WO2024092783A1 - 含氟聚合物、制备方法、绝缘涂层、二次电池、用电装置 - Google Patents

含氟聚合物、制备方法、绝缘涂层、二次电池、用电装置 Download PDF

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WO2024092783A1
WO2024092783A1 PCT/CN2022/130063 CN2022130063W WO2024092783A1 WO 2024092783 A1 WO2024092783 A1 WO 2024092783A1 CN 2022130063 W CN2022130063 W CN 2022130063W WO 2024092783 A1 WO2024092783 A1 WO 2024092783A1
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fluorine
formula
containing polymer
monomer represented
slurry
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PCT/CN2022/130063
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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
周永斌
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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/CN2022/130063 priority Critical patent/WO2024092783A1/zh
Publication of WO2024092783A1 publication Critical patent/WO2024092783A1/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
    • C08F210/00—Copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
    • C08F210/04—Monomers containing three or four carbon atoms
    • C08F210/06—Propene
    • 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 application relates to the technical field of secondary batteries, and in particular to a fluorine-containing polymer, a preparation method, an insulating coating, a secondary battery, and an electrical device.
  • an insulating coating is applied on the surface of the current collector to prevent the positive and negative electrodes from contacting each other during use, causing a short circuit, leading to safety accidents, and even fires and explosions.
  • the insulating coating is often prepared by coating the surface of the current collector with an insulating slurry formulated with a binder, inorganic insulating materials, and additives.
  • the insulating slurry in the prior art has a short process window, poor fluidity, and is prone to precipitation and clogging of the pipeline, which seriously affects the production efficiency of the pole piece. Therefore, it is urgent to develop a binder to improve the processing performance of the slurry.
  • the present application is made in view of the above-mentioned problems, and its purpose is to provide a fluorine-containing polymer and an insulating coating comprising the fluorine-containing polymer, so as to optimize the process window for preparing the insulating coating and improve the production efficiency of the insulating coating.
  • the first aspect of the present application provides a fluorine-containing polymer, which comprises a structural unit derived from a monomer represented by formula I, a structural unit derived from an olefin monomer, and a structural unit derived from a monomer represented by formula II, wherein the molar content of the structural unit derived from the monomer represented by formula I is 60% to 80%, based on the total molar number of the structural units in the fluorine-containing polymer.
  • R 1 , R 2 and R 3 are each independently selected from hydrogen, fluorine, chlorine or C 1-3 alkyl containing at least one fluorine atom, and R 4 , R 5 and R 6 are each independently selected from hydrogen, substituted or unsubstituted C 1-5 alkyl.
  • the fluorine-containing polymer provided in the present application can improve the filterability and fluidity of the slurry, so that the slurry does not gel after standing for 6 hours, significantly broadens the process window of the slurry, improves the processability of the slurry, and enables the slurry to meet the production requirements of the insulating coating without adding a dispersant, which is beneficial to optimizing the production process of the insulating coating and improving its production efficiency.
  • R 1 is fluorine
  • R 2 and R 3 are each independently selected from one or more of hydrogen, fluorine, chlorine, and trifluoromethyl
  • R 5 and R 6 are each independently selected from one or both of hydrogen and methyl.
  • the molar content of the structural unit derived from the monomer represented by formula II is 5% to 25%, based on the total molar number of all structural units in the fluorine-containing polymer.
  • the fluoropolymer Based on the total molar number of all structural units in the fluoropolymer, when the molar content of the structural unit derived from the monomer represented by Formula II is 5% to 25%, the fluoropolymer further improves the fluidity and filterability of the insulating slurry, further broadens the process window for insulating slurry processing, and the fluoropolymer enables the insulating coating to have effective adhesion.
  • the molar content of the structural unit derived from the olefin monomer is 5% to 30%, based on the total molar number of all structural units in the fluorine-containing polymer.
  • the fluoropolymer Based on the total molar number of all structural units in the fluoropolymer, when the molar content derived from olefin monomers is 5% to 30%, the fluoropolymer further improves the fluidity and filterability of the insulating slurry, further broadens the process window for insulating slurry processing, and the fluoropolymer enables the insulating coating to have effective adhesion.
  • the weight average molecular weight of the fluorine-containing polymer is 500,000-800,000.
  • Fluorine-containing polymers with a weight-average molecular weight between 500,000 and 800,000 are beneficial to further improving the fluidity and filterability of the insulating slurry, further broadening the process window for insulating slurry processing, and helping the insulating coating maintain effective adhesion.
  • the viscosity of the glue obtained by dissolving the fluorine-containing polymer in N-methylpyrrolidone is 1000-3000 mPa ⁇ s, and the mass content of the fluorine-containing polymer in the glue is 7%, based on the total mass of the glue.
  • the viscosity of the adhesive containing 7% by mass of the fluorinated polymer prepared by dissolving the fluorinated polymer in N-methylpyrrolidone is 1000-3000mPa ⁇ s, so that the insulating paste using the fluorinated polymer as a binder does not need to add additional additives, which can effectively optimize the production process, improve production efficiency, and is conducive to improving the batch stability of the insulating coating.
  • the monomer represented by formula I is selected from one or more of vinylidene fluoride, tetrafluoroethylene, chlorotrifluoroethylene, and hexafluoropropylene.
  • the olefin monomer is selected from one or more of propylene, 2-butene, and butadiene.
  • the monomer represented by formula II is selected from one or both of acrylic acid and methacrylic acid.
  • the second aspect of the present application provides a method for preparing a fluorine-containing polymer, comprising the following steps:
  • a fluorine-containing polymer is prepared by polymerizing at least one monomer represented by formula I, at least one olefin monomer and at least one monomer represented by formula II under polymerizable conditions, wherein the molar content of the monomer represented by formula I is 60% to 80%, based on the total molar number of the monomer represented by formula I, the olefin monomer and the monomer represented by formula II,
  • R 1 , R 2 and R 3 are each independently selected from hydrogen, fluorine, chlorine or C 1-3 alkyl containing at least one fluorine atom, and R 4 , R 5 and R 6 are each independently selected from hydrogen, substituted or unsubstituted C 1-5 alkyl.
  • the fluorinated polymer prepared by this method can improve the filterability and fluidity of the slurry, so that the slurry will not gel after standing for 6 hours, which significantly broadens the process window of the slurry and improves the processability of the slurry.
  • the slurry can meet the production requirements of the insulating coating without adding a dispersant, which is beneficial to optimize the production process of the insulating coating and improve its production efficiency.
  • R 1 is fluorine
  • R 2 and R 3 are each independently selected from one or more of hydrogen, fluorine, chlorine, and trifluoromethyl
  • R 5 and R 6 are each independently selected from one or both of hydrogen and methyl.
  • the polymerization reaction comprises the following steps:
  • First stage polymerization providing a first initiator, an emulsifier, at least one monomer represented by formula I and a solvent, starting the first stage polymerization, and continuously feeding the monomer represented by formula I during the first stage polymerization to maintain the initial reaction pressure;
  • Second stage polymerization After a period of reaction, olefin monomer and monomer represented by formula II are introduced into the reaction vessel for second stage polymerization; when the pressure in the reaction vessel drops to less than or equal to 0.5 MPa, the reaction is stopped, the solid and liquid are separated, and the solid phase is retained.
  • the method provided by 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 and the olefin monomer are 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 more effectively improve the filterability and fluidity of the insulating slurry than the fluorine-containing polymer prepared by simultaneously polymerizing all the monomers into the reaction vessel, further broaden the process window of the slurry, and help improve the production efficiency of the insulating coating.
  • the initial reaction pressure of the first stage polymerization is 5.5 MPa to 7.5 MPa, and the reaction temperature is 70° C. to 90° C.
  • the second stage polymerization comprises the following steps:
  • a mixed gas of the monomer represented by formula I and an olefin monomer is first fed into the reaction container.
  • Using the olefin monomer as a bridge helps to overcome the problems of large reaction differences and poor compatibility between the monomer represented by formula I and the monomer represented by formula II, thereby improving the degree of polymerization of the fluorine-containing polymer.
  • the ratio of the total moles of olefin monomers supplied during the polymerization reaction to the total moles of the monomers represented by formula I is 1:16-1:2.
  • the ratio of the total moles of olefin monomers supplied during the polymerization reaction to the total moles of the monomers represented by formula I is 1:16-1:3.
  • the molar ratio of the olefin monomer to the monomer represented by formula I is 1:1-2:1.
  • the molar ratio of the olefin monomer to the monomer represented by formula II is 3:1-4:1.
  • the second stage polymerization further comprises the following steps:
  • the first initiator and the second initiator are added into the reaction container.
  • the second stage polymerization further comprises the following steps:
  • a second initiator is added into the reaction container.
  • the first initiator is a persulfate, which can be selected from one or more of potassium persulfate and ammonium persulfate.
  • the second initiator is a thiosulfate salt, which can be selected from sodium thiosulfate.
  • the third aspect of the present application provides an application of the fluorine-containing polymer of the first aspect in a secondary battery.
  • 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 fourth aspect of the present application provides an insulating coating, comprising a binder and an inorganic insulating material, wherein the binder is the fluorine-containing polymer of the first aspect.
  • the insulating coating is easy to process and has good uniformity, which helps to improve battery production capacity.
  • the binder has a mass content of 7.0% to 13.0%, based on the total mass of the insulating coating.
  • the binder When the mass content of the binder is 7.0%-13.0% of the total mass of the insulating coating, the binder further improves the fluidity and filterability of the insulating slurry, further broadens the process window for insulating slurry processing, and the binder can ensure that the insulating coating maintains effective bonding.
  • the inorganic insulating material comprises a colored oxide, which may be selected from black zirconium dioxide, yellow zirconium dioxide, red zirconium dioxide or green zirconium dioxide.
  • the mass content of the colored oxide is 0.2%-3%, based on the total mass of the insulating coating.
  • a fifth aspect of the present application provides a method for preparing an insulating coating, comprising the following steps:
  • the slurry is coated on a current collector to prepare an insulating coating.
  • the insulating coating prepared by the method has high efficiency and uniform quality.
  • the viscosity of the slurry is 2500-4000 mPa ⁇ s.
  • the viscosity of the slurry with a solid content of 30%-40% is 2500-4000mPa ⁇ s, and it can be directly used for production coating without adding additional additives, which is beneficial to improving production efficiency and reducing production costs.
  • the mixing of the inorganic insulating material and the glue comprises the following steps:
  • the inorganic insulating material except the colored oxide is mixed with the glue solution, and the colored oxide is added after stirring, and the mixture is stirred again to prepare the slurry.
  • Adding colored oxides in the final stage of the slurry preparation process is beneficial to improving the uniformity of the color of the prepared insulating coating and to improving the subsequent laser cutting speed and laser cutting quality.
  • the sixth aspect of the present application provides a secondary battery, comprising a positive electrode plate, a separator, a negative electrode plate and an electrolyte, wherein the positive electrode plate and/or the negative electrode plate comprises the insulating coating of the fourth aspect of the present application; optionally, 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, or the battery pack of the eighth aspect of the present application.
  • FIG1 is a schematic diagram of a pole piece including an insulating coating
  • FIG2 is a schematic diagram of a secondary battery according to an embodiment of the present application.
  • FIG3 is an exploded view of the secondary battery of one embodiment of the present application shown in FIG2 ;
  • FIG4 is a schematic diagram of a battery module according to an embodiment of the present application.
  • FIG5 is a schematic diagram of a battery pack according to an embodiment of the present application.
  • FIG6 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG5 ;
  • FIG. 7 is a schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of the present application.
  • FIG8 is a microscope image of the pole piece after laser cutting of Example 26 of the present application, (A) is a plan view of the pole piece cut, and (B) is a cross-sectional view of the pole piece cut;
  • FIG. 9 is a microscope image of the pole piece after laser cutting of Example 6 of the present application, (A) is a plan view of the pole piece cut, and (B) is a cross-sectional view of the pole piece cut.
  • “Scope” disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range.
  • the scope limited in this way can include or exclude end values, and can be arbitrarily combined, that is, any lower limit can form a scope with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected.
  • the minimum range values 1 and 2 listed, and if the maximum range values 3,4 and 5 are listed, the following scope can be fully expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5.
  • 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).
  • an insulating coating 63 is coated between the current collector 61 used to form the pole ear and the active material layer 62 to prevent the positive and negative electrodes from directly contacting each other during use of the battery cell to form a short circuit, causing safety accidents, and even fires and explosions.
  • inorganic materials Due to the high resistance of inorganic materials, inorganic materials are often dispersed in a binder to form a slurry to prepare an insulating coating.
  • the viscosity of traditional binders is too large and the slurry is prone to precipitation, resulting in poor slurry uniformity and large performance variance between batches of insulating coatings.
  • the present application develops a binder that makes the slurry have better fluidity and filterability to improve the production efficiency and production quality of the insulating coating.
  • a fluorine-containing polymer which comprises a structural unit derived from a monomer represented by formula I, a structural unit derived from an olefin monomer, and a structural unit derived from a monomer represented by formula II, wherein the molar content of the structural unit derived from the monomer represented by formula I is 60% to 80%, based on the total molar number of the structural units in the fluorine-containing polymer.
  • R 1 , R 2 and R 3 are each independently selected from hydrogen, fluorine, chlorine or C 1-3 alkyl containing at least one fluorine atom, and R 4 , R 5 and R 6 are each independently selected from hydrogen, substituted or unsubstituted C 1-5 alkyl.
  • 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 1-5 alkyl refers to a straight or branched hydrocarbon chain radical consisting solely of carbon and hydrogen atoms, with no unsaturation in the radical, having from one to five carbon atoms, and attached to the remainder of the molecule by a single bond.
  • C 1-3 alkyl should be interpreted accordingly. Examples of C 1-5 alkyl include, but are not limited to, methyl, ethyl, n-propyl, 1-methylethyl (isopropyl), butyl, pentyl.
  • the C 1-3 alkyl radical containing at least one fluorine atom is -CF 3 , -CH 3 CH 2 F, or -CH 2 FCH 2 F.
  • 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.
  • examples of olefin monomers include, but are not limited to, ethylene, propylene, butene, and butadiene.
  • R 1 is fluorine
  • R 2 and R 3 are each independently selected from one or more of hydrogen, fluorine, chlorine, and trifluoromethyl
  • R 5 and R 6 are each independently selected from one or both of hydrogen and methyl.
  • the fluoropolymer includes at least two structural units derived from different monomers of Formula I, and one of the structural units is derived from vinylidene fluoride. Different monomer types help reduce the ordered arrangement of the fluoropolymer long chains, reduce crystallinity, and increase flexibility.
  • the monomer represented by formula I is selected from one or more of vinylidene fluoride, tetrafluoroethylene, chlorotrifluoroethylene, and hexafluoropropylene.
  • the olefin monomer is selected from one or more of propylene, 2-butene, and butadiene.
  • the monomer represented by formula II is selected from one or both of acrylic acid and methacrylic 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-ethylene-acrylic acid copolymer, vinylidene fluoride-butadiene-acrylic acid copolymer, vinylidene fluoride-propylene-acrylic acid copolymer, vinylidene fluoride-ethylene-methacrylic acid copolymer, vinylidene fluoride-hexafluoropropylene-ethylene-acrylic acid copolymer, vinylidene fluoride-hexafluoropropylene-ethylene-methacrylic acid copolymer, vinylidene fluoride-trifluorochloroethylene-butadiene-methacrylic acid copolymer.
  • the molar content of the structural unit derived from the monomer represented by Formula I can be 60%, 65%, 70%, 75% or 80%, based on the total moles of the structural unit in the fluorine-containing polymer.
  • the fluorine element in the structural unit derived from the monomer shown in formula I can form hydrogen bonds with the hydroxyl group or/and carboxyl group on the surface of the current collector, so that the insulating coating has good adhesion and is not easy to fall off during the manufacturing and use process, causing safety accidents.
  • the structural unit derived from the olefin monomer and the monomer shown in formula II can effectively reduce the fluorine content of the fluorine-containing polymer, so that the molar content of the structural unit derived from the monomer shown in formula I is 60%-80%, which can improve the slurry gel phenomenon caused by the fluorine element.
  • the structural unit derived from the olefin monomer and 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, stabilize the slurry, alleviate the sedimentation of the slurry, and effectively improve the filterability of the slurry.
  • the fluorinated polymer provided in the present application can improve the filterability and fluidity of the slurry, so that the slurry does not gel after standing for 6 hours, significantly broadens the process window of the slurry, improves the processability of the slurry, and enables the slurry to meet the production requirements of the insulating coating without adding a dispersant, which is beneficial to optimizing the production process of the insulating coating and improving its production efficiency.
  • 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.
  • the molar content of the structural unit derived from the monomer shown in formula II is 5% to 25%, 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 selected as any one of 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, and 25%, based on the total molar number of all structural units in the fluoropolymer.
  • the molar content of the structural unit derived from the olefin monomer is 5% to 30%, based on the total moles of all structural units in the fluoropolymer. In some embodiments, the molar content of the structural unit derived from the olefin monomer can be selected as any one of 5%, 10%, 15%, 20%, 25%, and 30%, based on the total moles of all structural units in the fluoropolymer.
  • the fluoropolymer Based on the total molar number of all structural units in the fluoropolymer, when the molar content derived from olefin monomers is 5% to 30%, the fluoropolymer further improves the fluidity and filterability of the insulating slurry, further broadens the process window for insulating slurry processing, and the fluoropolymer enables the insulating coating to maintain effective adhesion.
  • the weight average molecular weight of the fluorine-containing polymer is 500,000-800,000. In some embodiments, the weight average molecular weight of the fluorine-containing polymer can be any one of 500,000, 600,000, 650,000, 700,000, 750,000, and 800,000.
  • 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
  • Fluorine-containing polymers with a weight-average molecular weight between 500,000 and 800,000 give the adhesive a suitable viscosity, which is beneficial to further improve the fluidity and filterability of the insulating slurry and further broaden the process window for insulating slurry processing; at the same time, fluorine-containing polymers with a suitable weight-average molecular weight are conducive to forming a three-dimensional network bonding structure, which helps the insulating coating maintain effective bonding.
  • the viscosity of the glue obtained by dissolving the fluorinated polymer in N-methylpyrrolidone is 1000-3000 mPa ⁇ s, and the mass content of the fluorinated polymer in the glue is 7%, based on the total mass of the glue.
  • the viscosity of the glue obtained by dissolving the fluorinated polymer in N-methylpyrrolidone can be any one of 1000 mPa ⁇ s, 1500 mPa ⁇ s, 2000 mPa ⁇ s, 2500 mPa ⁇ s, and 3000 mPa ⁇ s, and the mass content of the fluorinated polymer in the glue is 7%, based on the total mass of the glue.
  • the viscosity of the fluorine-containing polymer glue can be tested by a method known in the art, such as using a rotary viscosity tester.
  • the viscosity of the glue obtained by dissolving the fluorinated polymer in N-methylpyrrolidone is 1000-3000mPa ⁇ s, and the mass content of the fluorinated polymer in the glue is 7%.
  • the insulating paste using the fluorinated polymer as a binder does not need to add additional additives, which can effectively optimize the production process and improve production efficiency.
  • the glue within this viscosity range has both fluidity and viscosity, which can not only improve the bonding force of the insulating coating, but also achieve uniform coating, which is conducive to improving the batch stability of the insulating coating.
  • a method for preparing a fluorine-containing polymer comprising the following steps:
  • a fluorine-containing polymer is prepared by polymerizing at least one monomer represented by formula I, at least one olefin monomer and at least one monomer represented by formula II under polymerizable conditions, wherein the molar content of the monomer represented by formula I is 60% to 80%, based on the total molar number of the monomer represented by formula I, the olefin monomer and the monomer represented by formula II,
  • R 1 , R 2 and R 3 are each independently selected from hydrogen, fluorine, chlorine or C 1-3 alkyl containing at least one fluorine atom, and R 4 , R 5 and R 6 are each independently selected from hydrogen, substituted or unsubstituted C 1-5 alkyl.
  • polymerizable conditions refers to those conditions including temperature, pressure, reactant concentrations, optional solvents/diluents, reactant mixing/addition parameters selected by one skilled in the art, and other conditions that facilitate the reaction of one or more monomers within at least one polymerization reactor.
  • the fluorinated polymer prepared by this method can improve the filterability and fluidity of the slurry, so that the slurry will not gel after standing for 6 hours, which significantly broadens the process window of the slurry and improves the processability of the slurry.
  • the slurry can meet the production requirements of the insulating coating without adding a dispersant, which is beneficial to optimize the production process of the insulating coating and improve its production efficiency.
  • R 1 is fluorine
  • R 2 and R 3 are each independently selected from one or more of hydrogen, fluorine, chlorine, and trifluoromethyl
  • R 5 and R 6 are each independently selected from one or both of hydrogen and methyl.
  • At least two monomers of Formula I are added during the polymer preparation process, wherein one monomer of Formula I is polyvinylidene fluoride.
  • the addition of different monomers helps to reduce the order of the long chain of the fluorine-containing polymer, reduce the crystallinity, and improve the flexibility of the fluorine-containing polymer.
  • the polymerization reaction comprises the following steps:
  • First stage polymerization providing a first initiator, an emulsifier, at least one monomer represented by formula I and a solvent to carry out first stage polymerization, and continuously feeding the monomer represented by formula I during the first stage polymerization to maintain the initial reaction pressure;
  • Second stage polymerization After a period of reaction, olefin monomer and monomer represented by formula II are introduced into the reaction vessel for second stage polymerization; when the pressure in the reaction vessel drops to less than or equal to 0.5 MPa, the reaction is stopped, the solid and liquid are separated, and the solid phase is retained.
  • continuous feed refers to the slow, small, incremental addition of monomers.
  • the first initiator is a persulfate, which can be selected from one or more of potassium persulfate and ammonium persulfate. Potassium persulfate effectively decomposes above 60° C. to generate free radical ions or ionic free radicals, which are suitable as an initiator for emulsion polymerization.
  • the emulsifier is an alkali metal salt of perfluorooctanoic acid, optionally a sodium salt of perfluorooctanoic acid.
  • the solvent is an aqueous solvent, which may be deionized water.
  • the method provided by the present application first continuously feeds the monomers shown in formula I to form fluorine-containing segments, so that the fluorine-containing polymer has high thermal stability; then the monomers shown in formula II and olefin monomers are introduced to reduce the contact between the fluorine-containing segments and the external environment, effectively alleviating the gel phenomenon caused by fluorine elements.
  • the fluorine-containing polymer prepared by this method can more effectively improve the filterability and fluidity of the slurry than the fluorine-containing polymer prepared by simultaneously polymerizing all the monomers into the reaction vessel, further broaden the process window of the slurry, and help improve the production efficiency of the insulating coating.
  • the initial reaction pressure of the first stage polymerization is 5.5 MPa to 7.5 MPa, and the reaction temperature is 70° C. to 90° C.
  • the second stage polymerization comprises the following steps:
  • a mixed gas of the monomer represented by formula I and an olefin monomer is first fed into the reaction container.
  • Using the olefin monomer as a bridge helps to overcome the problems of large reaction differences and poor compatibility between the monomer represented by formula I and the monomer represented by formula II, thereby improving the degree of polymerization of the fluorine-containing polymer.
  • the ratio of the total moles of olefin monomers supplied during the polymerization reaction to the total moles of the monomers represented by Formula I is 1:16-1:2.
  • the ratio of the total moles of the monomers of Formula II supplied during the polymerization reaction to the total moles of the monomers of Formula I is 1:16-1:3.
  • the molar ratio of the olefin monomer to the monomer represented by Formula I is 1:1-2:1.
  • the molar ratio of the olefin monomer to the monomer represented by Formula II is 3:1-4:1.
  • the second stage polymerization further comprises the following steps:
  • the first initiator and the second initiator are added into the reaction container.
  • the second initiator is thiosulfate, which can be selected from sodium thiosulfate.
  • thiosulfate is easy to react with the first initiator persulfate in the reaction container to generate two free radicals, effectively initiating the polymerization of olefin monomers.
  • the second stage polymerization further comprises the following steps:
  • a second initiator is added into the reaction container.
  • a fluorinated polymer in any embodiment is provided for use in a secondary battery, and optionally, 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.
  • the fluorinated polymer is used as a binder in a secondary battery.
  • the fluorinated polymer is used as a binder for an insulating coating in a secondary battery.
  • an insulating coating comprising a binder and an inorganic insulating material, wherein the binder is a fluorine-containing polymer in any embodiment.
  • binder refers to a chemical compound, polymer or mixture that forms a colloidal solution or colloidal dispersion in a dispersion medium.
  • inorganic insulating material refers to inorganic materials with a resistivity greater than 10 6 ⁇ cm and their precursors, including but not limited to boehmite, barium carbonate, barium sulfate, aluminum oxide, zirconium dioxide, calcium carbonate, and silicon dioxide.
  • the inorganic insulating material includes boehmite.
  • Boehmite (AlOOH) is a precursor of ⁇ -Al2O3, has excellent adhesion to the current collector, and is not easy to fall off as an insulating coating.
  • the inorganic insulating material includes zirconium dioxide. Zirconium dioxide has high electrical resistance and is suitable for preparing insulating coatings.
  • the dispersion medium of the binder is an aqueous solvent, such as deionized water, that is, the binder is dissolved in the aqueous solvent.
  • the dispersion medium of the binder 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. That is, the binder is dissolved in the oily solvent.
  • a binder is used to fix the inorganic insulating materials in place and adhere them to the current collector to form an insulating coating.
  • the insulating coating is easy to process and has good uniformity, which helps to improve battery production capacity.
  • the binder has a mass content of 7.0%-13.0%, based on the total mass of the insulating coating. In some embodiments, the binder has a mass content of 7.0%, 8.0%, 9.0%, 10.0%, 11.0%, 12.0%, 13.0%, based on the total mass of the insulating coating.
  • the insulating slurry When the mass content of the binder is 7.0%-13.0% of the total mass of the insulating coating, the insulating slurry has a suitable viscosity, which further improves the fluidity and filterability of the insulating slurry and further broadens the process window for insulating slurry processing; at the same time, the mass content of the binder in a suitable range ensures that the insulating coating and the current collector have sufficient bonding force.
  • the inorganic insulating material comprises a colored oxide, which can be selected from one or more of black zirconium dioxide, yellow zirconium dioxide, red zirconium dioxide, and green zirconium dioxide.
  • the colored oxide is colored zirconium dioxide.
  • the inorganic insulating material comprises black zirconium dioxide.
  • Laser cutting refers to the technology of processing the material by irradiating the workpiece with a focused high-power density laser beam to rapidly heat, melt, vaporize, ablate or decompose the irradiated material.
  • the application of laser cutting technology in secondary batteries mainly includes laser pole piece cutting, pole ear cutting and diaphragm cutting. At present, there are problems such as many burrs in the cutting area and limited maximum cutting speed in laser cutting of pole pieces.
  • inorganic insulating materials are generally colorless or white powders.
  • the inclusion of colored oxides in inorganic insulating materials can increase the maximum cutting speed of pole pieces by more than 30%, which helps to significantly increase the battery production capacity.
  • the colored oxides in the inorganic insulating materials can reduce the heat affected zone of the laser, improve the cutting quality, reduce cutting burrs, and reduce the impact of the processing process on battery performance.
  • the mass content of the colored oxide is 0.2%-3%, based on the total mass of the insulating coating.
  • the mass content of colored oxides in the insulating coating is 0.2%-3%, it can not only improve the cutting speed during the laser cutting and forming process of the pole piece, but also take into account the raw material cost, which helps to maximize the efficiency of laser cutting performance.
  • the colored oxide is black zirconium oxide.
  • the colored oxide accounts for more than 3.0% by mass of the insulating coating, there is no color difference between the insulating coating and the active material layer, and the laser cutting system is difficult to identify and locate, which is not conducive to accurate cutting of size.
  • a method for preparing an insulating coating comprising the following steps:
  • a binder Dispersing a binder in a solvent to prepare a glue solution, wherein the binder is a fluorine-containing polymer in any embodiment
  • the slurry is coated on a current collector to prepare an insulating coating.
  • the solid content of the slurry is 30% to 40%.
  • the slurry has a suitable viscosity, which is beneficial to the subsequent coating and drying work; on the other hand, the suitable slurry viscosity can improve the stability of the slurry and facilitate the preservation of the slurry.
  • the insulating coating prepared by the above method has high efficiency and does not require the addition of other additives, which is beneficial to saving production processes and improving production efficiency.
  • the viscosity of the slurry when the solid content of the slurry is 30%-40%, the viscosity of the slurry is 2500-4000 mPa ⁇ s. In some embodiments, when the solid content of the slurry is 30%-40%, the viscosity of the slurry can be any one of 2750 mPa ⁇ s, 3000 mPa ⁇ s, 3250 mPa ⁇ s, 3500 mPa ⁇ s, 3750 mPa ⁇ s, and 4000 mPa ⁇ s.
  • the viscosity of the slurry with a solid content of 30%-40% is 2500-4000mPa ⁇ s, and it can be directly used for production coating without adding additional additives, which is beneficial to improving production efficiency and reducing production costs.
  • mixing the inorganic insulating material with the glue comprises the following steps:
  • the inorganic insulating material except the colored oxide is mixed with the glue, and the colored oxide is added after stirring, and the colored oxide is stirred again to prepare the slurry.
  • Adding colored oxides in the final stage of the slurry preparation process is beneficial to improving the uniformity of the color of the prepared insulating coating and to improving the subsequent laser cutting speed and quality.
  • a secondary battery comprising a positive electrode sheet, a separator, a negative electrode sheet and an electrolyte, wherein the positive electrode sheet and/or the negative electrode sheet comprises an insulating coating as described in any embodiment.
  • 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.
  • active ions are embedded and removed back and forth between the positive electrode sheet and the negative electrode sheet.
  • the electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet.
  • the separator is arranged between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer and an insulating coating layer disposed on at least one surface of the positive electrode current collector.
  • the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material layer and the insulating coating layer are disposed on either or both of the two facing surfaces of the positive electrode current collector.
  • the positive electrode current collector may be a metal foil or a composite current collector.
  • aluminum foil may be used as the metal foil.
  • 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 active material layer may further 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-hexafluoropropylene-tetrafluoroethylene terpolymer vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer
  • the positive electrode active material layer may further optionally include:
  • the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.
  • the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode active material layer, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode active material layer is obtained.
  • a solvent such as N-methylpyrrolidone
  • the components for preparing the insulating coating such as the fluorine-containing polymer, are dispersed in a solvent (such as N-methylpyrrolidone) to form a glue solution; the inorganic insulating material and the glue solution are mixed and stirred to prepare an insulating slurry; the insulating slurry is coated on the positive electrode current collector along the edge of the positive electrode active material layer, and after drying, cold pressing and other processes, the insulating coating is obtained.
  • the positive electrode sheet can be obtained by using the same method to obtain the positive electrode active material layer and the insulating coating on the other side of the current collector.
  • the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer and an insulating coating layer disposed on at least one surface of the negative electrode current collector.
  • 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 adopt the negative electrode active material for the 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 active material 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 active material 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 active material layer may further 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 active material layer, 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 current collector, and after drying, cold pressing and other processes, the negative electrode active material layer is obtained.
  • a solvent such as deionized water
  • the components for preparing the insulating coating such as the fluorinated polymer, are dispersed in a solvent (such as N-methylpyrrolidone) to form a glue solution; the inorganic insulating material and the glue solution are mixed and stirred to prepare an insulating slurry; the insulating slurry is coated on the negative electrode current collector along the edge of the negative electrode active material layer, and after drying, cold pressing and other processes, the insulating coating is obtained.
  • the negative electrode sheet can be obtained by using the same method to obtain the negative electrode active material layer and the insulating coating on the other side of the negative electrode current collector.
  • 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 can 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 package of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.
  • the outer package 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.
  • FIG2 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.
  • FIG4 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.
  • FIG5 and FIG6 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 to these.
  • a secondary battery, a battery module or a battery pack may be selected according to its usage requirements.
  • FIG7 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.
  • a battery pack or a battery module may be used.
  • the device may be a mobile phone, a tablet computer, a notebook computer, etc.
  • a device is usually required to be light and thin, 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 85°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 pressure in the autoclave drops to 0.2 MPa, and the unreacted butadiene monomer is recovered for reaction; the product is condensed, washed, separated, dried, and crushed to obtain a vinylidene fluoride-butadiene-acrylic acid copolymer binder.
  • the above insulating slurry was coated on a 13 ⁇ m aluminum foil with a coating thickness of 15 ⁇ 1 ⁇ m.
  • the slurry was dried to form an insulating coating.
  • the insulating coating was obtained on the other side of the aluminum foil using the same method.
  • the thickness of the insulating coating on both sides plus the aluminum foil was 43 ⁇ 2 ⁇ m.
  • the preparation methods of the insulating coatings of Examples 2 to 26 and Comparative Examples 1 to 4 are similar to the preparation method of Example 1, but the parameters for preparing the binder and the proportion of black zirconium dioxide in the slurry are adjusted.
  • Example 8 to 11 the reaction conditions in the synthesis of the binder were adjusted so that the binder had different weight average molecular weights, and other parameters were kept the same as in Example 6.
  • the specific parameters are shown in Tables 1 and 2.
  • the preparation method of the fluorine-containing polymer with a weight average molecular weight of 500,000 in Example 8 is basically the same as that in Example 6, except that the amount of 5% potassium persulfate solution added was adjusted from 71.4 g to 78.54 g.
  • the preparation method of the fluorine-containing polymer with a weight average molecular weight of 800,000 in Example 9 is basically the same as the steps in Example 6, except that the reaction temperature is adjusted from 85°C to 80°C, and the amount of 5% potassium persulfate solution added is adjusted from 71.4g to 67.83g.
  • the preparation method of the fluorine-containing polymer with a weight average molecular weight of 900,000 in Example 10 is basically the same as the steps in Example 6, except that the reaction temperature is adjusted from 85°C to 80°C, and the amount of 5% potassium persulfate solution added is adjusted from 71.4g to 64.26g.
  • the preparation method of the fluorine-containing polymer with a weight average molecular weight of 400,000 in Example 11 is basically the same as the steps in Example 6, except that the amount of 5% potassium persulfate solution added is adjusted from 71.4 g to 82.11 g.
  • Example 12 the mass fraction of the binder in the slurry was adjusted, and other parameters remained consistent with those in Example 6.
  • the specific parameters are shown in Tables 1 and 2.
  • Example 16-19 the solid content of the slurry was adjusted, and other parameters were kept consistent with those in Example 6. The specific parameters are shown in Tables 1 and 2.
  • Example 20 butadiene in the binder synthesis monomer is replaced by propylene, and other parameters are consistent with Example 6.
  • the specific parameters are shown in Tables 1 and 2.
  • the binder is a vinylidene fluoride-butadiene-acrylic acid copolymer prepared by a conventional method, and the synthesis method thereof is as follows: 30 kg of deionized water (conductivity is less than or equal to 2 ⁇ s/cm), 21 g of alkali metal perfluorooctanoate, and 71.4 g of 5% potassium persulfate solution are sequentially added into a reactor, and the reactor is closed;
  • 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 85°C to start the reaction.
  • vinylidene fluoride monomer and butadiene monomer were continuously introduced to maintain the reaction pressure in the kettle unchanged.
  • the total weight of the vinylidene fluoride monomer and butadiene monomer introduced was 5120g and 540g respectively.
  • the pressure in the autoclave drops to 0.0-0.5 MPa, and the unreacted butadiene monomer is recovered; the reaction product is condensed, washed, separated, dried, and crushed to obtain a vinylidene fluoride-butadiene-acrylic acid copolymer binder.
  • Example 22 the mass content of black zirconium dioxide in the slurry was changed, and other parameters remained consistent with Example 6.
  • the specific parameters are shown in Table 3.
  • a vinylidene fluoride polymer is used as a binder, which is a HSV900 model produced by Arkema of France.
  • the binder is a vinylidene fluoride-butadiene copolymer, and its synthesis method is basically the same as that of Example 1, except that when the vinylidene fluoride monomer is 80% of the total mass of the vinylidene fluoride monomer, 30.6 g of a 5% concentration potassium persulfate solution and 19.2 g of a 5% concentration sodium thiosulfate are added, and the reaction pressure is maintained.
  • a mixed gas of vinylidene fluoride monomer and butadiene is introduced into the reactor, wherein the mass of butadiene in the mixed gas is 2160 g, and the mass of the vinylidene fluoride monomer is 756.7 g.
  • the binder is a vinylidene fluoride-acrylic acid copolymer, and its synthesis method is basically the same as that in Example 1, except that when the vinylidene fluoride monomer introduced is 80% of the total mass of the vinylidene fluoride monomer, 30.6 g of 5% concentration potassium persulfate solution and 19.2 g of 5% concentration sodium thiosulfate are added, 2880 g of acrylic acid is added to the reactor to maintain the reaction pressure, and 756.7 g of vinylidene fluoride monomer is continued to be introduced.
  • the binder is a vinylidene fluoride-butadiene-acrylic acid copolymer, and its synthesis method is the same as that of Example 1, except that the molar content of the synthetic monomers is adjusted. For details, see Tables 1 and 2.
  • the insulating coatings obtained in the above Examples 1 to 26 and Comparative Examples 1 to 4 were subjected to performance tests.
  • the test method is as follows:
  • 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 HT5DMF7.8 ⁇ 300mm+Styragel HT4) was selected.
  • a 3.0% fluorinated polymer 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
  • NMP N-methylpyrrolidone
  • the adhesion test process of the embodiments and comparative examples of the present application is as follows: Use a blade to cut a sample with a width of 30mm and a length of 100-160mm, and stick a special double-sided tape on the steel plate, with a tape width of 20mm and a length of 90-150mm. Stick the insulating coating surface of the pole piece sample cut 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 pole piece and a length of 250mm on the pole piece current 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 pole piece 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 of the electrode when the force is balanced is divided by the width of the tape as the bonding force of the insulating coating per unit length to characterize the bonding strength between the insulating coating and the current collector.
  • a Dazzle laser die-cutting machine was used, and the laser output power was set to 80% of the maximum output power and the laser frequency was 1000KHz.
  • the maximum cutting speed and cutting quality when cutting the pole pieces coated with insulating coatings in different embodiments were compared. If the CCD camera on the die-cutting machine can recognize it, it is judged as Y. If the CCD camera on the die-cutting machine cannot recognize it, it is judged as N. After laser cutting, the cross-sectional morphology after cutting is observed through an optical microscope. If there are obvious metal burrs on the cross-section after cutting, it is judged as not passing; if there are no obvious metal burrs on the cross-section after cutting, it is judged as passing. Samples are taken from one hundred batches of cut products, and the pass rate of one hundred batches is calculated.
  • FIG8 is a microscopic image of the pole piece coated with the insulating coating after laser cutting in Example 26, wherein FIG8A is a plan view of the pole piece cut, and FIG8B is a cross-sectional view of the pole piece cut.
  • FIG9 is a microscopic image of the pole piece after laser cutting in Example 6, wherein FIG9A is a plan view of the pole piece cut, and FIG9B is a cross-sectional view of the pole piece cut. From the comparison of FIG8 and FIG9, it can be seen that the pole piece with black zirconium dioxide added to the insulating coating has significantly reduced burr amount and burr length after laser cutting, which effectively improves the laser cutting quality of the pole piece.
  • the binders in Examples 1-21 are all fluoropolymers, including structural units derived from vinylidene fluoride, structural units derived from olefins (butadiene or propylene), and structural units derived from acrylic acid.
  • the molar content of the structural units derived from vinylidene fluoride in the polymer is 60% to 80%, based on the total molar number of the structural units in the fluoropolymer.
  • the above-mentioned fluoropolymers as binders have achieved good results.
  • the fluoropolymer provided in this application improves the slurry in terms of filterability and fluidity after standing for 6 hours.
  • the fluoropolymer disclosed in this application can comprehensively improve the fluidity, filterability and bonding properties of the slurry, taking into account the processing performance and performance of the slurry.
  • the molar content of the structural units derived from acrylic acid in the fluoropolymer is 5% to 20%. Based on the total molar number of all structural units in the fluoropolymer, the fluoropolymer also improves the fluidity of the slurry after standing for 12 hours, further broadening the process window of the slurry.
  • the molar content of the structural units derived from olefin monomers in the fluoropolymer is 5% to 30%. Based on the total molar number of all structural units in the fluoropolymer, the fluoropolymer enables the slurry to improve the processing performance while taking into account the bonding strength.
  • the viscosity of the slurry containing 7% by mass of the fluorinated polymer prepared by dissolving the fluorinated polymer in N-methylpyrrolidone is 2500-5000 mPa ⁇ s. This makes it unnecessary to add additional dispersants or thickeners to improve the processing performance of the insulating coating slurry prepared from the fluorinated polymer, which helps to improve production efficiency and optimize the production process.
  • Example 6 From the comparison between Example 6 and Example 21, it can be seen that the fluorine-containing polymer prepared by the method disclosed in the present application can more effectively improve the filterability and fluidity of the slurry and improve the processing performance of the slurry than the fluorine-containing binder synthesized by the traditional method.

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Abstract

一种含氟聚合物、制备方法、绝缘涂层、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、衍生自烯烃单体的结构单元和衍生自式II所示单体的结构单元；基于含氟聚合物中结构单元的总摩尔数计，衍生自式I所示单体的结构单元的摩尔含量为60%〜80%。其中，R 1、R 2、R 3各自独立地选自氢、氟、氯或至少含有一个氟原子的C 1-3烷基，R 4、R 5、R 6各自独立地选自氢或取代或未取代的C 1-5烷基。

Description

含氟聚合物、制备方法、绝缘涂层、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、制备方法、绝缘涂层、二次电池、用电装置。
背景技术
电芯极片在制备过程中，会在集流体表面涂覆绝缘涂层，以防止电芯在使用过程中正极和负极接触形成短路，引发安全事故，甚至导致火灾、爆炸的发生。绝缘涂层常通过以粘结剂、无机绝缘材料、助剂为配方的绝缘浆料在集流体表面的涂覆制备，然而现有技术中的绝缘浆料工艺窗口短、流动性差、易发生沉淀堵塞管道，严重影响极片的生产效率。因此，亟需开发出一种粘结剂以改善浆料的加工性能。
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绝缘涂层，以优化绝缘涂层制备的工艺窗口、提高绝缘涂层的生产效率。
本申请的第一方面提供了一种含氟聚合物，其包含衍生自式I所示单体的结构单元、衍生自烯烃单体的结构单元和衍生自式II所示单体的结构单元，所述衍生自式I所示单体的结构单元的摩尔含量为60％～80％，基于所述含氟聚合物中结构单元的总摩尔数计，
Figure PCTCN2022130063-appb-000001
其中，R 1、R 2、R 3各自独立地选自氢、氟、氯或至少含有一个氟原子的C 1-3烷基，R 4、R 5、R 6各自独立地选自氢、取代或未取代的C 1-5烷基。
本申请提供的含氟聚合物能够提高浆料的过滤性和流动性，使得浆料在静置6小时后不发生凝胶，显著拓宽了浆料的工艺窗口，改善了浆料的可加工性，使得浆料在无需添加分散剂的情况下就能够满足绝缘涂层的生产需求，有利于优化绝缘涂层的生产工艺和提高其生产效率。
在任意实施方式中，所述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，R 5、R 6各自独立地选自氢、甲基中的一种或两种。
在任意实施方式中，所述衍生自式II所示单体的结构单元的摩尔含量为5％～25％，基于所述含氟聚合物中所有结构单元的总摩尔数计。
基于含氟聚合物中所有结构单元的总摩尔数计，衍生自式II所示单体的结构单元的摩尔含量为5％～25％时，含氟聚合物使得绝缘浆料的流动性和过滤性进一步提高，绝缘浆料加工的工艺窗口进一步拓宽，且含氟聚合物使得绝缘涂层能够兼具有效的粘结力。
在任意实施方式中，所述衍生自烯烃单体的结构单元的摩尔含量为5％～30％，基于所述含氟聚合物中所有结构单元的总摩尔数计。
基于含氟聚合物中所有结构单元的总摩尔数计，衍生自烯烃单体的摩尔含量为5％～30％时，含氟聚合物使得绝缘浆料的流动性和过滤性进一步提高，绝缘浆料加工的工艺窗口进一步拓宽，且含氟聚合物使得绝缘涂层能够兼具有效的粘结力。
在任意实施方式中，所述含氟聚合物的重均分子量为50万-80万。
重均分子量在50万-80万之间的含氟聚合物有利于绝缘浆料的流动性和过滤性的进一步提高，绝缘浆料加工的工艺窗口进一步拓宽，且有助于绝缘涂层保持有效的粘结力。
在任意实施方式中，所述含氟聚合物溶解于N-甲基吡咯烷酮制得的胶液的粘度为1000-3000mPa·s，所述胶液中所述含氟聚合物的质量含量为7％，基于所述胶液的总质量计。
含氟聚合物溶解于N-甲基吡咯烷酮制得的含有质量含量为7％的含氟聚合物的胶液的粘度为1000-3000mPa·s，使得以此含氟聚合物作 为粘结剂的绝缘浆料无需再添加额外的助剂，能够有效优化生产工艺、提高生产效率，同时有利于提高绝缘涂层的批次稳定性。
在任意实施方式中，所述式Ⅰ所示单体选自偏二氟乙烯、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，所述烯烃单体选自丙烯、2-丁烯、丁二烯中的一种或多种。
在任意实施方式中，所述式II所示单体选自丙烯酸、甲基丙烯酸中的一种或两种。
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、至少一种烯烃单体和至少一种式II所示单体进行聚合反应制备含氟聚合物，所述式I所示单体的摩尔含量为60％～80％，基于式I所示单体、烯烃单体和式II所示的单体的总摩尔数计，
Figure PCTCN2022130063-appb-000002
其中，R 1、R 2、R 3各自独立地选自氢、氟、氯或至少含有一个氟原子的C 1-3烷基中，R 4、R 5、R 6各自独立地选自氢、取代或未取代的C 1-5烷基。
该方法制备出的含氟聚合物相比于传统粘结剂能够提高浆料的过滤性和流动性，使得浆料在静置6小时后不发生凝胶，显著拓宽了浆料的工艺窗口，改善了浆料的可加工性，使得浆料在无需添加分散剂的情况下就能够满足绝缘涂层的生产需求，有利于优化绝缘涂层的生产工艺和提高其生产效率。
在任意实施方式中，所述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，R 5、R 6各自独立地选自氢、甲基中的一种或两种。
在任意实施方式中，所述聚合反应包括以下步骤：
第一段聚合：提供第一引发剂、乳化剂、至少一种式I所示单体 以及溶剂，开始进行第一段聚合，在所述第一段聚合的过程中连续送入式I所示单体，以维持初始反应压力；
第二段聚合：反应一段时间后，向反应容器内送入烯烃单体和式II所示单体进行第二段聚合；待反应容器中压力降至小于等于0.5MPa，停止反应，固液分离，保留固相。
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所示单体和烯烃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更能有效提高绝缘浆料的过滤性和流动性，进一步拓宽浆料的工艺窗口，有助于提高绝缘涂层的生产效率。
在任意实施方式中，所述第一段聚合的初始反应压力为5.5MPa～7.5MPa、反应温度为70℃～90℃。
在任意实施方式中，所述第二段聚合包括以下步骤：
送入式I所示单体的质量为其在所述聚合反应过程中所供给的式I所示单体的总质量的70％-85％时，向反应容器内送入式I所示单体和烯烃单体的混合气体，维持初始反应压力继续反应；
待式I所示单体全部送入反应容器后，向反应容器内送入烯烃单体和式II所示单体的混合物。
在向反应容器内送入式II所示单体前，先向反应容器内送入式I所示单体和烯烃单体的混合气体，以烯烃单体作为桥梁有助于克服式I所示单体和式II所示单体间反应差异性大、相容性差的问题，提高含氟聚合物的聚合度。
在任意实施方式中，在所述聚合反应过程中所供给的烯烃单体的总摩尔数与所述式I所示单体的总摩尔数的比值为1:16-1:2。
在任意实施方式中，在所述聚合反应过程中所供给的烯烃单体的总摩尔数与所述式I所示单体的总摩尔数的比值为1:16-1:3。
在任意实施方式中，所述混合气体中，烯烃单体与式I所示单体的摩尔比例为1:1-2:1。
在任意实施方式中，所述混合物中，烯烃单体与式II所示单体的摩尔比例为3:1-4:1。
在任意实施方式中，所述第二段聚合还包括以下步骤：
向反应容器内送入式I所示单体和烯烃单体的混合气体前，在反应容器中加入第一引发剂和第二引发剂。
在任意实施方式中，所述第二段聚合还包括以下步骤：
向反应容器内送入烯烃单体和式II所示单体的混合物前，在反应容器中加入第二引发剂。
在任意实施方式中，所述第一引发剂为过硫酸盐，可选自过硫酸钾、过硫酸铵的一种或多种。
在任意实施方式中，所述第二引发剂为硫代硫酸盐，可选自硫代硫酸钠。
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，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。
本申请的第四方面提供一种绝缘涂层，包括粘结剂和无机绝缘材料，所述粘结剂为第一方面的含氟聚合物。
该绝缘涂层易于加工制备且均匀性好，有助于提高电池产能。
在任意实施方式中，所述粘结剂的质量含量为7.0％-13.0％，基于所述绝缘涂层的总质量计。
粘结剂的质量含量为绝缘涂层的总质量的7.0％-13.0％时，粘结剂使得绝缘浆料的流动性和过滤性进一步提高，绝缘浆料加工的工艺窗口进一步拓宽，且粘结剂能够保证绝缘涂层保持有效的粘结力。
在任意实施方式中，所述无机绝缘材料包含有色氧化物，可选自黑色二氧化锆、黄色二氧化锆、红色二氧化锆或绿色二氧化锆。
申请人意外地发现在绝缘涂层中包含有色氧化物，有助于提高极片的激光切割质量和激光切割速度。
在任意实施方式中，所述有色氧化物的质量含量为0.2％-3％，基于所述绝缘涂层的总质量计。
绝缘涂层中有色氧化物的质量含量为0.2％-3％时，有助于最大效 率地提高激光切割性能。
本申请的第五方面提供一种绝缘涂层的制备方法，包括以下步骤：
分散粘结剂于溶剂中制备胶液，所述粘结剂为本申请第一方面的含氟聚合物；
混合无机绝缘材料与所述胶液，搅拌制备浆料，所述浆料的固含量为30％-40％；
将所述浆料涂覆到集流体上，制备绝缘涂层。
上述方法制备的绝缘涂层效率高且质量均匀。
在任意实施方式中，所述浆料在30％-40％的固含量时，所述浆料的粘度为2500-4000mPa·s。
固含量在30％-40％的浆料粘度为2500-4000mPa·s，可以直接用于生产涂覆，无需增加额外的助剂，利于提高生产效率、降低生产成本。
在任意实施方式中，所述混合无机绝缘材料与所述胶液包括以下步骤：
将除有色氧化物外的无机绝缘材料与所述胶液混合，搅拌后加入所述有色氧化物，再次搅拌制备所述浆料。
在浆料制备过程的最后阶段加入有色氧化物，有利于提高制备的绝缘涂层颜色的均匀性，利于后续激光切割速度和激光切割质量的提高。
本申请的第六方面提供一种二次电池，包括正极极片、隔离膜、负极极片和电解质，所述正极极片和/或所述负极极片上包括本申请第四方面的绝缘涂层；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，包括本申请的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或本申请的第八方面的 电池包中的至少一种。
附图说明
图1是包括绝缘涂层的极片的示意图；
图2是本申请一实施方式的二次电池的示意图；
图3是图2所示的本申请一实施方式的二次电池的分解图；
图4是本申请一实施方式的电池模块的示意图；
图5是本申请一实施方式的电池包的示意图；
图6是图5所示的本申请一实施方式的电池包的分解图；
图7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；
图8是本申请实施例26的极片激光切割后的显微镜图，(A)为极片切口处的平面照片，(B)为极片切口处的截面照片；
图9是本申请实施例6的极片激光切割后的显微镜图，(A)为极片切口处的平面照片，(B)为极片切口处的截面照片。
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；6极片；61集流体；62活性材料层；63绝缘涂层。
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)。
安全性是二次电池最重要的研究课题之一。，如图1所示，极片6在制备过程中会在用于形成极耳的集流体61与活性材料层62之间涂覆绝缘涂层63，以防止电芯在使用过程中正极和负极直接接触形成短路，引发安全事故，甚至导致火灾、爆炸的发生。由于无机材料电阻高，常采用无机材料分散于粘结剂中形成浆料以制备绝缘涂层。然而传统粘结剂粘度过大、容易出现浆料沉淀的现象，导致浆料均匀度差，绝缘涂层各批次间性能方差大。而且传统粘结剂会使得浆料的流动性差、难以均匀涂布，因此，在浆料制备过程中需要加入分散剂以提高浆料的加工性能。这无疑会提高浆料的加工难度、影响生产效率且导致各批次间浆料稳定性差。基于上述技术问题，本申请开发出一种使浆料具有更好的流动性和过滤性的粘结剂，以提高绝缘涂层的生产效率和生产质量。
基于此，本申请提出了一种含氟聚合物，其包含衍生自式I所示单体的结构单元、衍生自烯烃单体的结构单元和衍生自式II所示单体的结构单元，衍生自式I所示单体的结构单元的摩尔含量为60％～80％，基于含氟聚合物中结构单元的总摩尔数计，
Figure PCTCN2022130063-appb-000003
其中，R 1、R 2、R 3各自独立地选自氢、氟、氯或至少含有一个氟原子的C 1-3烷基，R 4、R 5、R 6各自独立地选自氢、取代或未取代的C 1-5烷基。
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 1-5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。术语“C 1-3烷基”应相应解释。C 1-5烷基的示例包括但不限于：甲基、乙基、正丙基、1-甲基乙基(异丙基)、丁基、戊基。在一些实施方式中，至少含有一个氟原子的C 1-3烷基为-CF 3、-CH 3CH 2F或-CH 2FCH 2F。
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“烯烃单体”是指至少含有一个C＝C键(碳碳双键)的碳氢化合物。烯烃单体的示例包括但不限于乙烯、丙烯、丁烯、丁二烯。在一些实施方式中，所述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，R 5、R 6各自独立地选自氢、甲基中的一种或两种。
在一些实施方式中，含氟聚合物包括至少两种衍生自不同式I所示单体的结构单元，且其中一种结构单元衍生自偏二氟乙烯。不同的单体类型有助于减小含氟聚合物长链的有序排列，降低结晶度，提高柔性。
在一些实施方式中，式Ⅰ所示单体选自偏二氟乙烯、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，烯烃单体选自丙烯、2-丁烯、丁二烯中的一种或多种。
在一些实施方式中，式II所示单体选自丙烯酸、甲基丙烯酸中的一种或两种。
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-乙烯-丙烯酸共聚物、偏二氟乙烯-丁二烯-丙烯酸共聚物、偏二氟乙烯-丙烯-丙烯酸共聚物、偏二氟乙烯-乙烯-甲基丙烯酸共聚物、偏二氟乙烯-六氟丙烯-乙烯-丙烯酸共聚物、偏二氟乙烯-六氟丙烯-乙烯 -甲基丙烯酸共聚物、偏二氟乙烯-三氟氯乙烯-丁二烯-甲基丙烯酸共聚物。
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60％、65％、70％、75％或80％，基于含氟聚合物中结构单元的总摩尔数计。
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，使得绝缘涂层具有较好的粘结力，不易在制造使用过程中发生脱落、导致安全事故。衍生自烯烃单体和式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，使得衍生自式I所示单体的结构单元的摩尔含量在60％-80％，可以改善氟元素导致的浆料凝胶现象。而且衍生自烯烃单体和式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、起到稳定浆料、缓解浆料沉降的作用，有效改善浆料的过滤性。
本申请提供的含氟聚合物相比于传统粘结剂能够提高浆料的过滤性和流动性，使得浆料在静置6小时后不发生凝胶，显著拓宽了浆料的工艺窗口，改善了浆料的可加工性，使得浆料在无需添加分散剂的情况下就能够满足绝缘涂层的生产需求，有利于优化绝缘涂层的生产工艺和提高其生产效率。
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，衍生自式II所示单体的结构单元的摩尔含量为5％～25％，基于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5％、8％、10％、12％、15％、18％、20％、22％、25％中的任意一种，基于含氟聚合物中所有结构单元的总摩尔数计。
基于含氟聚合物中所有结构单元的总摩尔数计，衍生自式II所示单体的结构单元的摩尔含量为5％～25％时，一方面合适含量的极性羧基不会导致浆料出现凝胶的情况，使得绝缘浆料的流动性和过滤性进一步提高，绝缘浆料加工的工艺窗口进一步拓宽；另外一方面，合 适含量的羧基使得绝缘涂层能够保持有效的粘结力。
在一些实施方式中，衍生自烯烃单体的结构单元的摩尔含量为5％～30％，基于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，衍生自烯烃单体的结构单元的摩尔含量可选为5％、10％、15％、20％、25％、30％中的任意一种，基于含氟聚合物中所有结构单元的总摩尔数计。
基于含氟聚合物中所有结构单元的总摩尔数计，衍生自烯烃单体的摩尔含量为5％～30％时，含氟聚合物使得绝缘浆料的流动性和过滤性进一步提高，绝缘浆料加工的工艺窗口进一步拓宽，且含氟聚合物使得绝缘涂层能够保持有效的粘结力。
在一些实施方式中，含氟聚合物的重均分子量为50万-80万。在一些实施方式中，含氟聚合物的重均分子量可选为50万、60万、65万、70万、75万、80万中的任意一种。
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。
重均分子量在50万-80万之间的含氟聚合物使得胶液具有合适的粘度，有利于绝缘浆料的流动性和过滤性的进一步提高，绝缘浆料加工的工艺窗口进一步拓宽；同时合适的重均分子量的含氟聚合物，利于形成三维网状粘结结构，有助于绝缘涂层保持有效的粘结力。
在一些实施方式中，所述含氟聚合物溶解于N-甲基吡咯烷酮制 得的胶液的粘度为1000-3000mPa·s，所述胶液中所述含氟聚合物的质量含量为7％，基于所述胶液的总质量计。在一些实施方式中，所述含氟聚合物溶解于N-甲基吡咯烷酮制得的胶液的粘度可选为1000mPa·s、1500mPa·s、2000mPa·s、2500mPa·s、3000mPa·s中的任意一种，所述胶液中所述含氟聚合物的质量含量为7％，基于所述胶液的总质量计。
在本申请中，含氟聚合物的胶液的粘度可以选用本领域已知的方法进行测试，例如采用旋转粘度剂进行测试。
含氟聚合物溶解于N-甲基吡咯烷酮制得的胶液的粘度为1000-3000mPa·s，胶液中含氟聚合物的质量含量为7％，基于胶液的总质量计，使得以此含氟聚合物作为粘结剂的绝缘浆料无需再添加额外的助剂，能够有效优化生产工艺、提高生产效率。同时该粘度范围内的胶液兼具流动性与粘性，既能提高绝缘涂层的粘结力，又能够实现均匀涂覆，有利于提高绝缘涂层的批次稳定性。
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、至少一种烯烃单体和至少一种式II所示单体进行聚合反应制备含氟聚合物，式I所示单体的摩尔含量为60％～80％，基于式I所示单体、烯烃单体和式II所示单体的总摩尔数计，
Figure PCTCN2022130063-appb-000004
其中，R 1、R 2、R 3各自独立地选自氢、氟、氯或至少含有一个氟原子的C 1-3烷基，R 4、R 5、R 6各自独立地选自氢、取代或未取代的C 1-5烷基。
在本文中，术语“可聚合条件”是指包括本领域技术人员选择的温度、压力、反应物浓度、任选的溶剂/稀释剂、反应物混合/添加参数的那些条件，有助于一种或多种单体在至少一个聚合反应器内反应的其他条件。
该方法制备出的含氟聚合物相比于传统粘结剂能够提高浆料的过滤性和流动性，使得浆料在静置6小时后不发生凝胶，显著拓宽了浆料的工艺窗口，改善了浆料的可加工性，使得浆料在无需添加分散剂的情况下就能够满足绝缘涂层的生产需求，有利于优化绝缘涂层的生产工艺和提高其生产效率。
在一些实施方式中，所述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，R 5、R 6各自独立地选自氢、甲基中的一种或两种。
在一些实施方式中，在聚合物制备过程中投入至少两种式I所示单体，其中，一种式I所示单体为聚偏二氟乙烯。不同单体的加入有助于减少含氟聚合物长链的有序性，降低结晶度，提高含氟聚合物的柔性。
在一些实施方式中，聚合反应包括以下步骤：
第一段聚合：提供第一引发剂、乳化剂、至少一种式I所示单体以及溶剂，进行第一段聚合，在所述第一段聚合的过程中连续送入式I所示单体，以维持初始反应压力；
第二段聚合：反应一段时间后，向反应容器内送入烯烃单体和式II所示单体进行第二段聚合；待反应容器中压力降至小于等于0.5MPa，停止反应，固液分离，保留固相。
在本文中，术语“连续送入”是指缓慢地、小量地、增量地添加单体。
在一些实施方式中，第一引发剂为过硫酸盐，可选自过硫酸钾、过硫酸铵的一种或多种。过硫酸钾在60℃以上有效地分解，产生自由基离子或离子自由基，适宜作为乳液聚合的引发剂。
在一些实施方式中，乳化剂为全氟辛酸碱金属盐，可选为全氟辛酸钠盐。
在一些实施方式中，溶剂为水溶剂，可选为去离子水。
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所示单体和烯烃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更能有效提高浆料的过滤性和流动性，进一步拓宽浆料的工艺窗口，有助于提高绝缘涂层的生产效率。
在一些实施方式中，所述第一段聚合的初始反应压力为5.5MPa～7.5MPa、反应温度为70℃～90℃。
在一些实施方式中，所述第二段聚合包括以下步骤：
送入式I所示单体的质量为其在所述聚合反应过程中所供给的式I所示单体的总质量的70％-85％时，向反应容器内送入式I所示单体和烯烃单体的混合气体，维持初始反应压力继续反应；
待式I所示单体全部送入反应容器后，向反应容器内送入烯烃单体和式II所示单体的混合物。
在向反应容器内送入式II所示单体前，先向反应容器内送入式I所示单体和烯烃单体的混合气体，以烯烃单体作为桥梁有助于克服式I所示单体和式II所示单体间反应差异性大、相容性差的问题，提高含氟聚合物的聚合度。
在一些实施方式中，在聚合反应过程中所供给的烯烃单体的总摩尔数与式I所示单体的总摩尔数的比值为1:16-1:2。
在一些实施方式中，在聚合反应过程中所供给的式II所示单体的总摩尔数与式I所示单体的总摩尔数的比值为1:16-1:3。
在一些实施方式中，混合气体中，烯烃单体与式I所示单体的摩尔比例为1:1-2:1。
在一些实施方式中，混合物中，烯烃单体与式II所示单体的摩尔比例为3:1-4:1。
在一些实施方式中，第二段聚合还包括以下步骤：
向反应容器内送入式I所示单体和烯烃单体的混合气体前，在反应容器中加入第一引发剂和第二引发剂。
在一些实施方式中，第二引发剂为硫代硫酸盐，可选自硫代硫酸钠。硫代硫酸盐作为还原剂，易于与反应容器中的第一引发剂过硫酸盐反应产生两个自由基，有效地引发烯烃单体的聚合。
在一些实施方式中，第二段聚合还包括以下步骤：
向反应容器内送入烯烃单体和式II所示单体的混合物前，在反应容器中加入第二引发剂。
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。在一些实施方式中，含氟聚合物作为粘结剂在二次电池中的应用。在一些实施方式中，含氟聚合物作为绝缘涂层的粘结剂在二次电池中的应用。
[绝缘涂层]
本申请的一个实施方式中，提供一种绝缘涂层，包括粘结剂和无机绝缘材料，粘结剂为任意实施方式中的含氟聚合物。
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。
在本申请中，术语“无机绝缘材料”是指电阻系数大于10 6Ω·cm的无机材料及其前驱体，包括但不限于勃姆石、碳酸钡、硫酸钡、氧化铝、二氧化锆、碳酸钙、二氧化硅。
在一些实施方式中，无机绝缘材料包括勃姆石。勃姆石(AlOOH)是γ－Al2O3的前驱体，与集流体具有优秀的粘结力，作为绝缘涂层不易发生脱落。在一些实施方式中，无机绝缘材料包含二氧化锆。二氧化锆具有高电阻，适宜制备绝缘涂层。
在一些实施方式中，粘结剂的分散介质是水性溶剂，如去离子水。即，粘结剂溶解于水性溶剂中。
在一些实施方式中，粘结剂的分散介质是油性溶剂，油性溶剂的示例包括但不限于二甲基乙酰胺、N，N-二甲基甲酰胺、N-甲基吡咯烷酮、丙酮、碳酸二甲酯、乙基纤维素、聚碳酸酯。即，粘结剂溶解于油性溶剂中。
在一些实施方式中，粘结剂用于将无机绝缘材料固定在合适位置并将它们粘附在集流体上以形成绝缘涂层。
该绝缘涂层易于加工制备且均匀性好，有助于提高电池产能。
在一些实施方式中，粘结剂的质量含量为7.0％-13.0％，基于绝缘涂层的总质量计。在一些实施方式中，粘结剂的质量含量可选为7.0％、 8.0％、9.0％、10.0％、11.0％、12.0％、13.0％中的任意一种，基于绝缘涂层的总质量计。
粘结剂的质量含量为绝缘涂层的总质量的7.0％-13.0％时，使得绝缘浆料具有合适的粘度，使得绝缘浆料的流动性和过滤性进一步提高、绝缘浆料加工的工艺窗口进一步拓宽；同时合适范围的粘结剂的质量含量保证绝缘涂层与集流体具有足够的粘结力。
在一些实施方式中，无机绝缘材料包含有色氧化物，可选自黑色二氧化锆、黄色二氧化锆、红色二氧化锆、绿色二氧化锆中的一种或多种。在一些实施方式中，有色氧化物为有色二氧化锆。在一些实施方式中，无机绝缘材料包括黑色二氧化锆。
申请人意外地发现在绝缘涂层中包含有色氧化物，有助于提高极片的激光切割质量和激光切割速度。激光切割是指利用经聚焦的高功率密度激光束照射工件，使被照射的材料迅速加热熔化、汽化、烧蚀或分解，从而对材料进行加工的技术。激光切割技术在二次电池中的应用主要包括激光极片切割、极耳切割以及隔膜切割等。目前，激光切割极片存在切割区域毛刺多、最大切割速度有限等问题。现有技术中无机绝缘材料普遍为无色或白色粉末，申请人发现在无机绝缘材料中包含有色氧化物可以使得极片的最大切割速度提高幅度高于30％，这有助于大幅度增加电池产能。同时，无机绝缘材料中的有色氧化物能够减少激光的热影响区，提高切割质量，减少切割毛刺，降低加工过程对电池性能产生的影响。
在一些实施方式中，有色氧化物的质量含量为0.2％-3％，基于绝缘涂层的总质量计。
绝缘涂层中有色氧化物的质量含量为0.2％-3％时，不仅可以改善极片激光切割成型过程中的切割速度，还可以兼顾原料成本，有助于最大效率地提高激光切割性能。
在一些实施方式中，有色氧化物为黑色氧化锆。有色氧化物占绝缘涂层的质量含量大于3.0％时，绝缘涂层与活性材料层之间无色差，激光切割系统难以识别定位，不利于尺寸的准确切割。
本申请的一个实施方式中，提供一种绝缘涂层的制备方法，包括 以下步骤：
分散粘结剂于溶剂中制备胶液，粘结剂为任意实施方式中的含氟聚合物；
混合无机绝缘材料与胶液，搅拌制备浆料，浆料的固含量为30％-40％；
将浆料涂覆到集流体上，制备绝缘涂层。
浆料的固含量为30％～40％，一方面使得浆料具有合适的粘度，利于后续的涂覆和烘干工作；另一方面合适的浆料粘度可以提高浆料的稳定性，利于浆料的保存。
上述方法制备的绝缘涂层效率高，无需添加其他助剂，利于节约生产工序，提高生产效率。
在一些实施方式中，浆料在30％-40％的固含量时，浆料的粘度为2500-4000mPa·s。在一些实施方式中，浆料在30％-40％的固含量时的粘度可选为2750mPa·s、3000mPa·s、3250mPa·s、3500mPa·s、3750mPa·s、4000mPa·s中的任意一种。
固含量在30％-40％的浆料粘度为2500-4000mPa·s，可以直接用于生产涂覆，无需增加额外的助剂，利于提高生产效率、降低生产成本。
在一些实施方式中，混合无机绝缘材料与胶液包括以下步骤：
将除有色氧化物外的无机绝缘材料与胶液混合，搅拌后加入所述有色氧化物，再次搅拌制备所述浆料。
在浆料制备过程的最后阶段加入有色氧化物，有利于提高制备的绝缘涂层颜色的均匀性，利于后续激光切割速度和质量的提高。
本申请的一个实施方式中，提供一种二次电池，包括正极极片、隔离膜、负极极片和电解质，所述正极极片和/或所述负极极片上包括任意实施方式中所述的绝缘涂层。在一些实施方式中，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。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。电解质在正极极片和负极极片之间起到传导离子的作用。隔离膜设置在正极极片和负极极片之间，主要起到防止正负极短路的 作用，同时可以使离子通过。
[正极极片]
正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极活性材料层和绝缘涂层。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极活性材料层和绝缘涂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，正极活性材料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，正极活性材料层还可选地包括。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活性材料层的组分，例如正极活性材料、导电剂、粘结剂和任意其他的组分分散于溶剂(例如N-甲基吡咯烷酮)中，形成正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，得到正极活性材料层。将上述用于制备绝缘涂层的组分，例如含氟聚合物分散于溶剂(例如N-甲基吡咯烷酮)中，形成胶液；混合无机绝缘材料与胶液，搅拌制备绝缘浆料；将绝缘浆料沿正极活性材料层的边缘涂覆在正极集流体上，经烘干、冷压等工序后，得到绝缘涂层，在集流体的另一侧采用同样的方法获得正极活性材料层和绝缘涂层即可得到正极极片。
[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活性材料层和绝缘涂层。
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，负极活性材料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，负极活性材料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，负极活性材料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活性材料层的组分，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，即得到负极活性材料层。将上述用于制备绝缘涂层的组分，例如含氟聚合物分散于溶剂(例如N-甲基吡咯烷酮)中，形成胶液；混合无机绝缘材料与胶液，搅拌制备绝缘浆料；将绝缘浆料沿负极活性材料层的边缘涂覆在负极集流体上，经烘干、冷压等工序后，得到绝缘涂层。在负极集流体的另一侧采用同样的方法获得负极活性材料层和绝缘涂层即可得到负极极片。
[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2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3，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4是作为一个示例的电池模块4。参照图4，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5和图6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7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)粘结剂(含氟聚合物)的制备
将30kg的去离子水(电导率小于等于2μs/cm)、21g的全氟辛酸钠盐、71.4g的5％浓度的过硫酸钾溶液，依次加入反应釜内，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7.5MPa；
釜内升温至85℃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；
通入偏二氟乙烯单体为偏二氟乙烯单体总质量的80％时，加入30.6g的5％浓度的过硫酸钾溶液和19.2g的5％浓度的硫代硫酸钠，维持反应压力向反应釜内通入偏二氟乙烯单体和丁二烯混合气体，偏二氟乙烯单体和丁二烯单体的摩尔比为2:3；
3783.7偏二氟乙烯单体全部加入，丁二烯单体加入量占丁二烯总量的50％时，加入剩余的28.8g的5％浓度的硫代硫酸钠，维持反应压力向反应釜内通入剩余的丁二烯单体931g和丙烯酸单体354.7g；
反应完成时釜内压力降至0.2MPa，回收未反应的丁二烯单体反应；产物经凝聚、洗涤、分离、干燥、粉碎得到偏二氟乙烯-丁二烯-丙烯酸共聚物粘结剂。
2)绝缘浆料的制备
将13000g N-甲基吡咯烷酮加入到35L搅拌罐内；
将上述制备的700g的偏二氟乙烯-丁二烯-丙烯酸共聚物粉末加入到N-甲基吡咯烷酮内，设定搅拌速度1000转/分钟，搅拌时间60分钟，搅拌结束得预制胶液；
将6195g的勃母石粉末加入预制胶液，设定搅拌速度1200转/分钟，搅拌时间60分钟，搅拌罐开启冷却水循环，搅拌结束得到勃母石浆料；
将105g黑色氧化锆粉末加入到勃母石浆料，设定搅拌速度1200转/分钟，搅拌时间60分钟，搅拌罐开启冷却水循环，开启抽真空，搅拌结束得到绝缘浆料。
3)绝缘涂层的制备
将上述绝缘浆料涂覆在13μm的铝箔上，涂覆厚度为15±1μm，干燥浆料形成绝缘涂层，在铝箔的另外一侧采用同样的方法获得绝缘涂层，两侧绝缘涂层加铝箔厚度为43±2μm。
实施例2～26的绝缘涂层和对比例1～4的绝缘涂层的制备方法与实施例1的制备方法相似，但是调整了粘结剂制备的参数和黑色二氧化锆在浆料中的配比。
实施例2-实施例7中调节粘结剂各单体的配比，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8-实施例11中调整粘结剂合成中的反应条件，使得粘结剂具有不同的重均分子量，其他参数同实施例6保持一致，具体参数见表1和表2。具体而言，实施例8中重均分子量为50万的含氟聚合物的制备方法与实施例6步骤基本相同，区别在于将5％浓度的过硫酸钾溶液添加量由71.4g调整为78.54g。
实施例9中重均分子量为80万的含氟聚合物的制备方法与实施例6步骤基本相同，区别在于将反应温度由85℃调整为80℃，5％浓度的过硫酸钾溶液添加量由71.4g调整为67.83g。
实施例10中重均分子量为90万的含氟聚合物的制备方法与实施例6步骤基本相同，区别在于反应温度由85℃调整为80℃，5％浓度的过硫酸钾溶液添加量由71.4g调整为64.26g。
实施例11中重均分子量为40万的含氟聚合物的制备方法与实施例6步骤基本相同，区别在于将5％浓度的过硫酸钾溶液添加量由71.4g调整为82.11g。
实施例12-实施例15中调整浆料中的粘结剂的质量分数，其他参数同实施例6保持一致，具体参数见表1和表2。
实施例16-19中，调整浆料的固含量，其他参数同实施例6保持一致，具体参数见表1和表2。
实施例20中，将粘结剂合成单体中的丁二烯替换成丙烯，其他参数同实施例6保持一致，具体参数见表1和表2。
实施例21中，粘结剂为传统方法制备的偏二氟乙烯-丁二烯-丙烯酸共聚物，其合成方法为：将30kg的去离子水(电导率小于等于2μs/cm)、21g的全氟辛酸碱金属盐、71.4g的5％浓度的过硫酸钾溶液，依次加入反应釜内，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、丁二烯单体、720g丙烯酸单体至釜内压力7.5MPa，其中偏二氟乙烯单体与丁二烯单体的摩尔比为8：1；
釜内升温至85℃开始反应，反应过程中不断通入偏二氟乙烯单体、丁二烯单体维持釜内反应压力不变，通入的偏二氟乙烯单体、丁 二烯单体的总质量分别为5120g和540g；
反应完成时釜内压力降至0.0-0.5MPa，回收未反应的丁二烯单体；反应产物经凝聚、洗涤、分离、干燥、粉碎得到偏二氟乙烯-丁二烯-丙烯酸共聚物粘结剂。
实施例22-26中，改变浆料中黑色二氧化锆的质量含量，其他参数同实施例6保持一致，具体参数见表3。
对比例1中，以偏二氟乙烯聚合物作为粘结剂，其为法国阿科玛公司的HSV900型号。
对比例2中，粘结剂为偏二氟乙烯-丁二烯共聚物，其合成方法与实施例1基本相同，区别在于通入偏二氟乙烯单体为偏二氟乙烯单体总质量80％时，加入30.6g的5％浓度的过硫酸钾溶液和19.2g的5％浓度的硫代硫酸钠，维持反应压力向反应釜内通入偏二氟乙烯单体和丁二烯混合气体，其中混合气体中丁二烯的质量为2160g，偏二氟乙烯单体的质量为756.7g。
对比例3中，粘结剂为偏二氟乙烯-丙烯酸共聚物，其合成方法与实施例1基本相同，区别在于通入偏二氟乙烯单体为偏二氟乙烯单体总质量80％时，加入30.6g的5％浓度的过硫酸钾溶液和19.2g的5％浓度的硫代硫酸钠，维持反应压力向反应釜内加入2880g的丙烯酸，并继续通入756.7g的偏二氟乙烯单体。
对比例4中，粘结剂为偏二氟乙烯-丁二烯-丙烯酸共聚物，其合成方法与实施例1相同，调整了合成单体的摩尔含量，具体参见表1和表2。
上述实施例1～26、对比例1～4的绝缘涂层的相关参数如下述表1、表2和表3所示。
二、测试方法
将上述实施例1～26和对比例1～4中得到的绝缘涂层进行性能测试。测试方法如下：
1、重均分子量测试
采用Waters 2695 Isocratic HPLC型凝胶色谱仪(示差折光检测器2141)。以质量分数为3.0％的聚苯乙烯溶液试样做参比，选择匹 配的色谱柱(油性：Styragel HT5DMF7.8×300mm+Styragel HT4)。用纯化后的N-甲基吡咯烷酮(NMP)溶剂配置3.0％的含氟聚合物溶液，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、胶液粘度测试
将含氟聚合物溶解于N-甲基吡咯烷酮(NMP)溶剂中，配置固含量为7％的胶液，选取合适的转子，固定好粘度计，将胶液置于粘度计下方，浆料恰好淹没转子的刻度线，仪器型号：上海方瑞NDJ-5S，转子：62#(500-2500mPa·s)、63#(2500-10000mPa·s)，转速：12转/分钟，测试温度：25℃，测试时间为5min，待示数稳定读取数据。
3、浆料粘度测试
使用旋转粘度剂测量浆料的粘度。选取合适的转子，固定好粘度计转子，将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：63#(2000-10000mPa·s)、64#(10000-50000mPa·s)，转速：12转/分钟，测试温度：25℃，测试时间为5min，待示数稳定读取数据。
4、浆料固含量测试
固含量测试方法：准备一个玻璃培养皿并记录重量m 1，取一部分制得的浆料放到玻璃培养皿中并记录总重量m 2，将装有浆料的培养皿放到干燥箱中加热，加热温度120℃，加热时间1h。将干燥后的培养皿称取并记录重量m 3，固含量＝[(m 3-m 1)/(m 2-m 1)]×100％。
5、浆料流动性测试
浆料静置6h和12h后，用药匙取适量浆料，观察浆料的自然下流是否流畅。若自然下流顺畅判定为OK；若流动性不好，浆料出现果冻状，成块，表明出现凝胶，判定为NG。
6、浆料过滤性能测试
先确定过滤网200目，将过滤网用剪刀剪成25cm*25cm。找一干 净的500ml烧杯，确定烧杯干净。将200目过滤网折成三角形，取浆料500ml从过滤网上面倒入，一下子全部倒完，从滤网尖端开始往烧杯中流浆料时，开始记录时间。记录300ml过滤的时间。
7、粘结力测试
参考GB-T2790-1995国标《胶粘剂180°剥离强度实验方法》，本申请实施例和对比例的粘结力测试过程如下：用刀片截取宽度为30mm，长度为100-160mm的试样，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绝缘涂层面贴在双面胶上，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绝缘涂层的粘结力，以表征绝缘涂层与集流体之间的粘结强度。
8、激光切割测试
使用大族激光模切机，激光输出功率设定为最大输出功率的80％，激光频率为1000KHz。对比切割不同实施例中的涂覆绝缘涂层的极片时的最大切割速度以及切割质量。若模切机上的CCD相机能够识别，则判定为Y，若模切机上的CCD相机不能够识别，则判定为N。激光切割后通过光学显微镜观察切割后的断面形貌。切割后的断面明显存在金属毛刺，则判定为不通过；切割后的断面不存在明显的金属毛刺，则判定为通过。从一百批次的切割产品中抽取样品，计算百批次通过率。
表1实施例1～21和对比例1～4的参数和测试结果
Figure PCTCN2022130063-appb-000005
Figure PCTCN2022130063-appb-000006
表2实施例1～21和对比例1～4的参数和测试结果
Figure PCTCN2022130063-appb-000007
Figure PCTCN2022130063-appb-000008
表3绝缘涂层切割质量测试
Figure PCTCN2022130063-appb-000009
图8是实施例26中的涂覆绝缘涂层的极片激光切割后的显微图像，其中，图8A为极片切口处的平面照片，图8B为极片切口处的截面照片。图9是实施例6中的极片激光切割后的显微图像，其中，图9A为极片切口处的平面照片，图9B为极片切口处的截面照片。由图8和图9的对比可见，绝缘涂层中加入黑色二氧化锆的极片在激光切割后毛刺量和毛刺长度显著减少，有效地改善了极片的激光切割质量。
根据表1结果可知，实施例1-21中的粘结剂均为含氟聚合物，包含衍生自偏二氟乙烯的结构单元、衍生自烯烃(丁二烯或丙烯)的结构单元以及衍生自丙烯酸的结构单元，该聚合物中衍生自偏二氟乙烯的结构单元的摩尔含量为60％～80％，基于含氟聚合物中结构单元的总摩尔数计。以上述含氟聚合物作为粘结剂均取得了良好的效果，相比于对比例1中的传统PVDF粘结剂和对比例4中的衍生自偏二氟乙烯结构单元的质量含量为90％的含氟聚合物，本申请提供的含氟聚合物使得浆料在过滤性和静置6h后的流动性均有所提高。相比于对比例2和对比例3中的偏二氟乙烯-丁二烯共聚物和偏二氟乙烯-丙烯酸共聚物，本申请公开的含氟聚合物可以综合地改善浆料的流动性、过滤性和粘结性能，兼顾浆料的加工性 能和使用性能。
从实施例1-3、5-7与实施例4的对比可见，含氟聚合物中衍生自丙烯酸的结构单元的摩尔含量为5％～20％，基于含氟聚合物中所有结构单元的总摩尔数计时，含氟聚合物使得浆料静置12h后的流动性也有所提高，进一步拓宽了浆料的工艺窗口。
从实施例2-7与实施例1的对比可见，含氟聚合物中衍生自烯烃单体的结构单元的摩尔含量为5％～30％，基于含氟聚合物中所有结构单元的总摩尔数计时，含氟聚合物使得浆料在提高加工性能的同时能够兼顾粘结力。
从实施例8-11的对比可见，含氟聚合物的重均分子量为50万-80万时，含氟聚合物可以综合地改善浆料的流动性、过滤性和粘结性能，兼顾浆料的加工性能和使用性能。
从实施例1-20可见，含氟聚合物溶解于N-甲基吡咯烷酮制得的含有质量含量为7％的所述含氟聚合物的胶液的粘度为2500-5000mPa·s。这使得含氟聚合物制备的绝缘涂层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。
从实施例6与实施例21的对比可见，通过本申请公开的方法制备的含氟聚合物，相比于传统方法合成的含氟粘结剂，更能有效提高浆料的过滤性和流动性，改善浆料的加工性能。
从实施例6、22-25与实施例26的对比可见，绝缘涂层中加入黑色氧化锆有利于减少极片在激光切割中边缘产生的毛刺，提高极片激光切割的质量，改善极片品质。
从实施例6、23-24与实施例22、25的对比可见，绝缘涂层中黑色氧化锆的质量含量为0.2％-3％时，激光切割的速度有所提升，有助于进一步提高生产效率、增加产能；而且绝缘涂层与正极活性材料层之间的色差使得激光切割设备能够准确地定位和识别，提高加工精度。
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 (37)

  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、衍生自烯烃单体的结构单元和衍生自式II所示单体的结构单元，所述衍生自式I所示单体的结构单元的摩尔含量为60％～80％，基于所述含氟聚合物中结构单元的总摩尔数计，
    Figure PCTCN2022130063-appb-100001
    其中，R 1、R 2、R 3各自独立地选自氢、氟、氯或至少含有一个氟原子的C 1-3烷基，R 4、R 5、R 6各自独立地选自氢或取代或未取代的C 1-5烷基。
  2. 根据权利要求1所述的含氟聚合物，其特征在于，所述R 1为氟，R 2、R 3各自独立地选自氢、氟、氯或三氟甲基，R 5、R 6各自独立地选自氢或甲基。
  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II所示单体的结构单元的摩尔含量为5％～25％，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，所述衍生自烯烃单体的结构单元的摩尔含量为5％～30％，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50万-80万。
  6. 根据权利要求1至5中任一项所述的含氟聚合物，其特征在于，所述含氟聚合物溶解于N-甲基吡咯烷酮制得的胶液的粘度为 1000-3000mPa·s，所述胶液中所述含氟聚合物的质量含量为7％，基于所述胶液的总质量计。
  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Ⅰ所示单体选自偏二氟乙烯、四氟乙烯、三氟氯乙烯、六氟丙烯中的一种或多种。
  8. 根据权利要求1至7中任一项所述的含氟聚合物，其特征在于，所述烯烃单体选自丙烯、2-丁烯、丁二烯中的一种或多种。
  9. 根据权利要求1至8中任一项所述的含氟聚合物，其特征在于，所述式II所示单体选自丙烯酸、甲基丙烯酸中的一种或两种。
  10. 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、至少一种烯烃单体和至少一种式II所示单体进行聚合反应制备含氟聚合物，所述式I所示单体的摩尔含量为60％～80％，基于所述式I所示单体、所述烯烃单体和所述式II所示单体的总摩尔数计，
    Figure PCTCN2022130063-appb-100002
    其中，R 1、R 2、R 3各自独立地选自氢、氟、氯或至少含有一个氟原子的C 1-3烷基，R 4、R 5、R 6各自独立地选自氢、取代或未取代的C 1-5烷基。
  11. 根据权利要求10所述的制备方法，其特征在于，所述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，R 5、R 6各自独立地选自氢、甲基中的一种或两种。
  12. 根据权利要求10或11所述的制备方法，其特征在于，所述 聚合反应包括以下步骤：
    第一段聚合：提供第一引发剂、乳化剂、至少一种式I所示单体以及溶剂，进行第一段聚合，在所述第一段聚合的过程中连续送入式I所示单体，以维持初始反应压力；
    第二段聚合：反应一段时间后，向反应容器内送入烯烃单体和式II所示单体进行第二段聚合；待反应容器中压力降至小于等于0.5MPa，停止反应，固液分离，保留固相。
  13. 根据权利要求12所述的制备方法，其特征在于，所述第一段聚合的初始反应压力为5.5MPa～7.5MPa、反应温度为70℃～90℃。
  14. 根据权利要求12或13所述的制备方法，其特征在于，所述第二段聚合包括以下步骤：
    送入式I所示单体的质量为其在所述聚合反应过程中所供给的式I所示单体的总质量的70％-85％时，向反应容器内送入式I所示单体和烯烃单体的混合气体，维持初始反应压力继续反应；
    待式I所示单体全部送入反应容器后，向反应容器内送入烯烃单体和式II所示单体的混合物。
  15. 根据权利要求10至14中任一项所述的制备方法，其特征在于，在所述聚合反应过程中所供给的烯烃单体的总摩尔数与所述式I所示单体的总摩尔数的比值为1:16-1:2。
  16. 根据权利要求10至15中任一项所述的制备方法，其特征在于，在所述聚合反应过程中所供给的式II所示单体的总摩尔数与所述式I所示单体的总摩尔数的比值为1:16-1:3。
  17. 根据权利要求14所述的制备方法，其特征在于，所述混合气体中，烯烃单体与式I所示单体的摩尔比例为1:1-2:1。
  18. 根据权利要求14或17所述的制备方法，其特征在于，所述混合物中，烯烃单体与式II所示单体的摩尔比例为3:1-4:1。
  19. 根据权利要求14或18所述的制备方法，其特征在于，所述第二段聚合还包括以下步骤：
    向反应容器内送入式I所示单体和烯烃单体的混合气体前，在反应容器中加入第一引发剂和第二引发剂。
  20. 根据权利要求14或19所述的制备方法，其特征在于，所述第二段聚合还包括以下步骤：
    向反应容器内送入烯烃单体和式II所示单体的混合物前，在反应容器中加入第二引发剂。
  21. 根据权利要求19所述的制备方法，其特征在于，所述第一引发剂为过硫酸盐。
  22. 根据权利要求21所述的制备方法，其特征在于，所述过硫酸盐选自过硫酸钾、过硫酸铵的一种或多种。
  23. 根据权利要求19或20所述的制备方法，其特征在于，所述第二引发剂为硫代硫酸盐。
  24. 根据权利要求23所述的制备方法，其特征在于，所述硫代硫酸盐选自硫代硫酸钠。
  25. 权利要求1至9中任一项所述的含氟聚合物在二次电池中的应用。
  26. 一种绝缘涂层，包括粘结剂和无机绝缘材料，其特征在于，所述粘结剂为权利要求1至9中任一项所述的含氟聚合物。
  27. 根据权利要求26所述的绝缘涂层，其特征在于，所述粘结剂的质量含量为7.0％-13.0％，基于所述绝缘涂层的总质量计。
  28. 根据权利要求26或27所述的绝缘涂层，其特征在于，所述无机绝缘材料包含有色氧化物，所述有色氧化物选自黑色二氧化锆、黄色二氧化锆、红色二氧化锆、绿色二氧化锆中的一种或多种。
  29. 根据权利要求26至28中任一项所述的绝缘涂层，其特征在于，所述有色氧化物的质量含量为0.2％-3％，基于所述绝缘涂层的总质量计。
  30. 一种绝缘涂层的制备方法，其特征在于，包括以下步骤：
    分散粘结剂于溶剂中制备胶液，所述粘结剂为权利要求1至9中任一项所述的含氟聚合物；
    混合无机绝缘材料与所述胶液，搅拌制备浆料，所述浆料的固含量为30％-40％；
    将所述浆料涂覆到集流体上，制备绝缘涂层。
  31. 根据权利要求30所述的绝缘涂层的制备方法，其特征在于，
    所述浆料在30％-40％的固含量时，所述浆料的粘度为2500-4000mPa·s。
  32. 根据权利要求30或31所述的绝缘涂层的制备方法，其特征在于，所述混合无机绝缘材料与所述胶液包括以下步骤：
    将除有色氧化物外的无机绝缘材料与所述胶液混合，搅拌后加入 所述有色氧化物，再次搅拌制备所述浆料。
  33. 一种二次电池，其特征在于，包括正极极片、隔离膜、负极极片和电解质，所述正极极片和/或所述负极极片上包括权利要求26至29中任一项所述的绝缘涂层。
  34. 根据权利要求33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。
  35. 一种电池模块，其特征在于，包括权利要求33或34所述的二次电池。
  36. 一种电池包，其特征在于，包括权利要求33或权利要求34所述的二次电池、权利要求35所述的电池模块中的至少一种。
  37. 一种用电装置，其特征在于，包括选自权利要求33或权利要求34所述的二次电池、权利要求35所述的电池模块、权利要求36所述的电池包中的至少一种。
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CN115286728A (zh) * 2022-09-30 2022-11-04 宁德时代新能源科技股份有限公司 粘结剂、制备方法、正极极片、二次电池及用电装置

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