Composite material and preparation method therefor, separator, electrode sheet, battery and electric device

Abstract

Disclosed in the present application are a composite material and a preparation method therefor, a separator, an electrode sheet, a battery and an electric device. The composite material comprises an acrylate polymer and a dispersing agent, and has a Vicat softening point of 5-60ºC. Therefore, when being used for a separator, the composite material can achieve cold press bonding between the separator and an electrode sheet and improve the cycle performance of a battery.

Description

Composite material and preparation method thereof, isolation film, pole piece, battery and electrical device

[0001] Priority information

[0002] This application claims priority and benefits of patent application 202410020571.5 filed with the State Intellectual Property Office of China on January 5, 2024, and the entire text of which is incorporated herein by reference. Technical Field

[0003] The present application belongs to the field of batteries, and specifically relates to a composite material and a preparation method thereof, an isolation membrane, an electrode, a battery and an electrical device. Background Art

[0004] Secondary batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, but are also widely used in electric vehicles such as electric bicycles, electric motorcycles, electric cars, as well as in military equipment, aerospace and other fields.

[0005] Currently, the separator adhesive in batteries uses polyvinylidene fluoride. Polyvinylidene fluoride is coated on the separator, wound around the electrode, and then heated and pressed to bond the electrode to the separator, increasing the hardness of the battery cell and maintaining the consistency of the cell thickness. However, after hot pressing, the adhesion between the electrode and the separator is too strong, causing the positive and / or negative electrode sheets to easily release from the mold during battery cycling, thereby reducing the battery's cycling performance.

[0006] Summary of the Invention

[0007] In view of the technical problems existing in the background technology, the present application provides a composite material, which aims to achieve cold pressing bonding between the isolation membrane and the pole piece, thereby improving the cycle performance of the battery.

[0008] In order to achieve the above-mentioned object, one aspect of the present application provides a composite material, which includes: an acrylic polymer and a dispersant, and the Vicat softening point of the composite material is 5°C-60°C.

[0009] Therefore, when the composite material is used for an isolation membrane, at room temperature, the composite material has no adhesiveness under low pressure, which facilitates the winding and unwinding of the isolation membrane. When the isolation membrane is wound with the positive and negative pole pieces and then subjected to a cold pressing process, the composite material can fully penetrate into the pores of the positive and negative pole pieces and the isolation membrane, so that a strong mechanical linkage occurs between the composite material and the pole pieces. At the same time, the intermolecular force between the composite material and the pole pieces will also be enhanced, realizing cold pressing bonding between the composite material and the pole pieces, and the bonding force between the pole pieces and the isolation membrane is appropriate, thereby improving the cycle performance of the battery.

[0010] In some embodiments of the present application, the Vicat softening point of the composite material is 10° C.-50° C. This can improve the cycle performance of the battery.

[0011] In some embodiments of the present application, the acrylic polymer monomers include a first monomer, a second monomer and a third monomer.

[0012] The structure of the first monomer includes:

[0013] wherein R1 comprises a hydrogen atom or a hydroxyl group 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 which is substituted or unsubstituted by a hydroxyl group,

[0014] The structure of the second monomer includes:

[0015] wherein R3 and R4 independently include a hydrogen atom, a phenyl group, or an alkyl group of 1 to 20 carbon atoms;

[0016] The structure of the third monomer includes:

[0017] Wherein, R5 comprises a hydrogen atom or an alkyl group of 1 to 6 carbon atoms, and R6 comprises a hydrogen atom, an alkyl group of 1 to 6 carbon atoms substituted with a hydroxyl group, or an alkoxy group of 1 to 6 carbon atoms. This can improve the cold press bonding strength between the isolation film and the electrode.

[0018] In some embodiments of the present application, the first monomer includes at least one of ethyl acrylate, n-butyl acrylate, n-propyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, cyclohexyl acrylate, isooctyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, methyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, lauryl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, acrylic acid, methacrylic acid, butenoic acid, or heptenoic acid. Thus, by using the above-mentioned first monomer, the Vicat softening point temperature of the composite material can be adjusted, the anti-swelling ability of the composite material can be improved, and the molecular interaction between the composite material and the electrode can be improved.

[0019] In some embodiments of the present application, the second monomer includes at least one of styrene, pentene, hexene, heptene, octene, nonene, decene, dodecene, tridecene, tetradecene, pentadecene, or hexadecene. This can improve the cold press adhesion between the separator and the negative electrode.

[0020] In some embodiments of the present application, the third monomer includes at least one of acrylamide, methacrylamide, N-methylol acrylamide, N-butyl acrylamide, N-butoxymethyl acrylamide, and N-(N-butoxymethyl) acrylamide. Thus, the use of the third monomer can adjust the molecular weight of the acrylic polymer and enhance the molecular interaction between the composite material and the electrode. Thus, when the composite material is used in a separator, the cold press adhesion between the separator and the electrode can be enhanced, thereby improving the battery's cycling performance.

[0021] In some embodiments of the present application, the mass ratio of the first monomer, the second monomer, and the third monomer is 100:(10-30):(1-20), and can be optionally 100:(15-25):(5-15). Thus, the present application controls the first monomer, the second monomer, and the third monomer for preparing the acrylic polymer to be within the above-mentioned mixing ratio, which can reduce the Vicat softening point temperature of the acrylic polymer and increase the molecular force between the composite material and the electrode. When the resulting composite material is used in an isolation membrane, pressure is applied at room temperature, and the composite material can be well infiltrated into the pores of the electrode and the isolation membrane, resulting in a strong mechanical linkage between the composite material and the electrode. At the same time, the intermolecular force between the composite material and the electrode will also be enhanced, thereby improving the cold pressing bonding strength between the electrode and the isolation membrane.

[0022] In some embodiments of the present application, the mass ratio of the acrylic emulsion to the dispersant is 100:(1-15), and can optionally be 100:(5-12). Thus, when this composite material is used in a separator, it can improve the cold-pressed bonding strength between the separator and the electrode, thereby enhancing the cycle performance of the battery.

[0023] In some embodiments of the present application, the dispersant includes at least one of polyvinyl pyrrolidone, polyacrylamide, sodium polystyrene sulfonate, polyacrylic acid, sodium polyacrylate, or sodium polymethacrylate. Thus, when this composite material is used in a separator, it can enhance the cold-pressed adhesion between the separator and the electrode, improving the battery's cycling performance.

[0024] In some embodiments of the present application, the number average molecular weight of the dispersant is 100-100000, and can be optionally 5000-80000. Thus, when the composite material is used in a separator, the cold press bonding strength between the separator and the electrode can be improved, thereby improving the cycle performance of the battery.

[0025] In some embodiments of the present application, the composite material further includes a butadiene polymer, including at least one of polybutadiene, styrene / butadiene copolymer, acrylonitrile / butadiene copolymer, butadiene-isoprene copolymer, or butadiene-propylene copolymer. Thus, when this composite material is used in a separator, it can enhance the cold-press adhesion between the separator and the electrode, improving the battery's cycling performance.

[0026] In some embodiments of the present application, the mass ratio of the acrylic polymer to the dispersant and the butadiene polymer is 100:(1-15):(1-100), and can optionally be 100:(5-12):(5-50). Thus, when this composite material is used in a separator, it can improve the cold-pressed bonding strength between the separator and the electrode, thereby enhancing the cycle performance of the battery.

[0027] In some embodiments of the present application, the glass transition temperature of the butadiene polymer is less than or equal to 20° C., and may be less than or equal to 15° C. Therefore, when the composite material is used in a separator, the cold press bonding strength between the separator and the electrode can be improved, thereby improving the cycle performance of the battery.

[0028] In some embodiments of the present application, the Dv50 of the butadiene polymer is 100nm-300nm, optionally 150nm-250nm. Thus, when the composite material is used in a separator, the cold press bonding strength between the separator and the electrode can be improved, thereby improving the cycle performance of the battery.

[0029] In some embodiments of the present application, the butadiene polymer has a viscosity at 25°C of 10mPa·s to 300mPa·s, optionally 80mPa·s to 200mPa·s. Therefore, when this composite material is used in a separator, it can enhance the cold-pressed bonding strength between the separator and the electrode, improving the battery's cycling performance.

[0030] In some embodiments of the present application, the composite material has a volume average particle size Dv50 of 2 μm to 20 μm, optionally 5 μm to 15 μm. Thus, when used on a separator, the composite material can prevent pore blockage in the separator, improve the permeability of active ions through the separator, and mitigate the problem of forming a thick coating on the separator, which can affect the energy density of the subsequently manufactured battery.

[0031] A second aspect of the present application provides a method for preparing the above-mentioned composite material, comprising: mixing an acrylic polymer with a dispersant to obtain a composite material, wherein the composite material has a Vicat softening point of 5°C-60°C.

[0032] Thus, the above-mentioned composite material with excellent cold-pressing adhesion can be prepared by this method. When the composite material is used for the separator, the cold-pressing adhesion between the separator and the pole piece can be improved, thereby improving the cycle performance of the battery.

[0033] In a third aspect, the present application provides a separator comprising the composite material or a composite material obtained by the method described above. This allows for cold-press bonding of the separator to the electrode, with suitable adhesion between the separator and the electrode, thereby improving the cycling performance of the battery.

[0034] In a fourth aspect, the present application provides a pole piece comprising the composite material or the composite material obtained by the method described above, thereby enabling cold-press bonding of the separator to the pole piece, with suitable adhesion between the separator and the pole piece, thereby improving the cycle performance of the battery.

[0035] In a fifth aspect, the present application provides a battery comprising the aforementioned separator and / or the aforementioned electrode, thereby providing the battery with excellent cycle performance.

[0036] In a sixth aspect, the present application provides an electrical device, comprising the above-mentioned battery, so that the electrical device has excellent cycle performance.

[0037] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the optional embodiments below. The accompanying drawings are provided for illustration purposes only and are not to be considered as limiting the present application. The same reference numerals are used throughout the drawings to denote the same components. In the drawings:

[0039] FIG1 is a schematic diagram of a battery according to one embodiment of the present application.

[0040] FIG. 2 is an exploded view of the battery according to one embodiment of the present application shown in FIG. 1 .

[0041] FIG3 is a schematic diagram of a battery module according to an embodiment of the present application.

[0042] FIG4 is a schematic diagram of a battery pack according to an embodiment of the present application.

[0043] FIG. 5 is an exploded view of the battery pack shown in FIG. 4 according to an embodiment of the present application.

[0044] FIG6 is a schematic diagram of an electrical device using a battery as a power source according to an embodiment of the present application.

[0045] Explanation of reference numerals: 1 battery cell; 11 housing; 12 electrode assembly; 13 cover plate; 2 battery module; 3 battery pack; 31 upper case; 32 lower case. DETAILED DESCRIPTION

[0046] The following embodiments of the technical solution of the present application are described in detail. The following embodiments are only used to more clearly illustrate the technical solution of the present application and are therefore only used as examples and are not intended to limit the scope of protection of the present application.

[0047] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0048] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0049] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0050] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0051] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, and may optionally be performed sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may 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.

[0052] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0053] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: 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).

[0054] Currently, market developments indicate that secondary batteries are becoming increasingly widely used. They are not only used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, but are also widely used in electric vehicles like electric bicycles, electric motorcycles, and electric vehicles, as well as in military equipment and aerospace. As the application of secondary batteries continues to expand, market demand is also growing.

[0055] The battery cell includes a positive electrode sheet, a negative electrode sheet, and a separator. The battery cell has a certain hardness. That is, because the positive and negative electrode sheets and the separator are bonded together and support each other, a structure with a certain thickness is formed. A structure with a certain thickness has a certain hardness. The negative electrode will expand during the charge and discharge process. If the bonding force is weak, a gap will form between the positive and negative electrode sheets and the separator. The positive and negative electrode sheets and the separator cannot adhere to each other and support each other, causing the battery cell to become loose and the hardness to decrease. At this point, the battery's cycle performance deteriorates, which directly leads to a shortened battery life. Electric vehicles need to frequently replace batteries, and consumers' costs for electric vehicles increase.

[0056] A tight fit between the separator and the electrode can improve the battery's discharge capacity, reduce internal resistance, minimize polarization loss, extend the battery's cycle life, and increase the utilization rate of the secondary battery. The adhesive commonly used on existing separators is polyvinylidene fluoride, which requires a hot pressing process (heating during the pressing process after the separator and electrode are stacked) to achieve a tight bond between the separator and the electrode.

[0057] The composite material of the present application includes an acrylic polymer and a dispersant. The addition of the dispersant can not only adjust the Vicat softening point of the composite material, but also facilitate the granulation of the composite material, and control the Vicat softening point of the composite material to be 5°C-60°C. When the composite material is used for an isolating membrane, at room temperature, the composite material has no adhesion under low pressure, which facilitates the winding and unwinding of the isolating membrane. When the isolating membrane is wound with the positive and negative pole pieces and then subjected to a cold pressing process (no heating is performed during the pressing process after the isolating membrane and the pole piece are stacked), the composite material can fully penetrate into the pores of the positive and negative pole pieces and the isolating membrane, so that a strong mechanical linkage effect occurs between the composite material and the pole piece. At the same time, the intermolecular force between the composite material and the pole piece will also be enhanced, realizing cold pressing bonding between the composite material and the pole piece, and the bonding force between the pole piece and the isolating membrane is appropriate, thereby improving the cycle performance of the battery.

[0058] The composite materials disclosed in the embodiments of the present application are suitable for batteries, and the batteries disclosed in the embodiments of the present application can be used in electrical devices that use batteries as power sources or various energy storage systems that use batteries as energy storage elements. Electrical devices may include, but are not limited to, mobile phones, tablets, laptops, electric toys, power tools, battery cars, electric cars, ships, spacecraft, and the like. Among them, electric toys may include fixed or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, and the like, and spacecraft may include airplanes, rockets, space shuttles, and spacecraft, and the like.

[0059] In a first aspect, the present application provides a composite material, comprising: an acrylic polymer and a dispersant, wherein the composite material has a Vicat softening point of 5°C-60°C.

[0060] In this application, the Vicat softening point refers to the temperature at which the material begins to soften and loses its original strength and rigidity. The higher the Vicat softening point, the better the dimensional stability of the material when heated, the smaller the thermal deformation, that is, the better the heat deformation resistance and the greater the rigidity; the lower the Vicat softening point, the easier it is for the ambient temperature to exceed the Vicat softening point of the material, the greater the heat deformation capacity of the material, and the easier it is to soften. The Vicat softening point test can be carried out using instruments and methods known in the art. For example, it can be based on ISO 306:2013 Determination of Vicat softening temperature of thermoplastic materials, and the test method is A50 method. The equipment used is the WKT-VST300 heat deformation softening point temperature tester of Jessain Company for testing, with a load of 10N, a heating rate of 50℃ / h, and a sample thickness of 5mm.

[0061] When the Vicat softening point of the composite material is higher, the composite material still has a certain strength and stiffness, and the dimensional stability of the composite material is better. During cold pressing, it is not easy to penetrate into the pores of the electrode and the isolation membrane, so that the mechanical chain effect and the intermolecular force will be weakened, affecting the cold pressing bonding strength; when the Vicat softening point of the composite material is lower, the composite material is easier to deform and soften, and can more easily penetrate into the pores of the electrode and the isolation membrane during cold pressing, thereby improving the mechanical chain effect and the intermolecular force, thereby achieving cold pressing bonding between the electrode and the isolation membrane.

[0062] The composite material of the present application includes an acrylic polymer and a dispersant. The addition of the dispersant can not only adjust the Vicat softening point of the composite material, but also facilitate the granulation of the composite material, and control the Vicat softening point of the composite material to 5°C-60°C. When the composite material is used for an isolating membrane, after being wound with the positive and negative pole pieces and subjected to a cold pressing process, the composite material can penetrate well into the pores of the pole pieces and the isolating membrane, so that a strong mechanical linkage effect occurs between the composite material and the pole pieces. At the same time, the intermolecular force between the composite material and the pole pieces will also be enhanced, thereby realizing cold pressing bonding between the isolating membrane and the pole pieces. At the same time, the bonding force between the pole pieces and the isolating membrane is appropriate, thereby improving the cycle performance of the battery.

[0063] In some embodiments of the present application, the Vicat softening point of the composite material is 5°C-60°C, for example, 7°C-58°C, 10°C-55°C, 12°C-53°C, 15°C-50°C, 20°C-45°C, 25°C-40°C, 30°C-35°C, etc. In other embodiments of the present application, the Vicat softening point of the composite material is 10°C-50°C. Therefore, when the Vicat softening point of the composite material of the present application meets the above conditions, when the composite material is used for a separator, after being wound with the positive and negative electrode sheets and subjected to a cold pressing process, the composite material can penetrate well into the pores of the electrode sheets and the separator, so that a strong mechanical linkage effect occurs between the composite material and the electrode sheets. At the same time, the intermolecular force between the composite material and the electrode sheets is also enhanced, thereby achieving cold pressing bonding between the separator and the electrode sheets. At the same time, the bonding force between the electrode sheets and the separator is appropriate, thereby improving the cycle performance of the battery.

[0064] In some embodiments of the present application, the acrylic polymer monomers include a first monomer, a second monomer and a third monomer.

[0065] The structure of the first monomer includes:

[0066] wherein R1 comprises a hydrogen atom or a hydroxyl group 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 which is substituted or unsubstituted by a hydroxyl group,

[0067] The structure of the second monomer includes:

[0068] wherein R3 and R4 independently include a hydrogen atom, a phenyl group, or an alkyl group of 1 to 20 carbon atoms;

[0069] The structure of the third monomer includes:

[0070] Wherein, R5 includes a hydrogen atom or an alkyl group of 1 to 6 carbon atoms, and R6 includes a hydrogen atom, an alkyl group of 1 to 6 carbon atoms substituted with a hydroxyl group, or an alkoxy group of 1 to 6 carbon atoms.

[0071] The polymerization monomers of the acrylic ester polymer include the above-mentioned first monomer, second monomer and third monomer, the first monomer includes an unsaturated ester group or a carboxyl group or a hydroxy ester group, the second monomer includes an olefin group, and the structure of the third monomer includes an unsaturated amide group. By polymerizing the first monomer, the second monomer and the third monomer to prepare the acrylic ester polymer, the adhesion of the acrylic ester polymer can be improved. At the same time, the unsaturated ester group or carboxyl group or hydroxy ester group contained in the first monomer can form a binding force with the functional groups on the electrode and the isolation membrane material, thereby improving the bonding effect between the electrode and the isolation membrane.

[0072] In some embodiments of the present application, the structure of the first monomer includes:

[0073] Among them, R1 includes a hydrogen atom or a hydroxyl group or an alkyl group of 1-18 carbon atoms, R2 includes a hydrogen atom or an alkyl group of 1-18 carbon atoms which is substituted or unsubstituted by a hydroxyl group, and the first monomer includes an unsaturated ester group or a carboxyl group or a hydroxy ester group, which is beneficial to the polymerization of the monomer and at the same time improves the molecular interaction force between the composite material and the electrode. Moreover, as a flexible monomer segment in the molecular chain segment, it can adjust the Vicat softening point of the composite material, thereby helping to adjust the Vicat softening point of the composite material within an appropriate range.

[0074] As an example, an alkyl group with 1-18 carbon atoms can be understood as an alkyl group with 1-18 carbon atoms, such as methyl (-CH3), ethyl (-CH2CH3), n-propyl (-CH2CH2CH3), isopropyl (-CH(CH3)2), n-butyl (-CH2CH2CH2CH3), tert-butyl (-C(CH3)3), n-pentyl (-CH2CH2CH2CH2CH3), n-hexyl (-CH2CH2CH2CH2CH2CH3), etc.

[0075] As an example, an alkyl group with 1-18 carbon atoms substituted by hydroxyl can be understood as an alkyl group with 1-18 carbon atoms in which at least one hydrogen atom is replaced by hydroxyl, such as -CH2OH, -CH2CH2OH, -CH2CH2CH2OH, -CH(CH2OH)2, -CH2CH2CH2CH2OH, -C(CH2OH)3, -CH2CH2CH2CH2CH2OH, etc.

[0076] In some embodiments of the present application, the first monomer includes at least one of ethyl acrylate, n-butyl acrylate, n-propyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, cyclohexyl acrylate, isooctyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, methyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, lauryl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, acrylic acid, methacrylic acid, butenoic acid, or heptenoic acid. Thus, the use of the first monomer described above in the present application can not only increase the molecular interaction between the composite material and the electrode, but also adjust the Vicat softening point of the composite material.

[0077] In some embodiments of the present application, the structure of the second monomer includes:

[0078] R3 comprises a hydrogen atom or an alkyl group of 1-6 carbon atoms, and R4 comprises a hydrogen atom, a phenyl group, or an alkyl group of 1-20 carbon atoms. Thus, the second monomer includes an unsaturated double bond, which facilitates polymerization and improves the bonding strength between the separator and the negative electrode.

[0079] It should be noted that the alkyl group with 1-20 carbon atoms can be understood as an alkyl group with 1-20 carbon atoms, such as methyl (-CH3), ethyl (-CH2CH3), n-propyl (-CH2CH2CH3), isopropyl (-CH(CH3)2), n-butyl (-CH2CH2CH2CH3), tert-butyl (-C(CH3)3), n-pentyl (-CH2CH2CH2CH2CH3), n-hexyl (-CH2CH2CH2CH2CH2CH3), etc.

[0080] In some embodiments of the present application, the second monomer includes at least one of styrene, pentene, hexene, heptene, octene, nonene, decene, dodecene, tridecene, tetradecene, pentadecene, and hexadecene. Thus, the use of the second monomer described herein can adjust the bonding performance between the composite material and the electrode.

[0081] In some embodiments of the present application, the structure of the third monomer includes:

[0082] R4 comprises a hydrogen atom or an alkyl group of 1-6 carbon atoms, and R5 comprises a hydrogen atom, an alkyl group of 1-6 carbon atoms substituted with a hydroxyl group, or an alkoxy group of 1-6 carbon atoms. The inclusion of an unsaturated amide group in the structure of the third monomer not only facilitates polymerization of the monomers but also enhances the intermolecular forces between the electrode and the composite material, thereby improving the cold-pressed adhesion between the composite material and the electrode.

[0083] It should be noted that the alkyl group of 1-6 carbon atoms substituted by hydroxyl groups can be understood as a group in which at least one hydrogen atom on the alkyl group with 1-6 carbon atoms is replaced by a hydroxyl group, for example -CH2OH, -CH2CH2OH, -CH2CH2CH2OH, -CH(CH2OH)2, -CH2CH2CH2CH2OH, -C(CH2OH)3, -CH2CH2CH2CH2CH2OH, etc. At the same time, the alkoxy group of 1-6 carbon atoms substituted by hydroxyl groups can be understood as a group in which at least one hydrogen atom on the alkoxy group with 1-6 carbon atoms is replaced by a hydroxyl group, for example, methoxy (HOCH2O-), ethoxy (OHCH2CH2O-), propoxy (OHCH2CH2CH2O-), etc.

[0084] In some embodiments of the present application, the third monomer includes at least one of acrylamide, methacrylamide, N-methylol acrylamide, N-butyl acrylamide, N-butoxymethyl acrylamide, and N-(N-butoxymethyl) acrylamide. Thus, the use of the third monomer can not only adjust the molecular weight of the composite material but also increase the intermolecular force between the electrode and the composite material, thereby improving the cold-pressed adhesion between the composite material and the electrode.

[0085] In some embodiments of the present application, in the polymerization monomers of the acrylic ester polymer, the mass ratio of the first monomer, the second monomer and the third monomer is 100:(10-30):(1-20), for example, 100:(12-28):(1-20), 100:(15-25):(1-20), 100:(17-22):(1-20), 100:(18-20):(1-20), 100:(10-30):(5-15), 100:(10-30):(7-12), 100:(10-30):(8-10), etc. Thus, the present application controls the first monomer, the second monomer, and the third monomer in the preparation of the acrylic polymer to be controlled within the above-mentioned mixing ratio, and the resulting acrylic polymer has high adhesion, so that the obtained acrylic polymer is mixed with a dispersant, and the resulting composite material has a low Vicat softening point. When the composite material is used for the separator, at room temperature, the composite material has no adhesion under low pressure, which facilitates the winding and unwinding of the separator. When the separator is wound with the positive and negative electrode sheets and then undergoes a cold pressing process, the composite material can fully penetrate into the pores of the positive and negative electrode sheets and the separator, so that a strong mechanical linkage occurs between the composite material and the sheet. At the same time, the intermolecular force between the composite material and the sheet is also enhanced, thereby achieving cold pressing bonding between the composite material and the sheet, and the bonding force between the sheet and the separator is appropriate, thereby improving the cycle performance of the battery. In other embodiments of the present application, in the polymerized monomers of the acrylic composite material, the mass ratio of the first monomer, the second monomer, and the third monomer is 100:(15-25):(5-15).

[0086] In some embodiments of the present application, the dispersant includes at least one of polyvinyl pyrrolidone, polyacrylamide, sodium polystyrene sulfonate, polyacrylic acid, sodium polyacrylate, and sodium polymethacrylate. The addition of the dispersant of the above composition to the composite material of the present application not only has good dispersibility for the suspension system of acrylic polymers and reduces the irregular coagulation of the emulsion system, but also can adjust the Vicat softening point of the composite material and facilitate the granulation of the composite material. When the composite material is used for the separator, at room temperature, the composite material has no adhesiveness under low pressure, which facilitates the winding and unwinding of the separator. When the separator is wound with the positive and negative pole pieces and then undergoes a cold pressing process, the composite material can fully penetrate into the pores of the positive and negative pole pieces and the separator, so that a strong mechanical linkage occurs between the composite material and the pole piece. At the same time, the intermolecular force between the composite material and the pole piece is also enhanced, thereby achieving cold pressing bonding between the composite material and the pole piece, and the bonding force between the pole piece and the separator is appropriate, thereby improving the cycle performance of the battery.

[0087] In some embodiments of the present application, the mass ratio of the acrylic polymer to the dispersant is 100:(1-15), for example, 100:(2-14), 100:(3-13), 100:(4-12), 100:(5-11), 100:(6-10), 100:(7-9), 100:(7-8), etc. Therefore, the dispersant added to the composite material of the present application not only has excellent dispersibility for the suspension system of the acrylic polymer and reduces the irregular aggregation of the emulsion system, but also can adjust the Vicat softening point of the composite material and facilitate the granulation of the composite material. When the composite material is used for the separator, at room temperature, the composite material has no adhesiveness under low pressure, which facilitates the winding and unwinding of the separator. When the separator is wound with the positive and negative electrode sheets and then cold-pressed, the composite material can fully penetrate into the pores of the positive and negative electrode sheets and the separator, so that a strong mechanical linkage occurs between the composite material and the sheet. At the same time, the intermolecular force between the composite material and the sheet is also enhanced, thereby achieving cold-pressed bonding between the composite material and the sheet, and the bonding force between the sheet and the separator is appropriate, thereby improving the cycle performance of the battery. In some further embodiments of the present application, the mass ratio of the acrylic composite material to the dispersant is 100:(5-12).

[0088] In some embodiments of the present application, the number average molecular weight of the dispersant is 100-100,000, for example, 500-100,000, 3,000-100,000, 5,000-100,000, 8,000-100,000, 10,000-100,000, 30,000-90,000, 50,000-70,000, 50,000-60,000, 55,000-60,000, etc. Thus, the addition of a dispersant of the above molecular weight to the composite material in the present application can not only reduce the irregular aggregation of the acrylic polymer emulsion system, but also adjust the Vicat softening point of the composite material and facilitate the granulation of the composite material. When the composite material is used in a separator, it can improve the cold press adhesion between the separator and the electrode, thereby improving the cycle performance of the battery. In some embodiments of the present application, the number average molecular weight of the dispersant is 5,000-80,000.

[0089] In this application, the number average molecular weight of the dispersant can be determined by gel permeation chromatography according to standard GB / T 21863-2008. Specifically, this can be performed using the following method: an ultra-high performance polymer chromatograph (ACQUITY APC) and an ACQUITY differential refractive index detector (RI). Standards: polystyrene sleeve; run time: 30 minutes; detector: ACQUITY differential refractive index (RI) detector; column oven temperature: 90°C; detector temperature: 55°C. Sample testing: a. Standard sample and test sample preparation: Weigh 0.002g to 0.004g of standard sample / test sample respectively and add 2mL of mobile phase liquid to prepare a 0.1% to 0.5% mixed standard, and store in the refrigerator for >8h; b. Standard solution / sample testing: Edit the sample group to be tested, select the established sample group method, wait for the baseline to stabilize, click the run queue, and start testing the sample; (4) Data processing: Based on the relationship between retention time and molecular weight, use the chemical workstation to establish a calibration curve, integrate and quantify the sample spectrum, and the chemical workstation automatically generates the molecular weight and molecular weight distribution results.

[0090] In some embodiments of the present application, the composite material further includes a butadiene polymer, and the butadiene polymer includes at least one of polybutadiene, styrene / butadiene copolymer, acrylonitrile / butadiene copolymer, butadiene-isoprene copolymer, or butadiene-propylene copolymer. Thus, by adding the butadiene polymer of the above composition to the composite material, the present application can not only further adjust the Vicat softening point of the composite material, but also obtain an integrated composite material after mixing. Since the butadiene composite material contained in the composite material and the SBR (styrene-butadiene rubber) binder enriched on the negative electrode surface are of the same substance, the bonding force between the composite material and the negative electrode plate can be further improved.

[0091] In some embodiments of the present application, the mass ratio of the acrylic acid ester polymer to the dispersant and the butadiene polymer is 100:(1-15):(1-100), for example, 100:(2-13):(1-100), 100:(5-10):(1-100), 100:(8-10):(1-100), 100:(1-15):(5-95), 100:(1-15):(10-90), 100:(1-15):(20-80), 100:(1-15):(30-70), 100:(1-15):(40-60), 100:(1-15):(50-55), etc. Therefore, the present application mixes the acrylic composite material, dispersant, and butadiene composite material in the above proportions, which not only reduces the irregular aggregation of the acrylic polymer emulsion system and facilitates the dispersion of acrylic polymer particles, but also adjusts the Vicat softening point of the composite material. The resulting composite material has a low Vicat softening point. When the composite material is used in a separator, at room temperature, the composite material has no adhesiveness under low pressure, which facilitates the winding and unwinding of the separator. When the separator is wound with the positive and negative electrode sheets and then cold-pressed, the composite material can fully penetrate into the pores of the positive and negative electrode sheets and the separator, resulting in a strong mechanical linkage between the composite material and the electrode sheets. At the same time, the intermolecular force between the composite material and the electrode sheets is also enhanced, thereby achieving cold-pressed bonding between the composite material and the electrode sheets, and the bonding force between the electrode sheets and the separator is appropriate, thereby improving the cycle performance of the battery. In other embodiments of the present application, the mass ratio of the acrylic polymer to the dispersant and the butadiene polymer is 100:(5-12):(5-50).

[0092] In some embodiments of the present application, the glass transition temperature of the butadiene polymer is less than or equal to 20°C. Therefore, the addition of the butadiene polymer with a glass transition temperature to the composite material of the present application can reduce the Vicat softening point of the composite material. When the composite material is used for the separator, at room temperature, the composite material has no adhesiveness under low pressure, which facilitates the winding and unwinding of the separator. When the separator is wound with the positive and negative pole pieces and then subjected to a cold pressing process, the composite material can fully penetrate into the pores of the positive and negative pole pieces and the separator, resulting in a strong mechanical linkage between the composite material and the pole piece. At the same time, the intermolecular force between the composite material and the pole piece is also enhanced, thereby achieving cold pressing bonding between the composite material and the pole piece, and the bonding force between the pole piece and the separator is appropriate, thereby improving the cycle performance of the battery.

[0093] It should be noted that the glass transition temperature (Tg) is the temperature at which a polymer transitions from an elastic state to a glassy state. It refers to the transition temperature of an amorphous polymer (including the non-crystalline portion of a crystalline polymer) from the glassy state to the elastic state, or vice versa. It is the lowest temperature at which macromolecular segments of an amorphous polymer can move freely, and is typically denoted by Tg. Above the Tg, a polymer exhibits elasticity; below the Tg, it exhibits brittleness. The Tg can be measured using methods commonly used in the art, such as differential scanning calorimetry (DSC) as described in GB / T 19466.2.

[0094] In some embodiments of the present application, the Dv50 of the butadiene polymer is between 100nm and 300nm, for example, between 150nm and 250nm, or between 150nm and 200nm. Thus, when this composite material is used in an isolation membrane, it can improve the cold-press adhesion between the isolation membrane and the electrode, thereby enhancing the hardness of the battery cell and the cycle performance of the battery. In some embodiments of the present application, the Dv50 of the butadiene polymer is between 150nm and 250nm.

[0095] It should be noted that, in the examples of the present application, the Dv50 of the butadiene polymer is the particle size corresponding to when the cumulative particle size volume distribution percentage reaches 50%, and the test method is:

[0096] Reference standard GB / T 19077-2016 / ISO 13320:2009 particle size distribution laser diffraction method. Use a laser particle size analyzer (Malvern 3000, MasterSizer 3000) for testing, and use a helium-neon red light source as the main light source. Take a clean small beaker and add 1g of the sample to be tested, add a drop of surfactant, add 20ml of deionized water (the sample concentration ensures that the light shielding is 8-12%), and ultrasonicate at 53KHz / 120W for 5 minutes to ensure that the sample is completely dispersed. Turn on the laser particle size analyzer, clean the optical path system, and automatically test the background. Stir the ultrasonicated test solution to make it evenly dispersed, place it in the sample cell as required, and start measuring the particle size. The measurement results can be read from the instrument.

[0097] In some embodiments of the present application, the viscosity of the butadiene polymer at 25°C is 10mPa·s-300mPa·s, for example, 50mPa·s-250mPa·s, 100mPa·s-200mPa·s, 150mPa·s-220mPa·s, etc. Therefore, the present application adopts a butadiene polymer in this viscosity range. The butadiene polymer has good compatibility with the acrylic polymer, so that the composite material system is evenly dispersed, cold pressing bonding between the composite material and the pole piece is achieved, and the bonding force between the pole piece and the separator is appropriate, thereby improving the cycle performance of the battery. In other embodiments of the present application, the viscosity of the butadiene polymer at 25°C is 80mPa·s-200mPa·s.

[0098] It should be noted that in the examples of this application, the viscosity of butadiene polymers at 25°C is measured using the national standard GB / T10247-2008, "Methods for Measuring Viscosity." Specifically, at 25°C, a Brookfield viscometer is used. The shear force exerted by a 62# rotor rotating continuously at a constant speed within the sample generates a torque on the spring. This torque is proportional to the viscosity, and the viscosity value is obtained.

[0099] In some embodiments of the present application, the volume particle size distribution Dv50 of the composite material is 2μm-20μm, for example, 2μm, 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, 18μm, 19μm, 20μm, etc. In this application, when a composite material that meets the above volume average particle size Dv50 is used for an isolation membrane, it can not only improve the risk of the composite material clogging the isolation membrane pores, but also improve the problem of the composite material being coated on the isolation membrane to form a thicker coating and affecting the energy density of the battery prepared later. In other embodiments of the present application, the volume particle size distribution Dv50 of the composite material is 5μm-15μm.

[0100] It should be noted that, in the examples of the present application, the volume average particle size Dv50 of the composite material is the particle size corresponding to when the cumulative particle size volume distribution percentage reaches 50%, and the test method is:

[0101] Reference standard GB / T 19077-2016 / ISO 13320:2009 particle size distribution laser diffraction method. Use a laser particle size analyzer (Malvern 3000, MasterSizer 3000) for testing, and use a helium-neon red light source as the main light source. Take a clean small beaker and add 1g of the sample to be tested, add a drop of surfactant, add 20ml of deionized water (the sample concentration ensures that the light shielding is 8-12%), and ultrasonicate at 53KHz / 120W for 5 minutes to ensure that the sample is completely dispersed. Turn on the laser particle size analyzer, clean the optical path system, and automatically test the background. Stir the ultrasonicated test solution to make it evenly dispersed, place it in the sample cell as required, and start measuring the particle size. The measurement results can be read from the instrument.

[0102] In a second aspect, the present application proposes a method for preparing the composite material, comprising: mixing an acrylic polymer with a dispersant to obtain a composite material, wherein the composite material has a Vicat softening point of 5°C-60°C.

[0103] In some embodiments of the present invention, the method for preparing the composite material may include the following steps:

[0104] Mixing water, an emulsifier, an initiator, a first monomer, a second monomer, and a third monomer, and heating the mixture to react to obtain an acrylic acid ester emulsion;

[0105] The acrylic ester emulsion and a dispersant are blended to obtain a composite material.

[0106] The acrylic emulsion is prepared by emulsion polymerization of a first monomer, a second monomer and a third monomer. The acrylic composite material prepared using the above monomers has high adhesion. The composite material obtained by combining it with a dispersant has a suitable Vicat softening point. When the composite material is used for an isolation membrane, at room temperature, the composite material has no adhesion under low pressure, which facilitates the winding and unwinding of the isolation membrane. When the isolation membrane is wound with the positive and negative pole pieces and then subjected to a cold pressing process, the composite material can fully penetrate into the pores of the positive and negative pole pieces and the isolation membrane, so that a strong mechanical linkage occurs between the composite material and the pole piece. At the same time, the intermolecular force between the composite material and the pole piece will also be enhanced, thereby realizing cold pressing bonding between the composite material and the pole piece, and the bonding force between the pole piece and the isolation membrane is appropriate, thereby improving the cycle performance of the battery.

[0107] The present application obtains an acrylic emulsion by emulsion polymerization, and then mixes the acrylic ester emulsion with a dispersant and obtains a composite material by spray drying.

[0108] Emulsion polymerization is a process in which monomers are dispersed in water with the help of emulsifiers and mechanical stirring to form an emulsion, and then an initiator is added to initiate monomer polymerization.

[0109] Emulsifiers are substances that can transform mutually incompatible oils and water into an emulsion that is difficult to separate. Emulsifiers are typically surfactants that have both hydrophilic polar groups and hydrophobic (lipophilic) non-polar groups. For example, emulsifiers include at least one of sodium dodecyl sulfonate, sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, sodium dodecylbenzene sulfate, sodium laurate, sodium stearate, or sodium palmitoleate.

[0110] An initiator is a substance that can initiate polymerization of monomers. For example, a free radical initiator refers to a class of compounds that readily decompose into free radicals (i.e., primary free radicals) upon heating and can be used to initiate free radical polymerization and copolymerization of olefinic and dienic monomers. For example, initiators include at least one of potassium persulfate, ammonium persulfate, azobisisobutyronitrile, dimethyl azobisisobutyrate, benzoyl peroxide, or dioctanoyl peroxide.

[0111] Water, emulsifier, initiator, and monomers constituting acrylic polymers are blended and stirred. Water and emulsifier are stirred and dispersed to form an emulsion, that is, the emulsifier forms micelles in the aqueous phase, and monomers are solubilized in most of the micelles. Under heating conditions, the initiator initiates polymerization of the monomers inside the micelles to obtain an emulsion.

[0112] Spray drying, through mechanical action, disperses the material to be dried (a mixture of acrylic polymer emulsion and dispersant) into very fine mist-like particles, which come into contact with hot air (increasing the water evaporation area and accelerating the drying process), instantly removing most of the water and drying the solid matter in the material into powder.

[0113] In some embodiments of the present application, the method further comprises: adding a butadiene polymer during the mixing of the acrylic emulsion and the dispersant. Specifically, the dispersant added during the mixing of the acrylic emulsion of the present application has excellent dispersing properties for the suspension system, reducing irregular aggregation of the emulsion system. Furthermore, the butadiene copolymer added during the mixing of the acrylic emulsion and the dispersant can adjust the Vicat softening point of the composite material. When the composite material is used as a separator, it can improve the cold press adhesion between the separator and the electrode, thereby enhancing the cycle performance of the battery.

[0114] In a third aspect, the present application provides a separator, comprising the composite material of the first aspect or a composite material obtained using the method of the second aspect. Thus, when the composite material is applied to the separator, the cold-pressed adhesion between the separator and the electrode can be improved, thereby enhancing the hardness of the battery cell and the cycle performance of the battery.

[0115] In some embodiments of the present application, the isolation film of the present application includes a base film and an adhesive layer, wherein the adhesive layer is formed on at least one side of the base film, and the adhesive layer includes the composite material of the first aspect of the present application or the composite material obtained by the method of the second aspect of the present application. For example, the adhesive layer is formed on opposite sides of the base film.

[0116] In the present application, there is no particular limitation on the type of base membrane, and any known base membrane with a porous structure having good chemical stability and mechanical stability can be selected.

[0117] In some embodiments of the present application, the base film may include at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, or polyvinylidene fluoride. The base film may be a single-layer film or a multi-layer composite film, without particular limitation. When the base film is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0118] The isolation membrane described herein can be prepared using conventional methods in the art. For example, the composite material described in the first aspect of the present invention can be dissolved in an organic solvent to obtain a slurry, which can then be coated on a base film and then dried to remove the organic solvent, thereby obtaining the isolation membrane described herein.

[0119] In some embodiments of the present application, the coating density of the composite material on one side of the base film is 0.3 g / m 2 -1.0g / m 2 , for example 0.4g / m 2 -0.9g / m 2 , 0.5g / m 2 -0.8g / m 2 , 0.6g / m 2 -0.7g / m 2 In this way, the bonding strength between the separator and the electrode can be improved, and the safety performance of the battery can be improved. In other embodiments of the present application, the coating density of the composite material on one side of the base film can be 0.3g / m 2 -0.8g / m 2 .

[0120] It should be noted that the test method for the coating density of the composite material on one side of the base film is as follows: the isolation membrane sprayed with the composite material is cut according to the cutting plate, the length and width of the cut sample are measured to obtain the area S of the sample, and the weight of the membrane sample sprayed with the composite material is weighed as M1; according to the same method, the membrane sample of the same area without the coating of the composite material is cut, and the weighed mass is M2; the coating density of the isolation membrane is (M1-M2) / S.

[0121] In a fourth aspect, the present application provides a pole piece comprising the composite material of the first aspect or a composite material obtained by the method of the second aspect. This allows cold-press bonding of the separator to the pole piece, and the adhesion between the separator and the pole piece is suitable, thereby improving the cycle performance of the battery.

[0122] It should be noted that the electrode described in this application can be a positive electrode or a negative electrode.

[0123] The positive electrode sheet 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 includes the composite material of the first aspect of the present application or the composite material obtained by the second method of the present application. Specifically, the composite material can be used as a binder in the positive electrode active material layer.

[0124] As an example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material layer is provided on either or both of the two facing surfaces of the positive electrode current collector.

[0125] In some embodiments of the present application, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0126] In some embodiments of the present application, the positive electrode active material may be a positive electrode active material for batteries known in the art.

[0127] As an example, when the positive electrode plate is used in a lithium-ion battery, the positive electrode active material may adopt a positive electrode active material for lithium-ion batteries that is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.8 Co 0.15 Al 0.05 O2) or at least one of its modified compounds. Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, or a composite material of lithium iron manganese phosphate and carbon.

[0128] For example, when the positive electrode plate is used in a sodium ion battery, the positive electrode active material may be a positive electrode active material known in the art for use in sodium ion batteries. For example, the positive electrode active material may include, but is not limited to, at least one of a layered transition metal oxide, a polyanion compound, and a Prussian blue analog.

[0129] Examples of the layered transition metal oxides include:

[0130] Na 1-x Cu h Fe k Mn l M 1 m O 2-y , where M 1 Including at least one of Li, Be, B, Mg, Al, K, Ca, Ti, Co, Ni, Zn, Ga, Sr, Y, Nb, Mo, In, Sn or Ba, 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;

[0131] Na 0.67 Mn 0.7 Ni z M 2 0.3-z O2, where M 2 including at least one of Li, Mg, Al, Ca, Ti, Fe, Cu, Zn or Ba, 0 <z≤0.1;

[0132] 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。

[0133] Examples of the polyanionic compound include:

[0134] A 1 f M 3 g (PO4) i O j X 1 3-j , where A 1 including at least one of H, Li, Na, K or NH4, M 3 Contains at least one of Ti, Cr, Mn, Fe, Co, Ni, V, Cu or Zn, X 1 is at least one of F, Cl or Br, 0 <f≤4,0<g≤2,1≤i≤3,0≤j≤2;

[0135] Na n M 4 PO4X 2 , where M 4 Contains at least one of Mn, Fe, Co, Ni, Cu or Zn, X 2 is at least one of F, Cl or Br, 0 <n≤2;

[0136] Na p M 5 q (SO4)3, where M 5 including at least one of Mn, Fe, Co, Ni, Cu or Zn, 0 <p≤2,0<q≤2;

[0137] Na s Mn t Fe 3-t(PO4)2(P2O7), where 0 < s ≤ 4, 0 ≤ t ≤ 3, for example, t is 0, 1, 1.5, 2 or 3.

[0138] As an example of the above Prussian blue analogues, for example, the following can be listed:

[0139] A u M 6 v [M 7 (CN)6] w ·xH2O, where A includes H + 、NH4 + 、at least one of alkali metal cations or alkaline earth metal cations, M 6 and M 7 each independently includes at least one of transition metal cations, 0 < u ≤ 2, 0 < v ≤ 1, 0 < w ≤ 1, 0 < x < 6. For example, A includes H + 、Li + 、Na + 、K + 、NH4 + 、Rb + 、Cs + 、Fr + 、Be 2+ 、Mg 2+ 、Ca 2+ 、Sr 2+ 、Ba 2+ or Ra 2+ at least one of, M 6 and M 7 each independently includes at least cations of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Sn or W.

[0140] In some embodiments, the positive electrode active material layer may further optionally include other binders. As an example, the other binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride - tetrafluoroethylene - propylene terpolymer, vinylidene fluoride - hexafluoropropylene - tetrafluoroethylene terpolymer or tetrafluoroethylene - hexafluoropropylene copolymer and fluorinated acrylate resin.

[0141] In some embodiments of the present application, the positive electrode active material layer may further optionally include a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene or carbon nanofibers.

[0142] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the composite material and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0143] In some embodiments of the present application, based on the total mass of the positive electrode active material layer, the mass proportion of the composite material in the positive electrode sheet is 1%-3%, for example, 1.2%-2.8%, 1.5%-2.5%, 1.8%-2.2%, 2%-2.2%, etc. This can reduce the shedding of the positive electrode sheet, thereby improving the cycle performance of the battery containing the composite material.

[0144] Similarly, the electrode sheet described herein may also be a negative electrode sheet. The negative electrode sheet 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 includes the composite material described in the first aspect of this application or a composite material obtained using the method of the second aspect of this application. Specifically, the composite material can be used as a binder in the negative electrode active material layer.

[0145] As an example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode active material layer is provided on either or both of the two facing surfaces of the negative electrode current collector.

[0146] In some embodiments of the present application, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer base layer and a metal layer formed on at least one surface of the polymer base material. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0147] In some embodiments of the present application, the negative electrode active material may be a negative electrode active material for a battery that is well known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may include at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, or silicon alloys. The tin-based material may include at least one of elemental tin, tin oxides, or tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0148] In some embodiments of the present application, the negative electrode active material layer may optionally further include other binders, and the other binders may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

[0149] In some embodiments of the present application, the negative electrode active material layer may further include a conductive agent, which may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, or carbon nanofibers.

[0150] In some embodiments of the present application, the negative electrode active material layer may optionally further include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0151] In some embodiments of the present application, the negative electrode sheet can be prepared by the following method: the above-mentioned components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the composite material and any of the above-mentioned optional components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0152] In some embodiments of the present application, based on the total mass of the negative electrode active material layer, the composite material accounts for 1% to 3% by mass in the negative electrode sheet, for example, 1.2% to 2.8%, 1.5% to 2.5%, 1.8% to 2.2%, 2% to 2.2%, etc. This can reduce the shedding of the negative electrode sheet, thereby improving the cycle performance of the battery containing the composite material.

[0153] In a fifth aspect, the present application provides a battery comprising the separator according to the third aspect and / or the electrode according to the fourth aspect, thereby providing the battery with excellent cycle performance.

[0154] Typically, a battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0155] The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or solid.

[0156] In some embodiments of the present application, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0157] 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 dioxalatoborate, lithium difluorodioxalatophosphate, or lithium tetrafluorooxalatophosphate.

[0158] 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 difluorooxalatoborate, sodium tetrafluoroborate, sodium bisoxalatoborate, sodium perchlorate, sodium hexafluoroarsenate, sodium bis(fluorosulfonyl)imide, sodium trifluoromethylsulfonate or sodium bis(trifluoromethylsulfonyl)imide.

[0159] 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, methylpropyl carbonate, ethylpropyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane, dimethyl sulfone, methyl ethyl sulfone or diethyl sulfone.

[0160] In some embodiments of the present application, the electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0161] In some embodiments, the battery of the present application includes a battery cell form, a battery module form, and a battery pack form.

[0162] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

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

[0164] In some embodiments, the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the battery cell may be a soft shell, such as a pouch-type soft shell. The soft shell may be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0165] The present application has no particular limitation on the shape of the battery cell, which may be cylindrical, square, or any other shape. For example, FIG1 shows a battery cell 1 having a square structure as an example.

[0166] In some embodiments, referring to Figure 2, the outer packaging may include a shell 11 and a cover plate 13. The shell 11 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 11 has an opening connected to the receiving cavity, and the cover plate 13 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 12 through a winding process or a lamination process. The electrode assembly 12 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 12. The number of electrode assemblies 12 contained in the battery 1 can be one or more, and those skilled in the art can select according to specific actual needs.

[0167] In some embodiments, battery cells may be assembled into a battery module. The battery module may contain one or more battery cells. The specific number may be selected by those skilled in the art based on the application and capacity of the battery module.

[0168] Figure 3 shows an example battery module 2. Referring to Figure 3 , within the battery module 2, multiple battery cells 1 may be arranged sequentially along the length of the battery module 2. Of course, they may also be arranged in any other manner. Furthermore, the multiple battery cells 1 may be secured together using fasteners.

[0169] Optionally, the battery module 2 may further include a housing having an accommodation space, and the plurality of battery cells 1 are accommodated in the accommodation space.

[0170] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0171] Figures 4 and 5 illustrate an example battery pack 3. Referring to Figures 4 and 5 , a battery pack 1 may include a battery box and multiple battery modules 2 disposed within the box. The battery box comprises an upper case 31 and a lower case 32. The upper case 31 can be positioned over the lower case 32 to form an enclosed space for accommodating the battery modules 2. The multiple battery modules 2 can be arranged in any manner within the battery box.

[0172] In addition, the present application also provides an electrical device, which includes the battery provided in the present application. The battery cell, battery module, or battery pack can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device. The electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

[0173] As the electrical device, a battery cell, a battery module or a battery pack can be selected according to its usage requirements.

[0174] Figure 6 shows an example of an electric device. This device is a pure electric vehicle, hybrid electric vehicle, or plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the battery cells, a battery pack or battery module can be used.

[0175] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be lightweight and thin, and may use a battery cell as a power source.

[0176] Below, the embodiment of the present application is described. The embodiment described below is exemplary and is only used to explain the present application, and is not to be construed as limiting the present application. Where specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. Reagents or instruments used that do not specify the manufacturer are conventional products that can be obtained commercially.

[0177] Preparation Example A1

[0178] Weigh the first monomer, ethyl acrylate; the second monomer, styrene; and the third monomer, acrylamide (the mass ratio of the first monomer, the second monomer, and the third monomer is 100:15:10) and mix them thoroughly. Add 1000g of the mixed monomers, 30g of sodium lauryl sulfate emulsifier, 10g of ammonium persulfate initiator, and 1200g of deionized water to a 5000mL four-necked flask equipped with a mechanical stirrer, a thermometer, and a condenser. Emulsify at high speed for 30 minutes. Under nitrogen protection, heat to 75°C and react for 4 hours. Then cool to below 40°C, adjust the pH to neutral, and filter the product to obtain acrylic polymer emulsion A1.

[0179] Preparation Examples A2 to A11, Preparation Examples A2-A11, based on Preparation Example A1, adjusted the monomer types and mass ratios to obtain acrylic polymer emulsions A2-A11, see Table 1 for details.

[0180] Table 1

[0181] Example 1

[0182] 1. Preparation of composite materials

[0183] According to the acrylic polymer emulsion A1 and the dispersants polyvinyl pyrrolidone and polybutadiene in a weight ratio of 100:10:30, they were mixed and stirred evenly, and then spray-dried to obtain a composite material. The conditions of the spray-drying process were: inlet air temperature of 110°C, outlet air temperature of 50°C, and air pressure of 0.5 kPa.

[0184] 2. Preparation of isolation membrane

[0185] A commercially available PE microporous film with a thickness of 7 μm and an average pore size of 80 nm (from Zhuo Gao Electronic Technology Co., Ltd.) was used as the base film. The composite material prepared above was stirred and mixed uniformly in deionized water to obtain a slurry (solid content of 20%). The slurry was sprayed onto both surfaces of the base film and dried to remove the solvent. The coating density of the coating composition on the substrate was 1.5 g / m 2 , and obtain an isolation film.

[0186] 3. Preparation of positive electrode sheet

[0187] Polyvinylidene fluoride (PVDF), lithium iron phosphate (LFP), conductive carbon black, and N-methylpyrrolidone (NMP) were mixed in a mass ratio of 1.2:58.38:0.42:40 and stirred thoroughly to prepare a positive electrode slurry. 2 The loading amount is evenly coated on the positive electrode current collector aluminum foil, and then dried, cold pressed and cut to obtain the positive electrode sheet.

[0188] 4. Preparation of negative electrode sheet

[0189] Artificial graphite, conductive agent acetylene black, binder styrene butadiene rubber (SBR), thickener sodium carboxymethyl cellulose (CMC-Na) were added into deionized water in a mass ratio of 96.2:1.0:1.6:1.2, and stirred thoroughly to prepare a negative electrode slurry (solid content of 63%). 2 The loading amount is coated on the negative electrode current collector copper foil, and then dried, cold pressed and cut to obtain the negative electrode sheet.

[0190] 5. Preparation of electrolyte

[0191] At 25°C, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain a mixed solvent, and then LiPF6 is dissolved in the above mixed solvent to obtain an electrolyte, wherein the concentration of LiPF6 is 1 mol / L.

[0192] 6. Preparation of secondary batteries

[0193] The positive electrode sheet, separator, and negative electrode sheet are stacked in sequence, wound, and cold-pressed (during which the separator is bonded to the electrode sheet) to obtain a battery cell; the battery cell is placed in an outer package, and the above-prepared electrolyte is added. After packaging, standing, formation, aging and other processes, a secondary battery is obtained.

[0194] Examples 2-26 and Comparative Examples 1-4 are prepared by adjusting the compositions of the acrylic acid ester polymer, the dispersant, and the butadiene polymer on the basis of Example 1 to obtain Examples 2-26 and Comparative Examples 1-4.

[0195] Table 2

[0196] The particle size and Vicat softening point of the composite materials obtained in Examples 1-26 and Comparative Examples 1-4, as well as the cold pressing adhesion between the electrode and the separator in the obtained battery and the cycle performance of the battery were characterized. The characterization results are shown in Table 3.

[0197] Performance Testing

[0198] (1) Vicat softening point test of composite materials

[0199] The test was conducted in accordance with ISO 306:2013, Plastics—Determination of the Vicat softening temperature of thermoplastic materials, using the A50 method. The test was conducted using a Jesain WKT-VST300 heat distortion softening point thermometer, with a load of 10N, a heating rate of 50°C / h, and a sample thickness of 5mm.

[0200] (2) Composite material particle size test

[0201] The analysis was performed using a laser particle size analyzer (Malvern 3000, MasterSizer 3000) using a helium-neon red light source as the primary light source. 1g of the sample to be tested was placed in a clean small beaker, along with 20ml of deionized water. Ultrasonication was performed at 53kHz / 120W for 5 minutes to ensure complete dispersion of the sample. The laser particle size analyzer was turned on, the optical system cleaned, and the background was automatically measured. The ultrasonicated sample solution was stirred to ensure uniform dispersion, then placed in the sample cell as required, and the particle size measurement was initiated. The measurement results were then read from the instrument.

[0202] (3) Cold press bonding test steps

[0203] The battery negative electrode sheet and separator were stacked together and placed on a hot press. Pressing parameters were set at 25°C, 7t, and 15s to produce a bonded separator / negative electrode sheet sample. The separator / electrode sheet sample was cut into 150mm x 20mm rectangular strips. The electrode sheet side of the strip was affixed to a steel plate using double-sided tape. At one end of the strip, the separator and electrode sheet were separated by 2cm along the length to produce the test specimen.

[0204] The steel plate was held horizontally and secured with the lower clamp of a universal testing machine (Xie Qiang Instrument Manufacturing (Shanghai) Co., Ltd., Model CTM2100). The peeled end of the separator, as described above, was secured with the upper clamp of the universal testing machine and connected to a tensile testing machine. The test conditions were set to a tensile rate of 20 mm / min and a horizontal pull of 10 cm. Once the tensile force stabilized, the tensile force was recorded. The ratio of the tensile force to the sample width was used to determine the adhesion strength between the separator and the electrode.

[0205] (4) Battery cycle performance test steps

[0206] At 25°C, the prepared battery was charged at a constant current of 1 / 3C to 3.65V, then charged at a constant voltage of 3.65V to a current of 0.05C, left for 5 minutes, and then discharged at 1 / 3C to 2.5V. The obtained discharge capacity was recorded as the initial capacity C0. Repeat the above steps for the same battery and record the discharge capacity C of the battery after the nth cycle. n , then the battery capacity retention rate P after each cycle n =(C n / C0)×100%. The difference in cycle performance can be reflected by the battery capacity retention rate after 500 cycles.

[0207] Table 3

[0208] As can be seen from Table 3, the composite materials of Examples 1-26 all include an acrylic polymer and a dispersant, and the Vicat softening point of the composite materials is between 5°C and 60°C. The cold pressing adhesion between the separator and the negative electrode and the capacity retention rate of the battery are both higher than those of Comparative Examples 1-4. This shows that when the composite material of the present application is used for the separator, cold pressing adhesion between the separator and the electrode can be achieved, and the adhesion force is appropriate, thereby improving the cycle performance of the battery.

[0209] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0210] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A composite material, wherein, It includes an acrylate polymer and a dispersant, and the Vicat softening point of the composite material is 5°C - 60°C.

2. The composite material according to claim 1, wherein, The Vicat softening point of the composite material is 10°C - 50°C.

3. The composite material according to claim 1 or 2, wherein The polymerization monomers of the acrylate polymer include a first monomer, a second monomer, and a third monomer. The structure of the first monomer includes: Among them, R1 includes a hydrogen atom, a hydroxyl group, or an alkyl group with 1 - 18 carbon atoms, and R2 includes a hydrogen atom or an alkyl group with 1 - 18 carbon atoms that is substituted or unsubstituted by a hydroxyl group. The structure of the second monomer includes: Among them, R3 and R4 each independently include a hydrogen atom, a phenyl group, or an alkyl group with 1 - 20 carbon atoms. The structure of the third monomer includes: Among them, R5 includes a hydrogen atom or an alkyl group with 1 - 6 carbon atoms, and R6 includes a hydrogen atom, an alkyl group with 1 - 6 carbon atoms substituted by a hydroxyl group, or an alkoxy group with 1 - 6 carbon atoms.

4. The composite material according to claim 3, wherein, The first monomer includes at least one of ethyl acrylate, n-butyl acrylate, n-propyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, cyclohexyl acrylate, isooctyl acrylate, lauryl acrylate, 2-ethylhexyl acrylate, methyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, 2-ethylhexyl methacrylate, isobornyl methacrylate, lauryl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, acrylic acid, methacrylic acid, crotonic acid, or heptenoic acid.

5. The composite material according to claim 3 or 4, wherein, The second monomer includes at least one of styrene, pentene, hexene, heptene, octene, nonene, decene, dodecene, tridecene, tetradecene, pentadecene, or hexadecene.

6. The composite material according to any one of claims 3 - 5, wherein the third monomer includes at least one of acrylamide, methacrylamide, N-hydroxymethyl acrylamide, N-butyl acrylamide, N-butoxymethyl acrylamide, N-(N-butoxymethyl) acrylamide.

7. The composite material according to any one of claims 3-6, wherein, The mass ratio of the first monomer, the second monomer, and the third monomer is 100:(10 - 30):(1 - 20).

8. The composite material according to any one of claims 3-7, wherein, The mass ratio of the first monomer, the second monomer, and the third monomer is 100:(15 - 25):(5 - 15).

9. The composite material according to any one of claims 1-8, wherein, The mass ratio of the acrylate composite material and the dispersant is 100:(1 - 15).

10. The composite material according to any one of claims 1-9, wherein, The mass ratio of the acrylate composite material and the dispersant is 100:(5 - 12).

11. The composite material according to any one of claims 1-10, wherein, The dispersant includes at least one of polyvinylpyrrolidone, polyacrylamide, sodium polystyrene sulfonate, polyacrylic acid, sodium polyacrylate, or sodium polymethacrylate.

12. The composite material according to any one of claims 1-11, wherein, The number-average molecular weight of the dispersant is 100 - 100000.

13. The composite material according to any one of claims 1-12, wherein, It further includes a butadiene polymer, and the butadiene polymer includes at least one of polybutadiene, styrene / butadiene copolymer, acrylonitrile / butadiene copolymer, butadiene / isoprene copolymer, or butadiene / propylene copolymer.

14. The composite material according to claim 13, wherein, The mass ratio of the acrylate polymer, the dispersant, and the butadiene polymer is 100:(1 - 15):(1 - 100).

15. The composite material according to claim 13 or 14, wherein, The mass ratio of the acrylate polymer, the dispersant, and the butadiene polymer is 100:(5 - 12):(5 - 50).

16. The composite material according to any one of claims 13 - 15, wherein, The glass transition temperature of the butadiene-based polymer is less than or equal to 20 °C.

17. The composite material according to any one of claims 13-16, wherein, The Dv50 of the butadiene-based composite material is 100 nm - 300 nm.

18. The composite material according to any one of claims 13-17, wherein, The viscosity of the butadiene-based composite material at 25 °C is 10 mPa·s - 300 mPa·s.

19. The composite material according to any one of claims 1-18, wherein, The volume average particle size Dv50 of the composite material is 2 μm - 20 μm.

20. A method for preparing a composite material, wherein, Comprising: Mixing an acrylate-based polymer with a dispersant to obtain a composite material, the Vicat softening point of the composite material being 5 °C - 60 °C.

21. An isolation film, wherein, Comprising the composite material according to any one of claims 1 - 19 or the composite material prepared by the method according to claim 20.

22. A pole piece, wherein, Comprising the composite material according to any one of claims 1 - 19 or the composite material prepared by the method according to claim 20.

23. A battery, wherein, Comprising the separator according to claim 21 and / or the electrode sheet according to claim 22.

24. An electrical device, wherein, Comprising the battery according to claim 23.

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