Battery cell and preparation method therefor, battery device and electric device

Abstract

A battery cell and a preparation method therefor, a battery device and an electric device. The battery cell comprises an electrode assembly and an electrolyte solution. The electrode assembly comprises a positive electrode sheet, a negative electrode sheet and a separator, wherein the separator is located between the positive electrode sheet and the negative electrode sheet. The separator comprises a porous base film and a composite coating located on the surface of at least one side of the porous base film, and the composite coating comprises inorganic particles modified by a silane coupling agent, a gel polymer and a binder. The electrolyte solution comprises an organic solvent, an electrolyte salt, and an acrylate cross-linking agent. The inorganic particles modified by a silane coupling agent comprise inorganic particles and a silicon-containing organic group, wherein the inorganic particles and the silicon-containing organic group are linked via a hydrogen bond and / or an ether bond, the silicon-containing organic group comprises an active group, and the active group can undergo a polymerization reaction with the acrylate cross-linking agent. The separator and the electrolyte solution can undergo gelation to form a gel electrolyte separator. The battery cell has a long cycle life.

Description

Battery cells and their preparation methods, battery devices, and electrical devices.

[0001] Cross-reference to related applications

[0002] This application claims priority to Chinese Patent Application No. 202510191660.0, filed on February 20, 2025, entitled “Battery cell and method of preparation thereof, battery device, power device”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to a battery cell and its preparation method, a battery device, and an electrical device. Background Technology

[0004] As battery cells are used more widely, the demands on them are also increasing, such as higher requirements for energy density and cycle life. For high-energy-density battery cells, the introduction of thin separators is urgently needed. However, current separator designs are insufficient to meet the requirements for long cycle life in battery cells. Summary of the Invention

[0005] This disclosure provides a battery cell and its preparation method, a battery device, and an electrical device, wherein the battery cell has a long cycle life.

[0006] In a first aspect, this disclosure provides a battery cell, which includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode, a negative electrode, and a separator, with the separator located between the positive and negative electrodes. The separator includes a porous base membrane and a composite coating on at least one surface of the porous base membrane. The composite coating includes silane coupling agent-modified inorganic particles, a gel polymer, and a binder. The electrolyte includes an organic solvent, an electrolyte salt, and an acrylate crosslinking agent. The silane coupling agent-modified inorganic particles include inorganic particles and silicon-containing organic groups, which are connected by hydrogen bonds and / or ether bonds. The silicon-containing organic groups have active groups that can polymerize with the acrylate crosslinking agent. The separator and the electrolyte can gel to form a gel electrolyte separator.

[0007] The composite coating of the separator disclosed herein includes a gel polymer, which enables the separator and electrolyte to gel and form a gel electrolyte separator. The composite coating of the separator also includes silane coupling agent-modified inorganic particles. These silane coupling agent-modified inorganic particles have active groups on their surface. These active groups can polymerize with acrylate crosslinking agents in the electrolyte, thereby participating in the gelation process between the separator and the electrolyte. This allows for better interconnection of the polymer chains of the gel polymer, resulting in a structurally stable gel electrolyte separator with good heat resistance and mechanical strength. This reduces the self-discharge of individual battery cells and allows more electrolyte to be locked within the pores of the gel electrolyte separator, reducing free electrolyte and side reactions at the electrolyte-electrode interface. Furthermore, this results in a longer cycle life for the individual battery cells, making them better suited for energy storage applications.

[0008] In some embodiments, the active groups include one or more of acryloyloxy, carbon-carbon double bond, amino, hydroxyl, mercapto, glycidyl etheroxy, carbonyl, and carboxyl groups. These active groups can undergo polymerization reactions with acrylate crosslinking agents in the electrolyte, thereby participating in the gelation process of the separator and the electrolyte, enabling better interconnection of the polymer chains of the gel polymer, thus forming a stable, heat-resistant, and mechanically strong gel electrolyte separator, reducing the self-discharge of the battery cell, and locking more electrolyte in the pores of the gel electrolyte separator, reducing free electrolyte and side reactions at the electrolyte-electrode interface, thereby enabling the battery cell to have a long cycle life.

[0009] In some embodiments, the acrylate crosslinking agent includes one or more of the following: triethylene glycol diacrylate, triethylene glycol dimethacrylate, triethylene glycol divinyl acrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate, tetra(ethylene glycol) diacrylate, tetraethylene glycol dimethacrylate, 1,3-butanediol diacrylate, 1,3-butanediol dimethacrylate, neopentyl glycol diacrylate, neopentyl glycol dimethacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, and pentaerythritol tetraacrylate.

[0010] The inorganic particles modified with silane coupling agents have active groups on their surface. These active groups can polymerize with the aforementioned acrylate crosslinking agents, thereby participating in the gelation process of the separator and electrolyte. This allows the polymer chains of the gel polymer to be better interconnected, resulting in a stable, heat-resistant, and mechanically strong gel electrolyte separator. This reduces the self-discharge of the battery cells and also allows more electrolyte to be locked in the pores of the gel electrolyte separator, reducing free electrolyte and side reactions at the electrolyte-electrode interface. Consequently, the battery cells also have a long cycle life.

[0011] In some embodiments, the mass of the acrylate crosslinking agent is 1%-6% of the total mass of the electrolyte, optionally 4%-6%.

[0012] An appropriate amount of acrylate crosslinking agent can better polymerize with the active groups on the surface of inorganic particles modified by silane coupling agent without affecting the ionic conductivity and viscosity of the electrolyte. This allows it to better participate in the gelation process of the separator and the electrolyte, and further improve the cycle life of the battery cell.

[0013] In some embodiments, the mass of the silicon-containing organic groups in the silane coupling agent-modified inorganic particles is 0.2%-4% of the mass of the silane coupling agent-modified inorganic particles. An appropriate amount of silicon-containing organic groups can introduce suitable active groups onto the surface of the inorganic particles. These active groups can undergo polymerization reactions with the acrylate crosslinking agents in the electrolyte, thereby participating in the gelation process of the separator and the electrolyte. This allows for better interconnection of the polymer chains in the gel polymer and also improves the compatibility between the inorganic particles, the gel polymer, and the porous base membrane. This results in the formation of a stable, heat-resistant, and mechanically strong gel electrolyte separator, further enhancing the cycle life of the battery cells.

[0014] In some embodiments, the average particle size of the silane coupling agent-modified inorganic particles is 100 nm to 1000 nm. An average particle size within this range is advantageous for obtaining a thin composite coating with good heat resistance, which in turn contributes to high energy density in the battery cells.

[0015] In some embodiments, the relative permittivity of the inorganic particles is greater than or equal to 10. This can increase the electronic insulation of the separator, improve the withstand voltage breakdown strength of the separator, and reduce the self-discharge of individual battery cells.

[0016] In some embodiments, the inorganic particles include rutile nano-titanium dioxide, nano-barium titanate, and nano-CaCu3Ti4O. 12One or more of the following: strontium titanate, barium strontium titanate, lead titanate, lead zirconate titanate, lithium niobate, lead metaniobate, and lead barium lithium niobate. These inorganic particles possess high dielectric constant, low dielectric loss, and high heat resistance, thereby increasing the electronic insulation of the separator, improving its voltage breakdown strength, and imparting high heat resistance to the separator.

[0017] In some embodiments, the monomers of the gel polymer include one or more of vinylidene fluoride, acrylonitrile, methyl methacrylate, butyl acrylate, methacrylic acid, acrylic acid, and styrene. These gel polymers facilitate gelation with the electrolyte to form a gel electrolyte separator with better performance, and help reduce the amount of free electrolyte in the battery cell and reduce side reactions at the electrolyte-electrode interface, thereby improving the cycle life of the battery cell.

[0018] In some embodiments, the silane coupling agent modified inorganic particles account for 25%-68% by mass in the composite coating, optionally 28%-62%.

[0019] In some embodiments, the mass percentage of the gel polymer in the composite coating is 25%-68%, optionally 28%-62%.

[0020] When the mass ratio of silane coupling agent-modified inorganic particles and gel polymer is within the above range, the separator can have high mechanical strength, good heat resistance and high ionic conductivity. Furthermore, after the separator gels with the electrolyte, it can reduce the amount of free electrolyte in the battery cell and reduce the side reactions at the electrolyte-electrode interface, thereby further improving the cycle life of the battery cell.

[0021] In some embodiments, the composite coating further includes lubricating particles, which include one or more of polytetrafluoroethylene micropowder, polyimide particles, polyetherketone particles, and polyphenylene sulfide particles. The composite coating of the separator disclosed herein may also include lubricating particles, which possess excellent properties such as high heat resistance, low friction, non-stickiness, chemical stability, and electrical insulation. This allows the separator to have a low coefficient of friction, reducing static electricity generation and thus lowering self-discharge of individual battery cells. Simultaneously, it imparts good deformation resistance to the separator, significantly reducing thermal shrinkage and mechanical deformation, particularly reducing wrinkles on the electrode sheets.

[0022] In some embodiments, the mass percentage of lubricating particles in the composite coating is 3%-10%. An appropriate amount of lubricant can reduce static electricity generation in the separator without affecting its mechanical strength, decrease self-discharge of individual cells, and reduce thermal shrinkage and mechanical deformation of the separator, thereby improving the cycle life of individual cells.

[0023] In some embodiments, the average particle size of the lubricating particles is 0.5 μm-4 μm.

[0024] In some embodiments, the average pore size of the composite coating is 15nm-30nm.

[0025] In some embodiments, the thickness of the composite coating is 0.8 μm-3 μm.

[0026] In some embodiments, the porous membrane surface has carbonyl and / or hydroxyl groups. Carbonyl and hydroxyl groups are strongly polar groups, which can reduce the surface energy of the porous membrane, which is beneficial for the wetting of aqueous solutions and for increasing the adhesion of the composite coating to the porous membrane surface.

[0027] In some embodiments, a connecting layer, comprising a silane coupling agent, is further provided between the porous base membrane and the composite coating. This improves the peel strength of the composite coating and enhances the heat resistance of the separator.

[0028] In some embodiments, the areal density of the bonding layer is 0.1 g / m³. 2 -1.0g / m 2 When the areal density of the bonding layer is within the above range, the heat resistance of the separator can be improved and the cycle life of the battery cell can be increased without increasing the impedance of the separator.

[0029] In some embodiments, the thickness of the connecting layer is 0.01 μm to 0.1 μm. A thickness within this range can improve the heat resistance of the separator and increase the cycle life of the battery cell without increasing the separator's impedance.

[0030] In some embodiments, the air permeability of the porous base membrane is 100s / 100ml-300s / 100ml.

[0031] In some embodiments, the areal density of the porous base membrane is 8 g / m³. 2 -22g / m 2 .

[0032] In some embodiments, the thickness of the porous base film is 4 μm-17 μm.

[0033] In some embodiments, the porosity of the porous base membrane is 30%-50%.

[0034] In some embodiments, the average pore size of the porous base film is 20 nm-45 nm.

[0035] In some embodiments, the organic solvent includes one or more of ester solvents, fluorinated ester solvents, ether solvents, fluoroether solvents, sulfone solvents, and nitrile solvents.

[0036] In some embodiments, the cation of the electrolyte salt includes lithium ions and / or sodium ions, and the anion of the electrolyte salt includes one or more of the following: hexafluorophosphate anion, tetrafluoroborate anion, perchlorate anion, hexafluoroarsenate anion, bis(fluorosulfonyl)imide anion, bis(trifluoromethanesulfonyl)imide anion, trifluoromethanesulfonate anion, difluorooxalateborate anion, dioxalateborate anion, difluorophosphate anion, difluorodioxalate phosphate anion, and tetrafluorooxalate phosphate anion.

[0037] Secondly, this disclosure provides a battery device comprising a plurality of battery cells according to the first aspect of this disclosure.

[0038] Thirdly, this disclosure provides an electrical device that includes a battery cell according to the first aspect of this disclosure or a battery device according to the second aspect of this disclosure.

[0039] Fourthly, this disclosure provides a method for preparing a battery cell, comprising the following steps: providing an electrode assembly and an electrolyte, the electrode assembly including a positive electrode, a negative electrode, and a separator, the separator being located between the positive and negative electrode, the separator including a porous base membrane and a composite coating on at least one surface of the porous base membrane, the composite coating including silane coupling agent modified inorganic particles, a gel polymer, and a binder, the electrolyte including an organic solvent, an electrolyte salt, and an acrylate crosslinking agent, the silane coupling agent modified inorganic particles including inorganic particles and silicon-containing organic groups, the inorganic particles and the silicon-containing organic groups being connected by hydrogen bonds and / or ether bonds, the silicon-containing organic groups having active groups, and the active groups being capable of undergoing a polymerization reaction with the acrylate crosslinking agent; placing the electrode assembly in an outer packaging, drying it, injecting the electrolyte, and after encapsulation and standing, obtaining a battery cell, wherein the separator gels with the electrolyte to form a gel electrolyte separator.

[0040] In some embodiments, the settling temperature is 40°C-80°C.

[0041] In some embodiments, the settling time is greater than or equal to 1 hour. Attached Figure Description

[0042] To more clearly illustrate the technical solutions of the embodiments of this disclosure, the accompanying drawings used in the embodiments of this disclosure will be briefly described below. Obviously, the drawings described below are merely some embodiments of this disclosure. For those skilled in the art, other drawings can be obtained based on the drawings without any creative effort.

[0043] Figure 1 shows a schematic diagram of a battery cell provided in some embodiments of this disclosure.

[0044] Figure 2 shows a schematic diagram of an electrical device provided in some embodiments of this disclosure.

[0045] The accompanying drawings are not necessarily drawn to scale. Detailed Implementation

[0046] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the battery cell, its preparation method, battery device, and power-consuming device of this disclosure. However, unnecessary detailed descriptions may be omitted. 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 to enable those skilled in the art to fully understand this disclosure and are not intended to limit the subject matter of the claims.

[0047] The "range" disclosed in this disclosure is defined by a lower limit and an upper limit, whereby a given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the 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 expected. Furthermore, if minimum range values ​​1 and 2 are listed, and if maximum range values ​​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 disclosure, 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.

[0048] Unless otherwise specified, all embodiments and optional embodiments of this disclosure may be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of this disclosure.

[0049] Unless otherwise specified, all technical features and optional technical features of this disclosure can be combined to form new technical solutions, and such technical solutions should be considered as included in the disclosure of this disclosure.

[0050] Unless otherwise specified, all steps in this disclosure 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.

[0051] Unless otherwise specified, in this disclosure, the terms "first," "second," etc., are used to distinguish different objects, rather than to describe a specific order or primary / secondary relationship.

[0052] In this disclosure, the terms "multiple" or "a variety" refer to two or more kinds.

[0053] In the description of the embodiments of this disclosure, unless otherwise specified, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0054] Unless otherwise stated, the test temperature for all parameters mentioned in this disclosure is 25°C.

[0055] The battery cells mentioned in the embodiments of this disclosure are capable of charging and discharging independently. The battery cells may be cylindrical, cuboid, or other shapes, and this disclosure does not limit this. Figure 1 shows a cuboid battery cell 5 as an example.

[0056] The battery cells provided in the embodiments of this disclosure may include, but are not limited to, lithium battery cells and sodium battery cells, such as lithium-ion battery cells, sodium-ion battery cells, lithium metal battery cells, sodium metal battery cells, etc.

[0057] The battery apparatus mentioned in the embodiments of this disclosure may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells connected in series, parallel, or mixed connections via a busbar.

[0058] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells.

[0059] As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple battery cells together to form an independent module. As another example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0060] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more individual battery cells housed within the housing.

[0061] As an example, the battery cell assembly can be a battery module, and the battery cell assembly can be housed in the housing by fixing the battery module in the housing.

[0062] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple battery cells to the housing.

[0063] As an example, the enclosure may include a first enclosure and a second enclosure. The first enclosure and the second enclosure are fastened together to form a closed space inside the enclosure to house the individual battery cells. Here, "closed" refers to covering or closing, and can be either sealed or unsealed. The first enclosure may be a top cover or a bottom plate.

[0064] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the individual battery cells.

[0065] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0066] The technical solutions described in this disclosure are applicable to various electrical devices that use battery cells or battery devices, such as, but not limited to, mobile devices (e.g., mobile phones, tablets, 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. Battery cells and battery devices are used to store or provide electrical energy.

[0067] Figure 2 is a schematic diagram of an example electrical device. This electrical device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.

[0068] In this disclosure, the average particle size can be tested as follows: Using a scanning electron microscope (SEM) according to JY / T010-1996, obtain an SEM image of the separator. Randomly select a test sample with dimensions of 50mm x 100mm on the separator. Randomly select multiple test areas (e.g., 5) within the test sample, and read the particle size of each particle in each test area at a certain magnification (e.g., 500x or higher). Count the number and particle size values ​​of particles in each test area, and take the arithmetic mean of the particle sizes in all test areas as the average particle size. To ensure the accuracy of the test results, multiple test samples (e.g., 10) can be used for the above test, and the average value of each test sample can be taken as the final test result. The testing instrument can be a ZEISS Sigma 300. It should be noted that when the particle is irregularly shaped, the distance between the two farthest points on the particle is taken as the particle size.

[0069] The separator is a crucial component supporting the electrochemical processes of charging and discharging in a single battery cell. For high-energy-density battery cells, the introduction of thinner separators is urgently needed. In particular, energy storage battery cells must meet both high-capacity and high-volume energy-density design requirements, thus necessitating thinner separators to accommodate more electrode active materials within the limited space of the battery cell. However, thinner separators can easily lead to decreased mechanical properties, reduced heat resistance, and decreased electrolyte wettability.

[0070] Based on this, embodiments of the present disclosure provide a battery cell and a battery device and an electrical device comprising the same, wherein by designing the composition of the separator and the electrolyte, the battery cell can have a long cycle life.

[0071] The battery cell provided in this disclosure includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode, a negative electrode, and a separator, with the separator located between the positive and negative electrodes. The separator includes a porous base membrane and a composite coating on at least one surface of the porous base membrane. The composite coating includes silane coupling agent-modified inorganic particles, a gel polymer, and a binder. The electrolyte includes an organic solvent, an electrolyte salt, and an acrylate crosslinking agent. The silane coupling agent-modified inorganic particles include inorganic particles and silicon-containing organic groups, which are connected by hydrogen bonds and / or ether bonds. The silicon-containing organic groups have active groups that can polymerize with the acrylate crosslinking agent. The separator and the electrolyte can gel to form a gel electrolyte separator.

[0072] The composite coating of the separator disclosed herein includes a gel polymer, which enables the separator and electrolyte to gel and form a gel electrolyte separator. The composite coating of the separator also includes silane coupling agent-modified inorganic particles. These silane coupling agent-modified inorganic particles have active groups on their surface. These active groups can polymerize with acrylate crosslinking agents in the electrolyte, thereby participating in the gelation process between the separator and the electrolyte. This allows for better interconnection of the polymer chains of the gel polymer, resulting in a structurally stable gel electrolyte separator with good heat resistance and mechanical strength. This reduces the self-discharge of individual battery cells and allows more electrolyte to be locked within the pores of the gel electrolyte separator, reducing free electrolyte and side reactions at the electrolyte-electrode interface. Furthermore, this results in a longer cycle life for the individual battery cells, making them better suited for energy storage applications.

[0073] The battery cell also includes an outer packaging for encapsulating the electrode components and electrolyte. The outer packaging can be a rigid shell, such as a hard plastic shell, aluminum shell, or steel shell. It can also be a flexible package, such as a pouch. The flexible package can be made of plastic, such as one or more of aluminum-plastic film, polypropylene, polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0074] The electrode assembly can be a wound structure or a stacked structure, and the embodiments disclosed herein are not limited to this.

[0075] The number of electrode components contained in a single battery cell can be one or more, and this disclosure does not limit this.

[0076] In some embodiments, the active group may include one or more of acryloyloxy, carbon-carbon double bond, amino, hydroxyl, mercapto, glycidyl etheroxy, carbonyl, and carboxyl.

[0077] These active groups can undergo polymerization reactions with acrylate crosslinking agents in the electrolyte, thereby participating in the gelation process of the separator and the electrolyte. This allows the polymer chains of the gel polymer to be better interconnected, forming a stable, heat-resistant, and mechanically strong gel electrolyte separator. This reduces the self-discharge of the battery cells and allows more electrolyte to be locked in the pores of the gel electrolyte separator, reducing free electrolyte and side reactions at the electrolyte-electrode interface. Consequently, the battery cells can have a long cycle life.

[0078] In some embodiments, the silicon-containing organic group may be an organic group formed by bonding Si atoms with the following groups: acryloyloxy, methacryloyloxy, vinyl, allyl, amino, glycidyl etheroxy, hydroxyl, mercapto, or a group formed by combining the foregoing groups with alkyl groups.

[0079] Silane coupling agent modified inorganic particles are obtained by reacting silane coupling agent with inorganic particles in an aqueous solution and then drying. Silane coupling agent modified inorganic particles can be prepared alone or after drying a composite coating slurry.

[0080] Silane coupling agents are a class of organosilicon compounds with a bifunctional structure, whose molecules contain both hydrolyzable groups and organic reactive groups.

[0081] Inorganic particles typically have hydroxyl groups on their surface. Silane coupling agents can hydrolyze to produce silanol groups, which can form hydrogen bonds with the hydroxyl groups on the surface of inorganic particles or dehydrate to form ether bonds. The organic reactive groups of the silane coupling agent can improve the compatibility of inorganic particles with gel polymers and porous membranes, thereby enhancing the peel strength of the composite coating and improving the heat resistance and mechanical strength of the separator. The organic reactive groups contain the active groups disclosed herein. These active groups can undergo polymerization reactions with acrylate crosslinking agents in the electrolyte, thereby participating in the gelation process of the separator and the electrolyte. This allows the polymer chains of the gel polymer to be better interconnected, resulting in a stable, heat-resistant, and mechanically strong gel electrolyte separator, which can further improve the cycle life of the battery cells.

[0082] Optionally, the silane coupling agent may include one or more of the following: acryloyloxysilane coupling agent, methacryloxysilane coupling agent, vinylsilane coupling agent, allylsilane coupling agent, aminosilane coupling agent, glycidyl ether oxysilane coupling agent, and mercaptosilane coupling agent.

[0083] Alternatively, the molecular formula of the silane coupling agent can be R n SiX 4-n n is 1, 2 or 3, R contains the active group disclosed herein, and at least one of X can be hydrolyzed to a hydroxyl group.

[0084] Optionally, R represents an acryloyloxy, methacryloxy, vinyl, allyl, amino, glycidyl etheroxy, hydroxyl, mercapto, or a group formed by combining the foregoing groups with an alkyl group.

[0085] Optionally, X independently represents alkyl, alkoxy, aryloxy, acyl or chloro, and at least one of X is alkoxy, aryloxy, acyl or chloro.

[0086] As an example, silane coupling agents may include 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropyltriethoxysilane, 3-methacryloyloxypropylmethyldimethoxysilane, methacryloyloxypropyltriisopropoxysilane, acryloyloxypropyltrimethoxysilane, propyl 3-(trimethoxysilyl)acrylate, (3-methacryloyloxy-2-hydroxypropoxy)propylbis(trimethylsiloxy)methylsilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(β-methoxyethoxy)silane, vinyltrichlorosilane, vinyltriisopropoxysilane, vinyltritert-butoxysilane, and vinyltritert-butoxysilane. The product is one or more of the following: methylperoxysilane, vinyltriacetoxysilane, dimethylethoxyformylsilane, triacetoxyvinylsilane, allyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, 3-(2,3-epoxypropoxy)propyltrimethoxysilane, 3-(2,3-epoxypropoxy)propyltriethoxysilane, and γ-mercaptopropyltrimethoxysilane.

[0087] In some embodiments, the mass of the silicon-containing organic groups in the silane coupling agent-modified inorganic particles can be 0.2%-4% of the mass of the silane coupling agent-modified inorganic particles, for example, it can be 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.6%, 2.8%, 3%, 3.2%, 3.4%, 3.6%, 3.8%, 4%, or any range of the above values.

[0088] An appropriate amount of silicon-containing organic groups can introduce a suitable amount of active groups on the surface of inorganic particles. The active groups can undergo a polymerization reaction with the acrylate crosslinking agent in the electrolyte, thereby participating in the gelation process of the separator and the electrolyte. This allows the polymer chains of the gel polymer to be better connected to each other, and also makes the inorganic particles, gel polymer and porous base membrane more compatible. This results in the formation of a gel electrolyte separator with stable structure, good heat resistance and good mechanical strength, and can further improve the cycle life of the battery cell.

[0089] Optionally, the mass of the silicon-containing organic groups can be 0.2%-3% or 0.2%-2% of the mass of the silane coupling agent-modified inorganic particles.

[0090] In some embodiments, the acrylate crosslinker can be a multifunctional crosslinker.

[0091] Optionally, the acrylate crosslinking agent may include one or more of the following: triethylene glycol diacrylate, triethylene glycol dimethacrylate, triethylene glycol divinyl acrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate, tetra(ethylene glycol) diacrylate, tetraethylene glycol dimethacrylate, 1,3-butanediol diacrylate, 1,3-butanediol dimethacrylate, neopentyl glycol diacrylate, neopentyl glycol dimethacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, and pentaerythritol tetraacrylate.

[0092] The inorganic particles modified with silane coupling agents have active groups on their surface. These active groups can polymerize with the aforementioned acrylate crosslinking agents, thereby participating in the gelation process of the separator and electrolyte. This allows the polymer chains of the gel polymer to be better interconnected, resulting in a stable, heat-resistant, and mechanically strong gel electrolyte separator. This reduces the self-discharge of the battery cells and also allows more electrolyte to be locked in the pores of the gel electrolyte separator, reducing free electrolyte and side reactions at the electrolyte-electrode interface. Consequently, the battery cells also have a long cycle life.

[0093] In some embodiments, the mass of the acrylate crosslinking agent can be 1% to 6% of the total mass of the electrolyte, for example, it can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, or any range of the above values.

[0094] An appropriate amount of acrylate crosslinking agent can better polymerize with the active groups on the surface of inorganic particles modified by silane coupling agent without affecting the ionic conductivity and viscosity of the electrolyte. This allows it to better participate in the gelation process of the separator and the electrolyte, and further improve the cycle life of the battery cell.

[0095] Optionally, the mass of the acrylate crosslinking agent can be 2%-6%, 2.5%-6%, 3%-6%, 3.5%-6%, or 4%-6% of the total mass of the electrolyte.

[0096] In some embodiments, the electrolyte may also include an initiator.

[0097] Initiators can promote the polymerization of active groups on the surface of inorganic particles modified by acrylate crosslinking agents and silane coupling agents, thereby enabling them to better participate in the gelation process of the separator and electrolyte, and further improve the cycle life of battery cells.

[0098] Optionally, the initiator may be one or more of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, diisopropyl peroxide dicarbonate, dicyclohexyl peroxide dicarbonate, and bis(2-phenylethoxy) peroxide dicarbonate.

[0099] Optionally, the mass of the initiator can be 0.01%-1% of the total mass of the electrolyte.

[0100] In some embodiments, the electrolyte may also include other components, such as catalysts, for catalyzing the polymerization reaction of active groups on the surface of inorganic particles modified by acrylate crosslinking agents and silane coupling agents.

[0101] In some embodiments, the cations of the electrolyte salt may include lithium ions and / or sodium ions.

[0102] In some embodiments, the anion of the electrolyte salt may include one or more of the following: hexafluorophosphate anion, tetrafluoroborate anion, perchlorate anion, hexafluoroarsenate anion, bis(fluorosulfonyl)imide anion, bis(trifluoromethanesulfonyl)imide anion, trifluoromethanesulfonate anion, difluorooxalateborate anion, dioxalateborate anion, difluorophosphate anion, difluorodioxalate phosphate anion, and tetrafluorooxalate phosphate anion.

[0103] Taking a lithium battery cell as an example, the electrolyte salt may include, but is not limited to, one or more of the following: lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalate borate (LiDFOB), lithium dioxalate borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0104] Taking sodium battery cells as an example, the electrolyte salt may include, but is not limited to, one or more of the following: sodium hexafluorophosphate (NaPF6), sodium tetrafluoroborate (NaBF4), sodium perchlorate (NaClO4), sodium hexafluoroarsenate (NaAsF6), sodium difluorosulfonylimide (NaFSI), sodium difluoromethanesulfonylimide (NaTFSI), sodium trifluoromethanesulfonate (NaTFS), sodium difluorooxalate borate (NaDFOB), sodium dioxalate borate (NaBOB), sodium difluorophosphate (NaPO2F2), sodium difluorodioxalate phosphate (NaDFOP), and sodium tetrafluorooxalate phosphate (NaTFOP).

[0105] In some embodiments, the organic solvent of the electrolyte may include one or more of ester solvents, fluorinated ester solvents, ether solvents, fluoroether solvents, sulfone solvents, and nitrile solvents.

[0106] As an example, the organic solvent may include, but is not limited to, one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), diethyl sulfone (ESE), ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyl tetrahydrofuran, diphenyl ether, and crown ether.

[0107] In some embodiments, the electrolyte may also include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain properties of the battery cell, such as additives that improve overcharge performance, additives that improve high-temperature performance, additives that improve low-temperature performance, etc.

[0108] Optionally, the additive may include one or more of fluoroethylene carbonate (FEC), vinylene carbonate (VC), 1,3-propanesulfonate lactone (PS), and ethylene sulfate (DTD).

[0109] The types and mass contents of each component in the electrolyte can be obtained by one or more of the following methods: gas chromatography-mass spectrometry (GC-MS), ion chromatography (IC), liquid chromatography (LC), nuclear magnetic resonance spectroscopy (NMR), and gas chromatography-mass spectrometry (GC-MS). For example, referring to GB / T 9722-2006 and GB / T 6041-2002, gas chromatography and mass spectrometry are used. After separating the components in the sample by gas chromatography, the components are broken into ion fragments in mass spectrometry and separated according to the mass-to-charge ratio (m / z) to form specific mass spectra, thereby obtaining qualitative analysis of each organic component in the electrolyte. Then, the organic components in the electrolyte are separated in the chromatographic column and the detection signal spectrum of each component is generated. The retention time is used for component qualitative analysis, and the peak area is corrected by standardization to obtain quantitative analysis of the organic components in the electrolyte. Referring to JY / T 020-1996, ion chromatography is used to detect the types of electrolyte salt anions in the electrolyte and to perform quantitative analysis. Referring to JY / T 0578-2020, nuclear magnetic resonance spectroscopy (NMR) is used to obtain qualitative and quantitative analysis of the components in the electrolyte.

[0110] In some embodiments, the relative permittivity of the inorganic particles may be greater than or equal to 10.

[0111] The relative permittivity of inorganic particles refers to the relative permittivity at 25℃, which can be tested according to GB / T 11297.11-2015. For example, the battery cell can be disassembled first, and then the gel electrolyte separator can be calcined to ensure that all other components in the separator are sintered. Then, water is added and filtered to separate the inorganic particles. The inorganic particles and binder are prepared into circular samples, which are then rolled into raw ceramic cakes with a thickness of 1mm±0.15mm. The cakes are considered qualified if they have no color difference on the surface, uniform cross-section, and no obvious delamination. The raw ceramic cakes are placed under the pressure plate of a stamping machine and stamped into 10 thin circular ceramic sheets with a diameter of 11±1mm. The obtained thin circular ceramic sheets are placed on a clean and flat zirconia or alumina firing plate, and the firing plate is placed together in a muffle furnace. The temperature is raised to 300℃ at a heating rate of 0.3℃ / min and held for 6 hours for debinding. After the debinding is completed on the front side, the thin circular ceramic sheets are removed, and the back side is replaced. The above operation is repeated. Perform back-side debinding; place the debinded thin-layer circular ceramic sheet on a clean and flat zirconia or alumina firing plate, and use a fine brush to evenly apply silver paste to the front side of the thin-layer circular ceramic sheet. The silver paste is a high-temperature sintering conductive silver paste. The silver paste is applied in one direction for 2-3 coats, with a thickness of 80μm-100μm. Then, gently scrape off the silver layer adhering to the side of the silver-coated thin-layer circular ceramic sheet with a blade. Then, place the silver-coated thin-layer circular ceramic sheet together with the firing plate into a muffle furnace, and heat it to 800℃ at a heating rate of 5℃ / min, and hold it for 2 hours for silver firing. After the front side is silver fired, remove the thin-layer circular ceramic sheet and the firing plate, and silver fire the back side. Finally, use an LCR meter to test the capacitance C and calculate it according to the formula relative permittivity ε=(C×d) / (ε0×A). C represents capacitance, in farads (F); d represents sample thickness, in cm; A represents sample area, in cm². 2 ε0 represents the vacuum permittivity, ε0 ​​= 8.854 × 10⁻⁶. -14 F / cm.

[0112] Currently, ceramic-coated separators are widely used, with ceramic powders such as alumina, silicon oxide, and barium sulfate, which have low dielectric constants, being the most commonly used coating materials. However, the resulting separators exhibit poor ion conductivity and voltage breakdown resistance. The composite coating of the separator disclosed in this invention uses inorganic particles with high dielectric constants, which can increase the electronic insulation of the separator, improve its voltage breakdown resistance, and reduce the self-discharge of individual battery cells.

[0113] Optionally, the relative permittivity of the inorganic particles can be greater than or equal to 20, greater than or equal to 50, or greater than or equal to 100.

[0114] Optionally, the inorganic particles may include rutile nano-titanium dioxide, nano-barium titanate, or nano-CaCu3Ti4O. 12One or more of the following: strontium titanate, barium strontium titanate, lead titanate, lead zirconate titanate, lithium niobate, lead metaniobate, and lithium lead barium niobate.

[0115] These inorganic particles have high dielectric constant, low dielectric loss and high heat resistance, which can increase the electronic insulation of the separator, improve the voltage breakdown strength of the separator, and at the same time give the separator high heat resistance.

[0116] In some embodiments, the average particle size of the silane coupling agent modified inorganic particles can be 100nm-1000nm, for example, it can be 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1000nm, or any range of the above values.

[0117] The average particle size of inorganic particles modified by silane coupling agents is within the above range, which is beneficial to obtaining a thin composite coating with good heat resistance, and thus to the high energy density of battery cells.

[0118] In some embodiments, the mass percentage of silane coupling agent modified inorganic particles in the composite coating can be 25%-68%, for example, it can be 25%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60%, 62%, 64%, 66%, 68%, or any range of the above values.

[0119] In some embodiments, the mass percentage of the gel polymer in the composite coating can be 25%-68%, for example, it can be 25%, 28%, 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48%, 50%, 52%, 54%, 56%, 58%, 60%, 62%, 64%, 66%, 68%, or any range of the above values.

[0120] When the mass ratio of silane coupling agent-modified inorganic particles and gel polymer is within the above range, the separator can have high mechanical strength, good heat resistance and high ionic conductivity. Furthermore, after the separator gels with the electrolyte, it can reduce the amount of free electrolyte in the battery cell and reduce the side reactions at the electrolyte-electrode interface, thereby further improving the cycle life of the battery cell.

[0121] Optionally, in the composite coating, the mass percentage of silane coupling agent modified inorganic particles can be 28%-62%, 28%-60%, 28%-58%, 28%-56%, 28%-54%, 28%-52%, 28%-50%, 30%-60%, 30%-58%, 30%-56%, 30%-54%, 30%-52%, 30%-50%, 32%-60%, 32%-58%, 32%-56%, 32%-54%, 32%-52%, or 32%-50%.

[0122] Optionally, in the composite coating, the mass percentage of the gel polymer can be 28%-62%, 28%-60%, 28%-58%, 28%-56%, 28%-54%, 28%-52%, 28%-50%, 30%-60%, 30%-58%, 30%-56%, 30%-54%, 30%-52%, 30%-50%, 32%-60%, 32%-58%, 32%-56%, 32%-54%, 32%-52%, or 32%-50%.

[0123] In some embodiments, the monomers of the gel polymer may include one or more of vinylidene fluoride, acrylonitrile, methyl methacrylate, butyl acrylate, methacrylic acid, acrylic acid, and styrene.

[0124] Monomers are polymerized to form a gel polymer, which may be a homopolymer of the aforementioned monomers, a copolymer of at least two of the aforementioned monomers, or a copolymer of at least one of the aforementioned monomers with other monomers.

[0125] As an example, the gel polymer may include one or more of polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polybutyl acrylate, polymethyl methacrylate, and polyacrylic acid.

[0126] These gel polymers facilitate gelation with the electrolyte to form a gel electrolyte separator with better performance, and help reduce the amount of free electrolyte in the battery cell and reduce side reactions at the electrolyte-electrode interface, thereby improving the cycle life of the battery cell.

[0127] In some embodiments, the composite coating may further include lubricating particles, which may include one or more of polytetrafluoroethylene micropowder, polyimide particles, polyetherketone particles, and polyphenylene sulfide particles.

[0128] Most current battery cells use a winding structure to assemble electrode sheets and separators. However, when the internal stress of the separator is too high during high-speed winding, it will shrink after the winding is completed due to stress release. Since the inner electrode sheets of the winding structure are not restrained, they will deform along with the electrode sheets, resulting in redundancy. After the winding structure is pre-pressed and shaped, the redundant electrode sheets will wrinkle. In particular, the positive electrode sheet will have the problem of metal leakage due to wrinkles. The positive electrode sheet with wrinkles is prone to puncturing the separator during hot pressing and shaping, resulting in internal short circuits. It may even cause the positive electrode sheet to break during subsequent formation and cycle charging and discharging.

[0129] The composite coating of the separator disclosed herein may further include lubricating particles, which have excellent properties such as high heat resistance, low friction, non-stickiness, chemical stability, and electrical insulation. This allows the separator to have a low coefficient of friction, reducing the generation of static electricity in the separator and thus reducing the self-discharge of individual battery cells. At the same time, it also endows the separator with good deformation resistance, significantly reducing the degree of thermal shrinkage and mechanical deformation of the separator, especially significantly reducing the wrinkles of the electrode sheets.

[0130] Alternatively, the lubricating particles may include polytetrafluoroethylene microparticles.

[0131] In polytetrafluoroethylene (PTFE) molecules, the F atoms are symmetrical, and the C and F elements are bonded together by covalent bonds. There are no free electrons in the molecule, and the entire molecule is neutral. This gives PTFE excellent dielectric properties. Furthermore, since PTFE molecules are usually surrounded by an inert fluorine-containing shell, when used in composite coatings for separators, it can give the separator good non-stick properties and a low coefficient of friction, thereby reducing the shrinkage problem caused by separator creep.

[0132] Optionally, in the composite coating, the mass percentage of lubricating particles can be 3%-10%, for example, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, or any combination of the above values.

[0133] An appropriate amount of lubricant can reduce the generation of static electricity in the separator without affecting its mechanical strength, reduce the self-discharge of the battery cells, and also reduce the degree of thermal shrinkage and mechanical deformation of the separator, thereby helping to improve the cycle life of the battery cells.

[0134] Optionally, the average particle size of the lubricating particles can be 0.5μm-4μm, for example, it can be 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm, 1μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm, 1.5μm, 1.6μm, 1.7μm, 1.8μm, 1.9μm, 2μm, 2.2μm, 2.4μm, 2.6μm, 2.8μm, 3μm, 3.2μm, 3.4μm, 3.6μm, 3.8μm, 4μm, or any range of the above values.

[0135] Optionally, the average particle size of the lubricating particles can be 0.5μm-3μm, 0.5μm-2μm, or 0.5μm-1μm.

[0136] In some embodiments, the binder in the composite coating may be one or more of the following: polyacrylate binders, styrene-butadiene latex, nitrile rubber, polyacrylamide (PAM), polyvinyl alcohol (PVA), polyvinyl acetate, sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0137] In some embodiments, the mass percentage of the adhesive in the composite coating can be 1%-10%, for example, it can be 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, 10%, or any combination of the above values.

[0138] In some embodiments, the composite coating may also include surfactants and / or wetting agents.

[0139] Wetting agents can reduce the surface tension of solvents, thereby facilitating the formation of uniform dispersions and resulting in uniform composite coatings.

[0140] Surfactants can reduce the surface tension of solvents and form stable emulsion systems. When surfactants are adsorbed on the surface of latex particles, they can prevent particle aggregation and regulate polymerization behavior, thereby obtaining a uniform composite coating.

[0141] Optionally, the wetting agent may include one or more of fluoroalkyl methoxy ether alcohols, fluoroalkyl ethoxy ether alcohols, alkylphenol polyoxyethylene ethers, fatty alcohol polyoxyethylene ethers, and fatty acid polyoxyethylene ethers.

[0142] Alternatively, the surfactant may include a polyether siloxane copolymer.

[0143] Optionally, the surfactant may constitute 0.01% to 0.5% of the mass of the composite coating.

[0144] Optionally, the wetting agent may constitute 0.1% to 2% of the composite coating by mass.

[0145] In some embodiments, the average pore size of the composite coating can be 15nm-30nm, for example, it can be 15nm, 16nm, 17nm, 18nm, 19nm, 20nm, 21nm, 22nm, 23nm, 24nm, 25nm, 26nm, 27nm, 28nm, 29nm, 30nm, or any range of the above values.

[0146] The average pore size of the composite coating can be calculated from image analysis using scanning electron microscopy (SEM) images.

[0147] In some embodiments, the thickness of the composite coating can be 0.8 μm-3 μm, for example, it can be 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3 μm, or any combination of the above values. The thickness of the composite coating refers to the thickness of the composite coating located on one side of the porous base film.

[0148] In some embodiments, the surface of the porous base membrane may have carbonyl groups and / or hydroxyl groups.

[0149] Carbonyl and hydroxyl groups are highly polar groups, which can reduce the surface energy of porous membranes, which is beneficial for the wetting of aqueous solutions and for increasing the adhesion of composite coatings to the surface of porous membranes.

[0150] Chemical surface oxidation or physical methods, such as corona treatment, can be used to treat the surface of porous base membranes to give the porous base membranes carbonyl groups and / or hydroxyl groups.

[0151] In some embodiments, a connecting layer may also be present between the porous base membrane and the composite coating, and the connecting layer may include a silane coupling agent.

[0152] Silane coupling agents are a class of organosilicon compounds with a bifunctional structure, whose molecules contain both hydrolyzable groups and organic reactive groups.

[0153] Silane coupling agents can hydrolyze to produce silanol groups. These silanol groups can form hydrogen bonds with hydroxyl groups on the surface of inorganic particles or undergo dehydration to form ether bonds. The organic reactive groups of silane coupling agents exhibit good reactivity or compatibility with gel polymers and porous membranes. Therefore, placing silane coupling agents between the porous membrane and the composite coating can create a "molecular bridge" between them, thereby improving the peel strength of the composite coating and enhancing the heat resistance of the separator.

[0154] Optionally, the silane coupling agent may include one or more of the following: acryloyloxysilane coupling agent, methacryloxysilane coupling agent, vinylsilane coupling agent, allylsilane coupling agent, aminosilane coupling agent, glycidyl etheroxysilane coupling agent, and mercaptosilane coupling agent.

[0155] Alternatively, the molecular formula of the silane coupling agent can be R′ m SiY 4-m m is 1, 2 or 3, R′ is an organic reactive group, and at least one of the Y groups can be hydrolyzed to a hydroxyl group.

[0156] Alternatively, R′ represents one or more combinations of acryloyloxy, methacryloxy, vinyl, allyl, amino, glycidyl etheroxy, hydroxyl, mercapto, and alkyl.

[0157] Optionally, Y independently represents alkyl, alkoxy, aryloxy, acyl or chloro, and at least one of Y is alkoxy, aryloxy, acyl or chloro.

[0158] As an example, silane coupling agents may include 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropyltriethoxysilane, 3-methacryloyloxypropylmethyldimethoxysilane, methacryloyloxypropyltriisopropoxysilane, acryloyloxypropyltrimethoxysilane, propyl 3-(trimethoxysilyl)acrylate, (3-methacryloyloxy-2-hydroxypropoxy)propylbis(trimethylsiloxy)methylsilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltri(β-methoxyethoxy)silane, vinyltrichlorosilane, vinyltriisopropoxysilane, vinyltritert-butoxysilane, and vinyltritert-butoxysilane. The product is one or more of the following: methylperoxysilane, vinyltriacetoxysilane, dimethylethoxyformylsilane, triacetoxyvinylsilane, allyltrimethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane, 3-(2,3-epoxypropoxy)propyltrimethoxysilane, 3-(2,3-epoxypropoxy)propyltriethoxysilane, and γ-mercaptopropyltrimethoxysilane.

[0159] The connecting layer is typically formed by coating a solution containing a silane coupling agent and water onto the surface of a porous substrate membrane and then drying it. The connecting layer disclosed herein refers to the product obtained after drying a solution containing a silane coupling agent and water.

[0160] In some embodiments, the bonding layer may further include surfactants and / or wetting agents.

[0161] In some embodiments, the areal density of the bonding layer may be 0.1 g / m³. 2 -1.0g / m 2 For example, it can be 0.1g / m 2 0.2g / m 2 0.3g / m 2 0.4g / m 2 0.5g / m 2 0.6g / m 2 0.7g / m 2 0.8g / m 2 0.9g / m 2 1.0g / m 2 or a range consisting of any of the above values.

[0162] When the areal density of the bonding layer is within the above range, the heat resistance of the separator can be improved and the cycle life of the battery cell can be increased without increasing the impedance of the separator.

[0163] In some embodiments, the thickness of the connecting layer can be 0.01μm-0.1μm, for example, it can be 0.01μm, 0.02μm, 0.03μm, 0.04μm, 0.05μm, 0.06μm, 0.07μm, 0.08μm, 0.09μm, 0.1μm, or any range of the above values.

[0164] With the thickness of the connecting layer within the above range, the heat resistance of the separator can be improved and the cycle life of the battery cell can be increased without increasing the impedance of the separator.

[0165] In some embodiments, the air permeability of the porous base membrane can be 100s / 100ml-300s / 100ml, for example, it can be 100s / 100ml, 120s / 100ml, 140s / 100ml, 160s / 100ml, 180s / 100ml, 200s / 100ml, 220s / 100ml, 240s / 100ml, 260s / 100ml, 280s / 100ml, 300s / 100ml, or any range of the above values.

[0166] Optionally, the air permeability of the porous base membrane can be 100s / 100ml-240s / 100ml.

[0167] The air permeability of the porous base membrane can be tested as follows: Cut the porous base membrane into 5cm squares, apply a pressure of 1.21kPa using an air permeability meter, and test the permeability of 100ml of air by 6.45cm. 2 The time required for the porous base membrane to pass through is taken as its air permeability, expressed in seconds per 100 ml.

[0168] In some embodiments, the areal density of the porous base membrane can be 8 g / m³. 2 -22g / m 2 For example, it can be 8g / m 2 9g / m 2 10g / m 2 11g / m 2 12g / m 2 13g / m 2 14g / m 2 15g / m 2 16g / m 2 17g / m 2 18g / m 2 19g / m 2 20g / m 2 21g / m 2 22g / m 2 or a range consisting of any of the above values.

[0169] In some embodiments, the thickness of the porous base film can be 4μm-17μm, for example, it can be 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, 15μm, 16μm, 17μm, or any range of the above values.

[0170] Optionally, the thickness of the porous base film can be 4μm-12μm, 4μm-10μm, or 4μm-9μm.

[0171] In some embodiments, the porosity of the porous base membrane can be 30%-50%, for example, it can be 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 41%, 42%, 43%, 44%, 45%, 46%, 47%, 48%, 49%, 50%, or any range of the above values.

[0172] The porosity of porous membranes can be tested as follows: Cut the porous membrane into 30 small discs with a diameter of 14 mm. Based on the principle of gas adsorption, use helium as the medium and a true density meter (such as AccuPyc II 1340) to measure the true volume of the 30 discs. Then, calculate the relationship between the apparent volume and the true volume of the porous membrane based on the area, thickness, and number of discs to obtain the porosity. Porosity of porous membrane = (apparent volume - true volume) / apparent volume × 100%.

[0173] In some embodiments, the average pore size of the porous base film can be 20nm-45nm, for example, it can be 20nm, 21nm, 22nm, 23nm, 24nm, 25nm, 26nm, 27nm, 28nm, 29nm, 30nm, 31nm, 32nm, 33nm, 34nm, 35nm, 36nm, 37nm, 38nm, 39nm, 40nm, 41nm, 42nm, 43nm, 44nm, 45nm, or any range of the above values.

[0174] The average pore size of the porous membrane can be measured using a capillary porosity analyzer (bubble point method). The instrument can be a PMI CFP 1500 pore size analyzer, with a test pressure ranging from 100 psi to 350 psi.

[0175] In some embodiments, the porous base membrane may include a polyethylene membrane, a polypropylene membrane, or a polypropylene / polyethylene / polypropylene composite membrane.

[0176] Optionally, the porous base membrane is made of polyethylene, and the weight-average molecular weight of polyethylene is 150,000 to 600,000, for example, it can be 150,000, 200,000, 250,000, 300,000, 350,000, 400,000, 450,000, 500,000, 550,000, 600,000, or any combination of the above values.

[0177] Optionally, the porous base membrane is made of polypropylene, and the weight-average molecular weight of the polypropylene is 250,000 to 800,000, for example, it can be 250,000, 300,000, 350,000, 400,000, 450,000, 500,000, 550,000, 600,000, 650,000, 700,000, 750,000, 800,000, or any combination of the above values.

[0178] The weight-average molecular weight of the polymer can be obtained by gel permeation chromatography.

[0179] It should be noted that the composite coating parameters of the above-mentioned separator membrane are all composite coating parameters on one side of the porous base membrane. When the composite coating is disposed on both sides of the porous base membrane, if the composite coating parameters on either side meet the requirements of this disclosure, it is considered to fall within the protection scope of this disclosure.

[0180] It should be noted that the parameters of the separator membrane disclosed herein refer to the parameters of the separator membrane that has not gelled with the electrolyte.

[0181] This disclosure also provides a method for preparing a separator membrane, which can prepare the separator membrane provided in this disclosure.

[0182] The method for preparing the separator membrane includes the following steps: providing a porous base membrane; coating a slurry comprising silane coupling agent-modified inorganic particles, a gel polymer, and a binder onto at least one surface of the porous base membrane, and drying it to obtain the separator membrane.

[0183] In some embodiments, the solvent for the slurry may be water, such as deionized water.

[0184] In some embodiments, the slurry may also include surfactants and / or wetting agents.

[0185] In some embodiments, the slurry preparation method includes the following steps: adding inorganic particles and optional surfactants to a mixed solvent of water and alcohol, then adding a silane coupling agent and stirring, subsequently adjusting the pH of the system to 3-5 with acid to obtain a stable inorganic particle dispersion; transferring the inorganic particle dispersion into a polymerization reactor, adding polymerization monomers, initiators and emulsifiers, and simultaneously introducing a protective gas to carry out an emulsion polymerization reaction; subsequently adding a binder and optional wetting agent and stirring, and then filtering to obtain the slurry.

[0186] The types of inorganic particles, silane coupling agents, polymeric monomers, binders, surfactants, wetting agents, etc. can be found above and will not be repeated here.

[0187] The emulsifier may be one or more of the following known in the art: alkyl sulfates, alkyl sulfonates, Tween emulsifiers, fatty alcohol polyoxyethylene ethers, fatty alcohol polyoxypropylene ethers, alkylphenol polyoxyethylene ethers, cetearyl alcohol polyethers, and oleyl alcohol polyethers.

[0188] The initiator may be one or more of the initiators known in the art, including but not limited to sodium persulfate, potassium persulfate, ammonium persulfate, sodium sulfite, and sodium bisulfite.

[0189] Optionally, the slurry may also include lubricating particles. Optionally, the lubricating particles, water, and optionally a surfactant can be mixed to prepare a dispersion, and then added to the polymerization reactor together with the above-mentioned inorganic particle dispersion.

[0190] The types of lubricating particles can be found above, and will not be repeated here.

[0191] The battery cells disclosed herein may include, but are not limited to, lithium battery cells, sodium battery cells, etc. The composition of the positive electrode and negative electrode may differ depending on the type of battery cell.

[0192] [Positive electrode plate]

[0193] In some embodiments, the positive electrode may include a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector and comprising a positive electrode active material. For example, the positive current collector has two surfaces opposite each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0194] Taking a lithium-ion battery cell as an example, the positive electrode active material can include, but is not limited to, one or more of lithium transition metal oxides, lithium-containing phosphates, and their respective modified compounds. Examples of lithium transition metal oxides can include, but are not limited to, one or more of lithium cobalt oxides, lithium nickel oxides, lithium manganese oxides, lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides, lithium nickel cobalt aluminum oxides, and their respective modified compounds. Examples of lithium-containing phosphates can include, but are not limited to, lithium iron phosphate, lithium iron phosphate and carbon composites, lithium manganese phosphate, lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, lithium manganese iron phosphate and carbon composites, and their respective modified compounds.

[0195] In some embodiments, to further improve the energy density of a single battery cell, the positive electrode active material may include materials of the general formula Li. a Ni b Co c M d O e A fOne or more of lithium transition metal oxides and their modified compounds. 0.8≤a≤1.2, 0.5≤b<1, 0<c<1, 0<d<1, 1≤e≤2, 0≤f≤1, M includes but is not limited to one or more of Mn, Al, Zr, Zn, Cu, Cr, Mg, Fe, V, Ti and B, and A includes but is not limited to one or more of N, F, S and Cl.

[0196] As an example, the positive electrode active material may include, but is not limited to, LiCoO2, LiNiO2, LiMnO2, LiMn2O4, and LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM523), LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM811), LiNi 0.85 Co 0.1 Al 0.05 One or more of O2, LiFePO4, and LiMnPO4.

[0197] During the charging and discharging process, lithium (Li) undergoes insertion / extraction and consumption within a single battery cell, resulting in varying molar Li content at different discharge states. In the examples of positive electrode active materials in this disclosure, the molar Li content represents the initial state of the material, i.e., the state before material addition. As the positive electrode active material is applied to the battery cell, the molar Li content changes after charge-discharge cycles. Similarly, the molar O content in the examples of positive electrode active materials in this disclosure is only a theoretical value. Oxygen release from the crystal lattice causes changes in the molar O content, leading to fluctuations in the actual molar O content.

[0198] Taking sodium-ion battery cells as an example, the positive electrode active material can be one or more of the following, including but not limited to sodium-containing transition metal oxides, polyanionic materials (such as phosphates, fluorophosphates, pyrophosphates, sulfates, etc.), and Prussian blue materials. For example, the positive electrode active material can be, but is not limited to, NaFeO2, NaCoO2, NaCrO2, NaMnO2, NaNiO2, and NaNi 1 / 2 Ti 1 / 2 O2, NaNi 1 / 2 Mn 1 / 2 O2, Na 2 / 3 Fe 1 / 3 Mn 2 / 3O2, NaNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, NaFePO4, NaMnPO4, NaCoPO4, Prussian blue materials, with the general formula X p M' q (PO4) r O x Y 3-x One or more of the materials. In general formula X p M' q (PO4) r O x Y 3-x In this case, 0 < p ≤ 4, 0 < q ≤ 2, 1 ≤ r ≤ 3, 0 ≤ x ≤ 2, and X includes, but is not limited to, H. + Li + Na + K + and NH4 + One or more of the following, M' is a transition metal cation, optionally including but not limited to one or more of V, Ti, Mn, Fe, Co, Ni, Cu and Zn, and Y is a halide anion, optionally one or more of F, Cl and Br.

[0199] The modified compounds for the positive electrode active materials of the aforementioned lithium battery cells and sodium battery cells can be obtained by doping and / or surface coating modifications of the positive electrode active materials.

[0200] In some embodiments, the positive electrode film layer may further include a positive electrode conductive agent. As an example, the positive electrode conductive agent may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0201] In some embodiments, the positive electrode film layer may further include a positive electrode binder. As an example, the positive electrode binder may include, but is not limited to, one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resins.

[0202] In some embodiments, the positive current collector may be a metal foil or a composite current collector. An example of a metal foil is aluminum foil. The composite current collector may include a polymeric material substrate and a metal material layer formed on at least one surface of the polymeric material substrate. As an example, the metal material may include, but is not limited to, one or more of aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymeric material substrate may include, but is not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene, and polyethylene.

[0203] The positive electrode film is typically formed by coating a positive electrode slurry onto a positive electrode current collector, followed by drying and cold pressing. The positive electrode slurry is usually formed by dispersing positive electrode active materials, positive electrode conductive agents, positive electrode binders, and any other components in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP), but is not limited to this.

[0204] [Negative electrode plate]

[0205] In some embodiments, the negative electrode sheet may include a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector and comprising a negative electrode active material. For example, the negative electrode current collector has two surfaces opposite each other in its 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.

[0206] The negative electrode active material may be any material known in the art that can be used in battery cells. As an example, the negative electrode active material may include, but is not limited to, one or more of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. Silicon-based materials may include, but are not limited to, one or more of elemental silicon, silicon oxide, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include, but are not limited to, one or more of elemental tin, tin oxide, and tin alloys.

[0207] In some embodiments, the negative electrode film layer may further include a negative electrode conductive agent. As an example, the negative electrode conductive agent may include, but is not limited to, one or more of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0208] In some embodiments, the negative electrode film layer may further include a negative electrode binder. As an example, the negative electrode binder may include, but is not limited to, one or more of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, waterborne acrylic resins (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0209] In some embodiments, the negative electrode film layer may also include other additives. As an example, other additives may include thickeners, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, etc.

[0210] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. As an example of a metal foil, copper foil may be used. The composite current collector may include a polymeric material substrate and a metal material layer formed on at least one surface of the polymeric material substrate. As an example, the metal material may include, but is not limited to, one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. As an example, the polymeric material substrate may include, but is not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene, and polyethylene.

[0211] The negative electrode film is typically formed by coating a negative electrode slurry onto a negative electrode current collector, followed by drying and cold pressing. The negative electrode slurry is usually formed by dispersing the negative electrode active material, negative electrode conductive agent, negative electrode binder, and other optional additives in a solvent and stirring until homogeneous. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited to these.

[0212] The negative electrode sheet does not exclude other additional functional layers besides the negative electrode film layer. For example, in some embodiments, the negative electrode sheet also includes a conductive substrate composite coating (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector.

[0213] In some embodiments, the negative electrode sheet can be made of foamed metal. The foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloy, foamed carbon, etc. When foamed metal is used as the negative electrode sheet, the surface of the foamed metal may or may not contain a negative electrode active material.

[0214] This disclosure also provides a method for preparing the battery cell of this disclosure.

[0215] The preparation method of a battery cell includes the following steps: providing an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode, a negative electrode, and a separator. The separator is located between the positive and negative electrode. The separator includes a porous base membrane and a composite coating on at least one surface of the porous base membrane. The composite coating includes silane coupling agent-modified inorganic particles, a gel polymer, and a binder. The electrolyte includes an organic solvent, an electrolyte salt, and an acrylate crosslinking agent. The silane coupling agent-modified inorganic particles include inorganic particles and silicon-containing organic groups. The inorganic particles and silicon-containing organic groups are connected by hydrogen bonds and / or ether bonds. The silicon-containing organic groups have active groups, and the active groups can undergo a polymerization reaction with the acrylate crosslinking agent. The electrode assembly is placed in an outer packaging, dried, and then injected with electrolyte. After encapsulation and standing, a battery cell is obtained. In this case, the separator gels with the electrolyte to form a gel electrolyte separator.

[0216] After standing, the separator membrane gels with the electrolyte to form a gel electrolyte separator membrane.

[0217] Alternatively, the settling period can be a high-temperature settling period.

[0218] Optionally, the settling temperature can be 40℃-80℃.

[0219] Optionally, the settling time can be greater than or equal to 1 hour, and can be selected as 1 hour to 3 hours.

[0220] In some embodiments, after the battery cells have been left to stand, they undergo further processing steps such as formation.

[0221] Example

[0222] The following embodiments describe the disclosure of this disclosure in more detail. These embodiments are merely illustrative, as various modifications and variations will be apparent to those skilled in the art within the scope of this disclosure. Unless otherwise stated, all parts, percentages, and ratios reported in the following embodiments are based on mass, and all reagents used in the embodiments are commercially available or synthesized by conventional methods and can be used directly without further processing, and the instruments used in the embodiments are commercially available.

[0223] Example 1

[0224] Preparation of positive electrode sheet

[0225] Lithium iron phosphate (LiFePO4), acetylene black (Acetylene Black), and polyvinylidene fluoride (PVDF) (PVDF binder) were mixed in a mass ratio of 94:4:2. N-methylpyrrolidone (NMP) was added as a solvent, and the mixture was thoroughly stirred to prepare a positive electrode slurry. The positive electrode slurry was then uniformly coated onto both surfaces of an aluminum foil current collector. After drying, cold pressing, and slitting, the positive electrode sheet was obtained. The coating weight of the positive electrode slurry was 0.224 g / 1540.25 mm. 2 , by weight excluding solvent.

[0226] Preparation of negative electrode sheet

[0227] Artificial graphite (negative electrode active material), acetylene black (negative electrode conductive agent), styrene-butadiene rubber (SBR) (negative electrode binder), and sodium carboxymethyl cellulose (thickener) were mixed in a mass ratio of 95:1.5:3.1:0.4. Deionized water was added as a solvent, and the mixture was thoroughly stirred to prepare a negative electrode slurry. The negative electrode slurry was uniformly coated onto both surfaces of the copper foil (negative electrode current collector), followed by drying, cold pressing, and slitting to obtain the negative electrode sheet. The coating weight of the negative electrode slurry was 0.108 g / 1540.25 mm. 2 , by weight excluding solvent.

[0228] Preparation of electrolyte

[0229] In an argon-atmospheric glove box with a water content of <10 ppm, ethylene carbonate (EC), propylene carbonate (PC), and dimethyl carbonate (DMC) were mixed in a mass ratio of EC:PC:DMC = 3:3:3. LiPF6, vinylene carbonate (VC), vinyl sulfate (DTD), and 1,3-propanesulfonate lactone (PS) were then added to the mixed organic solvent. After stirring until homogeneous, triethylene glycol diacrylate (TEGDA), an acrylate crosslinking agent, and azobisisobutyronitrile (AIBN), an initiator, were added and stirred until homogeneous to obtain the electrolyte. The concentration of LiPF6 was 1 mol / L. The mass percentages of VC, DTD, and PS were 3%, 1%, and 5.94% respectively, all based on the total mass of the electrolyte.

[0230] Preparation of the separating membrane

[0231] (1) Mix 6 parts by weight of polytetrafluoroethylene (PTFE) micro powder, 0.15 parts by weight of surfactant polyether siloxane copolymer, and deionized water to uniformly disperse the PTFE micro powder and form a first dispersion; add 50 parts by weight of rutile nano-titanium dioxide, 5 parts by weight of nano-barium titanate, and 0.15 parts by weight of surfactant polysiloxane to a mixed solvent of water and ethanol, then add 1.2 parts by weight of vinyltriethoxysilane and stir. Adjust the pH of the system to 3-5 with nitric acid to obtain a stable dispersion, then ball mill it using a nano-ball mill for 2... h, the temperature of the dispersion system reaches 50℃-80℃ during ball milling to obtain a second dispersion; the first and second dispersions are transferred into a polymerization reactor, and 50 parts by mass of acrylonitrile monomer, 0.2 parts by mass of potassium persulfate initiator, and 1.5 parts by mass of Triton-100 emulsifier are added, while nitrogen gas is introduced for protection, and the polymerization temperature is controlled at 60℃-80℃; then 2 parts by mass of wetting agent fluoroalkyl methoxy ether alcohol and 3.5 parts by mass of binder styrene-butadiene latex are added and stirred, and then filtered through a 400-mesh sieve to obtain a composite coating slurry.

[0232] (2) Mix γ-aminopropyltriethoxysilane (KH550), deionized water and wetting agent CapstoneFS 31 evenly to prepare a silane coupling agent solution with a mass concentration of 1%.

[0233] (3) A silane coupling agent solution was uniformly coated on both sides of a 5 μm thick polypropylene porous base membrane, and then dried thoroughly at 60°C to form a bonding layer with a surface density of 0.1 g / m². 2 The composite coating slurry was then uniformly applied to the bonding layer and thoroughly dried at 60°C to form a composite coating with a thickness of 1 μm on each side. The composite coating comprises silane coupling agent-modified inorganic particles, a gel polymer, and lubricating particles. The silane coupling agent-modified inorganic particles include silane coupling agent-modified rutile nano-titanium dioxide and silane coupling agent-modified nano-barium titanate, accounting for approximately 47% of the composite coating by mass. The gel polymer is polyacrylonitrile, accounting for approximately 42% of the composite coating by mass. The lubricating particles are polytetrafluoroethylene (PTFE) micropowder, accounting for approximately 5% of the composite coating by mass.

[0234] Preparation of battery cells

[0235] The positive electrode, separator, and negative electrode are stacked in sequence to obtain an electrode assembly. The electrode assembly is placed in an outer package, injected with the prepared electrolyte and sealed. Then it is left to stand at 70°C for 2 hours and then formed to obtain a lithium-ion battery cell.

[0236] Example 2

[0237] Except for the following differences, the manufacturing process of the battery cells is the same as that in Example 1.

[0238] Preparation of the separating membrane

[0239] (1) Mix 6 parts by weight of polytetrafluoroethylene (PTFE) micro powder, 0.15 parts by weight of surfactant polyether siloxane copolymer, and deionized water to uniformly disperse the PTFE micro powder and form a first dispersion; add 50 parts by weight of rutile nano-titanium dioxide, 5 parts by weight of nano-barium titanate, and 0.15 parts by weight of surfactant polysiloxane to a mixed solvent of water and ethanol, then add 1.2 parts by weight of vinyltriethoxysilane and stir. Adjust the pH of the system to 3-5 with nitric acid to obtain a stable dispersion, then ball mill it using a nano-ball mill for 2... h, the temperature of the dispersion system reaches 50℃-80℃ during ball milling to obtain a second dispersion; the first and second dispersions are transferred into a polymerization reactor, and 50 parts by mass of acrylonitrile monomer, 0.2 parts by mass of potassium persulfate initiator, and 1.5 parts by mass of Triton-100 emulsifier are added, while nitrogen gas is introduced for protection, and the polymerization temperature is controlled at 60℃-80℃; then 2 parts by mass of wetting agent fluoroalkyl methoxy ether alcohol and 3.5 parts by mass of binder styrene-butadiene latex are added and stirred, and then filtered through a 400-mesh sieve to obtain a composite coating slurry.

[0240] (2) The composite coating slurry was uniformly coated on both sides of a 5 μm thick polypropylene porous base membrane and dried thoroughly at 60°C to form a composite coating. The thickness of the composite coating on each side was 1 μm. The composite coating consisted of silane coupling agent modified inorganic particles, gel polymer, and lubricating particles. The silane coupling agent modified inorganic particles included silane coupling agent modified rutile nano-titanium dioxide and silane coupling agent modified nano-barium titanate, with the silane coupling agent modified inorganic particles accounting for approximately 47% of the mass of the composite coating. The gel polymer was polyacrylonitrile, accounting for approximately 42% of the mass of the composite coating. The lubricating particles were polytetrafluoroethylene micropowder, accounting for approximately 5% of the mass of the composite coating.

[0241] Example 3

[0242] Except for the following differences, the manufacturing process of the battery cells is the same as that in Example 1.

[0243] Preparation of the separating membrane

[0244] (1) 50 parts by mass of rutile nano-titanium dioxide, 5 parts by mass of nano-barium titanate, and 0.15 parts by mass of surfactant polysiloxane were added to a mixed solvent of water and ethanol. Then, 1.2 parts by mass of vinyltriethoxysilane were added and stirred. The pH of the system was then adjusted to 3-5 with nitric acid to obtain a stable dispersion. The dispersion was then ball-milled for 2 hours using a nano-ball mill. During the ball milling process, the temperature of the dispersion system reached 50℃-80℃ to obtain a dispersion. The dispersion was transferred to a polymerization reactor, and 50 parts by mass of acrylonitrile monomer, 0.2 parts by mass of initiator potassium persulfate, and 1.5 parts by mass of emulsifier Triton-100 were added. Nitrogen gas was introduced for protection, and the polymerization temperature was controlled at 60℃-80℃. Then, 2 parts by mass of wetting agent fluoroalkyl methoxy ether alcohol and 3.5 parts by mass of binder styrene-butadiene latex were added and stirred. The mixture was then filtered through a 400-mesh sieve to obtain a composite coating slurry.

[0245] (2) Mix γ-aminopropyltriethoxysilane (KH550), deionized water and wetting agent CapstoneFS 31 evenly to prepare a silane coupling agent solution with a mass concentration of 1%.

[0246] (3) A silane coupling agent solution was uniformly coated on both sides of a 5 μm thick polypropylene porous base membrane, and then dried thoroughly at 60°C to form a bonding layer with a surface density of 0.1 g / m². 2 The composite coating slurry was then uniformly applied to the bonding layer and thoroughly dried at 60°C to form a composite coating with a thickness of 1 μm on each side. The composite coating comprises silane coupling agent-modified inorganic particles and a gel polymer. The silane coupling agent-modified inorganic particles include silane coupling agent-modified rutile nano-titanium dioxide and silane coupling agent-modified nano-barium titanate, with the silane coupling agent-modified inorganic particles accounting for approximately 50% of the composite coating by mass. The gel polymer is polyacrylonitrile, accounting for approximately 45% of the composite coating by mass.

[0247] Comparative Example 1

[0248] Except for the following differences, the manufacturing process of the battery cells is the same as that in Example 1.

[0249] Preparation of the separating membrane

[0250] (1) 55 parts by mass of rutile nano-titanium dioxide were added to a mixed solvent of water and ethanol, and then 1.2 parts by mass of vinyltriethoxysilane were added and stirred. The pH of the system was then adjusted to 3-5 with nitric acid to obtain a stable dispersion. The dispersion was then ball-milled for 2 hours using a nano-ball mill. During the ball milling process, the temperature of the dispersion system reached 50℃-80℃ to obtain a dispersion. The dispersion was then transferred to a polymerization reactor, and 50 parts by mass of acrylonitrile monomer, 0.2 parts by mass of potassium persulfate initiator, and 1.5 parts by mass of Triton-100 emulsifier were added. Nitrogen gas was introduced for protection, and the polymerization temperature was controlled at 60℃-80℃. Then, 2 parts by mass of wetting agent fluoroalkyl methoxy ether alcohol and 3.5 parts by mass of binder styrene-butadiene latex were added and stirred. The mixture was then filtered through a 400-mesh sieve to obtain a composite coating slurry.

[0251] (2) The composite coating slurry is uniformly coated on both sides of a 5μm thick polypropylene porous base film and dried at 60℃ to form a composite coating. The thickness of the composite coating on one side is 1μm.

[0252] Preparation of electrolyte

[0253] In an argon-atmospheric glove box with a water content of <10 ppm, ethylene carbonate (EC), propylene carbonate (PC), and dimethyl carbonate (DMC) were mixed in a mass ratio of EC:PC:DMC = 3:3:3. LiPF6, vinylene carbonate (VC), vinyl sulfate (DTD), and 1,3-propanesulfonate lactone (PS) were then added to the mixed organic solvent and stirred until homogeneous to obtain the electrolyte. The concentration of LiPF6 was 1 mol / L. The mass percentages of VC, DTD, and PS were 3%, 1%, and 1% respectively, all based on the total mass of the electrolyte.

[0254] Performance testing

[0255] (1) Room temperature shrinkage rate test of the isolation film

[0256] Test conditions: Temperature 25℃, humidity 40%.

[0257] A 1m long isolation membrane was placed on a horizontal plane, and the shrinkage rate of the isolation membrane in the MD direction was recorded after 12 hours.

[0258] Shrinkage rate of the separator in the MD direction = (initial size of the separator in the MD direction - size of the separator in the MD direction after 12 hours) / initial size of the separator in the MD direction × 100%.

[0259] (2) Thermal shrinkage rate test of the insulating film

[0260] The test was conducted in accordance with GB / T 36363-2018.

[0261] The prepared release film 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. The temperature of the forced-air drying oven was set to 130℃. After the temperature reached the set temperature and stabilized for 60 minutes, the A4 paper placed on the corrugated paper was placed into the forced-air drying oven, and the timing was started. After 1 hour, the length and width of the release film were measured, and the values ​​were marked as a and b, respectively. The heat shrinkage rate was calculated as follows: longitudinal (MD) heat shrinkage rate = [(100-a) / 100] × 100%, and the average value of the parallel samples was taken as the test result.

[0262] (3) Voltage breakdown strength test of the separator

[0263] The test was conducted in accordance with GB / T 13542.2-2009.

[0264] The release liner was cut into rectangular samples of 450mm × 650mm and tested using a pressure resistance tester. The test instrument used was a CS2671AX pressure resistance tester.

[0265] (4) Test of the dynamic friction coefficient of the separator

[0266] The test shall be conducted in accordance with GB / T10006-1988.

[0267] Measurement accuracy: 0.5 grade, stroke: 100mm, slider mass: 200g, slider movement speed: 100mm / min.

[0268] (5) Ionic conductivity test of the separator

[0269] The prepared separator sample was composited with two steel sheets to form a symmetrical cell. The number of separator layers in the symmetrical cell was designed to be stacked in a gradient manner, with the following layer numbers: 2, 4, 6, 8, 10, and 12. The ionic conductivity of the test samples of the symmetrical cells with different layer numbers was measured using EIS (Electrochemical Impedance Spectroscopy) on an electrochemical workstation. Then, the measured ionic conductivity values ​​were fitted with gradient data values, and the ionic conductivity of a single-layer test sample was calculated based on the fitting results.

[0270] (6) Cycle performance test of individual battery cells

[0271] The ambient temperature was set to 25℃. After charging at a constant current of 0.33C to the cutoff voltage of 3.65V, charging was continued at a constant voltage of 3.65V until the current decreased to 0.05C. Then, the battery was discharged at a constant current of 0.33C to 2.5V to obtain the initial discharge capacity. This charge-discharge cycle was repeated, and the discharge capacity after each cycle was recorded. When the discharge capacity decreased to 80% of the initial discharge capacity, the battery cell was considered to have reached the end of its lifespan. The number of charge-discharge cycles experienced by the battery cell at this point was recorded as its cycle life.

[0272] Table 1

[0273] As can be seen from the above test results, this disclosure, by including gel polymer and silane coupling agent modified inorganic particles in the composite coating of the separator, and by including acrylate crosslinking agents in the electrolyte, can form a gel electrolyte separator with stable structure, good heat resistance, and good mechanical strength, thereby reducing the self-discharge of the battery cell, locking more electrolyte in the pores of the gel electrolyte separator, reducing free electrolyte and reducing side reactions at the electrolyte-electrode interface, and thus enabling the battery cell to have a longer cycle life.

[0274] The test results of Examples 1 and 2 also show that by setting a silane coupling agent connecting layer between the porous base film and the composite coating, this disclosure can further improve the voltage breakdown strength and heat resistance of the separator, and improve the cycle life of the battery cell.

[0275] The test results of Examples 1 and 3 also show that by further including lubricating particles in the composite coating of the separator, this disclosure can reduce the coefficient of friction of the separator, improve the heat resistance of the separator, and also improve the cycle life of the battery cell.

[0276] Example 1-1

[0277] Except for the following differences, the manufacturing process of the battery cells is the same as that in Example 1.

[0278] Preparation of the separating membrane

[0279] (3) A silane coupling agent solution was uniformly coated onto one surface of a 5 μm thick polypropylene porous base membrane, and then thoroughly dried at 60°C to form a bonding layer with a surface density of 0.1 g / m². 2 Then, the composite coating slurry is uniformly coated onto the bonding layer and fully dried at 60°C to form a composite coating with a thickness of 1 μm.

[0280] Examples 1-2

[0281] Except for the following differences, the manufacturing process of the battery cells is the same as that in Example 1.

[0282] Preparation of the separating membrane

[0283] (3) A silane coupling agent solution was uniformly coated on both sides of a 5 μm thick polypropylene porous base membrane, and then dried thoroughly at 60°C to form a bonding layer with a surface density of 0.1 g / m². 2 Then, the composite coating slurry is uniformly coated onto the bonding layer and fully dried at 60°C to form a composite coating with a thickness of 2μm on each side.

[0284] Examples 1-3

[0285] Except for the following differences, the manufacturing process of the battery cells is the same as that in Example 1.

[0286] Preparation of the separating membrane

[0287] (3) A silane coupling agent solution was uniformly coated onto one surface of a 5 μm thick polypropylene porous base membrane, and then thoroughly dried at 60°C to form a bonding layer with a surface density of 0.1 g / m². 2 Then, the composite coating slurry is uniformly coated onto the bonding layer and fully dried at 60°C to form a composite coating with a thickness of 2μm.

[0288] Table 2

[0289] The test results above show that different thicknesses and placements of the composite coating will have different effects on improving the cycle life of individual battery cells.

[0290] Example 2-1

[0291] Except for the following differences, the manufacturing process of the battery cells is the same as that in Example 1.

[0292] Preparation of the separating membrane

[0293] (1) Mix 6 parts by weight of polytetrafluoroethylene (PTFE) micro powder, 0.15 parts by weight of surfactant polyether siloxane copolymer, and deionized water to uniformly disperse the PTFE micro powder and form a first dispersion; add 70 parts by weight of rutile nano-titanium dioxide, 5 parts by weight of nano-barium titanate, and 0.15 parts by weight of surfactant polysiloxane to a mixed solvent of water and ethanol, then add 1.2 parts by weight of vinyltriethoxysilane and stir. Adjust the pH of the system to 3-5 with nitric acid to obtain a stable dispersion, then ball mill it using a nano-ball mill for 2... h, the temperature of the dispersion system reaches 50℃-80℃ during ball milling to obtain a second dispersion; the first and second dispersions are transferred into a polymerization reactor, and 30 parts by mass of acrylonitrile monomer, 0.2 parts by mass of potassium persulfate initiator, and 1.5 parts by mass of Triton-100 emulsifier are added, while nitrogen gas is introduced for protection, and the polymerization temperature is controlled at 60℃-80℃; then 2 parts by mass of wetting agent fluoroalkyl methoxy ether alcohol and 3.5 parts by mass of binder styrene-butadiene latex are added and stirred, and then filtered through a 400-mesh sieve to obtain a composite coating slurry.

[0294] (2) Mix γ-aminopropyltriethoxysilane (KH550), deionized water and wetting agent CapstoneFS 31 evenly to prepare a silane coupling agent solution with a mass concentration of 1%.

[0295] (3) A silane coupling agent solution was uniformly coated on both sides of a 5 μm thick polypropylene porous base membrane, and then dried thoroughly at 60°C to form a bonding layer with a surface density of 0.1 g / m². 2 The composite coating slurry was then uniformly applied to the bonding layer and thoroughly dried at 60°C to form a composite coating with a thickness of 1 μm on each side. The composite coating comprises silane coupling agent-modified inorganic particles, a gel polymer, and lubricating particles. The silane coupling agent-modified inorganic particles include silane coupling agent-modified rutile nano-titanium dioxide and silane coupling agent-modified nano-barium titanate, accounting for approximately 64% of the composite coating by mass. The gel polymer is polyacrylonitrile, accounting for approximately 25% of the composite coating by mass. The lubricating particles are polytetrafluoroethylene (PTFE) micropowder, accounting for approximately 5% of the composite coating by mass.

[0296] Example 2-2

[0297] Except for the following differences, the manufacturing process of the battery cells is the same as that in Example 1.

[0298] Preparation of the separating membrane

[0299] (1) Mix 6 parts by weight of polytetrafluoroethylene (PTFE) micro powder, 0.15 parts by weight of surfactant polyether siloxane copolymer, and deionized water to uniformly disperse the PTFE micro powder and form a first dispersion; add 60 parts by weight of rutile nano-titanium dioxide, 5 parts by weight of nano-barium titanate, and 0.15 parts by weight of surfactant polysiloxane to a mixed solvent of water and ethanol, then add 1.2 parts by weight of vinyltriethoxysilane and stir. Adjust the pH of the system to 3-5 with nitric acid to obtain a stable dispersion, and then ball mill it using a nano-ball mill for 2... h, during the ball milling process, the temperature of the dispersion system reaches 50℃-80℃, resulting in a second dispersion; the first and second dispersions are transferred into a polymerization reactor, and 40 parts by mass of acrylonitrile monomer, 0.2 parts by mass of potassium persulfate initiator, and 1.5 parts by mass of Triton-100 emulsifier are added, while nitrogen gas is introduced for protection, and the polymerization temperature is controlled at 60℃-80℃; then 2 parts by mass of wetting agent fluoroalkyl methoxy ether alcohol and 3.5 parts by mass of binder styrene-butadiene latex are added and stirred, and then filtered through a 400-mesh sieve to obtain a composite coating slurry.

[0300] (2) Mix γ-aminopropyltriethoxysilane (KH550), deionized water and wetting agent CapstoneFS 31 evenly to prepare a silane coupling agent solution with a mass concentration of 1%.

[0301] (3) A silane coupling agent solution was uniformly coated on both sides of a 5 μm thick polypropylene porous base membrane, and then dried thoroughly at 60°C to form a bonding layer with a surface density of 0.1 g / m². 2 The composite coating slurry was then uniformly applied to the bonding layer and thoroughly dried at 60°C to form a composite coating with a thickness of 1 μm on each side. The composite coating comprises silane coupling agent-modified inorganic particles, a gel polymer, and lubricating particles. The silane coupling agent-modified inorganic particles include silane coupling agent-modified rutile nano-titanium dioxide and silane coupling agent-modified nano-barium titanate, with the silane coupling agent-modified inorganic particles accounting for approximately 55% of the composite coating by mass. The gel polymer is polyacrylonitrile, accounting for approximately 34% of the composite coating by mass. The lubricating particles are polytetrafluoroethylene (PTFE) micropowder, accounting for approximately 5% of the composite coating by mass.

[0302] Example 2-3

[0303] Except for the following differences, the manufacturing process of the battery cells is the same as that in Example 1.

[0304] Preparation of the separating membrane

[0305] (1) Mix 6 parts by weight of polytetrafluoroethylene (PTFE) micro powder, 0.15 parts by weight of surfactant polyether siloxane copolymer, and deionized water to uniformly disperse the PTFE micro powder and form a first dispersion; add 30 parts by weight of rutile nano-titanium dioxide, 5 parts by weight of nano-barium titanate, and 0.15 parts by weight of surfactant polysiloxane to a mixed solvent of water and ethanol, then add 1.2 parts by weight of vinyltriethoxysilane and stir. Adjust the pH of the system to 3-5 with nitric acid to obtain a stable dispersion, and then ball mill it using a nano-milling machine for 2... h, the temperature of the dispersion system reaches 50℃-80℃ during ball milling to obtain a second dispersion; the first and second dispersions are transferred into a polymerization reactor, and 70 parts by mass of acrylonitrile monomer, 0.2 parts by mass of potassium persulfate initiator, and 1.5 parts by mass of Triton-100 emulsifier are added, while nitrogen gas is introduced for protection, and the polymerization temperature is controlled at 60℃-80℃; then 2 parts by mass of wetting agent fluoroalkyl methoxy ether alcohol and 3.5 parts by mass of binder styrene-butadiene latex are added and stirred, and then filtered through a 400-mesh sieve to obtain a composite coating slurry.

[0306] (2) Mix γ-aminopropyltriethoxysilane (KH550), deionized water and wetting agent CapstoneFS 31 evenly to prepare a silane coupling agent solution with a mass concentration of 1%.

[0307] (3) A silane coupling agent solution was uniformly coated on both sides of a 5 μm thick polypropylene porous base membrane, and then dried thoroughly at 60°C to form a bonding layer with a surface density of 0.1 g / m². 2 The composite coating slurry was then uniformly applied to the bonding layer and thoroughly dried at 60°C to form a composite coating with a thickness of 1 μm on each side. The composite coating comprises silane coupling agent-modified inorganic particles, a gel polymer, and lubricating particles. The silane coupling agent-modified inorganic particles include silane coupling agent-modified rutile nano-titanium dioxide and silane coupling agent-modified nano-barium titanate, accounting for approximately 30% of the composite coating by mass. The gel polymer is polyacrylonitrile, accounting for approximately 59% of the composite coating by mass. The lubricating particles are polytetrafluoroethylene (PTFE) micropowder, accounting for approximately 5% of the composite coating by mass.

[0308] Table 3

[0309] The test results above show that by adjusting the mass ratio of silane coupling agent-modified inorganic particles and gel polymer, the separator can have good heat resistance, high voltage breakdown strength and high ionic conductivity, and the battery cells can also have a longer cycle life.

[0310] Example 3-1

[0311] Except for the following differences, the manufacturing process of the battery cells is the same as that in Example 1.

[0312] Preparation of electrolyte

[0313] In an argon-atmospheric glove box with a water content of <10 ppm, ethylene carbonate (EC), propylene carbonate (PC), and dimethyl carbonate (DMC) were mixed in a mass ratio of EC:PC:DMC = 3:3:3. LiPF6, vinylene carbonate (VC), vinyl sulfate (DTD), and 1,3-propanesulfonate lactone (PS) were then added to the mixed organic solvent. After stirring until homogeneous, triethylene glycol diacrylate (TEGDA), an acrylate crosslinking agent, and azobisisobutyronitrile (AIBN), an initiator, were added and stirred until homogeneous to obtain the electrolyte. The concentration of LiPF6 was 1 mol / L. The mass percentages of VC, DTD, and PS were 3%, 1%, and 4.5% respectively, all based on the total mass of the electrolyte.

[0314] Example 3-2

[0315] Except for the following differences, the manufacturing process of the battery cells is the same as that in Example 1.

[0316] Preparation of electrolyte

[0317] In an argon-atmospheric glove box with a water content of <10 ppm, ethylene carbonate (EC), propylene carbonate (PC), and dimethyl carbonate (DMC) were mixed in a mass ratio of EC:PC:DMC = 3:3:3. LiPF6, vinylene carbonate (VC), vinyl sulfate (DTD), and 1,3-propanesulfonate lactone (PS) were then added to the mixed organic solvent and stirred until homogeneous. Next, triethylene glycol diacrylate (TEGDA), an acrylate crosslinking agent, and azobisisobutyronitrile (AIBN), an initiator, were added and stirred until homogeneous to obtain the electrolyte. The concentration of LiPF6 was 1 mol / L. The mass percentages of VC, DTD, PS, and TEGDA were all based on the total mass of the electrolyte.

[0318] Example 3-3

[0319] Except for the following differences, the manufacturing process of the battery cells is the same as that in Example 1.

[0320] Preparation of electrolyte

[0321] In an argon-atmospheric glove box with a water content of <10 ppm, ethylene carbonate (EC), propylene carbonate (PC), and dimethyl carbonate (DMC) were mixed in a mass ratio of EC:PC:DMC = 3:3:3. LiPF6, vinylene carbonate (VC), vinyl sulfate (DTD), and 1,3-propanesulfonate lactone (PS) were then added to the mixed organic solvent and stirred until homogeneous. Next, triethylene glycol diacrylate (TEGDA), an acrylate crosslinking agent, and azobisisobutyronitrile (AIBN), an initiator, were added and stirred until homogeneous to obtain the electrolyte. The concentration of LiPF6 was 1 mol / L. The mass percentages of VC, DTD, PS, and TEGDA were all based on the total mass of the electrolyte.

[0322] Table 4

[0323] The test results above show that increasing the mass percentage of acrylate crosslinking agents in the electrolyte can improve the cycle life of the battery cells.

[0324] Example 4-1

[0325] Except for the following differences, the manufacturing process of the battery cells is the same as that in Example 1.

[0326] Preparation of the separating membrane

[0327] (1) Mix 6 parts by weight of polytetrafluoroethylene (PTFE) micro powder, 0.15 parts by weight of surfactant polyether siloxane copolymer, and deionized water to form a first dispersion by uniformly dispersing the PTFE micro powder; add 50 parts by weight of rutile nano-titanium dioxide, 5 parts by weight of nano-barium titanate, and 0.15 parts by weight of surfactant polysiloxane to a mixed solvent of water and ethanol, then add 1.2 parts by weight of 3-methacryloyloxypropyltrimethoxysilane (KH570) and stir. Adjust the pH of the system to 3-5 with nitric acid to obtain a stable dispersion. Then utilize nano... The dispersion system was ball-milled for 2 hours using a ball mill, and the temperature of the dispersion system reached 50℃-80℃ during the ball milling process to obtain a second dispersion. The first and second dispersions were transferred into a polymerization reactor, and 50 parts by mass of acrylonitrile monomer, 0.2 parts by mass of potassium persulfate initiator, and 1.5 parts by mass of Triton-100 emulsifier were added. Nitrogen gas was introduced for protection, and the polymerization temperature was controlled at 60℃-80℃. Subsequently, 2 parts by mass of fluoroalkyl methoxy ether alcohol wetting agent and 3.5 parts by mass of styrene-butadiene latex binder were added and stirred. The mixture was then filtered through a 400-mesh sieve to obtain a composite coating slurry.

[0328] Example 4-2

[0329] Except for the following differences, the manufacturing process of the battery cells is the same as that in Example 1.

[0330] Preparation of the separating membrane

[0331] (1) Mix 6 parts by weight of polytetrafluoroethylene micro powder, 0.15 parts by weight of surfactant polyether siloxane copolymer, and deionized water to form a first dispersion by uniformly dispersing the polytetrafluoroethylene micro powder; add 50 parts by weight of rutile nano-titanium dioxide, 5 parts by weight of nano-barium titanate, and 0.15 parts by weight of surfactant polysiloxane to a mixed solvent of water and ethanol, then add 1.2 parts by weight of γ-aminopropyltriethoxysilane (KH550) and stir. Then adjust the pH of the system to 3-5 with nitric acid to obtain a stable dispersion. Finally, use nano-grinding balls... The dispersion was ball-milled for 2 hours, during which the temperature of the dispersion system reached 50℃-80℃, resulting in a second dispersion. The first and second dispersions were then transferred into a polymerization reactor, and 50 parts by mass of acrylonitrile monomer, 0.2 parts by mass of potassium persulfate initiator, and 1.5 parts by mass of Triton-100 emulsifier were added. Nitrogen gas was introduced for protection, and the polymerization temperature was controlled at 60℃-80℃. Subsequently, 2 parts by mass of fluoroalkyl methoxy ether alcohol wetting agent and 3.5 parts by mass of styrene-butadiene latex binder were added and stirred. The mixture was then filtered through a 400-mesh sieve to obtain a composite coating slurry.

[0332] Example 4-3

[0333] Except for the following differences, the manufacturing process of the battery cells is the same as that in Example 1.

[0334] Preparation of the separating membrane

[0335] (1) Mix 6 parts by weight of polytetrafluoroethylene (PTFE) micro powder, 0.15 parts by weight of surfactant polyether siloxane copolymer, and deionized water to form a first dispersion by uniformly dispersing the PTFE micro powder; add 50 parts by weight of rutile nano-titanium dioxide, 5 parts by weight of nano-barium titanate, and 0.15 parts by weight of surfactant polysiloxane to a mixed solvent of water and ethanol, then add 1.2 parts by weight of 3-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560) and stir. Then adjust the pH of the system to 3-5 with nitric acid to obtain a stable dispersion. The dispersion was ball-milled for 2 hours using a nano-ball mill, during which the temperature of the dispersion system reached 50℃-80℃, resulting in a second dispersion. The first and second dispersions were then transferred into a polymerization reactor, and 50 parts by mass of acrylonitrile monomer, 0.2 parts by mass of potassium persulfate initiator, and 1.5 parts by mass of Triton-100 emulsifier were added. Nitrogen gas was introduced for protection, and the polymerization temperature was controlled at 60℃-80℃. Subsequently, 2 parts by mass of fluoroalkyl methoxy ether alcohol wetting agent and 3.5 parts by mass of styrene-butadiene latex binder were added and stirred. The mixture was then filtered through a 400-mesh sieve to obtain a composite coating slurry.

[0336] Table 5

[0337] The test results above show that modifying inorganic particles with different silane coupling agents can all result in a longer cycle life for battery cells.

[0338] It should be noted that this disclosure is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same essential structure and achieving the same effect as the technical concept within the scope of this disclosure are included in the technical scope of this disclosure. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, are also included in the scope of this disclosure without departing from the spirit of this disclosure.

Claims

1. A battery cell, wherein, The battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode, a negative electrode, and a separator, with the separator located between the positive electrode and the negative electrode. The isolation membrane includes a porous base membrane and a composite coating located on at least one surface of the porous base membrane, the composite coating including silane coupling agent modified inorganic particles, a gel polymer and a binder; The electrolyte includes an organic solvent, an electrolyte salt, and an acrylate crosslinking agent; The silane coupling agent modified inorganic particles include inorganic particles and silicon-containing organic groups, wherein the inorganic particles and the silicon-containing organic groups are connected by hydrogen bonds and / or ether bonds, the silicon-containing organic groups have active groups, and the active groups can undergo polymerization reactions with the acrylate crosslinking agent; The separator membrane and the electrolyte can gel to form a gel electrolyte separator membrane.

2. The battery cell according to claim 1, wherein, The active group includes one or more of the following: acryloyloxy, carbon-carbon double bond, amino, hydroxyl, mercapto, glycidyl etheroxy, carbonyl, and carboxyl; and / or, The acrylate crosslinking agent includes one or more of the following: triethylene glycol diacrylate, triethylene glycol dimethacrylate, triethylene glycol divinyl acrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate, tetra(ethylene glycol) diacrylate, tetraethylene glycol dimethacrylate, 1,3-butanediol diacrylate, 1,3-butanediol dimethacrylate, neopentyl glycol diacrylate, neopentyl glycol dimethacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, and pentaerythritol tetraacrylate.

3. The battery cell according to any one of claims 1-2, wherein, The mass of the acrylate crosslinking agent is 1%-6% of the total mass of the electrolyte.

4. The battery cell according to claim 3, wherein, The mass of the acrylate crosslinking agent is 4%-6% of the total mass of the electrolyte.

5. The battery cell according to any one of claims 1-4, wherein, In the silane coupling agent modified inorganic particles, the mass of the silicon-containing organic groups is 0.2%-4% of the mass of the silane coupling agent modified inorganic particles; and / or, The average particle size of the inorganic particles modified by the silane coupling agent is 100nm-1000nm.

6. The battery cell according to any one of claims 1-5, wherein, The relative permittivity of the inorganic particles is greater than or equal to 10; and / or, The monomers of the gel polymer include one or more of vinylidene fluoride, acrylonitrile, methyl methacrylate, butyl acrylate, methacrylic acid, acrylic acid, and styrene.

7. The battery cell according to any one of claims 1-6, wherein, The inorganic particles include rutile nano-titanium dioxide, nano-barium titanate, and nano-CaCu3Ti4O. 12 One or more of the following: strontium titanate, barium strontium titanate, lead titanate, lead zirconate titanate, lithium niobate, lead metaniobate, and lithium lead barium niobate.

8. The battery cell according to any one of claims 1-7, wherein, In the composite coating, the silane coupling agent-modified inorganic particles account for 25%-68% by mass; and / or, In the composite coating, the mass percentage of the gel polymer is 25%-68%.

9. The battery cell according to claim 8, wherein, In the composite coating, the silane coupling agent-modified inorganic particles account for 28%-62% by mass; and / or, In the composite coating, the mass percentage of the gel polymer is 28%-62%.

10. The battery cell according to any one of claims 1-9, wherein, The composite coating also includes lubricating particles, which include one or more of polytetrafluoroethylene micro powder, polyimide particles, polyetherketone particles, and polyphenylene sulfide particles.

11. The battery cell according to claim 10, wherein, In the composite coating, the mass percentage of the lubricating particles is 3%-10%; and / or, The average particle size of the lubricating particles is 0.5μm-4μm.

12. The battery cell according to any one of claims 1-11, wherein, The average pore size of the composite coating is 15nm-30nm; and / or, The thickness of the composite coating is 0.8μm-3μm.

13. The battery cell according to any one of claims 1-12, wherein, The porous base membrane has carbonyl groups and / or hydroxyl groups on its surface.

14. The battery cell according to any one of claims 1-13, wherein, The porous base membrane and the composite coating also have a connecting layer, which includes a silane coupling agent.

15. The battery cell according to claim 14, wherein, The areal density of the connecting layer is 0.1 g / m³. 2 -1.0g / m 2 ; and / or, The thickness of the connecting layer is 0.01μm-0.1μm.

16. The battery cell according to any one of claims 1-15, wherein, The porous base membrane satisfies at least one of the following conditions (1) to (5): (1) The air permeability of the porous base membrane is 100s / 100ml-300s / 100ml; (2) The areal density of the porous base membrane is 8 g / m³. 2 -22g / m 2 ; (3) The thickness of the porous base film is 4μm-17μm; (4) The porosity of the porous base membrane is 30%-50%; (5) The average pore size of the porous base film is 20nm-45nm.

17. The battery cell according to any one of claims 1-16, wherein, The organic solvent includes one or more of the following: ester solvents, fluorinated ester solvents, ether solvents, fluorinated ether solvents, sulfone solvents, and nitrile solvents; and / or, The cations of the electrolyte salt include lithium ions and / or sodium ions, and the anions of the electrolyte salt include one or more of the following: hexafluorophosphate anion, tetrafluoroborate anion, perchlorate anion, hexafluoroarsenate anion, bis(fluorosulfonyl)imide anion, bis(trifluoromethanesulfonyl)imide anion, trifluoromethanesulfonate anion, difluorooxalateborate anion, dioxalateborate anion, difluorophosphate anion, difluorodioxalate phosphate anion, and tetrafluorooxalate phosphate anion.

18. A battery device comprising a plurality of battery cells as described in any one of claims 1-17.

19. An electrical device comprising a battery cell as described in any one of claims 1-17 or a battery device as described in claim 18.

20. A method for preparing a single battery cell, comprising the following steps: An electrode assembly and an electrolyte are provided. The electrode assembly includes a positive electrode, a negative electrode, and a separator membrane located between the positive and negative electrode. The separator membrane includes a porous base membrane and a composite coating on at least one surface of the porous base membrane. The composite coating includes silane coupling agent-modified inorganic particles, a gel polymer, and a binder. The electrolyte includes an organic solvent, an electrolyte salt, and an acrylate crosslinking agent. The silane coupling agent-modified inorganic particles include inorganic particles and silicon-containing organic groups, which are connected by hydrogen bonds and / or ether bonds. The silicon-containing organic groups have active groups that can undergo polymerization reactions with the acrylate crosslinking agent. The electrode assembly is placed in an outer packaging, dried, and then injected with the electrolyte. After encapsulation and settling, a single battery cell is obtained. The separator membrane gels with the electrolyte to form a gel electrolyte separator membrane.

21. The preparation method according to claim 20, wherein, The settling temperature is 40℃-80℃; and / or, The settling time is greater than or equal to 1 hour.

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