Battery cell, battery apparatus, electrical apparatus, and separator

Abstract

The present application provides a battery cell, a battery apparatus, an electrical apparatus, and a separator. The battery cell comprises 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 comprises a porous base film and a coating disposed on at least one side of the porous base film. The coating comprises organic compound particles and a first binder. The first binder is used to bond the organic compound particles to the porous base film. The morphology of the organic compound particles is spherical or spheroidal. The length of a single organic compound particle is A, and the width of the single organic compound particle is B, wherein 1≤A:B≤5. The technical solution of the present application is beneficial to improving the voltage breakdown resistance of a separator and improving the cycle performance of a battery cell.

Description

Battery cell, battery assembly, electrical device, separator 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 and preparation method thereof, dispersion of silicon-containing organic resin particles, separator membrane, secondary battery cell, battery device and power device”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the field of battery technology, and more specifically, to a battery cell, a battery device, an electrical device, and a separator. Background Technology

[0003] In recent years, with the increasingly wide range of applications of batteries, batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power plants, as well as in many fields such as power tools, electric bicycles, electric motorcycles, electric cars, military equipment, and aerospace.

[0004] The development of battery technology requires consideration of various design factors, such as energy density, cycle life, storage performance, charge / discharge rate, and reliability. While battery cells have made significant progress, higher demands have been placed on their performance in various aspects. Among these, the separator is a crucial component supporting the electrochemical processes of charge and discharge in a rechargeable battery cell. However, the heat-resistant coating particles on its surface can easily cause electric field distortion and concentration, which reduces the separator's voltage breakdown resistance and thus affects the cycle performance of the battery cell.

[0005] Therefore, improving the voltage breakdown resistance of the separator to enhance the cycle performance of the battery cell is a technical problem that urgently needs to be solved. Summary of the Invention

[0006] This application is made in view of the above-mentioned problems, and provides a battery cell, battery device, power supply device, and separator, which are beneficial to improving the voltage breakdown resistance of the separator and enhancing the cycle performance of the battery cell.

[0007] In a first aspect, a battery cell is provided, including: a positive electrode plate, a negative electrode plate, and a separator membrane, where the separator membrane is located between the positive electrode plate and the negative electrode plate; the positive electrode plate includes a positive electrode current collector and at least one layer of positive electrode film layer provided on the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material; the positive electrode active material includes a lithium-containing transition metal oxide, and the lithium-containing transition metal oxide includes nickel element, cobalt element, and a first element, and the first element includes manganese element and / or aluminum element; or, the lithium-containing transition metal oxide includes a layered lithium manganese-based oxide, and the layered lithium manganese-based oxide has the following structural formula: xLi2MnO3·(1 - x)LiM1O2; where, 0 < X < 1; M1 includes at least one of nickel element, cobalt element, and manganese element; the separator membrane includes a porous base film and a coating provided on at least one side of the porous base film; the coating includes organic compound particles and a first binder; the first binder is used to bond the organic compound particles to the porous base film; the morphology of the organic compound particles is spherical or quasi-spherical; the major axis of a single organic compound particle is A, and the minor axis is B, where, 1 ≤ A:B ≤ 5.

[0008] In an embodiment of the present application, when the ratio of the major axis to the minor axis of a single organic compound particle in the coating satisfies the above range, the organic compound particles are more inclined to form a spherical or quasi-spherical structure with a minor difference between the major axis and the minor axis. On the one hand, this near-equiaxial morphology can effectively reduce local electric field distortion. This is because the surface curvature of spherical particles can be evenly distributed, so the electric field concentration effect caused by sharp protrusions can be reduced. On the other hand, spherical or quasi-spherical particles are more densely packed in the coating, which can reduce the microscopic electric field non-uniformity caused by the difference in particle orientation. Therefore, when the ratio of the major axis to the minor axis of a single organic compound particle in the coating is set within the above range, it is difficult for the organic compound particles to form a relatively sharp tip structure, which can reduce the occurrence of local electric field distortion and uneven electric field distribution, reduce the internal short circuit problem caused by tip discharge, and further improve the voltage breakdown resistance performance of the separator membrane. In addition, under the working conditions of high voltage, the materials in the coating may undergo oxidation reactions, affecting the structural stability of the materials, and even further causing material damage, thereby affecting the voltage breakdown resistance performance of the separator membrane and further affecting the cycle performance of the battery.

[0009] In a possible implementation manner, 1 ≤ A:B ≤ 4.5.

[0010] In an embodiment of the present application, the above organic compound particles have a more suitable ratio of the major axis to the minor axis, and can more easily present a spherical or quasi-spherical morphology with similar major and minor axes, thereby further improving the voltage breakdown resistance performance of the separator membrane.

[0011] In one possible implementation, A satisfies: 60nm≤A≤700nm; and B satisfies: 50nm≤B≤600nm.

[0012] In this embodiment, on the one hand, the major axis of the organic compound particles meets the above-mentioned range, which helps to reduce the risk of sharp protrusions formed by the organic compound particles, causing local electric field distortion and thus exacerbating the risk of tip discharge. Simultaneously, this also helps to increase the particle packing density, thereby improving the compactness and mechanical strength of the coating. On the other hand, setting the minor axis within the above-mentioned range helps to ensure a suitable number of organic compound particles per unit volume, thereby improving the heat resistance of the coating to the separator. Furthermore, this can reduce the tendency of particles to agglomerate, forming localized packing defects that affect the voltage breakdown resistance of the separator.

[0013] In one possible implementation, the convexity C of the organic compound particles satisfies: 1 ≤ C ≤ 1.5.

[0014] In this embodiment, setting the convexity of the organic compound particles within the aforementioned range is beneficial for ensuring that the tips of the organic compound particles have a suitable radius of curvature. This reduces the electric field strength, thereby reducing the likelihood of partial discharge or even breakdown of the separator, leading to short circuits within the battery. Simultaneously, this convexity range also improves coating uniformity, thereby enhancing the mechanical strength and thermal stability of the battery cells. Furthermore, the aforementioned convexity range can reduce stress concentration between particles, delaying coating aging. Therefore, by setting the organic compound particles with the aforementioned convexity, the electric field can be uniformly dispersed while maintaining the structural stability of the coating, thus improving the voltage breakdown resistance and long-term reliability of the separator.

[0015] In one possible implementation, the organic compound particle Dn50 satisfies: 150nm≤Dn50≤400nm; where Dn50 refers to the particle size corresponding to the cumulative particle size distribution reaching 50% in the particle size distribution curve of the organic compound particles.

[0016] In this embodiment, setting the Dn50 of the organic compound particles within the aforementioned range is beneficial for creating a coating with suitable porosity. This helps reduce the risk of a sharp increase in local current density during battery cell charging and discharging, which could lead to preferential lithium dendrite growth and thus improve the breakdown voltage of the separator. Simultaneously, this also reduces nanoparticle aggregation, thereby decreasing the likelihood of micro-short circuits caused by puncturing the base film.

[0017] In one possible implementation, the lithium-containing transition metal oxide comprises single particles.

[0018] In this embodiment, this improves the mechanical and interfacial chemical stability of the cathode active material at the microstructural level. Specifically, as a single particle, it effectively reduces stress accumulation and crack propagation at the grain boundaries of polycrystalline aggregates, maintains the integrity of the crystal structure during repeated lithium-ion intercalation and deintercalation, and thus reduces cathode active material failure and the increase of side reaction interfaces caused by particle breakage. Simultaneously, its lower specific surface area reduces the contact range with the electrolyte, decreases the severity of interfacial side reactions under high voltage conditions, and enhances the uniformity and stability of the surface passivation layer. Therefore, under high voltage conditions, the single-particle morphology can improve the cycle life of the battery cell.

[0019] In one possible implementation, the volume average particle size Dv50 of the lithium-containing transition metal oxide satisfies: 3μm≤Dv50≤5μm.

[0020] In this embodiment, setting the volume average particle size Dv50 of the lithium-containing transition metal oxide within the aforementioned range helps reduce the ion solid-phase diffusion path, resulting in more uniform lithium-ion insertion / extraction under high voltage, and reducing local stress concentration and particle cracking. This reduces the exposure of cracked surfaces to the high-voltage electrolyte, thereby minimizing the triggering of severe side reactions and reducing interface degradation and impedance. Furthermore, this also ensures that the lithium-containing transition metal oxide has a suitable specific surface area, reducing excessive catalytic oxidation and decomposition of the electrolyte by the active surface, thus forming a stable cathode-electrolyte interface film and reducing ion transport resistance. Simultaneously, this also reduces local overcharging and heat accumulation, improving thermal stability. Therefore, the aforementioned Dv50 range is beneficial for maintaining interface and structural balance under high-voltage conditions and improving the thermal stability of the battery cell.

[0021] In one possible implementation, the positive electrode active material has a mass content of 70% to 98% in the positive electrode film layer.

[0022] In the embodiments of this application, by controlling the mass content range of the positive electrode active material in the positive electrode film layer, it is beneficial to ensure that the conductive agent and binder have a suitable mass ratio, thereby giving the electrode suitable conductivity and alleviating polarization. Thus, under high-voltage conditions, the battery cell can reduce local overheating and structural instability, thereby improving its cycle life. At the same time, it also maintains the overall energy density of the battery cell.

[0023] In one possible implementation, the organic compound particles comprise a cross-linked polymer having a cross-linking degree of 70% to 98%.

[0024] In the embodiments of this application, the degree of crosslinking of the crosslinked polymer meets the above-mentioned range, enabling it to form a stable three-dimensional network structure. This structure can effectively maintain the integrity of its spatial configuration under high pressure, thereby giving the separator membrane good mechanical properties. This is beneficial to the structural stability of the separator membrane under high pressure conditions, thereby improving its voltage breakdown resistance.

[0025] In one possible implementation, the crosslinked polymer comprises an organosilicon polymer containing a silicon-oxygen structure.

[0026] In this embodiment, a silicon-oxygen-containing organosilicon polymer is used as the crosslinking polymer. The high bond energy of its silicon-oxygen bonds and the three-dimensional crosslinking network formed by the interlinking of the organosilicon polymer molecular chains give the silicon-oxygen-containing organosilicon polymer high mechanical strength, which is beneficial for improving the voltage breakdown resistance of the separator under high voltage. Specifically, the organosilicon polymer has stable Si-O bonds with high bond energy, making it less prone to decomposition under high voltage, thus improving the stability of the material under high-voltage environments. Furthermore, compared to inorganic particles, organosilicon polymers have a lower density, which can reduce the overall mass of the coating at the same thickness, thereby improving the energy density of the battery cell.

[0027] In one possible implementation, the organosilicon polymer containing a silicon-oxygen structure comprises a phenyl group, and the organosilicon polymer containing a silicon-oxygen structure is obtained by polymerization of the monomer shown in formula (I) and a crosslinking agent.

[0028]

[0029] R1 and R2 are each independently selected from C1-C4 alkyl groups and C2-C4 alkenyl groups, R3 includes C1-C4 alkyl groups or C4-C8 (meth)acryloyloxyalkyl groups, and R4 includes C2-C8 alkenyl groups or C4-C8 (meth)acryloyloxyalkyl groups; the crosslinking agent includes divinylbenzene.

[0030] In this embodiment, a phenyl-containing organosilicon polymer can be obtained by polymerizing the monomer shown in formula (I) with the crosslinking agent divinylbenzene. The particles possess a three-dimensional network framework formed by the phenyl structure and the monomer and crosslinking agent, resulting in higher material stability. This can improve the stability of the separator under high-voltage conditions and enhance the reliability of the battery cell.

[0031] In one possible implementation, the organosilicon polymer containing a silicon-oxygen structure satisfies one or more 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 content of silicon in the organosilicon polymer containing a silicon-oxygen structure is 10% to 25%; and (3) the mass content of phenyl in the organosilicon polymer containing a silicon-oxygen structure is 2% to 12%.

[0032] In the embodiments of this application, by limiting the degree of crosslinking, the mass content of silicon, and the mass content of phenyl, it is beneficial to improve the voltage breakdown resistance of the separator, thereby improving the cycle performance of the battery cell.

[0033] In one possible implementation, the organosilicon polymer containing a silicon-oxygen structure comprises a backbone formed by the compound shown in formula (II).

[0034] R a [SiO 3 / 2 ] n Equation (II),

[0035] Where n is at least one integer from 4 to 12, R a Including cycloalkyl, aryl, C1-C 12 Alkyl groups, C1-C 12 alkenyl, C1-C 12 The alkynyl group; optionally, n is 8, R a Including C1 to C3 alkyl groups.

[0036] In this embodiment, a three-dimensional polyhedral framework can be constructed by introducing the structural unit shown in formula (II) into the organosilicon polymer. This structure, linked by strong covalent bonds, forms a uniform and stable rigid support framework within the separator coating, which is beneficial to its structural stability. This structural stability allows the integrity of the three-dimensional polyhedral framework to be maintained under high-pressure conditions, thereby improving the stability of the battery cell under high-pressure environments. Simultaneously, by selecting R… a The substituents are C1-C3 alkyl groups, which helps to further enhance the stability of the molecular structure. Specifically, this design can not only effectively reduce the thermal shrinkage of the separator, but also improve the electrolyte wetting uniformity and promote efficient ion migration, thereby reducing polarization during high-voltage cycling, which is beneficial to improving the cycle life of the battery cells.

[0037] In one possible implementation, the organosilicon polymer containing a silicon-oxygen structure comprises one or more monomers of formula (II) obtained through hydrolysis and polycondensation.

[0038]

[0039] R'1 includes C1 to C3 alkyl groups.

[0040] In this embodiment, an organosilicon polymer with a cage-like structure can be obtained by employing the hydrolysis-condensation reaction of the monomer of formula (III). Simultaneously, this polymer can form a uniformly distributed and structurally stable three-dimensional network structure in the coating of the separator. This stable cage-like framework and three-dimensional network structure can enhance the mechanical strength and structural integrity of the coating, thereby improving the stability of the coating under high-voltage conditions, which is beneficial for promoting the voltage breakdown resistance of the separator.

[0041] In one possible implementation, the organosilicon polymer containing a silicon-oxygen structure satisfies one or more 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 content of silicon in the organosilicon polymer containing a silicon-oxygen structure is 25% to 45%; and (3) the mass content of the skeleton formed by the compound shown in formula (II) in the organosilicon polymer containing a silicon-oxygen structure is 40% to 60%.

[0042] In the embodiments of this application, by limiting the degree of crosslinking, the mass fraction of silicon element and the mass content of the skeleton composed of the compound shown in formula (II), it is beneficial to improve the voltage breakdown resistance of the separator, thereby improving the cycle performance of the battery cell.

[0043] In one possible implementation, the organic compound particles satisfy at least one of the following conditions (1) to (5): (1) the cyclic voltammetry curve of the organic compound particles in the first cycle does not have an 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 thermogravimetric temperature T of the organic compound particles. 3d Satisfy: T 3d ≥250℃; (4) The dissolution rate of the organic compound particles in a mixed solvent of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 3:7, after being soaked at 60℃ for 7 days, is less than or equal to 5%; (5) The true density of the organic compound particles is 0.8 g / cm³. 3 ~2.0g / cm 3 .

[0044] In the embodiments of this application, by limiting the oxidation peak, glass transition temperature, initial thermogravimetric temperature, dissolution rate and true density of the cyclic voltammetry curve of the organic compound particles in the first cycle, it is beneficial to improve the overall performance of the battery cell.

[0045] In one possible implementation, the organic compound particles in the coating constitute 50% to 97% by mass.

[0046] In this embodiment, setting the mass content of organic compound particles in the coating within the aforementioned range is beneficial for forming an effective heat-resistant network, reducing the likelihood of internal short circuits caused by the shrinkage of the separator at high temperatures, thereby decreasing the separator's voltage breakdown performance. Simultaneously, this also helps reduce the agglomeration of organic compound particles, which can clog pores and hinder ion conduction, thus increasing internal resistance and affecting the rate performance of the battery cells. Furthermore, this can reduce the coating's susceptibility to cracking during cycling, thereby reducing the separator's voltage breakdown performance and cycle stability.

[0047] In one possible implementation, the first adhesive satisfies one or more of the following conditions: (1) the first adhesive comprises at least one of polyimide, polyetherimide, polyacrylic acid, polyacrylate, ethylene vinyl acetate copolymer, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethylated polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose, acrylonitrile-styrene-butadiene copolymer, ethylene-propylene-diene terpolymer, sulfonated ethylene-propylene-diene terpolymer, styrene-butadiene rubber, and fluororubber; (2) the first adhesive has a mass content of 3% to 15% in the coating.

[0048] In this embodiment, the organic compound particles in the coating are interconnected and fixed by a first binder, reducing the likelihood of the organic compound particles falling off during coating and use. Setting the mass content of the first binder within the aforementioned range allows for a balance between adhesion and minimizing the reduction in the proportion of organic compound particles in the coating due to excessive binder. This balances the stability of the separator and its voltage breakdown resistance, thereby improving the cycle performance of the battery cell.

[0049] In one possible implementation, the separator further includes second adhesive particles located on the coating, or the separator further includes an adhesive layer disposed on at least one side of the coating away from the porous base membrane, wherein the second adhesive particles are located on the adhesive layer; the second adhesive particles satisfy one or more of the following conditions: (1) the second adhesive particles include at least one of polyvinylidene fluoride, poly(vinylidene fluoride-copolymer-trichloroethylene), poly(vinylidene fluoride-copolymer-trifluorochloroethylene), poly(vinylidene fluoride-copolymer-trifluoroethylene), poly(vinylidene fluoride-copolymer-tetrafluoroethylene), poly(vinylidene fluoride-copolymer-hexafluoropropylene), polyacrylate, polymethyl methacrylate, and polyacrylonitrile; (2) the average volume particle size of the second adhesive particles is 5 μm to 20 μm.

[0050] In this embodiment, by adding second binder particles to the coating or to the adhesive layer of the separator, the second binder particles can fill the gap between the negative electrode and the separator, forming a more robust bonding interface. This helps improve the bonding strength between the separator and the negative electrode, thereby enhancing the overall stability of the separator and reducing interlayer delamination between the separator and the negative electrode during cycling due to thermal stress or electrochemical effects, thus improving the cycle performance of the battery cell. Furthermore, setting the average volumetric particle size of the second binder particles within the aforementioned range facilitates uniform distribution of the particles while maintaining appropriate fluidity, further contributing to improved cycle performance of the battery cell.

[0051] In one possible implementation, the separating membrane 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 / m³. 2 ~6g / m 2 (3) The longitudinal thermal shrinkage rate of the isolation membrane is less than or equal to 5% after being heated at 130°C for 1 hour; (4) The transverse thermal shrinkage rate of the isolation membrane is less than or equal to 5% after being heated at 130°C for 1 hour; (5) The air permeability of the isolation membrane is 150s / 100mL~500s / 100mL.

[0052] In the embodiments of this application, by limiting the thickness, areal density, longitudinal thermal shrinkage rate, transverse thermal shrinkage rate and air permeability of the coating, it is beneficial to improve the overall performance of the separator.

[0053] In one possible implementation, the negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector, the negative electrode film layer including a negative electrode active material, the negative electrode active material including at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials and lithium titanate.

[0054] In the embodiments of this application, the appropriate type of negative electrode active material can be selected according to specific needs.

[0055] In a second aspect, a battery device is provided, comprising a battery cell as described in the first aspect and any possible implementation thereof.

[0056] Thirdly, an electrical device is provided, including the battery device described in the second aspect.

[0057] Fourthly, a separating membrane is provided, comprising: a porous base membrane and a coating disposed on at least one side of the porous base membrane; the coating comprising organic compound particles and a first binder; the first binder being used to bind the organic compound particles to the porous base membrane; the morphology of the organic compound particles being spherical or quasi-spherical; the major axis of a single organic compound particle being A and the minor axis being B, wherein 1 ≤ A:B ≤ 5.

[0058] In this embodiment, the ratio of the major to minor axis of individual organic compound particles in the coating meets the above-mentioned range, and the organic compound particles tend to form spherical or near-spherical structures with a small difference between their major and minor axes. On the one hand, this near-equiaxial morphology can effectively reduce local electric field distortion. This is because the surface curvature of spherical particles can be uniformly distributed, thus reducing the electric field concentration effect caused by sharp protrusions. On the other hand, the more densely packed spherical or near-spherical particles in the coating can reduce the microscopic electric field inhomogeneity caused by differences in particle orientation. Therefore, by setting the ratio of the major to minor axis of individual organic compound particles in the coating within the above-mentioned range, the organic compound particles are less likely to form relatively sharp tip structures, which can reduce the occurrence of local electric field distortion and uneven electric field distribution, reduce the internal short circuit problem caused by tip discharge, and thus improve the voltage breakdown resistance of the separator. In addition, under high-voltage operating conditions, the material in the coating may undergo oxidation reaction, affecting the structural stability of the material, or even further causing material damage, thereby affecting the voltage breakdown resistance of the separator and thus affecting the cycle performance of the battery.

[0059] In one possible implementation, 1 ≤ A: B ≤ 4.5.

[0060] In the embodiments of this application, the above-mentioned organic compound particles have a more suitable ratio of major diameter to minor diameter, and can more easily present a spherical or near-spherical morphology with similar major and minor diameters, thereby further improving the voltage breakdown resistance of the separator.

[0061] In one possible implementation, A satisfies: 60nm≤A≤700nm; and B satisfies: 50nm≤B≤600nm.

[0062] In this embodiment, on the one hand, the major axis of the organic compound particles meets the above-mentioned range, which helps to reduce the risk of sharp protrusions formed by the organic compound particles, causing local electric field distortion and thus exacerbating the risk of tip discharge. Simultaneously, this also helps to increase the particle packing density, thereby improving the compactness and mechanical strength of the coating. On the other hand, setting the minor axis within the above-mentioned range helps to ensure a suitable number of organic compound particles per unit volume, thereby improving the heat resistance of the coating to the separator. Furthermore, this can reduce the tendency of particles to agglomerate, forming localized packing defects that affect the voltage breakdown resistance of the separator.

[0063] In one possible implementation, the convexity C of the organic compound particles satisfies: 1 ≤ C ≤ 1.5.

[0064] In this embodiment, setting the convexity of the organic compound particles within the aforementioned range is beneficial for ensuring that the tips of the organic compound particles have a suitable radius of curvature. This reduces the electric field strength, thereby reducing the likelihood of partial discharge or even breakdown of the separator, leading to short circuits within the battery. Simultaneously, this convexity range also improves coating uniformity, thereby enhancing the mechanical strength and thermal stability of the battery cells. Furthermore, the aforementioned convexity range can reduce stress concentration between particles, delaying coating aging. Therefore, by setting the organic compound particles with the aforementioned convexity, the electric field can be uniformly dispersed while maintaining the structural stability of the coating, thus improving the voltage breakdown resistance and long-term reliability of the separator.

[0065] In one possible implementation, the organic compound particle Dn50 satisfies: 150nm≤Dn50≤400nm; where Dn50 refers to the particle size corresponding to the cumulative particle size distribution reaching 50% in the particle size distribution curve of the organic compound particles.

[0066] In this embodiment, setting the Dn50 of the organic compound particles within the aforementioned range is beneficial for creating a coating with suitable porosity. This helps reduce the risk of a sharp increase in local current density during battery cell charging and discharging, which could lead to preferential lithium dendrite growth and thus improve the breakdown voltage of the separator. Simultaneously, this also reduces nanoparticle aggregation, thereby decreasing the likelihood of micro-short circuits caused by puncturing the base film. Attached Figure Description

[0067] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0068] Figure 1 is a schematic diagram of the structure of the positive electrode sheet according to an embodiment of this application;

[0069] Figure 2 is a schematic diagram of the structure of a single battery cell according to an embodiment of this application;

[0070] Figure 3 is a schematic diagram of the structure of a battery cell according to another embodiment of this application;

[0071] Figure 4 is a schematic diagram of a battery device according to an embodiment of this application;

[0072] Figure 5 is a schematic diagram of the structure of a battery device according to an embodiment of this application;

[0073] Figure 6 is a schematic diagram of the structure of an electrical device according to an embodiment of this application;

[0074] Figure 7 is a pyrolysis spectrum of the organic compound powder of Example 1 of this application;

[0075] Figure 8 is a SEM image of the organic compound particles in Example 1 of this application;

[0076] Figure 9 is a SEM image of the inorganic particles in Comparative Example 1 of this application.

[0077] Figure label:

[0078] 1-Vehicle; 11-Housing shell; 12-Electrode assembly; 121-Positive electrode sheet; 1211-Positive current collector; 1212-Positive electrode film; 13-Cover plate; 100-Battery cell; 400-Battery assembly; 401-Upper casing; 402-Lower casing; 500-Motor; 600-Controller.

[0079] The accompanying drawings are not drawn to scale. Detailed Implementation

[0080] The following detailed description of embodiments of the battery cell, battery device, and power-consuming device of this application, with appropriate reference to the accompanying drawings, may omit unnecessary details. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0081] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, 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 specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, 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 expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0082] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in the description of this application is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms "comprising" and "having," and any variations thereof, in the description, claims, and accompanying drawings of this application are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the description, claims, or accompanying drawings of this application are used to distinguish different objects, not to describe a specific order or hierarchy.

[0083] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0084] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0085] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0086] The development of battery technology must consider multiple design factors simultaneously, such as energy density, cycle life, discharge capacity, charge / discharge rate, and reliability. To improve the energy density of rechargeable battery cells, researchers are developing high-voltage resistant cathode materials, which can significantly increase the battery's operating voltage (e.g., lithium iron phosphate operates at 3.65V-3.8V, and ternary materials at 4.2V-4.5V), thereby directly boosting the overall energy density of the rechargeable battery cell. However, for high-voltage cathode materials, how to combine them with suitable electrolytes, separators, and anodes to ensure better cycle performance and overall performance even at high energy densities is a pressing issue. As for the separator, it is a crucial component supporting the charge-discharge electrochemical process of the rechargeable battery cell. Commonly used separators are typically made of polyolefin materials. However, polyolefin materials have poor heat resistance and are prone to softening or melting at high temperatures, leading to internal short circuits in the rechargeable battery cell. To improve the heat resistance of the separator, a coating is usually applied to enhance its heat resistance. Boehmite, alumina, and other inorganic particles are commonly used heat-resistant fillers. However, these fillers have a high density and a large mass for the same packing volume, which affects the energy density of the secondary battery cell. Therefore, to improve the energy density of the secondary battery cell, inorganic particles such as boehmite and alumina are usually replaced with organic heat-resistant fillers.

[0087] However, in high-voltage battery systems, the organic particles in the coating often exhibit sharp, pointed morphologies, such as rod-shaped or needle-like structures with a high aspect ratio. These points are highly susceptible to localized electric field concentration, leading to tip discharge. When the electric field strength exceeds a critical value, micro-discharge may occur near the tip, potentially even breaking down the separator and creating a localized conductive path, causing an internal short circuit. This not only reduces the separator's voltage breakdown withstand capability and affects the cycle performance of individual cells but may also lead to thermal runaway in individual cells due to localized overheating.

[0088] Therefore, in the related art, the surface of organic particles is usually coated to reduce the electric field strength on the particle surface. However, the surface coating increases the ion transport impedance, thereby affecting the rate performance of the battery cell. At the same time, this may also affect the uniformity of the coating, thereby affecting the heat resistance effect of the separator.

[0089] In view of this, an embodiment of the present application provides a battery cell, including: a positive electrode sheet, a negative electrode sheet, and a separator located between the positive electrode sheet and the negative electrode sheet; the positive electrode sheet includes a positive electrode current collector and at least one layer of positive electrode film layer provided on the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material; the positive electrode active material includes a lithium-containing transition metal oxide, and the lithium-containing transition metal oxide includes nickel element, cobalt element, and a first element, and the first element includes manganese element and / or aluminum element; alternatively, the lithium-containing transition metal oxide includes a layered lithium manganese-based oxide, and the layered lithium manganese-based oxide has the following structural formula: xLi2MnO3·(1-x)LiM1O2; where 0 < X < 1; M1 includes at least one of nickel element, cobalt element, and manganese element; the separator includes a porous base film and a coating provided on at least one side of the porous base film; the coating includes organic compound particles and a first binder; the first binder is used to bond the organic compound particles to the porous base film; the morphology of the organic compound particles is spherical or quasi-spherical; the major axis of a single organic compound particle is A, and the minor axis is B, where 1 ≤ A:B ≤ 5.

[0090] In the above technical solution, when the ratio of the major axis to the minor axis of a single organic compound particle in the coating satisfies the above range, the organic compound particles are more likely to form a spherical or quasi-spherical structure with a minor difference between the major axis and the minor axis. On the one hand, this near-equiaxial morphology can effectively reduce local electric field distortion. This is because the surface curvature of spherical particles can be evenly distributed, so the electric field concentration effect caused by sharp protrusions can be reduced. On the other hand, spherical or quasi-spherical particles are more densely packed in the coating, which can reduce the microscopic electric field non-uniformity caused by the difference in particle orientation. Therefore, by setting the ratio of the major axis to the minor axis of a single organic compound particle in the coating within the above range, it is difficult for the organic compound particles to form a relatively sharp tip structure, which can reduce the occurrence of local electric field distortion and uneven electric field distribution, reduce the internal short-circuit problem caused by tip discharge, and thus improve the voltage breakdown resistance performance of the separator. In addition, under the working conditions of high voltage, the materials in the coating may undergo oxidation reactions, affecting the structural stability of the materials, and even further causing material damage, thereby affecting the voltage breakdown resistance performance of the separator, and further affecting the cycle performance of the battery.

[0091] The battery cell, battery device, electrical device, and separator of the present application will be described below with reference to the accompanying drawings.

[0092] [Battery cell]

[0093] This application provides a single battery cell. Typically, a single battery cell includes a positive electrode, a negative electrode, an electrolyte, and a separator. During the charging and discharging process of the battery cell, active ions repeatedly insert and extract between the positive and negative electrodes. The electrolyte, acting as a conductor for the active ions, lies between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing the passage of active ions. In some embodiments, the above-mentioned battery cell is also referred to as a secondary battery, and the battery cell can be the smallest possible battery unit.

[0094] The technical solution of this application can be applied to various battery cells, such as lithium-ion batteries, lithium metal batteries, sodium-ion batteries, potassium-ion batteries, etc., and this application does not limit them; for the sake of convenience, lithium-ion batteries will be used as an example for the following description.

[0095] During the charging process of a lithium-ion battery, lithium ions are released from the positive electrode active material, move and embed into the negative electrode material; while during the discharging process, lithium ions are released from the negative electrode material, move and embed into the positive electrode active material.

[0096] It should be understood that the “intercalation” process described in this application refers to the process in which lithium ions are intercalated in the positive electrode active material and the negative electrode material due to an electrochemical reaction, and the “deintercalation” and “deintercalation” processes described in this application refer to the process in which lithium ions are deintercalated in the positive electrode active material and the negative electrode material due to an electrochemical reaction.

[0097] Next, the separator, positive electrode, negative electrode, and electrolyte of the battery cell of this application will be described with appropriate reference to the accompanying drawings.

[0098] In some embodiments, the positive electrode sheet includes a positive current collector and a positive electrode film layer disposed on at least one layer of the positive current collector, the positive electrode film layer including a positive electrode active material.

[0099] Lithium-containing transition metal oxides refer to oxide crystalline materials containing lithium and one or more transition metal elements (such as cobalt, nickel, manganese, iron, etc.).

[0100] In some embodiments, the positive electrode active material includes a lithium-containing transition metal oxide.

[0101] In some embodiments, the lithium-containing transition metal oxide includes nickel, cobalt, and a first element, and the first element includes manganese and / or aluminum; alternatively, the lithium-containing transition metal oxide includes a layered lithium manganese-based oxide having the following structural formula: xLi2MnO3·(1-x)LiM1O2; where 0 < X < 1; M1 includes at least one of nickel, cobalt, and manganese. For the positive electrode active material, the above lithium-containing transition metal oxide has a relatively high working voltage and a relatively high specific capacity, which can improve the energy density of the battery cell. In its layered structure, the redox potential of transition metals (such as nickel and cobalt) is relatively high, providing a relatively high voltage platform. At the same time, an increase in the nickel content can also increase the specific capacity of the battery cell. Therefore, using a lithium-containing transition metal oxide in the positive electrode active material enables the battery cell to store more electrical energy under the same weight or volume, meeting the long-range demand.

[0102] Specifically, when the lithium-containing transition metal oxide includes nickel, cobalt, and a first element, and the first element includes manganese and / or aluminum, nickel is beneficial to improving the reversible capacity of the battery cell, thereby enhancing the energy density of the battery cell; cobalt helps to enhance the electronic conductivity and the stability of the layered structure of the material; manganese or aluminum can act as a "structural pillar", reducing cation mixing and phase change during the cycling process, thereby improving thermal stability. On the other hand, when the lithium-containing transition metal oxide includes the above-mentioned layered lithium manganese-based oxide, the Li2MnO3 component can de-lithiate and release oxygen under high voltage, enabling the battery cell to have a relatively high capacity and energy density while also having a relatively high working voltage.

[0103] In some embodiments, the lithium-containing transition metal oxide includes a ternary material, and the ternary material includes two types of single-layered lithium-containing transition metal oxides, lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide. The chemical formula of the ternary material is Li 1+d [Ni x Co y Mn z M e O 2-f ; where M includes at least one of Zr, Al, Ti, Sb, Nb, Te, Mg, B, Ca, V, Ta, or Sr, 0.2 ≥ d ≥ -0.2, 0.95 ≥ x ≥ 0.5, 0.2 ≥ y ≥ 0.05, 0.3 > z > 0, 0.3 > e ≥ 0, 0.5 ≥ f ≥ 0. By doping the M element in the lithium-containing transition metal oxide, its crystal structure can be effectively stabilized. Specifically, the M element can enhance the structural integrity of the positive electrode active material in a high-voltage environment by inhibiting phase change during charge and discharge, reducing the precipitation of lattice oxygen, and strengthening the metal-oxygen bond energy. This modification of element doping at the atomic scale can effectively reduce the structural failure of the material, thereby alleviating the risk of thermal runaway of the battery cell.

[0104] In some embodiments, the layered lithium manganese-based oxide is a cathode active material with a relatively high specific capacity.

[0105] In some embodiments, the layered lithium manganese-based oxide has the following structural formula: xLi2MnO3·(1-x)LiM1O2; wherein, 0 < X < 1; M1 includes at least one of nickel, cobalt, and manganese elements.

[0106] In some embodiments, the layered lithium manganese-based oxide has the following structural formula: xLi2MnO3·(1-x)LiNi y Co z Mn a M 1-y-z-a O2, where 0 < x < 1, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1, 0 ≤ a ≤ 1, 0 < y + z + a ≤ 1; M is at least one of Mg, B, Al, V, Ti, Zr, Sn, and Mo.

[0107] In some embodiments, the lithium-containing transition metal oxide includes single particles. This can improve the mechanical stability and interfacial chemical stability of the cathode active material at the microstructure level. Specifically, as a whole particle, the single particle can effectively reduce the stress accumulation and crack propagation generated at the grain boundaries of polycrystalline aggregates, maintain the integrity of the crystal structure during the repeated lithium-ion deintercalation and intercalation process, and thus reduce the failure of the cathode active material caused by particle fragmentation and the increase in the side reaction interface. At the same time, its relatively low specific surface area can reduce the contact range with the electrolyte, reduce the severity of the interfacial side reaction under high-voltage conditions, and enhance the uniformity and stability of the surface passivation layer. Therefore, in a high-voltage environment, the single-particle morphology can improve the cycle life of the battery cell.

[0108] In some embodiments, the volume average particle size Dv50 of the lithium-containing transition metal oxide satisfies: 3 μm ≤ Dv50 ≤ 5 μm. For example, the volume average particle size Dv50 of the lithium-containing transition metal oxide is 3 μm, 3.2 μm, 3.5 μm, 3.8 μm, 4 μm, 4.3 μm, 4.7 μm, 5 μm, or any value within the above range. Wherein, Dv50 represents the particle size corresponding to when the cumulative volume distribution percentage of the material reaches 50%.

[0109] In the above embodiments, setting the volume average particle size Dv50 of the lithium-containing transition metal oxide within the aforementioned range helps to reduce the ion solid-phase diffusion path, resulting in more uniform lithium-ion insertion / extraction under high voltage, and reducing local stress concentration and particle cracking. This reduces the exposure of cracked surfaces to the high-voltage electrolyte, thereby reducing the triggering of severe side reactions and lowering interface degradation and impedance. Furthermore, this also ensures that the lithium-containing transition metal oxide has a suitable specific surface area, reducing excessive catalytic oxidation and decomposition of the electrolyte by the active surface, thus forming a stable cathode-electrolyte interface film and reducing ion transport resistance. Simultaneously, this also reduces local overcharging and heat accumulation, improving thermal stability. Therefore, the aforementioned Dv50 range is beneficial for maintaining interface and structural balance under high-voltage conditions and improving the thermal stability of the battery cell.

[0110] As an example, referring to GB / T 19077-2016, a laser particle size analyzer can be used to test the volume average particle size (Dv50) of lithium transition metal oxides. During testing, 1g of the sample to be tested is added to a clean small beaker, followed by 20ml of deionized water. The sample is sonicated at 53kHz / 120W for 5 minutes to ensure complete dispersion. The laser particle size analyzer is then turned on, and after cleaning the optical path system, the background is automatically measured. The sonicated solution is stirred to ensure uniform dispersion, then placed into the sample cell as required, and particle size measurement begins. A MasterSizer 3000 laser particle size analyzer can be used as the testing instrument.

[0111] In some embodiments, the mass content D of the positive electrode active material in the positive electrode film layer satisfies: 70% ≤ D ≤ 98%. For example, the mass content D of the positive electrode active material in the positive electrode film layer is 70%, 72%, 75%, 78%, 80%, 83%, 86%, 88%, 90%, 92%, 94%, 96%, 98%, or any value within the above range. By controlling the range of the mass content of the positive electrode active material in the positive electrode film layer, it is beneficial to ensure that the conductive agent and binder have a suitable mass ratio, thereby ensuring that the electrode has suitable conductivity and mitigating polarization. In this way, under high voltage conditions, the battery cell can reduce local overheating and structural instability, thereby improving its cycle life. At the same time, the overall energy density of the battery cell can also be considered.

[0112] In some embodiments, the separating membrane includes a porous base membrane and a coating disposed on at least one side of the porous base membrane; the coating includes organic compound particles and a first binder; the first binder is used to bond the organic compound particles to the porous base membrane; the organic compound particles have a spherical or near-spherical morphology; the major axis of a single organic compound particle is A, and the minor axis is B, wherein 1 ≤ A:B ≤ 5. For example, A:B is 1, 1.1, 1.3, 1.6, 1.8, 2, 2.3, 2.5, 2.8, 3, 3.2, 3.5, 3.8, 4, 4.2, 4.4, 4.5, 4.6, 4.8, 5, or any value within the above range.

[0113] In this embodiment, a porous base membrane refers to a thin film material with a micron and / or nanometer-scale pore structure. The porous base membrane can be a single-layer thin film or a multilayer composite thin film. When the porous base membrane is a multilayer composite thin film, the materials of each layer can be the same or different.

[0114] In some embodiments, the porous base membrane may comprise a membrane or nonwoven web selected from any one or at least two of the following: polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene ether, cyclic olefin copolymer, polyphenylene sulfide, and polyvinylnaphthalene.

[0115] In some embodiments, the thickness of the porous base film can be 4μm-15μm, and optionally 4μm-9μm.

[0116] In some embodiments, the porosity of the porous base membrane can be 25%-60%, optionally 28%-50%.

[0117] In some embodiments, the average pore size of the porous base film can be 25 nm to 82 nm.

[0118] As an example, the average pore size of a porous membrane can be tested using a capillary porosity analyzer (bubble point method). An exemplary testing method is as follows: Take a circular sample with a diameter of 25 mm, and drop 3-5 drops of wetting solution onto it. After the sample is completely wetted, place it in a mold, and then use an inert gas (such as nitrogen) to compress the wetting solution in the pores of the sample. The compression pressure and flow rate are inversely proportional to the pore size. The average pore size of the sample is obtained through software sampling and pressure-pore size conversion analysis. The testing instrument can be a PMI CFP 1500 pore size analyzer, with a testing pressure ranging from 100 psi to 350 psi.

[0119] In the embodiments of this application, "organic compound" refers to carbon-containing compound, including not only simple compounds such as carbon oxides, carbonic acid, and carbonates, but also elements such as hydrogen, oxygen, nitrogen, and sulfur.

[0120] In this application, "organic compound particles" refers to solid particles mainly composed of elements such as carbon (C), hydrogen (H), oxygen (O), and nitrogen (N), linked by covalent bonds. For separators, incorporating organic compound particles into their coating can increase the energy density of individual battery cells and improve the heat resistance of the separator. These organic compound particles are the main components of the coating. These particles are micron or nano-sized solids with high melting points, high thermal stability, and high chemical inertness, and can be uniformly dispersed in the coating, thereby achieving the heat resistance characteristics of the separator.

[0121] In the embodiments of this application, "the shape of the particles is spherical or near-spherical" means that the particles are geometrically close to a sphere or the whole is in a state of approximately spherical shape.

[0122] As an example, the morphology of particles that are spherical or near-spherical can be tested using instruments and methods known in the art. Specifically, as an example, after disassembling the battery cell, the separator is peeled off, and a regular, clear area of ​​the separator is selected. Subsequently, a scanning electron microscope (SEM) is used, and the microstructure of the coating on the separator is measured with reference to standard JY / T010 1996. Then, the two-dimensional projected profile, edge curvature, surface morphology, and contrast variation of the particles in the coating are observed. If the particle edges are smooth, the curvature is consistent, the surface is uniform, the contrast transition is natural, and the particle projection is circular, then the particle morphology is determined to be spherical; if the particle profile is close to circular, the edges are slightly irregular, and the surface may have slight undulations, then the particle morphology is determined to be near-spherical.

[0123] The major axis of an organic compound particle is the length of its projection in all possible directions; the minor axis of an organic compound particle usually refers to the maximum width of the particle in the direction perpendicular to the major axis.

[0124] As an example, the ratio of the major to minor diameter of the organic compound particles in the coating has a range known in the art and can be tested using instruments and methods known in the art. Specifically, as an example, after disassembling the battery cell, the separator is peeled off, and a regular, clear area of ​​the separator is selected. Subsequently, a scanning electron microscope (SEM) is used, and the microstructure of the coating on the separator is measured with reference to standard JY / T010 1996. The number of organic compound particles in the Dn50±50nm range is counted, and the major and minor diameters of the corresponding individual organic compound particles in the SEM morphology image are fitted using ImageJ software. Then, the major and minor diameters of the organic compound particles in the Dn50±50nm range are counted again to obtain the major and minor diameters of each individual organic compound particle in the Dn50±50nm range. Finally, the ratio of the major to minor diameter of each individual organic compound particle in the Dn50±50nm range is calculated.

[0125] By incorporating the aforementioned organic compound particles into the coating, it is beneficial to reduce internal short circuits caused by the tip discharge of the organic compound particles, thereby improving the voltage breakdown withstand performance of the separator. This reduces the reduction in voltage breakdown withstand performance of the separator due to oxidation of the material under high voltage conditions, thus improving the cycle performance of the battery cells.

[0126] Optionally, 1 ≤ A:B ≤ 4.5. For example, A:B can be 1, 1.1, 1.3, 1.6, 1.8, 2, 2.3, 2.5, 2.8, 3, 3.2, 3.5, 3.8, 4, 4.2, 4.4, 4.5, or any value within the above range. This results in organic compound particles having a more suitable ratio of major to minor diameters, making it easier for them to exhibit spherical or near-spherical morphologies with similar major and minor diameters, thereby further improving the voltage breakdown resistance of the separator.

[0127] In some embodiments, A satisfies: 60nm ≤ A ≤ 700nm; B satisfies: 50nm ≤ B ≤ 600nm. For example, A can be 60nm, 80nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm or any value within the above range; B can be 50nm, 80nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm or any value within the above range.

[0128] In the above embodiments, on the one hand, the major diameter of the organic compound particles meets the aforementioned range, which helps reduce the risk of sharp protrusions formed by the organic compound particles, causing local electric field distortion and thus exacerbating the risk of tip discharge. Simultaneously, this also helps increase the particle packing density, improving the compactness and mechanical strength of the coating. On the other hand, setting the minor diameter within the aforementioned range helps ensure a suitable number of organic compound particles per unit volume, thereby improving the coating's heat resistance to the separator. Furthermore, this also reduces the tendency for particles to agglomerate, forming localized packing defects that could affect the separator's voltage breakdown resistance.

[0129] In some embodiments, the convexity C of the organic compound particles satisfies: 1 ≤ C ≤ 1.5. For example, the convexity C of the organic compound particles is 1, 1.1, 1.2, 1.3, 1.4, 1.5 or any value within the above range.

[0130] For spherical or near-spherical particles, convexity is calculated by varying the degree of deviation of the convex portions on the particle's surface, thus reflecting the outward protrusion characteristic of the particle's surface. Specifically, convexity C = actual surface area of ​​the particle / surface area of ​​its convex hull. The convex hull is the smallest circumscribed convex surface containing the particle, i.e., the shape after all the depressions on the particle's surface have been "filled in". The value of convexity C ranges from 0 to 1. The closer the convexity C value is to 1, the closer the particle surface is to an ideal convex surface, i.e., a perfect sphere; the smaller the convexity C value, the more pronounced the convexity of the particle's surface, for example, the more porous structures or the rougher the surface.

[0131] As an example, the convexity of organic compound particles in the coating has a well-known meaning in the art and can be tested using instruments and methods known in the art. Specifically, as an example, after disassembling the battery cell, the separator is peeled off, and a regular, clear area of ​​the separator is selected. Subsequently, a scanning electron microscope (SEM) is used, and the microstructure of the coating on the separator is measured with reference to standard JY / T010 1996. Then, the number of organic compound particles in the Dn50±50nm range is counted, and the convexity of the organic compound particles in the SEM morphology image is obtained by fitting using ImageJ software. Then, the convexity of the organic compound particles is obtained by calculating the average convexity of the organic compound particles in the Dn50±50nm range (obtaining the convexity value of each individual organic compound particle in the Dn50±50nm range, calculating the sum of the convexity values, average convexity = sum of convexity values ​​ / total number of organic compound particles in the Dn50±50nm range).

[0132] Setting the convexity of the organic compound particles within the aforementioned range helps to ensure that the particle tips have a suitable radius of curvature. This reduces the electric field strength, thereby decreasing the likelihood of partial discharge or even breakdown of the separator, leading to short circuits within the battery. Simultaneously, this convexity range also improves coating uniformity, thus enhancing the mechanical strength and thermal stability of the battery cells. Furthermore, the aforementioned convexity range reduces stress concentration between particles, delaying coating aging. Therefore, by setting the convexity of the organic compound particles as described above, the electric field can be uniformly dispersed while maintaining the structural stability of the coating, thereby improving the voltage breakdown resistance and long-term reliability of the separator.

[0133] In some embodiments, the particle size distribution of organic compounds, Dn50, satisfies the following condition: 150 nm ≤ Dn50 ≤ 400 nm; where Dn50 refers to the particle size corresponding to the cumulative particle size distribution reaching 50% in the particle size distribution curve of the organic compound particles. For example, the particle size distribution of organic compounds, Dn50, is 150 nm, 151 nm, 180 nm, 200 nm, 206 nm, 220 nm, 230 nm, 250 nm, 262 nm, 280 nm, 290 nm, 300 nm, 310 nm, 325 nm, 330 nm, 340 nm, 350 nm, 380 nm, 400 nm, or any value within the above range.

[0134] As an example, the Dn50 of organic compound particles has a well-known meaning in the art and can be tested using instruments and methods known in the art. For example, a scanning electron microscope (e.g., ZEISS Sigma 300) can be used to obtain a scanning electron microscope (SEM) image of the separator, referring to JY / T010-1996. As an example, the test can be performed as follows: Randomly select a test sample of length × width = 50 mm × 100 mm on the separator. Randomly select multiple test areas (e.g., 5 areas) within the test sample, and at a certain magnification (e.g., 500x or 1000x when measuring organic compound particles), read the particle size of the organic compound particles in each test area (i.e., take the distance between the two farthest points on the organic compound particle as the particle size). Count the number and particle size values ​​of organic compound particles in each test area, and take the arithmetic mean of the particle sizes in each test area, which is the number-average particle size of the organic compound particles in the test sample. To ensure the accuracy of the test results, the above test can be repeated with multiple test samples (e.g., 10). The average value of each test sample is taken as the final test result, thus obtaining the particle size distribution curve of the organic compound particles. Then, through statistical analysis, the Dn50 result is obtained. In the particle size distribution curve of organic compound particles, Dn50 refers to the particle size corresponding to when the cumulative particle size distribution reaches 50%.

[0135] For organic compound particles, setting their Dn50 within the aforementioned range is beneficial for achieving suitable porosity in the coating. This helps reduce the risk of a sharp increase in local current density during battery cell charging and discharging, which could lead to preferential lithium dendrite growth and thus improve the breakdown voltage of the separator. Simultaneously, it also reduces nanoparticle aggregation, thereby decreasing the likelihood of micro-short circuits caused by puncturing the base film.

[0136] In some embodiments, the organic compound particles comprise a crosslinked polymer with a crosslinking degree of 70% to 98%. For example, the crosslinking degree of the crosslinked polymer is 70%, 72%, 75%, 78%, 80%, 83%, 85%, 87%, 89%, 90%, 92%, 94%, 96%, 97%, 98%, or any value within the above range.

[0137] In this application, "crosslinked polymer" refers to a polymer material in which molecular chains are crosslinked through chemical bonds to form a three-dimensional network structure. This structure is typically formed by the crosslinking of multiple reactive functional groups during polymerization or post-processing, resulting in a stable spatial structure for the polymer as a whole. The degree of crosslinking refers to the extent to which the molecular chains of the crosslinked polymer are crosslinked through chemical bonds. A higher degree of crosslinking indicates more crosslinking points between molecular chains, leading to a more stable polymer structure, which can improve the stability of the separator under high pressure.

[0138] It should be noted that the degree of crosslinking in the embodiments of this application refers to the proportion of molecular chain segments bound by the crosslinking network in the crosslinked polymer, obtained by software fitting at a specific temperature and frequency using nuclear magnetic resonance (NMR). By performing NMR testing on the polymer, it can be observed that different components within the polymer backbone have different relaxation kinetics. For example, monomers or solvents have high fluidity and decay the slowest; non-crosslinked segments have certain molecular motion characteristics and decay relatively slowly; while crosslinked segments are more bound, have lower molecular motion characteristics, and decay faster. Therefore, by acquiring the signal of the entire polymer and calculating the proportion of the crosslinked portion, the degree of crosslinking of the polymer backbone can be obtained.

[0139] As an example, in this embodiment of the application, the degree of crosslinking of crosslinked polymers can be tested using a PQ001 nuclear magnetic resonance analyzer. The test temperature is 60°C, the resonance frequency of the NMR analyzer is set to 21MHz, and 0.5g of the cleaned and dried sample (the aforementioned organic compound particles) is placed in a clean sample tube and inserted to the specified depth into the probe. The probe coil diameter is 13mm. Measurements are performed according to the manufacturer's instructions. Specifically, by acquiring the signal of the entire polymer, the proportion of the crosslinked portion signal is calculated by fitting software to obtain the degree of crosslinking of the polymer. The "degree of crosslinking" or "T2 relaxation" test mode is selected in the software, and the PQ001 NMR analyzer automatically acquires the relaxation decay curve. During data processing, the software decomposes the relaxed components through exponential fitting, calculates and outputs the degree of crosslinking based on the degree of restriction of molecular chain motion.

[0140] The degree of crosslinking of the crosslinked polymer meets the above-mentioned range, enabling it to form a stable three-dimensional network structure. This structure can effectively maintain the integrity of its spatial configuration under high pressure, thus giving the separator membrane good mechanical properties. This is beneficial to the structural stability of the separator membrane under high pressure conditions, thereby improving its voltage breakdown resistance.

[0141] In some embodiments, the crosslinking polymer includes an organosilicon polymer containing a siloxane structure.

[0142] In the embodiments of this application, the silicon-oxygen structure refers to a Si–O–Si bond backbone formed by alternating connections of silicon atoms and oxygen atoms. Organosilicon polymers can refer to polymers containing silicon-oxygen bonds (Si–O–Si) and / or silicon-carbon bonds (Si–C) in their main chain or side chains.

[0143] As an example, the chemical structure and type of the organosilicon polymer are well-known in the art and can be tested using instruments and methods known in the art. Specifically, as an example, after disassembling the battery cell, the separator is peeled off, and a regular, clear area of ​​the separator is selected. Then, the separator is immersed in N,N-dimethylformamide, centrifuged, and the supernatant is collected. The supernatant is then coated onto a potassium bromide wafer. After drying the potassium bromide wafer, the organosilicon polymer is obtained, or the organosilicon polymer powder can be directly obtained. The organosilicon polymer is analyzed in an infrared spectrometer (e.g., Thermo Fisher Nicolet iS5 Fourier transform infrared spectrometer), and the test is performed according to GB / T6040-2002. Based on the measurement results, the organosilicon polymer is found to contain Si-O stretching vibration peaks.

[0144] By employing silicone polymers with a silicon-oxygen structure as crosslinking polymers, the high bond energy of their silicon-oxygen bonds and the three-dimensional crosslinking network formed by the interlinking of silicone polymer molecular chains enable these polymers to possess high mechanical strength, thereby improving the voltage breakdown resistance of the separator under high voltage. Specifically, silicone polymers have stable Si-O bonds with high bond energy, which are not easily decomposed under high voltage, thus enhancing the stability of the material under high-voltage environments. Furthermore, compared to inorganic particles, silicone polymers have a lower density, which can reduce the overall mass of the coating at the same thickness, thereby improving the energy density of the battery cell.

[0145] 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.

[0146]

[0147] R1 and R2 are each independently selected from C1-C4 alkyl groups and C2-C4 alkenyl groups, R3 includes C1-C4 alkyl groups or C4-C8 (meth)acryloyloxyalkyl groups, and R4 includes C2-C8 alkenyl groups or C4-C8 (meth)acryloyloxyalkyl groups; the crosslinking agent includes divinylbenzene.

[0148] In the embodiments of this application, R1 and R2 are each independently selected from 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.

[0149] 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.

[0150] 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.

[0151] R4 includes at least one of vinyl, propenyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl(meth)acryloyloxymethyl, 2-((meth)acryloyloxy)ethyl, 3-((meth)acryloyloxy)propyl or 4-((meth)acryloyloxy)butyl.

[0152] Acryloyloxyalkyl refers to an alkyl chain functional group containing an acryloyl oxygen terminal group. (Meth)acryloyloxyalkyl refers to a methyl group replacing a hydrogen atom on a carbon atom directly attached to a carbonyl group (C=O). The acrylate double bond (C=C) at the end of the molecular chain provides a reaction site, which can further undergo free radical polymerization with a crosslinking agent, which is beneficial to improving the crosslinking degree of organosilicon polymers.

[0153] In this application, a crosslinking agent refers to a compound containing two or more functional groups that can react with functional groups on polymer chains, thereby forming covalent bridges between polymer molecular chains and constructing a three-dimensional network structure. For example, the divinylbenzene in this application can undergo a crosslinking reaction with alkenyl or acryloyl groups to form covalent bonds between molecular chains with ethylene bridges and benzene rings as connection points, forming a three-dimensional network structure of a phenyl-containing organosilicon polymer, thereby improving the heat resistance of the phenyl-containing organosilicon polymer.

[0154] By polymerizing the monomer shown in formula (I) with the crosslinking agent divinylbenzene, a phenyl-containing organosilicon polymer can be obtained. These particles possess a three-dimensional network framework formed by the phenyl structure and the monomer and crosslinking agent, resulting in higher material stability. This can improve the stability of the separator under high-voltage conditions and enhance the reliability of the battery cell.

[0155] In some embodiments, the preparation method of the phenyl-containing organosilicon polymer includes the following steps: providing a pre-emulsion comprising monomers, crosslinking agents, emulsifiers, initiators, and water; and carrying out an emulsion polymerization reaction under heating, inert gas protection, and stirring conditions to obtain silicone-containing organosilicon resin particles. The monomers include silane coupling agents containing alkenyl and / or acryloyloxy groups, and the mass fraction of the crosslinking agent is 2%-30% based on the total mass of the monomers and crosslinking agents (100%).

[0156] The monomers include silane coupling agents containing alkenyl and / or acryloyloxy groups, thus initiating free radical generation and cross-linking reactions between monomers, and the monomers also undergo cross-linking reactions with the cross-linking agents. Therefore, using the monomers and cross-linking agents disclosed herein as raw materials, phenyl-containing organosilicon polymers with a three-dimensional network structure can be formed, which are not easily softened or deformed at high temperatures and have high heat resistance and electrochemical stability.

[0157] The mass fraction of the crosslinking agent is 2%-30%, based on the total mass of monomers and crosslinking agents as 100%. For example, it can be 2%, 3%, 4%, 5%, 6%, 7%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 15%, 18%, 20%, 23%, 25%, 28%, 30%, or any combination of the above values.

[0158] When the mass fraction of the crosslinking agent is within the above range, silicon-containing organic resin particles with high electrochemical stability and good heat resistance can be obtained.

[0159] Optionally, the mass fraction of the crosslinking agent can be 8%-14%, 8%-13%, 8%-12%, 9%-14%, 9%-13%, or 9%-12%.

[0160] In some embodiments, the monomer may include an acryloyloxysilane coupling agent.

[0161] Optionally, the monomer represented by formula (I) may include one or more of the following: γ-methacryloxypropyltris(trimethylsiloxane), (3-acryloxypropyl)tris(trimethylsiloxy)silane, 3-methacryloxypropyltrimethoxysilane, acryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, acryloxypropyltriethoxysilane, γ-methacryloxypropyltriisopropoxysilane, 3-(acryloxy)propyltrimethoxysilane, 3-methacryloxypropyltris(methoxyethoxy)silane, 3-methacryloxypropylmethyldimethoxysilane, 3-acryloxypropylmethyldimethoxysilane, methacryloxypropyldimethylmethoxysilane, (3-acryloxy)dimethylmethoxysilane, 3-methacryloxypropyldimethylethoxysilane, and 3-(methacryloxy)propylmethyldiethoxysilane.

[0162] In some embodiments, the monomer represented by formula (I) may include a first monomer and a second monomer.

[0163] The first monomer may include one or more of the following: γ-methacryloxypropyltris(trimethylsiloxane), (3-acryloxypropyl)tris(trimethylsiloxy)silane, 3-methacryloxypropyltrimethoxysilane, acryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, acryloxypropyltriethoxysilane, γ-methacryloxypropyltriisopropoxysilane, 3-(acryloxy)propyltrimethoxysilane, and 3-methacryloxypropyltris(methoxyethoxy)silane.

[0164] The second monomer may include one or more of 3-methacryloyloxypropylmethyldimethoxysilane, 3-acryloyloxypropylmethyldimethoxysilane, methacryloyloxypropyldimethylmethoxysilane, (3-acryloyloxy)dimethylmethoxysilane, 3-methacryloyloxypropyldimethylethoxysilane, and 3-(methacryloyloxy)propylmethyldiethoxysilane.

[0165] The first and second monomers have different activities. By combining them and reacting them with a crosslinking agent, a silicone polymer with a suitable ratio of major to minor diameters containing a silicon-oxygen structure can be obtained.

[0166] In some embodiments, the emulsifier may include, but is not limited to, one or more of alkyl sulfates, alkyl sulfonates, Tween emulsifiers, fatty alcohol polyoxyethylene ethers, fatty alcohol polyoxypropylene ethers, cetearyl alcohol polyethers, and oleyl alcohol polyethers. Optionally, the emulsifier includes one or more of sodium lauryl sulfate, sodium lauryl sulfonate, Tween 20, Tween 40, lauryl ether-7, lauryl ether-9, lauryl ether-10, and oleyl alcohol polyether-10.

[0167] In some embodiments, the initiator may be one or more of sodium persulfate, potassium persulfate, ammonium persulfate, sodium sulfite, sodium bisulfite, azobisisobutyronitrile, azobisisobutyramidine hydrochloride, azobisisobutyramidine imidazoline hydrochloride, and azobisisopropylimidazoline.

[0168] In some embodiments, the heating temperature during the ripening stage of the emulsion polymerization reaction can be 75℃-95℃, for example, 75℃, 76℃, 77℃, 78℃, 79℃, 80℃, 81℃, 82℃, 83℃, 84℃, 85℃, 90℃, 95℃, or any range of the above values.

[0169] In some embodiments, the heating time for the ripening stage of the emulsion polymerization reaction can be 1h-4h, for example, it can be 1h, 1.2h, 1.4h, 1.6h, 1.8h, 2h, 2.2h, 2.4h, 2.6h, 2.8h, 3h, 3.2h, 3.4h, 3.6h, 3.8h, 4h, or any range of the above values.

[0170] In some embodiments, the emulsion polymerization reaction may include the following steps: adding a pre-emulsion dropwise into a reactor containing water under a first heating temperature, inert gas protection, and stirring conditions; after a first reaction time, raising the temperature to the heating temperature of the maturation stage to carry out a maturation reaction, thereby obtaining silicon-containing organic resin particles.

[0171] Optionally, the first heating temperature can be 55℃-70℃.

[0172] Optionally, the first time can be 3h-8h.

[0173] In some embodiments, the preemulsion may further include a pH adjuster. Optionally, the pH adjuster may include, but is not limited to, one or more of sodium bicarbonate, sodium hydroxide, ammonia, etc. By adding a pH adjuster, the pH value of the preemulsion can be adjusted.

[0174] In some embodiments, the pH of the preemulsion is 7.5 to 10. For example, the pH of the preemulsion can be 7.5, 8, 9, 10 or any value within the above range.

[0175] In some embodiments, the preemulsion is added dropwise under nitrogen protection and with a reactor stirring rate of 50 rpm to 300 rpm. For example, the reactor stirring rate is 50 rpm to 300 rpm or any value within the above range.

[0176] In some embodiments, the morphology and structure of organosilicon polymer particles can be controlled by synergistically regulating the pH of the pre-emulsion and the stirring rate of the reactor. Specifically, the pH value affects the hydrolysis-condensation reaction equilibrium, determines the crosslinking network density and the hydrolytic stability of phenyl groups, thereby regulating the degree of crosslinking and the proportion of phenyl groups. On the other hand, the stirring rate of the reactor can affect the shear force and mass transfer efficiency, thereby affecting the droplet dispersion and nucleation growth process, and thus determining the major and minor diameters of the particles and the ratio of the major and minor diameters.

[0177] In some embodiments, the method for preparing silicone organic resin particles may further include a demagnetization treatment step after the emulsion polymerization reaction is completed.

[0178] In some embodiments, the organosilicon polymer containing a silicon-oxygen structure satisfies one or more 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 content of silicon in the organosilicon polymer containing a silicon-oxygen structure is 10% to 25%; and (3) the mass content of phenyl in the organosilicon polymer containing a silicon-oxygen structure is 2% to 12%.

[0179] For example, the degree of crosslinking of the organosilicon polymer containing the silicon-oxygen structure is 75%, 77%, 79%, 80%, 82%, 84%, 86%, 88%, 90%, 92%, 94%, 95%, or any value within the above range; the mass content of silicon in the organosilicon polymer containing the silicon-oxygen structure is 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 25%, or any value within the above range; the mass content of phenyl in the organosilicon polymer containing the silicon-oxygen structure is 2%, 3%, 4%, 5%, 6%, 7%, 8%, 7%, 9%, 10%, 11%, 12%, or any value within the above range.

[0180] In this embodiment, the degree of crosslinking of organosilicon polymers containing silicon-oxygen structures can be tested using a PQ001 nuclear magnetic resonance (NMR) analyzer. The test temperature is 60°C, the NMR analyzer's resonance frequency is set to 21MHz, and 0.5g of cleaned and dried sample (the aforementioned organosilicon compound particles) is placed in a clean sample tube and inserted to the specified depth into the probe. The probe coil diameter is 13mm. Measurements are performed according to the manufacturer's instructions. Specifically, by acquiring the signal of the entire polymer, the proportion of the crosslinked portion signal is calculated by fitting software to obtain the degree of crosslinking of the polymer. The "degree of crosslinking" or "T2 relaxation" test mode is selected in the software, and the PQ001 NMR analyzer automatically acquires the relaxation decay curve. During data processing, the software decomposes the relaxed components through exponential fitting, calculates and outputs the degree of crosslinking based on the degree of restriction of molecular chain motion.

[0181] In the above embodiments, setting the degree of crosslinking of the silicone polymer containing the silicon-oxygen structure within the aforementioned range is beneficial for ensuring that the polymer network has suitable rigidity. This helps maintain the mechanical strength of the coating, thereby improving the voltage breakdown resistance of the separator under high voltage.

[0182] As an example, in this embodiment, a powder sample (typically a few milligrams) of an organosilicon polymer containing a silicon-oxygen structure is taken and ultrasonically cleaned with anhydrous ethanol or deionized water for 1-2 minutes to remove surface impurities. It is then placed in an oven and dried at 60-80°C for 1-2 hours to completely remove moisture (to prevent sample evaporation from affecting the vacuum environment during testing). The dried powder is then evenly sprinkled onto conductive adhesive (ensuring no powder accumulation or scattering). A 5-10 nm thick layer of gold is then sputtered onto its surface using an ion sputtering instrument; alternatively, the battery cell is disassembled, the separator is peeled off, and a regular, clear area of ​​the separator is selected. The separator sample is then fixed on the sample stage and sputtered with gold or carbon to make its surface conductive. The sample stage containing the sample to be tested is placed in the SEM sample chamber, the chamber door is closed, and the vacuum system is activated to evacuate to the high vacuum required by the instrument (typically 10). -3 -10 -5After the vacuum reaches the standard, adjust the electron gun voltage (usually 5 - 20 kV) and the working distance (usually 5 - 15 mm). Move the sample stage through the control software to find the target observation area. Gradually adjust the focus and magnification (from a low magnification of 100 times to a high magnification of ten thousand times to observe details), obtain a clear SEM morphology image, and at the same time 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 scan or area scan can be performed), and set the acquisition time (usually 10 - 30 seconds, the longer the time, the more accurate the element signal). Use Energy-Dispersive X-ray Spectroscopy (EDS) equipped with ZEISS sigma300 to perform elemental analysis on the surface of the silicone polymer containing a silicon-oxygen structure to detect the content of silicon element in the silicone polymer containing a silicon-oxygen structure. According to the data results of the instrument, the distribution of each element can be obtained, and thus the mass percentage of the silicon element can be obtained.

[0183] Setting the mass content of the silicon element in the silicone polymer containing a silicon-oxygen structure within the above range is beneficial to improving the structural stability of the coating, and further promoting the stability of the separator in a high-voltage environment.

[0184] As an example, the mass content of phenyl in the silicone polymer has the meaning well-known in the art and can be tested using the instruments and methods known in the art. As an example, after disassembling the battery cell, peel off the separator. Then, scrape the powder of the organic compound particles of the coating in the separator as the test sample, dry it to remove adsorbed water, and then cool it in a dryer for standby. Specifically, a Pyrolysis-Gas Chromatography-Mass Spectrometry (Py-GC / MS) can be used to test the mass content of phenyl in the silicone polymer. Specifically, weigh 0.5 - 1 mg of the above silicone polymer as the test sample, load it into the quartz pyrolysis tube of the pyrolyzer, pyrolyze it at 550 °C for 1.2 s, test the sample is pyrolyzed into volatile small molecules in an inert gas (such as helium), and then introduce it into the gas mass spectrometry. Select the HP-5ms (30 m × 0.25 mm × 0.25 μm) chromatographic column, set the temperature to 30 °C and hold for 5 min, increase the temperature at a rate of 10 °C / min to 250 °C, and hold at 250 °C for 5 min. The carrier gas is high-purity helium with a flow rate of 1.0 mL / min. The mass spectrometry uses electrochemically ionization, the ion source temperature is 230 °C, and the fragment scanning range is m / z25 - 200. By comparing with the EVA standard pyrolysis spectrum in the NIST library, the characteristic ions corresponding to phenyl are detected, and it can be speculated that the silicone polymer includes a phenyl structure. The internal standard method is used to calculate the mass content of phenyl in the silicone polymer based on the peak area of the above-mentioned fragments corresponding to the characteristic phenyl.

[0185] Because phenyl-containing organosilicon polymers contain Si-O bonds with high bond energy, setting the mass content of phenyl in organosilicon polymers with silicon-oxygen structures within the aforementioned range helps to prevent them from decomposing under high pressure, thereby improving the stability of battery cells under high pressure.

[0186] Therefore, by limiting the degree of crosslinking, the mass content of silicon, and the mass content of phenyl, it is beneficial to improve the voltage breakdown resistance of the separator, thereby improving the cycle performance of the battery cell.

[0187] In some embodiments, the organosilicon polymer containing a silicon-oxygen structure comprises a backbone composed of compounds of formula (II).

[0188] R a [SiO 3 / 2 ] n Equation (II),

[0189] Where n is at least one integer from 4 to 12, R a Including cycloalkyl, aryl, C1-C 12 Alkyl groups, C1-C 12 alkenyl, C1-C 12 The alkynyl group; optionally, n is 8, R a Including C1 to C3 alkyl groups.

[0190] A three-dimensional polyhedral framework can be constructed by introducing the structural unit shown in formula (II) into the organosilicon polymer. This structure, linked by strong covalent bonds, forms a uniform and stable rigid support framework within the separator coating, which is beneficial to its structural stability. This structural stability allows the integrity of the three-dimensional polyhedral framework to be maintained under high-pressure conditions, thereby improving the stability of the battery cell under high-pressure environments. Furthermore, by selecting R… a The substituents are C1-C3 alkyl groups, which helps to further enhance the stability of the molecular structure. Specifically, this design can not only effectively reduce the thermal shrinkage of the separator, but also improve the electrolyte wetting uniformity and promote efficient ion migration, thereby reducing polarization during high-voltage cycling, which is beneficial to improving the cycle life of the battery cells.

[0191] In some embodiments, the organosilicon polymer containing a silicon-oxygen structure comprises one or more monomers of formula (I, II) obtained by hydrolysis and polycondensation.

[0192]

[0193] R'1 includes C1 to C3 alkyl groups. For example, R'1 is methyl, ethyl, or propyl.

[0194] By employing the hydrolysis-condensation reaction of monomer (III), an organosilicon polymer with a cage-like structure can be obtained. Simultaneously, this polymer can form a uniformly distributed and structurally stable three-dimensional network structure in the coating of the separator. This stable cage-like framework and three-dimensional network structure can enhance the mechanical strength and structural integrity of the coating, thereby improving the stability of the coating under high-voltage conditions, which is beneficial for promoting the voltage breakdown resistance of the separator.

[0195] Optionally, R'1 is methyl. This is beneficial for further improving the voltage breakdown resistance of the separator.

[0196] In the embodiments of this application, the organosilicon polymer containing a silicon-oxygen structure is prepared by the following method: the monomer shown in formula (ⅠII) is hydrolyzed, then a catalyst is added, and polycondensation is carried out under heating conditions to obtain the organosilicon polymer containing a silicon-oxygen structure.

[0197] Thus, an organosilicon polymer containing a silicon-oxygen structure is obtained through hydrolysis and condensation reactions.

[0198] In some embodiments of this application, the hydrolysis temperature of the monomer shown in formula (III) is 10℃-40℃. For example, the hydrolysis temperature can be 20℃-29℃, 21℃-28℃, 22℃-27℃, 23℃-26℃, 24℃-25℃, etc.

[0199] In some embodiments, the hydrolysis pH is 3–6, and the stirring rate is 300–500 rpm. For example, the hydrolysis pH can be 3, 4, 5, 6, or any value within the above range; the stirring rate can be 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, or any value within the above range. On the one hand, within the above pH range, the hydrolysis reaction rate is moderate, which is conducive to the complete hydrolysis of methyltrimethoxysilane into active condensation units, and can reduce localized aggregation growth caused by excessively rapid reaction, thereby promoting the uniform nucleation process. On the other hand, by setting the stirring rate within the above range, heterogeneous aggregation between particles can be effectively reduced, and droplets can be fully spherized under the action of interfacial tension, without particle breakage or deformation due to excessive shear. Therefore, by synergistically adjusting the pH and stirring rate, it is beneficial to prepare organic compound particles with a suitable ratio of major to minor diameters and a suitable degree of crosslinking.

[0200] In some embodiments of this 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.

[0201] In some embodiments of this application, the heating time is 2h-48h, for example, the heating time can be 2h, 3h, 8h, 10h, 15h, 20h, 24h, 36h, 48h, etc.

[0202] Specifically, the monomer shown in formula (III) first hydrolyzes to generate silanol, simultaneously releasing alcohol to form a mixed solution. The alcohol increases the solubility of the organosiloxane monomer in the solution. Then, under the action of a catalyst, the silanol begins to condense, forming Si-O-Si bonds between silanols, further forming a network structure, at which point nucleation begins. Finally, these nuclei continuously absorb silanol from the solution and continue to grow until they form an organosilicon polymer containing a cage-like polysilsesquioxane backbone. The nucleation and nucleus growth processes are competitive, and the reaction temperature affects both processes. When nucleation dominates, more nuclei are generated, resulting in a smaller particle size of the final organosilicon polymer; when nucleus growth dominates, the final microspheres have a larger particle size. Increased temperature intensifies the reaction, resulting in more nuclei being generated and more silanol being consumed in the initial stages of the reaction, thus limiting nucleus growth in the later stages and resulting in a smaller particle size of the final organosilicon polymer. By controlling the heating temperature within the range of 30℃-100℃, the (ab) / c ratio can be reduced, promoting uniform particle size of the organosilicon polymer and improving the cycle performance of the secondary battery.

[0203] In some embodiments, by controlling the temperature and time during the polycondensation reaction, organic compound particles with different aspect ratios can be obtained. Specifically, a suitable temperature facilitates uniform polycondensation, reduces particle adhesion or deformation due to excessive reaction, and maintains molding stability; while sufficient reaction time promotes complete solidification of the internal cross-linked network, allowing the particle morphology to fully relax under surface tension, thereby obtaining organic compound particles with suitable aspect ratios and spherical or near-spherical morphologies.

[0204] In some embodiments of this application, the catalyst includes at least one of ammonia, triethylamine, sodium hydroxide, magnesium hydroxide, or ammonium hydroxide.

[0205] In some embodiments, the organosilicon polymer containing a silicon-oxygen structure satisfies one or more 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 content of silicon element in the organosilicon polymer containing a silicon-oxygen structure is 25% to 45%; (3) the mass content of the skeleton composed of the compound shown in formula (II) in the organosilicon polymer containing a silicon-oxygen structure is 40% to 60%.

[0206] For example, the degree of crosslinking of the organosilicon polymer containing a silicon-oxygen structure is 85%, 87%, 89%, 90%, 91%, 93%, 95%, 96%, 97% or any value within the above range; the mass content of silicon element in the organosilicon polymer containing a silicon-oxygen structure is 25%, 27%, 29%, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 45% or any value within the above range; the mass content of the skeleton formed by the compound shown in formula (II) in the organosilicon polymer containing a silicon-oxygen structure is 40%, 41%, 43%, 45%, 48%, 50%, 53%, 56%, 58%, 60% or any value within the above range.

[0207] In this embodiment, the degree of crosslinking of organosilicon polymers containing silicon-oxygen structures can be tested using a PQ001 nuclear magnetic resonance (NMR) analyzer. The test temperature is 60°C, the NMR analyzer's resonance frequency is set to 21MHz, and 0.5g of cleaned and dried sample (the aforementioned organosilicon compound particles) is placed in a clean sample tube and inserted to the specified depth into the probe. The probe coil diameter is 13mm. Measurements are performed according to the manufacturer's instructions. Specifically, by acquiring the signal of the entire polymer, the proportion of the crosslinked portion signal is calculated by fitting software to obtain the degree of crosslinking of the polymer. The "degree of crosslinking" or "T2 relaxation" test mode is selected in the software, and the PQ001 NMR analyzer automatically acquires the relaxation decay curve. During data processing, the software decomposes the relaxed components through exponential fitting, calculates and outputs the degree of crosslinking based on the degree of restriction of molecular chain motion.

[0208] By controlling the degree of crosslinking of the organosilicon polymer within the above range, its structural stability can be enhanced, the mechanical strength of the coating can be improved, and thus the stability of the coating under high pressure environment can be improved.

[0209] As an example, the mass content of silicon in organosilicon polymers is a well-known concept in the art and can be tested using instruments and methods known in the art. Specifically, as an example, after disassembling the battery cell, the separator is peeled off, and a regular, clear area of ​​the separator is selected. Then, the separator sample is fixed on a sample stage and subjected to gold or carbon sputtering to make its surface conductive. Elemental analysis of the relevant area surface is performed using Energy-Dispersive X-ray Spectroscopy (EDS). Specifically, as an example, a SEM (model: German ZEISS Sigma 300, mapping mode) is used. Based on the instrument data, the distribution of each element can be obtained, thus determining the mass percentage of each element. Combined with the SEM scanning results, an elemental distribution map of the sample morphology is obtained.

[0210] The aforementioned silicon content can maintain the stability of the material structure, thereby promoting the stability of the separator under high pressure.

[0211] As an example, the mass content of the skeleton formed by the compound shown in formula (II) in the organosilicon polymer has a meaning known in the art and can be tested using instruments and methods known in the art. As an example, after the battery cell is disassembled, the separator is peeled off. Then, the organic compound particles powder coated in the separator are scraped off as the sample to be tested, dried to remove adsorbed water, and placed in a desiccator for cooling and later use. Specifically, the mass content of phenyl groups in the organosilicon polymer can be tested using thermal pyrolysis-gas chromatography-mass spectrometry (Py-GC / MS). Specifically, 0.5–1 mg of the above-mentioned organosilicon polymer was weighed as a test sample and placed in the quartz pyrolysis tube of a pyrolysis instrument. Pyrolysis was performed at 550 °C for 1.2 s. The sample was then tested in an inert gas (e.g., helium) to break down into volatile small molecules, which were then introduced into a gas chromatography-mass spectrometry (GC-MS) system. An HP-5ms (30 m × 0.25 mm × 0.25 μm) column was selected. The temperature was set at 30 °C for 5 min, then increased to 250 °C at a rate of 10 °C / min, and held at 250 °C for 5 min. High-purity helium was used as the carrier gas at a flow rate of 1.0 mL / min. Electrochemical ionization was used in the mass spectrometry, with an ion source temperature of 230 °C and a fragmentation scan range of m / z 25–200. By comparing the fragmentation spectrum of EVA standard in the NIST library, characteristic ions corresponding to the skeleton composed of the compound shown in formula (II) were detected, suggesting that the organosilicon polymer contains a skeleton composed of the compound shown in formula (II). The mass content of the compound in the organosilicon polymer was calculated using the internal standard method based on the area of ​​the fragment peaks corresponding to the skeleton formed by the compound shown in characteristic formula (II).

[0212] Because the organosilicon polymer containing the skeleton of the compound shown in formula (II) contains cage-like skeletal bonds, it has a three-dimensional structure with stable spatial structure. The mass content of the skeleton composed of the compound shown in formula (II) in the aforementioned organosilicon polymer containing silicon-oxygen structures within the above-mentioned range can make it less prone to decomposition at high temperatures, which is beneficial for further improving the stability of the battery cell at high temperatures.

[0213] Therefore, by limiting the degree of crosslinking, the mass fraction of silicon, and the mass content of the skeleton composed of the compound shown in formula (II), it is beneficial to improve the voltage breakdown resistance of the separator, thereby improving the cycle performance of the battery cell.

[0214] In some embodiments, the organic compound particles satisfy at least one of the following conditions (1) to (5): (1) the cyclic voltammetry curve of the organic compound particles in the first cycle does not have an 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 thermogravimetric temperature T of the organic compound particles is [missing information].3d Satisfy: T 3d ≥250℃; (4) The dissolution rate of organic compound particles in a mixed solvent of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 3:7, after being soaked at 60℃ for 7 days, is less than or equal to 5%; (5) The true density of organic compound particles is 0.8 g / cm³. 3 ~2.0g / cm 3 .

[0215] For example, the glass transition temperature Tg of the organic compound particles is 320℃, 350℃, 400℃, 500℃ or any value within the above range; the initial thermogravimetric temperature T of the organic compound particles is... 3d The temperatures are 250℃, 270℃, 290℃, 300℃, 320℃, 350℃, 370℃, 400℃, 500℃, or any value within the above ranges; the dissolution rate of organic compound particles in a mixed solvent of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 3:7, after being soaked at 60℃ for 7 days, is less than or equal to 5% (0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 4%, 4.5%, 5%, or any value within the above ranges); the true density of the organic compound particles is 0.8 g / cm³. 3 1.0g / cm 3 1.2g / cm 3 1.4g / cm 3 1.6g / cm 3 1.8g / cm 3 1.9g / cm 3 2.0g / cm 3 Or any value within the above range.

[0216] The cyclic voltammetry curves of the organic compound particles in the first cycle of this application embodiment do not have oxidation peaks in the voltage range of 0 to 4.40 V, indicating that the organic compound particles are stable in the voltage range of 0 V to 4.40 V and have good electrochemical stability.

[0217] As an example, the oxidation peak potential of the cyclic voltammetry curve of organic compound particles can be tested as follows: Organic compound particles, binder polyacrylate, and conductive carbon black are dissolved in water at a solid content mass ratio of 64:7:29 to prepare a slurry. The slurry is coated onto aluminum foil as the positive electrode, and lithium foil is used as the negative electrode to assemble a coin cell. Cyclic voltammetry (CV) is performed on the coin cell at a scan rate of 0.10 mV / s, a voltage range of 2.50 V–5.00 V, and 3 cycles. The voltage corresponding to the peak point of the first cyclic voltammetry curve is taken as the oxidation peak potential. The electrolyte used in the test is LiPF6 with a concentration of 1 mol / L. The solvent of the electrolyte is obtained by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of 3:7.

[0218] Because conventional organic particles generally have poor electrochemical stability and are prone to decomposition under high voltage, the organic compound particles in this application embodiment can be used in high-voltage battery cells, enabling the battery cells to exhibit good capacity performance under high voltage and improving the operating voltage and energy density of the battery cells.

[0219] The glass transition temperature (Tg) refers to the transition temperature at which a material changes from a glassy state to a highly elastic state, and it exhibits a step-like change on the DSC curve.

[0220] As an example, the glass transition temperature T g The test can be performed as follows: Take an appropriate amount of sample (e.g., 5mg-15mg) and place it in the crucible of the differential scanning calorimeter (DSC), level it, and cover the crucible. Parameter settings: nitrogen atmosphere, purge gas 60mL / min, protective gas 20mL / min; program settings: heat from 25℃ to 200℃ at a heating rate of 10℃ / min, hold for 5min to eliminate thermal history, then cool from 200℃ to -40℃ at a cooling rate of 10℃ / min, and then heat to 300℃ at a heating rate of 10℃ / min. The glass transition temperature T of the organic compound particles can be determined by the DSC curve. g .

[0221] The absence of a glass transition temperature (Tg) for organic compound particles at 300°C means that the DSC curve of the organic compound particles remains solid-state and rigid below 300°C, without molecular chain segment movement or softening. This improves the thermal stability of the separator. This reduces separator shrinkage at high temperatures and maintains the structural integrity of the separator under high voltage, thus reducing the risk of short circuits. Simultaneously, this Tg range also enhances the mechanical strength and rigidity of the separator, mitigating separator deformation caused by electrode volume changes during cycling, thereby improving the long-cycle performance of the battery cell.

[0222] The initial thermogravimetric temperature T of organic compound particles 3d A temperature of 250°C or higher indicates that the weight of the organic compound particles does not change significantly at high temperatures. Therefore, during the use of battery cells, the organic compound particles have high heat resistance and thermal stability and are not prone to thermal decomposition.

[0223] As an example, the initial thermogravimetric temperature T 3d This refers to the temperature at which the sample mass loses 3% relative to its initial mass in a thermogravimetric analysis test. The initial thermogravimetric temperature T for organic particles. 3d The test can be performed as follows: Take an appropriate amount of sample (e.g., 5mg-15mg) and place it in the alumina crucible of the thermogravimetric analyzer (TGA), level it, and cover the crucible with the lid; Parameter settings: nitrogen atmosphere, purge gas 60mL / min, protective gas 20mL / min; Temperature rise program: heating rate 10℃ / min, temperature range 35℃~600℃; Obtain the temperature corresponding to a 3% loss of sample mass relative to the initial mass (i.e., 97% of the initial mass) from the test curve, which is the initial thermogravimetric temperature T. 3d .

[0224] When the aforementioned organic compound particles are used in the separator membrane, the organic compound particles can better generate forces to resist the shrinkage of the separator membrane. This allows the separator membrane to maintain a stable pore structure at high temperatures, thereby reducing the occurrence of electrode contact short circuits. Simultaneously, this also reduces electrolyte oxidative decomposition, thus improving high-temperature storage performance and cycle life.

[0225] Dissolution rate can refer to the proportion of particles that dissolve or decompose in the electrolyte.

[0226] As an example, in this embodiment of the application, the swelling degree of organic compound particles can be tested as follows: Take an appropriate amount of sample (e.g., about 1g), the mass of which is recorded as m1, place it in a semi-permeable membrane sample bag, seal it, the sample bag can be permeated by solvent but not by sample; immerse the sample bag in an appropriate amount of solvent (e.g., about 50g) at a constant temperature of 60°C for 7 days, then remove the sample bag, remove the sample from the sample bag, wipe off excess solvent, and weigh the sample again, mass m2; swelling degree = (m2-m1) / m1×100%. The solvent is a mixed solvent obtained by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7.

[0227] After being soaked in electrolyte at 60°C for 7 days, the organic compound particles have a leaching rate of less than 5%, making them less likely to precipitate or dissolve in the electrolyte environment. This reduces the risk of electrolyte contamination or side reactions between organic compound particles and the electrolyte during battery cell cycling. The separator has good structural stability, which is beneficial to the cycle performance and reliability of the battery cells.

[0228] True density refers to the mass of a material in an absolutely dense state, per unit actual volume (excluding internal voids, i.e., excluding open and closed pores and interparticle voids).

[0229] As an example, true density can be tested using the following method. For example, weigh an organic compound particle with mass M, place the carbon-based component in a true density analyzer (AccuPyc II 1340 analyzer) at room temperature (15℃-25℃), seal the test system, and introduce helium gas according to the procedure. By detecting the gas pressure in the sample chamber and expansion chamber, and then calculating the gas volume in the sample chamber and expansion chamber respectively according to the ideal gas law, the difference between the two is the volume of gas displaced by the carbon-based component under certain temperature and pressure conditions, which is the true volume V of the organic compound particle. The true density of the organic compound particle is calculated as the organic compound particle mass M / the true volume V of the organic compound particle, and the unit of true density is g / cm³. 3 .

[0230] Compared to denser inorganic particles, such as boehmite and alumina, organic compound particles have a lower true density, which can increase the energy density of a single battery cell without increasing the coating thickness.

[0231] Therefore, by limiting the oxidation peak, glass transition temperature, initial thermal weight loss temperature, dissolution rate, and true density of the cyclic voltammetry curve of organic compound particles in the first cycle, it is beneficial to improve the overall performance of the battery cell.

[0232] In some embodiments, the organic compound particles constitute 50% to 97% of the coating by mass. For example, the organic compound particles may constitute 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 87%, 89%, 90%, 92%, 94%, 96%, 97%, or any value within the above range. Setting the organic compound particle content in the coating within the above range is beneficial for forming an effective heat-resistant network, reducing the tendency of the separator to shrink at high temperatures, which could lead to internal short circuits and thus reduce the voltage breakdown performance of the separator. Simultaneously, this also helps reduce the agglomeration of organic compound particles, which can clog pores and impede ion conduction, thereby increasing internal resistance and affecting the rate performance of the battery cells. Furthermore, this can reduce the likelihood of the coating cracking during cycling, thus reducing the voltage breakdown performance and cycle stability of the separator.

[0233] In some embodiments, the first adhesive satisfies one or more of the following conditions: (1) the first adhesive includes at least one of polyimide, polyetherimide, polyacrylic acid, polyacrylate, ethylene vinyl acetate copolymer, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethylated polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose, acrylonitrile-styrene-butadiene copolymer, ethylene-propylene-diene terpolymer, sulfonated ethylene-propylene-diene terpolymer, styrene-butadiene rubber, and fluororubber; (2) the first adhesive has a mass content of 3% to 15% in the coating.

[0234] For example, the mass content of the first adhesive in the coating is 3%, 5%, 7%, 9%, 10%, 12%, 13%, 14%, 15%, or any value within the range mentioned above.

[0235] In the above embodiments, the organic compound particles in the coating are interconnected and fixed by the first binder, reducing the likelihood of organic compound particles falling off during coating and use. Setting the mass content of the first binder within the aforementioned range allows for a balance between adhesion and minimizing the reduction in the proportion of organic compound particles in the coating due to excessive binder, thereby ensuring both the stability of the separator and its voltage breakdown resistance, and improving the cycle performance of the battery cells.

[0236] In some embodiments, the separator further includes second adhesive particles located in the coating, or the separator further includes an adhesive layer disposed on at least one side of the coating away from the porous base membrane, wherein the second adhesive particles are located in the adhesive layer; the second adhesive particles satisfy one or more of the following conditions: (1) the second adhesive particles include at least one of polyvinylidene fluoride, poly(vinylidene fluoride-copolymer-trichloroethylene), poly(vinylidene fluoride-copolymer-trifluorochloroethylene), poly(vinylidene fluoride-copolymer-trifluoroethylene), poly(vinylidene fluoride-copolymer-tetrafluoroethylene), poly(vinylidene fluoride-copolymer-hexafluoropropylene), polyacrylate, polymethyl methacrylate, and polyacrylonitrile; (2) the average volume particle size of the second adhesive particles is 5 μm to 20 μm.

[0237] For example, the average volumetric particle size of the second binder particles in the coating is 5 μm, 7 μm, 8 μm, 10 μm, 11 μm, 13 μm, 14 μm, 15 μm, 18 μm, 20 μm or any value within the above range.

[0238] In the above embodiments, by adding second binder particles to the coating or to the adhesive layer of the separator, the second binder particles can fill the gap between the negative electrode and the separator, forming a more robust bonding interface. This helps improve the bonding strength between the separator and the negative electrode, thereby enhancing the overall stability of the separator and reducing interlayer delamination between the separator and the negative electrode during cycling due to thermal stress or electrochemical effects, thus improving the cycle performance of the battery cell. Furthermore, setting the average volumetric particle size of the second binder particles within the aforementioned range facilitates uniform distribution of the particles while also providing appropriate fluidity, further contributing to improved cycle performance of the battery cell.

[0239] As an example, the average volumetric particle size of the second binder particles has a meaning known in the art and can be tested using instruments and methods known in the art. For example, the volume average particle size Dv50 of the second binder particles can be tested using a laser particle size analyzer, referring to GB / T 19077-2016. During testing, 1g of the sample to be tested is added to a clean small beaker, followed by 20ml of deionized water. The mixture is sonicated at 53kHz / 120W for 5 minutes to ensure complete dispersion. The laser particle size analyzer is then turned on, the optical path system is cleaned, and the background is automatically tested. The sonicated solution is stirred to ensure uniform dispersion, placed in the sample cell as required, and particle size measurement begins. The testing instrument can be a MasterSizer 3000 laser particle size analyzer.

[0240] It should be understood that the "first adhesive" in the embodiments of this application plays a role in bonding between organic compound particles in the porous coating of the separator, and the "second adhesive particles" play a role in improving the adhesion between the separator and the electrode in the porous coating of the separator.

[0241] In some embodiments, the coating of the isolation membrane includes organic compound particles and a second binder particle, wherein the second binder particle may be embedded in the organic compound particles and form a protrusion on the coating surface.

[0242] In some embodiments, the coating of the separator membrane includes a heat-resistant layer and an adhesive layer. The heat-resistant layer is disposed on a porous base membrane, and the adhesive layer is disposed on at least a portion of the surface of the heat-resistant layer on the side away from the porous base membrane. Organic compound particles are disposed in the heat-resistant layer, and second adhesive particles are disposed in the adhesive layer.

[0243] In some embodiments, the coating of the isolation membrane includes a heat-resistant layer and an adhesive layer. The heat-resistant layer is disposed on one side of the porous base membrane, and the adhesive layer is disposed on at least a portion of the surface of the other side of the porous base membrane. Organic compound particles are disposed in the heat-resistant layer, and second adhesive particles are disposed in the adhesive layer.

[0244] In some embodiments, the coating of the separator membrane includes a heat-resistant layer and an adhesive layer. The heat-resistant layer is disposed on one side of the porous base membrane, and the adhesive layer is disposed on at least a portion of the surface of the heat-resistant layer on the side away from the porous base membrane and on at least a portion of the surface of the other side of the porous base membrane. Organic compound particles are disposed in the heat-resistant layer, and second adhesive particles are disposed in the adhesive layer.

[0245] In some embodiments, the coating does not include inorganic particles.

[0246] In some embodiments, the coating includes inorganic particles, and the mass fraction of the inorganic particles is 0.1% to 50% based on the total mass of the coating.

[0247] In other embodiments, the coating includes inorganic particles, with the inorganic particles comprising 50% to 92% of the total mass of the coating.

[0248] In one example, the inorganic particles include at least one of SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, Y2O3, Al2O3, boehmite (AlO(OH)), Al(OH)3, TiO2, and SiC. These inorganic particles have a large dielectric constant, which is beneficial for improving the ion transport efficiency in the coating.

[0249] In some embodiments, the separator membrane satisfies one or more of the following conditions: (1) the coating thickness is 0.5 μm to 10 μm; (2) the coating areal density is 1.5 g / m³. 2 ~6g / m 2 (3) The longitudinal thermal shrinkage rate of the separator is less than or equal to 5% after being heated at 130℃ for 1 hour; (4) The transverse thermal shrinkage rate of the separator is less than or equal to 5% after being heated at 130℃ for 1 hour; (5) The air permeability of the separator is 150s / 100mL~500s / 100mL.

[0250] For example, the coating thickness can be 0.5μm, 0.7μm, 0.9μm, 1μm, 2μm, 3μm, 5μm, 7μm, 8μm, 9μm, 10μm or any value within the above range; the areal density of the coating can be 1.5g / m³. 2 1.8g / m 2 2g / m 2 2.2g / m 2 2.4g / m 2 2.6g / m 2 2.8g / m 2 3g / m 2 3.2g / m 2 3.5g / m 2 3.8g / m 24g / m 2 4.5g / m 2 5g / m 2 5.3g / m 2 5.7g / m 2 6g / m 2 Or any value within the above range; the longitudinal heat shrinkage rate of the separator after being heated at 130℃ for 1 hour can be 1%, 1.5%, 2%, 2.5%, 3%, 4%, 5% or any value within the above range; the transverse heat shrinkage rate of the separator after being heated at 130℃ for 1 hour can be 1%, 1.5%, 2%, 2.5%, 3%, 4%, 5% or any value within the above range; the air permeability of the separator can be 150s / 100mL, 200s / 100mL, 250s / 100mL, 300s / 100mL, 350s / 100mL, 400s / 100mL, 450s / 100mL, 500s / 100mL or any value within the above range.

[0251] The coating thickness refers to the thickness of the coating on one side of the porous base membrane. Setting the coating thickness within the above range can form a uniform and dense heat insulation layer, thereby balancing the energy density and cycle performance of the battery cells.

[0252] Setting the areal density of the coating within the above range is beneficial to balancing the stability and voltage breakdown resistance of the separator without increasing its weight, thus improving the energy density and reliability of the battery cells.

[0253] As an example, the areal density of the coating can be tested as follows: First, stack six layers of coated and uncoated single release liner substrates, respectively, and apply pressure to ensure tight adhesion and no air bubbles. Then, cut the two stacks according to a template to obtain six samples from each stack. Next, measure the total mass M1 of the six samples with coating and the total mass M2 of the six samples with uncoated substrates. Calculate the average mass of the coating on a single release liner using the formula M = (M1 - M2) / 6. Then, measure the area S of a single sample, and obtain the areal density of the coating using the formula "coating areal density = M / S".

[0254] Heat shrinkage rate refers to the percentage change in the size of the separator at high temperatures, and it is an important indicator for measuring the thermal stability of the separator.

[0255] As an example, the release liner is punched into samples with a width of 50 mm and a length of 100 mm using a punching machine. Five parallel samples are placed on A4 paper, and then the A4 paper containing the samples is placed on corrugated paper with a thickness of 1 mm to 5 mm. The temperature of the forced-air drying oven is set to 130℃. After the temperature reaches the set temperature and stabilizes for 60 minutes, the A4 paper placed on the corrugated paper is placed into the forced-air drying oven, and the timer is started. After the set time (1 hour in this disclosure) is reached, the length and width of the release liner are measured, and the values ​​are marked as a and b, respectively. The longitudinal (MD) heat shrinkage rate = [(100-a) / 100]×100%, and the transverse (TD) heat shrinkage rate = [(50-b) / 50]×100%. The average value of three parallel samples is taken as the test result.

[0256] Heating the separator at 130℃ for 1 hour ensures that the longitudinal and transverse thermal shrinkage rates meet the aforementioned ranges, which helps maintain the separator's stability and improve its mechanical integrity under high-temperature conditions. This reduces short circuits caused by exposed electrodes, thereby lowering the probability of thermal runaway and improving the cycle performance of individual battery cells.

[0257] The air permeability (Gurley value) of a separator membrane refers to the time required for 100 mL of air to pass through the separator membrane, characterizing the resistance of the separator membrane's pore structure to gas / liquid transport.

[0258] As an example, the air permeability value of the separator membrane can be tested according to GB / T 36363-2018. Specifically, the separator membrane is cut into 5cm squares, and using an air permeability meter, a pressure of 1.21kPa is applied; the test shows that 100ml of air permeates 6.45cm. 2 The time required for the membrane to separate is taken as the membrane's air permeability value, expressed in seconds per 100 ml. The average value of three parallel samples is taken as the test result.

[0259] Setting the permeability of the separator within the above range is beneficial for promoting uniform electrolyte wetting and maintaining rapid ion transport, while reducing electrochemical polarization caused by excessively low separator permeability, which in turn reduces the cycle performance of the battery cell.

[0260] Therefore, by limiting the coating thickness, areal density, longitudinal thermal shrinkage rate, transverse thermal shrinkage rate, and air permeability, it is beneficial to improve the overall performance of the separator.

[0261] In some embodiments, the peel force between the coating of the separator and the porous base membrane can be greater than or equal to 28 N / m. For example, the peel force between the coating of the separator and the porous base membrane can be 28 N / m, 30 N / m, 32 N / m, 34 N / m, 36 N / m, 38 N / m, or any value within the above range. This reduces the occurrence of delamination or detachment of the coating during the expansion and contraction of the electrode, thereby maintaining the integrity of the pore structure and promoting uniform ion transport. Simultaneously, this also reduces the risk of localized coating peeling leading to direct contact between the electrolyte and the base membrane, reducing interfacial side reactions and impedance growth.

[0262] As an example, the peel force between the coating of the separator and the porous base membrane can be tested as follows: Cut the separator into three 2.5cm × 15cm strips, attach the strips to a test steel plate, and attach 2cm wide test tape to the side of the separator to be tested. Use a tensile testing machine, clamping the steel plate on one side and the tape on the other, to perform a 180° peel test. Take the average peel force of the three strips as the peel force between the separator coating and the porous base membrane. The tensile rate is 50mm / min.

[0263] It should be noted that the coating parameters of the above-mentioned separators are coating parameters for one side of the porous base membrane. When the coating is applied to both sides of the porous base membrane, if the coating parameters of either side meet the requirements of this disclosure, it is considered to fall within the protection scope of this disclosure.

[0264] In some embodiments, the thickness of the separator can be 5μm-20μm, optionally 5μm-12μm or 6μm-12μm. This is beneficial for improving the energy density of the secondary battery cell.

[0265] In some embodiments, the porous base membrane of the separator may be made of at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene and polyvinylidene fluoride.

[0266] In some embodiments, the porous base membrane can be a single-layer thin film or a multi-layer composite thin film, without particular limitation. When the porous base membrane is a multi-layer composite thin film, the materials of each layer can be the same or different, without particular limitation.

[0267] The separator membrane can be prepared according to methods known in the art.

[0268] [Isolation membrane]

[0269] This application provides an isolation membrane.

[0270] In some embodiments, the separating membrane includes a porous base membrane and a coating disposed on at least one side of the porous base membrane; the coating includes organic compound particles and a first binder; the first binder is used to bond the organic compound particles to the porous base membrane; the organic compound particles have a spherical or near-spherical morphology; the major axis of a single organic compound particle is A, and the minor axis is B, wherein 1 ≤ A:B ≤ 5. For example, A:B is 1, 1.1, 1.3, 1.6, 1.8, 2, 2.3, 2.5, 2.8, 3, 3.2, 3.5, 3.8, 4, 4.2, 4.4, 4.5, 4.6, 4.8, 5, or any value within the above range.

[0271] By incorporating the aforementioned organic compound particles into the coating, it is beneficial to reduce internal short circuits caused by the tip discharge of the organic compound particles, thereby improving the voltage breakdown withstand performance of the separator. This reduces the reduction in voltage breakdown withstand performance of the separator due to oxidation of the material under high voltage conditions, thus improving the cycle performance of the battery cells.

[0272] Optionally, 1 ≤ A:B ≤ 4.5. For example, A:B can be 1, 1.1, 1.3, 1.6, 1.8, 2, 2.3, 2.5, 2.8, 3, 3.2, 3.5, 3.8, 4, 4.2, 4.4, 4.5, or any value within the above range. This results in organic compound particles having a more suitable ratio of major to minor diameters, making it easier for them to exhibit spherical or near-spherical morphologies with similar major and minor diameters, thereby further improving the voltage breakdown resistance of the separator.

[0273] In some embodiments, A satisfies: 60nm ≤ A ≤ 700nm; B satisfies: 50nm ≤ B ≤ 600nm. For example, A can be 60nm, 80nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm or any value within the above range; B can be 50nm, 80nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm or any value within the above range.

[0274] In the above embodiments, on the one hand, the major diameter of the organic compound particles meets the aforementioned range, which helps reduce the risk of sharp protrusions formed by the organic compound particles, causing local electric field distortion and thus exacerbating the risk of tip discharge. Simultaneously, this also helps increase the particle packing density, improving the compactness and mechanical strength of the coating. On the other hand, setting the minor diameter within the aforementioned range helps ensure a suitable number of organic compound particles per unit volume, thereby improving the coating's heat resistance to the separator. Furthermore, this also reduces the tendency for particles to agglomerate, forming localized packing defects that could affect the separator's voltage breakdown resistance.

[0275] In some embodiments, the convexity C of the organic compound particles satisfies: 1 ≤ C ≤ 1.5. For example, the convexity C of the organic compound particles is 1, 1.1, 1.2, 1.3, 1.4, 1.5 or any value within the above range.

[0276] Setting the convexity of the organic compound particles within the aforementioned range helps to ensure that the particle tips have a suitable radius of curvature. This reduces the electric field strength, thereby decreasing the likelihood of partial discharge or even breakdown of the separator, leading to short circuits within the battery. Simultaneously, this convexity range also improves coating uniformity, thus enhancing the mechanical strength and thermal stability of the battery cells. Furthermore, the aforementioned convexity range reduces stress concentration between particles, delaying coating aging. Therefore, by setting the convexity of the organic compound particles as described above, the electric field can be uniformly dispersed while maintaining the structural stability of the coating, thereby improving the voltage breakdown resistance and long-term reliability of the separator.

[0277] In some embodiments, the Dn50 of the organic compound particles satisfies: 150nm ≤ Dn50 ≤ 350nm; where Dn50 refers to the particle size corresponding to the cumulative number distribution of particles reaching 50% in the particle size distribution curve of the organic compound particles. For example, the Dn50 of the organic compound particles is 150nm, 151nm, 180nm, 200nm, 206nm, 220nm, 230nm, 250nm, 262nm, 280nm, 290nm, 300nm, 310nm, 325nm, 330nm, 340nm, 350nm, or any value within the above range. For organic compound particles, setting their Dn50 within the above range is beneficial for the coating to have suitable porosity. This helps to reduce the situation where the local current density rises sharply during the charging and discharging of the battery cell, leading to preferential growth of lithium dendrites, thereby improving the breakdown voltage of the separator. At the same time, this can also reduce the aggregation of nanoparticles, thereby reducing the possibility of micro-short circuits caused by puncturing the base film.

[0278] In some embodiments, the organic compound particles comprise a crosslinked polymer with a crosslinking degree of 70% to 98%. For example, the crosslinking degree of the polymer can be 70%, 72%, 75%, 78%, 80%, 83%, 85%, 87%, 89%, 90%, 92%, 94%, 96%, 97%, 98%, or any value within the above range. The crosslinking degree of the polymer within the above range allows it to form a stable three-dimensional network structure. This structure can effectively maintain the integrity of its spatial configuration under high pressure, thereby giving the separator membrane good mechanical properties. This is beneficial to the structural stability of the separator membrane under high pressure conditions, thereby improving its voltage breakdown resistance.

[0279] In some embodiments, the crosslinking polymer includes an organosilicon polymer containing a silicon-oxygen structure. Using an organosilicon polymer containing a silicon-oxygen structure as the crosslinking polymer is beneficial for improving the voltage breakdown resistance and cycle performance of the separator. Specifically, organosilicon polymers have stable Si-O bonds with high bond energy, making them less prone to decomposition under high voltage, which can further improve the stability of the material under high-voltage environments. Furthermore, compared to inorganic particles, organosilicon polymers have a lower density, which can reduce the overall mass of the coating at the same thickness, thereby contributing to increasing the energy density of the battery cell.

[0280] 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.

[0281]

[0282] R1 and R2 are each independently selected from C1-C4 alkyl groups and C2-C4 alkenyl groups, R3 includes C1-C4 alkyl groups or C4-C8 (meth)acryloyloxyalkyl groups, and R4 includes C2-C8 alkenyl groups or C4-C8 (meth)acryloyloxyalkyl groups; the crosslinking agent includes divinylbenzene.

[0283] In the embodiments of this application, R1 and R2 are each independently selected from 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.

[0284] 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.

[0285] R4 includes at least one of vinyl, propenyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl(meth)acryloyloxymethyl, 2-((meth)acryloyloxy)ethyl, 3-((meth)acryloyloxy)propyl or 4-((meth)acryloyloxy)butyl.

[0286] By polymerizing the monomer shown in formula (I) with the crosslinking agent divinylbenzene, a phenyl-containing organosilicon polymer can be obtained. These particles possess a three-dimensional network framework formed by the phenyl structure and the monomer and crosslinking agent, resulting in higher material stability. This can improve the stability of the separator under high-voltage conditions and enhance the reliability of the battery cell.

[0287] In some embodiments, the preparation method of the phenyl-containing organosilicon polymer includes the following steps: providing a pre-emulsion comprising monomers, crosslinking agents, emulsifiers, initiators, and water; and carrying out an emulsion polymerization reaction under heating, inert gas protection, and stirring conditions to obtain silicone-containing organosilicon resin particles. The monomers include silane coupling agents containing alkenyl and / or acryloyloxy groups, and the mass fraction of the crosslinking agent is 2%-30% based on the total mass of the monomers and crosslinking agents (100%).

[0288] The monomers include silane coupling agents containing alkenyl and / or acryloyloxy groups, thus initiating free radical generation and cross-linking reactions between monomers, and the monomers also undergo cross-linking reactions with the cross-linking agents. Therefore, using the monomers and cross-linking agents disclosed herein as raw materials, phenyl-containing organosilicon polymers with a three-dimensional network structure can be formed, which are not easily softened or deformed at high temperatures and have high heat resistance and electrochemical stability.

[0289] The mass fraction of the crosslinking agent is 2%-30%, based on the total mass of monomers and crosslinking agents as 100%. For example, it can be 2%, 3%, 4%, 5%, 6%, 7%, 8%, 8.5%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13%, 13.5%, 14%, 14.5%, 15%, 18%, 20%, 23%, 25%, 28%, 30%, or any combination of the above values.

[0290] When the mass fraction of the crosslinking agent is within the above range, silicon-containing organic resin particles with high electrochemical stability and good heat resistance can be obtained.

[0291] Optionally, the mass fraction of the crosslinking agent can be 8%-14%, 8%-13%, 8%-12%, 9%-14%, 9%-13%, or 9%-12%.

[0292] In some embodiments, the monomer may include an acryloyloxysilane coupling agent.

[0293] Optionally, the monomer represented by formula (I) may include one or more of the following: γ-methacryloxypropyltris(trimethylsiloxane), (3-acryloxypropyl)tris(trimethylsiloxy)silane, 3-methacryloxypropyltrimethoxysilane, acryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, acryloxypropyltriethoxysilane, γ-methacryloxypropyltriisopropoxysilane, 3-(acryloxy)propyltrimethoxysilane, 3-methacryloxypropyltris(methoxyethoxy)silane, 3-methacryloxypropylmethyldimethoxysilane, 3-acryloxypropylmethyldimethoxysilane, methacryloxypropyldimethylmethoxysilane, (3-acryloxy)dimethylmethoxysilane, 3-methacryloxypropyldimethylethoxysilane, and 3-(methacryloxy)propylmethyldiethoxysilane.

[0294] In some embodiments, the monomer represented by formula (I) may include a first monomer and a second monomer.

[0295] The first monomer may include one or more of the following: γ-methacryloxypropyltris(trimethylsiloxane), (3-acryloxypropyl)tris(trimethylsiloxy)silane, 3-methacryloxypropyltrimethoxysilane, acryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, acryloxypropyltriethoxysilane, γ-methacryloxypropyltriisopropoxysilane, 3-(acryloxy)propyltrimethoxysilane, and 3-methacryloxypropyltris(methoxyethoxy)silane.

[0296] The second monomer may include one or more of 3-methacryloyloxypropylmethyldimethoxysilane, 3-acryloyloxypropylmethyldimethoxysilane, methacryloyloxypropyldimethylmethoxysilane, (3-acryloyloxy)dimethylmethoxysilane, 3-methacryloyloxypropyldimethylethoxysilane, and 3-(methacryloyloxy)propylmethyldiethoxysilane.

[0297] The first and second monomers have different activities. By combining them and reacting them with a crosslinking agent, a silicone polymer with a suitable ratio of major to minor diameters containing a silicon-oxygen structure can be obtained.

[0298] In some embodiments, the emulsifier may include, but is not limited to, one or more of alkyl sulfates, alkyl sulfonates, Tween emulsifiers, fatty alcohol polyoxyethylene ethers, fatty alcohol polyoxypropylene ethers, cetearyl alcohol polyethers, and oleyl alcohol polyethers. Optionally, the emulsifier includes one or more of sodium lauryl sulfate, sodium lauryl sulfonate, Tween 20, Tween 40, lauryl ether-7, lauryl ether-9, lauryl ether-10, and oleyl alcohol polyether-10.

[0299] In some embodiments, the initiator may be one or more of sodium persulfate, potassium persulfate, ammonium persulfate, sodium sulfite, sodium bisulfite, azobisisobutyronitrile, azobisisobutyramidine hydrochloride, azobisisobutyramidine imidazoline hydrochloride, and azobisisopropylimidazoline.

[0300] In some embodiments, the heating temperature during the ripening stage of the emulsion polymerization reaction can be 75°C-95°C, for example, it can be 75°C, 76°C, 77°C, 78°C, 79°C, 80°C, 81°C, 82°C, 83°C, 84°C, 85°C, 88°C, 90°C, 93°C, 95°C or any combination of the above values.

[0301] In some embodiments, the heating time for the ripening stage of the emulsion polymerization reaction can be 1h-4h, for example, it can be 1h, 1.2h, 1.4h, 1.6h, 1.8h, 2h, 2.2h, 2.4h, 2.6h, 2.8h, 3h, 3.2h, 3.4h, 3.6h, 3.8h, 4h or any range of the above values.

[0302] In some embodiments, the emulsion polymerization reaction may include the following steps: adding a pre-emulsion dropwise into a reactor containing water under a first heating temperature, inert gas protection, and stirring conditions; after a first reaction time, raising the temperature to the heating temperature of the maturation stage to carry out a maturation reaction, thereby obtaining silicon-containing organic resin particles.

[0303] Optionally, the first heating temperature can be 55℃-95℃.

[0304] Optionally, the first time can be 3h-8h.

[0305] In some embodiments, the preemulsion may further include a pH adjuster. Optionally, the pH adjuster may include, but is not limited to, one or more of sodium bicarbonate, sodium hydroxide, ammonia, etc. By adding a pH adjuster, the pH value of the preemulsion can be adjusted.

[0306] In some embodiments, the pH of the preemulsion is 7.5 to 10. For example, the pH of the preemulsion can be 7.5, 8, 9, 10 or any value within the above range.

[0307] In some embodiments, the preemulsion is added dropwise under nitrogen protection and with a reactor stirring rate of 50 rpm to 300 rpm. For example, the reactor stirring rate is 50 rpm to 300 rpm or any value within the above range.

[0308] In some embodiments, the morphology and structure of organosilicon polymer particles can be controlled by synergistically regulating the pH of the pre-emulsion and the stirring rate of the reactor. Specifically, the pH value affects the hydrolysis-condensation reaction equilibrium, determines the crosslinking network density and the hydrolytic stability of phenyl groups, thereby regulating the degree of crosslinking and the proportion of phenyl groups. On the other hand, the stirring rate of the reactor can affect the shear force and mass transfer efficiency, thereby affecting the droplet dispersion and nucleation growth process, and thus determining the major and minor diameters of the particles and the ratio of the major and minor diameters.

[0309] In some embodiments, the method for preparing silicone organic resin particles may further include a demagnetization treatment step after the emulsion polymerization reaction is completed.

[0310] In some embodiments, the organosilicon polymer containing a silicon-oxygen structure satisfies one or more 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 content of silicon in the organosilicon polymer containing a silicon-oxygen structure is 10% to 25%; and (3) the mass content of phenyl in the organosilicon polymer containing a silicon-oxygen structure is 2% to 12%.

[0311] For example, the degree of crosslinking of the organosilicon polymer containing the silicon-oxygen structure is 75%, 77%, 79%, 80%, 82%, 84%, 86%, 88%, 90%, 92%, 94%, 95%, or any value within the above range; the mass content of silicon in the organosilicon polymer containing the silicon-oxygen structure is 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 25%, or any value within the above range; the mass content of phenyl in the organosilicon polymer containing the silicon-oxygen structure is 2%, 3%, 4%, 5%, 6%, 7%, 8%, 7%, 9%, 10%, 11%, 12%, or any value within the above range.

[0312] In the above embodiments, setting the degree of crosslinking of the silicone polymer containing the silicon-oxygen structure within the aforementioned range is beneficial for ensuring that the polymer network has suitable rigidity. This helps maintain the mechanical strength of the coating, thereby improving the voltage breakdown resistance of the separator under high voltage.

[0313] Setting the mass content of silicon in the organosilicon polymer containing silicon-oxygen structure within the above range is beneficial to improving the structural stability of the coating, thereby promoting the stability of the separator under high pressure.

[0314] Because phenyl-containing organosilicon polymers contain Si-O bonds with high bond energy, setting the mass content of phenyl in organosilicon polymers with silicon-oxygen structures within the aforementioned range helps to prevent them from decomposing under high pressure, thereby improving the stability of battery cells under high pressure.

[0315] Therefore, by limiting the degree of crosslinking, the mass content of silicon, and the mass content of phenyl, it is beneficial to improve the voltage breakdown resistance of the separator, thereby improving the cycle performance of the battery cell.

[0316] In some embodiments, the organosilicon polymer containing a silicon-oxygen structure comprises a backbone composed of compounds of formula (II).

[0317] R a [SiO 3 / 2 ] n Equation (II),

[0318] Where n is at least one integer from 4 to 12, R a Including cycloalkyl, aryl, C1-C 12 Alkyl groups, C1-C 12 alkenyl, C1-C 12 The alkynyl group; optionally, n is 8, R a Including C1 to C3 alkyl groups.

[0319] A three-dimensional polyhedral framework can be constructed by introducing the structural unit shown in formula (II) into the organosilicon polymer. This structure, linked by strong covalent bonds, forms a uniform and stable rigid support framework within the separator coating, which is beneficial to its structural stability. This structural stability allows the integrity of the three-dimensional polyhedral framework to be maintained under high-pressure conditions, thereby improving the stability of the battery cell under high-pressure environments. Furthermore, by selecting R… a The substituents are C1-C3 alkyl groups, which helps to further enhance the stability of the molecular structure. Specifically, this design can not only effectively reduce the thermal shrinkage of the separator, but also improve the electrolyte wetting uniformity and promote efficient ion migration, thereby reducing polarization during high-voltage cycling, which is beneficial to improving the cycle life of the battery cells.

[0320] In some embodiments, the organosilicon polymer containing a silicon-oxygen structure comprises one or more monomers of formula (I, II) obtained by hydrolysis and polycondensation.

[0321]

[0322] R'1 includes C1 to C3 alkyl groups. For example, R'1 is methyl, ethyl, or propyl.

[0323] By employing the hydrolysis-condensation reaction of monomer (III), an organosilicon polymer with a cage-like structure can be obtained. Simultaneously, this polymer can form a uniformly distributed and structurally stable three-dimensional network structure in the coating of the separator. This stable cage-like framework and three-dimensional network structure can enhance the mechanical strength and structural integrity of the coating, thereby improving the stability of the coating under high-voltage conditions, which is beneficial for promoting the voltage breakdown resistance of the separator.

[0324] Optionally, R'1 is methyl. This is beneficial for further improving the voltage breakdown resistance of the separator.

[0325] In the embodiments of this application, the organosilicon polymer containing a silicon-oxygen structure is prepared by the following method: the monomer shown in formula (ⅠII) is hydrolyzed, then a catalyst is added, and polycondensation is carried out under heating conditions to obtain the organosilicon polymer containing a silicon-oxygen structure.

[0326] Thus, an organosilicon polymer containing a silicon-oxygen structure is obtained through hydrolysis and condensation reactions.

[0327] In some embodiments of this application, the hydrolysis temperature of the monomer shown in formula (III) is 10℃-40℃. For example, the hydrolysis temperature can be 20℃-29℃, 21℃-28℃, 22℃-27℃, 23℃-26℃, 24℃-25℃, etc.

[0328] In some embodiments, the hydrolysis pH is 3–6, and the stirring rate is 300–500 rpm. For example, the hydrolysis pH can be 3, 4, 5, 6, or any value within the above range; the stirring rate can be 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, or any value within the above range. On the one hand, within the above pH range, the hydrolysis reaction rate is moderate, which is conducive to the complete hydrolysis of methyltrimethoxysilane into active condensation units, and can reduce localized aggregation growth caused by excessively rapid reaction, thereby promoting the uniform nucleation process. On the other hand, by setting the stirring rate within the above range, heterogeneous aggregation between particles can be effectively reduced, and droplets can be fully spherized under the action of interfacial tension, without particle breakage or deformation due to excessive shear. Therefore, by synergistically adjusting the pH and stirring rate, it is beneficial to prepare organic compound particles with a suitable ratio of major to minor diameters and a suitable degree of crosslinking.

[0329] In some embodiments of this 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.

[0330] Specifically, the monomer shown in formula (III) first hydrolyzes to generate silanol, simultaneously releasing alcohol to form a mixed solution. The alcohol increases the solubility of the organosiloxane monomer in the solution. Then, under the action of a catalyst, the silanol begins to condense, forming Si-O-Si bonds between silanols, further forming a network structure, at which point nucleation begins. Finally, these nuclei continuously absorb silanol from the solution and continue to grow until they form an organosilicon polymer containing a cage-like polysilsesquioxane skeleton. The nucleation and nucleus growth processes are competitive, and the reaction temperature affects both processes. When nucleation dominates, more nuclei are generated, resulting in a smaller final particle size of the organosilicon polymer; when nucleus growth dominates, the final microspheres have a larger particle size. Increased temperature intensifies the reaction, generating more nuclei and consuming more silanol in the initial stages, thus limiting nucleus growth in later stages and resulting in a smaller final organosilicon polymer particle size. Controlling the heating temperature within the range of 30℃-100℃ can promote uniform particle size of the organosilicon polymer and improve the cycle performance of the secondary battery.

[0331] In some embodiments, by controlling the temperature and time during the polycondensation reaction, organic compound particles with different aspect ratios can be obtained. Specifically, a suitable temperature facilitates uniform polycondensation, reduces particle adhesion or deformation due to excessive reaction, and maintains molding stability; while sufficient reaction time promotes complete solidification of the internal cross-linked network, allowing the particle morphology to fully relax under surface tension, thereby obtaining organic compound particles with suitable aspect ratios and spherical or near-spherical morphologies.

[0332] In some embodiments of this application, the catalyst includes at least one of ammonia, triethylamine, sodium hydroxide, magnesium hydroxide, or ammonium hydroxide.

[0333] In some embodiments, the organosilicon polymer containing a silicon-oxygen structure satisfies one or more 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 content of silicon element in the organosilicon polymer containing a silicon-oxygen structure is 25% to 45%; (3) the mass content of the skeleton composed of the compound shown in formula (II) in the organosilicon polymer containing a silicon-oxygen structure is 40% to 60%.

[0334] For example, the degree of crosslinking of the organosilicon polymer containing a silicon-oxygen structure is 85%, 87%, 89%, 90%, 91%, 93%, 95%, 96%, 97% or any value within the above range; the mass content of silicon element in the organosilicon polymer containing a silicon-oxygen structure is 25%, 27%, 29%, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 45% or any value within the above range; the mass content of the skeleton formed by the compound shown in formula (II) in the organosilicon polymer containing a silicon-oxygen structure is 40%, 41%, 43%, 45%, 48%, 50%, 53%, 56%, 58%, 60% or any value within the above range.

[0335] By controlling the degree of crosslinking of the organosilicon polymer within the above range, its structural stability can be enhanced, the mechanical strength of the coating can be improved, and thus the stability of the coating under high pressure environment can be improved.

[0336] The aforementioned silicon content can maintain the stability of the material structure, thereby promoting the stability of the separator under high pressure.

[0337] Since the organosilicon polymer with a framework composed of the compound shown in formula (II) contains Si-O bonds with high bond energy, setting its mass content within the above range is beneficial to improving its structural stability, thereby enhancing the stability of the battery cell under high voltage.

[0338] Therefore, by limiting the degree of crosslinking, the mass fraction of silicon, and the mass content of the skeleton composed of the compound shown in formula (II), it is beneficial to improve the voltage breakdown resistance of the separator, thereby improving the cycle performance of the battery cell.

[0339] In some embodiments, the organic compound particles satisfy at least one of the following conditions (1) to (5): (1) the cyclic voltammetry curve of the organic compound particles in the first cycle does not have an 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 thermogravimetric temperature T of the organic compound particles is [missing information]. 3d Satisfy: T 3d ≥250℃; (4) The dissolution rate of organic compound particles in a mixed solvent of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 3:7, after being soaked at 60℃ for 7 days, is less than or equal to 5%; (5) The true density of organic compound particles is 0.8 g / cm³. 3 ~2.0g / cm 3 .

[0340] For example, the glass transition temperature Tg of the organic compound particles is 320℃, 350℃, 400℃, 500℃ or any value within the above range; the initial thermogravimetric temperature T of the organic compound particles is... 3dThe temperatures are 250℃, 270℃, 290℃, 300℃, 320℃, 350℃, 370℃, 400℃, 500℃, or any value within the above ranges; the dissolution rate of organic compound particles in a mixed solvent of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 3:7, after being soaked at 60℃ for 7 days, is less than or equal to 5% (0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 4%, 4.5%, 5%, or any value within the above ranges); the true density of the organic compound particles is 0.8 g / cm³. 3 1.0g / cm 3 1.2g / cm 3 1.4g / cm 3 1.6g / cm 3 1.8g / cm 3 1.9g / cm 3 2.0g / cm 3 Or any value within the above range.

[0341] Because conventional organic particles generally have poor electrochemical stability and are prone to decomposition under high voltage, the organic compound particles in this application embodiment can be used in high-voltage battery cells, enabling the battery cells to exhibit good capacity performance under high voltage and improving the operating voltage and energy density of the battery cells.

[0342] The absence of a glass transition temperature (Tg) for organic compound particles at 300°C means that the DSC curve of the organic compound particles remains solid-state and rigid below 300°C, without molecular chain segment movement or softening. This improves the thermal stability of the separator. This reduces separator shrinkage at high temperatures and maintains the structural integrity of the separator under high voltage, thus reducing the risk of short circuits. Simultaneously, this Tg range also enhances the mechanical strength and rigidity of the separator, mitigating separator deformation caused by electrode volume changes during cycling, thereby improving the long-cycle performance of the battery cell.

[0343] The above-mentioned initial thermogravimetric temperature T 3d Organic compound particles are used in the separator membrane, and these particles can better generate forces to resist membrane shrinkage. This allows the separator membrane to maintain a stable pore structure at high temperatures, thereby reducing electrode contact short circuits. Simultaneously, this also reduces electrolyte oxidative decomposition, thus improving high-temperature storage performance and cycle life.

[0344] After being soaked in electrolyte at 60°C for 7 days, the organic compound particles have a leaching rate of less than 5%, making them less likely to precipitate or dissolve in the electrolyte environment. This reduces the risk of electrolyte contamination or side reactions between organic compound particles and the electrolyte during battery cell cycling. The separator has good structural stability, which is beneficial to the cycle performance and reliability of the battery cells.

[0345] Compared to denser inorganic particles, such as boehmite and alumina, organic compound particles have a lower true density, which can increase the energy density of a single battery cell without increasing the coating thickness.

[0346] Therefore, by limiting the oxidation peak, glass transition temperature, initial thermal weight loss temperature, dissolution rate, and true density of the cyclic voltammetry curve of organic compound particles in the first cycle, it is beneficial to improve the overall performance of the battery cell.

[0347] In some embodiments, the organic compound particles constitute 50% to 97% of the coating by mass. For example, the organic compound particles may constitute 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 87%, 89%, 90%, 92%, 94%, 96%, 97%, or any value within the above range. Setting the organic compound particle content in the coating within the above range is beneficial for forming an effective heat-resistant network, reducing the tendency of the separator to shrink at high temperatures, which could lead to internal short circuits and thus reduce the voltage breakdown performance of the separator. Simultaneously, this also helps reduce the agglomeration of organic compound particles, which can clog pores and impede ion conduction, thereby increasing internal resistance and affecting the rate performance of the battery cells. Furthermore, this can reduce the likelihood of the coating cracking during cycling, thus reducing the voltage breakdown performance and cycle stability of the separator.

[0348] In some embodiments, the first adhesive satisfies one or more of the following conditions: (1) the first adhesive includes at least one of polyimide, polyetherimide, polyacrylic acid, polyacrylate, ethylene vinyl acetate copolymer, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethylated polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose, acrylonitrile-styrene-butadiene copolymer, ethylene-propylene-diene terpolymer, sulfonated ethylene-propylene-diene terpolymer, styrene-butadiene rubber, and fluororubber; (2) the first adhesive has a mass content of 3% to 15% in the coating.

[0349] For example, the mass content of the first adhesive in the coating is 3%, 5%, 7%, 9%, 10%, 12%, 13%, 14%, 15%, or any value within the range mentioned above.

[0350] In the above embodiments, the organic compound particles in the coating are interconnected and fixed by the first binder, reducing the likelihood of organic compound particles falling off during coating and use. Setting the mass content of the first binder within the aforementioned range allows for a balance between adhesion and minimizing the reduction in the proportion of organic compound particles in the coating due to excessive binder, thereby ensuring both the stability of the separator and its voltage breakdown resistance, and improving the cycle performance of the battery cells.

[0351] In some embodiments, the separator further includes second adhesive particles located in the coating, or the separator further includes an adhesive layer disposed on at least one side of the coating away from the porous base membrane, wherein the second adhesive particles are located in the adhesive layer; the second adhesive particles satisfy one or more of the following conditions: (1) the second adhesive particles include at least one of polyvinylidene fluoride, poly(vinylidene fluoride-copolymer-trichloroethylene), poly(vinylidene fluoride-copolymer-trifluorochloroethylene), poly(vinylidene fluoride-copolymer-trifluoroethylene), poly(vinylidene fluoride-copolymer-tetrafluoroethylene), poly(vinylidene fluoride-copolymer-hexafluoropropylene), polyacrylate, polymethyl methacrylate, and polyacrylonitrile; (2) the average volume particle size of the second adhesive particles is 5 μm to 20 μm.

[0352] For example, the average volumetric particle size of the second binder particles in the coating is 5 μm, 7 μm, 8 μm, 10 μm, 11 μm, 13 μm, 14 μm, 15 μm, 18 μm, 20 μm or any value within the above range.

[0353] In the above embodiments, by adding second binder particles to the coating or to the adhesive layer of the separator, the second binder particles can fill the gap between the negative electrode and the separator, forming a more robust bonding interface. This helps improve the bonding strength between the separator and the negative electrode, thereby enhancing the overall stability of the separator and reducing interlayer delamination between the separator and the negative electrode during cycling due to thermal stress or electrochemical effects, thus improving the cycle performance of the battery cell. Furthermore, setting the average volumetric particle size of the second binder particles within the aforementioned range facilitates uniform distribution of the particles while also providing appropriate fluidity, further contributing to improved cycle performance of the battery cell.

[0354] In some embodiments, the coating of the isolation membrane includes organic compound particles and a second binder particle, wherein the second binder particle may be embedded in the organic compound particles and form a protrusion on the coating surface.

[0355] In some embodiments, the coating of the separator membrane includes a heat-resistant layer and an adhesive layer. The heat-resistant layer is disposed on a porous base membrane, and the adhesive layer is disposed on at least a portion of the surface of the heat-resistant layer on the side away from the porous base membrane. Organic compound particles are disposed in the heat-resistant layer, and second adhesive particles are disposed in the adhesive layer.

[0356] In some embodiments, the coating of the isolation membrane includes a heat-resistant layer and an adhesive layer. The heat-resistant layer is disposed on one side of the porous base membrane, and the adhesive layer is disposed on at least a portion of the surface of the other side of the porous base membrane. Organic compound particles are disposed in the heat-resistant layer, and second adhesive particles are disposed in the adhesive layer.

[0357] In some embodiments, the coating of the separator membrane includes a heat-resistant layer and an adhesive layer. The heat-resistant layer is disposed on one side of the porous base membrane, and the adhesive layer is disposed on at least a portion of the surface of the heat-resistant layer on the side away from the porous base membrane and on at least a portion of the surface of the other side of the porous base membrane. Organic compound particles are disposed in the heat-resistant layer, and second adhesive particles are disposed in the adhesive layer.

[0358] In some embodiments, the coating does not include inorganic particles.

[0359] In some embodiments, the coating includes inorganic particles, and the mass fraction of the inorganic particles is 0.1% to 50% based on the total mass of the coating.

[0360] In other embodiments, the coating includes inorganic particles, with the inorganic particles comprising 50% to 92% of the total mass of the coating.

[0361] In one example, the inorganic particles include at least one of SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, Y2O3, Al2O3, boehmite (AlO(OH)), Al(OH)3, TiO2, and SiC. These inorganic particles have a large dielectric constant, which is beneficial for improving the ion transport efficiency in the coating.

[0362] In some embodiments, the separator membrane satisfies one or more of the following conditions: (1) the coating thickness is 0.5 μm to 10 μm; (2) the coating areal density is 1.5 g / m³. 2 ~6g / m 2 (3) The longitudinal thermal shrinkage rate of the separator is less than or equal to 5% after being heated at 130℃ for 1 hour; (4) The transverse thermal shrinkage rate of the separator is less than or equal to 5% after being heated at 130℃ for 1 hour; (5) The air permeability of the separator is 150s / 100mL~500s / 100mL.

[0363] For example, the coating thickness can be 0.5μm, 0.7μm, 0.9μm, 1μm, 2μm, 3μm, 5μm, 7μm, 8μm, 9μm, 10μm or any value within the above range; the areal density of the coating can be 1.5g / m³. 2 1.8g / m 2 2g / m 2 2.2g / m 2 2.4g / m 2 2.6g / m 2 2.8g / m 2 3g / m 2 3.2g / m 2 3.5g / m 2 3.8g / m 2 4g / m 2 4.5g / m 2 5g / m 2 5.3g / m 2 5.7g / m 2 6g / m 2 Or any value within the above range; the longitudinal heat shrinkage rate of the separator after being heated at 130℃ for 1 hour can be 1%, 1.5%, 2%, 2.5%, 3%, 4%, 5% or any value within the above range; the transverse heat shrinkage rate of the separator after being heated at 130℃ for 1 hour can be 1%, 1.5%, 2%, 2.5%, 3%, 4%, 5% or any value within the above range; the air permeability of the separator can be 150s / 100mL, 200s / 100mL, 250s / 100mL, 300s / 100mL, 350s / 100mL, 400s / 100mL, 450s / 100mL, 500s / 100mL or any value within the above range.

[0364] The coating thickness refers to the thickness of the coating on one side of the porous base membrane. Setting the coating thickness within the above range can form a uniform and dense heat insulation layer, thereby balancing the energy density and cycle performance of the battery cells.

[0365] Setting the areal density of the coating within the above range is beneficial to balancing the stability and voltage breakdown resistance of the separator without increasing its weight, thus improving the energy density and reliability of the battery cells.

[0366] As an example, the areal density of the coating can be tested as follows: First, stack six layers of coated and uncoated single release liner substrates, respectively, and apply pressure to ensure tight adhesion and no air bubbles. Then, cut the two stacks according to a template to obtain six samples from each stack. Next, measure the total mass M1 of the six samples with coating and the total mass M2 of the six samples with uncoated substrates. Calculate the average mass of the coating on a single release liner using the formula M = (M1 - M2) / 6. Then, measure the area S of a single sample, and obtain the areal density of the coating using the formula "coating areal density = M / S".

[0367] Heat shrinkage rate refers to the percentage change in the size of the separator at high temperatures, and it is an important indicator for measuring the thermal stability of the separator.

[0368] As an example, the release liner is punched into samples with a width of 50 mm and a length of 100 mm using a punching machine. Five parallel samples are placed on A4 paper, and then the A4 paper containing the samples is placed on corrugated paper with a thickness of 1 mm to 5 mm. The temperature of the forced-air drying oven is set to 130℃. After the temperature reaches the set temperature and stabilizes for 60 minutes, the A4 paper placed on the corrugated paper is placed into the forced-air drying oven, and the timer is started. After the set time (1 hour in this disclosure) is reached, the length and width of the release liner are measured, and the values ​​are marked as a and b, respectively. The longitudinal (MD) heat shrinkage rate = [(100-a) / 100]×100%, and the transverse (TD) heat shrinkage rate = [(50-b) / 50]×100%. The average value of three parallel samples is taken as the test result.

[0369] Heating the separator at 130℃ for 1 hour ensures that the longitudinal and transverse thermal shrinkage rates meet the aforementioned ranges, which helps maintain the separator's stability and improve its mechanical integrity under high-temperature conditions. This reduces short circuits caused by exposed electrodes, thereby lowering the probability of thermal runaway and improving the cycle performance of individual battery cells.

[0370] The air permeability (Gurley value) of a separator membrane refers to the time required for 100 mL of air to pass through the separator membrane, characterizing the resistance of the separator membrane's pore structure to gas / liquid transport.

[0371] As an example, the air permeability value of the separator membrane can be tested according to GB / T 36363-2018. Specifically, the separator membrane is cut into 5cm squares, and using an air permeability meter, a pressure of 1.21kPa is applied; the test shows that 100ml of air permeates 6.45cm. 2 The time required for the membrane to separate is taken as the membrane's air permeability value, expressed in seconds per 100 ml. The average value of three parallel samples is taken as the test result.

[0372] Setting the permeability of the separator within the above range is beneficial for promoting uniform electrolyte wetting and maintaining rapid ion transport, while reducing electrochemical polarization caused by excessively low separator permeability, which in turn reduces the cycle performance of the battery cell.

[0373] Therefore, by limiting the coating thickness, areal density, longitudinal thermal shrinkage rate, transverse thermal shrinkage rate, and air permeability, it is beneficial to improve the overall performance of the separator.

[0374] In some embodiments, the peel force between the coating of the separator and the porous base membrane can be greater than or equal to 28 N / m. For example, the peel force between the coating of the separator and the porous base membrane can be 28 N / m, 30 N / m, 32 N / m, 34 N / m, 36 N / m, 38 N / m, or any value within the above range. This reduces the occurrence of delamination or detachment of the coating during the expansion and contraction of the electrode, thereby maintaining the integrity of the pore structure and promoting uniform ion transport. Simultaneously, this also reduces the risk of localized coating peeling leading to direct contact between the electrolyte and the base membrane, reducing interfacial side reactions and impedance growth.

[0375] As an example, the peel force between the coating of the separator and the porous base membrane can be tested as follows: Cut the separator into three 2.5cm × 15cm strips, attach the strips to a test steel plate, and attach 2cm wide test tape to the side of the separator to be tested. Use a tensile testing machine, clamping the steel plate on one side and the tape on the other, to perform a 180° peel test. Take the average peel force of the three strips as the peel force between the separator coating and the porous base membrane. The tensile rate is 50mm / min.

[0376] It should be noted that the coating parameters of the above-mentioned separators are coating parameters for one side of the porous base membrane. When the coating is applied to both sides of the porous base membrane, if the coating parameters of either side meet the requirements of this disclosure, it is considered to fall within the protection scope of this disclosure.

[0377] In some embodiments, the thickness of the separator can be 5μm-20μm, optionally 5μm-12μm or 6μm-12μm. This is beneficial for improving the energy density of the secondary battery cell.

[0378] In some embodiments, the porous base membrane of the separator may be made of at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene and polyvinylidene fluoride.

[0379] In some embodiments, the porous base membrane can be a single-layer thin film or a multi-layer composite thin film, without particular limitation. When the porous base membrane is a multi-layer composite thin film, the materials of each layer can be the same or different, without particular limitation.

[0380] The separator membrane can be prepared according to methods known in the art.

[0381] In some embodiments, a slurry comprising organic compound particles and first binder particles can be coated on at least one side of a porous base membrane, and after drying, a separation membrane is obtained.

[0382] In some embodiments, the slurry may further include second binder particles, which, after drying, are embedded in the organic particles and form protrusions on the coating surface.

[0383] In some embodiments, the method for preparing the separator membrane may include: coating a slurry comprising organic compound particles and a first binder particle onto at least one side of a porous base membrane, and drying it to form a coating layer; coating a slurry comprising a second binder particle onto at least a portion of the surface of the coating away from the porous base membrane, and drying it to obtain a separator membrane comprising an adhesive layer.

[0384] In some embodiments, the method for preparing the separator membrane may include: coating a slurry comprising organic compound particles and a first binder particle onto one side of a porous base membrane, coating a slurry comprising a second binder particle onto at least a portion of the surface of the other side of the porous base membrane, and drying to obtain a separator membrane comprising an adhesive layer.

[0385] In some embodiments, the solvent for the slurry may be water, such as deionized water.

[0386] In some embodiments, the slurry may also include other components, such as dispersants and / or wetting agents.

[0387] [Positive electrode plate]

[0388] The positive electrode sheet may include a positive current collector and a positive electrode film layer disposed on at least one layer of the positive current collector, the positive electrode film layer including a positive electrode active material.

[0389] Figure 1 is a schematic diagram of the structure of a positive electrode sheet according to an embodiment of this application. As shown in Figure 1, the positive electrode sheet 121 includes a positive current collector 1211 and a positive electrode film layer 1212 disposed on at least one side surface of the positive current collector 1211.

[0390] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector. As an example, as shown in FIG1, the positive electrode film layer 1212 is disposed on both sides of the positive current collector 1211.

[0391] In some embodiments, the positive electrode active material includes a lithium-containing transition metal oxide. The lithium-containing transition metal oxide includes nickel element, cobalt element and a first element. The first element includes manganese element and / or aluminum element; alternatively, the lithium-containing transition metal oxide includes a layered lithium manganese-based oxide having the following structural formula: xLi2MnO3·(1-x)LiM1O2; wherein, 0 < X < 1; M1 includes at least one of nickel element, cobalt element and manganese element. For the positive electrode active material, the lithium-containing transition metal oxide has a high working voltage and a high specific capacity, which can improve the energy density of the battery cell. In its layered structure, the redox potential of transition metals (such as nickel and cobalt) is relatively high, which can provide a high voltage platform. At the same time, the increase in nickel content can also increase the specific capacity of the battery cell. Therefore, using a lithium-containing transition metal oxide in the positive electrode active material can enable the battery cell to store more electrical energy under the same weight or volume, meeting the long endurance requirement.

[0392] Specifically, when the lithium-containing transition metal oxide includes nickel element, cobalt element and a first element, and the first element includes manganese element and / or aluminum element, nickel is beneficial to improving the reversible capacity of the battery cell, thereby improving the energy density of the battery cell; cobalt helps to improve the electronic conductivity and layered structure stability of the material; manganese or aluminum can act as a "structural pillar", which can reduce cation mixing and phase change during cycling, thereby improving thermal stability. On the other hand, when the lithium-containing transition metal oxide includes the above-mentioned layered lithium manganese-based oxide, the Li2MnO3 component can de-lithiate and release oxygen under high voltage, enabling the battery cell to have a high capacity and energy density while also having a high working voltage.

[0393] In some embodiments, the layered lithium manganese-based oxide has the following structural formula: xLi2MnO3·(1-x)LiNi y Co z Mn a M 1-y-z-a O2, where 0 < x < 1, 0 ≤ y ≤ 1, 0 ≤ z ≤ 1, 0 ≤ a ≤ 1, 0 < y + z + a ≤ 1; M is at least one of Mg, B, Al, V, Ti, Zr, Sn and Mo.

[0394] In some embodiments, the lithium-containing transition metal oxide includes a ternary material. The ternary material includes two types of single-layered lithium-containing transition metal oxides, namely lithium nickel cobalt manganate or lithium nickel cobalt aluminate. The chemical formula of the ternary material is Li 1+d [Ni x Co y Mn z M e O 2-fM includes at least one of Zr, Al, Ti, Sb, Nb, Te, Mg, B, Ca, V, Ta, or Sr, with 0.2 ≥ d ≥ -0.2, 0.95 ≥ x ≥ 0.5, 0.2 ≥ y ≥ 0.05, 0.3 > z > 0, 0.3 > e ≥ 0, and 0.5 ≥ f ≥ 0. Doping lithium-containing transition metal oxides with element M can effectively stabilize their crystal structure. Specifically, element M improves the structural integrity of the cathode active material under high-voltage conditions by suppressing phase transitions during charging and discharging, reducing lattice oxygen evolution, and enhancing metal-oxygen bond energy. This atomic-scale elemental doping modification can effectively reduce structural failure of the material, thereby mitigating the risk of thermal runaway in battery cells.

[0395] In some embodiments, the lithium-containing transition metal oxide comprises single particles. This can improve the mechanical stability and interfacial chemical stability of the cathode active material at the microstructural level. Specifically, as a single particle, it can effectively reduce stress accumulation and crack propagation at the grain boundaries of polycrystalline aggregates, maintain the integrity of the crystal structure during repeated lithium-ion intercalation and deintercalation, and thus reduce cathode active material failure and the increase of side reaction interfaces caused by particle breakage. Simultaneously, its lower specific surface area can reduce the contact range with the electrolyte, reduce the severity of interfacial side reactions under high voltage conditions, and enhance the uniformity and stability of the surface passivation layer. Therefore, under high voltage conditions, the single-particle morphology can improve the cycle life of the battery cell.

[0396] In some embodiments, the volume average particle size Dv50 of the lithium-containing transition metal oxide satisfies: 3 μm ≤ Dv50 ≤ 5 μm. For example, the volume average particle size Dv50 of the lithium-containing transition metal oxide is 3 μm, 3.2 μm, 3.5 μm, 3.8 μm, 4 μm, 4.3 μm, 4.7 μm, 5 μm, or any value within the above range. Here, Dv50 represents the particle size corresponding to a cumulative volume distribution percentage of 50% for the material.

[0397] In the above embodiments, setting the volume average particle size Dv50 of the lithium-containing transition metal oxide within the aforementioned range helps to reduce the ion solid-phase diffusion path, resulting in more uniform lithium-ion insertion / extraction under high voltage, and reducing local stress concentration and particle cracking. This reduces the exposure of cracked surfaces to the high-voltage electrolyte, thereby reducing the triggering of severe side reactions and lowering interface degradation and impedance. Furthermore, this also ensures that the lithium-containing transition metal oxide has a suitable specific surface area, reducing excessive catalytic oxidation and decomposition of the electrolyte by the active surface, thus forming a stable cathode-electrolyte interface film and reducing ion transport resistance. Simultaneously, this also reduces local overcharging and heat accumulation, improving thermal stability. Therefore, the aforementioned Dv50 range is beneficial for maintaining interface and structural balance under high-voltage conditions and improving the thermal stability of the battery cell.

[0398] As an example, referring to GB / T 19077-2016, a laser particle size analyzer can be used to test the volume average particle size (Dv50) of lithium transition metal oxides. During testing, 1g of the sample to be tested is added to a clean small beaker, followed by 20ml of deionized water. The sample is sonicated at 53kHz / 120W for 5 minutes to ensure complete dispersion. The laser particle size analyzer is then turned on, and after cleaning the optical path system, the background is automatically measured. The sonicated solution is stirred to ensure uniform dispersion, then placed into the sample cell as required, and particle size measurement begins. A MasterSizer 3000 laser particle size analyzer can be used as the testing instrument.

[0399] In some embodiments, the mass content D of the positive electrode active material in the positive electrode film layer satisfies: 70% ≤ D ≤ 98%. For example, the mass content D of the positive electrode active material in the positive electrode film layer is 70%, 72%, 75%, 78%, 80%, 83%, 86%, 88%, 90%, 92%, 94%, 96%, 98%, or any value within the above range. By controlling the range of the mass content of the positive electrode active material in the positive electrode film layer, it is beneficial to ensure that the conductive agent and binder have a suitable mass ratio, thereby ensuring that the electrode has suitable conductivity and mitigating polarization. In this way, under high voltage conditions, the battery cell can reduce local overheating and structural instability, thereby improving its cycle life. At the same time, the overall energy density of the battery cell can also be considered.

[0400] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0401] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0402] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0403] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry, coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0404] [Negative electrode plate]

[0405] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0406] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0407] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0408] In some embodiments, the negative electrode active material includes at least one selected from artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material may be selected from one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. However, this application is not limited to these materials, and other conventional materials that can be used as battery negative electrode active materials may also be used. These negative electrode active materials may be used alone or in combination of two or more. In the actual application scenarios of battery cells, the appropriate type of negative electrode active material can be selected according to specific needs.

[0409] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0410] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0411] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0412] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0413] [Electrolytes]

[0414] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific limitations on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel-like, or entirely solid.

[0415] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0416] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0417] In some embodiments, the solvent may 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, butyl 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.

[0418] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0419] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0420] In some embodiments, the battery cell may include an outer packaging. This outer packaging can be used to encapsulate the electrode assembly and electrolyte described above.

[0421] In some embodiments, the outer packaging of the battery cell can be a rigid shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the battery cell can also be a flexible package, such as a pouch. The material of the flexible package can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0422] This application does not impose any particular limitation on the shape of the battery cell; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 2 is a schematic diagram of the structure of a battery cell according to an embodiment of this application.

[0423] Figure 3 is a schematic diagram of the structure of a battery cell according to another embodiment of this application. As shown in Figure 3, the outer packaging of the battery cell 100 includes a shell 11 and a cover plate 13. The shell 11 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates forming a receiving cavity. The shell 11 has an opening communicating with the receiving cavity, and the cover plate 13 can cover the opening to close the receiving cavity. A positive electrode sheet, a negative electrode sheet, and a separator can be formed into an electrode assembly 12 by a winding process or a stacking process. The electrode assembly 12 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 12. The number of electrode assemblies 12 contained in the battery cell 100 can be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0424] In some embodiments, the battery cells 100 can also be assembled into a battery module. The number of battery cells 100 contained in the battery module can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0425] [Battery Device]

[0426] This application provides a battery device including one or more battery cells as described in the above embodiments. When there are multiple battery cells, they are connected in series, parallel, or mixed connections via a busbar.

[0427] In some embodiments, the battery device may be a battery pack, which includes a housing and individual battery cells, with the individual battery cells or battery modules housed within the housing.

[0428] In some embodiments, the battery device may be located within an energy storage device. Energy storage devices include energy storage containers, energy storage cabinets, etc.

[0429] Figure 4 is a schematic diagram of a battery device according to an embodiment of this application, and Figure 5 is a structural schematic diagram of a battery device according to an embodiment of this application. Referring to Figures 4 and 5, the battery device 400 may include a battery box and a plurality of battery cells 100 disposed in the battery box. The battery box includes an upper box body 401 and a lower box body 402. The upper box body 401 can cover the lower box body 402 and form a closed space for accommodating the battery cells 100. The plurality of battery cells 100 can be arranged in the battery box in any manner.

[0430] [Electrical appliances]

[0431] This application also provides an electrical device that includes the battery described in the foregoing embodiments. The electrical device includes at least one of the battery cell 100 or battery device 400 provided in this application. The battery cell 100 or battery device 400 can be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0432] For example, Figure 6 is a schematic diagram of the structure of an electrical device according to one embodiment of this application. As shown in Figure 6, the electrical device is a vehicle 1, which can be a gasoline vehicle, a natural gas vehicle, or a new energy vehicle. A new energy vehicle can be a pure electric vehicle, a hybrid electric vehicle, or a range-extended electric vehicle, etc. A motor 500, a controller 600, and a battery device 400 can be installed inside the vehicle 1. The controller 600 controls the battery device 400 to supply power to the motor 500. For example, the battery device 400 can be installed at the bottom, front, or rear of the vehicle 1. The battery device 400 can be used to power the vehicle 1. For example, the battery device 400 can serve as the operating power source for the vehicle 1's electrical system, such as meeting the power requirements for starting, navigation, and operation of the vehicle 1. In another embodiment of this application, the battery device 400 can not only serve as the operating power source for the vehicle 1 but also as the driving power source for the vehicle 1, replacing or partially replacing gasoline or natural gas to provide driving power for the vehicle 1.

[0433] As the electrical device, either the battery cell 100 or the battery device 400 can be selected according to its usage requirements.

[0434] The electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements of the battery for this electrical device, a single battery cell of 100 or a battery pack of 400 can be used.

[0435] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a single battery cell (100) as their power source.

[0436] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0437] [Examples and Comparative Examples]

[0438] [Example 1]

[0439] (1) Preparation of negative electrode sheet:

[0440] Preparation of the negative electrode sheet: Artificial graphite, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC-Na) were added to deionized water at a mass ratio of 96.0:1.5:1.5:1.0. The mixture was thoroughly stirred and mixed to prepare a negative electrode slurry (solid content 63%). This negative electrode slurry was then subjected to a concentration of 98 g / m³. 2 The loading amount is coated on the copper foil of the negative electrode current collector, and then dried, cold-pressed and slit to obtain the negative electrode sheet.

[0441] (2) Preparation of the positive electrode sheet:

[0442] LiNi with a mass ratio of 97:2:1 was used 0.65 Co 0.1 Mn 0.24 Zr 0.01 O2 (LiNi) 0.65 Co 0.1 Mn 0.24 Zr 0.01 A positive electrode slurry was prepared by dissolving single O2 particles (Dv50 of 3.5 μm), polyvinylidene fluoride (PVDF) as a binder, and carbon black as a conductive agent in nitrogen-methylpyrrolidone (NMP). This positive electrode slurry was then subjected to a concentration of 200 g / m³. 2 The loading is uniformly coated on the positive current collector aluminum foil, and then dried, cold-pressed and cut to obtain the positive electrode sheet.

[0443] (3) Preparation of the separating membrane:

[0444] ① Preparation of organic compound particles (organosilicon polymers containing cage-like polysilsesquioxane backbones):

[0445] In a 500ml flask equipped with a stirrer, thermometer, and reflux condenser, deionized water was added, followed by hydrochloric acid to adjust the hydrolysis pH to 5. The stirring speed was set to 300 rpm, and methyltrimethoxysilane was added to achieve a mass ratio of methyltrimethoxysilane to deionized water of 1:23. The hydrolysis reaction was then carried out at 25°C for 2 hours. Sodium hydroxide was added to adjust the pH to 9, and the reaction was continued at 25°C for 2 hours. The temperature was then raised to 90°C and the reaction was continued for 12 hours to obtain organic compound particles. Subsequent evaporation of the water content yielded a dispersion with a solid content of 20%. This dispersion was then dried to obtain the corresponding organic compound powder.

[0446] 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 94.3%.

[0447] The organic compound particles were tested using a thermal pyrolysis-gas chromatography-mass spectrometry (Py-GC / MS) method. Figure 7 shows the pyrolysis spectrum of the organic compound particles in this embodiment. As shown in Figure 7, by comparing the pyrolysis spectrum of EVA standard particles in the NIST library, it was detected that... The corresponding characteristic ions suggest that the organic compound particles include a cage-like polysilsesquioxane skeleton.

[0448] Differential scanning calorimetry (DSC) was used to test the glass transition temperature (Tg) and melting point of organic compound particles. The organic compound particles had no Tg and no melting point below 300℃.

[0449] The density of the organic compound particles was tested using a true density meter, and the true density of the organic compound particles was 1.3 g / cm³. 3 .

[0450] The number-average particle size (Dn50) of the organic compound particles was measured using a scanning electron microscope (e.g., ZEISS Sigma 300), and the number-average particle size (Dn50) of the organic compound particles was 265 nm.

[0451] 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 0.3%.

[0452] Figure 8 is a SEM image of the organic compound particles in Example 1. As shown in Figure 8, the organic compound particles are spherical or near-spherical in shape and have a relatively regular shape.

[0453] ② Preparation of the isolation membrane: A commercially available polyethylene microporous membrane (Zhuogao Electronic Technology Co., Ltd.) with a thickness of 7μm and an average pore size of 50nm was used as the porous base membrane; the dispersion containing organic compound particles prepared above and the binder polyacrylic acid were stirred and mixed evenly in deionized water at a solid mass ratio of 92:8 to obtain the coating slurry.

[0454] Commercially available polyvinylidene fluoride (PVDF) granules (Arkema), binder polyacrylic acid, and dispersant sodium carboxymethyl cellulose were mixed evenly in deionized water at a solid content mass ratio of 88:10:2 to obtain a binder slurry. The PVDF granules had a Dv50 of 6.8 μm.

[0455] The coating slurry was applied at a concentration of 2.6 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 1.2 g / m². 2 The loading amount (single-sided) is sprayed onto the coating on both sides, and then dried and slit to obtain the release membrane. The air permeability of the release membrane is 205s / 100mL. Specific implementation parameters are shown in Table 1.

[0456] (4) Preparation of electrolyte:

[0457] In an argon-atmospheric glove box (H₂O < 0.1 ppm, O₂ < 0.1 ppm), ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) were mixed in a volume ratio of 1:1:1 to obtain a mixed solvent. LiPF₆ and vinylene carbonate (VC) were then dissolved in this mixed solvent to obtain the electrolyte. The concentration of LiPF₆ was 1 mol / L, and the mass fraction of VC was 5%.

[0458] (5) Preparation of battery cells:

[0459] Preparation of a single battery cell: The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to isolate them. The electrode assembly is then wound to obtain an electrode assembly. The tabs of the electrode assembly are connected to the end cap (e.g., by welding the tabs to the end cap using a connecting member). The electrode assembly is placed in an aluminum casing, dried, and then injected with electrolyte. Finally, it is encapsulated to obtain a single battery cell.

[0460] [Examples 2-3]

[0461] The difference between Example 2 and Example 1 is that in the preparation process of organic compound particles, "adding hydrochloric acid to adjust the hydrolysis pH to 5 and setting the stirring speed to 300 rpm" in Example 1 is changed to "adding hydrochloric acid to adjust the hydrolysis pH to 4 and setting the stirring speed to 400 rpm" to obtain an organic compound particle dispersion. The rest of the preparation process is similar to that of Example 1.

[0462] The difference between Example 3 and Example 1 is that in the preparation process of organic compound particles, "adding hydrochloric acid to adjust the hydrolysis pH to 5 and setting the stirring speed to 300 rpm" in Example 1 is changed to "adding hydrochloric acid to adjust the hydrolysis pH to 3 and setting the stirring speed to 500 rpm" to obtain an organic compound particle dispersion. The rest of the preparation process is similar to that in Example 1.

[0463] [Examples 4-5]

[0464] The difference between Example 4 and Example 1 is that in the process of preparing organic compound particles, the "heating to 90°C and continuing the reaction for 12 hours" in Example 1 is adjusted to "heating to 90°C and continuing the reaction for 24 hours" to obtain an organic compound particle dispersion. The rest of the preparation process is similar to that in Example 1.

[0465] The difference between Example 5 and Example 1 is that in the process of preparing organic compound particles, "heating to 90°C and continuing the reaction for 12 hours" in Example 1 is adjusted to "heating to 75°C and continuing the reaction for 12 hours" to obtain an organic compound particle dispersion. The rest of the preparation process is similar to that in Example 1.

[0466] [Example 6]

[0467] The difference between Example 6 and Example 1 is:

[0468] (3) Preparation of the separating membrane:

[0469] ① Preparation of organic compound particles (phenyl-containing organosilicon polymers):

[0470] A pre-emulsion was prepared by emulsifying 0.3g potassium persulfate, 0.9g sodium dodecyl sulfate, and 30g deionized water with 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropylmethyldimethoxysilane, and divinylbenzene (3g of which was added) in a mass ratio of 90%:5%:5%. Sodium bicarbonate was then added to adjust the pH of the pre-emulsion to 8. In a reactor, 350g of deionized water was added, and the temperature was raised to 82°C. Under nitrogen protection and with a stirring speed of 120 rpm, the pre-emulsion was added dropwise. After reacting for 3.5 hours, the temperature was raised to 90°C and the reaction was allowed to mature for another 3.5 hours to obtain an emulsion containing organic compound particles.

[0471] 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 90.3%.

[0472] Powdered organic compound particles were tested using pyrolysis-gas chromatography-mass spectrometry (Py-GC / MS). The pyrolysis spectra of EVA standard particles were compared with those in the NIST library, and detection was achieved. The corresponding characteristic ions suggest that the organic compound particles may include benzene rings.

[0473] Differential scanning calorimetry (DSC) was used to test the glass transition temperature (Tg) and melting point of organic compound particles. The organic compound particles had no Tg and no melting point below 300℃.

[0474] The density of the organic compound particles was tested using a true density meter, and the true density of the organic compound particles was 1.36 g / cm³. 3 .

[0475] Organic compound particles were placed in a mixed solvent of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 3:7 and immersed 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%.

[0476] ② Preparation of the isolation membrane: A commercially available polyethylene microporous membrane with a thickness of 7μm and an average pore size of 50nm (Zhuogao Electronic Technology Co., Ltd.) was used as the porous base membrane; the dispersion containing organic compound particles prepared above and the binder polyacrylic acid were stirred and mixed evenly in deionized water at a solid mass ratio of 93:7 to obtain the coating slurry.

[0477] Commercially available polyvinylidene fluoride (PVDF) granules (Arkema), binder polyacrylic acid, and dispersant sodium carboxymethyl cellulose were mixed evenly in deionized water at a solid content mass ratio of 88:10:2 to obtain a binder slurry. The PVDF granules had a Dv50 of 6.8 μm.

[0478] The coating slurry was applied at a concentration of 2.6 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 1.2 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 205 s / 100 mL. Specific implementation parameters are shown in Table 3.

[0479] [Examples 7-8]

[0480] The difference between Example 7 and Example 6 is that in the preparation process of organic compound particles, the phrase "adjusting the pH of the pre-emulsion to 8 with sodium bicarbonate and stirring the reactor at 120 rpm" in Example 6 is changed to "adjusting the pH of the pre-emulsion to 7.5 with sodium bicarbonate and stirring the reactor at 50 rpm" to obtain an emulsion containing organic compound particles. The rest of the preparation process is similar to that in Example 6.

[0481] The difference between Example 8 and Example 6 is that in the process of preparing organic compound particles, the phrase "adjusting the pH of the pre-emulsion to 8 with sodium bicarbonate and stirring the reactor at 120 rpm" in Example 6 is changed to "adjusting the pH of the pre-emulsion to 10 with sodium bicarbonate and stirring the reactor at 300 rpm", resulting in an emulsion containing organic compound particles. The rest of the preparation process is similar to that in Example 6.

[0482] [Examples 9-10]

[0483] The difference between Example 9 and Example 6 is that, in the preparation process of organic compound particles, the phrase "using 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropylmethyldimethoxysilane and divinylbenzene in a mass ratio of 90%:5%:5% (wherein, divinylbenzene is 3g)" in Example 6 is adjusted to "using 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropylmethyldimethoxysilane and divinylbenzene in a mass ratio of 85%:5%:10% (wherein, divinylbenzene is 6g)" to obtain an emulsion containing organic compound particles. The remaining preparation process is similar to that in Example 6.

[0484] The difference between Example 10 and Example 6 is that, in the preparation process of the organic compound particles, the phrase "using 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropylmethyldimethoxysilane and divinylbenzene in a mass ratio of 90%:5%:5% (wherein, divinylbenzene is 3g)" in Example 6 is adjusted to "using 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropylmethyldimethoxysilane and divinylbenzene in a mass ratio of 80%:5%:15% (wherein, divinylbenzene is 9g)" to obtain an emulsion containing organic compound particles. The remaining preparation process is similar to that in Example 6.

[0485] [Comparative Example 1]

[0486] The difference between Comparative Example 1 and Example 1 is that the particles added to the coating slurry are inorganic particles, which are commercially available alumina with an average number-average particle size Dn50 of 140 nm.

[0487] Figure 9 shows the SEM image of the inorganic particles in Comparative Example 1. As shown in Figure 9, the inorganic particles exhibit a non-spherical and irregular shape.

[0488] Table 1 shows the specific parameters of Examples 1-5 and Comparative Example 1; Table 2 shows the test results of Examples 1-5 and Comparative Example 1; Table 3 shows the specific parameters of Examples 6-10; Table 4 shows the test results of Examples 6-10.

[0489] Table 1. Relevant test data for Examples 1-5 and Comparative Example 1

[0490] In Table 1, “A” represents the major diameter of a single organic compound particle; “B” represents the minor diameter of a single organic compound particle; “A:B” represents the ratio of the major diameter A to the minor diameter B of a single organic compound particle; and “Dn50” represents the particle size corresponding to the cumulative particle size distribution curve of organic compound particles reaching 50%.

[0491] Table 2 shows the test results of Examples 1-5 and Comparative Example 1.

[0492] Referring to Tables 1 and 2, and based on Examples 1-5 and Comparative Example 1, it is evident that the technical solution of this application employs an organosilicon polymer containing a cage-like polysilsesquioxane backbone as the organic compound particles. This results in individual organic compound particles having suitable ratios of major diameter A to minor diameter B, suitable convexity, Dn50, crosslinking degree, and the mass proportion of the cage-like backbone. This not only improves the voltage breakdown resistance of the separator and reduces the thermal shrinkage rate but also enhances the cycle performance of the battery cells.

[0493] Table 3 Specific parameters of Examples 6-10

[0494] In Table 3, “A” represents the major diameter of a single organic compound particle; “B” represents the minor diameter of a single organic compound particle; “A:B” represents the ratio of the major diameter A to the minor diameter B of a single organic compound particle; and “Dn50” represents the particle size corresponding to the cumulative particle size distribution curve of organic compound particles reaching 50%.

[0495] Table 4 Test results of Examples 6-10

[0496] Referring to Tables 3 and 4, and based on Examples 6-10 and Comparative Example 1 above, it can be seen that in the technical solution of this application, within a certain range, a phenyl-containing organosilicon polymer is used as the organic compound particles, so that each organic compound particle has a suitable ratio of major diameter A to minor diameter B, suitable major diameter A, suitable minor diameter B, suitable convexity, Dn50, suitable degree of crosslinking, and suitable mass ratio of phenyl. This not only helps to improve the voltage breakdown resistance of the separator and reduce the thermal shrinkage rate, but also improves the cycle performance of the battery cell.

[0497] The following is a brief description of the testing methods for the physicochemical and performance parameters involved in the embodiments of this application. It should be understood that the following testing methods are only examples, and other testing methods known in the art can also be used for testing.

[0498] 1. Test method for degree of crosslinking

[0499] As an example, the degree of crosslinking of cross-linked polymers can be tested using a PQ001 NMR analyzer. The test temperature is 60℃, the NMR analyzer's resonance frequency is set to 21MHz, and 0.5g of cleaned and dried sample (the aforementioned organic compound particles) is placed in a clean sample tube and inserted to the specified depth into the probe. The probe coil diameter is 13mm. Measurements are performed according to the manufacturer's instructions. Specifically, by acquiring the signal of the entire polymer, the proportion of the cross-linked portion signal is calculated by the fitting software to obtain the degree of crosslinking of the polymer. In the software, either the "degree of crosslinking" or "T2 relaxation" test mode is selected, and the PQ001 NMR analyzer automatically acquires the relaxation decay curve. During data processing, the software decomposes the relaxed components through exponential fitting, calculates and outputs the degree of crosslinking based on the degree of restriction of molecular chain motion.

[0500] 2. Test methods for phenyl groups and cage-like framework structures

[0501] In this embodiment, a thermal pyrolysis-gas chromatography-mass spectrometry (Py-GC / MS) instrument can be used to test the rigid phenyl structure and cage-like framework structure in organic compound particles. Specifically, 0.5–1 mg of the above-mentioned organic compound particles are weighed as test samples and placed in the quartz pyrolysis tube of the thermal pyrolysis instrument. Pyrolysis is performed at 550°C for 1.2 s. The sample is then pyrolyzed into volatile small molecules in an inert gas (such as helium), and subsequently introduced into the gas chromatography-mass spectrometry. An HP-5ms (30m × 0.25mm × 0.25μm) column is selected, and the temperature is set as follows: 30°C for 5 min, then increased to 250°C at a rate of 10°C / min, and held at 250°C for 5 min. High-purity helium is used as the carrier gas at a flow rate of 1.0 mL / min. Electrochemical ionization is used in the mass spectrometry, with an ion source temperature of 230°C and a fragmentation scan range of m / z 25–200. By comparing the fragmentation spectra of EVA standard fragments in the NIST library, characteristic ions corresponding to the benzene ring and the cage-like skeleton were detected, suggesting that the organosilicon polymer may contain phenyl or cage-like skeleton structures. Using the internal standard method, the mass percentage of the fragments corresponding to the characteristic benzene ring or cage-like skeleton in the organic compound particles was calculated based on their respective peak areas.

[0502] 3. Testing of the major and minor diameters, and the ratio of major to minor diameters, of individual organic compound particles.

[0503] As an example, the ratio of the major to minor diameter of the organic compound particles in the coating has a range known in the art and can be tested using instruments and methods known in the art. Specifically, as an example, after disassembling the battery cell, the separator is peeled off, and a regular, clear area of ​​the separator is selected. Subsequently, a scanning electron microscope (SEM) is used, and the microstructure of the coating on the separator is measured with reference to standard JY / T010 1996. The number of organic compound particles in the Dn50±50nm range is counted, and the major and minor diameters of the corresponding individual organic compound particles in the SEM morphology image are fitted using ImageJ software. Then, the major and minor diameters of the organic compound particles in the Dn50±50nm range are counted again to obtain the major and minor diameters of each individual organic compound particle in the Dn50±50nm range. Finally, the ratio of the major to minor diameter of each individual organic compound particle in the Dn50±50nm range is calculated.

[0504] 4. Testing the convexity of organic compound particles

[0505] As an example, the convexity of organic compound particles in the coating has a well-known meaning in the art and can be tested using instruments and methods known in the art. Specifically, as an example, after disassembling the battery cell, the separator is peeled off, and a regular, clear area of ​​the separator is selected. Subsequently, a scanning electron microscope (SEM) is used, and the microstructure of the coating on the separator is measured with reference to standard JY / T010 1996. Then, the number of organic compound particles in the Dn50±50nm range is counted, and the convexity of the organic compound particles in the SEM morphology image is obtained by fitting using ImageJ software. Then, the convexity of the organic compound particles is obtained by calculating the average convexity of the organic compound particles in the Dn50±50nm range (obtaining the convexity value of each individual organic compound particle in the Dn50±50nm range, calculating the sum of the convexity values, average convexity = sum of convexity values ​​ / total number of organic compound particles in the Dn50±50nm range).

[0506] 5. Test of Dn50 of organic compound particles

[0507] As an example, the Dn50 of organic compound particles has a well-known meaning in the art and can be tested using instruments and methods known in the art. For example, a scanning electron microscope (e.g., ZEISS Sigma 300) can be used to obtain a scanning electron microscope (SEM) image of the separator, referring to JY / T010-1996. As an example, the test can be performed as follows: Randomly select a test sample of length × width = 50 mm × 100 mm on the separator. Randomly select multiple test areas (e.g., 5 areas) within the test sample, and at a certain magnification (e.g., 500x or 1000x when measuring organic compound particles), read the particle size of the organic compound particles in each test area (i.e., take the distance between the two farthest points on the organic compound particle as the particle size). Count the number and particle size values ​​of organic compound particles in each test area, and take the arithmetic mean of the particle sizes in each test area, which is the number-average particle size of the organic compound particles in the test sample. To ensure the accuracy of the test results, the above test can be repeated with multiple test samples (e.g., 10). The average value of each test sample is taken as the final test result, thus obtaining the particle size distribution curve of the organic compound particles. Then, through statistical analysis, the Dn50 result is obtained. In the particle size distribution curve of organic compound particles, Dn50 refers to the particle size corresponding to when the cumulative particle size distribution reaches 50%.

[0508] 6. Testing the withstand voltage breakdown performance of the separator

[0509] The prepared separator membrane was cut into samples 10 cm in length and 2 cm in width. Scratched samples were selected, and their surfaces were cleaned. A voltage breakdown tester (model: XGCL-301) was used for testing. The voltage was gradually increased using a high-voltage power supply, and the current changes were recorded. When the current suddenly increased, the test was immediately stopped, and the breakdown voltage value at that moment was recorded.

[0510] 7. Thermal shrinkage rate test of the release liner

[0511] The prepared separator was punched into samples with a width of 50 mm and a length of 100 mm using a punching machine. Five parallel samples were placed on A4 paper, and then the A4 paper containing the samples was placed on corrugated paper with a thickness of 1 mm to 5 mm.

[0512] Sample testing: The temperature of the forced-air drying oven was set to 130℃. After the temperature reached the set temperature and stabilized for 30 minutes, the A4 paper placed on the corrugated paper was put into the forced-air drying oven and the timer was started. After the set time was reached (1 hour in this embodiment of the application), the length and width of the isolation film were measured and the values ​​were marked as m and n, respectively.

[0513] Calculation of heat shrinkage rate: Longitudinal (MD) heat shrinkage rate = [(100-m) / 100]×100%, Transverse (TD) heat shrinkage rate = [(50-n) / 50]×100%, take the average value of 5 parallel samples as the test result.

[0514] 8. Cyclic performance testing

[0515] At 25℃, charge the battery to 4.4V with a constant current of 1 / 3C, then charge it to 0.05C with a constant voltage of 4.4V. Let it rest for 5 minutes, then discharge it to 2.5V with a constant current of 1 / 3C. The resulting capacity is recorded as the initial capacity C0. Repeat the above steps and record the discharge capacity C500 of the secondary battery after 500 cycles. Then, the capacity retention rate of the secondary battery after 500 cycles is P500 = C500 / C0 × 100%.

[0516] Although this application has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of this application. In particular, the technical features mentioned in the various embodiments can be combined in any manner, provided there is no structural conflict. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery cell, characterized in that, Comprising: a positive electrode plate, a negative electrode plate, and a separator, the separator being located between the positive electrode plate and the negative electrode plate; the positive electrode plate includes a positive current collector and at least one layer of positive electrode film layers provided on the positive current collector, and the positive electrode film layers include positive electrode active materials; the positive electrode active materials include lithium-containing transition metal oxides, the lithium-containing transition metal oxides include nickel element, cobalt element, and a first element, the first element includes manganese element and / or aluminum element; or, the lithium-containing transition metal oxides include layered lithium manganese-based oxides, and the layered lithium manganese-based oxides have the following structural formula: xLi2MnO3·(1-x)LiM1O2; wherein, 0 < X < 1; M1 includes at least one of nickel element, cobalt element, and manganese element; the separator includes a porous base film and a coating provided on at least one side of the porous base film; the coating includes organic compound particles and a first binder; the first binder is used to bond the organic compound particles to the porous base film; the morphology of the organic compound particles is spherical or quasi-spherical; the major axis of a single organic compound particle is A, and the minor axis is B, wherein, 1 ≤ A:B ≤ 5.

2. The battery cell according to claim 1, characterized in that, 1 ≤ A:B ≤ 4.

5.

3. The battery cell according to claim 1 or 2, characterized in that, A satisfies: 60nm ≤ A ≤ 700nm; B satisfies: 50nm ≤ B ≤ 600nm.

4. The battery cell according to any one of claims 1 to 3, characterized in that, the convexity C of the organic compound particles satisfies: 1 ≤ C ≤ 1.

5.

5. The battery cell according to any one of claims 1 to 4, characterized in that, the Dn50 of the organic compound particles satisfies: 150nm ≤ Dn50 ≤ 400nm; wherein, Dn50 refers to the particle diameter corresponding to when the particle cumulative quantity distribution reaches 50% in the particle size quantity distribution curve of the organic compound particles.

6. The battery cell according to any one of claims 1 to 5, characterized in that, the lithium-containing transition metal oxides include single particles; 7. The battery cell according to claim 6, characterized in that, the volume average particle diameter Dv50 of the lithium-containing transition metal oxides satisfies: 3μm ≤ Dv50 ≤ 5μm; 8. The battery cell according to any one of claims 1 to 7, characterized in that, the mass content of the positive electrode active materials in the positive electrode film layers is 70% - 98%; 9. The battery cell according to any one of claims 1 to 8, characterized in that, the organic compound particles include crosslinked polymers, and the crosslinking degree of the crosslinked polymers is 70% - 98%; 10. The battery cell according to claim 9, characterized in that, the crosslinked polymers include organosilicon polymers containing silicon-oxygen structures; 11. The battery cell according to claim 10, characterized in that, The organosilicon polymer containing a silicon-oxygen structure includes phenyl groups, and is obtained by polymerization of the monomers shown in formula (I) and a crosslinking agent. wherein, R1 and R2 each independently selected from C1-C4 alkyl groups, C2-C4 alkenyl groups, R3 includes a C1-C4 alkyl group or a C4-C8 (meth)acryloyloxyalkyl group, R4 includes a C2-C8 alkenyl group or a C4-C8 (meth)acryloyloxyalkyl group; the crosslinking agent includes divinylbenzene; 12. The battery cell according to claim 10 or 11, characterized in that, the organosilicon polymers containing silicon-oxygen structures satisfy one or more of the following conditions: (1) the crosslinking degree of the organosilicon polymers containing silicon-oxygen structures is 75% - 95%; 13. The battery cell according to claim 10, characterized in that, R a [SiO 3 / 2 ] n Equation (II), Where n is at least one integer from 4 to 12, R a Including cycloalkyl, aryl, C1-C 12 Alkyl groups, C1-C 12 alkenyl, C1-C 12 acetylin group; Optionally, n is 8, R a Including C1 to C3 alkyl groups.

14. The battery cell according to claim 10, characterized in that, The organosilicon polymer containing a silicon-oxygen structure is obtained by hydrolysis and condensation polymerization of one or more monomers shown in formula (ⅠII). (2) the mass content of silicon element in the organosilicon polymers containing silicon-oxygen structures is 10% - 25%; 15. The battery cell according to claim 13 or 14, characterized in that, (3) the mass content of phenyl group in the organosilicon polymers containing silicon-oxygen structures is 2% - 12%; the organosilicon polymers containing silicon-oxygen structures include a framework composed of compounds shown in formula (II), wherein, R'1 includes a C1-C3 alkyl group; the organosilicon polymers containing silicon-oxygen structures satisfy one or more of the following conditions: (1) The degree of crosslinking of the organosilicon polymer containing silicon-oxygen structure is 85% to 97%; (2) The mass content of silicon in the organosilicon polymer containing silicon-oxygen structure is 25% to 45%; (3) The skeleton formed by the compound shown in formula (II) has a mass content of 40% to 60% in the organosilicon polymer containing silicon-oxygen structure.

16. The battery cell according to any one of claims 1 to 15, characterized in that, The organic compound particles satisfy at least one of the following conditions (1) to (5): (1) The cyclic voltammetry curve of the organic compound particles in the first cycle does not have an 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 of the organic compound particles 3d Satisfy: T 3d ≥250℃; (4) The dissolution rate of the organic compound particles in a mixed solvent of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 3:7, after being soaked at a constant temperature of 60°C for 7 days is less than or equal to 5%. (5) The true density of the organic compound particles is 0.8 g / cm³. 3 ~2.0g / cm 3 .

17. The battery cell according to any one of claims 1 to 16, characterized in that, The organic compound particles in the coating contain 50% to 97% by mass.

18. The battery cell according to any one of claims 1 to 17, characterized in that, The first adhesive satisfies one or more of the following conditions: (1) The first adhesive 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, cyanoethyl 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 content of 3% to 15% in the coating.

19. The battery cell according to any one of claims 1 to 18, characterized in that, The release membrane further includes second adhesive particles located within the coating. Alternatively, the separator may further include an adhesive layer disposed on at least one side of the coating away from the porous base membrane, wherein the second adhesive particles are located in the adhesive layer; the second adhesive particles satisfy one or more of the following conditions: (1) The second adhesive particles include at least one of polyvinylidene fluoride, poly(vinylidene fluoride-copolymer-trichloroethylene), poly(vinylidene fluoride-copolymer-trichlorotrifluoroethylene), poly(vinylidene fluoride-copolymer-trifluoroethylene), poly(vinylidene fluoride-copolymer-tetrafluoroethylene), poly(vinylidene fluoride-copolymer-hexafluoropropylene), polyacrylate, polymethyl methacrylate, and polyacrylonitrile; (2) The average volumetric particle size of the second binder particles is 5 μm to 20 μm.

20. The battery cell according to any one of claims 1 to 19, characterized in that, The isolation membrane satisfies one or more of the following conditions: (1) The thickness of the coating is 0.5μm to 10μm; (2) The areal density of the coating is 1.5 g / m³. 2 ~6g / m 2 ; (3) The longitudinal thermal shrinkage rate of the isolation membrane is less than or equal to 5% when heated at 130°C for 1 hour. (4) The separation membrane is heated at 130°C for 1 hour and the transverse thermal shrinkage rate is less than or equal to 5%; (5) The air permeability of the isolation membrane is 150s / 100mL to 500s / 100mL.

21. The battery cell according to any one of claims 1 to 20, characterized in that, The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one side of the negative current collector. The negative electrode film layer includes a negative electrode active material, which includes at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate.

22. A battery device, characterized in that, include: The battery cell according to any one of claims 1 to 21.

23. An electrical appliance, characterized in that, include: The battery cell according to any one of claims 1 to 21 or the battery device according to claim 22.

24. A separating membrane, characterized in that, include: A porous base membrane and a coating disposed on at least one side of the porous base membrane; The coating comprises organic compound particles and a first binder; The first binder is used to bond the organic compound particles to the porous base membrane; The organic compound particles are spherical or near-spherical in shape. The major axis of a single organic compound particle is A, and the minor axis is B, wherein 1 ≤ A:B ≤ 5.

25. The separator according to claim 24, characterized in that, 1≤A:B≤4.

5.

26. The separator according to claim 24 or 25, characterized in that, The condition A satisfies: 60nm≤A≤700nm; the condition B satisfies: 50nm≤B≤600nm.

27. The separator membrane according to any one of claims 24 to 26, characterized in that, The convexity C of the organic compound particles satisfies: 1≤C≤1.

5.

28. The separator membrane according to any one of claims 24 to 27, characterized in that, The organic compound particle Dn50 satisfies: 150nm≤Dn50≤400nm; where Dn50 refers to the particle size corresponding to the cumulative number distribution of particles reaching 50% in the particle size distribution curve of the organic compound particles.

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