Polymer, method for preparing polymer, separator, battery, and electric device

Abstract

The present disclosure provides a polymer, a method for preparing the polymer, a separator, a battery, and an electric device. The polymer comprises an acrylate copolymer, the monomer of the acrylate copolymer at least comprises a first monomer, and the first monomer comprises a fluorine-substituted acrylate monomer.

Description

Polymer, method for preparing polymer, separator, battery, and electrical device Technical Field

[0001] The present disclosure relates to the field of battery technology, and in particular, to a polymer, a method for preparing a polymer, a separator, a battery, and an electrical device. Background Art

[0002] In recent years, batteries have been widely used in energy storage systems such as hydropower, thermal, wind, and solar power stations, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields. In batteries, the amount and cost of binders are relatively small, but they can effectively improve battery performance and are an indispensable component of batteries. Binders, as inactive materials in batteries, can bond the various components and adjacent parts together, reducing the expansion and shedding of active materials during the battery's charge and discharge processes and lowering the battery's internal resistance. However, current batteries still suffer from problems such as insufficient bonding strength, which requires further improvement.

[0003] It should be noted that the above statements are only used to provide background technical information related to this application and do not necessarily constitute prior art.

[0004] Application Contents

[0005] In a first aspect, the present application proposes a polymer comprising an acrylic ester copolymer, wherein the monomers of the acrylic ester copolymer include at least a first monomer, wherein the first monomer comprises a fluorine-substituted acrylic ester monomer. This improves the polymer's adhesive strength. When used as a binder in a battery, for example, as a binder on a separator, the polymer exhibits minimal swelling in the electrolyte, effectively improving the adhesion between the separator and the electrode, thereby enhancing the battery's cycling performance.

[0006] In some embodiments, the structure of the first monomer is as shown in Formula 1:

[0007] Wherein, R1 includes hydrogen atom or C1-C6 alkyl, R2 includes C1-C6 fully substituted or partially substituted fluorine. 15 This is beneficial to the formation of the polymer and improves the anti-swelling performance of the polymer.

[0008] In some embodiments, the first monomer includes at least one of trifluoroethyl acrylate, trifluoroethyl methacrylate, hexafluorobutyl acrylate, hexafluorobutyl methacrylate, perfluoroalkylethyl acrylate, perfluoroalkyl acrylate, dodecafluoroheptyl acrylate, dodecafluoroheptyl methacrylate, 1H,1H-perfluorooctyl methacrylate, 2-fluoroethyl acrylate, 2-fluoroethyl acrylate, perfluorooctylethyl methacrylate, perfluorohexylethyl methacrylate, and trifluoropentyl acrylate. This can further improve the anti-swelling properties of the polymer.

[0009] In some embodiments, the first monomer includes at least one of trifluoroethyl acrylate, trifluoroethyl methacrylate, hexafluorobutyl acrylate, hexafluorobutyl methacrylate, and perfluoroalkylethyl acrylate.

[0010] In some embodiments, the monomers of the acrylic ester copolymer further include a second monomer, and the structure of the second monomer is shown in Formula 2:

[0011] Wherein, R3 includes hydrogen atom or C1-C6 alkyl, R4 includes substituted or unsubstituted C1-C 15 alkyl, substituted or unsubstituted C3-C6 isobornyl, wherein the C1-C 15 Substituents of the alkyl group include hydroxyl or C1-C6 alkyl.

[0012] In some embodiments, the second monomer includes at least one of ethyl acrylate, n-butyl acrylate, n-propyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, cyclohexyl acrylate, isooctyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, methyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, lauryl methacrylate, vinyl acetate, trimethylolpropane triacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate. Thus, the anti-swelling ability of the polymer can be further improved.

[0013] In some embodiments, the second monomer includes at least one of ethyl acrylate, n-butyl acrylate, n-propyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, isooctyl acrylate, methyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, and isobornyl methacrylate.

[0014] In some embodiments, the monomers of the acrylic ester copolymer further include a third monomer, and the structure of the third monomer is shown in Formula 3 and / or Formula 4:

[0015] Wherein, R5 includes hydrogen atom or C1-C 18 R6 includes a hydrogen atom or a C1-C6 alkyl group. This can improve the ionic conductivity and bonding properties of the polymer.

[0016] In some embodiments, the third monomer includes at least one of acrylonitrile, methacrylonitrile, ethacrylonitrile, acrylic acid, methacrylic acid, crotonic acid, and heptenoic acid, thereby further improving the ionic conductivity and bonding properties of the polymer.

[0017] In some embodiments, the third monomer includes at least one of acrylonitrile, methacrylonitrile, acrylic acid, and methacrylic acid.

[0018] In some embodiments, the monomers of the acrylic ester copolymer further include a fourth monomer, and the structure of the fourth monomer is shown in Formula 5:

[0019] Wherein, R7 comprises a hydrogen atom, a hydroxyl-substituted C1-C6 alkyl group, or a C1-C6 alkoxy group, and R8 comprises a hydrogen atom or a C1-C6 alkyl group. Thus, the fourth monomer can play a role in regulating the molecular weight of the polymer, helping the polymer to have better adhesion.

[0020] In some embodiments, the fourth monomer includes at least one of acrylamide, N-methylol acrylamide, and N-butoxymethyl acrylamide, thereby further improving the bonding performance of the polymer.

[0021] In some embodiments, the fourth monomer includes at least one of acrylamide and N-methylol acrylamide.

[0022] In some embodiments, the polymer further includes a dispersant, and the dispersant includes at least one of polyvinyl pyrrolidone, polyacrylamide, sodium polystyrene sulfonate, polyacrylic acid, sodium polyacrylate, and sodium polymethacrylate. Thus, the addition of the dispersant can reduce polymer agglomeration and thereby improve the particle size uniformity of the polymer.

[0023] In some embodiments, the mass ratio of the acrylic ester copolymer to the dispersant in the polymer is 100:(1-15). This can further reduce adhesion between acrylic ester copolymer particles.

[0024] In some embodiments, the polymer has a Dv50 particle size of 3 μm to 18 μm, thereby reducing the blockage of the isolation membrane pores by the polymer while ensuring a moderate thickness of the coating formed by the polymer.

[0025] In a second aspect of the present application, a method for preparing the aforementioned polymer is provided, comprising: blending an emulsifier, an initiator, and monomers constituting an acrylic copolymer in a mass ratio of (0.2-2):(0.1-0.5):100, heating and reacting to obtain a polymer emulsion; and spray-drying the polymer emulsion to obtain the polymer. Thus, the aforementioned polymer can be prepared by a simple method.

[0026] In some embodiments, the monomers constituting the acrylic copolymer include a first monomer, a second monomer, a third monomer, and a fourth monomer, wherein the mass ratio of the first monomer, the second monomer, the third monomer, and the fourth monomer is (20-30):(40-50):(1-10):(1-10). Thus, a polymer with excellent adhesion can be obtained.

[0027] In some embodiments, the method further comprises adding a dispersant to the polymer emulsion before spray drying, thereby reducing random aggregation in the polymer emulsion and improving the dispersibility of the polymer emulsion.

[0028] In a third aspect of the present application, a separator is provided, comprising the aforementioned polymer and / or a polymer prepared by the aforementioned method. Thus, the separator has all the features and advantages of the aforementioned polymer and the method for preparing the polymer, which will not be further elaborated here.

[0029] In a fourth aspect of the present application, a battery is provided, comprising the aforementioned separator, thereby having all the features and advantages of the aforementioned separator, which will not be described in detail here.

[0030] In a fifth aspect of the present application, the present application provides an electrical device comprising the aforementioned battery. Thus, the electrical device has all the features and advantages of the aforementioned battery, which will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The above and / or additional aspects and advantages of the present application will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0032] FIG1 is a schematic flow diagram of a method for preparing a polymer according to one embodiment of the present application;

[0033] FIG2 is a schematic flow diagram of a method for preparing a polymer according to another embodiment of the present application;

[0034] FIG3 is a schematic structural diagram of a battery according to an embodiment of the present application;

[0035] FIG4 is a schematic diagram of a battery cell according to an embodiment of the present application;

[0036] FIG5 is an exploded view of the battery cell according to an embodiment of the present application shown in FIG4 ;

[0037] FIG6 is a schematic diagram of a battery module according to an embodiment of the present application;

[0038] FIG7 is a schematic diagram of a battery pack according to an embodiment of the present application;

[0039] FIG8 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG8 ;

[0040] FIG9 is a schematic diagram of an electrical device using a battery as a power source according to an embodiment of the present application.

[0041] Explanation of the reference numerals: 1 battery pack; 2 upper case; 3 lower case; 4 battery module; 5 battery cell; 11 negative electrode current collector; 12 negative electrode active material layer; 21 positive electrode current collector; 22 positive electrode active material layer; 31 base film; 32 polymer; 51 shell; 52 electrode assembly; 53 top cover assembly. DETAILED DESCRIPTION

[0042] The following describes in detail embodiments of the present application. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application and are not to be construed as limiting the present application.

[0043] Unless otherwise defined, all technical and scientific terms used in this application have the same meanings as those commonly understood by technicians in the technical field to which this application belongs; the terms used in this application are only for the purpose of describing specific embodiments and are not intended to limit this application; unless otherwise specified, the numerical values ​​of the various parameters mentioned in this application can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the embodiments of this application).

[0044] The terms "include" and "have" in the description and claims of this application and any variations thereof are open expressions, that is, including the contents specified in this application but not excluding other contents.

[0045] " scope " disclosed in the application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a scope with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 listed, and if the maximum range value 3,4 and 5 are listed, then the following scope can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0046] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0047] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0048] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly specifying the quantity of the technical features indicated. "First feature" and "second feature" may include one or more of the features.

[0049] In the description of this application, "A and / or B" may include the case of A alone, the case of B alone, or any of the cases of A and B, where A and B are only used for example, and may be any technical feature connected by "and / or" in this application.

[0050] In this application, the writing order of each step does not mean a strict execution order and does not constitute any limitation on the implementation process. The specific execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of this application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or steps (b) and (a) performed sequentially. For example, it is mentioned that the method may also include step (c), indicating that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0051] Typically, a battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. An adhesive needs to be placed between the separator and the electrode sheet to tightly bond the adjacent parts together. The bonded positive electrode sheet, negative electrode sheet, and separator adhere to each other and support each other, forming a structure with a certain thickness, which gives the battery a certain hardness. The negative electrode sheet will expand and contract during the charge and discharge process. When the bonding force between the separator and the electrode sheet is weak, after the negative electrode sheet shrinks, the separator cannot continue to adhere to the surface of the negative electrode sheet well, resulting in a gap between the positive electrode sheet, negative electrode sheet, and separator. The positive electrode sheet, negative electrode sheet, and separator cannot adhere to each other and support each other, resulting in a loose battery, a lower hardness, a significant increase in the internal resistance of the battery, and a significant reduction in the battery's cycle performance.

[0052] By setting a binder on the surface of the isolation membrane, the bonding performance of the isolation membrane can be effectively improved, and the bonding effect between the isolation membrane and the electrode can be enhanced. However, the polymer binders currently used in isolation membranes have the problem of poor anti-swelling performance. Specifically, the electrolyte is mainly composed of ester organic solvents, lithium salts and additives. The polymer will swell in the electrolyte. The swelling of the polymer will lead to problems such as increased volume expansion during the charge and discharge process of the battery, further causing the internal resistance of the battery to increase, the reversible capacity to decay faster, and the cycle stability to deteriorate. The strength of the swollen polymer will decrease, and the bonding effect between the isolation membrane and the electrode will deteriorate. It is impossible to effectively suppress the pulverization and rupture of the active material during the charge and discharge cycle, resulting in a decrease in the peel strength of the electrode and a shortened battery life.

[0053] In this application, by modifying and designing acrylate copolymers and synthesizing them using fluorine-substituted acrylate monomers, the chemical inertness of the acrylate copolymers can be enhanced by utilizing the shielding effect of fluorine atoms. This results in the polymer having both excellent adhesion and excellent anti-swelling properties. Specifically, because fluorine atoms have low polarizability and an atomic radius second only to hydrogen, the carbon-fluorine bond formed by fluorine atoms replacing hydrogen atoms has a shorter bond length and higher bond energy than carbon-hydrogen bonds. Furthermore, due to the large electronegativity of fluorine atoms, when fluorine atoms replace hydrogen atoms in acrylic copolymers, repulsion occurs between the fluorine atoms. This repulsion causes the carbon-fluorine bonds in the acrylic copolymers to be in different planes, thereby reducing the bond angles of the carbon-carbon bonds in the acrylic copolymers. Fluorine-containing groups are enriched on the surface of the polymer, which helps the fluorine atoms to wrap around the carbon atoms connected to the fluorine atoms and the main carbon chain, making it difficult for other atoms to enter the interior of the copolymer, ultimately improving the anti-swelling properties of the polymer. Batteries using this polymer as a binder have better cycle performance.

[0054] Binder refers to a material with adhesive properties that is used to bond different substances together.

[0055] Copolymer, a polymerization reaction in which two or more monomers participate together, is called copolymerization. The polymer formed contains two or more monomer units. This type of polymer is called a copolymer, also known as an interpolymer.

[0056] In a first aspect of the present application, a polymer is proposed, comprising an acrylate copolymer, wherein the monomers of the acrylate copolymer include at least a first monomer, wherein the first monomer includes a fluorine-substituted acrylate monomer. By employing a fluorine-substituted acrylate monomer as a synthetic monomer for the acrylate copolymer, the enrichment of fluorine-containing groups on the surface of the acrylate copolymer can be utilized to achieve coating of the copolymer, thereby making it difficult for other atoms to enter the interior of the copolymer, thereby effectively improving the polymer's anti-swelling properties. When the polymer is used as a binder on an isolation membrane, the polymer swells less in the electrolyte and has a strong tolerance to the electrolyte, which can effectively improve the bonding effect between the isolation membrane and the electrode, thereby improving the cycle performance of the battery.

[0057] In some embodiments, the structure of the first monomer is as shown in Formula 1:

[0058] Wherein, R1 includes hydrogen atom or C1-C6 alkyl, R2 includes C1-C6 fully substituted or partially substituted fluorine. 15 of alkyl.

[0059] When the first monomer satisfies the aforementioned structural formula, the first monomer can provide more fluorine-containing groups, thereby improving the anti-swelling properties of the acrylic ester copolymer. Moreover, the first monomer is easily copolymerized with other acrylic ester monomers with similar structures, and the surface energy and surface tension of the polymer generated after copolymerization are significantly reduced, thereby obtaining a fluorine-containing acrylic ester copolymer emulsion with good hydrophobicity and oleophobicity. The polymer emulsion has high stability, which is conducive to subsequent granulation processing.

[0060] In some embodiments, the first monomer includes at least one of trifluoroethyl acrylate, trifluoroethyl methacrylate, hexafluorobutyl acrylate, hexafluorobutyl methacrylate, perfluoroalkylethyl acrylate, perfluoroalkyl acrylate, dodecafluoroheptyl acrylate, dodecafluoroheptyl methacrylate, 1H,1H-perfluorooctyl methacrylate, 2-fluoroethyl acrylate, 2-fluoroethyl acrylate, perfluorooctyl ethyl methacrylate, perfluorohexyl ethyl methacrylate, and trifluoropentyl acrylate.

[0061] Using any one or more of the above first monomers can improve the anti-swelling performance of the polymer.

[0062] In some embodiments, the first monomer includes at least one of trifluoroethyl acrylate, trifluoroethyl methacrylate, hexafluorobutyl acrylate, hexafluorobutyl methacrylate, and perfluoroalkylethyl acrylate, thereby further improving the anti-swelling performance of the polymer.

[0063] In some embodiments, the acrylic ester copolymer may include only the first monomer, and thus, the acrylic ester copolymer may be polymerized from at least two different types of the aforementioned first monomers.

[0064] In some embodiments, the monomers of the acrylic ester copolymer further include a second monomer, and the structure of the second monomer is shown in Formula 2:

[0065] Wherein, R3 includes hydrogen atom or C1-C6 alkyl, R4 includes substituted or unsubstituted C1-C 15 Alkyl, substituted or unsubstituted C3-C6 isobornyl, wherein C1-C 15 Substituents of the alkyl group include hydroxyl or C1-C6 alkyl.

[0066] During battery manufacturing, hot or cold pressing is required to ensure a tight bond between the separator and the electrode. When the second monomer satisfies the aforementioned structural formula, the second monomer has a similar structure to the first monomer, both containing unsaturated ester groups, which facilitates copolymerization of the second and first monomers. Furthermore, the soft and hard monomers in the second monomer can form the backbone of the polymer molecular segments through polymerization, giving the polymer excellent stability and good adhesion, while also helping to improve the polymer's anti-swelling properties.

[0067] In some embodiments, the second monomer includes at least one of ethyl acrylate, n-butyl acrylate, n-propyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, cyclohexyl acrylate, isooctyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, methyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, lauryl methacrylate, vinyl acetate, trimethylolpropane triacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate. Thus, the anti-swelling ability of the polymer can be further improved.

[0068] By using any one or more of the above second monomers, the adhesive properties and anti-swelling properties of the polymer can be adjusted.

[0069] In some embodiments, the second monomer includes at least one of ethyl acrylate, n-butyl acrylate, n-propyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, isooctyl acrylate, methyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, and isobornyl methacrylate. This can further improve the polymer's adhesive properties and anti-swelling properties.

[0070] In some embodiments, the monomers of the acrylic ester copolymer further include a third monomer, and the structure of the third monomer is shown in Formula 3 and / or Formula 4:

[0071] Wherein, R5 includes hydrogen atom or C1-C 18 R6 includes a hydrogen atom or a C1-C6 alkyl group. This can improve the ionic conductivity and bonding properties of the polymer.

[0072] The third monomer contains an unsaturated double bond, which is beneficial to the polymerization of the monomer. It also has carboxyl and / or cyano functional groups. The carboxyl and cyano groups can combine with the functional groups on the base membrane of the isolation membrane to improve the adhesion between the polymer and the base membrane, and can also increase the cross-linking active sites of the polymer, thereby improving the creep resistance and cohesive strength of the polymer.

[0073] In some embodiments, the third monomer includes at least one of acrylonitrile, methacrylonitrile, ethacrylonitrile, acrylic acid, methacrylic acid, crotonic acid, and heptenoic acid, thereby further improving the ionic conductivity and bonding properties of the polymer.

[0074] By using any one or more third monomers mentioned above, the adhesive properties of the polymer can be adjusted. Among them, the monomer containing a cyano group can also improve the ionic conductivity of the polymer.

[0075] In some embodiments, the third monomer includes at least one of acrylonitrile, methacrylonitrile, acrylic acid, and methacrylic acid. Thus, the third monomer can more effectively improve the ionic conductivity of the polymer.

[0076] In some embodiments, the monomers of the acrylic ester copolymer further include a fourth monomer, and the structure of the fourth monomer is shown in Formula 5:

[0077] Wherein, R7 comprises a hydrogen atom, a hydroxyl-substituted C1-C6 alkyl group, or a C1-C6 alkoxy group, and R8 comprises a hydrogen atom or a C1-C6 alkyl group. Thus, the fourth monomer can play a role in regulating the molecular weight of the polymer, helping the polymer to have better adhesion.

[0078] The fourth monomer contains an unsaturated amide group, which is beneficial to the polymerization of the monomer. This type of monomer can play a role in regulating the molecular weight and can also improve the adhesion and anti-swelling properties of the polymer.

[0079] In some embodiments, the fourth monomer includes at least one of acrylamide, N-methylol acrylamide, and N-butoxymethyl acrylamide, thereby further improving the bonding performance of the polymer.

[0080] The use of any one or more fourth monomers mentioned above can play a role in regulating the molecular weight, so as to adjust the molecular weight of the polymer. The molecular weight of the polymer is helpful to improve the adhesion of the polymer within a certain range.

[0081] In some embodiments, the fourth monomer includes at least one of acrylamide and N-methylol acrylamide, thereby improving the adhesion of the polymer.

[0082] The test of fluorine-containing groups, ester groups, carboxyl groups, acrylamide groups, carbonyl groups, amide groups, and cyano groups in the organic polymer structure: The test is carried out according to the national standard GB / T 6040-2002 General Rules for Infrared Spectroscopy Analysis Methods. The sample is pressed into a KBr pellet using the pellet transmission method. The KBr background blank is subtracted by the transmission method to obtain the sample test spectrum (resolution: 4 cm -1 , wave number range: 400cm -1-4000cm -1 ).

[0083] In some embodiments, the polymer may further include a dispersant, and the dispersant includes at least one of polyvinyl pyrrolidone, polyacrylamide, sodium polystyrene sulfonate, polyacrylic acid, sodium polyacrylate, and sodium polymethacrylate.

[0084] The cold pressing process refers to a process in which wound battery cells are shaped at a lower ambient temperature than the hot pressing process, so that the elasticity of the battery cells is reduced, and the qualified rate of the core assembly and the consistency of the thickness of the finished battery cells are improved. The aforementioned acrylic copolymers have a relatively low glass transition temperature and can be applied to the cold pressing process to achieve effective bonding between the electrode and the diaphragm. However, the relatively low glass transition temperature and reactive groups on the surface of the aforementioned acrylic copolymers make it easy for particles to agglomerate and adhere to the inner wall of the drying tower during spray drying. The dispersant can form an adsorption layer on the surface of the solid copolymer particles, reducing the interfacial tension between the liquid and the liquid or the solid and the liquid during the spray drying process. The polar end of the dispersant has a strong affinity with water, making the surface of the solid copolymer particles easier to be wetted by water and less likely to agglomerate with other copolymer particles at high temperatures.

[0085] In some embodiments, the mass ratio of the acrylic acid ester copolymer to the dispersant in the polymer is 100:(1-15).

[0086] As an example, the mass ratio of the acrylic copolymer to the dispersant in the polymer can be 100:1, 100:2, 100:3, 100:4, 100:5, 100:6, 100:7, 100:8, 100:9, 100:10, 100:11, 100:12, 100:13, 100:14 or 100:15.

[0087] Since polymer dispersants have long carbon chains, more active adsorption points and side chains that can play a role in spatial repulsion, by mixing polymer dispersants with acrylic copolymers, the dispersants can be adsorbed on the surface of acrylic copolymer particles, reducing the adhesion between adjacent acrylic copolymer particles.

[0088] In some embodiments, the polymer has a Dv50 particle size of 3 μm to 18 μm.

[0089] As an example, the Dv50 particle size of the polymer can be 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm, 9.5μm, 10μm, 10.5μm, 11μm, 11.5μm, 12μm, 12.5μm, 13μm, 13.5μm, 14μm, 14.5μm, 15μm, 15.5μm, 16μm, 16.5μm, 17μm, 17.5μm, 18μm.

[0090] The particle size of the polymer spheres in emulsion polymers is typically nanometers. Directly coating these spheres onto the base membrane can lead to pore clogging or insufficient adhesion due to the small particle size of the spheres. When synthesizing polymer materials through emulsion polymerization, granulation can be used to obtain granular polymer materials, which helps produce polymers with larger particle sizes. When the polymer's Dv50 particle size falls within the aforementioned range, it can mitigate the problem of base membrane pore clogging caused by nanometer-sized polymer particles, improve the permeability of metal active ions through the separator, and alleviate the problem of a thick coating on the base membrane that affects battery energy density.

[0091] The Dv50 particle size indicates that among the sample particles, 50% of the total volume of the particles have a particle size larger than this value, and another 50% of the total volume of the particles have a particle size smaller than this value; Dv50 can represent the median particle size of the sample.

[0092] The volume particle size distribution Dv50 of the polymer can be measured using methods known in the art. For example, GB / T 19077-2016 can be used for characterization testing using a Malvern laser particle size analyzer, such as a Malvern Mastersizer-3000.

[0093] In some embodiments, the polymer has a glass transition temperature of 20°C to 80°C.

[0094] In some embodiments, the glass transition temperature of the polymer may be less than or equal to 40°C.

[0095] When the glass transition temperature of the polymer is within the aforementioned range, the acrylic copolymer has a lower glass transition temperature and can well penetrate into the gap of the electrode at room temperature, so that a stronger mechanical linkage occurs between the acrylic copolymer and the electrode, thereby improving the bonding force of the polymer to the electrode.

[0096] As an example, the glass transition temperature test of a polymer can refer to the following: weigh 6±0.05 mg of sample into an aluminum crucible, shake it flat, cover it with a lid, and test it using the measuring instrument Netzsch DSC 3500Sirius; nitrogen atmosphere, purge gas rate of 50 mL / min, protective gas rate of 100 mL / min; heating conditions: heating rate of 10°C / min, temperature range of (-70)°C to 200°C.

[0097] The glass transition temperature (Tg) is the temperature at which a polymer transitions from an elastic state to a glassy state. It refers to the transition temperature of an amorphous polymer (including the non-crystalline portion of a crystalline polymer) from the glassy state to the elastic state, or vice versa. It is the lowest temperature at which the macromolecular segments of an amorphous polymer can move freely, and is usually denoted by Tg. Above the Tg, a polymer exhibits elasticity and a certain degree of fluidity; below the Tg, a polymer exhibits brittleness. The Tg can be measured using methods commonly used in the art, such as differential scanning calorimetry (DSC) as described in GB / T 19466.2.

[0098] In a second aspect of the present application, the present application proposes a method for preparing the aforementioned polymer, referring to FIG1 , comprising:

[0099] S100: Mix and stir the emulsifier, initiator, and monomers of the acrylic copolymer, and heat to react

[0100] In some embodiments, the emulsifier, initiator, and monomers constituting the acrylic copolymer are blended and stirred in a mass ratio of (0.2-2):(0.1-0.5):100, and heated for reaction, thereby obtaining a polymer emulsion through emulsion polymerization, which can effectively improve the yield of the polymer.

[0101] Emulsion polymerization is a process in which monomers are dispersed in water with the help of emulsifiers and mechanical stirring to form an emulsion, and then an initiator is added to initiate monomer polymerization.

[0102] Emulsifiers are substances that can transform mutually incompatible oil and water into an emulsion that is difficult to separate. Emulsifiers are usually surfactants that have both hydrophilic polar groups and hydrophobic (lipophilic) non-polar groups.

[0103] An initiator is a substance that can initiate polymerization of monomers. For example, free radical initiators, which are compounds that readily decompose into free radicals (i.e., primary free radicals) upon exposure to heat, can be used to initiate free radical polymerization and copolymerization of olefinic and diene monomers.

[0104] In some embodiments, the emulsifier may include at least one of sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, sodium dodecylbenzene sulfate, sodium laurate, sodium stearate, and sodium palmitoleate.

[0105] In some embodiments, the initiator may include at least one of the following: a persulfate initiator including at least one of potassium persulfate and ammonium persulfate; an acyl peroxide initiator including at least one of benzoyl peroxide and dioctanoyl peroxide; and an azo initiator including at least one of azobisisobutyronitrile and dimethyl azobisisobutyrate.

[0106] In some embodiments, the constituent monomers of the acrylic ester copolymer include a first monomer, a second monomer, a third monomer, and a fourth monomer, wherein the mass ratio of the first monomer, the second monomer, the third monomer, and the fourth monomer is (20-30):(40-50):(1-10):(1-10), so that the polymer has better adhesion while combining the advantages of the first monomer, the second monomer, the third monomer, and the fourth monomer.

[0107] The aforementioned acrylic copolymers can be produced by combining fluorine-containing functional monomers with different functional monomers. On the one hand, the prepared acrylic copolymers have a low glass transition temperature and can penetrate well into the gaps of the electrode at room temperature, resulting in a strong mechanical linkage between the acrylic copolymer and the electrode, improving the adhesion to the electrode. On the other hand, through the selection of monomer combinations, reactive groups are introduced into the acrylic copolymers, making them more hydrophilic, improving the surface wettability of the copolymer particles in the polymer emulsion, and reducing the occurrence of irregular aggregation.

[0108] In some embodiments, the temperature of the heating reaction may be 60°C-100°C.

[0109] As an example, the temperature of the heating reaction can be 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C or 100°C.

[0110] When the temperature of the heating reaction is within the aforementioned range, the yield of the emulsion polymerization is higher and the energy consumption is lower.

[0111] S200: Spray drying of polymer emulsions

[0112] In some embodiments, in this step, the polymer emulsion prepared above is spray-dried to obtain polymer particles with a moderate particle size.

[0113] When synthesizing polymer materials through emulsion polymerization, since the copolymer particle size in the emulsion-type acrylic copolymer is 100nm-200nm, if it is directly scraped onto the diaphragm, pore blockage or insufficient adhesion will occur due to the small particle size of the copolymer. Granulation treatment helps to obtain polymers with larger particle sizes.

[0114] Spray drying, through mechanical action, disperses the material to be dried (polymer emulsion) into very fine mist-like particles (increasing the water evaporation area and accelerating the drying process). Most of the water is removed at the moment of contact with hot air, and the solid matter in the material is dried into powder.

[0115] In some embodiments, referring to FIG2 , before spray drying, the method for preparing a polymer may further include:

[0116] S110: Adding dispersant to polymer emulsion

[0117] When granulating an acrylic polymer emulsion, due to the strong intermolecular forces of the acrylic copolymer, the copolymer particles are prone to agglomeration, which makes it difficult to granulate well. The addition of a dispersant can reduce the random agglomeration of the acrylic copolymer in the polymer emulsion and reduce agglomeration during the drying process.

[0118] Due to its special structure, it has excellent dispersing properties for suspension systems. Due to the hydrophobicity of the main chain and the hydrophilicity of the side chains, as well as the presence of the side chains, it also plays a certain steric stabilizing role, preventing the acrylic polymer emulsion from random aggregation, thereby facilitating the dispersion of emulsion particles.

[0119] In some embodiments, the number average molecular weight of the dispersant may be 100-100,000.

[0120] As an example, the number average molecular weight of the dispersant can be 500-100,000, 3,000-100,000, 5,000-100,000, 8,000-100,000, 10,000-100,000, 30,000-90,000, 50,000-70,000, 50,000-60,000, 55,000-60,000, etc.

[0121] In some embodiments, the number average molecular weight of the dispersant is 5,000-80,000.

[0122] By adding a dispersant of the above molecular weight to the polymer, the irregular coagulation in the polymer emulsion system can be reduced and the particle size uniformity of the polymer can be improved. When the polymer is used as a binder on the isolation membrane, the bonding force between the isolation membrane and the electrode can be improved, thereby improving the cycle performance of the battery.

[0123] In this application, the number average molecular weight of the dispersant can be determined by gel permeation chromatography according to standard GB / T 21863-2008. Specifically, this can be performed using the following method: an ultra-high performance polymer chromatograph (ACQUITY APC) and an ACQUITY differential refractive index detector (RI). Standards: polystyrene sleeve; run time: 30 minutes; detector: ACQUITY differential refractive index (RI) detector; column oven temperature: 90°C; detector temperature: 55°C. Sample testing: a. Standard sample and test sample preparation: Weigh 0.002g to 0.004g of standard sample / test sample respectively and add 2mL of mobile phase liquid to prepare a 0.1% to 0.5% mixed standard, and store in the refrigerator for >8h; b. Standard solution / sample testing: Edit the sample group to be tested, select the established sample group method, wait for the baseline to stabilize, click the run queue, and start testing the sample; (4) Data processing: Based on the relationship between retention time and molecular weight, use the chemical workstation to establish a calibration curve, integrate and quantify the sample spectrum, and the chemical workstation automatically generates the molecular weight and molecular weight distribution results.

[0124] In a third aspect of the present application, a separator is provided, comprising the aforementioned polymer and / or a polymer prepared by the aforementioned method. Thus, the separator has all the features and advantages of the aforementioned polymer and the method for preparing the polymer, which will not be further elaborated here.

[0125] In some embodiments, referring to FIG. 3 , the isolation film may include a base film 31 and a polymer 32 located on at least one side of the base film 31 ; in other embodiments, the polymer 32 may be located on two opposite surfaces of the base film 31 .

[0126] In some embodiments, the base film may include at least one of polyethylene, polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, and non-woven fabric. Using a base film made of the above materials can effectively improve the adhesion of the polymer on the base film and improve the structural stability of the separator.

[0127] In a fourth aspect of the present application, a battery is provided, comprising the aforementioned separator, thereby having all the features and advantages of the aforementioned separator, which will not be described in detail here.

[0128] During the battery's charge and discharge processes, active ions are embedded in and extracted from the positive and negative electrodes. The electrolyte conducts these active ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0129] [Positive electrode]

[0130] The positive electrode sheet includes a positive electrode current collector 21 and a positive electrode active material layer 22 disposed on at least one side of the positive electrode current collector 21 . The positive electrode active material layer 22 includes a positive electrode active material.

[0131] As an example, referring to FIG. 3 , the positive electrode current collector 21 has two surfaces facing each other in its thickness direction, and the positive electrode active material layer 22 is provided on either or both of the two facing surfaces of the positive electrode current collector 21 .

[0132] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one side of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0133] In some embodiments, when the battery is a lithium ion battery, the positive electrode active material may be a positive electrode active material for lithium ion batteries known in the art.

[0134] As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, the lithium transition metal oxide may include lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.8 Co 0.15 Al 0.05 O2) and its modified compounds. Examples of olivine-structured lithium-containing phosphates include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon. The modified compounds of the above materials may be modified by doping and / or surface coating the materials.

[0135] The battery's charge and discharge processes involve the intercalation and deintercalation of lithium, leading to different molar Li contents at different discharge states. The molar Li contents listed in this application for the positive electrode active materials refer to the initial state of the material, i.e., the state before addition. When the positive electrode active material is used in a battery system, the molar Li content will change after charge and discharge cycles.

[0136] In some embodiments, when the battery is a sodium ion battery, the positive electrode active material may be a positive electrode active material for sodium ion batteries known in the art.

[0137] As an example, the positive electrode active material may include at least one of the following materials: a sodium transition metal oxide, a polyanion compound, a Prussian blue-type sodium compound, and their respective modified compounds. However, this application is not limited to these materials; other conventional materials that can be used as battery positive electrode active materials may also be used. The modified compounds of the above materials may be modified by doping and / or surface coating.

[0138] In some embodiments, the transition metal in the sodium transition metal oxide may be at least one of Ti, V, Mn, Co, Ni, Fe, Zn, V, Zr, Ce, Cr, and Cu. The chemical formula of the sodium transition metal oxide may satisfy Na x MO2, wherein M includes at least one of Ti, V, Mn, Co, Ni, Fe, Zn, V, Zr, Ce, Cr, and Cu, and 0<x≤1.

[0139] In some embodiments, the polyanionic compound may be a compound having sodium ions, transition metal ions and tetrahedral (YO4) n-A class of compounds with anionic units. Among them, the transition metal may include at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y may include at least one of P, S, and Si; n represents (YO4) n- valence.

[0140] In some embodiments, the polyanionic compound can also be a compound having sodium ions, transition metal ions, tetrahedral (YO4) n- A class of compounds of anion units and halogen anions. The transition metal may include at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y may include at least one of P, S, and Si, and n represents (YO4) n- The halogen may include at least one of F, Cl, and Br.

[0141] In some embodiments, the polyanionic compound may also be a compound having sodium ions, tetrahedral (YO4) n- Anion unit, polyhedron unit (ZO y ) m+ and an optional halogen anion. M may include at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce, Y may include at least one of P, S and Si, and n represents (YO4) n- valence state, Z represents a transition metal, m represents (ZO y ) m+ The halogen may include at least one of F, Cl, and Br.

[0142] As an example, the polyanionic compound may satisfy the chemical formula NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2(P2O7), NaM'PO4F (M' includes at least one of V, Fe, Mn and Ni) and Na3(VO y )2(PO4)2F 3-2y At least one of (0≤y≤1).

[0143] In some embodiments, the Prussian blue compound may be a compound having sodium ions, transition metal ions and cyanide ions (CN - The transition metal may include at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce.

[0144] As an example, a Prussian blue-like compound may satisfy the chemical formula Na a Me b Me'c (CN)6, wherein Me and Me' each independently include at least one of Ni, Cu, Fe, Mn, Co, and Zn, 0<a≤2, 0<b<1, and 0<c<1.

[0145] The battery's charge and discharge processes are accompanied by the deintercalation and consumption of Na, resulting in different molar contents of Na at different discharge states. The molar contents of Na in the positive electrode active materials listed in this application refer to the initial state of the material, i.e., the state before the materials are added. The molar contents of Na will change after the positive electrode active materials are applied to the battery system and undergo charge and discharge cycles.

[0146] In the list of positive electrode active materials in this application, the molar content of O is only a theoretical value. Lattice oxygen release will cause the molar content of oxygen to change, and the actual molar content of O will fluctuate.

[0147] In some embodiments, the positive active material layer may further optionally include a binder.

[0148] As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0149] In some embodiments, the positive active material layer may further optionally include a conductive agent.

[0150] As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0151] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0152] [Negative electrode]

[0153] The negative electrode sheet includes a negative electrode current collector 11 and a negative electrode active material layer 12 disposed on at least one side of the negative electrode current collector 11 . The negative electrode active material layer 12 includes a negative electrode active material.

[0154] As an example, the negative electrode current collector 11 has two surfaces facing each other in its thickness direction, and the negative electrode active material layer 12 is provided on either or both of the two facing surfaces of the negative electrode current collector 11 .

[0155] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0156] In some embodiments, the negative electrode active material may adopt the negative electrode active material for batteries known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. Silicon-based materials include at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials include at least one of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0157] In some embodiments, the negative active material layer may further optionally include a binder.

[0158] As an example, the binder in the negative electrode active material layer may include 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).

[0159] In some embodiments, the negative active material layer may further optionally include a conductive agent.

[0160] As an example, the conductive agent includes at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0161] In some embodiments, the negative electrode active material layer may further optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0162] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0163] [Electrolytes]

[0164] The electrolyte conducts ions between the positive and negative electrodes. This application does not specify the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0165] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0166] In some embodiments, the electrolyte salt includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium bisoxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0167] In some embodiments, the solvent includes at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0168] In some embodiments, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0169] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0170] In some embodiments, the battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0171] In some embodiments, the battery outer packaging may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the battery outer packaging may be a soft shell, such as a pouch-type soft shell. The soft shell may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0172] In some embodiments, the battery may include at least one of a battery cell, a battery module, and a battery pack.

[0173] The present application has no particular limitation on the shape of the battery, which can be cylindrical, square, or any other shape. For example, FIG4 shows a square-structured battery cell 5 as an example.

[0174] In some embodiments, referring to Figure 5, the outer packaging may include a shell 51 and a top cover assembly 53. Among them, the shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the top cover assembly 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0175] In some embodiments, battery cells may be assembled into a battery module. The battery module may contain one or more battery cells. The specific number may be selected by those skilled in the art based on the application and capacity of the battery module.

[0176] Figure 6 shows an example battery module 4. Referring to Figure 6 , within the battery module 4, multiple battery cells 5 may be arranged sequentially along the length of the battery module 4. Of course, they may also be arranged in any other manner. Furthermore, the multiple battery cells 5 may be secured together using fasteners.

[0177] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0178] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0179] Figures 7 and 8 illustrate an example battery pack 1. Referring to Figures 7 and 8 , the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 can be positioned over the lower case 3 to form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0180] In a fifth aspect of the present application, the present application provides an electrical device comprising the aforementioned battery. Thus, the electrical device has all the features and advantages of the aforementioned battery, which will not be described in detail here.

[0181] The electrical device may include at least one of the battery cells, battery modules, and battery packs provided in this application. The battery cells, battery modules, and battery packs may be used as power sources for the electrical device, or as energy storage units for the electrical device. The electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (refer to Figure 9, such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc.

[0182] As an electrical device, a battery cell, battery module or battery pack can be selected according to its usage requirements.

[0183] The present invention will be described below by way of specific examples. It should be noted that the following examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. Where specific techniques or conditions are not specified in the examples, they are determined according to the techniques or conditions described in the literature in this area or according to the product specifications. Reagents or instruments not specified by manufacturer are all commercially available conventional products.

[0184] Example 1

[0185] 1. Preparation of polymer

[0186] (1) Preparation of polymer emulsion

[0187] Weigh 1000g of the first monomer (trifluoroethyl acrylate), the second monomer (n-butyl methacrylate), the third monomer (methacrylonitrile), and the fourth monomer (acrylamide) in a mass ratio of 25:45:5:5. Mix the monomers thoroughly. Add 1000g of the mixed monomers, 20g of the emulsifier (sodium dodecylbenzenesulfonate), 5g of the initiator (potassium persulfate), and 1200g of deionized water to a 5L four-necked flask equipped with a mechanical stirrer, a thermometer, and a condenser. Emulsify at high speed for 30 minutes. Under nitrogen, heat to 80°C for 4 hours, then cool to below 40°C, adjust the pH to neutral, and filter the product to obtain a polymer emulsion.

[0188] (2) The polymer emulsion was subjected to a spray drying process to obtain an adhesive for an isolation film. The conditions of the spray drying process were: an inlet air temperature of 110° C., an outlet air temperature of 50° C., and an air pressure of 0.5 kPa.

[0189] 2. Preparation of batteries

[0190] (1) Preparation of isolation membrane

[0191] A commercially available PE microporous film with a thickness of 7 μm and an average pore size of 80 nm (from Zhuo Gao Electronic Technology Co., Ltd.) was used as the base membrane. The polymer prepared above was stirred and mixed uniformly in deionized water to obtain a binder slurry (solid content of 20%). The binder slurry was sprayed onto both surfaces of the base membrane and dried to remove the solvent. The polymer coating density on the base membrane was 1.5 g / m 2 , and obtain an isolation film.

[0192] (2) Preparation of positive electrode sheet

[0193] Polyvinylidene fluoride (PVDF), lithium iron phosphate (LFP), conductive carbon black, and N-methylpyrrolidone (NMP) were mixed in a mass ratio of 1.2:58.38:0.42:40 and stirred thoroughly to prepare a positive electrode slurry. 2 The loading amount is evenly coated on the positive electrode current collector aluminum foil, and then dried, cold pressed and cut to obtain the positive electrode sheet.

[0194] (3) Preparation of negative electrode sheet

[0195] Artificial graphite, conductive agent acetylene black, binder styrene butadiene rubber (SBR), thickener sodium carboxymethyl cellulose (CMC-Na) were added into deionized water in a mass ratio of 96.2:1.0:1.6:1.2, and stirred thoroughly to prepare a negative electrode slurry (solid content of 63%). 2 The loading amount is coated on the negative electrode current collector copper foil, and then dried, cold pressed and cut to obtain the negative electrode sheet.

[0196] (4) Preparation of electrolyte

[0197] At 25°C, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain a mixed solvent, and then LiPF6 is dissolved in the above mixed solvent to obtain an electrolyte, wherein the concentration of LiPF6 is 1 mol / L.

[0198] (5) Battery assembly

[0199] The positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, wound, and cold-pressed (during which the separator is bonded to the electrode sheet) to obtain a battery cell; the battery cell is placed in an outer package, and the above-prepared electrolyte is added. After packaging, standing, formation, aging and other processes, a battery is obtained.

[0200] The differences between other embodiments and comparative examples and embodiment 1 are shown in Table 1. Specifically, compared with embodiment 1, embodiments 2 to 4 use different monomer types; embodiments 5 to 10 use different monomer mass ratios; embodiment 11 uses two first monomers with a mass ratio of 1:1 as polymer monomers; a dispersant is also added to the polymer emulsions in embodiments 12 to 15 before spray drying; the polymer monomer in comparative example 1 does not contain the first monomer, and the binder on the surface of the base film in comparative example 2 is styrene-butadiene rubber.

[0201] Table 1

[0202] The polymers in the above examples and comparative examples were subjected to polymer swelling tests. The test results are shown in Table 2. The test method is as follows:

[0203] (1) Dissolution: 10 g of polymer powder was mixed with 90 g of N-methylpyrrolidone (NMP), and the mixture was stirred and dissolved at 40 °C for 5 h to obtain a polymer glue solution;

[0204] (2) Film preparation: Pour the stirred polymer solution into a polytetrafluoroethylene drying tray and bake at 70°C for 7 days to obtain a dry film;

[0205] (3) Swelling degree test: Take a dry film of about 1g in size with a thickness of 2mm, weigh its exact mass and record it as M1, soak it in electrolyte, place it in a 70℃ oven and bake it for 24h, take out the sample and let it stand for 1h, then wipe it clean, weigh its mass M2, and calculate the swelling degree of the polymer according to the mass swelling degree = (M2-M1) / M1×100%. The electrolyte preparation method is as follows: ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) are mixed in a mass ratio of 3:5:2 to obtain an electrolyte solvent, and the electrolyte solvent is prepared with lithium hexafluorophosphate (LiPF6) to form an electrolyte with a molar concentration of LiPF6 of 1 mol / L.

[0206] The battery in the above embodiment and comparative example was subjected to cycle performance test. The test results are shown in Table 2. The test method is as follows:

[0207] At 25°C, the prepared battery was charged at a constant current of 1 / 3C to 3.65V, then charged at a constant voltage of 3.65V to a current of 0.05C, left for 5 minutes, and then discharged at 1 / 3C to 2.5V. The obtained discharge capacity was recorded as the initial capacity C0. Repeat the above steps for the same battery and record the discharge capacity C of the battery after the nth cycle. n , then the battery capacity retention rate P after each cycle n =(C n / C0)×100%, the battery capacity retention rate P after 500 cycles 500 To reflect the difference in cycle performance.

[0208] Table 2

[0209] As can be seen from the test results in Table 2, in Examples 1 to 11, by using fluorine-substituted acrylate monomers as monomers of the acrylate copolymer, the shielding effect of fluorine atoms can be used to improve the chemical inertness of the acrylate copolymer, thereby making the polymer have better adhesion and better anti-swelling performance, thereby improving the cycle performance of the battery using the polymer as the binder on the isolation membrane; in Examples 12 to 15, the addition of a dispersant can reduce the adhesion between the acrylate copolymer particles obtained by spray drying, while alleviating the swelling of the polymer, helping to obtain a polymer with a moderate particle size, further improving the adhesion between the isolation membrane and the electrode, and improving the cycle performance of the battery using the polymer as the binder on the isolation membrane. In Comparative Example 1, since fluorine-substituted acrylate monomers are not used as monomers of the acrylate copolymer, the polymer has poor anti-swelling ability. At the beginning of the charge and discharge cycle, the bonding effect between the isolation membrane and the electrode is relatively good. However, as the charge and discharge cycle proceeds, the swelling of the polymer continues to intensify, which in turn leads to problems such as increased volume expansion of the battery, increased internal resistance of the battery, and poor cycle stability. In Comparative Example 2, styrene-butadiene rubber is used as the binder on the isolation membrane. The anti-swelling and bonding properties of styrene-butadiene rubber are poor, and the bonding effect between the isolation membrane and the electrode is poor. It cannot effectively suppress the pulverization and rupture of the active material during the charge and discharge cycle, resulting in reduced electrode peeling strength and poor battery service life.

[0210] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A polymer, wherein, It includes an acrylate copolymer, and the monomers of the acrylate copolymer at least include a first monomer, and the first monomer includes a fluorine-substituted acrylate monomer.

2. The polymer according to claim 1, wherein The structure of the first monomer is shown in Formula 1: Among them, R1 includes a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R2 includes a fully fluorinated or partially fluorinated alkyl group having 1 to 15 carbon atoms.

3. The polymer according to claim 2, wherein, The first monomer includes at least one of trifluoroethyl acrylate, trifluoroethyl methacrylate, hexafluorobutyl acrylate, hexafluorobutyl methacrylate, perfluoroalkyl ethyl acrylate, perfluoroalkyl acrylate, dodecafluoroheptyl acrylate, dodecafluoroheptyl methacrylate, 1H,1H-perfluorooctyl methacrylate, 2-fluoroethyl acrylate, 2-fluoroethyl acrylate, perfluorohexyl ethyl methacrylate, and trifluoropentyl acrylate.

4. The polymer according to claim 3, wherein, The first monomer includes at least one of trifluoroethyl acrylate, trifluoroethyl methacrylate, hexafluorobutyl acrylate, hexafluorobutyl methacrylate, and perfluoroalkyl ethyl acrylate.

5. The polymer according to claim 1, wherein, The monomer of the acrylate copolymer further includes a second monomer, and the structure of the second monomer is shown in Formula 2: Among them, R3 includes a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and R4 includes a substituted or unsubstituted alkyl group having 1 to 15 carbon atoms, or a substituted or unsubstituted isobornyl group having 3 to 6 carbon atoms, wherein the substituent of the alkyl group having 1 to 15 carbon atoms includes a hydroxyl group or an alkyl group having 1 to 6 carbon atoms.

6. The polymer according to claim 5, wherein, The second monomer includes at least one of ethyl acrylate, n-butyl acrylate, n-propyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, cyclohexyl acrylate, isooctyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, methyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, lauryl methacrylate, vinyl acetate, trimethylolpropane triacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate.

7. The polymer according to claim 6, wherein, The second monomer includes at least one of ethyl acrylate, n-butyl acrylate, n-propyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, isooctyl acrylate, methyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, and isobornyl methacrylate.

8. The polymer according to claim 1, wherein, The monomer of the acrylate copolymer further comprises a third monomer, and the structure of the third monomer is as shown in Formula 3 and / or Formula 4: Among them, R5 includes a hydrogen atom or an alkyl group having 1 to 18 carbon atoms, and R6 includes a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

9. The polymer according to claim 8, wherein The third monomer includes at least one of acrylonitrile, methacrylonitrile, ethyl acrylonitrile, acrylic acid, methacrylic acid, crotonic acid, and heptenoic acid.

10. The polymer according to claim 9, wherein, The third monomer includes at least one of acrylonitrile, methacrylonitrile, acrylic acid, and methacrylic acid.

11. The polymer according to claim 1, wherein, The monomer of the acrylate copolymer further includes a fourth monomer, and the structure of the fourth monomer is shown in Formula 5: Wherein, R7 includes a hydrogen atom, a C1-C6 alkyl group substituted by a hydroxyl group or a C1-C6 alkoxy group, and R8 includes a hydrogen atom or a C1-C6 alkyl group.

12. The polymer according to claim 11, wherein, The fourth monomer includes at least one of acrylamide, N-hydroxymethylacrylamide, and N-butoxymethylacrylamide.

13. The polymer according to claim 12, wherein, The fourth monomer includes at least one of acrylamide and N-hydroxymethylacrylamide.

14. The polymer according to any one of claims 1-13, wherein, The polymer further includes a dispersant, and the dispersant includes at least one of polyvinylpyrrolidone, polyacrylamide, sodium polystyrene sulfonate, polyacrylic acid, sodium polyacrylate, and sodium polymethacrylate.

15. The polymer according to claim 14, wherein, The mass ratio of the acrylate copolymer to the dispersant in the polymer is 100:(1-15).

16. The polymer according to any one of claims 1-15, wherein, The Dv50 particle size of the polymer is 3μm - 18μm.

17. A method for preparing the polymer according to any one of claims 1-16, wherein, It includes: Blending and stirring an emulsifier, an initiator, and the constituent monomers of the acrylate copolymer in a mass ratio of (0.2-2):(0.1-0.5):100, and heating and reacting to obtain a polymer emulsion; The polymer emulsion is spray-dried to obtain the polymer.

18. The method according to claim 17, wherein The constituent monomers of the acrylate copolymer include a first monomer, a second monomer, a third monomer, and a fourth monomer, wherein the mass ratio of the first monomer, the second monomer, the third monomer, and the fourth monomer is (20-30):(40-50):(1-10):(1-10).

19. The method according to claim 17 or 18, wherein Before the spray drying, it further includes adding a dispersant to the polymer emulsion.

20. An isolation film, wherein, It includes the polymer according to any one of claims 1-16, and / or the polymer prepared by the method according to any one of claims 17-19.

21. A battery, wherein, It includes the separator membrane according to claim 20.

22. An electrical device, wherein, It includes the battery according to claim 21.

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