Cross-linked styrenic organic particle and preparation method therefor, cross-linked styrenic organic particle emulsion, separator, secondary battery cell, battery device, and electric device

Abstract

The present disclosure provides a cross-linked styrenic organic particle and a preparation method therefor, a cross-linked styrenic organic particle emulsion, a separator, a secondary battery cell, a battery device, and an electric device. The separator comprises a porous base film and a coating located on at least one side of the porous base film, wherein the coating comprises the cross-linked styrenic organic particle, the cross-linked styrenic organic particle comprises a polar group, and the polar group comprises one or more of an ester group, a carboxyl group, a carboxylate, a hydroxyl group, a cyano group, and an amide group. The secondary battery cell has high mass energy density, high reliability, and good cycle performance.

Description

Cross-linked styrene organic particles and their preparation methods, cross-linked styrene organic particle emulsions, separators, secondary battery cells, battery devices and electrical devices.

[0001] Cross-references to related applications

[0002] This application claims priority to Chinese Patent Application No. 202410946487.6, filed on July 15, 2024, entitled “Cross-linked styrene-based organic particles and their preparation method, separator membrane, battery cell, and electrical device”, and Chinese Patent Application No. 202411387983.9, filed on September 30, 2024, entitled “Cross-linked styrene-based organic particles and their preparation method, cross-linked styrene-based organic particle emulsion, separator membrane, secondary battery cell, battery device, and electrical device”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to a cross-linked styrene-based organic particle and its preparation method, a cross-linked styrene-based organic particle emulsion, a separator, a secondary battery cell, a battery device, and an electrical device. Background Technology

[0004] As the application range of rechargeable battery cells becomes increasingly widespread, the demands on them are also growing, with higher requirements for energy density, lifespan, and reliability. Therefore, how to achieve higher energy density and better cycle performance in rechargeable battery cells while maintaining high reliability is a pressing technical problem that needs to be solved. Summary of the Invention

[0005] This disclosure provides a cross-linked styrene-based organic particle and its preparation method, a cross-linked styrene-based organic particle emulsion, a separator, a secondary battery cell, a battery device, and an electrical device. The secondary battery cell has high energy density, high reliability, and good cycle performance.

[0006] In a first aspect, this disclosure provides a separating membrane, comprising a porous base membrane and a coating located on at least one side of the porous base membrane, the coating comprising cross-linked styrene-based organic particles, the cross-linked styrene-based organic particles containing polar groups, the polar groups comprising one or more of ester groups, carboxyl groups, carboxylates, hydroxyl groups, cyano groups, and amide groups.

[0007] Cross-linked styrene-based organic particles have low density, allowing secondary battery cells to achieve higher gravimetric energy density. The cross-linked styrene-based organic particles disclosed herein exhibit good heat resistance. By using these particles in separators, they generate forces that resist separator shrinkage, thereby improving the overall thermal shrinkage of the separator, enhancing its heat resistance, and increasing the reliability of the secondary battery cell. The cross-linked styrene-based organic particles contain polar groups, including one or more of ester, carboxyl, carboxylate, hydroxyl, cyano, and amide groups. These polar groups have good electrolyte affinity, thereby reducing the surface tension of the cross-linked styrene-based organic particles, improving their electrolyte wettability, reducing the internal resistance of the secondary battery cell, and improving its cycle performance. These polar groups also readily form intermolecular forces with other substances in the separator coating, such as binders, thus improving compatibility with binders. Furthermore, these polar groups facilitate better coating of the coating slurry, improving coating quality and enhancing the cycle performance of the secondary battery cell. Therefore, the separator disclosed herein enables secondary battery cells to possess high energy density, high reliability, and good cycle performance.

[0008] In some embodiments, the cross-linked styrene-based organic particles include styrene or styrene derivative structural units and cross-linked structural units.

[0009] Optionally, the styrene or styrene derivative structural unit includes one or more of the following: styrene structural unit, 1-methyl-1-styrene structural unit, 4-methylstyrene structural unit, 2-methylstyrene structural unit, 2,4-dimethylstyrene structural unit, and 2,5-dimethylstyrene structural unit.

[0010] Optionally, the crosslinking structural unit includes one or more of the following: divinylbenzene structural unit, ethylene glycol dimethacrylate structural unit, pentaerythritol tetraacrylate structural unit, 1,4-butanediol diacrylate structural unit, 1,6-hexanediol diacrylate structural unit, 1,8-octanediol diacrylate structural unit, trimethylolpropane triacrylate structural unit, pentaerythritol trimethacrylate structural unit, tetraethylene glycol dimethacrylate structural unit, tripropylene glycol diacrylate structural unit, N,N-methylenebisacrylamide structural unit, N,N'-vinylbisacrylamide structural unit, 1,3,5-triacryloylhexahydro-1,3,5-triazine structural unit, and triallyl isocyanurate structural unit.

[0011] In some embodiments, the cross-linked styrene-based organic particles have no melting point.

[0012] The cross-linked styrene-based organic particles disclosed herein have no melting point, indicating that they have good heat resistance and thermal stability. This allows them to better resist the thermal shrinkage of the separator, improve the heat resistance of the separator, and enhance the reliability of the secondary battery cell.

[0013] In some embodiments, the glass transition temperature T of the cross-linked styrene organic particles g The temperature range is 110℃-165℃, or 115℃-165℃.

[0014] Glass transition temperature T of cross-linked styrene organic particles g Within the aforementioned range, it exhibits better thermal stability, better resisting the thermal shrinkage of the separator, improving the heat resistance of the separator, and enhancing the reliability of the secondary battery cell.

[0015] In some embodiments, the cross-linked styrene-based organic particles are amorphous polymers.

[0016] In some embodiments, the swelling degree of the cross-linked styrene organic particles after being soaked in a mixed solvent of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 3:7 at 60°C for 7 days is less than or equal to 3%.

[0017] Cross-linked styrene organic particles have low swelling in organic solvents and high structural stability during long-term use of secondary battery cells, thereby improving the problem of decreased air permeability of the separator during use.

[0018] In some embodiments, the dissolution rate of the cross-linked styrene organic particles after being soaked at 60°C for 7 days in a mixed solvent of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 3:7 is less than or equal to 3%.

[0019] Cross-linked styrene organic particles have a low dissolution rate in organic solvents, high structural stability during long-term use of secondary battery cells, and high chemical stability in electrolytes, thus enabling secondary battery cells to have long-cycle stability.

[0020] In some embodiments, the cyclic voltammetric curve of the cross-linked styrene organic particles in the first cycle does not have an oxidation peak in the voltage range of 2.5V to 4.4V.

[0021] The cyclic voltammetry curve of cross-linked styrene organic particles in the first cycle does not have an oxidation peak in the voltage range of 2.5V to 4.4V, indicating that the cross-linked styrene organic particles are stable in the voltage range of 2.5V to 4.4V and have good electrochemical stability. They can be applied to high-voltage secondary battery cells to improve the working voltage and energy density of secondary battery cells.

[0022] In some embodiments, the volume distribution particle size Dv10 of the cross-linked styrene organic particles is 40 nm-200 nm.

[0023] In some embodiments, the volume distribution particle size Dv50 of the cross-linked styrene organic particles is 82nm-300nm.

[0024] In some embodiments, the volume distribution particle size Dv90 of the cross-linked styrene organic particles is 140 nm-840 nm.

[0025] In some embodiments, the particle size distribution (Dv90-Dv10) / Dv50 of the cross-linked styrene organic particles is less than or equal to 3.2.

[0026] In some embodiments, the true density of the cross-linked styrene-based organic particles is 1.0 g / cm³. 3 -1.4g / cm 3 This allows secondary battery cells using the separator membrane disclosed herein to have a higher mass energy density.

[0027] In some embodiments, the cross-linked styrene-based organic particles in the coating constitute 50%-99% of the total mass of the coating.

[0028] In some embodiments, the thickness of the coating is 0.5 μm-5 μm.

[0029] In some embodiments, the areal density of the coating is 0.5 g / m³. 2 -5g / m 2 .

[0030] In some embodiments, the peel force between the coating and the porous base film is greater than or equal to 70 N / m.

[0031] In some embodiments, the ratio of the volume distribution particle size Dv50 of the cross-linked styrene organic particles to the average pore size of the porous base membrane is greater than or equal to 1.1.

[0032] Secondly, this disclosure provides cross-linked styrene-based organic particles, wherein the cross-linked styrene-based organic particles contain polar groups, and the polar groups include one or more of ester groups, carboxyl groups, carboxyl salts, hydroxyl groups, cyano groups, and amide groups.

[0033] In some embodiments, the cross-linked styrene-based organic particles include styrene or styrene derivative structural units and cross-linked structural units.

[0034] Optionally, the styrene or styrene derivative structural unit includes one or more of the following: styrene structural unit, 1-methyl-1-styrene structural unit, 4-methylstyrene structural unit, 2-methylstyrene structural unit, 2,4-dimethylstyrene structural unit, and 2,5-dimethylstyrene structural unit.

[0035] Optionally, the crosslinking structural unit includes one or more of the following: divinylbenzene structural unit, ethylene glycol dimethacrylate structural unit, pentaerythritol tetraacrylate structural unit, 1,4-butanediol diacrylate structural unit, 1,6-hexanediol diacrylate structural unit, 1,8-octanediol diacrylate structural unit, trimethylolpropane triacrylate structural unit, pentaerythritol trimethacrylate structural unit, tetraethylene glycol dimethacrylate structural unit, tripropylene glycol diacrylate structural unit, N,N-methylenebisacrylamide structural unit, N,N'-vinylbisacrylamide structural unit, 1,3,5-triacryloylhexahydro-1,3,5-triazine structural unit, and triallyl isocyanurate structural unit.

[0036] In some embodiments, the cross-linked styrene-based organic particles have no melting point.

[0037] In some embodiments, the glass transition temperature T of the cross-linked styrene organic particles g The temperature range is 110℃-165℃, or 115℃-165℃.

[0038] In some embodiments, the cross-linked styrene-based organic particles are amorphous polymers.

[0039] In some embodiments, the swelling degree of the cross-linked styrene organic particles after being soaked in a mixed solvent of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 3:7 at 60°C for 7 days is less than or equal to 3%.

[0040] In some embodiments, the dissolution rate of the cross-linked styrene organic particles after being soaked at 60°C for 7 days in a mixed solvent of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 3:7 is less than or equal to 3%.

[0041] In some embodiments, the cyclic voltammetric curve of the cross-linked styrene organic particles in the first cycle does not have an oxidation peak in the voltage range of 2.5V to 4.4V.

[0042] In some embodiments, the volume distribution particle size Dv10 of the cross-linked styrene organic particles is 40 nm-200 nm.

[0043] In some embodiments, the volume distribution particle size Dv50 of the cross-linked styrene organic particles is 82nm-300nm.

[0044] In some embodiments, the volume distribution particle size Dv90 of the cross-linked styrene organic particles is 140 nm-840 nm.

[0045] In some embodiments, the particle size distribution (Dv90-Dv10) / Dv50 of the cross-linked styrene organic particles is less than or equal to 3.2.

[0046] In some embodiments, the true density of the cross-linked styrene-based organic particles is 1.0 g / cm³. 3 -1.4g / cm 3 .

[0047] Thirdly, this disclosure provides a method for preparing crosslinked styrene-based organic particles, comprising the following steps: providing a pre-emulsion containing monomers, crosslinking agents, emulsifiers, initiators, water, and optionally functional monomers; performing an emulsion polymerization reaction under heating, inert gas protection, and stirring conditions to obtain crosslinked styrene-based organic particles, wherein the monomers include one or more of styrene and its derivatives; the mass fraction of the crosslinking agent is 3%-40% based on the total mass of the monomers, the crosslinking agent, and the functional monomers being 100%; at least one of the crosslinking agent, the emulsifier, and the functional monomers has a polar group, wherein the polar group includes one or more of ester groups, carboxyl groups, carboxylates, hydroxyl groups, cyano groups, and amide groups.

[0048] In some embodiments, the functional monomer includes one or more of an organic small molecule monomer having unsaturated bonds and a polymer, wherein at least one of the organic small molecule monomer having unsaturated bonds and the polymer has a polar group.

[0049] In some embodiments, the organic small molecule monomer having unsaturated bonds includes one or more of (meth)acrylic acid and its derivatives, (meth)acrylates and their derivatives, (meth)acrylates and their derivatives, acrylamide and its derivatives, acrylonitrile and its derivatives, and maleic anhydride and its derivatives.

[0050] In some embodiments, the polymer includes one or more of polyvinyl alcohol, polyvinylpyrrolidone, poly(meth)acrylic acid and its alkali metal salts, methoxy polyethylene glycol acrylate, polyethylene glycol acrylate, polypropylene glycol acrylate, polyethylene glycol diacrylate, polyethylene glycol methyl ether acrylate, polyethylene glycol ethyl ether acrylate, methoxy polyethylene glycol methacrylate, polyethylene glycol methacrylate, polypropylene glycol methacrylate, polyethylene glycol dimethacrylate, polyethylene glycol methyl ether methacrylate, polyethylene glycol ethyl ether methacrylate, and their respective derivatives.

[0051] In some embodiments, the monomer includes one or more of styrene, 1-methyl-1-styrene, 4-methylstyrene, 2-methylstyrene, 2,4-dimethylstyrene, and 2,5-dimethylstyrene.

[0052] In some embodiments, the crosslinking agent includes one or more of divinylbenzene, ethylene glycol dimethacrylate, pentaerythritol tetraacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,8-octanediol diacrylate, trimethylolpropane triacrylate, pentaerythritol trimethacrylate, tetraethylene glycol dimethacrylate, tripropylene glycol diacrylate, N,N-methylenebisacrylamide, N,N'-vinylbisacrylamide, 1,3,5-triacryloylhexahydro-1,3,5-triazine, and triallyl isocyanurate.

[0053] In some embodiments, the emulsifier includes one or more of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium polyacrylate, polyvinylpyrrolidone, polyvinyl alcohol, polyoxyethylene ether emulsifier, cellulose and its derivatives.

[0054] In some embodiments, the initiator includes one or more of sodium persulfate, potassium persulfate, ammonium persulfate, sodium sulfite, sodium bisulfite, azobisisobutyramidine hydrochloride, azobisisobutyramidine hydrochloride, and azobisisopropylimidazoline.

[0055] In some embodiments, the emulsifier has a mass fraction of 0.3%-5% based on the total mass of the monomer, the crosslinking agent, and the functional monomer (100%).

[0056] In some embodiments, the mass fraction of the functional monomer is 0%-10%, optionally 0.1%-9%, based on the total mass of the monomer, the crosslinking agent, and the functional monomer as 100%.

[0057] Fourthly, this disclosure provides a cross-linked styrene-based organic particle emulsion, which includes the cross-linked styrene-based organic particles of the second aspect, or is obtained by the method of the third aspect.

[0058] Fifthly, this disclosure provides a secondary battery cell, which includes a positive electrode, a negative electrode, and a separator according to the first aspect of this disclosure, wherein the separator is disposed between the positive electrode and the negative electrode.

[0059] In a sixth aspect, this disclosure provides a battery device comprising a plurality of secondary battery cells according to the fifth aspect of this disclosure.

[0060] In a seventh aspect, this disclosure provides an electrical device that includes a secondary battery cell according to the fifth aspect of this disclosure or a battery device according to the sixth aspect of this disclosure. Attached Figure Description

[0061] 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.

[0062] Figure 1 shows a schematic diagram of a secondary battery cell provided in some embodiments of this disclosure.

[0063] Figure 2 shows a schematic diagram of an electrical device provided in some embodiments of this disclosure.

[0064] The accompanying drawings are not necessarily drawn to scale. Detailed Implementation

[0065] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of cross-linked styrene-based organic particles, methods for preparing the same, cross-linked styrene-based organic particle emulsions, separators, secondary battery cells, battery devices, and electrical devices 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.

[0066] 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.

[0067] 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 as included in the disclosure of this disclosure.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] In this disclosure, the terms "multiple" or "a variety" refer to two or more kinds.

[0072] 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.

[0073] Unless otherwise stated, the test temperature for all parameters mentioned in this disclosure is 25°C.

[0074] The secondary battery cell mentioned in the embodiments of this disclosure can independently perform charge and discharge functions. After discharge, it can be recharged to activate the active materials and continue to be used. The secondary battery cell can be cylindrical, cuboid, or other shapes, etc., and the embodiments of this disclosure are not limited to this. Figure 1 shows a cuboid secondary battery cell 5 as an example.

[0075] The secondary 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.

[0076] The secondary battery cell provided in the embodiments of this disclosure includes an electrode assembly. The electrode assembly can be a wound structure or a stacked structure, and the embodiments of this disclosure are not limited in this regard. The secondary battery cell also includes an outer packaging, which can be used to encapsulate the electrode assembly. The outer packaging can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging can also be a soft package, such as a pouch-type soft package. The material of the soft package can be plastic, such as one or more of aluminum-plastic film, polypropylene, polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0077] 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 secondary battery cells, which are connected in series, parallel, or mixed connections via a busbar.

[0078] In some embodiments, a battery cell assembly is typically formed by arranging multiple secondary battery cells.

[0079] As an example, a battery cell assembly can be a battery module, which is formed by arranging and fixing multiple secondary battery cells together to form an independent module. As another example, a battery module can be formed by bundling multiple secondary battery cells together with cable ties.

[0080] 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.

[0081] As an example, the battery cell assembly can be a battery module, which can be housed in a housing by fixing the battery module in the housing.

[0082] As an example, battery cell assemblies can also be housed in a housing by directly fixing multiple secondary battery cells to the housing.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] The technical solutions described in this disclosure are applicable to various electrical devices that use secondary 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. Secondary battery cells and battery devices are used to store or provide electrical energy.

[0087] 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.

[0088] In the context of this disclosure, the "crosslinked styrene-based organic particles" primarily serve to improve heat resistance in the coating of the release liner, and they have almost no adhesive properties.

[0089] The separator is a crucial component supporting the electrochemical processes of charging and discharging in a secondary battery cell. Commonly used separators are often made of polyolefins; however, polyolefins have poor heat resistance and are prone to softening or melting at high temperatures, which can lead to short circuits in the secondary battery cells. To improve the heat resistance of the separator, a coating is usually applied. Boehmite, alumina, and other inorganic particles are commonly used heat-resistant fillers; however, these fillers have high density and a large mass for the same bulk volume, thus affecting the energy density of the secondary battery cells.

[0090] Based on this, embodiments of this disclosure provide cross-linked styrene-based organic particles, which, when used in a separator membrane, enable secondary battery cells to possess high energy density, high reliability, and good cycle performance.

[0091] The cross-linked styrene-based organic particles disclosed herein contain polar groups, which include one or more of the following: ester group, carboxyl group, carboxyl salt, hydroxyl group, cyano group, and amide group.

[0092] Cross-linked styrene organic particles have low density, and secondary battery cells using them can have higher gravimetric energy density.

[0093] Glass transition temperature T of non-crosslinked styrene organic particles g Small size and poor heat resistance. The cross-linked styrene-based organic particles disclosed herein have better heat resistance. By using cross-linked styrene-based organic particles in a separator, the cross-linked styrene-based organic particles can generate a force that resists the shrinkage of the separator, thereby improving the overall thermal shrinkage of the separator, enhancing the heat resistance of the separator, and improving the reliability of the secondary battery cells.

[0094] Cross-linked styrene-based organic particles contain polar groups, including one or more of ester, carboxyl, carboxyl, hydroxyl, cyano, and amide groups. These polar groups have good electrolyte affinity, which can reduce the surface tension of the cross-linked styrene-based organic particles, improve their electrolyte wettability, reduce the internal resistance of the secondary battery cells, and enhance the cycle performance of the secondary battery cells. These polar groups also readily form intermolecular forces with other substances in the separator coating, such as binders, thereby improving compatibility with binders, etc. These polar groups also facilitate better coating of the coating slurry, improve the coating quality, and enhance the cycle performance of the secondary battery cells.

[0095] Therefore, the cross-linked styrene organic particles disclosed herein, when used in separator membranes, enable secondary battery cells to possess high energy density, high reliability, and good cycle performance.

[0096] In some embodiments, the true density of cross-linked styrene-based organic particles can be 1.0 g / cm³. 3 -1.4g / cm3 .

[0097] Currently, the true density of inorganic particles such as boehmite and alumina is typically 2.5 g / cm³. 3 -3.5g / cm 3 The cross-linked styrene-based organic particles of this disclosure have a low true density, thereby enabling secondary battery cells using the separator of this disclosure to have a higher mass energy density.

[0098] In some embodiments, cross-linked styrene-based organic particles include styrene or styrene derivative structural units and cross-linked structural units.

[0099] The cross-linking structural unit of cross-linked styrene organic particles refers to the structural unit used to connect styrene or styrene derivative structural units.

[0100] Optionally, the styrene or styrene derivative structural unit may include one or more of the following: styrene structural unit, 1-methyl-1-styrene structural unit, 4-methylstyrene structural unit, 2-methylstyrene structural unit, 2,4-dimethylstyrene structural unit, and 2,5-dimethylstyrene structural unit.

[0101] Optionally, the crosslinking structural unit may include one or more of the following: divinylbenzene structural unit, ethylene glycol dimethacrylate structural unit, pentaerythritol tetraacrylate structural unit, 1,4-butanediol diacrylate structural unit, 1,6-hexanediol diacrylate structural unit, 1,8-octanediol diacrylate structural unit, trimethylolpropane triacrylate structural unit, pentaerythritol trimethacrylate structural unit, tetraethylene glycol dimethacrylate structural unit, tripropylene glycol diacrylate structural unit, N,N-methylenebisacrylamide structural unit, N,N'-vinylbisacrylamide structural unit, 1,3,5-triacryloylhexahydro-1,3,5-triazine structural unit, and triallyl isocyanurate structural unit.

[0102] The cross-linked styrene organic particles disclosed herein are poorly soluble in both water and organic solvents, such as tetrahydrofuran (THF), dichloromethane (DCM), dimethylformamide (DMF), trichlorobenzene (TCB), and chloroform, at 25°C. They are also insoluble in the mobile phase used in gel permeation chromatography and the molecular weight of the cross-linked styrene organic particles cannot be determined by gel permeation chromatography.

[0103] In some embodiments, cross-linked styrene-based organic particles have no melting point.

[0104] The cross-linked styrene-based organic particles disclosed herein have no melting point, indicating that they have good heat resistance and thermal stability. This allows them to better resist the thermal shrinkage of the separator, improve the heat resistance of the separator, and enhance the reliability of the secondary battery cell.

[0105] Melting point can be tested as follows: Take an appropriate amount of sample (e.g., 5mg-15mg) and place it in the crucible of a differential scanning calorimeter (DSC), level it, and cover the crucible. Parameter settings: nitrogen atmosphere, purge gas 60mL / min, protective gas 20mL / min; program settings: heat from 25℃ to 200℃ at a heating rate of 10℃ / min, hold for 5min to eliminate thermal history, then cool from 200℃ to -40℃ at a cooling rate of 10℃ / min, and then heat to 300℃ at a heating rate of 10℃ / min. The DSC curve is used to determine whether the organic particles have a melting point below 300℃. Cross-linked styrene organic particles having no melting point means that the DSC curve of the cross-linked styrene organic particles does not show a melting peak.

[0106] In some embodiments, the glass transition temperature T of cross-linked styrene organic particles g The temperature range is 110℃-165℃, for example, 110℃, 111℃, 112℃, 113℃, 114℃, 115℃, 116℃, 117℃, 118℃, 119℃, 120℃, 121℃, 122℃, 123℃, 124℃, 125℃, 126℃, 127℃, 128℃, 129℃, 130℃, 131℃, 132℃, 133℃, 134℃, 135℃, 136℃, 13... 7℃, 138℃, 139℃, 140℃, 141℃, 142℃, 143℃, 144℃, 145℃, 146℃, 147℃, 148℃, 149℃, 150℃, 151℃, 152℃, 153℃, 154℃, 155℃, 156℃, 157℃, 158℃, 159℃, 160℃, 161℃, 162℃, 163℃, 164℃, 165℃, or any range of the above values.

[0107] Currently, the glass transition temperature Ti of non-crosslinked styrene organic particles and commercially available crosslinked styrene organic particles is... g Small, typically below 100°C. The glass transition temperature Tcrosslinked styrene-based organic particles disclosed herein are... g With a temperature range of 110℃-165℃, it has high thermal stability, which can better resist the thermal shrinkage of the separator, improve the heat resistance of the separator, and improve the reliability of the secondary battery cells.

[0108] Optionally, the glass transition temperature T of the cross-linked styrene-based organic particles... gThe temperature ranges are 114℃-165℃, 115℃-165℃, 118℃-165℃, 120℃-165℃, 126℃-165℃, 132℃-165℃, 136℃-165℃, 140℃-165℃, and 145℃-165℃.

[0109] Glass transition temperature T of cross-linked styrene organic particles g The test can be performed as follows: Take an appropriate amount of sample (e.g., 5mg-15mg) and place it in the crucible of the differential scanning calorimeter (DSC), level it, and cover the crucible. Parameter settings: nitrogen atmosphere, purge gas 60mL / min, protective gas 20mL / min; program settings: heat from 25℃ to 200℃ at a heating rate of 10℃ / min, hold for 5min to eliminate thermal history, then cool from 200℃ to -40℃ at a cooling rate of 10℃ / min, and then heat to 300℃ at a heating rate of 10℃ / min. The glass transition temperature T is obtained from the DSC curve. g .

[0110] In some embodiments, the cross-linked styrene-based organic particles are amorphous polymers.

[0111] In some embodiments, the swelling degree of cross-linked styrene organic particles soaked in a mixed solvent of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 3:7 at 60°C for 7 days can be less than or equal to 3%.

[0112] Cross-linked styrene organic particles have low swelling in organic solvents and high structural stability during long-term use of secondary battery cells, thereby improving the problem of decreased air permeability of the separator during use.

[0113] The swelling degree of cross-linked styrene organic particles can be tested as follows: Take an appropriate amount of sample (e.g., about 1g), denoted as m1, and place it in a semi-permeable membrane sample bag. Seal the bag; the sample bag should be permeable to the solvent but not to the sample. Immerse the sample bag in an appropriate amount of solvent (e.g., about 50g) at 60°C for 7 days. After immersion, remove the sample bag and the sample from the bag. Wipe away excess solvent and weigh the sample again, m2. Swelling degree = (m2-m1) / m1×100%. The solvent is a mixed solvent obtained by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7.

[0114] In some embodiments, the dissolution rate of cross-linked styrene organic particles after being soaked at 60°C for 7 days in a mixed solvent of ethylene carbonate and ethyl methyl carbonate in a volume ratio of 3:7 can be less than or equal to 3%.

[0115] Cross-linked styrene organic particles have a low dissolution rate in organic solvents, high structural stability during long-term use of secondary battery cells, and high chemical stability in electrolytes, thus enabling secondary battery cells to have long-cycle stability.

[0116] The dissolution rate of cross-linked styrene organic particles can be tested as follows: Take an appropriate amount of sample (e.g., about 1g), and record its mass as m1. Place it in a semi-permeable membrane sample bag, seal it, and record the total mass of the sample bag as m2. The sample bag is permeable to the solvent but not to the sample. Immerse the sample bag in an appropriate amount of solvent (e.g., about 50g) at 60°C for 7 days. After that, remove the sample bag, drain it, dry it, and weigh the total mass of the sample bag again as m3. Dissolution rate = (m2-m3) / m1 × 100%. The solvent is a mixed solvent obtained by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 3:7.

[0117] In some embodiments, the cyclic voltammetry curves of the cross-linked styrene organic particles during the first cycle do not exhibit oxidation peaks in the voltage range of 2.5V to 4.4V.

[0118] The cyclic voltammetry curve of cross-linked styrene organic particles in the first cycle does not have an oxidation peak in the voltage range of 2.5V to 4.4V, indicating that the cross-linked styrene organic particles are stable in the voltage range of 2.5V to 4.4V and have good electrochemical stability. They can be applied to high-voltage secondary battery cells to improve the working voltage and energy density of secondary battery cells.

[0119] The oxidation peak potential of the cyclic voltammetric curve of cross-linked styrene-based organic particles can be tested as follows: Organic particles, binder polyacrylate, and conductive agent conductive carbon black are dissolved in water at a solid content mass ratio of 64:7:29 to prepare a slurry. The slurry is coated onto aluminum foil as the positive electrode, and lithium foil is used as the negative electrode to assemble a coin cell. Cyclic voltammetry (CV) is performed on the coin cell at a scan rate of 0.10 mV / s, a voltage range of 2.50 V–5.00 V, and 3 cycles. The voltage corresponding to the peak point of the first cyclic voltammetric curve is taken as the oxidation peak potential. The electrolyte used in the test is LiPF6 with a concentration of 1 mol / L. The solvent of the electrolyte is obtained by mixing ethylene carbonate (EC) and ethyl methyl carbonate (EMC) at a volume ratio of 3:7.

[0120] In some embodiments, the volume distribution particle size Dv10 of cross-linked styrene organic particles can be 40 nm to 200 nm.

[0121] In some embodiments, the volume distribution particle size Dv50 of the cross-linked styrene organic particles can be 82nm-300nm.

[0122] In some embodiments, the volume distribution particle size Dv90 of the cross-linked styrene organic particles can be 140 nm to 840 nm.

[0123] In some embodiments, the particle size distribution (Dv90-Dv10) / Dv50 of the cross-linked styrene organic particles can be less than or equal to 3.2.

[0124] Dv10, Dv50, and Dv90 represent the particle sizes corresponding to a cumulative volumetric distribution percentage of 10%, 50%, and 90%, respectively. These values ​​can be determined using a laser particle size analyzer, referring to GB / T 19077-2016. During testing, add 1g of the sample to a clean small beaker and 20ml of deionized water. Sonicate at 53kHz / 120W for 5 minutes to ensure complete dispersion. Turn on the laser particle size analyzer, clean the optical path system, and automatically test the background. Stir the sonicated solution to ensure uniform dispersion, place it in the sample cell as required, and begin measuring the particle size. A MasterSizer 3000 laser particle size analyzer can be used as the testing instrument.

[0125] This disclosure also provides a method for preparing cross-linked styrene-based organic particles, which can prepare the above-mentioned cross-linked styrene-based organic particles.

[0126] A method for preparing crosslinked styrene-based organic particles includes the following steps: providing a pre-emulsion comprising monomers, a crosslinking agent, an emulsifier, an initiator, water, and optionally a functional monomer; and carrying out an emulsion polymerization reaction under heating, inert gas protection, and stirring conditions to obtain crosslinked styrene-based organic particles. The monomers include one or more of styrene and its derivatives. The crosslinking agent has a mass fraction of 3%-40% based on the total mass of the monomers, crosslinking agent, and functional monomers (100%). At least one of the crosslinking agent, emulsifier, and functional monomer has a polar group, which includes one or more of ester, carboxyl, carboxylate, hydroxyl, cyano, and amide groups.

[0127] The cross-linked styrene-based organic particles provided in this embodiment are obtained by emulsion polymerization, and a high content of cross-linking agent is added during the emulsion polymerization process. This high content of cross-linking agent gives the obtained cross-linked styrene-based organic particles good heat resistance. At least one of the cross-linking agent, emulsifier, and functional monomer has a polar group, including one or more of ester, carboxyl, carboxylate, hydroxyl, cyano, and amide groups. These polar groups have good electrolyte affinity, thereby reducing the surface tension of the cross-linked styrene-based organic particles, improving their electrolyte wettability, reducing the internal resistance of the secondary battery cell, and improving the cycle performance of the secondary battery cell. These polar groups also readily form intermolecular forces with other substances in the separator coating, such as binders, thereby improving compatibility with binders, etc. These polar groups also facilitate better coating of the coating slurry, improving the coating quality and enhancing the cycle performance of the secondary battery cell.

[0128] The presence of a polar group in at least one of the crosslinking agent, emulsifier, and functional monomer includes the following cases: the preemulsion does not contain a functional monomer, and the crosslinking agent and / or emulsifier has a polar group; the preemulsion contains a functional monomer, and one, two, or three of the crosslinking agent, emulsifier, and functional monomer have a polar group.

[0129] In some embodiments, the functional monomer may include one or more of an organic small molecule monomer having unsaturated bonds and a polymer, wherein at least one of the organic small molecule monomer having unsaturated bonds and the polymer has a polar group.

[0130] Optionally, the organic small molecule monomer having unsaturated bonds may include one or more of (meth)acrylic acid and its derivatives, (meth)acrylates and their derivatives, (meth)acrylates and their derivatives, acrylamide and its derivatives, acrylonitrile and its derivatives, and maleic anhydride and its derivatives.

[0131] Optionally, the polymer may include one or more of polyvinyl alcohol, polyvinylpyrrolidone, poly(meth)acrylic acid and its alkali metal salts, methoxy polyethylene glycol acrylate, polyethylene glycol acrylate, polypropylene glycol acrylate, polyethylene glycol diacrylate, polyethylene glycol methyl ether acrylate, polyethylene glycol ethyl ether acrylate, methoxy polyethylene glycol methacrylate, polyethylene glycol methacrylate, polypropylene glycol methacrylate, polyethylene glycol dimethacrylate, polyethylene glycol methyl ether methacrylate, polyethylene glycol ethyl ether methacrylate, and their respective derivatives.

[0132] Optionally, the polymer has a molecular weight of less than 5000.

[0133] In some embodiments, the mass fraction of the functional monomer can be 0%-10% based on the total mass of the monomer, crosslinking agent, and functional monomer as 100%. 0% indicates that the preemulsion does not contain functional monomer.

[0134] Optionally, based on the total mass of monomers, crosslinking agents, and functional monomers of 100%, the mass fraction of functional monomers can be 0.1%-9%, for example, it can be 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or any range of the above values.

[0135] Alternatively, the mass fraction of the functional monomer can be 0.5%-8%, 1%-8%, or 2%-8%, based on the total mass of the monomer, crosslinking agent, and functional monomer as 100%.

[0136] The mass fraction of the crosslinking agent is 3%-40%, for example, it can be 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, or any combination of the above values.

[0137] Optionally, the mass fraction of the crosslinking agent can be 7%-40%, 9%-40%, 11%-40%, 13%-40%, 15%-40%, 7%-35%, 9%-35%, 11%-35%, 13%-35%, 15%-35%, 7%-31%, 9%-31%, 11%-31%, 13%-31%, or 15%-31%.

[0138] In some embodiments, the monomer may include one or more of styrene, 1-methyl-1-styrene, 4-methylstyrene, 2-methylstyrene, 2,4-dimethylstyrene, and 2,5-dimethylstyrene.

[0139] The cross-linking agent polymerizes with the monomer to form cross-linked styrene organic particles, which are cross-linked structural units.

[0140] In some embodiments, the crosslinking agent may include one or more of divinylbenzene, ethylene glycol dimethacrylate, pentaerythritol tetraacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,8-octanediol diacrylate, trimethylolpropane triacrylate, pentaerythritol trimethacrylate, tetraethylene glycol dimethacrylate, tripropylene glycol diacrylate, N,N-methylenebisacrylamide, N,N'-vinylbisacrylamide, 1,3,5-triacryloylhexahydro-1,3,5-triazine, and triallyl isocyanurate.

[0141] In some embodiments, the emulsifier may include one or more of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, sodium polyacrylate, polyvinylpyrrolidone, polyvinyl alcohol, polyoxyethylene ether emulsifier, cellulose and its derivatives.

[0142] Optionally, the polyoxyethylene ether emulsifier may include OP-type emulsifiers, such as OP-4, OP-7, OP-10, OP-15, OP-20, etc.

[0143] In some embodiments, the mass fraction of the emulsifier may be 0.3%-5% based on the total mass of monomers, crosslinking agents, and functional monomers as 100%.

[0144] In some embodiments, the initiator may be one or more of sodium persulfate, potassium persulfate, ammonium persulfate, sodium sulfite, sodium bisulfite, azobisisobutyramidine hydrochloride, azobisisobutyramidine hydrochloride, and azobisisopropylimidazoline.

[0145] In some embodiments, the maturation temperature of the emulsion polymerization reaction can be 70℃-92℃, for example, it can be 70℃, 71℃, 72℃, 73℃, 74℃, 75℃, 76℃, 77℃, 78℃, 79℃, 80℃, 81℃, 82℃, 83℃, 84℃, 85℃, 86℃, 87℃, 88℃, 89℃, 90℃, 91℃, 92℃, or any range of the above values. Optionally, the maturation temperature of the emulsion polymerization reaction can be 72℃-92℃.

[0146] In some embodiments, the maturation time of the emulsion polymerization reaction can be 1h-6h, for example, it can be 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, 6h or any range of the above values.

[0147] In some embodiments, the emulsion polymerization reaction may include the following steps: adding a pre-emulsion dropwise into a reactor containing water under a first heating temperature, inert gas protection, and stirring conditions; after a first reaction time, raising the temperature to a ripening temperature for ripening reaction to obtain cross-linked styrene-based organic particles.

[0148] Optionally, the first heating temperature can be 55℃-70℃.

[0149] Optionally, the first time can be 3h-6h.

[0150] In some embodiments, the method for preparing cross-linked styrene-based organic particles may further include a demagnetization treatment step after the emulsion polymerization reaction is completed.

[0151] This disclosure also provides a cross-linked styrene-based organic particulate emulsion.

[0152] The cross-linked styrene organic particle emulsion includes the cross-linked styrene organic particles of this disclosure, or is obtained by the preparation method of the cross-linked styrene organic particles of this disclosure.

[0153] This disclosure also provides a separating membrane. The separating membrane includes a porous base membrane and a coating located on at least one side of the porous base membrane. The coating includes an adhesive and cross-linked styrene-based organic particles of this disclosure or cross-linked styrene-based organic particles prepared by the method of this disclosure.

[0154] Both the porous base membrane and the coating have a porous structure, which gives the separator good air permeability and facilitates ion passage. The cross-linked styrene-based organic particles in the coating are interconnected and fixed by a binder; the gaps between these particles form a porous structure.

[0155] In some embodiments, the mass content of cross-linked styrene-based organic particles in the coating may be 50%-99% based on the total mass of the coating.

[0156] Optionally, the mass content of cross-linked styrene-based organic particles in the coating can be 60%-99%, 70%-99%, 80%-99%, 85%-99%, 88%-99%, 80%-97%, 85%-97%, 88%-97%, 80%-95%, 85%-95%, or 88%-95%.

[0157] In some embodiments, the binder in the coating may include, but is not limited to, one or more of the following: polyacrylate binders, nitrile rubber binders, polyacrylic acid, polymethacrylic acid, sodium polyacrylate, polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0158] In some embodiments, the coating may further include a dispersant, such as one or more of alkylphenol polyoxyethylene ethers, polyacrylic acid dispersants, and cellulose dispersants, including but not limited to. For example, the dispersant may include one or more of sodium carboxymethyl cellulose, sodium polyacrylate, and ammonium polyacrylate.

[0159] In some embodiments, the separator may also include polymer binder particles.

[0160] The "polymer binder particles" in the porous coating of the separator membrane play a role in improving the adhesion between the separator membrane and the electrode, but they have virtually no high-temperature resistance.

[0161] In some embodiments, polymer binder particles may be embedded in cross-linked styrene-based organic particles and form protrusions on the coating surface.

[0162] In other embodiments, the coating of the separator includes a heat-resistant layer and an adhesive layer. The heat-resistant layer is disposed on a porous base membrane, and the adhesive layer is disposed on at least a portion of the surface of the heat-resistant layer on the side away from the porous base membrane. Crosslinked styrene-based organic particles are disposed in the heat-resistant layer, and polymer adhesive particles are disposed in the adhesive layer.

[0163] In some other embodiments, the coating of the separator includes a heat-resistant layer and an adhesive layer. The heat-resistant layer is disposed on one side of the porous base membrane, and the adhesive layer is disposed on at least a portion of the surface of the other side of the porous base membrane. Crosslinked styrene-based organic particles are disposed in the heat-resistant layer, and polymer adhesive particles are disposed in the adhesive layer.

[0164] In some embodiments, the average particle size of the polymer binder particles can be 6 μm-18 μm.

[0165] In some embodiments, the polymer binder particles may include vinylidene fluoride polymer particles, such as polyvinylidene fluoride (PVDF) particles and / or copolymer particles of vinylidene fluoride monomer and comonomer.

[0166] Comonomers may include at least one of olefin monomers, fluorinated olefin monomers, chlorinated olefin monomers, acrylate monomers, acrylic monomers, and fluoroether monomers.

[0167] Optionally, the comonomer may include at least one of the following: trifluoroethylene, trifluorochloroethylene, 1,2-difluoroethylene, tetrafluoroethylene, hexafluoropropylene, perfluoro(alkyl vinyl) ether (e.g., perfluoro(methyl vinyl) ether, perfluoro(ethyl vinyl) ether, perfluoro(propyl vinyl) ether), perfluoro(1,3-m-dioxacyclopentene), and perfluoro(2,2-dimethyl-1,3-m-dioxacyclopentene).

[0168] In some embodiments, the coating thickness can be 0.5 μm-5 μm. The coating thickness refers to the thickness of the coating on one side of the porous base film. Optionally, the coating thickness can be 0.5 μm-4 μm, 0.5 μm-3 μm, 0.5 μm-2 μm, 0.8 μm-4 μm, 0.8 μm-3 μm, or 0.8 μm-2 μm.

[0169] In some embodiments, the areal density of the coating may be 0.5 g / m³. 2 -5g / m 2 .

[0170] In some embodiments, the porous base membrane may comprise a membrane selected from any one or at least two of the following: polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyamide, polycarbonate, polyimide, polyetheretherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene ether, cyclic olefin copolymer, polyphenylene sulfide, and polyvinyl naphthalene.

[0171] Porous base membranes can be single-layer thin films or multi-layer composite thin films. When a porous base membrane is a multi-layer composite thin film, the materials of each layer can be the same or different.

[0172] In some embodiments, the thickness of the porous base film can be 4μm-12μm, and optionally 4μm-9μm.

[0173] In some embodiments, the porosity of the porous base membrane can be 25%-60%, optionally 28%-50%.

[0174] In some embodiments, the ratio of the volume distribution particle size Dv50 of the cross-linked styrene organic particles to the average pore size of the porous base membrane can be greater than or equal to 1.1.

[0175] The volume distribution particle size Dv50 of cross-linked styrene organic particles has the same unit, e.g., nm, as the average pore size of the porous base membrane.

[0176] This can reduce pore blockage and improve the air permeability and ion conduction properties of the separator.

[0177] In some embodiments, the average pore size of the porous base film can be 25 nm to 82 nm.

[0178] The average pore size of the porous membrane can be measured using a capillary porosity analyzer (bubble point method). An exemplary testing method is as follows: Take a circular sample with a diameter of 25 mm, and drop 3-5 drops of wetting solution onto it. After the sample is completely wetted, place it in a mold. Then, use an inert gas (such as nitrogen) to compress the wetting solution in the pores of the sample. The compression pressure and flow rate are inversely proportional to the pore size. The average pore size of the sample is obtained through software sampling and pressure-pore size conversion analysis. The testing instrument can be a PMI CFP 1500 pore size analyzer, with a testing pressure ranging from 100 psi to 350 psi.

[0179] In some embodiments, the thickness of the separator can be 5μm-14μm, optionally 5μm-12μm or 6μm-12μm. This is beneficial for improving the energy density of the secondary battery cell.

[0180] In some embodiments, the peel force between the coating and the porous base film can be greater than or equal to 70 N / m, and optionally greater than or equal to 75 N / m, 80 N / m, 85 N / m, or 90 N / m. This can improve the heat resistance of the separator, enhance the overall structural stability of the coating, and reduce powder shedding.

[0181] The peel force between the coating and the porous base membrane can be tested as follows: Cut the release liner into three 2.5cm × 15cm strips, attach the strips to a test steel plate, and attach 2cm wide test tape to the side of the release liner to be tested. Use a tensile testing machine, clamping the steel plate on one side and the tape on the other, to perform a 180° peel test. Take the average peel force of the three strips as the peel force between the release liner coating and the porous base membrane. The tensile rate is 50mm / min.

[0182] It should be noted that the coating parameters of the above-mentioned separators are coating parameters for one side of the porous base membrane. When the coating is applied to both sides of the porous base membrane, if the coating parameters of either side meet the requirements of this disclosure, it is considered to fall within the protection scope of this disclosure.

[0183] The separator membrane can be prepared according to methods known in the art.

[0184] In some embodiments, a slurry comprising cross-linked styrene organic particles and a binder can be coated on at least one side of a porous base membrane, and after drying, a separation membrane is obtained.

[0185] In some embodiments, the slurry may further include polymer binder particles, which, after drying, are embedded in cross-linked styrene-based organic particles and form protrusions on the coating surface.

[0186] In some embodiments, the method for preparing the isolation membrane may include: applying a heat-resistant layer slurry comprising cross-linked styrene organic particles and a binder to at least one side of a porous base membrane, and drying it to form a heat-resistant layer; and applying an adhesive layer slurry comprising polymer binder particles and a binder to at least a portion of the surface of the heat-resistant layer, and drying it to obtain the isolation membrane.

[0187] In some embodiments, the method for preparing the separator membrane may include: coating a heat-resistant slurry comprising cross-linked styrene organic particles and a binder onto one side of a porous base membrane, and coating an adhesive layer slurry comprising polymer binder particles and a binder onto at least a portion of the surface of the other side of the porous base membrane, and drying the slurry to obtain the separator membrane.

[0188] In some embodiments, the solvent for the slurry may be water, such as deionized water.

[0189] In some embodiments, the slurry may also include other components, such as dispersants and / or wetting agents.

[0190] This disclosure also provides a secondary battery cell. The secondary battery cell includes the separator provided in this disclosure. This allows the secondary battery cell to possess high energy density, high reliability, and good cycle performance.

[0191] A secondary battery cell also includes a positive electrode, a negative electrode, and an electrolyte, with a separator disposed between the positive and negative electrodes. The positive electrode, separator, and negative electrode can be formed into an electrode assembly through a winding process and / or a stacking process.

[0192] The secondary battery cells disclosed herein may include, but are not limited to, lithium battery cells, sodium battery cells, etc. The composition of the positive electrode, negative electrode and electrolyte may differ depending on the type of secondary battery cell.

[0193] [Positive electrode plate]

[0194] 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.

[0195] Taking a lithium-ion battery cell as an example, the positive electrode active material may 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 may 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 may 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. In some embodiments, to further improve the energy density of the secondary battery cell, the positive electrode active material may include materials with 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, Li undergoes insertion / extraction and consumption in a single secondary 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 feeding. When the positive electrode active material is applied to a secondary battery cell, the molar Li content changes after charge-discharge cycles. Similarly, in the examples of positive electrode active materials in this disclosure, the molar O content is only a theoretical value. Lattice oxygen release causes changes in the molar O content, and the actual molar O content will also fluctuate.

[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 current collector and a negative electrode film layer disposed on at least one surface of the negative current collector and comprising a negative electrode active material. For example, the negative 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 current collector.

[0206] The negative electrode active material may be any material known in the art for use in secondary 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 undercoat layer (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] [Electrolytes]

[0215] The electrolyte plays a role in conducting ions between the positive and negative electrode plates.

[0216] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and an organic solvent.

[0217] 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).

[0218] 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 difluorosulfonyl imide (NaFSI), sodium difluoromethanesulfonyl imide (NaTFSI), sodium trifluoromethanesulfonate (NaTFS), sodium difluorooxalate borate (NaDFOB), sodium dioxalate borate (NaBOB), sodium difluorophosphate (NaPO2F2), sodium difluorodioxalate phosphate (NaDFOP), and sodium tetrafluorooxalate phosphate (NaTFOP).

[0219] In some embodiments, 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), butyl ester 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.

[0220] 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 secondary battery cell, such as additives that improve overcharge performance, additives that improve high-temperature performance, additives that improve low-temperature performance, etc.

[0221] Optionally, the additive may include one or more of fluoroethylene carbonate (FEC), vinylene carbonate (VC), 1,3-propanesulfonate lactone (PS), and ethylene sulfate (DTD).

[0222] Methods for preparing secondary battery cells are well known. In some embodiments, a positive electrode, a separator, a negative electrode, and an electrolyte can be assembled to form a secondary battery cell. As an example, the positive electrode, separator, and negative electrode can be formed into an electrode assembly through a winding process and / or a stacking process. The electrode assembly is placed in an outer packaging, dried, and then injected with the aforementioned electrolyte. After vacuum sealing, settling, and formation processes, a secondary battery cell is obtained.

[0223] Example

[0224] 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.

[0225] 0.8 g sodium dodecyl sulfate, 80 mg sodium persulfate, 20 ml deionized water, 31.4 g styrene, 6 g divinylbenzene, 2 g acrylic acid, and 0.6 g methoxy polyethylene glycol acrylate were emulsified to obtain a pre-emulsion for later use. 140 g deionized water was added to a reactor, the temperature was raised to 70 °C, and the prepared pre-emulsion was added dropwise under nitrogen protection and stirring. After reacting for 4 hours, the temperature was raised to 85 °C and the reaction was allowed to mature for 1.5 hours to obtain organic particle emulsion #1.

[0226] A pre-emulsion was prepared by emulsifying 0.8 g sodium dodecyl sulfate, 80 mg sodium persulfate, 20 ml deionized water, 31.4 g styrene, 6 g divinylbenzene, 2 g acrylonitrile, and 0.6 g methoxy polyethylene glycol acrylate. 140 g deionized water and 15 mg sodium polyacrylate were added to a reactor, and the temperature was raised to 70 °C. Under nitrogen protection and stirring, the prepared pre-emulsion was added dropwise. After reacting for 4 hours, the temperature was raised to 85 °C and the reaction was allowed to mature for 1.5 hours to obtain organic particle emulsion #2.

[0227] A pre-emulsion was prepared by emulsifying 0.8 g sodium dodecyl sulfate, 80 mg sodium persulfate, 20 ml deionized water, 31.4 g styrene, 6 g divinylbenzene, 2 g acrylamide, and 0.6 g methoxy polyethylene glycol acrylate. 140 g deionized water and 15 mg sodium polyacrylate were added to a reactor, and the temperature was raised to 70 °C. Under nitrogen protection and stirring, the prepared pre-emulsion was added dropwise. After reacting for 4 hours, the temperature was raised to 85 °C and the reaction was allowed to mature for 1.5 hours to obtain organic particle emulsion #3.

[0228] A pre-emulsion was prepared by emulsifying 0.8 g sodium dodecyl sulfate, 80 mg sodium persulfate, 20 ml deionized water, 31.4 g styrene, 6 g divinylbenzene, 1 g acrylonitrile, 1 g acrylamide, and 0.6 g methoxy polyethylene glycol acrylate. 140 g deionized water and 15 mg sodium polyacrylate were added to a reactor, and the temperature was raised to 70 °C. Under nitrogen protection and stirring, the prepared pre-emulsion was added dropwise. After reacting for 4 hours, the temperature was raised to 85 °C and the reaction was allowed to mature for 1.5 hours to obtain organic particle emulsion #4.

[0229] 0.8 g sodium dodecyl sulfate, 80 mg sodium persulfate, 20 ml deionized water, 31.4 g styrene, 6 g divinylbenzene, 1 g acrylonitrile, 1 g acrylamide, and 0.6 g methoxy polyethylene glycol acrylate were emulsified to obtain a pre-emulsion for later use. 140 g deionized water was added to a reactor, and the temperature was raised to 70 °C. Under nitrogen protection and stirring, the prepared pre-emulsion was added dropwise. After reacting for 4 hours, the temperature was raised to 85 °C and the reaction was allowed to mature for 1.5 hours to obtain organic particle emulsion #5.

[0230] A pre-emulsion was prepared by emulsifying 0.8g sodium dodecyl sulfate, 80mg sodium persulfate, 20ml deionized water, 33.4g styrene, 6g divinylbenzene, and 0.6g methoxy polyethylene glycol acrylate. 140g deionized water and 15mg sodium polyacrylate were added to a reactor, and the temperature was raised to 70℃. Under nitrogen protection and stirring, the prepared pre-emulsion was added dropwise. After reacting for 4 hours, the temperature was raised to 85℃ and the reaction was allowed to mature for 1.5 hours to obtain organic particle emulsion #6.

[0231] 0.8 g sodium dodecyl sulfate, 80 mg sodium persulfate, 20 ml deionized water, 33.4 g styrene, 6 g pentaerythritol tetraacrylate, and 0.6 g methoxy polyethylene glycol acrylate were emulsified to obtain a pre-emulsion for later use. 140 g deionized water was added to a reactor, the temperature was raised to 70 °C, and the prepared pre-emulsion was added dropwise under nitrogen protection and stirring. After reacting for 4 hours, the temperature was raised to 85 °C and the reaction was allowed to mature for 1.5 hours to obtain organic particle emulsion #7.

[0232] A pre-emulsion was prepared by emulsifying 0.8 g sodium dodecyl sulfate, 80 mg sodium persulfate, 20 ml deionized water, 33.4 g styrene, 6 g pentaerythritol tetraacrylate, and 0.6 g methoxy polyethylene glycol acrylate. 140 g deionized water and 15 mg sodium polyacrylate were added to a reactor, and the temperature was raised to 70 °C. Under nitrogen protection and stirring, the prepared pre-emulsion was added dropwise. After reacting for 4 hours, the temperature was raised to 85 °C and the reaction was allowed to mature for 1.5 hours to obtain organic particle emulsion #8.

[0233] 0.8 g sodium dodecyl sulfate, 80 mg sodium persulfate, 20 ml deionized water, 31.4 g styrene, 6 g pentaerythritol tetraacrylate, 1 g acrylonitrile, 1 g acrylamide, and 0.6 g methoxy polyethylene glycol acrylate were emulsified to obtain a pre-emulsion for later use. 140 g deionized water was added to a reactor, and the temperature was raised to 70 °C. Under nitrogen protection and stirring, the prepared pre-emulsion was added dropwise. After reacting for 4 hours, the temperature was raised to 85 °C and the reaction was allowed to mature for 1.5 hours to obtain organic particle emulsion #9.

[0234] A pre-emulsion was prepared by emulsifying 0.8g sodium dodecyl sulfate, 80mg sodium persulfate, 20ml deionized water, 31.4g styrene, 6g pentaerythritol tetraacrylate, 1g acrylonitrile, 1g acrylamide, and 0.6g methoxy polyethylene glycol acrylate. 140g deionized water and 15mg sodium polyacrylate were added to a reactor, and the temperature was raised to 70℃. Under nitrogen protection and stirring, the prepared pre-emulsion was added dropwise. After reacting for 4 hours, the temperature was raised to 85℃ and the reaction was allowed to mature for 1.5 hours to obtain organic particle emulsion #10.

[0235] 0.8 g sodium dodecyl sulfate, 80 mg sodium persulfate, 20 ml deionized water, 39.5 g styrene, and 0.5 g divinylbenzene were emulsified to obtain a pre-emulsion for later use. 140 g deionized water was added to a reactor, and the temperature was raised to 70 °C. Under nitrogen protection and stirring, the prepared pre-emulsion was added dropwise. After reacting for 4 hours, the temperature was raised to 85 °C and the reaction was allowed to mature for 1.5 hours to obtain organic particle D1# emulsion.

[0236] Take an appropriate amount of sample (e.g., 5mg-15mg) and place it in the crucible of the differential scanning calorimeter (DSC). Level the sample and cover the crucible. Parameter settings: nitrogen atmosphere, purge gas 60mL / min, protective gas 20mL / min; program settings: heat from 25℃ to 200℃ at a heating rate of 10℃ / min, hold for 5min to eliminate thermal history, then cool from 200℃ to -40℃ at a cooling rate of 10℃ / min, and then heat to 300℃ at a heating rate of 10℃ / min. Determine whether the organic particles have a melting point using the DSC curve.

[0237] The organic particles 1# to 10# prepared above also meet the following characteristics: no melting point.

[0238] Next, the organic particles prepared above were used in the separator to verify their impact on the performance of the separator and the secondary battery cells.

[0239] The manufacturing process of a secondary battery cell is as follows.

[0240] A commercially available 7μm thick polyethylene microporous membrane was used as the porous base membrane. The prepared organic particle emulsion, along with dispersant sodium carboxymethyl cellulose and binder polyacrylate, were mixed evenly in deionized water at a solid mass ratio of 90:2:8 to obtain a coating slurry. This slurry was then uniformly coated onto both surfaces of the porous base membrane, and dried to remove the solvent, yielding a release membrane. The coating surface density was 2.4 g / m³. 2 The thickness is 1.5μm, and the thickness of the separator is 10μm.

[0241] Lithium iron phosphate, a positive electrode active material, polyvinylidene fluoride (PVDF), a positive electrode binder, and carbon black, a positive electrode conductive agent, are added to N-methylpyrrolidone (NMP) at a mass ratio of 97:2:1. The mixture is stirred and mixed thoroughly to prepare a positive electrode slurry. The positive electrode slurry is then uniformly coated onto aluminum foil, a positive electrode current collector, and subsequently dried, cold-pressed, and slit to obtain the positive electrode sheet.

[0242] Artificial graphite (anode active material), acetylene black (anode conductive agent), styrene-butadiene rubber (SBR) (anode binder), and sodium carboxymethyl cellulose (thickener) were added to deionized water at a mass ratio of 96.0:1.4:1.5:1.1 and thoroughly mixed to prepare a cathode slurry. The cathode slurry was then uniformly coated onto copper foil (anode current collector), and subsequently dried, cold-pressed, and slit to obtain the cathode sheet.

[0243] At 25°C, ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a volume ratio of 3:7 to obtain a mixed solvent. LiPF6 and vinylene carbonate (VC) were then dissolved in this mixed solvent to obtain the electrolyte. The concentration of LiPF6 was 1 mol / L. The mass fraction of VC was 3%, based on the mass of the electrolyte.

[0244] The positive electrode, separator, and negative electrode are stacked, wound, and hot-pressed in sequence to obtain an electrode assembly. The electrode assembly is placed in a hard outer packaging, and the electrolyte prepared above is added. After processes such as encapsulation, standing, formation, and aging, a secondary battery cell is obtained.

[0245] Performance testing

[0246] (1) Electrolyte wettability test of the separator

[0247] Cut the separator membrane into three 5mm × 100mm strips. Drop 1mL of electrolyte into the center of each strip and let it stand for 2 minutes until the electrolyte stops diffusing. Record the electrolyte diffusion distance as the electrolyte wetting length of the separator membrane. Take the average value of the three parallel samples as the test result. The larger this value, the better the electrolyte wetting of the separator membrane.

[0248] (2) Peel force test between the separator coating and the porous base membrane

[0249] The peel force between the coating and the porous base membrane can be tested as follows: Cut the release liner into three 2.5cm × 15cm strips, attach the strips to a test steel plate, and attach 2cm wide test tape to the side of the release liner to be tested. Use a tensile testing machine, clamping the steel plate on one side and the tape on the other, to perform a 180° peel test. Take the average peel force of the three strips as the peel force between the release liner coating and the porous base membrane. The tensile rate is 50mm / min.

[0250] (3) Thermal shrinkage rate test of the separator film

[0251] The heat shrinkage rate test of the release liner can be referenced in GB / T 36363-2018.

[0252] Cut the release film into samples with a width of 50mm and a length of 100mm using a punching machine. Take 5 parallel samples and place them on A4 paper. Then place the A4 paper containing the samples on corrugated paper with a thickness of 1mm to 5mm.

[0253] Set the temperature of the forced-air drying oven to 130℃. After the temperature reaches the set temperature and stabilizes for 60 minutes, place the A4 paper placed on the corrugated paper into the forced-air drying oven and start timing. After the set time (1 hour in this disclosure) is reached, measure the length and width of the isolation film, and mark the values ​​as a and b respectively.

[0254] Calculation of heat shrinkage rate: Longitudinal (MD) heat shrinkage rate = [(100-a) / 100]×100%, Transverse (TD) heat shrinkage rate = [(50-b) / 50]×100%, take the average value of 3 parallel samples as the test result.

[0255] (4) Cycle performance test of secondary battery cells

[0256] At 25℃, a single secondary battery cell is charged to 3.8V with a constant current of 1 / 3C, then charged to a current of 0.05C with a constant voltage of 3.8V, left to rest for 5 minutes, and then discharged to 2.0V with a constant current of 1 / 3C. The resulting discharge capacity is recorded as the initial capacity C0. The above charging and discharging steps are repeated, and the discharge capacity Cn of the single secondary battery cell after the nth cycle is recorded. The capacity retention rate of the single secondary battery cell after each cycle is Pn = (Cn / C0) × 100%. The capacity retention rate of the single secondary battery cell after 500 cycles can be used to reflect the difference in cycle performance of the single secondary battery cell.

[0257] Table 1

[0258] The test results above show that cross-linked styrene-based organic particles with polar groups have good electrolyte wettability, which can improve the electrolyte wettability of the separator, enhance the peel force between the coating and the porous base film, and give the secondary battery cell good cycle performance. The cross-linked styrene-based organic particles prepared in this embodiment can also give the separator better heat resistance.

[0259] 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. An isolation membrane comprising a porous base membrane and a coating on at least one side of the porous base membrane, wherein, The coating comprises crosslinked styrene-based organic particles, the crosslinked styrene-based organic particles comprise polar groups, the polar groups comprise one or more of ester groups, carboxyl groups, carboxylate groups, hydroxyl groups, cyano groups, amide groups.

2. The separator film according to claim 1, wherein The crosslinked styrene-based organic particles comprise styrene or styrene derivative structural units and crosslinking structural units; Optionally, the styrene or styrene derivative structural units comprise one or more of styrene structural units, 1-methyl-1-styrene structural units, 4-methylstyrene structural units, 2-methylstyrene structural units, 2,4-dimethylstyrene structural units, 2,5-dimethylstyrene structural units; Optionally, the crosslinking structural units comprise one or more of divinylbenzene structural units, ethylene glycol dimethacrylate structural units, pentaerythritol tetraacrylate structural units, 1,4-butanediol diacrylate structural units, 1,6-hexanediol diacrylate structural units, 1,8-octanediol diacrylate structural units, trimethylolpropane triacrylate structural units, pentaerythritol trimethacrylate structural units, tetraethylene glycol dimethacrylate structural units, tripropylene glycol diacrylate structural units, N,N-methylenebisacrylamide structural units, N,N'-vinylbisacrylamide structural units, 1,3,5-triacryloylhexahydro-1,3,5-triazine structural units, trisallyl isocyanurate structural units.

3. The separator film according to any one of claims 1-2, wherein, The crosslinked styrene-based organic particles have no melting point.

4. The separator film according to any one of claims 1 to 3, wherein The glass transition temperature T of the crosslinked styrenic organic particles g is 110 °C to 165 °C, optionally 115 °C to 165 °C.

5. The separator film according to any one of claims 1 to 4, wherein The crosslinked styrene-based organic particles are amorphous polymers.

6. The separator film according to any one of claims 1-5, wherein, The crosslinked styrene-based organic particles have a swelling degree of 3% or less when immersed in a mixed solvent of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 3:7 at 60°C for 7 days; and / or, The crosslinked styrene-based organic particles have a dissolution rate of 3% or less when immersed in a mixed solvent of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 3:7 at 60°C for 7 days.

7. The separator film according to any one of claims 1 to 6, wherein The crosslinked styrene-based organic particles have no oxidation peak in the voltage range of 2.5V to 4.4V in the first cycle of cyclic voltammetry.

8. The separator film according to any one of claims 1 to 7, wherein The crosslinked styrene-based organic particles satisfy at least one of the following conditions (1) to (4): (1) The crosslinked styrene-based organic particles have a volume distribution particle size Dv10 of 40nm-200nm; (2) The crosslinked styrene-based organic particles have a volume distribution particle size Dv50 of 82nm-300nm; (3) The crosslinked styrene-based organic particles have a volume distribution particle size Dv90 of 140nm-840nm; (4) The crosslinked styrene-based organic particles have a particle size distribution (Dv90-Dv10) / Dv50 of 3.2 or less.

9. The separator film according to any one of claims 1 to 8, wherein The crosslinked styrenic organic particles have a true density of 1.0 g / cm 3 -1.4 g / cm 3 .

10. The separator film according to any one of claims 1-9, wherein, The mass content of the crosslinked styrene-based organic particles in the coating is 50%-99% based on the total mass of the coating; and / or, The thickness of the coating is 0.5μm-5μm; and / or, The areal density of the coating is 0.5 g / m 2 - 5 g / m 2 ; and / or, The peeling force between the coating and the porous base film is greater than or equal to 70 N / m.

11. The separator film according to any one of claims 1 to 10, wherein The ratio of the volume distribution particle size Dv50 of the crosslinked styrene-based organic particles to the average pore size of the porous base film is greater than or equal to 1.

1.

12. Crosslinked styrenic organic particles, wherein, The crosslinked styrene-based organic particles comprise a polar group, which includes one or more of an ester group, a carboxyl group, a carboxylate, a hydroxyl group, a cyano group, and an amide group.

13. The crosslinked styrenic organic particle of claim 12, wherein, The crosslinked styrene-based organic particles comprise styrene or styrene derivative structural units and crosslinking structural units. Optionally, the styrene or styrene derivative structural units include one or more of a styrene structural unit, a 1-methyl-1-styrene structural unit, a 4-methylstyrene structural unit, a 2-methylstyrene structural unit, a 2,4-dimethylstyrene structural unit, and a 2,5-dimethylstyrene structural unit. Optionally, the crosslinking structural units include one or more of a divinylbenzene structural unit, a diethylene glycol dimethacrylate structural unit, a pentaerythritol tetraacrylate structural unit, a 1,4-butanediol diacrylate structural unit, a 1,6-hexanediol diacrylate structural unit, a 1,8-octanediol diacrylate structural unit, a trimethylolpropane triacrylate structural unit, a pentaerythritol trimethacrylate structural unit, a tetraethylene glycol dimethacrylate structural unit, a tripropylene glycol diacrylate structural unit, an N,N-methylenebisacrylamide structural unit, an N,N'-vinylbisacrylamide structural unit, and a 1,3,5-triacryloylhexahydro-1,3,5-triazine structural unit.

14. The crosslinked styrenic organic particles according to claim 12 or 13, wherein, The crosslinked styrene-based organic particles have no melting point.

15. The crosslinked styrenic organic particles according to any one of claims 12-14, wherein, The glass transition temperature T of the crosslinked styrenic organic particles g is 110 °C to 165 °C, optionally 115 °C to 165 °C.

16. The crosslinked styrenic organic particles according to any one of claims 12-15, wherein, The crosslinked styrene-based organic particles are amorphous polymers.

17. The crosslinked styrene-based organic particles according to any one of claims 12-16, wherein, The crosslinked styrene-based organic particles have a swelling degree of less than or equal to 3% when immersed in a mixed solvent composed of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 3:7 at 60°C for 7 days; and / or, The crosslinked styrene-based organic particles have a dissolution rate of less than or equal to 3% when immersed in a mixed solvent composed of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 3:7 at 60°C for 7 days.

18. The crosslinked styrenic organic particles according to any one of claims 12-17, wherein, The crosslinked styrene-based organic particles have no oxidation peak in the voltage range of 2.5 V to 4.4 V in the cyclic voltammogram of the first cycle.

19. The crosslinked styrenic organic particles according to any one of claims 12-18, wherein, The crosslinked styrene-based organic particles satisfy at least one of the following conditions (1) to (4): (1) The volume distribution particle size Dv10 of the crosslinked styrene-based organic particles is 40 nm-200 nm; (2) The volume distribution particle size Dv50 of the crosslinked styrene-based organic particles is 82 nm-300 nm; (3) The volume distribution particle size Dv90 of the crosslinked styrene-based organic particles is 140 nm-840 nm; (4) The particle size distribution (Dv90-Dv10) / Dv50 of the crosslinked styrene-based organic particles is less than or equal to 3.

2.

20. The crosslinked styrenic organic particles according to any one of claims 12-19, wherein, The crosslinked styrenic organic particles have a true density of 1.0 g / cm 3 -1.4 g / cm 3 .

21. A method for preparing crosslinked styrene-based organic particles, comprising the following steps: A pre-emulsion comprising monomers, a crosslinking agent, an emulsifier, an initiator, water, and optionally a functional monomer is provided, and an emulsion polymerization reaction is carried out under heating, inert gas protection, and stirring to obtain crosslinked styrene-based organic particles, The monomers include one or more of styrene and derivatives thereof; The mass fraction of the crosslinking agent is 3%-40% based on the total mass of the monomers, the crosslinking agent, and the functional monomer being 100%; At least one of the crosslinking agent, the emulsifier, and the functional monomer has a polar group, and the polar group includes one or more of an ester group, a carboxyl group, a carboxylate, a hydroxyl group, a cyano group, and an amide group.

22. The method of claim 21, wherein, The functional monomer includes one or more of an organic small molecule monomer having an unsaturated bond and a polymer, and at least one of the organic small molecule monomer having an unsaturated bond and the polymer has a polar group.

23. The method of claim 22, wherein, The organic small molecule monomer having an unsaturated bond includes one or more of (meth)acrylic acid and derivatives thereof, (meth)acrylate and derivatives thereof, (meth)acrylate and derivatives thereof, acrylamide and derivatives thereof, acrylonitrile and derivatives thereof, and maleic anhydride and derivatives thereof; and / or, The polymer includes one or more of polyvinyl alcohol, polyvinylpyrrolidone, poly(meth)acrylic acid and alkali metal salts thereof, methoxypolyethylene glycol acrylate, polyethylene glycol acrylate, polypropylene glycol acrylate, polyethylene glycol diacrylate, polyethylene glycol methyl ether acrylate, polyethylene glycol ethyl ether acrylate, methoxypolyethylene glycol methacrylate, polyethylene glycol methacrylate, polypropylene glycol methacrylate, polyethylene glycol dimethacrylate, polyethylene glycol methyl ether methacrylate, and derivatives of each thereof.

24. The method of any one of claims 21-23, wherein, The monomers include one or more of styrene, 1-methyl-1-phenylethylene, 4-methylphenylethylene, 2-methylphenylethylene, 2,4-dimethylphenylethylene, and 2,5-dimethylphenylethylene; and / or, The crosslinking agent includes one or more of divinylbenzene, ethylene glycol dimethacrylate, pentaerythritol tetraacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,8-octanediol diacrylate, trimethylolpropane triacrylate, pentaerythritol trimethacrylate, tetraethylene glycol dimethacrylate, tripropyleneglycol diacrylate, N,N-methylenebisacrylamide, N,N'-vinylbisacrylamide, 1,3,5-triacryloylhexahydro-1,3,5-triazine, and triallyl isocyanurate; and / or, The emulsifier includes one or more of sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, sodium polyacrylate, polyvinylpyrrolidone, polyvinyl alcohol, polyoxyethylene ether emulsifier, cellulose, and derivatives thereof; and / or, The initiator comprises one or more of sodium persulfate, potassium persulfate, ammonium persulfate, sodium sulfite, sodium bisulfite, azobisdimethylamid hydrochloride, azobisdimethylimidazoline hydrochloride, and azobisisopropylimidazoline.

25. The method of any one of claims 21-24, wherein, a mass fraction of the emulsifier is 0.3%-5% based on a total mass of the monomer, the crosslinking agent, and the functional monomer being 100%; and / or, a mass fraction of the functional monomer is 0%-10% based on a total mass of the monomer, the crosslinking agent, and the functional monomer being 100%.

26. The method of any one of claims 21-25, wherein, a mass fraction of the functional monomer is 0.1%-9% based on a total mass of the monomer, the crosslinking agent, and the functional monomer being 100%.

27. A crosslinked styrene-based organic particle emulsion comprising the crosslinked styrene-based organic particle of any one of claims 12-20, or obtained by the method of any one of claims 21-26.

28. A secondary battery cell comprising a positive electrode sheet, a negative electrode sheet, and the separator film of any one of claims 1-11, the separator film being disposed between the positive electrode sheet and the negative electrode sheet.

29. A battery device comprising a plurality of the secondary battery cell of claim 28.

30. An electrically powered device comprising the secondary battery cell of claim 28 or the battery device of claim 29.

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