Battery cell, battery device and electric device

Abstract

Provided in the present application are a battery cell, a battery device and an electric device. The battery cell comprises a positive electrode sheet, a negative electrode sheet and a separator, wherein the separator is located between the positive electrode sheet and the negative electrode sheet; the separator comprises a porous base film and a coating arranged on at least one side of the porous base film; the coating comprises organic compound particles having a spherical or near-spherical morphology; and in the cross section of the coating in the thickness direction of the separator, on the basis of the total number of the organic compound particles, particles having a particle size R1 that satisfies 0<R1≤100 nm account for 0% to 0.5%, particles having a particle size R2 that satisfies 100<R2≤300 nm account for 65% to 85%, and particles having a particle size R3 that satisfies 300<R2≤800 nm account for 15% to 35%. The technical solution of the present application is beneficial for improving the reliability and cycle performance of the battery cell.

Description

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

[0001] This application claims priority to Chinese Patent Application No. 202411388765.7, filed on September 30, 2024, entitled “Silicon-containing organic resin particles, method for producing silicon-containing organic resin particles, dispersion liquid of silicon-containing organic resin particles, separator, secondary battery cell, battery device, and electric device,” the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[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 to energy storage power systems such as hydroelectric, thermal, wind, and solar power stations, as well as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields, thereby achieving great development.

[0004] With the development and application of battery technology, higher requirements are placed on the cycle performance of battery cells. The separator and the electrolyte are important development parts of the battery cell, and the heat resistance of the separator and the wettability of the electrolyte in the separator will affect the cycle performance of the battery cell. Therefore, how to improve the cycle performance 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 and cycle performance 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 organic compound particles; the morphology of the organic compound particles is spherical or spheroidal; and in a cross section of the coating layer along the thickness direction of the separator, based on the total number of the organic compound particles, the number ratio of particles with a particle size R1 satisfying 0 < R1 ≤ 100 nm is 0% to 0.5%, the number ratio of particles with a particle size R2 satisfying 100 < R2 ≤ 300 nm is 65% to 85%, and the number ratio of particles with a particle size R3 satisfying 300 < R2 ≤ 800 nm is 15% to 35%.

[0006] Compared with inorganic particles with a large density, the organic compound particles have a small density and light mass, which is conducive to improving the energy density of the battery monomer. In the spherical or spherical organic compound particles, 0% to 0.5% of the small particle size R1 can fill the gap between the larger particles, reduce the large pores and surface defects in the coating, thereby improving the compactness and overall uniformity of the coating, enhancing the structural stability of the isolation film under high temperature conditions, and reducing the risk of thermal shrinkage. 65% to 85% of the medium particle size R2 are stacked with each other to provide a continuous penetration path for the electrolyte, which is conducive to the rapid infiltration of the electrolyte throughout the coating. 15% to 35% of the larger particle size R3 can form a supporting force in the coating to help maintain the stability of the infiltration channel and ensure the normal penetration of the electrolyte in the isolation film. By setting the organic compound particles with different particle size ranges in the coating and controlling the proportion of the total particle number, the battery monomer can have high energy density, the isolation film can have heat resistance and good electrolyte infiltration performance, and the reliability and cycle performance of the battery monomer can be improved.

[0007] In a possible implementation, the average particle size of the organic compound particles is 80nm to 720nm, and / or the maximum particle size of the organic compound particles is 500nm to 800nm, and / or the minimum particle size of the organic compound particles is 50nm to 100nm.

[0008] In the embodiments of the present application, by limiting the average particle size, the maximum particle size and the minimum particle size of the organic compound particles, the electrolyte infiltration channel inside the coating can be further controlled. The average particle size is 80nm to 720nm, which ensures the overall uniformity of the organic compound particles accumulated in the coating, and is conducive to obtaining a coating with connected channels. The maximum particle size is 500nm to 800nm, which prevents surface protrusions or uneven infiltration channels caused by too large particles in the coating, thereby reducing coating defects and local electrolyte infiltration. The minimum particle size is 50nm to 100nm, which can reduce the phenomenon of excessive filling of channels in the coating by superfine particles, and ensure that the coating maintains a smooth penetration path. Through the above control of the particle size of the organic compound particles, the electrolyte can quickly and uniformly penetrate in the coating, thereby improving the cycle performance of the battery monomer.

[0009] In a possible implementation, the roundness of the organic compound particles is 0.5 to 1.0.

[0010] In the embodiments of the present application, when the roundness of the organic compound particles is high, the shape of the particles is closer to a regular sphere, the friction and stacking resistance between the particles are small during the dispersion of the slurry, and thus the slurry flows more uniformly, which can form a coating with uniform thickness and good pore structure after coating and drying, so that the electrolyte can enter the interior more quickly and uniformly when contacting the coating, thereby facilitating the improvement of the wettability of the electrolyte in the separator membrane. The particles with regular morphology have fewer corners and irregular protrusions, and the probability of local stress concentration or micro-cracks in the coating is low, which is beneficial to the structural stability of the coating. At the same time, the surface of the particles with high roundness can fully contact with the electrolyte, the surface wetting resistance is low, the electrolyte can quickly penetrate along the uniform and continuous electrolyte infiltration channel between the particles, and the local retention and uneven infiltration phenomenon is reduced, thereby achieving good electrolyte wetting effect and ion conduction efficiency. Therefore, the roundness of the organic compound particles meets the above range, which can improve the wettability of the electrolyte in the separator membrane, thereby improving the cycle performance of the battery cell.

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

[0012] On the one hand, the cross-linked polymer has a three-dimensional network structure, which can maintain a stable spatial configuration under thermal stress, so that the separator membrane has good heat resistance. On the other hand, by controlling the cross-linking degree of the cross-linked polymer to be 70% to 98%, the coating particles can have good heat resistance at high temperatures, the heat resistance of the separator membrane is improved, the overall structural integrity of the separator membrane at high temperatures is ensured, and thus the reliability of the battery cell at high temperatures is improved.

[0013] In a possible implementation, the cross-linked polymer includes a silicone polymer containing a siloxane structure.

[0014] In the embodiments of the present application, the siloxane structure of the silicone polymer can improve the surface polarity of the cross-linked polymer, produce strong interaction with the solvent molecules in the electrolyte, improve the affinity of the coating for the electrolyte, and thus improve the wettability of the electrolyte. The cross-linked polymer includes a silicone polymer containing a siloxane structure, and because the silicone polymer contains a siloxane bond, the bond energy of the siloxane bond is high and the siloxane bond is not easy to decompose at high temperatures, which can be beneficial to further improve the thermal stability of the material, thereby enhancing the heat resistance of the coating of the separator membrane. In addition, compared with inorganic particles, the density of the silicone polymer is low, and the overall mass of the coating can be reduced at the same thickness, which is beneficial to improve the energy density of the battery cell. Therefore, the cross-linked polymer includes a silicone polymer containing a siloxane structure, which can improve the structural stability of the coating and also improve the wettability of the electrolyte, thereby improving the cycle performance of the battery cell.

[0015] In a possible implementation, the organosilicon polymer containing siloxane structure includes phenyl groups, and the organosilicon polymer containing siloxane structure is obtained by polymerization of the monomer and the crosslinking agent shown in formula (I), In formula (I), R1 and R2 are each independently selected from C1-C4 alkyl groups, C2-C4 alkenyl groups, R3 includes C1-C4 alkyl groups or C4-C8 (meth) acryloxyalkyl groups, and R4 includes C2-C8 alkenyl groups or C4-C8 (meth) acryloxyalkyl groups; and the crosslinking agent includes divinylbenzene.

[0016] In the embodiments of the present application, the organosilicon polymer containing siloxane structure is obtained by polymerization of the monomer and the crosslinking agent divinylbenzene, and the organosilicon polymer containing siloxane structure has a three-dimensional network skeleton formed by phenyl groups, the monomer and the crosslinking agent, so that the material has higher glass transition temperature and thermal decomposition temperature, thereby improving the heat resistance of the isolation film and the reliability of the battery cell.

[0017] In a possible implementation, the organosilicon polymer containing siloxane structure satisfies at least one of the following conditions: (1) the crosslinking degree of the organosilicon polymer containing siloxane structure is 75% to 95%; (2) the mass fraction of silicon elements in the organosilicon polymer containing siloxane structure is 10% to 25%; (3) the mass fraction of phenyl groups in the organosilicon polymer containing siloxane structure is 2% to 12%; and (4) the organosilicon polymer containing siloxane structure includes silicon hydroxyl groups.

[0018] In the embodiments of the present application, the organosilicon polymer containing siloxane structure is 75% to 95%, and 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 siloxane skeleton in the organosilicon polymer. The siloxane skeleton including silicon elements provides higher thermal decomposition temperature and oxidation resistance, so that the isolation film has structural stability in a high-temperature environment. The mass fraction of phenyl groups is 2% to 12%, which can introduce rigid structures of aromatic structures and conjugate effects, thereby further improving the heat resistance of the isolation film.

[0019] In a possible implementation, the organosilicon polymer containing siloxane structure includes a skeleton formed by a compound shown in formula (II), R a [SiO 3 / 2 ] n Formula (II) wherein n is an integer of 4 to 12, R a includes cycloalkyl groups, aryl groups, C1-C 12 alkyl groups, C1-C 12 alkenyl groups, and C1-C 12 alkynyl groups; and n is 8 and Ra Including C1 to C3 alkyl groups.

[0020] In this embodiment, by introducing the covalent polyhedral framework shown in formula (II) into the organic compound, a stable three-dimensional structure can be formed inside the molecule of the organic compound. This type of polyhedral framework has high symmetry and regularity, and the internal atoms are connected by strong covalent bonds. The molecular structure is not easily broken or collapsed under high temperature conditions, which is beneficial to improving the heat resistance of the isolation film. Moreover, the covalent polyhedral framework shown in formula (II) contains Si-O bonds, which have high bond energy and are not easily decomposed at high temperatures, which can further improve the thermal stability of the material. By selecting n as 8, R a The presence of C1 to C3 alkyl groups can further improve the rigidity and thermal stability of organic compounds. Organic compound particles can act as rigid support points at high temperatures, improving the heat resistance of the separator and thus enhancing the reliability of battery cells.

[0021] In one possible implementation, the organosilicon polymer containing a silicon-oxygen structure comprises one or more monomers of formula (II) obtained by hydrolysis and condensation polymerization. R'1 includes C1 to C3 alkyl groups.

[0022] In this embodiment, an organosilicon polymer with a complete cage-like structure and uniformly dispersed molecular chains can be obtained by employing the hydrolysis-condensation reaction of the monomer of formula (III). The resulting organosilicon polymer particles are uniformly distributed in the separator coating, forming a coating structure with good pore connectivity, which facilitates continuous electrolyte penetration and improves the wetting performance of the separator. Sufficient electrolyte wetting in the separator ensures uniform utilization of the negative electrode active material during charging and discharging, reducing low utilization or capacity decay of the negative electrode active material due to insufficient local wetting, thereby slowing down the battery capacity decay rate and improving the cycle performance of the battery cell.

[0023] In one possible implementation, the organosilicon polymer containing a silicon-oxygen structure satisfies at least one of the following conditions: (1) the degree of crosslinking of the organosilicon polymer containing a silicon-oxygen structure is 85% to 97%; (2) the mass fraction of silicon in the organosilicon polymer containing a silicon-oxygen structure is 25% to 45%; (3) the mass fraction of the skeleton composed of the compound shown in formula (II) in the organosilicon polymer containing a silicon-oxygen structure is 40% to 60%; (4) the organosilicon polymer containing a silicon-oxygen structure includes silanol groups.

[0024] In the embodiments of the present application, the cross-linking degree of the organosilicon polymer containing a siloxane structure is 85% to 97%, which ensures the structural stability of the organosilicon polymer at high temperatures; the higher mass fraction of silicon elements makes the polarity of the organosilicon polymer higher, and the affinity of the organosilicon polymer to the electrolyte is enhanced, thereby improving the diffusion speed and wetting ability of the electrolyte in the coating; the mass fraction of the skeleton formed by the compound represented by formula (II) in the organosilicon polymer containing a siloxane structure is 40% to 60%, which can ensure that the cross-linked polymer has good rigidity and structural stability, reduces the structural collapse of the separator film at high temperatures, and is beneficial to improving the heat resistance of the separator film, thereby improving the reliability of the battery cell at high temperatures.

[0025] By limiting the organosilicon polymer to meet at least one of the above conditions, the wetting performance of the electrolyte to the separator film and the heat resistance of the separator film can be improved, thereby improving the reliability and cycle performance of the battery cell.

[0026] In a possible implementation, the organic compound particles meet at least one of the following conditions: (1) the cyclic voltammetry curve of the organic compound particles in the first cycle has no oxidation peak in the voltage range of 0 to 4.4 V; (2) the organic compound particles have no glass transition temperature at 300°C; (3) the initial thermal weight loss temperature T 3d of the organic compound particles is greater than or equal to 250°C; (4) the dissolution rate of the organic compound particles is less than or equal to 5% when the organic compound particles are soaked in a mixed solvent composed of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 3:7 at 60°C for 7 days; (5) the true density of the organic compound particles is 0.8 g / cm 3 to 2.0 g / cm 3 .

[0027] In the embodiments of the present application, the cyclic voltammetry curve of the organic compound particles in the first cycle has no oxidation peak in the voltage range of 0 V to 4.40 V, which indicates that the organic compound particles are stable in the voltage range of 0 V to 4.40 V and 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 organic compound particles have no glass transition temperature below 300℃, which means that the DSC curve of the organic compound particles remains solid rigid below 300℃ and no molecular chain segment movement or softening occurs, 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 organic compound particles does not change significantly at high temperature, thereby the organic compound particles have high thermal stability and are not prone to thermal decomposition during the use of the battery cell and in a high temperature environment.

[0030] The organic compound particles have a dissolution of less than 5% after 7 days of electrolyte immersion at 60℃, and are not prone to precipitation or dissolution in the electrolyte environment, reducing the occurrence of electrolyte contamination or side reactions between the organic compound particles and the electrolyte during the cycle process 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.

[0031] The true density of the organic compound particles is 0.8g / cm 3 ~2.0g / cm 3 , which is beneficial to improve the capacity of the battery cell and obtain a battery cell with high energy density.

[0032] In one possible implementation, the mass ratio of the organic compound particles in the coating is 50% to 97%.

[0033] In the embodiments of the present application, by limiting the mass fraction of the organic compound 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.

[0034] In one possible implementation, the coating further includes a first binder, and the first binder satisfies at least one of the following conditions: (1) the first binder includes at least one of polyimide, polyetherimide, polyacrylic acid, polyacrylate, ethylene-vinyl acetate copolymer, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethylated polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose, acrylonitrile-styrene-butadiene copolymer, ethylene-propylene-diene terpolymer, sulfonated ethylene-propylene-diene terpolymer, styrene-butadiene rubber, and fluorine rubber; and (2) the mass fraction of the first binder in the coating is 3% to 15%.

[0035] In the embodiments of the present application, the organic compound particles in the coating layer are connected and fixed to each other by the first binder, reducing the situation of falling off of the organic compound particles during coating and use. The mass fraction of the first binder meets the above range, which can reduce the proportion of the organic compound particles in the coating layer due to excessive binder while ensuring the adhesion, so as to balance the stability and heat resistance of the coating layer, and improve the heat resistance of the isolation film.

[0036] In a possible implementation, the isolation film further comprises second binder particles, and the second binder particles are located in the coating layer, or the isolation film further comprises a bonding layer, the bonding layer is arranged on at least one side of the coating layer away from the base film, and the second binder particles are located in the bonding layer; the second binder particles meet at least one 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 of the second binder particles is 5 μm to 20 μm.

[0037] In the embodiments of the present application, the second binder particles are added in the coating layer or the bonding layer of the isolation film. The second binder particles can fill the gap between the negative electrode sheet and the isolation film, form a relatively firm bonding interface, help to improve the bonding strength between the isolation film and the negative electrode sheet, thereby improving the overall stability of the isolation film, reducing the interlayer peeling phenomenon between the isolation film and the negative electrode sheet caused by thermal stress or electrochemical action in the cycle process, and improving the cycle performance of the battery cell. The volume average particle size Dv50 of the second binder particles meets the above range, which ensures that the second binder particles can be uniformly distributed and maintain moderate fluidity during hot pressing, thereby further improving the cycle performance of the battery cell.

[0038] In a possible implementation, the isolation film meets 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 rate of the isolation film is less than or equal to 5% when heated at 130°C for 1 h; (4) the transverse thermal shrinkage rate of the isolation film is less than or equal to 5% when heated at 130°C for 1 h; (5) the air permeability of the isolation film is 150 s / 100 mL to 500 s / 100 mL.

[0039] In the embodiments of the present application, the coating is too thin to form an effective thermal insulation layer, and is too thick to increase the thickness of the separator and reduce the energy density of the battery cell. The 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.

[0040] The areal density of the coating is 1.5 g / m 2 to 6 g / m 2 , which can ensure moderate coating quality, 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.

[0041] The separator can still maintain very low longitudinal and transverse thermal shrinkage rates at 130°C, that is, the separator has good heat resistance at high temperatures.

[0042] The air permeability of the separator is 150 s / 100 mL to 500 s / 100 mL, which ensures that the electrolyte can be uniformly infiltrated and maintain fast ion transport, ensures the ion transport efficiency of the separator, reduces the case that the low air permeability of the separator leads to electrochemical polarization and reduces the reliability of the battery cell.

[0043] In a second aspect, a battery device is provided, which includes the battery cell in any possible implementation manner.

[0044] In a third aspect, a power consumption device is provided, which includes the battery cell in any possible implementation manner, or the battery device of the second aspect.

[0045] In a fourth aspect, the embodiments of the present application provide a separator, 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 organic compound particles, the morphology of the organic compound particles is spherical or spherical-like; and in a cross section of the coating layer along the thickness direction of the separator, based on the total number of the organic compound particles, the number ratio of particles with a particle size R1 satisfying 0 < R1 ≤ 100 nm is 0% to 0.5%, the number ratio of particles with a particle size R2 satisfying 100 < R2 ≤ 300 nm is 65% to 85%, and the number ratio of particles with a particle size R3 satisfying 300 < R2 ≤ 800 nm is 15% to 35%.

[0046] Compared with inorganic particles with a large density, the organic compound particles have a small density and light mass, which is conducive to improving the energy density of the battery monomer. In the spherical or spherical organic compound particles, 0% to 0.5% of the small particle size R1 can fill the gap between the larger particles, reduce the large pores and surface defects in the coating, thereby improving the compactness and overall uniformity of the coating, enhancing the structural stability of the isolation film under high temperature conditions, and reducing the risk of thermal shrinkage. 65% to 85% of the medium particle size R2 are stacked with each other to provide a continuous penetration path for the electrolyte, which is conducive to the rapid infiltration of the electrolyte throughout the coating. 15% to 35% of the larger particle size R3 can form a supporting force in the coating to help maintain the stability of the infiltration channel and ensure the normal penetration of the electrolyte in the isolation film. By setting the organic compound particles with different particle size ranges in the coating and controlling the proportion of the total particle number, the battery monomer can have high energy density, the isolation film can have heat resistance and good electrolyte infiltration performance, and the reliability and cycle performance of the battery monomer can be improved.

[0047] In a possible implementation, the average particle size of the organic compound particles is 80nm to 720nm, and / or the maximum particle size of the organic compound particles is 500nm to 800nm, and / or the minimum particle size of the organic compound particles is 50nm to 100nm.

[0048] In the embodiments of the present application, by limiting the average particle size, the maximum particle size and the minimum particle size of the organic compound particles, the electrolyte infiltration channel inside the coating can be further controlled. The average particle size is 80nm to 720nm, which ensures the overall uniformity of the organic compound particles accumulated in the coating, and is conducive to obtaining a coating with connected channels. The maximum particle size is 500nm to 800nm, which prevents surface protrusions or uneven infiltration channels caused by too large particles in the coating, thereby reducing coating defects and local electrolyte infiltration. The minimum particle size is 50nm to 100nm, which can reduce the phenomenon of excessive filling of channels in the coating by superfine particles, and ensure that the coating maintains a smooth penetration path. Through the above control of the particle size of the organic compound particles, the electrolyte can quickly and uniformly penetrate in the coating, thereby improving the cycle performance of the battery monomer.

[0049] In a possible implementation, the roundness of the organic compound particles is 0.5 to 1.0.

[0050] In the embodiments of the present application, when the roundness of the organic compound particles is high, the shape of the particles is closer to a regular sphere, the friction and stacking resistance between the particles are small during the dispersion of the slurry, and thus the slurry flows more uniformly, which can form a coating with uniform thickness and good pore structure after coating and drying, so that the electrolyte can enter the interior more quickly and uniformly when contacting the coating, thereby facilitating the improvement of the wettability of the electrolyte in the separator membrane. The particles with regular morphology have fewer corners and irregular protrusions, and the probability of local stress concentration or micro-cracks in the coating is low, which is beneficial to the structural stability of the coating. At the same time, the surface of the particles with high roundness can fully contact with the electrolyte, the surface wetting resistance is low, the electrolyte can quickly penetrate along the uniform and continuous electrolyte infiltration channel between the particles, and the local retention and uneven infiltration phenomenon is reduced, thereby achieving good electrolyte wetting effect and ion conduction efficiency. Therefore, the roundness of the organic compound particles meets the above range, which can improve the wettability of the electrolyte in the separator membrane, thereby improving the cycle performance of the battery cell.

[0051] In a possible implementation, the organic compound particles include a cross-linked polymer, and the cross-linking degree of the cross-linked polymer is 70% to 98%.

[0052] On the one hand, the cross-linked polymer has a three-dimensional network structure, which can maintain a stable spatial configuration under thermal stress, so that the separator membrane has good heat resistance. On the other hand, by controlling the cross-linking degree of the cross-linked polymer to be 70% to 98%, the coating particles can have good heat resistance at high temperatures, the heat resistance of the separator membrane is improved, the overall structural integrity of the separator membrane at high temperatures is ensured, and thus the reliability of the battery cell at high temperatures is improved.

[0053] In a possible implementation, the cross-linked polymer includes a silicone polymer containing a siloxane structure.

[0054] In the embodiments of the present application, the siloxane structure of the silicone polymer can improve the surface polarity of the cross-linked polymer, produce strong interaction with the solvent molecules in the electrolyte, improve the affinity of the coating for the electrolyte, and thus improve the wettability of the electrolyte. The cross-linked polymer includes a silicone polymer containing a siloxane structure, and because the silicone polymer contains a siloxane bond, the bond energy of the siloxane bond is high and the siloxane bond is not easy to decompose at high temperatures, which can be beneficial to further improving the thermal stability of the material, thereby enhancing the heat resistance of the coating of the separator membrane. In addition, compared with inorganic particles, the density of the silicone polymer is low, and the overall mass of the coating can be reduced at the same thickness, which is beneficial to improving the energy density of the battery cell. Therefore, the cross-linked polymer includes a silicone polymer containing a siloxane structure, which can improve the structural stability of the coating and also improve the wettability of the electrolyte, thereby improving the cycle performance of the battery cell.

[0055] In a possible implementation, the organosilicon polymer containing siloxane structure includes a phenyl group, the organosilicon polymer containing siloxane structure includes a monomer and a crosslinking agent represented by formula (I) and is polymerized to obtain, In formula (I), R1 and R2 are each independently selected from C1-C4 alkyl, C2-C4 alkenyl, R3 includes C1-C4 alkyl or C4-C8 (meth) acryloxyalkyl, and R4 includes C2-C8 alkenyl or C4-C8 (meth) acryloxyalkyl; the crosslinking agent includes divinylbenzene.

[0056] In the embodiments of the present application, the organosilicon polymer containing siloxane structure is obtained by polymerization of the monomer represented by formula (I) and the crosslinking agent divinylbenzene, the particle has a three-dimensional network skeleton formed by the phenyl structure and the monomer and the crosslinking agent, and the material has higher glass transition temperature and thermal decomposition temperature, thereby improving the heat resistance of the isolation film and the reliability of the battery cell.

[0057] In a possible implementation, the organosilicon polymer containing siloxane structure satisfies at least one of the following conditions: (1) the crosslinking degree of the organosilicon polymer containing siloxane structure is 75% to 95%; (2) the mass fraction of silicon elements in the organosilicon polymer containing siloxane structure is 10% to 25%; (3) the mass fraction of phenyl groups in the organosilicon polymer containing siloxane structure is 2% to 12%; and (4) the organosilicon polymer containing siloxane structure includes a silicon hydroxyl group.

[0058] In the embodiments of the present application, the organosilicon polymer containing siloxane structure is 75% to 95%, and has good heat resistance at high temperature, so that the isolation film has good heat resistance, thereby improving the reliability of the battery cell. The mass fraction of silicon elements is 10% to 25%, which helps to improve the proportion of inorganic siloxane skeleton in the organosilicon polymer. The siloxane skeleton including silicon elements provides higher thermal decomposition temperature and oxidation resistance, so that the isolation film has structural stability in a high-temperature environment. The mass fraction of phenyl groups is 2% to 12%, which can introduce a rigid structure of aromatic structure and conjugate effect, thereby further improving the heat resistance of the isolation film.

[0059] In a possible implementation, the organosilicon polymer containing siloxane structure includes a skeleton composed of a compound represented by formula (II), R a [SiO 3 / 2 ] n Formula (II) wherein n is an integer of 4 to 12, R a includes a cycloalkyl group, an aryl group, a C1-C4 alkyl group, a C1-C4 alkenyl group, and a C1-C4 alkynyl group; and n is 8 and R 12 includes a cycloalkyl group, an aryl group, a C1-C4 alkyl group, a C1-C4 alkenyl group, and a C1-C4 alkynyl group; and n is 8 and R 12 includes a cycloalkyl group, an aryl group, a C1-C4 alkyl group, a C1-C4 alkenyl group, and a C1-C4 alkynyl group; and n is 8 and R 12 includes a cycloalkyl group, an aryl group, a C1-C4 alkyl group, a C1-C4 alkenyl group, and a C1-C4 alkynyl group; and n is 8 and Ra Including C1 to C3 alkyl groups.

[0060] In this embodiment, by introducing the covalent polyhedral framework shown in formula (II) into the organic compound, a stable three-dimensional structure can be formed inside the molecule of the organic compound. This type of polyhedral framework has high symmetry and regularity, and the internal atoms are connected by strong covalent bonds. The molecular structure is not easily broken or collapsed under high temperature conditions, which is beneficial to improving the heat resistance of the isolation film. Moreover, the covalent polyhedral framework shown in formula (II) contains Si-O bonds, which have high bond energy and are not easily decomposed at high temperatures, which can further improve the thermal stability of the material. By selecting n as 8, R a The presence of C1 to C3 alkyl groups can further improve the rigidity and thermal stability of organic compounds. Organic compound particles can act as rigid support points at high temperatures, improving the heat resistance of the separator and thus enhancing the reliability of battery cells.

[0061] In one possible implementation, the organosilicon polymer containing a silicon-oxygen structure is obtained by hydrolysis and polycondensation of one or more monomers of formula (ⅠII). R'1 includes C1 to C3 alkyl groups.

[0062] In this embodiment, an organosilicon polymer with a complete cage-like structure and uniformly dispersed molecular chains can be obtained by employing the hydrolysis-condensation reaction of the monomer of formula (III). The resulting organosilicon polymer particles are uniformly distributed in the separator coating, forming a coating structure with good pore connectivity, which facilitates continuous electrolyte penetration and improves the wetting performance of the separator. Sufficient electrolyte wetting in the separator ensures uniform utilization of the negative electrode active material during charging and discharging, reducing low utilization or capacity decay of the negative electrode active material due to insufficient local wetting, thereby slowing down the battery capacity decay rate and improving the cycle performance of the battery cell.

[0063] In one possible implementation, the organosilicon polymer containing a silicon-oxygen structure satisfies at least one of the following conditions: (1) the degree of crosslinking of the organosilicon polymer containing a silicon-oxygen structure is 85% to 97%; (2) the mass fraction of silicon in the organosilicon polymer containing a silicon-oxygen structure is 25% to 45%; (3) the mass fraction of the skeleton composed of the compound shown in formula (II) in the organosilicon polymer containing a silicon-oxygen structure is 40% to 60%; (4) the organosilicon polymer containing a silicon-oxygen structure includes silanol groups.

[0064] In the embodiments of the present application, the cross-linking degree of the organosilicon polymer containing siloxane structure is 85% to 97%, which ensures the structural stability of the organosilicon polymer at high temperature; the higher mass fraction of silicon element makes the polarity of the organosilicon polymer higher, and the affinity of the organosilicon polymer to the electrolyte is enhanced, thereby improving the diffusion speed and wetting ability of the electrolyte in the coating; the skeleton composed of the compound shown in formula (II) has a mass fraction of 40% to 60% in the organosilicon polymer containing siloxane structure, which can ensure that the cross-linked polymer has good rigidity and structural stability, reduces the structural collapse of the separator film at high temperature, and is beneficial to improving the heat resistance of the separator film, thereby improving the reliability of the battery cell at high temperature; the silicon hydroxyl group can increase the interaction between the polymer and the electrolyte molecules, and further improve the wettability and interface stability of the coating. The organosilicon polymer includes the silicon hydroxyl group, which can provide additional active sites. On the one hand, the silicon hydroxyl group and the polar solvent molecules in the electrolyte can easily form hydrogen bonds or strong dipole interactions, thereby further improving the liquid affinity and wettability of the coating; on the other hand, the silicon hydroxyl group can undergo condensation or cross-linking reaction with other functional groups (such as epoxy group and carboxyl group) during heat treatment or cross-linking process, which reduces the structural collapse or shedding phenomenon of the coating at high temperature and under long cycle conditions, thereby improving the wettability of the electrolyte in the separator film.

[0065] In a possible implementation, the mass ratio of the organic compound particles in the coating is 50% to 97%.

[0066] By limiting the mass fraction of the organic compound particles in the coating to meet the above range, the coating has structural stability and air permeability, the heat resistance of the separator film is improved, and the reliability of the battery cell is improved. BRIEF DESCRIPTION OF DRAWINGS

[0067] 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 as follows. 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.

[0068] FIG. 1 is a schematic diagram of a battery cell according to an embodiment of the present application.

[0069] FIG. 2 is a structural schematic diagram of a battery cell according to another embodiment of the present application.

[0070] FIG. 3 is a schematic diagram of a battery device according to an embodiment of the present application.

[0071] FIG. 4 is a schematic diagram of an electrical equipment according to an embodiment of the present application.

[0072] FIG. 5 is a schematic diagram of an electrical equipment according to another embodiment of the present application.

[0073] FIG. 6 is a pyrolysis spectrum of an organic compound powder according to an embodiment of the present application.

[0074] FIG. 7 is an SEM image of a coating according to an embodiment of the present application.

[0075] FIG. 8 is an SEM image of a coating according to another embodiment of the present application.

[0076]

[0077]

[0078] Reference Signs:

[0079] 3: battery cell; 30: outer case; 31: case; 313: pressure relief mechanism; 32: end cap; 322: electrode terminal; 33: electrode assembly; 331: tab; 34: connecting member; 10: battery device; 11: box; 111: first box portion; 112: second box portion; 1: vehicle; 4: controller; 5: motor; 2: energy storage device. DETAILED DESCRIPTION

[0080] Hereinafter, embodiments of the battery cell, the battery device, and the electrically powered apparatus according to the present application are described in detail with appropriate reference to the accompanying drawings, but there are cases where unnecessary detailed description is omitted. For example, there are cases where detailed description of matters that are already well known, repeated description of actually identical structures are omitted. This is to avoid the following description becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the drawings and the following description 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.

[0081] "RANGES" disclosed herein are defined by both a lower and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, the selected lower limit and upper limit defining the boundaries of a particular range. Ranges defined in this manner 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. In addition, if minimum range values of 1 and 2 are listed, and if maximum range values of 3, 4, and 5 are listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise indicated, a numerical range "a-b" means a range of any combination of the numbers a and b, in which a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed herein, "0-5" is merely a shorthand for these numerical combinations. Also, when a parameter is stated to be an integer > 2, it is equivalent to disclose that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0082] 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 application; the description and claims of this application as well as the above abstract are intended to cover any and all alternatives, modifications, equivalents, and / or improvements for the various embodiments of the application described herein; and the terms "comprising", "including", "containing", etc. used herein are intended to be inclusive and mean that there can be additional elements other than the listed elements. The terms "first", "second", etc. are used herein to distinguish one element from another, and are not used to describe a particular sequential or chronological order.

[0083] If not specifically explained, all the embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

[0084] If not specifically explained, all the technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

[0085] If not specifically explained, the following terms have the following meanings. Any undefined terms have their art-recognized meanings.

[0086] In the embodiments of the present application, "alkyl" refers to straight-chain and branched-chain alkyl groups. For example, alkyl can be C1-C 20 alkyl, C1-C 12 alkyl, C1-C 10alkyl, C1-C6 alkyl, C1-C4 alkyl. In some embodiments, alkyl includes methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, t-butyl, cyclobutyl, pentyl, isopentyl, neopentyl, t-pentyl, cyclopentyl, hexyl, cyclohexyl, heptyl, cycloheptyl, octyl, cyclooctyl, nonyl, and decyl, among others. Additionally, alkyl groups can be optionally substituted, for example, alkyl groups are substituted with halogen to form haloalkyl groups. The term "haloalkyl" refers to an alkyl group in which some or all of the hydrogen atoms are replaced by halogen atoms, the term "halogen atom" refers to fluorine atom, chlorine atom, bromine atom, iodine atom, among others.

[0087] In embodiments of the present application, substituents of compounds are disclosed in combination ranges. For example, "C1-C12 alkyl" can represent C1, C2, C3, C4, C5, C6, C7, C8, C9, C10, C11, C12, C1-C12, C1-C11, C1-C10, C1-C9, C1-C8, C1-C7, C1-C6, C1-C5, C1-C4, C1-C3, C1-C2, C2-C12, C2-C11, C2-C10, C2-C9, C2-C8, C2-C7, C2-C6, C2-C5, C2-C4, C2-C3, C3-C12, C3-C11, C3-C10, C3-C9, C3-C8, C3-C7, C3-C6, C3-C5, C3-C4, C4-C12, C4-C11, C4-C10, C4-C9, C4-C8, C4-C7, C4-C6, C4-C5, C5-C12, C5-C11, C5-C10, C5-C9, C5-C8, C5-C7, C5-C6, C6-C12, C6-C11, C6-C10, C6-C9, C6-C8, C6-C7, C7-C12, C7-C11, C7-C10, C7-C9, C7-C8, C8-C12, C8-C11, C8-C10, C8-C9, C9-C12, C9-C11, C9-C10, C10-C12, C10-C11, and C11-C12 alkyl.

[0088] In embodiments of the present application, "alkenyl" refers to a non-aromatic unsaturated hydrocarbon group containing one or more carbon-carbon double bonds (C=C), for example, alkenyl can be C2-C20 alkenyl, C2-C12 alkenyl, C2-C10 alkenyl, C2-C6 alkenyl, C2-C4 alkenyl. In some embodiments, alkenyl includes ethenyl, 1-propenyl, 2-propenyl (allyl), 1-butenyl, 2-butenyl, 3-butenyl, 1,3-butanedienyl, pentenyl, hexenyl, cyclohexenyl, heptenyl, octenyl, nonenyl, and decenyl, among others.

[0089] The "cycloalkyl" in the embodiments of the present application refers to saturated cyclic alkyl groups with single ring, double ring and multiple rings. Specifically, the cycloalkyl is a hydrocarbon group composed of one or more saturated carbon rings, which can be a single ring structure or a fused ring structure formed by connecting multiple rings through sharing one or more atoms. For example, the cycloalkyl with a single ring structure can be cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclodecyl, etc.; the cycloalkyl with a fused ring structure can be cyclopentenyl, cyclohexenyl, tricycloalkyl, etc.

[0090] The "alkynyl" in the embodiments of the present application refers to a hydrocarbon group with carbon-carbon triple bond (C≡C).

[0091] In the present application, the terms "plurality" and "multiple" refer to two or more.

[0092] Generally, the battery monomer includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator. In the charging and discharging process of the battery monomer, active ions are embedded and extracted between the positive electrode sheet and the negative electrode sheet. Among them, the electrolyte plays a role in conducting active ions between the positive electrode sheet and the negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet, which prevents the positive and negative electrodes from short-circuiting while allowing the active ions to pass through, so that the electrochemical reaction of the battery monomer can proceed normally.

[0093] The development of battery technology needs to consider various design factors, such as energy density, cycle life, discharge capacity, charge-discharge rate, reliability, etc. Among them, the separator is an important component to support the secondary battery cell to complete the charge-discharge chemical process. The commonly used separator is mostly polyolefin material, but the heat resistance of polyolefin material is poor, which can soften or melt at high temperature, thereby causing short circuit of the secondary battery cell. In order to improve the heat resistance of the separator, a coating layer is usually coated on the separator to improve the heat resistance of the separator. Boehmite, alumina and other inorganic particles are currently commonly used heat-resistant fillers, but the density of such heat-resistant fillers is large, and the mass is 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, some processing methods replace boehmite, alumina and other inorganic particles with organic heat-resistant fillers, and the existing organic heat-resistant fillers are usually irregular particles after nanocrystallization, and there are large and small particles. If the particle size difference of the organic heat-resistant filler is large after the coating layer is stacked, the particles and the particles will be loosely stacked, and the anti-shrinkage force of the separator will be weak. On the contrary, if the particle size difference of the organic heat-resistant filler is small, the particles and the particles will be too tightly stacked, which can easily lead to a decrease in the porosity of the coating layer, a decrease in the permeation rate of the electrolyte in the separator, and an influence on the wettability of the separator. Therefore, the heat resistance of the separator and the wettability of the electrolyte to the separator need to be considered; how to make the battery cell have higher energy density while the separator has good heat resistance and wettability is a technical problem to be solved at present.

[0094] Therefore, the heat resistance of the separator and the wettability of the electrolyte to the separator need to be considered; how to make the battery cell have higher energy density while the separator has good heat resistance and wettability is a technical problem to be solved at present.

[0095] Compared with inorganic particles with a large density, the organic compound particles have a small density and light mass, which is conducive to improving the energy density of the battery monomer. In the spherical or spherical organic compound particles, 0% to 0.5% of the smaller particle size R1 can fill the gaps between the larger particles, reduce the large pores and surface defects in the coating, thereby improving the compactness and overall uniformity of the coating, enhancing the structural stability of the isolation film under high temperature conditions, and reducing the risk of thermal contraction. 65% to 85% of the medium particle size R2 are stacked with each other to provide a continuous penetration path for the electrolyte, which is conducive to the rapid infiltration of the electrolyte throughout the coating. 15% to 35% of the larger particle size R3 can form a supporting force in the coating to help maintain the stability of the infiltration channel and ensure the normal penetration of the electrolyte in the isolation film. By setting organic compound particles with different particle size ranges in the coating and controlling their proportion in the total number of particles, the battery monomer can have high energy density while the isolation film has good heat resistance and good electrolyte infiltration performance, improving the reliability and cycle performance of the battery monomer.

[0096] Next, the battery monomer provided by the embodiments of the present application is introduced.

[0097] [Battery monomer]

[0098] The embodiments of the present application provide a battery monomer, 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 organic compound particles; the morphology of the organic compound particles is spherical or spherical-like, and in the section of the coating layer along the thickness direction of the isolation film, based on the total number of the organic compound particles, the number proportion of particles with a particle size R1 satisfying 0

[0099] In the embodiments of the present application, the porous base film refers to a thin film material with micron and / or nanometer 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.

[0100] In some embodiments, the porous base film can comprise a film or non-woven web selected from any one or at least two of the following: polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyamide, polycarbonate, polyimide, polyether ether ketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyether sulfone, polyphenylene ether, cyclic olefin copolymer, polyphenylene sulfide, polyvinyl naphthalene.

[0101] In some embodiments, the porous base film can have a thickness of 4-15 μm, optionally 4-9 μm.

[0102] In some embodiments, the porous base film can have a porosity of 25-60%, optionally 28-50%.

[0103] In some embodiments, the porous base film can have an average pore size of 25-82 nm.

[0104] The average pore size of the porous base film can be tested using a capillary porosimeter (bubble point method). An exemplary testing method is as follows: a circular sample with a diameter of 25 mm is taken and 3-5 drops of wetting liquid are dropped thereon. 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. The pressure and flow rate 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 testing instrument can be a CFP 1500 pore size analyzer from PMI, and the testing pressure can be 100-350 psi.

[0105] The "organic compound particles" in the embodiments of the present application refer to solid particles composed of molecules mainly composed of elements such as carbon (C), hydrogen (H), oxygen (O), nitrogen (N), etc. and connected by covalent bonds. For the separator film, the heat resistance of the separator film can be increased by providing organic compound particles in the coating layer thereof. The organic compound particles are the main component of the coating layer. These organic compound particles are micron or nanometer-sized solid particles with high melting point, high thermal stability, and high chemical inertness, and can be uniformly dispersed in the coating layer, thereby achieving the heat resistance of the separator film.

[0106] In the embodiments of the present application, the "morphology of the particles is spherical or spheroidal" means that the particles are close to a sphere in geometric shape or are in an approximately spherical state as a whole.

[0107] As an example, the morphology of the particles can be tested by using instruments and methods known in the art. Specifically, after the battery monomer is disassembled, the separator film is peeled off, and the separator film in a regular and clear area is selected. Subsequently, the micro-morphology of the coating layer on the separator film is measured by using a scanning electron microscope (SEM) and referring to the standard JY / T010 1996. Then, the two-dimensional projection profile, edge curvature, cross-sectional morphology, and contrast change of the particles in the coating layer are observed. If the particle edge is smooth, the curvature is consistent, the surface is uniform, the contrast transition is natural, and the particle projection is circular, it is determined that the particle morphology is spherical. If the particle profile is close to circular, the edge is slightly irregular, and the surface can have slight undulations, it is determined that the particle morphology is spheroidal.

[0108] For example, the amount ratio of R1 can be 0%, 0.02%, 0.04%, 0.06%, 0.08%, 0.10%, 0.12%, 0.14%, 0.16%, 0.18%, 0.20%, 0.22%, 0.24%, 0.26%, 0.28%, 0.30%, 0.32%, 0.34%, 0.36%, 0.38%, 0.40%, 0.42%, 0.44%, 0.46%, 0.48%, 0.50%, or any value within the above range. The amount ratio of R2 can be 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%, or any value within the above range. The amount ratio of R3 can be 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, or any value within the above range.

[0109] In the embodiments of the present application, the amount ratios of the particle sizes R1, R2 and R3 can be obtained by the following method: the organic compound particle powder is laid and adhered on the conductive glue to form a sample to be tested with a length of 6 cm and a width of 1.1 cm; the particle morphology is tested by using a scanning electron microscope (for example, ZEISS Sigma 300), and the test can refer to JY / T010-1996. The amount ratios of the particle sizes R1, R2 and R3 are measured in the scanning electron microscope image of the test. Specifically, the scanning electron microscope (for example, ZEISS Sigma 300) is used to obtain the scanning electron microscope (SEM) picture of the release film by referring to JY / T010-1996. A region with a length of 50 mm and a width of 100 mm is randomly selected on the release film and cut as a test sample, a plurality of test regions (for example, 5) are randomly selected in the test sample, the distance between the two farthest points on the organic compound particle is taken as the particle size of the organic compound particle, the number and particle size values of the organic compound particles in each test region are counted, the arithmetic mean of the particle sizes of the organic compound particles in each test region is taken, and the amount ratios of different particle sizes of the organic compound particles in each test region are counted. Ten test samples are selected in parallel for testing, and the arithmetic mean of the amount ratios of different particle sizes of the ten test samples is taken as the final test result.

[0110] Compared with inorganic particles with a larger density, the organic compound particles have a smaller density and lighter mass, which is conducive to improving the energy density of the battery monomer. In the spherical or spherical organic compound particles, 0% to 0.5% of the smaller particle size R1 can fill the gaps between larger particles, reduce large pores and surface defects in the coating, thereby improving the density and overall uniformity of the coating, enhancing the structural stability of the isolation film under high temperature conditions, and reducing the risk of thermal contraction. 65% to 85% of the medium particle size R2 is stacked with each other to provide a continuous penetration path for the electrolyte, which is conducive to the rapid infiltration of the electrolyte throughout the coating. 15% to 35% of the larger particle size R3 can form a supporting force in the coating to help maintain the stability of the infiltration channel and ensure the normal penetration of the electrolyte in the isolation film. By setting organic compound particles with different particle size ranges in the coating and controlling their proportion in the total number of particles, the battery monomer can have high energy density while the isolation film has heat resistance and good electrolyte infiltration performance, improving the reliability and cycle performance of the battery monomer.

[0111] In some embodiments, the average particle size of the organic compound particles is 80 nm to 720 nm, and / or the maximum particle size of the organic compound particles is 500 nm to 800 nm, and / or the minimum particle size of the organic compound particles is 50 nm to 100 nm.

[0112] For example, the average particle size of the organic compound particles can be 80 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, or any value within the above range. The maximum particle size can be 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm, or any value within the above range. The minimum particle size can be 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, or any value within the above range.

[0113] In the embodiments of the present application, the average particle size of the organic compound particles can be tested by known methods in the art. As an example, the particle distribution electron microscope image in the coating is obtained by scanning electron microscope, the number and particle size of single crystal particles are counted by ImageJ analysis software, the equivalent circle diameter of single crystal particles is taken as the particle size, the number distribution graph is made, the skewness distribution is fitted, and the average particle size of the particles is obtained. In the statistical results, the maximum particle size is the maximum particle size of the particles, and the minimum particle size is the minimum particle size of the particles.

[0114] As an example, the average particle size, the maximum particle size, and the minimum particle size can be tested by the following method.

[0115] After disassembling the battery cell, the separator film was obtained after discharging the battery cell at 0.33C to 0% SOC. The separator film was cut along the thickness direction to expose the cross section, and then the cross section of the coating along the thickness direction of the separator film was observed using a scanning electron microscope. The field emission scanning electron microscope was used to collect images by secondary electron mode at a magnification of 3k times on the cross section of the positive electrode film layer at a non-edge position (after observing the edge of the separator film under the scanning electron microscope, the field of view was adjusted to the center part of the sample). The energy dispersive X-ray spectrometer (EDS) was used to test the elements in the particles. Then the single crystal particles of organic compounds in the electron microscope images were analyzed using ImageJ software (1.46r, win64 version).

[0116] In addition, for multiple particles attached, stacked or adhered together, they were distinguished into multiple single crystal particles after being identified by software (according to parameters such as gray scale / contrast / brightness, etc.) or manual assistance.

[0117] The above method identifies the particles in the coating cross section of the separator film, and the area of the particles in the cross section of the coating along the thickness direction of the separator film is analyzed using the "Feret diameter" analysis function in ImageJ. According to the software manual (ImageJ User Guide IJ 1.46r), the "Feret" parameter obtained by analysis represents the maximum distance between all parallel lines in the two-dimensional projection of the particle, which characterizes the particle size of the particle.

[0118] According to the above method, in order to meet the sample number with statistical significance, at least 10 non-overlapping scanning electron microscope images (for example, the field of view size is 150 μm x 120 μm) are collected for each separator film, and the particle size of at least 800 particles is counted. The particle size of at least 800 particles obtained is arranged in order from small to large, and the cumulative distribution curve of the particle size of the organic compound particles is drawn.

[0119] It should be noted that the average particle size, maximum particle size and minimum particle size obtained by scanning electron microscope testing of the cross section of the separator film along the thickness direction will be different from the average particle size, maximum particle size and minimum particle size selected during the preparation of the battery cell. For example, the larger the single crystal particle, the greater the deviation.

[0120] In the above embodiments, by limiting the average particle size, the maximum particle size and the minimum particle size of the organic compound particles, the electrolyte infiltration channel in the coating can be further controlled. The average particle size is 80 nm to 720 nm, which ensures the overall uniformity of the organic compound particles in the coating, and is conducive to obtaining a coating with connected channels. The maximum particle size is 500 nm to 800 nm, which prevents surface protrusions or uneven infiltration channels caused by excessively large particles in the coating, thereby reducing coating defects and local electrolyte infiltration deficiencies; the minimum particle size is 50 nm to 100 nm, which can reduce the phenomenon of excessive filling of ultra-fine particles in the channels in the coating, and ensure that the coating maintains a smooth infiltration path. Through the above control of the particle size of the organic compound particles, the electrolyte can quickly and uniformly penetrate in the coating, thereby improving the cycle performance of the battery cell.

[0121] In some embodiments, the roundness of the organic compound particles is 0.5 to 1.0.

[0122] In the embodiments of the present application, the roundness refers to the ratio of the surface area of a sphere with the same volume to the actual surface area of the particles. The closer the roundness is to the value 1, the more round and regular the shape of the particles is. For example, the roundness can be 0.5, 0.55, 0.6, 0.65, 0.7, 0.73, 0.76, 0.78, 0.8, 0.83, 0.86, 0.87, 0.88, 0.9, 0.93, 0.95, 0.97, 1.0, or any value within the above range.

[0123] As an example, the roundness of the organic compound particles is the meaning known in the art, which can be tested by instruments and methods known in the art. Specifically, as an example, after disassembling the battery cell, the separator film is peeled off, and the separator film in a regular and clear area is selected. Then, a scanning electron microscope (SEM) is used, and the cross-sectional morphology of the coating is measured according to the standard JY / T010 1996. The roundness of the organic compound particles in the SEM morphology diagram is fitted by the Image J software. Wherein, the roundness (SC) = (4π×area) / (perimeter×perimeter). Three test samples are selected in parallel for testing, and the arithmetic mean of the roundness of the three test samples is taken as the final result. The closer the value of the roundness is to 1, the more round and regular the shape of the particles is.

[0124] In the above embodiments, when the roundness of the organic compound particles is high, the particles are closer to regular spheres in shape, the friction and stacking resistance between the particles are small during the dispersion of the slurry, the slurry flows more uniformly, and a coating with uniform thickness and good pore structure can be formed after coating and drying, so that the electrolyte can enter the interior more quickly and uniformly when contacting the coating, thereby improving the wettability of the electrolyte in the separator membrane. The regular-shaped particles have fewer edges and irregular protrusions, and the probability of local stress concentration or micro-cracks in the coating is low, which is beneficial to the structural stability of the coating. At the same time, the surface of the particles with high roundness can fully contact with the electrolyte, the surface wetting resistance is low, the electrolyte can quickly penetrate along the uniform and continuous electrolyte infiltration channel between the particles, and the local retention and uneven infiltration phenomenon is reduced, thereby achieving good electrolyte wetting effect and ion conduction efficiency. Therefore, when the roundness of the organic compound particles meets the above range, the wettability of the electrolyte in the separator membrane can be improved, thereby improving the cycle performance of the battery cell.

[0125] In some embodiments, the organic compound particles comprise a cross-linked polymer, and the cross-linking degree of the cross-linked polymer is 70% to 98%.

[0126] The "cross-linked polymer" in the embodiments of the present application refers to a polymer material in which the molecular chains are cross-linked to form a three-dimensional network structure through chemical bonds. This structure is usually formed by cross-linking of multiple reactive functional groups during polymerization or post-processing, so that the whole polymer forms a stable spatial structure. The cross-linking degree refers to the degree of cross-linking between the molecular chains of the cross-linked polymer through chemical 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 beneficial to improve the heat resistance and thermal decomposition temperature of the organic compound particles, thereby improving the heat resistance of the separator membrane. 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 fitting the software through nuclear magnetic 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; and the cross-linked segment is bound to a large extent and has small molecular motion characteristics, and decays relatively quickly; therefore, by collecting the entire high molecular signal and calculating the proportion of the cross-linked signal, the cross-linking degree of the polymer backbone can be obtained.

[0127] 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 numerical combinations.

[0128] In the embodiments of the present application, the cross-linking degree of the cross-linked polymer can be tested by a PQ001 nuclear magnetic resonance analyzer. The test temperature is 60°C, the resonance frequency of the nuclear magnetic resonance analyzer is set to 21 MHz, 0.5 g of the cleaned and dried sample (the above-mentioned organic compound particles) to be tested is taken, is loaded into a clean sample tube and is inserted into a probe at a specified depth, the probe coil diameter is 13 mm, and the measurement is performed according to the manufacturer's instructions. Specifically, the cross-linking degree of the cross-linked polymer is obtained by collecting the entire 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 result according to the degree of restriction of molecular chain movement.

[0129] In the above technical solution, on the one hand, the cross-linked polymer has a three-dimensional network structure, which can maintain a stable spatial configuration under thermal stress, so that the isolation film has good heat resistance. On the other hand, by controlling the cross-linking degree of the cross-linked polymer to be 70% to 98%, the coating particles can have good heat resistance at high temperatures, the heat resistance of the isolation film is improved, the overall structural integrity of the isolation film at high temperatures is ensured, and the reliability of the battery monomer at high temperatures is improved.

[0130] In some embodiments, the cross-linked polymer includes a silicone polymer containing a silicon-oxygen structure.

[0131] In the embodiments of the present application, the silicon-oxygen structure can refer to a skeleton structure formed by alternating connection of silicon atoms (Si) and oxygen atoms (O) through covalent bonds; and the silicone polymer containing a silicon-oxygen structure refers to a high molecular compound containing a silicon-oxygen bond in the main chain or side chain.

[0132] As an example, the chemical structure and type of the silicone polymer are well known in the art, and can be tested by using instruments and methods known in the art. Specifically, as an example, after the battery monomer is disassembled, the isolation film is peeled off, and the isolation film in a regular and clear area is selected. Then, the isolation film is soaked in N,N-dimethylformamide, and after centrifugal separation, the supernatant is taken, and then the supernatant is coated on a potassium bromide wafer. After drying the potassium bromide wafer, the silicone polymer is obtained or the silicone polymer powder is directly taken. The silicone polymer is placed in an infrared spectrum analyzer (for example, model: Thermo Nicolet iS5 Fourier infrared spectrometer) for analysis, and the test is performed according to GB / T6040-2002, and it is analyzed according to the measurement result that the silicone polymer contains a Si-O stretching vibration peak.

[0133] In the above embodiments, the silicon-oxygen structure of the organosilicon polymer can improve the surface polarity of the crosslinked polymer, resulting in a strong interaction with solvent molecules in the electrolyte, thereby increasing the coating's affinity for the electrolyte and improving its wetting performance. The crosslinked polymer includes organosilicon polymers containing silicon-oxygen structures. Due to the presence of silicon-oxygen bonds, these bonds have high bond energies and are not easily decomposed at high temperatures, which helps to further improve the thermal stability of the material, thus enhancing the heat resistance of the separator coating. Furthermore, compared to inorganic particles, organosilicon polymers have a lower density, which can reduce the overall mass of the coating at the same thickness, thus improving the energy density of the battery cell. Therefore, crosslinked polymers including organosilicon polymers containing silicon-oxygen structures improve the structural stability of the coating while also enhancing the wetting performance of the electrolyte, thereby improving the cycle performance of the battery cell.

[0134] In some embodiments, the organosilicon polymer containing a siloxane structure includes phenyl groups, and the organosilicon polymer containing a siloxane structure is obtained by polymerization of the monomers shown in formula (I) and a crosslinking agent. In formula (I), R1 and R2 each independently include C1-C4 alkyl and C2-C4 alkenyl groups, R3 includes C1-C4 alkyl or C4-C8 (meth)acryloyloxyalkyl groups, and R4 includes C2-C8 alkenyl or C4-C8 (meth)acryloyloxyalkyl groups; the crosslinking agent includes divinylbenzene.

[0135] In the embodiments of this application, R1 and R2 each independently include at least one of methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, vinyl, 1-propenyl, 2-propenyl (allyl), 1-butenyl, 2-butenyl, 3-butenyl, 1-methyl-1-propenyl, and 2-methyl-1-propenyl.

[0136] R3 includes at least one of methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, (meth)acryloyloxymethyl, 2-((meth)acryloyloxy)ethyl, 3-((meth)acryloyloxy)propyl or 4-((meth)acryloyloxy)butyl.

[0137] In some embodiments, R3 is methyl or (meth)acryloyloxyalkyl. When R3 is methyl, it is beneficial to the stability of the main chain in the crosslinked polymer. When R3 is acryloyloxypropyl, it can further participate in crosslinking and improve the degree of crosslinking of the crosslinked polymer. When R4 is alkenyl or acryloyloxyalkyl, it can achieve efficient crosslinking through free radical polymerization reaction, which is beneficial to improving the degree of crosslinking of the crosslinked polymer, thereby improving the high temperature stability of the crosslinked polymer.

[0138] R4 includes at least one of vinyl, propenyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, (meth)acryloyloxy methyl, 2-((meth)acryloyloxy)ethyl, 3-((meth)acryloyloxy)propyl, or 4-((meth)acryloyloxy)butyl.

[0139] Acryloyloxyalkyl refers to an alkyl chain structure functional group containing an acryloyloxy end group, (meth)acryloyloxyalkyl refers to a (meth)acryloyloxy group replacing one hydrogen atom on a carbon atom directly connected to a carbonyl (C=O) group, providing a reaction site through a molecular chain end acrylate double bond (C=C), which can further undergo a free radical polymerization reaction with a crosslinking agent, thereby facilitating an increase in the crosslinking degree of the silicone polymer.

[0140] In the embodiments of the present application, the crosslinking agent refers to a compound containing two or more functional groups capable of reacting with the functional groups on the polymer chain in the molecule, thereby forming a covalent bridge between the polymer molecular chains and constructing a three-dimensional network structure. For example, the divinylbenzene in the embodiments of the present application can undergo a crosslinking reaction with an alkenyl group or an acryloyl group, forming a covalent bond between the molecular chains with ethylene bridge and benzene ring as the connecting points, forming a three-dimensional network structure of the organosilicon polymer containing a siloxane structure, thereby improving the heat resistance of the organosilicon polymer containing a siloxane structure.

[0141] In the above embodiments, the polymerization of the monomer represented by formula (I) and the crosslinking agent divinylbenzene can obtain organosilicon polymer particles containing a siloxane structure, which have a three-dimensional network skeleton formed by the phenyl structure and the monomer and the crosslinking agent, so that the material exhibits higher glass transition temperature and thermal decomposition temperature, thereby improving the heat resistance of the isolation film and the reliability of the battery cell.

[0142] In some embodiments, the method for preparing the organosilicon polymer containing a siloxane structure comprises the following steps: providing a pre-emulsion containing a monomer, a crosslinking agent, an emulsifier, an initiator, and water, and performing an emulsion polymerization reaction under the conditions of heating, inert gas protection, and stirring to obtain the organosilicon polymer containing a siloxane structure. The monomer includes a silane coupling agent containing an alkenyl group and / or an acryloyloxy group, and the mass fraction of the crosslinking agent is 2% to 30% based on the total mass of the monomer and the crosslinking agent being 100%. By controlling the mass fraction of the crosslinking agent, the mass fraction of the phenyl group in the organosilicon polymer containing a siloxane structure and the crosslinking degree of the organosilicon polymer containing a siloxane structure can be adjusted.

[0143] The monomer includes a silane coupling agent containing an alkenyl group and / or an acryloyloxy group, so that free radicals are generated between the monomers, crosslinking reactions occur, and the monomers also undergo crosslinking reactions with the crosslinking agent. Therefore, the organosilicon polymer containing a phenyl group and a siloxane structure with a three-dimensional network structure can be formed using the monomer and the crosslinking agent of the present disclosure, which is not easy to soften or deform at high temperatures and has high heat resistance.

[0144] The crosslinking agent can be present in a mass fraction of 2% to 30%, for example 2%, 7%, 12%, 17%, 22%, 27%, 30%, or a range defined by any of the foregoing values, based on the total mass of the monomer and the crosslinking agent being 100%.

[0145] The crosslinking agent can be present in a mass fraction of 2% to 30%, for example 2%, 7%, 12%, 17%, 22%, 27%, 30%, or a range defined by any of the foregoing values, based on the total mass of the monomer and the crosslinking agent being 100%.

[0146] Alternatively, the crosslinking agent can be present in a mass fraction of 2% to 30%, 2% to 25%, 2% to 20%, 2% to 15%, 3% to 30%, 3% to 25%, 3% to 20%, 3% to 15%.

[0147] In some embodiments, the monomer can include an acryloyloxy silane coupling agent.

[0148] Alternatively, the monomer of Formula (I) can include one or more of γ-methacryloxypropyl tris(trimethylsiloxy)silane, (3-acryloyloxypropyl)tris(trimethylsiloxy)silane, 3-methacryloxypropyltrimethoxysilane, acryloyloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, acryloyloxypropyltriethoxysilane, γ-methacryloxypropyl triisopropoxysilane, 3-(acryloyloxy)propyltrimethoxysilane, 3-methacryloxypropyl tri(methoxyethoxy)silane, 3-methacryloxypropyl methyl dimethoxysilane, 3-acryloxypropyl methyl dimethoxysilane, methacryloxypropyl dimethyl methoxysilane, (3-acryloyloxy)dimethyl methoxysilane, 3-methacryloxypropyl dimethylethoxysilane, 3-(methacryloxy)propyl methyl diethoxysilane.

[0149] In some embodiments, the monomer of Formula (I) can include a first monomer and a second monomer.

[0150] The first monomer can include one or more of γ-methacryloxypropyl tris(trimethylsiloxy)silane, (3-acryloyloxypropyl)tris(trimethylsiloxy)silane, 3-methacryloxypropyltrimethoxysilane, acryloyloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, acryloyloxypropyltriethoxysilane, γ-methacryloxypropyl triisopropoxysilane, 3-(acryloyloxy)propyltrimethoxysilane, 3-methacryloxypropyl tri(methoxyethoxy)silane.

[0151] The second monomer can include one or more of 3-methacryloxypropylmethyldimethoxysilane, 3-acryloxypropylmethyldimethoxysilane, methacryloxypropyldimethylmethoxysilane, (3-acryloxy)dimethylmethoxysilane, 3-methacryloxypropyldimethylethoxysilane, 3-(methacryloxy)propylmethyldiethoxysilane.

[0152] The first monomer and the second monomer are different in activity, by matching the two and reacting with the crosslinking agent, a silicone polymer with a narrow particle size distribution and a siloxane structure can be obtained.

[0153] 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 ether. Alternatively, the emulsifier includes one or more of sodium dodecyl sulfate, sodium dodecyl sulfonate, Tween 20, Tween 40, lauryl alcohol polyether-7, lauryl alcohol polyether-9, lauryl alcohol polyether-10, oleyl ether-10.

[0154] 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, azobis isopropyl imidazole.

[0155] In some embodiments, the heating temperature of the maturation stage of the emulsion polymerization reaction can be 75-95°C, for example, can be 75°C, 76°C, 77°C, 78°C, 79°C, 80°C, 81°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 consisting of any of the above values.

[0156] In some embodiments, the heating time of the maturation stage of the emulsion polymerization reaction can be 1-4h, for example, 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.

[0157] 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, to obtain a silicon-containing organic resin particle.

[0158] Alternatively, the second heating temperature can be 55-95°C.

[0159] Optionally, the second time can be 3h-8h.

[0160] In some embodiments, the pre-emulsion can further include a Ph adjuster. Optionally, the Ph adjuster can include, but not limited to, one or more of sodium bicarbonate, sodium hydroxide, ammonia, etc.

[0161] In some embodiments of the present application, the heating temperature is 30℃-100℃, for example, the heating temperature can be 30℃-99℃, 35℃-95℃, 40℃-90℃, 45℃-85℃, 50℃-80℃, 55℃-75℃, 60℃-70℃, etc.

[0162] In some embodiments of the present application, the heating time is 2h-8h, for example, the heating time can be 2h, 3h, 4h, 5h, 6h, 7h, 8h, etc.

[0163] By controlling the heating temperature and the heating time within the above ranges, the reaction degree of the polycondensation reaction can be controlled, and the organosilicon polymer with a high mass percentage of silicon hydroxyl groups can be obtained.

[0164] In some embodiments of the present application, the dropping rate of the pre-emulsion described above can be 100ml / min-400ml / min. In emulsion polymerization, the formation of particles mainly goes through two stages, including a nucleation stage and a growth stage, and the dropping rate affects the monomer concentration.

[0165] For example, the dropping rate can be 100ml / min, 120ml / min, 140ml / min, 160ml / min, 180ml / min, 200ml / min, 220ml / min, 240ml / min, 260ml / min, 280ml / min, 300ml / min, 320ml / min, 340ml / min, 360ml / min, 380ml / min, 400ml / min, or any value within the above range. By controlling the dropping rate within the above range, the number percentage of particles in different particle size ranges in the organosilicon polymer containing siloxane structures can be controlled, and the organosilicon polymer containing siloxane structures with the number percentage of particles with a particle size R1 satisfying 0

[0166] When the dropping rate meets the above-mentioned range, the monomer concentration in the system increases with the dropping process. When this concentration exceeds the critical micelle concentration, excess emulsifier molecules in the solution dynamically aggregate, generating new micelles. These new micelles can dissolve and encapsulate monomers, becoming new reaction centers. Free radicals in the aqueous phase then diffuse into these new micelles, initiating a new round of nucleation (i.e., "secondary nucleation"), generating smaller latex particles. Simultaneously, before and after secondary nucleation, the existing initial particles continuously and rapidly engulf monomers and capture free radicals, resulting in a continuous increase in particle size. Therefore, during the dropping process, the earlier nucleated initial particles have ample time to grow into large particles, while the new particles generated through secondary nucleation in the later stages of the reaction mainly form small particles. The prepared organosilicon polymer containing silicon-oxygen structures will contain both large and small particles. Therefore, by controlling the dropping rate, it is possible to achieve a different number and proportion of particles with different size ranges in the organosilicon polymer containing silicon-oxygen structures.

[0167] In other embodiments, the dropping process can be divided into three stages. The dropping rate of the first stage (initial dropping rate) determines the initial number of nuclei. A sufficiently large initial number of nuclei enables complete and concentrated one-time nucleation in the early stages of the reaction, resulting in relatively uniform and stable particle size of the resulting silicone polymer particles with silicon-oxygen structures. The dropping rate of the second stage ensures that sufficient monomer is supplied to the particles already formed in the system, promoting their uniform growth. The dropping rate of the second stage also ensures that the monomer is fully consumed and the reaction is complete. In some embodiments, the method for preparing silicone organic resin particles may further include a demagnetization treatment step after the emulsion polymerization reaction.

[0168] In some embodiments, the organosilicon polymer containing a silicon-oxygen structure satisfies at least one of the following conditions: (1) the degree of crosslinking of the organosilicon polymer containing a silicon-oxygen structure is 75% to 95%; (2) the mass fraction of silicon in the organosilicon polymer containing a silicon-oxygen structure is 10% to 25%; (3) the mass fraction of phenyl in the organosilicon polymer containing a silicon-oxygen structure is 2% to 12%; and (4) the organosilicon polymer containing a silicon-oxygen structure includes silanol groups.

[0169] For example, the degree of crosslinking of organosilicon polymers containing silicon-oxygen structures can be 75%, 77%, 79%, 81%, 83%, 85%, 87%, 89%, 91%, 93%, or 95%, or values ​​within the range obtained by any combination of the above two values. The mass fraction of silicon can be 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, or 25%, or values ​​within the range obtained by any combination of the above two values. The mass fraction of phenyl groups in organosilicon polymers containing silicon-oxygen structures can be 5%, 7%, 9%, 11%, or 12%, or values ​​within the range obtained by any combination of the above two values.

[0170] In the embodiments of the present application, the silicon hydroxyl group refers to a hydroxyl group (Si-OH) directly connected to a silicon atom. As an example, the silicon hydroxyl group in the organosilicon polymer containing a siloxane structure can be tested by an acid-base titration method. Based on the weak acidity of the silicon hydroxyl group, a strong base is used to quantitatively neutralize the silicon hydroxyl group. The specific testing steps are as follows: accurately weigh the organosilicon polymer containing a siloxane structure as a test sample (usually a few milligrams), and dissolve it in anhydrous toluene / isopropyl alcohol mixed solvent, and an equal amount of pure solvent without sample as a blank control. Add a few drops of acid-base indicator (such as bromothymol blue, which is yellow under acidic to neutral conditions and blue under alkaline conditions) to the sample solution and the blank solution, respectively. At this time, the sample solution is yellow, which can be inferred to contain silicon hydroxyl groups.

[0171] The organosilicon polymer containing a siloxane structure is 75% to 95%, which has good heat resistance at high temperatures, so that the isolation film has good heat resistance, thereby improving the reliability of the battery cell.

[0172] The mass fraction of silicon element is 10% to 25%, which helps to improve the proportion of inorganic siloxane skeleton in the organosilicon polymer. The siloxane skeleton containing silicon element provides a higher thermal decomposition temperature and oxidation resistance, so that the isolation film has structural stability in a high temperature environment.

[0173] 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 siloxane structure 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 layer of 5-10 nm thick 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 the isolation film with a regular and clear area 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 containing the sample to be tested is placed in the SEM sample chamber, and after the door is closed, the vacuum system is started to be pumped to a high vacuum state required by the instrument (usually 10 -3 -10 -5Pa). After the vacuum is up to the standard, adjust the electron gun voltage (usually 5-20 kV), working distance (usually 5-15 mm), move the sample stage by 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 organosilicon polymer containing siloxane structure is analyzed to detect the content of silicon element in the organosilicon polymer containing siloxane structure. According to the data results of the instrument, the distribution of each element can be obtained, and the mass fraction of silicon element can be obtained.

[0174] The mass fraction of phenyl is 2% to 12%, which can introduce aromatic structure and rigid structure with conjugation effect, and further improve the heat resistance of the isolation film.

[0175] In the organosilicon polymer containing siloxane structure, the mass fraction of silicon hydroxyl in the organosilicon polymer containing siloxane structure is 100-1500ppm, which can provide additional active sites. On the one hand, the silicon hydroxyl can form hydrogen bonds or strong dipole interactions with polar solvent molecules in the electrolyte, thereby further improving the wettability and wetting of the coating; on the other hand, the silicon hydroxyl can undergo condensation or crosslinking reaction with other functional groups (such as epoxy group, carboxyl group) during heat treatment or crosslinking process, reducing the structure collapse or shedding phenomenon of the coating under high temperature and long cycle conditions, thereby improving the wettability of the electrolyte in the isolation film.

[0176] 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 phenyl groups in the organosilicon polymer. Specifically, 0.5-1 mg of the organosilicon polymer is weighed as a test sample, and is loaded into a quartz cracking tube of a pyrolysis instrument, and is pyrolyzed at 550°C for 1.2 s. The sample is tested for pyrolysis into volatile small molecules in an inert gas (such as helium), and is then introduced into a gas chromatograph-mass spectrometer. An HP-5ms (30 m x 0.25 mm x 0.25 μm) chromatographic column is selected, and the temperature is set to 30°C for 5 min, 10°C / min to 250°C, and 250°C for 5 min. The carrier gas is high-purity helium, and the flow rate is 1.0 mL / min. The mass spectrometry uses electrochemical ionization, the ion source temperature is 230°C, and the fragment scan range is m / z 25-200. By comparing with the EVA standard 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 fraction of the benzene ring in the organosilicon polymer based on the above-mentioned fragment peak area corresponding to the characteristic benzene ring.

[0177] Therefore, by limiting the crosslinking degree of the crosslinked polymer, the mass fraction of silicon elements, and the mass fraction of phenyl groups to meet the above ranges, respectively, the structure of the organosilicon polymer containing a siloxane structure can be controlled, so that the organosilicon polymer has high thermal stability, the heat resistance of the isolation film is improved, and the reliability of the battery cell at high temperature is improved.

[0178] In some embodiments, the organosilicon polymer containing a siloxane structure includes a skeleton composed of a compound shown in formula (II), R a [SiO 3 / 2 ] n Formula (II), wherein n is any value in the integer range of 4 to 12, R a 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; optionally, n is 8, and Ra includes a C1-C3 alkyl group. 12 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; optionally, n is 8, and Ra includes a C1-C3 alkyl group. 12 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; optionally, n is 8, and Ra includes a C1-C3 alkyl group. 12 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; optionally, n is 8, and Ra includes a C1-C3 alkyl group.

[0179] R amay include one or more of cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclononyl, phenyl, naphthyl, anthryl, phenanthryl, methyl, ethyl, n-propyl, i-propyl, n-butyl, s-butyl, i-butyl, t-butyl, n-pentyl, i-pentyl, neopentyl, t-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-dodecyl, ethenyl, 1- propenyl, 2-propenyl (allyl), 1-butenyl, 2-butenyl, 3-butenyl, 1,3-butenyl, and pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, dodecenyl, ethynyl, 1-propynyl, 2-propynyl (propargyl), 1-butynyl, 3-butynyl, 1-pentynyl, 3-pentynyl, and hexynyl, heptynyl, octynyl, nonynyl, decynyl, undecynyl, dodecynyl.

[0180] Optionally, n is 8, R a includes at least one of methyl, ethyl, n-propyl, i-propyl.

[0181] In the above embodiments, by introducing the covalent polyhedral skeleton shown in formula (II) 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 (II) 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, R a C1-C3 alkyl, the rigidity and thermal stability of the organic compound can be further improved, and 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.

[0182] In some embodiments, the organosilicon polymer containing a silicon-oxygen structure includes one or more of monomers shown in formula (II), wherein R'1 includes C1-C3 alkyl.

[0183] The hydrolysis-polycondensation reaction of the monomer of formula (III) can obtain the organosilicon polymer with complete cage structure and uniform molecular chain dispersion. The organosilicon polymer particles obtained in this way are uniformly distributed in the coating of the separator film, and can form a coating structure with good pore connectivity, which is beneficial to the continuous penetration of the electrolyte, thereby improving the wettability of the electrolyte on the separator film. The sufficient wettability of the electrolyte in the separator film can ensure that the negative active material is uniformly utilized during the charging and discharging process, reduce the low utilization rate of the negative active material or capacity attenuation caused by insufficient local wettability, thereby delaying the capacity attenuation rate of the battery and improving the cycle performance of the battery cell.

[0184] In the embodiments of the present application, the organosilicon polymer containing a cage-like polysilsesquioxane skeleton is prepared by the following method: hydrolyzing the monomer of formula (III), then adding a catalyst, and performing polycondensation under heating to obtain an organosilicon polymer containing a siloxane structure.

[0185] Thus, the organosilicon polymer containing a siloxane structure is obtained by hydrolysis and polycondensation reaction.

[0186] 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 10-40°C, 10-30°C, 10-20°C, 20-30°C, 22-27°C, 23-26°C, 24-25°C, etc. Thus, the organosilicon polymer containing a siloxane structure with high crosslinking degree can be obtained.

[0187] In some embodiments, the Ph of the hydrolysis solution is 3-6. For example, the hydrolysis PH can be 3, 4, 5, 6 or any value within the above range; Ph within the above range, on the one hand, ensures the continuous and stable generation of active condensation units, providing sufficient and uniform reaction precursors for subsequent condensation reaction; on the other hand, avoids the reaction lag caused by too slow hydrolysis rate due to too low Ph, and reduces the local aggregation phenomenon caused by rapid hydrolysis and intense condensation due to too high Ph. Therefore, by controlling the Ph of the hydrolysis solution to be 3-6, the hydrolysis reaction rate is moderate, which is beneficial to the sufficient hydrolysis of the above-mentioned monomer into active condensation units, reduces the local aggregation growth caused by too fast reaction, thereby promoting the process of uniform nucleation, obtaining organosilicon polymers containing siloxane structures with different particle size intervals and different proportions.

[0188] In some embodiments, the siloxane-structure-containing organosilicon polymer satisfies one or more of the following conditions: (1) the crosslinking degree of the siloxane-structure-containing organosilicon polymer is 85% to 97%; (2) the mass fraction of silicon element in the siloxane-structure-containing organosilicon polymer is 25% to 45%; (3) the mass fraction of the skeleton composed of the compound represented by formula (II) in the siloxane-structure-containing organosilicon polymer is 40% to 60%; and (4) the siloxane-structure-containing organosilicon polymer includes silicon hydroxyl groups.

[0189] For example, the crosslinking degree of the siloxane-structure-containing organosilicon polymer can be 85%, 87%, 89%, 91%, 93%, 95%, 97%, or a value within the range obtained by any two of the above-mentioned numerical combinations. The mass fraction of silicon element can be 25%, 27%, 29%, 31%, 33%, 35%, 37%, 39%, 41%, 43%, 45%, or a value within the range obtained by any two of the above-mentioned numerical combinations. The mass fraction of the skeleton composed of the compound represented by formula (II) in the siloxane-structure-containing organosilicon polymer can be 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60%, or a value within the range obtained by any two of the above-mentioned numerical combinations.

[0190] The crosslinking degree of the siloxane-structure-containing organosilicon polymer is 85% to 97%, which ensures the structural stability of the organosilicon polymer at high temperatures. The higher mass fraction of silicon element makes the polarity of the organosilicon polymer higher, which enhances the affinity of the organosilicon polymer with the electrolyte, thereby improving the diffusion speed and wetting ability of the electrolyte in the coating. The mass fraction of the skeleton composed of the compound represented by formula (II) in the siloxane-structure-containing organosilicon polymer is 40% to 60%, which can ensure that the crosslinked polymer has good rigidity and structural stability, reduces the structural collapse of the separator film at high temperatures, and is conducive to improving the heat resistance of the separator film, thereby improving the reliability of the battery cell at high temperatures. The silicon hydroxyl groups can increase the interaction between the polymer and the electrolyte molecules, further improving the wettability and interface stability of the coating. The inclusion of silicon hydroxyl groups in the organosilicon polymer can provide additional active sites. On the one hand, the silicon hydroxyl groups can easily form hydrogen bonds or strong dipole interactions with the polar solvent molecules in the electrolyte, thereby further improving the liquid affinity and wettability of the coating; on the other hand, the silicon hydroxyl groups can undergo condensation or crosslinking reactions with other functional groups (such as epoxy groups and carboxyl groups) during heat treatment or crosslinking, reducing the structural collapse or shedding of the coating at high temperatures and under long cycle conditions, thereby improving the wetting performance of the electrolyte in the separator film.

[0191] By limiting the organosilicon polymer to satisfy at least one of the above-mentioned conditions, the wettability of the electrolyte to the separator film and the heat resistance of the separator film can be improved, thereby improving the reliability and cycle performance of the battery cell.

[0192] In some embodiments, the method for preparing the organosilicon polymer containing siloxane structure comprises the following steps: (1) hydrolyzing the monomer represented by formula (III) and an emulsifier (e.g., methyltrimethoxysilane), and then adding a catalyst to perform polycondensation under heating to obtain the organosilicon polymer containing siloxane structure. Thus, the organosilicon polymer containing siloxane structure is obtained through hydrolysis and polycondensation reactions.

[0193] In some embodiments, the monomer represented by formula (III) is first hydrolyzed to generate silanol, while releasing alcohol to form a mixed solution, and the alcohol increases the solubility of the organosiloxane monomer in the solution to obtain a pre-emulsion containing silanol; then, the pre-emulsion is added dropwise under the conditions of nitrogen protection and stirring after the temperature is raised to 30-100°C in a reaction kettle or reactor. Under the action of the catalyst, the silanol starts to polycondense, and Si-O-Si bonds are generated between silanols to further form a network structure, and nucleation begins at this time. Finally, these nuclei continuously absorb silanol from the solution to continue to grow until the organosilicon polymer containing siloxane structure is formed. The nucleation process and the nucleus growth process are competitive, and the reaction temperature will affect these two processes. When the nucleation process dominates, more nuclei are generated, and the particle size of the organosilicon polymer containing siloxane structure obtained ultimately is larger. The increase in temperature intensifies the reaction, so that more nuclei are generated in the initial stage of the reaction, more silanol is consumed, thereby limiting the growth of the nuclei in the later stage, and the particle size of the organosilicon polymer containing siloxane structure ultimately generated is smaller.

[0194] In some embodiments, the organic compound particles satisfy at least one of the following conditions: (1) the cyclic voltammogram of the organic compound particles in the first cycle has no oxidation peak in the voltage range of 0 to 4.4 V; (2) the glass transition temperature of the organic compound particles has no glass transition temperature T g at 300°C; (3) the initial thermal weight loss temperature T 3d of the organic compound particles is greater than or equal to 250°C; (4) the dissolution rate of the organic compound particles is less than or equal to 5% when the organic compound particles are soaked in a mixed solvent composed of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 3:7 at 60°C for 7 days; and (5) the true density of the organic compound particles is 0.8 g / cm 3 ~ 2.0 g / cm 3 .

[0195] For example, the initial thermal weight loss temperature T 3d5%, 4%, 3%, 2%, 1%, or a value within a range obtained by any two of the above-mentioned numerical combinations. The dissolution rate of the organic compound particles can be 5%, 4%, 3%, 2%, 1%, or a value within a range obtained by any two of the above-mentioned numerical combinations. The true density of the organic compound particles can be 0.8 g / cm 3 , 0.9 g / cm 3 , 1.0 g / cm 3 , 1.1 g / cm 3 , 1.2 g / cm 3 , 1.3 g / cm 3 , 1.4 g / cm 3 , 1.5 g / cm 3 , 1.6 g / cm 3 , 1.7 g / cm 3 , 1.8 g / cm 3 , 1.9 g / cm 3 , 2.0 g / cm 3 , or a value within a range obtained by any two of the above-mentioned numerical combinations.

[0196] The electrochemical stability of conventional organic particles is generally poor and is prone to decomposition under high pressure. The cyclic voltammetry curve of the organic compound particles in the embodiments of the present application in the first cycle has no oxidation peak in the voltage range of 0V to 4.40V, indicating that the organic compound particles are stable in the voltage range of 0V to 4.40V and have good electrochemical stability, which can be applied to high-voltage battery cells, so that the battery cells have good capacity performance under high pressure, and the working voltage and energy density of the battery cells are improved.

[0197] As an example, the oxidation peak potential of the cyclic voltammetry curve of the organic compound particles can be tested as follows: the organic compound particles, the binder polyacrylate, and the conductive agent conductive carbon black are dissolved in water according to a solid content mass ratio of 64:7:29 to prepare a slurry, the slurry is coated on an aluminum foil as a positive electrode, a lithium foil is used as a negative electrode, and a button cell is assembled; the button cell is subjected to cyclic voltammetry (CV) test, the scanning rate is 0.10 mV / s, the voltage range is 0V-5.00V, and the cycle is 3 cycles, and the voltage corresponding to the peak point of the cyclic voltammetry curve in the first cycle is taken as the oxidation peak potential. The electrolyte salt of the electrolyte used for testing is LiPF6, and the concentration is 1 mol / L. The solvent of the electrolyte is obtained by mixing ethylene carbonate (EC) and methyl ethyl carbonate (EMC) according to a volume ratio of 3:7.

[0198] The glass transition temperature T gThe glass transition temperature refers to the transition temperature of the material from glass state to high-elastic state, which presents a step change on the DSC curve. The organic compound particles have no glass transition temperature below 300°C, which means that the DSC curve of the organic compound particles remains solid rigid below 300°C, and no molecular chain segment movement or softening occurs, so as to improve the heat resistance of the isolation film.

[0199] As an example, the glass transition temperature T g The test can be performed as follows: take an appropriate amount of sample (for example, 5-15 mg) and place it in a differential scanning calorimeter (DSC) crucible, shake it flat, and cover it with a crucible cover; parameter settings: nitrogen atmosphere, purge gas 60 mL / min, and protective gas 20 mL / min; program settings: temperature rise from 25°C to 200°C at a rate of 10°C / min, hold for 5 min to eliminate thermal history, temperature drop from 200°C to -40°C at a rate of 10°C / min, and temperature rise from -40°C to 300°C at a rate of 10°C / min. The glass transition temperature T g .

[0200] The initial thermal weight loss temperature T 3d of the organic compound particles is greater than or equal to 250°C, indicating that the weight of the organic compound particles does not change significantly at high temperatures, so that the organic compound particles have high thermal stability and are not prone to thermal decomposition during the use of the battery cell and in high-temperature environments. The organic compound particles are used in the isolation film, and the organic compound particles can better generate a force to resist the shrinkage of the isolation film, so as to improve the overall thermal shrinkage of the isolation film, improve the heat resistance of the isolation film, and improve the reliability of the battery cell.

[0201] The initial thermal weight loss temperature T 3d 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 3d of the organic particles can be tested as follows: take an appropriate amount of sample (for example, 5-15 mg) and place it in an alumina crucible of a thermal gravimetric analyzer (TGA), shake it flat, and cover it with a crucible cover; parameter settings: nitrogen atmosphere, purge gas 60 mL / min, and protective gas 20 mL / min; temperature rise program: temperature rise rate 10°C / min, temperature range 35°C-600°C; obtain 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) from the test curve, which is the initial thermal weight loss temperature T 3d .

[0202] The dissolution rate can refer to the proportion of the particles dissolved or decomposed in the electrolyte. After the organic compound particles are soaked in the electrolyte at 60°C for 7 days, the dissolution is less than 5%, the organic compound particles are not easy to precipitate or dissolve in the electrolyte environment, the electrolyte pollution or the side reaction between the organic compound particles and the electrolyte is reduced in the cycle process of the battery cell, the isolation film has good structural stability, and the cycle performance and reliability of the battery cell are improved.

[0203] As an example, the swelling degree of the organic compound particles can be tested according to the following method: take an appropriate amount of sample (for example, about 1 g), and record the mass as m1, and place it in a semi-permeable membrane sample bag, seal the bag, and the sample bag can permeate the solvent but cannot permeate the sample; soak the sample bag in an appropriate amount of solvent (for example, about 50 g) at 60°C for 7 days, then take out the sample bag, take out the sample from the sample bag, wipe off the excess solvent, and weigh the mass of the sample again 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.

[0204] The true density refers to the mass of a material per unit actual volume (excluding internal voids, i.e., not including open and closed pores and inter-particle voids) in an absolutely dense state. The true density of the organic compound particles is 0.8 g / cm 3 ~2.0 g / cm 3 , which is conducive to improving the capacity of the battery cell and obtaining a battery cell with high energy density.

[0205] The true density of the organic compound particles has the meaning known in the art and can be tested by methods known in the art. As an example, an organic compound particle with a mass of M is placed in a true density tester (AccuPyc II 1340 analyzer) at room temperature (15°C-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, i.e., the true volume V of the organic compound particles. The true density of the organic compound particles is the mass M of the organic compound particles / the true volume V of the organic compound particles, and the unit of the true density is g / cm 3 .

[0206] In some embodiments, the mass fraction of the organic compound particles in the coating is 50%-97%.

[0207] The mass fraction of organic compound particles in the coating can be 50%, 52%, 54%, 56%, 58%, 60%, 62%, 64%, 66%, 68%, 70%, 72%, 74%, 76%, 78%, 80%, 82%, 84%, 86%, 88%, 90%, 92%, 94%, 96%, 97%, or a value within the range obtained by any combination of the above two values.

[0208] By limiting the mass fraction of organic compound particles in the coating to meet the above range, the coating can have structural stability and air permeability, improve the heat resistance of the separator, and thus improve the reliability of the battery cell.

[0209] In some embodiments, the coating further includes a first adhesive, which satisfies at least one 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.

[0210] For example, the mass fraction of the first adhesive in the coating can be 3%, 5%, 7%, 9%, 11%, 13%, 15%, or a value within the range obtained by any combination of the above two values.

[0211] The organic compound particles in the coating are interconnected and fixed by the first binder, reducing the likelihood of these particles detaching 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 organic compound 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.

[0212] In some embodiments, the separator film further comprises second binder particles, the second binder particles being located in the coating layer, or the separator film further comprises a bonding layer, the bonding layer being provided on at least one side of the coating layer away from the base film, and the second binder particles being located in the bonding layer; the second binder particles satisfy one or more of the following conditions: (1) the second binder particles comprise at least one of polyvinylidene fluoride, poly(vinylidene fluoride-co-trichloroethylene), poly(vinylidene fluoride-co-trifluorochloroethylene), poly(vinylidene fluoride-co-trifluoroethylene), poly(vinylidene fluoride-co-tetrafluoroethylene), poly(vinylidene fluoride-co-hexafluoropropylene), polyacrylate, polymethyl methacrylate, polyacrylonitrile; (2) the volume average particle size Dv50 of the second binder particles is 5 μm to 20 μm.

[0213] For example, the volume average particle size Dv50 of the second binder particles can be 5 μm, 7 μm, 9 μm, 11 μm, 13 μm, 15 μm, 17 μm, 19 μm, 20 μm, or a value within a range obtained by combining any two of the above values.

[0214] The addition of the second binder particles in the coating layer or the bonding layer of the separator film can fill the gap between the negative electrode sheet and the separator film, form a relatively firm bonding interface, and 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 during the cycle process, and improving the cycle performance of the battery cell. The volume average particle size Dv50 of the second binder particles satisfies 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.

[0215] It should be understood that the "first binder" in the embodiments of the present application plays a bonding role between the organic compound particles in the porous coating layer of the separator film, and the "second binder particles" play a role in improving the adhesion between the separator film and the electrode sheet.

[0216] In some embodiments, the coating layer of the separator film comprises organic compound particles and second binder particles, the second binder particles can be embedded in the organic compound particles and form protrusions on the surface of the coating layer.

[0217] In some embodiments, the coating layer of the separator film comprises a heat-resistant layer and a bonding layer, the heat-resistant layer is provided on the porous base film, the bonding layer is provided on at least a part of the surface of the heat-resistant layer away from the porous base film, the organic compound particles are provided in the heat-resistant layer, and the second binder particles are provided in the bonding layer.

[0218] In some embodiments, the coating of the separator film comprises 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, organic compound particles are disposed in the heat-resistant layer, and second binder particles are disposed in the bonding layer.

[0219] In some embodiments, the coating of the separator film comprises 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 heat-resistant layer and on at least a portion of the surface of the other side of the porous base film, organic compound particles are disposed in the heat-resistant layer, and second binder particles are disposed in the bonding layer.

[0220] In some embodiments, the coating comprises inorganic particles, the mass fraction of the inorganic particles is 0.1 wt.% to 50 wt.% based on the total mass of the coating.

[0221] In other embodiments, the coating comprises inorganic particles, the mass fraction of the inorganic particles is 50 wt.% to 92 wt.% based on the total mass of the coating. In one example, the inorganic particles comprise 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 beneficial to improving the ion transport efficiency in the coating.

[0222] In some embodiments, the separator film satisfies one or more of the following conditions: (1) the thickness of the coating is 0.5 μm to 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 to 500 s / 100 mL.

[0223] 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.

[0224] A coating that is too thin cannot form an effective heat-resistant layer, and a coating that is too thick increases the thickness of the separator film and reduces the energy density of the battery cell. A coating with a thickness of 0.5 μm to 10 μm can provide a uniform and dense heat-resistant coating, improve the heat-resistant performance of the separator film, and thus improve the reliability of the battery cell.

[0225] The area density of the coating layer is 1.5 g / m 2 ~ 6 g / m 2 , which can ensure moderate coating quality, improve the stability and heat resistance of the separator film, and will not significantly increase the weight of the separator film, thereby being conducive to the energy density and reliability of the battery cell. For example, the area density of the coating layer can be 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.

[0226] The area density of the coating layer can be controlled by controlling the amount of coating slurry coated on the porous base film during the preparation of the separator film. As an example, the area density of the coating layer can be tested by the following method: first, a single separator film containing a coating layer in the embodiments of the present application and a single separator film substrate without a coating layer are independently stacked to 6 layers, and pressure is applied to make each layer tightly adhere and have no bubbles. Subsequently, the two groups of stacks are cut according to the sample template, and 6 samples are obtained. Then, the total mass M1 of the 6 samples with the coating layer and the total mass M2 of the 6 samples of the substrate without the coating layer are measured, and the average mass of the coating layer 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 area density of the coating layer can be obtained according to the formula "coating layer area density = M / S".

[0227] The heat 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 still maintain very low longitudinal and transverse heat shrinkage rates at 130℃, i.e., the separator film in the embodiments of the present application has good heat resistance at high temperature.

[0228] As an example, the heat shrinkage rate test of the separator film can refer to GB / T 36363-2018. As an example, the separator 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 placed in the air 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) heat shrinkage rate is [(100-a) / 100]x100%, and the transverse (TD) heat shrinkage rate is [(50-b) / 50]x100%. The average value of 3 parallel samples is taken as the test result.

[0229] 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, which 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 fast 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.

[0230] As an example, the air permeability of the separator film can be tested according to GB / T 36363-2018. Specifically, the separator film is cut into a square of 5 cm in size, and a gas permeability instrument is used to test the time required for 100 ml of air to pass through 6.45 cm 2 of the separator film under the application of 1.21 kPa pressure, as the air permeability of the separator film, in s / 100 ml. The average value of 3 parallel samples is taken as the test result.

[0231] In some embodiments, the thickness of the separator film can be 5 μm-20 μm, optionally 5 μm-12 μm, 6 μm-12 μm. Thus, it is beneficial to improve the energy density of the secondary battery cell.

[0232] 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.

[0233] The shape of the battery cell is not particularly limited in the embodiments of the present application, and can be cylindrical, square, or any other shape. For example, FIG. 1 is a schematic structural diagram of a battery cell according to an embodiment of the present application, and the battery cell is square.

[0234] FIG. 2 is a schematic structural 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 encapsulate the electrode assembly and the electrolyte.

[0235] 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, or the like. 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, polybutylene succinate, or the like can be listed.

[0236] In some embodiments, referring to FIG. 2, the battery cell 3 includes an outer shell 30 and an electrode assembly 33 disposed in the outer shell 30, and the outer shell 30 includes a shell body 31 and a cover plate 32 for covering an opening of the shell body 31.

[0237] The electrode assembly 33 can be made by a winding process or a stacking process from a positive electrode sheet, a negative electrode sheet, and a separator. The electrode assembly 33 can include an electrode assembly body and a tab 331 extending from the electrode assembly body.

[0238] The cover plate 32 includes an electrode terminal 322, and FIG. 3 is a schematic diagram of a battery device according to an embodiment of the present application. 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.

[0239] 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.

[0240] In some embodiments, the battery cell 3 includes a pressure relief mechanism 313 for relieving substances in the battery cell 3 when thermal runaway occurs in the battery cell, so as to reduce the risk that the emissions in the battery cell 3 cannot be discharged in time.

[0241] 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 at least one, and the specific number can be selected by a person skilled in the art according to the application and capacity of the battery module.

[0242] [Positive electrode sheet]

[0243] 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.

[0244] As an example, the positive electrode current collector has two surfaces opposite in the thickness direction thereof, and the positive electrode active material layer is disposed on either one or both of the two surfaces of the positive electrode current collector.

[0245] In some embodiments, the positive electrode current collector can employ a metal foil or a composite current collector. For example, as the metal foil, an aluminum foil can be employed. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer material base material such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0246] 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 modified compounds of each thereof. However, the present application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries can also be used. These positive electrode active materials can be used alone only one or in combination of two or more. Among them, examples of the lithium transition metal oxide can include, but are not limited to, lithium cobalt oxide (e.g., LiCoO2), lithium nickel oxide (e.g., LiNiO2), lithium manganese oxide (e.g., LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (e.g., LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(also referred to simply as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2(also referred to simply as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2(also referred to simply as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2(also referred to simply as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2(also referred to simply as NCM 811), lithium nickel cobalt aluminum oxide (e.g., LiNi 0.85 Co 0.15 Al 0.05 O2) and modified compounds thereof. Examples of lithium-containing olivine-structured phosphates can include, but are not limited to, at least one of lithium iron phosphate (e.g., LiFePO4 (also referred to simply as LFP)), a composite of lithium iron phosphate and carbon, lithium manganese phosphate (e.g., LiMnPO4), a composite of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite of lithium manganese iron phosphate and carbon. The battery undergoes deintercalation and consumption of Li during the charge and discharge process, and the molar content of Li in the positive active material is different when the battery is discharged to different states.

[0247] 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.

[0248] 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.

[0249] In some embodiments, the positive electrode sheet can be prepared by forming a positive electrode slurry from the components described above for preparing the positive electrode sheet. For example, the positive active material, the conductive agent, the binder, and any other components are dispersed in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry. The positive electrode slurry is then coated on the positive current collector, and after processes such as drying, cold pressing, etc., the positive electrode sheet is obtained.

[0250] The battery undergoes deintercalation and consumption of Li during the charge and discharge process, and the molar content of Li is different when the battery is discharged to different states. In the listing of positive electrode materials 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 charge and discharge cycles, the molar content of Li changes.

[0251] In the listing of positive electrode materials 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 fluctuate.

[0252] [Positive electrode sheet]

[0253] The negative electrode sheet includes a negative current collector and a negative film layer disposed on at least one surface of the negative current collector, the negative film layer including a negative active material.

[0254] As an example, the negative electrode current collector has two surfaces opposite in the thickness direction thereof, and the negative electrode film layer is provided on either one or both of the two surfaces of the negative electrode current collector.

[0255] In some embodiments, the negative electrode current collector can employ a metal foil or a composite current collector. For example, as the metal foil, a copper foil can be employed. 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, 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.

[0256] In some embodiments, the negative electrode active material can employ a negative electrode active material for a battery known in the art. As an example, the negative electrode active material can include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, a silicon-based material, a tin-based material, and lithium titanate, etc. The silicon-based material can be selected from at least one of elemental silicon, a silicon oxide compound, a silicon-carbon composite, a silicon-nitrogen composite, and a silicon alloy. The tin-based material can be selected from at least one of elemental tin, a tin oxide compound, and a tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as a negative electrode active material for a battery can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0257] In some embodiments, the negative electrode 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).

[0258] In some embodiments, the negative electrode 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 dots, carbon nanotubes, graphene, and carbon nanofibers.

[0259] In some embodiments, the negative electrode film layer can further optionally include other auxiliary agents, such as a thickening agent (e.g., sodium carboxymethyl cellulose (CMC-Na)) and the like.

[0260] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as the negative electrode active material, the spherical particles, the conductive agent, the binder, and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry on a negative electrode current collector, and after processes such as drying, cold pressing, etc., the negative electrode sheet can be obtained.

[0261] [Electrolyte]

[0262] The electrolyte functions to conduct ions between the positive electrode sheet and the negative electrode sheet. The type of electrolyte is not specifically limited in the present application and can be selected as needed. For example, the electrolyte can be liquid, semi-solid, or all-solid.

[0263] In some embodiments, the electrolyte employs an electrolyte solution. The electrolyte solution includes the catalyst in any of the possible embodiments described above.

[0264] In some embodiments, the electrolyte solution includes an electrolyte salt and a solvent.

[0265] 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 difluorobisoxalate borate, lithium bisoxalate borate, lithium difluorobisoxalate phosphate, and lithium tetrafluorobisoxalate phosphate.

[0266] For a lithium-ion battery cell or a lithium metal battery cell, the solvent can include one or more of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0267] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0268] In some embodiments, the electrolyte solution can optionally further include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, and can further include an additive capable of improving certain performance of the battery, such as an additive for improving overcharge performance of the battery, an additive for improving high-temperature or low-temperature performance of the battery, etc.

[0269] [Separator]

[0270] The separator, i.e., the diaphragm, is not particularly limited in the present application, and any known porous structure separator having good chemical stability and mechanical stability can be selected.

[0271] In some embodiments, the separator includes the coating layer in any of the possible embodiments described above. The coating layer includes organic compound particles; the morphology of the organic compound particles is spherical or spheroidal, and in a cross-section of the coating layer along the thickness direction of the separator, based on the total number of the organic compound particles, the number of particles with a particle size R1 satisfying 0 < R1≤ 100 nm accounts for 0% to 0.5%, the number of particles with a particle size R2 satisfying 100 < R2≤ 300 nm accounts for 65% to 85%, and the number of particles with a particle size R3 satisfying 300 < R2≤ 800 nm accounts for 15% to 35%.

[0272] In the above technical solution, compared with inorganic particles with a larger density, the organic compound particles have a smaller density and lighter mass, which is conducive to improving the energy density of the battery monomer. In the spherical or spheroidal organic compound particles, 0% to 0.5% of the smaller particle size R1 can fill the gaps between larger particles, reduce large pores and surface defects in the coating layer, thereby improving the compactness and overall uniformity of the coating layer, enhancing the structural stability of the separator under high-temperature conditions, and reducing the risk of thermal shrinkage. 65% to 85% of the medium particle size R2 are stacked with each other to provide a continuous penetration path for the electrolyte, which is conducive to rapid infiltration of the electrolyte throughout the coating layer. 15% to 35% of the larger particle size R3 can form a supporting force in the coating layer to help maintain the stability of the infiltration channel and ensure normal penetration of the electrolyte in the separator. By setting organic compound particles with different particle size ranges in the coating layer and controlling their proportion in the total number of particles, the battery monomer can have high energy density while the separator has heat resistance and good electrolyte infiltration performance, improving the reliability and cycle performance of the battery monomer.

[0273] In some embodiments, the average particle size of the organic compound particles is 80 nm to 720 nm, and / or the maximum particle size of the organic compound particles is 500 nm to 800 nm, and / or the minimum particle size of the organic compound particles is 50 nm to 100 nm.

[0274] In the above embodiments, by limiting the average particle size, the maximum particle size and the minimum particle size of the organic compound particles, the electrolyte infiltration channel in the coating can be further controlled. The average particle size is 80 nm to 720 nm, which ensures the overall uniformity of the accumulation of the organic compound particles in the coating, and is conducive to obtaining a coating with connected channels. The maximum particle size is 500 nm to 800 nm, which prevents surface protrusions or uneven infiltration channels caused by excessively large particles in the coating, thereby reducing coating defects and local electrolyte infiltration deficiencies. The minimum particle size is 50 nm to 100 nm, which can reduce the phenomenon of excessive filling of ultra-fine particles in the channels in the coating, and ensure that the coating maintains a smooth infiltration path. Through the above control of the particle size of the organic compound particles, the electrolyte can quickly and uniformly penetrate in the coating, thereby improving the cycle performance of the battery cell.

[0275] In some embodiments, the roundness of the organic compound particles is 0.5 to 1.0.

[0276] In the above embodiments, when the roundness of the organic compound particles is high, the shape of the particles is closer to a regular sphere, and the friction and accumulation resistance between the particles are smaller during the dispersion of the slurry, so that the slurry flows more uniformly, and a coating with uniform thickness and good pore structure can be formed after coating and drying, so that the electrolyte can enter the interior more quickly and uniformly when contacting the coating, thereby facilitating the improvement of the electrolyte infiltration performance in the separator membrane. The regular-shaped particles have fewer corners and irregular protrusions, and the probability of local stress concentration or micro-cracks in the coating is lower, which is conducive to the structural stability of the coating. At the same time, the particles with high roundness have a surface that can fully contact the electrolyte, and the surface wetting resistance is low, so that the electrolyte can quickly penetrate along the relatively uniform and continuous electrolyte infiltration channel between the particles, reducing local retention and uneven infiltration, thereby achieving good electrolyte wetting effect and ion conduction efficiency. Therefore, when the roundness of the organic compound particles meets the above range, the electrolyte infiltration performance in the separator membrane can be improved, thereby improving the cycle performance of the battery cell.

[0277] In some embodiments, the organic compound particles include a cross-linked polymer, and the cross-linking degree of the cross-linked polymer is 70% to 98%.

[0278] 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 separator membrane 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 particles in the coating can have good heat resistance at high temperatures, the heat resistance of the separator membrane can be improved, the overall structural integrity of the separator membrane at high temperatures can be ensured, and the reliability of the battery cell at high temperatures can be improved.

[0279] In some embodiments, the cross-linked polymer includes a silicone polymer containing a siloxane structure.

[0280] In the above embodiments, the siloxane structure of the organic silicon polymer can improve the surface polarity of the cross-linked polymer, and produce strong interaction with the solvent molecules in the electrolyte, thereby improving the affinity of the coating to the electrolyte and the wettability of the electrolyte. The cross-linked polymer includes the organic silicon polymer containing the siloxane structure. Due to the presence of the siloxane bond, the siloxane bond has high bond energy and is not easy to decompose at high temperature, which can further improve the thermal stability of the material and enhance the heat resistance of the coating of the separator film. In addition, compared with inorganic particles, the density of the organic silicon polymer is relatively low, and the overall mass of the coating can be reduced under the same thickness, which is beneficial to improve the energy density of the battery cell. Therefore, the cross-linked polymer including the organic silicon polymer containing the siloxane structure can improve the structural stability of the coating, and also improve the wettability of the electrolyte, thereby improving the cycle performance of the battery cell.

[0281] In some embodiments, the organic silicon polymer containing the siloxane structure includes a phenyl group, and the organic silicon polymer containing the siloxane structure is obtained by polymerization of a monomer represented by formula (I) and a cross-linking agent, In formula (I), R1 and R2 each independently include a C1-C4 alkyl group, a C2-C4 alkenyl group, R3 includes a C1-C4 alkyl group or a C4-C8 (meth) acryloyloxyalkyl group, and R4 includes a C2-C8 alkenyl group or a C4-C8 (meth) acryloyloxyalkyl group; and the cross-linking agent includes divinylbenzene.

[0282] In the above embodiments, the organic silicon polymer containing the siloxane structure can be obtained by polymerization of the monomer represented by formula (I) 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 higher glass transition temperature and thermal decomposition temperature, thereby improving the heat resistance of the separator film and the reliability of the battery cell.

[0283] In some embodiments, the organic silicon polymer containing the siloxane structure satisfies at least one of the following conditions: (1) the cross-linking degree of the organic silicon polymer containing the siloxane structure is 75% to 95%; (2) the mass fraction of silicon in the organic silicon polymer containing the siloxane structure is 10% to 25%; (3) the mass fraction of the phenyl group in the organic silicon polymer containing the siloxane structure is 2% to 12%; and (4) the organic silicon polymer containing the siloxane structure includes a silicon hydroxyl group.

[0284] The cross-linking degree of the organic silicon polymer containing the siloxane structure is 75% to 95%, and the organic silicon polymer containing the siloxane structure has good heat resistance at high temperature, so that the separator film has good heat resistance, thereby improving the reliability of the battery cell.

[0285] The silicon content, ranging from 10% to 25% by mass, helps to increase the proportion of inorganic silicon-oxygen backbone in organosilicon polymers. The silicon-oxygen backbone, including silicon, provides a higher thermal decomposition temperature and oxidation resistance, resulting in structural stability of the separator at high temperatures.

[0286] Silicon hydroxyl groups readily form hydrogen bonds or strong dipole interactions with polar solvent molecules in the electrolyte, thereby further improving the hydrophilicity and wettability of the coating. On the other hand, silicon hydroxyl groups can undergo condensation or cross-linking reactions with other functional groups (such as epoxy groups and carboxyl groups) during heat treatment or cross-linking, reducing the structural collapse or peeling of the coating under high temperature and long cycling conditions, thereby improving the wettability of the electrolyte in the separator.

[0287] The phenyl content is 2% to 12%, which can introduce a rigid structure with aromatic structure and conjugation effect, further improving the heat resistance of the separator.

[0288] In organosilicon polymers containing silicon-oxygen structures, the silanol groups constitute 100-1500 ppm by mass, providing additional active sites. On one hand, silanol groups readily form hydrogen bonds or strong dipole interactions with polar solvent molecules in the electrolyte, further enhancing the hydrophilicity and wettability of the coating. On the other hand, silanol groups can undergo condensation or crosslinking reactions with other functional groups (e.g., epoxy groups, carboxyl groups) during heat treatment or crosslinking, reducing structural collapse or detachment of the coating under high temperature and long-cycle conditions, thereby improving the wettability of the electrolyte in the separator.

[0289] Therefore, by limiting the degree of crosslinking of the crosslinked polymer, the mass fraction of silicon, and the mass fraction of phenyl to meet the above ranges, the structure of organosilicon polymers containing silicon-oxygen structures can be controlled to make them have higher thermal stability, improve the heat resistance of the separator, and thus improve the reliability of the battery cell at high temperatures.

[0290] In some embodiments, the organosilicon polymer containing a silicon-oxygen structure comprises a backbone formed by compounds of formula (II), R a [SiO 3 / 2 ] n Equation (II),

[0291] Where n is any integer from 4 to 12, R a Including cycloalkyl, aryl, C1-C 12 Alkyl groups, C1-C 12 alkenyl, C1-C 12 At least one of the alkynyl groups; optionally, n is 8, R a Including C1 to C3 alkyl groups.

[0292] In the above embodiments, by introducing the covalent polyhedral skeleton shown in formula (II) 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. By selecting n as 8, R a 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.

[0293] In some embodiments, the organosilicon polymer containing a siloxane structure includes one or more of the monomers shown in formula (II), which are hydrolyzed and polycondensed to form a skeleton composed of formula (II), wherein R'1 includes C1-C3 alkyl.

[0294] In the embodiments of the present application, R'1 specifically includes at least one of methyl, ethyl, n-propyl, and isopropyl.

[0295] By using the hydrolysis-polycondensation reaction of the monomer of formula (III), an organosilicon polymer with a complete cage structure and uniformly dispersed molecular chains can be obtained. The organosilicon polymer particles obtained in this way are uniformly distributed in the coating of the isolation film, and can form a coating structure with good pore connectivity, which is conducive to the continuous penetration of the electrolyte, thereby improving the wettability of the electrolyte in the isolation film. The full wettability of the electrolyte in the isolation film can ensure that the negative active material is uniformly utilized during the charging and discharging process, reducing the low utilization rate of the negative active material or capacity decay caused by insufficient local wettability, thereby delaying the battery capacity decay rate and improving the cycle performance of the battery cell.

[0296] In some embodiments, the organosilicon polymer containing a siloxane structure satisfies one or more of the following conditions: (1) the crosslinking degree of the organosilicon polymer containing a siloxane structure is 85% to 97%; (2) the mass fraction of silicon in the organosilicon polymer containing a siloxane structure is 25% to 45%; (3) the mass fraction of the skeleton composed of the compound shown in formula (II) in the organosilicon polymer containing a siloxane structure is 40% to 60%; (4) the organosilicon polymer containing a siloxane structure includes a silicon hydroxyl group.

[0297] The cross-linking degree of the organosilicon polymer containing siloxane structure is 85% to 97%, which ensures the structural stability of the organosilicon polymer at high temperature; the higher mass fraction of silicon elements makes the polarity of the organosilicon polymer higher, and the affinity between the organosilicon polymer and the electrolyte is enhanced, so as to improve the diffusion speed and wetting ability of the electrolyte in the coating; the skeleton composed of the compound shown in formula (II) has a mass fraction of 40% to 60% in the organosilicon polymer containing siloxane structure, which can ensure that the cross-linked polymer has good rigidity and structural stability, reduces the structural collapse of the separator film at high temperature, and is beneficial to improving the heat resistance of the separator film, thereby improving the reliability of the battery cell at high temperature; the silicon hydroxyl group can increase the interaction between the polymer and the electrolyte molecules, and further improve the wettability and interface stability of the coating. The organosilicon polymer includes the silicon hydroxyl group, which can provide additional active sites. On the one hand, the silicon hydroxyl group and the polar solvent molecules in the electrolyte can easily form hydrogen bonds or strong dipole interactions, thereby further improving the liquid affinity and wettability of the coating; on the other hand, the silicon hydroxyl group can undergo condensation or cross-linking reaction with other functional groups (such as epoxy group and carboxyl group) during heat treatment or cross-linking process, reducing the structural collapse or shedding phenomenon of the coating at high temperature and long cycle conditions, thereby improving the wetting performance of the electrolyte in the separator film.

[0298] By limiting the organosilicon polymer to meet at least one of the above conditions, the wettability of the electrolyte to the separator film and the heat resistance of the separator film can be improved, thereby improving the reliability and cycle performance of the battery cell.

[0299] In some embodiments, the mass fraction of the organic compound particles in the coating is 50% to 97%.

[0300] By limiting the mass fraction of the organic compound particles in the coating to meet the above range, the coating can have structural stability and air permeability, and the heat resistance of the separator film can be improved, thereby improving the reliability of the battery cell.

[0301] In some embodiments, the coating further includes a first binder, and the first binder meets 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; and (2) the mass fraction of the first binder in the coating is 3% to 15%.

[0302] The organic compound particles in the coating layer are connected and fixed to each other by the first binder, reducing the situation of falling off of the organic compound particles during coating and use. The mass fraction of the first binder meets the above range, which can reduce the proportion of the organic compound particles in the coating layer due to excessive binder while ensuring adhesion, so as to balance the stability and heat resistance of the coating layer and improve the heat resistance of the isolation film.

[0303] 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.

[0304] 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 to improve the bonding strength between the isolation film and the negative electrode sheet, thereby improving the overall stability of the isolation film, reducing the interlayer peeling phenomenon between the isolation film and the negative electrode sheet caused by thermal stress or electrochemical action during the cycle process, and improving the cycle performance of the battery cell. The volume average particle size Dv50 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.

[0305] In some embodiments, the second binder particles are arranged in the coating layer.

[0306] In other embodiments, the bonding layer can also be arranged on at least a part of the surface of the side of the coating layer away from the porous base film, the organic compound particles are arranged in the coating layer, and the second binder particles are arranged in the bonding layer.

[0307] In yet other embodiments, the coating layer is arranged on one side of the porous base film, and the bonding layer is arranged on at least a part of the surface of the other side of the porous base film, the organic compound particles are arranged in the coating layer, and the second binder particles are arranged in the bonding layer.

[0308] The porous base film can be a single-layer film or a multi-layer composite film. When the porous base film is a multi-layer composite film, the materials of the layers can be the same or different.

[0309] In some embodiments, the second binder particles are disposed in the coating layer.

[0310] In other embodiments, the adhesive layer can also be disposed on at least a portion of the surface of the heat-resistant layer away from the porous base film, the organic compound particles are disposed in the heat-resistant layer, and the second binder particles are disposed in the adhesive layer.

[0311] In yet other embodiments, the coating layer is disposed on one side of the porous base film, the adhesive layer is disposed on at least a portion of the surface of the other side of the porous base film, the organic compound particles are disposed in the coating layer, and the second binder particles are disposed in the adhesive layer.

[0312] The separation film can be prepared according to methods known in the art.

[0313] In some embodiments, a slurry including the organic compound particles and the first binder particles can be coated on at least one side of the porous base film, and after drying, the separation film is obtained.

[0314] 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 compound particles and form protrusions on the surface of the coating layer.

[0315] In some embodiments, the method for preparing the separation film can include: coating a slurry including the organic compound particles and the first binder particles on at least one side of the porous base film, and after drying, forming a coating layer; coating a slurry including the second binder particles on at least a portion of the surface of the coating layer away from the porous base film, and after drying, obtaining the separation film including the adhesive layer.

[0316] In some embodiments, the method for preparing the separation film can include: coating a slurry including the organic compound particles and the first binder particles on one side of the porous base film, and coating a slurry including the second binder particles on at least a portion of the surface of the other side of the porous base film, and after drying, obtaining the separation film including the adhesive layer.

[0317] In some embodiments, the solvent of the slurry can be water, such as deionized water.

[0318] In some embodiments, the slurry can further include other components, such as a dispersant and / or a wetting agent, etc.

[0319] In some embodiments, the separation film satisfies one or more of the following conditions: (1) the thickness of the coating layer is 0.5 μm to 10 μm; (2) the areal density of the coating layer is 1.5 g / m 2 ~ 6 g / m 2(3) the heat shrinkage of the separator film in the longitudinal direction is less than or equal to 5% when heated at 130°C for 1 hour; (4) the heat shrinkage of the separator film in the transverse direction is less than or equal to 5% when heated at 130°C for 1 hour; and (5) the air permeability of the separator film is 150 s / 100 mL to 500 s / 100 mL.

[0320] The thickness of the coating refers to the thickness of the coating on one side of the porous base film. For example, the thickness of the coating can be 1 μm, 3 μm, 5 μm, 7 μm, 9 μm, 10 μm, or a value within a range obtained by combining any two of the above values.

[0321] A coating that is too thin cannot form an effective thermal insulation layer, and a coating that is too thick increases the thickness of the separator film and reduces the energy density of the battery cell. A coating with a thickness of 1 μm to 10 μm can provide a uniform and dense heat-resistant coating, thereby improving the heat resistance of the separator film and the reliability of the battery cell.

[0322] The areal density of the coating is 0.5 g / m 2 to 5 g / m 2 , which can ensure that the coating has a moderate mass, can improve the stability and heat resistance of the separator film, and will not significantly increase the weight of the separator film, thereby being conducive to the energy density and reliability of the battery cell.

[0323] 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 rapid ion transmission, ensures the ion transmission efficiency in the separator film, and reduces the case of electrochemical polarization caused by too low air permeability of the separator film, thereby reducing the reliability of the battery cell.

[0324] In some embodiments, the peeling force between the coating of the separator film and the porous base film can be greater than or equal to 28 N / m.

[0325] In the embodiments of the present application, the peeling force between the coating of the separator film and the porous base 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, pasting a test tape with a width of 2 cm 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 value of the peeling forces of the 3 pieces as the peeling force between the coating of the separator film and the porous base film. The tensile rate is 50 mm / min.

[0326] It should be noted that the coating parameters of the above-mentioned separation 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, as long as the coating parameters of any one side meet the present disclosure, it is considered to fall within the protection scope of the present disclosure.

[0327] In some embodiments, the material of the separation film can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separation film can be a single-layer film or a multi-layer composite film, and is not particularly limited. When the separation film is a multi-layer composite film, the materials of the layers can be the same or different, and are not particularly limited.

[0328] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separation film can be used to make an electrode assembly through a winding process or a stacking process.

[0329] [Battery device]

[0330] In some embodiments, the battery cell is a battery device, and the battery device can include at least one battery cell.

[0331] 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 accommodated in the box body, and the plurality of battery cells are connected in series, in parallel, or in a mixed connection manner. Among them, the battery cells can be directly composed into a battery pack, or first composed into a battery module, and then composed into a battery pack by a plurality of battery modules.

[0332] The battery device 10 can also include a box body 11, and the box body 11 has a hollow structure inside, and the plurality of battery cells 3 are accommodated in the box body 11. For example, the plurality of battery cells 3 are combined in parallel or in series or in a mixed connection manner and then placed in the box body 11. The box body 11 can include a first box body part 111 and a second box body part 112, and the first box body part 111 and the second box body part 112 are overlapped with each other to form the box body 11. The shapes of the first box body part 111 and the second box body part 112 can be determined according to the shapes of the components accommodated inside, for example, can be determined according to the shape of the combination of the plurality of battery cells 3, and at least one of the first box body part 111 and the second box body part 112 has an opening. For example, as shown in FIG. 3, the first box body part 111 and the second box body part 112 can both be hollow cuboids and each have an opening face, the opening of the first box body part 111 and the opening of the second box body part 112 are oppositely arranged, and the first box body part 111 and the second box body part 112 are buckled with each other to form a box body 11 having a closed cavity, which can be used to accommodate the plurality of battery cells 3. The plurality of battery cells 3 are combined in parallel or in series or in a mixed connection manner and then placed in the box body 11 formed by buckling the first box body part 111 and the second box body part 112.

[0333] For another example, unlike the case 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 case that the second box part 112 is a hollow cuboid with an opening and the first box part 111 is a plate as an example, the first box part 111 covers the opening of the second box part 112 to form a box 11 with a closed cavity, which can be used to accommodate a plurality of battery cells 3.

[0334] In some embodiments, the battery device 10 can further include other components. For example, the battery device 10 can further include a busbar component, which can be used to achieve electrical connection between a plurality of battery cells 3, such as parallel connection or series connection or hybrid connection. Specifically, the busbar component can achieve electrical connection between the battery cells 3 by connecting the electrode terminals of the battery cells 3; or the busbar component can also achieve electrical connection between the battery cells 3 by connecting other components of the battery cells 3. The busbar component can be fixed to the corresponding 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.

[0335] 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.

[0336] 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.

[0337] [Electric equipment]

[0338] The battery device 10 can include at least one of the battery cell, the battery module, or the battery pack provided by the present application. The lithium ion battery, the battery module, or the battery pack can be used as a power supply of an electric equipment, or can be used as an energy storage unit of an electric equipment. The electric equipment can include a mobile device (such as a mobile phone, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto.

[0339] As an electric equipment, the battery cell, the battery module or the battery pack can be selected according to the use requirement thereof.

[0340] 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 machine, 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.

[0341] 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.

[0342] 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 source of the vehicle 1, and is used for the circuit system of the vehicle 1, such as 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 source of the vehicle 1, but also be used as a driving power source of the vehicle 1, to replace or partially replace fuel or natural gas to provide driving power for the vehicle 1.

[0343] As another example, the device can be a mobile phone, a tablet computer, a notebook computer, etc. The device usually requires thinning, and the battery cell can be used as a power source.

[0344] FIG. 5 is a schematic diagram of an electric device according to another embodiment of the present application. As shown in FIG. 5, the present application provides an electric device, which is an energy storage device 2, and the energy storage device 2 can include a plurality of battery devices 10. The energy storage device 2 can be applied to an energy storage station to store and release electric energy.

[0345] Optionally, the electric device can also be an energy storage device, an illumination device, a spacecraft, etc., and the embodiments of the present application include but are not limited to the above.

[0346] Hereinafter, the examples of the present application will be described. The examples described below are illustrative and are intended to be purely exemplary of the application and are not intended to limit the application. Unless otherwise indicated, the techniques or conditions described in the examples are in accordance with those that are well known in the art. Unless otherwise indicated, the reagents or instruments used in the examples are conventional products that can be obtained commercially.

[0347] [Examples and Comparative Examples]

[0348] Example 1

[0349] (1) Preparation of the negative electrode tab:

[0350] Preparation of the negative electrode tab: 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 96.2:1.1:1.5:1.2, and after being fully stirred and mixed uniformly, a negative electrode slurry was prepared. The negative electrode slurry was uniformly coated on a negative electrode current collector copper foil, and then dried, cold-pressed, and cut to obtain the negative electrode tab. The solid content of the negative electrode slurry was 62.5%.

[0351] (2) Preparation of the positive electrode tab:

[0352] Lithium iron phosphate (LiFeP04), polyvinylidene fluoride (PVDF), conductive carbon black (Super-P), and dispersant polyvinylpyrrolidone (PVP) were mixed at a mass ratio of 95:2.8:1.2:1.0, and stirred uniformly in a vacuum stirrer to obtain a positive electrode slurry. The slurry was coated on both sides of an aluminum foil, dried, cold-pressed, and cut to obtain the positive electrode tab.

[0353] (3) Preparation of the separator film (organic silicon polymer containing a silicon-oxygen structure):

[0354] ① Preparation of organic compound particles: In a 5L flask equipped with a stirrer, a thermometer, and a reflux condenser, 2800g of deionized water and 8ml of hydrochloric acid were added. After starting stirring, 120g of methyltrimethoxysilane was added. After hydrolysis reaction at 33°C for 2h, 70ml of ammonia water was added to adjust the pH to 9. After reaction at 33°C for 2h, the temperature was increased to 90°C and the reaction was continued for 12h to obtain a dispersion liquid of organic compound particles. The water content was evaporated to obtain a dispersion liquid with a solid content of 20% for standby use. The standby dispersion liquid was dried to obtain the corresponding organic compound powder.

[0355] The proportion of organic compound particles was tested using a scanning electron microscope (ZEISS Sigma 300). The proportion of organic compound particles was R1 (0 < R1 ≤ 100 nm) 0.2%, R2 (100 nm < R2 ≤ 300 nm) 70.9%, and R3 (300 nm < R2 ≤ 800 nm) 28.9%.

[0356] The glass transition temperature To of organic compound particles was determined using differential scanning calorimetry (DSC). g Tests were conducted on the melting point; below 300℃, there was no Tg and no melting point.

[0357] The true density of the organic compound particles was tested using a true density meter, and the true density of the organic compound particles was 1.33 g / cm³. 3 .

[0358] The crosslinking degree of organic compound particles was tested using a PQ001 nuclear magnetic resonance analyzer. The organic compound particles were crosslinked polymers, and the calculated crosslinking degree was 94.1%.

[0359] The pyrolysis of organic compound particles was tested using Py-GC / MS. Figure 6 shows the pyrolysis spectrum of the organic compound particles in this embodiment. As shown in Figure 6, by comparing the pyrolysis spectrum with the standard EVA pyrolysis spectrum in the NIST library, pyrolysis was detected. The corresponding characteristic ions suggest that the organic compound particles include a cage-like polysilsesquioxane skeleton.

[0360] Organic compound particles were dissolved in a mixture of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 3:7 and then soaked at 60°C for 7 days. The dissolution rate of the organic compound particles was tested, and the dissolution rate of the organic compound particles after soaking at 60°C for 7 days was 0.1%.

[0361] Figures 7 and 8 are SEM images of the coating in Embodiment 1 of this application. Figure 7 is a cross-sectional SEM image of the coating, and Figure 8 is a surface SEM image of the coating. As shown in Figures 7 and 8, the coating includes organic compound particles of different sizes. The organic compound particles have spherical or near-spherical morphologies, are relatively regular in shape, and have a high degree of roundness.

[0362] ② A commercially available polyethylene microporous film (Zhuogao Electronic Technology Co., Ltd.) with a thickness of 7μm and an average pore size of 50nm was used as the porous base film; the dispersion containing organic compound particles prepared above and the binder polyacrylate were stirred and mixed evenly in deionized water at a solid mass ratio of 92:8 to obtain the coating slurry.

[0363] The commercially available polyvinylidene fluoride particles (Arkema), the binder polyacrylate were stirred uniformly in deionized water according to a solid content mass ratio of 91.5:8.5 to obtain the adhesive layer slurry.

[0364] 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 adhesive layer slurry was sprayed on the coating on both sides at a loading (single side) of 1.0 g / m 2 After drying and slitting, the separator film was obtained. The air permeability of the separator film was 201 s / 100 mL. The specific implementation parameters are shown in Table 1.

[0365] (4) Preparation of electrolyte:

[0366] In an argon atmosphere glove box (H2O <0.1 ppm, O2 <0.1 ppm), ethylene carbonate (EC), methyl ethyl carbonate (EMC), and dimethyl carbonate (DMC) were mixed according to a volume ratio of 1:1:1 to obtain an organic solvent. Then LiPF6 and the additive vinylene carbonate (VC) were dissolved in the above mixed organic solvent to obtain the electrolyte. The concentration of LiPF6 was 1 mol / L, and the mass content of vinylene carbonate (VC) was 2%.

[0367] (5) Preparation of battery cell:

[0368] Preparation of battery cell: The positive electrode sheet, the separator film, and the negative electrode sheet were stacked in order, with the separator film between the positive and negative electrode sheets to separate the positive and negative electrode sheets. The electrode assembly was obtained by winding. The tab of the electrode assembly was connected to the end cover (for example, the tab and the end cover were welded by a connecting member). The electrode assembly was placed in an aluminum shell, and after drying, the electrolyte was injected, and then the battery cell was obtained by packaging.

[0369] [Example 2-5]

[0370] Example 2 differs from Example 1 in that in the preparation of the organic compound particles, the “add 70 ml of ammonia water to adjust the pH to 9” in Example 1 is adjusted to “add ammonia water to adjust the pH to 8” to obtain the organic compound particle dispersion liquid, and the rest of the preparation process is similar to Example 1.

[0371] Example 3 differs from Example 1 in that in the preparation of the organic compound particles, the “add 70 ml of ammonia water to adjust the pH to 9” in Example 1 is adjusted to “add ammonia water to adjust the pH to 10” to obtain the organic compound particle dispersion liquid, and the rest of the preparation process is similar to Example 1.

[0372] Example 4 differs from Example 1 in that, in the preparation of the organic compound particle, the "add 70 ml of ammonia water to adjust the pH to 9" in Example 1 is adjusted to "add ammonia water to adjust the pH to 7.5", to obtain an organic compound particle dispersion liquid, and the rest of the preparation process is similar to Example 1.

[0373] Example 5 differs from Example 1 in that, in the preparation of the organic compound particle, the "add 70 ml of ammonia water to adjust the pH to 9" in Example 1 is adjusted to "add ammonia water to adjust the pH to 10.5", to obtain an organic compound particle dispersion liquid, and the rest of the preparation process is similar to Example 1.

[0374] [Examples 6-7]

[0375] Example 6 differs from Example 1 in that, in the preparation of the organic compound particle, the "warm up to 90°C and continue to react for 12h" in Example 1 is adjusted to "warm up to 90°C and continue to react for 20h", to obtain an organic compound particle dispersion liquid, and the rest of the preparation process is similar to Example 1.

[0376] Example 7 differs from Example 1 in that, in the preparation of the organic compound particle, the "warm up to 90°C and continue to react for 12h" in Example 1 is adjusted to "warm up to 70°C and continue to react for 12h", to obtain an organic compound particle dispersion liquid, and the rest of the preparation process is similar to Example 1.

[0377] [Example 8]

[0378] (3) Preparation of the isolation film

[0379] ① Preparation of organic compound particles (organosilicon polymer containing phenyl and silicon hydroxyl groups):

[0380] Mix 0.3 g of potassium persulfate, 0.3 g of sodium bicarbonate, 0.9 g of sodium dodecyl sulfate, 30 g of deionized water, 3% 3-methacryloyloxypropylmethyldimethoxysilane, 85% 3-methacryloyloxypropyltrimethoxysilane, and 12% divinylbenzene (7.2 g) to obtain a pre-emulsion for standby (wherein the mass ratio of 3-methacryloyloxypropylmethyldimethoxysilane, 3-methacryloyloxypropyltrimethoxysilane and divinylbenzene is 3:85:12, and the added mass of 3-methacryloyloxypropylmethyldimethoxysilane is 1.8 g). Take a reactor, add 300 g of deionized water, and warm up to 78°C. Under the conditions of nitrogen protection and stirring, the pre-emulsion is added according to the three-stage dropwise flow rate, the first-stage dropwise flow rate is 220 ml / min, the second-stage dropwise flow rate is 350 ml / min, and the third-stage dropwise flow rate is 450 ml / min. After 3h of reaction, warm up to 95°C for 3h of curing reaction, to obtain an emulsion containing organic compound particles.

[0381] The crosslinking degree of the organic compound particles was tested using a PQ001 nuclear magnetic resonance analyzer, and the crosslinking degree of the organic compound particles was 90.2%.

[0382] The organic compounds were analyzed using a thermal pyrolysis-gas chromatography-mass spectrometry (Py-GC / MS) method. The powder was tested, and by comparing it with the standard EVA fragmentation spectrum in the NIST library, the corresponding characteristic ions were detected, which suggests that the organic compound particles include benzene rings.

[0383] The glass transition temperature To of organic compound particles was determined using differential scanning calorimetry (DSC). g Tests were conducted on the melting point; the organic compound particles showed no T below 300°C. g It has no melting point.

[0384] The density of the organic compound particles was tested using a true density meter, and the true density of the organic compound particles was 1.39 g / cm³. 3 .

[0385] Organic compound particles were immersed in a mixed solvent of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 3:7 at 60°C for 7 days. The dissolution rate of the organic compound particles was tested, and the dissolution rate of the organic compound particles after immersion at 60°C for 7 days was 0.5%.

[0386] ② A commercially available polyethylene microporous film (Zhuogao Electronic Technology Co., Ltd.) with a thickness of 7μm and an average pore size of 50nm was used as the porous base film; the emulsion containing organic compound particles prepared above and the binder polyacrylate were stirred and mixed evenly in deionized water at a solid mass ratio of 92:8 to obtain the coating slurry.

[0387] Commercially available polyvinylidene fluoride (PVDF) particles (Arkema) and adhesive polyacrylate were mixed evenly in deionized water at a solid content ratio of 90:10 to obtain an adhesive slurry. The PVDF particles had a Dv50 of 6.5 μm.

[0388] The coating slurry was applied at a concentration of 2.5 g / m³. 2 The loading amount (one-sided) was uniformly coated on both surfaces of the porous base membrane. After drying to remove the solvent, the thickness of the one-sided coating was 1.5 μm. Then, the adhesive layer slurry was applied at a loading of 1.0 g / m². 2 The loading capacity (single-sided) is applied to both sides of the coating, followed by drying and slitting processes to obtain the release membrane. The air permeability of the release membrane is 196 s / 100 mL. Specific implementation parameters are shown in Table 3.

[0389] [Examples 9-11]

[0390] Example 9 differs from Example 8 in that, in the preparation of the organic compound particles, the "dropping flow rate of the first section is 220 ml / min" in Example 8 is adjusted to "dropping flow rate of the first section is 180 ml / min", to obtain an emulsion containing organic compound particles, and the rest of the preparation process is similar to Example 8.

[0391] Example 10 differs from Example 8 in that, in the preparation of the organic compound particles, the "dropping flow rate of the first section is 220 ml / min" in Example 8 is adjusted to "dropping flow rate of the first section is 250 ml / min", to obtain an emulsion containing organic compound particles, and the rest of the preparation process is similar to Example 8.

[0392] Example 11 differs from Example 8 in that, in the preparation of the organic compound particles, the "dropping flow rate of the first section is 220 ml / min" in Example 8 is adjusted to "dropping flow rate of the first section is 300 ml / min", to obtain an emulsion containing organic compound particles, and the rest of the preparation process is similar to Example 8.

[0393] [Example 12]

[0394] Example 12 differs from Example 8 in that, in the preparation of the organic compound particles, the "temperature is raised to 90°C and the reaction is matured for 4h" in Example 8 is adjusted to "temperature is raised to 95°C and the reaction is matured for 12h", to obtain an emulsion containing organic compound particles, and the rest of the preparation process is similar to Example 1.

[0395] [Comparative Example 1]

[0396] Comparative Example 1 differs from Example 1 in that, in the preparation of the organic compound particles, the "stirring is started and 120g of methyltrimethoxysilane is added" in Example 1 is adjusted to "stirring is started and 220g of methyltrimethoxysilane is added", to obtain an organic compound particle dispersion liquid, and the rest of the preparation process is similar to Example 1. Among them, the R3 proportion is 61.60%. For specific parameters, please refer to Table 1.

[0397] [Comparative Example 2]

[0398] Comparative Example 2 differs from Example 8 in that, in the preparation of the organic compound particles, the "dropping flow rate of the first section is 220 ml / min" in Example 8 is adjusted to "dropping flow rate of the first section is 500 ml / min", to obtain an emulsion containing organic compound particles, and the rest of the preparation process is similar to Example 8. Among them, the R3 proportion is 50.40%. For specific parameters, please refer to Table 3.

[0399] Table 1 Product parameters of Examples 1-7 and Comparative Example 1

[0400] Performance parameters of examples 1-7 and comparative example 1

[0401] As shown in examples 1-6 and comparative example 1 in table 1 and table 2, by limiting the small particle size R1 to 0%~0.5%, the medium particle size R2 to 65%~85% and the large particle size R3 to 15%~35%, the small particle size R1 can fill the gap between the large particles, the medium particle size R2 can stack with each other to provide a continuous penetration path for the electrolyte, and the large particle size R3 can form a supporting force in the coating to help maintain the stability of the infiltration channel. The separator membrane has both heat resistance and good electrolyte infiltration performance, and improves the reliability and cycle performance of the battery cell. In addition, the cross-linking degree of the organic compound particles is 85%~97%, and the mass fraction of the cage polysilsesquioxane skeleton is 40%~60%. The cage polysilsesquioxane skeleton can provide structural support and ensure that the organic compound particles have good structural stability, improve the overall structural integrity of the separator membrane at high temperatures, and further improve the reliability and cycle performance of the battery cell.

[0402] Product parameters of examples 8-13 and comparative example 2 in table 3

[0403] Performance parameters of examples 8-13 and comparative example 2 in table 4

[0404] As shown in examples 8-13 and comparative example 1 in table 3 and table 4, by limiting the small particle size R1 to 0%~0.5%, the medium particle size R2 to 65%~85% and the large particle size R3 to 15%~35%, the small particle size R1 can fill the gap between the large particles, the medium particle size R2 can stack with each other to provide a continuous penetration path for the electrolyte, and the large particle size R3 can form a supporting force in the coating to help maintain the stability of the infiltration channel. The separator membrane has both heat resistance and good electrolyte infiltration performance, and improves the reliability and cycle performance of the battery cell. In addition, the cross-linking degree of the organic compound particles is 70%~98%, the mass fraction of the phenyl group is 2%~12%, and the mass fraction of the silicon hydroxyl group is 9.98%. The cage polysilsesquioxane skeleton can provide structural support and ensure that the organic compound particles have good structural stability, improve the overall structural integrity of the separator membrane at high temperatures, and further improve the reliability and cycle performance of the battery cell.

[0405] The following briefly introduces the test methods of the physicochemical parameters and performance parameters involved in the examples of the present application. 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.

[0406] 1. A method for testing the mass content of silicon hydroxyl groups

[0407] As an example, the mass content of silicon hydroxyl groups can be tested by acid-base titration. The silicon hydroxyl groups on the surface of silicon dioxide have weak acidity, and can react with strong alkali (such as sodium hydroxide) in a non-aqueous solvent (such as a sodium chloride-saturated methanol-water system). By titrating the sample suspension with a standard sodium hydroxide solution to a specific pH end point (usually from pH = 4 to pH = 9), the total amount of silicon hydroxyl groups on the surface of the sample that can be titrated can be calculated from the volume of standard alkali consumed, minus the blank test value.

[0408] Specifically, the separator of a battery monomer is taken as a sample, and the powder of the coating part of the separator is scraped off as the sample to be tested. The sample to be tested is subjected to drying treatment to remove the physically adsorbed water on the surface, and is placed in a desiccator after cooling for standby use. Control group: a certain volume (such as 50 mL) of titration solvent is added to a clean titration cell, a calibrated pH electrode is inserted into the solution, titration is performed using a sodium hydroxide standard solution, the titration curve is recorded, and the volume of NaOH consumed from pH = 4.00 to pH = 9.00 is accurately read and recorded as the blank value V0 (unit: mL). A certain amount of the sample subjected to drying treatment is added to the titration cell, the same volume of titration solvent as the control group is added, the titration cell is placed in an ultrasonic cleaner for ultrasonic treatment for 3-5 minutes to fully disperse the sample, the titration cell is placed back on the titration table, a stirring rod is inserted, a calibrated pH electrode is inserted into the solution, titration is performed using a sodium hydroxide standard solution, the titration curve is recorded, and the volume of NaOH consumed from pH = 4.00 to pH = 9.00 is accurately read and recorded as the sample value V ph+2 , and the mass content of silicon hydroxyl groups is calculated according to the following formula: wherein a (out) represents the surface silicon hydroxyl content (μg / g), C Aout represents the actual concentration of the NaOH standard solution (mol / L), V pH+2 represents the volume of NaOH solution consumed by the sample during titration from pH = 4 to pH = 9 (mL), m represents the mass of the sample to be tested added (g), represents the mass percentage content of volatile components (such as the amount of reduction after drying treatment) in the sample to be tested (%). The same sample needs to be subjected to at least two parallel tests, and the arithmetic mean of the results of the two parallel tests is taken as the final result.

[0409] 2. A method for testing the amount ratio

[0410] In the embodiments of the present application, the particle sizes R1, R2 and R3 can be tested by the following method: the organic compound particle powder is laid and adhered on the conductive glue to make a sample to be tested with a length x width of 6 cm x 1.1 cm; the particle morphology is tested using a scanning electron microscope (for example, ZEISS Sigma 300), and the test can refer to JY / T010-1996. The number proportions of the particle sizes R1, R2 and R3 are measured in the scanning electron microscope image of the test.

[0411] As an example, using a scanning electron microscope (for example, ZEISS Sigma 300), referring to JY / T010-1996, a scanning electron microscope (SEM) picture of the release film is obtained. A region with a length x width of 50 mm x 100 mm on the release film is randomly selected and cut to serve as a test sample, a plurality of test regions (for example, 5) are randomly selected in the test sample, the distance between the two farthest points on the organic compound particle is taken as the particle size of the organic compound particle, the number and particle size values of the organic compound particles in each test region are counted, the arithmetic mean of the particle sizes of the organic compound particles in each test region is taken, and the number proportions of different particle sizes of the organic compound particles in each test region are counted. Ten test samples are randomly selected for testing, and the arithmetic mean of the number proportions of different particle sizes of the ten test samples is taken as the final test result.

[0412] 3. Test method of crosslinking degree

[0413] 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 21 MHz, 0.5 g of the test sample (the above organic compound particle) after cleaning and drying treatment is taken, is loaded into a clean sample tube and inserted into a probe with a specified depth, the probe coil diameter is 13 mm, and the measurement is performed according to the manufacturer's instructions. Specifically: the proportion of the crosslinked part signal is calculated by fitting software to obtain the crosslinking degree of the crosslinked polymer by collecting the entire polymer signal; the "crosslinking degree" or "T2 relaxation" test mode is selected in the software, and the PQ001 nuclear magnetic resonance analyzer automatically obtains the relaxation decay curve. During data processing, the software decomposes the relaxation components by exponential fitting, and calculates and outputs the crosslinking degree result according to the degree of restriction of molecular chain movement.

[0414] 4. Specific test method of phenyl and cage skeleton

[0415] The pyrolysis-gas chromatography-mass spectrometry (Py-GC / MS) can be used to test the phenyl and cage skeleton structure in the organic compound particles. Specifically, 0.5-1 mg of the above organic compound particles is weighed as a test sample, loaded into a quartz cracking tube of a pyrolysis instrument, cracked at 550°C for 1.2 s, and tested in an inert gas (such as helium) to crack the sample into volatile small molecules, which are then introduced into a gas chromatograph-mass spectrometer. The HP-5ms (30 m x 0.25 mm x 0.25 μm) chromatographic column is selected, the temperature is set to 30°C for 5 min, the temperature is increased to 250°C at 10°C / min, and the temperature is 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 or the characteristic ions corresponding to the cage skeleton are detected, and it can be inferred that the organic silicon polymer includes phenyl and cage skeleton structure. The internal standard method is used to calculate the mass proportion of the characteristic benzene ring or cage skeleton in the organic compound particles based on the area of the above fragment peak.

[0416] 5. Test method of wettability

[0417] The separator of the battery monomer is taken as a sample, and the separator is cut into a 20 mm x 260 mm strip along the length direction of the separator (which is perpendicular to the thickness direction of the separator) as a to-be-tested sample, and is vertically placed in the hanging wettability device for testing the electrolyte climbing rate. The experimental platform size is 55 mm (thickness) x 174 mm (length) x 200 mm (height). The to-be-tested sample is fixed in the grooves at the upper and lower ends of the separator of the device by using double-sided tape, and the fixing process needs to ensure that the sample is straight without bending. Then, the separator with the sample strip is slowly placed into the shell, the initial liquid level height H0 is measured, the unit is cm, and then the current liquid level height H1 is measured every certain time, the unit is cm, the climbing height ΔH of the electrolyte in the time period is recorded, ΔH = H1-H0, and the corresponding time t1 is recorded. Finally, the relationship between the climbing height of the electrolyte and the time is obtained. In the same time, the greater the value of the climbing height ΔH of the electrolyte, the greater the wettability of the electrolyte in the separator, and the better the wettability.

[0418] 6. Test of thermal puncture

[0419] A piece of the prepared flat, clean, and crease-free separator film sample was cut into a 50 mm x 50 mm sample piece. The separator film was clamped flat in a clamp and tested using a separator film hot puncture tester. The target temperature of the puncture needle was set to 300°C, and the puncture rate was set to 50 mm / min. The device was started, and the puncture needle vertically penetrated the separator film at a constant speed. Then, the separator film was removed, and the diameter of the puncture hole was measured under a CCD microscope. The smaller the diameter of the puncture hole, the better the heat resistance of the separator film. Three sample pieces were tested in parallel, and the arithmetic mean of the diameters of the three samples was taken as the final result.

[0420] 7. Test of storage performance

[0421] The secondary battery cell was charged at 1 / 3 C constant current to 3.65 V at 25°C, and then charged at 3.65 V constant voltage to a current of 0.05 C. After 5 min, the secondary battery cell was discharged at 1 / 3 C constant current to 2.5 V. Then, the secondary battery cell was charged at 1 / 3 C constant current to 3.65 V, and then charged at 3.65 V constant voltage to a current of 0.05 C. At this time, the secondary battery cell was in a full charge state, and the obtained charge capacity was recorded as the pre-storage capacity CO. The full charge state secondary battery cell was placed in a 60°C constant temperature oven for storage for 100 days, and the capacity after storage was recorded as the post-storage capacity CI. The capacity retention rate of the secondary battery cell after storage for 100 days at 60°C = post-storage capacity CI / pre-storage capacity CO x 100%.

[0422] It should be noted 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 and exerting the same effects as the technical idea within the scope of the technical solution of the present application are all included in the technical scope of the present application. Furthermore, within the scope of the gist of the present application, various modifications that can be thought of by those skilled in the art, and other modes constructed by combining part of the configuration elements of the embodiments 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 organic compound particles; the morphology of the organic compound particles is spherical or spheroidal; and in a cross section of the coating layer along the thickness direction of the separator film, based on the total number of the organic compound particles, the number ratio of particles with a particle size R1 satisfying 0 R2≤800nm is 15%~35%.

2. The battery cell of claim 1, wherein, The average particle size of the organic compound particles is 80nm~720nm, and / or the maximum particle size of the organic compound particles is 500nm~800nm, and / or the minimum particle size of the organic compound particles is 50nm~100nm.

3. The battery cell according to claim 1 or 2, characterized in that, The roundness of the organic compound particles is 0.5~1.

0.

4. The battery cell of any one of claims 1-3, wherein, The organic compound particles comprise a cross-linked polymer, and the cross-linking degree of the cross-linked polymer is 70%~98%.

5. The battery cell of claim 4, wherein, The cross-linked polymer comprises a silicone polymer containing a siloxane structure.

6. The battery cell of claim 5, wherein, The silicone polymer containing a siloxane structure includes a phenyl group, and is obtained by polymerizing a monomer represented by formula (I) and a crosslinking agent, In formula (I), R1 and R2 are each independently selected from C1-C4 alkyl and C2-C4 alkenyl, R3 comprises C1-C4 alkyl or C4-C8 (meth)acryloxyalkyl, and R4 comprises C2-C8 alkenyl or C4-C8 (meth)acryloxyalkyl; and the cross-linking agent comprises divinylbenzene.

7. The battery cell according to claim 5 or 6, characterized in that, The silicone polymer containing a siloxane structure satisfies at least one of the following conditions: (1) the cross-linking degree of the silicone polymer containing a siloxane structure is 75%~95%; (2) the mass fraction of silicon in the silicone polymer containing a siloxane structure is 10%~25%; (3) the mass fraction of phenyl in the silicone polymer containing a siloxane structure is 2%~12%; (4) the silicone polymer containing a siloxane structure comprises silicon hydroxyl.

8. The battery cell of claim 5, wherein, The silicone polymer containing a siloxane structure comprises a skeleton composed of a compound represented by formula (II), R a [SiO 3 / 2 ] n Formula (II) wherein n is any integer from 4 to 12, R a including cycloalkyl, aryl, C1-C 12 alkyl, C1-C 12 alkenyl, C1-C 12 alkynyl; optionally n is 8, R a including C1-C3 alkyl.

9. The battery cell of claim 8, wherein, The silicone polymer containing a siloxane structure is obtained by hydrolysis and polycondensation of one or more monomers represented by formula (II), wherein R'1 comprises C1-C3 alkyl.

10. The battery cell of any one of claims 7-9, wherein, The silicone polymer containing a siloxane structure satisfies at least one of the following conditions: (1) the cross-linking degree of the silicone polymer containing a siloxane structure is 85%~97%; (2) the mass fraction of silicon in the silicone polymer containing a siloxane structure is 25%~45%; (3) the mass fraction of the skeleton composed of the compound represented by formula (II) in the silicone polymer containing a siloxane structure is 40%~60%; (4) the silicone polymer containing a siloxane structure comprises silicon hydroxyl.

11. The battery cell of any one of claims 1-9, wherein, The organic compound particles satisfy at least one of the following conditions: (1) the cyclic voltammetry curve of the organic compound particles in the first cycle has no oxidation peak in the voltage range of 0 to 4.4V; (2) the organic compound particles have no glass transition temperature at 300℃; (3) the initial thermal weight loss temperature T of the organic compound particles 3d greater than or equal to 250°C; (4) the organic compound particles have a dissolution rate of 5%or less when soaked in a mixed solvent of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 3:7 at 60℃ for 7 days; (5) the true density of the organic compound particles is 0.8 g / cm 3 ~ 2.0 g / cm 3 .

12. The battery cell of any one of claims 1-11, wherein, The mass ratio of the organic compound 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 comprises a first binder satisfying at least one of the following conditions: (1) the first binder comprises at least one of polyimide, polyetherimide, polyacrylic acid, polyacrylate, ethylene-vinyl acetate copolymer, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, 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 separation film further comprises second binder particles located in the coating layer, or the separation film further comprises a bonding layer disposed 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 at least one 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 of the second binder particles is 5μm to 20μm.

15. The battery cell of any one of claims 1-14, wherein, The separation film satisfies at least one of the following conditions: (1) the thickness of the coating layer is 0.5μm to 10μm; (2) the coating has an areal density of 1.5 g / m 2 ~ 6 g / m 2 ; (3) the longitudinal heat shrinkage rate of the separation film is 5%or less when heated at 130℃ for 1h; (4) the transverse heat shrinkage rate of the separation film is 5%or less when heated at 130℃ for 1h; (5) the air permeability of the separation film is 150s / 100mL to 500s / 100mL.

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

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

18. An isolating film, characterized by, The battery device comprises: a porous base film and a coating layer disposed on at least one side of the porous base film; The coating layer comprises organic compound particles, the morphology of the organic compound particles is spherical or spheroidal, and in a section of the coating layer along the thickness direction of the separation film, the number ratio of particles with a particle size R1 satisfying 0 < R1 ≤ 100 nm is 0% to 0.5% based on the total number of the organic compound particles, the number ratio of particles with a particle size R2 satisfying 100 < R2 ≤ 300 nm is 65% to 85%, and the number ratio of particles with a particle size R3 satisfying 300 < R2 ≤ 800 nm is 15% to 35%.

19. The separator membrane of claim 18, wherein, The average particle size of the organic compound particles is 80 nm to 720 nm, and / or the maximum particle size of the organic compound particles is 500 nm to 800 nm, and / or the minimum particle size of the organic compound particles is 50 nm to 100 nm.

20. The separator membrane according to claim 18 or 19, characterized in that, The roundness of the organic compound particles is 0.5 to 1.

0.

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

22. The separator membrane of claim 21, wherein, The cross-linked polymer comprises a silicone polymer containing a siloxane structure.

23. The separator membrane of claim 22, wherein, The silicone polymer containing siloxane structure includes a phenyl group, the silicone polymer containing siloxane structure is polymerized by a monomer and a crosslinking agent shown in formula (I), In formula (I), R1 and R2 are each independently selected from C1-C4 alkyl and C2-C4 alkenyl, R3 comprises C1-C4 alkyl or C4-C8 (meth)acryloxyalkyl, and R4 comprises C2-C8 alkenyl or C4-C8 (meth)acryloxyalkyl; and the cross-linking agent comprises divinylbenzene.

24. The separator membrane according to claim 22 or 23, characterized in that, The silicone polymer containing a siloxane structure satisfies at least one of the following conditions: (1) the cross-linking degree of the silicone polymer containing a siloxane structure is 75% to 95%; (2) the mass fraction of silicon in the silicone polymer containing a siloxane structure is 10% to 25%; (3) the mass fraction of phenyl in the silicone polymer containing a siloxane structure is 2% to 12%; (4) the silicone polymer containing a siloxane structure comprises silicon hydroxyl.

25. The separator membrane of claim 24, wherein, The silicone polymer containing a siloxane structure comprises a skeleton formed by a compound represented by formula (II), R a [SiO 3 / 2 ] n Formula (II) wherein n is any integer from 4 to 12, R a including cycloalkyl, aryl, C1-C 12 alkyl, C1-C 12 alkenyl, C1-C 12 alkynyl; optionally n is 8, R a including C1-C3 alkyl.

26. The separator membrane of claim 25, wherein, The silicone polymer containing a siloxane structure is obtained by hydrolysis and polycondensation of one or more monomers represented by formula (II), wherein R'1 comprises C1-C3 alkyl.

27. The separator membrane of any one of claims 24-26, wherein, The silicone polymer containing a siloxane structure satisfies at least one of the following conditions: (1) the cross-linking degree of the silicone polymer containing a siloxane structure is 85% to 97%; (2) the mass fraction of silicon in the silicone polymer containing a siloxane structure is 25% to 45%; (3) the mass fraction of the skeleton formed by the compound represented by formula (II) in the silicone polymer containing a siloxane structure is 40% to 60%; (4) the silicone polymer containing a siloxane structure comprises silicon hydroxyl.

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

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