Fluorine-containing polymer, production method, insulating coating, secondary battery, power consumption device

Abstract

The present application provides a fluorine-containing polymer, a production method, an insulating coating, a secondary battery, and an electric power consumption device. The fluorine-containing polymer contains 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. The molar content of the structural unit derived from the monomer represented by Formula I is 60% to 80% based on the total number of moles of the structural units in the fluorine-containing polymer. Here, R 1 , R 2 , R 3 are each independently selected from hydrogen, fluorine, chlorine, or a C 1-3 alkyl group containing at least one fluorine atom, and R 4 , R 5 , R 6 are each independently selected from hydrogen, or a substituted or unsubstituted C 1-5 alkyl group.

Description

Technical Field

[0001] This application relates to the technical field of secondary batteries, and particularly to fluorine-containing polymers, manufacturing methods, insulating coatings, secondary batteries, and power-consuming devices.

Background Art

[0002] During the manufacturing process of the electrode sheet of a battery cell, an insulating coating is applied to the surface of the current collector to prevent the positive and negative electrodes from coming into contact and forming a short circuit during the use of the battery cell, which may cause a safety accident and ultimately lead to a fire or explosion. The insulating coating is often manufactured by coating an insulating slurry containing an adhesive, an inorganic insulating material, and an additive on the surface of the current collector. However, the process window of the insulating slurry in the prior art is short, the fluidity is poor, and pipe blockage due to precipitation is likely to occur, which greatly affects the production efficiency of the electrode sheet. Therefore, the development of an adhesive for improving the processing performance of the slurry is an urgent task.

Summary of the Invention

Problems to be Solved by the Invention

[0003] This application is made in view of the above problems, and aims to provide a fluorine-containing polymer that optimizes the process window of insulating coating manufacturing and improves the production efficiency of the insulating coating, and an insulating coating containing the fluorine-containing polymer.

Means for Solving the Problems

[0004] The first aspect of this application provides a fluorine-containing polymer, which includes structural units derived from monomers represented by Formula I, structural units derived from olefin monomers, and structural units derived from monomers represented by Formula II. The molar content of the structural units derived from the monomers represented by Formula I is 60% - 80% based on the total molar number of the structural units in the fluorine-containing polymer.

Chemical Formula

[0005] The fluorine-containing polymer according to the present application can improve the filterability and fluidity of the slurry. Therefore, even if the slurry is allowed to stand for 6 hours, gelation does not occur, the process window of the slurry is significantly widened, the processability of the slurry is improved, the slurry can meet the production needs of the insulating coating without adding a dispersant, which is advantageous for optimizing the production process of the insulating coating and improving its production efficiency.

[0006] In any embodiment, the R 1 is fluorine, and R 2 and R 3 are each independently selected from one or more of hydrogen, fluorine, chlorine, and trifluoromethyl group, and R 5 and R 6 are each independently selected from one or two of hydrogen and methyl group.

[0007] In any embodiment, the molar content of the structural unit derived from the monomer represented by the formula II is 5% - 25% based on the total molar number of all the structural units in the fluorine-containing polymer.

[0008] When the molar content of the structural unit derived from the monomer represented by the formula II is 5% - 25% based on the total molar number of all the structural units in the fluorine-containing polymer, the fluorine-containing polymer further improves the fluidity and filterability of the insulating slurry, the process window of the insulating slurry processing is further widened, and the insulating coating can have effective adhesion by the fluorine-containing polymer.

[0009] In any embodiment, the molar content of the structural unit derived from the olefin monomer is 5% to 30% based on the total number of moles of all structural units in the fluorine-containing polymer.

[0010] When the molar content derived from the olefin monomer is 5% to 30% based on the total number of moles of all structural units in the fluorine-containing polymer, the fluorine-containing polymer further improves the fluidity and filterability of the insulating slurry, the process window of the insulating slurry processing is further widened, and the insulating coating can have effective adhesion by the fluorine-containing polymer.

[0011] In any embodiment, the weight-average molecular weight of the fluorine-containing polymer is 500,000 to 800,000.

[0012] A fluorine-containing polymer with a weight-average molecular weight of 500,000 to 800,000 is advantageous for further improving the fluidity and filterability of the insulating slurry, widening the process window of the insulating slurry processing, and promoting the maintenance of effective adhesion of the insulating coating.

[0013] In any embodiment, the viscosity of the adhesive solution prepared by dissolving the fluorine-containing polymer in N-methylpyrrolidone is 1000 to 3000 mPa·s, and the mass content of the fluorine-containing polymer in the adhesive solution is 7% of the total mass of the adhesive solution.

[0014] Since the viscosity of the adhesive solution containing 7% of the fluorine-containing polymer prepared by dissolving the fluorine-containing polymer in N-methylpyrrolidone is 1000 to 3000 mPa·s, it is not necessary to add additional additives to the insulating slurry using this fluorine-containing polymer as an adhesive, the production process can be effectively optimized, the production efficiency can be improved, and at the same time, it helps to improve the batch stability of the insulating coating.

[0015] In any embodiment, the monomer represented by the formula I is selected from one or more of vinylidene fluoride, tetrafluoroethylene, trifluorochloroethylene, and hexafluoropropylene.

[0016] In any embodiment, the olefin monomer is selected from one or more of propylene, 2-butene, and butadiene.

[0017] In any embodiment, the monomer represented by the formula II is selected from one or both of acrylic acid and methacrylic acid.

[0018] The second aspect of the present application provides a method for producing a fluorine-containing polymer, including the step of polymerizing at least one monomer represented by the formula I, at least one olefin monomer, and at least one monomer represented by the formula II under polymerizable conditions to produce a fluorine-containing polymer, wherein the molar content of the monomer represented by the formula I is 60% - 80% based on the total number of moles of the monomer represented by the formula I, the olefin monomer, and the monomer represented by the formula II.

Chemical formula

[0019] Compared with conventional adhesives, the fluorine-containing polymer produced by the method can improve the filterability and fluidity of the slurry. Therefore, even if the slurry is allowed to stand for 6 hours, gelation does not occur, the process window of the slurry is significantly widened, the processability of the slurry is improved, the slurry can meet the production needs of the insulating coating without adding a dispersant, which is advantageous for optimizing the production process of the insulating coating and improving its production efficiency.

[0020] In any embodiment, the R 1 is fluorine, and R 2 , R 3 are each independently selected from one or more of hydrogen, fluorine, chlorine, and trifluoromethyl groups, and R 5 , R 6 are each independently selected from one or two of hydrogen and methyl groups.

[0021] In any embodiment, the polymerization reaction includes a first-stage polymerization and a second-stage polymerization. In the first-stage polymerization, a first initiator, an emulsifier, at least one monomer represented by formula I, and a solvent are provided to initiate the first-stage polymerization. During the process of the first-stage polymerization, the monomer represented by formula I is continuously fed in to maintain the initial reaction pressure. In the second-stage polymerization, after reacting for a certain period of time, an olefin monomer and a monomer represented by formula II are fed into the reaction vessel to carry out the second-stage polymerization. When the pressure in the reaction vessel drops to 0.5 MPa or less, the reaction is stopped, the solid and liquid are separated, and the solid phase is left.

[0022] The method according to the present application first continuously feeds the monomer represented by Formula I to form a fluorine-containing segment, so that the fluorine-containing polymer has high thermal stability. Next, the monomer represented by Formula II and an olefin monomer are introduced to reduce the contact between the fluorine-containing segment and the external environment, thereby effectively alleviating the gelation phenomenon caused by fluorine elements. The fluorine-containing polymer produced by this method effectively improves the filterability and fluidity of the insulating slurry compared with the fluorine-containing polymer produced by introducing all the monomers into the reaction vessel and polymerizing them, further expands the process window of the slurry, and promotes the improvement of the production efficiency of the insulating coating.

[0023] In any embodiment, 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.

[0024] In any embodiment, the second-stage polymerization When the mass of the monomer represented by Formula I fed is 70%-85% of the total mass of the monomer represented by Formula I supplied in the polymerization reaction process, a mixed gas of the monomer represented by Formula I and an olefin monomer is fed into the reaction vessel, and the reaction is continued while maintaining the initial reaction pressure; After all the monomer represented by Formula I is fed into the reaction vessel, a mixture of an olefin monomer and the monomer represented by Formula II is fed into the reaction vessel.

[0025] Before feeding the monomer represented by Formula II into the reaction vessel, first, a mixed gas of the monomer represented by Formula I and an olefin monomer is fed into the reaction vessel, which helps to overcome the problem that the reaction difference between the monomer represented by Formula I and the monomer represented by Formula II is large and the compatibility is low with the olefin monomer as a crosslinking agent, and improves the degree of polymerization of the fluorine-containing polymer.

[0026] In any embodiment, the ratio of the total molar number of the olefin monomer supplied in the polymerization reaction process to the total molar number of the monomer represented by Formula I is 1:16 to 1:2.

[0027] In any embodiment, the ratio of the total molar number of the olefinic monomer supplied in the polymerization reaction process to the total molar number of the monomer represented by the formula I is 1:16 to 1:3.

[0028] In any embodiment, in the mixed gas, the molar ratio of the olefinic monomer to the monomer represented by the formula I is 1:1 to 2:1.

[0029] In any embodiment, in the mixture, the molar ratio of the olefinic monomer to the monomer represented by the formula II is 3:1 to 4:1.

[0030] In any embodiment, the second-stage polymerization further includes the step of adding a first initiator and a second initiator into the reaction vessel before feeding a mixed gas of the monomer represented by the formula I and the olefinic monomer into the reaction vessel.

[0031] In any embodiment, the second-stage polymerization further includes the step of adding a second initiator into the reaction vessel before feeding a mixture of the olefinic monomer and the monomer represented by the formula II into the reaction vessel.

[0032] In any embodiment, the first initiator is a persulfate and can be selected from one or more of potassium persulfate and ammonium persulfate.

[0033] In any embodiment, the second initiator is a thiosulfate and can be selected from sodium thiosulfate.

[0034] According to the third aspect of the present application, there is provided the use of the fluorine-containing polymer of the first aspect in a secondary battery. 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.

[0035] The fourth aspect of the present application provides an insulating coating, which includes an adhesive and an inorganic insulating material, and the adhesive is the fluorine-containing polymer of the first aspect.

[0036] The insulating coating is easy to process and manufacture, has good uniformity, and helps to improve the productivity of the battery.

[0037] In any embodiment, the mass content of the adhesive is 7.0% - 13.0% of the total mass of the insulating coating.

[0038] When the mass content of the adhesive is 7.0% - 13.0% of the total mass of the insulating coating, the adhesive further improves the fluidity and filterability of the insulating slurry, the process window of the insulating slurry processing is further widened, and the adhesive can ensure that the insulating coating maintains an effective adhesive force.

[0039] In any embodiment, the inorganic insulating material includes a colored oxide, and can be selected from black zirconia, yellow zirconia, red zirconia or green zirconia.

[0040] The applicant has surprisingly discovered that when the insulating coating contains a colored oxide, it helps to improve the laser cutting quality and laser cutting speed of the electrode sheet.

[0041] In any embodiment, the mass content of the colored oxide is 0.2% - 3% of the total mass of the insulating coating.

[0042] When the mass content of the colored oxide in the insulating coating is 0.2% - 3%, it helps to maximize the improvement of the laser cutting performance.

[0043] The fifth aspect of the present application provides a method for manufacturing an insulating coating. The step of dispersing the adhesive, which is the fluorine-containing polymer of the first aspect of the present application, in a solvent to produce an adhesive solution. Mixing the inorganic insulating material and the adhesive solution and stirring to produce a slurry with a solid content of 30% to 40%. Coating the slurry on the current collector to produce an insulating coating, including this step.

[0044] The insulating coating produced by the above method is highly efficient and has a uniform mass.

[0045] In any embodiment, when the solid content of the slurry is 30% to 40%, the viscosity of the slurry is 2500 to 4000 mPa·s.

[0046] The viscosity of the slurry with a solid content of 30% to 40% is 2500 to 4000 mPa·s, and it can be directly used in the production of the coating without the need to increase additional additives, which is beneficial to improving production efficiency and reducing production costs.

[0047] In any embodiment, the step of mixing the inorganic insulating material and the adhesive solution includes mixing an inorganic insulating material other than the colored oxide and the adhesive solution, stirring, then adding the colored oxide, and stirring again to produce the slurry.

[0048] By adding the colored oxide at the last stage of the slurry production process, it helps to improve the color uniformity of the produced insulating coating and the subsequent laser cutting speed and laser cutting quality.

[0049] The sixth aspect of the present application provides a secondary battery, which includes a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte. The insulating coating of the fourth aspect of the present application is included in the positive electrode sheet and / or the negative electrode sheet. 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.

[0050] The seventh aspect of the present application provides a battery module, which includes the secondary battery of the sixth aspect of the present application.

[0051] The eighth aspect of the present application provides a battery pack, which includes the secondary battery of the sixth aspect of the present application or the battery module of the seventh aspect of the present application.

[0052] The ninth aspect of the present application provides 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, or the battery pack of the eighth aspect of the present application.

Brief Description of the Drawings

[0053]

Figure 1

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Figure 9

Modes for Carrying Out the Invention

[0054] Hereinafter, embodiments specifically disclosing the adhesive, preparation method, electrode, battery, and power consumption device of the present application with appropriate reference to the drawings will be described in detail. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of matters that are already well-known and duplicate descriptions of actually identical structures may be omitted. This is to avoid the following description from becoming unnecessarily long and to facilitate the understanding of those skilled in the art. Note that the drawings and the following description are provided for those skilled in the art to fully understand the present application and do not limit the subject matter described in the scope of the claims.

[0055] The "range" disclosed in the present application is limited in the form of a lower limit and an upper limit. A predetermined range is limited by selecting one lower limit and one upper limit, and the boundary of a special range is limited by the selected lower limit and upper limit. The range thus limited may or may not include the boundary values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form one range. For example, when ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are also understood to be expected. Note that if the minimum range values 1 and 2, and the maximum range values 3, 4, and 5 are listed, the following ranges, 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5 can all be expected. In the present application, unless otherwise explained, the numerical range "a - b" represents an abbreviated expression of any combination of real numbers from a to b, and both a and b are real numbers. For example, the numerical range "0 - 5" indicates all real numbers between "0 - 5" listed in this specification, and "0 - 5" is just an abbreviated expression of the combination of these numerical values. Also, if a certain parameter indicates an integer ≧2, the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0056] Unless otherwise specified, all embodiments and preferably embodiments of the present application can be combined with each other to form new technical solutions.

[0057] Unless otherwise specified, all technical features of this application, and preferably the technical features, can be combined with each other to form new technical solutions.

[0058] Unless otherwise specified, all steps of this application can be carried out in order or randomly, and it is preferable to carry them out in order. For example, the fact that the method includes steps (a) and (b) means that the method may include steps (a) and (b) carried out in order, or may include steps (b) and (a) carried out in order. For example, the fact that the method mentioned above may include step (c) means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c), may include steps (a), (c) and (b), or may include steps (c), (a) and (b).

[0059] Unless otherwise specified, the terms "comprise" and "include" mentioned in this application may be either non - limiting or limiting. For example, the "comprise" and "include" may further comprise or include other components not listed, or may comprise or include only the listed components.

[0060] Unless otherwise specified, in this application, the term "or" is inclusive. For example, the word "A or B" means "A, B, or both A and B". More specifically, any of the following conditions: A is true (or exists) and B is false (or does not exist), A is false (or does not exist) but B is true (or exists), or both A and B are true (or exist) satisfies the condition of "A or B".

[0061] Safety is one of the most important research topics for secondary batteries. As shown in FIG. 1, the electrode sheet 6 is coated with an insulating coating 63 between the current collector 61 for forming tabs and the active material layer 62 during the manufacturing process, so as to prevent the positive and negative electrodes from contacting and forming a short circuit during the use of the battery cell, which may cause a safety accident and eventually lead to a fire or explosion. Inorganic materials have high resistance, and it is common to disperse inorganic materials in an adhesive to form a slurry for manufacturing the insulating coating. However, conventional adhesives have too high viscosity, prone to slurry precipitation, poor slurry uniformity, and large performance dispersion between batches of the insulating coating. Moreover, due to conventional adhesives, the slurry has poor fluidity and is difficult to apply uniformly, so it is necessary to add a dispersant to improve the processing performance of the slurry during the manufacturing process of the slurry. Needless to say, this increases the processing difficulty of the slurry, affects the production efficiency, and worsens the stability of the slurry between batches. Based on the above technical problems, the present application develops an adhesive that gives the slurry better fluidity and filterability to improve the production efficiency and quality of the insulating coating.

[0062] Based on this, the present application proposes a fluorine-containing polymer, which contains structural units derived from monomers represented by Formula I, structural units derived from olefin monomers, and structural units derived from monomers represented by Formula II. The molar content of the structural units derived from the monomers represented by Formula I is 60% - 80% based on the total number of moles of the structural units in the fluorine-containing polymer.

Chemical formula

[0063] In this specification, the term "fluorine-containing polymer" refers to a polymer in which a fluorine element is contained in the structural unit.

[0064] In this specification, the term "polymer" includes an aggregate of macromolecules that are chemically uniform and are produced by a polymerization reaction, but have different degrees of polymerization, molar masses, and chain lengths. On the other hand, the term also includes derivatives of such an aggregate of macromolecules formed by a polymerization reaction, that is, products that are chemically uniform or chemically non-uniform and are obtained by reactions of functional groups in the above macromolecules, for example, addition or substitution.

[0065] In this specification, "C 1-5 alkyl group" means a straight-chain or branched hydrocarbon chain group consisting only of carbon and hydrogen atoms, having no unsaturation in the group, having 1 to 5 carbon atoms, and being bonded to the rest of the molecule by a single bond. "C 1-3 alkyl group" should be interpreted accordingly. Examples of C 1-5 alkyl groups include, but are not limited to, methyl group, ethyl group, n-propyl group, 1-methylethyl group (isopropyl group), butyl group, and pentyl group. In some embodiments, a C 1-3 alkyl group containing at least one fluorine atom is -CF 3 , -CH 3 CH 2 F or -CH 2 FCH 2 F.

[0066] In this specification, the term "substituted" means that at least one hydrogen atom of the compound or chemical moiety is substituted with a substituent by another chemical moiety, where the substituents are each independently a hydroxyl group, a mercapto 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, or a C 1-6 alkoxy group.

[0067] As used herein, the term "olefinic monomer" refers to a hydrocarbon containing at least one C=C bond (carbon-carbon double bond). Examples of olefinic monomers include, but are not limited to, ethylene, propylene, butene, and butadiene. In some embodiments, said R 1 is fluorine, and R 2 , R 3 are each independently selected from one or more of hydrogen, fluorine, chlorine, and trifluoromethyl groups, and R 5 , R 6 are each independently selected from one or two of hydrogen and methyl groups.

[0068] In some embodiments, the fluorinated polymer contains structural units derived from at least two different monomers represented by formula I, and one of the structural units is derived from vinylidene fluoride. Different types of monomers contribute to reducing the long-chain regularity of the fluorinated polymer, lowering the crystallinity, and improving the flexibility.

[0069] In some embodiments, the monomer represented by formula I is selected from one or more of vinylidene fluoride, tetrafluoroethylene, trifluorochloroethylene, and hexafluoropropylene.

[0070] In some embodiments, the olefinic monomer is selected from one or more of propylene, 2-butene, and butadiene.

[0071] In some embodiments, the monomer represented by formula II is selected from one or two of acrylic acid and methacrylic acid.

[0072] In some embodiments, the polymer comprises structural units derived from one or more monomers represented by Formula I. In some embodiments, the polymer comprises structural units derived from one or more monomers represented by 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.

[0073] In some embodiments, the molar content of the structural units derived from the monomer represented by Formula I may be 60%, 65%, 70%, 75% or 80% based on the total number of moles of the structural units in the fluorine-containing polymer.

[0074] The fluorine element in the structural units derived from the monomer represented by Formula I forms a hydrogen bond with the hydroxyl group and / or carboxyl group on the surface of the current collector, so that the insulating coating has excellent adhesion and is not likely to fall off during manufacturing and use, thus causing safety accidents. Since the structural units derived from the olefin monomer and the monomer represented by Formula II can effectively reduce the fluorine content of the fluorine-containing polymer, the molar content of the structural units derived from the monomer represented by Formula I is 60%-80%, which can improve the gelation phenomenon of the slurry caused by fluorine. In addition, the structural units derived from the olefin monomer and the monomer represented by Formula II further increase the steric hindrance of the fluorine-containing polymer, reduce the aggregation of the fluorine-containing units, stabilize the slurry, play a role in alleviating the sedimentation of the slurry, and effectively improve the filterability of the slurry.

[0075] The fluorine-containing polymer according to the present application can improve the filterability and fluidity of the slurry compared with conventional adhesives. Therefore, even if the slurry is allowed to stand for 6 hours, gelation does not occur, the process window of the slurry is significantly widened, the processability of the slurry is improved, the slurry can meet the production needs of the insulating coating without adding a dispersant, which is advantageous for optimizing the production process of the insulating coating and improving its production efficiency.

[0076] In this specification, the term "process window" means that the process interval of product quality includes, but is not limited to, a temperature interval, a pressure interval, a storage time length, etc. It can be understood that the wider the process window, the lower the requirement for process accuracy.

[0077] In some embodiments, 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 the 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 may be any one of 5%, 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25% based on the total molar number of all the structural units in the fluorine-containing polymer.

[0078] When 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 the structural units in the fluorine-containing polymer, a suitable content of polar carboxyl groups can further improve the fluidity and filterability of the insulating slurry without causing gelation of the slurry, and the process window of the insulating slurry processing is further widened. On the other hand, due to the appropriate content of carboxyl groups, the insulating coating can maintain an effective adhesive force.

[0079] In some embodiments, the molar content of the structural units derived from the olefinic monomer is 5% to 30% based on the total number of moles of all the structural units in the fluorine-containing polymer. In some embodiments, the molar content of the structural units derived from the olefinic monomer may be any one of 5%, 10%, 15%, 20%, 25%, and 30% based on the total number of moles of all the structural units in the fluorine-containing polymer.

[0080] When the molar content derived from the olefinic monomer is 5% to 30% based on the total number of moles of all the structural units in the fluorine-containing polymer, the fluorine-containing polymer can further improve the fluidity and filterability of the insulating slurry, the process window of the insulating slurry processing is further widened, and the insulating coating can maintain effective adhesion by the fluorine-containing polymer.

[0081] In some embodiments, the weight average molecular weight of the fluorine-containing polymer is 500,000 to 800,000. In some embodiments, the weight average molecular weight of the fluorine-containing polymer may be any one of 500,000, 600,000, 650,000, 700,000, 750,000, and 800,000.

[0082] As used herein, the term "weight average molecular weight" means the sum of the products of the weight fractions occupied by molecules of different molecular weights in the polymer and the corresponding molecular weights.

[0083] In the present application, the weight-average molecular weight of the polymer can be measured using methods known in the art. For example, it can be measured using gel chromatography, such as a Waters 2695 Isocratic HPLC type gel chromatograph (differential refractive index detector 2141). In some embodiments, the measurement method is as follows: using a polystyrene solution sample with a mass fraction of 3.0% as a reference, a suitable column (oil-based: Styragel HT5DMF7.8*300mm + Styragel HT4) is selected. After purification, a 3.0% fluoropolymer adhesive solution is prepared with N-methylpyrrolidone (NMP) solvent, and the prepared solution is allowed to stand for one day and prepared for use. During measurement, first, suck tetrahydrofuran with a syringe for cleaning and repeat several times. Next, suck 5 ml of the experimental solution, remove the air in the syringe, and wipe the needle tip. Finally, slowly inject the sample solution into the injection port. After the display number stabilizes, data is acquired and the weight-average molecular weight is read.

[0084] A fluoropolymer with a weight-average molecular weight of 500,000 to 800,000 is advantageous in that the adhesive solution has an appropriate viscosity, further improves the fluidity and filterability of the insulating slurry, and further widens the process window of the insulating slurry processing. At the same time, a fluoropolymer with an appropriate weight-average molecular weight is advantageous in forming a three-dimensional network mesh-like adhesion structure, which helps the insulating coating to maintain an effective adhesive force.

[0085] In some embodiments, the viscosity of the adhesive solution prepared by dissolving the fluoropolymer in N-methylpyrrolidone is 1000 to 3000 mPa·s, and the mass content of the fluoropolymer in the adhesive solution is 7% of the total mass of the adhesive solution. In some embodiments, the viscosity of the adhesive solution prepared by dissolving the fluoropolymer in N-methylpyrrolidone may be any one of 1000 mPa·s, 1500 mPa·s, 2000 mPa·s, 2500 mPa·s, 3000 mPa·s, and the mass content of the fluoropolymer in the adhesive solution is 7% of the total mass of the adhesive solution.

[0086] In the present application, the viscosity of the adhesive solution of the fluorine-containing polymer can be measured by methods known in the art, for example, using a rotational viscometer.

[0087] The viscosity of the adhesive solution prepared by dissolving the fluorine-containing polymer in N-methylpyrrolidone is 1000 to 3000 mPa·s, and the mass content of the fluorine-containing polymer in the adhesive solution is 7% of the total mass of the adhesive solution. There is no need to add additional additives to the insulating slurry using this fluorine-containing polymer as an adhesive, which can effectively optimize the production process and improve production efficiency. At the same time, the adhesive solution within this viscosity range has both fluidity and viscosity, which can not only improve the adhesion of the insulating coating, but also achieve a uniform coating, and is helpful for improving the batch stability of the insulating coating.

[0088] In one embodiment of the present application, a method for producing a fluorine-containing polymer is provided. It includes the step of 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 to produce a fluorine-containing polymer. The molar content of the monomer represented by formula I is 60% to 80% based on the total number of moles of the monomer represented by formula I, the olefin monomer and the monomer represented by formula II.

Chemical formula

[0089] In this specification, the term "polymerizable conditions" refers to conditions including temperature, pressure, reactant concentration, any solvent / diluent, conditions including reactant mixing / addition parameters, and other conditions that facilitate the reaction of one or more monomers in at least one polymerization reactor, selected by those skilled in the art.

[0090] Compared with conventional adhesives, the fluorine-containing polymer produced by this method can improve the filterability and fluidity of the slurry. Therefore, even if the slurry is left standing for 6 hours, gelation does not occur, the process window of the slurry is significantly widened, the processability of the slurry is improved, the slurry can meet the production needs of the insulating coating without adding a dispersant, which is advantageous for optimizing the production process of the insulating coating and improving its production efficiency.

[0091] In some embodiments, the R 1 is fluorine, and R 2 , R 3 are each independently selected from one or more of hydrogen, fluorine, chlorine, and trifluoromethyl groups, and R 5 , R 6 are each independently selected from one or two of hydrogen and methyl groups.

[0092] In some embodiments, at least two monomers represented by Formula I are introduced during the production process of the polymer, wherein one monomer represented by Formula I is vinylidene fluoride. The addition of different monomers helps to reduce the long-chain regularity of the fluorine-containing polymer, lower the crystallinity, and improve the flexibility.

[0093] In some embodiments, the polymerization reaction includes a first-stage polymerization and a second-stage polymerization. In the first-stage polymerization, a first initiator, an emulsifier, at least one monomer represented by Formula I, and a solvent are provided to initiate the first-stage polymerization. During the process of the first-stage polymerization, the monomer represented by Formula I is continuously fed in to maintain the initial reaction pressure. In the second-stage polymerization, after reacting for a certain period of time, an olefin monomer and a monomer represented by Formula II are fed into the reaction vessel to conduct the second-stage polymerization. When the pressure in the reaction vessel drops to 0.5 MPa or less, the reaction is stopped, the solid-liquid is separated, and the solid phase is left behind.

[0094] In this specification, the term "continuously fed" means adding the monomer slowly, in small amounts, and step by step.

[0095] In some embodiments, the first initiator is a persulfate and can be selected from one or more of potassium persulfate and ammonium persulfate. Potassium persulfate decomposes efficiently at 60 °C or higher to generate radical ions or ion radicals and is suitable as an initiator for emulsion polymerization.

[0096] In some embodiments, the emulsifier is an alkali metal salt of perfluorooctanoic acid, and may be sodium perfluorooctanoate.

[0097] In some embodiments, the solvent is an aqueous solvent and may be deionized water.

[0098] The method according to the present application first continuously feeds the monomer represented by Formula I to form a fluorine-containing segment, so that the fluorine-containing polymer has high thermal stability. Next, the monomer represented by Formula II and an olefin monomer are introduced to reduce the contact between the fluorine-containing segment and the external environment, thereby effectively alleviating the gelation phenomenon caused by fluorine elements. The fluorine-containing polymer produced by this method can more effectively improve the filterability and fluidity of the slurry compared with the fluorine-containing polymer produced by introducing all the monomers into the reaction vessel and polymerizing, further expanding the process window of the slurry, and promoting the improvement of the production efficiency of the insulating coating.

[0099] In some embodiments, 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.

[0100] In some embodiments, the second-stage polymerization is When the mass of the monomer represented by Formula I fed is 70% to 85% of the total mass of the monomer represented by Formula I supplied in the polymerization reaction process, a mixed gas of the monomer represented by Formula I and an olefinic monomer is fed into the reaction vessel, and the reaction is continued while maintaining the initial reaction pressure; After all the monomer represented by Formula I is fed into the reaction vessel, a mixture of an olefinic monomer and the monomer represented by Formula II is fed into the reaction vessel.

[0101] Before feeding the monomer represented by Formula II into the reaction vessel, first, a mixed gas of the monomer represented by Formula I and an olefinic monomer is fed into the reaction vessel, which helps to overcome the problem that the reaction difference between the monomer represented by Formula I and the monomer represented by Formula II is large and the compatibility is low with the olefinic monomer as a crosslink, and improves the degree of polymerization of the fluoropolymer.

[0102] In some embodiments, the ratio of the total number of moles of the olefinic monomer supplied in the polymerization reaction process to the total number of moles of the monomer represented by Formula I is 1:16 to 1:2.

[0103] In some embodiments, the ratio of the total number of moles of the monomer represented by Formula II supplied in the polymerization reaction process to the total number of moles of the monomer represented by Formula I is 1:16 to 1:3.

[0104] In some embodiments, in the mixed gas, the molar ratio of the olefinic monomer to the monomer represented by Formula I is 1:1 to 2:1.

[0105] In some embodiments, in the mixture, the molar ratio of the olefinic monomer to the monomer represented by Formula II is 3:1 to 4:1.

[0106] In some embodiments, the second-stage polymerization is Before feeding a mixed gas of the monomer represented by Formula I and the olefinic monomer into the reaction vessel, the method further includes adding a first initiator and a second initiator into the reaction vessel.

[0107] In some embodiments, the second initiator is a thiosulfate and can be selected from sodium thiosulfate. The thiosulfate acts as a reducing agent and reacts with the persulfate, which is the first initiator in the reaction vessel, to generate two free radicals, effectively causing the polymerization of the olefinic monomer.

[0108] In some embodiments, the second-stage polymerization Before feeding a mixture of the olefinic monomer and the monomer represented by Formula II into the reaction vessel, the method further includes adding a second initiator into the reaction vessel.

[0109] One embodiment of the present application provides the use of a fluorine-containing polymer according to any embodiment in a secondary battery. 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. In some embodiments, the fluorine-containing polymer is used as an adhesive in the secondary battery. In some embodiments, the fluorine-containing polymer is used as an adhesive for an insulating coating in the secondary battery.

[0110] [Insulating coating] One embodiment of the present application provides an insulating coating including an adhesive and an inorganic insulating material, and the adhesive is a fluorine-containing polymer according to any embodiment.

[0111] As used herein, the term "adhesive" is a chemical compound, polymer, or mixture that forms a colloidal solution or colloidal dispersion in a dispersion medium.

[0112] In the present application, the term "inorganic insulating material" has a resistivity of 10 6Refers to inorganic materials and their precursors with a resistivity exceeding Ω·cm, including but not limited to boehmite, barium carbonate, barium sulfate, alumina, zirconia, calcium carbonate, and silica.

[0113] In some embodiments, the inorganic insulating material includes boehmite. Boehmite (AlOOH) is a precursor of γ-Al 2 O 3 and has excellent adhesion to the current collector. As an insulating coating, it is not easily detached. In some embodiments, the inorganic insulating material includes zirconia. Zirconia has a high resistance and is suitable for manufacturing insulating coatings.

[0114] In some embodiments, the dispersion medium of the adhesive is an aqueous solvent such as deionized water. That is, the adhesive is dissolved in the aqueous solvent.

[0115] In some embodiments, the dispersion medium of the adhesive is an oil-based solvent. Examples of the oil-based solvent include, but are not limited to, dimethylacetamide, N,N-dimethylacetamide, N-methylpyrrolidone, acetone, dimethyl carbonate, ethyl cellulose, and polycarbonate. That is, the adhesive is dissolved in the oil-based solvent.

[0116] In some embodiments, the adhesive is used to fix the inorganic insulating materials in place and adhere them to the current collector to form an insulating coating.

[0117] The insulating coating is easy to process and manufacture, has good uniformity, and helps improve the productivity of the battery.

[0118] In some embodiments, the mass content of the adhesive is 7.0% - 13.0% of the total mass of the insulating coating. In some embodiments, the mass content of the adhesive may be any one of 7.0%, 8.0%, 9.0%, 10.0%, 11.0%, 12.0%, and 13.0% of the total mass of the insulating coating.

[0119] When the mass content of the adhesive is 7.0% to 13.0% of the total mass of the insulating coating, the insulating slurry has an appropriate viscosity, further improves the fluidity and filterability of the insulating slurry, further expands the process window of the insulating slurry processing, and at the same time, the mass content of the adhesive within an appropriate range ensures that the insulating coating has sufficient adhesion to the current collector.

[0120] In some embodiments, the inorganic insulating material includes a colored oxide, which can be selected from one or more of black zirconia, yellow zirconia, red zirconia, and green zirconia. In some embodiments, the colored oxide is colored zirconia. In some embodiments, the inorganic insulating material includes black zirconia.

[0121] The applicant has surprisingly discovered that when the insulating coating contains a colored oxide, it promotes the improvement of the laser cutting quality and laser cutting speed of the electrode sheet. Laser cutting is a technology in which a focused laser beam with a high power density is irradiated onto a workpiece, and the irradiated material is rapidly heated to be melted, vaporized, ablated or decomposed, thereby processing the material. The use of laser cutting technology in secondary batteries mainly includes laser electrode sheet cutting, tab cutting, separator cutting, etc. Currently, laser cutting of electrode sheets has problems such as many burrs in the cutting area and limited maximum cutting speed. In the prior art, the inorganic insulating material is generally a colorless or white powder. The applicant has found that by including a colored oxide in the inorganic insulating material, the improvement range of the maximum cutting speed of the electrode sheet exceeds 30%, which promotes a significant increase in the productivity of the battery. At the same time, the colored oxide in the inorganic insulating material can reduce the thermal influence area of the laser, improve the cutting quality, reduce the cutting burrs, and reduce the influence of the processing process on the battery performance.

[0122] In some embodiments, the mass content of the colored oxide is 0.2% to 3% of the total mass of the insulating coating.

[0123] When the mass content of the colored oxide in the insulating coating is 0.2% - 3%, it can not only improve the cutting speed in the laser cutting and forming process of the electrode sheet, but also take into account the raw material cost, promoting the maximum improvement of the laser cutting performance.

[0124] In some embodiments, the colored oxide is black zirconia. When the mass content of the colored oxide in the insulating coating exceeds 3.0%, there is no color difference between the insulating coating and the active material layer, which makes it difficult for the laser cutting system to recognize and position, and is disadvantageous for accurate cutting of the size.

[0125] In one embodiment of the present application, a method for manufacturing an insulating coating is provided. Dispersing an adhesive, which is a fluorine-containing polymer in any embodiment, in a solvent to produce an adhesive solution. Mixing an inorganic insulating material and the adhesive solution, and stirring to produce a slurry with a solid content of 30% - 40%. Coating the slurry on a current collector to produce an insulating coating.

[0126] Since the solid content of the slurry is 30% - 40%, the slurry has an appropriate viscosity, which is advantageous for subsequent coating and drying operations. On the other hand, an appropriate slurry viscosity can improve the stability of the slurry, which is advantageous for the storage of the slurry.

[0127] The method for manufacturing the insulating coating has high production efficiency, does not require adding other additives, saves the production process, and is advantageous for improving the production efficiency.

[0128] In some embodiments, 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 may be any one of 2750 mPa·s, 3000 mPa·s, 3250 mPa·s, 3500 mPa·s, 3750 mPa·s, 4000 mPa·s.

[0129] The slurry with a solid content of 30% to 40% has a viscosity of 2500 to 4000 mPa·s, can be directly used in the production of the coating without the need to increase additional additives, is beneficial to improving production efficiency and reducing production costs.

[0130] In some embodiments, the step of mixing the inorganic insulating material and the adhesive solution includes mixing the inorganic insulating material other than the colored oxide with the adhesive solution, stirring, then adding the colored oxide, and stirring again to produce the slurry.

[0131] Adding the colored oxide at the last stage of the slurry manufacturing process helps to improve the color uniformity of the produced insulating coating and is useful for improving the subsequent laser cutting speed and laser cutting quality.

[0132] In one embodiment of the present application, a secondary battery is provided that includes a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte, and the insulating coating described in any embodiment is included in the positive electrode sheet and / or the negative electrode sheet. In some embodiments, 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. During the charging and discharging process of the battery, active ions are reversibly intercalated and deintercalated between the positive electrode sheet and the negative electrode sheet. The electrolyte is located between the positive electrode sheet and the negative electrode sheet and plays a role in conducting ions. The separator is provided between the positive electrode sheet and the negative electrode sheet and mainly plays a role in preventing short circuit between the positive electrode and the negative electrode, and at the same time, can allow ions to pass through.

[0133] [Positive Electrode Sheet] The positive electrode sheet includes a positive electrode current collector, a positive electrode active material layer provided on at least one surface of the positive electrode current collector, and an insulating coating.

[0134] As an example, 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 are provided on either one or both of the two opposing surfaces of the positive electrode current collector.

[0135] In some embodiments, a metal foil sheet or a composite current collector can be employed for the positive electrode current collector. For example, as the metal foil sheet, an aluminum foil can be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material base (such as a base of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0136] In some embodiments, a positive electrode active material well-known in the art for batteries can be employed for the positive electrode active material. As an example, the positive electrode active material can include at least one of olivine-structured lithium-containing phosphates, lithium transition metal oxides, and their respective modified compounds. The present application is not limited to these materials, and conventional materials that can be used as other battery positive electrode active materials may also be used. These positive electrode active materials can be used alone or in combination of two or more. Examples of lithium transition metal oxides include lithium cobalt oxide (e.g., LiCoO 2 ), lithium nickel oxide (e.g., LiNiO 2 ), lithium manganese oxide (e.g., LiMnO 2 , LiMn 2 O 4 ), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (e.g., LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 (which can also be abbreviated as NCM 333 ), LiNi0.5 Co 0.2 Mn 0.3 O 2 (which can also be abbreviated as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (which can also be abbreviated as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (which can also be abbreviated as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (which can also be abbreviated as NCM 811 ), lithium nickel cobalt aluminum oxide (for example, LiNi 0.85 Co 0.15 Al 0.05 O 2 ), and at least one of modified compounds thereof, etc., but not limited thereto. Examples of olivine-structured lithium-containing phosphates include lithium iron phosphate (for example, LiFePO 4 (which can also be abbreviated as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (for example, LiMnPO 4 ), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and at least one of a composite material of lithium manganese iron phosphate and carbon, but not limited thereto.

[0137] In some embodiments, the positive electrode active material layer optionally further includes an adhesive. As an example, the adhesive can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0138] In some embodiments, the positive electrode active material layer further optionally includes a conductive agent. By way of example, the conductive agent can include at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0139] In some embodiments, the positive electrode sheet can be manufactured as follows. Components for manufacturing the above positive electrode active material layer, such as a positive electrode active material, a conductive agent, an adhesive, 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 a positive electrode current collector, and after processes such as drying and cold pressing, a positive electrode active material layer is obtained. Components for manufacturing the above insulating coating, such as a fluorine-containing polymer, are dispersed in a solvent (such as N-methylpyrrolidone) to form an adhesive solution. An inorganic insulating material and the adhesive solution are mixed and stirred to manufacture 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 processes such as drying and cold pressing, an insulating coating is obtained. A positive electrode active material layer and an insulating coating can be obtained in a similar manner on the other side of the current collector to obtain a positive electrode sheet.

[0140] [Negative electrode sheet] The negative electrode sheet includes a negative electrode current collector, a negative electrode active material layer provided on at least one surface of the negative electrode current collector, and an insulating coating.

[0141] By way of example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode film layer is provided on either one or both of the two opposing surfaces of the negative electrode current collector.

[0142] In some embodiments, a metal foil sheet or a composite current collector can be employed for the negative electrode current collector. For example, a copper foil can be used as the metal foil sheet. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymer material base (such as a base of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0143] In some embodiments, well-known positive electrode active materials for batteries in the art can be employed for the negative electrode active material. As an example, the negative electrode active material can include at least one of materials such as artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material can be selected from at least one of silicon alone, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy. The tin-based material can be selected from at least one of tin alone, tin acid compounds, and tin alloys. However, the present application is not limited to these materials, and other conventional materials that can be used as the negative electrode active material of the battery may also be used. These negative electrode active materials can be used alone or in combination of two or more kinds.

[0144] In some embodiments, the negative electrode active material layer optionally further includes an adhesive. The adhesive can 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).

[0145] In some embodiments, the negative electrode active material layer further optionally includes a conductive agent. The conductive agent can be selected from at least one of superconducting carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0146] In some embodiments, the negative electrode active material layer may further include other auxiliary agents such as, for example, a thickening agent (such as sodium carboxymethyl cellulose (CMC-Na)).

[0147] In some embodiments, the negative electrode sheet can be manufactured as follows. Components for manufacturing the above negative electrode active material layer, such as a negative electrode active material, a conductive agent, an adhesive, 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 a negative electrode current collector, and after processes such as drying and cold pressing, a negative electrode active material layer is obtained. Components for manufacturing the above insulating coating, such as a fluorine-containing polymer, are dispersed in a solvent (such as N-methylpyrrolidone) to form an adhesive solution. An inorganic insulating material and the adhesive solution are mixed and stirred to manufacture 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 processes such as drying and cold pressing, an insulating coating is obtained. A negative electrode active material layer and an insulating coating can be obtained in the same manner on the other side of the negative electrode current collector to obtain a negative electrode sheet.

[0148] [Electrolyte] The electrolyte serves to conduct ions between the positive electrode sheet and the negative electrode sheet. The present application is not specifically limited to the type of electrolyte and can be selected as needed. For example, the electrolyte can be in a liquid, gelled, or all-solid state.

[0149] In some embodiments, the electrolyte uses an electrolytic solution. The electrolytic solution includes an electrolyte salt and a solvent.

[0150] In some embodiments, 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 difluoroborate oxalate, lithium bis(oxalato)borate, lithium difluorophosphate oxalate, and lithium tetrafluorophosphate oxalate.

[0151] In some embodiments, 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, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0152] In some embodiments, the electrolyte solution further optionally contains an additive. For example, the additive can include a negative electrode film - forming additive and a positive electrode film - forming additive, and may also include additives that can improve certain performances of the battery, such as additives for improving the over - charge performance of the battery, additives for improving the high - temperature or low - temperature performance of the battery, etc.

[0153] [Separator] In some embodiments, the secondary battery further includes a separator. The present application is not particularly limited to the type of the separator, and any known porous - structure separator having excellent chemical stability and mechanical stability can be selected.

[0154] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator is not particularly limited and may be a single-layer thin film or a multi-layer composite thin film. When the separator is a multi-layer composite thin film, the material of each layer is not particularly limited and may be the same or different.

[0155] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be used to manufacture an electrode assembly by a winding process or a lamination process.

[0156] In some embodiments, the secondary battery may include an exterior. The exterior can be used to seal the above electrode assembly and electrolyte.

[0157] In some embodiments, the exterior of the secondary battery may be a hard shell such as a hard plastic shell, an aluminum shell, or a steel shell. The exterior of the secondary battery may also be a soft bag such as a pouch soft bag. The material of the soft bag may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0158] The present application is not particularly limited with respect to the shape of the secondary battery, and it may be cylindrical, rectangular, or any other arbitrary shape. For example, FIG. 2 is an example of a rectangular-structured secondary battery 5.

[0159] In some embodiments, referring to FIG. 3, the exterior can include a housing 51 and a cover plate 53. Here, the housing 51 can include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates can surround to form a storage chamber. The housing 51 has an opening communicating with the storage chamber, and the cover plate 53 can cover the opening so as to close the storage chamber. The positive electrode sheet, the negative electrode sheet and the separator can form an electrode assembly 52 by a winding process or a lamination process. The electrode assembly 52 is sealed within the storage chamber. The electrolyte infiltrates into the electrode assembly 52. The number of electrode assemblies 52 included in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual requirements.

[0160] In some embodiments, the secondary battery can be assembled as a battery module, and the number of secondary batteries included in the battery module can be one or more. Regarding the specific number, those skilled in the art can select according to the application and capacity of the battery module.

[0161] FIG. 4 is an example of the battery module 4. Referring to FIG. 4, in the battery module 4, a plurality of secondary batteries 5 are sequentially arranged and installed along the length direction of the battery module 4. Of course, they can be distributed in any other manner. Further, the plurality of secondary batteries 5 can be fixed with fasteners.

[0162] Optionally, the battery module 4 may further include an external case having a storage space, and the plurality of secondary batteries 5 are stored in the storage space.

[0163] In some embodiments, the above battery module can also be assembled as a battery pack, and the number of battery modules included in the battery pack can be one or more. Regarding the specific number, those skilled in the art can select according to the use and capacity of the battery module.

[0164] Figs. 5 and 6 show an example of the battery pack 1. Referring to Figs. 5 and 6, the battery pack 1 may include a battery box and a plurality of battery modules 4 provided in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can be covered by the lower box body 3 to form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be distributed in the battery box in any manner.

[0165] Furthermore, the present application further provides a power consumption device, which includes at least one of the secondary battery, battery module, or battery pack provided by the present application. The secondary battery, battery module, or battery pack can be used as the power source of the power consumption device and can also be used as the energy storage unit of the power consumption device. Examples of the power consumption device include, but are not limited to, mobile devices (such as mobile phones, notebook computers, 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.), trains, ships, satellites, energy storage systems, etc.

[0166] As the power consumption device, a secondary battery, battery module, or battery pack can be selected according to the usage requirements.

[0167] Fig. 7 shows an example of the power consumption device. The power consumption device is a pure electric vehicle, hybrid electric vehicle, or plug-in hybrid electric vehicle, etc. In order to meet the requirements of high output and high energy density of the secondary battery of the power consumption device, a battery pack or battery module can be used.

[0168] As another example of the device, it may be a mobile phone, tablet, notebook computer, etc. The device usually requires thinning and can use a secondary battery as the power source.

[0169] Example

[0170] The embodiments of the present application will be described below. The embodiments described below are merely illustrative and are only used for interpreting the present application, and should not be understood as limiting the present application. When specific technologies or conditions are not indicated in the embodiments, it is necessary to execute in accordance with the technologies or conditions described in the literature in this field or in accordance with the product specifications. When the manufacturer of the reagents or equipment used is not indicated, it is a conventional product that can be purchased commercially.

[0171] I. Manufacturing Method

[0172] Example 1 1) Production of Adhesive (Fluoropolymer-containing) 30 kg of deionized water (with a conductivity of 2 μs / cm or less), 21 g of sodium perfluorooctanoate, and 71.4 g of a 5% potassium persulfate solution were sequentially added into the reaction kettle, and the reaction kettle was closed. The inside of the kettle was evacuated and filled with nitrogen gas, and the operation was repeated until the oxygen concentration in the reaction kettle was less than 100 ppm. Vinylidene fluoride monomer was introduced into the reaction kettle until the kettle pressure reached 7.5 MPa. The temperature inside the kettle was raised to 85 °C to start the reaction. During the reaction process, vinylidene fluoride monomer was continuously introduced to keep the reaction pressure in the kettle constant. Vinylidene fluoride monomer was introduced until it reached 80% of the total mass of vinylidene fluoride monomer. 30.6 g of a 5% potassium persulfate solution and 19.2 g of a 5% sodium thiosulfate were added. While maintaining the reaction pressure, a mixed gas of vinylidene fluoride monomer and butadiene was introduced into the reaction kettle. The molar ratio of vinylidene fluoride monomer to butadiene monomer was 2:3. When 3783.7 g of vinylidene fluoride monomer was all added and the addition amount of butadiene monomer accounted for 50% of the total amount of butadiene, the remaining 28.8 g of a 5% sodium thiosulfate was added. While maintaining the reaction pressure, the remaining 931 g of butadiene monomer and 354.7 g of acrylic acid monomer were introduced into the reaction kettle. When the reaction is completed, the pressure in the kettle is reduced to 0.2 MPa, and the unreacted butadiene monomer is recovered and reacted. The product is aggregated, washed, separated, dried, and pulverized to obtain a vinylidene fluoride-butadiene-acrylic acid copolymer adhesive.

[0173] 2) Production of insulating slurry Add 13000 g of N-methylpyrrolidone into a 35 L stirring tank. Add 700 g of the powder of the vinylidene fluoride-butadiene-acrylic acid copolymer produced above into N-methylpyrrolidone, set the stirring speed at 1000 revolutions per minute, with a stirring time of 60 minutes. After the stirring is completed, a temporary adhesive solution is obtained. Add 6195 g of boehmite powder to the temporary adhesive solution, set the stirring speed at 1200 revolutions per minute, with a stirring time of 60 minutes. The cooling water circulation in the stirring tank is started. After the stirring is completed, a boehmite slurry is obtained. Add 105 g of black zirconia powder to the boehmite slurry, set the stirring speed at 1200 revolutions per minute, with a stirring time of 60 minutes. The cooling water circulation in the stirring tank is started, and vacuum pumping is started. After the stirring is completed, an insulating slurry is obtained.

[0174] 3) Production of insulating coating Coat the above insulating slurry on a 13 μm aluminum foil, with a coating thickness of 15 ± 1 μm. The slurry is dried to form an insulating coating. An insulating coating is obtained on the other side of the aluminum foil in the same way. The sum of the thicknesses of the insulating coatings on both sides and the aluminum foil is 43 ± 2 μm.

[0175] The manufacturing methods of the insulating coatings in Examples 2 to 26 and Comparative Examples 1 to 4 are similar to the manufacturing method of Example 1, but the manufacturing parameters of the adhesive and the proportion of black zirconia in the slurry are adjusted.

[0176] In Examples 2 to 7, the proportions of the monomers of the adhesive are adjusted, and other parameters are the same as those in Example 1. The specific parameters are shown in Tables 1 and 2.

[0177] In Examples 8 to 11, by adjusting the reaction conditions in the synthesis of the adhesive, the adhesive was made to have different weight average molecular weights, and other parameters were the same as in Example 6. The specific parameters are shown in Tables 1 and 2. Specifically, the method for producing a fluorine-containing polymer having a weight average molecular weight of 500,000 in Example 8 is almost the same as the steps in Example 6, and the difference is that the addition amount of the 5% potassium persulfate solution is adjusted from 71.4 g to 78.54 g.

[0178] The method for producing a fluorine-containing polymer having a weight average molecular weight of 800,000 in Example 9 is almost the same as the steps in Example 6, and the differences are that the reaction temperature is adjusted from 85 °C to 80 °C, and the addition amount of the 5% potassium persulfate solution is adjusted from 71.4 g to 67.83 g.

[0179] The method for producing a fluorine-containing polymer having a weight average molecular weight of 900,000 in Example 10 is almost the same as the steps in Example 6, and the differences are that the reaction temperature is adjusted from 85 °C to 80 °C, and the addition amount of the 5% potassium persulfate solution is adjusted from 71.4 g to 64.26 g.

[0180] The method for producing a fluorine-containing polymer having a weight average molecular weight of 400,000 in Example 11 is almost the same as the steps in Example 6, and the difference is that the addition amount of the 5% potassium persulfate solution is adjusted from 71.4 g to 82.11 g.

[0181] In Examples 12 to 15, the mass fraction of the adhesive in the slurry was adjusted, and other parameters were the same as in Example 6. The specific parameters are shown in Tables 1 and 2.

[0182] In Examples 16 to 19, the solid content of the slurry was adjusted, and other parameters were the same as in Example 6. The specific parameters are shown in Tables 1 and 2.

[0183] In Example 20, butadiene in the adhesive synthesis monomer was replaced with propylene, and other parameters were the same as in Example 6. The specific parameters are shown in Tables 1 and 2.

[0184] In Example 21, the adhesive was a vinylidene fluoride-butadiene-acrylic acid copolymer produced by a conventional method. The synthesis method was as follows: 30 kg of deionized water (with a conductivity of 2 μs / cm or less), 21 g of an alkali metal perfluorooctanoate, and 71.4 g of a 5% potassium persulfate solution were sequentially added into the reaction kettle. The reaction kettle was closed, the inside of the kettle was evacuated and filled with nitrogen gas, and the operation was repeated until the oxygen concentration in the reaction kettle was less than 100 ppm. vinylidene fluoride monomer, butadiene monomer, and 720 g of acrylic acid monomer were introduced into the reaction kettle until the kettle pressure reached 7.5 MPa. Here, the molar ratio of vinylidene fluoride monomer to butadiene monomer was 8:1. The temperature inside the kettle was raised to 85 °C to start the reaction. During the reaction process, vinylidene fluoride monomer and butadiene monomer were continuously introduced to maintain a constant reaction pressure inside the kettle. The total masses of the introduced vinylidene fluoride monomer and butadiene monomer were 5120 g and 540 g respectively. When the reaction was completed, the kettle pressure was reduced to 0.0 - 0.5 MPa, and the unreacted butadiene monomer was recovered and reacted. The product was aggregated, washed, separated, dried, and pulverized to obtain a vinylidene fluoride-butadiene-acrylic acid copolymer adhesive.

[0185] In Examples 22 - 26, the mass content of black zirconia in the slurry was changed, and other parameters were the same as in Example 6. The specific parameters are shown in Table 3.

[0186] In Comparative Example 1, a vinylidene fluoride polymer was used as the adhesive, and it was the HSV900 model number of Arkema in France.

[0187] In Comparative Example 2, the adhesive is a vinylidene fluoride-butadiene copolymer, and its synthesis method is substantially the same as that of Example 1. The difference is that when the introduced vinylidene fluoride monomer is 80% of the total mass of the vinylidene fluoride monomer, 30.6 g of a 5% potassium persulfate solution and 19.2 g of a 5% sodium thiosulfate are added. While maintaining the reaction pressure, a mixed gas of vinylidene fluoride monomer and butadiene is introduced into the reaction kettle. Here, the mass of butadiene in the mixed gas is 2160 g, and the mass of the vinylidene fluoride monomer is 756.7 g.

[0188] In Comparative Example 3, the adhesive is a vinylidene fluoride-acrylic acid copolymer, and its synthesis method is substantially the same as that of Example 1. The difference is that when the introduced vinylidene fluoride monomer is 80% of the total mass of the vinylidene fluoride monomer, 30.6 g of a 5% potassium persulfate solution and 19.2 g of a 5% sodium thiosulfate are added. While maintaining the reaction pressure, 2880 g of acrylic acid is added into the reaction kettle, and 756.7 g of vinylidene fluoride monomer is continuously introduced.

[0189] In Comparative Example 4, the adhesive is a vinylidene fluoride-butadiene-acrylic acid copolymer, and its synthesis method is the same as that of Example 1, and the molar content of the synthetic monomers is adjusted. Specifically, refer to Table 1 and Table 2.

[0190] The related parameters of the insulating coatings in the above Examples 1 to 26 and Comparative Examples 1 to 4 are shown in Table 1, Table 2 and Table 3 below.

[0191] II. Measurement method

[0192] Performance measurements are carried out on the insulating coatings obtained in the above Examples 1 to 26 and Comparative Examples 1 to 4. The measurement method is as follows.

[0193] 1. Measurement of weight-average molecular weight Measure using a Waters 2695 Isocratic HPLC type gel chromatograph (differential refractive index detector 2141). Using a polystyrene solution sample with a mass fraction of 3.0% as a reference, select a suitable column (oil-based: Styragel HT5DMF 7.8 * 300 mm + Styragel HT4). Prepare a 3.0% fluoropolymer solution with purified N-methylpyrrolidone (NMP) solvent, let the prepared solution stand for one day, and prepare it for use. During measurement, first, aspirate tetrahydrofuran with a syringe, wash, and repeat several times. Next, aspirate 5 ml of the experimental solution, remove the air in the syringe, and wipe the needle tip. Finally, slowly inject the sample solution into the injection port. After the display number stabilizes, acquire data and read the weight average molecular weight.

[0194] 2. Measurement of the viscosity of the adhesive solution Dissolve the fluoropolymer in N-methylpyrrolidone (NMP) solvent to prepare an adhesive solution with a solid content of 7%. Select a suitable rotor, fix the viscometer, place the adhesive solution below the viscometer, ensure that the slurry just submerges the graduation line of the rotor, instrument model number: Shanghai Fangrui NDJ-5S, rotor: 62# (500 - 2500 mPa·s), 63# (2500 - 10000 mPa·s), rotation speed: 12 revolutions per minute, measurement temperature: 25 °C, measurement time: 5 min. Read the data after the display number stabilizes.

[0195] 3. Measurement of the viscosity of the slurry Use a rotational viscometer to measure the viscosity of the slurry. Select a suitable rotor, fix the viscometer rotor, place the slurry below the viscometer, ensure that the slurry just submerges the graduation line of the rotor, instrument model number: Shanghai Fangrui NDJ-5S, rotor: 63# (2000 - 10000 mPa·s), 64# (10000 - 50000 mPa·s), rotation speed: 12 revolutions per minute, measurement temperature: 25 °C, measurement time: 5 min. Read the data after the display number stabilizes.

[0196] 4. Measurement of the solid content of the slurry Measurement method of the solid content: Prepare a glass petri dish with a weight of m 1Record it, put a part of the produced slurry into a glass petri dish, and record the total weight m 2 Record it, put the petri dish containing the slurry into a drying box and heat it. The heating temperature is 120 °C and the heating time is 1 h. Weigh the dried petri dish and record the weight m 3 Record it, solid content = [(m 3 - m 1 ) / (m 2 - m 1 )] × 100%.

[0197] 5. Measurement of slurry fluidity After the slurry has been left standing for 6 h and 12 h, take an appropriate amount of the slurry with a spoon and observe whether the natural flow of the slurry is smooth. If the natural flow is smooth, it is judged as OK. If the flow is not smooth and the slurry appears jelly-like and forms lumps, indicating the appearance of gelation, it is judged as NG.

[0198] 6. Measurement of slurry filtration performance First, determine the filter screen to be 200 mesh and cut the filter screen into 25 cm * 25 cm with scissors. Find a clean 500 ml beaker and confirm that the beaker is clean. Fold the 200 mesh filter screen into a triangle, take 500 ml of the slurry and pour it from the upper surface of the filter screen. Pour it all in at once, let the slurry flow from the tip of the filter screen into the beaker, and start recording the time. Record the filtration time for 300 ml.

[0199] 7. Measurement of adhesion Referring to the international standard "Adhesives - Method of test for 180° peel strength" GB-T2790-1995, the process of measuring the adhesion force of the examples and comparative examples of this application is as follows: Samples with a width of 30 mm and a length of 100 - 160 mm are cut with a blade, and a special double-sided tape is attached to a steel plate. The width of the tape is 20 mm, and the length is 90 - 150 mm. The insulating coating surface of the electrode sheet sample cut above is attached to the double-sided tape, and then rolled 3 times along the same direction with a 2 kg pressing roll. A paper tape with the same width as the electrode sheet and a length of 250 mm is fixed to the electrode sheet current collector and fixed with a corrugated rubber. Turn on the power supply (sensitivity is 1 N) of the tensile machine (manufactured by Shenzhen Sensen Sansi), the lamp lights up, adjust the stopper to an appropriate position, and fix one end of the electrode sheet on the steel plate that is not pasted with a lower jig. Fold the paper tape upward and fix it with an upper jig, and adjust the position of the upper jig with the "up" and "down" buttons on the manual controller attached to the tensile machine. Then, measure and read the value, and the tensile speed is 50 mm / min. The force obtained by dividing the force when the force applied to the electrode sheet is balanced by the width of the tape is used as the adhesion force of the insulating coating per unit length, indicating the adhesion strength between the insulating coating and the current collector.

[0200] 8. Measurement of Laser Cutting Use a laser dicing machine (manufactured by Han’s Laser Technology Industry Group), set the laser output power to 80% of the maximum output power, and the laser frequency is 1000 KHz. Compare the maximum cutting speed and cutting quality when cutting the electrode sheets coated with insulating coatings in different examples. If the CCD camera on the dicing machine can recognize it, it is judged as Y; if the CCD camera on the dicing machine cannot recognize it, it is judged as N. Observe the cross-sectional morphology after cutting with an optical microscope after laser cutting. If obvious metal burrs exist on the cross-section after cutting, it is judged as unqualified; if there are no obvious metal burrs on the cross-section after cutting, it is judged as qualified. Extract samples from 100 batches of cut products and calculate the qualification rate of 100 batches.

[0201]

Table 1-1

[0202]

Table 1-2

[0203]

Table 2-1

[0204]

Table 2-2

[0205]

Table 3

[0206] FIG. 8 is a microscopic image of an electrode sheet coated with an insulating coating in Example 26 after laser cutting. Here, FIG. 8A is a plan view of the electrode sheet notch, and FIG. 8B is a cross-sectional view of the electrode sheet notch. FIG. 9 is a microscopic image of an electrode sheet in Example 6 after laser cutting. Here, FIG. 9A is a plan view of the electrode sheet notch, and FIG. 9B is a cross-sectional view of the electrode sheet notch. As can be seen from the comparison between FIG. 8 and FIG. 9, the electrode sheet with black zirconia added to the insulating coating has significantly reduced burr amount and burr length after laser cutting, effectively improving the laser cutting quality of the electrode sheet.

[0207] As can be seen from the results in Table 1, all the adhesives in Examples 1 to 21 are fluorine-containing polymers, which contain 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 number of moles of the structural units in the fluorine-containing polymer. When the above fluorine-containing polymer is used as an adhesive, good effects are obtained in all cases. Compared with the conventional PVDF adhesive in Comparative Example 1 and the fluorine-containing polymer with a mass content of 90% of the structural units derived from vinylidene fluoride in Comparative Example 4, the fluorine-containing polymer according to the present application improves both the filterability of the slurry and the fluidity after standing for 6 h. Comparing the vinylidene fluoride-butadiene copolymer and the vinylidene fluoride-acrylic acid copolymer in Comparative Example 2 and Comparative Example 3, the fluorine-containing polymer disclosed in the present application comprehensively improves the fluidity, filterability and adhesion performance of the slurry, and can balance the processing performance and the use performance of the slurry.

[0208] As can be seen from the comparison between Examples 1 to 3, 5 to 7 and Example 4, when the molar content of the structural units derived from acrylic acid in the fluorine-containing polymer is 5% to 20% based on the total number of moles of all the structural units in the fluorine-containing polymer, the fluorine-containing polymer improves the fluidity of the slurry after standing for 12 h, and further broadens the process window of the slurry.

[0209] As can be seen from the comparison between Examples 2 to 7 and Example 1, when the molar content of the structural units derived from olefin monomers in the fluorine-containing polymer is 5% to 30% based on the total number of moles of all the structural units in the fluorine-containing polymer, the fluorine-containing polymer improves the processing performance of the slurry and at the same time can also serve as an adhesive force.

[0210] As can be seen from the comparison between Examples 8 to 11, when the weight average molecular weight of the fluorine-containing polymer is 500,000 to 800,000, the fluorine-containing polymer comprehensively improves the fluidity, filterability and adhesion performance of the slurry, and can balance the processing performance and the use performance of the slurry.

[0211] As can be seen from Examples 1 to 20, the viscosity of the adhesive solution containing 7% by mass of the fluorine-containing polymer prepared by dissolving the fluorine-containing polymer in N-methylpyrrolidone is 2500 to 5000 mPa·s. This eliminates the need to add additional dispersants or thickeners to improve the processing performance of the slurry for the insulating coating produced by the fluorine-containing polymer, promotes the improvement of production efficiency, and optimizes the production process.

[0212] As can be seen from the comparison between Example 6 and Example 21, the fluorine-containing polymer produced by the method disclosed in the present application can effectively improve the filterability and fluidity of the slurry and the processing performance of the slurry, as compared with the fluorine-containing adhesive synthesized by the conventional method.

[0213] As can be seen from the comparison between Examples 6, 22 to 25 and Example 26, by adding black zirconia to the insulating coating, the burrs generated at the edges during laser cutting of the electrode sheet are reduced, the quality of laser cutting of the electrode sheet is improved, and the quality of the electrode sheet is improved.

[0214] As can be seen from the comparison between Examples 6, 23 to 24 and Examples 22, 25, when the mass content of black zirconia in the insulating coating is 0.2% to 3%, the laser cutting speed is improved, further promoting the improvement of production efficiency and productivity. Moreover, due to the color difference between the insulating coating and the positive electrode active material layer, the laser cutting equipment can be accurately positioned and recognized, improving the processing accuracy.

[0215] It should be noted that the present application is not limited to the above embodiments. The above embodiments are merely illustrative, and any embodiments that have the same technical idea and exhibit the same configuration and the same operational effects within the scope of the technical solution of the present application should be included within the technical scope of the present application. In addition, within the scope not departing from the gist of the present application, various modifications that can be conceived by those skilled in the art to the embodiments, and other forms constructed by combining some components in the embodiments are also included within the scope of the present application.

Description of Symbols

[0216] 1 Battery pack 2 Upper box body 3 Lower box body 4 Battery module 5 Secondary battery 51 Housing 52 Electrode assembly 53 Cover plate 6 Electrode sheet 61 Current collector 62 Active material layer 63 Insulating coating

Claims

1. A fluorine-containing polymer, comprising 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 number of moles of the structural units in the fluorine-containing polymer, 【Chemical 1】 Here, R １ , R ２ , R ３ is each independently selected from hydrogen, fluorine, chlorine, or a C １－３ alkyl group containing at least one fluorine atom, and R ４ , R ５ , R ６ are each independently selected from hydrogen, or a substituted or unsubstituted C １－５ alkyl group, a fluorine-containing polymer characterized by this.

2. The aforementioned R １ is fluorine, and R ２ , R ３ are each independently selected from hydrogen, fluorine, chlorine or a trifluoromethyl group, and R ５ , R ６ are each independently selected from hydrogen or a methyl group, The fluorine-containing polymer according to claim 1, characterized in that.

3. The fluorine-containing polymer according to claim 1 or 2, wherein the molar content of the structural unit derived from the monomer represented by Formula II is 5% to 25% based on the total number of moles of all the structural units in the fluorine-containing polymer.

4. The fluorine-containing polymer according to any one of claims 1 to 3, wherein the molar content of the structural unit derived from the olefin monomer is 5% to 30% based on the total number of moles of all the structural units in the fluorine-containing polymer.

5. The fluorine-containing polymer according to any one of claims 1 to 4, wherein the weight average molecular weight of the fluorine-containing polymer is 500,000 to 800,000.

6. The fluorine-containing polymer according to any one of claims 1 to 5, wherein the viscosity of the adhesive solution prepared by dissolving the fluorine-containing polymer in N-methylpyrrolidone is 1000 to 3000 mPa·s, and the mass content of the fluorine-containing polymer in the adhesive solution is 7% based on the total mass of the adhesive solution.

7. The fluorine-containing polymer according to any one of claims 1 to 6, wherein the monomer represented by Formula I is selected from one or more of vinylidene fluoride, tetrafluoroethylene, trifluorochloroethylene, and hexafluoropropylene.

8. The fluorine-containing polymer according to any one of claims 1 to 7, wherein the olefin monomer is selected from one or more of propylene, 2-butene, and butadiene.

9. The fluorine-containing polymer according to any one of claims 1 to 8, wherein the monomer represented by Formula II is selected from one or two of acrylic acid and methacrylic acid.

10. A method for producing a fluorine-containing polymer, A step of 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 to produce a fluorine-containing polymer, wherein the molar content of the monomer represented by formula I is 60% to 80% based on the total number of moles of the monomer represented by formula I, the olefin monomer and the monomer represented by formula II, [Chemical 2] Here, R １ R ２ R ３ is independently selected from hydrogen, fluorine, chlorine, or a C １－３ alkyl group containing at least one fluorine atom, and R ４ R ５ R ６ is independently selected from hydrogen, a substituted or unsubstituted C １－５ alkyl group, a method for producing a fluorine-containing polymer, characterized in that.

11. The aforementioned R １ is fluorine, and R ２ , R ３ are each independently selected from one or more of hydrogen, fluorine, chlorine, and trifluoromethyl groups, and R ５ , R ６ are each independently selected from one or two of hydrogen and methyl groups. The manufacturing method according to claim 10 is characterized by this.

12. The polymerization reaction includes a first-stage polymerization and a second-stage polymerization. In the first-stage polymerization, a first initiator, an emulsifier, at least one monomer represented by formula I and a solvent are provided to carry out the first-stage polymerization. During the process of the first-stage polymerization, the monomer represented by formula I is continuously fed in to maintain the initial reaction pressure. In the second-stage polymerization, after reacting for a certain period of time, an olefin monomer and a monomer represented by formula II are fed into the reaction vessel to carry out the second-stage polymerization. When the pressure in the reaction vessel drops to 0.5 MPa or less, the reaction is stopped, and the solid and liquid are separated to leave the solid phase. The production method according to claim 10 or 11, characterized in that.

13. 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 production method according to claim 12, characterized in that.

14. The second-stage polymerization is as follows: When the mass of the monomer represented by formula I fed in is 70% to 85% of the total mass of the monomer represented by formula I supplied in the polymerization reaction process, a mixed gas of the monomer represented by formula I and an olefin monomer is fed into the reaction vessel, and the initial reaction pressure is maintained to continue the reaction. After all the monomer represented by formula I is fed into the reaction vessel, a mixture of an olefin monomer and a monomer represented by formula II is fed into the reaction vessel. The production method according to claim 12 or 13, characterized in that it includes.

15. The ratio of the total number of moles of the olefin monomer supplied in the polymerization reaction process to the total number of moles of the monomer represented by formula I is 1:16 to 1:

2. The production method according to any one of claims 10 to 14, characterized in that.

16. The ratio of the total number of moles of the monomer represented by formula II supplied in the polymerization reaction process to the total number of moles of the monomer represented by formula I is 1:16 to 1:

3. The production method according to any one of claims 10 to 15, characterized in that.

17. The manufacturing method according to claim 14, wherein in the mixed gas, the molar ratio of the olefin monomer to the monomer represented by formula I is 1:1 to 2:

1.

18. The manufacturing method according to claim 14 or 17, wherein in the mixture, the molar ratio of the olefin monomer to the monomer represented by formula II is 3:1 to 4:

1.

19. The second-stage polymerization The manufacturing method according to claim 14 or 18, further comprising the step of adding a first initiator and a second initiator into the reaction vessel before feeding a mixed gas of the monomer represented by formula I and an olefin monomer into the reaction vessel.

20. The second-stage polymerization The manufacturing method according to claim 14 or 19, further comprising the step of adding a second initiator into the reaction vessel before feeding a mixture of an olefin monomer and the monomer represented by formula II into the reaction vessel.

21. The manufacturing method according to claim 19, wherein the first initiator is a persulfate.

22. The manufacturing method according to claim 21, wherein the persulfate is selected from one or more of potassium persulfate and ammonium persulfate.

23. The manufacturing method according to claim 19 or 20, wherein the second initiator is a thiosulfate.

24. The manufacturing method according to claim 23, wherein the thiosulfate is selected from sodium thiosulfate.

25. Use of the fluorine-containing polymer according to any one of claims 1 to 9 in a secondary battery.

26. An insulating coating containing an adhesive and an inorganic insulating material, wherein the adhesive is the fluorine-containing polymer according to any one of claims 1 to 9.

27. The insulating coating according to claim 26, wherein the mass content of the adhesive is 7.0% to 13.0% based on the total mass of the insulating coating.

28. The insulating coating according to claim 26 or 27, wherein the inorganic insulating material contains a colored oxide, and the colored oxide is selected from one or more of black zirconia, yellow zirconia, red zirconia, and green zirconia.

29. The insulating coating according to any one of claims 26 to 28, wherein the mass content of the colored oxide is 0.2% to 3% based on the total mass of the insulating coating.

30. A method for manufacturing an insulating coating, comprising: dispersing an adhesive, which is a fluorine-containing polymer according to any one of claims 1 to 9, in a solvent to produce an adhesive solution; mixing an inorganic insulating material and the adhesive solution, and stirring to produce a slurry having a solid content of 30% to 40%; coating the slurry on a current collector to produce an insulating coating. The method for manufacturing an insulating coating is characterized by including the above steps.

31. The method for manufacturing an insulating coating according to claim 30, wherein when the solid content of the slurry is 30% to 40%, the viscosity of the slurry is 2500 to 4000 mPa·s.

32. The step of mixing the inorganic insulating material and the adhesive solution includes mixing an inorganic insulating material other than a colored oxide and the adhesive solution, stirring, adding the colored oxide, and stirring again to produce the slurry. The method for manufacturing an insulating coating according to claim 30 or 31 is characterized by this.

33. A secondary battery, comprising a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte, wherein the insulating coating according to any one of claims 26 to 29 is included in the positive electrode sheet and / or the negative electrode sheet.

34. The secondary battery according to claim 33, wherein 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.

35. A battery module, characterized by including the secondary battery according to claim 33 or 34.

36. A battery pack, characterized by including at least one of the secondary battery according to claim 33 or 34 and the battery module according to claim 35.

37. A power consumption device, characterized by including at least one selected from the secondary battery according to claim 33 or 34, the battery module according to claim 35, and the battery pack according to claim 36.

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