Fluorine-containing polymer, conductive slurry, positive electrode plate, secondary battery, power consumption device

Abstract

The present application provides a fluorine-containing polymer, a conductive slurry, a positive electrode plate, a secondary battery, and a power consumption device. The fluorine-containing polymer includes a structural unit derived from a monomer represented by formula I and a structural unit derived from a monomer represented by formula II, wherein R1, R2, and R3 are each independently hydrogen, fluorine, chlorine, or a C group substituted with fluorine. 1-3 alkyl group, and R4, R5 are selected from hydrogen, substituted or unsubstituted C 1-5 alkyl group, and R6 is selected from C 1-5 The fluorine-containing polymer can improve the filterability of the conductive slurry, as well as the gelation resistance and storage stability of the conductive slurry, thereby significantly widening the process window of the conductive slurry and improving the processability of the conductive slurry.

Description

[Technical Field]

[0001] The present application relates to the field of secondary battery technology, and in particular to fluorine-containing polymers, conductive slurries, positive electrode plates, secondary batteries, and power consuming devices. [Background technology]

[0002] The low conductivity of the active material itself in secondary batteries can lead to problems during battery manufacturing, such as high internal resistance and poor rate and cycle performance. Therefore, it is necessary to add a conductive agent to improve the conductivity of the active material and improve the overall performance of the battery. However, conventional conductive agents generally have a relatively large specific surface area and are highly susceptible to aggregation due to the action of van der Waals forces, which affects their conductive effect and easily leads to uneven distribution in the positive electrode plate, thereby affecting the performance of the active material. Therefore, there is an urgent need to solve this technical problem. Summary of the Invention

[0003] The present application has been made in view of the above-mentioned problems, and an object of the present application is to provide a fluorine-containing polymer and a conductive slurry containing the fluorine-containing polymer, thereby improving the dispersibility of a conductive agent and optimizing the performance of a battery. According to a first aspect of the present application, there is provided a fluorine-containing polymer, the fluorine-containing polymer comprising a structural unit derived from a monomer represented by formula I and a structural unit derived from a monomer represented by formula II, TIFF2025535450000002.tif26150 where R1, R2, and R3 each independently represent hydrogen, fluorine, chlorine, or fluorine-substituted C. 1-3 alkyl group, and R4 and R5 are each independently selected from hydrogen, substituted or unsubstituted C 1-5 alkyl groups, and R6 is selected from one or more of C 1-5 The alkyl group may be selected from one or more of a substituted or unsubstituted aryl group. The fluorine-containing polymer of the present application can reduce the viscosity of the conductive slurry, improve the filterability of the conductive slurry, and prevent the slurry from gelling even after standing for 60 days, thereby improving the gelling resistance and storage stability of the conductive slurry and improving the processability and stability of the conductive slurry. This meets the production needs of the conductive slurry without adding any dispersant to the conductive slurry, and can further reduce the film resistance of the electrode plate and the DC impedance of the battery.

[0004] In any embodiment, R1 in formula I is fluorine, and R2 and R3 are each independently selected from one or more of hydrogen, fluorine, chlorine, and a trifluoromethyl group. In any embodiment, the molar content of the structural unit derived from the monomer represented by formula I is 50% to 70% based on the total number of moles of all structural units in the fluorine-containing polymer. By controlling the molar content of the structural units derived from the monomer represented by formula I within an appropriate range, it is possible to achieve both the viscosity of the conductive slurry and the adhesiveness of the electrode plate, thereby comprehensively improving the processing performance and use performance of the conductive slurry. In any embodiment, the molar content of the structural unit derived from the monomer represented by formula II is 30% to 50% based on the total number of moles of all structural units in the fluorine-containing polymer. By controlling the molar content of the structural unit derived from the monomer shown in Formula II within an appropriate range, it is possible to achieve both the viscosity of the conductive slurry and the adhesiveness of the electrode plate, thereby comprehensively improving the processing performance and use performance of the conductive slurry.

[0005] In any embodiment, the mass average molecular weight of the fluorine-containing polymer is 100,000 to 140,000. By controlling the mass average molecular weight of the fluorine-containing polymer within an appropriate range, it is possible to achieve both the viscosity of the conductive slurry and the adhesiveness of the electrode plate, thereby improving the processing performance and use performance of the conductive slurry overall. In any embodiment, the monomer according to Formula I is selected from one or more of vinyl fluoride, vinylidene fluoride, tetrafluoroethylene, chlorotrifluoroethylene, hexafluoropropylene. In any embodiment, the monomer shown in Formula II is selected from one or more of 2-benzylacrylic acid, 2-(4-isobutylbenzyl)acrylic acid, 2-methylene-4-phenylbutyric acid, 2-(1-phenylethyl)acrylic acid. According to a second aspect of the present application, there is provided a method for producing a fluorine-containing polymer, the method comprising: polymerizing at least one monomer of formula I with at least one monomer of formula II under polymerizable conditions; TIFF2025535450000003.tif26150 where R1, R2, and R3 are each independently hydrogen, fluorine, chlorine, or fluorine-substituted C. 1-3 alkyl group, and R4 and R5 are each independently selected from hydrogen, substituted or unsubstituted C 1-5 alkyl groups, and R6 is selected from one or more of C 1-5 The alkyl group may be selected from one or more of a substituted or unsubstituted aryl group.

[0006] Compared with conventional adhesives, the fluorine-containing polymer produced by this method can reduce the viscosity of the conductive slurry and improve the filterability of the conductive slurry, which prevents the slurry from gelling after standing for 60 days, improving the gelling resistance and storage stability of the conductive slurry, greatly widening the process window of the conductive slurry and improving the processability of the conductive slurry, thereby meeting the production needs of conductive slurry without adding dispersants to the conductive slurry, and further reducing the film resistance of the electrode plate and the DC impedance of the battery. In any embodiment, R1 in formula I is fluorine, and R2 and R3 are each independently selected from one or more of hydrogen, fluorine, chlorine, and a trifluoromethyl group. In any embodiment, the molar content of the monomer represented by formula I is 50% to 70% based on the total number of moles of the monomer represented by formula I and the monomer represented by formula II. In any embodiment, the molar content of the monomer represented by formula II is 30% to 50% based on the total number of moles of the monomer represented by formula I and the monomer represented by formula II. In any embodiment, the polymerization reaction comprises a first stage polymerization and a second stage polymerization; First-stage polymerization: adding an initiator, an emulsifier, at least one monomer represented by formula I and an aqueous medium to a reaction vessel to carry out a first-stage polymerization, and continuously feeding the monomer represented by formula I in the first-stage polymerization; Second-stage polymerization: After reacting for a certain period of time, at least one monomer represented by formula II is added to the reaction vessel to carry out second-stage polymerization, and the monomer represented by formula I is continuously fed in the second-stage polymerization.

[0007] The method of the present application first continuously feeds the monomer represented by Formula I to form fluorine-containing segments, thereby imparting high thermal stability to the fluorine-containing polymer. Then, the monomer represented by Formula II is introduced to reduce contact between the fluorine-containing segments and the external environment, thereby effectively mitigating the gelation phenomenon caused by elemental fluorine. Compared with fluorine-containing polymers produced by simultaneously polymerizing all monomers in a reaction vessel, the fluorine-containing polymer produced by this method effectively improves the stability of the conductive slurry, improves the anti-settling properties of the slurry, improves the adhesion of the electrode plates, reduces the membrane resistance of the electrode plates and the DC internal resistance of the battery, and improves the dynamic performance of the battery. Furthermore, when the monomer represented by Formula II is fed into the reaction vessel to carry out the second-stage polymerization reaction, subsequently feeding the monomer represented by Formula I into the reaction vessel improves the compatibility between the segments produced in the first-stage polymerization reaction and the segments produced in the second-stage polymerization reaction, thereby improving the stability of the fluorine-containing polymer.

[0008] In any embodiment, the mass of the monomer represented by formula I introduced in the first polymerization stage is 80% to 85% of the total mass of the monomer represented by formula I supplied in the polymerization reaction, and the mass of the monomer represented by formula I introduced in the second polymerization stage is 15% to 20% of the total mass of the monomer represented by formula I supplied in the polymerization reaction. In any embodiment, the weight percent of the initiator is 0.5% to 1.4% based on the total weight of the monomer shown in Formula I and the monomer shown in Formula II. In any embodiment, the weight percent of the emulsifier is 0.1% to 0.4% based on the total weight of the monomer shown in Formula I and the monomer shown in Formula II.

[0009] In any embodiment, the weight percent of the aqueous medium provided in the first stage polymerization is 400% to 600% based on the total weight of the monomers shown in Formula I and Formula II. In an optional embodiment, the reaction pressure of the first-stage polymerization and the second-stage polymerization are both 6.0 MPa to 9.0 MPa, and the reaction temperature is 80°C to 120°C. In an optional embodiment, the emulsifier is an alkali metal salt of perfluorooctanoic acid. In any embodiment, the initiator is one or two of N,N dimethylbenzylamine, N-methamphetamine.

[0010] According to a third aspect of the present application, there is provided an application of the fluorine-containing polymer according to the first aspect to a secondary battery. According to a fourth aspect of the present application, there is provided a conductive slurry, which comprises a conductive agent, a solvent, and the fluorine-containing polymer according to the first aspect. Compared with the conventional technology of directly adding a conductive agent during the production process of a positive electrode slurry, the conductive slurry of the present application improves the dispersibility of the conductive agent in the positive electrode slurry, enhances the conductive effect of the conductive agent in the electrode plate, and more effectively reduces the content of the conductive agent in the electrode plate, thereby increasing the load of the positive electrode active material in the electrode plate and advantageously improving the output performance of the battery. In any embodiment, the mass fraction of the conductive agent is 10.0% to 15.0% based on the total mass of the conductive slurry.

[0011] The mass fraction of the conductive agent is controlled within an appropriate range based on the total mass of the conductive slurry. A slurry with an appropriate viscosity can provide good adhesion to the electrode plate, and can comprehensively improve the processing and use performance of the slurry. In any embodiment, the mass fraction of the fluorine-containing polymer is 0.5% to 2.5% based on the total mass of the conductive slurry. The mass fraction of the fluorine-containing polymer is controlled within an appropriate range based on the total mass of the conductive slurry, so that the slurry has an appropriate viscosity and good adhesion to the electrode plate, thereby comprehensively improving the processing and use performance of the slurry. In any embodiment, the conductive slurry has a solid content of 10.5% to 17.5%, and a viscosity of 300 mPa·s to 900 mPa·s. With a solid content of 10.5% to 17.5% and a viscosity of 300 mPa·s to 900 mPa·s, the cathode slurry can be produced by directly mixing and stirring with the active material and adhesive, eliminating the need to add additional auxiliary agents, which is advantageous for improving production efficiency and reducing production costs.

[0012] According to a fifth aspect of the present application, there is provided a positive electrode plate, the positive electrode plate including a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, the positive electrode film layer including a positive electrode active material, a conductive agent, and an adhesive, and the conductive agent being a deposit of the conductive slurry according to the fourth aspect. Compared to positive electrode plates manufactured by directly adding conductive agent powder in conventional technology, the conductive agent in the positive electrode plate disclosed in the present application is present in the positive electrode plate in the form of a conductive slurry deposit, which can reduce the membrane resistance of the positive electrode plate when the amount of conductive agent added is small, providing the possibility of further improving the loading amount of positive electrode active material in the plate. In any embodiment, when the mass content of the conductive agent is 0.5% to 0.8% based on the total mass of the positive electrode membrane layer, the film resistance of the positive electrode plate is less than 0.2Ω. In any embodiment, the adhesive strength per unit length between the positive electrode film layer and the positive electrode current collector is 14 N / m or more.

[0013] According to a sixth aspect of the present application, there is provided a secondary battery, the secondary battery including a separator, a negative electrode plate, an electrolyte, and the positive electrode plate according to the fifth aspect. 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. According to a seventh aspect of the present application, there is provided a battery module, which includes the secondary battery according to the sixth aspect of the present application. According to an eighth aspect of the present application, there is provided a battery pack, which includes the secondary battery according to the sixth aspect of the present application or the battery module according to the seventh aspect of the present application. According to a ninth aspect of the present application, there is provided a power consumption device, which includes at least one selected from the secondary battery of the sixth aspect of the present application, the battery module of the seventh aspect of the present application, and the battery pack of the eighth aspect of the present application. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic diagram of a secondary battery according to an embodiment of the present application; [Figure 2] FIG. 2 is an exploded view of the secondary battery shown in FIG. 1 according to the embodiment of the present application. [Figure 3] 1 is a schematic diagram of a battery module according to an embodiment of the present application; [Figure 4] 1 is a schematic diagram of a battery pack according to an embodiment of the present application. [Figure 5] FIG. 5 is an exploded view of the battery pack shown in FIG. 4 according to an embodiment of the present application. [Figure 6] 1 is a schematic diagram of a power consumption device that uses a secondary battery as a power source according to an embodiment of the present application. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, with appropriate reference to the drawings, embodiments specifically disclosing the adhesive, preparation method, electrode, battery, and power consumption device of the present application will be described in detail. However, unnecessary detailed description may be omitted. For example, detailed description of well-known matters and redundant description of actually identical structures may be omitted. This is to avoid the following description becoming unnecessarily long and to facilitate understanding by those skilled in the art. Note that the drawings and the following description are provided to enable those skilled in the art to fully understand the present application, and are not intended to limit the subject matter described in the claims. The "ranges" disclosed in this application are defined in the form of lower and upper limits, and a given range is defined by selecting one lower limit and one upper limit, and the selected lower and upper limits define the boundaries of the particular range. Such defined ranges may be inclusive or exclusive of the end values, and are arbitrarily combinable; i.e., any lower limit can be combined with any upper limit to form a single range. For example, if ranges of 60 to 120 and 80 to 110 are listed for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if 1 and 2 are listed as minimum range values ​​and 3, 4, and 5 are listed as maximum range values, the ranges 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5 are all contemplated. In this application, unless otherwise specified, a numerical range "a to b" represents a shorthand notation for any combination of real numbers a to b, where a and b are both real numbers. For example, the numerical range "0-5" indicates that this specification has already listed all real numbers between "0-5," and "0-5" is merely a shorthand representation of combinations of these numbers. Also, expressing a parameter as an integer ≧2 is equivalent to disclosing that this parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0016] Unless otherwise stated, all embodiments and optional embodiments in the present application can be combined with each other to form a new technical solution. Unless otherwise stated, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution. Unless otherwise specified, all steps in this application may be performed in order or randomly, and are preferably performed in order. For example, when the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed in order, or steps (b) and (a) performed in order. For example, when the method mentioned above may further include step (c), it means that step (c) may be added to the method in any order, and for example, 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.

[0017] Unless otherwise specified, the terms "comprise" and "include" used in this application may be open-ended or closed-ended. For example, the terms "comprise" and "include" may indicate that other components not listed may be further included or included, or that only the listed components may be included or included. Unless otherwise stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if A is true (or exists) and B is false (or does not exist), if A is false (or does not exist) and B is true (or exists), or if both A and B are true (or exist).

[0018] The low conductivity of the active material in secondary batteries can lead to problems during battery fabrication, such as high internal resistance and poor rate and cycle performance. Therefore, it is necessary to add a conductive agent to improve the conductivity of the active material and overall battery performance. However, conventional conductive agents generally have a relatively large specific surface area, which makes them prone to aggregation due to van der Waals forces, thereby affecting their conductive properties. The applicant discovered that preparing a conductive agent as a conductive slurry and then mixing it with the active material and / or adhesive to produce a slurry helps slow aggregation during the slurry mixing process, but that a dispersant must be added to the conductive slurry to improve the dispersibility and stability of the conductive slurry. Adding a dispersant to the conductive slurry can affect the electrochemical performance, cycle performance, and batch stability of the battery, and can also lead to incompatibility between the dispersant and the positive electrode slurry system. Based on the above technical challenges, the present application has developed a fluorine-containing polymer, which gives the conductive slurry suitable viscosity and excellent filterability, improves the gelation resistance and storage stability of the conductive slurry, significantly widens the process window of the conductive slurry, and improves the processability of the conductive slurry. [Fluorine-containing polymer] In view of this, the present application provides a fluorine-containing polymer, comprising a structural unit derived from a monomer represented by formula I and a structural unit derived from a monomer represented by formula II, TIFF2025535450000004.tif26150 where R1, R2, and R3 each independently represent hydrogen, fluorine, chlorine, or fluorine-substituted C. 1-3 alkyl group, and R4 and R5 are each independently selected from hydrogen, substituted or unsubstituted C 1-5 alkyl groups, and R6 is selected from one or more of C 1-5 The alkyl group may be selected from one or more of a substituted or unsubstituted aryl group.

[0019] As used herein, the term "fluorine-containing polymer" refers to a polymer whose structural units contain fluorine atoms. As used herein, the term "polymer" refers, on the one hand, to an assembly of macromolecules produced by a polymerization reaction, which are chemically homogeneous but differ in degree of polymerization, molar mass and chain length, and, on the other hand, the term may also include derivatives of such macromolecular assemblies formed by a polymerization reaction, i.e., products that may be obtained by reaction, for example addition or substitution, of functional groups in said macromolecules and that may be chemically homogeneous or chemically heterogeneous. In this specification, "C 1-3 The term "alkyl group" refers to a straight or branched hydrocarbon chain radical consisting solely of carbon and hydrogen atoms, the radical being free of unsaturation, having from 1 to 3 carbon atoms, and attached to the rest of the molecule by a single bond. As used herein, "fluorine-substituted C 1-3 The term "alkyl group" refers to a C alkyl group in which at least one hydrogen atom is replaced by a fluorine atom. 1-3 Refers to an alkyl group.

[0020] In this specification, "C 1-5 The term "alkyl group" refers to a straight or branched hydrocarbon chain radical consisting solely of carbon and hydrogen atoms, the radical being free of unsaturation, having from 1 to 5 carbon atoms, and attached to the rest of the molecule by a single bond. As used herein, the term "substituted" refers to the replacement of at least one hydrogen atom of the compound or chemical moiety with a substituent on another chemical moiety, each of which may independently be a hydroxyl group, a thiol group, an amino group, a cyano group, a nitro group, an aldehyde group, a halogen atom, an alkenyl group, an alkynyl group, an aryl group, a heteroaryl group, a C 1-6 Alkyl group, C 1-6 The alkoxy group is selected from the group consisting of alkoxy groups.

[0021] As used herein, the term "aryl group" refers to an aromatic ring system in which at least one ring is aromatic, including, but not limited to, phenyl, biphenyl, indanyl, 1-naphthyl, 2-naphthyl, and tetrahydronaphthyl groups. As used herein, the term "process window" refers to a process interval within which product quality can be ensured, including, but not limited to, a temperature interval, a pressure interval, storage time length, etc. As can be appreciated, the wider the process window, the lower the demand for process precision. In some embodiments, R6 is a C substituted with an aryl group. 1-5 The alkyl group is an alkyl group, and the aryl group is a substituted or unsubstituted aryl group. In some embodiments, the monomer according to Formula I is selected from one or more of vinyl fluoride, vinylidene fluoride, tetrafluoroethylene, chlorotrifluoroethylene, hexafluoropropylene. In some embodiments, the monomer shown in Formula II is selected from one or more of 2-benzylacrylic acid, 2-(4-isobutylbenzyl)acrylic acid, 2-methylene-4-phenylbutyric acid, and 2-(1-phenylethyl)acrylic acid. In some embodiments, the polymer comprises one or more structural units derived from a monomer shown in Formula I. In some embodiments, the polymer comprises one or more structural units derived from a monomer shown in Formula II. In some embodiments, the polymer comprises vinylidene fluoride-2-benzyl acrylic acid copolymer, vinylidene fluoride-2-(4-isobutylbenzyl) acrylic acid copolymer, vinylidene fluoride-2-methylene-4-phenylbutyric acid copolymer, vinylidene fluoride-2-(1-phenylethyl) acrylic acid copolymer, vinyl fluoride-2-benzyl acrylic acid copolymer, tetrafluoroethylene-2-benzyl acrylic acid copolymer, tetrafluoroethylene-2-(4-isobutylbenzyl) acrylic acid copolymer, vinylidene fluoride-chlorotrifluoroethylene-2-benzyl acrylic acid copolymer.

[0022] The fluorine element in the structural unit derived from the monomer shown in Formula I can form hydrogen bonds with the hydroxyl and / or carboxyl groups on the current collector surface. The carboxyl group contained in the structural unit derived from the monomer shown in Formula II can also form hydrogen bonds with the hydroxyl and / or carboxyl groups on the current collector surface, thereby providing good adhesion to the positive electrode plate. The structural unit derived from the monomer shown in Formula II can effectively reduce the fluorine content of the fluorine-containing polymer and improve the gelation of the slurry caused by the fluorine element. Furthermore, the structural unit derived from the monomer shown in Formula II can further increase the steric hindrance of the fluorine-containing polymer, reducing the aggregation of the fluorine-containing units, thereby reducing the viscosity of the slurry and slowing the gelation of the slurry, thereby effectively improving the filterability of the slurry. Furthermore, the aryl group contained in the structural unit derived from the monomer shown in Formula II has a similar element and structure to the conductive agent, and can interact with the conductive agent to improve the stability of the conductive slurry and improve the anti-settling properties of the conductive slurry.

[0023] Compared with conventional polyvinylidene fluoride adhesives, the fluorine-containing polymer of the present application can reduce the viscosity of the conductive slurry and improve the filterability of the conductive slurry, making the slurry less likely to gel during storage, improving the gelation resistance and storage stability of the conductive slurry, significantly widening the process window of the conductive slurry, and improving the processability of the conductive slurry, thereby meeting the production needs of the conductive slurry without adding a dispersant to the conductive slurry, and thereby further reducing the film resistance of the electrode plate and the DC impedance of the battery. In some embodiments, R 1 in Formula I is fluorine, and R 2 and R 3 are each independently selected from one or more of hydrogen, fluorine, chlorine, and a trifluoromethyl group. In some embodiments, the molar content of the structural unit derived from the monomer represented by formula I is 50% to 70% based on the total number of moles of all structural units in the fluorine-containing polymer. In some embodiments, the molar content of the structural unit derived from the monomer represented by formula I is optionally any one of 50%, 60%, and 70% based on the total number of moles of all structural units in the fluorine-containing polymer.

[0024] By controlling the molar content of the structural units derived from the monomer shown in Formula I within an appropriate range, the conductive slurry can have an appropriate viscosity, achieving a balance between the viscosity of the conductive slurry and the adhesiveness of the electrode plate, thereby comprehensively improving the processing performance and use performance of the conductive slurry. In some embodiments, the molar content of the structural unit derived from the monomer represented by formula II is 30% to 50% based on the total number of moles of all structural units in the fluorine-containing polymer. In some embodiments, the molar content of the structural unit derived from the monomer represented by formula II is optionally any one of 30%, 40%, and 50% based on the total number of moles of all structural units in the fluorine-containing polymer. By controlling the molar content of the structural unit derived from the monomer shown in Formula II within an appropriate range, the conductive slurry can have an appropriate viscosity, achieving a balance between the viscosity of the conductive slurry and the adhesiveness of the electrode plate, thereby comprehensively improving the processing performance and use performance of the conductive slurry. In some embodiments, the mass average molecular weight of the fluorine-containing polymer is 100,000 to 140,000. In some embodiments, the mass average molecular weight of the fluorine-containing polymer is optionally any one of 100,000, 110,000, 120,000, 130,000, and 140,000.

[0025] As used herein, the term "weight average molecular weight" refers to the sum of the weight fractions of molecules of different molecular weights in a polymer multiplied by the corresponding molecular weights. In this application, the weight-average molecular weight of a polymer can be tested by methods known in the art, such as gel chromatography, using, for example, a Waters 2695 Isocratic HPLC-type gel chromatograph (differential refractive index detector 2141). In some embodiments, the test method involves selecting a matching chromatography column (oil-based: Styragel HT5 DMF 7.8 x 300 mm + Styragel HT4) based on a mass fraction of 3.0%. A viscous solution of 3.0% fluorine-containing polymer is prepared in purified N-methylpyrrolidone (NMP) solvent and allowed to stand for one day. During testing, tetrahydrofuran is first drawn into a syringe, washed, and repeated several times. 5 ml of test solution is then drawn into the syringe, the air is expelled, and the needle tip is wiped dry. Finally, the sample solution is slowly injected into the injection port. When the displayed number stops changing, data is acquired and the weight-average molecular weight is read.

[0026] Controlling the mass average molecular weight of the fluorine-containing polymer within an appropriate range imparts an appropriate viscosity to the slurry, which is advantageous for the subsequent production of a positive electrode slurry. At the same time, a fluorine-containing polymer having an appropriate mass average molecular weight is advantageous for forming a three-dimensional net-like adhesive structure, imparting good adhesive strength to the electrode plate, achieving a balance between the viscosity of the conductive slurry and the adhesiveness of the electrode plate, and comprehensively improving the processing performance and use performance of the conductive slurry. In one embodiment of the present application, there is provided a method for producing a fluorine-containing polymer, comprising the steps of: polymerizing at least one monomer of formula I with at least one monomer of formula II under polymerizable conditions; TIFF2025535450000005.tif26150 where R1, R2, and R3 are each independently hydrogen, fluorine, chlorine, or fluorine-substituted C. 1-3 alkyl group, and R4 and R5 are each independently selected from hydrogen, substituted or unsubstituted C 1-5 alkyl groups, and R6 is selected from one or more of C 1-5The alkyl group may be selected from one or more of a substituted or unsubstituted aryl group.

[0027] Compared with conventional adhesives, the fluorine-containing polymer produced by this method can reduce the viscosity of the conductive slurry and improve the filterability of the conductive slurry, thereby making the slurry less likely to gel during storage, improving the gelation resistance and storage stability of the conductive slurry, significantly widening the process window of the conductive slurry, and improving the processability of the conductive slurry, thereby meeting the production needs of conductive slurry without adding a dispersant to the conductive slurry. In some embodiments, R 1 in Formula I is fluorine, and R 2 and R 3 are each independently selected from one or more of hydrogen, fluorine, chlorine, and a trifluoromethyl group. In some embodiments, the molar content of the monomer represented by formula I is 50% to 70% based on the total number of moles of the monomer represented by formula I and the monomer represented by formula II. In some embodiments, the molar content of the monomer represented by formula II is 30% to 50% based on the total number of moles of the monomer represented by formula I and the monomer represented by formula II. In some embodiments, the polymerization reaction comprises a first stage polymerization and a second stage polymerization; First-stage polymerization: adding an initiator, an emulsifier, at least one monomer represented by formula I and an aqueous medium to a reaction vessel to carry out a first-stage polymerization, and continuously feeding the monomer represented by formula I in the first-stage polymerization; Second-stage polymerization: After reacting for a certain period of time, at least one monomer represented by formula II is added to the reaction vessel to carry out second-stage polymerization, and the monomer represented by formula I is continuously fed in the second-stage polymerization.

[0028] The method of the present application first continuously feeds the monomer represented by Formula I to form fluorine-containing segments, thereby imparting high thermal stability to the fluorine-containing polymer. Then, the monomer represented by Formula II is introduced to reduce contact between the fluorine-containing segments and the external environment, thereby effectively mitigating the gelation phenomenon caused by elemental fluorine. Compared with fluorine-containing polymers produced by simultaneously polymerizing all monomers in a reaction vessel, the fluorine-containing polymer produced by this method effectively improves the stability of the conductive slurry, improves the anti-settling properties of the slurry, improves the adhesion of the electrode plates, reduces the membrane resistance of the electrode plates and the DC internal resistance of the battery, and improves the dynamic performance of the battery. Furthermore, when the monomer represented by Formula II is fed into the reaction vessel to carry out the second-stage polymerization reaction, subsequently feeding the monomer represented by Formula I into the reaction vessel improves the compatibility between the segments produced in the first-stage polymerization reaction and the segments produced in the second-stage polymerization reaction, thereby improving the stability of the fluorine-containing polymer. In some embodiments, the mass of the monomer represented by formula I introduced in the first-stage polymerization is 80% to 85% of the total mass of the monomer represented by formula I supplied in the polymerization reaction, and the mass of the monomer represented by formula I introduced in the second-stage polymerization is 15% to 20% of the total mass of the monomer represented by formula I supplied in the polymerization reaction. In some embodiments, the weight percent of the initiator is 0.5% to 1.4% based on the total weight of the monomers shown in Formula I and Formula II. In some embodiments, the weight percent of the emulsifier is 0.1% to 0.4% based on the total weight of the monomer of Formula I and the monomer of Formula II. In some embodiments, the weight percent of the aqueous medium provided in the first-stage polymerization is 400% to 600% based on the total weight of the monomers shown in Formula I and Formula II. In some embodiments, the reaction pressure for both the first-stage polymerization and the second-stage polymerization is 6.0 MPa to 9.0 MPa, and the reaction temperature is 80°C to 120°C. In some embodiments, the emulsifier is an alkali metal salt of perfluorooctanoic acid. In some embodiments, the initiator is one or two of N,N dimethylbenzylamine, N-methamphetamine.

[0029] In one embodiment of the present application, there is provided an application of the fluorine-containing polymer in any embodiment 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. [Conductive slurry] In one embodiment of the present application, a conductive slurry is provided, which includes a conductive agent, a solvent, and, in an optional embodiment, a fluorine-containing polymer. In some embodiments, the solvent is an aqueous solvent, for example, deionized water. In some embodiments, the solvent is an oil-based solvent, examples of which include, but are not limited to, dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, acetone, dimethyl carbonate, ethyl cellulose, and polycarbonate.

[0030] Compared with conventional techniques in which a conductive agent is directly added during the preparation of a positive electrode slurry, the conductive slurry of the present application improves the dispersibility of the conductive agent in the positive electrode slurry, enhances the conductive effect of the conductive agent in the electrode plate, and more effectively reduces the conductive agent content in the electrode plate, further increasing the electrode plate loading capacity and improving the battery output performance. Furthermore, the fluorine-containing polymer in the conductive slurry can function as both an adhesive and a dispersant, eliminating the need for additional dispersants in the conductive slurry, which is advantageous for further improving the active material loading capacity in the electrode plate and the electrode plate adhesive strength. In some embodiments, the mass fraction of the conductive agent is 10.0% to 15.0% based on the total mass of the conductive slurry, and optionally, the mass fraction of the conductive agent is any one of 10%, 11%, 12%, 13%, 14%, and 15%.

[0031] The mass fraction of the conductive agent is controlled within an appropriate range based on the total mass of the conductive slurry, so that the slurry has an appropriate viscosity and good adhesion to the electrode plate, thereby comprehensively improving the processing and application performance of the slurry. In some embodiments, the mass fraction of the fluorine-containing polymer is 0.5% to 2.5% based on the total mass of the conductive slurry, and optionally, is any one of 0.5%, 1.0%, 1.5%, 2.0%, and 2.5%. The mass fraction of the fluorine-containing polymer is controlled within an appropriate range based on the total mass of the conductive slurry, so that the slurry has an appropriate viscosity, which is advantageous for the subsequent preparation of a positive electrode slurry, and also provides good adhesion to the electrode plate, thereby comprehensively improving the processing and use performance of the slurry. In some embodiments, the conductive slurry has a solids content of 10.5% to 17.5%, and a viscosity of 300 mPa·s to 900 mPa·s. In some embodiments, the viscosity of the conductive slurry is optionally any one of 400 mPa·s to 900 mPa·s, 400 mPa·s to 800 mPa·s, 400 mPa·s to 750 mPa·s, 400 mPa·s to 600 mPa·s, 450 mPa·s to 800 mPa·s, 450 mPa·s to 750 mPa·s, 450 mPa·s to 650 mPa·s, and 500 mPa·s to 750 mPa·s.

[0032] The conductive slurry has a solid content of 10.5% to 17.5% and a viscosity of 300 mPa·s to 900 mPa·s, and can be directly mixed with an active material and adhesive and stirred to produce a positive electrode slurry. This eliminates the need to add additional additives to the conductive slurry, which is advantageous for improving production efficiency and reducing production costs.

[0033] [Positive electrode plate] Some examples of the present application provide a positive electrode plate, which includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, the positive electrode film layer including a positive electrode active material, a conductive agent, and an adhesive, and the conductive agent is a deposit of a conductive slurry in any embodiment. As used herein, the term "adhesive" refers to a chemical compound, polymer, or mixture that forms a colloidal solution or dispersion in a dispersing medium.

[0034] Compared to positive electrode plates manufactured by directly adding conductive agent powder in conventional technology, the conductive agent in the positive electrode plate disclosed in the present application is present in the positive electrode plate in the form of a conductive slurry deposit, which can reduce the membrane resistance of the positive electrode plate when the amount of conductive agent added is small, providing the possibility of further improving the loading amount of positive electrode active material in the plate. In some embodiments, when the mass content of the conductive agent is 0.5% to 0.8% based on the total mass of the positive electrode membrane layer, the membrane resistance of the positive electrode plate is less than 0.2Ω. In some embodiments, the adhesive strength per unit length between the positive electrode membrane layer and the positive electrode current collector is 14 N / m or greater.

[0035] For example, the positive electrode current collector has two surfaces that are opposite to each other in the thickness direction of the positive electrode current collector, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector. In some embodiments, the positive electrode current collector may be a metal foil sheet or a composite current collector. For example, aluminum foil may be used as the metal foil sheet. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base layer. The composite current collector may be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, or silver alloy) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)). In some embodiments, the positive electrode active material may be a positive electrode active material for batteries known in the art. For example, the positive electrode active material may include at least one of an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and a modified compound thereof. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery positive electrode active material may also be used. These positive electrode active materials may be used alone or in combination of two or more. Here, examples of lithium transition metal oxides include lithium cobalt oxide (e.g., LiCoO), lithium nickel oxide (e.g., LiNiO), lithium manganese oxide (e.g., LiMnO, LiMnO), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, and lithium nickel cobalt manganese oxide (e.g., LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM 333 (may be abbreviated as "LiNi") 0.5 Co 0.2 Mn 0.3 O2(NCM 523 (may be abbreviated as "LiNi") 0.5 Co 0.25 Mn 0.25 O2(NCM 211 (may be abbreviated as "LiNi") 0.6 Co 0.2 Mn 0.2 O2(NCM 622 (may be abbreviated as "LiNi") 0.8 Co 0.1 Mn 0.1 O2(NCM 811 ), lithium nickel cobalt aluminum oxide (e.g., LiNi 0.85 Co 0.15 Al 0.05O2) and modified compounds thereof, etc. Examples of the lithium-containing phosphate having an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (e.g., LiFePO4 (which may be abbreviated as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (e.g., LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon.

[0036] In some embodiments, the positive electrode membrane layer optionally further includes an adhesive. For example, the adhesive 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 a fluorine-containing acrylate resin. In some embodiments, the positive electrode film layer optionally further includes a conductive agent, for example, superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, a positive electrode plate can be manufactured by the following method: the components for manufacturing a positive electrode plate, such as a fluorine-containing polymer, a conductive agent, and a solvent, are stirred to prepare a conductive slurry, and a positive electrode active material, an adhesive, and any other components are dispersed in the conductive slurry to form a positive electrode slurry. The positive electrode slurry is then applied onto a positive electrode current collector, and after undergoing steps such as drying and cold pressing, a positive electrode plate is obtained.

[0037] [Negative electrode plate] The negative electrode plate includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material. For example, the negative electrode current collector has two surfaces that are opposite to each other in the thickness direction of the negative electrode current collector, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector. In some embodiments, the negative electrode current collector may be a metal foil sheet or a composite current collector. For example, a copper foil may be used as the metal foil sheet. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, or silver alloy) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0038] In some embodiments, the negative electrode active material may be a battery negative electrode active material known in the art. For example, the negative electrode active material may include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, a silicone-based material, a tin-based material, and lithium titanate. The silicone-based material may be selected from at least one of a silicone element, a silicone oxide, a silicone carbon composite, a silicone nitrogen composite, and a silicone alloy. The tin-based material may be selected from at least one of a tin element, a tin oxide, and a tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery negative electrode active material may also be used. These negative electrode active materials may be used alone or in combination of two or more. In some embodiments, the negative electrode membrane layer optionally further comprises an adhesive, which 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).

[0039] In some embodiments, the negative electrode film layer further optionally includes 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. In some embodiments, the negative electrode membrane layer further optionally includes other auxiliary agents, such as a thickener (e.g., carboxymethylcellulose sodium (CMC-Na)). In some embodiments, the negative electrode plate can be manufactured in the following manner: Components for manufacturing the negative electrode plate, such as a negative electrode active material, a conductive agent, an adhesive, and any other components, are dispersed in a solvent (e.g., deionized water) to form a negative electrode slurry, which is then applied to a negative electrode current collector, and the negative electrode plate is obtained after processes such as drying and cold pressing.

[0040] [Electrolyte] The electrolyte serves to conduct ions between the positive and negative electrodes. The present application does not specifically limit the type of electrolyte, and it can be selected according to needs. For example, the electrolyte may be liquid, gel, or all solid. In some embodiments, the electrolyte is an electrolytic solution, which includes an electrolyte salt and a solvent.

[0041] In some embodiments, the electrolyte salt may be chosen 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 difluoro(oxalato)borate, lithium bis(oxalato)borate, lithium difluorobis(oxalato)phosphate, and lithium tetrafluoro(oxalato)phosphate. In some embodiments, the solvent may be chosen 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, sulfolane, dimethyl sulfone, ethyl methyl sulfone, and diethyl sulfone. In some embodiments, the electrolyte solution further optionally contains additives. For example, the additives may include a negative electrode film-forming additive, a positive electrode film-forming additive, and may further include additives that can improve some battery performance, such as an additive that improves the overcharge performance of the battery, or an additive that improves the high-temperature or low-temperature performance of the battery.

[0042] [Separator] In some embodiments, the secondary battery further includes a separator. The present application does not particularly limit the type of separator, and any known porous separator with good chemical stability and mechanical stability may be selected. In some embodiments, the separator may be made of at least one material selected from glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without any particular limitations. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without any particular limitations. In some embodiments, the positive and negative electrodes and the separator can be fabricated into an electrode assembly by a winding or lamination process. In some embodiments, the secondary battery may include an exterior body, which may be used to package the electrode assembly and the electrolyte. In some embodiments, the exterior of the secondary battery may be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The exterior of the secondary battery may be a pouch, such as a bag-shaped pouch. The pouch may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0043] The present application does not particularly limit the shape of the secondary battery, which may be cylindrical, rectangular, or any other shape. For example, Figure 1 shows an example of a rectangular secondary battery 5. In some embodiments, referring to FIG. 2 , the exterior body may include a case 51 and a cover plate 53. Here, the case 51 may include a bottom plate and a side plate connected to the bottom plate, where the bottom plate and the side plate together form a surrounding accommodating cavity. The case 51 has an opening communicating with the accommodating cavity, and the cover plate 53 can cover the opening and seal the accommodating cavity. The positive electrode plate, the negative electrode plate, and the separator may be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is packaged in the accommodating cavity. An electrolyte is impregnated into the electrode assembly 52. ​​The number of electrode assemblies 52 included in the secondary battery 5 may be one or more, and those skilled in the art can select the number according to actual needs. In some embodiments, the secondary batteries may be assembled into a battery module, and the number of secondary batteries included in the battery module may be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module. Fig. 3 shows an example of a battery module 4. Referring to Fig. 3, in the battery module 4, a plurality of secondary batteries 5 may be arranged in order along the longitudinal direction of the battery module 4. Of course, they may be arranged in any other manner. Furthermore, the plurality of secondary batteries 5 may be fixed by fasteners.

[0044] Optionally, the battery module 4 may further include a housing having an accommodating space, and the plurality of secondary batteries 5 are accommodated in this accommodating space. In some embodiments, the battery modules may be further assembled into a battery pack, and the number of battery modules included in the battery pack may be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack. 4 and 5 show an example of a battery pack 1. Referring to FIG. 5 and the drawings, the battery pack 1 may include a battery box and a plurality of battery modules 4 installed in the battery box. The battery box includes an upper housing 2 and a lower housing 3, and the upper housing 2 is provided to cover the lower housing 3, forming an enclosed space for accommodating the battery modules 4. The plurality of battery modules 4 may be arranged in the battery box in any manner. The present application also provides a power consuming device, the power consuming device including at least one of a secondary battery, a battery module, or a battery pack according to the present application. The secondary battery, the battery module, or the battery pack may be used as a power source for the power consuming device or as an energy storage unit for the power consuming device. The power consuming device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc.

[0045] The power consumption device can be selected from a secondary battery, a battery module, or a battery pack depending on its usage needs. 6 shows an example of a power consuming device, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, in which a battery pack or a battery module can be used to meet the demand for high power output and high energy density of the secondary battery of the power consuming device. Other examples of the device may be a mobile phone, a tablet computer, a laptop computer, etc. These devices are generally required to be lightweight and can use a secondary battery as a power source.

[0046] Example The following examples of the present application are described. The examples described below are illustrative and are intended only to interpret the present application and should not be understood as limitations on the present application. If specific techniques or conditions are not specified in the examples, they will be carried out according to the techniques or conditions described in literature in the field or according to the product specifications. If the manufacturer of the reagents or equipment used is not specified, they are all ordinary products that are commercially available. 1. Manufacturing method

[0047] Example 1 1) Production of fluorine-containing polymers 22.6 kg of deionized water (electrical conductivity of 2 μs / cm or less), 11.3 g of sodium perfluorooctanoate, and 40.7 g of N,N-dimethylbenzylamine were added in this order to a 50 L reactor, and the reactor was closed. The reactor is evacuated and nitrogen gas is introduced. This process is repeated until the oxygen concentration in the reactor is less than 100 ppm. Vinylidene fluoride monomer was introduced into the reactor until the pressure inside the reactor reached 8.0 MPa. The temperature in the vessel is raised to 100°C to start the reaction, and during the reaction, vinylidene fluoride monomer is continuously introduced to maintain the reaction pressure in the vessel constant. After introducing 16.8 mol of vinylidene fluoride monomer, add 20 mol of 2-benzylacrylic acid into the reactor, maintain the reaction pressure at 8.0 MPa and the temperature at 100°C, introduce the remaining 3.2 mol of vinylidene fluoride monomer into the reactor, and continue the reaction for 2 hours. When the reaction is completed, the pressure in the vessel is reduced to 0.2 MPa, and the unreacted vinylidene fluoride monomer is recovered. The reaction product was coagulated, washed, separated, dried and ground to obtain vinylidene fluoride-2-benzyl acrylic acid copolymer.

[0048] 2) Manufacturing of conductive slurry 17,600 g of N-methylpyrrolidone was added to a 35 L stirring tank. 200g of vinylidene fluoride-2-benzyl acrylic acid copolymer was added to N-methylpyrrolidone, and the stirring speed was set to 1000 rpm and the stirring time was set to 60 minutes. After the stirring was completed, a primary slurry was obtained. 2200 g of conductive carbon black powder was added to the primary slurry, the stirring speed was set to 1000 rpm, the stirring time was set to 60 minutes, cooling water circulation was started, and after stirring was completed, a conductive carbon black slurry was obtained.

[0049] 3) Manufacturing of positive electrode plates 2840 g of lithium iron phosphate material, 62.8 g of polyvinylidene fluoride, and 2000 g of conductive slurry were stirred to uniformly mix to obtain a positive electrode slurry. The positive electrode slurry was then uniformly applied onto a positive electrode current collector, and then dried, cold pressed, and slit to obtain a positive electrode plate.

[0050] 4) Manufacturing of negative electrode plates The active material, artificial graphite, the conductive agent, carbon black, the adhesive, styrene butadiene rubber (SBR), and the thickener, sodium carboxymethyl cellulose (CMC), were dissolved in deionized water as a solvent in a weight ratio of 96.2:0.8:0.8:1.2 and mixed uniformly to produce anode slurry. The cathode slurry was then uniformly applied to the copper foil of the cathode current collector in one or more coats, followed by drying, cold pressing, and slitting to obtain a cathode plate. 5) Separator A polypropylene membrane was used as the separator.

[0051] 6) Electrolyte production In an argon atmosphere glove box (H2O<0.1 ppm, O2<0.1 ppm), organic solvents ethylene carbonate (EC) / ethyl methyl carbonate (EMC) were mixed uniformly in a volume ratio of 3 / 7, and 12.5% ​​LiPF6 lithium salt was added and dissolved in the organic solvent, followed by stirring uniformly to obtain the electrolyte solution of Example 1.

[0052] 7) Battery manufacturing The positive electrode plate, separator, and negative electrode plate of Example 1 were stacked in this order, with a separator between the positive and negative electrodes to provide isolation, and then wound to obtain a bare cell. Tabs were welded to the bare cell, and the bare cell was placed in an aluminum shell and baked at 80°C to remove moisture. After that, an electrolyte was immediately injected and the shell was sealed to obtain a non-chargeable battery. The non-chargeable battery was then subjected to processes such as standing, hot and cold pressing, chemical formation, shaping, and capacity testing in order to obtain the lithium-ion battery product of Example 1. In Examples 2 to 5, the molar ratio of each monomer in the fluorine-containing polymer was adjusted, and other parameters were the same as those in Example 1. For specific parameters, see Tables 1 and 2. In Examples 6 to 9, the polymerization temperature and the mass of the initiator N,N-dimethylbenzylamine used to prepare the fluorine-containing polymer were adjusted to give the fluorine-containing polymer different mass average molecular weights, and other parameters were the same as those in Example 1. For specific parameters, see Tables 1 and 2. In Example 6, the polymerization reaction temperature was adjusted to 95°C, and the mass of N,N-dimethylbenzylamine was adjusted to 51.3 g. In Example 7, the mass of N,N-dimethylbenzylamine was adjusted to 56.7 g, In Example 8, the mass of N,N-dimethylbenzylamine was adjusted to 59.4 g, In Example 9, the polymerization reaction temperature was adjusted to 95° C., and the mass of N,N-dimethylbenzylamine was adjusted to 48.6 g. In Examples 10 to 13, the mass fraction of the fluorine-containing polymer in the conductive slurry was adjusted, and other parameters were the same as those in Example 1; see Tables 1 and 2 for specific parameters. In Examples 14 to 17, the mass fraction of the conductive agent in the conductive undercoat slurry was adjusted, and other parameters were the same as in Example 1; see Tables 1 and 2 for specific parameters. In Example 18, the 2-benzyl acrylic acid monomer is replaced with 2-(4-isobutylbenzyl) acrylic acid monomer, and other parameters are consistent with those in Example 1. For specific parameters, see Tables 1 and 2. In Example 19, the fluorine-containing polymer is vinylidene fluoride-2-benzyl acrylic acid copolymer prepared by a conventional method, and its synthesis method is as follows: 22.6 kg of deionized water (electrical conductivity of 2 μs / cm or less), 11.3 g of sodium perfluorooctanoate, and 40.7 g of N,N-dimethylbenzylamine were added in this order to a 50 L reactor, and the reactor was closed. The reactor is evacuated and nitrogen gas is introduced. This process is repeated until the oxygen concentration in the reactor is less than 100 ppm. 20 mol of vinylidene fluoride monomer was introduced into the reactor until the pressure inside the reactor reached 8.0 MPa, and 20 mol of 2-benzylacrylic acid was added. The temperature in the vessel is raised to 100°C to start the reaction, and during the reaction, vinylidene fluoride monomer is continuously introduced to maintain the reaction pressure in the vessel constant. When the pressure inside the vessel drops to 0.2 MPa, the reaction is stopped. Cool to room temperature, flocculate, wash, separate, dry and pulverize to obtain a fluorine-containing polymer, i.e., vinylidene fluoride-2-benzyl acrylic acid copolymer, with other parameters being the same as in Example 1. See Tables 1 and 2 for specific parameters.

[0053] In Comparative Example 1, a vinylidene fluoride polymer was used as the fluorine-containing polymer. In Comparative Example 2, the 2-benzyl acrylic acid monomer was replaced with acrylic acid monomer, and the other parameters were the same as those in Example 1. For specific parameters, see Tables 1 and 2. Comparative Example 3 is substantially the same as Example 1, except that the conductive slurry containing a fluorine-containing polymer is replaced with a conductive slurry containing a dispersant, and the specific production method is as follows: 17,600 g of N-methylpyrrolidone, 200 g of polyvinylpyrrolidone, and 2,200 g of conductive carbon black powder were added to a 35 L stirring tank, the stirring speed was set to 1,000 rpm, and the stirring time was set to 60 minutes. Cooling water circulation was started, and after stirring was completed, a conductive carbon black slurry was obtained.

[0054] Comparative Example 4 is substantially the same as Example 1, except that the positive electrode plate is directly manufactured using conductive carbon black instead of the conductive slurry. Comparative Example 5 is substantially the same as Comparative Example 4, except that the mass content of the conductive carbon black is adjusted to 2.0% based on the total mass of the positive electrode membrane layer.

[0055] II. Test Method 1. Characterization of fluorine-containing polymer properties (1) Measurement of the mass average molecular weight of fluorine-containing polymers A Waters 2695 Isocratic HPLC gel chromatograph (refractive index detector 2141) was used. A matching chromatography column (oil-based: Styragel HT5 DMF 7.8 x 300 mm + Styragel HT4) was selected based on a 3.0% mass fraction polystyrene solution sample. A 3.0% fluorine-containing polymer solution was prepared in purified N-methylpyrrolidone (NMP) solvent and allowed to stand for one day. During testing, tetrahydrofuran was first drawn into the syringe, followed by washing and rinsing. This was repeated several times. 5 ml of test solution was then drawn into the syringe, the air removed, and the needle wiped dry. Finally, the sample solution was slowly injected into the injection port. When the displayed number stabilized, data was acquired and the mass-average molecular weight was read.

[0056] 2. Conductive slurry characteristic test (1) Conductive slurry viscosity test The viscosity of the primer slurry was measured using a rotational viscosity tester. An appropriate rotor was selected and secured in place. The primer slurry was placed under the rotor so that the rotor's graduations were just below the slurry. The instrument model number was Shanghai Fangrui NDJ-5S. The rotor was 62mm, the rotation speed was 30 rpm, and the measurable slurry viscosity range was 0-1000 mPa·s. The rotor was 63mm, the rotation speed was 30 rpm, and the measurable slurry viscosity range was 0-2000 mPa·s. The test temperature was 25°C, and the test time was 5 minutes. The data was read when the display stopped changing. (2) Filtration performance test of conductive slurry A 500 ml beaker was placed on the bottom end of a 200 mesh filter net bracket, and 500 ml of conductive slurry was taken and put into the filter net to filter. The time when the slurry volume in the beaker reached 300 ml was recorded and used to judge the filtration performance of the slurry. If the filtration time was less than 120 seconds, it indicated that the filtration performance of the slurry was good and was recorded as "Y". If the filtration time of the slurry was more than 120 seconds or it could not pass through the filter net, it indicated that the filtration performance of the slurry was poor and was judged as "N".

[0057] (3) The solid content of the conductive slurry and the difference between the solid content of the upper and lower layers after leaving it for 24 hours Take the copper foil and weigh it in the weight loss measuring instrument, record it as M0, and reset it to zero. Take the conductive slurry, apply a small amount on the copper foil, and then put it into a moisture meter and weigh it, record it as M1; Close the device and start drying. Upon completion, record the weighing data as M2 and calculate the solids content, which is (M2-M0) / (M1-M0), The solid contents of the upper and lower layers of conductive slurry after standing for 24 hours were measured using the same method, and the difference in solid contents between the upper and lower layers of conductive slurry after standing for 24 hours was determined by subtracting the solid content of the upper layer conductive slurry from the solid content of the lower layer conductive slurry.

[0058] (4) Conductive slurry gelation test after leaving for 60 days The slurry in the beaker was lifted with a steel ruler, and the fluidity of the slurry was judged to determine whether the slurry had gelled. If the slurry did not gel, it was recorded as "OK." If the slurry gelled, it was recorded as "NG." Gelling: The slurry hardens or fails to flow continuously on its own. No gelation: The slurry flows naturally and continuously, and the slurry flows evenly on the surface of the steel ruler, with no lumps.

[0059] 3. Plate performance test (1) Adhesion strength of electrode plates Referring to the Chinese standard GB-T2790-1995, "Test Method for 180° Peel Strength of Adhesives," the adhesive strength test process for the examples and comparative examples of this application was as follows: A 30 mm wide, 100-160 mm long sample was cut with a blade, and a 20 mm wide, 90-150 mm long piece of special double-sided tape was attached to a steel plate. The positive electrode film layer surface of the previously cut electrode plate sample was then attached to the double-sided tape, and then rolled three times in the same direction with a 2 kg rolling roller. A 250 mm long paper tape with the same width as the electrode plate was fixed to the electrode plate current collector, and this was also fixed with crepe tape. The Sansi tensile tester (1 N sensitivity) was turned on, the lamp was lit, the stopper block was adjusted to the appropriate position, and the end of the steel plate not attached to the electrode plate was fixed with the lower jig. The paper tape was folded upward and fixed in place with the upper jig. The position of the upper jig was adjusted using the "up" and "down" buttons on the manual controller with the tensioner. The test was then performed and the numerical readings were read. The tension speed was 50 mm / min. The force at which the plate forces were balanced was divided by the tape width to determine the adhesive strength of the plate per unit length, which characterized the adhesive strength between the positive electrode film layer and the current collector.

[0060] (2) Film resistance of the electrode plate The dried electrode plate was cut into small 10mm diameter disks on the left, center, and right sides. Power on the Yuan Neng Technology electrode plate resistance meter, place it in the appropriate position on the electrode plate resistance meter "probe," click the "Start" button, and read when the displayed number stops changing. Each small disk was tested in two places, and the average of the final six measurements was calculated to determine the film resistance of the electrode plate.

[0061] 4. Battery performance test (1) Battery DC impedance test At 25°C, the secondary battery was charged at a constant current of 1 / 3C to 4.2V, then charged at a constant voltage of 4.2V until the current reached 0.05C and left for 5 minutes. It was then discharged at 1 / 3C for 90 minutes, and the electrode assembly was adjusted to 50% SOC, left for 60 minutes, and then discharged at 4C for 30 seconds. Based on the test data, the 50% SOC discharge DCR was obtained.

[0062] 3. Analysis of Test Results for Each Example and Comparative Example According to the above-mentioned methods, the fluorine-containing polymer, conductive slurry, positive electrode plate and secondary battery of each example and comparative example were produced, and each parameter was measured. See Tables 1 and 2 for the results. TIFF2025535450000006.tif220158 TIFF2025535450000007.tif230158 TIFF2025535450000008.tif219158 TIFF2025535450000009.tif193158 TIFF2025535450000010.tif188158 TIFF2025535450000011.tif193158 TIFF2025535450000012.tif177158 TIFF2025535450000013.tif193158 As can be seen from Table 1, Examples 1 to 19 disclose fluorine-containing polymers, and each of the fluorine-containing polymers contains a structural unit derived from vinylidene fluoride and a structural unit derived from 2-benzyl acrylic acid or 2-(4-isobutylbenzyl) acrylic acid.

[0063] As can be seen by comparing Examples 1 to 5 and Example 19 with Comparative Example 1, compared to conventional polyvinylidene fluoride, the fluorine-containing polymer of the present application reduces the viscosity of the conductive slurry and improves the filterability of the conductive slurry, thereby making the conductive slurry less likely to gel during storage and improving the gelation resistance and storage stability of the conductive slurry. The improved dispersion performance of the conductive slurry further reduces the membrane resistance of the electrode plate and the DC impedance of the battery. As can be seen by comparing Example 1 with Comparative Example 2, compared to vinylidene fluoride-acrylic acid copolymer, the vinylidene fluoride-2-benzyl acrylic acid copolymer disclosed in the present application improves the anti-settling properties of the conductive slurry and improves the adhesion of the electrode plate.

[0064] As can be seen from a comparison of Examples 1 to 3 with Examples 4 and 5, the mass content of the structural units derived from vinylidene fluoride is 50% to 70% based on the mass of the fluorine-containing polymer, which makes it possible to achieve both the viscosity of the conductive slurry and the adhesiveness of the electrode plate, thereby comprehensively improving the processing performance and use performance of the conductive slurry. As can be seen from a comparison of Examples 1 to 3 with Examples 4 and 5, the mass content of the structural units derived from 2-benzylacrylic acid is 30% to 50% based on the mass of the fluorine-containing polymer, which makes it possible to achieve both the viscosity of the conductive slurry and the adhesiveness of the electrode plate, thereby comprehensively improving the processing performance and use performance of the conductive slurry. As can be seen from comparing Examples 1, 6 and 7 with Examples 8 and 9, the mass average molecular weight of the fluorine-containing polymer is 100,000 to 140,000, which makes it possible to achieve both the viscosity of the conductive slurry and the adhesiveness of the electrode plate, thereby comprehensively improving the processing performance and use performance of the conductive slurry.

[0065] As can be seen from the comparison between Example 1 and Example 19, compared with the vinylidene fluoride-2-benzyl acrylic acid copolymer prepared by the conventional method, the vinylidene fluoride-2-benzyl acrylic acid copolymer disclosed in the present application can improve the anti-settling property of the conductive slurry, improve the adhesion of the electrode plates, reduce the membrane resistance of the electrode plates and the DC internal resistance of the battery, and improve the dynamic performance of the battery. The conductive slurries in Examples 1 to 19 all contain conductive carbon black, N-methylpyrrolidone, and vinylidene fluoride-2-benzyl acrylic acid copolymer or vinylidene fluoride-2-(4-isobutylbenzyl) acrylic acid copolymer. As can be seen from comparing Examples 1 to 19 with Comparative Example 3, compared with conductive slurries containing dispersants prepared by conventional methods, the fluorine-containing polymer disclosed in the present application can reduce the viscosity of the conductive slurry, which is advantageous for subsequent coating processing, improve the filterability of the conductive slurry, significantly delay the gelation of the conductive slurry during storage, and improve the gelation resistance and storage stability of the conductive slurry. At the same time, it can also improve the adhesion of the electrode plates, reduce the membrane resistance of the electrode plates, and reduce the DC internal resistance of the battery, thereby improving the dynamic performance of the battery.

[0066] Comparing Examples 1, 10, and 11 with Examples 12 and 13, it can be seen that the mass fraction of the fluorine-containing polymer is 0.5% to 2.5% based on the total mass of the conductive slurry. The slurry has an appropriate viscosity and good adhesion to the electrode plate, which comprehensively improves the processing performance and use performance of the slurry. Comparing Examples 1, 14, and 15 with Examples 16 and 17, the mass fraction of the conductive agent is 10.0% to 15.0% based on the total mass of the conductive slurry, which provides the slurry with appropriate viscosity and good adhesion to the electrode plate, thereby improving the processing and use performance of the slurry overall.

[0067] As can be seen from Examples 1 to 15 and 18, the solid content of the conductive slurry is 10.5% to 17.5%, and the viscosity of the conductive slurry is 300 mPa·s to 900 mPa·s. The conductive slurry made from the fluorine-containing polymer does not require the addition of additional dispersants or thickeners to improve processing performance, which helps to improve production efficiency and optimize the production process. The positive electrode plates in Examples 1 to 19 all include a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, the positive electrode film layer including a positive electrode active material, a conductive agent, and an adhesive, and the conductive agent is a deposit of conductive slurry. As can be seen from comparing Examples 1 to 18 with Comparative Example 4, compared to the positive electrode plates commonly used in the prior art, which are manufactured by directly adding conductive agent powder, the positive electrode plates of the present application contain a conductive agent in the form of a conductive slurry deposit, which is advantageous in improving the adhesion of the positive electrode plate, reducing the membrane resistance of the electrode plate and the DC internal resistance of the battery, and improving the dynamic performance of the battery.

[0068] As can be seen from comparing Examples 1 to 19 with Comparative Example 5, compared to the positive electrode plate commonly used in the prior art, which is manufactured by directly adding conductive agent powder, the positive electrode plate disclosed in the present application contains a conductive agent in the form of a conductive slurry deposit, which can effectively reduce the amount of conductive agent that needs to be added to the positive electrode plate, which is advantageous for improving the energy density of the battery. As can be seen from Examples 1 to 18, when the mass content of the conductive agent is 0.5% to 0.8% based on the total mass of the positive electrode membrane layer, the membrane resistance of the positive electrode plate is less than 0.2Ω. As can be seen from Examples 1 to 18, the adhesive strength per unit length between the positive electrode film layer and the positive electrode current collector is 14 N / m or more, and the positive electrode plate can meet the practical use needs. It should be noted that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any embodiment that has substantially the same configuration as the technical idea and achieves the same effects within the scope of the technical solution of the present application is included within the technical scope of the present application. In addition, various modifications that a person skilled in the art can make to the embodiments and other forms formed by combining some of the components of the embodiments are also included within the scope of the present application, as long as they do not deviate from the spirit of the present application. [Explanation of symbols]

[0069] 1 battery pack, 2 upper housing, 3 lower housing, 4 battery module, 5 secondary battery, 51 case, 52 electrode assembly, 53 cover plate.

Claims

1. A fluorine-containing polymer comprising a structural unit derived from a monomer represented by formula I and a structural unit derived from a monomer represented by formula II, Here, R 1 , R 2 , R 3 are each independently hydrogen, fluorine, chlorine, or fluorine-substituted C 1-3 alkyl groups, R 4 , R 5 are each independently hydrogen, substituted or unsubstituted C 1-5 alkyl groups, R 6 is a C substituted with an aryl group 1-5 A fluorine-containing polymer, characterized in that the fluorine-containing group is selected from one or more of an alkyl group and a substituted or unsubstituted aryl group.

2. R in Formula I 1 is fluorine, and R 2 , R 3 and each independently are selected from one or more of hydrogen, fluorine, chlorine, and a trifluoromethyl group.

3. 3. The fluorine-containing polymer according to claim 1, wherein the molar content of the structural unit derived from the monomer represented by formula I is 50% to 70% based on the total number of moles of all structural units in the fluorine-containing polymer.

4. The fluorine-containing polymer according to any one of claims 1 to 3, wherein a molar content of the structural unit derived from the monomer represented by formula II is 30% to 50% based on the total number of moles of all structural units in the fluorine-containing polymer.

5. 5. The fluorine-containing polymer according to claim 1, wherein the mass average molecular weight of the fluorine-containing polymer is 100,000 to 140,000.

6. 2. The fluorine-containing polymer of claim 1, wherein the monomer shown in formula I is selected from one or more of vinyl fluoride, vinylidene fluoride, tetrafluoroethylene, chlorotrifluoroethylene, and hexafluoropropylene.

7. The fluorine-containing polymer according to any one of claims 1 to 6, wherein the monomer represented by formula II is selected from one or more of 2-benzyl acrylic acid, 2-(4-isobutylbenzyl) acrylic acid, 2-methylene-4-phenyl butyric acid, and 2-(1-phenylethyl) acrylic acid.

8. A method for producing a fluorine-containing polymer, comprising: polymerizing at least one monomer of formula I with at least one monomer of formula II under polymerizable conditions; Here, R 1 , R 2 , R 3 are each independently hydrogen, fluorine, chlorine, or fluorine-substituted C 1-3 alkyl groups, R 4 , R 5 are each independently hydrogen, substituted or unsubstituted C 1-5 alkyl groups, R 6 is a C substituted with an aryl group 1-5 A method for producing a fluorine-containing polymer, wherein the fluorine-containing group is selected from one or more of an alkyl group and a substituted or unsubstituted aryl group.

9. R in Formula I 1 is fluorine, and R 2 , R 3 and are each independently selected from one or more of hydrogen, fluorine, chlorine, and a trifluoromethyl group.

10. The method according to claim 8 or 9, wherein the molar content of the monomer represented by formula I is 50% to 70% based on the total number of moles of the monomer represented by formula I and the monomer represented by formula II.

11. The method according to any one of claims 8 to 10, wherein the molar content of the monomer represented by formula II is 30% to 50% based on the total number of moles of the monomer represented by formula I and the monomer represented by formula II.

12. the polymerization reaction includes a first stage polymerization and a second stage polymerization, First-stage polymerization: adding an initiator, an emulsifier, at least one monomer represented by Formula I and an aqueous medium to a reaction vessel to carry out a first-stage polymerization, and continuously feeding the monomer represented by Formula I in the first-stage polymerization; The method according to any one of claims 8 to 11, characterized in that second-stage polymerization: after reacting for a certain period of time, at least one monomer represented by formula II is added to the reaction vessel to carry out second-stage polymerization, and the monomer represented by formula I is continuously fed in the second-stage polymerization.

13. 13. The method according to claim 12, wherein the mass of the monomer represented by formula I introduced in the first polymerization stage is 80% to 85% of the total mass of the monomer represented by formula I supplied in the polymerization reaction, and the mass of the monomer represented by formula I introduced in the second polymerization stage is 15% to 20% of the total mass of the monomer represented by formula I supplied in the polymerization reaction.

14. 14. The method of claim 12 or 13, wherein the weight percent of the initiator is 0.5% to 1.4% based on the total weight of the monomers shown in formula I and formula II.

15. The method according to any one of claims 12 to 14, wherein the weight percent of the emulsifier is 0.1% to 0.4% based on the total weight of the monomer shown in formula I and the monomer shown in formula II.

16. 16. The method of claim 12, wherein the weight percent of the aqueous medium provided in the first stage polymerization is 400% to 600% based on the total weight of the monomers shown in Formula I and Formula II.

17. The method according to any one of claims 12 to 16, wherein the reaction pressure in the first-stage polymerization and the second-stage polymerization are both 6.0 MPa to 9.0 MPa and the reaction temperature is 80°C to 120°C.

18. The method according to any one of claims 12 to 17, wherein the emulsifier is an alkali metal salt of perfluorooctanoic acid.

19. The method according to any one of claims 12 to 18, wherein the initiator is one or two of N,N-dimethylbenzylamine and N-methamphetamine.

20. 8. The use of the fluorine-containing polymer according to claim 1 in a secondary battery.

21. A conductive slurry comprising a conductive agent, a solvent, and the fluorine-containing polymer according to any one of claims 1 to 7.

22. 22. The conductive slurry according to claim 21, wherein the mass fraction of the conductive agent is 10.0% to 15.0% based on the total mass of the conductive slurry.

23. 23. The conductive slurry according to claim 21, wherein the mass fraction of the fluorine-containing polymer is 0.5% to 2.5% based on the total mass of the conductive slurry.

24. The conductive slurry according to any one of claims 21 to 23, characterized in that the solid content of the conductive slurry is 10.5% to 17.5%, and the viscosity of the conductive slurry is 300 mPa s to 900 mPa s.

25. 25. A positive electrode plate comprising: a positive electrode current collector; and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode film layer comprises a positive electrode active material, a conductive agent, and an adhesive, and the conductive agent is a deposit of the conductive slurry according to any one of claims 21 to 24.

26. 26. The positive electrode plate according to claim 25, wherein the film resistance of the positive electrode plate is less than 0.2 Ω when the mass content of the conductive agent is 0.5% to 0.8%, based on the total mass of the positive electrode film layer.

27. 27. The positive electrode plate according to claim 25, wherein the adhesive strength per unit length between the positive electrode film layer and the positive electrode current collector is 14 N / m or more.

28. A secondary battery comprising a negative electrode plate, a separator, an electrolyte, and the positive electrode plate according to any one of claims 25 to 27.

29. 30. The secondary battery of claim 28, wherein 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.

30. A battery module comprising the secondary battery according to claim 28 or 29.

31. A battery pack comprising at least one of the secondary battery according to claim 28 or 29 and the battery module according to claim 30.

32. 32. A power consuming device comprising at least one selected from the group consisting of the secondary battery according to claim 28 or 29, the battery module according to claim 30, and the battery pack according to claim 31.

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