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

Abstract

The invention discloses a polymer, a method for preparing the polymer, an isolating membrane, a battery and a power utilization device, the polymer comprises an acrylate copolymer, monomers of the acrylate copolymer at least comprise a first monomer, and the first monomer comprises a fluorine-substituted acrylate monomer. Therefore, the binding power of the polymer can be improved, when the polymer is used as a binding agent in a battery, for example, the polymer is used as a binding agent on an isolating membrane, the swelling of the polymer in electrolyte is small, the binding effect between the isolating membrane and a pole piece can be effectively improved, and the cycle performance of the battery is further improved.

Description

Technical Field

[0001] This application relates to the technical field of batteries, and specifically, to polymers, methods for preparing polymers, separator membranes, batteries, and electrical devices. Background Art

[0002] In recent years, batteries have been widely used in energy storage power systems such as hydroelectric, thermal, wind, and solar power stations, as well as in many fields such as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, and aerospace. In batteries, the dosage and cost proportion of the binder are both relatively small, but it can effectively improve battery performance and is an indispensable important component in batteries. As an inactive material in the battery, the binder can bond the various components in the battery and adjacent components together, reduce the expansion and shedding of the active material during the charge and discharge process of the battery, and reduce the internal resistance of the battery. However, there are still problems such as insufficient bonding force in current batteries, which need to be further improved.

[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. Summary of the Invention

[0004] In a first aspect of this application, a polymer is proposed, which includes an acrylate copolymer. The monomers of the acrylate copolymer include at least a first monomer, and the first monomer includes a fluorine-substituted acrylate monomer. Thus, the bonding force of the polymer can be improved. When this polymer is used as a binder in a battery, for example, as a binder on the separator membrane, the swelling of the polymer in the electrolyte is small, which can effectively improve the bonding effect between the separator membrane and the electrode sheet, and further improve the cycling performance of the battery.

[0005] In some embodiments, the structure of the first monomer is shown in Formula 1:

[0006]

[0007] Wherein, R1 includes a hydrogen atom or an alkyl group with 1 to 6 carbon atoms, and R2 includes a fully fluorinated or partially fluorinated alkyl group with 1 to 15 carbon atoms. Thus, it is beneficial to the formation of the polymer and the improvement of 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, perfluoroalkyl ethyl acrylate, perfluoroalkyl acrylate, dodecafluoroheptyl acrylate, dodecafluoroheptyl methacrylate, 1H,1H-perfluorooctyl methacrylate, 2-fluoroethyl acrylate, ethyl 2-fluoropropenoate, perfluorooctylethyl methacrylate, perfluorohexylethyl methacrylate, and trifluoropentyl acrylate. Thereby, the anti-swelling performance of the polymer can be further improved.

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

[0010] In some embodiments, the monomer of the acrylate copolymer further includes a second monomer, and the structure of the second monomer is shown in Formula 2:

[0011]

[0012] wherein, R3 includes a hydrogen atom or an alkyl group of C1-C6, and R4 includes a substituted or unsubstituted alkyl group of C1-C 15 an alkyl group, a substituted or unsubstituted isobornyl group of C3-C6, wherein the substituent of the alkyl group of C1-C 15 the alkyl group includes a hydroxyl group or an alkyl group of C1-C6.

[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, 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. Thereby, the anti-swelling ability of the polymer can be further improved.

[0014] 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.

[0015] In some embodiments, the monomer of the acrylate copolymer further includes a third monomer, and the structure of the third monomer is as shown in Formula 3 and / or Formula 4:

[0016]

[0017] Wherein, R5 includes a hydrogen atom or an alkyl group of C1-C 18 alkyl, and R6 includes a hydrogen atom or an alkyl group of C1-C6. Thereby, the ionic conductivity and adhesion performance of the polymer can be improved.

[0018] In some embodiments, the third monomer includes at least one of acrylonitrile, methacrylonitrile, ethylacrylonitrile, acrylic acid, methacrylic acid, crotonic acid, and heptenoic acid. Thereby, the ionic conductivity and adhesion performance of the polymer can be further improved.

[0019] In some embodiments, the third monomer includes at least one of acrylonitrile, methacrylonitrile, acrylic acid, and methacrylic acid.

[0020] In some embodiments, the monomer of the acrylate copolymer further includes a fourth monomer, and the structure of the fourth monomer is as shown in Formula 5:

[0021]

[0022] Wherein, R7 includes a hydrogen atom, a C1-C6 alkyl group substituted with a hydroxyl group or a C1-C6 alkoxy group, and R8 includes a hydrogen atom or a C1-C6 alkyl group. Thereby, the fourth monomer can play a role in regulating the molecular weight of the polymer and helps the polymer to have better adhesion.

[0023] In some embodiments, the fourth monomer includes at least one of acrylamide, N-hydroxymethylacrylamide, and N-butoxymethylacrylamide. Thereby, the adhesion performance of the polymer can be further improved.

[0024] In some embodiments, the fourth monomer includes at least one of acrylamide and N-hydroxymethylacrylamide.

[0025] In some embodiments, 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. Thereby, the addition of the dispersant can reduce the aggregation of the polymer, and further improve the particle size uniformity of the polymer.

[0026] In some embodiments, the mass ratio of the acrylate copolymer to the dispersant in the polymer is 100:(1-15). Thereby, the adhesion between the acrylate copolymer particles can be further reduced.

[0027] In some embodiments, the Dv50 particle size of the polymer is 3 μm - 18 μm. Thus, the blockage of the polymer to the pores of the separator membrane can be reduced, and at the same time, the thickness of the coating formed by the polymer can be made moderate.

[0028] In the second aspect of the present application, a method for preparing the aforementioned polymer is proposed, including: blending and stirring an emulsifier, an initiator, and the constituent monomers of an acrylate copolymer in a mass ratio of (0.2 - 2):(0.1 - 0.5):100, and heating and reacting to obtain a polymer emulsion; spray-drying the polymer emulsion to obtain the polymer. Thus, the aforementioned polymer can be prepared by a simple method.

[0029] In some embodiments, 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). Thus, a polymer with relatively excellent adhesiveness can be obtained.

[0030] In some embodiments, before the spray-drying, it further includes: adding a dispersant to the polymer emulsion. Thus, the random aggregation in the polymer emulsion can be reduced, and the dispersibility of the polymer emulsion can be improved.

[0031] In the third aspect of the present application, a separator membrane is proposed, including the aforementioned polymer, and / or a polymer prepared by the aforementioned method. Thus, the separator membrane has all the features and advantages of the aforementioned polymer and the method for preparing the polymer, which will not be elaborated herein.

[0032] In the fourth aspect of the present application, a battery is proposed, including the aforementioned separator membrane. Thus, the battery has all the features and advantages of the aforementioned separator membrane, which will not be elaborated herein.

[0033] In the fifth aspect of the present application, an electrical device is proposed, including the aforementioned battery. Thus, the electrical device has all the features and advantages of the aforementioned battery, which will not be elaborated herein. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The above and / or additional aspects and advantages of the present application will become apparent and easy to understand from the description of the embodiments in conjunction with the following drawings, where:

[0035] Figure 1 is a schematic flow chart of a method for preparing a polymer according to an embodiment of the present application;

[0036] Figure 2It is a schematic flow chart of a method for preparing a polymer according to another embodiment of the present application;

[0037] Figure 3 It is a schematic structural diagram of a battery according to an embodiment of the present application;

[0038] Figure 4 It is a schematic diagram of a battery cell according to an embodiment of the present application;

[0039] Figure 5 is Figure 4 An exploded view of the battery cell shown in an embodiment of the present application;

[0040] Figure 6 It is a schematic diagram of a battery module according to an embodiment of the present application;

[0041] Figure 7 It is a schematic diagram of a battery pack according to an embodiment of the present application;

[0042] Figure 8 is Figure 8 An exploded view of the battery pack shown in an embodiment of the present application;

[0043] Figure 9 It is a schematic diagram of an electrical device using the battery as a power source according to an embodiment of the present application.

[0044] Explanation of reference numerals:

[0045] 1 Battery pack; 2 Upper box body; 3 Lower box body; 4 Battery module; 5 Battery cell;

[0046] 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 of specific embodiments

[0047] The following describes in detail the embodiments of the present application. Examples of the embodiments are shown in the drawings, where the same or similar reference numerals represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are only used to explain the present application and should not be construed as a limitation of the present application.

[0048] Unless otherwise defined, all technical and scientific terms used in the present application have the same meaning as commonly understood by those skilled in the technical field to which the present application belongs; the terms used in the present application are only for the purpose of describing specific embodiments and are not intended to limit the present application; unless otherwise specified, the numerical values of the various parameters mentioned in the present application can be measured by various commonly used measurement methods in the art (for example, they can be tested according to the methods given in the embodiments of the present application).

[0049] In the description and claims of this application, the terms "comprising" and "having" and any variations thereof are open-ended expressions, that is, they include the content specified in this application, but do not exclude other aspects.

[0050] The "range" disclosed in this application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The ranges defined in this way can include or exclude the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, ranges of 60-110 and 80-120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise specified, the numerical range "a-b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been fully listed herein, and "0-5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0051] If there is no special instruction, all embodiments and optional embodiments of this application can be combined with each other to form new technical solutions.

[0052] If there is no special instruction, all technical features and optional technical features of this application can be combined with each other to form new technical solutions.

[0053] In the description of this application, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. The "first feature" and "second feature" can include one or more of such features.

[0054] In the description of this application, "A and / or B" can include the case of A alone, the case of B alone, and any one of the cases of A and B, where A and B are only for illustration and can be any technical features connected by "and / or" in this application.

[0055] In this application, the writing order of each step does not mean a strict execution order that constitutes any limitation to the implementation process. The specific execution order of each step should be determined by its function and possible internal logic. Without special instructions, all steps of this application can be carried out sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) carried out sequentially, or may also include steps (b) and (a) carried out sequentially. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may also include steps (a), (c) and (b), or may also include steps (c), (a) and (b), etc.

[0056] Generally, a battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator. A binder needs to be provided between the separator and the electrode sheet to tightly bond adjacent parts together. The bonded positive electrode sheet, negative electrode sheet and separator are mutually attached and supported to form a structure with a certain thickness, so that the battery has a certain hardness. The negative electrode sheet expands and contracts during charge and discharge. When the bonding force between the separator and the electrode sheet is weak, after the negative electrode sheet contracts, the separator cannot continuously fit well with the surface of the negative electrode sheet, resulting in a gap between the positive electrode sheet, negative electrode sheet and separator. The positive electrode sheet, negative electrode sheet and separator cannot be mutually attached and supported, causing the battery to become loose, with a lower hardness, a significant increase in the internal resistance of the battery, and further a significant reduction in the cycle performance of the battery.

[0057] By providing a binder on the surface of the separator, the bonding performance of the separator can be effectively improved, and the bonding effect between the separator and the electrode sheet can be enhanced. However, currently, polymer binders applied to separators have the problem of poor anti-swelling performance. Specifically, the electrolyte mainly consists of ester-based organic solvents, lithium salts and additives. The polymer will swell in the electrolyte. The swelling of the polymer will cause problems such as increased volume expansion during the charge and discharge process of the battery, further resulting in an increase in the internal resistance of the battery, an accelerated decay of the reversible capacity, a deterioration of the cycle stability, and a decrease in the strength of the swollen polymer. The bonding effect between the separator and the electrode sheet becomes poor, and it cannot effectively inhibit the pulverization and rupture of the active material during the charge and discharge cycle, resulting in a reduction in the peel strength of the electrode sheet and a decrease in the service life of the battery.

[0058] In the present application, through the modification design of acrylate copolymers, the synthesis of acrylate copolymers using fluorine-substituted acrylate monomers is carried out. Thus, the chemical inertness of acrylate copolymers can be improved by utilizing the shielding effect of fluorine atoms. Subsequently, while the polymer has relatively excellent adhesion, it also has relatively excellent anti-swelling performance. Specifically, due to the characteristics of fluorine atoms having a low polarizability and an atomic radius second only to hydrogen, the carbon-fluorine bond formed after fluorine atoms replace hydrogen atoms has a shorter bond length and a higher bond energy compared to the carbon-hydrogen bond. Further, due to the relatively large electronegativity of fluorine atoms, when fluorine atoms replace the hydrogen atoms in the acrylate copolymer, repulsive forces will occur between the fluorine atoms. This repulsive force causes the carbon-fluorine bonds in the acrylate copolymer to be in different planes. Subsequently, the bond angle of the carbon-carbon bonds in the acrylate copolymer becomes smaller, and the fluorine-containing groups will accumulate on the surface of the polymer, which helps the fluorine atoms to enclose 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. Finally, the anti-swelling performance of the polymer is improved, and a battery using this polymer as a binder has relatively excellent cycling performance.

[0059] A binder refers to a material with adhesive properties used to bond different substances together.

[0060] A copolymer is formed by a polymerization reaction in which two or more monomers participate together. This is called copolymerization, and the resulting polymer contains two or more monomer units. Such polymers are called copolymers, also known as copolymers.

[0061] In the first aspect of the present application, the present application proposes a polymer comprising an acrylate copolymer. The monomers of the acrylate copolymer at least include a first monomer, and the first monomer includes a fluorine-substituted acrylate monomer. By using a fluorine-substituted acrylate monomer as the monomer for synthesizing the acrylate copolymer, the coating of the copolymer can be achieved by the enrichment of fluorine-containing groups on the surface of the acrylate copolymer. Subsequently, it is difficult for other atoms to enter the interior of the copolymer, and the anti-swelling performance of the polymer is effectively improved. When this polymer is used as a binder on the separator, the swelling of the polymer in the electrolyte is small, and the tolerance to the electrolyte is strong, which can effectively improve the bonding effect between the separator and the electrode sheet, and further improve the cycling performance of the battery.

[0062] In some embodiments, the structure of the first monomer is shown in Formula 1:

[0063]

[0064] Among them, R1 includes a hydrogen atom or an alkyl group of C1-C6, and R2 includes a fully fluorinated or partially fluorinated C1-C 15 alkyl group.

[0065] When the first monomer satisfies the aforementioned structural formula, the first monomer can provide more fluorine-containing groups, thereby improving the anti-swelling performance of the acrylate copolymer. Moreover, the first monomer is easily copolymerized with other acrylate monomers with similar structures, and the surface energy and surface tension of the polymer formed after copolymerization are significantly reduced, so that a fluorinated acrylate copolymer emulsion with good hydrophobic and oleophobic properties can be obtained, and the stability of the polymer emulsion is relatively high, which is beneficial to subsequent granulation treatment.

[0066] In some embodiments, 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, perfluorooctyl ethyl methacrylate, perfluorohexyl ethyl methacrylate, and trifluoropentyl acrylate.

[0067] Using any one or more of the above first monomers can improve the anti-swelling performance of the polymer.

[0068] In some embodiments, the first monomer includes at least one of trifluoroethyl acrylate, trifluoroethyl methacrylate, hexafluorobutyl acrylate, hexafluorobutyl methacrylate, and perfluoroalkyl ethyl acrylate, so as to further improve the anti-swelling performance of the polymer.

[0069] In some embodiments, the acrylate copolymer may only include the first monomer. Thus, the acrylate copolymer may be polymerized from at least two different kinds of the aforementioned first monomers.

[0070] In some embodiments, the monomer of the acrylate copolymer further includes a second monomer, and the structure of the second monomer is shown in Formula 2:

[0071]

[0072] Among them, R3 includes a hydrogen atom or an alkyl group of C1-C6, and R4 includes a substituted or unsubstituted alkyl group of C1-C 15 an alkyl group, a substituted or unsubstituted isobornyl group of C3-C6, wherein the substituent of the alkyl group of C1-C 15 the alkyl group includes a hydroxyl group or an alkyl group of C1-C6.

[0073] During the manufacturing process of the battery, it is necessary to use a hot pressing process or a cold pressing process to make the separator bond tightly with the electrode sheet. When the second monomer satisfies the aforementioned structural formula, the second monomer is similar in structure to the first monomer and both contain unsaturated ester groups, which is conducive to the copolymerization of the second monomer and the first monomer. Moreover, the soft and hard monomers in the second monomer can form the backbone of the polymer molecular chain segment through polymerization, making the polymer have excellent stability and good adhesion, and at the same time helping to improve the anti-swelling performance of the polymer.

[0074] 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, 2-hydroxypropyl methacrylate. Thereby, the anti-swelling ability of the polymer can be further improved.

[0075] By using any one or more of the above-mentioned second monomers, the adhesion performance and anti-swelling performance of the polymer can be adjusted.

[0076] 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, isobornyl methacrylate. Thereby, the adhesion performance and anti-swelling performance of the polymer can be further improved.

[0077] In some embodiments, the monomer of the acrylate copolymer further includes a third monomer, and the structure of the third monomer is as shown in Formula 3 and / or Formula 4:

[0078]

[0079] Among them, R5 includes a hydrogen atom or an alkyl group of C1-C 18 and R6 includes a hydrogen atom or an alkyl group of C1-C6. Thereby, the ionic conductivity and adhesion performance of the polymer can be improved.

[0080] The third monomer contains unsaturated double bonds, which is beneficial to the polymerization of the monomer. At the same time, it also has carboxyl and / or cyano functional groups. The carboxyl and cyano groups can not only combine with the functional groups on the base film of the separator to improve the adhesion performance between the polymer and the base film, but also increase the crosslinking active sites of the polymer, thereby improving the creep resistance and cohesive strength of the polymer.

[0081] In some embodiments, the third monomer includes at least one of acrylonitrile, methacrylonitrile, ethylacrylonitrile, acrylic acid, methacrylic acid, crotonic acid, and heptenoic acid. Thereby, the ionic conductivity and bonding performance of the polymer can be further improved.

[0082] By using any one or more of the above-mentioned third monomers, the bonding performance of the polymer can be adjusted. Among them, the monomer containing a cyano group can also increase the ionic conductivity of the polymer.

[0083] 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 increase the ionic conductivity of the polymer.

[0084] In some embodiments, the monomer of the acrylate copolymer further includes a fourth monomer, and the structure of the fourth monomer is shown in Formula 5:

[0085]

[0086] Among them, 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. Thus, the fourth monomer can play a role in adjusting the molecular weight of the polymer, which helps the polymer to have better adhesiveness.

[0087] 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 adjusting the molecular weight, and at the same time, it can also improve the adhesiveness and anti-swelling property of the polymer.

[0088] In some embodiments, the fourth monomer includes at least one of acrylamide, N-hydroxymethylacrylamide, and N-butoxymethylacrylamide. Thereby, the bonding performance of the polymer can be further improved.

[0089] By using any one or more of the above-mentioned fourth monomers, it can play a role in adjusting the molecular weight to adjust the molecular weight of the polymer. The molecular weight of the polymer within a certain range helps to improve the adhesiveness of the polymer.

[0090] In some embodiments, the fourth monomer includes at least one of acrylamide and N-hydroxymethylacrylamide. Thereby, the adhesiveness of the polymer can be improved.

[0091] Testing 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 General Rules for Infrared Spectral Analysis Method of the national standard GB / T 6040-2002. The tablet pressing transmission method is adopted. The sample is pressed into a KBr tablet, and the KBr background blank is deducted by the transmission method to obtain the sample test spectrum (resolution: 4 cm -1 , wave number range: 400 cm -1 -4000 cm -1 ).

[0092] In some embodiments, the polymer may further include a dispersant, and the dispersant includes at least one of polyvinylpyrrolidone, polyacrylamide, sodium polystyrene sulfonate, polyacrylic acid, sodium polyacrylate, and sodium polymethacrylate.

[0093] The cold pressing process refers to a process in which the wound electric core is shaped at a lower ambient temperature compared to the hot pressing process, reducing the elasticity of the electric core and improving the qualification rate of core loading and the consistency of the thickness of the finished electric core. The aforementioned acrylate copolymer has a relatively low glass transition temperature and can be applied to the cold pressing process to achieve effective adhesion between the electrode sheet and the separator. However, the relatively low glass transition temperature and the reactive groups on the surface of the aforementioned acrylate copolymer will cause particle agglomeration and adhesion 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 liquid-liquid or solid-liquid during the spray drying process. Moreover, the affinity between the polar end of the dispersant and water is relatively strong, making the surface of the solid copolymer particles more easily wetted by water and less likely to agglomerate with other copolymer particles at high temperatures.

[0094] In some embodiments, the mass ratio of the acrylate copolymer to the dispersant in the polymer is 100:(1 - 15).

[0095] As an example, the mass ratio of the acrylate 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.

[0096] Since the polymer dispersant has a long carbon chain, many active adsorption points, and branches that can play a steric repulsion role, by mixing the polymer dispersant with the acrylate copolymer, the dispersant can be adsorbed on the surface of the acrylate copolymer particles, reducing the adhesion between adjacent acrylate copolymer particles.

[0097] In some embodiments, the Dv50 particle size of the polymer is 3 μm - 18 μm.

[0098] As an example, the Dv50 particle size of the polymer can be 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm, 15 μm, 15.5 μm, 16 μm, 16.5 μm, 17 μm, 17.5 μm, 18 μm.

[0099] The particle size of polymer microspheres in the emulsion-type polymer is usually at the nanometer level. If it is directly scrape-coated on the base film, problems such as pore blockage or insufficient adhesion may occur due to the too small particle size of the polymer microspheres. When synthesizing polymer materials by emulsion polymerization, granulation treatment can be carried out to obtain particulate polymer materials, which helps to obtain polymers with larger particle sizes. When the Dv50 particle size of the polymer is within the aforementioned range, it can not only improve the problem of blockage of the base film pores caused by nanoscale polymer particles and improve the permeability of metal active ions on the separator membrane, but also alleviate the problem that the coating formed by coating the polymer on the base film is too thick and affects the battery energy density.

[0100] The Dv50 particle size means that in the sample particles, the particle size of 50% of the total volume of the particles is larger than this value, and the particle size of another 50% of the total volume of the particles is smaller than this value; Dv50 can represent the median particle size of the sample.

[0101] The volume particle size distribution Dv50 of the polymer can be tested by methods well-known in the art. As an example, reference can be made to GB / T 19077-2016, and a Malvern laser particle size analyzer can be used for characterization testing, such as using instruments such as Malvern's Mastersizer-3000 for testing.

[0102] In some embodiments, the glass transition temperature of the polymer is 20°C - 80°C.

[0103] In some embodiments, the glass transition temperature of the polymer can be less than or equal to 40°C.

[0104] When the glass transition temperature of the polymer is within the aforementioned range, the acrylate copolymer has a relatively low glass transition temperature and can well infiltrate into the gaps of the electrode sheet at room temperature, causing a strong mechanical interlocking effect between the acrylate copolymer and the electrode sheet and improving the adhesion of the polymer to the electrode sheet.

[0105] As an example, for the test of the glass transition temperature of the polymer, the following can be referred to: Weigh 6 ± 0.05 mg of the sample into an aluminum crucible. After leveling it, cover the lid and use the measuring instrument Netzsch DSC 3500Sirius for the test; in a nitrogen atmosphere, the purge gas rate is 50 mL / min and the protective gas rate is 100 mL / min; heating conditions: the heating rate is 10 °C / min and the temperature range is (-70) °C - 200 °C.

[0106] The glass transition temperature is the temperature at which a polymer changes from a high elastic state to a glassy state. It refers to the transition temperature of an amorphous polymer (including the non-crystalline part of a crystalline polymer) from a glassy state to a high elastic state or from a high elastic state to a glassy state. It is the lowest temperature at which the macromolecular chain segments of an amorphous polymer can move freely and is usually denoted as Tg. Above the glass transition temperature, the polymer exhibits elasticity and a certain degree of fluidity; below the glass transition temperature, the polymer exhibits brittleness. The glass transition temperature can be measured by methods commonly used in the art. For example, it can be tested by differential scanning calorimetry with reference to GB / T19466.2.

[0107] In the second aspect of the present application, the present application proposes a method for preparing the aforementioned polymer, referring to Figure 1 , including:

[0108] S100: Mix and stir the emulsifier, initiator, and the constituent monomers of the acrylate copolymer, and heat for reaction

[0109] In some embodiments, the emulsifier, initiator, and the constituent monomers of the acrylate copolymer are blended and stirred in a mass ratio of (0.2 - 2):(0.1 - 0.5):100, and then heated for reaction, so as to obtain a polymer emulsion through emulsion polymerization, and the yield of the polymer can be effectively improved.

[0110] Emulsion polymerization: In emulsion polymerization, monomers are dispersed in water to form an emulsion with the aid of an emulsifier and mechanical stirring, and then an initiator is added to initiate the polymerization of the monomers.

[0111] An emulsifier is a substance that can transform immiscible oil and water into an emulsion that is difficult to layer. Emulsifiers are usually surfactants with both hydrophilic polar groups and hydrophobic (lipophilic) non-polar groups.

[0112] An initiator is a substance that can initiate the polymerization reaction of monomers. For example, a radical initiator refers to a class of compounds that are easily decomposed by heat into free radicals (i.e., primary free radicals) and can be used to initiate the radical polymerization and copolymerization reactions of vinyl monomers and diene monomers.

[0113] In some embodiments, the emulsifier may include at least one of sodium dodecyl sulfonate, sodium dodecyl benzene sulfonate, sodium dodecyl sulfate, sodium dodecyl benzene sulfate, sodium laurate, sodium stearate, and sodium palmitate.

[0114] In some embodiments, the initiator may include at least one of the following: the persulfate initiator includes at least one of potassium persulfate and ammonium persulfate; the acyl peroxide initiator includes at least one of benzoyl peroxide and di-n-octanoyl peroxide; the azo initiator includes at least one of azobisisobutyronitrile and dimethyl azobisisobutyrate.

[0115] In some embodiments, the constituent monomers of the acrylate copolymer include a first monomer, a second monomer, a third monomer, and a fourth monomer. Among them, 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, while the polymer combines the respective advantages of the first monomer, the second monomer, the third monomer, and the fourth monomer, it also has relatively excellent adhesiveness.

[0116] By combining and matching the fluorine-containing functional monomer with different functional monomers, the aforementioned acrylate copolymer can be prepared. On the one hand, the prepared acrylate copolymer has a relatively low glass transition temperature and can well infiltrate into the gaps of the electrode sheet at room temperature, enabling a strong mechanical interlocking effect between the acrylate copolymer and the electrode sheet and improving the adhesion to the electrode sheet. On the other hand, through the selection of monomer combinations, reactive groups are introduced into the acrylate copolymer, making it have better hydrophilicity, improving the surface wettability of the copolymer particles in the polymer emulsion, and reducing the occurrence of irregular agglomeration.

[0117] In some embodiments, the temperature of the heating reaction may be 60°C - 100°C.

[0118] As an example, the temperature of the heating reaction may be 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, or 100°C.

[0119] When the temperature of the heating reaction is within the aforementioned range, the yield of emulsion polymerization is relatively high and the energy consumption is relatively low.

[0120] S200: Spray-dry the polymer emulsion

[0121] In some embodiments, in this step, the previously prepared polymer emulsion is subjected to spray-drying treatment to granulate and obtain polymer particles with a moderate particle size.

[0122] When synthesizing polymer materials by emulsion polymerization, since the copolymer particle size in the emulsion-type acrylate copolymer is 100 nm - 200 nm, if it is directly scrape-coated onto the separator, problems such as pore blockage or insufficient adhesion may occur due to the too small particle size of the copolymer. Granulation treatment helps obtain polymers with larger particle sizes.

[0123] Spray drying, through mechanical action, disperses the material to be dried (polymer emulsion) into very fine particles like fog (increasing the water evaporation area and accelerating the drying process), and removes most of the water instantaneously when contacting with hot air, drying the solid substances in the material into powder.

[0124] In some embodiments, referring to Figure 2 , before spray drying, the method for preparing the polymer may further include:

[0125] S110: Adding a dispersant to the polymer emulsion

[0126] When granulating the acrylate polymer emulsion, due to the strong intermolecular forces of the acrylate copolymer, phenomena such as agglomeration of copolymer particles are likely to occur, and granulation cannot be carried out well. By adding a dispersant, the random aggregation of the acrylic copolymer in the polymer emulsion can be reduced, as well as the agglomeration during the drying process.

[0127] Due to its special structure, it has good dispersion performance for the suspension system. Due to the hydrophobicity of the main chain and the hydrophilicity and the existence of the side chains of the molecule, it also plays a certain steric stabilization role to prevent the random aggregation of the acrylate polymer emulsion, thus contributing to the dispersion of the emulsion particles.

[0128] In some embodiments, the number-average molecular weight of the dispersant can be 100 - 100000.

[0129] As an example, the number-average molecular weight of the dispersant can be 500 - 100000, 3000 - 100000, 5000 - 100000, 8000 - 100000, 10000 - 100000, 30000 - 90000, 50000 - 70000, 50000 - 60000, 55000 - 60000, etc.

[0130] In some embodiments, the number-average molecular weight of the dispersant is 5000 - 80000.

[0131] By adding a dispersant with the above molecular weight to the polymer, the random aggregation in the polymer emulsion system can be reduced, the particle size uniformity of the polymer can be improved, and when using this polymer as a binder on the separator, the adhesion between the separator and the electrode sheet can be improved, and the cycle performance of the battery can be enhanced.

[0132] In this application, the number-average molecular weight of the dispersant can be determined with reference to the gel permeation chromatography method of Standard GB / T 21863-2008. Specifically, in this application, it can be carried out in the following manner: Use an ultra-high performance polymer chromatograph: ACQUITY APC; detector: ACQUITY refractive index detector. Standard: polystyrene set; running time: 30 min; detector: ACQUITY refractive index (RI) detector; column oven temperature: 90 °C; detector temperature: 55 °C. Sample test: a. Standard sample and test sample preparation: Weigh 0.002 g to 0.004 g of the standard sample / test sample respectively and add 2 mL of mobile phase liquid to prepare a mixed standard of 0.1% to 0.5%, and place it in the refrigerator for > 8 h; b. Standard solution / sample test: Edit the sample group to be measured, select the established sample group method, and click the run queue to start testing the sample after the baseline is stable; (4) Data processing: According to the relationship between the retention time and the 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.

[0133] In the third aspect of this application, this application proposes a separator membrane, including the aforementioned polymer and / or the polymer prepared by the aforementioned method. Thus, this separator membrane has all the characteristics and advantages of the aforementioned polymer and the method for preparing the polymer, which will not be elaborated here.

[0134] In some embodiments, with reference to Figure 3 , the separator membrane may include a base film 31 and at least a polymer 32 located on one side of the base film 31; in other embodiments, the polymer 32 may be located on the opposite two surface sides of the base film 31.

[0135] In some embodiments, the base film may include at least one of polyethylene, polypropylene, polyvinylidene fluoride, polytetrafluoroethylene, and non-woven fabric. By using the base film of the above materials, the adhesion of the polymer on the base film can be effectively improved, and the structural stability of the separator membrane can be improved.

[0136] In the fourth aspect of this application, this application proposes a battery, including the aforementioned separator membrane. Thus, this battery has all the characteristics and advantages of the aforementioned separator membrane, which will not be elaborated here.

[0137] During the charge and discharge process of the battery, active ions are embedded and removed back and forth between the positive electrode plate and the negative electrode plate. The electrolyte plays a role in conducting active ions between the positive electrode plate and the negative electrode plate. The separator membrane is arranged between the positive electrode plate and the negative electrode plate, mainly playing a role in preventing the short circuit between the positive and negative electrodes of the battery, and at the same time allowing ions to pass through.

[0138] [Positive electrode plate]

[0139] The positive electrode plate includes a positive current collector 21 and a positive active material layer 22 provided on at least one surface of the positive current collector 21, and the positive active material layer 22 includes a positive active material.

[0140] As an example, referring to Figure 3 , the positive current collector 21 has two surfaces opposite to each other in its own thickness direction, and the positive active material layer 22 is provided on any one or both of the two opposite surfaces of the positive current collector 21.

[0141] In some embodiments, the positive current collector can be a metal foil or a composite current collector. For example, as the metal foil, aluminum foil can be used. 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 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.).

[0142] In some embodiments, when the battery is a lithium-ion battery, the positive active material can be a positive active material for lithium-ion batteries well-known in the art.

[0143] As an example, the positive active material can include at least one of the following materials: lithium phosphate with olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as battery positive active materials can also be used. These positive active materials can be used alone or in combination of two or more. Among them, the lithium transition metal oxides can 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 (which can also be abbreviated as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (which can also be abbreviated as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (which can also be abbreviated as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2O2 (which can also be abbreviated as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (which can also be abbreviated as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and at least one of its modified compounds, etc. Examples of the lithium-containing phosphate with olivine structure may include but are not limited to lithium iron phosphate (such as LiFePO4 (which can also be abbreviated 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 manganese iron phosphate, and at least one of a composite material of lithium manganese iron phosphate and carbon. The modified compounds of the above materials can be doping modification and / or surface coating modification of the materials.

[0144] During the charge and discharge process of the battery, the insertion and extraction and consumption of Li will occur, and the molar content of Li is different when the battery is discharged to different states. In the listing of the positive electrode active materials in this application, the molar content of Li is the initial state of the material, that is, the state before feeding. When the positive electrode active material is applied to the battery system, the molar content of Li will change after charge and discharge cycles.

[0145] In some embodiments, when the battery is a sodium-ion battery, the positive electrode active material can adopt the positive electrode active materials known in the art for sodium-ion batteries.

[0146] As an example, the positive electrode active material may include at least one of the following materials: sodium transition metal oxides, polyanion compounds, and Prussian blue-based sodium compounds and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as the positive electrode active material of the battery can also be used. The modified compounds of the above materials can be doping modification and / or surface coating modification of the materials.

[0147] In some embodiments, the transition metal in the sodium transition metal oxide can be at least one of Ti, V, Mn, Co, Ni, Fe, Zn, V, Zr, Ce, Cr, Cu. The chemical formula of the sodium transition metal oxide can satisfy Na x MO2, where M includes at least one of Ti, V, Mn, Co, Ni, Fe, Zn, V, Zr, Ce, Cr, Cu, and 0 < x ≤ 1.

[0148] In some embodiments, the polyanion-type compound can be a compound having sodium ions, transition metal ions, and a tetrahedral (YO4) n-A class of compounds with anionic units. Among them, the transition metal can include at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can include at least one of P, S, and Si; n represents the valence state of (YO4) n- valence state.

[0149] In some embodiments, the polyanionic compound can also be a class of compounds having sodium ions, transition metal ions, tetrahedral (YO4) n- anionic units and halogen anions. The transition metal can include at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can include at least one of P, S, and Si, n represents the valence state of (YO4) n- valence state, and the halogen can include at least one of F, Cl, and Br.

[0150] In some embodiments, the polyanionic compound can also be a class of compounds having sodium ions, tetrahedral (YO4) n- anionic units, polyhedral units (ZO y ) m+ and optionally halogen anions. M can include at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce, Y can include at least one of P, S, and Si, n represents the valence state of (YO4) n- valence state, Z represents a transition metal, m represents the valence state of (ZO y ) m+ valence state, and the halogen can include at least one of F, Cl, and Br.

[0151] As an example, the polyanionic compound can satisfy at least one of the chemical formulas 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 (0 ≤ y ≤ 1).

[0152] In some embodiments, the Prussian blue compound can be a class of compounds having sodium ions, transition metal ions, and cyanide ions (CN - )). The transition metal can include at least one of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce.

[0153] As an example, the Prussian blue compound can satisfy the chemical formula Na a Me b Me’c (CN)6, where Me and Me’ each independently include at least one of Ni, Cu, Fe, Mn, Co, and Zn, 0 < a ≤ 2, 0 < b < 1, 0 < c < 1.

[0154] During the charge and discharge process of the battery, the insertion and extraction of Na will occur along with consumption, and the molar content of Na is different when the battery is discharged to different states. In the list of the positive electrode active material in this application, the molar content of Na is the initial state of the material, that is, the state before feeding. When the positive electrode active material is applied to the battery system, after charge and discharge cycles, the molar content of Na will change.

[0155] In the list of the positive electrode active material in this application, the molar content of O is only the theoretical state value, and the release of oxygen from the lattice will cause the molar content of oxygen to change, and the actual molar content of O will show fluctuations.

[0156] In some embodiments, the positive electrode active material layer may further optionally include a binder.

[0157] 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 fluorinated acrylate resin.

[0158] In some embodiments, the positive electrode active material layer may further optionally include a conductive agent.

[0159] 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.

[0160] In some embodiments, the positive electrode plate can be prepared by the following method: dispersing the components for preparing the positive electrode plate described above, such as the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on the positive electrode current collector, and after processes such as drying and cold pressing, the positive electrode plate can be obtained.

[0161] [Negative electrode plate]

[0162] The negative electrode plate includes a negative electrode current collector 11 and a negative electrode active material layer 12 provided on at least one surface of the negative electrode current collector 11, and the negative electrode active material layer 12 includes a negative electrode active material.

[0163] As an example, the negative electrode current collector 11 has two surfaces opposite to each other in its own thickness direction, and the negative electrode active material layer 12 is provided on any one or both of the two opposite surfaces of the negative electrode current collector 11.

[0164] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, copper foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (such as 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.).

[0165] In some embodiments, the negative electrode active material may be a 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, and lithium titanate, etc. The silicon-based materials include at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The 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 conventional materials that can be used as the negative electrode active material of the battery may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0166] In some embodiments, the negative electrode active material layer may optionally further include a binder.

[0167] 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).

[0168] In some embodiments, the negative electrode active material layer may optionally further include a conductive agent.

[0169] 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.

[0170] In some embodiments, the negative electrode active material layer may optionally further include other additives, such as thickeners (such as sodium carboxymethyl cellulose (CMC-Na)), etc.

[0171] In some embodiments, the negative electrode sheet can be prepared in the following manner: the above-mentioned components for preparing the negative electrode sheet, such as the negative electrode active material, conductive agent, 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 processes such as drying and cold pressing, the negative electrode sheet can be obtained.

[0172] [Electrolyte]

[0173] The electrolyte plays a role in conducting ions between the positive electrode sheet and the negative electrode sheet. There is no specific limitation on the type of electrolyte in this application, and it can be selected according to requirements. For example, the electrolyte can be liquid, gel-like, or all-solid-state.

[0174] In some embodiments, the electrolyte uses an electrolytic solution. The electrolytic solution includes an electrolyte salt and a solvent.

[0175] In some embodiments, the electrolyte salt includes 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 difluorooxalate borate, lithium bis(oxalato)borate, lithium difluoro bis(oxalato)phosphate, lithium tetrafluorooxalate phosphate.

[0176] In some embodiments, the solvent includes 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, diethyl sulfone.

[0177] In some embodiments, the electrolytic solution may optionally further include additives. For example, the additives can include negative electrode film-forming additives, positive electrode film-forming additives, and can also include additives that can improve certain battery performances, such as additives for improving the overcharge performance of the battery, additives for improving the high-temperature or low-temperature performance of the battery, etc.

[0178] In some embodiments, the positive electrode sheet, negative electrode sheet, and separator can be made into an electrode assembly through a winding process or a stacking process.

[0179] In some embodiments, the battery can include an outer package. The outer package can be used to encapsulate the above-mentioned electrode assembly and electrolyte.

[0180] In some embodiments, the outer packaging of the battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the battery can also be a soft package, such as a pouch soft package. The material of the soft package can be plastic. As plastics, polypropylene, polybutylene terephthalate, and polybutylene succinate can be listed, etc.

[0181] In some embodiments, the battery can include at least one of battery cells, battery modules, and battery packs.

[0182] This application has no particular limitation on the shape of the battery, and it can be cylindrical, square, or any other arbitrary shape. For example, Figure 4 is a battery cell 5 with a square structure as an example.

[0183] In some embodiments, referring to Figure 5 , the outer packaging can include a housing 51 and a top cover assembly 53. Among them, the housing 51 can include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose to form a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the top cover assembly 53 can be covered on the opening to close the receiving cavity. The positive electrode plate, the negative electrode plate, and the separator can be formed into an electrode assembly 52 through a winding process or a stacking 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 included in the battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0184] In some embodiments, battery cells can be assembled into a battery module. The number of battery cells included in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0185] Figure 6 is a battery module 4 as an example. Referring to Figure 6 , in the battery module 4, a plurality of battery cells 5 can be arranged in sequence along the length direction of the battery module 4. Of course, they can also be arranged in any other arbitrary manner. Further, the plurality of battery cells 5 can be fixed by fasteners.

[0186] Optionally, the battery module 4 can further include a housing having a receiving space, and a plurality of battery cells 5 are received in the receiving space.

[0187] In some embodiments, the above battery module can be further assembled into a battery pack. The number of battery modules included in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0188] Figure 7 and Figure 8 is a battery pack 1 as an example. Referring toFigure 7 and Figure 8 In the battery pack 1, a battery box and a plurality of battery modules 4 disposed in the battery box can be included. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can be covered on the lower box body 3 to form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0189] In the fifth aspect of the present application, an electric device is proposed, including the aforementioned battery. Thus, the electric device has all the features and advantages of the aforementioned battery, which will not be elaborated herein.

[0190] The electric device can include at least one of the battery cells, battery modules, and battery packs provided in the present application. The battery cells, battery modules, and battery packs can be used as the power source of the electric device or as the energy storage unit of the electric device. The electric device can include mobile devices (such as mobile phones, laptop computers, 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.

[0191] As an electric device, the battery cells, battery modules, or battery packs can be selected according to its usage requirements.

[0192] The solution of the present application will be described below through specific embodiments. It should be noted that the following embodiments are only used to illustrate the present application and should not be regarded as limiting the scope of the present application. For those not specified in the embodiments regarding specific technologies or conditions, they shall be carried out according to the technologies or conditions described in the literature in the field or according to the product specifications. For the reagents or instruments not specified for the manufacturers, they are all conventional products that can be obtained through commercial purchase.

[0193] Example 1

[0194] 1. Preparation of polymer

[0195] (1) Preparation of polymer emulsion

[0196] Weigh 1000 g in total of the first monomer trifluoroethyl acrylate, the second monomer n-butyl methacrylate, the third monomer methacrylonitrile, and the fourth monomer acrylamide according to the mass ratio of the first monomer, the second monomer, the third monomer, and the fourth monomer of 25:45:5:5. Mix the monomers evenly. Add 1000 g of the mixed monomers, 20 g of the emulsifier sodium dodecylbenzenesulfonate, 5 g of the initiator potassium persulfate, and 1200 g of deionized water into a 5 L four-necked flask equipped with a mechanical stirrer, a thermometer, and a condenser. Stir and emulsify at high speed for 30 min. Under nitrogen protection, heat up to 80 °C and react for 4 h, then cool down to below 40 °C, adjust the pH to neutral, filter and discharge to obtain a polymer emulsion.

[0197] (2) Prepare the binder for the separator membrane by spray drying the polymer emulsion. The conditions of the spray drying process are an inlet air temperature of 110 °C, an outlet air temperature of 50 °C, and a wind pressure of 0.5 kPa.

[0198] 2. Preparation of the battery

[0199] (1) Preparation of the separator membrane

[0200] Use a commercially available PE microporous film with a thickness of 7 μm and an average pore size of 80 nm (from Zhuogao Electronic Technology Co., Ltd.) as the base film. Stir and mix the polymer prepared as above evenly in deionized water to obtain a binder slurry (solid content of 20%). Spray the binder slurry on both surfaces of the base film, dry to remove the solvent, and the coating density of the polymer on the base film is 1.5 g / m 2 , to obtain the separator membrane.

[0201] (2) Preparation of the positive electrode plate

[0202] Mix polyvinylidene fluoride (PVDF), lithium iron phosphate (LFP), conductive agent carbon black, and N-methylpyrrolidone (NMP) according to a mass ratio of 1.2:58.38:0.42:40, and stir and mix evenly to prepare a positive electrode slurry. Coat the positive electrode slurry evenly on the positive electrode current collector aluminum foil at a loading amount of 200 g / m 2 , and then through drying, cold pressing, and slitting, obtain the positive electrode plate.

[0203] (3) Preparation of the negative electrode plate

[0204] Add artificial graphite, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC-Na) according to a mass ratio of 96.2:1.0:1.6:1.2 into deionized water, stir and mix evenly to prepare a negative electrode slurry (solid content of 63%). Coat the negative electrode slurry on the negative electrode current collector copper foil at a loading amount of 98 g / m 2 , and then through drying, cold pressing, and slitting, obtain the negative electrode plate.

[0205] (4) Preparation of electrolyte

[0206] 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. Then, LiPF6 is dissolved in the above-mentioned mixed solvent to obtain an electrolyte, where the concentration of LiPF6 is 1 mol / L.

[0207] (5) Assembly of battery

[0208] The above-mentioned positive electrode sheet, separator, and negative electrode sheet are stacked, wound, and cold-pressed in sequence (during which the separator is bonded to the electrode sheet) to obtain an electrode core; the electrode core is placed in an outer package, the above-prepared electrolyte is added, and after processes such as encapsulation, standing, formation, and aging, a battery is obtained.

[0209] For the differences between other examples, comparative examples and Example 1, see Table 1. Specifically, compared with Example 1, Examples 2 - 4 use different monomer types; Examples 5 - 10 use different monomer mass ratios; Example 11 uses two first monomers with a mass ratio of 1:1 as polymer monomers; a dispersant is added to the polymer emulsion in Examples 12 - 15 before spray drying treatment; 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 selected as styrene-butadiene rubber.

[0210] Table 1

[0211]

[0212]

[0213] The polymer in the above examples and comparative examples is subjected to polymer swelling test, and the test results are shown in Table 2. The test method is as follows:

[0214] (1) Dissolution: Take 10 g of polymer powder and 90 g of N-methylpyrrolidone (NMP), mix them, and stir and dissolve at 40 °C for 5 h to obtain a polymer solution;

[0215] (2) Preparation of film: Pour the stirred polymer solution into a polytetrafluoroethylene drying tray and bake at 70 °C for 7 days to obtain a dried film;

[0216] (3) Swelling degree test: Take about 1 g of the dry gel film with a thickness of 2 mm, weigh its exact mass and record it as M1. Immerse it in the electrolyte solution, place it in an oven at 70 °C for baking for 24 h, take out the sample piece, let it stand for 1 h, wipe it clean, and weigh its mass M2. According to the mass swelling degree = (M2 - M1) / M1 × 100%, calculate the swelling degree of the polymer. Among them, the electrolyte preparation method is as follows: Mix ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC) in a mass ratio of 3:5:2 to obtain an electrolyte solvent, and configure the electrolyte solvent with lithium hexafluorophosphate (LiPF6) into an electrolyte with a molar concentration of 1 mol / L of LiPF6.

[0217] Perform a cycle performance test on the batteries in the above-mentioned examples and comparative examples. The test results are shown in Table 2. The test method is as follows:

[0218] At 25 °C, charge the prepared battery at a constant current of 1 / 3C to 3.65 V, then charge it at a constant voltage of 3.65 V until the current is 0.05C, let it stand for 5 min, and then discharge it at 1 / 3C to 2.5 V. The obtained discharge capacity is recorded as the initial capacity C0. Repeat the above steps for the same battery, and at the same time 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%. Use the battery capacity retention rate P at 500 cycles 500 to reflect the difference in cycle performance.

[0219] Table 2

[0220] Number Degree of polymer swelling / % <![CDATA[Capacity retention rate P 500 / %]]> Example 1 32.5 93.6 Example 2 33.5 93.4 Example 3 36.2 92.7 Example 4 31.8 93.7 Example 5 41.2 91.7 Example 6 36.7 92.5 Example 7 35.6 92.7 Example 8 45.2 91.5 Example 9 39.5 92.0 Example 10 35.2 92.9 Example 11 50.7 89.6 Example 12 31.7 93.9 Example 13 28.9 94.6 Example 14 25.3 95.2 Example 15 30.5 94.5 Comparative Example 1 55.2 87.3 Comparative Example 2 72.1 85.6

[0221] As can be seen from the test results in Table 2, in Examples 1 - 11, by using fluorine-substituted acrylate monomers as monomers of the acrylate copolymer, the shielding effect of fluorine atoms can be utilized to improve the chemical inertness of the acrylate copolymer. Subsequently, while the polymer has excellent adhesion, it also has excellent anti-swelling performance, improving the cycling performance of the battery using this polymer as the binder on the separator; in Examples 12 - 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, it helps to obtain polymer particles with a moderate particle size, further improving the adhesion between the separator and the electrode sheet, and improving the cycling performance of the battery using this polymer as the binder on the separator. In Comparative Example 1, since fluorine-substituted acrylate monomers were not used as monomers of the acrylate copolymer, the anti-swelling ability of the polymer was poor. At the beginning of the charge-discharge cycle, the adhesion effect between the separator and the electrode sheet was excellent. However, as the charge-discharge cycle proceeded, the swelling of the polymer continued to intensify, resulting in problems such as increased volume expansion of the battery, increased internal resistance of the battery, and poor cycling stability; in Comparative Example 2, styrene-butadiene rubber was used as the binder on the separator. The anti-swelling performance and adhesion performance of styrene-butadiene rubber were both poor, and the adhesion effect between the separator and the electrode sheet was poor, unable to effectively inhibit the pulverization and rupture of the active material during the charge-discharge cycle, resulting in a decrease in the peel strength of the electrode sheet and poor service life of the battery.

[0222] It should be noted that this application is not limited to the above embodiments. The above embodiments are only examples, and embodiments with the same structure and the same function and effect as the technical idea within the technical solution scope of this application are all included in the technical scope of this application. In addition, within the scope of not departing from the main idea of this application, various deformations that those skilled in the art can think of applied to the embodiments, and other ways constructed by combining some constituent elements in the embodiments are also included in the scope of this application.

Claims

1. A polymer, characterized in that, 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 perfluorinated 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 monomers of the acrylate copolymer further include 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, characterized in that, The monomers of the acrylate copolymer further include a third monomer, and the structure of the third monomer is 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, characterized in that, The third monomer includes at least one of acrylonitrile, methacrylonitrile, ethylacrylonitrile, acrylic acid, methacrylic acid, crotonic acid, and heptenoic acid.

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

11. The polymer according to claim 1, wherein, The monomers of the acrylate copolymer further include 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, characterized in that, 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, characterized in that, The polymer further comprises a dispersant, and the dispersant comprises at least one of polyvinylpyrrolidone, polyacrylamide, sodium polystyrene sulfonate, polyacrylic acid, sodium polyacrylate, and sodium polymethacrylate.

15. The polymer according to claim 14, characterized in that, 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, characterized in that, The Dv50 particle size of the polymer is 3 μm - 18 μm.

17. A method for preparing the polymer according to any one of claims 1-16, characterized in that, Comprising: 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; Performing spray drying on the polymer emulsion 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, characterized in that Before the spray drying, further comprising: adding a dispersant to the polymer emulsion.

20. A separator, characterized in that, Comprising the polymer according to any one of claims 1-16, and / or, the polymer prepared by using the method according to any one of claims 17-19.

21. A battery, characterized in that, Comprising the separator membrane according to claim 20.

22. An electrical device, characterized in that, Comprising the battery according to claim 21.

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