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

Abstract

Provided are a cross-linked styrene organic particle and a preparation method therefor, a cross-linked styrene 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, the coating comprises cross-linked styrene organic particles, and the particle size distribution (Dv90-Dv10) / Dv50 of the cross-linked styrene organic particles is less than or equal to 3.0. The secondary battery cell has high reliability, high-quality energy density and good cycle performance.

Description

Crosslinked styrene-based organic particles, method for producing the same, crosslinked styrene-based organic particle emulsion, separator, secondary battery cell, battery device, and power using device

[0001] Cross-reference to Related Applications

[0002] This application claims priority to Chinese Patent Application No. 202410947830.9, filed on July 15, 2024, entitled “Crosslinked styrene-based organic particles, method for producing the same, separator, secondary battery cell, battery device, and power using device,” and Chinese Patent Application No. 202411384967.4, filed on September 30, 2024, entitled “Crosslinked styrene-based organic particles, method for producing the same, crosslinked styrene-based organic particle emulsion, separator, secondary battery cell, battery device, and power using device,” the entire contents of which are incorporated herein by reference. TECHNICAL FIELD

[0003] The present disclosure relates to a crosslinked styrene-based organic particle, a method for producing the same, a crosslinked styrene-based organic particle emulsion, a separator, a secondary battery cell, a battery device, and a power using device. BACKGROUND

[0004] With the increasingly wide range of applications of secondary battery cells, people’s demand for the use of secondary battery cells is also increasing, such as the increasingly high requirements for their energy density and reliability. Therefore, how to make the secondary battery cell have a higher energy density under the premise of high reliability is a technical problem to be solved at present. SUMMARY

[0005] The present disclosure provides a crosslinked styrene-based organic particle, a method for producing the same, a crosslinked styrene-based organic particle emulsion, a separator, a secondary battery cell, a battery device, and a power using device, which has high reliability, high quality energy density, and good cycle performance.

[0006] In a first aspect, the present disclosure provides a separator, comprising a porous base film and a coating layer on at least one side of the porous base film, wherein the coating layer comprises crosslinked styrene-based organic particles, and the particle size distribution (Dv90-Dv10) / Dv50 of the crosslinked styrene-based organic particles is less than or equal to 3.0.

[0007] The crosslinked styrene-based organic particles have a small density, and a secondary battery cell using the same can have a higher mass energy density. The crosslinked styrene-based organic particles of the present disclosure have good heat resistance. By using the crosslinked styrene-based organic particles in a separator film, the crosslinked styrene-based organic particles can generate a force to resist the shrinkage of the separator film, thereby improving the overall heat shrinkage of the separator film, improving the heat resistance of the separator film, and improving the reliability of the secondary battery cell. The crosslinked styrene-based organic particles have a particle size distribution (Dv90-Dv10) / Dv50 of less than or equal to 3.0, thereby allowing the crosslinked styrene-based organic particles to be closely arranged, which can improve the heat resistance of the separator film, and also allow the separator film to have good air permeability, and thus the secondary battery cell can have high reliability and good cycle performance. Therefore, the separator film of the present disclosure can allow the secondary battery cell to have high reliability, high mass energy density, and good cycle performance.

[0008] In some embodiments, the crosslinked styrene-based organic particles have a particle size distribution (Dv90-Dv10) / Dv50 of 0.8-2.6.

[0009] This can further improve the heat resistance of the separator film, and also allow the separator film to have better air permeability, and thus the secondary battery cell can have good cycle performance.

[0010] In some embodiments, the crosslinked styrene-based organic particles have a volume distribution particle size Dv10 of 40-200 nm, which can be 40-70 nm.

[0011] In some embodiments, the crosslinked styrene-based organic particles have a volume distribution particle size Dv50 of 80-300 nm, which can be 90-150 nm.

[0012] In some embodiments, the crosslinked styrene-based organic particles have a volume distribution particle size Dv90 of 100-800 nm, which can be 160-500 nm.

[0013] The volume distribution particle size of the crosslinked styrene-based organic particles in the above range is advantageous for further improving the heat resistance of the separator film, improving the reliability of the secondary battery cell, and also allowing the separator film to have a lower impedance, thereby improving the cycle performance of the secondary battery cell.

[0014] In some embodiments, the crosslinked styrene-based organic particles have a true density of 1.0 g / cm 3 -1.4 g / cm 3 This can allow the secondary battery cell using the separator film of the present disclosure to have a higher mass energy density.

[0015] In some embodiments, the crosslinked styrene-based organic particles comprise styrene or styrene derivative structural units and crosslinking structural units.

[0016] 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.

[0017] 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.

[0018] In some embodiments, the crosslinked styrene-based organic particles have a glass transition temperature T g 108℃-160℃, optionally 122℃-160℃.

[0019] The crosslinked styrene-based organic particles have a glass transition temperature T g Within the above range, the crosslinked styrene-based organic particles have better thermal stability and can better resist thermal shrinkage of the separator film, thereby improving the heat resistance of the separator film and the reliability of the secondary battery cell.

[0020] In some embodiments, the crosslinked styrene-based organic particles have no melting point.

[0021] The crosslinked styrene-based organic particles of the present disclosure have no melting point, indicating that the crosslinked styrene-based organic particles have good heat resistance and thermal stability, thereby better resisting thermal shrinkage of the separator film, improving the heat resistance of the separator film, and improving the reliability of the secondary battery cell.

[0022] In some embodiments, 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℃ for 7 days.

[0023] The crosslinked styrene-based organic particles have a low swelling degree in organic solvents, and have high structural stability during long-term use of the secondary battery cell, thereby improving the problem of decreased air permeability of the separator film during use.

[0024] In some embodiments, the crosslinked styrene-based organic particles have a dissolution rate of less than or equal to 3% 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.

[0025] The crosslinked styrene-based organic particles have a low dissolution rate in organic solvents, high structural stability during long-term use of the secondary battery cell, and high chemical stability in electrolyte, thereby enabling the secondary battery cell to have long cycle stability.

[0026] In some embodiments, the crosslinked styrene-based organic particles have no oxidation peak in the cyclic voltammetry curve of the first cycle in a voltage range of 2.5V to 4.4V.

[0027] The crosslinked styrene-based organic particles have no oxidation peak in the cyclic voltammetry curve of the first cycle in a voltage range of 2.5V to 4.4V, indicating that the crosslinked styrene-based organic particles are stable in the voltage range of 2.5V to 4.4V and have good electrochemical stability, and can be applied to high-voltage secondary battery cells to improve the operating voltage and energy density of the secondary battery cells.

[0028] In some embodiments, the mass content of the crosslinked styrene-based organic particles in the coating is 50%-99% based on the total mass of the coating.

[0029] In some embodiments, the thickness of the coating is 0.5μm-5μm.

[0030] In some embodiments, the areal density of the coating is 0.5g / m 2 -5g / m 2 .

[0031] In some embodiments, 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.

[0032] In a second aspect, the present disclosure provides crosslinked styrene-based organic particles having a particle size distribution (Dv90-Dv10) / Dv50 of less than or equal to 3.0.

[0033] In some embodiments, the particle size distribution (Dv90-Dv10) / Dv50 of the crosslinked styrene-based organic particles is 0.8-2.6.

[0034] In some embodiments, the volume distribution particle size Dv10 of the crosslinked styrene-based organic particles is 40nm-200nm, and optionally 40nm-70nm.

[0035] In some embodiments, the crosslinked styrene-based organic particles have a volume distribution particle size Dv50 of 80-300 nm, optionally 90-150 nm.

[0036] In some embodiments, the crosslinked styrene-based organic particles have a volume distribution particle size Dv90 of 100-800 nm, optionally 160-500 nm.

[0037] In some embodiments, the crosslinked styrene-based organic particles have a true density of 1.0-1.4 g / cm3. 3 -1.4 g / cm3. 3 .

[0038] In some embodiments, the crosslinked styrene-based organic particles comprise styrene or styrene derivative structural units and crosslinking structural units.

[0039] 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.

[0040] 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, ditrimethylolpropane diacrylate structural units, N,N-methylenebisacrylamide structural units, N,N'-vinylbisacrylamide structural units.

[0041] In some embodiments, the crosslinked styrene-based organic particles have a glass transition temperature Tg of 108-160 °C, optionally 122-160 °C. g

[0042] In some embodiments, the crosslinked styrene-based organic particles have no melting point.

[0043] In some embodiments, the crosslinked styrene-based organic particles have a swelling degree of less than or equal to 3% 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.

[0044] ​In some embodiments, the crosslinked styrenic organic particles have a dissolution rate of less than or equal to 3% 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.

[0045] In some embodiments, the crosslinked styrenic organic particles do not have an oxidation peak in a cyclic voltammetry curve of the first cycle in a voltage range of 2.5V to 4.4V.

[0046] In a third aspect, the present disclosure provides a method for preparing crosslinked styrenic organic particles, comprising the steps of: providing a pre-emulsion comprising monomers, a crosslinking agent, an emulsifier, an initiator, water, and optionally an oligomer, wherein the monomers comprise one or more of styrene and derivatives thereof, and the oligomer is free-radically polymerizable; and performing an emulsion polymerization reaction under heating, inert gas protection, and stirring conditions to obtain the crosslinked styrenic organic particles, wherein the crosslinked styrenic organic particles have a particle size distribution (Dv90-Dv10) / Dv50 of less than or equal to 3.0.

[0047] In some embodiments, the emulsion polymerization reaction has a maturation temperature of 76°C-90°C.

[0048] In some embodiments, the emulsion polymerization reaction has a maturation time of 1h-6h.

[0049] In some embodiments, the emulsion polymerization reaction comprises the steps of: adding the pre-emulsion into a reactor containing water under a first heating temperature, inert gas protection, and stirring conditions; and increasing the temperature to a maturation temperature to perform a maturation reaction after a first time, to obtain the crosslinked styrenic organic particles.

[0050] Optionally, the first heating temperature is 55°C-70°C.

[0051] Optionally, the first time is 3h-6h.

[0052] In some embodiments, the oligomer comprises one or more of 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, polyethylene glycol ethyl ether methacrylate, and derivatives thereof.

[0053] In some embodiments, the oligomer has a weight average molecular weight of 300-5000.

[0054] In some embodiments, the mass fraction of the oligomer is 0%-7.5% based on 100% of the total mass of the monomer, the crosslinking agent, and the oligomer.

[0055] In some embodiments, the crosslinking agent comprises 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.

[0056] In some embodiments, the mass fraction of the crosslinking agent is 3%-40% based on 100% of the total mass of the monomer, the crosslinking agent, and the oligomer.

[0057] In some embodiments, the monomer comprises one or more of styrene, 1-methyl-1-phenylethylene, 4-methylphenylethylene, 2-methylphenylethylene, 2,4-dimethylphenylethylene, 2,5-dimethylphenylethylene.

[0058] In some embodiments, the emulsifier comprises one or more of sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, sodium polyacrylate, polyvinylpyrrolidone, polyvinyl alcohol, polyoxyethylene ether emulsifier, cellulose, and derivatives thereof.

[0059] In some embodiments, the mass fraction of the emulsifier is 0.5%-5% based on 100% of the total mass of the monomer, the crosslinking agent, and the oligomer.

[0060] In some embodiments, the pre-emulsion satisfies: the mass fraction of the crosslinking agent is 12%-40% and the mass fraction of the oligomer is 0.25%-7.5% based on 100% of the total mass of the monomer, the crosslinking agent, and the oligomer.

[0061] In some embodiments, the pre-emulsion satisfies: the mass fraction of the crosslinking agent is greater than or equal to 3% and less than 12% based on 100% of the total mass of the monomer, the crosslinking agent, and the oligomer, and the pre-emulsion further satisfies at least one of conditions (1) to (3) as follows: (1) the mass fraction of the emulsifier is 1%-5%; (2) the emulsifier comprises a polyoxyethylene ether emulsifier; (3) the mass fraction of the oligomer is 0.25%-7.5%.

[0062] In a fourth aspect, the present disclosure provides a crosslinked styrene-based organic particle emulsion, which comprises the crosslinked styrene-based organic particle of the second aspect, or is obtained by the method of the third aspect.

[0063] In a fifth aspect, the present disclosure provides a secondary battery cell including a positive electrode sheet, a negative electrode sheet, and the separator of the first aspect of the present disclosure, the separator being disposed between the positive electrode sheet and the negative electrode sheet.

[0064] In a sixth aspect, the present disclosure provides a battery device including a plurality of the secondary battery cell of the fifth aspect of the present disclosure.

[0065] In a seventh aspect, the present disclosure provides an electric device including the secondary battery cell of the fifth aspect of the present disclosure or the battery device of the sixth aspect of the present disclosure. BRIEF DESCRIPTION OF DRAWINGS

[0066] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings needed to be used in the embodiments of the present disclosure will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present disclosure, and other drawings can be obtained by the drawings without paying creative labor under the premise of the ordinary skill in the art.

[0067] FIG. 1 shows a schematic diagram of a secondary battery cell according to some embodiments of the present disclosure.

[0068] FIG. 2 shows a schematic diagram of an electric device according to some embodiments of the present disclosure.

[0069] In the drawings, the drawings are not necessarily drawn according to the actual scale. DETAILED DESCRIPTION

[0070] Hereinafter, specific embodiments of the crosslinked styrene-based organic particles and the method for producing the same, the crosslinked styrene-based organic particle emulsion, the separator, the secondary battery cell, the battery device, and the electric device of the present disclosure will be specifically described with appropriate reference to the accompanying drawings. However, there will be cases where unnecessary detailed description is omitted. For example, there will be cases where detailed description of matters known well, repeated description of substantially the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the drawings and the following description are provided in order for those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter recited in the claims.

[0071] The ranges disclosed herein are defined by their lower and upper endpoints, given that a range is defined by selecting a lower endpoint and an upper endpoint, the selected lower and upper endpoints define the boundaries of the particular range. Ranges defined by endpoints can be either inclusive or exclusive of the endpoints, and can be arbitrarily combined, i.e., any lower endpoint can be combined with any upper endpoint to form a range. For example, if ranges of 60-120 and 80-110 are listed, it is understood that ranges of 60-110 and 80-120 are also contemplated. Also, if minimum range values of 1 and 2 are listed, and if maximum range values of 3, 4, and 5 are listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In the present disclosure, unless otherwise stated, a numerical range "a-b" indicates a shorthand way of describing all of the individual real combinations that fall between "a" and "b", where "a" and "b" are both real numbers. For example, the numerical range "0-5" indicates that all of the real numbers between "0" and "5" have been listed herein, and "0-5" is merely a shorthand way of describing these numerical combinations. In addition, when a parameter is stated to be an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0072] Unless otherwise specified, all embodiments and optional embodiments of the present disclosure can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present disclosure.

[0073] Unless otherwise specified, all technical features and optional technical features of the present disclosure can be combined with each other to form new technical solutions, and such technical solutions should be considered to be included in the disclosure of the present disclosure.

[0074] Unless otherwise specified, all steps of the present disclosure can be performed in sequence or randomly, and preferably in sequence. For example, the method comprises steps (a) and (b), which means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method also comprises step (c), which means that step (c) can be added to the method in any order, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0075] Unless otherwise specified, in the present disclosure, the terms "first", "second", etc. are used to distinguish different objects, and are not used to describe a particular order or primary and secondary relationship.

[0076] In the present disclosure, the terms "a plurality of" and "a plurality of" refer to two or more.

[0077] In the description of the embodiments of the present disclosure, if there is no special indication, the first feature is "on" or "under" the second feature, which can be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature can be "above", "over" and "on" the second feature, which can be that the first feature is directly above or obliquely above the second feature, or only means that the horizontal height of the first feature is higher than that of the second feature. The first feature can be "below", "under" and "under" the second feature, which can be that the first feature is directly below or obliquely below the second feature, or only means that the horizontal height of the first feature is less than that of the second feature.

[0078] Unless otherwise specified, the test temperature of each parameter mentioned in the present disclosure is 25°C.

[0079] The secondary battery cell mentioned in the embodiments of the present disclosure can realize the function of charging and discharging independently, and can continue to be used by activating the active material through charging after discharging. The secondary battery cell can be in the shape of a cylinder, a cuboid or other shapes, which are not limited in the embodiments of the present disclosure. As shown in FIG. 1, the secondary battery cell 5 is a cuboid structure as an example.

[0080] The secondary battery cell provided by the embodiments of the present disclosure can include but is not limited to lithium battery cells, sodium battery cells, such as lithium ion battery cells, sodium ion battery cells, lithium metal battery cells, sodium metal battery cells, etc.

[0081] The secondary battery cell provided by the embodiments of the present disclosure includes an electrode assembly. The electrode assembly can be a winding structure or a stacking structure, which is not limited in the embodiments of the present disclosure. The secondary battery cell further includes an outer package, which can be used to package the electrode assembly. The outer package can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package can also be a soft package, such as a bag-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).

[0082] The battery apparatus mentioned in the embodiments of the present disclosure can include one or more battery cell assemblies for providing voltage and capacity. The battery cell assembly can include a plurality of secondary battery cells connected in series, in parallel or in a mixed manner through a busbar component.

[0083] In some embodiments, the battery cell assembly is usually formed by arranging a plurality of secondary battery cells.

[0084] As an example, the battery cell assembly can be a battery module, which is formed by arranging and fixing a plurality of secondary battery cells into one independent module. As an example, the battery module can be formed by bundling a plurality of secondary battery cells with a cable tie.

[0085] In some embodiments, the battery device can be a battery pack, which includes a case and one or more battery cell assemblies accommodated in the case.

[0086] As an example, the battery cell assembly can be a battery module, which can be accommodated in the case by fixing the battery module in the case.

[0087] As an example, the battery cell assembly can also be accommodated in the case by directly fixing a plurality of secondary battery cells in the case.

[0088] As an example, the case can include a first case and a second case. The first case and the second case are fastened so that an enclosed space is formed inside the case to accommodate the battery cell assembly. Here, the enclosed means covered or closed, which can be sealed or unsealed. The first case can be a top cover or a bottom plate.

[0089] As an example, the case can include a top cover, a frame, and a bottom plate. The top cover and the bottom plate are connected to the frame, respectively, so that an enclosed space is formed inside the case to accommodate the battery cell assembly.

[0090] In some embodiments, the case can be part of a chassis structure of a vehicle. For example, part of the case can be at least part of a floor of the vehicle, or part of the case can be at least part of a cross beam and a longitudinal beam of the vehicle.

[0091] The technical solutions described in the embodiments of the present disclosure are applicable to various electric devices using secondary battery cells and battery devices, such as, but not limited to, mobile devices (such as mobile phones, tablet computers, notebook computers, etc.), electric vehicles (such as 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. The secondary battery cells and the battery devices are used to store or provide electric energy.

[0092] FIG. 2 is a schematic diagram of an electric device as an example. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc.

[0093] In the context of the present disclosure, the crosslinked styrene-based organic particles mainly play a role in improving heat resistance in the coating layer of the separator film, and almost have no adhesiveness.

[0094] The separator film is an important component for supporting the secondary battery cell to complete the charge-discharge electrochemical process. The commonly used separator film is mostly polyolefin material. However, the heat resistance of the polyolefin material is poor, and it is easy to soften or melt at high temperature, which may cause short circuit of the secondary battery cell. In order to improve the heat resistance of the separator film, a coating layer is usually coated on the separator film to improve the heat resistance of the separator film. Boehmite, alumina and other inorganic particles are currently commonly used heat-resistant fillers. However, the density of such heat-resistant fillers is large, and the mass is large under the same packing volume, which affects the energy density of the secondary battery cell.

[0095] Therefore, the cross-linked styrene-based organic particles of the present disclosure are used in the separator film, which can make the secondary battery cell have high reliability, high mass energy density and good cycle performance.

[0096] The particle size distribution (Dv90-Dv10) / Dv50 of the cross-linked styrene-based organic particles of the present disclosure is less than or equal to 3.0.

[0097] The cross-linked styrene-based organic particles have small density, and the secondary battery cell using the same can have higher mass energy density.

[0098] The glass transition temperature T g of the non-cross-linked styrene-based organic particles is small, and the heat resistance is poor. The cross-linked styrene-based organic particles of the present disclosure have good heat resistance. By using the cross-linked styrene-based organic particles in the separator film, the cross-linked styrene-based organic particles can generate a force to resist the shrinkage of the separator film, thereby improving the overall thermal shrinkage of the separator film, improving the heat resistance of the separator film, and improving the reliability of the secondary battery cell.

[0099] The particle size distribution (Dv90-Dv10) / Dv50 of the cross-linked styrene-based organic particles is less than or equal to 3.0, which can make the cross-linked styrene-based organic particles closely arranged, which can not only improve the heat resistance of the separator film, but also make the separator film have good air permeability, and further make the secondary battery cell have high reliability and good cycle performance.

[0100] Therefore, the cross-linked styrene-based organic particles of the present disclosure are used in the separator film, which can make the secondary battery cell have high reliability, high mass energy density and good cycle performance.

[0101] The crosslinked styrenic organic particles can have a particle size distribution (Dv90-Dv10) / Dv50 of less than or equal to 3.0, in some embodiments, the crosslinked styrenic organic particles can have a particle size distribution (Dv90-Dv10) / Dv50 of 0.8-3.0, for example, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, or a range of any of the foregoing.

[0102] Due to the current polymer production process, the minimum value of the particle size distribution (Dv90-Dv10) / Dv50 of the crosslinked styrenic organic particles that can be achieved is 0.8.

[0103] Alternatively, in some embodiments, the particle size distribution (Dv90-Dv10) / Dv50 of the crosslinked styrenic organic particles can be 0.8-2.6, 0.8-2.2, 0.8-2.0, 0.8-1.9, 1.2-2.6, 1.2-2.2, 1.2-2.0, 1.2-1.9, 1.4-2.2, 1.4-2.0, 1.4-1.9.

[0104] Thus, the heat resistance of the separator film can be further improved, and the separator film can also have better air permeability, so that the secondary battery cell has good cycle performance.

[0105] In some embodiments, the crosslinked styrenic organic particles can have a volume distribution particle size Dv10 of 40 nm-200 nm, for example, 40 nm, 45 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, or a range of any of the foregoing.

[0106] Alternatively, the crosslinked styrenic organic particles can have a volume distribution particle size Dv10 of 40 nm-120 nm, 40 nm-100 nm, 40 nm-80 nm, 40 nm-70 nm, 40 nm-60 nm, 45 nm-120 nm, 45 nm-100 nm, 45 nm-80 nm, 45 nm-70 nm, 45 nm-60 nm.

[0107] In some embodiments, the crosslinked styrene-based organic particles can have a volume distribution particle size Dv50 of 80-300 nm, for example, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, 210 nm, 220 nm, 230 nm, 240 nm, 250 nm, 260 nm, 270 nm, 280 nm, 290 nm, 300 nm, or a range defined by any two of the above values.

[0108] Alternatively, the crosslinked styrene-based organic particles can have a volume distribution particle size Dv50 of 80-240 nm, 80-220 nm, 80-200 nm, 80-180 nm, 80-170 nm, 80-160 nm, 80-150 nm, 90-200 nm, 90-180 nm, 90-170 nm, 90-160 nm, 90-150 nm.

[0109] In some embodiments, the crosslinked styrene-based organic particles can have a volume distribution particle size Dv90 of 100-800 nm, for example, 100 nm, 120 nm, 140 nm, 160 nm, 180 nm, 200 nm, 220 nm, 240 nm, 260 nm, 280 nm, 300 nm, 320 nm, 340 nm, 360 nm, 380 nm, 400 nm, 420 nm, 440 nm, 460 nm, 480 nm, 500 nm, 520 nm, 540 nm, 560 nm, 580 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm, or a range defined by any two of the above values.

[0110] Alternatively, the crosslinked styrene-based organic particles can have a volume distribution particle size Dv90 of 100-700 nm, 100-600 nm, 100-500 nm, 100-400 nm, 160-700 nm, 160-600 nm, 160-500 nm, 160-400 nm.

[0111] The volume distribution particle size of the crosslinked styrene-based organic particles in the above range is advantageous for further improving the heat resistance of the separator film, improving the reliability of the secondary battery cell; and is also advantageous for the separator film to have a lower impedance, thereby also improving the cycle performance of the secondary battery cell.

[0112] Dv10, Dv50, Dv90 respectively represent the particle size corresponding to the cumulative volume distribution percentage of 10%, 50%, 90% of the material, which can be tested by laser particle size analyzer according to GB / T 19077-2016. During the test, a clean small beaker is taken and 1g of the sample to be tested is added, 20ml of deionized water is added, and ultrasonic is performed at 53KHz / 120W for 5min to ensure that the sample is completely dispersed; after the light path system is cleaned, the background is automatically tested by opening the laser particle size analyzer; the solution to be tested which has been ultrasonic is stirred to make it uniformly dispersed, and is placed in the sample cell according to the requirement, and the particle size is measured. The testing instrument can be MasterSizer3000 laser particle size analyzer.

[0113] In some embodiments, the true density of the crosslinked styrene-based organic particles can be 1.0g / cm 3 -1.4g / cm 3 .

[0114] At present, the true density of inorganic particles such as boehmite and alumina is usually 2.5g / cm 3 -3.5g / cm 3 The true density of the crosslinked styrene-based organic particles of the present disclosure is small, so that the secondary battery cell using the separator film of the present disclosure has a higher mass energy density.

[0115] In some embodiments, the crosslinked styrene-based organic particles comprise styrene or styrene derivative structural units and crosslinking structural units.

[0116] The crosslinking structural unit of the crosslinked styrene-based organic particles refers to a structural unit for connecting the styrene or styrene derivative structural unit.

[0117] Optionally, the styrene or styrene derivative structural unit can comprise 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.

[0118] Optionally, the crosslinking structural unit can comprise 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, and an N,N’-vinylbisacrylamide structural unit.

[0119] The crosslinked styrene-based organic particles of the present disclosure are neither soluble in water nor in organic solvents such as tetrahydrofuran (THF), dichloromethane (DCM), dimethylformamide (DMF), trichlorobenzene (TCB), chloroform at 25℃, i.e. insoluble in the mobile phase for gel permeation chromatography test, nor can the molecular weight of the crosslinked styrene-based organic particles be tested by gel permeation chromatography.

[0120] In some embodiments, the glass transition temperature T g may be 108℃-160℃, for example, can be 108℃, 109℃, 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℃, 137℃, 138℃, 139℃, 140℃, 141℃, 142℃, 143℃, 144℃, 145℃, 146℃, 147℃, 148℃, 149℃, 150℃, 151℃, 152℃, 153℃, 154℃, 155℃, 156℃, 157℃, 158℃, 159℃, 160℃, or a range consisting of any of the aforementioned values.

[0121] At present, the glass transition temperature T g of the non-crosslinked styrene-based organic particles and the commercially available crosslinked styrene-based organic particles is small, usually below 100℃. The glass transition temperature T g of the crosslinked styrene-based organic particles of the present disclosure is 108℃-160℃, which has higher thermal stability, thereby better resisting the thermal shrinkage of the isolation film, improving the heat resistance of the isolation film, and improving the reliability of the secondary battery cell.

[0122] Optionally, the glass transition temperature T g of the crosslinked styrene-based organic particles can be 116℃-160℃, 120℃-160℃, 122℃-160℃, 124℃-160℃, 128℃-160℃, 132℃-160℃, 136℃-160℃, 142℃-160℃.

[0123] The glass transition temperature T gThe test can be performed as follows: take an appropriate amount of sample (for example, 5 mg-15 mg) and place it in a differential scanning calorimeter (DSC) crucible, shake it flat, and cover it with a crucible cover; parameter settings: nitrogen atmosphere, purge gas 60 mL / min, protective gas 20 mL / min; program settings: temperature increase from 25°C to 200°C at a rate of 10°C / min, hold for 5 min to eliminate thermal history, temperature decrease from 200°C to -40°C at a rate of 10°C / min, and temperature increase from -40°C to 300°C at a rate of 10°C / min. The glass transition temperature Tg of the organic particles is obtained from the DSC curve. g .

[0124] In some embodiments, the crosslinked styrene-based organic particles have no melting point.

[0125] The crosslinked styrene-based organic particles of the present disclosure have no melting point, indicating that the crosslinked styrene-based organic particles have good heat resistance and thermal stability, and thus can better resist thermal shrinkage of the separator film, improve the heat resistance of the separator film, and improve the reliability of the secondary battery cell.

[0126] The melting point can be tested as follows: take an appropriate amount of sample (for example, 5 mg-15 mg) and place it in a differential scanning calorimeter (DSC) crucible, shake it flat, and cover it with a crucible cover; parameter settings: nitrogen atmosphere, purge gas 60 mL / min, protective gas 20 mL / min; program settings: temperature increase from 25°C to 200°C at a rate of 10°C / min, hold for 5 min to eliminate thermal history, temperature decrease from 200°C to -40°C at a rate of 10°C / min, and temperature increase from -40°C to 300°C at a rate of 10°C / min. Whether the organic particles have a melting point below 300°C is determined by the DSC curve. The crosslinked styrene-based organic particles have no melting point, meaning that the DSC curve of the crosslinked styrene-based organic particles has no melting peak.

[0127] In some embodiments, the crosslinked styrene-based organic particles have a swelling degree of less than or equal to 3% when soaked in a mixed solvent composed of ethylene carbonate and methyl ethyl carbonate at a volume ratio of 3:7 at 60°C for 7 days.

[0128] The crosslinked styrene-based organic particles have a low swelling degree in organic solvents, and have high structural stability during long-term use of the secondary battery cell, thereby improving the problem of decreased air permeability of the separator film during use.

[0129] The swelling degree of the crosslinked styrene-based organic particles can be tested by the following method: take an appropriate amount of sample (for example, about 1 g), and record the mass as m1, and place it in a semi-permeable membrane sample bag, seal the bag, and the sample bag can permeate the solvent but cannot permeate the sample; immerse the sample bag in an appropriate amount of solvent (for example, about 50 g) at 60°C for 7 days, then take out the sample bag, take out the sample from the sample bag, wipe off the excess solvent, and then weigh the sample again to obtain the mass m2; the swelling degree = (m2-m1) / m1 x 100%. The solvent is a mixed solvent of ethylene carbonate (EC) and methyl ethyl carbonate (EMC) in a volume ratio of 3:7.

[0130] In some embodiments, the dissolution rate of the crosslinked styrene-based organic particles in a mixed solvent of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 3:7 at 60°C for 7 days can be less than or equal to 3%.

[0131] The crosslinked styrene-based organic particles have a low dissolution rate in organic solvents, high structural stability during long-term use of the secondary battery cell, and high chemical stability in the electrolyte, thereby allowing the secondary battery cell to have long cycle stability.

[0132] The dissolution rate of the crosslinked styrene-based organic particles can be tested by the following method: take an appropriate amount of sample (for example, about 1 g), and record the mass as m1, and place it in a semi-permeable membrane sample bag, seal the bag, and the sample bag can permeate the solvent but cannot permeate the sample; immerse the sample bag in an appropriate amount of solvent (for example, about 50 g) at 60°C for 7 days, then take out the sample bag, take out the sample from the sample bag, wipe off the excess solvent, and then weigh the sample again to obtain the mass m2; the swelling degree = (m2-m1) / m1 x 100%. The solvent is a mixed solvent of ethylene carbonate (EC) and methyl ethyl carbonate (EMC) in a volume ratio of 3:7.

[0133] In some embodiments, the cyclic voltammogram of the crosslinked styrene-based organic particles in the first cycle does not have an oxidation peak in the voltage range of 2.5V to 4.4V.

[0134] The cyclic voltammogram of the crosslinked styrene-based 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 crosslinked styrene-based organic particles are stable in the voltage range of 2.5V to 4.4V and have good electrochemical stability, and can be applied to high-voltage secondary battery cells to improve the operating voltage and energy density of the secondary battery cells.

[0135] The oxidation peak potential of the cross-linked styrene-based organic particles can be tested by the following method: organic particles, binder polyacrylate, and conductive agent conductive carbon black are dissolved in water to form a slurry at a solid content mass ratio of 64:7:29, the slurry is coated on an aluminum foil as a positive electrode, a lithium foil is used as a negative electrode, and a button cell is assembled; the button cell is subjected to cyclic voltammetry (CV) test at a scanning rate of 0.10 mV / s, a voltage range of 2.50 V-5.00 V, and 3 cycles, and the voltage corresponding to the peak point of the first cycle of the cyclic voltammetry curve is taken as the oxidation peak potential. The electrolyte salt of the electrolyte used for testing is LiPF6, and the concentration is 1 mol / L. The solvent of the electrolyte is obtained by mixing ethylene carbonate (EC) and methyl ethyl carbonate (EMC) at a volume ratio of 3:7.

[0136] The disclosure also provides a preparation method of the cross-linked styrene-based organic particles.

[0137] The preparation method of the cross-linked styrene-based organic particles comprises the following steps: providing a pre-emulsion comprising monomers, a cross-linking agent, an emulsifier, an initiator, water, and optionally an oligomer, and performing emulsion polymerization under the conditions of heating, inert gas protection, and stirring to obtain the cross-linked styrene-based organic particles. The particle size distribution (Dv90-Dv10) / Dv50 of the cross-linked styrene-based organic particles is less than or equal to 3. The monomers comprise one or more of styrene and derivatives thereof. The oligomer is free-radically polymerizable.

[0138] The cross-linked styrene-based organic particles provided by the disclosure are obtained by the emulsion polymerization method, and a cross-linking agent is added during the emulsion polymerization process. The cross-linking agent can make the obtained cross-linked styrene-based organic particles have good heat resistance.

[0139] In some embodiments, the maturation temperature of the emulsion polymerization reaction can be 76-90°C, for example, 76°C, 77°C, 78°C, 79°C, 80°C, 81°C, 82°C, 83°C, 84°C, 85°C, 86°C, 87°C, 88°C, 89°C, 90°C, or a range formed by any of the above values.

[0140] As the temperature of the emulsion polymerization reaction increases, the solubility of the monomers in the aqueous phase increases, that is, the concentration of the monomers in the aqueous phase increases, so that the concentration of free radicals in water increases. Furthermore, the increase in temperature can promote the generation rate of free radicals, so that the concentration of free radicals in water further increases, thereby increasing the diffusion rate of free radicals from the aqueous phase to the micelles, that is, increasing the nucleation rate, increasing the number of latex particles, and reducing the particle size. Therefore, the particle size of the obtained cross-linked styrene-based organic particles is reduced.

[0141] In some embodiments, the ripening time of the emulsion polymerization reaction can be 1 h-6 h, for example, can be 1 h, 1.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, 4.5 h, 5 h, 5.5 h, 6 h, or a range consisting of any of the aforementioned values.

[0142] In some embodiments, the emulsion polymerization reaction can include the following steps: under the conditions of a first heating temperature, inert gas protection and stirring, the pre-emulsion is added dropwise into a reactor containing water, after a first time, the temperature is raised to a ripening temperature for ripening reaction, and cross-linked styrene-based organic particles are obtained.

[0143] Optionally, the first heating temperature can be 55°C-70°C.

[0144] Optionally, the first time can be 3 h-6 h.

[0145] In some embodiments, the stirring speed of the emulsion polymerization reaction can be 60 rpm / min-1000 rpm / min.

[0146] The faster the stirring speed during the reaction, the smaller the particle size of the obtained cross-linked styrene-based organic particles. Within the above range, the stirring speed can avoid emulsion polymerization demulsification, and cross-linked styrene-based organic particles with narrow particle size distribution can be obtained.

[0147] Optionally, the stirring speed of the emulsion polymerization reaction can be 60 rpm / min-500 rpm / min, 60 rpm / min-200 rpm / min, 80 rpm / min-200 rpm / min.

[0148] In some embodiments, the monomer can include one or more of styrene, 1-methyl-1-phenylethylene, 4-methylstyrene, 2-methylstyrene, 2,4-dimethylstyrene, and 2,5-dimethylstyrene.

[0149] In some embodiments, the oligomer can include one or more of 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, polyethylene glycol ethyl ether methacrylate, and derivatives of each thereof.

[0150] In some embodiments, the weight average molecular weight of the oligomer can be 300-5000.

[0151] In some embodiments, the mass fraction of the oligomer can be 0%-7.5%, for example, can be 0%, 0.1%, 0.25%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, or a range consisting of any of the aforementioned values, based on the total mass of the monomer, the crosslinking agent, and the oligomer being 100%. 0% indicates that the pre-emulsion does not contain oligomers.

[0152] The crosslinking agent forms a crosslinking structural unit of the crosslinked styrene-based organic particles after polymerization with the monomer.

[0153] In some embodiments, the crosslinking agent can include one or more of divinylbenzene, ethylene glycol dimethacrylate, pentaerythritol tetraacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,8-octanediol diacrylate, trimethylolpropane triacrylate, pentaerythritol trimethacrylate, tetraethylene glycol dimethacrylate, tripropylene glycol diacrylate, N,N-methylenebisacrylamide, N,N'-vinylbisacrylamide.

[0154] In some embodiments, the mass fraction of the crosslinking agent can be 3%-40%, for example, 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 a range consisting of any of the aforementioned values, based on the total mass of the monomer, the crosslinking agent, and the oligomer being 100%. The content of the crosslinking agent in the above range can obtain crosslinked styrene-based organic particles with good heat resistance.

[0155] In some embodiments, the emulsifier can include one or more of sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, sodium polyacrylate, polyvinylpyrrolidone, polyvinyl alcohol, polyoxyethylene ether emulsifier, cellulose and its derivatives. Optionally, the polyoxyethylene ether emulsifier can include OP-type emulsifiers such as OP-4, OP-7, OP-10, OP-15, OP-20, etc.

[0156] In some embodiments, the mass fraction of the emulsifier can be 0.5%-5%, for example, can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.2%, 1.4%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.6%, 2.8%, 3%, 3.2%, 3.4%, 3.6%, 3.8%, 4%, 4.2%, 4.4%, 4.6%, 4.8%, 5%, or a range consisting of any of the above values, based on the total mass of the monomer, the crosslinking agent and the oligomer being 100%.

[0157] In some embodiments, the initiator can include, but is not limited to, one or more of sodium persulfate, potassium persulfate, ammonium persulfate, sodium sulfite, sodium bisulfite, azobisdimethylaminoformamide hydrochloride, azobisdimethylaminoformamide hydrochloride, azobisdimethylaminoformamide hydrochloride.

[0158] In some embodiments, the mass fraction of the initiator can be 0.05%-3%, based on the total mass of the monomer, the crosslinking agent and the oligomer being 100%.

[0159] The more the amount of the initiator, the smaller the particle size of the obtained crosslinked styrene-based organic particles. The amount of the initiator within the above range can obtain crosslinked styrene-based organic particles with narrow particle size distribution without causing explosive polymerization.

[0160] In some embodiments, the pre-emulsion satisfies: the mass fraction of the crosslinking agent is 12%-40%, and the mass fraction of the oligomer is 0.25%-7.5%, based on the total mass of the monomer, the crosslinking agent and the oligomer being 100%.

[0161] The more the amount of the crosslinking agent, the better the heat resistance of the obtained crosslinked styrene-based organic particles. However, the reaction speed of the system can be too fast at this time, and the addition of an appropriate amount of the oligomer that can be radically polymerized can slow down the reaction speed, so that the latex particles are not easy to aggregate, thereby the particle size uniformity can be maintained, and crosslinked styrene-based organic particles with narrow particle size distribution can be obtained.

[0162] The mass fraction of the crosslinking agent can be 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 a range consisting of any of the above values. Alternatively, the mass fraction of the crosslinking agent can be 12%-36%, 12%-32%.

[0163] The mass fraction of the oligomer can be 0.25%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, or a range consisting of any of the aforementioned numerical values. Alternatively, the mass fraction of the oligomer can be 0.5%-7.5%, 0.8%-7.5%, 1%-7.5%, 1.5%-7.5%.

[0164] Alternatively, the pre-emulsion satisfies: the mass fraction of the crosslinking agent is 12%-40%, the mass fraction of the oligomer is 0.25%-7.5%, and the mass fraction of the emulsifier is 1%-5%, based on the total mass of the monomer, the crosslinking agent, and the oligomer being 100%.

[0165] By further adjusting the mass fraction of the emulsifier within the aforementioned range, crosslinked styrene-based organic particles with a narrow particle size distribution can be obtained.

[0166] Alternatively, the pre-emulsion satisfies: the mass fraction of the crosslinking agent is 12%-40%, the mass fraction of the oligomer is 0.25%-7.5%, and the emulsifier includes a polyoxyethylene ether emulsifier, and the mass fraction of the emulsifier is 0.5%-5%, based on the total mass of the monomer, the crosslinking agent, and the oligomer being 100%.

[0167] Alternatively, the pre-emulsion satisfies: the mass fraction of the crosslinking agent is 12%-40%, the mass fraction of the oligomer is 0.25%-7.5%, and the mass fraction of the emulsifier is 1%-5%, and the emulsifier includes a polyoxyethylene ether emulsifier, based on the total mass of the monomer, the crosslinking agent, and the oligomer being 100%.

[0168] By further adjusting the type of the emulsifier within the aforementioned range, crosslinked styrene-based organic particles with a narrow particle size distribution can be obtained.

[0169] In some embodiments, the pre-emulsion satisfies: the mass fraction of the crosslinking agent is greater than or equal to 3% and less than 12%, and the pre-emulsion further satisfies at least one of the following conditions (1) to (3): (1) the mass fraction of the emulsifier is 1%-5%; (2) the emulsifier includes a polyoxyethylene ether emulsifier; and (3) the mass fraction of the oligomer is 0.25%-7.5%, based on the total mass of the monomer, the crosslinking agent, and the oligomer being 100%.

[0170] The mass fraction of the crosslinking agent is greater than or equal to 3% and less than 12%, and by adjusting any one or more of the type of the emulsifier, the mass fraction of the emulsifier, and the mass fraction of the oligomer within the aforementioned range, crosslinked styrene-based organic particles with a narrow particle size distribution can be obtained.

[0171] The mass fraction of the crosslinking agent can be 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, or a range composed of any of the above values. Alternatively, the mass fraction of the crosslinking agent is greater than or equal to 5% and less than 12%, the mass fraction of the crosslinking agent is greater than or equal to 6% and less than 12%, or the mass fraction of the crosslinking agent is greater than or equal to 7% and less than 12%.

[0172] Alternatively, the pre-emulsion satisfies: the mass fraction of the crosslinking agent is greater than or equal to 3% and less than 12%, the mass fraction of the emulsifier is 1%-5%, and the mass fraction of the oligomer is 0%, based on the total mass of the monomer, the crosslinking agent, and the oligomer being 100%.

[0173] Alternatively, the pre-emulsion satisfies: the mass fraction of the crosslinking agent is greater than or equal to 3% and less than 12%, the emulsifier includes a polyoxyethylene ether emulsifier, the mass fraction of the emulsifier is 0.5%-5%, and the mass fraction of the oligomer is 0%, based on the total mass of the monomer, the crosslinking agent, and the oligomer being 100%.

[0174] Alternatively, the pre-emulsion satisfies: the mass fraction of the crosslinking agent is greater than or equal to 3% and less than 12%, the emulsifier includes a polyoxyethylene ether emulsifier, the mass fraction of the emulsifier is 1%-5%, and the mass fraction of the oligomer is 0%, based on the total mass of the monomer, the crosslinking agent, and the oligomer being 100%.

[0175] Alternatively, the pre-emulsion satisfies: the mass fraction of the crosslinking agent is greater than or equal to 3% and less than 12%, the mass fraction of the emulsifier is 1%-5%, and the mass fraction of the oligomer is 0.25%-7.5%, based on the total mass of the monomer, the crosslinking agent, and the oligomer being 100%.

[0176] Alternatively, the pre-emulsion satisfies: the mass fraction of the crosslinking agent is greater than or equal to 3% and less than 12%, the emulsifier includes a polyoxyethylene ether emulsifier, the mass fraction of the emulsifier is 0.5%-5%, and the mass fraction of the oligomer is 0.25%-7.5%, based on the total mass of the monomer, the crosslinking agent, and the oligomer being 100%.

[0177] Alternatively, the pre-emulsion satisfies: the mass fraction of the crosslinking agent is greater than or equal to 3% and less than 12%, the emulsifier includes a polyoxyethylene ether emulsifier, the mass fraction of the emulsifier is 1%-5%, and the mass fraction of the oligomer is 0.25%-7.5%, based on the total mass of the monomer, the crosslinking agent, and the oligomer being 100%.

[0178] In some embodiments, the pre-emulsion can further include a functional monomer having a polar group, the polar group including one or more of an ester group, a carboxyl group, a carboxylate salt, a hydroxyl group, a cyano group, and an amide group.

[0179] The pre-emulsion includes a functional monomer having a polar group, which can reduce the surface tension of the cross-linked styrene-based organic particles, so as to facilitate coating on the surface of the porous base film.

[0180] Optionally, the functional monomer can include one or more of (meth)acrylic acid and derivatives thereof, (meth)acrylate and derivatives thereof, (meth)acrylate and derivatives thereof, acrylonitrile and derivatives thereof, acrylamide and derivatives thereof.

[0181] The mass fraction of the functional monomer can be 0.01%-10%, based on the total mass of the monomer, cross-linking agent and oligomer being 100%.

[0182] In some embodiments, the method for preparing the cross-linked styrene-based organic particles can further include a step of removing the magnetic treatment after the emulsion polymerization reaction is completed.

[0183] The present disclosure also provides a cross-linked styrene-based organic particle emulsion.

[0184] The cross-linked styrene-based organic particle emulsion includes the cross-linked styrene-based organic particles of the present disclosure, or is obtained by the method for preparing the cross-linked styrene-based organic particles of the present disclosure.

[0185] The present disclosure also provides an isolation film. The isolation film includes a porous base film and a coating layer on at least one side of the porous base film, and the coating layer includes a binder and the cross-linked styrene-based organic particles of the present disclosure or the cross-linked styrene-based organic particles prepared by the method of the present disclosure.

[0186] Both the porous base film and the coating layer have a pore structure, so that the isolation film has good air permeability and facilitates ion passing. The cross-linked styrene-based organic particles in the coating layer are connected to each other and fixed by the binder, and the gaps between the cross-linked styrene-based organic particles can form the pore structure.

[0187] In some embodiments, the mass content of the cross-linked styrene-based organic particles in the coating layer can be 50%-99%, based on the total mass of the coating layer.

[0188] Optionally, the mass content of the cross-linked styrene-based organic particles in the coating layer can be 60%-99%, 70%-99%, 80%-99%, 85%-99%, 88%-99%, 80%-97%, 85%-97%, 88%-97%, 80%-95%, 85%-95%, 88%-95%.

[0189] In some embodiments, the binder in the coating layer can include, but is not limited to, one or more of polyacrylate-based binders, nitrile rubber-based binders, polyacrylic acid, polymethacrylic acid, sodium polyacrylate, polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0190] In some embodiments, the coating layer can further include a dispersant, which can include, but is not limited to, one or more of alkylphenol polyoxyethylene ether and the like, polyacrylate-based dispersants, cellulose-based dispersants. As an example, the dispersant can include, but is not limited to, one or more of sodium carboxymethyl cellulose, sodium polyacrylate, and ammonium polyacrylate.

[0191] In some embodiments, the separator film can further include polymeric binder particles.

[0192] The "polymeric binder particles" in the porous coating layer of the separator film play a role in improving the adhesion of the separator film to the electrode sheet, and have substantially no high-temperature resistance.

[0193] In some embodiments, the polymeric binder particles can be embedded in the crosslinked styrene-based organic particles and form protrusions on the surface of the coating layer.

[0194] In other embodiments, the coating layer of the separator film includes a heat-resistant layer disposed on the porous base film and a bonding layer disposed on at least a portion of the surface of the heat-resistant layer away from the porous base film, the crosslinked styrene-based organic particles are disposed in the heat-resistant layer, and the polymeric binder particles are disposed in the bonding layer.

[0195] In yet other embodiments, the coating layer of the separator film includes a heat-resistant layer disposed on one side of the porous base film and a bonding layer disposed on at least a portion of the surface of the other side of the porous base film, the crosslinked styrene-based organic particles are disposed in the heat-resistant layer, and the polymeric binder particles are disposed in the bonding layer.

[0196] In some embodiments, the average particle size of the polymeric binder particles can be 6 μm to 18 μm.

[0197] In some embodiments, the polymeric binder particles can include a vinylidene fluoride-based polymer particle, such as a polyvinylidene fluoride (PVDF) particle and / or a copolymer particle of a vinylidene fluoride monomer and a comonomer.

[0198] The comonomer can include at least one of an olefin monomer, a fluorine-containing olefin monomer, a chlorine-containing olefin monomer, an acrylate monomer, an acrylic monomer, and a fluorine ether monomer.

[0199] Optionally, the comonomer can include at least one of 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-dioxolane), and perfluoro(2,2-dimethyl-1,3-dioxolane).

[0200] In some embodiments, the thickness of the coating layer can be 0.5 μm-5 μm. The thickness of the coating layer refers to the thickness of the coating layer on one side of the porous base film. Optionally, the thickness of the coating layer 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, 0.8 μm-2 μm.

[0201] In some embodiments, the areal density of the coating layer can be 0.5 g / m 2 -5 g / m 2 .

[0202] In some embodiments, the porous base film can include any one or at least two of the following films: polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyamide, polycarbonate, polyimide, polyether ether ketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyether sulfone, polyphenylene ether, cyclic olefin copolymer, polyphenylene sulfide, polyvinyl naphthalene.

[0203] The porous base film can be a single-layer film or a multi-layer composite film. When the porous base film is a multi-layer composite film, the materials of the layers can be the same or different.

[0204] In some embodiments, the thickness of the porous base film can be 4 μm-12 μm, optionally 4 μm-9 μm.

[0205] In some embodiments, the porosity of the porous base film can be 25%-60%, optionally 28%-50%.

[0206] In some embodiments, 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 can be greater than or equal to 1.1.

[0207] The volume distribution particle size Dv50 of the crosslinked styrene-based organic particles and the average pore size of the porous base film have the same unit, such as nm.

[0208] This can reduce the problem of pore blocking and improve the air permeability and ion conductivity of the separation film.

[0209] In some embodiments, the average pore size of the porous base film can be 25 nm-82 nm.

[0210] The average pore size of the porous base film can be tested using a capillary porosimeter (bubble point method). An exemplary testing method is as follows: a circular sample with a diameter of 25 mm is taken and 3-5 drops of wetting liquid are dropped on it, and after the sample is completely wetted, it is placed in a mold, and then an inert gas (such as nitrogen) is used to press the wetting liquid in the pores of the sample to be tested, and the pressure and flow of the pressurized gas are inversely proportional to the pore size. By sampling and pressure and pore size conversion analysis through software, the average pore size of the sample to be tested is obtained. The testing instrument can be a CFP 1500 pore size analyzer from PMI, and the testing pressure can be 100 psi to 350 psi.

[0211] In some embodiments, the thickness of the separator film can be 5 μm-14 μm, optionally 5 μm-12 μm, 6 μm-12 μm. This is advantageous for improving the energy density of the secondary battery cell.

[0212] It should be noted that the coating parameters of the separator film described above are the coating parameters of one side of the porous base film. When the coating is provided on both sides of the porous base film, the coating parameters of any one side meet the present disclosure, and it is considered to fall within the protection scope of the present disclosure.

[0213] The separator film can be prepared according to methods known in the art.

[0214] In some embodiments, a slurry including cross-linked styrene-based organic particles and a binder can be coated on at least one side of the porous base film, and after drying, the separator film is obtained.

[0215] In some embodiments, the slurry can further include polymer binder particles, and after drying of the slurry, the polymer binder particles are embedded in the cross-linked styrene-based organic particles and form protrusions on the surface of the coating.

[0216] In some embodiments, the method for preparing the separator film can include: a step of coating a heat-resistant layer slurry including cross-linked styrene-based organic particles and a binder on at least one side of the porous base film, and after drying, forming a heat-resistant layer; and a step of coating an adhesive layer slurry including polymer binder particles and a binder on at least a part of the surface of the heat-resistant layer, and after drying, obtaining the separator film.

[0217] In some embodiments, the method for preparing the separator film can include: a step of coating a heat-resistant slurry including cross-linked styrene-based organic particles and a binder on one side of the porous base film, and a step of coating an adhesive layer slurry including polymer binder particles and a binder on at least a part of the surface of the other side of the porous base film, and after drying, obtaining the separator film.

[0218] In some embodiments, the solvent of the slurry can be water, such as deionized water.

[0219] In some embodiments, the slurry can further include other components, for example, can further include dispersants and / or wetting agents, etc.

[0220] The embodiments of the present disclosure also provide a secondary battery cell. The secondary battery cell includes the separator film provided by the embodiments of the present disclosure. Thus, the secondary battery cell can have high reliability, high quality energy density, and good cycle performance.

[0221] The secondary battery cell further includes a positive electrode tab, a negative electrode tab, and an electrolyte. The separator film is disposed between the positive electrode tab and the negative electrode tab. The positive electrode tab, the separator film, and the negative electrode tab can form an electrode assembly through a rolling process and / or a stacking process.

[0222] The secondary battery cell provided by the present disclosure can include, but is not limited to, a lithium battery cell, a sodium battery cell, etc. The composition of the positive electrode tab, the negative electrode tab, and the electrolyte can be different for different types of secondary battery cells.

[0223] [Positive electrode tab]

[0224] In some embodiments, the positive electrode tab can include a positive current collector and a positive film layer disposed on at least one surface of the positive current collector and including a positive active material. For example, the positive current collector has two surfaces opposite in the thickness direction of the positive current collector, and the positive film layer is disposed on any one or both of the two opposite surfaces of the positive current collector.

[0225] For example, in a lithium battery cell, the positive active material can include, but is not limited to, one or more of lithium transition metal oxides, lithium-containing phosphates, and their respective modified compounds. Examples of lithium transition metal oxides can include, but are not limited to, one or more of lithium cobalt oxides, lithium nickel oxides, lithium manganese oxides, lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, lithium nickel cobalt manganese oxides, lithium nickel cobalt aluminum oxides, and their respective modified compounds. Examples of lithium-containing phosphates can include, but are not limited to, one or more of lithium iron phosphate, a composite of lithium iron phosphate and carbon, lithium manganese phosphate, a composite of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite of lithium manganese iron phosphate and carbon, and their respective modified compounds. In some embodiments, in order to further improve the energy density of the secondary battery cell, the positive active material can include a compound represented by 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.

[0226] 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.

[0227] 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.

[0228] 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.

[0229] 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.

[0230] 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.

[0231] 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.

[0232] In some embodiments, the positive current collector can employ a metal foil or a composite current collector. As an example of a metal foil, an aluminum foil can be employed. The composite current collector can include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material can include, but is not limited to, one or more of aluminum, an aluminum alloy, nickel, a nickel alloy, titanium, a titanium alloy, silver, and a silver alloy. As an example, the polymer material base layer can include, but is not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene, and polyethylene.

[0233] The positive electrode film layer is typically formed by coating a positive electrode slurry on a positive electrode current collector, drying, and cold-pressing. The positive electrode slurry is typically formed by dispersing and uniformly stirring a positive electrode active material, a positive electrode conductive agent, a positive electrode binder, and any other components in a solvent. The solvent can be N-methyl pyrrolidone (NMP), but is not limited thereto.

[0234] [Negative electrode tab]

[0235] In some embodiments, the negative electrode tab can include a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector and including a negative electrode active material. For example, the negative electrode current collector has two surfaces opposite in the thickness direction thereof, and the negative electrode film layer is disposed on either one or both of the two opposite surfaces of the negative electrode current collector.

[0236] The negative electrode active material can employ a material known in the art that can be used for a secondary battery cell. As an example, the negative electrode active material can include, but is not limited to, one or more of natural graphite, artificial graphite, soft carbon, hard carbon, a silicon-based material, a tin-based material, and lithium titanate. The silicon-based material can include, but is not limited to, one or more of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy material. The tin-based material can include, but is not limited to, one or more of elemental tin, tin oxide, and tin alloy material.

[0237] In some embodiments, the negative electrode film layer can further include a negative electrode conductive agent. As an example, the negative electrode conductive agent can include, but is not limited to, one or more of super P, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0238] In some embodiments, the negative electrode film layer can further include a negative electrode binder. As an example, the negative electrode binder can include, but is not limited to, one or more of styrene butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, water-based acrylic resin (e.g., polyacrylic acid PAA, polymethylacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0239] In some embodiments, the negative electrode film layer can further include other auxiliary agents. As an example, the other auxiliary agents can include thickening agents, such as sodium carboxymethyl cellulose (CMC), PTC thermistor materials, and the like.

[0240] In some embodiments, the negative electrode current collector can employ a metal foil or a composite current collector. As an example of the metal foil, a copper foil can be employed. The composite current collector can include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material can include, but is not limited to, one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer can include, but is not limited to, one or more of polypropylene, polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene, and polyethylene.

[0241] The negative electrode film layer is typically formed by coating a negative electrode slurry on a negative electrode current collector, drying, and cold-pressing. The negative electrode slurry is typically formed by dispersing a negative electrode active material, a negative electrode conductive agent, a negative electrode binder, and other optional auxiliary agents in a solvent and stirring uniformly. The solvent can be N-methyl pyrrolidone (NMP) or deionized water, but is not limited thereto.

[0242] The negative electrode tab does not exclude other additional functional layers other than the negative electrode film layer. For example, in some embodiments, the negative electrode tab further includes a conductive primer layer (e.g., composed of a conductive agent and a binder) interposed between the negative electrode current collector and the negative electrode film layer and disposed on the surface of the negative electrode current collector.

[0243] In some embodiments, the negative electrode tab can employ a foamed metal. The foamed metal can be foamed nickel, foamed copper, foamed aluminum, foamed alloy, foamed carbon, or the like. When the foamed metal is employed as the negative electrode tab, the surface of the foamed metal can not be provided with a negative electrode active material, and of course, can be provided with a negative electrode active material.

[0244] [Electrolyte]

[0245] The electrolyte functions to conduct ions between the positive electrode tab and the negative electrode tab.

[0246] In some embodiments, the electrolyte employs an electrolytic solution including an electrolyte salt and an organic solvent.

[0247] For example, in the case of lithium battery cells, the electrolyte salt can include, but is not limited to, one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonylimide (LiFSI), lithium bis-trifluoromethanesulfonylimide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalato borate (LiDFOB), lithium bisoxalato borate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalato phosphate (LiDFOP), and lithium tetrafluorooxalato phosphate (LiTFOP).

[0248] For example, in the case of sodium battery cells, the electrolyte salt can include, but is not limited to, one or more of sodium hexafluorophosphate (NaPF6), sodium tetrafluoroborate (NaBF4), sodium perchlorate (NaClO4), sodium hexafluoroarsenate (NaAsF6), sodium bisfluorosulfonylimide (NaFSI), sodium bis-trifluoromethanesulfonylimide (NaTFSI), sodium trifluoromethanesulfonate (NaTFS), sodium difluorooxalato borate (NaDFOB), sodium bisoxalato borate (NaBOB), sodium difluorophosphate (NaPO2F2), sodium difluorodioxalato phosphate (NaDFOP), and sodium tetrafluorooxalato phosphate (NaTFOP).

[0249] In some embodiments, the organic solvent can include, but is not limited to, one or more of ethylene carbonate (EC), propylene carbonate (PC), methyl ethyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS), diethyl sulfone (ESE), ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyl tetrahydrofuran, diphenyl ether, crown ether.

[0250] In some embodiments, an additive can also be included in the electrolyte. For example, the additive can include a negative electrode film-forming additive, can also include a positive electrode film-forming additive, and can also include an additive capable of improving certain properties of the secondary battery cell, such as an additive capable of improving overcharge performance, an additive capable of improving high-temperature performance, an additive capable of improving low-temperature performance, and the like.

[0251] Optionally, the additive can include one or more of fluoroethylene carbonate (FEC), vinylene carbonate (VC), 1,3-propane sultone (PS), and vinyl sulfate (DTD).

[0252] Methods for preparing secondary battery cells are well known. In some embodiments, a positive electrode sheet, a separator, a negative electrode sheet, and an electrolyte can be assembled to form a secondary battery cell. As an example, a positive electrode sheet, a separator, and a negative electrode sheet can be formed into an electrode assembly through a winding process and / or a stacking process, the electrode assembly can be placed in an outer package, an electrolyte described above can be injected after drying, and the secondary battery cell can be obtained after processes such as vacuum packaging, standing, and formation.

[0253] Embodiments

[0254] The present disclosure is more particularly described in the following examples that are intended to be illustrative only, as numerous modifications and variations within the scope of the present disclosure will become apparent to those skilled in the art. Unless otherwise noted, all parts, percentages, and ratios reported herein are on a mass basis, and all reagents used in the examples are commercially available or synthesized according to conventional methods, and used without further purification, and the equipment used in the examples is commercially available.

[0255] A pre-emulsion was prepared by emulsifying 0.08 g of sodium dodecyl sulfate, 80 mg of sodium persulfate, 20 ml of deionized water, 39.5 g of styrene, and 0.5 g of divinylbenzene. 140 g of deionized water was added to a reactor, and the temperature was raised to 70°C. The pre-emulsion was added dropwise under nitrogen protection and stirring. After 4 h of reaction, the temperature was raised to 80°C for 1.5 h of curing reaction, and an organic particle D1# emulsion was obtained.

[0256] A pre-emulsion was prepared by emulsifying 0.8 g of sodium dodecyl sulfate, 80 mg of sodium persulfate, 20 ml of deionized water, 33.4 g of styrene, 6 g of divinylbenzene, and 0.6 g of methoxypolyethylene glycol acrylate with a weight average molecular weight of 500. 140 g of deionized water was added to a reactor, and the temperature was raised to 70°C. The pre-emulsion was added dropwise under nitrogen protection and stirring. After 4 h of reaction, the temperature was raised to 80°C for 1.5 h of curing reaction, and an organic particle 1# emulsion was obtained.

[0257] A pre-emulsion was prepared by emulsifying 0.8 g of sodium dodecyl sulfate, 80 mg of sodium persulfate, 20 ml of deionized water, 31.4 g of styrene, 8 g of divinylbenzene, and 0.6 g of methoxypolyethylene glycol acrylate with a weight average molecular weight of 500. 140 g of deionized water was added to a reactor, and the temperature was raised to 70°C. The above-prepared pre-emulsion was added dropwise under nitrogen protection and stirring, and the reaction was allowed to proceed for 4 h. The temperature was then raised to 80°C for aging for 1.5 h, and an organic particle 2# emulsion was obtained.

[0258] A pre-emulsion was prepared by emulsifying 0.8 g of sodium dodecyl sulfate, 80 mg of sodium persulfate, 20 ml of deionized water, 29.4 g of styrene, 10 g of divinylbenzene, and 0.6 g of methoxypolyethylene glycol acrylate with a weight average molecular weight of 500. 140 g of deionized water was added to a reactor, and the temperature was raised to 70°C. The above-prepared pre-emulsion was added dropwise under nitrogen protection and stirring, and the reaction was allowed to proceed for 4 h. The temperature was then raised to 80°C for aging for 1.5 h, and an organic particle 3# emulsion was obtained.

[0259] A pre-emulsion was prepared by emulsifying 0.8 g of sodium dodecyl sulfate, 80 mg of sodium persulfate, 20 ml of deionized water, 33.1 g of styrene, 6 g of divinylbenzene, and 0.9 g of methoxypolyethylene glycol acrylate with a weight average molecular weight of 500. 140 g of deionized water was added to a reactor, and the temperature was raised to 70°C. The above-prepared pre-emulsion was added dropwise under nitrogen protection and stirring, and the reaction was allowed to proceed for 4 h. The temperature was then raised to 80°C for aging for 1.5 h, and an organic particle 4# emulsion was obtained.

[0260] A pre-emulsion was prepared by emulsifying 0.8 g of sodium dodecyl sulfate, 80 mg of sodium persulfate, 20 ml of deionized water, 32 g of styrene, 6 g of divinylbenzene, and 2 g of methoxypolyethylene glycol acrylate with a weight average molecular weight of 500. 140 g of deionized water was added to a reactor, and the temperature was raised to 70°C. The above-prepared pre-emulsion was added dropwise under nitrogen protection and stirring, and the reaction was allowed to proceed for 4 h. The temperature was then raised to 80°C for aging for 1.5 h, and an organic particle 5# emulsion was obtained.

[0261] A pre-emulsion was prepared by emulsifying 0.8 g of sodium dodecyl sulfate, 80 mg of sodium persulfate, 20 ml of deionized water, 31 g of styrene, 6 g of divinylbenzene, and 3 g of methoxypolyethylene glycol acrylate with a weight average molecular weight of 500. 140 g of deionized water was added to a reactor, and the temperature was raised to 70°C. The above-prepared pre-emulsion was added dropwise under nitrogen protection and stirring, and the reaction was allowed to proceed for 4 h. The temperature was then raised to 80°C for aging for 1.5 h, and an organic particle 6# emulsion was obtained.

[0262] A pre-emulsion was prepared by emulsifying 0.8 g of sodium dodecyl sulfate, 80 mg of sodium persulfate, 20 ml of deionized water, 33.9 g of styrene, 6 g of divinylbenzene, and 0.1 g of methoxypolyethylene glycol acrylate with a weight average molecular weight of 500. 140 g of deionized water was added to a reactor, and the temperature was raised to 70°C. The pre-emulsion was added dropwise under nitrogen protection and stirring. After 4 h of reaction, the temperature was raised to 80°C for 1.5 h of curing reaction to obtain organic particle emulsion 7#.

[0263] A pre-emulsion was prepared by emulsifying 1.5 g of sodium dodecyl sulfate, 80 mg of sodium persulfate, 20 ml of deionized water, 33.4 g of styrene, 6 g of divinylbenzene, and 0.6 g of methoxypolyethylene glycol acrylate with a weight average molecular weight of 500. 140 g of deionized water was added to a reactor, and the temperature was raised to 70°C. The pre-emulsion was added dropwise under nitrogen protection and stirring. After 4 h of reaction, the temperature was raised to 80°C for 1.5 h of curing reaction to obtain organic particle emulsion 8#.

[0264] A pre-emulsion was prepared by emulsifying 0.32 g of OP-10, 80 mg of sodium persulfate, 20 ml of deionized water, 36 g of styrene, and 4 g of divinylbenzene. 140 g of deionized water was added to a reactor, and the temperature was raised to 70°C. The pre-emulsion was added dropwise under nitrogen protection and stirring. After 4 h of reaction, the temperature was raised to 80°C for 1.5 h of curing reaction to obtain organic particle emulsion 9#.

[0265] A pre-emulsion was prepared by emulsifying 1 g of OP-10, 80 mg of sodium persulfate, 20 ml of deionized water, 36 g of styrene, and 4 g of divinylbenzene. 140 g of deionized water was added to a reactor, and the temperature was raised to 70°C. The pre-emulsion was added dropwise under nitrogen protection and stirring. After 4 h of reaction, the temperature was raised to 80°C for 1.5 h of curing reaction to obtain organic particle emulsion 10#.

[0266] Organic particle performance test

[0267] (1) Glass transition temperature T of organic particles g Test

[0268] An appropriate amount of sample (e.g., 5 mg-15 mg) was placed in a differential scanning calorimeter (DSC) crucible, shaken flat, and covered with a crucible cover. The parameter settings were: nitrogen atmosphere, purging gas 60 mL / min, and protective gas 20 mL / min. The program settings were: heating from 25°C to 200°C at a rate of 10°C / min, holding for 5 min to eliminate thermal history, cooling from 200°C to -40°C at a rate of 10°C / min, and heating from -40°C to 300°C at a rate of 10°C / min. The glass transition temperature T was obtained from the DSC curve. g .

[0269] (2) Melting point test of organic particles

[0270] Take an appropriate amount of sample (e.g. 5-15 mg) and place it in a DSC crucible, shake it flat, and cover it with a crucible cover; parameter settings: nitrogen atmosphere, purging gas 60 mL / min, protective gas 20 mL / min; program settings: increase the temperature from 25°C to 200°C at a rate of 10°C / min, hold for 5 min to eliminate thermal history, then decrease the temperature from 200°C to -40°C at a rate of 10°C / min, and then increase the temperature to 300°C at a rate of 10°C / min. Determine whether the organic particles have a melting point by the DSC curve.

[0271] (3) Particle size test

[0272] Dv10, Dv50, Dv90 respectively represent the particle size corresponding to the cumulative volume distribution percentage of 10%, 50%, and 90% of the material. The test standard refers to GB / T 19077-2016. The test instrument is a MasterSizer 3000 laser particle size analyzer. During testing, add 1 g of the sample to be tested into a clean beaker, add 20 ml of deionized water, and ultrasonic at 53 KHz / 120 W for 5 min to ensure complete dispersion of the sample; turn on the laser particle size analyzer, clean the light path system, and then automatically test the background; stir the ultrasonically treated sample solution to make it evenly dispersed, place it in the sample cell as required, and start measuring the particle size.

[0273] The above-prepared organic particles 1# to 10# meet the following characteristics: no melting point, glass transition temperature T g between 108°C and 160°C.

[0274] Next, the above-prepared organic particles are used in the isolation film to verify their effect on the performance of the isolation film and the secondary battery cell.

[0275] A commercially available polyethylene microporous film with a thickness of 7 μm is used as the porous base film; the above-prepared organic particle emulsion, dispersant sodium carboxymethyl cellulose, and binder polyacrylate are mixed uniformly in deionized water at a solid mass ratio of organic particles: dispersant: binder of 90:2:8 to obtain a coating slurry; the coating slurry is uniformly coated on both surfaces of the porous base film, and the solvent is removed by drying to obtain an isolation film. The coating area density is 2.4 g / m 2 .

[0276] The positive electrode active material lithium iron phosphate, the positive electrode binder polyvinylidene fluoride (PVDF), and the positive electrode conductive agent carbon black are mixed in N-methyl pyrrolidone (NMP) at a mass ratio of 97:2:1, and the mixture is stirred thoroughly to prepare a positive electrode slurry; the positive electrode slurry is uniformly coated on the positive electrode current collector aluminum foil, and then dried, cold-pressed, and cut to obtain a positive electrode sheet.

[0277] The negative active material artificial graphite, the negative conductive agent acetylene black, the negative binder styrene-butadiene rubber (SBR), and the thickening agent sodium carboxymethyl cellulose were added into deionized water according to a mass ratio of 96.0:1.4:1.5:1.1, and a negative slurry was prepared after being fully stirred and mixed uniformly; the negative slurry was uniformly coated on the negative current collector copper foil, and then was subjected to drying, cold pressing, and slitting to obtain a negative electrode sheet.

[0278] Vinyl carbonate (EC), methyl ethyl carbonate (EMC) were mixed according to a volume ratio of 3:7 to obtain a mixed solvent, and then LiPF6 and vinylene carbonate (VC) were dissolved in the mixed solvent to obtain an electrolyte. The concentration of LiPF6 was 1 mol / L. The mass fraction of VC was 3% based on the mass of the electrolyte.

[0279] The positive electrode sheet, the separator, and the negative electrode sheet were stacked in sequence and wound and hot-pressed to obtain an electrode assembly; the electrode assembly was placed in a hard-shell outer package, and the electrolyte prepared above was added, and after processes such as packaging, standing, formation, and aging, a secondary battery monomer was obtained.

[0280] Performance test

[0281] (1) Test of heat shrinkage rate of the separator

[0282] The test of the heat shrinkage rate of the separator can refer to GB / T 36363-2018.

[0283] The separator was punched into a sample with a width of 50 mm and a length of 100 mm by a punch machine, 5 parallel samples were placed on an A4 paper, and then the A4 paper with the samples was placed on corrugated paper with a thickness of 1 mm to 5 mm.

[0284] The temperature of the air-blast oven was set to 130℃, and after the temperature reached the set temperature and stabilized for 60 min, the A4 paper placed on the corrugated paper was placed in the air-blast oven, and the timing was started, and after reaching the set time (1 h in the present disclosure), the length and width of the separator were measured, and the values were marked as a and b respectively.

[0285] Heat shrinkage rate calculation: longitudinal (MD) heat shrinkage rate = [(100-a) / 100]x100%, transverse (TD) heat shrinkage rate = [(50-b) / 50]x100%, and the average value of 3 parallel samples was taken as the test result.

[0286] (2) Test of cycle performance of the secondary battery monomer

[0287] The secondary battery cell was charged at 25℃ with a constant current of 1 / 3C to 3.8V, then charged at a constant voltage of 3.8V until the current was 0.05C, rested for 5min, then discharged at a constant current of 1 / 3C to 2.0V, and the obtained discharge capacity was recorded as the initial capacity CO; the above charging and discharging steps were repeated, and the discharge capacity of the secondary battery cell after the nth cycle was recorded as Cn, then the capacity retention rate Pn of the secondary battery cell after each cycle was Pn=(Cn / CO)×100%.

[0288] Table 1

[0289] From the above test results, it can be seen that the crosslinked styrene-based organic particles satisfying the particle size distribution (Dv90-Dv10) / Dv50 less than or equal to 3.0 can make the separator film have better heat resistance, and the secondary battery cell has better cycle performance.

[0290] It should be noted that the present disclosure is not limited to the above embodiments. The above embodiments are only examples, and embodiments having substantially the same configuration and playing the same role and effect within the scope of the technical solutions of the present disclosure are all included in the technical scope of the present disclosure. In addition, within the scope of the main idea of the present disclosure, various modifications that can be thought of by those skilled in the art are applied to the embodiments, and other modes constructed by combining part of the constituent elements in the embodiments are also included in the scope of the present 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 layer comprises crosslinked styrene-based organic particles, and a particle size distribution (Dv90-Dv10) / Dv50 of the crosslinked styrene-based organic particles is less than or equal to 3.

0.

2. The separator film according to claim 1, wherein The particle size distribution (Dv90-Dv10) / Dv50 of the crosslinked styrene-based organic particles is 0.8-2.

6.

3. The separator film according to claim 1 or 2, wherein The crosslinked styrene-based organic particles satisfy at least one of the following conditions (1) to (3): (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 80 nm-300 nm; (3) The volume distribution particle size Dv90 of the crosslinked styrene-based organic particles is 100 nm-800 nm.

4. The separator film according to any one of claims 1 to 3, wherein The crosslinked styrene-based organic particles satisfy at least one of the following conditions (1) to (3): (1) The volume distribution particle size Dv10 of the crosslinked styrene-based organic particles is 40 nm-70 nm; (2) The volume distribution particle size Dv50 of the crosslinked styrene-based organic particles is 90 nm-150 nm; (3) The volume distribution particle size Dv90 of the crosslinked styrene-based organic particles is 160 nm-500 nm.

5. The separator film according to any one of claims 1 to 4, wherein The crosslinked styrenic organic particles have a true density of 1.0 g / cm 3 -1.4 g / cm 3 .

6. The separator film according to any one of claims 1 to 5, 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, and 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, and N,N'-vinylbisacrylamide structural units.

7. The separator film according to any one of claims 1 to 6, wherein The crosslinked styrenic organic particles have a glass transition temperature Tg g of 108°C to 160°C.

8. The separator film according to claim 7, wherein The glass transition temperature T of the crosslinked styrenic organic particles is in the range of 120 °C to 160 °C. g is 122 °C - 160 °C.

9. The separator film according to any one of claims 1-8, wherein The crosslinked styrene-based organic particles have no melting point.

10. The separator film according to any one of claims 1-9, wherein The crosslinked styrene-based organic particles have a swelling degree of less than or equal to 3% 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 less than or equal to 3% 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.

11. The separator film according to any one of claims 1 to 10, wherein The crosslinked styrene-based organic particles do not have an oxidation peak in a voltage range of 2.5V to 4.4V in a cyclic voltammogram of the first cycle.

12. The separator membrane according to any one of claims 1 to 11, wherein, a mass content of the crosslinked styrenic organic particles in the coating layer is 50% to 99% based on the total mass of the coating layer; and / or, a thickness of the coating layer is 0.5 pm to 5 pm; and / or, The areal density of the coating is 0.5 g / m 2 - 5 g / m 2 .

13. The separator membrane according to any one of claims 1 to 12, wherein, a ratio of a volume distribution particle size Dv50 of the crosslinked styrenic organic particles to an average pore size of the porous base membrane is greater than or equal to 1.

1.

14. Crosslinked styrenic organic particles, wherein, a particle size distribution (Dv90-Dv10) / Dv50 of the crosslinked styrenic organic particles is less than or equal to 3.

0.

15. The crosslinked styrenic organic particle of claim 14, wherein, a particle size distribution (Dv90-Dv10) / Dv50 of the crosslinked styrenic organic particles is 0.8 to 2.

6.

16. The crosslinked styrenic organic particles according to claim 14 or 15, wherein, the crosslinked styrenic organic particles satisfy at least one of the following conditions (1) to (3): (1) a volume distribution particle size Dv10 of the crosslinked styrenic organic particles is 40 nm to 200 nm; (2) a volume distribution particle size Dv50 of the crosslinked styrenic organic particles is 80 nm to 300 nm; (3) a volume distribution particle size Dv90 of the crosslinked styrenic organic particles is 100 nm to 800 nm.

17. The crosslinked styrenic organic particles according to any one of claims 14-16, wherein, the crosslinked styrenic organic particles satisfy at least one of the following conditions (1) to (3): (1) a volume distribution particle size Dv10 of the crosslinked styrenic organic particles is 40 nm to 70 nm; (2) a volume distribution particle size Dv50 of the crosslinked styrenic organic particles is 90 nm to 150 nm; (3) a volume distribution particle size Dv90 of the crosslinked styrenic organic particles is 160 nm to 500 nm.

18. The crosslinked styrenic organic particles according to any one of claims 14-17, wherein, The crosslinked styrenic organic particles have a true density of 1.0 g / cm 3 -1.4 g / cm 3 .

19. The crosslinked styrenic organic particles according to any one of claims 14-18, wherein, the crosslinked styrenic organic particles include a styrene or styrene derivative structural unit and a crosslinking structural unit; optionally, the styrene or styrene derivative structural unit includes 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, a 2,5-dimethylstyrene structural unit; optionally, the crosslinking structural unit includes 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, a N,N-methylenebisacrylamide structural unit, a N,N'-vinylbisacrylamide structural unit.

20. The crosslinked styrenic organic particles according to any one of claims 14-19, wherein, The crosslinked styrenic organic particles have a glass transition temperature Tg g of 108°C to 160°C.

21. The crosslinked styrenic organic particle of claim 20, wherein, The glass transition temperature T of the crosslinked styrenic organic particles is g from 122 °C to 160 °C.

22. The crosslinked styrenic organic particles according to any one of claims 14 to 21, wherein, the crosslinked styrenic organic particles have no melting point.

23. The crosslinked styrenic organic particles according to any one of claims 14 to 22, wherein, The crosslinked styrene-based organic particles have a swelling degree of less than or equal to 3% 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 less than or equal to 3% 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.

24. The crosslinked styrenic organic particles according to any one of claims 14-23, wherein, The crosslinked styrene-based organic particles do not have an oxidation peak in the voltage range of 2.5V to 4.4V in the cyclic voltammetry curve of the first cycle.

25. A method for preparing crosslinked styrene-based organic particles, comprising the steps of: providing a pre-emulsion comprising monomers, a crosslinking agent, an emulsifier, an initiator, water, and optionally oligomers, wherein the monomers comprise one or more of styrene and derivatives thereof, and the oligomers are free-radically polymerizable, and performing an emulsion polymerization reaction under heating, inert gas protection, and stirring conditions to obtain the crosslinked styrene-based organic particles, wherein the crosslinked styrene-based organic particles have a particle size distribution (Dv90-Dv10) / Dv50 of less than or equal to 3.

0.

26. The method of claim 25, wherein, The maturation temperature of the emulsion polymerization reaction is 76°C-90°C; and / or, the maturation time of the emulsion polymerization reaction is 1h-6h.

27. The method of claim 25 or 26, wherein, The emulsion polymerization reaction comprises the steps of: under a first heating temperature, inert gas protection, and stirring conditions, dropping the pre-emulsion into a reactor containing water, and after a first time, increasing the temperature to a maturation temperature to perform a maturation reaction to obtain the crosslinked styrene-based organic particles, Optionally, the first heating temperature is 55°C-70°C; Optionally, the first time is 3h-6h.

28. The method of any one of claims 25-27, wherein, The pre-emulsion satisfies at least one of the following conditions (1) to (3): (1) the oligomers comprise one or more of 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; (2) the weight average molecular weight of the oligomers is 300-5000; (3) the mass fraction of the oligomers is 0%-7.5% based on 100% of the total mass of the monomers, the crosslinking agent, and the oligomers.

29. The method of any one of claims 25-28, wherein the crosslinking agent comprises 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, and N,N'-vinylbisacrylamide; and / or, a mass fraction of the crosslinking agent is 3% to 40% based on 100% of the total mass of the monomer, the crosslinking agent, and the oligomer; and / or, the monomer includes one or more of styrene, 1-methyl-1-styrene, 4-methylstyrene, 2-methylstyrene, 2,4-dimethylstyrene, and 2,5-dimethylstyrene.

30. The method according to any one of claims 25 to 29, wherein, 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, a mass fraction of the emulsifier is 0.5% to 5% based on 100% of the total mass of the monomer, the crosslinking agent, and the oligomer.

31. The method of any one of claims 25-30, wherein, the pre-emulsion satisfies: a mass fraction of the crosslinking agent is 12% to 40% and a mass fraction of the oligomer is 0.25% to 7.5% based on 100% of the total mass of the monomer, the crosslinking agent, and the oligomer.

32. The method of any one of claims 25-31, wherein, the pre-emulsion satisfies: a mass fraction of the crosslinking agent is greater than or equal to 3% and less than 12% based on 100% of the total mass of the monomer, the crosslinking agent, and the oligomer, and the pre-emulsion further satisfies at least one of the following conditions (1) to (3): (1) a mass fraction of the emulsifier is 1% to 5%; (2) the emulsifier includes a polyoxyethylene ether emulsifier; and (3) a mass fraction of the oligomer is 0.25% to 7.5%.

33. A crosslinked styrene-based organic particle emulsion including the crosslinked styrene-based organic particle according to any one of claims 14 to 24, or obtained by the method according to any one of claims 25 to 32.

34. A secondary battery cell including a positive electrode sheet, a negative electrode sheet, and the separator according to any one of claims 1 to 13, the separator being disposed between the positive electrode sheet and the negative electrode sheet.

35. A battery device including a plurality of the secondary battery cell according to claim 34.

36. An electric device including the secondary battery cell according to claim 34 or the battery device according to claim 35.

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