单体；
反应产物经凝聚、洗涤、分离、干燥、粉碎得到偏二氟乙烯-2-苄基丙烯酸共聚物。
2)制备导电浆料
将17600g的N-甲基吡咯烷酮加入到35L搅拌罐内；
将200g的偏二氟乙烯-2-苄基丙烯酸共聚物加入到N-甲基吡咯烷酮内，设定搅拌速度为1000转/分钟，搅拌时间为60分钟，搅拌结束，得到初级浆料；
将2200g导电炭黑粉末加入到初级浆料中，设定搅拌速度为1000转/分钟，搅拌时间为60分钟，开启冷却水循环，搅拌结束得到导电炭黑浆料。
3)正极极片的制备
将2840g磷酸铁锂材料、62.8g聚偏二氟乙烯、2000g导电浆料搅拌混合均匀，得到正极浆料；之后将正极浆料均匀涂覆于正极集流体上，之后经过烘干、冷压、分切，得到正极极片。
4)负极极片的制备
将活性物质人造石墨、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；将负极浆料一次或多次均匀涂覆在负极集流体铜箔上，经过烘干、冷压、分切得到负极极片。
5)隔离膜
以聚丙烯膜作为隔离膜。
6)电解液的制备
在氩气气氛手套箱中(H 2O<0.1ppm，O 2<0.1ppm)，将有机溶剂 碳酸乙烯酯(EC)/碳酸甲乙酯(EMC)按照体积比3/7混合均匀，加入12.5％LiPF 6锂盐溶解于有机溶剂中，搅拌均匀，得到实施例1的电解液。
7)电池的制备
将实施例1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1的锂离子电池产品。
实施例2～实施例5中调节含氟聚合物中各单体的摩尔配比，其他参数同实施例1保持一致，具体参数见表1和表2。
实施例6～实施例9中调整制备含氟聚合物的聚合温度和引发剂N,N二甲基苄胺的质量，使得含氟聚合物具有不同的重均分子量，其他参数同实施例1保持一致，具体参数见表1和表2。
实施例6中将聚合反应温度调整为95℃，将N,N二甲基苄胺的质量调整为51.3g；
实施例7中将N,N二甲基苄胺的质量调整为56.7g；
实施例8中将N,N二甲基苄胺的质量调整为59.4g；
实施例9中聚合反应温度调整为95℃，将N,N二甲基苄胺的质量调整为48.6g。
实施例10～实施例13中调整导电浆料中的含氟聚合物的质量分数，其他参数同实施例1保持一致，具体参数见表1和表2。
实施例14～实施例17中，调整导电底涂浆料中导电剂的质量分数，其他参数同实施例1保持一致，具体参数见表1和表2。
实施例18中，将2-苄基丙烯酸单体替换成2-(4-异丁基苄基)丙烯酸单体，其他参数同实施例1，具体参数参见表1和表2。
实施例19中，含氟聚合物为传统方法制备的偏二氟乙烯-2-苄基丙烯酸共聚物，其合成方法为：
将22.6kg的去离子水(电导率小于等于2μs/cm)、11.3g的全氟辛酸钠盐、40.7g的N,N二甲基苄胺，依次加入50L反应釜内，关闭反应釜；
釜内抽真空，充氮气，重复操作至反应釜内氧气浓度小于100ppm；
向反应釜内通入20mol的偏二氟乙烯单体、加入20mol的2-苄基丙烯酸至釜内压力8.0MPa；
釜内升温至100℃开始反应，反应过程中不断通入偏二氟乙烯单体维持釜内反应压力不变；
釜内压力降至0.2MPa时停止反应；
冷却至室温，经凝聚、洗涤、分离、干燥、粉碎得到含氟聚合物，即偏二氟乙烯-2-苄基丙烯酸共聚物，其他参数与实施例1相同，具体参数参见表1和表2。
对比例1中，以偏二氟乙烯聚合物作为含氟聚合物。
对比例2中，将2-苄基丙烯酸单体替换成丙烯酸单体，其他参数与实施例1相同，具体参数参见表1和表2。
对比例3与实施例1基本相同，区别在于，将包含含氟聚合物的导电浆料替换成包含分散剂的导电浆料，具体的制备方法为：
将17600g的N-甲基吡咯烷酮、200g聚乙烯吡咯烷酮和2200g导电炭黑粉末加入到35L搅拌罐内，设定搅拌速度为1000转/分钟，搅拌时间为60分钟，开启冷却水循环，搅拌结束得到导电炭黑浆料。
对比例4与实施例1基本相同，区别在于，以导电炭黑替代导电浆料直接制备正极极片。
对比例5与对比例4基本相同，区别在于，将导电炭黑的质量含量调整为2.0％，基于正极膜层的总质量计。
二、测试方法
1、含氟聚合物的性质表征
(1)含氟聚合物的重均分子量的测量
采用Waters2695Isocratic 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：StyragelHT5DMF7.8×300mm+Styragel HT4)。用纯化后的N-甲基吡咯烷酮(NMP)溶剂配置3.0％的含氟聚合物溶液，配置好的溶液静置一天，备用。测试时，先用注射器吸取四氢呋喃，进行冲洗，重复几次。然后吸取5ml实验溶液，排除注射器中的空气，将针尖擦干。最后将试样溶液缓缓注入进样口。待示数稳定后获取数据，读取重均分子量。
2、导电浆料的性质测试
(1)导电浆料的粘度测试
使用旋转粘度剂测量底涂浆料的粘度。选取合适的转子，固定好粘度计转子，将底涂浆料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，转子为62#，转速为30转/分钟，可测量浆料的粘度范围为0～1000mPa·s；转子为63#，转速为30转/分钟，可测量浆料的粘度范围为0～2000mPa·s)，测试温度为25℃，测试时间为5分钟，待示数稳定读取数据。
(2)导电浆料的过滤性能测试
取500ml烧杯置于200目滤网支架下端，取导电浆料500ml，置于滤网中过滤，记录烧杯中浆料体积到达300ml时的时间，此时间用于判段浆料的过滤性能，过滤时间低于120s，表明浆料的过滤性能好，记为“Y”；若浆料过滤时间高于120s或不能透过滤网，表明浆料的过滤性能差，判定为“N”。
(3)导电浆料固含量以及静置24小时之后上/下层固含量的差值
取铜箔于失重率测量仪内称重，记为M0，清零；
取导电浆料，少量涂覆于铜箔上，然后放入水分测定仪内称重，记为M1；
合上设备，开始烘干；
结束后，记录称重数据，记录为M2，并计算固含量，固含量为 (M2-M0)/(M1-M0)；
以同样的方法测量静置24小时后上层和下层导电浆料的固含量，以下层导电浆料的固含量减上层导电浆料的固含量作为导电浆料静置24小时之后上/下层固含量的差值。
(4)导电浆料静置60天之后的凝胶状态测试
使用钢直尺挑起烧杯中的浆料，根据浆料流动状态判断浆料是否凝胶。如果浆料无凝胶，记为“OK”，如果浆料有凝胶，记为“NG”；
有凝胶：浆料出现结块或者无法自然流动不断流。
无凝胶：浆料自然流动不断流，浆料在钢尺表面平流，无结块。
3、极片性能测试
(1)极片的粘结力
参考GB-T2790-1995国标《胶粘剂180°剥离强度实验方法》，本申请实施例和对比例的粘结力测试过程如下：用刀片截取宽度为30mm，长度为100-160mm的试样，将专用双面胶贴于钢板上，胶带宽度20mm，长度90-150mm。将前面截取的极片试样的正极膜层面贴在双面胶上，后用2kg压辊沿同一个方向滚压三次。将宽度与极片等宽，长度为250mm的纸带固定于极片集流体上，并且用皱纹胶固定。打开三思拉力机电源(灵敏度为1N)，指示灯亮，调整限位块到合适位置，将钢板未贴极片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，拉伸速度为50mm/min。将极片受力平衡时的力除以胶带的宽度作为单位长度的极片的粘结力，以表征正极膜层与集流体之间的粘结强度。
(2)极片的膜片电阻
在极片左、中、右处裁剪烘干后的极片，裁剪为10mm直径的小圆片。开启元能科技极片电阻仪电源，将其置于极片电阻仪“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。
4、电池的性能测试
(1)电池直流阻抗测试
在25℃下，将二次的电池以1/3C的倍率恒流充电至4.2V，再以4.2V恒定电压充电至电流为0.05C，搁置5min后。然后以1/3C的倍率放电90min，调节电极组件为50％SOC，静置60min，然后以4C的倍率放电30S，根据测试数据得到50％SOC放电DCR。
三、各实施例、对比例测试结果分析
按照上述方法分别制备各实施例和对比例的含氟聚合物、导电浆料、正极极片和二次电池，并测量各项参数，结果见下表1和表2。
表1实施例和对比例的制备参数和结果
Figure PCTCN2022130117-appb-000005
Figure PCTCN2022130117-appb-000006
表2实施例和对比例的制备参数和结果
Figure PCTCN2022130117-appb-000007
Figure PCTCN2022130117-appb-000008
从表1可见，实施例1～19中公开了一种含氟聚合物，所述含氟聚合物均包含衍生自偏二氟乙烯的结构单元和衍生自2-苄基丙烯酸或2-(4-异丁基苄基)丙烯酸的结构单元。
实施例1～5、实施例19与对比例1对比可见，相比于的传统聚偏二氟乙烯，本申请提供的含氟聚合物能够降低导电浆料的粘度，提高导电浆料的过滤性，使得导电浆料在储存过程中不易发生凝胶，提高导电浆料的抗凝胶性和存储性。由于导电浆料分散性能的提高，进一步降低了极片的膜片电阻和电池的直流阻抗。实施例1与对比例2的对比可见，相比于偏二氟乙烯-丙烯酸共聚物，本申请公开的偏二氟乙烯-2-苄基丙烯酸共聚物可以提高导电浆料的抗沉降性，提高极片的粘结性。
实施例1～3与实施例4～5对比可见，衍生自偏二氟乙烯的结构单元的质量含量为50％～70％，基于所述含氟聚合物的质量计，可以兼顾导电浆料的粘度和极片的粘结性，综合改善导电浆料的加工性能和使用性能。
实施例1～3与实施例4～5对比可见，衍生自2-苄基丙烯酸的结构单元的质量含量为30％～50％，基于所述含氟聚合物的质量计，可以兼顾导电浆料的粘度和极片的粘结性，综合改善导电浆料的加工性能和使用性能。
从实施例1、实施例6～7与实施例8～9对比可见，含氟聚合物的重均分子量为10万～14万，可以兼顾导电浆料的粘度和极片的粘结性，综合改善导电浆料的加工性能和使用性能。
从实施例1与实施例19的对比可见，相比于传统方法制备的偏二氟乙烯-2-苄基丙烯酸共聚物，本申请公开的偏二氟乙烯-2-苄基丙烯酸共聚物可以提高导电浆料的抗沉降性，提高极片的粘结性，降低极片的膜片电阻和电池的直流内阻，提高电池的动力学性能。
实施例1～19中的导电浆料，均包括导电炭黑、N-甲基吡咯烷酮和偏二氟乙烯-2-苄基丙烯酸共聚物或偏二氟乙烯-2-(4-异丁基苄基)丙烯酸共聚物。
从实施例1～19与对比例3对比可见，相比于传统方法制备的含有分散剂的导电浆料，本申请公开的含氟聚合物可以降低导电浆料的粘度，有利于后续的涂布加工，另外能够提高导电浆料的过滤性，明显缓解导电浆料在储存过程中的凝胶，提高导电浆料的抗凝胶性和存储性，同时还能够提高极片的粘结性、降低极片的膜片电阻、降低电池的直流内阻，进而改善电池的动力学性能。
实施例1、实施例10～11与实施例12～13对比可见，含氟聚合物的质量分数为0.5％～2.5％，基于导电浆料的总质量计。浆料具有适宜的粘度，并使得极片的具有良好的粘结性，综合改善浆料的加工性能和使用性能。
实施例1、实施例14～15与实施例16～17对比可见，导电剂的质量分数为10.0％～15.0％，基于导电浆料的总质量计。浆料具有适宜的粘度，并使得极片的具有良好的粘结性，综合改善浆料的加工性能和使用性能。
从实施例1～15和实施例18可见，导电浆料的固含量为10.5％～17.5％，且所述导电浆料的粘度为300mPa·s～900mPa·s。含氟聚合物制备的导电浆料无需添加额外的分散剂或增稠剂以改善加工性能，有助于提高生产效率，优化生产工艺。
实施例1～19中的正极极片均包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，所述正极膜层包括正极活性材料、导电剂和粘结剂，所述导电剂为导电浆料的沉积物。
实施例1～18与对比例4对比可见，相比于现有技术中常用的直接加入导电剂粉体制备的正极极片，本申请的正极极片包含以导电浆料的沉积物形式的导电剂，有利于提高正极极片的粘结性，降低极片的膜片电阻和电池的直流内阻，改善电池的动力学性能。
实施例1～19与对比例5对比可见，相比于现有技术中常用的直接加入导电剂粉体制备的正极极片，本申请公开正极极片包含以导电浆料的沉积物形式的导电剂，能够有效降低正极极片中需要添加的导电剂的含量，有利于电池的能量密度的提高。
实施例1～18可见，基于所述正极膜层的总质量剂，导电剂质量含量为0.5％～0.8％时，所述正极极片的膜片电阻低于0.2Ω。
实施例1～18可见，正极膜层与正极集流体间单位长度的粘结力不小于14N/m，正极极片能满足实际的使用需求。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。

Claims (32)

  1. 一种含氟聚合物，其特征在于，其包含衍生自式I所示单体的结构单元和衍生自式II所示单体的结构单元，
    Figure PCTCN2022130117-appb-100001
    其中，R 1、R 2、R 3各自独立地选自氢、氟、氯、氟取代的C 1-3烷基中的一种或多种，R 4、R 5各自独立地选自氢、取代或未取代的C 1-5烷基中的一种或多种，R 6选自芳香基取代的C 1-5烷基、取代或取代的芳香基中的一种或多种。
  2. 根据权利要求1中所述的含氟聚合物，其特征在于，所述式I中的R 1为氟，R 2、R 3各自独立地选自氢、氟、氯、三氟甲基中的一种或多种。
  3. 根据权利要求1或2所述的含氟聚合物，其特征在于，所述衍生自式I所示单体的结构单元的摩尔含量为50％～70％，基于所述含氟聚合物中所有结构单元的总摩尔数计。
  4. 根据权利要求1至3中任一项所述的含氟聚合物，其特征在于，所述衍生自式II所示单体的结构单元的摩尔含量为30％～50％，基于所述含氟聚合物中所有结构单元的总摩尔数计。
  5. 根据权利要求1至4中任一项所述的含氟聚合物，其特征在于，所述含氟聚合物的重均分子量为10万～14万。
  6. 根据权利要求1所述的含氟聚合物，其特征在于，所述式I所示单体选自氟乙烯、偏二氟乙烯、四氟乙烯、三氟氯乙烯、六氟丙烯中的一种或多种。
  7. 根据权利要求1至6中任一项所述的含氟聚合物，其特征在于，所述式II所示单体选自2-苄基丙烯酸、2-(4-异丁基苄基)丙烯酸、2-亚甲基-4-苯基丁酸、2-(1-苯基乙基)丙烯酸的一种或多种。
  8. 一种含氟聚合物的制备方法，其特征在于，包括以下步骤：
    在可聚合条件下，将至少一种式I所示单体和至少一种式II所示单体进行聚合反应，
    Figure PCTCN2022130117-appb-100002
    其中，R 1、R 2、R 3各自独立地选自氢、氟、氯、氟取代的C 1-3烷基中的一种或多种，R 4、R 5各自独立地选自氢、取代或未取代的C 1-5烷基中的一种或多种，R 6选自芳香基取代的C 1-5烷基、取代或取代的芳香基中的一种或多种。
  9. 根据权利要求8所述的制备方法，其特征在于，所述式I中的R 1为氟，R 2、R 3各自独立地选自氢、氟、氯、三氟甲基中的一种或多种。
  10. 根据权利要求8或9所述的制备方法，其特征在于，所述式I所示单体的摩尔含量为50％～70％，基于式I所示单体和式II所示单体的总摩尔数计。
  11. 根据权利要求8至10中任一项所述的制备方法，其特征在于，所述式II所示单体的摩尔含量为30％～50％，基于式I所示单体和式II所示单体的总摩尔数计。
  12. 根据权利要求8至11中任一项所述的制备方法，其特征在于，所述聚合反应包括第一段聚合和第二段聚合，
    第一段聚合：向反应容器内加入引发剂、乳化剂、至少一种式I所示单体以及水性介质进行第一段聚合，在所述第一段聚合中连续送入式I所示单体；
    第二段聚合：反应一段时间后，向反应容器内加入至少一种式II所示单体进行第二段聚合，在所述第二段聚合中连续送入式I所示单体。
  13. 根据权利要求12所述的制备方法，其特征在于，所述第一段聚合中通入的式I所示单体的质量为聚合反应中所供给的式I所示单体的总质量的80％～85％，所述第二段聚合中通入的式I所示单体的质量为聚合反应中所供给的式I所示单体的总质量的15％～20％。
  14. 根据权利要求12或13所述的制备方法，其特征在于，所述引发剂的质量百分比为0.5％～1.4％，基于所述式I所示单体和式II所示单体的总质量计。
  15. 根据权利要求12至14中任一项所述的制备方法，其特征在于，所述乳化剂的质量百分比为0.1％～0.4％，基于所述式I所示单体和式II所示单体的总质量计。
  16. 根据权利要求12至15中任一项所述的制备方法，其特征在于，所述第一段聚合中提供的水性介质的质量百分比为400％～600％，基于所述式I所示单体和式II所示单体的总质量计。
  17. 根据权利要求12至16中任一项所述的制备方法，其特征在于，所述第一段聚合和第二段聚合的反应压力均为6.0MPa～9.0MPa，反应温度为80℃～120℃。
  18. 根据权利要求12至17中任一项所述的制备方法，其特征在 于，所述乳化剂为全氟辛酸碱金属盐。
  19. 根据权利要求12至18中任一项所述的制备方法，其特征在于，所述引发剂为N,N二甲基苄胺、N-甲基苯丙胺中的一种或两种。
  20. 权利要求1至7中任一项所述的含氟聚合物在二次电池中的应用。
  21. 一种导电浆料，其特征在于，包括导电剂、溶剂和权利要求1至7中任一项所述的含氟聚合物。
  22. 根据权利要求21所述的导电浆料，其特征在于，所述导电剂的质量分数为10.0％～15.0％，基于所述导电浆料的总质量计。
  23. 根据权利要求21或22所述的导电浆料，其特征在于，所述含氟聚合物的质量分数为0.5％～2.5％，基于所述导电浆料的总质量计。
  24. 根据权利要求21至23中任一项所述的导电浆料，其特征在于，所述导电浆料的固含量为10.5％～17.5％，且所述导电浆料的粘度为300mPa·s～900mPa·s。
  25. 一种正极极片，包括正极集流体以及设置在正极集流体至少一个表面的正极膜层，所述正极膜层包括正极活性材料、导电剂和粘结剂，所述导电剂为权利要求21至24中任一项所述的导电浆料的沉积物。
  26. 根据权利要求25所述的正极极片，其特征在于，基于所述 正极膜层的总质量计，所述导电剂质量含量为0.5％～0.8％时，所述正极极片的膜片电阻低于0.2Ω。
  27. 根据权利要求25或26所述的正极极片，其特征在于，所述正极膜层与所述正极集流体间单位长度的粘结力不小于14N/m。
  28. 一种二次电池，其特征在于，包括负极极片、隔离膜、电解液和权利要求25至27中任一项所述正极极片。
  29. 根据权利要求28所述的二次电池，其特征在于，所述二次电池包括锂离子电池、钠离子电池、镁离子电池、钾离子电池中的至少一种。
  30. 一种电池模块，其特征在于，包括权利要求28或29所述的二次电池。
  31. 一种电池包，其特征在于，包括权利要求28或29所述的二次电池、权利要求30所述的电池模块中的至少一种。
  32. 一种用电装置，其特征在于，包括选自权利要求28或29所述的二次电池、权利要求30所述的电池模块或权利要求31所述的电池包中的至少一种。
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