Battery cell, battery device and electric device

Abstract

Provided in the present application are a battery cell, a battery device and an electric device. The battery cell comprises a positive electrode sheet, a negative electrode sheet and a separator, wherein the separator is located between the positive electrode sheet and the negative electrode sheet; the separator comprises a porous base film and a coating arranged on at least one side of the porous base film; the coating comprises heat-resistant particles, and the heat-resistant particles comprise a cross-linked polymer; and the cross-linking degree of the cross-linked polymer is 80%-97%. The technical solution of the present application is beneficial to improvement of the reliability of the battery cell.

Description

Battery cell, battery device, and electric device Cross-reference to related applications

[0001] This application claims priority to Chinese Patent Application No. 202411388765.7, filed on September 30, 2024, entitled “Silicon-containing organic resin particles, method for producing silicon-containing organic resin particles, dispersion liquid of silicon-containing organic resin particles, separator, secondary battery cell, battery device, and electric device,” the entire contents of which are incorporated herein by reference. TECHNICAL FIELD The present application relates to the technical field of batteries, and more particularly, to a battery cell, a battery device, and an electric device. BACKGROUND In recent years, battery technology has been widely applied to energy storage power systems such as hydroelectric, thermal, wind, and solar power stations, as well as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields, thereby achieving great development. With the development and application of battery technology, higher requirements are placed on the cycle performance of battery cells. The heat resistance of the separator is too low, which affects the reliability of the battery cell. Therefore, how to improve the reliability of the battery cell is a technical problem to be solved. SUMMARY The present application is made in view of the above problem, and aims to provide a battery cell, a battery device, and an electric device, which are advantageous in improving the reliability of the battery cell. In a first aspect, an embodiment of the present application provides a battery cell, which includes a positive electrode sheet, a negative electrode sheet, and a separator, the separator being located between the positive electrode sheet and the negative electrode sheet; the separator includes a porous base film and a coating layer provided on at least one side of the porous base film; the coating layer includes heat-resistant particles, the heat-resistant particles including a cross-linked polymer; and the cross-linking degree of the cross-linked polymer is 80% to 97%. In an embodiment of the present application, on the one hand, the cross-linked polymer has a three-dimensional network structure, which can maintain a stable spatial configuration under thermal stress, so that the separator has good heat resistance. On the other hand, by controlling the cross-linking degree of the cross-linked polymer to be 60% to 98%, the coating layer particles can have good heat resistance at high temperatures, the heat resistance of the separator can be improved, the overall structural integrity of the separator at high temperatures can be ensured, and thus the reliability of the battery cell under high temperature conditions can be improved. In a possible implementation manner, the cross-linked polymer includes a planar ring-shaped conjugated group and / or a covalent polyhedral skeleton. In the embodiments of the present application, the cross-linked polymer includes a planar ring conjugated group and / or a covalent polyhedral skeleton. The planar ring conjugated group is not prone to twist and deformation at high temperatures due to the conjugation effect and planar structure, and exhibits high rigidity, so that the polymer molecule is difficult to pyrolyze or soften, thereby making the cross-linked polymer containing the planar ring conjugated group have high thermal stability. The covalent polyhedral skeleton is not prone to break or collapse at high temperatures due to its highly symmetrical three-dimensional geometric structure and strong covalent bond connection higher than ionic bond or intermolecular force, thereby making the cross-linked polymer containing the covalent polyhedral skeleton have high thermal stability. Therefore, the cross-linked polymer containing the planar ring conjugated group and / or the covalent polyhedral skeleton has good heat resistance and thermal stability, and when used in the separator film, the heat resistance of the whole separator film is improved, and the reliability of the battery cell under high temperature conditions is improved. In a possible implementation, the planar ring conjugated group includes any one of a substituted or unsubstituted phenyl group, a substituted or unsubstituted heteroatom-containing aromatic group, a substituted or unsubstituted condensed ring aromatic group, and a substituted or unsubstituted triazine ring group. Optionally, the planar ring conjugated group includes any one of a phenyl group and a triazine ring group. In the embodiments of the present application, by limiting the types of the planar ring conjugated group in the cross-linked polymer, the heat resistance and chemical stability of the cross-linked polymer can be further improved, thereby improving the heat resistance of the separator film. The phenyl group has good structural stability and conjugation effect, which can improve the thermal stability of the cross-linked polymer. The heteroatom-containing aromatic group can make the electronic structure of the cross-linked polymer more stable and enhance the oxidation resistance of the cross-linked polymer, thereby reducing the probability of reaction between the cross-linked polymer and the electrolyte. The condensed ring aromatic group has a larger π conjugation system, higher rigidity, and higher thermal decomposition temperature. The triazine ring group contains multiple nitrogen atoms, which can keep the structure stable at high temperatures. The cross-linked polymer includes the above-mentioned groups, so that the cross-linked polymer particles in the coating are more difficult to deform or break at high temperatures, thereby making the separator film have good heat resistance and improving the reliability of the battery cell. In a possible implementation, the cross-linked polymer includes at least one of a phenol formaldehyde resin polymer, a polymer containing a triazine ring group, a phenyl-containing organic silicon polymer, and a cross-linked styrene polymer. In the embodiments of the present application, by introducing the above-mentioned at least one group, the separator film including the cross-linked polymer has good heat resistance, thereby improving the reliability of the battery cell under extreme conditions. In a possible implementation, the phenyl-containing organic silicon polymer includes a monomer and a cross-linking agent polymerized according to Formula (I), In formula I, R1, R2 each independently includes C1-C4 alkyl, C2-C4 alkenyl, R3 includes C1-C4 alkyl or C4-C8 (methyl) acryloyloxyalkyl, R4 includes C2-C8 alkenyl or C4-C8 (methyl) acryloyloxyalkyl; the crosslinking agent includes divinylbenzene. In the embodiment of the present application, through polymerization of the monomer shown in formula (I) and the crosslinking agent divinylbenzene, a phenyl-containing silicone polymer particle can be obtained, which has a rigid skeleton composed of a phenyl structure and the monomer shown in formula (I), and exhibits higher glass transition temperature and thermal decomposition temperature, thereby improving the heat resistance of the isolation film and the reliability of the battery cell. In a possible implementation, the phenyl-containing silicone polymer satisfies one or more of the following conditions: (1) the crosslinking degree of the phenyl-containing silicone polymer is 75% to 95%; (2) the phenyl-containing silicone polymer includes silicon elements, and the mass fraction of the silicon elements in the phenyl-containing silicone crosslinking resin is 10% to 25%; (3) the mass fraction of the phenyl in the phenyl-containing silicone polymer is 2% to 12%. In the embodiment of the present application, the crosslinking degree of the phenyl-containing silicone polymer is 75% to 95%, and the phenyl-containing silicone polymer has good heat resistance at high temperature, so that the isolation film has good heat resistance, thereby improving the reliability of the battery cell. The mass fraction of the silicon elements is 10% to 25%, which helps to improve the proportion of the inorganic siloxane skeleton in the silicone polymer. The siloxane skeleton including silicon elements provides higher thermal decomposition temperature and oxidation resistance, so that the isolation film has structural stability in a high-temperature environment. The mass fraction of the phenyl is 2% to 12%, which can introduce a rigid structure of aromatic structure and conjugation effect, and further helps to improve the heat resistance of the isolation film. In a possible implementation, the covalent polyhedral skeleton includes a skeleton composed of a compound shown in formula (II), R a [SiO 3 / 2 ] n formula (II) wherein n is an integer of 4 to 12, R a including cycloalkyl, aryl, C1-C 12 alkyl, C1-C 12 alkenyl, C1-C 12 alkynyl; optionally n is 8, R a including C1-C3 alkyl. In this embodiment, by introducing the covalent polyhedral framework shown in formula (II) into the crosslinked polymer, a stable three-dimensional structure can be formed within the polymer molecule. This type of polyhedral framework has high symmetry and regularity, and its internal atoms are connected by strong covalent bonds. The molecular structure is not easily broken or collapsed under high temperature conditions, which is beneficial to improving the heat resistance of the separator. By selecting n as 8, R... a The presence of C1 to C3 alkyl groups can further improve the rigidity and thermal stability of cross-linked polymers. Cross-linked polymer particles can act as rigid support points at high temperatures, improving the heat resistance of the separator and thus enhancing the reliability of battery cells. In one possible implementation, the crosslinked polymer comprises an organosilicon polymer containing a cage-like polysilsesquioxane backbone. In this embodiment, by introducing a cage-like polysilsesquioxane backbone, the cage-like structure in the organosilicon polymer containing the cage-like polysilsesquioxane backbone provides structural support, reducing the possibility of backbone collapse or chain segment dissociation at high temperatures. This results in higher thermal stability at high temperatures. Furthermore, the cage-like structure contains Si-O bonds with high bond energy, making it less prone to decomposition at high temperatures, further enhancing the material's thermal stability. Simultaneously, in addition to the cage-like polysilsesquioxane backbone, the organosilicon polymer containing the cage-like polysilsesquioxane backbone also possesses a three-dimensional network structure formed by the random cross-linking of Si-O bonds. This further confines the thermal motion of the molecular chains, preventing the material from softening and deforming at high temperatures. The cage-like structure, as the rigid cross-linking point of the network structure, further enhances the thermal stability of the network. The material is resistant to both high-temperature decomposition and high-temperature deformation; the two factors synergistically increase the material's heat resistance. In one possible implementation, the organosilicon polymer containing a cage-like polysilsesquioxane backbone comprises one or more monomers of formula (ⅠII) obtained by hydrolysis and condensation polymerization. R'1 includes C1 to C3 alkyl groups. In the embodiments of this application, the organosilicon polymer formed from the monomer of formula (III) is relatively regular and stable at the molecular scale. During the polycondensation process, the polyhedral units are uniformly connected by covalent bonds, reducing the local stacking and entanglement of molecular chains. The organosilicon polymer exhibits a high degree of uniform dispersion. The uniform dispersion of molecular chains not only facilitates the uniform distribution of crosslinking points and reduces the phenomenon of internal stress concentration, but also improves the dispersion and bonding stability of crosslinked polymer particles in the separator coating. This makes the organosilicon polymer particles in the coating less prone to structural breakage or collapse at high temperatures, improving the overall heat resistance of the separator and thus enhancing the reliability of the battery cell. In a possible implementation, the cage-containing polysilsesquioxane skeleton-containing silicone polymer satisfies at least one of the following conditions: (1) the crosslinking degree is 85% to 97%; (2) the cage-containing polysilsesquioxane skeleton-containing silicone polymer comprises silicon elements, and the mass fraction of the silicon elements in the cage-containing polysilsesquioxane skeleton-containing silicone polymer is 25% to 45%; (3) in the cage-containing polysilsesquioxane skeleton-containing silicone polymer, the mass fraction of the cage-containing polysilsesquioxane skeleton is 40% to 60%. In the embodiments of the present application, the crosslinking degree of 85% to 97% can ensure that the silicone polymer has good heat resistance at high temperatures, and improve the heat resistance of the isolation film. The mass fraction of silicon elements reflects the proportion of inorganic siloxane skeleton in the crosslinked polymer. The mass fraction of silicon elements is 25% to 45%, which can improve the thermal decomposition temperature and structural stability of the polymer, and improve the heat resistance of the isolation film at high temperatures. The mass fraction of the cage-containing polysilsesquioxane skeleton is 40% to 60%, which can ensure that the crosslinked polymer has good rigidity and structural stability, reduce the occurrence of structural collapse or brittle fracture in the isolation film under heat abuse, and is conducive to improving the heat resistance of the isolation film, thereby improving the reliability of the battery monomer at high temperatures. In a possible implementation, the heat-resistant particles satisfy at least one of the following conditions: (1) the volume distribution particle size Dv50 of the heat-resistant particles is 80 nm to 900 nm; (2) the cyclic voltammogram of the heat-resistant particles in the first cycle has no oxidation peak in the voltage range of 0 to 4.4 V; (3) the glass transition temperature T g of the heat-resistant particles is greater than or equal to 150°C, or, the heat-resistant particles have no glass transition temperature T g at 300°C; (4) the initial thermal weight loss temperature T 3d of the heat-resistant particles is greater than or equal to 250°C; (5) the elution rate of the heat-resistant particles is less than or equal to 5% after being soaked in a mixed solvent composed of ethylene carbonate and methyl ethyl carbonate at a volume ratio of 3:7 at 60°C for 7 days; (6) the true density of the heat-resistant particles is 0.8 g / cm 3 to 2.0 g / cm 3 . In the embodiments of the present application, the volume distribution particle size Dv50 of the heat-resistant particles is within the above range, which can make the coating have more particle stacking layers within a limited thickness range, and improve the heat resistance of the isolation film. The cyclic voltammogram of the heat-resistant particles circulating for the first time has no oxidation peak in the voltage range of 2.50V to 4.40V, indicating that the heat-resistant particles are stable in the voltage range of 0V to 4.40V, have good electrochemical stability, and can be applied to high-voltage battery cells, so that the battery cells have good capacity performance at high voltage, and the working voltage and energy density of the battery cells are improved. The glass transition temperature of the heat-resistant particles is greater than or equal to 150℃, or there is no glass transition temperature below 300℃, which means that the DSC curve of the heat-resistant particles remains rigid in the solid state in the above temperature range and does not undergo molecular chain segment movement or softening, thereby improving the heat resistance of the isolation film. The initial thermal weight loss temperature T 3d greater than or equal to 250℃, indicating that the weight of the heat-resistant particles does not change significantly at high temperatures, so that the heat-resistant particles have high thermal stability during the use of the battery cell and in a high-temperature environment, and are not prone to thermal decomposition. The heat-resistant particles have a dissolution of less than 5% after being soaked in electrolyte at 60℃ for 7 days, and are not prone to precipitation or dissolution in the electrolyte environment, reducing the occurrence of electrolyte contamination or side reactions between the heat-resistant particles and the electrolyte during the cycle of the battery cell, and the isolation film has good structural stability, which is beneficial to the cycle performance and reliability of the battery cell. The true density of the heat-resistant particles is 0.8g / cm 3 ~2.0g / cm 3 which is beneficial to improving the capacity of the battery cell and obtaining a battery cell with high energy density. In one possible implementation, the mass fraction of the heat-resistant particles in the coating is 50% to 97%. In the embodiments of the present application, by limiting the mass fraction of the heat-resistant particles in the coating to satisfy the above range, the coating can have structural stability and air permeability, and the heat resistance of the isolation film is improved, thereby improving the reliability of the battery cell. In one possible implementation, the coating further includes a first binder, and the first binder satisfies at least one of the following conditions: (1) the first binder includes at least one of polyimide, polyetherimide, polyacrylic acid, polyacrylate, ethylene-vinyl acetate copolymer, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethylated polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose, acrylonitrile-styrene-butadiene copolymer, ethylene-propylene-diene terpolymer, sulfonated ethylene-propylene-diene terpolymer, butadiene-styrene rubber, and fluorine rubber; and (2) the mass fraction of the first binder in the coating is 3% to 15%. In the embodiments of the present application, the heat-resistant particles in the coating are connected and fixed to each other by the first binder, reducing the situation of falling off of the heat-resistant particles during coating and use. The mass fraction of the first binder meets the above range, which can reduce the proportion of heat-resistant particles in the coating due to excessive binder while ensuring adhesion, so as to balance the stability and heat resistance of the coating and improve the heat resistance of the isolation film. In a possible implementation, the isolation film further comprises second binder particles, and the second binder particles are located in the coating, or the isolation film further comprises a bonding layer, the bonding layer is arranged on at least one side of the coating away from the base film, and the second binder particles are located in the bonding layer; the second binder particles meet one or more of the following conditions: (1) the second binder particles comprise at least one of polyvinylidene fluoride, poly(vinylidene fluoride-co-trichloroethylene), poly(vinylidene fluoride-co-trifluorochloroethylene), poly(vinylidene fluoride-co-trifluoroethylene), poly(vinylidene fluoride-co-tetrafluoroethylene), poly(vinylidene fluoride-co-hexafluoropropylene), polyacrylate, polymethyl methacrylate, and polyacrylonitrile; (2) the number average particle size of the second binder particles is 5 μm to 20 μm. In the embodiments of the present application, the second binder particles are added in the coating or the bonding layer of the isolation film. The second binder particles can fill the gap between the negative electrode sheet and the isolation film, form a relatively firm bonding interface, help to improve the bonding strength between the isolation film and the negative electrode sheet, thereby improving the overall stability of the isolation film, reducing the interlayer peeling phenomenon between the isolation film and the negative electrode sheet caused by thermal stress or electrochemical action during the cycle process, and thereby improving the cycle performance of the battery cell. The number average particle size of the second binder particles meets the above range, which ensures that the second binder particles can be uniformly distributed and maintain moderate fluidity during hot pressing, thereby further improving the cycle performance of the battery cell. In a possible implementation, the isolation film meets at least one of the following conditions: (1) the thickness of the coating is 0.5 μm to 10 μm; (2) the area density of the coating is 1.5 g / m 2 ~ 6 g / m 2 ; (3) the longitudinal thermal shrinkage rate of the isolation film is less than or equal to 5% after being heated at 130°C for 1 h; (4) the transverse thermal shrinkage rate of the isolation film is less than or equal to 5% after being heated at 130°C for 1 h; (5) the air permeability of the isolation film is 150 s / 100 mL to 500 s / 100 mL. In the embodiments of the present application, the thickness of the coating is 0.5 μm to 10 μm, which can provide a uniform and dense heat-resistant coating, improve the heat resistance of the isolation film, and thereby improve the reliability of the battery cell. The area density of the coating is 1.5 g / m 2 ~ 6 g / m2 The coating layer can ensure moderate coating quality, improve the stability and heat resistance of the separator film, and does not significantly increase the weight of the separator film, thereby facilitating the energy density and reliability of the battery cell. The separator film still has very low longitudinal and transverse thermal shrinkage at 130℃, and the separator film has good heat resistance at high temperatures. The air permeability of the separator film is 150s / 100mL-500s / 100mL, which ensures that the electrolyte can be uniformly infiltrated and maintain fast ion transport, ensures the ion transport efficiency in the separator film, reduces the case of electrochemical polarization caused by too low air permeability of the separator film, and reduces the reliability of the battery cell. In a second aspect, a battery device is provided, including the battery cell in any possible implementation manner. In a third aspect, a use electric device is provided, including the battery cell in any possible implementation manner, or the battery device of the second aspect. In a fourth aspect, a separator film is provided, including a porous base film and a coating layer arranged on at least one side of the porous base film; the coating layer includes heat-resistant particles, and the heat-resistant particles include a cross-linked polymer; the cross-linking degree of the cross-linked polymer is 70%-98%. In the embodiments of the present application, on the one hand, the cross-linked polymer has a three-dimensional network structure, which can maintain a stable spatial configuration under thermal stress, so that the separator film has good heat resistance. On the other hand, by controlling the cross-linking degree of the cross-linked polymer to be 70%-98%, the coating particles can have good heat resistance at high temperatures, improve the heat resistance of the separator film, ensure the overall structural integrity of the separator film at high temperatures, and thus improve the reliability of the battery cell under high temperature conditions. In a possible implementation manner, the cross-linked polymer includes a planar ring conjugated group and / or a covalent polyhedral skeleton. In the embodiments of the present application, the cross-linked polymer includes a planar ring conjugated group and / or a covalent polyhedral skeleton. The planar ring conjugated group has high rigidity due to the conjugation effect and planar structure, and the polymer molecules are difficult to pyrolyze or soften at high temperatures, so that the cross-linked polymer containing the planar ring conjugated group has high thermal stability. The covalent polyhedral skeleton has a highly symmetrical three-dimensional geometric structure and a strong covalent bond connection higher than ionic bonds or intermolecular forces, and its structure is not easy to break or collapse at high temperatures, so that the cross-linked polymer containing the covalent polyhedral skeleton has high thermal stability. Therefore, the cross-linked polymer containing the planar ring conjugated group and / or the covalent polyhedral skeleton has good heat resistance and thermal stability, and when used in the separator film, the overall heat resistance of the separator film is improved, and the reliability of the battery cell under high temperature conditions is improved. In a possible implementation, the planar ring-shaped conjugated group includes any one of a substituted or unsubstituted phenyl group, a substituted or unsubstituted heteroatom-containing aromatic group, a substituted or unsubstituted condensed ring aromatic group, and a substituted or unsubstituted triazine ring group; optionally, the planar ring-shaped conjugated group includes any one of a phenyl group and a triazine ring group. In the embodiments of the present application, by limiting the types of the planar ring-shaped conjugated group in the cross-linked polymer, the heat resistance and chemical stability of the cross-linked polymer can be further enhanced, thereby improving the heat resistance of the isolation film. The phenyl group has good structural stability and conjugation effect, which can improve the thermal stability of the cross-linked polymer; the heteroatom-containing aromatic group has a more stable electronic structure and enhanced oxidation resistance due to the participation of the heteroatom in conjugation, thereby reducing the probability of reaction between the cross-linked polymer and the electrolyte; the condensed ring aromatic group has a larger π conjugation system, is more rigid, and has a higher thermal decomposition temperature; the triazine ring group contains multiple nitrogen atoms and can maintain structural stability at high temperatures. The inclusion of the above-mentioned groups in the cross-linked polymer makes the cross-linked polymer particles in the coating more difficult to deform or break at high temperatures, thereby making the isolation film have good heat resistance and improving the reliability of the battery cell. In a possible implementation, the cross-linked polymer includes one or more of a phenol formaldehyde resin polymer, a polymer containing a triazine ring group, a phenyl-containing silicone polymer, and a cross-linked styrene polymer. In the embodiments of the present application, by introducing the at least one group, the isolation film including the cross-linked polymer has good heat resistance, thereby improving the reliability of the battery cell under extreme conditions. In a possible implementation, the phenyl-containing silicone polymer is obtained by polymerization of a monomer represented by Formula (I) and a cross-linking agent, In Formula (I), R1 and R2 each independently include a C1-C4 alkyl group or a C2-C4 alkenyl group, R3 includes a C1-C4 alkyl group or a C4-C8 (meth)acryloxyalkyl group, and R4 includes a C2-C8 alkenyl group or a C4-C8 (meth)acryloxyalkyl group; and the cross-linking agent includes divinylbenzene. In the embodiments of the present application, by polymerization of the monomer represented by Formula (I) and the cross-linking agent divinylbenzene, a phenyl-containing silicone polymer particle can be obtained, which has a rigid skeleton composed of a phenyl structure and the monomer represented by Formula (I) and exhibits a higher glass transition temperature and thermal decomposition temperature, thereby improving the heat resistance of the isolation film and improving the reliability of the battery cell. In a possible implementation, the phenyl-containing organic silicon polymer satisfies one or more of the following conditions: (1) the cross-linking degree of the phenyl-containing organic silicon polymer is 75% to 95%; (2) the phenyl-containing organic silicon polymer includes silicon elements, and the mass fraction of the silicon elements in the phenyl-containing organic silicon cross-linking resin is 10% to 25%; and (3) the mass fraction of phenyl in the phenyl-containing organic silicon polymer is 2% to 12%. In the embodiment of the present application, the cross-linking degree of the phenyl-containing organic silicon polymer is 75% to 95%, which has good heat resistance at high temperatures, so that the isolation film has good heat resistance, thereby improving the reliability of the battery cell. The mass fraction of silicon elements is 10% to 25%, which helps to improve the proportion of inorganic silicon-oxygen skeleton in the organic silicon polymer. The silicon-oxygen skeleton including silicon elements provides a higher thermal decomposition temperature and oxidation resistance, so that the isolation film has structural stability in a high-temperature environment. The mass fraction of phenyl is 2% to 12%, which can introduce a rigid structure of aromatic structure and conjugate effect, thereby further improving the heat resistance of the isolation film. In a possible implementation, the covalent polyhedral skeleton includes a skeleton composed of a compound shown in formula (II), R a [SiO 3 / 2 ] n formula (II) wherein n is any value in the integer 4 to 12, R a including cycloalkyl, aryl, C1-C 12 alkyl, C1-C 12 alkenyl, C1-C 12 alkynyl; optionally n is 8, R a including C1-C3 alkyl. In the embodiment of the present application, by introducing the covalent polyhedral skeleton shown in formula (II) into the cross-linked polymer, a stable three-dimensional structure can be formed inside the molecule of the cross-linked polymer. The polyhedral skeleton has high symmetry and regularity, and the internal atoms are connected by strong covalent bonds. The molecular structure is not easy to break or collapse in a high-temperature environment, which is conducive to improving the heat resistance of the isolation film. By selecting n as 8 and R1 as C1-C3 alkyl, the rigidity and thermal stability of the cross-linked polymer can be further improved. The cross-linked polymer particles can act as rigid support points at high temperatures, thereby improving the heat resistance of the isolation film and the reliability of the battery cell. In a possible implementation, the cross-linked polymer includes an organic silicon polymer containing a cage-like polysilsesquioxane skeleton. In the embodiments of the present application, by introducing a cage-like polysilsesquioxane skeleton, the cage structure can provide structural support in the organic silicon polymer containing the cage-like polysilsesquioxane skeleton, reducing the occurrence of skeleton collapse or chain segment dissociation at high temperatures, and the cage structure contains Si-O bonds with high bond energy, which are not easy to decompose at high temperatures, which can further improve the thermal stability of the material. At the same time, the organic silicon polymer containing the cage-like polysilsesquioxane skeleton has a three-dimensional network structure formed by random cross-linking of Si-O bonds in addition to the cage-like polysilsesquioxane skeleton, which can further limit the thermal motion of the molecular chain and avoid material softening and deformation at high temperatures; the cage structure as a rigid cross-linking point of the network structure can further enhance the thermal stability of the network, and the material can withstand high temperature decomposition and high temperature deformation, and the combination of the two can further increase the heat resistance of the material. In a possible implementation, the organic silicon polymer containing the cage-like polysilsesquioxane skeleton includes one or more of the monomers shown in formula (III) obtained by hydrolysis and polycondensation, wherein R'1 includes C1-C3 alkyl. In the embodiments of the present application, by using the hydrolysis-polycondensation reaction of the monomer of formula (III), an organic silicon polymer with a relatively complete cage structure and uniformly dispersed molecular chains can be obtained. Therefore, a highly ordered and stable covalent polyhedral skeleton can be formed in the organic silicon polymer, so that the organic silicon polymer is not easy to be structurally fractured or collapsed at high temperatures, the heat resistance of the isolation film is enhanced, and the reliability of the battery cell is improved. In a possible implementation, the organic silicon polymer containing the cage-like polysilsesquioxane skeleton satisfies at least one of the following conditions: (1) the cross-linking degree is 85% to 97%; (2) the organic silicon polymer containing the cage-like polysilsesquioxane skeleton includes a silicon element, and the mass fraction of the silicon element in the organic silicon polymer containing the cage-like polysilsesquioxane skeleton is 25% to 45%; (3) in the organic silicon polymer containing the cage-like polysilsesquioxane skeleton, the mass fraction of the cage-like polysilsesquioxane skeleton is 40% to 60%. In the embodiments of the present application, the cross-linking degree of 85% to 97% can ensure that the organic silicon polymer has good heat resistance at high temperatures, thereby improving the heat resistance of the isolation film. The mass fraction of silicon element reflects the proportion of inorganic silicon-oxygen skeleton in the cross-linked polymer. The mass fraction of silicon element is 25% to 45%, which can improve the thermal decomposition temperature and structural stability of the polymer, and improve the heat resistance of the isolation film at high temperatures. The mass fraction of cage containing cage-like poly silyl siloxane skeleton is 40% to 60%, which can ensure that the cross-linked polymer has good rigidity and structural stability, reduce the structural collapse or brittle fracture of the isolation film under heat abuse, and is beneficial to improve the heat resistance of the isolation film, thereby improving the reliability of the battery monomer at high temperatures. In a possible implementation, the mass fraction of the heat-resistant particles in the coating is 50% to 97%. By limiting the mass fraction of the heat-resistant particles in the coating to meet the above range, the coating can have structural stability and air permeability, improve the heat resistance of the isolation film, and thus improve the reliability of the battery monomer. BRIEF DESCRIPTION OF DRAWINGS In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments of the present application. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by the drawings without creative labor for those skilled in the art. FIG. 1 is a schematic diagram of a battery monomer according to an embodiment of the present application. FIG. 2 is a structural schematic diagram of a battery monomer according to another embodiment of the present application. FIG. 3 is a schematic diagram of a battery device according to an embodiment of the present application. FIG. 4 is a schematic diagram of an electric equipment according to an embodiment of the present application. FIG. 5 is a schematic diagram of an electric equipment according to another embodiment of the present application. FIG. 6 is a cross-linking degree test result diagram of the heat-resistant particle powder according to an embodiment of the present application. FIG. 7 is a thermal cracking spectrum diagram of the heat-resistant particle powder according to an embodiment of the present application. Reference signs: 3: battery monomer; 30: shell; 31: housing; 313: pressure relief mechanism; 32: end cover; 322: electrode terminal; 33: electrode assembly; 331: tab; 34: connecting member; 10: battery device; 11: box body; 111: first box body part; 112: second box body part; 1: vehicle; 4: controller; 5: motor; 2: energy storage device. DETAILED DESCRIPTION Hereinafter, the embodiments of the battery cell, the battery device, and the electric device of the present application are described in detail with appropriate reference to the accompanying drawings, but there are cases where unnecessary detailed description is omitted. For example, there are cases where detailed description of matters known well, repeated description of substantially identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for those skilled in the art to fully understand the present application, and are not intended to limit the subject matter recited in the claims. The ranges disclosed herein are defined by their lower and upper limits. Ranges created by the upper and lower limits are inclusive of the endpoints. Ranges created by the upper and lower limits are also inclusive of any point or sub-range falling within the range. For example, if a range is stated as 60-120 and 80-110, it is understood that the range created by the endpoints 60-110 and 80-120 are also contemplated. Additionally, if a range is stated as 1-2 and 3-5, it is understood that the ranges created by the endpoints 1-3, 1-5, 2-3, 2-5, and 3-5 are also contemplated. In this application, the use of "or" means "and / or" unless specifically stated otherwise, e.g., the phrase "X employs A or B" means that X employs A or B or both. Also, the use of "comprise", "comprises", "comprising", "containing", "contains", "contained", "include", "includes" or "including" throughout this application are taken to specify the presence of stated features, integers, steps or components but not to preclude the presence or addition of one or more other features, integers, steps, components, or groups thereof. Furthermore, to the extent that the term "includes" is used in either the detailed description or the claims, such term is intended to be inclusive in a manner similar to the term "comprising" as "comprising" is interpreted when employed as a transitional word in the introductory clauses of the claims. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The use of the terms "including," "comprising," or "having" in the detailed description and the claims herein are used to mean one or more of the listed features or aspects desired can be present alone or in any combination of one or more other features or aspects. Other combinations and / or permutations of one or more of the above described features and aspects can be learned by those skilled in the art given the benefit of this description. If not specifically stated, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions. If not specifically stated, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions. If not specifically stated, the following terms have the following meanings. Any undefined terms have their art-recognized meanings. In embodiments of the present application, "alkyl" is intended to encompass straight chain and branched alkyl groups. For example, alkyl can be C1-C20 alkyl, C1-C12 alkyl, C1-C10 alkyl, C1-C6 alkyl, C1-C4 alkyl. In some embodiments, alkyl includes methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, t-butyl, cyclobutyl, pentyl, isopentyl, neopentyl, t-pentyl, cyclopentyl, hexyl, cyclohexyl, heptyl, cycloheptyl, octyl, cyclooctyl, nonyl, and decyl, among others. Additionally, alkyl groups can be optionally substituted, for example, alkyl groups substituted with halogen are haloalkyl groups. The term "haloalkyl" refers to alkyl groups in which some or all of the hydrogen atoms are replaced by halogen atoms, where the term "halogen atom" refers to fluorine, chlorine, bromine, iodine, and the like. 20 alkyl, C1-C12 alkyl, C1-C10 alkyl, C1-C6 alkyl, C1-C4 alkyl. In some embodiments, alkyl includes methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, t-butyl, cyclobutyl, pentyl, isopentyl, neopentyl, t-pentyl, cyclopentyl, hexyl, cyclohexyl, heptyl, cycloheptyl, octyl, cyclooctyl, nonyl, and decyl, among others. Additionally, alkyl groups can be optionally substituted, for example, alkyl groups substituted with halogen are haloalkyl groups. The term "haloalkyl" refers to alkyl groups in which some or all of the hydrogen atoms are replaced by halogen atoms, where the term "halogen atom" refers to fluorine, chlorine, bromine, iodine, and the like. In embodiments of the present application, substituents of compounds are disclosed in combination ranges. For example, "C1-C12 alkyl" can represent C1, C2, C3, C4, C5, C6, C7, C8, C9, C10, C11, C12, C1-C12, C1-C11, C1-C10, C1-C9, C1-C8, C1-C7, C1-C6, C1-C5, C1-C4, C1-C3, C1-C2, C2-C12, C2-C11, C2-C10, C2-C9, C2-C8, C2-C7, C2-C6, C2-C5, C2-C4, C2-C3, C3-C12, C3-C11, C3-C10, C3-C9, C3-C8, C3-C7, C3-C6, C3-C5, C3-C4, C4-C12, C4-C11, C4-C10, C4-C9, C4-C8, C4-C7, C4-C6, C4-C5, C5-C12, C5-C11, C5-C10, C5-C9, C5-C8, C5-C7, C5-C6, C6-C12, C6-C11, C6-C10, C6-C9, C6-C8, C6-C7, C7-C12, C7-C11, C7-C10, C7-C9, C7-C8, C8-C12, C8-C11, C8-C10, C8-C9, C9-C12, C9-C11, C9-C10, C10-C12, C10-C11, and C11-C12 alkyl. In embodiments of the present application, "alkenyl" refers to non-aromatic unsaturated hydrocarbon groups containing one or more carbon-carbon double bonds (C=C) in the molecular structure. For example, alkenyl can be C2-C20 alkenyl, C2-C12 alkenyl, C2-C10 alkenyl, C2-C6 alkenyl, C2-C4 alkenyl. In some embodiments, alkenyl includes ethenyl, 1-propenyl, 2-propenyl (allyl), 1-butenyl, 2-butenyl, 3-butenyl, 1,3-butanedienyl, pentenyl, hexenyl, cyclohexenyl, heptenyl, octenyl, nonenyl, decenyl, and the like. The "cycloalkyl" in the embodiments of the present application refers to saturated cyclic alkyl groups with single ring, double ring and multiple rings. Specifically, the cycloalkyl group is a hydrocarbon group composed of one or more saturated carbon rings, which can be a single ring structure or a fused ring structure formed by connecting multiple rings through sharing one or more atoms. For example, the cycloalkyl group with a single ring structure can be cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclodecyl, etc.; the cycloalkyl group with a fused ring structure can be cyclopentenyl, cyclohexenyl, tricycloalkyl, etc. The "alkynyl" in the embodiments of the present application refers to a hydrocarbon group with carbon-carbon triple bond (C≡C). In the present application, the terms "a plurality of" and "a plurality of" refer to two or more than two. Generally, the battery monomer includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator. In the charging and discharging process of the battery monomer, the active ions are embedded and extracted between the positive electrode sheet and the negative electrode sheet. Among them, the electrolyte plays a role in conducting active ions between the positive electrode sheet and the negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet, which prevents the positive and negative electrodes from short-circuiting while allowing the active ions to pass through, so that the electrochemical reaction of the battery monomer can proceed normally. The development of battery technology needs to consider many design factors, such as energy density, cycle life, discharge capacity, charge-discharge rate, reliability, etc. Among them, the separator membrane is an important component to support the battery monomer to complete the charging and discharging electrochemical process, and the commonly used separator membrane is mostly polyolefin material, but the heat resistance of polyolefin material is poor, which is easy to soften or melt at high temperature, which is easy to cause the battery monomer to short circuit. In order to improve the heat resistance of the separator membrane, a coating layer is usually coated on the separator membrane to improve the heat resistance of the separator membrane. Boehmite, alumina and other inorganic particles are currently commonly used heat-resistant particles, but the density of such heat-resistant particles is relatively large, and the mass is relatively large under the same packing volume, which will affect the energy density of the battery monomer. In order to further improve the energy density of the battery monomer, the inorganic particles such as boehmite and alumina are replaced by organic heat-resistant particles in the prior art, and the existing organic heat-resistant particles are often easy to break chain and decompose at high temperature, resulting in poor heat resistance of the separator. How to make the separator membrane of the high-energy-density battery monomer have better heat resistance is a technical problem to be solved at present. Therefore, the embodiments of the present application provide a battery monomer, which comprises a positive electrode sheet, a negative electrode sheet and a separator membrane, the separator membrane is located between the positive electrode sheet and the negative electrode sheet; the separator membrane comprises a porous base film and a coating layer arranged on at least one side of the porous base film; the coating layer comprises heat-resistant particles, the heat-resistant particles comprise a cross-linked polymer, and the cross-linking degree of the cross-linked polymer is 70% to 98%. In the above technical solution, on the one hand, the cross-linked polymer has a three-dimensional network structure, which can maintain a stable spatial configuration under thermal stress, so that the isolation film has good heat resistance. On the other hand, by controlling the cross-linking degree of the cross-linked polymer to be 70% to 98%, the coating particles can have good heat resistance at high temperatures, the heat resistance of the isolation film is improved, the overall structural integrity of the isolation film at high temperatures is ensured, and the reliability of the battery cell under high temperature conditions is improved. Next, the battery cell provided by the embodiments of the present application is introduced. [Battery cell] The embodiments of the present application provide a battery cell, which comprises a positive electrode sheet, a negative electrode sheet and an isolation film, the isolation film being located between the positive electrode sheet and the negative electrode sheet; the isolation film comprises a porous base film and a coating layer arranged on at least one side of the porous base film; the coating layer comprises heat-resistant particles, and the heat-resistant particles comprise a cross-linked polymer, and the cross-linking degree of the cross-linked polymer is 70% to 98%. In the embodiments of the present application, the porous base film refers to a thin film material having a micrometer and / or nanometer level pore structure. The porous base film can be a single-layer thin film or a multi-layer composite thin film. When the porous base film is a multi-layer composite thin film, the materials of the layers can be the same or different. In some embodiments, the porous base film can comprise a film or non-woven web selected from any one or at least two of the following: polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyamide, polycarbonate, polyimide, polyether ether ketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyether sulfone, polyphenylene ether, cyclic olefin copolymer, polyphenylene sulfide, polyvinyl naphthalene. In some embodiments, the thickness of the porous base film can be 4 μm to 15 μm, and can be optionally 4 μm to 9 μm. In some embodiments, the porosity of the porous base film can be 25% to 60%, and can be optionally 28% to 50%. In some embodiments, the average pore size of the porous base film can be 25 nm to 82 nm. The average pore size of the porous base film can be tested by using a capillary porosimetry tester (bubble point method). An exemplary testing method is as follows: a circular sample with a diameter of 25 mm is taken, 3-5 drops of wetting liquid are dropped on it, and after the sample is completely wetted, it is placed in a mold, and then an inert gas (such as nitrogen) is used to extrude the wetting liquid in the pore channel of the sample to be tested, the extrusion gas pressure and flow rate are inversely proportional to the pore size, and the average pore size of the sample to be tested is obtained by software sampling and pressure and pore size conversion analysis. The testing instrument can be a CFP 1500 pore size analyzer of PMI Company, and the testing pressure can be 100 psi to 350 psi. In the embodiments of the present application, the heat-resistant particles refer to particles that have certain thermal stability, can maintain their physical and chemical properties in a high-temperature environment, and are not prone to cracking, melting or softening. In the embodiments of the present application, the “cross-linked polymer” refers to a polymer material that forms a three-dimensional network structure through chemical cross-linking between molecular chains. This structure is usually formed by cross-linking during polymerization or post-processing with multiple reactive functional groups, so that the whole polymer forms a stable spatial structure. The cross-linking degree refers to the degree of cross-linking between the molecular chains of the cross-linked polymer through chemical cross-linking. The higher the cross-linking degree, the more cross-linking points between the molecular chains, and the more stable the structure of the polymer, which is conducive to improving the heat resistance and thermal decomposition temperature of the heat-resistant particles, thereby improving the heat resistance of the isolation film. In the embodiments of the present application, the cross-linking degree refers to the proportion of the molecular chain segments bound by the cross-linked network in the total chain segments of the cross-linked polymer obtained by fitting the software at a specific temperature and a specific test frequency through nuclear magnetic resonance (NMR). Through nuclear magnetic resonance testing of the polymer, different components in the polymer backbone have different relaxation kinetics, for example, the monomer or solvent part has strong fluidity and decays the slowest; the non-cross-linked segment has certain molecular motion characteristics and decays relatively slowly; and the cross-linked segment is highly constrained and has small molecular motion characteristics, and decays relatively quickly. Therefore, by collecting the entire high molecular signal and calculating the proportion of the cross-linked signal, the cross-linking degree of the polymer backbone can be obtained. Specifically, the cross-linking degree of the cross-linked polymer can be 70%, 72%, 74%, 76%, 78%, 80%, 82%, 84%, 86%, 88%, 90%, 92%, 94%, 96%, 97%, 98%, or a value within the range obtained by any two of the above combinations. In the embodiments of the present application, the cross-linking degree of the cross-linked polymer can be tested by a PQ001 nuclear magnetic resonance analyzer. The test temperature is 60°C, the resonance frequency of the nuclear magnetic resonance analyzer is set to 21 MHz, 0.5 g of the cleaned and dried sample (the above heat-resistant particles) to be tested is taken, is loaded into a clean sample tube and is inserted into a probe at a specified depth, the probe coil diameter is 13 mm, and the measurement is performed according to the manufacturer's instructions. Specifically, the cross-linking degree of the cross-linked polymer is obtained by collecting the entire high molecular signal and calculating the proportion of the cross-linked signal by fitting software; the “cross-linking degree” or “T2 relaxation” test mode is selected in the software, and the PQ001 nuclear magnetic resonance analyzer automatically obtains the relaxation decay curve. During data processing, the software decomposes the relaxation components by exponential fitting, calculates and outputs the cross-linking degree result according to the degree of restriction of molecular chain movement. In the technical solution, on the one hand, the cross-linked polymer has a three-dimensional network structure, which can maintain a stable spatial configuration under thermal stress, so that the isolation film has good heat resistance. On the other hand, by controlling the cross-linking degree of the cross-linked polymer to be 70% to 98%, the coating particles can have good heat resistance at high temperatures, the heat resistance of the isolation film is improved, the overall structural integrity of the isolation film at high temperatures is ensured, and the reliability of the battery cell under high temperature conditions is improved. In some embodiments, the cross-linked polymer includes a planar cyclic conjugated group and / or a covalent polyhedral skeleton. In the embodiments of the present application, the "planar cyclic conjugated group" refers to a closed ring structure formed by a plurality of atoms connected by covalent bonds, and all atoms participating in bonding are coplanar, and there is a delocalized Π bond. Due to the existence of conjugation effect and planar structure, the structure is difficult to deform at high temperature, showing strong rigidity, so that the cross-linked polymer containing the planar cyclic conjugated group has high thermal stability. In the embodiments of the present application, the "covalent polyhedral skeleton" refers to a skeleton structure formed by a plurality of atoms connected by covalent bonds, having polyhedral geometric characteristics, such as tetrahedron, octahedron, and icosahedron. The polyhedral skeleton has a highly symmetrical geometric structure, and the atoms in the skeleton are connected by covalent bonds, which are higher than ionic bonds or intermolecular forces, and the structure is not easy to break or collapse at high temperature. Therefore, the cross-linked polymer containing the covalent polyhedral skeleton has high thermal stability. In the above embodiments, the cross-linked polymer includes a planar cyclic conjugated group and / or a covalent polyhedral skeleton. The planar cyclic conjugated group is not easy to deform at high temperature due to the conjugation effect and planar structure, showing high rigidity, and the polymer molecules are difficult to pyrolyze or soften, so that the cross-linked polymer containing the planar cyclic conjugated group has high thermal stability. The covalent polyhedral skeleton has a highly symmetrical three-dimensional geometric structure and a strong covalent bond connection higher than ionic bonds or intermolecular forces, and its structure is not easy to break or collapse at high temperature, so that the cross-linked polymer containing the covalent polyhedral skeleton has high thermal stability. Therefore, the cross-linked polymer containing the planar cyclic conjugated group and / or the covalent polyhedral skeleton has good heat resistance and thermal stability, and when it is used in the isolation film, the overall heat resistance of the isolation film is improved, and the reliability of the battery cell at high temperature is improved. In some embodiments, the coating layer includes heat-resistant particles and a first binder, the first binder is used to bond the heat-resistant particles to the porous base film; the heat-resistant particles include a cross-linked polymer; the main chain or side chain of the cross-linked polymer has a rigid structure, the rigid structure includes a planar cyclic conjugated group and / or a covalent polyhedral skeleton The "organic compound" in the embodiments of the present application refers to a carbon-containing compound. In addition to simple compounds such as carbon oxides, carbonic acid, and carbonates, an organic compound usually also includes hydrogen, oxygen, nitrogen, sulfur, and other elements. In the embodiments of the present application, the main chain or side chain of an organic compound having a rigid structure refers to a functional group having a low degree of freedom, and the atoms in the molecule are not easy to rotate or twist freely. In some embodiments, the planar cyclic conjugated group includes any one of a substituted or unsubstituted phenyl group, a substituted or unsubstituted heteroatom-containing aromatic group, a substituted or unsubstituted fused ring aromatic group, or a substituted or unsubstituted triazine ring group. Optionally, the planar cyclic conjugated group includes any one of a phenyl group or a triazine ring group. In the embodiments of the present application, the "substituted or unsubstituted phenyl group" refers to a phenyl group in which one or more hydrogen atoms on the benzene ring structure are substituted by one or more substituents, or a phenyl group in which the hydrogen atoms on the benzene ring structure are not substituted by other substituents. The substituents include one or more of halogen atoms, alkyl groups, alkenyl groups, cycloalkyl groups, and alkoxy groups, independently. In some embodiments, the "halogen atom" includes a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, and the like. The "alkyl group" includes a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a cyclobutyl group, a pentyl group, an isopentyl group, a neopentyl group, a tert-pentyl group, a cyclopentyl group, a hexyl group, a cyclohexyl group, a heptyl group, a cycloheptyl group, an octyl group, a cyclooctyl group, a nonyl group, and a decyl group, and the like. The "alkenyl group" includes an ethylene group, an allyl group, a n-butene group, and the like. The "cycloalkyl group" includes a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, and the like. The "alkoxy group" (alkyl group connected by an oxygen atom) includes a methoxy group, an ethoxy group, a propoxy group, and the like. In the embodiments of the present application, the "substituted or unsubstituted heteroatom-containing aromatic group" refers to an aromatic group in which one or more hydrogen atoms in the aromatic ring structure are substituted by one or more heteroatoms, or an aromatic group in which the hydrogen atoms in the aromatic ring structure are not substituted by other substituents. The "heteroatom" refers to an atom other than a carbon atom and a hydrogen atom, such as a nitrogen atom, an oxygen atom, a sulfur atom, a phosphorus atom, and the like. For example, the heteroatom-containing aromatic group can include, but is not limited to, a nitrogen-containing pyrrole group, a pyridine group, an imidazole group, a thiophene group, a thiazole group, and the like. The "substituted or unsubstituted fused ring aromatic group" refers to a structure formed by the mutual connection of multiple aromatic rings, in which the hydrogen atoms on each aromatic ring can be substituted by one or more substituents, or the hydrogen atoms in the aromatic ring structure are not substituted by other substituents. For example, the fused ring aromatic group can include, but is not limited to, a naphthyl group, a phenanthryl group, an anthryl group, an acenaphthyl group, a fluorenyl group, a fluoranthene group, a dinaphthyl group, and the like. A triazine ring group refers to a six-membered ring structure composed of three nitrogen atoms. A "substituted or unsubstituted triazine ring group" refers to a structure in which each nitrogen atom in the triazine ring structure can be substituted with one or more substituents, or a structure in which the hydrogen atoms in the nitrogen atom structure are not substituted with other substituents. The substituents include one or more combinations of an alkyl group, an alkenyl group, a phenyl group, a cycloalkyl group, an amine group, a hydroxyl group, and a halogen. For example, the triazine ring group can include, but is not limited to, a triazene group, a triazine group, a chlorotriazine group, an aminotriazine group, a methyltriazine group, and the like. In the above embodiments, by limiting the types of planar cyclic conjugated groups in the cross-linked polymer, the heat resistance and chemical stability of the cross-linked polymer can be further enhanced, thereby improving the heat resistance of the separation membrane. The phenyl group has good structural stability and conjugation effect, which can improve the thermal stability of the cross-linked polymer; the heteroatom-containing aromatic group has a more stable electronic structure and enhances its oxidation resistance due to the participation of the heteroatom in conjugation, reducing the probability of reaction between the cross-linked polymer and the electrolyte; the fused ring aromatic group has a larger π conjugated system, is more rigid, and has a higher thermal decomposition temperature; the triazine ring group contains multiple nitrogen atoms, which can maintain structural stability at high temperatures. The inclusion of the above-mentioned groups in the cross-linked polymer makes it more difficult for the cross-linked polymer particles in the coating to deform or break at high temperatures, thereby making the separation membrane have good heat resistance and improving the reliability of the battery cell. In some embodiments, the cross-linked polymer includes at least one of a phenolic resin-based polymer, a polymer containing a triazine ring group, a phenyl-containing silicone polymer, and a cross-linked styrene-based polymer. In some embodiments, the phenolic resin-based polymer is a thermosetting resin. In some embodiments, the phenolic resin-based polymer is a thermosetting resol resin. The synthetic monomers of the phenolic resin-based polymer can include a phenolic compound and an aldehyde compound. In some embodiments, the phenolic compound can include one or more of phenol, p-benzenediol, m-benzenediol, o-benzenediol, cresol, and cardanol. In some embodiments, the aldehyde compound can include one or more of formaldehyde, paraformaldehyde, acetaldehyde, propionaldehyde, n-butyraldehyde, glyoxal, and furfural. In some embodiments, the phenolic resin-based polymer has no glass transition temperature below 300°C. The fact that the phenolic resin-based polymer has no glass transition temperature below 300°C indicates that the organic particles have good heat resistance and thermal stability, thereby better resisting the thermal shrinkage of the porous base film, improving the heat resistance of the separation membrane, and improving the reliability of the secondary battery cell. In some embodiments, the phenolic resin-based polymer can have a volume distribution particle size Dv50 of 200 nm-840 nm. The volume distribution particle size Dv50 of the phenolic resin polymer is within the above range, which is beneficial to the coating of the separation membrane to have good heat resistance and air permeability. In some embodiments, the phenolic resin polymer does not have an oxidation peak in the cyclic voltammetry curve of the first cycle in the voltage range of 0V to 4.40V. In some embodiments, the method for preparing the phenolic resin polymer comprises the following steps: providing a resol resin material; curing the resol resin material at a first temperature in an oxygen-containing atmosphere for a first time, then curing the resol resin material at a second temperature in an oxygen-containing atmosphere for a second time, and then crushing to obtain the phenolic resin polymer. The first temperature is 100℃-170℃, and the second temperature is 220℃-290℃. In some embodiments, the phenolic resin polymer with high crosslinking degree is obtained by segmental curing of the resol resin material. First, the resol resin material is cured at 100℃-170℃, in which process, the resol resin material gradually cures, and small molecular groups and easily oxidizable groups in the resol resin material begin to eliminate; then the resol resin material is cured again at 220℃-290℃, in which process, the resol resin material continues to carry out crosslinking curing reaction and is more fully cured; further, the first stage curing and the second stage curing are carried out in an oxygen-containing atmosphere, and the oxidation treatment of the easily oxidizable groups in the resol resin material is carried out in advance in the oxygen-containing atmosphere, at which time the phenol structure is oxidized into a benzoquinone structure, and the benzoquinone structure is not easy to be oxidized, thereby obtaining the phenolic resin polymer with high crosslinking degree. In some embodiments, the oxygen-containing atmosphere can include oxygen and inert gas, and the volume fraction of oxygen in the oxygen-containing atmosphere can be 5%-50%. Alternatively, the inert gas can include one or more of nitrogen, argon, and helium, but is not limited thereto. Alternatively, the volume fraction of oxygen in the oxygen-containing atmosphere can be 10%-30%. More alternatively, the oxygen-containing atmosphere can be an air atmosphere, thereby further reducing the cost. The first temperature is 100℃-170℃, for example, can be 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, 130℃, 135℃, 140℃, 145℃, 150℃, 155℃, 160℃, 165℃, 170℃, or a range consisting of any of the above values. Alternatively, the first temperature can be 110℃-170℃, 110℃-160℃, 110℃-150℃, 120℃-170℃, 120℃-160℃, 120℃-150℃. The first temperature is within the above range, which can make the curing of the resol resin material in the first stage more uniform and sufficient, and thus a phenolic resin polymer with high crosslinking degree can be obtained. In some embodiments, the first time can be 2h-4h, for example, can be 2h, 2.2h, 2.4h, 2.6h, 2.8h, 3h, 3.2h, 3.4h, 3.6h, 3.8h, 4h, or a range consisting of any of the above values. The first time is within the above range, which can make the curing of the resol resin material in the first stage more uniform and sufficient, and thus a phenolic resin polymer with high crosslinking degree can be obtained. The second temperature is 220℃-290℃, for example, can be 220℃, 225℃, 230℃, 235℃, 240℃, 245℃, 250℃, 255℃, 260℃, 265℃, 270℃, 275℃, 280℃, 285℃, 290℃, or a range consisting of any of the above values. Alternatively, the second temperature can be 220℃-280℃, 220℃-270℃. The second temperature is within the above range, which can make the curing of the resol resin material in the first stage more uniform and sufficient, and thus a phenolic resin polymer with high crosslinking degree can be obtained. In some embodiments, the second time can be 2h-6h, for example, can be 2h, 2.2h, 2.4h, 2.6h, 2.8h, 3h, 3.2h, 3.4h, 3.6h, 3.8h, 4h, 4.2h, 4.4h, 4.6h, 4.8h, 5h, 5.2h, 5.4h, 5.6h, 5.8h, 6h, or a range consisting of any of the above values. The second time is within the above range, which can make the curing of the resol resin material in the first stage more uniform and sufficient, and thus a phenolic resin polymer with high crosslinking degree can be obtained. In some embodiments, the preparation method of the phenolic resin polymer further comprises the steps of sieving treatment and magnetic removal treatment after the crushing treatment. In some embodiments, the free phenol content of the resol resin material can be 5% or less, optionally 4% or less, 3% or less, 2% or less. In some embodiments, the free aldehyde content of the resol resin material can be 5% or less, optionally 4% or less, 3% or less, 2% or less. Low content of free phenol and free aldehyde helps to obtain a phenolic resin polymer with higher crosslinking degree. The resol resin material can be commercially available or synthesized according to methods known in the art. In some embodiments, the method for preparing the resol resin-like material comprises the following steps: reacting a phenolic compound and an aldehyde compound under catalysis of a basic substance to obtain the resol resin-like material. Optionally, the basic substance can comprise one or more of ammonia, NaOH, Na2CO3. Optionally, the phenolic compound can comprise one or more of phenol, hydroquinone, resorcinol, catechol, cresol, cardanol. Optionally, the aldehyde compound can comprise one or more of formaldehyde, paraformaldehyde, acetaldehyde, propyl aldehyde, n-butyl aldehyde, glyoxal, and furfural. Optionally, the molar ratio of the phenolic hydroxyl group of the phenolic compound to the aldehyde group of the aldehyde compound can be 1:1.1 to 1:2.5; thereby, the mass percentage of the phenol group in the phenolic resin-like polymer can be controlled. In some embodiments, the polymer containing triazine ring groups further comprises a bridging structure connecting the triazine ring structural units. The polymer containing triazine ring groups comprises a plurality of triazine ring structural units in the molecular structure, and the bridging structure refers to a group connecting the triazine ring structural units, and each bridging structure is the same or different. Optionally, the bridging structure can comprise one or a combination of two or more of alkylene, alkylene ether, and alkylene amine. In some embodiments, the polymer containing triazine ring groups can comprise melamine-aldehyde polymer and derivatives thereof. In some embodiments, the melamine-aldehyde polymer and derivatives thereof can comprise melamine formaldehyde polymer and derivatives thereof. Optionally, the melamine-aldehyde polymer and derivatives thereof can comprise one or more of melamine formaldehyde, benzotriazine formaldehyde, melamine-benzotriazine formaldehyde, melamine-(2,4-diamino-1,3,5-triazine) formaldehyde, melamine-(6-methyl-1,3,5-triazine-2,4-diamine) formaldehyde, melamine-(2,4,6-triethylamino-1,3,5-triazine) formaldehyde, trihydrazinyl-s-triazine formaldehyde, melamine-(2-amino-4-methylamino-1,3,5-triazine) formaldehyde, melamine-(2,4-diamino-6-dimethylamino-1,3,5-triazine) formaldehyde. In some embodiments, the polymer containing triazine ring groups has no glass transition temperature below 300°C. The polymer containing triazine ring groups has no glass transition temperature below 300°C, indicating that the organic particles have good heat resistance and thermal stability, thereby better resisting thermal shrinkage of the porous base film, improving the heat resistance of the isolation film, and improving the reliability of the secondary battery cell. In some embodiments, the volume distribution particle size Dv50 of the polymer containing triazine ring group can be 200 nm to 840 nm. The volume distribution particle size Dv50 of the polymer containing triazine ring group in the above range is beneficial to the coating of the separation membrane having good heat resistance and air permeability. In some embodiments, the cyclic voltammogram of the polymer containing triazine ring group in the first cycle has no oxidation peak in the voltage range of 0 V to 4.40 V. In some embodiments, the method for preparing the polymer containing triazine ring group comprises the following steps: providing a precursor containing triazine ring structure; heating and curing the precursor containing triazine ring structure in an oxygen-containing atmosphere, and then crushing to obtain polymer particles containing triazine ring structure units, and the heating and curing temperature is 220°C to 290°C. After the heating and curing of the precursor containing triazine ring structure, a bridging structure is formed between the triazine ring structure units. The heating and curing temperature is 220°C to 290°C, for example, it can be 220°C, 225°C, 230°C, 235°C, 240°C, 245°C, 250°C, 255°C, 260°C, 265°C, 270°C, 275°C, 280°C, 290°C, or a range consisting of any of the above values. Heating and curing the precursor containing triazine ring structure at 220°C to 290°C can obtain polymer particles containing triazine ring structure units with higher cross-linking degree. Alternatively, the heating and curing temperature can be 225°C to 290°C, 230°C to 290°C, 225°C to 280°C, or 230°C to 280°C. In some embodiments, the heating and curing time can be 3h to 6h, for example, it can be 3h, 3.2h, 3.4h, 3.6h, 3.8h, 4h, 4.2h, 4.4h, 4.6h, 4.8h, 5h, 5.2h, 5.4h, 5.6h, 5.8h, 6h, or a range consisting of any of the above values. The heating and curing time in the above range is beneficial to the precursor containing triazine ring structure to form a polymer containing triazine ring group with higher cross-linking degree. In some embodiments, the oxygen-containing atmosphere can include oxygen and an inert gas. Alternatively, the inert gas can include, but is not limited to, one or more of nitrogen, argon, and helium. In some embodiments, the volume fraction of oxygen in the oxygen-containing atmosphere can be 5% to 50%. Alternatively, the volume fraction of oxygen in the oxygen-containing atmosphere can be 10% to 30%. More alternatively, the oxygen-containing atmosphere can be an air atmosphere. In some embodiments, the polymer containing triazine ring group further comprises the steps of sieving and demagnetizing after the crushing treatment. In some embodiments, the precursor containing a triazine ring structure may include melamine aldehyde resins. Melamine aldehyde resins may be obtained by reacting an aldehyde compound with an amine-substituted triazine compound, which may include melamine and / or melamine derivatives. In some embodiments, aldehyde compounds may include one or more of formaldehyde, paraformaldehyde, acetaldehyde, propionaldehyde, n-butyraldehyde, glyoxal, and furfural. In some embodiments, the amine-substituted triazine compound may include one or more compounds of the following general formula, wherein R1 and R2 are each independently selected from H, -NH2, and C1-C8 alkyl, and R3 is selected from H, -NH2, -NHR4, C1-C8 alkyl, C2-C8 alkenyl, phenyl, and C7-C 12 alkylphenyl, C7-C 12 R4 is selected from any of the phenylalkyl group or C5-C8 cycloalkyl group, and R3 is selected from any of the -NH2 group or C1-C8 alkyl group. Optionally, R3 is selected from -NH2 or -NHR4. Optionally, the amine-substituted triazine compound may include melamine, benzomelamine, 2,4-diamino-1,3,5-triazine, 6-methyl-1,3,5-triazine-2,4-diamine, 2,4,6-triethylamino-1,3,5-triazine, trihydrazine, 2-amino-4-methylamino-1,3,5-triazine, 2,4-diamino-6-dimethylamino-1,3,5-triazine, 6-ethyl-1,3,5-triazine-2,4-diamine, 6-isopropyl-1,3,5-triazine-2,4-diamine, 6-pentyl-2,4-diamino-1,3,5-triazine, 6-heptyl-2,4-diamino-triazine, 2-ethyl Alkenyl-4,6-diamino-1,3,5-triazine, 2,4-diamino-6-(4-methylphenyl)-1,3,5-triazine, 6-cyclohexyl-1,3,5-triazine-2,4-diamine, 6-(3-methylphenyl)-1,3,5-triazine-2,4-diamine, 6-o-tolyl-1,3,5-triazine-2,4-diamine, 6-(2,4-dimethylphenyl)-1,3,5-triazine-2,4-diamine, 6-phenylmethyl-1,3,5-triazine-2,4-diamine, (diamino-1,3,5-triazine-2-yl)methanol, and 2-chloro-4,6-diamino-1,3,5-triazine. Alternatively, the amine-substituted triazine compound may include one or more of melamine, benzomelamine, 2,4-diamino-1,3,5-triazine, 6-methyl-1,3,5-triazine-2,4-diamine, 2,4,6-triethylamino-1,3,5-triazine, trihydrazine, 2-amino-4-methylamino-1,3,5-triazine, and 2,4-diamino-6-dimethylamino-1,3,5-triazine. The molar ratio of the aldehyde compound to the amine-substituted triazine compound can be 1.75:1-3:1, for example, can be 1.75:1, 1.8:1, 1.9:1, 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, 3:1, or a range consisting of any of the above values; by controlling the molar ratio of the aldehyde compound and the amine-substituted triazine compound within the above range, the mass ratio of the triazine ring group in the polymer containing the triazine ring group can be controlled. More optionally, the molar ratio of the aldehyde compound to the amine-substituted triazine compound can be 2:1-3:1, 2.1:1-3:1, 2.2:1-3:1, 2.3:1-3:1, 2.4:1-3:1. In some embodiments, the phenyl-containing organosilicon polymer contains carbon-carbon bonds and siloxane structures; the phenyl-containing organosilicon polymer contains Si-O bonds, which have high bond energy and are not easy to decompose at high temperatures, and can be beneficial to further improve the thermal stability of the material. Optionally, the phenyl-containing organosilicon polymer is a network structure formed with carbon-carbon bonds as the main chain, and the side chain contains siloxane structures. Optionally, the phenyl-containing organosilicon polymer is a network structure formed with carbon-carbon bonds as the main chain, and the side chain contains siloxane structures and benzene ring structures; the organosilicon polymer contains benzene rings, which have good structural stability and conjugation effect (rigid structure), and can improve the thermal stability of the crosslinked polymer; the carbon-carbon bonds in the organosilicon polymer form a network structure as the main chain, which can crosslink and fix the originally freely sliding linear molecular chains, form an overall network, and cannot slide on a large scale at high temperatures, thereby avoiding material softening and deformation, and being beneficial to improve the thermal stability of the material. In some embodiments, the phenyl-containing organosilicon polymer has no glass transition temperature below 300°C. The fact that the phenyl-containing organosilicon polymer has no glass transition temperature below 300°C indicates that the phenyl-containing organosilicon polymer has good heat resistance and thermal stability, and thus can better resist the thermal shrinkage of the porous base film, improve the heat resistance of the isolation film, and improve the reliability of the secondary battery cell. In some embodiments, the volume distribution particle size Dv50 of the phenyl-containing organosilicon polymer can be 88nm-600nm. The volume distribution particle size Dv50 of the phenyl-containing organosilicon polymer within the above range is beneficial to the coating of the isolation film having good heat resistance and air permeability. In some embodiments, the phenyl-containing organosilicon polymer has no oxidation peak in the cyclic voltammetry curve of the first cycle in the voltage range of 0V to 4.40V. In some embodiments, the crosslinked styrene-based polymer comprises styrene or styrene derivative structural units and crosslinking structural units. In some embodiments, the styrene or styrene derivative structural units can comprise one or more of styrene structural units, 1-methyl-1-styrene structural units, 4-methylstyrene structural units, 2-methylstyrene structural units, 2,4-dimethylstyrene structural units, 2,5-dimethylstyrene structural units. In some embodiments, the crosslinking structural units can comprise one or more of divinylbenzene structural units, ethylene glycol dimethacrylate structural units, pentaerythritol tetraacrylate structural units, 1,4-butanediol diacrylate structural units, 1,6-hexanediol diacrylate structural units, 1,8-octanediol diacrylate structural units, trimethylolpropane triacrylate structural units, pentaerythritol trimethacrylate structural units, tetraethylene glycol dimethacrylate structural units, tripropylene glycol diacrylate structural units, N,N-methylenebisacrylamide structural units, N,N'-vinylbisacrylamide structural units, 1,3,5-triacryloylhexahydro-1,3,5-triazine structural units, trisallyl isocyanurate structural units. In some embodiments, the crosslinked styrene-based organic particles have a glass transition temperature Tg g greater than or equal to 150℃. The crosslinked styrene-based polymer has a glass transition temperature Tg g high, good heat resistance and thermal stability, thereby better resisting thermal shrinkage of the porous base film, improving the heat resistance of the separator film, and improving the reliability of the secondary battery cell. In some embodiments, the crosslinked styrene-based polymer has a volume distribution particle size Dv50 of 88nm-295nm. The crosslinked styrene-based polymer has a volume distribution particle size Dv50 within the above range, which is beneficial to the coating of the separator film having good heat resistance and air permeability. In some embodiments, the cyclic voltammogram of the first cycle of the crosslinked styrene-based polymer has no oxidation peak in the voltage range of 0V-4.40V. In some embodiments, the preparation method of the crosslinked styrene-based polymer comprises the following steps: providing a pre-emulsion comprising monomers, a crosslinking agent, an emulsifier, an initiator, and water, and performing emulsion polymerization under the conditions of heating, inert gas protection, and stirring to obtain crosslinked styrene-based organic particles; the monomers comprise one or more of styrene and derivatives thereof; the maturation temperature of the emulsion polymerization is 80℃-92℃, and the maturation time of the emulsion polymerization is 1h-4h. The ripening temperature of the emulsion polymerization reaction is 70-95°C, for example, it can be 70°C, 75°C, 80°C, 81°C, 82°C, 82°C, 83°C, 84°C, 85°C, 86°C, 87°C, 88°C, 89°C, 90°C, 91°C, 92°C, 93°C, 94°C, 95°C, or a range formed by any of the above values. The ripening time of the emulsion polymerization reaction is 1-4h, for example, it can be 1h, 1.2h, 1.4h, 1.6h, 1.8h, 2h, 2.2h, 2.4h, 2.6h, 2.8h, 3h, 3.2h, 3.4h, 3.6h, 3.8h, 4h, or a range formed by any of the above values. The ripening temperature and the ripening time of the emulsion polymerization reaction are within the above ranges, and a cross-linked styrene-based polymer with high cross-linking degree can be obtained. In some embodiments, the emulsion polymerization reaction can include the following steps: under the conditions of a first heating temperature, inert gas protection and stirring, the pre-emulsion is added dropwise into a reactor containing water, and after a first time, the temperature is raised to a ripening temperature for ripening reaction, to obtain a cross-linked styrene-based polymer. Optionally, the first heating temperature can be 55-70°C. Optionally, the first time can be 3-7h. In some embodiments, the mass fraction of the cross-linking agent can be 4-28%, for example, it can be 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 22%, 24%, 26%, 28%, or a range formed by any of the above values, based on 100% of the total mass of the monomer and the cross-linking agent. The mass fraction of the monomer is within the above range, which can control the mass proportion of the benzene ring in the cross-linked styrene-based organic polymer The mass fraction of the cross-linking agent is within the above range, which can improve the heat resistance of the cross-linked styrene-based organic particles. Optionally, the mass fraction of the cross-linking agent can be 6-28%, 8-28%, 10-28%, 4-26%, 6-26%, 8-26%, 10-26%. In some embodiments, the solid content of the emulsion polymerization reaction system can be 10-25%, for example, it can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, or a range formed by any of the above values. The solid content of the emulsion polymerization reaction system refers to the mass fraction of the monomer and the cross-linking agent in the reaction system. The solid content of the emulsion polymerization reaction system is within the above range, which can improve the conversion rate of monomers and increase the crosslinking degree of the crosslinked styrene-based polymer. Optionally, the solid content of the emulsion polymerization reaction system can be 12%-25%, 14%-25%, 16%-25%. In some embodiments, the monomers can include one or more of styrene, 1-methyl-1-styrene, 4-methylstyrene, 2-methylstyrene, 2,4-dimethylstyrene, and 2,5-dimethylstyrene. In some embodiments, the crosslinking agent can include one or more of divinylbenzene, ethylene glycol dimethacrylate, pentaerythritol tetraacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,8-octanediol diacrylate, trimethylolpropane triacrylate, pentaerythritol trimethacrylate, tetraethylene glycol dimethacrylate, tripropylene glycol diacrylate, N,N-methylenebisacrylamide, N,N'-vinylbisacrylamide, 1,3,5-triacryloylhexahydro-1,3,5-triazine, and triallyl isocyanurate. Optionally, the crosslinking agent can include one or more of divinylbenzene, N,N-methylenebisacrylamide, and N,N'-vinylbisacrylamide. In some embodiments, the emulsifier can include, but is not limited to, one or more of sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, fatty acid sorbitan, polysorbate, sodium polyacrylate, polyvinylpyrrolidone, polyvinyl alcohol, polyoxyethylene ether emulsifier, cellulose and its derivatives. Optionally, the polyoxyethylene ether emulsifier can include OP-type emulsifiers such as OP-4, OP-7, OP-10, OP-15, OP-20, and the like. In some embodiments, the mass fraction of the emulsifier can be 0.1%-3% based on 100% of the total mass of the monomers and the crosslinking agent. In some embodiments, the initiator can include, but is not limited to, one or more of sodium persulfate, potassium persulfate, ammonium persulfate, sodium sulfite, sodium bisulfite, azobisdimethylaminoformamide hydrochloride, azobisdimethylaminoimidazole hydrochloride, and azobisdimethylpropyl imidazole. In some embodiments, the mass fraction of the initiator can be 0.16%-3%, optionally 0.2%-2%, 0.25%-2%, based on 100% of the total mass of the monomers and the crosslinking agent. In some embodiments, the method for preparing the crosslinked styrene-based polymer further includes a step of removing the magnetic field after the emulsion polymerization reaction is completed. In the above embodiments, the cross-linked structure formed between the aromatic ring skeleton and the molecular chain contained in the phenolic resin polymer can jointly improve the heat resistance of the cross-linked polymer; the polymer containing a triazine ring can jointly improve the high-temperature resistance and oxidation resistance of the material due to the high conjugation of the triazine ring and the chemical inertness provided by the nitrogen atom, and the three-dimensional cross-linked network formed by the cross-linking between the polymer molecular chains of the triazine ring, so that the isolation film maintains structural integrity during long-term use; the cross-linked styrene polymer can improve the heat resistance of the isolation film through the highly rigid carbon skeleton and the three-dimensional cross-linked network formed by the cross-linking between the molecular chains. By introducing the above at least one cross-linked polymer, the isolation film including the cross-linked polymer has good heat resistance, thereby improving the reliability of the battery cell under high temperature conditions. In some embodiments, the phenyl-containing silicone polymer includes monomers and cross-linking agents represented by formula (I) polymerized to obtain a cross-linked polymer, In formula (I), R1 and R2 each independently include C1-C4 alkyl, C2-C4 alkenyl, R3 includes C1-C4 alkyl or C4-C8 (meth)acryloxyalkyl, and R4 includes C2-C8 alkenyl or C4-C8 (meth)acryloxyalkyl; the cross-linking agent includes divinylbenzene. In the embodiments of the present application, R1 and R2 each independently include at least one of methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, ethenyl, 1-propenyl, 2-propenyl (allyl), 1-butenyl, 2-butenyl, 3-butenyl, 1-methyl-1-propenyl, and 2-methyl-1-propenyl. R3 includes at least one of methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, (meth)acryloyloxy methyl, 2-((meth)acryloyloxy) ethyl, 3-((meth)acryloyloxy) propyl, or 4-((meth)acryloyloxy) butyl. In some embodiments, R3 is methyl or (meth)acryloxyalkyl, which is conducive to the stability of the main chain of the cross-linked polymer when R3 is methyl, and which can further participate in cross-linking when R3 is acryloyloxypropyl, thereby improving the cross-linking degree of the cross-linked polymer; R4 is alkenyl or acryloxyalkyl, which can realize efficient cross-linking through a free radical polymerization reaction, and is further conducive to improving the cross-linking degree of the cross-linked polymer, thereby improving the high-temperature stability of the cross-linked polymer. R4 includes at least one of ethenyl, propenyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl (meth)acryloyloxymethyl, 2-((meth)acryloyloxy) ethyl, 3-((meth)acryloyloxy) propyl, or 4-((meth)acryloyloxy) butyl. Acryloxyalkyl refers to an alkyl chain structure functional group containing an acryloxy end group, (meth)acryloxyalkyl refers to a (meth)acryloxy group substituted with a methyl group on a carbon atom directly connected to a carbonyl group (C=O), which provides a reaction site through a molecular chain end acrylate double bond (C=C), and can further undergo a free radical polymerization reaction with a crosslinking agent, thereby facilitating an increase in the crosslinking degree of the silicone polymer. In the embodiments of the present application, the crosslinking agent refers to a compound containing two or more functional groups capable of reacting with the functional groups on the polymer chain in the molecule, thereby forming covalent bridges between the polymer molecular chains and constructing a three-dimensional network structure. For example, the divinylbenzene in the embodiments of the present application can undergo a crosslinking reaction with an alkenyl group or an acryloyl group to form a covalent bond between the molecular chains with ethylene bridges and benzene rings as connecting points, thereby forming a three-dimensional network structure of the phenyl-containing silicone polymer and improving the heat resistance of the phenyl-containing silicone polymer. In the above embodiments, the polymerization of the monomer represented by formula (I) and the crosslinking agent divinylbenzene can obtain phenyl-containing silicone polymer particles, which have a three-dimensional network skeleton formed by the phenyl structure and the monomer and the crosslinking agent, so that the material exhibits higher glass transition temperature and thermal decomposition temperature, thereby improving the heat resistance of the isolation film and the reliability of the battery cell. In some embodiments, the method for preparing the phenyl-containing silicone polymer comprises the following steps: providing a pre-emulsion containing monomers, a crosslinking agent, an emulsifier, an initiator, and water, and performing an emulsion polymerization reaction under the conditions of heating, inert gas protection, and stirring to obtain silicone organic resin particles. The monomers include silane coupling agents containing alkenyl groups and / or acryloxy groups, and the mass fraction of the crosslinking agent is 2% to 30% based on the total mass of the monomers and the crosslinking agent. By controlling the mass fraction of the crosslinking agent, the mass fraction of the phenyl group in the phenyl-containing silicone polymer and the crosslinking degree of the phenyl-containing silicone polymer can be adjusted. The monomers include silane coupling agents containing alkenyl groups and / or acryloxy groups, so that free radicals are generated between the monomers to undergo crosslinking reactions, and the monomers also undergo crosslinking reactions with the crosslinking agent. Therefore, the phenyl-containing silicone polymer with a three-dimensional network structure can be formed using the monomers and the crosslinking agent of the present disclosure, which is not easy to soften or deform at high temperatures and has high heat resistance and electrochemical stability. The mass fraction of the crosslinking agent is 2% to 30% based on the total mass of the monomers and the crosslinking agent, for example, it can be 2%, 7%, 12%, 17%, 22%, 27%, 30%, or a range composed of any of the above values, and a phenyl-containing silicone polymer with high crosslinking degree can be obtained. The mass fraction of the crosslinking agent is in the above range, and silicone organic resin particles with high electrochemical stability and good heat resistance can be obtained. Optionally, the crosslinking agent can have a mass fraction of 2-30%, 2-25%, 2-20%, 2-15%, 3-30%, 3-25%, 3-20%, 3-15%. In some embodiments, the monomer can include an acryloyloxy silane coupling agent. Optionally, the monomer of formula (I) can include one or more of gamma-methacryloxypropyl tris(trimethylsiloxy)silane, (3-acryloyloxypropyl)tris(trimethylsiloxy)silane, 3-methacryloxypropyltrimethoxysilane, acryloyloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, acryloyloxypropyltriethoxysilane, gamma-methacryloxypropyltriisopropoxysilane, 3-(acryloyloxy)propyltrimethoxysilane, 3-methacryloxypropyltris(methoxyethoxy)silane, 3-methacryloxypropylmethyldimethoxysilane, 3-acryloxypropylmethyldimethoxysilane, methacryloxypropyldimethylmethoxysilane, (3-acryloyloxy)dimethylmethoxysilane, 3-methacryloxypropyldimethylethoxysilane, 3-(methacryloxy)propylmethyldiethoxysilane. In some embodiments, the monomer of formula (I) can include a first monomer and a second monomer. The first monomer can include one or more of gamma-methacryloxypropyl tris(trimethylsiloxy)silane, (3-acryloyloxypropyl)tris(trimethylsiloxy)silane, 3-methacryloxypropyltrimethoxysilane, acryloyloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, acryloyloxypropyltriethoxysilane, gamma-methacryloxypropyltriisopropoxysilane, 3-(acryloyloxy)propyltrimethoxysilane, 3-methacryloxypropyltris(methoxyethoxy)silane. The second monomer can include one or more of 3-methacryloxypropylmethyldimethoxysilane, 3-acryloxypropylmethyldimethoxysilane, methacryloxypropyldimethylmethoxysilane, (3-acryloyloxy)dimethylmethoxysilane, 3-methacryloxypropyldimethylethoxysilane, 3-(methacryloxy)propylmethyldiethoxysilane. The first monomer and the second monomer are different in activity, and by combining the two and reacting with the crosslinking agent, a phenyl-containing silicone polymer with a narrow particle size distribution can be obtained. In some embodiments, the emulsifier can include, but is not limited to, one or more of alkyl sulfate, alkyl sulfonate, Tween emulsifier, fatty alcohol polyoxyethylene ether, fatty alcohol polyoxypropylene ether, cetyl stearyl alcohol polyether, oleyl alcohol polyether. Alternatively, the emulsifier includes one or more of sodium dodecyl sulfate, sodium dodecyl sulfonate, Tween 20, Tween 40, laureth-7, laureth-9, laureth-10, oleyl alcohol polyether-10. In some embodiments, the initiator can include, but is not limited to, one or more of sodium persulfate, potassium persulfate, ammonium persulfate, sodium sulfite, sodium bisulfite, azobisisobutyronitrile, azobisisobutyramidine hydrochloride, azobisisobutylimidazole hydrochloride, azobisisopropylimidazole. In some embodiments, the heating temperature of the maturation stage of the emulsion polymerization reaction can be 75-95℃, for example, can be 75℃, 76℃, 77℃, 78℃, 79℃, 80℃, 81℃, 82℃, 83℃, 84℃, 85℃, or a range consisting of any of the above values. The heating temperature in the above range can ensure the reaction rate, prevent the reaction from being too violent, and obtain a phenyl-containing silicone polymer with high crosslinking degree. In some embodiments, the heating time of the maturation stage of the emulsion polymerization reaction can be 1-4h, which can provide continuous and sufficient time for the condensation reaction, the condensation reaction is sufficient, and a phenyl-containing silicone polymer with high crosslinking degree can be obtained. For example, it can be 1h, 1.2h, 1.4h, 1.6h, 1.8h, 2h, 2.2h, 2.4h, 2.6h, 2.8h, 3h, 3.2h, 3.4h, 3.6h, 3.8h, 4h, or a range consisting of any of the above values. In some embodiments, the emulsion polymerization reaction can include the following steps: under the conditions of a second heating temperature, inert gas protection and stirring, the pre-emulsion is added dropwise into a reactor containing water, and after reacting for a second time, the temperature is raised to the heating temperature of the maturation stage for maturation reaction to obtain the silicon-containing organic resin particles. Alternatively, the second heating temperature can be 55-95℃. Alternatively, the second time can be 3-8h. In some embodiments, the pre-emulsion can further include a pH adjuster. Alternatively, the pH adjuster can include, but is not limited to, one or more of sodium bicarbonate, sodium hydroxide, ammonia, etc. In some embodiments, the method for preparing the silicon-containing organic resin particles can further include a step of magnetic removal after the emulsion polymerization reaction is completed. In some embodiments, the phenyl-containing silicone polymer satisfies one or more of the following conditions: (1) the crosslinking degree of the phenyl-containing silicone polymer is 75% to 95%; (2) the phenyl-containing silicone polymer includes silicon elements, and the mass fraction of the silicon elements in the phenyl-containing silicone crosslinked resin is 10% to 25%; and (3) the mass fraction of the phenyl groups in the phenyl-containing silicone polymer is 2% to 12%. The crosslinking degree of the phenyl-containing silicone polymer can be 75%, 77%, 79%, 81%, 83%, 85%, 87%, 89%, 91%, 93%, 95%, or a value within a range obtained by combining any two of the above values. The mass fraction of the silicon elements in the phenyl-containing silicone crosslinked resin can be 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 25%, or a value within a range obtained by combining any two of the above values. The mass fraction of the phenyl groups in the phenyl-containing silicone polymer can be 5%, 7%, 9%, 11%, 12%, or a value within a range obtained by combining any two of the above values. The crosslinking degree of the phenyl-containing silicone polymer is 75% to 95%, which provides good heat resistance at high temperatures, so that the insulation film has good heat resistance, thereby improving the reliability of the battery cell. The mass fraction of the silicon elements is 10% to 25%, which helps to increase the proportion of inorganic siloxane skeleton in the silicone polymer. The siloxane skeleton including the silicon elements provides a high thermal decomposition temperature and oxidation resistance, so that the insulation film has structural stability in a high-temperature environment. As an example, in the embodiments of the present application, a small amount of powder sample (usually a few milligrams) of the phenyl-containing silicone polymer is ultrasonically cleaned with anhydrous ethanol or deionized water for 1-2 minutes to remove surface impurities; then it is placed in an oven and dried at 60-80°C for 1-2 hours to completely remove water (to avoid sample volatilization affecting the vacuum environment during testing). The dried powder is evenly spread on conductive glue (to ensure that the powder does not accumulate or scatter); then a 5-10 nm thick layer of gold is sprayed on the surface thereof using an ion sputtering instrument; or after the battery cell is disassembled, the insulation film is peeled off, and a regular and clear area of the insulation film is selected. Then, the insulation film sample is fixed on a sample stage and subjected to gold or carbon spraying treatment to make the surface conductive. The sample stage with the sample to be tested is placed in the SEM sample chamber, and after the door is closed, the vacuum system is started to be pumped to a high vacuum state required by the instrument (usually 10-3-10 -5Pa). After the vacuum is up to the standard, the electron gun voltage (usually 5-20 kV) and working distance (usually 5-15 mm) are adjusted, the sample stage is moved by the control software to find the target observation area. The focus and magnification (from low magnification 100x positioning to high magnification 10000x for observing details) are gradually adjusted to obtain clear SEM morphology images, and the feature points or areas that need to be analyzed by EDS are marked. In the SEM software, the EDS detector is started, the marked analysis area (single-point analysis, line scanning or area scanning can be selected) is selected, and the collection time (usually 10-30 seconds, the longer the time, the more accurate the element signal) is set. The energy-dispersive x-ray spectroscopy (EDS) matched with ZEISS sigma300 is used to analyze the elements on the surface of the phenyl-containing organosilicon polymer to detect the content of silicon element in the phenyl-containing organosilicon polymer. According to the data results of the instrument, the distribution of each element can be obtained, and thus the mass percentage of silicon element can be obtained. The mass fraction of the phenyl group is 2% to 12%, which can introduce a rigid structure with aromatic structure and conjugate effect, and further helps to improve the heat resistance of the isolation film. In the embodiments of the present application, the mass fraction of the phenyl group in the organosilicon polymer can be tested by a pyrolysis-gas chromatography-mass spectrometer (Py-GC / MS). Specifically, 0.5-1 mg of the above organosilicon polymer is weighed as a test sample, loaded into a quartz cracking tube of a pyrolysis instrument, cracked at 550℃ for 1.2s, and tested in an inert gas (such as helium) to crack the sample into volatile small molecules, which are then introduced into a gas chromatograph-mass spectrometer. An HP-5ms (30m x 0.25mm x 0.25μm) chromatographic column is selected, the temperature is set to 30℃ for 5min, increased to 250℃ at a rate of 10℃ / min, and maintained at 250℃ for 5min. The carrier gas is high-purity helium with a flow rate of 1.0mL / min. The mass spectrometer uses electrochemical ionization, the ion source temperature is 230℃, and the fragment scan range is m / z 25-200. By comparing with the EVA standard cracking spectrum in the NIST library, the characteristic ions corresponding to the benzene ring are detected, and it can be inferred that the organosilicon polymer includes a benzene ring structure. The internal standard method is used to calculate the mass percentage of the benzene ring in the organosilicon polymer based on the above fragment peak area corresponding to the characteristic benzene ring. Therefore, by limiting the crosslinking degree of the crosslinked polymer, the mass fraction of silicon element and the mass fraction of phenyl group to meet the above ranges respectively, the structure of the phenyl-containing organosilicon polymer can be controlled, so that it has high thermal stability, improves the heat resistance of the isolation film, and further improves the reliability of the battery cell at high temperature. In some embodiments, the covalent polyhedral framework comprises a framework of a compound represented by formula (I), R a [SiO 3 / 2 ]n Formula (II), wherein n is any value from the range of 4 to 12, and R a including at least one of cycloalkyl, aryl, C1-C3 alkyl, C1-C3 alkenyl, and C1-C3 alkynyl; optionally, n is 8, and Ra includes C1-C3 alkyl. 12 including at least one of cycloalkyl, aryl, C1-C3 alkyl, C1-C3 alkenyl, and C1-C3 alkynyl; optionally, n is 8, and Ra includes C1-C3 alkyl. 12 including at least one of cycloalkyl, aryl, C1-C3 alkyl, C1-C3 alkenyl, and C1-C3 alkynyl; optionally, n is 8, and Ra includes C1-C3 alkyl. 12 including at least one of cycloalkyl, aryl, C1-C3 alkyl, C1-C3 alkenyl, and C1-C3 alkynyl; optionally, n is 8, and Ra includes C1-C3 alkyl. In some embodiments, n can be 4, 5, 6, 7, 8, 9, 10, 11, 12, or any value within the range of 4 to 12. R a may include one or more of cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, phenyl, naphthyl, anthryl, phenanthryl, methyl, ethyl, n-propyl, i-propyl, n-butyl, sec-butyl, i-butyl, t-butyl, n-pentyl, i-pentyl, neopentyl, t-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, ethenyl, 1-propenyl, 2-propenyl (allyl), 1-butenyl, 2-butenyl, 3-butenyl, 1,3-butanedienyl, and pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, dodecenyl, ethynyl, 1-propynyl, 2-propynyl (propargyl), 1-butynyl, 3-butynyl, 1-pentynyl, 3-pentynyl, and hexynyl, heptynyl, octynyl, nonynyl, decynyl, undecynyl, dodecynyl. Optionally, n is 8, and Ra includes at least one of methyl, ethyl, n-propyl, and i-propyl. In the above embodiments, by introducing the covalent polyhedral skeleton shown in Formula (II) into the cross-linked polymer, a stable three-dimensional structure can be formed inside the molecule of the cross-linked polymer. Such a polyhedral skeleton has high symmetry and regularity, and the internal atoms are connected by strong covalent bonds. The molecular structure is not easy to break or collapse under high temperature, which is conducive to improving the heat resistance of the isolation film. The Si-O bond in the covalent polyhedral skeleton shown in Formula (II) has high bond energy and is not easy to decompose under high temperature, which can further improve the thermal stability of the material. By selecting n as 8 and Ra as C1-C3 alkyl, the rigidity and thermal stability of the cross-linked polymer can be further improved. The cross-linked polymer particles can act as rigid support points under high temperature, improving the heat resistance of the isolation film, thereby improving the reliability of the battery cell. In some embodiments, the cross-linked polymer includes a siloxane polymer including a cage-like polysilsesquioxane skeleton. In the embodiments of the present application, the organic silicon polymer containing a cage-like polyhedral oligomeric silsesquioxane skeleton refers to a new type of organic-inorganic hybrid polymer obtained by using cage-like polyhedral oligomeric silsesquioxane (POSS) as a skeleton and connecting organic functional groups or polymer chains on the cage structure through chemical modification; the cage-like polyhedral oligomeric silsesquioxane skeleton in the organic silicon polymer has high symmetry and regularity, the internal atoms are connected by strong covalent bonds, the molecular structure is not easy to break or collapse in a high-temperature environment, and the covalent polyhedral skeleton contains Si-O bonds with high bond energy and is not easy to decompose at high temperature, which can help to further improve the thermal stability of the material. In some embodiments, the organic silicon polymer containing a cage-like polyhedral oligomeric silsesquioxane skeleton further includes a network structure (i.e., a three-dimensional network structure) formed by random crosslinking of Si-O bonds. The three-dimensional network structure formed by random crosslinking of Si-O bonds can further limit the thermal motion of the molecular chain and avoid deformation of the material at high temperature. The organic silicon polymer containing a cage-like polyhedral oligomeric silsesquioxane skeleton in the present application includes both a regular cage-like polyhedral oligomeric silsesquioxane skeleton formed by Si-O bonds and a network structure formed by random crosslinking of Si-O bonds; the material contains both a cage structure and a network structure, and the cage structure acts as a rigid crosslinking point of the network structure, which can further enhance the thermal stability of the network, so that the material can withstand high-temperature decomposition and high-temperature deformation, and the combination of the two can further increase the heat resistance of the material. In some embodiments, the organic silicon polymer containing a cage-like polyhedral oligomeric silsesquioxane skeleton has no glass transition temperature below 300°C. In the above embodiments, the organic silicon polymer containing a cage-like polyhedral oligomeric silsesquioxane skeleton has no glass transition temperature below 300°C, which indicates that the heat resistance and thermal stability of the organic silicon polymer containing a cage-like polyhedral oligomeric silsesquioxane skeleton are good, so that the thermal contraction of the porous base film can be better resisted, the heat resistance of the isolation film can be improved, and the reliability of the battery cell can be improved. In some embodiments, the volume distribution particle size Dv50 of the organic silicon polymer containing a cage-like polyhedral oligomeric silsesquioxane skeleton can be 200 nm to 600 nm. The volume distribution particle size Dv50 of the organic silicon polymer containing a cage-like polyhedral oligomeric silsesquioxane skeleton in the above range is beneficial to the coating of the isolation film having good heat resistance and air permeability. In some embodiments, the organic silicon polymer containing a cage-like polyhedral oligomeric silsesquioxane skeleton has no oxidation peak in the cyclic voltammetry curve of the first cycle in the voltage range of 0V to 4.40V. In the above embodiments, the phenyl-containing organosilicon polymer has both the rigidity of aromatic ring and the high bond energy of siloxane bond, and a three-dimensional crosslinked network formed by the crosslinking between the molecular chains of the organosilicon polymer, which can jointly improve the heat resistance of the isolation film; in the organosilicon polymer containing a cage-shaped polysilsesquioxane skeleton, the cage structure can provide structural support and reduce the occurrence of skeleton collapse or chain segment dissociation at high temperatures, and the cage structure contains Si-O bonds with high bond energy, which are not easy to decompose at high temperatures, which can further improve the thermal stability of the material. At the same time, the organosilicon polymer containing a cage-shaped polysilsesquioxane skeleton has a three-dimensional network structure formed by the random crosslinking of Si-O bonds in addition to the cage-shaped polysilsesquioxane skeleton, which can further limit the thermal motion of the molecular chain and avoid material softening and deformation at high temperatures; the cage structure as a rigid crosslinking point of the network structure can further enhance the thermal stability of the network, and the material can resist both high-temperature decomposition and high-temperature deformation, and the two can further increase the heat resistance of the material. In some embodiments, the organosilicon polymer containing a cage-shaped polysilsesquioxane skeleton is obtained by hydrolysis and polycondensation of one or more monomers represented by formula (III), wherein R'1 includes C1-C3 alkyl. In the embodiments of the present application, R'1 specifically includes at least one of methyl, ethyl, n-propyl and isopropyl. By using the hydrolysis-polycondensation reaction of the monomer of formula (III), an organosilicon polymer with a relatively complete cage structure and uniformly dispersed molecular chains can be obtained. Thus, a highly ordered and stable covalent polyhedral skeleton can be formed in the organosilicon polymer, so that the organosilicon polymer is not easy to have structural rupture or collapse at high temperatures, the heat resistance of the isolation film is enhanced, and the reliability of the battery cell is improved. In the embodiments of the present application, the organosilicon polymer containing a cage-shaped polysilsesquioxane skeleton is prepared by the following method: (1) hydrolyzing the monomer represented by formula (III), then adding a catalyst, and performing polycondensation under heating to obtain the organosilicon polymer containing a cage-shaped polysilsesquioxane skeleton. Thus, the organosilicon polymer containing a cage-shaped polysilsesquioxane skeleton is obtained by hydrolysis and polycondensation reaction. ​Specifically, the monomer of formula (III) is first hydrolyzed to generate silanol, while releasing alcohol to form a mixed solution, and the alcohol increases the solubility of the organosiloxane monomer in the solution; then, under the action of the catalyst, the silanol begins to condense, and Si-O-Si bonds are formed between the silanols, further forming a network structure, and nucleation begins. Finally, these nuclei continuously absorb silanol from the solution and continue to grow until the organosilicon polymer containing a cage-like polysilsesquioxane skeleton is formed. The nucleation process and the nucleus growth process are competitive, and the reaction temperature will affect the two processes. When the nucleation process dominates, more nuclei are generated, and the particle size of the polysilsesquioxane is smaller; when the nucleus growth dominates, the reaction kinetics is slower, the molecular rearrangement time is sufficient, the crosslinking degree increases at a slower rate, and the proportion of rigid groups increases at a faster rate; the increase of the temperature intensifies the reaction, the nucleation speed is fast, the condensation reaction rate between the silanols increases, and the crosslinking degree increases, and finally the organosilicon polymer with high crosslinking degree and high cage-like polysilsesquioxane skeleton proportion is obtained. In some embodiments of the present application, the temperature for hydrolysis of the monomer of formula (III) is 10-40℃, for example, the temperature for hydrolysis can be 20-29℃, 21-28℃, 22-27℃, 23-26℃, 24-25℃, etc. By controlling the temperature for hydrolysis of the monomer within the above range, the rate of the hydrolysis reaction can be controlled, and the situation that part of the silane coupling agent is self-condensed due to too violent reaction and the proportion of the cage-like polysilsesquioxane skeleton is reduced can be avoided. In some embodiments of the present application, the heating temperature is 30-100℃, for example, the heating temperature can be 30-99℃, 35-95℃, 40-90℃, 45-85℃, 50-80℃, 55-75℃, 60-70℃, etc. In some embodiments of the present application, the heating time is 2-48h, for example, the heating time can be 2h, 3h, 8h, 10h, 15h, 20h, 24h, 36h, 48h, etc. By controlling the heating temperature and the heating time within the above range, the reaction degree of the condensation reaction can be controlled, and the organosilicon polymer with high crosslinking degree is obtained. In some embodiments of the present application, the catalyst includes at least one of ammonia, triethylamine, sodium hydroxide, magnesium hydroxide, or ammonium hydroxide. Specifically, the organic silicon polymer formed by the monomer of formula (III) is relatively regular and stable at the molecular scale, the polyhedral units are uniformly connected by covalent bonds during the condensation process, the local accumulation and entanglement of the molecular chain is reduced, and the organic silicon polymer exhibits a high uniform dispersion state. The uniform dispersion of the molecular chain not only facilitates the uniform distribution of the crosslinking points and reduces the stress concentration phenomenon, but also improves the dispersibility and binding stability of the crosslinked polymer particles in the separator coating, so that the organic silicon polymer particles in the coating are less likely to be structurally broken or collapsed at high temperatures, the overall heat resistance of the separator is improved, and the reliability of the battery cell is enhanced. In some embodiments, the organic silicon polymer containing a cage-like polysilsesquioxane skeleton satisfies one or more of the following conditions: (1) the crosslinking degree of the organic silicon polymer containing a cage-like polysilsesquioxane skeleton is 85% to 97%; (2) the organic silicon polymer containing a cage-like polysilsesquioxane skeleton includes silicon elements, and the mass fraction of the silicon elements in the organic silicon polymer containing a cage-like polysilsesquioxane skeleton is 25% to 45%; (3) in the organic silicon polymer containing a cage-like polysilsesquioxane skeleton, the mass fraction of the cage-like polysilsesquioxane skeleton is 40% to 60%. For example, the crosslinking degree of the organic silicon polymer containing a cage-like polysilsesquioxane skeleton can be 85%, 87%, 89%, 91%, 93%, 95%, 97%, or a value within the range obtained by any two numerical combinations. The mass fraction of silicon elements in the organic silicon polymer containing a cage-like polysilsesquioxane skeleton can be 25%, 27%, 29%, 31%, 33%, 35%, 37%, 39%, 41%, 43%, 45%, or a value within the range obtained by any two numerical combinations. In the organic silicon polymer containing a cage-like polysilsesquioxane skeleton, the mass fraction of the cage-like polysilsesquioxane skeleton can be 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60%, or a value within the range obtained by any two numerical combinations. A crosslinking degree that is too low can easily result in a low degree of crosslinking between molecular chains, insufficient thermal stability, and a decrease in the heat resistance of the separator. A crosslinking degree of 85% to 97% can ensure that the organic silicon polymer has good heat resistance at high temperatures, thereby improving the heat resistance of the separator. The mass fraction of silicon elements reflects the proportion of inorganic siloxane skeletons in the crosslinked polymer. A mass fraction of silicon elements of 25% to 45% can improve the thermal decomposition temperature and structural stability of the polymer, thereby improving the heat resistance of the separator at high temperatures. As an example, in the embodiments of the present application, a small amount of powder sample (usually a few milligrams) of the organic silicon polymer containing the cage-shaped polysilsesquioxane skeleton is ultrasonically cleaned with anhydrous ethanol or deionized water for 1-2 minutes to remove surface impurities; then it is placed in an oven and dried at 60-80°C for 1-2 hours to completely remove the moisture (to avoid the influence of sample volatilization on the vacuum environment during testing). The dried powder is evenly spread on the conductive glue (ensuring that the powder does not accumulate or scatter); then a 5-10 nm thick layer of gold is sprayed on its surface using an ion sputtering instrument; or after the battery monomer is disassembled, the separator film is peeled off, and a regular and clear area of the separator film is selected. Then, the separator film sample is fixed on the sample stage and subjected to gold or carbon spraying treatment to make its surface conductive; the sample stage containing the sample to be tested is placed in the SEM sample chamber, and after the hatch is closed, the vacuum system is started to reach the required high vacuum state of the instrument (usually 10-3-10 -5 Pa). After the vacuum is reached, the electron gun voltage (usually 5-20 kV) and working distance (usually 5-15 mm) are adjusted, the sample stage is moved by the control software to find the target observation area. The focus and magnification (from low magnification 100 times positioning to high magnification for observing details) are gradually adjusted to obtain clear SEM morphology images, and the feature points or areas that need to be analyzed by EDS are marked. In the SEM software, the EDS detector is started, the marked analysis area (single-point analysis, line scanning or area scanning can be selected) is selected, and the collection time (usually 10-30 seconds, the longer the time, the more accurate the element signal) is set. The energy-dispersive x-ray spectroscopy (EDS) provided with the ZEISS sigma300 is used to analyze the elements on the surface of the organic silicon polymer containing the cage-shaped polysilsesquioxane skeleton to detect the content of silicon elements in the organic silicon polymer containing the cage-shaped polysilsesquioxane skeleton. According to the data results of the instrument, the distribution of each element can be obtained, and thus the mass percentage of silicon elements can be obtained. The mass fraction of the cage-shaped polysilsesquioxane skeleton is crucial for improving the three-dimensional structure stability of the cross-linked polymer. The mass fraction of the cage-shaped polysilsesquioxane skeleton in the cage is 40%-60%, which can ensure that the cross-linked polymer has good rigidity and structural stability, reduces the occurrence of structural collapse or brittle fracture in the separator film under high temperature, is conducive to improving the heat resistance of the separator film, and thus improves the reliability of the battery monomer under high temperature. The mass fraction of the cage-shaped polysilsesquioxane skeleton is crucial for improving the three-dimensional structure stability of the cross-linked polymer. The mass fraction of the cage-shaped polysilsesquioxane skeleton in the cage is 40%-60%, which can ensure that the cross-linked polymer has good rigidity and structural stability, reduces the occurrence of structural collapse in the separator film under high temperature, is conducive to improving the heat resistance of the separator film, and thus improves the reliability of the battery monomer under high temperature. In the embodiments of the present application, a pyrolysis-gas chromatography-mass spectrometry (Py-GC / MS) can be used to test the mass fraction of the cage-like backbone structure in the silicone polymer. Specifically, 0.5-1 mg of the silicone polymer is weighed as a test sample, and is loaded into a quartz cracking tube of a pyrolysis instrument, and is pyrolyzed at 550°C for 1.2 s. The sample is tested for pyrolysis into volatile small molecules in an inert gas (such as helium), and is then introduced into a gas chromatograph-mass spectrometer. An HP-5ms (30 m x 0.25 mm x 0.25 μm) chromatographic column is selected, and the temperature is set to 30°C for 5 min, 10°C / min to 250°C, 250°C for 5 min. The carrier gas is high-purity helium, and the flow rate is 1.0 mL / min. The mass spectrometry uses electrochemical ionization, the ion source temperature is 230°C, and the fragment scan range is m / z 25-200. By comparing with the EVA standard pyrolysis spectrum in the NIST library, the characteristic ions corresponding to the cage-like backbone structure are detected, and it can be inferred that the silicone polymer contains the cage-like backbone structure. The internal standard method is used to calculate the mass fraction of the characteristic cage-like backbone structure in the silicone polymer based on the area of the above-mentioned fragment peak. Therefore, by limiting the crosslinking degree, the mass fraction of silicon elements, and the mass fraction of the cage-like polysilsesquioxane backbone of the silicone polymer to meet the above ranges respectively, the structure of the silicone polymer containing the cage-like polysilsesquioxane backbone can be controlled, so that the isolation film including the polymer has good heat resistance at high temperatures, thereby improving the reliability of the battery cell. In some embodiments, the heat-resistant particles satisfy at least one of the following conditions: (1) the volume distribution particle size Dv50 of the heat-resistant particles is 80 nm-900 nm; (2) the cyclic voltammogram of the heat-resistant particles in the first cycle has no oxidation peak in the voltage range of 0-4.4 V; (3) the glass transition temperature T g of the heat-resistant particles is greater than or equal to 150°C, or the heat-resistant particles have no glass transition temperature T g at 300°C; (4) the initial thermal weight loss temperature T 3d of the heat-resistant particles is greater than or equal to 250°C; (5) the elution rate of the heat-resistant particles is less than or equal to 5% when the heat-resistant particles are soaked in a mixed solvent of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 3:7 at 60°C for 7 days; and (6) the true density of the heat-resistant particles is 0.8 g / cm 3 -2.0 g / cm 3 . For example, the volume distribution particle size Dv50 of the heat-resistant particles can be 80 nm, 120 nm, 160 nm, 200 nm, 240 nm, 280 nm, 320 nm, 360 nm, 400 nm, 440 nm, 480 nm, 520 nm, 560 nm, 600 nm, 640 nm, 680 nm, 720 nm, 760 nm, 800 nm, 840 nm, 880 nm, 900 nm, or a value within a range obtained by combining any two of the above values. The glass transition temperature Tg of the heat-resistant particles can be 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, or a value within a range obtained by combining any two of the above values, or the heat-resistant particles have no glass transition temperature Tg at 300°C. The initial thermal weight loss temperature T g of the heat-resistant particles can be 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, or a value within a range obtained by combining any two of the above values, or the heat-resistant particles have no glass transition temperature Tg at 300°C. The initial thermal weight loss temperature T 3d of the heat-resistant particles can be 5%, 4%, 3%, 2%, 1%, or a value within a range obtained by combining any two of the above values. The dissolution rate of the heat-resistant particles can be 5%, 4%, 3%, 2%, 1%, or a value within a range obtained by combining any two of the above values. The true density of the heat-resistant particles can be 0.8 g / cm 3 , 0.9 g / cm 3 , 1.0 g / cm 3 , 1.1 g / cm 3 , 1.2 g / cm 3 , 1.3 g / cm 3 , 1.4 g / cm 3 , 1.5 g / cm 3 , 1.6 g / cm 3 , 1.7 g / cm 3 , 1.8 g / cm 3 , 1.9 g / cm 3 , 2.0 g / cm 3 , or a value within a range obtained by combining any two of the above values. The volume distribution particle size Dv50 of the heat-resistant particles within the above range can allow the coating layer to have more particle stacking layers within a limited thickness range, thereby improving the heat resistance of the isolation film. If the Dv50 is too small, the heat-resistant particles are prone to agglomeration; if the Dv50 is too large, the heat-resistant particles have poor dispersibility, which can cause pore blockage and local stress concentration in the coating layer. The heat-resistant particles within the above particle size range can be uniformly distributed in the coating layer and filled on the pore surface of the porous base film, which is further conducive to improving the heat resistance and air permeability of the isolation film. Compared with inorganic particles with relatively large density, such as boehmite and alumina, the heat-resistant particles have smaller true density, which can improve the energy density of the battery cell and the energy density and high-temperature reliability of the battery cell without increasing the thickness of the coating layer. As an example, the volume particle size distribution of the heat-resistant particles can be determined by a particle size analyzer-laser diffraction method, specifically, a laser diffraction scattering particle size analyzer can be used to measure according to the manufacturer's instructions, with reference to the standard GB / T 19077-2016. For example, before preparing the isolation film, an appropriate amount of sample is taken, and the average volume particle size of the material is tested by a MasterSizer 3000 laser particle size analyzer. An appropriate amount of sample to be tested (the sample concentration ensures that the light intensity is 8-12%) is added to 20 ml of deionized water, and at the same time, the outside is superimposed for 5 min (53 KHz / 120 W) to ensure that the sample is completely dispersed, and then the sample is measured according to the standard GB / T 19077-2016 / ISO 13320:2009. The electrochemical stability of conventional organic particles is generally poor and is easily decomposed under high pressure. The cyclic voltammetry curve of the heat-resistant particles in the first cycle in the present application does not have an oxidation peak in the voltage range of 0V to 4.40V, indicating that the heat-resistant particles are stable in the voltage range of 0V to 4.40V and have good electrochemical stability, which can be applied to high-voltage battery cells, so that the battery cells have good capacity performance under high pressure, and the working voltage and energy density of the battery cells are improved. As an example, the oxidation peak potential of the cyclic voltammetry curve of the heat-resistant particles can be tested as follows: heat-resistant particles, binder polyacrylate, and conductive agent conductive carbon black are dissolved in water according to a solid content mass ratio of 64:7:29 to prepare a slurry, the slurry is coated on an aluminum foil as a positive electrode, lithium foil is used as a negative electrode, and a button cell is assembled; the button cell is subjected to cyclic voltammetry (CV) test, the scanning rate is 0.10 mV / s, the voltage range is 2.50V-5.00V, and the cycle is 3 cycles, and the voltage corresponding to the peak point of the first cycle cyclic voltammetry curve is taken as the oxidation peak potential. The electrolyte salt of the electrolyte used for testing is LiPF6, and the concentration is 1 mol / L. The solvent of the electrolyte is obtained by mixing ethylene carbonate (EC) and methyl ethyl carbonate (EMC) according to a volume ratio of 3:7. Glass transition temperature T g refers to the transition temperature of the material from glass state to high-elasticity state, which shows a step change on the DSC curve. The glass transition temperature of the heat-resistant particles is greater than or equal to 150℃, or below 300℃, such as the glass transition temperature, refers to the DSC curve of the heat-resistant particles remaining in a solid state below 150℃ or below 300℃, without molecular chain segment movement or softening, thereby improving the heat resistance of the isolation film. As an example, the glass transition temperature T gThe test can be carried out as follows: take an appropriate amount of sample (for example, 5 mg-15 mg) and place it in a differential scanning calorimeter (DSC) crucible, shake it flat, and cover it with a crucible cover; parameter settings: nitrogen atmosphere, purge gas 60 mL / min, protective gas 20 mL / min; program settings: temperature rise at a rate of 10°C / min from 25°C to 200°C, hold for 5 min to eliminate thermal history, temperature drop at a rate of 10°C / min from 200°C to -40°C, and temperature rise at a rate of 10°C / min from -40°C to 300°C. The glass transition temperature Tg of the heat-resistant particles is determined by the DSC curve. g . The initial thermal weight loss temperature T 3d of the heat-resistant particles is greater than or equal to 250°C, indicating that the weight of the heat-resistant particles does not change significantly at high temperatures, and thus the heat-resistant particles have high thermal stability and are less likely to decompose during the use of the battery cell and in high-temperature environments. When the heat-resistant particles are used in the separator film, the heat-resistant particles can better generate a force to resist the shrinkage of the separator film, thereby improving the overall thermal shrinkage of the separator film, improving the heat resistance of the separator film, and improving the reliability of the battery cell. The initial thermal weight loss temperature T 3d is the temperature corresponding to a 3% loss in the mass of the sample tested by thermogravimetric analysis relative to the initial mass. The initial thermal weight loss temperature T 3d of the organic particles can be tested as follows: take an appropriate amount of sample (for example, 5 mg-15 mg) and place it in an alumina crucible of a thermogravimetric analyzer (TGA), shake it flat, and cover it with a crucible cover; parameter settings: nitrogen atmosphere, purge gas 60 mL / min, protective gas 20 mL / min; temperature rise program: temperature rise rate 10°C / min, temperature range 35°C-600°C; from the test curve, the temperature corresponding to a 3% loss in the mass of the sample (i.e., 97% of the initial mass) is obtained, which is the initial thermal weight loss temperature T 3d . The dissolution rate can refer to the proportion of particles that dissolve or decompose in the electrolyte. The dissolution of the heat-resistant particles is less than 5% after 7 days of electrolyte immersion at 60°C, and the heat-resistant particles are less likely to precipitate or dissolve in the electrolyte environment, reducing the likelihood of electrolyte contamination or side reactions between the heat-resistant particles and the electrolyte during the cycling process of the battery cell, and improving the structural stability of the separator film, which is beneficial to the cycling performance and reliability of the battery cell. As an example, the swelling degree of heat-resistant particles can be tested as follows: Take an appropriate amount of sample (e.g., about 1g), denoted as m1, and place it in a semi-permeable membrane sample bag. Seal the bag; the sample bag should be permeable to the solvent but not to the sample. Immerse the sample bag in an appropriate amount of solvent (e.g., about 50g) at 60°C for 7 days. After immersion, remove the sample bag and then remove the sample from the bag. Wipe away excess solvent and weigh the sample again, m2. Swelling degree = (m2-m1) / m1 × 100%. The solvent is a mixed solvent obtained by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7. True density refers to the mass of a material per unit volume (excluding internal voids, i.e., open and closed pores, and inter-particle voids) in an absolutely dense state. The true density of heat-resistant granules is 0.8 g / cm³. 3 ~2.0g / cm 3 This is beneficial for increasing the capacity of individual battery cells and obtaining battery cells with higher energy density. The true density of heat-resistant particles has a well-known meaning in the art and can be tested using methods known in the art. As an example, a mass M of heat-resistant particles is weighed, and the carbon-based material is placed in a true density analyzer (AccuPyc II 1340 analyzer) at room temperature (15℃-25℃). The test system is sealed, and helium gas is introduced according to the procedure. By detecting the gas pressure in the sample chamber and the expansion chamber, and then calculating the gas volume in the sample chamber and the expansion chamber respectively according to the ideal gas law, the difference between the two is obtained as the volume of gas displaced by the carbon-based material under certain temperature and pressure conditions, which is the true volume V of the heat-resistant particles. The true density of the heat-resistant particles is calculated as the mass M of the heat-resistant particles / the true volume V of the heat-resistant particles, and the unit of true density is g / cm³. 3 . In some embodiments, the heat-resistant particles constitute 50% to 97% of the coating by mass. The mass fraction of heat-resistant particles in the coating can be 50%, 52%, 54%, 56%, 58%, 60%, 62%, 64%, 66%, 68%, 70%, 72%, 74%, 76%, 78%, 80%, 82%, 84%, 86%, 88%, 90%, 92%, 94%, 96%, 97%, or a value within the range obtained by any combination of the above two values. By limiting the mass fraction of heat-resistant particles in the coating to meet the above range, the coating can have structural stability and air permeability, improve the heat resistance of the separator, and thus improve the reliability of the battery cell. In some embodiments, the coating further comprises a first binder, the first binder satisfying at least one of the following conditions: (1) the first binder comprises at least one of polyimide, polyetherimide, polyacrylic acid, polyacrylate, ethylene-vinyl acetate copolymer, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylated polyvinyl alcohol, cyanoethyl cellulose, cyanoethylsucrose, pullulan, carboxymethyl cellulose, acrylonitrile-styrene-butadiene copolymer, ethylene-propylene-diene terpolymer, sulfonated ethylene-propylene-diene terpolymer, styrene butadiene rubber, fluoroelastomer; (2) the mass fraction of the first binder in the coating is 3% to 15%. For example, the mass fraction of the first binder in the coating can be 3%, 5%, 7%, 9%, 11%, 13%, 15%, or a value within a range obtained by combining any two of the above values. The heat-resistant particles in the coating are connected and fixed to each other by the first binder, reducing the situation of falling off of the heat-resistant particles during coating and use. The mass fraction of the first binder satisfies the above range, which can reduce the proportion of heat-resistant particles in the coating due to excessive binder while ensuring adhesion, thereby balancing the stability and heat resistance of the coating and improving the heat resistance of the isolation film. In some embodiments, the isolation film further comprises second binder particles, the second binder particles being located in the coating, or the isolation film further comprises a bonding layer, the bonding layer being arranged on at least one side of the coating away from the base film, and the second binder particles being located in the bonding layer; the second binder particles satisfy one or more of the following conditions: (1) the second binder particles comprise at least one of polyvinylidene fluoride, poly(vinylidene fluoride-co-trichloroethylene), poly(vinylidene fluoride-co-trifluorochloroethylene), poly(vinylidene fluoride-co-trifluoroethylene), poly(vinylidene fluoride-co-tetrafluoroethylene), poly(vinylidene fluoride-co-hexafluoropropylene), polyacrylate, polymethyl methacrylate, polyacrylonitrile; (2) the volume average particle size Dv50 of the second binder particles is 5 μm to 20 μm. For example, the volume average particle size Dv50 of the second binder particles can be 5 μm, 7 μm, 9 μm, 11 μm, 13 μm, 15 μm, 17 μm, 19 μm, 20 μm, or a value within a range obtained by combining any two of the above values. The second binder particles can fill the gap between the negative electrode sheet and the separator film, form a more firm bonding interface, help to improve the bonding strength between the separator film and the negative electrode sheet, thereby improving the overall stability of the separator film, reducing the interlayer peeling phenomenon between the separator film and the negative electrode sheet caused by thermal stress or electrochemical action in the cycle process, and thereby improving the cycle performance of the battery cell. The number average particle size of the second binder particles meets the above range, which ensures that it can be uniformly distributed and can maintain moderate fluidity during hot pressing, thereby further helping to improve the cycle performance of the battery cell. It should be understood that the "first binder" in the embodiments of the present application plays a bonding role between the heat-resistant particles in the porous coating of the separator film, and the "second binder particles" play a role in improving the adhesion of the separator film to the electrode sheet in the porous coating of the separator film. In some embodiments, the coating of the separator film includes heat-resistant particles and second binder particles, which can be embedded in the heat-resistant particles and form protrusions on the surface of the coating. In some embodiments, the coating of the separator film includes a heat-resistant layer and a bonding layer, the heat-resistant layer is arranged on the porous base film, the bonding layer is arranged on at least a part of the surface of the side of the heat-resistant layer away from the porous base film, the heat-resistant particles are arranged in the heat-resistant layer, and the second binder particles are arranged in the bonding layer. In some embodiments, the coating of the separator film includes a heat-resistant layer and a bonding layer, the heat-resistant layer is arranged on one side of the porous base film, the bonding layer is arranged on at least a part of the surface of the other side of the porous base film, the heat-resistant particles are arranged in the heat-resistant layer, and the second binder particles are arranged in the bonding layer. In some embodiments, the coating of the separator film includes a heat-resistant layer and a bonding layer, the heat-resistant layer is arranged on one side of the porous base film, the bonding layer is arranged on at least a part of the surface of the side of the heat-resistant layer away from the porous base film and on at least a part of the surface of the other side of the porous base film, the heat-resistant particles are arranged in the heat-resistant layer, and the second binder particles are arranged in the bonding layer. In some embodiments, the coating includes inorganic particles, and the mass fraction of the inorganic particles is 0.1-50% based on the total mass of the coating. In other embodiments, the coating includes inorganic particles, and the mass fraction of the inorganic particles is 50-92% based on the total mass of the coating. In one example, the inorganic particles include at least one of SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, Y2O3, Al2O3, boehmite (AlO(OH)), Al(OH)3, TiO2, and SiC. The above inorganic particles have a large dielectric constant, which is conducive to improving the ion transmission efficiency in the coating. In some embodiments, the separator film satisfies one or more of the following conditions: (1) the thickness of the coating layer is 0.5 μm to 10 μm; (2) the areal density of the coating layer is 1.5 g / m 2 ~ 6 g / m 2 ; (3) the longitudinal heat shrinkage of the separator film is less than or equal to 5% when heated at 130°C for 1 h; (4) the transverse heat shrinkage of the separator film is less than or equal to 5% when heated at 130°C for 1 h; and (5) the air permeability of the separator film is 150 s / 100 mL to 500 s / 100 mL. The thickness of the coating layer refers to the thickness of the coating layer on one side of the porous base film. For example, the thickness of the coating layer can be 0.5 μm, 1 μm, 3 μm, 5 μm, 7 μm, 9 μm, 10 μm, or a value within a range obtained by combining any two of the above values. A coating layer that is too thin cannot form an effective thermal insulation layer, and a coating layer that is too thick increases the thickness of the separator film and reduces the energy density of the battery cell. A coating layer having a thickness of 0.5 μm to 10 μm can provide a uniform and dense heat-resistant coating layer, thereby improving the heat resistance of the separator film and thus the reliability of the battery cell. The areal density of the coating layer is 1.5 g / m 2 ~ 6 g / m 2 , which can ensure that the coating layer has a moderate mass, thereby improving the stability and heat resistance of the separator film without significantly increasing the weight of the separator film, thereby being beneficial to the energy density and reliability of the battery cell. For example, the areal density of the coating layer can be 0.5 g / m 2 , 0.7 g / m 2 , 0.9 g / m 2 , 1.1 g / m 2 , 1.3 g / m 2 , 1.5 g / m 2 , 1.7 g / m 2 , 1.9 g / m 2 , 2.1 g / m 2 , 2.3 g / m 2 , 2.5 g / m 2 , 2.7 g / m 2 , 2.9 g / m 2 , 3.1 g / m 2 , 3.3 g / m 2 , 3.5 g / m 2 , 3.7 g / m 2 , 3.9 g / m 2 , 4.1 g / m 2 , 4.3 g / m 2 , 4.5 g / m 2 , 4.7 g / m 2 , 4.9 g / m 2 , 5 g / m 25.1 g / m 2 5.3 g / m 2 5.5 g / m 2 5.7 g / m 2 5.9 g / m 2 6 g / m 2 or a value within a range obtained by any two of the above combinations. The areal density of the coating can be controlled during the preparation of the isolation film by controlling the amount of coating slurry applied to the porous base film. As an example, the areal density of the coating can be tested by first stacking 6 layers of the single isolation film containing the coating according to the embodiments of the present application and 6 layers of the single isolation film substrate without the coating independently, and applying pressure to make each layer closely attached and without air bubbles. Then, according to the sample cutting template, cut the two groups of stacks respectively, and obtain 6 samples for each group. Measure the total mass M1 of the 6 samples of the group with the coating and the total mass M2 of the 6 samples of the group without the coating, and calculate the average mass of the coating on the single isolation film by the formula M = (M1-M2) / 6. Then, measure the area S of a single sample, and according to the formula "coating areal density = M / S", the areal density of the coating can be obtained. The heat shrinkage rate refers to the percentage of the dimensional change of the isolation film at high temperature, and is an important indicator for measuring the thermal stability of the isolation film. The isolation film can maintain very low longitudinal and transverse heat shrinkage rates at 130°C, i.e., the isolation film according to the embodiments of the present application has good heat resistance at high temperature. As an example, the heat shrinkage rate of the isolation film can be tested according to GB / T 36363-2018. As an example, the isolation film is cut into a sample with a width of 50 mm and a length of 100 mm by a punch machine, 5 parallel samples are placed on an A4 paper, and the A4 paper with the samples is placed on a corrugated paper with a thickness of 1 mm to 5 mm. The temperature of the air blast oven is set to 130°C, and after the temperature reaches the set temperature and stabilizes for 60 min, the A4 paper placed on the corrugated paper is placed in the air blast oven, and the timing starts. After reaching the set time (1 h in the present disclosure), the length and width of the isolation film are measured, and the values are marked as a and b, respectively. The longitudinal (MD) heat shrinkage rate = [(100-a) / 100] x 100%, and the transverse (TD) heat shrinkage rate = [(50-b) / 50] x 100%. The average value of 3 parallel samples is taken as the test result. The air permeability (Gurley value) of the separator film refers to the time required for 100 mL of air to pass through the separator film, and characterizes the resistance of the pore structure of the separator film to gas / liquid transmission. The air permeability of the separator film is 150 s / 100 mL-500 s / 100 mL, which ensures that the electrolyte can be uniformly infiltrated and maintain rapid ion transmission, ensures the ion transmission efficiency in the separator film, reduces the case that the air permeability of the separator film is too low to cause electrochemical polarization and reduce the reliability of the battery cell. As an example, the air permeability of the separator film can be tested according to GB / T 36363-2018. Specifically, the separator film is cut into a square of 5 cm in size, a gas permeameter is used, a pressure of 1.21 kPa is applied, and the time required for 100 ml of air to pass through 6.45 cm2 of the separator film is tested as the air permeability of the separator film, in s / 100 ml. The average value of 3 parallel samples is taken as the test result. In some embodiments, the thickness of the separator film can be 5 μm-20 μm, optionally 5 μm-12 μm, 6 μm-12 μm. Thus, it is beneficial to improve the energy density of the secondary battery cell. It should be noted that the coating parameters of the above-mentioned separator film are the coating parameters of one side of the porous base film. When the coating is arranged on both sides of the porous base film, the coating parameters of any one side meet the present disclosure, which is considered to fall within the protection scope of the present disclosure. The shape of the battery cell in the embodiments of the present application is not particularly limited, and it can be cylindrical, square or any other shape. For example, FIG. 1 is a structural schematic diagram of a battery cell according to an embodiment of the present application, and the battery cell is square. FIG. 2 is a structural schematic diagram of a battery cell according to another embodiment of the present application. As shown in FIG. 2, in some embodiments, the battery cell 3 can include an outer package. The outer package can be used to package the above-mentioned electrode assembly and electrolyte. In some embodiments, the outer package of the battery cell 3 can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the battery cell 3 can also be a soft package, such as a bag-type soft package. The material of the soft package can be plastic, and as plastic, polypropylene, polybutylene terephthalate, and polybutylene succinate, etc. can be listed. In some embodiments, referring to FIG. 2, the battery cell 3 includes a shell 30 and an electrode assembly 33 arranged in the shell 30, and the shell 30 includes a shell body 31 and a cover plate 32 for covering the opening of the shell body 31. The electrode assembly 33 can be made of a positive electrode sheet, a negative electrode sheet and a separator film by a winding process or a stacking process. The electrode assembly 33 can include an electrode assembly body and a tab 331 extending from the electrode assembly body. The cover plate 32 includes electrode terminals 322, as shown in FIG. 3. The cover plate 32 includes two electrode terminals 322, one of which is a positive electrode terminal and the other of which is a negative electrode terminal. The battery cell 3 also includes connection members 34 for connecting the tabs 331 of the electrode assembly 33 and the electrode terminals 322. For example, one connection member 34 is used to connect the tab of the positive electrode and the positive electrode terminal, and another connection member 34 is used to connect the tab of the negative electrode and the negative electrode terminal. In some embodiments, the battery cell 3 includes a pressure relief mechanism 313 for releasing substances within the battery cell 3 when thermal runaway occurs in the battery cell, to reduce the risk that the emissions within the battery cell 3 cannot be promptly released. In some embodiments, the battery cell can be assembled into a battery module, and the number of battery cells included in the battery module can be one or more, and the specific number can be selected by a person skilled in the art according to the application and capacity of the battery module. [Positive electrode tab] The positive electrode tab includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, the positive electrode active material layer including a positive electrode active material. As an example, the positive electrode current collector has two opposite surfaces in the thickness direction thereof, and the positive electrode active material layer is disposed on either one or both of the opposite surfaces of the positive electrode current collector. In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. For example, as the metal foil, an aluminum foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer material base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.). The positive electrode active material layer can also optionally include at least one of the positive electrode active materials known in the art for use in batteries: lithium-containing phosphates of olivine structure, lithium transition metal oxides, and modified compounds of each thereof. However, the present application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries can also be used. These positive electrode active materials can be used alone or in combination with two or more. Examples of the lithium transition metal oxide can 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 Co 1 / 3Mn 1 / 3 O2(also can be referred to as NCM 333 )), LiNi 0.5 Co 0.2 Mn 0.3 O2(also can be referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2(also can be referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2(also can be referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2(also can be referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2), and modified compounds thereof. Examples of lithium-containing phosphates of olivine structure can include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4(also can be referred to as LFP)), a composite of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite of lithium manganese iron phosphate and carbon. The battery will be accompanied by Li deintercalation and consumption during charging and discharging, and the molar content of Li in the positive active material is different when the battery is discharged to different states. In some embodiments, the positive active material layer includes a conductive agent. As an example, the conductive agent can include at least one of super P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the positive active material layer can also optionally include a binder. As an example, the binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylic ester resin. In some embodiments, the positive electrode sheet can be prepared by forming a positive electrode slurry from the components described above for preparing the positive electrode sheet. For example, the positive active material, the conductive agent, the binder, and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry. The positive electrode slurry is then coated on the positive electrode current collector, and after processes such as drying, cold pressing, etc., the positive electrode sheet is obtained. The battery will be accompanied by Li deintercalation and consumption during charging and discharging process, and the molar content of Li is different when the battery is discharged to different states. In the enumeration of the positive electrode material in the present application, the molar content of Li is the initial state of the material, i.e. the state before feeding, and the positive electrode material is applied to the battery system. After charging and discharging cycle, the molar content of Li will change. In the enumeration of the positive electrode material in the present application, the molar content of O is only the theoretical state value, and the lattice oxygen release will cause the change of the molar content of oxygen, and the actual molar content of O will appear floating. [Negative electrode sheet] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material. As an example, the negative electrode current collector has two surfaces opposite in the thickness direction of itself, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector. In some embodiments, the negative electrode current collector can adopt a metal foil or a composite current collector. For example, as a metal foil, a copper foil can be adopted. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base material. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.). In some embodiments, the negative electrode active material can adopt a negative electrode active material for a battery known in the art. As an example, the negative electrode active material can include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based material, tin-based material, and lithium titanate, etc. The silicon-based material can be selected from at least one of elemental silicon, silicon oxide compound, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy. The tin-based material can be selected from at least one of elemental tin, tin oxide compound, and tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries can also be used. These negative electrode active materials can be used alone or in combination with two or more. In some embodiments, the negative electrode film layer can also optionally include a binder. The binder can be selected from at least one of styrene butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS). In some embodiments, the negative electrode film layer can also optionally include a conductive agent. The conductive agent can be selected from at least one of super-P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the negative electrode film layer can also optionally include other additives, such as a thickening agent (e.g., sodium carboxymethyl cellulose (CMC-Na), etc. In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as the negative electrode active material, the spherical particles, the conductive agent, the binder, and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry on a negative electrode current collector, and after drying, cold pressing, etc., a negative electrode sheet can be obtained. [Electrolyte] The electrolyte functions to conduct ions between the positive electrode sheet and the negative electrode sheet. The type of electrolyte is not specifically limited in the present application and can be selected as needed. For example, the electrolyte can be liquid, semi-solid, or all-solid. In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes the catalyst in any of the possible embodiments described above. In some embodiments, the electrolyte solution includes an electrolyte salt and a solvent. For a lithium-ion battery cell or a lithium metal battery cell, the electrolyte salt can include one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonylimide, lithium bis-trifluoromethanesulfonylimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluoro oxalato borate, lithium di oxalato borate, lithium difluoro di oxalato phosphate, and lithium tetrafluoro oxalato phosphate. For a lithium-ion battery cell or a lithium metal battery cell, the solvent can include one or more of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone. In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone. In some embodiments, the electrolyte solution can optionally further include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and can further include an additive capable of improving certain performance of the battery, such as an additive capable of improving overcharge performance of the battery, an additive capable of improving high-temperature or low-temperature performance of the battery, and the like. [Separator] In some embodiments, the separator includes the coating in any of the possible embodiments described above. The coating includes heat-resistant particles, the heat-resistant particles include a cross-linked polymer, and the cross-linked polymer has a cross-linking degree of 70% to 98%. In the technical solutions described above, on the one hand, the cross-linked polymer has a three-dimensional network structure, which can maintain a stable spatial configuration under thermal stress, so that the separator has good heat resistance. On the other hand, by controlling the cross-linking degree of the cross-linked polymer to be 70% to 98%, the coating particles can have good heat resistance at high temperatures, the heat resistance of the separator can be improved, the overall structural integrity of the separator at high temperatures can be ensured, and thus the reliability of the battery cell under high-temperature conditions can be improved. In some embodiments, the cross-linked polymer includes a planar cyclic conjugated group and / or a covalent polyhedral skeleton. In the embodiments described above, the cross-linked polymer includes a planar cyclic conjugated group and / or a covalent polyhedral skeleton. The planar cyclic conjugated group has high rigidity due to the conjugation effect and planar structure, and the polymer molecules are difficult to pyrolyze or soften at high temperatures, so that the cross-linked polymer containing the planar cyclic conjugated group has high thermal stability. The covalent polyhedral skeleton has a highly symmetrical three-dimensional geometric structure and a strong covalent bond connection higher than ionic bonds or intermolecular forces, and its structure is not easy to break or collapse at high temperatures, so that the cross-linked polymer containing the covalent polyhedral skeleton has high thermal stability. Therefore, the cross-linked polymer containing the planar cyclic conjugated group and / or the covalent polyhedral skeleton has good heat resistance and thermal stability, and when used in the separator, the overall heat resistance of the separator can be improved, and the reliability of the battery cell under high-temperature conditions can be improved. In some embodiments, the planar cyclic conjugated group includes any one of a substituted or unsubstituted phenyl group, a substituted or unsubstituted heteroatom-containing aromatic group, a substituted or unsubstituted condensed ring aromatic group, and a substituted or unsubstituted triazine ring group; optionally, the planar cyclic conjugated group includes any one of a phenyl group and a triazine ring group. In the above embodiments, by limiting the types of planar ring conjugated groups in the cross-linked polymer, the heat resistance and chemical stability of the cross-linked polymer can be further enhanced, thereby improving the heat resistance of the isolation film. The phenyl group has good structural stability and conjugation effect, which can improve the thermal stability of the cross-linked polymer; the aromatic group containing a heteroatom can make the electronic structure of the cross-linked polymer more stable and enhance its oxidation resistance, thereby reducing the probability of reaction between the cross-linked polymer and the electrolyte; the fused ring aromatic group has a larger π conjugated system and is more rigid, and has a higher thermal decomposition temperature; the triazine ring group contains multiple nitrogen atoms and can maintain structural stability at high temperatures. The inclusion of the above-mentioned groups in the cross-linked polymer makes the cross-linked polymer particles in the coating more difficult to deform or break at high temperatures, thereby making the isolation film have good heat resistance and improving the reliability of the battery cell. In some embodiments, the cross-linked polymer includes at least one of a phenolic resin-based polymer, a polymer containing a triazine ring group, a phenyl-containing silicone polymer, and a cross-linked styrene-based polymer. In the above embodiments, the cross-linked structure formed between the aromatic ring skeleton and the molecular chain in the phenolic resin-based polymer can collectively improve the heat resistance of the cross-linked polymer; the polymer containing a triazine ring can collectively improve the high-temperature resistance and oxidation resistance of the material due to the high conjugation of the triazine ring and the chemical inertness provided by the nitrogen atom, and the three-dimensional cross-linked network formed by the cross-linking between the polymer molecular chains of the triazine ring; the cross-linked styrene-based polymer can improve the heat resistance of the isolation film through the highly rigid carbon skeleton and the three-dimensional cross-linked network formed by the cross-linking between the molecular chains. By introducing the above-mentioned at least one cross-linked polymer, the isolation film including the cross-linked polymer has good heat resistance, thereby improving the reliability of the battery cell under high temperature conditions. In some embodiments, the phenyl-containing silicone polymer includes a monomer represented by formula (I) and a cross-linking agent polymerized to obtain In formula (I), R1 and R2 each independently include a C1-C4 alkyl group, a C2-C4 alkenyl group, R3 includes a C1-C4 alkyl group or a C4-C8 (meth) acryloyloxy alkyl group, and R4 includes a C2-C8 alkenyl group or a C4-C8 (meth) acryloyloxy alkyl group; the cross-linking agent includes divinylbenzene. Through the polymerization of the monomer represented by formula (I) and the cross-linking agent divinylbenzene, a phenyl-containing silicone polymer particle can be obtained, which has a three-dimensional network skeleton formed by the phenyl structure and the monomer and the cross-linking agent, so that the material exhibits higher glass transition temperature and thermal decomposition temperature, thereby improving the heat resistance of the isolation film and improving the reliability of the battery cell. In some embodiments, the phenyl-containing organosilicon polymer satisfies one or more of the following conditions: (1) the crosslinking degree of the phenyl-containing organosilicon polymer is 75% to 95%; (2) the phenyl-containing organosilicon polymer includes silicon elements, and the mass fraction of the silicon elements in the phenyl-containing organosilicon crosslinking resin is 10% to 25%; and (3) the mass fraction of the phenyl groups in the phenyl-containing organosilicon polymer is 2% to 12%. The crosslinking degree of the phenyl-containing organosilicon polymer is 85% to 97%, which provides good heat resistance at high temperatures, so that the isolation film has good heat resistance, thereby improving the reliability of the battery cell. The mass fraction of the silicon elements is 10% to 25%, which helps to improve the proportion of the inorganic siloxane skeleton in the organosilicon polymer. The siloxane skeleton including the silicon elements provides a high thermal decomposition temperature and oxidation resistance, so that the isolation film has structural stability in a high-temperature environment. The mass fraction of the phenyl groups is 2% to 12%, which can introduce the rigidity and conjugation effect of the aromatic structure, further helping to improve the heat resistance of the isolation film. Therefore, by limiting the crosslinking degree of the crosslinked polymer, the mass fraction of the silicon elements, and the mass fraction of the phenyl groups to satisfy the above ranges respectively, the structure of the phenyl-containing organosilicon polymer can be controlled, so that it has high thermal stability, improves the heat resistance of the isolation film, and further improves the reliability of the battery cell at high temperatures. In some embodiments, the covalent polyhedral skeleton includes a skeleton composed of a compound represented by formula (II), R a [SiO 3 / 2 ] n formula (II), wherein n is any value in the integer range of 4 to 12, and Ra includes at least one of a cycloalkyl group, an aryl group, a C1-C3 alkyl group, a C1-C3 alkenyl group, and a C1-C3 alkynyl group; and optionally, n is 8, and Ra includes a C1-C3 alkyl group. 12 12 12 In the above embodiments, by introducing the covalent polyhedral skeleton represented by formula (II) into the crosslinked polymer, a stable three-dimensional structure can be formed inside the molecule of the crosslinked polymer. Such a polyhedral skeleton has high symmetry and regularity, and the internal atoms are connected by strong covalent bonds, so that the molecular structure is not easy to break or collapse in a high-temperature environment, which helps to improve the heat resistance of the isolation film. By selecting n to be 8 and Ra to be a C1-C3 alkyl group, the rigidity and thermal stability of the crosslinked polymer can be further improved. The crosslinked polymer particles can act as rigid support points at high temperatures, improving the heat resistance of the isolation film, thereby helping to improve the reliability of the battery cell. ​​​In some embodiments, the cross-linked polymer comprises a siloxane polymer containing a cage-like polyhedral oligomeric silsesquioxane skeleton. In the above embodiments, the siloxane polymer containing a cage-like polyhedral oligomeric silsesquioxane skeleton has no glass transition temperature below 300°C, indicating that the siloxane polymer containing a cage-like polyhedral oligomeric silsesquioxane skeleton has good heat resistance and thermal stability, thereby better resisting thermal shrinkage of the porous base film, improving the heat resistance of the separation film, and improving the reliability of the battery cell. In some embodiments, the siloxane polymer containing a cage-like polyhedral oligomeric silsesquioxane skeleton is obtained by hydrolysis and condensation of one or more monomers represented by formula (III), wherein R'1 comprises a C1-C3 alkyl group. In the above embodiments, by using the hydrolysis and condensation reaction of the monomer of formula (III), a siloxane polymer with a relatively complete cage structure and uniform molecular chain dispersion can be obtained. As a result, a highly ordered and stable covalent polyhedral skeleton can be formed in the siloxane polymer, making the siloxane polymer less likely to undergo structural rupture or collapse at high temperatures, enhancing the heat resistance of the separation film, and thus improving the reliability of the battery cell. Specifically, the siloxane polymer formed from the monomer of formula (III) is relatively regular and stable at the molecular scale, with the polyhedral units uniformly connected by covalent bonds during the condensation process, reducing the local accumulation and entanglement of molecular chains, and the siloxane polymer exhibits a high uniform dispersion state. The uniform dispersion of the molecular chains not only facilitates the uniform distribution of cross-linking points and reduces the stress concentration phenomenon, but also improves the dispersibility and binding stability of the cross-linked polymer particles in the separation film coating, making the siloxane polymer particles in the coating less likely to undergo structural rupture or collapse at high temperatures, improving the overall heat resistance of the separation film, and thus enhancing the reliability of the battery cell. In some embodiments, the siloxane polymer containing a cage-like polyhedral oligomeric silsesquioxane skeleton satisfies one or more of the following conditions: (1) the cross-linking degree is 85%-97%; (2) the siloxane polymer containing a cage-like polyhedral oligomeric silsesquioxane skeleton comprises silicon elements, and the mass fraction of silicon elements in the siloxane polymer containing a cage-like polyhedral oligomeric silsesquioxane skeleton is 25%-45%; (3) in the siloxane polymer containing a cage-like polyhedral oligomeric silsesquioxane skeleton, the mass fraction of the cage-like polyhedral oligomeric silsesquioxane skeleton is 40%-60%. The cross-linking degree that is too low can easily result in a low cross-linking degree between molecular chains, insufficient thermal stability, and a decreased heat resistance of the separation film. A cross-linking degree of 85% to 97% can ensure that the organic silicon polymer has good heat resistance at high temperatures, thereby improving the heat resistance of the separation film. The mass fraction of silicon elements reflects the proportion of inorganic silicon-oxygen skeleton in the cross-linked polymer. A mass fraction of silicon elements of 25% to 45% can improve the thermal decomposition temperature and structural stability of the polymer, thereby improving the heat resistance of the separation film at high temperatures. The mass fraction of cage-like polyhedral oligomeric silsesquioxane skeleton is crucial to improving the three-dimensional structural stability of the cross-linked polymer. A mass fraction of cage-like polyhedral oligomeric silsesquioxane skeleton of 30% to 60% can ensure that the cross-linked polymer has good rigidity and structural stability, reduces the occurrence of structural collapse or brittle fracture in the separation film under thermal abuse, and is conducive to improving the heat resistance of the separation film, thereby improving the reliability of the battery cell at high temperatures. Therefore, by limiting the cross-linking degree, the mass fraction of silicon elements, and the mass fraction of cage-like polyhedral oligomeric silsesquioxane skeleton of the organic silicon polymer to meet the above ranges, respectively, the structure of the organic silicon polymer containing the cage-like polyhedral oligomeric silsesquioxane skeleton can be controlled, so that the separation film including the polymer has good heat resistance at high temperatures, thereby improving the reliability of the battery cell. In some embodiments, the mass fraction of the heat-resistant particles in the coating layer is 50% to 97%. By limiting the mass fraction of the heat-resistant particles in the coating layer to meet the above range, the coating layer can have structural stability and air permeability, thereby improving the heat resistance of the separation film and the reliability of the battery cell. In some embodiments, the coating layer does not include inorganic particles. In some embodiments, the coating layer includes inorganic particles, and the mass fraction of the inorganic particles is 0.1% to 50% based on the total mass of the coating layer. In some other embodiments, the coating layer includes inorganic particles, and the mass fraction of the inorganic particles is 50% to 92% based on the total mass of the coating layer. In one example, the inorganic particles include at least one of SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, Y2O3, Al2O3, boehmite (AlO(OH)), Al(OH)3, TiO2, and SiC. The above inorganic particles have a large dielectric constant, which is conducive to improving the ion transport efficiency in the coating layer. In some embodiments, the coating further comprises a first binder, the first binder satisfying one or more of the following conditions: (1) the first binder comprises at least one of polyimide, polyetherimide, polyacrylic acid, polyacrylate, ethylene-vinyl acetate copolymer, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylated polyvinyl alcohol, cyanoethyl cellulose, cyanoethylsucrose, pullulan, carboxymethyl cellulose, acrylonitrile-styrene-butadiene copolymer, ethylene-propylene-diene terpolymer, sulfonated ethylene-propylene-diene terpolymer, styrene-butadiene rubber, fluoroelastomer; (2) the mass fraction of the first binder in the coating is 3% to 15%. The heat-resistant particles in the coating are connected and fixed to each other by the first binder, reducing the situation of falling off of the heat-resistant particles during coating and use. The mass fraction of the first binder satisfies the above range, which can reduce the proportion of the heat-resistant particles in the coating due to excessive binder while ensuring adhesion, so as to balance the stability and heat resistance of the coating and improve the heat resistance of the isolation film. In some embodiments, the isolation film further comprises second binder particles, the second binder particles being located in the coating, or the isolation film further comprises a bonding layer, the bonding layer being arranged on at least one side of the coating away from the porous base film, and the second binder particles being located in the bonding layer; the second binder particles satisfy one or more of the following conditions: (1) the second binder particles comprise at least one of polyvinylidene fluoride, poly(vinylidene fluoride-co-trichloroethylene), poly(vinylidene fluoride-co-trifluorochloroethylene), poly(vinylidene fluoride-co-trifluoroethylene), poly(vinylidene fluoride-co-tetrafluoroethylene), poly(vinylidene fluoride-co-hexafluoropropylene), polyacrylate, polymethyl methacrylate, polyacrylonitrile; (2) the number average particle size of the second binder particles is 5 μm to 20 μm. The addition of the second binder particles in the coating or the bonding layer of the isolation film can fill the gap between the negative electrode sheet and the isolation film, form a relatively firm bonding interface, and help to improve the bonding strength between the isolation film and the negative electrode sheet, thereby improving the overall stability of the isolation film, reducing the interlayer peeling phenomenon between the isolation film and the negative electrode sheet caused by thermal stress or electrochemical action during the cycle process, and improving the cycle performance of the battery cell. The number average particle size of the second binder particles satisfies the above range, which ensures that the second binder particles can be uniformly distributed and maintain moderate fluidity during hot pressing, thereby further improving the cycle performance of the battery cell. In some embodiments, the second binder particles are arranged in the coating. In other embodiments, the bonding layer can also be arranged on at least a part of the surface of the side of the coating away from the porous base film, the heat-resistant particles are arranged in the coating, and the second binder particles are arranged in the bonding layer. In some embodiments, the second binder particles are disposed in the coating layer. In some embodiments, the second binder particles are disposed in the coating layer. In some embodiments, the second binder particles are disposed in the coating layer. In some embodiments, the second binder particles are disposed in the coating layer. The separation film can be prepared according to methods known in the art. In some embodiments, a slurry including the heat-resistant particles and the first binder particles can be coated on at least one side of the porous base film, and the separation film can be obtained after drying. In some embodiments, the slurry can further include the second binder particles, and after drying of the slurry, the polymer binder particles can be embedded in the organic particles and form protrusions on the surface of the coating layer. In some embodiments, the method for preparing the separation film can include: coating a slurry including the heat-resistant particles and the first binder particles on at least one side of the porous base film, and forming a coating layer after drying; and coating a slurry including the second binder particles on at least a portion of the surface of the coating layer away from the porous base film, and obtaining the separation film including the bonding layer after drying. In some embodiments, the method for preparing the separation film can include: coating a slurry including the heat-resistant particles and the first binder particles on one side of the porous base film, and coating a slurry including the second binder particles on at least a portion of the surface of the other side of the porous base film, and obtaining the separation film including the bonding layer after drying. In some embodiments, the solvent of the slurry can be water, for example, deionized water. In some embodiments, the slurry can further include other components, for example, can further include a dispersant and / or a wetting agent, etc. In some embodiments, the separation film can satisfy one or more of the following conditions: (1) the thickness of the coating layer is 0.5 μm to 10 μm; (2) the areal density of the coating layer is 1.5 g / m 2 ~ 6 g / m 2 ; (3) the longitudinal heat shrinkage of the separation film is less than or equal to 5% after constant temperature heating at 130°C for 1 h; (4) the transverse heat shrinkage of the separation film is less than or equal to 5% after constant temperature heating at 130°C for 1 h; and (5) the air permeability of the separation film is 150 s / 100 mL to 500 s / 100 mL. The thickness of the coating refers to the thickness of the coating on one side of the porous base film. For example, the thickness of the coating can be 1 μm, 3 μm, 5 μm, 7 μm, 9 μm, 10 μm, or a value within the range obtained by combining any two of the above values. A coating that is too thin cannot form an effective thermal insulation layer, and a coating that is too thick increases the thickness of the separator and reduces the energy density of the battery cell. A coating with a thickness of 1 μm to 10 μm can provide a uniform and dense heat-resistant coating, improve the heat resistance of the separator, and thus improve the reliability of the battery cell. The areal density of the coating is 0.5 g / m 2 to 5 g / m 2 , which can ensure a moderate coating quality, improve the stability and heat resistance of the separator, and not significantly increase the weight of the separator, thereby facilitating the energy density and reliability of the battery cell. The air permeability (Gurley value) of the separator refers to the time required for 100 mL of air to pass through the separator, and characterizes the resistance of the pore structure of the separator to gas / liquid transmission. The air permeability of the separator is 150 s / 100 mL to 500 s / 100 mL, which ensures that the electrolyte can be uniformly infiltrated and maintain rapid ion transmission, ensures the ion transmission efficiency in the separator, and reduces the case of low air permeability of the separator leading to electrochemical polarization and reducing the reliability of the battery cell. In some embodiments, the peeling force between the coating of the separator and the porous base film can be greater than or equal to 28 N / m. In the embodiments of the present application, the peeling force between the coating of the separator and the porous base film can be tested according to the following method: cutting the separator into 3 pieces of 2.5 cm x 15 cm, pasting the pieces on a test steel plate, pasting a test tape with a width of 2 cm on the side of the separator to be tested, using a tensile testing machine, clamping the steel plate on one side and the tape on the other side for 180° peeling test, taking the average of the peeling forces of the 3 pieces as the peeling force between the coating of the separator and the porous base film. The tensile rate is 50 mm / min. It should be noted that the coating parameters of the above-mentioned separator are the coating parameters on one side of the porous base film. When the coating is provided on both sides of the porous base film, the coating parameters of any one side meet the present disclosure, and it is considered to fall within the protection scope of the present disclosure. In some embodiments, the material of the porous base film of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The porous base film can be a single-layer film or a multi-layer composite film, and is not particularly limited. When the porous base film is a multi-layer composite film, the materials of the layers can be the same or different, and are not particularly limited. In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be made into an electrode assembly by a winding process or a stacking process. [Battery device] In some embodiments, the battery cell is a battery device, which can include one or more battery cells. FIG. 3 is a structural schematic diagram of a battery device according to an embodiment of the present application. For example, as shown in FIG. 3, the battery device 10 is a battery pack. The battery pack can include a box and a plurality of battery cells accommodated in the box, which are connected in series, in parallel or in a mixed connection. The battery cells can be directly composed into the battery pack, or can be first composed into a battery module, and then the battery pack is composed of a plurality of battery modules. The battery device 10 can also include a box 11, which has a hollow structure inside, and the plurality of battery cells 3 are accommodated in the box 11. For example, the plurality of battery cells 3 are combined in parallel, in series or in a mixed connection and then placed in the box 11. The box 11 can include a first box part 111 and a second box part 112, which are covered with each other to form the box 11. The shapes of the first box part 111 and the second box part 112 can be determined according to the shapes of the components accommodated inside, for example, according to the shape of the combination of the plurality of battery cells 3 accommodated inside, and at least one of the first box part 111 and the second box part 112 has an opening. For example, as shown in FIG. 3, the first box part 111 and the second box part 112 can each be a hollow cuboid with one face as an opening face. The opening of the first box part 111 and the opening of the second box part 112 are oppositely arranged, and the first box part 111 and the second box part 112 are buckled with each other to form the box 11 with a closed cavity, which can be used to accommodate the plurality of battery cells 3. The plurality of battery cells 3 are combined in parallel, in series or in a mixed connection and then placed in the box 11 formed by buckling the first box part 111 and the second box part 112. For another example, unlike that shown in FIG. 3, only one of the first box part 111 and the second box part 112 can be a hollow cuboid with an opening, and the other can be a plate to cover the opening. Taking the second box part 112 as a hollow cuboid with an opening and the first box part 111 as a plate as an example, the first box part 111 covers the opening of the second box part 112 to form the box 11 with a closed cavity, which can be used to accommodate the plurality of battery cells 3. In some embodiments, the battery device 10 can further include other components. For example, the battery device 10 can further include a busbar component, which can be used to achieve electrical connection between a plurality of battery cells 3, such as parallel connection or series connection or hybrid connection. Specifically, the busbar component can achieve electrical connection between the battery cells 3 by connecting the electrode terminals of the battery cells 3; or the busbar component can also achieve electrical connection between the battery cells 3 by connecting other components of the battery cells 3. The busbar component can be fixed to the corresponding component of the battery cell 3 by welding, such as the electrode terminal, the sealing structure or the shell, etc., and the embodiments of the present application are not limited thereto. The battery cells 3 can directly constitute the battery device 10, or can first constitute a battery module, and then a plurality of battery modules constitute the battery device 10. In some embodiments, the battery device 10 can be located in an energy storage device. The energy storage device includes an energy storage container, an energy storage cabinet, etc. [Electric equipment] At least one of the battery cell, the battery module, or the battery pack provided by the present application is included. The lithium ion battery, the battery module, or the battery pack can be used as a power supply of an electric equipment, or can be used as an energy storage unit of an electric equipment. The electric equipment can include a mobile device (such as a mobile phone, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto. As an electric equipment, the battery cell, the battery module or the battery pack can be selected according to the use requirement thereof. The electric equipment can be a vehicle, a mobile phone, a portable device, a notebook computer, a ship, a spacecraft, an electric toy and an electric tool, etc. The vehicle can be a fuel automobile, a gas automobile or a new energy automobile, and the new energy automobile can be a pure electric automobile, a hybrid electric automobile or a range extended automobile, etc.; the spacecraft includes an airplane, a rocket, a space shuttle and a spacecraft, etc.; the electric toy includes a fixed or mobile electric toy, such as a game console, an electric automobile toy, an electric ship toy and an electric airplane toy, etc.; the electric tool includes a metal cutting electric tool, a grinding electric tool, an assembling electric tool and a railway electric tool, such as an electric drill, an electric grinder, an electric wrench, an electric screwdriver, an electric hammer, an impact electric drill, a concrete vibrator and an electric planer, etc. The embodiments of the present application do not specially limit the above electric equipment. FIG. 4 is a schematic diagram of an electric equipment according to an embodiment of the present application. As shown in FIG. 4, the present application provides an electric equipment, which can be a vehicle 1, and the electric equipment includes the battery cell in the above embodiments. The vehicle 1 can be a fuel automobile, a gas automobile, or a new energy automobile, and the new energy automobile can be a pure electric automobile, a hybrid automobile, or a range extended automobile, etc. The vehicle 1 can be provided with a motor 5, a controller 4, and a battery device 10, and the controller 4 is used to control the battery device 10 to supply power to the motor 5. For example, the battery device 10 can be arranged below the vehicle 1 or at the front or rear of the vehicle 1. The battery device 10 can be used to supply power to the vehicle 1, for example, the battery device 10 can be used as an operating power source of the vehicle 1, and can be used for the circuit system of the vehicle 1, for example, for the power demand of starting, navigation, and working of the vehicle 1. In another embodiment of the present application, the battery device 10 can not only be used as an operating power source of the vehicle 1, but also be used as a driving power source of the vehicle 1, to replace or partially replace fuel or natural gas to provide driving power for the vehicle 1. As another example, the device can be a mobile phone, a tablet computer, a notebook computer, etc. The device usually requires thinning, and a battery monomer can be used as a power source. FIG. 5 is a schematic diagram of a power consumption device according to another embodiment of the present application. As shown in FIG. 5, the present application provides a power consumption device, which is a storage energy device 2, and the storage energy device 2 can include a plurality of battery devices 10. The storage energy device 2 can be applied to a power storage station to store and release electric energy. Optionally, the power consumption device can also be a storage energy device, a lighting device, a spacecraft, etc., and the embodiments of the present application include but are not limited to the above. Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and cannot be understood as a limitation of the present application. If a specific technology or condition is not specified in the embodiments, the technology or condition is performed according to the technology or condition described in the literature in the art or according to the product instruction. If the reagent or instrument used is not specified by the manufacturer, it is a conventional product that can be obtained from the market. [Examples and Comparative Examples] Example 1 (1) Preparation of the negative electrode sheet: Preparation of the negative electrode sheet: the negative electrode active material artificial graphite, the conductive agent carbon black, the binder styrene-butadiene rubber (SBR), and the thickening agent sodium hydroxymethyl cellulose (CMC-Na) were dispersed in deionized water according to a weight ratio of 96.5:1.0:1.3:1.2, and then fully stirred and mixed to prepare a negative electrode slurry; the negative electrode slurry was uniformly coated on a negative electrode current collector copper foil, and then subjected to drying, cold pressing, and slitting to obtain a negative electrode sheet. The solid content of the negative electrode slurry was 60%. (2) Preparation of the positive electrode sheet: An anode slurry is obtained by uniformly stirring lithium iron phosphate (LiFePO4), polyvinylidene fluoride (PVDF), conductive carbon black (Super-P) and dispersant polyvinylpyrrolidone (PVP) in a mass ratio of 95:2.5:1.5:1.0 in a solvent, i.e., N-methylpyrrolidone (NMP), in a vacuum stirrer. The slurry is coated on both sides of an aluminum foil, dried, cold-pressed and cut to obtain an anode sheet. (3) Preparation of the separation film ① Preparation of heat-resistant particles (organic silicon polymer containing a cage polysilsesquioxane skeleton): In a 5L flask equipped with a stirrer, a thermometer and a reflux condenser, 3200g of deionized water and 9ml of hydrochloric acid were added, stirred and 120g of methyltrimethoxysilane was added. After hydrolysis at 32℃ for 2h, 75ml of ammonia water was added, and the reaction was continued at 32℃ for 2h. The temperature was then raised to 90℃ and the reaction was continued for 12h to obtain a dispersion of heat-resistant particles. The water content was then evaporated to obtain a dispersion with a solid content of 20% for standby use. The standby dispersion was dried to obtain the corresponding heat-resistant particle powder. The crosslinking degree of the heat-resistant particle powder was tested using a PQ001 nuclear magnetic resonance analyzer. Figure 6 shows the crosslinking degree test results of the heat-resistant particle powder of the present application. As shown in Figure 6, the heat-resistant particles are crosslinked polymers, and the calculated crosslinking degree is 93.3%. The heat-resistant particle powder was tested by pyrolysis-gas chromatography-mass spectrometry (Py-GC / MS). Figure 7 shows the pyrolysis spectrum of the heat-resistant particle powder of the present application. As shown in Figure 7, by comparing with the standard pyrolysis spectrum of EVA in the NIST library, the characteristic ions of the heat-resistant particles were detected. It can be inferred that the heat-resistant particles include a cage polysilsesquioxane skeleton. The glass transition temperature T g and melting point of the heat-resistant particles were tested by differential scanning calorimetry (DSC). The heat-resistant particles had no T g and no melting point below 300℃. The density of the heat-resistant particles was tested by a true density tester. The true density of the heat-resistant particles was 1.33g / cm 3 . The volume distribution particle size Dv50 of the heat-resistant particles was tested by a Malvern 3000 (MasterSizer 3000) laser particle size analyzer. The volume distribution particle size Dv50 of the heat-resistant particles was 320nm. The heat-resistant granular ethylene carbonate, the heat-resistant granular ethylene carbonate, and the mixed solvent of methyl ethylene carbonate in a volume ratio of 3:7 were soaked at 60°C for 7 days, and the dissolution rate of the heat-resistant granular was tested. The dissolution rate of the heat-resistant granular after soaking at 60°C for 7 days was 0.1%. ② Preparation of the isolation film: A commercially available polyethylene microporous film (Zhao Gao Electronics Technology Co., Ltd.) with a thickness of 7 μm and an average pore size of 50 nm was used as the porous base film; the heat-resistant granular dispersion liquid prepared above and the binder polyacrylic acid were mixed uniformly in deionized water at a solid mass ratio of 93:7 to obtain a coating slurry. The commercially available polyvinylidene fluoride particles (Arkema) and the binder polyacrylate were stirred uniformly in deionized water at a solid content mass ratio of 90:10 to obtain a binder layer slurry. The Dv50 of the polyvinylidene fluoride particles was 6.5 μm. The coating slurry was uniformly coated on both surfaces of the porous base film at a loading of 2.6 g / m 2 , and the solvent was removed by drying. The thickness of the single-sided coating was 1.5 μm. Then, the binder layer slurry was sprayed on the coating, and the isolation film was obtained through drying and slitting processes. The air permeability of the isolation film was 201 s / 100 mL. (4) Preparation of the electrolyte: In an argon atmosphere glove box (H2O <0.1 ppm, O2 <0.1 ppm), ethylene carbonate (EC), methyl ethylene carbonate (EMC), and dimethyl carbonate (DMC) were mixed in a volume ratio of 1:1:1 to obtain an organic solvent. Then, LiPF6 and the additive vinylene carbonate (VC) were dissolved in the above mixed organic solvent to obtain the electrolyte. The concentration of LiPF6 was 1 mol / L, and the mass fraction of vinylene carbonate (VC) was 2%. (5) Preparation of the battery cell: Preparation of the battery cell: The positive electrode sheet, the isolation film, and the negative electrode sheet were stacked in order, with the isolation film between the positive and negative electrode sheets to separate the positive and negative electrode sheets. The electrode assembly was obtained by winding. The tab of the electrode assembly was connected to the end cover (for example, by welding connection of the tab and the end cover through a connecting member). The electrode assembly was placed in an aluminum shell, and the electrolyte was injected after drying. Then, the battery cell was obtained by packaging. [Example 2-5] The difference between Example 2 and Example 1 was that in the preparation process of the heat-resistant granular, the “temperature was raised to 90°C and the reaction was continued for 12 h” in Example 1 was adjusted to “temperature was raised to 90°C and the reaction was continued for 6 h” to obtain the heat-resistant granular dispersion liquid. The rest of the preparation process was similar to that of Example 1. Example 3 is different from Example 1 in that, in the preparation of heat-resistant particles, the "temperature is raised to 90°C and the reaction is continued for 12h" in Example 1 is adjusted to "temperature is raised to 70°C and the reaction is continued for 24h", to obtain a heat-resistant particle dispersion liquid, and the rest of the preparation process is similar to Example 1. Example 4 is different from Example 1 in that, in the preparation of heat-resistant particles, the "temperature is raised to 90°C and the reaction is continued for 12h" in Example 1 is adjusted to "temperature is raised to 70°C and the reaction is continued for 12h", to obtain a heat-resistant particle dispersion liquid, and the rest of the preparation process is similar to Example 1. Example 5 is different from Example 1 in that, in the preparation of heat-resistant particles, 3200g of deionized water, 9ml of hydrochloric acid, stirring and adding 120g of methyl trimethoxysilane, hydrolysis reaction for 2h at 32°C, then adding 75ml of ammonia water, reaction for 2h at 32°C, to obtain a dispersion liquid of heat-resistant particles, and the solid content is 20% by subsequent evaporation of water content. The dispersion liquid is dried to obtain the corresponding heat-resistant particle powder. [Example 6] (3) Preparation of the separation film (organic silicon polymer containing phenyl) ① Preparation of heat-resistant particles: 0.3g of potassium persulfate, 0.3g of sodium bicarbonate, 1.5g of sodium dodecyl sulfate, 30g of deionized water, 3-methacryloxypropyl methyl dimethoxysilane, 3-methacryloxypropyl trimethoxysilane, and divinylbenzene were mixed to obtain a pre-emulsion for standby (wherein the mass ratio of 3-methacryloxypropyl methyl dimethoxysilane, 3-methacryloxypropyl trimethoxysilane and divinylbenzene is 3:85:12, and the added mass of 3-methacryloxypropyl methyl dimethoxysilane is 1.8g). Take a reactor, add 210g of deionized water, heat to 80°C, and drop the above pre-emulsion under the conditions of nitrogen protection and stirring, react for 4h, then heat to 90°C and mature for 4h, to obtain an emulsion containing heat-resistant particles. The heat-resistant particle powder was tested by PQ001 nuclear magnetic resonance analyzer for crosslinking degree test. The heat-resistant particles are crosslinked polymers, and the calculated crosslinking degree is 90.7%. The heat-resistant particle powder was tested by pyrolysis-gas chromatography-mass spectrometry (Py-GC / MS), and by comparing with the EVA standard pyrolysis spectrum in the NIST library, it was detected that The corresponding characteristic ions can be inferred that the heat-resistant particles include benzene ring. The glass transition temperature Tg of the heat-resistant particles was tested by Differential Scanning Calorimetry (DSC), and the result was -45.6°C. gand melting point, the heat-resistant particles have no T g , no melting point. The density of the heat-resistant particles was tested by using a true density tester, and the true density of the heat-resistant particles was 1.39 g / cm 3 . The volume distribution particle size Dv50 of the heat-resistant particles was tested by using a Malvern 3000 (MasterSizer 3000) laser particle size analyzer, and the volume distribution particle size Dv50 of the heat-resistant particles was 250 nm. The heat-resistant particles were soaked in ethylene carbonate, the heat-resistant particles were soaked in ethylene carbonate, and the mixed solvent of methyl ethyl carbonate was composed of a volume ratio of 3:7 at 60°C for 7 days. The dissolution rate of the heat-resistant particles was tested, and the dissolution rate of the heat-resistant particles soaked at 60°C for 7 days was 0.5%. ② Preparation of the isolation film: a commercially available polyethylene microporous film (Zhao Gao Electronics Technology Co., Ltd.) with a thickness of 7 μm and an average pore size of 50 nm was used as the porous base film; the above-prepared dispersion liquid containing heat-resistant particles and the adhesive polyacrylic acid were mixed uniformly in deionized water at a solid mass ratio of 92:8 to obtain a coating slurry. The commercially available polyvinylidene fluoride particles (Arkema) and the adhesive polyacrylate were stirred uniformly in deionized water at a solid content mass ratio of 90:10 to obtain an adhesive layer slurry. The Dv50 of the polyvinylidene fluoride particles was 6.5 μm. The coating slurry was uniformly coated on both surfaces of the porous base film at a loading of 2.5 g / m 2 (the single side), and the solvent was removed by drying. The thickness of the single-sided coating was 1.5 μm, and then the adhesive layer slurry was sprayed on the coating at a loading of 1.0 g / m 2 (the single side) on both sides, and then the isolation film was obtained through drying and slitting processes. The air permeability of the isolation film was 196 s / 100 mL. The specific implementation parameters are shown in Table 3. [Examples 6-10] Example 7 differs from Example 6 in that, in the preparation process of the heat-resistant particles, the mass ratio of "3-methacryloxypropyl trimethoxysilane to divinylbenzene is 85:12" in Example 6 is adjusted to "3-methacryloxypropyl trimethoxysilane to divinylbenzene is 92:5", and the heat-resistant particle-containing emulsion, and the rest of the preparation process is similar to Example 6. Example 8 differs from Example 6 in that, in the preparation process of the heat-resistant particles, the mass ratio of "3-methacryloxypropyl trimethoxysilane to divinylbenzene is 85:12" in Example 6 is adjusted to "3-methacryloxypropyl trimethoxysilane to divinylbenzene is 89:8", and the heat-resistant particle-containing emulsion, and the rest of the preparation process is similar to Example 6. Example 9 differs from Example 6 in that the "mass ratio of 3-methacryloxypropyl trimethoxysilane and divinylbenzene is 85:12" in the preparation of heat-resistant particles in Example 6 is adjusted to "mass ratio of 3-methacryloxypropyl trimethoxysilane and divinylbenzene is 87:10", and the rest of the preparation process is similar to Example 6. Example 10 differs from Example 6 in that the "mass ratio of 3-methacryloxypropyl trimethoxysilane and divinylbenzene is 85:12" in the preparation of heat-resistant particles in Example 6 is adjusted to "mass ratio of 3-methacryloxypropyl trimethoxysilane and divinylbenzene is 82:15", and the rest of the preparation process is similar to Example 6. [Examples 11-14] In Example 11, commercially available phenol and formaldehyde as raw materials for resol resin material are placed in a curing oven (molar ratio of phenol and formaldehyde is 1:2.5), the atmosphere is set to air atmosphere, the temperature is set to 130°C, and the temperature is kept for 3h; after the end, the temperature of the curing oven is raised to 240°C, and the temperature is kept for 4h. After the end of the two curing, the cured phenolic resin material is taken out, placed in air for natural cooling, then crushed, sand ground, sieved, and de-magnetized to obtain a phenolic resin with a volume average particle size Dv50 of 400nm; the heat-resistant particles of Example 1 are replaced with phenolic resin heat-resistant particles, and the rest of the preparation method is similar to Example 1. In Example 12, commercially available resol melamine formaldehyde resin particles are cured in air atmosphere at 255°C for 4h, and then crushed, sand ground, sieved, and de-magnetized to obtain melamine formaldehyde resin particles with a volume average particle size Dv50 of 420nm. The molar ratio of formaldehyde to melamine in the resol melamine formaldehyde resin is 2.5:1. In Example 13, 0.8g of sodium dodecyl sulfate, 80mg of sodium persulfate, 20ml of deionized water, 31g of styrene, and 9g of divinylbenzene are emulsified to obtain a pre-emulsion for standby. 140g of deionized water is added to the reactor, heated to 65°C, and the above standby pre-emulsion is added dropwise under nitrogen protection and stirring conditions. After 4h of reaction, the temperature is raised to 72°C for 2.5h of maturation reaction to obtain a cross-linked styrene organic particle emulsion with a volume average particle size Dv50 of 185nm; the heat-resistant particles of Example 1 are replaced with cross-linked styrene, and the rest of the preparation method is similar to Example 1. In Example 14, commercially available polybenzoxazine resin is completely cured by heating, and then crushed, sieved, and sand ground to obtain polybenzoxazine resin nanoparticles with a volume average particle size Dv50 of 350nm; the heat-resistant particles of Example 1 are replaced with polybenzoxazine resin nanoparticles, and the rest of the preparation method is similar to Example 1. [Comparative Example 1] Comparative Example 1 differs from Example 1 in that an acrylate, acrylic acid, and acrylamide latex is selected to perform emulsion polymerization to obtain a polyacrylate latex of about 180 nm. A 1000 mL four-necked flask equipped with a mechanical stirrer, thermometer, and condenser is charged with 200 g of mixed monomers, 70:15:15 mass ratio of methyl acrylate, acrylic acid, and acrylamide, 6 g of sodium dodecyl sulfate emulsifier, 2 g of ammonium persulfate initiator, 350 g of deionized water, and the mixture is emulsified at high speed for 40 min. Under nitrogen protection, the temperature is raised to 80°C and reacted for 4 h, then cooled to below 35°C, the pH is adjusted to neutral, and the polyacrylate nanoparticles are obtained by filtration, with an average particle size Dv50 of 180 nm. The heat-resistant particles of Example 1 are replaced with the polyacrylate nanoparticles. [Comparative Example 2] In Comparative Example 2, 0.3 g of potassium persulfate, 0.3 g of sodium bicarbonate, 1.5 g of sodium dodecyl sulfate, 30 g of deionized water, 3-methacryloxypropylmethyldimethoxysilane, and 3-methacryloxypropyltrimethoxysilane are mixed to obtain a pre-emulsion for standby (wherein the mass ratio of 3-methacryloxypropylmethyldimethoxysilane and 3-methacryloxypropyltrimethoxysilane is 3:97, and the addition amount of 3-methacryloxypropylmethyldimethoxysilane is 1.8 g). A reactor is taken, 210 g of deionized water is added, and the temperature is raised to 80°C. Under nitrogen protection and stirring conditions, the above-mentioned pre-emulsion is added dropwise, and after reaction for 4 h, the temperature is raised to 90°C for curing reaction for 4 h to obtain an emulsion containing heat-resistant particles. Table 1 Product parameters of Examples 1-5 and Comparative Example 1 Table 2 Performance parameters of Examples 1-5 and Comparative Example 1 As shown in Examples 1-5 and Comparative Example 1 in Tables 1 and 2, the crosslinking degree of the heat-resistant particles is 70% to 98%, and the mass fraction of the cage-like polysilsesquioxane skeleton is 40% to 60%. The cage-like polysilsesquioxane skeleton can provide structural support and ensure that the heat-resistant particles have good heat resistance, improve the overall structural integrity of the isolation film at high temperatures, and thus improve the reliability of the battery cell at high temperatures. Table 3 Product parameters of Examples 6-10 and Comparative Example 2 Table 4 Performance parameters of Examples 6-10 and Comparative Example 2 As shown in Examples 6-10 and Comparative Example 2 in Tables 3 and 4, the heat-resistant particles have a cross-linking degree of 85% to 97%, a mass fraction of phenyl groups of 2% to 12%, and good heat resistance at high temperatures, so that the separator film has a low heat shrinkage rate, a high cycle capacity retention rate, and a high storage capacity retention rate, and the separator film has good heat resistance. Product parameters of Examples 1 and 11-14 in Table 5 Performance parameters of Examples 11-14 in Table 6 As shown in Examples 1, 11-14 in Tables 5 and 6, the heat-resistant particles in the examples include the above-mentioned substances, have a low dissolution rate and heat shrinkage rate, a high cycle capacity retention rate, and a high storage capacity retention rate, the separator film has good heat resistance, the battery cell has good high-temperature cycle performance, and the reliability of the battery cell is improved. The following briefly describes the test methods of the physicochemical parameters and performance parameters involved in the examples. It should be understood that the following test methods are only examples, and other test methods known in the art can also be used for testing. 1. Test method of cross-linking degree As an example, the cross-linking degree of the cross-linked polymer can be tested by a PQ001 nuclear magnetic resonance analyzer. The test temperature is 60°C, the resonance frequency of the nuclear magnetic resonance analyzer is set to 21 MHz, 0.5 g of the cleaned and dried sample (the above-mentioned heat-resistant particles) to be tested is taken, is loaded into a clean sample tube and is inserted into a probe at a specified depth, the probe coil diameter is 13 mm, and the measurement is performed according to the manufacturer's instructions. Specifically, the cross-linking degree of the cross-linked polymer is obtained by calculating the proportion of the cross-linking signal from the fitting software by collecting the entire polymer signal; the "cross-linking degree" or "T2 relaxation" test mode is selected in the software, and the PQ001 nuclear magnetic resonance analyzer automatically obtains the relaxation decay curve. During data processing, the software decomposes the relaxation components by exponential fitting, calculates and outputs the cross-linking degree result according to the degree of restriction of molecular chain movement. 2. Test method of rigid structure The rigid structure in the heat-resistant particles can be tested by a pyrolysis-gas chromatography-mass spectrometry (Py-GC / MS) instrument. Specifically, 0.5-1 mg of the heat-resistant particles described above is weighed as a test sample, loaded into a quartz cracking tube of a pyrolysis instrument, cracked at 550°C for 1.2 s, and tested in an inert gas (such as helium) to crack the sample into volatile small molecules, which are then introduced into a gas chromatograph-mass spectrometer. The HP-5ms (30 m x 0.25 mm x 0.25 μm) chromatographic column is selected, the temperature is set to 30°C for 5 min, increased to 250°C at 10°C / min, and maintained at 250°C for 5 min. The carrier gas is high-purity helium with a flow rate of 1.0 mL / min. The mass spectrometer uses electrochemical ionization, the ion source temperature is 230°C, and the fragment scan range is m / z 25-200. By comparing with the EVA standard cracking spectrum in the NIST library, the characteristic ions corresponding to the rigid structure are detected, which can be inferred that the organic silicon polymer includes the rigid structure. The internal standard method is used to calculate the mass proportion of the characteristic rigid structure in the heat-resistant particles based on the area of the above fragment peak corresponding to the characteristic rigid structure. 3. Test of heat shrinkage rate The heat shrinkage rate of the release film can be tested according to GB / T 36363-2018. As an example, the release film is punched into a sample with a width of 50 mm and a length of 100 mm by a punch machine, 5 parallel samples are placed on an A4 paper, and then the A4 paper with the samples is placed on a corrugated paper with a thickness of 1 mm to 5 mm. The temperature of the air-blowing oven is set to 130°C, and after the temperature reaches the set temperature and stabilizes for 60 min, the A4 paper placed on the corrugated paper is put into the air-blowing oven, and the timing starts. After reaching the set time (1 h in the present disclosure), the length and width of the release film are measured, and the values are marked as a and b, respectively. The longitudinal (MD) heat shrinkage rate is [(100-a) / 100] x 100%, and the transverse (TD) heat shrinkage rate is [(50-b) / 50] x 100%. The average value of 3 parallel samples is taken as the test result. 4. Test of cycle performance The battery cell prepared above is charged at 1C to 3.65V at a test temperature of 45°C and a voltage of 2.5-3.65V, then charged at 3.65V until the current is less than or equal to 0.05 mA, and then rested for 5 min. Then, it is discharged at 1C to 2.5V, which is one charge-discharge cycle process. The discharge capacity of this time is the discharge capacity of the first cycle, denoted as Cap1. The battery cell is subjected to the cycle charge-discharge test in the above manner, and the above operation is repeated for 500 cycles. The discharge capacity of the 500th cycle is taken as Cap500. The capacity retention rate C of the secondary battery cell after 500 cycles is [Cap500 / Cap1] x 100%, and the capacity retention rate after cycling is recorded. The greater the capacity retention rate after cycling, the smaller the capacity loss of the battery cell, and the better the cycle performance. 5. Test of storage performance The secondary battery cell was charged at 1 / 3 C constant current to 3.65 V, then charged at 3.65 V constant voltage to a current of 0.05 C, and rested for 5 min, and then discharged at 1 / 3 C constant current to 2.5 V at 25°C. Then the secondary battery cell was charged at 1 / 3 C constant current to 3.65 V, and then charged at 3.65 V constant voltage to a current of 0.05 C, at which time the secondary battery cell was in a full charge state, and the obtained charge capacity was recorded as the pre-storage capacity CO. The capacity of the secondary battery cell in the full charge state after being stored in a 45°C constant temperature oven for 100 days was recorded as the post-storage capacity CI. The capacity retention rate of the secondary battery cell after being stored at 45°C for 100 days = post-storage capacity CI / pre-storage capacity CO x 100%. Note that the present application is not limited to the above-described embodiments. The above-described embodiments are merely examples, and embodiments having substantially the same configuration as the technical idea and exerting the same effects within the scope of the technical solution of the present application are all included in the technical scope of the present application. Furthermore, within the scope of the gist of the present application, other modes obtained by applying various modifications that can be thought of by those skilled in the art to the embodiments, or by combining part of the constituent elements of the embodiments, are also included in the scope of the present application.

Claims

A battery cell characterized by The battery cell comprises a positive electrode sheet, a negative electrode sheet, and a separator film between the positive electrode sheet and the negative electrode sheet. The separator film comprises a porous base film and a coating layer provided on at least one side of the porous base film; the coating layer comprises heat-resistant particles, and the heat-resistant particles comprise a cross-linked polymer; the cross-linking degree of the cross-linked polymer is 70% to 98%. The battery cell of claim 1, wherein The cross-linked polymer comprises a planar ring conjugated group and / or a covalent polyhedral skeleton. The battery cell according to claim 1 or 2, characterized in that, The planar ring conjugated group comprises any one of a substituted or unsubstituted phenyl group, a substituted or unsubstituted heteroatom-containing aromatic group, a substituted or unsubstituted condensed ring aromatic group, and a substituted or unsubstituted triazine ring group; optionally, the planar ring conjugated group comprises any one of a phenyl group and a triazine ring group. The battery cell according to claim 3, wherein The cross-linked polymer comprises at least one of a phenol-formaldehyde resin-based polymer, a polymer containing a triazine ring group, a phenyl-containing silicone polymer, and a cross-linked styrene-based polymer. The battery cell according to claim 4, characterized in that The phenyl-containing organosilicon polymer includes monomers and crosslinking agents represented by formula (I) and polymerized, wherein R1 and R2 each independently comprise a C1-C4 alkyl group or a C2-C4 alkenyl group, R3 comprises a C1-C4 alkyl group or a C4-C8 (meth)acryloxyalkyl group, and R4 comprises a C2-C8 alkenyl group or a C4-C8 (meth)acryloxyalkyl group; and the cross-linking agent comprises divinylbenzene. The battery cell according to claim 4 or 5, characterized in that The phenyl-containing silicone polymer satisfies at least one of the following conditions: (1) the cross-linking degree of the phenyl-containing silicone polymer is 75% to 95%; (2) the phenyl-containing silicone polymer comprises a silicon element, and the mass fraction of the silicon element in the phenyl-containing silicone cross-linking resin is 10% to 25%; (3) the mass fraction of the phenyl group in the phenyl-containing silicone polymer is 2% to 12%. The battery cell according to claim 1 or 2, characterized in that, The covalent polyhedral skeleton comprises a skeleton formed by a compound represented by formula (I), R a [SuO 3 / 2 ] n Formula (II) wherein n is any integer from 4 to 12, R a including cycloalkyl, aryl, C1-C 12 alkyl, C1-C 12 alkenyl, C1-C 12 alkynyl; optionally n is 8, R a including C1-C3 alkyl. The battery cell according to claim 7, characterized in that The cross-linked polymer comprises a silicone polymer containing a cage polysilsesquioxane skeleton. The battery cell according to claim 8, characterized in that The cage polysilsesquioxane skeleton-containing organic silicon polymer includes one or more kinds of monomers represented by formula (III) obtained by hydrolysis and polycondensation, wherein R1 and R2 each independently comprise a C1-C4 alkyl group or a C2-C4 alkenyl group, R3 comprises a C1-C4 alkyl group or a C4-C8 (meth)acryloxyalkyl group, and R4 comprises a C2-C8 alkenyl group or a C4-C8 (meth)acryloxyalkyl group; and the cross-linking agent comprises divinylbenzene. The battery cell according to any one of claims 7-9, characterized in that The silicone polymer containing a cage polysilsesquioxane skeleton satisfies at least one of the following conditions: (1) the cross-linking degree of the silicone polymer containing a cage polysilsesquioxane skeleton is 85% to 97%; (2) the silicone polymer containing a cage polysilsesquioxane skeleton comprises a silicon element, and the mass fraction of the silicon element in the silicone polymer containing a cage polysilsesquioxane skeleton is 25% to 45%; (3) in the silicone polymer containing a cage polysilsesquioxane skeleton, the mass fraction of the cage polysilsesquioxane skeleton is 40% to 60%. The battery cell of any one of claims 1-10, wherein The heat-resistant particles satisfy at least one of the following conditions: (1) the volume average particle size Dv50 of the heat-resistant particles is 80 nm to 900 nm; (2) the cyclic voltammogram of the heat-resistant particle after one cycle does not have an oxidation peak in the voltage range of 0 to 4.4V; (3) the glass transition temperature of the heat-resistant particle is greater than or equal to 150℃, or the heat-resistant particle has no glass transition temperature at 300℃; (4) the initial thermal weight loss temperature T of the heat-resistant particles 3d greater than or equal to 250°C; (5) the dissolution rate of the heat-resistant particle is less than or equal to 5% when the heat-resistant particle is soaked in a mixed solvent of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 3:7 at 60℃ for 7 days; (6) the heat resistant particles have a true density of 0.8 g / cm 3 ~ 2.0 g / cm 3 . The battery cell according to any one of claims 1-11, characterized in that The mass fraction of the heat-resistant particle in the coating layer is 50% to 97%. The battery cell of any one of claims 1-12, wherein The coating layer further comprises a first binder, and the first binder satisfies at least one of the following conditions: (1) the first binder comprises at least one of polyimide, polyetherimide, polyacrylic acid, polyacrylate, ethylene-vinyl acetate copolymer, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethylated polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose, acrylonitrile-styrene-butadiene copolymer, ethylene-propylene-diene terpolymer, sulfonated ethylene-propylene-diene terpolymer, styrene-butadiene rubber, and fluorine rubber; (2) the mass fraction of the first binder in the coating layer is 3% to 15%. The battery cell of any one of claims 1-13, wherein The separation film further comprises second binder particles, and the second binder particles are located in the coating layer, or the separation film further comprises a bonding layer, and the bonding layer is arranged on at least one side of the coating layer away from the base film, and the second binder particles are located in the bonding layer; the second binder particles satisfy one or more of the following conditions: (1) the second binder particles comprise at least one of polyvinylidene fluoride, poly(vinylidene fluoride-co-trichloroethylene), poly(vinylidene fluoride-co-trifluorochloroethylene), poly(vinylidene fluoride-co-trifluoroethylene), poly(vinylidene fluoride-co-tetrafluoroethylene), poly(vinylidene fluoride-co-hexafluoropropylene), polyacrylate, polymethyl methacrylate, and polyacrylonitrile; (2) the volume average particle size Dv50 of the second binder particles is 5μm to 20μm. The battery cell of any one of claims 1-14, wherein, The separation film satisfies at least one of the following conditions: (1) the thickness of the coating layer is 0.5μm to 10μm; (2) the coating has an areal density of 1.5 g / m 2 ~ 6 g / m 2 ; (3) the longitudinal heat shrinkage rate of the separation film is less than or equal to 5% when the separation film is heated at 130℃ for 1h; (4) the transverse heat shrinkage rate of the separation film is less than or equal to 5% when the separation film is heated at 130℃ for 1h; (5) the air permeability of the separation film is 150s / 100mL to 500s / 100mL. A battery device characterized by comprising: The battery cell comprises the battery cell as claimed in any one of claims 1 to 15. An electric device characterized by comprising: The battery device comprises the battery cell as claimed in any one of claims 1 to 15, or the battery device as claimed in claim 16. An isolation film characterized by It comprises: a porous base film and a coating layer arranged on at least one side of the porous base film; the heat-resistant particle comprises a cross-linked polymer; the cross-linking degree of the cross-linked polymer is 70% to 98%. The separator film according to claim 18, wherein The cross-linked polymer comprises a planar cyclic conjugated group and / or a covalent polyhedral skeleton. The separator film according to claim 18 or 19, characterized in that, The planar ring-shaped conjugated group includes any one of a substituted or unsubstituted phenyl group, a substituted or unsubstituted heteroatom-containing aromatic group, a substituted or unsubstituted condensed ring aromatic group, and a substituted or unsubstituted triazine ring group; optionally, the planar ring-shaped conjugated group includes any one of a phenyl group and a triazine ring group. The separator film according to claim 20, wherein The cross-linking polymer includes at least one of a phenol-formaldehyde resin polymer, a polymer containing a triazine ring group, a phenyl-containing silicone polymer, and a cross-linked styrene polymer. The separator film according to claim 21, wherein The phenyl-containing organosilicon polymer includes monomers and crosslinking agents represented by formula (I) and polymerized, R1, R2 each independently include a C1-C4 alkyl group or a C2-C4 alkenyl group, R3 includes a C1-C4 alkyl group or a C4-C8 (meth)acryloxyalkyl group, and R4 includes a C2-C8 alkenyl group or a C4-C8 (meth)acryloxyalkyl group; and the cross-linking agent includes divinylbenzene. The separator film according to claim 21 or 22, characterized in that, The phenyl-containing silicone polymer satisfies at least one of the following conditions: (1) the cross-linking degree of the phenyl-containing silicone polymer is 75% to 95%; (2) the phenyl-containing silicone polymer includes a silicon element, and the mass fraction of the silicon element in the phenyl-containing silicone cross-linking resin is 10% to 25%; (3) the mass fraction of the phenyl group in the phenyl-containing silicone polymer is 2% to 12%. The separator film according to claim 18 or 19, characterized in that, The covalent polyhedral skeleton includes a skeleton formed by a compound represented by formula (I), R a [SuO 3 / 2 ] n Formula (II) wherein n is any integer from 4 to 12, R a including cycloalkyl, aryl, C1-C 12 alkyl, C1-C 12 alkenyl, C1-C 12 alkynyl; optionally n is 8, R a including C1-C3 alkyl. The separator film according to claim 24, wherein The cross-linking polymer includes a silicone polymer containing a cage polysilsesquioxane skeleton. The separator film according to claim 25, wherein The phenyl-containing organosilicon polymer includes one or more of monomers represented by Formula (III), which are hydrolyzed and polycondensed to obtain, R1, R2 each independently include a C1-C4 alkyl group or a C2-C4 alkenyl group, R3 includes a C1-C4 alkyl group or a C4-C8 (meth)acryloxyalkyl group, and R4 includes a C2-C8 alkenyl group or a C4-C8 (meth)acryloxyalkyl group; and the cross-linking agent includes divinylbenzene. The separator film according to claim 22 or 23, the silicone polymer containing a cage polysilsesquioxane skeleton satisfies at least one of the following conditions: (1) the cross-linking degree of the silicone polymer containing a cage polysilsesquioxane skeleton is 85% to 97%; (2) the silicone polymer containing a cage polysilsesquioxane skeleton includes a silicon element, and the mass fraction of the silicon element in the silicone polymer containing a cage polysilsesquioxane skeleton is 25% to 45%; (3) in the silicone polymer containing a cage polysilsesquioxane skeleton, the mass fraction of the cage polysilsesquioxane skeleton is 40% to 60%. The isolating film according to any one of claims 18-27, characterized in that The mass fraction of the heat-resistant particles in the coating layer is 50% to 97%.

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