Battery cell, battery apparatus, and electric device

Abstract

The present application provides a battery cell, a battery apparatus, 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 membrane and a coating disposed on at least one side of the porous base membrane, wherein the coating comprises heat-resistant particles and a first binder. The first binder is used for bonding the heat-resistant particles onto the porous base membrane. The heat-resistant particles comprise an organic compound; the main chain or the side chain of the organic compound has a rigid structure; and the rigid structure comprises a planar cyclic conjugated group and / or a covalent polyhedral framework. When the organic compound is a small molecule compound, a condensation polymer or a copolymer, the mass proportion of the rigid structure in the organic compound is 40-99%; and when the organic compound is a polycondensation-type copolymer, the mass proportion of the rigid structure in the organic compound is 2-30%. The technical solution of the present application is beneficial to improving the reliability of a 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 particle, method for producing same, silicon-containing organic resin particle dispersion, separator, secondary battery cell, battery device, and electric device,” the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0002] 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

[0003] In recent years, battery technology has been widely applied in energy storage power systems such as hydroelectric, thermal, wind, and solar power stations, as well as in multiple fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc., thereby achieving great development.

[0004] 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 will affect the reliability of the battery cell. Therefore, how to improve the reliability of the battery cell is a technical problem to be solved. SUMMARY

[0005] The present application is made in view of the above-mentioned 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, 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 and a first binder, the first binder being used to bond the heat-resistant particles to the porous base film; the heat-resistant particles include an organic compound; the main chain or side chain of the organic compound has a rigid structure, the rigid structure including a planar cyclic conjugated group and / or a covalent polyhedral skeleton; when the organic compound is a small molecule compound, a condensation polymer, or a copolymer, the mass fraction of the rigid structure in the organic compound is 40% to 99%; when the organic compound is a condensation type copolymer, the mass fraction of the rigid structure in the organic compound is 2% to 30%.

[0006] In the embodiments of the present application, in the organic compound containing the rigid structure including the planar ring conjugated group and / or the covalent polyhedral skeleton, the molecular chain has low degree of freedom, by controlling the mass ratio of the rigid structure in the small molecule compound, the polycondensate or the copolymer to be 40% to 99%, or the mass ratio of the rigid structure in the polycondensation copolymer to be 2% to 30%, the probability of deformation of the organic compound under high temperature environment is low, the thermal stability is good, the heat resistance of the isolation film can be improved, and the reliability of the battery monomer under high temperature can be improved.

[0007] In a possible implementation, the planar ring conjugated group includes any one of a substituted or unsubstituted phenyl, 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 and a triazine ring group.

[0008] In the embodiments of the present application, by limiting the types of the planar ring conjugated group in the organic compound, the heat resistance and chemical stability of the organic compound can be further enhanced, so as to improve the heat resistance of the isolation film. The phenyl has good structural stability and conjugation effect, which can improve the thermal stability of the organic compound; the heteroatom-containing aromatic group makes the electronic structure of the organic compound more stable and enhances the oxidation resistance of the organic compound due to the participation of the heteroatom in the conjugation, thereby reducing the probability of reaction between the organic compound and the electrolyte; the condensed ring aromatic group has a larger π conjugation 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 temperature. The organic compound includes the above groups, so that the organic compound particles in the coating are more difficult to deform or break at high temperature, so that the isolation film has good heat resistance and improves the reliability of the battery monomer.

[0009] In a possible implementation, the covalent polyhedral skeleton includes a skeleton composed of a compound shown in formula (I), R a [SiO 3 / 2 ] n Formula (I) wherein n is any value in the integer 4 to 12, and Ra includes a cycloalkyl group, an aryl group, a C1-C12 alkyl group, a C1-C12 alkenyl group, and a C1-C12 alkynyl group; optionally, n is 8, and Ra includes a C1-C3 alkyl group.

[0010] In the embodiments of the present application, by introducing the covalent polyhedral skeleton shown in formula (I) into the organic compound, a stable three-dimensional structure can be formed inside the molecule of the organic compound. The polyhedral skeleton has high symmetry and regularity, the internal atoms are connected by strong covalent bonds, and the molecular structure is not easy to break or collapse under high temperature environment, which is conducive to improving the heat resistance of the isolation film. The covalent polyhedral skeleton shown in formula (I) contains Si-O bonds, which have high bond energy and are not easy to decompose under high temperature, which can further improve the thermal stability of the material. By selecting n as 8 and R1 as C1-C3 alkyl, the rigidity and thermal stability of the organic compound can be further improved. The organic compound 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.

[0011] In a possible implementation, the organic compound is the cross-linked polymer, and the cross-linking degree of the cross-linked polymer is 70% to 98%.

[0012] In the embodiments of the present application, on the one hand, the cross-linked polymer has a three-dimensional network structure and 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 under high temperature, the heat resistance of the isolation film is improved, the overall structural integrity of the isolation film under high temperature is ensured, and the reliability of the battery cell under high temperature conditions is improved.

[0013] 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 silicone polymer, a cage-like polysilsesquioxane skeleton-containing silicone polymer, and a cross-linked styrene polymer.

[0014] In the embodiments of the present application, the cross-linking structure formed between the aromatic ring skeleton and the molecular chain 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-linking network formed by the mutual cross-linking between the polymer molecular chains of the triazine ring; the organic silicon polymer containing a phenyl group can jointly improve the heat resistance of the isolation film due to the rigidity of the aromatic ring and the high bond energy of the silicon-oxygen bond, and the three-dimensional cross-linking network formed by the mutual cross-linking between the organic silicon polymer molecular chains; in the organic silicon 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 and is 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 a cage-shaped polysilsesquioxane skeleton has a three-dimensional network structure formed by random cross-linking 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 deformation due to high-temperature softening; 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 resist high-temperature decomposition and high-temperature deformation, and the two can further increase the heat resistance of the material. 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-linking network formed by the mutual 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.

[0015] In a possible implementation manner, the organic silicon polymer containing a phenyl group is obtained by polymerization of a monomer represented by formula (II) and a cross-linking agent, In formula (II), R1 and R2 each independently include C1-C4 alkyl or C2-C4 alkenyl, R3 includes C1-C4 alkyl or C4-C8 (methyl) acryloyloxyalkyl, and R4 includes C2-C8 alkenyl or C4-C8 (methyl) acryloyloxyalkyl; and the cross-linking agent includes divinylbenzene.

[0016] In the embodiments of the present application, the organic silicon polymer containing a phenyl group can be obtained by polymerization of the monomer represented by formula (II) and the cross-linking agent divinylbenzene. The particle has a three-dimensional network skeleton formed by the phenyl structure and the monomer and the cross-linking agent, so that the material exhibits a higher glass transition temperature and a higher thermal decomposition temperature, thereby improving the heat resistance of the isolation film and improving the reliability of the battery cell.

[0017] 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%.

[0018] In the embodiment, the cross-linking degree of the phenyl-containing organic silicon polymer is 75% to 95%, and the phenyl-containing organic silicon polymer 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, and further helps to improve the heat resistance of the isolation film.

[0019] In a possible implementation, the organic silicon 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 includes C1 to C3 alkyl.

[0020] In the embodiment, 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 in the condensation process, the local accumulation and entanglement of the molecular chain are reduced, and the organic silicon polymer exhibits a relatively high uniform dispersion state. The uniform dispersion of the molecular chain not only helps to uniformly distribute the cross-linking points and reduce the stress concentration phenomenon, but also improves the dispersity and binding stability of the cross-linked polymer particles in the coating of the isolation film, so that the organic silicon polymer particles in the coating are not prone to structural rupture or collapse at high temperatures, the overall heat resistance of the isolation film is improved, and the reliability of the battery cell is enhanced.

[0021] In a possible implementation, the organic silicon polymer containing a cage-like polyhedral oligomeric silsesquioxane skeleton satisfies at least one of the following conditions: (1) the cross-linking degree of the organic silicon polymer containing a cage-like polyhedral oligomeric silsesquioxane skeleton is 85% to 97%; (2) the organic silicon polymer containing a cage-like polyhedral oligomeric silsesquioxane skeleton includes silicon elements, and the mass fraction of the silicon elements in the organic silicon polymer containing a cage-like polyhedral oligomeric silsesquioxane skeleton is 25% to 45%; and (3) in the organic silicon polymer containing a cage-like polyhedral oligomeric silsesquioxane skeleton, the mass fraction of the cage-like polyhedral oligomeric silsesquioxane skeleton is 40% to 60%.

[0022] In the embodiments of the present application, the cross-linking degree of 85% to 97% can ensure that the organic silicone 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 siloxane skeleton in the cross-linked 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 separation film at high temperatures. The mass fraction of the cage containing the cage-shaped polysilsesquioxane skeleton is 40% to 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 separation film under heat abuse, and is beneficial to improve the heat resistance of the separation film, thereby improving the reliability of the battery monomer at high temperatures.

[0023] In a possible implementation, the organic compound is a small molecule compound, and the small molecule compound includes one or more of melamine cyanurate, melamine polyphosphate, and melamine pyrophosphate.

[0024] In the embodiments of the present application, the small molecule compounds such as melamine cyanurate, melamine polyphosphate, and melamine pyrophosphate have excellent thermal stability and flame retardant performance, can maintain good thermal stability in a high-temperature environment, and improve the heat resistance of the separation film.

[0025] 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 T3d of the heat-resistant particles is greater than or equal to 250°C; (5) the dissolution rate of the heat-resistant particles is less than or equal to 5% when the heat-resistant particles are 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; and (6) the true density of the heat-resistant particles is 0.8 g / cm 3 to 2.0 g / cm 3 .

[0026] In the embodiments of the present application, the volume distribution particle size Dv50 of the heat-resistant particles is in the above range, the heat-resistant particles can be uniformly distributed in the coating, and filled on the pore surface of the porous base film, which is further beneficial to improve the heat resistance and air permeability of the separation film. Compared with inorganic particles with relatively large density, such as boehmite and alumina, the true density of the heat-resistant particles is smaller, which can improve the energy density of the battery monomer without increasing the thickness of the coating, and improve the energy density and high-temperature reliability of the battery monomer.

[0027] The cyclic voltammogram of the heat-resistant particles circulating for the first time has no 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, 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.

[0028] The glass transition temperature of the heat-resistant particles is greater than or equal to 150℃, or 300℃ or less, such as the glass transition temperature, which means that the DSC curve of the heat-resistant particles remains rigid in the solid state below 200℃, and does not undergo molecular chain segment movement or softening, thereby improving the heat resistance of the isolation film.

[0029] 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, thereby having high thermal stability in the use process of the battery cell and in a high-temperature environment, and being less likely to undergo 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 less likely to precipitate or dissolve 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.

[0030] 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.

[0031] In one possible implementation, the mass fraction of the heat-resistant particles in the coating is 50% to 97%.

[0032] In the embodiments of the present application, 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, and the heat resistance of the isolation film is improved, thereby improving the reliability of the battery cell.

[0033] In a possible implementation, the coating 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 fluororubber; and (2) the mass fraction of the first binder in the coating is 3% to 15%.

[0034] 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 that the heat-resistant particles fall off 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 the adhesion, so as to balance the stability and heat resistance of the coating and improve the heat resistance of the isolation film.

[0035] 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 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; and (2) the number average particle size of the second binder particles is 5 μm to 20 μm.

[0036] 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, 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.

[0037] In a possible implementation, the isolation film satisfies at least one of the following conditions: (1) the thickness of the coating layer is 0.5 μm to 10 μm; (2) the area density of the coating layer is 1.5 g / m 2 ~ 6 g / m 2 ; (3) the longitudinal thermal shrinkage of the isolation film is less than or equal to 5% when the isolation film is heated at 130 ℃ for 1 h; (4) the transverse thermal shrinkage of the isolation film is less than or equal to 5% when the isolation film is heated at 130 ℃ for 1 h; and (5) the air permeability of the isolation film is 150 s / 100 mL to 500 s / 100 mL.

[0038] In the embodiments of the present application, the thickness of the coating layer is 0.5 μm to 10 μm, which can provide a uniform and dense heat-resistant coating layer, improve the heat resistance of the isolation film, and thus improve the reliability of the battery cell. The area density of the coating layer is 1.5 g / m 2 ~ 6 g / m 2 , which can ensure that the coating layer has moderate quality, can improve the stability and heat resistance of the isolation film, and will not significantly increase the weight of the isolation film, thereby being conducive to the energy density and reliability of the battery cell. The isolation film still has very low longitudinal thermal shrinkage and transverse thermal shrinkage at 130 ℃, and the isolation film has good heat resistance at high temperatures. The air permeability of the isolation film is 150 s / 100 mL to 500 s / 100 mL, which ensures that the electrolyte can be uniformly infiltrated and maintain fast ion transmission, ensures the ion transmission efficiency in the isolation film, reduces the case that the air permeability of the isolation film is too low to cause electrochemical polarization, and reduces the reliability of the battery cell.

[0039] In a second aspect, a battery device is provided, which includes the battery cell in any of the possible implementations.

[0040] In a third aspect, a use-electricity device is provided, which includes the battery cell in any of the possible implementations or the battery device of the second aspect.

[0041] In a fourth aspect, an isolation film is provided, which includes 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 a first binder for bonding the heat-resistant particles to the porous base film. The heat-resistant particles include an organic compound. The main chain or side chain of the organic compound has a rigid structure, and the rigid structure includes a planar ring conjugated group and / or a covalent polyhedral skeleton. When the organic compound is a small molecule compound, a condensate, or a copolymer, the mass fraction of the rigid structure in the organic compound is 40% to 99%. When the organic compound is a condensate copolymer, the mass fraction of the rigid structure in the organic compound is 2% to 30%.

[0042] In the embodiments of the present application, in the organic compound containing the rigid structure including the planar ring conjugated group and / or the covalent polyhedral skeleton, the molecular chain has low degree of freedom, by controlling the mass ratio of the rigid structure in the small molecule compound, the polycondensate or the copolymer to be 40% to 99%, or the mass ratio of the rigid structure in the polycondensation copolymer to be 2% to 30%, the probability of deformation of the organic compound under high temperature environment is low, the thermal stability is good, the heat resistance of the isolation film can be improved, and the reliability of the battery monomer under high temperature can be improved.

[0043] In a possible implementation, the planar ring conjugated group includes any one of a substituted or unsubstituted phenyl, 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 and a triazine ring group.

[0044] In the embodiments of the present application, by limiting the types of the planar ring conjugated group in the organic compound, the heat resistance and the chemical stability of the organic compound can be further enhanced, so that the heat resistance of the isolation film is improved. The phenyl has good structural stability and conjugation effect, which can improve the thermal stability of the organic compound; the heteroatom-containing aromatic group has stable electronic structure and enhanced oxidation resistance due to the participation of the heteroatom in conjugation, which reduces the probability of reaction between the organic compound and the electrolyte; the condensed ring aromatic group has a larger π conjugation 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 temperature. The organic compound includes the above-mentioned groups, so that the organic compound particles in the coating are more difficult to deform or break at high temperature, so that the isolation film has good heat resistance, and the reliability of the battery monomer is improved.

[0045] In a possible implementation, the covalent polyhedral skeleton includes a skeleton composed of a compound shown in formula (I), R a [SiO 3 / 2 ] n Formula (I) wherein n is any value in the integer 4 to 12, and Ra includes a cycloalkyl group, an aryl group, a C1-C12 alkyl group, a C1-C12 alkenyl group, and a C1-C12 alkynyl group; optionally, n is 8, and Ra includes a C1-C3 alkyl group.

[0046] In the embodiments of the present application, by introducing the covalent polyhedral skeleton shown in formula (I) into the organic compound, a stable three-dimensional structure can be formed inside the molecule of the organic compound. The polyhedral skeleton has high symmetry and regularity, the internal atoms are connected by strong covalent bonds, and the molecular structure is not easy to break or collapse under high temperature environment, which is conducive to improving the heat resistance of the isolation film. The covalent polyhedral skeleton shown in formula (I) contains Si-O bonds, which have high bond energy and are not easy to decompose under high temperature, which can further improve the thermal stability of the material. By selecting n as 8 and R1 as C1-C3 alkyl, the rigidity and thermal stability of the organic compound can be further improved. The organic compound 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.

[0047] In a possible implementation, the organic compound is the cross-linked polymer, and the cross-linking degree of the cross-linked polymer is 70% to 98%.

[0048] In the embodiments of the present application, on the one hand, the cross-linked polymer has a three-dimensional network structure and 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 under high temperature, improving the heat resistance of the isolation film and ensuring the overall structural integrity of the isolation film under high temperature, thereby improving the reliability of the battery cell under high temperature conditions.

[0049] 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 silicone polymer, a cage-like polysilsesquioxane skeleton-containing silicone polymer, and a cross-linked styrene polymer.

[0050] In the embodiments of the present application, the cross-linking structure formed between the aromatic ring skeleton and the molecular chain 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-linking network formed by the mutual cross-linking between the polymer molecular chains of the triazine ring; the organic silicon polymer containing a phenyl group can jointly improve the heat resistance of the isolation film due to the rigidity of the aromatic ring and the high bond energy of the silicon-oxygen bond, and the three-dimensional cross-linking network formed by the mutual cross-linking between the organic silicon polymer molecular chains; in the organic silicon 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 and is 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 a cage-shaped polysilsesquioxane skeleton has a three-dimensional network structure formed by random cross-linking 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 deformation due to high-temperature softening; 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 resist high-temperature decomposition and high-temperature deformation, and the two can further increase the heat resistance of the material. 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-linking network formed by the mutual 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.

[0051] In a possible implementation, the organic silicon polymer containing a phenyl group includes a monomer and a cross-linking agent represented by formula (II) and is polymerized to obtain, In formula (II), 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 (methyl) acryloyloxy alkyl group, and R4 includes a C2-C8 alkenyl group or a C4-C8 (methyl) acryloyloxy alkyl group; and the cross-linking agent includes divinylbenzene.

[0052] In the embodiments of the present application, the polymerization of the monomer represented by formula (II) and the cross-linking agent divinylbenzene can obtain the organic silicon polymer containing a phenyl group, 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 a higher glass transition temperature and a higher thermal decomposition temperature, thereby improving the heat resistance of the isolation film and improving the reliability of the battery cell.

[0053] 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%.

[0054] In the embodiments of the present application, the cross-linking degree of the phenyl-containing organic silicon polymer is 75% to 95%, and the phenyl-containing organic silicon polymer 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, and further helps to improve the heat resistance of the isolation film.

[0055] In a possible implementation, the organic silicon polymer containing a cage-like poly-silsesquioxane skeleton is obtained by hydrolysis and condensation of one or more monomers shown in formula (III), wherein R'1 includes C1 to C3 alkyl.

[0056] In the embodiments of the present application, 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 in the condensation process, the local accumulation and entanglement of the molecular chain are reduced, and the organic silicon polymer exhibits a relatively high uniform dispersion state. The uniform dispersion of the molecular chain not only helps to uniformly distribute the cross-linking points and reduce the stress concentration phenomenon, but also improves the dispersity and binding stability of the cross-linked polymer particles in the separator coating, so that the organic silicon polymer particles in the coating are not prone to structural rupture or collapse at high temperatures, the overall heat resistance of the isolation film is improved, and the reliability of the battery cell is enhanced.

[0057] In a possible implementation, the organic silicon polymer containing a cage-like poly-silsesquioxane skeleton satisfies at least one of the following conditions: (1) the cross-linking degree of the organic silicon polymer containing a cage-like poly-silsesquioxane skeleton is 85% to 97%; (2) the organic silicon polymer containing a cage-like poly-silsesquioxane skeleton includes silicon elements, and the mass fraction of the silicon elements in the organic silicon polymer containing a cage-like poly-silsesquioxane skeleton is 25% to 45%; and (3) in the organic silicon polymer containing a cage-like poly-silsesquioxane skeleton, the mass fraction of the cage-like poly-silsesquioxane skeleton is 40% to 60%.

[0058] 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 temperature, and improve 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 temperature. 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 temperature.

[0059] In a possible implementation, the mass fraction of the heat-resistant particles in the coating is 50% to 97%.

[0060] In the embodiments of the present application, 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

[0061] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the drawings.

[0062] FIG. 1 is a schematic diagram of a battery monomer according to an embodiment of the present application.

[0063] FIG. 2 is a structural schematic diagram of a battery monomer according to another embodiment of the present application.

[0064] FIG. 3 is a schematic diagram of a battery device according to an embodiment of the present application.

[0065] FIG. 4 is a schematic diagram of an electric device according to an embodiment of the present application.

[0066] FIG. 5 is a schematic diagram of an electric device according to another embodiment of the present application.

[0067] FIG. 6 is a cross-linking degree test result diagram of the heat-resistant particle powder according to an embodiment of the present application.

[0068] FIG. 7 is a thermal cracking spectrum diagram of the heat-resistant particle powder according to an embodiment of the present application.

[0069] Reference signs:

[0070] 3: battery cell; 30: case; 31: housing; 313: pressure relief mechanism; 32: end cap; 322: electrode terminal; 33: electrode assembly; 331: tab; 34: connecting member; 10: battery device; 11: case; 111: first case portion; 112: second case portion; 1: vehicle; 4: controller; 5: motor; 2: energy storage device. DETAILED DESCRIPTION

[0071] Hereinafter, embodiments of the battery cell, the battery device, and the electric device of the present application are explained in detail with appropriate reference to the accompanying drawings, but there are cases where unnecessary detailed explanations are omitted. For example, there are cases where detailed explanations of matters well-known, repeated explanations of actually identical structures are omitted. This is to avoid the following explanation from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the drawings and the following explanations are provided so that those skilled in the art can fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0072] The "ranges" disclosed in the present application are defined in the form of lower and upper limits, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The ranges defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. Furthermore, if a minimum range value of 1 and 2 is listed, and if a maximum range value of 3, 4, and 5 is listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In the present application, unless otherwise stated, a numerical range "a-b" represents a shorthand manner of describing each and every number that is contained in the range, wherein "a" and "b" are both real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0" and "5" have been listed herein, and "0-5" is merely a shorthand manner of describing each and every number that is contained in the range. In addition, when it is stated that a parameter is an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0073] 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 specification herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application; the use of the terms "including," "comprising," or "having" in the specification herein (including the claims) and the accompanying drawings are used in the sense of "including at least" for any term found in the specification and claims (including the drawings) are intended to be open-ended. Use of terms such as "first", "second", and the like do not imply a limitation on the number of such objects, but rather the order in which they are described.

[0074] All embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions, if not specifically stated.

[0075] 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.

[0076] If not specifically stated, the following terms have the following meanings. Any undefined terms have their art-recognized meanings.

[0077] The "alkyl" in the embodiments of the present application refers to cover straight chain and branched chain alkyl. For example, the alkyl can be C1-C 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, etc. In addition, the alkyl group can be optionally substituted, for example, the alkyl group is substituted by halogen as halogenated alkyl. The term "halogenated alkyl" refers to the alkyl group, in which part or all of the hydrogen atoms are replaced by halogen atoms, and the term "halogen atom" refers to fluorine atom, chlorine atom, bromine atom, iodine atom, etc.

[0078] In embodiments of the present application, substituents of compounds are disclosed in combination ranges. For example, "Ci-Ci2alkyl" can mean Ci, C2, C3, C4, C5, C6, C7, C8, C9, C10, C11, C12, Ci-Ci2, Ci-Cn, Ci-C10, Ci-C9, Ci-C8, Ci-C7, Ci-C6, Ci-C5, Ci-C4, Ci-C3, Ci-C2, C2-Ci2, C2-Cn, C2-C10, C2-C9, C2-C8, C2-C7, C2-C6, C2-C5, C2-C4, C2-C3, C3-Ci2, C3-Cn, C3-C10, C3-C9, C3-C8, C3-C7, C3-C6, C3-C5, C3-C4, C4-Ci2, C4-Cn, C4-C10, C4-C9, C4-C8, C4-C7, C4-C6, C4-C5, C5-Ci2, C5-Cn, C5-C10, C5-C9, C5-C8, C5-C7, C5-C6, C6-Ci2, C6-Cn, C6-C10, C6-C9, C6-C8, C6-C7, C7-Ci2, C7-Cn, C7-C10, C7-C9, C7-C8, C8-Ci2, C8-Cn, C8-C10, C8-C9, C9-Ci2, C9-Cn, C9-C10, C10-Ci2, C10-Cn, and Cn-Ci2alkyl.

[0079] In embodiments of the present application, "alkenyl" refers to a non-aromatic unsaturated hydrocarbon group having one or more carbon-carbon double bonds (C=C). For example, alkenyl can be C2-C20alkenyl, C2-Ci2alkenyl, C2-C10alkenyl, C2-C6alkenyl, C2-C4alkenyl. 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.

[0080] In embodiments of the present application, "cycloalkyl" refers to saturated cyclic alkyl groups having single, double, and multiple rings. Specifically, cycloalkyl groups are hydrocarbon groups consisting of one or more saturated carbon rings, which can be a single ring structure or a fused ring structure formed by multiple rings connected through sharing one or more atoms. For example, cycloalkyl groups having a single ring structure can be cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclodecyl, and the like; cycloalkyl groups having a fused ring structure can be cyclopentenyl, cyclohexenyl, tricycloalkyl, and the like.

[0081] In embodiments of the present application, "alkynyl" refers to a hydrocarbon group having a carbon-carbon triple bond (C≡C).

[0082] In the present application, the terms "a plurality of" and "a plurality" refer to two or more than two.

[0083] Generally, the battery cell includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator. In the charging and discharging process of the battery cell, 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 cell can proceed normally.

[0084] 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 film is an important component to support the battery cell to complete the charging and discharging electrochemical process. The commonly used separator film is mostly polyolefin material, but the heat resistance of polyolefin material is poor, which is easy to soften or melt at high temperature, which can easily lead to short circuit of the battery cell. In order to improve the heat resistance of the separator film, a coating layer is usually coated on the separator film to improve the heat resistance of the separator film. 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 can affect the energy density of the battery cell. In order to further improve the energy density of the battery cell, the inorganic particles such as boehmite and alumina are replaced by organic heat-resistant particles in the prior art, but the existing organic heat-resistant particles are often prone to chain scission and decomposition at high temperature, which can lead to poor heat resistance of the separator film. How to make the separator film of the high-energy-density battery cell have better heat resistance is a technical problem to be solved at present.

[0085] Therefore, the embodiments of the present application provide a battery cell, which comprises a positive electrode sheet, a negative electrode sheet and a separator film, the separator film being located between the positive electrode sheet and the negative electrode sheet; the separator 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 a first binder, the first binder being used to bond the heat-resistant particles to the porous base film; the heat-resistant particles comprise an organic compound; the main chain or side chain of the organic compound has a rigid structure, the rigid structure comprising a planar cyclic conjugated group and / or a covalent polyhedral skeleton; when the organic compound is a small molecule compound, a condensation polymer or a copolymer, the mass proportion of the rigid structure in the organic compound is 40% to 99%; when the organic compound is a condensation type copolymer, the mass proportion of the rigid structure in the organic compound is 2% to 30%.

[0086] In the technical solution, the organic compound containing the rigid structure including the planar ring conjugated group and / or the covalent polyhedral skeleton has a low molecular chain freedom degree, and by controlling the mass ratio of the rigid structure in the small molecule compound, the polycondensate or the copolymer to be 40% to 99% or the mass ratio of the rigid structure in the polycondensation type copolymer to be 2% to 30%, the probability of deformation of the organic compound in a high temperature environment is low, the thermal stability is good, the heat resistance of the isolation film can be improved, and the reliability of the battery cell in a high temperature environment can be improved.

[0087] Next, the battery cell provided by the embodiments of the present application is introduced.

[0088] [Battery cell]

[0089] 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 a first binder, the first binder being used to bond the heat-resistant particles to the porous base film; the heat-resistant particles comprise an organic compound; the main chain or side chain of the organic compound has a rigid structure, the rigid structure comprising a planar ring conjugated group and / or a covalent polyhedral skeleton; when the organic compound is a small molecule compound, a polycondensate or a copolymer, the mass ratio of the rigid structure in the organic compound is 40% to 99%; when the organic compound is a polycondensation type copolymer, the mass ratio of the rigid structure in the organic compound is 2% to 30%.

[0090] 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.

[0091] In some embodiments, the porous base film can comprise a film or nonwoven 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.

[0092] In some embodiments, the thickness of the porous base film can be 4 μm to 15 μm, and optionally 4 μm to 9 μm.

[0093] In some embodiments, the porosity of the porous base film can be 25% to 60%, and optionally 28% to 50%.

[0094] In some embodiments, the average pore size of the porous base film can be 25 nm to 82 nm.

[0095] The average pore size of the porous base film can be tested using a capillary porosimeter (bubble point method). An exemplary test method is as follows: a circular sample with a diameter of 25 mm is taken and 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 press the wetting liquid in the pores of the sample to be tested, and the pressure and flow of the press are inversely proportional to the pore size. The average pore size of the sample to be tested is obtained by software sampling and pressure and pore size conversion analysis. The test instrument can be a CFP 1500 pore size analyzer from PMI, and the test pressure can be 100 psi to 350 psi.

[0096] In the embodiments of the present application, the heat-resistant particles refer to particles that have certain thermal stability, can maintain their physical properties and chemical properties in a high-temperature environment, and are not prone to cracking, melting or softening.

[0097] In the embodiments of the present application, the "organic compound" refers to a carbon-containing compound, which generally includes hydrogen, oxygen, nitrogen, sulfur and other elements in addition to simple compounds such as carbon oxides, carbonic acid, carbonates, etc.

[0098] In the embodiments of the present application, the main chain or side chain of the organic compound having a rigid structure refers to the main chain or side chain of the organic compound having a functional group with low degree of freedom, and the atoms inside the molecule are not prone to free rotation or twisting.

[0099] In the embodiments of the present application, the "planar cyclic conjugated group" refers to a closed ring structure formed by connecting multiple atoms through 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, its structure is difficult to deform and twist at high temperature, showing strong rigidity, so that the organic compound containing the planar cyclic conjugated group has high thermal stability.

[0100] In the embodiments of the present application, the "covalent polyhedral skeleton" refers to a skeleton structure formed by connecting multiple atoms through covalent bonds, having polyhedral geometric characteristics, such as tetrahedron, octahedron, 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 prone to bond rupture or structural collapse at high temperature. Therefore, the organic compound containing the covalent polyhedral skeleton has high thermal stability.

[0101] In the embodiments of the present application, the small molecule compound refers to a compound with small molecular weight.

[0102] In the embodiments of the present application, the small molecule compound refers to an organic compound with a weight average molecular weight of less than 1000 g / mol.

[0103] In the embodiments of the present application, the polycondensate refers to a high molecular compound formed by monomers (which can be single or multiple) connected to each other through condensation reaction. The copolymer refers to a high molecular compound formed by two or more monomers with different structures connected to each other through polymerization reaction. The polycondensation type copolymer refers to a high molecular compound formed by two or more monomers with different structures through condensation reaction and polymerization reaction (both condensation reaction and polymerization reaction occur).

[0104] Specifically, when the organic compound is a small molecule compound, a polycondensate or a copolymer, the mass fraction of the rigid structure in the organic compound is 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60%, 62%, 64%, 66%, 68%, 70%, 72%, 74%, 76%, 78%, 80%, 82%, 84%, 86%, 88%, 90%, 92%, 94%, 96%, 98%, 99%, or a value within the range obtained by any two of the above value combinations. When the organic compound is a polycondensation type copolymer, the mass fraction of the rigid structure in the organic compound is 2%, 3%, 5%, 7%, 9%, 11%, 13%, 15%, 17%, 19%, 21%, 23%, 25%, 27%, 29%, 30%, or a value within the range obtained by any two of the above value combinations.

[0105] In the above embodiments, in the organic compound containing the rigid structure including the planar ring-shaped conjugated group and / or the covalent polyhedral skeleton, the molecular chain has low degree of freedom. By controlling the mass fraction of the rigid structure in the small molecule compound, the polycondensate or the copolymer to be 40% to 99%, or the mass fraction of the rigid structure in the polycondensation type copolymer to be 2% to 30%, the probability of deformation of the organic compound under high temperature environment is low, the thermal stability is good, the heat resistance of the isolation film can be improved, and the reliability of the battery cell under high temperature can be improved.

[0106] Specifically, the rigid structure includes a planar ring conjugated group and / or a covalent polyhedral skeleton. The planar ring conjugated group is not prone to distortion at high temperatures due to the conjugation effect and planar structure, and exhibits high rigidity, so that the polymer molecules are difficult to pyrolyze or soften, thereby making the organic compound containing the planar ring conjugated group have high thermal stability. The covalent polyhedral skeleton is not prone to structure rupture or collapse at high temperatures due to its highly symmetrical three-dimensional geometry and strong covalent bond connection higher than ionic bond or intermolecular force, thereby making the organic compound containing the covalent polyhedral skeleton have high thermal stability. Therefore, the organic compound containing the rigid structure including 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 at high temperature is improved. In the present application, the mass fraction of the rigid structure in the small molecule compound, the polycondensate or the copolymer is limited to 40% to 99%, and the mass fraction of the rigid structure in the polycondensation copolymer is limited to 2% to 30%. The high proportion of the rigid structure limits the flexible movement of the molecular chain, avoids the structure collapse caused by the chain segment creep and winding of the organic compound at high temperature, and further improves the thermal stability, the heat resistance of the separator film, and the reliability of the battery cell at high temperature.

[0107] In some embodiments, 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.

[0108] 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 independently include one or more of halogen atoms, alkyl groups, alkenyl groups, cycloalkyl groups, and alkoxy groups.

[0109] In some embodiments, "halogen atom" includes fluorine atom, chlorine atom, bromine atom, iodine atom, and the like. "Alkyl" includes methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, cyclobutyl, pentyl, isopentyl, neopentyl, tert-pentyl, cyclopentyl, hexyl, cyclohexyl, heptyl, cycloheptyl, octyl, cyclooctyl, nonyl, and decyl, and the like. "Alkenyl" includes ethenyl, allyl, n-butenyl, and the like. "Cycloalkyl" includes cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and the like. "Alkoxy" (alkyl connected through an oxygen atom) includes methoxy, ethoxy, propoxy, and the like. In the embodiments of the present application, "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 with one or more heteroatoms, or an aromatic group in which the hydrogen atoms in the aromatic ring structure are not substituted with other substituents. The "heteroatom" refers to an atom other than carbon atom and hydrogen atom, such as nitrogen atom, oxygen atom, sulfur atom, phosphorus atom, and the like. For example, the heteroatom-containing aromatic group can include, but is not limited to, nitrogen-containing pyrrole group, pyridine group, imidazole group, thiophene group, thiazole group, and the like.

[0110] "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 with one or more substituents, or the hydrogen atoms in the aromatic ring structure are not substituted with other substituents. For example, the fused ring aromatic group can include, but is not limited to, naphthyl, phenanthryl, anthryl, acenaphthyl, fluorenyl, fluoranthene, dinaphthyl, and the like.

[0111] "Triazine ring group" refers to a six-membered ring structure containing three nitrogen atoms. "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 the hydrogen atoms in the nitrogen atom structure are not substituted with other substituents. The substituents include one or more combinations of alkyl, alkenyl, phenyl, cycloalkyl, amine group, hydroxyl group, halogen, and the like. For example, the triazine ring group can include, but is not limited to, triazene group, triazine group, chlorotriazine group, aminotriazine group, methyltriazine group, and the like.

[0112] In the above embodiments, by limiting the types of planar cyclic conjugated groups in the organic compound, the heat resistance and chemical stability of the organic compound can be further enhanced, thereby improving the heat resistance of the separation film. The phenyl group has good structural stability and conjugation effect, which can improve the thermal stability of the organic compound; the aromatic group containing a heteroatom can make the electronic structure of the organic compound more stable and enhance the oxidation resistance, thereby reducing the probability of reaction between the organic compound and the electrolyte; the fused ring aromatic group has a larger π conjugation 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 organic compound makes the organic compound particles in the coating more difficult to deform or break at high temperatures, thereby making the separation film have good heat resistance and improving the reliability of the battery cell.

[0113] In some embodiments, the covalent polyhedral framework comprises a framework of a compound represented by formula (I), R a [SiO 3 / 2 ] n Formula (I), wherein n is any value in the integer range of 4 to 12, R a includes at least one of a cycloalkyl group, an aryl group, a C1-C3 alkyl group, a C1-C3 alkenyl group, a C1-C3 alkynyl group, and a C1-C3 heteroalkyl group; and optionally, n is 8 and Ra includes a C1-C3 alkyl group. 12 12 12

[0114] In the embodiments of the present application, n can be 4, 5, 6, 7, 8, 9, 10, 11, 12, or any value within the range obtained by combining the two values of 4 to 12.

[0115] R a may include one or more of a cyclopropyl group, a cyclobutyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a cyclononyl group, a phenyl group, a naphthyl group, an anthryl group, a phenanthryl group, a methyl group, an ethyl group, a n-propyl group, an i-propyl group, a n-butyl group, a sec-butyl group, an i-butyl group, a t-butyl group, a n-pentyl group, an i-pentyl group, a neopentyl group, a t-pentyl group, a n-hexyl group, a n-heptyl group, a n-octyl group, a n-nonyl group, a n-decyl group, a n-undecyl group, a n-dodecyl group, an ethenyl group, a 1-propenyl group, a 2-propenyl (allyl) group, a 1-butenyl group, a 2-butenyl group, a 3-butenyl group, a 1,3-butanedienyl group, and a pentenyl group, a hexenyl group, a heptenyl group, an octenyl group, a nonenyl group, a decenyl group, an undecenyl group, a dodecenyl group, an ethynyl group, a 1-propynyl group, a 2-propynyl (propargyl) group, a 1-butynyl group, a 3-butynyl group, a 1-pentynyl group, a 3-pentynyl group, and a hexynyl group, a heptynyl group, an octynyl group, a nonynyl group, a decynyl group, an undecynyl group, and a dodecynyl group.

[0116] ​​​Optionally, n is 8, and Ra includes at least one of methyl, ethyl, n-propyl, and isopropyl.

[0117] In the above embodiments, by introducing the covalent polyhedral skeleton shown in formula (I) into the organic compound, a stable three-dimensional structure can be formed inside the molecule of the organic compound. The polyhedral skeleton has high symmetry and regularity, the internal atoms are connected by strong covalent bonds, and 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. The covalent polyhedral skeleton shown in formula (I) contains Si-O bonds, which have high bond energy and are not easy to decompose at high temperatures, which can further improve the thermal stability of the material. By selecting n as 8 and R1 as C1-C3 alkyl, the rigidity and thermal stability of the organic compound can be further improved. The organic compound particles can act as rigid support points at high temperatures, improving the heat resistance of the isolation film, thereby improving the reliability of the battery cell.

[0118] In some embodiments, the organic compound is a cross-linked polymer, and the cross-linking degree of the cross-linked polymer is 70% to 98%.

[0119] The "cross-linked polymer" in the embodiments of the present application refers to a polymer material whose molecular chains are cross-linked to form a three-dimensional network structure through chemical bonds. 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. Cross-linking degree refers to the degree of cross-linking between the molecular chains of the cross-linked polymer through chemical bonds. 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. The cross-linking degree in the embodiments of the present application refers to the proportion of the molecular chain segments bound by the cross-linked network in the total chain segments obtained by software fitting through nuclear magnetic resonance (NMR) testing at a specific temperature and specific test frequency. 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. The cross-linked segment is highly constrained and has small molecular motion characteristics, and decays 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.

[0120] 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.

[0121] 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 heat-resistant particles described above) 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 polymer signal, calculating the proportion of the cross-linking signal by fitting software, and selecting the "cross-linking degree" or "T2 relaxation" test mode 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 results according to the degree of restriction of molecular chain movement.

[0122] 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, improve the heat resistance of the isolation film, ensure the overall structural integrity of the isolation film at high temperatures, and thus improve the reliability of the battery cell under high temperature conditions.

[0123] 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, a cage-like polysilsesquioxane skeleton-containing silicone polymer, and a cross-linked styrene-based polymer.

[0124] In some embodiments, the phenolic resin-based polymer is a thermosetting resin.

[0125] In some embodiments, the phenolic resin-based polymer is a thermosetting resol resin.

[0126] 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, propyl aldehyde, n-butyl aldehyde, glyoxal, and furfural.

[0127] In some embodiments, the phenolic resin-based polymer has no glass transition temperature below 300°C.

[0128] The phenolic resin-based polymer has no glass transition temperature below 300°C, which indicates that the heat resistance and thermal stability of the organic particles are good, thereby the porous base film can be better resisted from thermal shrinkage, the heat resistance of the isolation film is improved, and the reliability of the secondary battery cell is improved.

[0129] In some embodiments, the phenolic resin-based polymer has a volume distribution particle size Dv50 of 200 nm-840 nm.

[0130] The volume distribution particle size Dv50 of the phenolic resin-based polymer within the above range is conducive to the coating of the separator film having good heat resistance and air permeability.

[0131] In some embodiments, the phenolic resin-based polymer has no oxidation peak in the cyclic voltammetry curve of the first cycle in the voltage range of 0 V to 4.40 V.

[0132] In some embodiments, the method for preparing the phenolic resin-based polymer comprises the following steps: providing a resol resin-based material; curing the resol resin-based material at a first temperature in an oxygen-containing atmosphere for a first time, and then curing the resol resin-based material at a second temperature in an oxygen-containing atmosphere for a second time, and then crushing to obtain the phenolic resin-based polymer. The first temperature is 100°C-170°C, and the second temperature is 220°C-290°C.

[0133] In some embodiments, the phenolic resin-based polymer with high crosslinking degree is obtained by segmenting curing the resol resin-based material. First, the resol resin-based material is cured at 100°C-170°C, in which process the resol resin-based material gradually cures, and small molecular groups and easily oxidizable groups in the resol resin-based material begin to eliminate; then the resol resin-based material is cured again at 220°C-290°C, in which process the resol resin-based material continues to perform crosslinking curing reaction and is more fully cured; further, the first stage curing and the second stage curing are performed in an oxygen-containing atmosphere, and the curing in the oxygen-containing atmosphere can make the easily oxidizable groups of the resol resin-based material be oxidized in advance, 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-based polymer with high crosslinking degree.

[0134] 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%. Optionally, the inert gas can include one or more of nitrogen, argon, and helium, but is not limited thereto.

[0135] Optionally, the volume fraction of oxygen in the oxygen-containing atmosphere can be 10%-30%.

[0136] More optionally, the oxygen-containing atmosphere can be an air atmosphere. Thus, the cost can also be reduced.

[0137] The first temperature can be 100-170°C, for example, 100°C, 105°C, 110°C, 115°C, 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, or a range defined by any two of the above values.

[0138] Optionally, the first temperature can be 110-170°C, 110-160°C, 110-150°C, 120-170°C, 120-160°C, 120-150°C.

[0139] The first temperature in the above range can make the curing of the resol resin-based material in the first stage more uniform and sufficient, so that a phenolic resin-based polymer with high crosslinking degree can be obtained.

[0140] In some embodiments, the first time can be 2-4h, for example, 2h, 2.2h, 2.4h, 2.6h, 2.8h, 3h, 3.2h, 3.4h, 3.6h, 3.8h, 4h, or a range defined by any two of the above values.

[0141] The first time in the above range can make the curing of the resol resin-based material in the first stage more uniform and sufficient, so that a phenolic resin-based polymer with high crosslinking degree can be obtained.

[0142] The second temperature can be 220-290°C, for example, 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, 285°C, 290°C, or a range defined by any two of the above values.

[0143] Optionally, the second temperature can be 220-280°C, 220-270°C.

[0144] The second temperature in the above range can make the curing of the phenolic resin-based polymer more sufficient and the crosslinking degree higher while avoiding denaturation (such as degradation) of the phenolic resin-based polymer.

[0145] In some embodiments, the second time can be 2-6h, for example, 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 defined by any two of the above values.

[0146] The second time in the above range can make the curing of the phenolic resin-based organic particles more sufficient and the crosslinking degree higher.

[0147] In some embodiments, the method for preparing the phenolic resin-based polymer further comprises a step of sieving and a step of removing magnetism after the crushing treatment.

[0148] In some embodiments, the free phenol content of the resol-based material can be 5% or less, optionally 4% or less, 3% or less, 2% or less.

[0149] In some embodiments, the free aldehyde content of the resol-based material can be 5% or less, optionally 4% or less, 3% or less, 2% or less.

[0150] The low content of free phenol and free aldehyde helps to obtain a phenolic resin-based polymer with a higher degree of crosslinking.

[0151] The resol-based material can be commercially available or synthesized according to methods known in the art.

[0152] In some embodiments, the method for preparing the resol-based material comprises a step of reacting a phenolic compound and an aldehyde compound under catalysis of an alkaline substance to obtain the resol-based material.

[0153] Optionally, the alkaline substance can include one or more of ammonia, NaOH, Na2CO3.

[0154] Optionally, the phenolic compound can include one or more of phenol, p-dihydroxybenzene, m-dihydroxybenzene, o-dihydroxybenzene, cresol, cardanol.

[0155] Optionally, the aldehyde compound can include one or more of formaldehyde, paraformaldehyde, acetaldehyde, propyl aldehyde, n-butyl aldehyde, glyoxal, and furfural.

[0156] 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-based polymer can be controlled.

[0157] In some embodiments, the polymer containing a triazine ring group further comprises a bridging structure connecting the triazine ring structural units.

[0158] The bridging structure refers to a group connecting the triazine ring structural units, and each bridging structure is the same or different.

[0159] Optionally, the bridging structure can include one or a combination of two or more of alkylene, alkylene ether, alkylene amine.

[0160] In some embodiments, the polymer containing a triazine ring group can include melamine aldehyde-based polymers and derivatives thereof.

[0161] In some embodiments, the melamine aldehyde polymer and derivatives thereof can include melamine formaldehyde polymers and derivatives thereof.

[0162] Optionally, the melamine aldehyde polymer and derivatives thereof can include one or more of melamine formaldehyde, benzoguanamine formaldehyde, melamine-benzoguanamine 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, trihydrazinotriazine formaldehyde, melamine-(2-amino-4-methylamino-1,3,5-triazine) formaldehyde, melamine-(2,4-diamino-6-dimethylamino-1,3,5-triazine) formaldehyde.

[0163] In some embodiments, the polymer containing triazine ring group has no glass transition temperature below 300℃.

[0164] The polymer containing triazine ring group has no glass transition temperature below 300℃, which indicates that the organic particles have 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 separator film, and improve the reliability of the secondary battery cell.

[0165] In some embodiments, the volume distribution particle size Dv50 of the polymer containing triazine ring group can be 200nm-840nm.

[0166] The volume distribution particle size Dv50 of the polymer containing triazine ring group in the above range is beneficial to the coating of the separator film having good heat resistance and air permeability.

[0167] In some embodiments, the polymer containing triazine ring group has no oxidation peak in the cyclic voltammetry curve of the first cycle in the voltage range of 0V to 4.40V.

[0168] In some embodiments, the method for preparing the polymer containing triazine ring group includes 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℃-290℃. After the heating and curing of the precursor containing triazine ring structure, a bridging structure is formed between the triazine ring structure units.

[0169] The heating and curing temperature is 220℃-290℃, for example, it can be 220℃, 225℃, 230℃, 235℃, 240℃, 245℃, 250℃, 255℃, 260℃, 265℃, 270℃, 275℃, 280℃, 290℃, or a range consisting of any of the above values.

[0170] The precursor containing the triazine ring structure can be heated and cured at 220°C to 290°C to obtain the polymer particles containing the triazine ring structure with higher cross-linking degree.

[0171] Optionally, the temperature for heating and curing can be 225°C to 290°C, 230°C to 290°C, 225°C to 280°C, 230°C to 280°C.

[0172] In some embodiments, the time for heating and curing can be 3h to 6h, for example, 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 aforementioned values.

[0173] The time for heating and curing within the aforementioned range is conducive to the precursor containing the triazine ring structure to form the polymer containing the triazine ring group with higher cross-linking degree.

[0174] In some embodiments, the oxygen-containing atmosphere can include oxygen and an inert gas. Optionally, 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%. Optionally, the volume fraction of oxygen in the oxygen-containing atmosphere can be 10% to 30%. More optionally, the oxygen-containing atmosphere can be an air atmosphere.

[0175] In some embodiments, the polymer containing the triazine ring group further includes the steps of sieving and demagnetizing after the crushing treatment.

[0176] In some embodiments, the precursor containing the triazine ring structure can include a melamine-aldehyde resin. The melamine-aldehyde resin can be obtained by reacting an aldehyde compound with an amine-substituted triazine compound, and the amine-substituted triazine compound can include melamine and / or melamine derivatives.

[0177] In some embodiments, the aldehyde compound can include one or more of formaldehyde, paraformaldehyde, acetaldehyde, propyl aldehyde, n-butyl aldehyde, glyoxal, and furfural.

[0178] In some embodiments, the amine-substituted triazine compound can include one or more of the following general compounds, R1, R2are each independently selected from any one of H, -NH2, C1-C8 alkyl, and R3is selected from H, -NH2, -NHR4, C1-C8 alkyl, C2-C8 alkenyl, phenyl, C7-C 12 alkylphenyl, C7-C 12R4 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.

[0179] 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.

[0180] The molar ratio of aldehyde compounds to amine-substituted triazine compounds can be 1.75:1 to 3:1, for example, 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 any range of the above ratios; by controlling the molar ratio of aldehyde compounds to amine-substituted triazine compounds within the above range, the mass percentage of triazine ring groups in polymers containing triazine ring groups can be controlled.

[0181] 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.

[0182] 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.

[0183] Optionally, the phenyl-containing organosilicon polymer is a network structure formed with carbon-carbon bonds as the main chain, and the side chains contain siloxane structures.

[0184] Optionally, the phenyl-containing organosilicon polymer is a network structure formed with carbon-carbon bonds as the main chain, and the side chains contain 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 organic compound; 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 improving the thermal stability of the material.

[0185] In some embodiments, the phenyl-containing organosilicon polymer has no glass transition temperature below 300°C.

[0186] The phenyl-containing organosilicon polymer has no glass transition temperature below 300°C, indicating 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.

[0187] In some embodiments, the volume distribution particle size Dv50 of the phenyl-containing organosilicon polymer can be 88 nm-600 nm.

[0188] The volume distribution particle size Dv50 of the phenyl-containing organosilicon polymer is within the above range, which is beneficial to the coating of the isolation film having good heat resistance and air permeability.

[0189] 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.

[0190] In some embodiments, the cage-like polysilsesquioxane skeleton-containing organosilicon polymer refers to a new type of organic-inorganic hybrid polymer obtained by taking cage-like polysilsesquioxane (POSS) as a skeleton and connecting organic functional groups or polymer chains on the cage structure thereof through chemical modification; the cage-like polysilsesquioxane skeleton in the organosilicon polymer has high symmetry and regularity, the internal atoms are connected through 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, which have high bond energy and are not easy to decompose at high temperatures, which can help to further improve the thermal stability of the material.

[0191] In some embodiments, the cage-like polysilsesquioxane skeleton-containing organosilicon polymer 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.

[0192] The cage-like polysilsesquioxane skeleton-containing organosilicon polymer in the present application includes both the regular cage-like polysilsesquioxane skeleton formed by Si-O bonds and the network structure formed by random crosslinking of Si-O bonds; the material contains both the cage structure and the network structure, wherein 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 both high-temperature decomposition and high-temperature deformation, and the two can synergistically further increase the heat resistance of the material.

[0193] In some embodiments, the cage-like polysilsesquioxane skeleton-containing organosilicon polymer has no glass transition temperature below 300°C.

[0194] The cage-like polysilsesquioxane skeleton-containing organosilicon polymer has no glass transition temperature below 300°C, which indicates that the cage-like polysilsesquioxane skeleton-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 battery cell.

[0195] In some embodiments, the volume distribution particle size Dv50 of the cage-like polysilsesquioxane skeleton-containing organosilicon polymer can be 200 nm to 600 nm.

[0196] The volume distribution particle size Dv50 of the cage-like polysilsesquioxane skeleton-containing organosilicon polymer is within the above range, which is beneficial to the coating of the isolation film to have good heat resistance and air permeability.

[0197] In some embodiments, the cage-like polysilsesquioxane skeleton-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.

[0198] In some embodiments, the crosslinked styrenic polymer comprises styrene or styrene derivative structural units and crosslinking structural units.

[0199] 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.

[0200] 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.

[0201] In some embodiments, the crosslinked styrenic organic particles have a glass transition temperature T g greater than or equal to 150°C.

[0202] The crosslinked styrenic polymer has a glass transition temperature T g high, and has good heat resistance and thermal stability, thereby being able to better resist thermal shrinkage of the porous base film, improve the heat resistance of the separator film, and improve the reliability of the secondary battery cell.

[0203] In some embodiments, the crosslinked styrenic polymer has a volume distribution particle size Dv50 of 88 nm to 295 nm.

[0204] The crosslinked styrenic 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.

[0205] In some embodiments, the crosslinked styrenic polymer has a cyclic voltammogram of the first cycle within a voltage range of 0 V to 4.40 V without an oxidation peak.

[0206] In some embodiments, the method for preparing the crosslinked styrene-based polymer comprises the following steps: providing a pre-emulsion comprising monomers, crosslinking agent, emulsifier, initiator, and water, 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°C, and the maturation time of the emulsion polymerization is 1-4 hours.

[0207] The maturation temperature of the emulsion polymerization 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.

[0208] The maturation time of the emulsion polymerization is 1-4 hours, for example, it can be 1 hour, 1.2 hours, 1.4 hours, 1.6 hours, 1.8 hours, 2 hours, 2.2 hours, 2.4 hours, 2.6 hours, 2.8 hours, 3 hours, 3.2 hours, 3.4 hours, 3.6 hours, 3.8 hours, 4 hours, or a range formed by any of the above values.

[0209] The maturation temperature and the maturation time of the emulsion polymerization within the above ranges can obtain crosslinked styrene-based polymers with high crosslinking degree.

[0210] In some embodiments, the emulsion polymerization can comprise 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, after a first time, the temperature is raised to the maturation temperature for maturation reaction, and crosslinked styrene-based polymers are obtained.

[0211] Optionally, the first heating temperature can be 55-70°C.

[0212] Optionally, the first time can be 3-7 hours.

[0213] In some embodiments, the mass fraction of the crosslinking agent can be 4-28% based on the total mass of the monomers and the crosslinking agent being 100%, 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.

[0214] The mass fraction of the monomers within the above range can control the mass proportion of benzene rings in the crosslinked styrene-based organic polymer

[0215] The mass fraction of the crosslinking agent within the above range can improve the heat resistance of the crosslinked styrene-based organic particles.

[0216] Optionally, the mass fraction of the crosslinking agent can be 6%-28%, 8%-28%, 10%-28%, 4%-26%, 6%-26%, 8%-26%, 10%-26%.

[0217] In some embodiments, the solid content of the emulsion polymerization reaction system can be 10%-25%, for example, can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, or a range consisting of any of the above values. The solid content of the emulsion polymerization reaction system refers to the mass fraction of monomers and crosslinking agents in the reaction system.

[0218] The solid content of the emulsion polymerization reaction system in the above range can improve the conversion rate of monomers and improve the crosslinking degree of the crosslinked styrene-based polymer.

[0219] Optionally, the solid content of the emulsion polymerization reaction system can be 12%-25%, 14%-25%, 16%-25%.

[0220] In some embodiments, the monomers can include one or more of styrene, 1-methyl-1-phenylethylene, 4-methylstyrene, 2-methylstyrene, 2,4-dimethylstyrene, and 2,5-dimethylstyrene.

[0221] 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.

[0222] Optionally, the crosslinking agent can include one or more of divinylbenzene, N,N-methylenebisacrylamide, and N,N'-vinylbisacrylamide.

[0223] 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.

[0224] 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.

[0225] In some embodiments, the mass fraction of the emulsifier can be 0.1%-3%, based on the total mass of the monomer and the crosslinking agent being 100%.

[0226] 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, azobisdimethylamid hydrochloride, azobisdimethylimidazoline hydrochloride, and azobisisopropylimidazoline.

[0227] In some embodiments, the mass fraction of the initiator can be 0.16%-3%, optionally 0.2%-2%, 0.25%-2%, based on the total mass of the monomer and the crosslinking agent being 100%.

[0228] 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.

[0229] In the above embodiments, the crosslinked 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 crosslinked 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 crosslinked network formed by the crosslinking between the polymer molecular chains of the triazine ring; the organic silicon polymer containing a phenyl group can collectively improve the heat resistance of the isolation film due to the rigidity of the aromatic ring and the high bond energy of the silicon-oxygen bond, and the three-dimensional crosslinked network formed by the crosslinking between the molecular chains of the organic silicon polymer; the organic silicon polymer containing a cage-shaped polysilsesquioxane skeleton can provide structural support and reduce the collapse of the skeleton or the dissociation of the chain segment at high temperatures, and can exhibit high thermal stability at high temperatures, and the cage structure contains Si-O bonds with high bond energy and is 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 a cage-shaped polysilsesquioxane skeleton has a three-dimensional network structure formed by 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 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 high-temperature decomposition and high-temperature deformation, and the two can further increase the heat resistance of the material. The crosslinked styrene-based polymer can improve the heat resistance of the isolation film through the highly rigid carbon skeleton and the three-dimensional crosslinked network formed by the crosslinking between the molecular chains. By introducing the above at least one crosslinked polymer, the isolation film including the crosslinked polymer has good heat resistance, thereby improving the reliability of the battery cell under high temperature conditions.

[0230] In some embodiments, the phenyl-containing organosilicon polymer comprises monomers and cross-linking agents represented by formula (II) polymerized to form, In formula (II), R1, R2 each independently comprises C1-C4 alkyl, C2-C4 alkenyl, R3 comprises C1-C4 alkyl or C4-C8 (meth)acryloxyalkyl, and R4 comprises C2-C8 alkenyl or C4-C8 (meth)acryloxyalkyl; the cross-linking agent comprises divinylbenzene.

[0231] In the embodiments of the present application, R1 and R2 each independently comprises 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.

[0232] R3 comprises 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.

[0233] In some embodiments, R3 is methyl or (meth)acryloxyalkyl, the methyl is conducive to the stability of the main chain in the cross-linked polymer, and the acryloyloxy propyl can further participate in cross-linking to improve 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, further conducive to improving the cross-linking degree of the cross-linked polymer, thereby improving the high-temperature stability of the cross-linked polymer.

[0234] R4 comprises 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.

[0235] The acryloxyalkyl refers to an alkyl chain structure functional group containing an acryloyloxy end group, and the (meth)acryloxyalkyl refers to a (meth)acryloxyalkyl in which a hydrogen atom on a carbon atom directly connected to a carbonyl (C=O) is substituted with a methyl group, a reaction site is provided through an acrylate double bond (C=C) at the end of the molecular chain, and a free radical polymerization reaction with a cross-linking agent can be further carried out, which is conducive to improving the cross-linking degree of the organosilicon polymer.

[0236] In the embodiments of the present application, the cross-linking agent refers to a compound containing two or more functional groups capable of reacting with the functional groups on the polymer chain, 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 cross-link with the alkenyl or acryloyl group to form a covalent bond between the molecular chains with ethylene bridge and benzene ring as the 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.

[0237] In the above embodiments, the polymerization of the monomer represented by formula (II) and the cross-linking agent divinylbenzene can obtain the phenyl-containing silicone polymer particles, which have 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 the reliability of the battery cell.

[0238] In some embodiments, the method for preparing the phenyl-containing silicone polymer comprises the following steps: providing a pre-emulsion containing monomers, a cross-linking 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 the silicon-containing organic resin particles. The monomers include silane coupling agents containing alkenyl and / or acryloyloxy groups, and the mass fraction of the cross-linking agent is 2% to 30% based on the total mass of the monomers and the cross-linking agent. By controlling the mass fraction of the cross-linking agent, the mass fraction of the phenyl group in the phenyl-containing silicone polymer and the cross-linking degree of the phenyl-containing silicone polymer can be adjusted.

[0239] The monomers include silane coupling agents containing alkenyl and / or acryloyloxy groups, so that free radicals can be generated between the monomers to initiate cross-linking reactions, and the monomers can also cross-link with the cross-linking agent. Therefore, the phenyl-containing silicone polymer with a three-dimensional network structure can be formed using the monomers and the cross-linking agent as raw materials, which is not easy to soften or deform at high temperatures and has high heat resistance and electrochemical stability.

[0240] The mass fraction of the cross-linking agent is 2% to 30% based on the total mass of the monomers and the cross-linking agent, for example, it can be 2%, 7%, 12%, 17%, 22%, 27%, 30%, or a range composed of any of the above values, so that the phenyl-containing silicone polymer with high cross-linking degree can be obtained.

[0241] The mass fraction of the cross-linking agent is in the above range, so that the silicon-containing organic resin particles with high electrochemical stability and good heat resistance can be obtained.

[0242] Alternatively, the mass fraction of the cross-linking agent can be 2%-30%, 2%-25%, 2%-20%, 2%-15%, 3%-30%, 3%-25%, 3%-20%, 3%-15%.

[0243] In some embodiments, the monomer can include an acryloxy silane coupling agent.

[0244] Optionally, the monomer of formula (II) can include one or more of gamma- methacryloxypropyl tris(trimethylsiloxy)silane, (3-acryloyloxypropyl)tris(trimethylsiloxy)silane, 3-methacryloxypropyltrimethoxysilane, acryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, acryloxypropyltriethoxysilane, gamma- methacryloxypropyltriisopropoxysilane, 3-(acryloxy)propyltrimethoxysilane, 3- methacryloxypropyltris(methoxyethoxy)silane, 3-methacryloxypropylmethyldimethoxysilane, 3-acryloxypropylmethyldimethoxysilane, methacryloxypropyldimethylmethoxysilane, (3-acryloxy)dimethylmethoxysilane, 3-methacryloxypropyldimethylethoxysilane, 3- (methacryloxy)propylmethyldiethoxysilane.

[0245] In some embodiments, the monomer of formula (I) can include a first monomer and a second monomer.

[0246] The first monomer can include one or more of gamma-methacryloxypropyl tris(trimethylsiloxy)silane, (3-acryloyloxypropyl)tris(trimethylsiloxy)silane, 3- methacryloxypropyltrimethoxysilane, acryloxypropyltrimethoxysilane, 3- methacryloxypropyltriethoxysilane, acryloxypropyltriethoxysilane, gamma- methacryloxypropyltriisopropoxysilane, 3-(acryloxy)propyltrimethoxysilane, 3- methacryloxypropyltris(methoxyethoxy)silane.

[0247] The second monomer can include one or more of 3-methacryloxypropylmethyldimethoxysilane, 3-acryloxypropylmethyldimethoxysilane, methacryloxypropyldimethylmethoxysilane, (3-acryloxy)dimethylmethoxysilane, 3-methacryloxypropyldimethylethoxysilane, 3- (methacryloxy)propylmethyldiethoxysilane.

[0248] 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.

[0249] 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.

[0250] 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.

[0251] 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.

[0252] In some embodiments, the heating time of the maturation stage of the emulsion polymerization reaction can be 1h-4h, which can provide continuous and sufficient time for the condensation reaction, and 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.

[0253] 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 to carry out the maturation reaction, and the silicon-containing organic resin particles are obtained.

[0254] Alternatively, the second heating temperature can be 55-95℃.

[0255] Alternatively, the second time can be 3-8h.

[0256] 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.

[0257] 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.

[0258] 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 75-95%; (2) the phenyl-containing silicone polymer comprises a silicon element, and the mass fraction of the silicon element in the phenyl-containing silicone crosslinking resin is 10-25%; (3) the mass fraction of phenyl in the phenyl-containing silicone polymer is 2-12%.

[0259] 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 the range obtained by any two numerical combinations. The mass fraction of the silicon element in the phenyl-containing silicone crosslinking resin can be 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 25%, or a value within the range obtained by any two numerical combinations. The mass fraction of phenyl in the phenyl-containing silicone polymer can be 5%, 7%, 9%, 11%, 12%, or a value within the range obtained by any two numerical combinations.

[0260] The crosslinking degree of the phenyl-containing silicone polymer is 75-95%, 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.

[0261] The mass fraction of the silicon element is 10-25%, which helps to improve the proportion of inorganic siloxane skeleton in the silicone polymer. The siloxane skeleton comprising the silicon element provides a high thermal decomposition temperature and oxidation resistance, so that the isolation film has structural stability in a high temperature environment.

[0262] 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 its surface using an ion sputtering instrument; or after the battery cell is disassembled, the isolation film is peeled off, and a regular and clear area of the isolation film is selected. Then, the isolation film sample is fixed on the sample stage and subjected to gold or carbon spraying treatment to make its 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 extract to the required high vacuum state (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, and the target observation area is found. 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 the ZEISS sigma300 is used to analyze the elements on the surface of the phenyl-containing organosilicon polymer to detect the content of silicon elements 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 elements can be obtained.

[0263] 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.

[0264] In the embodiments of the present application, a pyrolysis-gas chromatography-mass spectrometer (Py-GC / MS) can be used to test the mass fraction of the phenyl group in the organosilicon polymer. 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°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. An 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 a rate of 10°C / min, and maintained at 250°C for 5 min, the carrier gas is high-purity helium, and the flow rate is 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 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.

[0265] Therefore, by limiting the crosslinking degree of the crosslinked polymer, the mass fraction of silicon elements and the mass fraction of the 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.

[0266] In some embodiments, the cage polysilsesquioxane skeleton-containing silicone polymer is obtained by hydrolysis and polycondensation of one or more of monomers represented by formula (III), wherein R'1 includes C1-C3 alkyl.

[0267] In the embodiments of the present application, R'1 specifically includes at least one of methyl, ethyl, n-propyl and isopropyl.

[0268] By using the hydrolysis-polycondensation reaction of the monomers represented by formula (III), the cage polysilsesquioxane skeleton-containing silicone 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 cage polysilsesquioxane skeleton-containing silicone polymer, so that the cage polysilsesquioxane skeleton-containing silicone polymer is not prone to 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.

[0269] In the embodiments of the present application, the cage polysilsesquioxane skeleton-containing silicone polymer is prepared by the following method:

[0270] (1) hydrolyzing the monomers represented by formula (III), then adding a catalyst, and performing polycondensation under heating to obtain the cage polysilsesquioxane skeleton-containing silicone polymer.

[0271] Thus, the cage polysilsesquioxane skeleton-containing silicone polymer is obtained by hydrolysis and polycondensation.

[0272] Specifically, the monomers represented by formula (III) are first hydrolyzed to generate silanol, and alcohol is released to form a mixed solution, and the alcohol increases the solubility of the organosiloxane monomers in the solution; then, under the action of the catalyst, the silanol starts to polycondense, and Si-O-Si bonds are formed between the silanols to further form a network structure, and nucleation begins. Finally, these nuclei continuously absorb silanol from the solution and continue to grow until the cage polysilsesquioxane skeleton-containing silicone polymer is formed. The nucleation process and the nucleus growth process are competitive, and the reaction temperature affects 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 polycondensation reaction rate between the silanols increases, and the crosslinking degree increases, so that the cage polysilsesquioxane skeleton-containing silicone polymer with a high crosslinking degree and a large proportion of cage polysilsesquioxane skeleton is obtained.

[0273] In some embodiments of the present application, the temperature for hydrolysis of the monomer of formula (III) is 10-40°C, for example, the temperature for hydrolysis can be 20-29°C, 21-28°C, 22-27°C, 23-26°C, 24-25°C, etc. By controlling the temperature for hydrolysis of the monomer within the above range, the rate of the hydrolysis reaction can be controlled, avoiding the situation that part of the silane coupling agent is self-polymerized due to the reaction being too violent, and the proportion of the cage polysilsesquioxane skeleton is reduced.

[0274] In some embodiments of the present application, the temperature for heating is 30-100°C, for example, the temperature for heating can be 30-99°C, 35-95°C, 40-90°C, 45-85°C, 50-80°C, 55-75°C, 60-70°C, etc.

[0275] In some embodiments of the present application, the time for heating is 2-48h, for example, the time for heating can be 2h, 3h, 8h, 10h, 15h, 20h, 24h, 36h, 48h, etc.

[0276] By controlling the temperature for heating and the time for heating within the above range, the degree of the polycondensation reaction can be controlled, and a silicone polymer with high crosslinking degree is obtained.

[0277] at least one of ammonia, triethylamine, sodium hydroxide, magnesium hydroxide, or ammonium hydroxide.

[0278] Specifically, the silicone 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 polycondensation process, the local accumulation and entanglement of the molecular chain are reduced, and the silicone polymer exhibits a high uniform dispersion state. The uniform dispersion of the molecular chain not only facilitates the uniform distribution of the crosslinking points, 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 silicone polymer particles in the coating are not prone to structural rupture or collapse at high temperatures, the overall heat resistance of the separator is improved, and the reliability of the battery cell is enhanced.

[0279] In some embodiments, the silicone polymer containing the cage polysilsesquioxane skeleton satisfies one or more of the following conditions: (1) the crosslinking degree of the silicone polymer containing the cage polysilsesquioxane skeleton is 85%-97%; (2) the silicone polymer containing the cage polysilsesquioxane skeleton includes silicon elements, and the mass fraction of the silicon elements in the silicone polymer containing the cage polysilsesquioxane skeleton is 25%-45%; (3) in the silicone polymer containing the cage polysilsesquioxane skeleton, the mass fraction of the cage polysilsesquioxane skeleton is 40%-60%.

[0280] For example, the cross-linking degree of the organosilicon polymer containing a cage polysilsesquioxane skeleton can be 85%, 87%, 89%, 91%, 93%, 95%, 97%, or a value within a range obtained by combining any two of the above values. The mass fraction of silicon elements in the organosilicon polymer containing a cage polysilsesquioxane skeleton can be 25%, 27%, 29%, 31%, 33%, 35%, 37%, 39%, 41%, 43%, 45%, or a value within a range obtained by combining any two of the above values. In the organosilicon polymer containing a cage polysilsesquioxane skeleton, the mass fraction of the cage polysilsesquioxane skeleton can be 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60%, or a value within a range obtained by combining any two of the above values.

[0281] A cross-linking degree that is too low can easily result in a low degree of cross-linking between molecular chains, insufficient thermal stability, and a decline in the heat resistance of the insulation film. A cross-linking degree of 85% to 97% can ensure that the organosilicon polymer has good heat resistance at high temperatures, thereby improving the heat resistance of the insulation film.

[0282] The mass fraction of silicon elements reflects the proportion of inorganic siloxane skeletons 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 insulation film at high temperatures.

[0283] As an example, in the embodiments of the present application, a small amount of powder sample (usually a few milligrams) of the organosilicon polymer containing a cage 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 moisture (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 fall off); then a layer of 5-10 nm thick gold is sprayed on the surface thereof using an ion sputtering instrument; or after the battery monomer 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 containing the sample to be tested is placed in the SEM sample chamber, the hatch is closed, and the vacuum system is started to extract to the required high vacuum state of the instrument (usually 10 -3 -10 -5Pa). After the vacuum is up to standard, adjust the electron gun voltage (usually 5-20 kV), working distance (usually 5-15 mm), move the sample stage through the control software, and find the target observation area. Adjust the focus and magnification (from low magnification 100 times positioning to high magnification 10000 times to observe details) step by step to obtain clear SEM morphology images, and mark the feature points or areas that need to be analyzed by EDS. Start the EDS detector in the SEM software, select the marked analysis area (single-point analysis, line scanning or area scanning can be performed), set the collection time (usually 10-30 seconds, the longer the time, the more accurate the element signal). Using the energy-dispersive x-ray spectroscopy (EDS) matched with ZEISS sigma300, the surface of the organic silicon polymer containing a cage-like polysilsesquioxane skeleton is analyzed to detect the content of silicon element in the organic silicon polymer containing a cage-like 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 element can be obtained.

[0284] The mass fraction of the cage-like polysilsesquioxane skeleton is crucial to improve the three-dimensional structure stability of the cross-linked polymer. The mass fraction of the cage-like polysilsesquioxane skeleton in the cage is 40% to 60%, which can ensure that the cross-linked polymer has good rigidity and structural stability, reduce the occurrence of structural collapse or brittle fracture in the separator film under heat abuse, and is conducive to improving the heat resistance of the separator film, thereby improving the reliability of the battery monomer at high temperature.

[0285] The mass fraction of the cage-like polysilsesquioxane skeleton is crucial to improve the three-dimensional structure stability of the cross-linked polymer. The mass fraction of the cage-like polysilsesquioxane skeleton in the cage is 40% to 60%, which can ensure that the cross-linked polymer has good rigidity and structural stability, reduce the occurrence of structural collapse in the separator film under high temperature, and is conducive to improving the heat resistance of the separator film, thereby improving the reliability of the battery monomer at high temperature.

[0286] 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 skeleton structure in the silicone polymer. Specifically, 0.5-1 mg of the silicone polymer 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. An 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, and the flow rate is 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 cage skeleton structure are detected, and it can be inferred that the silicone polymer contains the cage skeleton structure. The internal standard method is used to calculate the mass fraction of the cage skeleton structure in the silicone polymer based on the area of the above-mentioned fragment peak corresponding to the characteristic cage skeleton structure.

[0287] Therefore, by limiting the crosslinking degree, the mass fraction of silicon elements, and the mass fraction of the cage polysilsesquioxane skeleton of the silicone polymer to meet the above ranges, respectively, the structure of the silicone polymer containing the cage polysilsesquioxane skeleton 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.

[0288] In some embodiments, the organic compound is a small molecule compound, and the small molecule compound includes one or more of melamine cyanurate, melamine polyphosphate, and melamine pyrophosphate.

[0289] In the above technical solution, the small molecule compounds such as melamine cyanurate, melamine polyphosphate, and melamine pyrophosphate have excellent thermal stability and flame retardant performance, can maintain good thermal stability in a high-temperature environment, and improve the heat resistance of the isolation film.

[0290] 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 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 g at 300°C; and (4) the initial thermal weight loss temperature T 3d(5) The leaching rate of the heat-resistant particles after being 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 is less than or equal to 5%; (6) The true density of the heat-resistant particles is 0.8 g / cm³. 3 ~2.0g / cm 3 .

[0291] For example, the volumetric particle size Dv50 of the heat-resistant particles can be 80nm, 120nm, 160nm, 200nm, 240nm, 280nm, 320nm, 360nm, 400nm, 440nm, 480nm, 520nm, 560nm, 600nm, 640nm, 680nm, 720nm, 760nm, 800nm, 840nm, 880nm, or 900nm, or a value within the range obtained by any combination of two of the above values. The glass transition temperature T of the heat-resistant particles... g It can be 150℃, 160℃, 170℃, 180℃, 190℃, 200℃, or a value within the range obtained by any combination of the above two values, or, the heat-resistant particles have no glass transition temperature Tg at 300℃. The initial thermogravimetric temperature T of the heat-resistant particles. 3d The percentage can be 5%, 4%, 3%, 2%, 1%, or any value within the range obtained by any combination of two of the above values. The dissolution rate of the heat-resistant particles can be 5%, 4%, 3%, 2%, 1%, or any value within the range obtained by any combination of two of the above values. The true density of the heat-resistant particles can be 0.8 g / cm³. 3 0.9g / cm 3 1.0g / cm 3 1.1g / cm 3 1.2g / cm 3 1.3g / cm 3 1.4g / cm 3 1.5g / cm 3 1.6g / cm 3 1.7g / cm 3 1.8g / cm 3 1.9g / cm 3 2.0g / cm 3 , or its value is within the range obtained by combining any two of the above values.

[0292] 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, thereby improving the heat resistance of the isolation film. If Dv50 is too small, the heat-resistant particles are prone to agglomeration. If Dv50 is too large, the heat-resistant particles have poor dispersibility, which can cause pore blockage and local stress concentration of the coating. The heat-resistant particles within the above particle size range can be uniformly distributed in the coating, filled on the surface of the pore channel of the porous base film, and further help to improve 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 without increasing the thickness of the coating, thereby improving the energy density and high-temperature reliability of the battery cell.

[0293] 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, the laser diffraction scattering particle size analyzer can be used to measure the average volume particle size of the material according to the manufacturer's instructions, with reference to the standard GB / T19077-2016. 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 using a MasterSizer 3000 laser particle size analyzer. An appropriate amount of sample to be tested (the sample concentration is guaranteed to have 8-12% obscuration) is added to 20 ml of deionized water, and simultaneously ultrasonic treatment is performed for 5 min (53 KHz / 120 W) to ensure that the sample is completely dispersed. Then, the sample is measured according to the standard GB / T19077-2016 / ISO 13320:2009.

[0294] The electrochemical stability of conventional organic particles is generally poor, and they are prone to decomposition under high pressure. The cyclic voltammetry curve of the heat-resistant particles in the present application in the first cycle has no 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. The heat-resistant particles can be applied to high-voltage battery cells, so that the battery cells have good capacity performance under high voltage, thereby improving the working voltage and energy density of the battery cells.

[0295] As an example, the oxidation peak potential of the heat-resistant particle can be tested as follows: take the heat-resistant particle, the binder polyacrylate, and the conductive agent conductive carbon black, and dissolve them in water to form a slurry according to a solid content mass ratio of 64:7:29, coat the slurry on an aluminum foil as a positive electrode, take a lithium foil as a negative electrode, and assemble a button cell. Perform a cyclic voltammetry (CV) test on the button cell at a scanning rate of 0.10 mV / s and a voltage range of 0V-5.00V, and cycle 3 times. Take the voltage corresponding to the peak point of the first cycle of the cyclic voltammetry curve 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.

[0296] Glass transition temperature T g refers to the transition temperature of a material from a glass state to a high-elasticity state, which shows a step change on a DSC curve. The glass transition temperature of the heat-resistant particle is greater than or equal to 150°C, or less than or equal to 300°C. For example, the glass transition temperature refers to the fact that the DSC curve of the heat-resistant particle remains solid and rigid at a temperature below 150°C or below 300°C, and does not undergo molecular chain segment movement or softening, thereby improving the heat resistance of the isolation film.

[0297] As an example, the glass transition temperature T g can be tested as follows: take an appropriate amount of sample (for example, 5mg-15mg) and place it in a differential scanning calorimeter (DSC) crucible, shake it flat, and cover it with a crucible cover. Parameter settings: nitrogen atmosphere, purging gas 60mL / min, and protective gas 20mL / min. Program settings: increase the temperature from 25°C to 200°C at a rate of 10°C / min, maintain for 5min to eliminate thermal history, then decrease the temperature from 200°C to -40°C at a rate of 10°C / min, and then increase the temperature to 300°C at a rate of 10°C / min. The glass transition temperature T g of the heat-resistant particle is determined by the DSC curve.

[0298] The initial thermal weight loss temperature T 3d of the heat-resistant particle is greater than or equal to 250°C, indicating that the weight of the heat-resistant particle does not change significantly at high temperatures. Therefore, the heat-resistant particle has high thermal stability and is not prone to thermal decomposition during the use of the battery cell and in a high-temperature environment. When the heat-resistant particle is used in the isolation film, the heat-resistant particle can better generate a force to resist the shrinkage of the isolation film, thereby improving the overall thermal shrinkage of the isolation film, improving the heat resistance of the isolation film, and improving the reliability of the battery cell.

[0299] The initial thermal weight loss temperature T 3dThe initial thermal weight loss temperature T of the organic particle refers to the temperature corresponding to a 3% loss in the mass of the sample relative to the initial mass in the thermal gravimetric analysis. The initial thermal weight loss temperature T of the organic particle 3d The test can be performed as follows: an appropriate amount of sample (e.g., 5 mg-15 mg) is placed in an alumina crucible of a thermal gravimetric analyzer (TGA), leveled, and covered with a crucible cover; the parameters are set as follows: nitrogen atmosphere, purging gas 60 mL / min, and protective gas 20 mL / min; the temperature rising program is set as follows: temperature rising rate 10 ℃ / min, and temperature range 35 ℃-600 ℃; the temperature corresponding to a 3% loss in the mass of the sample relative to the initial mass (i.e., 97% of the initial mass) is obtained from the test curve, which is the initial thermal weight loss temperature T 3d .

[0300] The dissolution rate can refer to the proportion of the particles dissolved or decomposed in the electrolyte. The dissolution of the heat-resistant particles is less than 5% after the electrolyte is soaked at 60 ℃ for 7 days, and the heat-resistant particles are not easy to precipitate or dissolve in the electrolyte environment, reducing the occurrence of electrolyte pollution or side reactions between the heat-resistant particles and the electrolyte in the cycle process of the battery cell, so that the separator membrane has good structural stability, which is beneficial to the cycle performance and reliability of the battery cell.

[0301] As an example, the swelling degree of the heat-resistant particles can be tested as follows: an appropriate amount of sample (e.g., about 1 g) is weighed as m1, placed in a semi-permeable membrane sample bag, sealed, and the sample bag can permeate the solvent but cannot permeate the sample; the sample bag is soaked in an appropriate amount of solvent (e.g., about 50 g) at 60 ℃ for 7 days, then the sample bag is taken out, and the sample is taken out from the sample bag, the excess solvent is wiped off, and the mass of the sample is weighed again as m2; the swelling degree = (m2-m1) / m1x100%. The solvent is a mixed solvent obtained by mixing ethylene carbonate (EC) and methyl ethyl carbonate (EMC) in a volume ratio of 3:7.

[0302] The true density refers to the mass of a material per unit actual volume (excluding internal voids, i.e., not including open pores and closed pores and inter-particle voids) in an absolutely dense state. The true density of the heat-resistant particles is 0.8 g / cm 3 -2.0 g / cm 3 , which is beneficial to improve the capacity of the battery cell and obtain a battery cell with high energy density.

[0303] The true density of the heat-resistant particles has the meaning commonly known in the art and can be tested using methods known in the art. As an example, a heat-resistant particle having a mass of M is placed in a carbon base in a true density tester (AccuPyc II 1340 analyzer) at room temperature (15-25 °C), the test system is closed and helium is introduced according to the program. By detecting the gas pressure in the sample chamber and the expansion chamber, the gas volumes in the sample chamber and the expansion chamber are calculated respectively according to the ideal gas state equation, and the difference between the two is the gas volume displaced by the carbon base under certain temperature and pressure conditions, which is the true volume V of the heat-resistant particle. The true density of the heat-resistant particle is the mass M of the heat-resistant particle divided by the true volume V of the heat-resistant particle, and the unit of true density is g / cm3. 3 .

[0304] In some embodiments, the mass fraction of the heat-resistant particles in the coating layer is 50%-97%.

[0305] The mass fraction of the heat-resistant particles in the coating layer 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 two of the above numerical combinations.

[0306] 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, improve the heat resistance of the isolation film, and thus improve the reliability of the battery cell.

[0307] In some embodiments, 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; and (2) the mass fraction of the first binder in the coating layer is 3%-15%.

[0308] For example, the mass fraction of the first binder in the coating layer can be 3%, 5%, 7%, 9%, 11%, 13%, 15%, or a value within the range obtained by any two of the above numerical combinations.

[0309] The heat-resistant particles in the coating layer are connected and fixed to each other by the first binder, reducing the situation of heat-resistant particles falling off 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 layer due to excessive binder while ensuring adhesion, thereby balancing the stability and heat resistance of the coating layer and improving the heat resistance of the isolation film.

[0310] In some embodiments, the isolation film further comprises second binder particles, which are located in the coating layer, or the isolation film further comprises a bonding layer, which 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 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 volume average particle size Dv50 of the second binder particles is 5 μm to 20 μm.

[0311] 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 the range obtained by combining any two of the above values.

[0312] The addition of the second binder particles in the coating layer 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 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 meets the above range, which ensures that it can be uniformly distributed and maintain moderate fluidity during hot pressing, thereby further improving the cycle performance of the battery cell.

[0313] 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 layer of the isolation film, and the "second binder particles" play a role in improving the adhesion between the isolation film and the electrode sheet in the porous coating layer of the isolation film.

[0314] In some embodiments, the coating layer of the isolation film comprises 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 layer.

[0315] In some embodiments, the coating of the separator film includes a heat-resistant layer disposed on one side of the porous base film and a bonding layer disposed on at least a portion of the surface of the other side of the porous base film, heat-resistant particles are disposed in the heat-resistant layer, and second binder particles are disposed in the bonding layer.

[0316] In some embodiments, the coating of the separator film includes a heat-resistant layer disposed on one side of the porous base film and a bonding layer disposed on at least a portion of the surface of the other side of the porous base film, heat-resistant particles are disposed in the heat-resistant layer, and second binder particles are disposed in the bonding layer.

[0317] In some embodiments, the coating of the separator film includes a heat-resistant layer disposed on one side of the porous base film and a bonding layer disposed on at least a portion of the surface of the other side of the porous base film, heat-resistant particles are disposed in the heat-resistant layer, and second binder particles are disposed in the bonding layer.

[0318] In some embodiments, the inorganic particles are included in the coating in a mass fraction of 0.1-50% based on the total mass of the coating.

[0319] In other embodiments, the inorganic particles are included in the coating in a mass fraction of 50-92% based on the total mass of the coating.

[0320] 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, which have a large dielectric constant and are advantageous for improving the ion transport efficiency in the coating.

[0321] In some embodiments, the separator film satisfies one or more of the following conditions: (1) the thickness of the coating is 0.5 μm-10 μm; (2) the areal density of the coating is 1.5 g / m 2 ~ 6 g / m 2 ; (3) the longitudinal thermal shrinkage of the separator film is less than or equal to 5% when heated at 130°C for 1 h; (4) the transverse thermal 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-500 s / 100 mL.

[0322] 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 0.5 μm, 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.

[0323] If the coating is too thin, it cannot form an effective thermal insulation layer, and if it is too thick, it increases the thickness of the separator and reduces the energy density of the battery cell. A coating thickness of 0.5 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.

[0324] The areal density of the coating is 1.5 g / m 2 to 6 g / m 2 , which can ensure that the coating has a moderate mass, can improve the stability and heat resistance of the separator, and will not significantly increase the weight of the separator, thereby being conducive to the energy density and reliability of the battery cell. For example, the areal density of the coating 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 2 , 5.1 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 the range obtained by any two of the above combinations.

[0325] The areal density of the coating can be controlled during the preparation of the separator 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 separator film containing the coating according to embodiments of the present application and 6 layers of the single separator film substrate without the coating, and applying pressure to make the layers adhere closely and without air bubbles. Then, the two groups of stacks are cut according to a sample cutting template, each obtaining 6 samples. The total mass of the 6 samples of the group with the coating M1 and the total mass of the 6 samples of the group without the coating M2 are measured, and the average mass of the coating on a single separator film is calculated by the formula M = (M1-M2) / 6. Then, the area S of a single sample is measured, and the areal density of the coating is obtained according to the formula “coating areal density = M / S”.

[0326] The thermal shrinkage rate refers to the percentage of the dimensional change of the separator film at high temperature, and is an important indicator for measuring the thermal stability of the separator film. The separator film can maintain very low longitudinal and transverse thermal shrinkage rates at 130°C, i.e., the separator film according to embodiments of the present application has good heat resistance at high temperature.

[0327] As an example, the thermal shrinkage rate of the separator film can be tested according to GB / T 36363-2018. As an example, the separator film is cut into samples with a width of 50 mm and a length of 100 mm using a punch machine, and 5 parallel samples are placed on an A4 paper, and then the A4 paper with the samples is placed on 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 separator film are measured, and the values are marked as a and b, respectively. The longitudinal (MD) thermal shrinkage rate = [(100-a) / 100] x 100%, and the transverse (TD) thermal shrinkage rate = [(50-b) / 50] x 100%. The average value of 3 parallel samples is taken as the test result.

[0328] 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 to 500 s / 100 mL, which ensures that the electrolyte can be uniformly infiltrated and maintain fast ion transmission, ensures the ion transmission efficiency in the separator film, and 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.

[0329] As an example, the air permeability of the separator can be tested according to GB / T 36363-2018. Specifically, the separator is cut into a square of 5 cm in size, an air permeability instrument is used, a pressure of 1.21 kPa is applied, and the time required for 100 ml of air to permeate through 6.45 cm2of the separator is tested as the air permeability of the separator, in s / 100 ml. The average value of three parallel samples is taken as the test result.

[0330] In some embodiments, the thickness of the separator can be 5-20 μm, optionally 5-12 μm, 6-12 μm. This is advantageous for improving the energy density of the secondary battery cell.

[0331] It should be noted that the coating parameters of the separator described above are the coating parameters of 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 thereof meet the present disclosure, and it is considered to fall within the protection scope of the present disclosure.

[0332] The shape of the battery cell according to 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.

[0333] 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 electrode assembly and the electrolyte described above.

[0334] 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 pouch-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.

[0335] In some embodiments, referring to FIG. 2, the battery cell 3 includes a shell 30 and an electrode assembly 33 disposed in the shell 30, and the shell 30 includes a housing 31 and a cover plate 32 for covering the opening of the housing 31.

[0336] The electrode assembly 33 can be made of a positive electrode sheet, a negative electrode sheet, and a separator 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.

[0337] The cover plate 32 includes an electrode terminal 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.

[0338] The battery cell 3 further includes a connecting member 34 for connecting the tab 331 of the electrode assembly 33 and the electrode terminal 322. For example, one connecting member 34 is used to connect the tab of the positive electrode and the positive electrode terminal, and another connecting member 34 is used to connect the tab of the negative electrode and the negative electrode terminal.

[0339] 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 timely released.

[0340] In some embodiments, the battery cell can be assembled into a battery module, and the number of battery cells contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0341] [Positive electrode sheet]

[0342] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector, the positive electrode active material layer including a positive electrode active material.

[0343] As an example, the positive electrode current collector has two surfaces opposite in its own thickness direction, and the positive electrode active material layer is disposed on either one or both of the two opposite surfaces of the positive electrode current collector.

[0344] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. For example, as a 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, 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.).

[0345] The positive electrode active material layer can also optionally include at least one of the positive electrode active materials known in the art for batteries: lithium-containing phosphates of olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as 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 lithium transition metal oxides 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 LiNi1 / 3Co1 / 3Mn1 / 3O2), lithium manganese nickel oxide, lithium manganese nickel cobalt oxide, lithium iron phosphate (such as LiFePO4), and lithium vanadium oxide (such as LiV2O5).1 / 3 Co 1 / 3 Mn 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 olivine phosphate 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.

[0346] 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.

[0347] 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.

[0348] In some embodiments, the positive electrode sheet can be prepared by forming the above-mentioned components for preparing the positive electrode sheet into a positive electrode slurry. For example, the positive electrode active material, the conductive agent, the binder, and any other components are dispersed in a solvent (e.g., 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.

[0349] The battery will be accompanied by Li de-intercalation and consumption during charging and discharging, 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 this 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 cycles, the molar content of Li will change.

[0350] In the enumeration of the positive electrode material in this application, the molar content of O is only the theoretical state value, and the release of oxygen from the lattice will cause the molar content of oxygen to change, and the actual molar content of O will appear to be floating.

[0351] [Negative electrode sheet]

[0352] 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.

[0353] As an example, the negative electrode current collector has two surfaces opposite in the thickness direction of the negative electrode current collector 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.

[0354] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. For example, as a metal foil, a copper 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 (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material base layer (such as a base layer of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0355] In some embodiments, the negative active material can employ a negative active material for a battery known in the art. As an example, the negative active material can include at least one of 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 a negative active material for a battery can also be used. These negative active materials can be used alone or in combination of two or more.

[0356] In some embodiments, the negative film layer can further 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).

[0357] In some embodiments, the negative film layer can further optionally include a conductive agent. The conductive agent can be selected from at least one of super conductive carbon, acetylene black, carbon black, ketjen black, carbon dot, carbon nanotube, graphene, and carbon nanofiber.

[0358] In some embodiments, the negative film layer can further optionally include other auxiliary agents, such as a thickening agent (e.g., sodium carboxymethyl cellulose (CMC-Na)) and the like.

[0359] 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 active material, the spherical particle, 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 current collector, and after processes such as drying, cold pressing, etc., the negative electrode sheet can be obtained.

[0360] [Electrolyte]

[0361] The electrolyte functions to conduct ions between the positive electrode sheet and the negative electrode sheet. The present application does not have a specific limitation on the type of electrolyte, which can be selected as needed. For example, the electrolyte can be liquid, semi-solid, or all-solid.

[0362] In some embodiments, the electrolyte employs an electrolyte solution. The electrolyte solution includes the catalyst in any of the above-mentioned possible embodiments.

[0363] In some embodiments, the electrolyte solution includes an electrolyte salt and a solvent.

[0364] 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 difluoroboric oxalate, lithium difluoroboric bisoxalate, lithium difluorophosphoric bisoxalate, and lithium tetrafluorophosphoric oxalate.

[0365] For a lithium-ion battery cell or a lithium metal battery cell, the solvent can include one or more of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclobutane sulfone, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0366] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclobutane sulfone, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0367] In some embodiments, the electrolyte solution can also optionally include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and can also include an additive capable of improving certain performance of the battery, such as an additive for improving overcharge performance of the battery, an additive for improving high-temperature or low-temperature performance of the battery, etc.

[0368] [Separator]

[0369] In some embodiments, the separator includes the coating in any of the possible embodiments described above. The coating includes heat-resistant particles and a first binder for bonding the heat-resistant particles to the porous base film; the heat-resistant particles include an organic compound; the main chain or side chain of the organic compound has a rigid structure, the rigid structure includes a planar ring conjugated group and / or a covalent polyhedral skeleton; when the organic compound is a small molecule compound, a condensation polymer, or a copolymer, the mass fraction of the rigid structure in the organic compound is 40% to 99%; when the organic compound is a condensation copolymer, the mass fraction of the rigid structure in the organic compound is 2% to 30%.

[0370] In the technical solution, the organic compound containing the rigid structure including the planar ring conjugated group and / or the covalent polyhedral skeleton has low molecular chain freedom degree. By controlling the mass ratio of the rigid structure in the small molecule compound, the polycondensate or the copolymer to be 40% to 99%, or the mass ratio of the rigid structure in the polycondensation copolymer to be 2% to 30%, the probability of deformation of the organic compound in a high-temperature environment is low, the thermal stability is good, the heat resistance of the isolation film can be improved, and the reliability of the battery cell in a high-temperature environment can be improved.

[0371] Specifically, the rigid structure includes the planar ring conjugated group and / or the covalent polyhedral skeleton. The planar ring conjugated group is not easy to be twisted and deformed in a high-temperature environment due to the conjugation effect and the planar structure, has high rigidity, and the polymer molecule is difficult to pyrolyze or soften, so that the organic compound containing the planar ring conjugated group has high thermal stability. The covalent polyhedral skeleton is not easy to be broken or collapsed in a high-temperature environment due to the highly symmetrical three-dimensional geometric structure and the strong covalent bond connection which is higher than the ionic bond or the intermolecular force, so that the organic compound containing the covalent polyhedral skeleton has high thermal stability. Therefore, the organic compound containing the rigid structure including the planar ring 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 heat resistance of the whole isolation film can be improved, and the reliability of the battery cell in a high-temperature environment can be improved.

[0372] In some embodiments, the planar ring conjugated group includes any one of a substituted or unsubstituted phenyl, 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 and a triazine ring group.

[0373] In the above embodiments, by limiting the types of the planar ring conjugated group in the organic compound, the heat resistance and chemical stability of the organic compound can be further enhanced, so that the heat resistance of the isolation film can be improved. The phenyl has good structural stability and conjugation effect, and can improve the thermal stability of the organic compound. The aromatic group containing a heteroatom can make the electronic structure of the organic compound more stable and enhance the oxidation resistance of the organic compound, and reduce the probability of reaction between the organic compound 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 groups in the organic compound makes the organic compound particles in the coating more difficult to deform or break at high temperatures, so that the isolation film has good heat resistance and improves the reliability of the battery cell.

[0374] In some embodiments, the covalent polyhedral skeleton includes a skeleton composed of a compound shown in formula (I), R a [SiO3 / 2 ] n Formula (I), wherein n is an integer of any value in the range of 4 to 12, 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

[0375] In the above embodiments, by introducing the covalent polyhedral skeleton shown in Formula (I) into the organic compound, a stable three-dimensional structure can be formed inside the molecule of the organic compound. 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 under high temperature environment, which is conducive to improving the heat resistance of the isolation film. By selecting n as 8 and R1 as a C1-C3 alkyl group, the rigidity and thermal stability of the organic compound can be further improved. The organic compound particles can act as rigid support points under high temperature, thereby improving the heat resistance of the isolation film and the reliability of the battery cell.

[0376] In some embodiments, the organic compound is a cross-linked polymer, and the cross-linking degree of the cross-linked polymer is 70% to 98%.

[0377] In the above embodiments, 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 under high temperature, thereby improving the heat resistance of the isolation film and ensuring the overall structural integrity of the isolation film under high temperature, thereby improving the reliability of the battery cell under high temperature conditions. In some embodiments, the cross-linked polymer includes at least one of a phenolic resin polymer, a polymer containing a triazine ring group, an organic silicon polymer containing a phenyl group, an organic silicon polymer containing a cage-like poly silyl siloxane skeleton, and a cross-linked styrene polymer.

[0378] ​​​In the above embodiments, the aromatic ring skeleton and cross-linking structure contained in the phenolic resin-based polymer can improve the heat resistance of the cross-linked polymer; the polymer containing a triazine ring can improve the high-temperature resistance and oxidation resistance due to the high conjugation of the triazine ring and the chemical inertness provided by the nitrogen atom, as well as the three-dimensional cross-linked network of the polymer of the triazine ring, so that the isolation film can maintain structural integrity during long-term use; the phenyl-containing silicone polymer has the rigidity of the aromatic ring and the three-dimensional cross-linked network, and the structure can improve the heat resistance of the isolation film; in the phenyl-containing silicone polymer containing a cage-shaped polyhedral oligomeric silsesquioxane skeleton, the cage structure can provide structural support and reduce the collapse of the cross-linked polymer particles or the dissociation of the chain segments at high temperatures, and can exhibit high thermal stability at high temperatures. At the same time, due to the inorganic-organic hybrid characteristics of the polyhedral oligomeric silsesquioxane skeleton, it can also help to improve the compatibility of the cross-linked polymer and the organic electrolyte, reduce the risk of dissolution of the cross-linked polymer particles, and help to maintain the structural integrity of the isolation film. The cross-linked styrene-based polymer can improve the structural stability of the isolation film through the highly rigid carbon skeleton and the three-dimensional cross-linked network. By introducing at least one of the above groups, the isolation film including the cross-linked polymer has good heat resistance, thereby improving the reliability of the battery cell under extreme conditions.

[0379] In some embodiments, the phenyl-containing silicone polymer is obtained by polymerization of a monomer represented by formula (II) and a cross-linking agent, In formula (II), 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)acryloxyalkyl group, and R4 includes a C2-C8 alkenyl group or a C4-C8 (meth)acryloxyalkyl group; the cross-linking agent includes divinylbenzene.

[0380] In the above embodiments, by polymerization of the monomer represented by formula (II) 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 a monomer represented by 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.

[0381] In some embodiments, the phenyl-containing silicone polymer satisfies one or more 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 contains silicon elements, and the mass fraction of silicon elements in the phenyl-containing silicone cross-linked resin is 10% to 25%; (3) the mass fraction of phenyl groups in the phenyl-containing silicone polymer is 2% to 12%.

[0382] The cross-linking degree of the phenyl-containing organosilicon polymer is 85% to 97%, and the organosilicon polymer 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 increase the proportion of inorganic siloxane skeleton in the organosilicon polymer. The siloxane skeleton including 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 phenyl groups is 2% to 12%, which can introduce the rigidity and conjugation effect of aromatic structures, further helping to improve the heat resistance of the isolation film.

[0383] Therefore, by limiting the cross-linking degree of the cross-linked polymer, the mass fraction of silicon elements, and the mass fraction of phenyl groups to meet the above ranges, respectively, the structure of the phenyl-containing organosilicon polymer can be controlled to have high thermal stability, improve the heat resistance of the isolation film, and further improve the reliability of the battery cell at high temperatures.

[0384] In some embodiments, the organosilicon polymer containing a cage-like polyhedral silsesquioxane skeleton is obtained by hydrolysis and condensation of one or more monomers represented by formula (III), wherein R'1 includes C1 to C3 alkyl groups.

[0385] In the above embodiments, the hydrolysis and condensation reaction of the monomer of formula (III) can obtain an organosilicon polymer with a relatively complete cage structure and uniform molecular chain dispersion. Therefore, a highly ordered and stable covalent polyhedral skeleton can be formed in the organosilicon polymer, so that the organosilicon polymer is less likely to have structural rupture or collapse at high temperatures, enhancing the heat resistance of the isolation film and thereby improving the reliability of the battery cell.

[0386] Specifically, the organosilicon polymer formed from the monomer of formula (III) is relatively regular and stable at the molecular scale, and the polyhedral units are uniformly connected by covalent bonds during the condensation process, reducing the local accumulation and entanglement of molecular chains. The organosilicon 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 dispersity and binding stability of the cross-linked polymer particles in the coating of the isolation film, so that the organosilicon polymer particles in the coating are less likely to have structural rupture or collapse at high temperatures, improving the overall heat resistance of the isolation film and thereby enhancing the reliability of the battery cell.

[0387] In some embodiments, the organosilicon polymer containing a cage polysilsesquioxane skeleton satisfies one or more of the following conditions: (1) the crosslinking degree is 85% to 97%; (2) the organosilicon polymer containing a cage polysilsesquioxane skeleton includes silicon elements, and the mass fraction of the silicon elements in the organosilicon polymer containing a cage polysilsesquioxane skeleton is 25% to 45%; (3) in the organosilicon polymer containing a cage polysilsesquioxane skeleton, the mass fraction of the cage polysilsesquioxane skeleton is 40% to 60%.

[0388] 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 film. A crosslinking degree of 85% to 97% can ensure that the organosilicon polymer has good heat resistance at high temperatures, improving the heat resistance of the separator film. 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, improving the heat resistance of the separator film at high temperatures. The mass fraction of the cage polysilsesquioxane skeleton is crucial for improving the three-dimensional structural stability of the crosslinked polymer. A mass fraction of the cage polysilsesquioxane skeleton of 30% to 60% can ensure that the crosslinked polymer has good rigidity and structural stability, reducing the occurrence of structural collapse or brittle fracture in the separator film under heat abuse, which is conducive to improving the heat resistance of the separator film, thereby improving the reliability of the battery cell at high temperatures.

[0389] Therefore, by limiting the crosslinking degree, the mass fraction of silicon elements, and the mass fraction of the cage polysilsesquioxane skeleton of the organosilicon polymer to satisfy the above ranges, respectively, the structure of the organosilicon polymer containing a cage polysilsesquioxane skeleton can be regulated, so that the separator film including the polymer has good heat resistance at high temperatures, thereby improving the reliability of the battery cell.

[0390] In some embodiments, the mass fraction of the heat-resistant particles in the coating layer is 50% to 97%.

[0391] By limiting the mass fraction of the heat-resistant particles in the coating layer to satisfy the above range, the coating layer can have structural stability and air permeability, improving the heat resistance of the separator film, thereby improving the reliability of the battery cell.

[0392] In some embodiments, the coating layer does not include inorganic particles.

[0393] In some embodiments, the coating layer includes inorganic particles, and the mass fraction of the inorganic particles is 0.1 wt.% to 50 wt.% based on the total mass of the coating layer.

[0394] In other embodiments, the coating includes inorganic particles, with a mass fraction of 50 wt.% to 92 wt.% 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. These inorganic particles have a large dielectric constant, which is beneficial for improving the ion transport efficiency in the coating.

[0395] In some embodiments, the coating further includes a first adhesive, which satisfies one or more of the following conditions: (1) the first adhesive 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, styrene-butadiene rubber, and fluororubber; (2) the first adhesive has a mass fraction of 3% to 15% in the coating.

[0396] The heat-resistant particles in the coating are interconnected and fixed by the first binder, reducing the likelihood of them falling off during coating and use. The mass fraction of the first binder meets the aforementioned range, ensuring adhesion while minimizing the reduction in the proportion of heat-resistant particles in the coating due to excessive binder. This balances the stability and heat resistance of the coating, improving the heat resistance of the release liner.

[0397] In some embodiments, the separator further includes second adhesive particles located in the coating, or the separator further includes an adhesive layer disposed on at least one side of the coating away from the base film, and the second adhesive particles are located in the adhesive layer; the second adhesive particles satisfy one or more of the following conditions: (1) the second adhesive particles include at least one of polyvinylidene fluoride, poly(vinylidene fluoride-copolymer-trichloroethylene), poly(vinylidene fluoride-copolymer-trifluorochloroethylene), poly(vinylidene fluoride-copolymer-trifluoroethylene), poly(vinylidene fluoride-copolymer-tetrafluoroethylene), poly(vinylidene fluoride-copolymer-hexafluoropropylene), polyacrylate, polymethyl methacrylate, and polyacrylonitrile; (2) the number average particle size of the second adhesive particles is 5 μm to 20 μm.

[0398] 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 improving the cycle performance of the battery cell.

[0399] In some embodiments, the second binder particles are disposed in the coating layer.

[0400] In some other embodiments, the adhesive layer can also be disposed on at least a part of the surface of the coating layer away from the porous base film, the heat-resistant particles are disposed in the coating layer, and the second binder particles are disposed in the adhesive layer.

[0401] In some other embodiments, the adhesive layer can also be disposed on at least a part of the surface of the coating layer away from the porous base film, the heat-resistant particles are disposed in the coating layer, and the second binder particles are disposed in the adhesive layer.

[0402] In some embodiments, the second binder particles are disposed in the coating layer.

[0403] In some other embodiments, the adhesive layer can also be disposed on at least a part of the surface of the coating layer away from the porous base film, the heat-resistant particles are disposed in the coating layer, and the second binder particles are disposed in the adhesive layer.

[0404] In some other embodiments, the adhesive layer can also be disposed on at least a part of the surface of the coating layer away from the porous base film, the heat-resistant particles are disposed in the coating layer, and the second binder particles are disposed in the adhesive layer.

[0405] The separator film can be prepared according to methods known in the art.

[0406] In some embodiments, the 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 after drying, the separator film is obtained.

[0407] In some embodiments, the slurry can further include the second binder particles, and after drying of the slurry, the polymer binder particles are embedded in the organic particles and form protrusions on the surface of the coating layer.

[0408] In some embodiments, the method for preparing the separation film can include: coating a slurry including heat-resistant particles and first binder particles on at least one side of a porous base film to form a coating layer after drying; and coating a slurry including second binder particles on at least a portion of a surface of the coating layer away from the porous base film to obtain a separation film including a bonding layer after drying.

[0409] In some embodiments, the method for preparing the separation film can include: coating a slurry including heat-resistant particles and first binder particles on one side of a porous base film, and coating a slurry including second binder particles on at least a portion of a surface of the other side of the porous base film to obtain a separation film including a bonding layer after drying.

[0410] In some embodiments, the solvent of the slurry can be water, for example, deionized water.

[0411] In some embodiments, the slurry can further include other components, for example, can further include dispersants and / or wetting agents, etc.

[0412] 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 thermal shrinkage of the separation film is less than or equal to 5% when heated at 130°C for 1 h; (4) the transverse thermal shrinkage of the separation film is less than or equal to 5% when heated 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.

[0413] 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 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.

[0414] 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 separation film and reduces the energy density of the battery cell. A coating layer with a thickness of 1 μm to 10 μm can provide a uniform and dense heat-resistant coating layer, thereby improving the heat resistance of the separation film and the reliability of the battery cell.

[0415] The areal density of the coating layer is 0.5 g / m 2 ~ 5 g / m 2 , which can ensure that the coating layer has moderate quality, can improve the stability and heat resistance of the separation film, and will not significantly increase the weight of the separation film, thereby being conducive to the energy density and reliability of the battery cell.

[0416] 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.

[0417] In some embodiments, the peeling force between the coating layer and the porous base film of the separator film can be greater than or equal to 28 N / m.

[0418] In the embodiments of the present application, the peeling force between the coating layer and the porous base film of the separator film can be tested according to the following method: cutting the separator film into 3 pieces of 2.5 cm x 15 cm, pasting the pieces on a test steel plate, using a test tape with a width of 2 cm to paste on the side of the separator film to be tested, using a tensile testing machine, clamping the steel plate on one side and the tape on the other side to perform 180° peeling test, taking the average of the peeling forces of the 3 pieces as the peeling force between the coating layer and the porous base film of the separator film. The tensile rate is 50 mm / min.

[0419] 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.

[0420] In some embodiments, the material of the porous base film of the separator film 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, without particular limitation. When the porous base film is a multi-layer composite film, the materials of the layers can be the same or different, without particular limitation.

[0421] In some embodiments, the positive electrode sheet, the negative electrode sheet and the separator film can be made into an electrode assembly by a winding process or a stacking process.

[0422] [Battery device]

[0423] In some embodiments, the battery cell is a battery device, and the battery device can include one or more battery cells.

[0424] 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 body and a plurality of battery cells contained in the box body, and the plurality of battery cells are connected in series, in parallel or in a mixed manner. Among them, the battery cells can directly form the battery pack, or first form a battery module, and then form the battery pack by a plurality of battery modules.

[0425] The battery device 10 can further include a box 11, which is a hollow structure inside which the plurality of battery cells 3 are accommodated. For example, the plurality of battery cells 3 are placed in the box 11 in parallel, series or mixed combination with each other. The box 11 can include a first box part 111 and a second box part 112, which are mutually covered 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, 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 and each have 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 mutually buckled to form a box 11 having a closed cavity, which can be used to accommodate the plurality of battery cells 3. The plurality of battery cells 3 are placed in the box 11 formed by buckling the first box part 111 and the second box part 112 in parallel, series or mixed combination with each other.

[0426] 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 is covered at the opening of the second box part 112 to form a box 11 having a closed cavity, which can be used to accommodate the plurality of battery cells 3.

[0427] In some embodiments, the battery device 10 can further include other components. For example, the battery device 10 can further include a current collecting component, which can be used to realize the electrical connection between the plurality of battery cells 3, for example, in parallel, series or mixed combination. Specifically, the current collecting component can realize the electrical connection between the battery cells 3 by connecting the electrode terminals of the battery cells 3; or the current collecting component can also realize the electrical connection between the battery cells 3 by connecting other components of the battery cells 3. The current collecting component can be fixed to the corresponding components of the battery cells 3 by welding, for example, can be fixed to the electrode terminals, the sealing structure or the shell, etc., and the embodiments of the present application are not limited thereto.

[0428] 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.

[0429] 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.

[0430] [Electric device]

[0431] 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 device, and can also be used as an energy storage unit of an electric device. The electric device 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.

[0432] As an electric device, the battery cell, the battery module or the battery pack can be selected according to the use requirement thereof.

[0433] The electric device 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 electric device is not specially limited in the embodiments of the present application.

[0434] FIG. 4 is a schematic diagram of an electric device according to an embodiment of the present application. As shown in FIG. 4, the present application provides an electric device, which can be a vehicle 1, and the electric device includes the battery cell in the above embodiments.

[0435] 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 electric 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 inside, 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 for power supply of the vehicle 1, for example, the battery device 10 can be used as an operating power supply of the vehicle 1, and is used for the circuit system of the vehicle 1, for example, for the working power demand of the vehicle 1 during starting, navigation and running. In another embodiment of the present application, the battery device 10 can not only be used as an operating power supply of the vehicle 1, but also be used as a driving power supply of the vehicle 1, to replace or partially replace fuel or natural gas to provide driving power for the vehicle 1.

[0436] As another example, the device can be a mobile phone, a tablet computer, a notebook computer, etc. The device generally requires thinning, and a battery monomer can be used as a power source.

[0437] Fig. 5 is a schematic diagram of a power consuming device according to another embodiment of the present application. As shown in Fig. 5, the present application provides a power consuming device, which is a storage device 2. The storage device 2 can include a plurality of battery devices 10. The storage device 2 can be applied to a power storage station to store and release electric energy.

[0438] Alternatively, the power consuming device can also be a storage device, a lighting device, a spacecraft, etc., and embodiments of the present application include but are not limited to the above.

[0439] Hereinafter, embodiments of the present application will be described. The embodiments described below are exemplary and are intended to explain the present application only, and should not be understood as limiting the present application. In the embodiments, specific techniques or conditions not mentioned are performed according to the techniques or conditions described in the literature in the art or according to the product manual. The reagents or instruments not mentioned by the manufacturer are all conventional products that can be obtained commercially.

[0440] [Examples and Comparative Examples]

[0441] Example 1

[0442] (1) Preparation of the negative electrode sheet:

[0443] 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 at a weight ratio of 96.5:1.0:1.3:1.2, and then fully stirred and mixed uniformly 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 the negative electrode sheet. The solid content of the negative electrode slurry was 60%.

[0444] (2) Preparation of the positive electrode sheet:

[0445] The lithium iron phosphate (LiFePO4), polyvinylidene fluoride (PVDF), conductive carbon black (Super-P), and dispersant polyvinylpyrrolidone (PVP) were dissolved in the solvent N-methyl pyrrolidone (NMP) at a mass ratio of 95:2.5:1.5:1.0, and then uniformly stirred in a vacuum stirrer to obtain a positive electrode slurry. The slurry was coated on both sides of an aluminum foil, and then dried, cold pressed, and cut to obtain the positive electrode sheet.

[0446] (3) Preparation of the separator

[0447] ① Preparation of heat-resistant particles (organic silicon polymer containing a cage polysilsesquioxane skeleton):

[0448] In a 5L flask equipped with a stirrer, a thermometer and a reflux condenser, 3200g of deionized water, 9ml of hydrochloric acid were added, stirred and 120g of methyltrimethoxysilane was added, hydrolysis reaction at 32°C for 2h, then 75ml of ammonia was added, reaction at 32°C for 2h, and then the temperature was raised to 90°C and the reaction was continued for 12h to obtain a dispersion of heat-resistant particles. The water content was evaporated to obtain a dispersion with a solid content of 20% for standby. The standby dispersion was dried to obtain the corresponding heat-resistant particle powder. The crosslinking degree of the heat-resistant particle powder was tested by PQ001 nuclear magnetic resonance analyzer. Figure 6 is the crosslinking degree test result of the heat-resistant particle powder of the application example, as shown in Figure 6, the heat-resistant particle is a crosslinked polymer, and the calculated crosslinking degree is 93.3%.

[0449] The heat-resistant particle powder was tested by pyrolysis-gas chromatography-mass spectrometry (Py-GC / MS). Figure 7 is the pyrolysis spectrum of the heat-resistant particle powder of the application example. As shown in Figure 7, by comparing with the EVA standard pyrolysis spectrum in the NIST library, the characteristic ions corresponding to The heat-resistant particle includes a cage-like polysilsesquioxane skeleton.

[0450] The glass transition temperature T g and the melting point of the heat-resistant particle were tested by differential scanning calorimetry (DSC). The heat-resistant particle had no T g g and no melting point below 300°C.

[0451] The density of the heat-resistant particle was tested by a true density tester. The true density of the heat-resistant particle was 1.33g / cm 3 .

[0452] The volume distribution particle size Dv50 of the heat-resistant particle was tested by a Malvern 3000 (MasterSizer 3000) laser particle size analyzer. The volume distribution particle size Dv50 of the heat-resistant particle was 320nm.

[0453] The heat-resistant particle ethylene carbonate, the heat-resistant particle ethylene carbonate, and the methyl ethyl carbonate mixed solution with a volume ratio of 3:7 were soaked at 60°C for 7 days. The dissolution rate of the heat-resistant particle was tested. The dissolution rate of the heat-resistant particle soaked at 60°C for 7 days was 0.1%.

[0454] ②Preparation of the isolation film: a commercially available polyethylene microporous film (Zhao Gao Electronics Technology Co., Ltd.) with a thickness of 7μm and an average pore size of 50nm was used as the porous base film; the dispersion liquid containing the heat-resistant particles prepared above and the adhesive polyacrylic acid were mixed uniformly in deionized water at a solid mass ratio of 93:7 to obtain a coating slurry.

[0455] The commercially available polyvinylidene fluoride particles (Arkema), the binder polyacrylate were uniformly stirred in deionized water according to a solid content mass ratio of 90:10 to obtain a binder layer slurry. Among them, the Dv50 of the polyvinylidene fluoride particles was 6.5 μm.

[0456] The coating slurry was uniformly coated on both surfaces of the porous base film at a loading (single side) of 2.6 g / m 2 , the solvent was removed by drying, and the thickness of the single-side coating was 1.5 μm. Then the binder layer slurry was sprayed on the coating, and the isolation film was obtained by drying and slitting processes. Among them, the air permeability of the isolation film was 201 s / 100 mL.

[0457] (4) Preparation of electrolyte:

[0458] In an argon atmosphere glove box (H2O <0.1 ppm, O2 <0.1 ppm), ethylene carbonate (EC), methyl ethyl carbonate (EMC), dimethyl carbonate (DMC) were mixed according to a volume ratio of 1:1:1 to obtain an organic solvent, and then LiPF6 and the additive vinylene carbonate (VC) were dissolved in the above mixed organic solvent to obtain an electrolyte. Among them, the concentration of LiPF6 was 1 mol / L, and the mass fraction of vinylene carbonate (VC) was 2%.

[0459] (5) Preparation of battery cell:

[0460] Preparation of 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 isolate the positive and negative electrode sheets, and the electrode assembly was obtained by winding. The tab of the electrode assembly was connected with the end cover (for example, the tab was welded and connected with the end cover through a connecting member), the electrode assembly was placed in an aluminum shell, and after drying, the electrolyte was injected, and then packaged to obtain a battery cell.

[0461] [Example 2-5]

[0462] The difference between Example 2 and Example 1 is that in the preparation process of heat-resistant particles, the "temperature is raised to 90℃ and the reaction is continued for 12h" in Example 1 is adjusted to "temperature is raised to 90℃ and the reaction is continued for 6h", and the heat-resistant particle dispersion liquid is obtained, and the rest of the preparation process is similar to Example 1.

[0463] The difference between Example 3 and Example 1 is that in the preparation process of heat-resistant particles, the "temperature is raised to 90℃ and the reaction is continued for 12h" in Example 1 is adjusted to "temperature is raised to 70℃ and the reaction is continued for 24h", and the heat-resistant particle dispersion liquid is obtained, and the rest of the preparation process is similar to Example 1.

[0464] Example 4 differs 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", and a heat-resistant particle dispersion liquid is obtained, and the rest of the preparation process is similar to Example 1.

[0465] Example 5 differs 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 of the dispersion liquid is 20% by subsequent evaporation of water content. The dispersion liquid is dried to obtain the corresponding heat-resistant particle powder.

[0466] [Example 6]

[0467] (3) Preparation of the separation film (organic silicon polymer containing phenyl)

[0468] 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 add the above pre-emulsion under nitrogen protection and stirring conditions, react for 4h, then heat to 90°C and cure for 4h to obtain an emulsion containing heat-resistant particles.

[0469] The crosslinking degree of the heat-resistant particle powder was tested by PQ001 nuclear magnetic resonance analyzer. The heat-resistant particles are crosslinked polymers, and the calculated crosslinking degree is 90.7%.

[0470] 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, the characteristic ions corresponding to were detected, which can be inferred that the heat-resistant particles contain benzene rings.

[0471] The glass transition temperature T g and the melting point of the heat-resistant particles were tested by differential scanning calorimetry (DSC), and the heat-resistant particles had no T g.g No melting point.

[0472] The density of the heat-resistant particles was tested by a true density tester, and the true density of the heat-resistant particles was 1.39 g / cm 3 .

[0473] The volume distribution particle size Dv50 of the heat-resistant particles was tested by a Malvern 3000 (MasterSizer 3000) laser particle size instrument, and the volume distribution particle size Dv50 of the heat-resistant particles was 250 nm.

[0474] The heat-resistant particles were 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 the dissolution rate of the heat-resistant particles was tested. The dissolution rate of the heat-resistant particles soaked at 60°C for 7 days was 0.5%.

[0475] 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 dispersion liquid containing heat-resistant particles prepared above and the adhesive polyacrylic acid were mixed uniformly in deionized water at a solid mass ratio of 92:8 to obtain a coating slurry.

[0476] 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.

[0477] 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. 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 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.

[0478] [Examples 6-10]

[0479] Example 7 differed from Example 6 in that in the preparation process of the heat-resistant particles, the mass ratio of "3-methacryloxypropyl trimethoxysilane to divinylbenzene was 85:12" in Example 6 was adjusted to "3-methacryloxypropyl trimethoxysilane to divinylbenzene was 92:5", and the heat-resistant particle-containing emulsion, and the rest of the preparation process was similar to Example 6.

[0480] Example 8 differs from Example 6 in that, in the heat-resistant particle preparation process, the "mass ratio of 3-methacryloxypropyltrimethoxysilane to divinylbenzene is 85:12" in Example 6 is adjusted to "mass ratio of 3-methacryloxypropyltrimethoxysilane to divinylbenzene is 89:8", the rest of the preparation process is similar to Example 6.

[0481] Example 9 differs from Example 6 in that, in the heat-resistant particle preparation process, the "mass ratio of 3-methacryloxypropyltrimethoxysilane to divinylbenzene is 85:12" in Example 6 is adjusted to "mass ratio of 3-methacryloxypropyltrimethoxysilane to divinylbenzene is 87:10", the rest of the preparation process is similar to Example 6.

[0482] Example 10 differs from Example 6 in that, in the heat-resistant particle preparation process, the "mass ratio of 3-methacryloxypropyltrimethoxysilane to divinylbenzene is 85:12" in Example 6 is adjusted to "mass ratio of 3-methacryloxypropyltrimethoxysilane to divinylbenzene is 82:15", the rest of the preparation process is similar to Example 6.

[0483] [Examples 11-14]

[0484] In Example 11, commercially available phenol and formaldehyde raw materials are placed in a curing oven (molar ratio of phenol to formaldehyde is 1:2.5), the atmosphere is set to air atmosphere, the temperature is set to 130°C, and the temperature is maintained for 3h; after the end, the temperature of the curing oven is raised to 240°C, and the temperature is maintained for 4h. After the end of the two curing, the cured phenolic resin material is taken out, placed in air for natural cooling, and then crushed, sanded, sieved, and demagnetized 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.

[0485] In Example 12, commercially available melamine formaldehyde resin particles are cured in an air atmosphere at 255°C for 4h, and then crushed, sanded, sieved, and demagnetized to obtain melamine formaldehyde resin particles with a volume average particle size Dv50 of 420nm. The molar ratio of formaldehyde to melamine in the melamine formaldehyde resin is 2.5:1.

[0486] In Example 13, 0.8 g of sodium dodecyl sulfate, 80 mg of sodium persulfate, 20 ml of deionized water, 31 g of styrene, and 9 g of divinylbenzene were emulsified to obtain a pre-emulsion for standby. 140 g of deionized water was added to the reactor, and the temperature was raised to 65°C. The above-mentioned standby pre-emulsion was added dropwise under the conditions of nitrogen protection and stirring. After 4 hours of reaction, the temperature was raised to 72°C for 2.5 hours of curing reaction to obtain a cross-linked styrene organic particle emulsion with a volume average particle size Dv50 of 185 nm. The heat-resistant particles of Example 1 were replaced with the cross-linked styrene, and the remaining preparation method was similar to that of Example 1.

[0487] In Example 14, commercially available polybenzoxazine resin was completely cured by heating, and then subjected to crushing, screening and sanding treatment to obtain polybenzoxazine resin nanoparticles with a volume average particle size Dv50 of 350 nm. The heat-resistant particles of Example 1 were replaced with the polybenzoxazine resin nanoparticles, and the remaining preparation method was similar to that of Example 1.

[0488] Example 15 is different from Example 1 in that the heat-resistant particles of Example 1 are replaced with commercially available melamine cyanurate with a volume average particle size Dv50 of 550 nm.

[0489] [Comparative Example 1]

[0490] Comparative Example 1 is different from Example 1 in that an acrylate, acrylic acid, and acrylamide latex is used to carry out emulsion polymerization to obtain a polyacrylate latex with a particle size of about 180 nm. A 1000 mL four-necked flask equipped with mechanical stirring, a thermometer, and a condenser tube was charged with 200 g of mixed monomers, 6 g of sodium dodecyl sulfate emulsifier, 2 g of ammonium persulfate initiator, and 350 g of deionized water. The monomers were in a mass ratio of 70:15:15 of methyl acrylate, acrylic acid, and acrylamide. The mixture was emulsified at high speed for 40 min. Under the protection of nitrogen, the temperature was raised to 80°C for 4 hours of reaction, and then the temperature was lowered to below 35°C. The pH was adjusted to neutral, and the polyacrylate nanoparticles with a volume average particle size Dv50 of 180 nm were obtained by filtration. The heat-resistant particles of Example 1 were replaced with the polyacrylate nanoparticles.

[0491] Preparation of polyacrylate nanoparticles: An acrylate, acrylic acid, and acrylamide latex was used to carry out emulsion polymerization to obtain a polyacrylate latex with a particle size of about 180 nm. A 1000 mL four-necked flask equipped with mechanical stirring, a thermometer, and a condenser tube was charged with 200 g of mixed monomers, 6 g of sodium dodecyl sulfate emulsifier, 2 g of ammonium persulfate initiator, and 350 g of deionized water. The monomers were in a mass ratio of 70:15:15 of methyl acrylate, acrylic acid, and acrylamide. The mixture was emulsified at high speed for 40 min. Under the protection of nitrogen, the temperature was raised to 80°C for 4 hours of reaction, and then the temperature was lowered to below 35°C. The pH was adjusted to neutral, and the polyacrylate nanoparticles with a volume average particle size Dv50 of 180 nm were obtained by filtration. The heat-resistant particles of Example 1 were replaced with the polyacrylate nanoparticles.

[0492] [Comparative Example 2]

[0493] 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 were mixed to obtain a pre-emulsion (wherein the mass ratio of 3-methacryloxypropylmethyldimethoxysilane and 3-methacryloxypropyltrimethoxysilane was 3:97, and the added mass of 3-methacryloxypropylmethyldimethoxysilane was 1.8 g). A reactor was taken, 210 g of deionized water was added, and the temperature was raised to 80°C. Under the conditions of nitrogen protection and stirring, the above-mentioned pre-emulsion was added dropwise, and after 4 h of reaction, the temperature was raised to 90°C for 4 h of curing reaction, to obtain an emulsion containing heat-resistant particles.

[0494] Table 1 Product parameters of Examples 1-5 and Comparative Example 1 Table 2 Performance parameters of Examples 1-5 and Comparative Example 1

[0495] As shown in Examples 1-5 and Comparative Example 1 in Tables 1 and 2, the crosslinking degree of the heat-resistant particles was 85%-97%, and the mass fraction of the cage-like polysilsesquioxane skeleton was 40%-60%. The cage-like polysilsesquioxane skeleton could provide structural support and ensure that the heat-resistant particles had good heat resistance, thereby improving the overall structural integrity of the separator film at high temperatures and improving the reliability of the battery cell at high temperatures.

[0496] Table 3 Product parameters of Examples 6-10 and Comparative Example 2

[0497] Table 4 Performance parameters of Examples 6-10 and Comparative Example 2

[0498] As shown in Examples 6-10 and Comparative Example 2 in Tables 3 and 4, the crosslinking degree of the heat-resistant particles was 70%-98%, and the mass fraction of the phenyl group was 2%-12%. The heat-resistant particles had good heat resistance at high temperatures, and the separator film had a low thermal shrinkage rate, as well as a high cycle capacity retention rate and a high storage capacity retention rate, thereby having good heat resistance.

[0499] Table 5 Product parameters of Example 1 and Examples 11-15

[0500] Table 6 Performance parameters of Examples 11-15

[0501] In combination with the embodiments 1, 11-15 shown in Table 5 and Table 6, the heat-resistant particles in the embodiments of the present application include the above-mentioned substances, have lower dissolution rate and heat shrinkage rate, and higher cycle capacity retention rate and storage capacity retention rate, the isolation film has good heat resistance, the battery monomer has good high-temperature cycle performance, and the reliability of the battery monomer is improved.

[0502] The test methods of the physicochemical parameters and performance parameters involved in the embodiments of the present application are briefly introduced below. 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.

[0503] 1. Test method of crosslinking degree

[0504] As an example, the crosslinking degree of the crosslinked 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 21MHz, 0.5g of the cleaned and dried sample (the above-mentioned heat-resistant particles) is taken, is loaded into a clean sample tube and inserted into a probe with a specified depth, the probe coil diameter is 13mm, and the measurement is performed according to the manufacturer's instructions. Specifically: the proportion of the crosslinked part signal is calculated by collecting the entire polymer signal, and the crosslinking degree of the crosslinked polymer is obtained; the "crosslinking degree" or "T2 relaxation" test mode is selected in the software, and the relaxation decay curve is automatically obtained by the PQ001 nuclear magnetic resonance analyzer. During data processing, the software decomposes the relaxation components by exponential fitting, calculates and outputs the crosslinking degree results according to the degree of restriction of molecular chain movement.

[0505] 2. Test method of rigid structure

[0506] A thermal cracking-gas chromatography-mass spectrometry (Py-GC / MS) instrument can be used to test the rigid structure in the heat-resistant particles. Specifically, 0.5-1mg of the above-mentioned heat-resistant particles is weighed as a test sample, loaded into a quartz cracking tube of a thermal cracking instrument, cracked at 550°C for 1.2s, and the sample is tested for cracking into volatile small molecules in an inert gas (such as helium). Then it is introduced into a gas chromatograph-mass spectrometer, a HP-5ms (30m x 0.25mm x 0.25μm) chromatographic column is selected, the temperature is set to 30°C for 5min, increased to 250°C at 10°C / min, and maintained at 250°C for 5min, the carrier gas is high-purity helium, and the flow rate is 1.0mL / 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 cracking spectrum in the NIST library, the characteristic ions corresponding to the rigid structure are detected, it can be inferred that the organic silicon polymer includes rigid structure. The internal standard method is used to calculate the mass proportion of the characteristic rigid structure in the heat-resistant particles.

[0507] 3. Test of thermal shrinkage

[0508] The test of thermal shrinkage of the release film can refer 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 oven is set to 130℃, 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 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) thermal shrinkage is [(100-a) / 100]x100%, and the transverse (TD) thermal shrinkage is [(50-b) / 50]x100%. The average value of 3 parallel samples is taken as the test result.

[0509] 4. Test of cycle performance

[0510] The battery cell prepared above is charged to 3.65V at 1C under the condition that the test temperature is 45℃ and the voltage is 2.5-3.65V, then charged to 3.65V under constant voltage until the current is less than or equal to 0.05mA, and then rested for 5 min. Then, it is discharged to 2.5V at 1C, which is one charge-discharge cycle process. The discharge capacity of this time is the discharge capacity of the first cycle, which is recorded as Cap1. The battery cell is subjected to 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 of the secondary battery cell after 500 cycles is C=[Cap500 / Cap1]x100%, 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.

[0511] 5. Test of storage performance

[0512] The secondary battery cell is charged to 3.65V at 1 / 3C under constant current at 25℃, then charged to 3.65V under constant voltage until the current is 0.05C, and then rested for 5 min. Then, it is discharged to 2.5V at 1 / 3C constant current. Then, the secondary battery cell is charged to 3.65V at 1 / 3C constant current, and then charged to 3.65V under constant voltage until the current is 0.05C. At this time, the secondary battery cell is in a full charge state, and the obtained charge capacity is recorded as the pre-storage capacity C0. The capacity of the secondary battery cell in a full charge state after being stored in a 45℃ constant temperature box for 100 days is recorded as the post-storage capacity C1. The capacity retention rate of the secondary battery cell stored at 45℃ for 100 days is C1 / C0x100%.

[0513] 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, function, and effect as the technical idea of the present application are included in the technical scope of the present application. Furthermore, other modes constructed by applying various modifications to the embodiments, or by combining part of the configurations of the embodiments, which can be conceived by those skilled in the art without departing from the spirit of the present application, are also included in the scope of the present application.

Claims

1. 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 a first binder, The first binder is used to bond the heat-resistant particles to the porous base film; The heat-resistant particles comprise an organic compound; the main chain or side chain of the organic compound has a rigid structure, the rigid structure comprises a planar cyclic conjugated group and / or a covalent polyhedral skeleton; when the organic compound is a small molecule compound, a condensation polymer or a copolymer, the mass fraction of the rigid structure in the organic compound is 40% to 99%; when the organic compound is a condensation type copolymer, the mass fraction of the rigid structure in the organic compound is 2% to 30%.

2. The battery cell of claim 1, wherein, The planar cyclic 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 cyclic conjugated group comprises any one of a phenyl group and a triazine ring group.

3. 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 [SiO 3 / 2 ] n Formula (I) 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.

4. The battery cell according to any one of claims 1 to 3, characterized in that The organic compound is a cross-linked polymer, and the cross-linking degree of the cross-linked polymer is 70% to 98%.

5. The battery cell of any one of claims 1-4, wherein, The cross-linked polymer comprises at least one of a phenol aldehyde resin type polymer, a polymer containing a triazine ring group, a phenyl-containing organic silicon polymer, a cage-like poly silesquioxane skeleton-containing organic silicon polymer, and a cross-linked styrene type polymer.

6. The battery cell of claim 5, wherein, The phenyl group-containing silicone polymer includes monomers and crosslinking agents represented by formula (II) and is polymerized, wherein R1, R2 each independently comprises a C1-C4 alkyl group, 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 a divinylbenzene.

7. The battery cell according to claim 5 or 6, wherein the phenyl-containing organic silicon polymer satisfies at least one 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 comprises a silicon element, and the mass fraction of the silicon element in the phenyl-containing organic silicon cross-linking resin is 10% to 25%; (3) the mass fraction of phenyl in the phenyl-containing organic silicon polymer is 2% to 12%.

8. The battery cell of claim 5, wherein, The cage-like poly silesquioxane skeleton-containing organic silicon polymer is obtained by hydrolysis and condensation of one or more monomers represented by formula (II), wherein R'1 comprises a C1-C3 alkyl group.

9. The battery cell according to claim 5 or 6, characterized in that, The cage-like poly silesquioxane skeleton-containing organic silicon polymer satisfies at least one of the following conditions: (1) the cross-linking degree of the cage-like poly silesquioxane skeleton-containing organic silicon polymer is 85% to 97%; (2) the cage-like poly silesquioxane skeleton-containing organic silicon polymer comprises a silicon element, and the mass fraction of the silicon element in the cage-like poly silesquioxane skeleton-containing organic silicon 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%.

10. The battery cell according to claim 1 or 2, characterized in that, The organic compound is a small molecule compound, and the small molecule compound includes one or more of melamine cyanurate, melamine polyphosphate, and melamine pyrophosphate.

11. 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 heat-resistant particles do not have an oxidation peak in a cyclic voltammetry curve in a voltage range of 0 to 4.4 V in the first cycle; (3) The glass transition temperature of the heat-resistant particles is greater than or equal to 150 DEG C, or the heat-resistant particles do not have a glass transition temperature at 300 DEG C; (4) the initial thermal weight loss temperature T of the heat-resistant particles 3d greater than or equal to 250°C; (5) The heat-resistant particles have a dissolution rate of less than or equal to 5% when immersed in a mixed solvent of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 3:7 at 60 DEG C for 7 days; (6) the heat resistant particles have a true density of 0.8 g / cm 3 ~ 2.0 g / cm 3 .

12. The battery cell of any one of claims 1-11, wherein, The mass fraction of the heat-resistant particles in the coating layer is 50% to 97%.

13. The battery cell of any one of claims 1-12, wherein, The coating layer further includes a first binder satisfying 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, styrene-butadiene rubber, and fluorine rubber; (2) The mass fraction of the first binder in the coating layer is 3% to 15%.

14. The battery cell of any one of claims 1-13, wherein, The release film further includes second binder particles located in the coating layer, or the release film further includes a bonding layer provided 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 include 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 5 μm to 20 μm.

15. The battery cell of any one of claims 1-14, wherein, The release film satisfies at least one of the following conditions: (1) The thickness of the coating layer is 0.5 μm to 10 μm; (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 release film is less than or equal to 5% when heated at 130 DEG C for 1 h; (4) The transverse heat shrinkage rate of the release film is less than or equal to 5% when heated at 130 DEG C for 1 h; (5) The air permeability of the release film is 150 s / 100 mL to 500 s / 100 mL.

16. A battery device characterized by comprising: A battery cell as claimed in any one of claims 1 to 15.

17. An electrical device, characterized by A battery cell as claimed in any one of claims 1 to 15, or a battery device as claimed in claim 16.

18. An isolating film, characterized by, Comprising: a porous base film and a coating layer disposed on at least one side of the porous base film; the coating layer comprises 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 comprise an organic compound; the main chain or side chain of the organic compound has a rigid structure, the rigid structure comprises a planar cyclic conjugated group and / or a covalent polyhedral skeleton; when the organic compound is a small molecule compound, a condensation polymer or a copolymer, the mass fraction of the rigid structure in the organic compound is 40% to 99%; when the organic compound is a condensation type copolymer, the mass fraction of the rigid structure in the organic compound is 2% to 30%.

19. The separator membrane of claim 18, wherein, the planar cyclic 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, a substituted or unsubstituted triazine ring group; optionally, the planar cyclic conjugated group comprises any one of a phenyl group and a triazine ring group.

20. The separator membrane according to claim 18 or 19, characterized in that, the covalent polyhedral skeleton comprises a skeleton formed by a compound represented by formula (I), R a [SiO 3 / 2 ] n Formula (I) 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.

21. The separator membrane according to any one of claims 18-20, characterized in that, the organic compound is a cross-linked polymer, and the cross-linking degree of the cross-linked polymer is 70% to 98%.

22. The separator membrane according to any one of claims 18-21, 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 organosilicon polymer, a cage-like polyhedral silsesquioxane skeleton-containing organosilicon polymer, and a cross-linked styrene-based polymer.

23. The separator membrane of claim 22, wherein, The phenyl group-containing silicone polymer includes monomers and crosslinking agents represented by formula (II) and is polymerized, wherein R1, R2 each independently comprises a C1-C4 alkyl group, 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.

24. The separator membrane according to claim 22 or 23, characterized in that, the phenyl-containing organosilicon polymer satisfies at least one of the following conditions: (1) the cross-linking degree of the phenyl-containing organosilicon polymer is 75% to 95%; (2) the phenyl-containing organosilicon polymer comprises a silicon element, and the mass fraction of the silicon element in the phenyl-containing organosilicon cross-linking resin is 10% to 25%; (3) the mass fraction of the phenyl group in the phenyl-containing organosilicon polymer is 2% to 12%.

25. The separator membrane of claim 22, wherein, the cage-like polyhedral silsesquioxane skeleton-containing organosilicon polymer is obtained by hydrolysis and condensation of one or more monomers represented by formula (II), wherein R'1 comprises a C1-C3 alkyl group.

26. The separator membrane of claim 22 or 23, wherein, the cage-like polyhedral silsesquioxane skeleton-containing organosilicon polymer satisfies at least one of the following conditions: (1) the cross-linking degree is 85% to 97%; (2) the cage-like polyhedral silsesquioxane skeleton-containing organosilicon polymer comprises a silicon element, and the mass fraction of the silicon element in the cage-like polyhedral silsesquioxane skeleton-containing organosilicon polymer is 25% to 45%. (3) in the cage polysilsesquioxane skeleton-containing silicone polymer, the mass fraction of the cage polysilsesquioxane skeleton-containing is 40%-60%.

27. The separator film according to claim 18 or 19, characterized in that, The organic compound is a small molecule compound, and the small molecule compound comprises one or more of melamine cyanurate, melamine polyphosphate, and melamine pyrophosphate.

28. The separator membrane of any one of claims 18-27, wherein, The mass fraction of the heat-resistant particles in the coating is 50%-97%.

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