Polymers, separator films, pole pieces, batteries and electrical devices

Abstract

The present application discloses a polymer, a separator film, a pole piece, a battery, and an electric device, the polymer comprising a first organic polymer and a second organic polymer, the polymerized monomers of the first organic polymer comprising a first polymerized monomer, a second polymerized monomer, and a third polymerized monomer, the polymerized monomers of the second organic polymer comprising the first polymerized monomer, the third polymerized monomer, and a fourth polymerized monomer, the structure of the first polymerized monomer comprising (I), wherein R1 comprises a hydrogen atom or an alkyl group of 1 to 18 carbon atoms, and R2 comprises a hydrogen atom or an alkyl group of 1 to 18 carbon atoms. the structure of the second polymerizable monomer comprises (II), R3 comprises a hydrogen atom or a substituted or unsubstituted alkyl group of 1 to 18 carbon atoms, the structure of the third polymerizable monomer comprises (III), R4 comprises a hydrogen atom or an alkyl group of 1 to 6 carbon atoms, R5 comprises a hydrogen atom, a hydroxy group-substituted alkyl group of 1 to 6 carbon atoms, or an alkoxy group of 1 to 6 carbon atoms, the structure of the fourth polymerizable monomer comprises (IV), R6 comprises a hydrogen atom or an alkyl group of 1 to 6 carbon atoms.

Description

[Technical Field]

[0001] This application is in the field of batteries, and specifically relates to polymers, separator films, pole pieces, batteries and electrical devices. [Background technology]

[0002] In recent years, the demand for power batteries has increased dramatically with the rapid increase in portable electronic devices and electric vehicles, and the electrochemical performance of batteries has also been attracting increasing attention.

[0003] Currently, polyvinylidene fluoride is used as an adhesive for separator films in batteries. Polyvinylidene fluoride is applied to the separator film, which is then wrapped around the electrode pieces and heated and pressed to bond the electrode pieces to the separator film, increasing the hardness of the battery core and maintaining the consistency of the battery core thickness. Without the hot welding process, gaps would exist between the separator film and the electrode pieces, resulting in openings in the battery core, a soft battery core, and wrinkles in the separator film. However, because the adhesive strength between the electrode pieces and the separator film is too strong after hot welding, the positive and / or negative electrode pieces are prone to peeling during battery cycling, which reduces the battery's cycle performance. Summary of the Invention

[0004] In view of the technical problems existing in the background art, the present application aims to provide a polymer that can realize cold pressure bonding between a separator film and a pole piece, thereby improving the cycle performance of the battery.

[0005] To achieve the above object, one aspect of the present application provides a polymer, the polymer comprising a first organic polymer and a second organic polymer, the polymerized monomers of the first organic polymer comprising a first polymerized monomer, a second polymerized monomer, and a third polymerized monomer, the polymerized monomers of the second organic polymer comprising the first polymerized monomer, the third polymerized monomer, and a fourth polymerized monomer, and the structure of the first polymerized monomer comprises:

[0006] [ka] wherein R1 comprises a hydrogen atom or an alkyl group having 1 to 18 carbon atoms, and R2 comprises an alkyl group having 1 to 18 carbon atoms; The structure of the second polymerized monomer comprises: [ka] wherein R3 comprises a hydrogen atom or a substituted or unsubstituted alkyl group of 1 to 18 carbon atoms; The structure of the third polymerizable monomer comprises: [ka] wherein R4 comprises a hydrogen atom or an alkyl group of 1 to 6 carbon atoms, R5 comprises a hydrogen atom, a hydroxyl-substituted alkyl group of 1 to 6 carbon atoms, or an alkoxy group of 1 to 6 carbon atoms; The structure of the fourth polymerizable monomer comprises: [ka] wherein R6 comprises a hydrogen atom or an alkyl group of 1 to 6 carbon atoms.

[0007] The present invention has at least the following beneficial effects: when the polymer of the present invention is used in a separator film, the polymer is non-adhesive at a certain temperature, making it easy to wind and unwind the separator film, but when wound together with positive and negative electrode pieces and subjected to a cold pressing process, the polymer has favorable adhesive strength, allowing the positive and negative electrode pieces and the separator film to adhere to each other. Therefore, when the polymer of the present invention is used in a separator film, adhesion between the separator film and the electrode pieces can be achieved by cold pressing, and the adhesive strength between the electrode pieces and the separator film is appropriate, thereby improving the cycle performance of the battery.

[0008] In some embodiments of the present application, the mass ratio of the first organic polymer to the second organic polymer is 1:(0.1 to 10), optionally 1:(0.5 to 3), which, when used in a separator film, not only facilitates winding and unwinding of the separator film but also improves the cold pressure adhesive strength between the separator film and the positive and negative electrode pieces, thereby improving the cycle performance of the battery.

[0009] In some embodiments of the present application, the mass ratio of the first polymerizable monomer to the second polymerizable monomer to the third polymerizable monomer in the polymerizable monomer of the first organic polymer is 1:0.05-0.5:0.05-0.5, optionally 1:0.056-0.5:0.056-0.5. By controlling the mixing ratio of the first polymerizable monomer, the second polymerizable monomer, and the third polymerizable monomer used to produce the first organic polymer in the present application, not only can the adhesiveness of the polymer be improved, but the glass transition temperature of the first organic polymer can be adjusted to an appropriate range, and the carboxyl group contained in the second polymerizable monomer can form a bond with the functional groups on the electrode pieces and separator film material, thereby improving the adhesive effect between the electrode pieces and the separator film.

[0010] In some embodiments of the present application, the mass ratio of the first polymerizable monomer to the third polymerizable monomer to the fourth polymerizable monomer in the polymerizable monomers of the second organic polymer is 1:0.05-0.5:0.05-0.5, and optionally 1:0.056-0.5:0.056-0.5. Thus, in the present application, by controlling the mixing ratio of the first polymerizable monomer, the third polymerizable monomer, and the fourth polymerizable monomer used to produce the second organic polymer, not only can the glass transition temperature of the second organic polymer be adjusted, but also the glass transition temperature of the second organic polymer can be adjusted to a suitable range, and the ionic conductivity and adhesiveness of the second organic polymer can be improved.

[0011] In some embodiments, the first polymerizable monomer may include at least one of methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, n-propyl acrylate, cyclohexyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, ethyl 2-hydroxyacrylate, 2-hydroxypropyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, or 2-hydroxypropyl methacrylate, thereby adjusting the glass transition temperature of the polymer and improving the swelling resistance of the polymer.

[0012] In some embodiments of the present application, the second polymerizable monomer comprises at least one of acrylic acid, methacrylic acid, crotonic acid, and heptenoic acid, thereby adjusting the adhesiveness of the first polymer, and when the polymer is used in a separator film, improving the cold pressing adhesive strength between the separator film and the pole pieces, thereby improving the cycle performance of the battery.

[0013] In some embodiments of the present application, the third polymerizable monomer comprises at least one of acrylamide, N-methylolacrylamide, and N-butoxymethylacrylamide, thereby adjusting the molecular weight of the first polymer and, when the polymer is used in a separator film, improving the cold pressing adhesion between the separator film and the pole pieces and improving the cycle performance of the battery.

[0014] In some embodiments of the present application, the fourth polymerizable monomer comprises at least one of acrylonitrile and methacrylonitrile, thereby improving the adhesiveness and ionic conductivity of the polymer, and when the polymer is used in a separator film, improving the cold pressing adhesion between the separator film and the electrode pieces and reducing the battery resistance, thereby improving the cycle performance of the battery.

[0015] In some embodiments of the present application, the polymer further comprises a dispersant containing at least one of sodium polystyrene sulfonate, sodium gluconate, sodium polyacrylate, sodium polymethacrylate, sodium polyphosphate, sodium lignosulfonate, or sodium polycarboxylate, which, when used in a separator film, can improve the cold pressure adhesion between the separator film and the electrode pieces and improve the cycle performance of the battery.

[0016] In some embodiments of the present application, the number average molecular weight of the dispersant is 100 to 100,000, optionally 5,000 to 80,000. This can improve the cold pressure adhesive strength between the separator film and the electrode pieces when the polymer is used in the separator film, thereby improving the cycle performance of the battery.

[0017] In some embodiments of the present application, the mass ratio of the first organic polymer to the second organic polymer to the dispersant is 1:0.1-10:0.01-2, and optionally 1:0.5-3:0.05-1.5, which, when used in a separator film, can improve the cold pressure adhesive strength between the separator film and the electrode pieces, thereby improving the cycle performance of the battery.

[0018] In some embodiments of the present application, the polymer further comprises a butadiene-based polymer, which, when used in a separator film, can improve the cold pressure adhesion between the separator film and the electrode pieces, thereby improving the cycle performance of the battery.

[0019] In some embodiments of the present application, the glass transition temperature of the butadiene-based polymer is 20° C. or lower, and optionally 15° C. or lower, so that when the polymer is used in a separator film, the cold pressure adhesion between the separator film and the electrode pieces can be improved, thereby improving the cycle performance of the battery.

[0020] In some embodiments of the present application, the butadiene-based polymer has a volume average particle size Dv50 of 100 nm to 300 nm, optionally 120 nm to 250 nm, which, when used in a separator film, can improve the cold pressure adhesive strength between the separator film and the electrode pieces, thereby improving the cycle performance of the battery.

[0021] In some embodiments of the present application, the viscosity of the butadiene-based polymer at 25°C is 10 mPa·s to 300 mPa·s, optionally 80 mPa·s to 200 mPa·s. This improves the cold pressure adhesive strength between the separator film and the electrode pieces when the polymer is used in a separator film, thereby improving the cycle performance of the battery.

[0022] In some embodiments of the present application, the butadiene-based polymer includes at least one of polybutadiene, styrene / butadiene copolymer, and acrylonitrile / butadiene copolymer, which, when used in a separator film, can improve the cold pressure adhesion between the separator film and the electrode pieces, thereby improving the cycle performance of the battery.

[0023] In some embodiments of the present application, the mass ratio of the first organic polymer, the second organic polymer, and the butadiene-based polymer is 1:0.1-10:0.1-10, and optionally 1:0.5-3:0.5-8. This can improve the cold pressure adhesive strength between the separator film and the electrode pieces when the polymer is used in a separator film, thereby improving the cycle performance of the battery.

[0024] In some embodiments of the present application, the polymer has a first glass transition temperature of 25° C. or less and a second glass transition temperature of more than 25° C. When the polymer is used in a separator film, this can improve the cold pressure adhesion between the separator film and the electrode pieces, thereby improving the cycle performance of the battery.

[0025] In some embodiments of the present application, the first glass transition temperature is −80° C. to 25° C., and optionally −60° C. to 25° C. This is advantageous for the polymer to exhibit its adhesive properties during cold pressing, which is advantageous for the adhesion between the separator film and the electrode pieces after cold pressing, and is advantageous for improving the cycle performance of the battery.

[0026] In some embodiments of the present application, the second glass transition temperature is 26° C. to 100° C., and optionally 26° C. to 90° C. This facilitates winding and unwinding of the separator film at a constant temperature when the polymer is used in the separator film.

[0027] In some embodiments of the present application, the volume average particle diameter Dv50 of the polymer is 1 μm to 15 μm, and optionally 5 μm to 10 μm, which can prevent the polymer from blocking the channels of the separator film when the polymer is used in the separator film, thereby improving the active ion permeability of the separator film.

[0028] In some embodiments of the present application, the polymer has a number particle size distribution Dn10 of 1 μm to 5 μm, optionally 1 μm to 3 μm, which, when used in a separator film, can reduce the blocking of the channels in the separator film by the polymer, improve the active ion permeability of the separator film, and alleviate the problem of forming a relatively thick coating on the separator film, which can reduce the energy density of the battery in the later stages of production.

[0029] In a second aspect of the present application, there is provided a method for producing the polymer described above, comprising: mixing together water, an emulsifier, an initiator, a first organic monomer, a second polymerizable monomer, and a third polymerizable monomer to obtain a first polymer emulsion; mixing together water, an emulsifier, an initiator, a first polymerizable monomer, a third polymerizable monomer, and a fourth polymerizable monomer to obtain a second polymer emulsion; mixing the first polymer emulsion with the second polymer emulsion to obtain a polymer.

[0030] This method can be used to produce a polymer with the excellent cold pressure adhesion described above, and when this polymer is used in a separator film, it can improve the cold pressure adhesion between the separator film and the electrode pieces, thereby improving the cycle performance of the battery.

[0031] In some embodiments of the present application, a dispersant and / or a butadiene-based polymer is further added during the mixing of the first polymer emulsion and the second polymer emulsion, which, when used in a separator film, can improve the cold pressure adhesion between the separator film and the electrode pieces, thereby improving the cycle performance of the battery.

[0032] In a third aspect of the present application, there is provided a separator film comprising the above polymer or a polymer obtained by employing the above method, which can improve the cold pressure adhesion between the separator film and the electrode pieces, thereby improving the cycle performance of the battery.

[0033] In a fourth aspect of the present application, there is provided a pole piece comprising the above polymer or a polymer obtained by employing the above method, which can improve the cold pressure adhesion between the pole piece and the separator film, thereby improving the cycle performance of the battery.

[0034] In a fifth aspect of the present application, there is provided a battery comprising the separator film and / or the pole piece, whereby the battery has excellent cycle performance.

[0035] In a sixth aspect of the present application, there is provided an electric device including the above battery, whereby the electric device has excellent cycle performance and safety performance.

[0036] Additional aspects and advantages of the present application will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the present application. [Brief explanation of the drawings]

[0037] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of the preferred embodiments. The drawings are for the purpose of illustrating the preferred embodiments only and are not to be construed as limiting the present application. In the drawings, like elements are designated by like reference numerals throughout. [Figure 1] 1 is a schematic diagram of a battery according to an embodiment of the present application. [Figure 2] FIG. 2 is an exploded view of the battery shown in FIG. 1 according to one embodiment of the present application. [Figure 3] 1 is a schematic diagram of a battery module according to an embodiment of the present application; [Figure 4] 1 is a schematic diagram of a battery pack according to an embodiment of the present application; [Figure 5] FIG. 5 is an exploded view of the battery pack shown in FIG. 4 according to the embodiment of the present application. [Figure 6] 1 is a schematic diagram of an electrical device that uses a battery as a power source according to an embodiment of the present application. Reference numerals: 1 battery, 11 casing, 12 electrode assembly, 13 cover plate, 2 battery module, 3 battery pack, 31 upper case, 32 lower case. DETAILED DESCRIPTION OF THE INVENTION

[0038] The following detailed description will be given of the embodiments of the technical solution of the present application, which are merely used as examples to more clearly explain the technical solution of the present application and cannot limit the scope of the claims of the present application.

[0039] The term "embodiment" as used herein means that the specific feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. Those skilled in the art will understand, both explicitly and implicitly, that the embodiments described herein can be combined with other embodiments.

[0040] The "ranges" disclosed herein are defined by lower and upper limits, and a given range is defined by selecting one lower limit and one upper limit, with the selected lower and upper limits defining the boundaries of that particular range. Such defined ranges may be inclusive or exclusive of both endpoints and may be arbitrarily combined; i.e., any lower limit can be combined with any upper limit to form a single range. For example, if ranges of 60 to 120 and 80 to 110 are recited for a particular parameter, it is understood that ranges of 60 to 110 and 80 to 120 are also contemplated. Furthermore, if the recited minimum range values ​​are 1 and 2, and the recited maximum range values ​​are 3, 4, and 5, then the ranges 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5 are all contemplated. Unless otherwise specified, the numerical range "a to b" herein represents a shorthand notation for any combination of real numbers between a and b, where a and b are both real numbers. For example, a numerical range of "0 to 5" indicates that all real numbers between "0 and 5" have already been listed in this specification, and "0 to 5" is simply an abbreviation for a combination of those numerical values. Note that when a parameter is described as an integer ≧2, this is equivalent to disclosing that the parameter is an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0041] Unless otherwise specified, all embodiments and optional embodiments in the present application can be combined with each other to form a new technical solution.

[0042] Unless otherwise specified, all technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

[0043] Unless otherwise specified, all steps in the present application may be performed sequentially or randomly, but are preferably performed sequentially. For example, when the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, when the method described above may further include step (c), it 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 include steps (a), (c), and (b), or may include steps (c), (a), and (b), etc.

[0044] Unless otherwise specified, the terms "comprise" and "comprises" used in this application may be open or closed. For example, the terms "comprise" and "comprises" may further include or include other components not listed, or may include or include only the listed components.

[0045] Unless otherwise stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, any of the following conditions satisfy the condition "A or B": A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), or both A and B are true (or exist).

[0046] Judging from the current development of the market situation, the application of secondary batteries will become increasingly widespread. Secondary batteries are not only applied to energy storage power systems such as hydroelectric power generation, thermal power generation, wind power generation, and solar power generation, but also widely used in electric transportation such as electric bicycles, electric motorcycles, and electric cars, as well as in multiple fields such as military equipment and aerospace. As the application fields of secondary batteries continue to expand, their market demand also continues to increase.

[0047] The battery core includes positive electrode pieces, negative electrode pieces, and a separator film. The battery core has a certain hardness; that is, the bonded positive and negative electrode pieces and the separator film are bonded together and support each other to form a structure with a certain thickness, and this structure with a certain thickness has a certain hardness. The negative electrode expands during charging and discharging. If the adhesive strength is relatively weak, gaps will form between the positive and negative electrode pieces and the separator film, preventing the positive and negative electrode pieces and the separator film from bonding together and supporting each other, causing the battery core to sag and reduce hardness. This will directly result in poor battery cycle performance and a shortened battery life, requiring frequent battery replacement in electric vehicles and increasing the costs incurred by consumers.

[0048] Separator films adhere closely to the electrode pieces, improving the battery's discharge capacity, reducing internal resistance, reducing polarization loss, extending the battery's cycle life, and improving the utilization rate of secondary batteries. The adhesive commonly used for conventional separator films is polyvinylidene fluoride, but at present, polyvinylidene fluoride is expensive and in short supply in the market. At the same time, a hot welding process (heating is involved in the welding process after the separator film and electrode pieces are stacked) is required to tightly bond the separator film and electrode pieces. However, after the hot welding process, the adhesive strength between the separator film and the positive and negative electrode pieces is too strong. During battery cycling, the negative electrode expands excessively, causing the positive electrode active material in the positive electrode piece and the negative electrode active material in the negative electrode piece to peel off, i.e., the positive and negative electrode pieces delaminate, resulting in reduced battery cycle performance.

[0049] The polymer of the present application includes a first organic polymer and a second organic polymer, wherein the polymerizable monomers of the first organic polymer include a first polymerizable monomer, a second polymerizable monomer, and a third polymerizable monomer, and the polymerizable monomers of the second organic polymer include the first polymerizable monomer, the third polymerizable monomer, and a fourth polymerizable monomer, and the structure of the first polymerizable monomer is: [ka] wherein R1 comprises a hydrogen atom or an alkyl group of 1 to 18 carbon atoms, R2 comprises an alkyl group of 1 to 18 carbon atoms, and the structure of the second polymerizable monomer is [ka] wherein R3 comprises a hydrogen atom or a substituted or unsubstituted alkyl group of 1 to 18 carbon atoms, and the structure of the third polymerizable monomer is [ka] wherein R4 comprises a hydrogen atom or an alkyl group of 1 to 6 carbon atoms, and R5 comprises a hydrogen atom, a hydroxyl-substituted alkyl group of 1 to 6 carbon atoms, or an alkoxy group of 1 to 6 carbon atoms, and the fourth polymerizable monomer comprises: [ka] and R6 comprises a hydrogen atom or an alkyl group of 1 to 6 carbon atoms.

[0050] The first organic polymer, prepared using the first, second, and third polymerizable monomers, and the second organic polymer, prepared using the first, third, and fourth polymerizable monomers, have different glass transition temperatures, and the first organic polymer has a lower glass transition temperature than the second organic polymer. When the polymer is heated to a temperature between the glass transition temperatures of the first and second organic polymers and no pressure is applied to the polymer, the second organic polymer structure is in a glassy state, relatively hard, and functions as a framework for the polymer powder material, not adhesive to the polymer, allowing for smooth winding and unwinding of the separator film. At this temperature, the first organic polymer structure is in a rubbery state and, after application of a certain pressure, can have a certain "fluidity." The structure containing the first organic polymer in the polymer can fully penetrate the pores of the positive and negative electrode pieces and the separator film, enhancing the mechanical interlocking effect and fully exerting its adhesive properties, further contributing to improved battery cycling performance.

[0051] Therefore, when the polymer of the present application is used for a separator film, the polymer is non-adhesive at a certain temperature, making it easy to wind and unwind the separator film, but when it is wound together with the positive and negative electrode pieces and subjected to a cold pressing process (no heating is performed during the pressing process after the separator film and the electrode pieces are stacked), the polymer has favorable adhesive strength, allowing the positive and negative electrode pieces and the separator film to adhere to each other. Therefore, when the polymer of the present application is used for a separator film, adhesion between the separator film and the electrode pieces can be achieved by cold pressing, and the adhesive strength between the electrode pieces and the separator film is appropriate, thereby improving the cycle performance of the battery.

[0052] The polymers disclosed in the embodiments of the present application can be applied to batteries, and the batteries disclosed in the embodiments of the present application can be used in various energy storage systems using batteries as energy storage elements and in electrical devices powered by batteries. Electrical devices include, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric scooters, electric vehicles, boats, and spacecraft. Electric toys can include stationary or mobile electric toys, such as game consoles, electric toy cars, electric toy boats, and electric toy airplanes. Spacecraft can include airplanes, rockets, space shuttles, and spaceships.

[0053] A first aspect of the present application proposes a polymer, the polymer comprising a first organic polymer and a second organic polymer, the first organic polymer comprising a first polymerized monomer, a second polymerized monomer, and a third polymerized monomer, the polymerized monomers of the second organic polymer comprising the first polymerized monomer, the third polymerized monomer, and a fourth polymerized monomer, the structure of the first polymerized monomer comprising: [ka] wherein R1 comprises a hydrogen atom or an alkyl group having 1 to 18 carbon atoms, and R2 comprises an alkyl group having 1 to 18 carbon atoms; The structure of the second polymerized monomer comprises: [ka] wherein R3 comprises a hydrogen atom or a substituted or unsubstituted alkyl group of 1 to 18 carbon atoms; The structure of the third polymerizable monomer comprises: [ka] wherein R4 comprises a hydrogen atom or an alkyl group of 1 to 6 carbon atoms, R5 comprises a hydrogen atom, a hydroxyl-substituted alkyl group of 1 to 6 carbon atoms, or an alkoxy group of 1 to 6 carbon atoms; The structure of the fourth polymerizable monomer comprises: [ka] wherein R6 comprises a hydrogen atom or an alkyl group of 1 to 6 carbon atoms.

[0054] The polymer of the present application comprises a first organic polymer and a second organic polymer, and the polymerizable monomers of the first organic polymer comprise a first polymerizable monomer, a second polymerizable monomer, and a third polymerizable monomer, wherein the first polymerizable monomer comprises an unsaturated ester group, the second polymerizable monomer comprises an unsaturated carboxyl group, and the structure of the third polymerizable monomer comprises an unsaturated amide group. By polymerizing the first polymerizable monomer, the second polymerizable monomer, and the third polymerizable monomer to produce the first organic polymer, not only can the adhesiveness of the polymer be improved, but the glass transition temperature of the first organic polymer can be adjusted to an appropriate range, and the carboxyl group contained in the second polymerizable monomer can form a bond with the functional groups on the electrode pieces and separator film material, thereby improving the adhesive effect between the electrode pieces and the separator film. The polymerizable monomers of the second organic polymer include the first polymerizable monomer, the third polymerizable monomer, and a fourth polymerizable monomer, and the structure of the fourth polymerizable monomer contains an unsaturated cyano group. By polymerizing the first polymerizable monomer, the third polymerizable monomer, and the fourth polymerizable monomer to produce the second organic polymer, it is possible to adjust the glass transition temperature of the second organic polymer, which is useful for adjusting the glass transition temperature of the second organic polymer to a suitable range, and also to improve the ionic conductivity and adhesiveness of the second organic polymer.

[0055] The first organic polymer, which is made from the first, second, and third polymerizable monomers, and the second organic polymer, which is made from the first, third, and fourth polymerizable monomers, have different glass transition temperatures, and the first organic polymer has a lower glass transition temperature than the second organic polymer. When the polymer is heated to a temperature between the glass transition temperatures of the first and second organic polymers and no pressure is applied to the polymer, the second organic polymer structure is in a glassy state, which is relatively hard and functions as a framework for the polymer powder material, and is not adhesive to the polymer, allowing for easy winding and unwinding of the separator film. At this temperature, the first organic polymer structure is in a rubbery state and, after applying a certain amount of pressure, can have a certain "fluidity." The structure containing the first organic polymer in the polymer can fully penetrate the pores of the positive and negative electrode pieces and the separator film, enhancing the mechanical interlocking effect and fully demonstrating its adhesive properties, further contributing to improved battery performance.

[0056] Therefore, when the polymer of the present application is used for a separator film, the polymer is not adhesive at a certain temperature, making it easy to wind and unwind the separator film, but when it is wound together with positive and negative electrode pieces and subjected to a cold pressing process, the polymer has favorable adhesive strength to tightly adhere the positive and negative electrode pieces to the separator film. Therefore, when the polymer of the present application is used for a separator film, the cold pressing adhesive strength between the separator film and positive and negative electrode pieces is improved, and the adhesive strength between the electrode pieces and the separator film is appropriate, thereby improving the cycle performance of the battery.

[0057] In some embodiments of the present application, the structure of the first polymerized monomer comprises:

[0058] [ka] wherein R1 comprises a hydrogen atom or an alkyl group having 1 to 18 carbon atoms, R2 comprises an alkyl group having 1 to 18 carbon atoms, and the first polymerizable monomer comprises an unsaturated ester group, which is advantageous for the polymerization of the monomer and can improve the swelling resistance of the polymer. Furthermore, as a flexible monomer segment in the molecular segment, it can adjust the glass transition temperature of the organic polymer, contributing to adjusting the glass transition temperatures of the first organic polymer and the second organic polymer within a suitable range.

[0059] By way of example, an alkyl group of 1 to 18 carbon atoms is understood to mean an alkyl group of 1 to 18 carbon atoms, such as methyl (-CH), ethyl (-CHCH), n-propyl (-CHCHCH), isopropyl (-CH(CH), n-butyl (-CHCHCHCH, tert-butyl (-C(CH)), n-pentyl (-CHCHCHCHCHCH), n-hexyl (-CHCHCHCHCHCHCH), etc.

[0060] In some embodiments, the first polymerized monomer may include at least one of methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, n-propyl acrylate, cyclohexyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, ethyl 2-hydroxyacrylate, 2-hydroxypropyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, or 2-hydroxypropyl methacrylate. The first polymerized monomer described herein can be used to adjust the glass transition temperatures of the first and second organic polymers and improve the swelling resistance of the polymers.

[0061] In some embodiments of the present application, the structure of the second polymerized monomer comprises:

[0062] [ka] Wherein, R3 comprises a hydrogen atom or a substituted or unsubstituted alkyl group of 1 to 18 carbon atoms, whereby the second polymerization monomer comprises an unsaturated carboxyl group, which is advantageous for the polymerization of the monomer, and in the process of producing the first organic polymer, the second polymerization monomer comprising a carboxyl group is used, and in the process of pressing the separator film and the pole pieces together using a cold pressing process, the carboxyl group forms a bond with the functional groups on the pole pieces and separator film material, thereby improving the adhesive effect.

[0063] By way of illustration, a substituted alkyl group of 1 to 18 carbon atoms may be understood to be an alkyl group of 1 to 18 carbon atoms in which at least one hydrogen atom has been replaced with another group, such as, for example, -CHOH, -CHCHOH, -CHCHCHOH, -CH(CHOH) -CHCHCHCHCHOH, -C(CHOH) -CHCHCHCHCHCHOH, etc.

[0064] In some embodiments of the present application, the second polymerizable monomer comprises at least one of acrylic acid, methacrylic acid, crotonic acid, or heptenoic acid, thereby allowing the second polymerizable monomer described herein to be employed to adjust the adhesive properties of the first organic polymer.

[0065] In some embodiments of the present application, the structure of the third polymerized monomer comprises:

[0066] [ka] Wherein, R4 comprises a hydrogen atom or an alkyl group of 1 to 6 carbon atoms, and R5 comprises a hydrogen atom, a hydroxyl-substituted alkyl group of 1 to 6 carbon atoms, or an alkoxy group of 1 to 6 carbon atoms, so that the structure of the third polymerizable monomer contains an unsaturated amide group, which is advantageous for the polymerization of the monomer and can adjust the molecular weight of the first organic polymer, thereby improving the adhesion of the polymer.

[0067] For illustrative purposes, a hydroxy-substituted alkyl group of 1 to 6 carbon atoms can be understood to mean an alkyl group of 1 to 6 carbon atoms in which at least one hydrogen atom has been substituted with a hydroxy group, such as, for example, -CHOH, -CHCHOH, -CHCHCHOH, -CH(CHOH) -CHCHCHCHOH, -C(CHOH) -CHCHCHCHCHOH, etc. Similarly, a hydroxy-substituted alkoxy group of 1 to 6 carbon atoms can be understood to mean an alkoxy group of 1 to 6 carbon atoms in which at least one hydrogen atom has been substituted with a hydroxy group, such as, for example, methoxy (HOCHO-), ethoxy (OHCHCHO-), propoxy (OHCHCHCHO-), etc.

[0068] In some embodiments of the present application, the third polymerizable monomer includes at least one of acrylamide, N-methylolacrylamide, or N-butoxymethylacrylamide, thereby adjusting the molecular weight of the polymer and improving the adhesiveness of the polymer.

[0069] In some embodiments of the present application, the structure of the fourth polymerized monomer comprises:

[0070] [ka] Wherein, R6 contains a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, which allows the structure of the fourth polymerizable monomer to contain an unsaturated cyano group, which is advantageous for the polymerization of the monomer and improves the ionic conductivity and adhesiveness of the second organic polymer.

[0071] In some embodiments of the present application, the fourth polymerizable monomer includes at least one of acrylonitrile and methacrylonitrile, thereby improving the ionic conductivity and the adhesion of the polymer.

[0072] In some embodiments of the present application, the mass ratio of the first organic polymer to the second organic polymer is 1:(0.1 to 10), for example, 1:(0.5 to 9.5), 1:(1 to 9), 1:(1.5 to 8.5), 1:(2 to 8), 1:(2.5 to 7.5), 1:(3 to 7), 1:(3.5 to 6.5), 1:(4 to 6), 1:(4.5 to 5.5), 1:(5 to 5.5), etc.

[0073] The polymer of the present application is a secondary particle formed by aggregation of primary particles of a first organic polymer and primary particles of a second organic polymer, and both the primary particles of the first organic polymer and the primary particles of the second organic polymer have the opportunity to be exposed on the surface of the secondary particles. Adjusting the mass ratio of the first organic polymer to the second organic polymer adjusts the opportunity for the first organic polymer to be exposed on the surface of the secondary particles, thereby adjusting the adhesiveness of the polymer. By setting the mass ratio of the first organic polymer to the second organic polymer within the above range, the polymer can be made to have both a rubbery state and a relatively hard glassy state at a certain temperature. When pressure is not applied to the polymer, the glassy state structure functions as the skeletal structure of the polymer powder material, making the polymer non-adhesive and suitable for winding and unwinding of the separator film. Furthermore, the polymer structure is a rubbery structure and can have a certain "fluidity" after applying a certain amount of pressure. The rubbery structure in the polymer can fully penetrate the pores of the positive and negative electrode pieces and the separator film, enhancing the mechanical interlocking effect and fully demonstrating its adhesive performance, further contributing to improving the cycle performance of the battery. At the same time, the above composition is not so hard that it affects the adhesive effect between the separator film and the electrode pieces. In some other embodiments of the present application, the mass ratio of the first organic polymer to the second organic polymer is 1:(0.5-3).

[0074] In some embodiments of the present application, in the polymerizable monomers of the first organic polymer, the mass ratio of the first polymerizable monomer to the second polymerizable monomer to the third polymerizable monomer is 1:0.05-0.5:0.05-0.5, for example, 1:0.1-0.5:0.05-0.5, 1:0.15-0.45:0.05-0.5, or 1:0.2-0.4. :0.05~0.5, 1:0.25~0.35:0.05~0.5, 1:0.3~0.35:0.05~0.5, 1:0.05~0.5:0.1~0.5, 1:0.05~0.5:0.15~0.45, 1:0.05~0.5:0.2~0.4, 1:0.05~0.5:0.25~0.35, 1:0.05~0.5:0.3~0.35, etc. Thus, in the present application, by controlling the mixing ratio of the first polymerizable monomer, the second polymerizable monomer, and the third polymerizable monomer used to produce the first organic polymer, not only can the adhesiveness of the polymer be improved, but the glass transition temperature of the first organic polymer be adjusted to an appropriate range, and the carboxyl group contained in the second polymerizable monomer forms a bond with the functional groups on the electrode pieces and separator film material, thereby improving the adhesive effect between the electrode pieces and the separator film. In some other embodiments of the present application, the mass ratio of the first polymerizable monomer, the second polymerizable monomer, and the third polymerizable monomer in the polymerizable monomers of the first organic polymer is 1:0.056-0.5:0.056-0.5.

[0075] In some embodiments of the present application, in the polymerizable monomers of the second organic polymer, the mass ratio of the first polymerizable monomer, the third polymerizable monomer, and the fourth polymerizable monomer is 1:0.05-0.5:0.05-0.5, for example, 1:0.1-0.5:0.05-0.5, 1:0.15-0.45:0.05-0.5, or 1:0.2-0.4. 1:0.05-0.5, 1:0.25-0.35:0.05-0.5, 1:0.3-0.35:0.05-0.5, 1:0.05-0.5:0.1-0.5, 1:0.05-0.5:0.15-0.45, 1:0.05-0.5:0.2-0.4, 1:0.05-0.5:0.25-0.35, 1:0.05-0.5:0.3-0.35, etc. Thus, in the present application, by controlling the mixing ratio of the first polymerizable monomer, the third polymerizable monomer, and the fourth polymerizable monomer used to produce the second organic polymer to the above-mentioned range, not only can the glass transition temperature of the second organic polymer be adjusted, but also the glass transition temperature of the second organic polymer can be adjusted to a suitable range, and the ionic conductivity and adhesiveness of the second organic polymer can be improved. In some other embodiments of the present application, in the polymerizable monomers of the second organic polymer, the mass ratio of the first polymerizable monomer to the third polymerizable monomer to the fourth polymerizable monomer is 1:0.056-0.5:0.056-0.5.

[0076] It should be explained that in the present application, the first polymerizable monomer employed in the polymerizable monomer for producing the first organic polymer and the first polymerizable monomer employed in the polymerizable monomer for producing the second organic polymer may be the same or different, and similarly, the third polymerizable monomer employed in the polymerizable monomer for producing the first organic polymer and the third polymerizable monomer employed in the polymerizable monomer for producing the second organic polymer may be the same or different, and a person skilled in the art can select them as needed.

[0077] In some embodiments of the present application, the polymer further comprises a dispersing agent comprising at least one of sodium polystyrene sulfonate, sodium gluconate, sodium polyacrylate, sodium polymethacrylate, sodium polyphosphate, sodium lignosulfonate, or sodium polycarboxylate.

[0078] The polymer of the present invention is added with a dispersant having the above composition, which has excellent dispersing properties for suspension systems and reduces irregular aggregation in emulsion systems. When the polymer is used in separator films, it can improve the cold pressure adhesion between the separator film and the pole pieces, thereby improving the cycle performance of the battery.

[0079] In some embodiments of the present application, the number-average molecular weight of the dispersant is 100 to 100,000, e.g., 500 to 100,000, 3,000 to 100,000, 5,000 to 100,000, 8,000 to 100,000, 10,000 to 100,000, 30,000 to 90,000, 50,000 to 70,000, 50,000 to 60,000, or 55,000 to 60,000. Thus, in the present application, adding a dispersant of the above molecular weight to a polymer can reduce irregular aggregation in the emulsion system. When the polymer is used in a separator film, this can improve the cold-press adhesion between the separator film and the electrode pieces, thereby improving the hardness of the battery core and the cycle performance of the battery. In some embodiments of the present application, the number-average molecular weight of the dispersant is 5,000 to 80,000.

[0080] In this application, the number-average molecular weight of a polymer can be determined by referring to the GB / T 21863-2008 standard, Gel Permeation Chromatography. Specifically, this application can be performed in the following manner: Ultra-High Performance Polymer Chromatography (ACQUITY APC) is used with an ACQUITY refractive index detector. Standard: Polystyrene sleeve; Run time: 30 min; Detector: ACQUITY refractive index (RI) detector; Column oven temperature: 90°C; Detector temperature: 55°C. Sample Testing: a. Standard and Test Sample Composition: Weigh out 0.002g-0.004g of each standard / test sample and add it to 2mL of mobile phase to prepare a 0.1%-0.5% mixed standard. Store in a refrigerator for >8 hours. b. Standard / Sample Testing: Edit the sample set to be measured, select the established sample set method, and after the baseline stabilizes, click Run Queue to start the sample testing. (4) Data processing: Based on the relationship between retention time and molecular weight, a calibration curve is established using a chemical workstation, and integral quantification is performed on the sample spectrum. The chemical workstation then automatically generates the number average molecular weight results.

[0081] In some embodiments of the present application, the mass ratio of the first organic polymer to the second organic polymer to the dispersant is 1:0.1-10:0.01-2, for example, 1:0.5-10:0.01-2, 1:1-10:0.01-2, 1:2-9:0.01-2, 1:3-8:0.01-2, 1:4-7:0.01-2, 1:5-6:0.01-2, 1:0.1-10:0.05-2, 1:0.1-10:0.08-2, 1:0.1-10:0.1-2, 1:0.1-10:0.3-1.8, 1:0.1-10:0.5-1.5, 1:0.1-10:0.7-1.2, 1:0.1-10:1-1.2, etc. Thus, the polymer of the present application contains the first organic polymer, the second organic polymer, and the dispersant in the above-mentioned mixing ratio, which can significantly reduce irregular aggregation in the emulsion system, and when the polymer is used in a separator film, it can improve the cold pressing adhesion between the separator film and the pole pieces, and can improve the hardness of the battery core and the cycle performance of the battery. In some other embodiments of the present application, the mass ratio of the first organic polymer, the second organic polymer, and the dispersant is 1:0.5-3:0.05-1.5.

[0082] In some embodiments of the present application, the polymer further contains a butadiene-based polymer. Specifically, the weak point in the adhesion between the separator film and the electrode pieces is the adhesive strength between the separator film and the cathode pieces. Meanwhile, the adhesive commonly used for cathode pieces is styrene-butadiene rubber (SBR). SBR has characteristics such as very strong alkali resistance, a soft film formation, good breathability, and strong adhesive strength. Furthermore, cathode pieces often suffer from adhesive floatation, where a portion of the SBR is enriched on the surface of the cathode pieces. In the present application, adding a butadiene-based polymer to the polymer improves the adhesive strength between the two phases because the butadiene-based polymer contained in the polymer and the SBR adhesive enriched on the surface of the cathode pieces are the same substance. Therefore, adding a butadiene-based copolymer to the polymer improves the cold pressure adhesive strength between the separator film and the cathode pieces when the polymer is used for the separator film, thereby improving the cycle performance of the battery.

[0083] In some embodiments of the present application, the glass transition temperature of the butadiene-based polymer is 20°C or lower, for example, 5°C to 20°C, 7°C to 17°C, or 10°C to 15°C. This allows the butadiene-based polymer, which has a glass transition temperature of 20°C or lower, to be in a rubbery state at room temperature. When cold-pressed at room temperature, the polymer is more likely to have "fluidity," penetrate better into the slits on the electrode piece surface, enhance the mechanical interlocking effect, and ensure sufficient contact with the SBR on the cathode piece surface, improving adhesive strength. In other embodiments of the present application, the glass transition temperature of the butadiene-based polymer is 15°C or lower.

[0084] In some embodiments of the present application, the butadiene-based polymer has a volume average particle diameter Dv50 of 100 nm to 300 nm, for example, 150 nm to 250 nm, or 150 nm to 200 nm. This improves the cold pressure adhesive strength between the separator film and the electrode pieces when the polymer is used in a separator film, and also provides appropriate adhesive strength between the separator film and the electrode pieces, thereby improving the cycle performance of the battery. In some embodiments of the present application, the butadiene-based polymer has a Dv50 of 120 nm to 250 nm.

[0085] For illustrative purposes, in the examples of the present application, the volume average particle size Dv50 of the butadiene-based polymer is the particle size corresponding to the point where the cumulative particle size distribution percentage reaches 50%, and the test method is as follows: The particle size distribution was measured using a laser diffraction method in accordance with GB / T 19077-2016 / ISO 13320:2009. The test was performed using a laser particle sizer (Malvern 3000, MasterSizer 3000) with a helium-neon red light source as the primary light source. 1 g of sample to be measured was placed in a clean beaker, followed by one drop of surfactant and 20 mL of deionized water (ensuring a sample concentration of 8-12%). The sample was then sonicated at 53 kHz / 120 W for 5 minutes to ensure complete dispersion. The laser particle sizer was then turned on, the optical path was cleaned, and the background was automatically tested. The sonicated sample was then stirred to ensure uniform dispersion. The sample was then placed in the sample cell, if necessary, and the particle size measurement was initiated. The measurement results were then read from the instrument.

[0086] In some embodiments of the present application, the viscosity of the butadiene-based polymer at 25°C is 10 mPa·s to 300 mPa·s, for example, 50 mPa·s to 250 mPa·s, 100 mPa·s to 200 mPa·s, or 150 mPa·s to 220 mPa·s. By using a butadiene-based polymer with such a viscosity, the compatibility of the butadiene-based polymer with the first organic polymer and the second organic polymer can be improved. Therefore, when the polymer is used in a separator film, the cold press adhesive strength between the separator film and the electrode pieces can be improved, and the adhesive strength between the separator film and the electrode pieces can be optimized, resulting in improved battery cycle performance. In other embodiments of the present application, the viscosity of the butadiene-based polymer at 25°C is 80 mPa·s to 200 mPa·s.

[0087] For illustrative purposes, in the examples of this application, the viscosity of the above-mentioned butadiene-based polymers at 25°C is measured by referring to the national standard GB / T10247-2008 "Viscosity Measurement Method." Specifically, a Brookfield rotational viscometer is used at 25°C, and the shear force generated when the 62# rotor rotates at a constant speed on the sample is used to generate a torque on the spring proportional to the viscosity, thereby obtaining the viscosity value.

[0088] In some embodiments of the present application, the butadiene-based polymer includes at least one of polybutadiene, styrene / butadiene copolymer, and acrylonitrile / butadiene copolymer, thereby improving the cold pressing adhesive strength between the separator film and the electrode pieces and providing appropriate adhesive strength between the separator film and the electrode pieces, thereby improving the cycle performance of the battery.

[0089] In some embodiments of the present application, the mass ratio of the first organic polymer to the second organic polymer to the butadiene-based polymer is 1:0.1-10:0.1-10, for example, 1:0.5-10:0.1-10, 1:1-10:0.1-10, 1:2-9:0.1-10, 1:3-8:0.1-10, 1:4-7:0.1-10, 1:5-6:0.1-10, 1:0.1-10:0.5-10, 1:0.1-10:1-10, 1:0.1-10:2-9, 1:0.1-10:3-8, 1:0.1-10:4-7, or 1:0.1-10:5-6. Thus, the polymer of the present application contains the first organic polymer, the second organic polymer, and the butadiene-based polymer in the above-mentioned mixing ratio, and when the polymer is used in a separator film, it can improve the cold pressing adhesive strength between the separator film and the electrode pieces, thereby improving the hardness of the battery core and the cycle performance of the battery. In some other embodiments of the present application, the mass ratio of the first organic polymer, the second organic polymer, and the butadiene-based polymer is 1:0.5-3:0.5-8.

[0090] It should be noted that the polymer of the present application may simultaneously include the first organic polymer, the second organic polymer, and the dispersant; alternatively, the polymer may simultaneously include the first organic polymer, the second organic polymer, and the butadiene-based polymer; or alternatively, the polymer may simultaneously include the first organic polymer, the second organic polymer, the dispersant, and the butadiene-based polymer.

[0091] In some embodiments of the present application, the polymer has a first glass transition temperature less than or equal to 25° C. and a second glass transition temperature greater than 25° C. Specifically, the first organic polymer of the present application corresponds to the first glass transition temperature and the second organic polymer corresponds to the second glass transition temperature.

[0092] The glass transition temperature is the temperature at which a high polymer transitions from a highly elastic state to a glassy state, and refers to the temperature at which an amorphous polymer (including the amorphous portion of a crystalline polymer) transitions from a glassy state to a highly elastic state, or from the latter to the former. It is the lowest temperature at which the large molecular segments of an amorphous polymer can move freely, and is usually represented by Tg. A high polymer exhibits elasticity above the glass transition temperature, and below the glass transition temperature, the polymer exhibits brittleness. The glass transition temperature can be measured by a method commonly used in the art, for example, by differential scanning calorimetry, referring to GB / T19466.2.

[0093] It is understood that when the first glass transition temperature is 25°C or lower, and the structure of the polymer containing the first organic polymer is in a rubbery state when it is equal to or higher than the first glass transition temperature, and when the second glass transition temperature is higher than 25°C and equal to or lower than the second glass transition temperature, the structure of the polymer containing the second organic polymer is in a glassy state.

[0094] For example, the first glass transition temperature is lower than room temperature, and the second glass transition temperature is higher than room temperature. At room temperature, when no pressure is applied to the polymer, the second glass transition temperature is higher than room temperature, and the structure of the polymer containing the second organic polymer is in a glassy state, which is relatively hard and functions as the skeleton structure of the polymer powder material, making the polymer non-adhesive. At room temperature, the first glass transition temperature is lower than room temperature, and the structure of the polymer containing the first organic polymer is in a rubbery state. When a certain pressure is applied, it can have a certain "fluidity." The structure of the first organic polymer in the polymer can fully penetrate the pores of the positive and negative electrode pieces and separator film, enhancing the mechanical interlocking effect and fully exerting its adhesive properties, contributing to improving the cycle performance of the battery.

[0095] At temperatures above the first glass transition temperature, the polymer structure containing the first organic polymer is in a soft state and can deform when pressure is applied, and the separator film and electrode piece structure have pores that act on the polymer when pressure is applied, and it is understood that part of the first organic polymer structure penetrates into the pores of the separator film and electrode piece, bonding the separator film and the polymer and exerting a mechanical interlocking effect to realize the adhesive function.

[0096] Because the glass transition temperatures of the first and second organic polymers in the polymer are significantly different, when cold pressing is performed at a temperature between the first and second glass transition temperatures, the structure of the first organic polymer in the polymer is in a rubbery state, and the structure of the second organic polymer in the polymer is in a glassy state, giving the polymer "soft and hard" properties. After coating it on a separator film, at a temperature between the first and second glass transition temperatures and without pressure, the polymer has no adhesion and can meet the winding and unwinding needs of the separator film. After applying a certain amount of pressure, the polymer exhibits pressure sensitivity and good adhesion, meeting the adhesive strength needs of the separator film and the positive and negative electrode pieces.

[0097] Therefore, when the polymer of the present application is applied to a separator film, the polymer is non-adhesive at temperatures between the first and second glass transition temperatures, making it easy to wind and unwind the separator film, but when wound together with positive and negative electrode pieces and subjected to a cold pressing process, the polymer has favorable adhesive strength to tightly adhere the separator film to the positive and negative electrode pieces. Therefore, when the polymer of the present application is used in a separator film, the cold pressing adhesive strength between the separator film and the positive and negative electrode pieces is improved, thereby improving the hardness of the battery core and the battery cycle performance.

[0098] In some embodiments of the present application, the first glass transition temperature may be any value, such as -100°C, -90°C, -80°C, -70°C, -50°C, -30°C, -10°C, 10°C, 20°C, 24°C, 25°C, and a range value between any two of the above points, but is not particularly limited thereto.

[0099] In some embodiments of the present application, the second glass transition temperature may be any value, such as 26°C, 30°C, 50°C, 80°C, 100°C, 200°C, and a range value between any two of the above points, but is not specifically limited thereto.

[0100] In some embodiments of the present application, the range of the first glass transition temperature is -80°C to 25°C, preferably -60°C to 25°C.

[0101] In the above range, the structure of the polymer having the first glass transition temperature is in a rubbery state above the first glass transition temperature, which is advantageous for exhibiting its adhesiveness during the cold pressing process, which is advantageous for the adhesiveness between the separator film and the electrode pieces after cold pressing, and which is advantageous for improving the performance of the battery.

[0102] In the above range of -80°C to 25°C, the values ​​include the minimum and maximum values ​​of the range, as well as each value between such minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the examples, as well as values ​​such as -80°C, -70°C, -60°C, -50°C, -40°C, -30°C, -20°C, -10°C, 0°C, 10°C, 20°C, 25°C, and the like, as well as range values ​​between any two of the above point values.

[0103] In the above range of -60°C to 25°C, the values ​​include the minimum and maximum values ​​of the range, as well as each value between such minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the examples, as well as values ​​such as -60°C, -50°C, -40°C, -30°C, -20°C, -10°C, 0°C, 10°C, 20°C, 25°C, and the like, as well as range values ​​between any two of the above point values.

[0104] In some embodiments of the present application, the second glass transition temperature range is 26°C to 100°C, preferably 26°C to 90°C.

[0105] Within the above range, the structure of the polymer having the second glass transition temperature is in a glassy state at or below the second glass transition temperature, and is advantageous in that it becomes a polymer skeleton structure at a temperature between the first glass transition temperature and the second glass transition temperature, and the polymer does not have adhesive properties, making it easy to operate the steps of winding and unwinding the separator film at a constant temperature.

[0106] In the above range of 26°C to 100°C, the values ​​include the minimum and maximum values ​​of the range, as well as each value between such minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the examples, as well as 26°C, 28°C, 30°C, 50°C, 80°C, 90°C, 100°C, etc., and range values ​​between any two of the above point values.

[0107] In the above range of 26°C to 90°C, the values ​​include the minimum and maximum values ​​of the range, as well as each value between such minimum and maximum values. Specific examples include, but are not limited to, the point values ​​in the examples, as well as 26°C, 28°C, 30°C, 50°C, 80°C, 90°C, etc., and range values ​​between any two of the above point values.

[0108] In some embodiments of the present application, the volume particle size distribution Dv50 of the polymer is 1 μm to 15 μm, for example, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, etc. In the present application, when a polymer satisfying the above volume average particle size Dv50 is used for a separator film, not only can the risk of the polymer blocking the separator film channels be reduced, but also the problem of the polymer forming a relatively thick coating on the separator film, which can affect the energy density of the final battery, can be alleviated. In other embodiments of the present application, the volume particle size distribution Dv50 of the polymer is 5 μm to 10 μm.

[0109] For illustrative purposes, in the examples of the present application, the volume average particle size Dv50 of the polymer is the particle size corresponding to the point where the particle cumulative particle size distribution percentage reaches 50%, and the test method is as follows: Refer to the GB / T 19077-2016 / ISO 13320:2009 laser diffraction particle size distribution standard. Tests are performed using a laser particle sizer (Malvern 3000, MasterSizer 3000) with a helium-neon red light source as the primary light source. Add 1 g of sample to a clean beaker, add one drop of surfactant, and 20 mL of deionized water (ensuring a sample concentration of 8-12% light). Sonicate at 53 kHz / 120 W for 5 minutes to ensure complete dispersion. Turn on the laser particle sizer, clean the optical path, and automatically test the background. Stir the sonicated sample to ensure uniform dispersion. If necessary, add it to the sample cell and begin particle size measurement. The measurement results can be read from the instrument.

[0110] In some embodiments of the present application, the number particle size distribution Dn10 of the polymer is 1 μm to 5 μm, for example, 1 μm, 2 μm, 3 μm, 4 μm, or 5 μm. In the present application, when a polymer satisfying this number particle size distribution Dn10 is used for a separator film, not only can the risk of the polymer blocking the separator film channels be reduced, but also the problem of the polymer forming a relatively thick coating on the separator film affecting the energy density of the final manufactured battery can be alleviated. This reduces the risk of the polymer blocking the separator film channels, improves the active ion permeability of the separator film, and alleviates the problem of the polymer forming a relatively thick coating on the separator film affecting the energy density of the final manufactured battery. In other embodiments of the present application, the number particle size distribution Dn10 of the polymer is 1 μm to 3 μm.

[0111] It should be noted that in the examples of the present application, the number particle size distribution Dn10 of the polymer is the particle size corresponding to the particle cumulative number distribution percentage reaching 10%, and the test method is based on GB / T 19077-2016, and the characterization test is performed using a Malvern laser particle sizer, for example, a Malvern Mastersizer-3000 or other such instrument.

[0112] In a second aspect of the present application, a method for producing the above polymer is proposed, comprising: mixing together water, an emulsifier, an initiator, a first organic monomer, a second polymerizable monomer, and a third polymerizable monomer to obtain a first polymer emulsion; mixing together water, an emulsifier, an initiator, a first polymerizable monomer, a third polymerizable monomer, and a fourth polymerizable monomer to obtain a second polymer emulsion; mixing the first polymer emulsion with the second polymer emulsion to obtain a polymer.

[0113] The first organic polymer is prepared by emulsion polymerization using a first polymerization monomer, a second polymerization monomer, and a third polymerization monomer, and the second organic polymer is prepared by emulsion polymerization using a first polymerization monomer, a third polymerization monomer, and a fourth polymerization monomer. The first organic polymer and the second organic polymer prepared by using the above monomers have suitable first and second glass transition temperatures, and when applied to a separator film, the polymer satisfies the polymer's non-adhesive properties at room temperature and satisfies the cold pressing adhesion between the separator film and the positive and negative electrode pieces during the cold pressing process, improving the hardness of the battery core and resolving problems such as opening and softening of the battery core. At the same time, when the polymer is applied to a separator film and then applied to a battery, the adhesion between the separator film and the positive and negative electrode pieces is appropriate, thereby improving the battery's cycle performance.

[0114] In the present invention, a first polymer emulsion and a second polymer emulsion are obtained by emulsion polymerization, and then the polymer is obtained by spray drying. That is, the polymer includes a first organic polymer and a second organic polymer.

[0115] Emulsion polymerization: In emulsion polymerization, the monomer is dispersed in water with an emulsifier and mechanical stirring to form an emulsion, and then an initiator is added to start the polymerization of the monomer.

[0116] Emulsifier: An emulsifier is a substance that can convert oil and water, which are incompatible with each other, into an emulsion that is difficult to delaminate. Emulsifiers are usually surfactants that combine the properties of both several hydrophilic polar groups and hydrophobic (lipophilic) non-polar groups. The emulsifier can be, for example, at least one of sodium dodecyl sulfonate, sodium dodecyl benzene sulfonate, sodium dodecyl sulfate, sodium dodecyl benzene sulfate, sodium laurate, sodium stearate, or sodium palmitoleate.

[0117] Initiator: An initiator is a substance capable of initiating the polymerization reaction of a monomer. For example, a radical initiator is a compound that easily decomposes thermally into a radical (i.e., a primary radical), and can be used to initiate the radical polymerization and copolymerization of olefin-based and diene-based monomers. For example, the initiator can be at least one of potassium persulfate, ammonium persulfate, azobisisobutyronitrile, dimethyl azobisisobutyrate, benzoyl peroxide, or di-n-octanoyl peroxide.

[0118] Water, an emulsifier, an initiator, and the constituent monomers of the polymer are mixed and stirred together, and after the water and the emulsifier are stirred and dispersed, an emulsion is formed; that is, the emulsifier forms micelles in the aqueous phase, and the monomers are solubilized in most of the micelles. Under heating conditions, the initiator initiates polymerization of the monomers inside the micelles, thereby obtaining an emulsion.

[0119] In spray drying, the material to be dried (a mixture of the first and second polymer emulsions) is dispersed into fine, mist-like particles through mechanical action (increasing the surface area for water evaporation and accelerating the drying process), and then contacted with hot air to instantly remove most of the water and dry the solids in the material into a powder.

[0120] The process of spray drying results in a polymer comprising a first organic polymer and a second organic polymer.

[0121] In some embodiments of the present application, the step of mixing and stirring a first polymer emulsion and a second polymer emulsion and spray-drying to obtain a polymer includes the step of mixing and stirring the first polymer emulsion and the second polymer emulsion to obtain a mixed emulsion, wherein the ratio of the mass of the first organic polymer to the mass of the second organic polymer in the mixed emulsion is 1:(0.1 to 10), preferably 1:(0.5 to 3).

[0122] In some embodiments of the present application, the method further includes adding a dispersant and / or a butadiene-based polymer during the mixing process of the first polymer emulsion and the second polymer emulsion. Specifically, the dispersant added during the mixing process of the first polymer emulsion and the second polymer emulsion has good dispersion properties for the suspension system and reduces irregular aggregation of the emulsion system. When the polymer is used in a separator film, it can improve the cold-press adhesion between the separator film and the electrode pieces, thereby improving the hardness of the battery core and the cycle performance of the battery. Furthermore, a butadiene-based copolymer is added during the mixing process of the first polymer emulsion and the second polymer emulsion. When the polymer is used in a separator film, it can improve the cold-press adhesion between the separator film and the electrode pieces, thereby improving the hardness of the battery core and the cycle performance of the battery.

[0123] It should be noted that in the present application, the dispersant or the butadiene-based polymer may be added separately during the process of mixing the first polymer emulsion and the second polymer emulsion, or the dispersant and the butadiene-based polymer may be added simultaneously.

[0124] This improves the cold pressure adhesive strength between the separator film and the electrode pieces when the polymer is used for the separator film, and also makes the adhesive strength between the separator film and the electrode pieces appropriate, thereby improving the cycle performance of the battery.

[0125] In a third aspect of the present application, we propose a separator film containing the polymer of the first aspect of the present application or a polymer obtained by employing the method of the second aspect of the present application, whereby when the above polymer of the present application is applied to a separator film, the cold pressing adhesion between the separator film and the electrode pieces is improved and the adhesion between the separator film and the electrode pieces is appropriate, thereby improving the cycle performance of the battery.

[0126] In some embodiments of the present application, the separator film of the present application includes a substrate film and an adhesive layer formed on at least one side of the substrate film, the adhesive layer including the polymer of the first aspect of the present application or the polymer obtained by employing the method of the second aspect of the present application. For example, adhesive layers are formed on both opposing sides of the substrate film.

[0127] The present application does not have any particular limitation on the type of substrate film, and any substrate film having a known porous structure and having good chemical and mechanical stability can be selected.

[0128] In some other embodiments of the present application, the substrate film may include at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The substrate film may be a single-layer film or a multi-layer composite film, without any particular limitation. When the substrate film is a multi-layer composite film, the materials of each layer may be the same or different, without any particular limitation.

[0129] The separator film described herein can be produced by a conventional method in the art. For example, the separator film described herein can be produced by dissolving the polymer described in the first embodiment of the present invention in an organic solvent to obtain a slurry, applying the slurry to a substrate film, and then drying to remove the organic solvent.

[0130] In some embodiments of the present application, the polymer has a coating density of 0.3 g / m on one side of the substrate film. 2 ~1.0g / m 2 , e.g., 0.4 g / m 2 ~0.9g / m 2 , 0.5g / m 2 ~0.8g / m 2 , 0.6g / m 2 ~0.7g / m 2 This can improve the adhesive strength between the separator film and the pole pieces, thereby improving the safety performance of the battery. In some other embodiments of the present application, the polymer is applied at a coating density of 0.3 g / m on one side of the substrate film. 2 ~0.8g / m 2 may be.

[0131] For illustrative purposes, the test method for the coating density on one side of the above-mentioned polymer substrate film is as follows: cut a separator film sprayed with adhesive based on a sample cutting board, measure the length and width of the cut sample to obtain the sample area S, weigh the separator film sample sprayed with adhesive and define it as M1, cut a separator film sample with the same area without adhesive in the same way, weigh the mass and define it as M2, and define the coating density of the separator film as (M1-M2) / S.

[0132] In a fourth aspect of the present application, there is provided a pole piece comprising the polymer of the first aspect or the polymer obtained by employing the method of the second aspect, which can improve the stability of the pole piece and improve the cycle performance and safety performance of the battery.

[0133] It should be noted that the pole pieces of the present application may be positive pole pieces or negative pole pieces.

[0134] The positive electrode piece includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, the positive electrode active material layer including the polymer of the first aspect of the present application.

[0135] As an example, the positive electrode current collector has two surfaces that face each other in the thickness direction of the positive electrode current collector, and the positive electrode active material layer is disposed on one or both of the two facing surfaces of the positive electrode current collector.

[0136] In some embodiments of the present application, the positive electrode current collector may be a metal foil piece or a composite current collector. For example, the metal foil piece may be an aluminum foil. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric material base layer. The composite current collector may be formed by forming a metal material (such as aluminum, an aluminum alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, or a silver alloy) on a polymeric material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0137] In some embodiments of the present application, the positive electrode active material can be any positive electrode active material used in batteries known in the art.

[0138] For example, when the positive electrode strip is used in a lithium-ion battery, the positive electrode active material can be a positive electrode active material known in the art for use in lithium-ion batteries. For example, the positive electrode active material can 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 conventional materials that can be used as the positive electrode active material of a battery can also be used. These positive electrode active materials can be used alone or in combination of two or more. Examples of lithium transition metal oxides include lithium cobalt oxide (e.g., LiCoO), lithium nickel oxide (e.g., LiNiO), lithium manganese oxide (e.g., LiMnO, LiMnO), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, and lithium nickel cobalt manganese oxide (e.g., LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM 333 (may be abbreviated as "LiNi") 0.5 Co 0.2 Mn 0.3O2(NCM 523 (may be abbreviated as "LiNi") 0.5 Co 0.25 Mn 0.25 O2(NCM 211 (may be abbreviated as "LiNi") 0.6 Co 0.2 Mn 0.2 O2(NCM 622 (may be abbreviated as "LiNi") 0.8 Co 0.1 Mn 0.1 O2(NCM 811 ), lithium nickel cobalt aluminum oxide (e.g., LiNi 0.8 Co 0.15 Al 0.05 O2) or modified compounds thereof, etc. Examples of the lithium-containing phosphate having an olivine structure may include, but are not limited to, at least one of lithium iron phosphate (e.g., LiFePO4 (which may be abbreviated as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (e.g., LiMnPO4), a composite material of lithium manganese phosphate and carbon, and a composite material of lithium manganese iron phosphate or lithium manganese iron phosphate and carbon.

[0139] For example, when the positive electrode piece is used in a sodium ion battery, the positive electrode active material may be any positive electrode active material known in the art for use in sodium ion batteries, including, but not limited to, layered transition metal oxides, polyanionic compounds, and Prussian blue analogs.

[0140] Examples of the layered transition metal oxide include the following: Na 1-x Cu h Fe k Mn l M 1 m O 2-y , among which, M 1contains at least one of Li, Be, B, Mg, Al, K, Ca, Ti, Co, Ni, Zn, Ga, Sr, Y, Nb, Mo, In, Sn, and Ba, and 0 <x≦0.33、0<h≦0.24、0≦k≦0.32、0<l≦0.68、0≦m<0.1、h+k+l+m=1、0≦y<0.2であり、 Na 0.67 Mn 0.7 Ni z M 2 0.3-z O2, among which M 2 contains at least one of Li, Mg, Al, Ca, Ti, Fe, Cu, Zn, and Ba, and 0 <z≦0.1であり、 Na a Li b Ni c Mn d Fe e O2, of which 0.67 <a≦1、0<b<0.2、0<c<0.3、0.67<d+e<0.8、b+c+d+e=1である。

[0141] Examples of the polyanionic compounds include the following: A 1 f M 3 g (PO4) i O j X 1 3-j ,A 1 contains at least one of H, Li, Na, K, and NH4, and M 3 contains at least one of Ti, Cr, Mn, Fe, Co, Ni, V, Cu, and Zn, and X 1 is at least one of F, Cl, and Br, and 0 <f≦4、0<g≦2、1≦i≦3、0≦j≦2であり、 Na n M 4 PO4X 2 , among which, M 4 contains at least one of Mn, Fe, Co, Ni, Cu, and Zn, and X 2 is at least one of F, Cl, and Br, and 0 <n≦2であり、 Nap M 5 q (SO4)3, among which, M 5 contains at least one of Mn, Fe, Co, Ni, Cu or Zn, 0 < p ≤ 2, 0 < q ≤ 2, Na s Mn t Fe 3-t (PO4)2(P2O7, among which, 0 < s ≤ 4, 0 ≤ t ≤ 3, for example, t is 0, 1, 1.5, 2 or 3.

[0142] Examples of the above Prussian blue analogs include, for example, the following: A u M 6 v [M 7 (CN)6] w ×H2O, among which, A is H + , NH4 + , at least one of an alkali metal cation or an alkaline earth metal cation, M 6 and M 7 each independently contains at least one of transition metal cations, 0 < u ≤ 2, 0 < v ≤ 1, 0 < w ≤ 1,​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​In some embodiments of the present application, the positive electrode active material layer may further optionally include a conductive agent. For 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.

[0144] In some embodiments, the positive electrode pieces can be manufactured by a method in which the above-mentioned components for manufacturing the positive electrode pieces, such as the positive electrode active material, the conductive agent, the polymer, and any other components, are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry, and the positive electrode slurry is applied onto a positive electrode current collector, followed by processes such as drying and cold pressing to obtain the positive electrode pieces.

[0145] In some embodiments of the present application, the mass proportion of the polymer in the positive electrode piece is 1% to 3%, for example, 1.2% to 2.8%, 1.5% to 2.5%, 1.8% to 2.2%, 2% to 2.2%, etc., based on the total mass of the positive electrode active material layer, which can reduce shedding of the positive electrode piece and thereby improve the cycle performance of the battery including the same.

[0146] Similarly, the electrode piece of the present application may be a negative electrode piece, which includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, the negative electrode active material layer including the polymer described in the first aspect of the present application or the polymer obtained by employing the method of the second aspect of the present application.

[0147] As an example, the negative electrode current collector has two surfaces that face each other in the thickness direction thereof, and the negative electrode active material layer is disposed on either one or both of the two facing surfaces of the negative electrode current collector.

[0148] In some embodiments of the present application, the negative electrode current collector may be a metal foil piece or a composite current collector. For example, the metal foil piece may be a copper foil. The composite current collector may include a polymeric material base layer and a metal layer formed on at least one surface of the polymeric 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, or silver alloy) on a polymeric material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0149] In some embodiments of the present application, the negative electrode active material may be a negative electrode active material for batteries known in the art. For example, the negative electrode active material may include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may include at least one of elemental silicon, silicon-oxygen compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may include at least one of elemental tin, tin-oxygen compounds, and tin alloys. However, the present application is not limited to these materials, and other conventional materials usable as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination.

[0150] In some embodiments of the present application, the negative electrode active material layer may further optionally include a conductive agent, which 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 of the present application, the negative electrode active material layer may further optionally contain other auxiliary agents, for example, a thickener (for example, sodium carboxymethyl cellulose (CMC-Na)).

[0152] In some embodiments of the present application, the negative electrode pieces can be produced as follows: the above-mentioned components for producing the negative electrode pieces, such as the negative electrode active material, the conductive agent, and the polymer described in the first aspect of the present application, are dispersed in a solvent (e.g., deionized water) to form a negative electrode slurry, and the negative electrode slurry is applied onto a negative electrode current collector. After undergoing processes such as drying and cold pressing, the negative electrode pieces can be obtained.

[0153] In some embodiments of the present application, the mass proportion of the polymer in the negative electrode piece is 1% to 3%, for example, 1.2% to 2.8%, 1.5% to 2.5%, 1.8% to 2.2%, 2% to 2.2%, etc., based on the total mass of the negative electrode active material, which can reduce shedding of the negative electrode piece and thereby improve the cycle performance of the battery containing it.

[0154] In a fifth aspect of the present application, there is provided a battery including the separator film of the third aspect and / or the pole piece of the fourth aspect, whereby the battery has excellent safety performance.

[0155] A typical battery consists of positive and negative electrodes, an electrolyte, and a separator film. During the charge and discharge process, active ions are inserted and removed between the positive and negative electrodes. The electrolyte serves to conduct ions between the positive and negative electrodes. The separator film, located between the positive and negative electrodes, primarily serves to prevent short circuits between the positive and negative electrodes while allowing ions to pass through.

[0156] The present application does not specifically limit the type of electrolyte, which can be selected according to needs. For example, the electrolyte may be in a liquid state, a gel state, or a completely solid state.

[0157] In some embodiments of the present application, the electrolyte employs an electrolytic solution, which includes an electrolyte salt and a solvent.

[0158] In some embodiments of the present application, when the battery is a lithium-ion battery, the electrolyte salt may include at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium bisoxalatoborate, lithium difluorobisoxalatophosphate, or lithium tetrafluorooxalatophosphate.

[0159] In some embodiments of the present application, when the battery is a sodium-ion battery, the electrolyte sodium salt may include at least one of sodium hexafluorophosphate, sodium difluoro(oxalato)borate, sodium tetrafluoroborate, sodium bis(oxalato)borate, sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethanesulfonate, or sodium bis(trifluoromethylsulfonyl)imide.

[0160] In some embodiments of the present application, the solvent may include 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, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, or diethyl sulfone.

[0161] In some embodiments of the present application, the electrolyte solution optionally further contains additives. For example, the additives may include a negative electrode film-forming additive, a positive electrode film-forming additive, or an additive that can improve certain battery performance, such as an additive that improves the overcharge performance of the battery or an additive that improves the high-temperature or low-temperature performance of the battery.

[0162] In some embodiments, the positive electrode strips, negative electrode strips, and separator film can be fabricated into an electrode assembly by a winding or lamination process.

[0163] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and electrolyte.

[0164] In some embodiments, the exterior packaging of the secondary battery may be a hard casing, such as a hard plastic casing, an aluminum casing, a steel casing, etc. The exterior packaging of the secondary battery may also be a pouch, such as a bag-type pouch. The pouch may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0165] The present application does not particularly limit the shape of the battery, which may be cylindrical, prismatic, or any other shape. For example, Figure 1 illustrates a battery 1 having a prismatic structure as an example.

[0166] In some embodiments, referring to FIG. 2 , the outer packaging may include a casing 11 and a cover plate 13. The casing 11 includes a base plate and a side plate connected to the base plate, which together form a surrounding accommodating cavity. The casing 11 has an opening communicating with the accommodating cavity, and the cover plate 13 can close the opening to close the accommodating cavity. The positive electrode piece, the negative electrode piece, and the separator film can be formed into an electrode assembly 12 by a winding process or a lamination process. The electrode assembly 12 is sealed in the accommodating cavity. An electrolyte is impregnated into the electrode assembly 12. The number of electrode assemblies 12 included in the battery 1 may be one or more, and can be selected by those skilled in the art according to specific actual needs.

[0167] In some embodiments, the batteries can be assembled into a battery module, and the number of batteries included in the battery module can be one or more, with the specific number being selectable by those skilled in the art depending on the application and capacity of the battery module.

[0168] 3 shows a battery module 2 as an example. Referring to FIG. 3, in the battery module 2, the plurality of batteries 1 may be arranged in order along the length of the battery module 2. Of course, they may be arranged in any other manner. Furthermore, the plurality of batteries 1 may be fixed with fastening members.

[0169] Optionally, the battery module 2 may further include an exterior casing having an accommodating space, and the plurality of batteries 1 are accommodated in the accommodating space.

[0170] In some embodiments, the battery modules can also be assembled into a battery pack, and 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.

[0171] 4 and 5 show a battery pack 3 as an example. Referring to FIGS. 4 and 5, the battery pack 3 may include a battery box and a plurality of battery modules 2 installed in the battery box. The battery box includes an upper case 31 and a lower case 32, and the upper case 31 is attached to the lower case 32 as a lid, forming an enclosed space for accommodating the battery modules 2. The plurality of battery modules 2 may be arranged in any desired position in the battery box.

[0172] The present application also provides an electric device including at least one of the secondary battery, battery module, or battery pack provided by the present application. The secondary battery, battery module, or battery pack may be used as a power source for the electric device or as an energy storage unit for the electric device. The electric device includes, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc.

[0173] The electric device can be selected as a secondary battery, a battery module or a battery pack according to the needs of the use.

[0174] 6 shows an example of an electric device, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the electric device's need for high power and high energy density from secondary batteries, a battery pack or a battery module can be employed.

[0175] As another example, the device may be a mobile phone, a tablet, a laptop, etc. Such devices are typically required to be lightweight and thin, and may employ a battery as a power source.

[0176] The following examples are provided for illustrative purposes only and are not intended to limit the scope of the present application. Unless specific techniques or conditions are described in the examples, they may be performed in accordance with techniques or conditions described in technical documents or in accordance with the product instructions. Unless the manufacturer of the reagents or equipment used is specified, they may be commercially available products.

[0177] Preparation of the first polymer emulsion Manufacturing example A1 The first polymerizable monomer, methyl acrylate, the second polymerizable monomer, acrylic acid, and the third polymerizable monomer, acrylamide (the mass ratio of the first polymerizable monomer / second polymerizable monomer to the third polymerizable monomer was 90:5:5) were weighed and mixed uniformly. A 5000 mL four-neck flask equipped with a mechanical stirrer, thermometer, and condenser was charged with 1000 g of the mixed monomers, 30 g of sodium dodecyl sulfate emulsifier, 10 g of ammonium persulfate initiator, and 1200 g of deionized water, and the mixture was emulsified for 30 minutes with high-speed stirring. Under nitrogen gas protection, the mixture was heated to 75°C and reacted for 4 hours. After that, the temperature was lowered to below 40°C, the pH was adjusted to neutral, and the material was filtered to remove the material. This yielded the first polymer emulsion A1.

[0178] Production Examples A2 to A21: First polymer emulsions A2 to A21 were obtained based on Production Example A1 by adjusting the type and mass ratio of monomers. The details are as shown in Table 1.

[0179] [Table 1]

[0180] A21: A first polymerizable monomer, methyl acrylate, a second polymerizable monomer, acrylic acid, a third polymerizable monomer, acrylamide, and a fourth polymerizable monomer, acrylonitrile (the mass ratio of the first polymerizable monomer, the second polymerizable monomer, the third polymerizable monomer, and the fourth polymerizable monomer is 70:10:10:10) are weighed out, and the rest is the same as the manufacturing method of A1.

[0181] Preparation of the second polymer emulsion Manufacturing example B1 The first polymerization monomer, methyl acrylate, the third polymerization monomer, acrylamide, and the fourth polymerization monomer, acrylonitrile, were weighed out and mixed uniformly in a weight ratio of 80:10:10 for the three monomers. A 1000 mL four-neck flask equipped with a mechanical stirrer, thermometer, and condenser was charged with 200 g of the mixed monomers, 6 g of sodium dodecyl sulfate emulsifier, 2 g of ammonium persulfate initiator, and 300 g of deionized water. The mixture was emulsified for 30 minutes with high-speed stirring. Under nitrogen gas protection, the mixture was heated to 75°C and reacted for 4 hours. The temperature was then lowered to below 40°C, the pH was adjusted to neutral, and the material was filtered to obtain the second polymer emulsion B1.

[0182] Production Examples B2 to B20: Based on Production Example B1, the types and mass ratios of monomers were adjusted to obtain second polymer emulsions B2 to B20, the details of which are shown in Table 2.

[0183] [Table 2]

[0184] Example 1 (1) Polymer manufacturing According to a weight ratio of the first polymer to the second polymer of 1:1, the first polymer emulsion A1 and the second polymer emulsion B2 were weighed, mixed uniformly, and stirred. Then, the mixture was spray-dried under the following conditions: intake air temperature 110°C, exhaust air temperature 50°C, and air pressure 0.5 kPa to obtain a polymer.

[0185] (2) Separator film manufacturing A commercially available PE microporous film (from Zhuoga Electronics Technology Co., Ltd.) with a thickness of 7 μm and an average pore size of 80 nm was used as the substrate film. The polymer prepared as described above was stirred with deionized water to uniformly mix, yielding a slurry (solid content 20%). The slurry was spray-coated onto two surfaces of the substrate film and dried to remove the solvent, resulting in a coating density of 1.5 g / m2 of the coating composition on the substrate. 2 Thus, a separator film was obtained.

[0186] (3) Manufacturing of positive electrode pieces Polyvinylidene fluoride (PVDF), lithium iron phosphate (LFP), conductive carbon black, and N-methylpyrrolidone (NMP) were thoroughly stirred and homogeneously mixed in a mass ratio of 1.2:58.38:0.42:40 to prepare a positive electrode slurry. The positive electrode slurry was applied to a positive electrode current collector aluminum foil at a concentration of 200 g / m. 2 After uniformly applying the paste at a loading amount of 1000 ppm, the paste was dried, cold pressed, and cut into slits to obtain positive electrode pieces.

[0187] (4) Manufacturing of negative electrode pieces Artificial graphite, conductive agent acetylene black, adhesive styrene butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC-Na) were added to deionized water in a mass ratio of 96.2:1.0:1.6:1.2, and then thoroughly stirred to homogeneously mix, producing anode slurry (solid content 63%). The anode slurry was applied to anode current collector copper foil at a rate of 98 g / m. 2 After coating with a load of 1000 ppm, the coating was dried, cold pressed, and cut into slits to obtain negative electrode pieces.

[0188] (5) Electrolyte production Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed at 25°C in a volume ratio of 1:1:1 to obtain a mixed solvent. LiPF6 was then dissolved in the mixed solvent to obtain an electrolyte solution with a LiPF6 concentration of 1 mol / L.

[0189] (6) Secondary battery manufacturing The positive electrode piece, separator film, and negative electrode piece are stacked in this order, wound, and cold-pressed (during which the separator film and the electrode piece are bonded together) to obtain a battery core. The battery core is then placed in an outer package, and the above-prepared electrolyte solution is added. After undergoing processes such as sealing, standing, chemical conversion, and aging, a secondary battery is obtained.

[0190] The manufacturing methods of the lithium ion batteries of Examples 2 to 60 and Comparative Examples 1 to 14 are the same as those of Examples 2 to 60, except that the types and mass ratios of the first polymer emulsion, the second polymer emulsion, the dispersant, and the butadiene-based polymer are adjusted based on Example 1 to obtain the polymers of Examples 2 to 60 and Comparative Examples 1 to 14, as shown in Table 3.

[0191] [Table 3(1)] [Table 3(2)] [Table 3(3)] [Table 3(4)]

[0192] The particle size and glass transition temperature of the polymers obtained in Examples 1 to 60 and Comparative Examples 1 to 14, as well as the cold pressing adhesive strength between the pole pieces and the separator film in the obtained batteries, the hardness of the battery core, and the cycle performance of the batteries were characterized, and the characterization results are shown in Table 4.

[0193] Performance Test (1) Polymer particle size test The test was performed using a laser particle sizer (Malvern 3000, MasterSizer 3000) with a helium-neon red light source as the main light source. 1 g of the sample to be measured was placed in a clean beaker, 20 mL of deionized water was added, and the mixture was sonicated at 53 kHz / 120 W for 5 minutes to ensure complete dispersion of the sample. The laser particle sizer was then turned on, the optical path was cleaned, and the background was automatically tested. The sonicated solution to be measured was stirred to ensure uniform dispersion, and then added to the sample cell as needed, and particle size measurement was initiated. The measurement results could then be read from the instrument.

[0194] (2) Glass transition temperature test A sample of 6±0.05 mg was weighed and placed in an Al crucible, shaken evenly, and then covered with a lid. The test was performed using a Netzsch DSC 3500 Sirius measuring instrument in a nitrogen atmosphere with a purge gas flow rate of 50 mL / min and a protective gas flow rate of 100 mL / min. The heating conditions were a heating rate of 10°C / min and a temperature range of -70 to 200°C.

[0195] (3) Cold pressure adhesion test step The negative electrode piece and separator film were placed together in a hot pressure welding machine. The machine parameters were set to a temperature of 25°C, a pressure of 7T, and a time of 15 seconds to produce a bonded separator film / negative electrode piece sample. The separator film / negative electrode piece sample was then cut into a 150mm x 20mm rectangular spline. One side of the rectangular spline pole piece was attached to a steel plate with double-sided tape, and the separator film and pole piece were separated at one end of the rectangular spline by a length of 2cm along the length to obtain a test sample.

[0196] The steel plate was held horizontally and fixed in the lower clamp of a universal testing machine (Xieqiang Tester Manufacturing (Shanghai) Co., Ltd., model CTM2100), and the peeled end of the separator film was fixed in the upper clamp of the universal testing machine and connected to a tensile machine. The test conditions were set to a pulling speed of 20 mm / min and a horizontal pulling of 10 cm. After the tensile force stabilized, the tensile force value was recorded, and the ratio of the tensile force value to the sample width was used to determine the adhesion strength between the separator film and the pole piece.

[0197] (4) Battery core hardness test steps The obtained battery core was placed on a table with both ends horizontal, the width of the openwork portion in the middle was fixed at 12 cm, the battery cell was placed naturally horizontal, and the width of the deviation of the center position of the battery core from the horizontal reference line was measured to evaluate the hardness of the battery core. The greater the width of the deviation of the center position of the battery core from the horizontal reference line, the poorer the hardness of the battery core.

[0198] (5) Battery cycle performance test steps At 25°C, the prepared battery was charged to 3.65V at a constant current of 1 / 3C, and then charged at a constant voltage of 3.65V until the current reached 0.05C. After leaving the battery for 5 minutes, it was discharged to 2.5V at a constant current of 1 / 3C. The discharge capacity was recorded as the initial capacity C0. The above steps were repeated for the same battery as above, and the discharge capacity C of the battery after n cycles was recorded. n At the same time, the battery capacity retention rate P after each cycle is recorded. n =(C n / C0) × 100%. In other words, the difference in cycle performance can be expressed by the battery capacity retention rate at 500 cycles.

[0199] [Table 4(1)] [Table 4(2)]

[0200] As can be seen from Table 4, the polymers of Examples 1 to 60 all have two glass transition temperatures, and the cold pressure adhesion between the separator film and the negative electrode piece, the hardness of the battery core, and the battery capacity retention rate are all higher than those of Comparative Examples 1 to 14. This shows that when the polymers of the present application are used in the separator film, cold pressure adhesion between the separator film and the electrode piece can be achieved, and the adhesion strength is appropriate, thereby improving the cycle performance of the battery.

[0201] In the description herein, references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples" mean that the specific features, structures, materials, or characteristics described in combination with the embodiment or example are included in at least one embodiment or example of the present application. In the description herein, descriptive expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, those skilled in the art may combine different embodiments or examples and features of different embodiments or examples described herein without mutually contradicting each other.

[0202] Although the embodiments of the present application have been shown and described above, the above embodiments are illustrative and should not be understood as limiting the present application, and it will be understood that those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present application.

Claims

1. A polymer comprising a first organic polymer and a second organic polymer, wherein the polymerized monomers of the first organic polymer comprise a first polymerized monomer, a second polymerized monomer, and a third polymerized monomer, and the polymerized monomers of the second organic polymer comprise the first polymerized monomer, the third polymerized monomer, and a fourth polymerized monomer, and the structure of the first polymerized monomer comprises: 【Chemistry 1】 Among them, R １ contains a hydrogen atom or an alkyl group of 1 to 18 carbon atoms, and R ２ comprises an alkyl group of 1 to 18 carbon atoms; The structure of the second polymerized monomer comprises: 【Chemistry 2】 Among them, R ３ contains a hydrogen atom, a substituted or unsubstituted alkyl group of 1 to 18 carbon atoms, The structure of the third polymerized monomer comprises: 【Transformation 3】 Among them, R ４ contains a hydrogen atom or an alkyl group of 1 to 6 carbon atoms, and R ５ contains a hydrogen atom, a hydroxy-substituted alkyl group of 1 to 6 carbon atoms, or an alkoxy group of 1 to 6 carbon atoms; The structure of the fourth polymerized monomer comprises: 【Chemistry 4】 Among them, R ６ contains a hydrogen atom or an alkyl group of 1 to 6 carbon atoms; polymer.

2. the mass ratio of the first organic polymer to the second organic polymer is 1:(0.1-10), optionally 1:(0.5-3); The polymer of claim 1.

3. In the polymerized monomers of the first organic polymer, the mass ratio of the first polymerized monomer to the second polymerized monomer to the third polymerized monomer is 1:0.05-0.5:0.05-0.5, optionally 1:0.056-0.5:0.056-0.5; The polymer according to claim 1 or 2.

4. In the polymerized monomers of the second organic polymer, the mass ratio of the first polymerized monomer to the third polymerized monomer to the fourth polymerized monomer is 1:0.05-0.5:0.05-0.5, optionally 1:0.056-0.5:0.056-0.5; The polymer according to any one of claims 1 to 3.

5. the first polymerizable monomer comprises at least one of methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, n-propyl acrylate, cyclohexyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, ethyl 2-hydroxyacrylate, 2-hydroxypropyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, lauryl methacrylate, 2-hydroxyethyl methacrylate, or 2-hydroxypropyl methacrylate; The polymer according to any one of claims 1 to 4.

6. the second polymerizable monomer comprises at least one of acrylic acid, methacrylic acid, crotonic acid, or heptenoic acid; The polymer according to any one of claims 1 to 5.

7. the third polymerized monomer comprises at least one of acrylamide, N-methylolacrylamide, or N-butoxymethylacrylamide; The polymer according to any one of claims 1 to 6.

8. the fourth polymerizable monomer comprises at least one of acrylonitrile or methacrylonitrile; The polymer according to any one of claims 1 to 7.

9. further comprising a dispersing agent comprising at least one of sodium polystyrene sulfonate, sodium gluconate, sodium polyacrylate, sodium polymethacrylate, sodium polyphosphate, sodium lignosulfonate, or sodium polycarboxylate; The polymer according to any one of claims 1 to 8.

10. the number average molecular weight of the dispersant is from 1,000 to 100,000, optionally from 5,000 to 80,000; The polymer of claim 9.

11. the mass ratio of the first organic polymer to the second organic polymer to the dispersant is 1:0.1-10:0.01-2, optionally 1:0.5-3:0.05-1.5; 11. The polymer of claim 9 or 10.

12. further comprising a butadiene-based polymer, The polymer according to any one of claims 1 to 11.

13. the butadiene-based polymer has a glass transition temperature of 20°C or less, optionally 15°C or less; The polymer of claim 12.

14. The butadiene-based polymer has a volume average particle diameter Dv50 of 100 nm to 300 nm, optionally 120 nm to 250 nm; 14. The polymer of claim 12 or 13.

15. the viscosity of the butadiene-based polymer at 25°C is from 10 mPa·s to 300 mPa·s, optionally from 80 mPa·s to 200 mPa·s; The polymer according to any one of claims 12 to 14.

16. The butadiene-based polymer comprises at least one of polybutadiene, a styrene / butadiene copolymer, or an acrylonitrile / butadiene copolymer. The polymer according to any one of claims 12 to 15.

17. a mass ratio of the first organic polymer to the second organic polymer to the butadiene-based polymer is 1:0.1-10:0.1-10, optionally 1:0.5-3:0.5-8; The polymer according to any one of claims 12 to 16.

18. the polymer has a first glass transition temperature less than or equal to 25°C and a second glass transition temperature greater than 25°C; A polymer according to any one of claims 1 to 17.

19. the first glass transition temperature is from −80° C. to 25° C., optionally from −60° C. to 25° C.; 19. The polymer of claim 18.

20. the second glass transition temperature is from 26°C to 100°C, optionally from 26°C to 90°C; 20. The polymer of claim 18 or 19.

21. the polymer has a volume average particle size Dv50 of 1 μm to 15 μm, optionally 5 μm to 10 μm; and / or the number particle size distribution Dn10 of the polymer is from 1 μm to 5 μm, optionally from 1 μm to 3 μm; A polymer according to any one of claims 1 to 20.

22. A method for producing a polymer according to any one of claims 1 to 21, comprising the steps of: mixing together water, an emulsifier, an initiator, a first organic monomer, a second polymerizable monomer, and a third polymerizable monomer to obtain a first polymer emulsion; mixing together water, an emulsifier, an initiator, a first polymerizable monomer, a third polymerizable monomer, and a fourth polymerizable monomer to obtain a second polymer emulsion; mixing the first polymer emulsion with the second polymer emulsion to obtain a polymer; method.

23. a dispersant and / or a butadiene-based polymer is further added during the process of mixing the first polymer emulsion and the second polymer emulsion; 23. The method of claim 22.

24. The polymer comprises a polymer according to any one of claims 1 to 21 or a polymer produced by employing the method according to claim 22 or 23. Separator film.

25. The polymer comprises a polymer according to any one of claims 1 to 21 or a polymer produced by employing the method according to claim 22 or 23. Pole piece.

26. 26. A separator film according to claim 24 and / or a pole piece according to claim 25. battery.

27. 27. A battery comprising the battery of claim 26. Electrical equipment.

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