Crosslinked styrene organic particles, method for preparing same, crosslinked styrene organic particle emulsion, separator, secondary battery cell, battery device, and power device

Abstract

The invention provides cross-linked styrene organic particles, a preparation method thereof, a cross-linked styrene organic particle emulsion, an isolating membrane, a secondary battery monomer, a battery device and a power utilization device. The particle size distribution (Dv90-Dv10) / Dv50 of the cross-linked styrene organic particles is less than or equal to 3.0. The crosslinked styrene organic particles are used in the isolating membrane, so that the secondary battery monomer has high reliability, high mass energy density and good cycle performance.

Description

[0001] This application claims priority to Chinese Patent Application No. 202410947830.9, filed on July 15, 2024, entitled “Cross-linked styrene organic particles and their preparation method, separator membrane, battery cell, and electrical device”, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This disclosure relates to a cross-linked styrene-based organic particle and its preparation method, a cross-linked styrene-based organic particle emulsion, a separator, a secondary battery cell, a battery device, and an electrical device. Background Technology

[0003] As the application range of rechargeable battery cells becomes increasingly widespread, the demands on them are also growing, with higher requirements for energy density and reliability. Therefore, how to achieve higher energy density in rechargeable battery cells while maintaining high reliability is a pressing technical problem that needs to be solved. Summary of the Invention

[0004] This disclosure provides cross-linked styrene-based organic particles and their preparation method, a cross-linked styrene-based organic particle emulsion, a separator, a secondary battery cell, a battery device, and an electrical device. The cross-linked styrene-based organic particles, when used in the separator, enable the secondary battery cell to possess high reliability, high energy density, and good cycle performance.

[0005] In a first aspect, this disclosure provides a cross-linked styrene-based organic particle, wherein the particle size distribution (Dv90-Dv10) / Dv50 of the cross-linked styrene-based organic particle is less than or equal to 3.0.

[0006] Cross-linked styrene-based organic particles have low density, allowing secondary battery cells to achieve higher mass energy density. The cross-linked styrene-based organic particles disclosed herein exhibit good heat resistance. By using these particles in a separator membrane, they generate forces that resist membrane shrinkage, thereby improving the overall thermal shrinkage of the separator, enhancing its heat resistance, and increasing the reliability of the secondary battery cell. The particle size distribution (Dv90-Dv10) / Dv50 of the cross-linked styrene-based organic particles is less than or equal to 3.0, allowing for close packing of the particles. This improves both the heat resistance and air permeability of the separator membrane, resulting in high reliability and good cycle performance for the secondary battery cell. Therefore, the cross-linked styrene-based organic particles of this disclosure, when used in a separator membrane, enable secondary battery cells to possess high reliability, high mass energy density, and good cycle performance.

[0007] In some embodiments, the crosslinked styrene-based organic particles have a particle size distribution (Dv90-Dv10) / Dv50 of 0.8-2.6.

[0008] In this way, 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.

[0009] 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.

[0010] 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.

[0011] 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.

[0012] The volume distribution particle size of the crosslinked styrene-based organic particles in the above range is beneficial to further improve the heat resistance of the separator film and improve the reliability of the secondary battery cell. It is also beneficial for the separator film to have lower impedance, so that the cycle performance of the secondary battery cell can also be improved.

[0013] In some embodiments, the crosslinked styrene-based organic particles have a true density of 1.0 g / cm 3 -1.4 g / cm 3 In this way, the secondary battery cell using the separator film of the present disclosure can have a higher mass energy density.

[0014] In some embodiments, the crosslinked styrene-based organic particles include styrene or styrene derivative structural units and crosslinking structural units.

[0015] Optionally, the styrene or styrene derivative structural units include 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.

[0016] Optionally, the crosslinking structure unit comprises one or more of a divinylbenzene structure unit, a ethylene glycol dimethacrylate structure unit, a pentaerythritol tetraacrylate structure unit, a 1,4-butanediol diacrylate structure unit, a 1,6-hexanediol diacrylate structure unit, a 1,8-octanediol diacrylate structure unit, a trimethylolpropane triacrylate structure unit, a pentaerythritol trimethacrylate structure unit, a tetraethylene glycol dimethacrylate structure unit, a tripropylene glycol diacrylate structure unit, a N,N-methylenebisacrylamide structure unit, and a N,N'-vinylbisacrylamide structure unit.

[0017] In some embodiments, the glass transition temperature T g is 108°C-160°C, optionally 122°C-160°C.

[0018] The glass transition temperature T g In the above range, the thermal stability is better, and the heat shrinkage of the separator film can be better resisted, the heat resistance of the separator film is improved, and the reliability of the secondary battery cell is improved.

[0019] In some embodiments, the crosslinking styrene-based organic particles have no melting point.

[0020] The crosslinking styrene-based organic particles of the present disclosure have no melting point, indicating that the heat resistance and thermal stability of the crosslinking styrene-based organic particles are good, and thus the heat shrinkage of the separator film can be better resisted, the heat resistance of the separator film is improved, and the reliability of the secondary battery cell is improved.

[0021] In some embodiments, the swelling degree of the crosslinking styrene-based organic particles in a mixed solvent composed of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 3:7 is less than or equal to 3% when immersed at 60°C for 7 days.

[0022] The crosslinking styrene-based organic particles have a small swelling degree in an organic solvent, and have a high structural stability during long-term use of the secondary battery cell, and thus the problem of a decrease in the air permeability of the separator film during use is improved.

[0023] In some embodiments, the dissolution rate of the crosslinking styrene-based organic particles in a mixed solvent composed of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 3:7 is less than or equal to 3% when immersed at 60°C for 7 days.

[0024] The crosslinking styrene-based organic particles have a small dissolution rate in an organic solvent, and have a high structural stability during long-term use of the secondary battery cell, and have a high chemical stability in the electrolyte, and thus the secondary battery cell has a long cycle stability.

[0025] 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.

[0026] 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, have good electrochemical stability, and can be applied in high-voltage secondary battery cells to improve the operating voltage and energy density of the secondary battery cells.

[0027] In the second aspect, the present disclosure provides a method for preparing crosslinked styrene-based organic particles, comprising the following steps: providing a pre-emulsion comprising monomers, a crosslinking agent, an emulsifier, an initiator, water, and optionally an oligomer, and performing an emulsion polymerization reaction under heating, inert gas protection, and stirring conditions to obtain the crosslinked styrene-based organic particles, wherein the monomers include one or more of styrene and its derivatives, the oligomer is free-radically polymerizable, and the particle size distribution (Dv90-Dv10) / Dv50 of the crosslinked styrene-based organic particles is less than or equal to 3.0.

[0028] In some embodiments, the maturation temperature of the emulsion polymerization reaction is 76°C-90°C.

[0029] In some embodiments, the maturation time of the emulsion polymerization reaction is 1h-6h.

[0030] In some embodiments, the emulsion polymerization reaction comprises the following steps: dropping the pre-emulsion into a reactor containing water under a first heating temperature, inert gas protection, and stirring conditions, and then increasing the temperature to a maturation temperature for a maturation reaction after a first time to obtain the crosslinked styrene-based organic particles.

[0031] Optionally, the first heating temperature is 55°C-70°C.

[0032] Optionally, the first time is 3h-6h.

[0033] In some embodiments, the oligomer includes 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.

[0034] In some embodiments, the weight average molecular weight of the oligomer is 300-5000.

[0035] 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.

[0036] In some embodiments, the crosslinking agent includes one or more of divinylbenzene, ethylene glycol dimethacrylate, pentaerythritol tetraacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate, 1,8-octanediol diacrylate, trimethylolpropane triacrylate, pentaerythritol trimethacrylate, tetraethylene glycol dimethacrylate, tripropylene glycol diacrylate, N,N-methylenebisacrylamide, N,N'-vinylbisacrylamide.

[0037] 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.

[0038] In some embodiments, the monomer includes one or more of styrene, 1-methyl-1-phenylethylene, 4-methylphenylethylene, 2-methylphenylethylene, 2,4-dimethylphenylethylene, 2,5-dimethylphenylethylene.

[0039] In some embodiments, the emulsifier includes one or more of sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, sodium polyacrylate, polyvinylpyrrolidone, polyvinyl alcohol, polyoxyethylene ether emulsifier, cellulose, and derivatives thereof.

[0040] 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.

[0041] 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.

[0042] 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 includes a polyoxyethylene ether emulsifier; (3) the mass fraction of the oligomer is 0.25%-7.5%.

[0043] In a third aspect, the present disclosure provides a crosslinked styrene-based organic particle emulsion including the crosslinked styrene-based organic particle of the first aspect, or obtained by the method of the second aspect.

[0044] 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.

[0045] 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.

[0046] In some embodiments, the thickness of the coating is 0.5-5 μm.

[0047] In some embodiments, the areal density of the coating is 0.5 g / m 2 -5 g / m 2 .

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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. BRIEF DESCRIPTION OF DRAWINGS

[0052] 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 as follows. Obviously, the drawings described below are only some of the embodiments of the present disclosure, and other drawings can also be obtained by those of ordinary skill in the art without any creative effort based on the drawings.

[0053] Figure 1 A schematic diagram of a secondary battery cell provided by some embodiments of the present disclosure is shown.

[0054] Figure 2 A schematic diagram of an electric device provided by some embodiments of the present disclosure is shown.

[0055] In the drawings, the drawings are not necessarily drawn according to the actual proportions. DETAILED DESCRIPTION

[0056] Hereinafter, specific embodiments of the crosslinked styrene-based organic particles, the method for producing the same, the crosslinked styrene-based organic particle emulsion, the separator, the secondary battery cell, the battery device, and the power using device of the present disclosure are described in detail with appropriate reference to the accompanying drawings. However, there are cases where unnecessary detailed description is omitted. For example, there are cases where detailed description of matters that are already well known, repeated description of 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. Furthermore, the accompanying drawings and the following description are provided so that those skilled in the art can fully understand the present disclosure, and are not intended to limit the subject matter recited in the claims.

[0057] The "ranges" disclosed in the present disclosure are defined in the form of lower and upper limits, and a given range is defined by selecting one lower limit and one upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The ranges defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. For example, if the ranges 60-120 and 80-110 are listed for a particular parameter, it is understood that the ranges 60-110 and 80-120 are also contemplated. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 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" represents a shorthand manner of describing the arbitrary combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed herein, and "0-5" is just a shorthand notation for these numerical combinations. In addition, when it is stated that a certain parameter is an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and the like.

[0058] 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.

[0059] 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.

[0060] If not otherwise specified, all steps of the present disclosure can be performed in sequence or randomly, preferably in sequence. For example, the method comprises steps (a) and (b) means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method can further comprise step (c) means that step (c) can be added to the method in any sequence, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0061] If not otherwise specified, in the present disclosure, the terms "first", "second", etc. are used to distinguish different objects, rather than to describe a specific sequence or primary and secondary relationship.

[0062] In the present disclosure, the terms "a plurality of" and "a plurality of" refer to two or more.

[0063] In the description of the embodiments of the present disclosure, if not otherwise specified, the first feature is "on" or "under" the second feature 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.

[0064] Unless otherwise specified, the test temperature of each parameter mentioned in the present disclosure is 25℃.

[0065] 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. For example, Figure 1 is a cuboid structure of a secondary battery cell 5 as an example.

[0066] 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.

[0067] Embodiments of the present disclosure provide a secondary battery cell including an electrode assembly. The electrode assembly can be in a jelly-roll structure or in a stacked structure, and the present disclosure is not limited in this regard. The secondary battery cell further includes an outer package that can be used to encapsulate the electrode assembly. The outer package can be a hard case, such as a hard plastic case, an aluminum case, a steel case, etc. The outer package can also be a soft package, such as a pouch-type soft package. The soft package can be made of plastic, such as one or more of an aluminum-plastic film, polypropylene, polybutylene terephthalate (PBT), and polybutylene succinate (PBS).

[0068] A battery apparatus as referred to in embodiments of the present disclosure can include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly can include a plurality of secondary battery cells connected in series, in parallel, or in a mixed connection through a busbar component.

[0069] In some embodiments, a battery cell assembly is generally formed by arranging a plurality of secondary battery cells.

[0070] As an example, a battery cell assembly can be a battery module formed by arranging and fixing a plurality of secondary battery cells into one independent module. As an example, a battery module can be formed by bundling a plurality of secondary battery cells with a cable tie.

[0071] In some embodiments, a battery apparatus can be a battery pack including a case and one or more battery cell assemblies housed in the case.

[0072] As an example, a battery cell assembly can be a battery module, and the battery cell assembly can be housed in the case by fixing the battery module in the case.

[0073] As an example, a battery cell assembly can also be housed in the case by directly fixing a plurality of secondary battery cells in the case.

[0074] As an example, the case can include a first case and a second case. The first case and the second case are coupled so that an enclosed space is formed inside the case to receive the battery cell assembly. Here, enclosed means covered or closed, and can be sealed or unsealed. The first case can be a top cover or a bottom plate.

[0075] As an example, the case can include a top cover, a frame, and a bottom plate. The top cover and the bottom plate are respectively coupled to the frame so that an enclosed space is formed inside the case to receive the battery cell assembly.

[0076] In some embodiments, the box can be part of a chassis structure of the vehicle. For example, portions of the box can be part of a floor of the vehicle, or portions of the box can be part of cross members and longitudinal members of the vehicle.

[0077] 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, tablets, laptops, 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 battery devices are used to store or provide electric energy.

[0078] Figure 2 FIG. 1 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.

[0079] In the context of the present disclosure, the cross-linked styrene-based organic particles mainly play a role in improving the heat resistance of the coating of the separator film, and have almost no adhesion.

[0080] The separator film is an important component for supporting the secondary battery cell to complete the electrochemical process of charging and discharging. Commonly used separator films are mostly polyolefin materials, but the heat resistance of polyolefin materials is poor, and they are easy to soften or melt at high temperatures, 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. Inorganic particles such as boehmite and aluminum oxide are commonly used heat-resistant fillers, but such heat-resistant fillers have a large density and a large mass under the same packing volume, which affects the energy density of the secondary battery cell.

[0081] Based on this, the embodiments of the present disclosure provide a cross-linked styrene-based organic particle, which is used in a separator film and can make the secondary battery cell have high reliability, high mass energy density, and good cycle performance.

[0082] The particle size distribution (Dv90-Dv10) / Dv50 of the cross-linked styrene-based organic particle of the present disclosure is less than or equal to 3.0.

[0083] The cross-linked styrene-based organic particle has a small density, and the secondary battery cell using the same can have a higher mass energy density.

[0084] The glass transition temperature T gThe cross-linked styrene-based organic particles 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 heat shrinkage of the separator film, improving the heat resistance of the separator film, and improving the reliability of the secondary battery cell.

[0085] The particle size distribution (Dv90-Dv10) / Dv50 of the cross-linked styrene-based organic particles is less than or equal to 3.0, thereby allowing the cross-linked styrene-based organic particles to be closely arranged, improving the heat resistance of the separator film, and allowing the separator film to have good air permeability, thereby allowing the secondary battery cell to have high reliability and good cycle performance.

[0086] Therefore, by using the cross-linked styrene-based organic particles of the present disclosure in the separator film, the secondary battery cell can have high reliability, high quality energy density, and good cycle performance.

[0087] The particle size distribution (Dv90-Dv10) / Dv50 of the cross-linked styrene-based organic particles is less than or equal to 3.0, and in some embodiments, the particle size distribution (Dv90-Dv10) / Dv50 of the cross-linked styrene-based organic particles can be 0.8-3.0, such as 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 formed by any of the above values.

[0088] Due to the current polymer production process, the minimum value of the particle size distribution (Dv90-Dv10) / Dv50 of the cross-linked styrene-based organic particles that can be achieved is 0.8.

[0089] Alternatively, in some embodiments, the particle size distribution (Dv90-Dv10) / Dv50 of the cross-linked styrene-based 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.

[0090] This can further improve the heat resistance of the separator film, and also allow the separator film to have better air permeability, allowing the secondary battery cell to have good cycle performance.

[0091] In some embodiments, the crosslinked styrenic organic particles can have a volume distribution particle size Dv10 of 40 nm to 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 defined by any of the foregoing.

[0092] Alternatively, the crosslinked styrenic organic particles can have a volume distribution particle size Dv10 of 40 nm to 120 nm, 40 nm to 100 nm, 40 nm to 80 nm, 40 nm to 70 nm, 40 nm to 60 nm, 45 nm to 120 nm, 45 nm to 100 nm, 45 nm to 80 nm, 45 nm to 70 nm, 45 nm to 60 nm.

[0093] In some embodiments, the crosslinked styrenic organic particles can have a volume distribution particle size Dv50 of 80 nm to 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 of the foregoing.

[0094] Alternatively, the crosslinked styrenic organic particles can have a volume distribution particle size Dv50 of 80 nm to 240 nm, 80 nm to 220 nm, 80 nm to 200 nm, 80 nm to 180 nm, 80 nm to 170 nm, 80 nm to 160 nm, 80 nm to 150 nm, 90 nm to 200 nm, 90 nm to 180 nm, 90 nm to 170 nm, 90 nm to 160 nm, 90 nm to 150 nm.

[0095] In some embodiments, the crosslinked styrenic organic particles can have a volume distribution particle size Dv90 of 100 nm to 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 of the foregoing.

[0096] Optionally, the volume distribution particle size Dv90 of the crosslinked styrene-based organic particles can be 100-700 nm, 100-600 nm, 100-500 nm, 100-400 nm, 160-700 nm, 160-600 nm, 160-500 nm, 160-400 nm.

[0097] The volume distribution particle size of the crosslinked styrene-based organic particles in the above range is beneficial to further improve the heat resistance of the separator film and improve the reliability of the secondary battery cell; it is also beneficial to the separator film to have a lower impedance, thereby also improving the cycle performance of the secondary battery cell.

[0098] Dv10, Dv50, Dv90 respectively represent the particle size corresponding to the cumulative volume distribution percentage of 10%, 50%, and 90% of the material, which can be tested by a laser particle size analyzer according to GB / T 19077-2016. During testing, a clean small beaker is taken and 1 g of the sample to be tested is added, 20 ml of deionized water is added, and ultrasonic treatment is performed at 53 KHz / 120 W for 5 min to ensure complete dispersion of the sample; after cleaning the light path system, the laser particle size analyzer is automatically tested; the solution to be tested is stirred to make it uniformly dispersed, and then placed in the sample cell according to the requirements, and the particle size is measured. The testing instrument can be a MasterSizer 3000 laser particle size analyzer.

[0099] In some embodiments, the true density of the crosslinked styrene-based organic particles can be 1.0 g / cm 3 -1.4 g / cm 3 .

[0100] At present, the true density of inorganic particles such as boehmite and alumina is usually 2.5 g / cm 3 -3.5 g / 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.

[0101] In some embodiments, the crosslinked styrene-based organic particles comprise styrene or styrene derivative structural units and crosslinking structural units.

[0102] Optionally, the styrene or styrene derivative structural units can 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.

[0103] Optionally, the crosslinking structural unit can include one or more of a divinylbenzene structural unit, an ethylene 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.

[0104] 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°C, i.e., are insoluble in the mobile phase tested by gel permeation chromatography, and the molecular weight of the crosslinked styrene-based organic particles cannot be tested by gel permeation chromatography.

[0105] In some embodiments, the glass transition temperature T g may be 108°C-160°C, for example, can be 108°C, 109°C, 110°C, 111°C, 112°C, 113°C, 114°C, 115°C, 116°C, 117°C, 118°C, 119°C, 120°C, 121°C, 122°C, 123°C, 124°C, 125°C, 126°C, 127°C, 128°C, 129°C, 130°C, 131°C, 132°C, 133°C, 134°C, 135°C, 136°C, 137°C, 138°C, 139°C, 140°C, 141°C, 142°C, 143°C, 144°C, 145°C, 146°C, 147°C, 148°C, 149°C, 150°C, 151°C, 152°C, 153°C, 154°C, 155°C, 156°C, 157°C, 158°C, 159°C, 160°C, or a range consisting of any of the aforementioned values.

[0106] 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°C. The glass transition temperature T g of the crosslinked styrene-based organic particles of the present disclosure is 108°C-160°C, which has a higher thermal stability, thereby better resisting thermal shrinkage of the isolation film, improving the heat resistance of the isolation film, and improving the reliability of the secondary battery cell.

[0107] Optionally, the glass transition temperature T gmay be 116℃-160℃, 120℃-160℃, 122℃-160℃, 124℃-160℃, 128℃-160℃, 132℃-160℃, 136℃-160℃, 142℃-160℃.

[0108] The glass transition temperature T of the crosslinked styrene-based organic particles g may be tested as follows: take an appropriate amount of sample (for example, 5mg-15mg) 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 60mL / min, protective gas 20mL / min; program settings: temperature rise from 25℃ to 200℃ at a rate of 10℃ / min, hold for 5min to eliminate thermal history, temperature drop from 200℃ to -40℃ at a rate of 10℃ / min, and temperature rise from -40℃ to 300℃ at a rate of 10℃ / min. The glass transition temperature T is obtained from the DSC curve g .

[0109] In some embodiments, the crosslinked styrene-based organic particles have no melting point.

[0110] 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.

[0111] The melting point can be tested as follows: take an appropriate amount of sample (for example, 5mg-15mg) 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 60mL / min, protective gas 20mL / min; program settings: temperature rise from 25℃ to 200℃ at a rate of 10℃ / min, hold for 5min to eliminate thermal history, temperature drop from 200℃ to -40℃ at a rate of 10℃ / min, and temperature rise from -40℃ to 300℃ at a rate of 10℃ / min. Whether the organic particles have a melting point below 300℃ 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.

[0112] 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 of ethylene carbonate and methyl ethyl carbonate in a volume ratio of 3:7 at 60℃ for 7 days.

[0113] 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.

[0114] The swelling degree of the crosslinked styrene-based organic particles can be tested according to the following method: take an appropriate amount of sample (for example, about 1 g), and record the mass as m1, and place it in a semi-permeable membrane sample bag, seal the bag, and the sample bag can permeate the solvent but cannot permeate the sample; 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.

[0115] 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%.

[0116] 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 enabling the secondary battery cell to have long cycle stability.

[0117] The dissolution rate of the crosslinked styrene-based organic particles can be tested according to the following method: take an appropriate amount of sample (for example, about 1 g), and record the mass as m1, and place it in a semi-permeable membrane sample bag, seal the bag, and the sample bag can permeate the solvent but cannot permeate the sample; 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.

[0118] 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.

[0119] 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.

[0120] 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.

[0121] The disclosure embodiments also provide a preparation method of cross-linked styrene-based organic particles.

[0122] 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.

[0123] The cross-linked styrene-based organic particles provided by the disclosure embodiments are obtained by an 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.

[0124] 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.

[0125] 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, which increases the concentration of free radicals in water. In addition, the increase in temperature can promote the generation rate of free radicals, which further increases the concentration of free radicals in water. As a result, the diffusion rate of free radicals from the aqueous phase to the micelles increases, that is, the nucleation rate increases, the number of latex particles increases, the particle size decreases, and thus the particle size of the obtained cross-linked styrene-based organic particles decreases.

[0126] 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.

[0127] In some embodiments, the emulsion polymerization reaction can include the following steps: dropping the pre-emulsion into the reactor containing water under the conditions of the first heating temperature, inert gas protection and stirring, and after the first time, heating to the ripening temperature for ripening reaction to obtain the cross-linked styrene-based organic particles.

[0128] Optionally, the first heating temperature can be 55°C-70°C.

[0129] Optionally, the first time can be 3 h-6 h.

[0130] In some embodiments, the stirring speed of the emulsion polymerization reaction can be 60 rpm / min-1000 rpm / min.

[0131] 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 obtain cross-linked styrene-based organic particles with narrow particle size distribution without breaking the emulsion polymerization.

[0132] 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.

[0133] 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.

[0134] 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.

[0135] In some embodiments, the weight average molecular weight of the oligomer can be 300-5000.

[0136] 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 composed of any of the above numerical 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.

[0137] 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.

[0138] 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 composed of any of the above numerical 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.

[0139] 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.

[0140] 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 composed of any of the above numerical values, based on the total mass of the monomer, the crosslinking agent, and the oligomer being 100%.

[0141] 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, azobisdimethylamid hydrochloride, azobisdimethylimidazoline hydrochloride, azobisisopropylimidazoline.

[0142] 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%.

[0143] 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.

[0144] 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%.

[0145] 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 free-radically polymerizable oligomer 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.

[0146] 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%.

[0147] 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 above 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%.

[0148] 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%.

[0149] By further adjusting the mass fraction of the emulsifier within the above range, crosslinked styrene-based organic particles with a narrow particle size distribution can be obtained.

[0150] Optionally, 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, 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%.

[0151] Optionally, 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%, the emulsifier includes a polyoxyethylene ether emulsifier, based on the total mass of the monomer, the crosslinking agent, and the oligomer being 100%.

[0152] By further adjusting the kind of the emulsifier within the above range, crosslinked styrene-based organic particles with a narrow particle size distribution can be obtained.

[0153] 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; (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%.

[0154] 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 kind of the emulsifier, the mass fraction of the emulsifier, and the mass fraction of the oligomer within the above range, crosslinked styrene-based organic particles with a narrow particle size distribution can be obtained.

[0155] The mass fraction of the crosslinking agent can be 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, or a range consisting of any of the aforementioned values. Optionally, 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%, the mass fraction of the crosslinking agent is greater than or equal to 7% and less than 12%.

[0156] Optionally, 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%.

[0157] Optionally, the pre-emulsion satisfies: the mass fraction of the crosslinking agent is greater than or equal to 3% and less than 12%, based on the total mass of the monomers, the crosslinking agent and the oligomers being 100%; the emulsifier includes a polyoxyethylene ether emulsifier; the mass fraction of the emulsifier is 0.5%-5%; and the mass fraction of the oligomers is 0%.

[0158] Optionally, the pre-emulsion satisfies: the mass fraction of the crosslinking agent is greater than or equal to 3% and less than 12%, based on the total mass of the monomers, the crosslinking agent and the oligomers being 100%; the emulsifier includes a polyoxyethylene ether emulsifier; the mass fraction of the emulsifier is 1%-5%; and the mass fraction of the oligomers is 0%.

[0159] Optionally, the pre-emulsion satisfies: the mass fraction of the crosslinking agent is greater than or equal to 3% and less than 12%, based on the total mass of the monomers, the crosslinking agent and the oligomers being 100%; the mass fraction of the emulsifier is 1%-5%; and the mass fraction of the oligomers is 0.25%-7.5%.

[0160] Optionally, the pre-emulsion satisfies: the mass fraction of the crosslinking agent is greater than or equal to 3% and less than 12%, based on the total mass of the monomers, the crosslinking agent and the oligomers being 100%; the emulsifier includes a polyoxyethylene ether emulsifier; the mass fraction of the emulsifier is 0.5%-5%; and the mass fraction of the oligomers is 0.25%-7.5%.

[0161] Optionally, the pre-emulsion satisfies: the mass fraction of the crosslinking agent is greater than or equal to 3% and less than 12%, based on the total mass of the monomers, the crosslinking agent and the oligomers being 100%; the emulsifier includes a polyoxyethylene ether emulsifier; the mass fraction of the emulsifier is 1%-5%; and the mass fraction of the oligomers is 0.25%-7.5%.

[0162] 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 group, a hydroxyl group, a cyano group, and an amide group.

[0163] The pre-emulsion including the functional monomer having the polar group can reduce the surface tension of the crosslinked styrene-based organic particles, making it convenient to coat on the surface of the porous base film.

[0164] 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, and acrylamide and derivatives thereof.

[0165] The mass fraction of the functional monomer can be 0.01%-10%, based on the total mass of the monomers, the crosslinking agent and the oligomers being 100%.

[0166] In some embodiments, the method of preparing the crosslinked styrene-based organic particles can further include a step of removing the magnetic treatment after the emulsion polymerization reaction ends.

[0167] The present disclosure also provides a crosslinked styrene-based organic particle emulsion.

[0168] The crosslinked styrene-based organic particle emulsion includes the crosslinked styrene-based organic particle of the present disclosure, or is obtained by the preparation method of the crosslinked styrene-based organic particle of the present disclosure.

[0169] The present disclosure also provides an isolation membrane. The isolation membrane includes a porous base membrane and a coating layer on at least one side of the porous base membrane, and the coating layer includes a binder and the crosslinked styrene-based organic particle of the present disclosure or the crosslinked styrene-based organic particle prepared by the method of the present disclosure.

[0170] Both the porous base membrane and the coating layer have a pore structure, so that the isolation membrane has good air permeability and facilitates ion passage. The crosslinked styrene-based organic particles in the coating layer are connected to each other and fixed by the binder, and the gaps between the crosslinked styrene-based organic particles can form a pore structure.

[0171] In some embodiments, the mass content of the crosslinked styrene-based organic particles in the coating layer can be 50%-99% based on the total mass of the coating layer.

[0172] Optionally, the mass content of the crosslinked 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%.

[0173] In some embodiments, the binder in the coating layer can include, but is not limited to, one or more of polyacrylate binder, nitrile rubber binder, polyacrylic acid, polymethacrylic acid, sodium polyacrylate, polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0174] In some embodiments, the coating layer can further include a dispersant, for example, can include but is not limited to one or more of alkylphenol polyoxyethylene ether and other dispersants, polyacrylic acid dispersant, cellulose dispersant. As an example, the dispersant can include but is not limited to one or more of sodium carboxymethyl cellulose, sodium polyacrylate, and ammonium polyacrylate.

[0175] In some embodiments, the isolation membrane can further include polymeric binder particles.

[0176] 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.

[0177] In other embodiments, the coating of the separation membrane includes a heat-resistant layer disposed on the porous base membrane and a bonding layer disposed on at least a portion of a surface of the heat-resistant layer away from the porous base membrane, the crosslinked styrene-based organic particles are disposed in the heat-resistant layer, and the polymeric binder particles are disposed in the bonding layer.

[0178] In yet other embodiments, the coating of the separation membrane includes a heat-resistant layer disposed on one side of the porous base membrane and a bonding layer disposed on at least a portion of a surface of the other side of the porous base membrane, the crosslinked styrene-based organic particles are disposed in the heat-resistant layer, and the polymeric binder particles are disposed in the bonding layer.

[0179] In some embodiments, the average particle diameter of the polymeric binder particles can be 6 μm to 18 μm.

[0180] In some embodiments, the polymeric binder particles can include vinylidene fluoride-based polymeric particles, such as polyvinylidene fluoride (PVDF) particles and / or copolymer particles of a vinylidene fluoride monomer and a comonomer.

[0181] 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 fluorinated ether monomer.

[0182] 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).

[0183] In some embodiments, the thickness of the coating can be 0.5 μm to 5 μm. The thickness of the coating refers to the thickness of the coating on one side of the porous base membrane. Optionally, the thickness of the coating can be 0.5 μm to 4 μm, 0.5 μm to 3 μm, 0.5 μm to 2 μm, 0.8 μm to 4 μm, 0.8 μm to 3 μm, 0.8 μm to 2 μm.

[0184] In some embodiments, the areal density of the coating can be 0.5 g / m 2 -5 g / m 2 .

[0185] In some embodiments, the porous base film can comprise a film selected from any one or at least two of the following: polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyacetal, polyamide, polycarbonate, polyimide, polyether ether ketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyether sulfone, polyphenylene ether, cyclic olefin copolymer, polyphenylene sulfide, polyvinyl naphthalene.

[0186] 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.

[0187] In some embodiments, the thickness of the porous base film can be 4-12 μm, optionally 4-9 μm.

[0188] In some embodiments, the porosity of the porous base film can be 25-60%, optionally 28-50%.

[0189] 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.

[0190] 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.

[0191] This can reduce the problem of plugging pores and improve the air permeability and ion conductivity of the separation film.

[0192] In some embodiments, the average pore size of the porous base film can be 25-82 nm.

[0193] 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. After the sample is completely wetted, it is placed in a mold, and then an inert gas (such as nitrogen) is used to press the wetting liquid in the pores of the sample to be tested. The pressure and flow rate of the pressurized gas are inversely proportional to the pore size. By sampling and pressure and pore size conversion analysis using 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 100-350 psi.

[0194] In some embodiments, the thickness of the separation film can be 5-14 μm, optionally 5-12 μm, 6-12 μm. This is beneficial for improving the energy density of the secondary battery cell.

[0195] It should be noted that the coating parameters of the above-mentioned separation membrane are the coating parameters of one side of the porous base film. When the coating is arranged on both sides of the porous base film, as long as the coating parameters of any one side meet the present disclosure, it is considered to fall within the protection scope of the present disclosure.

[0196] The separation membrane can be prepared according to methods known in the art.

[0197] 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 separation membrane is obtained.

[0198] 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.

[0199] In some embodiments, the preparation method of the separation membrane 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, a heat-resistant layer is formed; 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, the separation membrane is obtained.

[0200] In some embodiments, the preparation method of the separation membrane 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, the separation membrane is obtained.

[0201] In some embodiments, the solvent of the slurry can be water, for example, deionized water.

[0202] In some embodiments, the slurry can further include other components, for example, can further include dispersants and / or wetting agents, etc.

[0203] The present disclosure also provides a secondary battery cell. The secondary battery cell includes the separation membrane provided by the present disclosure. Thus, the secondary battery cell can have high reliability, high quality energy density, and good cycle performance.

[0204] The secondary battery cell further includes a positive electrode sheet, a negative electrode sheet, and an electrolyte, and the separation membrane is arranged between the positive electrode sheet and the negative electrode sheet. The positive electrode sheet, the separation membrane, and the negative electrode sheet can form an electrode assembly through a rolling process and / or a stacking process.

[0205] 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., and the composition of the positive electrode sheet, the negative electrode sheet, and the electrolyte will be different for different types of secondary battery cells.

[0206] [Positive electrode sheet]

[0207] In some embodiments, the positive electrode sheet can include a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector and including a positive electrode active material. For example, the positive electrode current collector has two surfaces opposite in the thickness direction of itself, and the positive electrode film layer is disposed on either one or both of the two opposite surfaces of the positive electrode current collector.

[0208] For example, the positive electrode active material can include, but is not limited to, one or more of lithium transition metal oxides, lithium-containing phosphates, and modified compounds thereof. Examples of the 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 modified compounds thereof. Examples of the 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 modified compounds thereof. In some embodiments, in order to further improve the energy density of the secondary battery cell, the positive electrode active material can include one or more of lithium transition metal oxides of the general formula Li a Ni b Co c M d O e A f 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.

[0209] For example, the positive electrode active material can include, but is not limited to, LiCoO2, LiNiO2, LiMnO2, LiMn2O4, 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 Al0.05 one or more of O2, LiFePO4, LiMnPO4.

[0210] The secondary battery cell will be accompanied by Li de-intercalation and consumption during charging and discharging process, and the molar content of Li is different when the secondary battery cell is discharged to different states. In the enumeration of the positive electrode active material in the present disclosure, the molar content of Li is the initial state of the material, i.e. the state before feeding, and the positive electrode active material is applied to the secondary battery cell, and after charging and discharging cycle, the molar content of Li will change. In the enumeration of the positive electrode active material in the present disclosure, the molar content of O is only the theoretical state value, and the lattice oxygen release will cause the change of the molar content of O, and the actual molar content of O will also appear floating.

[0211] Taking a sodium battery cell as an example, the positive electrode active material can include but is not limited to one or more of sodium-containing transition metal oxides, polyanion materials (such as phosphates, fluorophosphates, pyrophosphates, sulfates, etc.), prussian blue type materials. As an example, the positive electrode active material can include but is not limited to one or more of NaFeO2, NaCoO2, NaCrO2, NaMnO2, NaNiO2, NaNi 1 / 2Ti 1 / 2 O2, NaNi 1 / 2 Mn 1 / 2 O2, Na 2 / 3 Fe 1 / 3 Mn 2 / 3 O2, NaNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, NaFePO4, NaMnPO4, NaCoPO4, prussian blue type material, material of general formula X p M’ q (PO4) r O x Y 3-x . In the general formula X p M’ q (PO4) r O x Y 3-x , 0 < p < 4, 0 < q < 2, 1 < r < 3, 0 < x < 2, X includes but is not limited to one or more of H + , Li + , Na + , K + and NH4 + , M’ is a transition metal cation, which can optionally include but is not limited to one or more of V, Ti, Mn, Fe, Co, Ni, Cu and Zn, and Y is a halide anion, which can optionally be one or more of F, Cl and Br.

[0212] The modifying compound of the positive electrode active material of each of the lithium battery cell and the sodium battery cell described above can be a doping modification and / or a surface coating modification to the positive electrode active material.

[0213] In some embodiments, the positive electrode film layer can further include a positive electrode conductive agent. As an example, the positive electrode conductive agent can include, but is not limited to, one or more of super-p carbon, conductive graphite, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0214] In some embodiments, the positive electrode film layer can further include a positive electrode binder. As an example, the positive electrode binder can include, but is not limited to, one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylic resin.

[0215] In some embodiments, the positive electrode current collector can employ a metal foil or a composite current collector. As an example of the 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.

[0216] The positive electrode film layer is generally formed by coating a positive electrode slurry on a positive electrode current collector, drying, and cold-pressing. The positive electrode slurry is generally 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.

[0217] [Negative electrode tab]

[0218] 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 of itself, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0219] The negative active material can employ materials known in the art that are useful for secondary battery cells. As an example, the negative active material can include, but is not limited to, one or more of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based materials can include, but are not limited to, one or more of elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy materials. The tin-based materials can include, but are not limited to, one or more of elemental tin, tin oxide, and tin alloy materials.

[0220] 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.

[0221] 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).

[0222] 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.

[0223] In some embodiments, the negative electrode current collector can employ a metal foil or a composite current collector. As an example of a 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.

[0224] 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 the negative active material, the negative electrode conductive agent, the 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.

[0225] The negative electrode tab does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode tab also includes a conductive primer layer (e.g., composed of a conductive agent and a binder) sandwiched between the negative electrode current collector and the negative electrode film layer, disposed on the surface of the negative electrode current collector.

[0226] 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, etc. When the foamed metal is used 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.

[0227] [Electrolyte]

[0228] The electrolyte plays a role in conducting ions between the positive electrode tab and the negative electrode tab.

[0229] In some embodiments, the electrolyte employs an electrolyte solution, which includes an electrolyte salt and an organic solvent.

[0230] Taking a lithium battery cell as an example, 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 difluorooxalate borate (LiDFOB), lithium difluorophosphate (LiPO2F2), lithium difluorodioxalate phosphate (LiDFOP), and lithium tetrafluorooxalate phosphate (LiTFOP).

[0231] Taking a sodium battery cell as an example, 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 difluorooxalate borate (NaDFOB), sodium difluorophosphate (NaPO2F2), sodium difluorodioxalate phosphate (NaDFOP), and sodium tetrafluorooxalate phosphate (NaTFOP).

[0232] 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.

[0233] 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 performance 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.

[0234] Optionally, the additive can include one or more of fluoroethylene carbonate (FEC), vinylene carbonate (VC), 1,3-propane sultone (PS), and vinyl sulfate (DTD).

[0235] 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 through processes such as vacuum packaging, standing, and formation.

[0236] Examples

[0237] The following examples more specifically describe the disclosure disclosed in the present disclosure, and these examples are merely illustrative, because various modifications and changes within the scope of the disclosure disclosed in the present disclosure will be apparent to those skilled in the art. Unless otherwise stated, all parts, percentages, and ratios reported in the following examples are based on mass, and all reagents used in the examples are commercially available or synthesized according to conventional methods and used directly without further purification, and the instruments used in the examples are commercially available.

[0238] 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, which was heated to 70°C. The pre-emulsion was added dropwise under nitrogen protection and stirring. After 4 h of reaction, the temperature was increased to 80°C for 1.5 h of curing reaction to obtain an organic particle D1# emulsion.

[0239] 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, which was heated to 70°C. The pre-emulsion was added dropwise under nitrogen protection and stirring. After 4 h of reaction, the temperature was increased to 80°C for 1.5 h of curing reaction to obtain an organic particle 1# emulsion.

[0240] 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, which was heated to 70°C. The pre-emulsion was added dropwise under nitrogen protection and stirring. After 4 h of reaction, the temperature was increased to 80°C for 1.5 h of curing reaction to obtain an organic particle 2# emulsion.

[0241] 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, which was heated to 70°C. The pre-emulsion was added dropwise under nitrogen protection and stirring. After 4 h of reaction, the temperature was increased to 80°C for 1.5 h of curing reaction to obtain an organic particle 3# emulsion.

[0242] 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, which was heated to 70°C. The pre-emulsion was added dropwise under nitrogen protection and stirring. After 4 h of reaction, the temperature was increased to 80°C for 1.5 h of curing reaction to obtain an organic particle 4# emulsion.

[0243] 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, which was heated to 70°C. The above-prepared pre-emulsion was added dropwise under the protection of nitrogen and stirring. After 4 h of reaction, the temperature was increased to 80°C for 1.5 h of curing reaction to obtain an organic particle 5# emulsion.

[0244] 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, which was heated to 70°C. The above-prepared pre-emulsion was added dropwise under the protection of nitrogen and stirring. After 4 h of reaction, the temperature was increased to 80°C for 1.5 h of curing reaction to obtain an organic particle 6# emulsion.

[0245] 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, which was heated to 70°C. The above-prepared pre-emulsion was added dropwise under the protection of nitrogen and stirring. After 4 h of reaction, the temperature was increased to 80°C for 1.5 h of curing reaction to obtain an organic particle 7# emulsion.

[0246] 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, which was heated to 70°C. The above-prepared pre-emulsion was added dropwise under the protection of nitrogen and stirring. After 4 h of reaction, the temperature was increased to 80°C for 1.5 h of curing reaction to obtain an organic particle 8# emulsion.

[0247] 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, which was heated to 70°C. The above-prepared pre-emulsion was added dropwise under the protection of nitrogen and stirring. After 4 h of reaction, the temperature was increased to 80°C for 1.5 h of curing reaction to obtain an organic particle 9# emulsion.

[0248] Emulsify 1 g of OP-10, 80 mg of sodium persulfate, 20 ml of deionized water, 36 g of styrene, and 4 g of divinylbenzene to obtain a pre-emulsion for standby. Add 140 g of deionized water to the reactor, heat to 70°C, and drop the above standby pre-emulsion under the condition of nitrogen protection and stirring. After 4 h of reaction, heat to 80°C for 1.5 h of curing reaction to obtain organic particle 10# emulsion.

[0249] Organic particle performance testing

[0250] (1) Glass transition temperature T of organic particles g Test

[0251] Take an appropriate amount of sample (e.g., 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, and protective gas 20 mL / min; program settings: heat from 25°C to 200°C at a rate of 10°C / min, hold for 5 min to eliminate thermal history, then cool from 200°C to -40°C at a rate of 10°C / min, and then heat to 300°C at a rate of 10°C / min. The glass transition temperature T is obtained by the DSC curve. g .

[0252] (2) Melting point test of organic particles

[0253] Take an appropriate amount of sample (e.g., 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, and protective gas 20 mL / min; program settings: heat from 25°C to 200°C at a rate of 10°C / min, hold for 5 min to eliminate thermal history, then cool from 200°C to -40°C at a rate of 10°C / min, and then heat to 300°C at a rate of 10°C / min. Determine whether the organic particles have a melting point by the DSC curve.

[0254] (3) Particle size test

[0255] Dv10, Dv50, and 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 MasterSizer 3000 laser particle size analyzer. During testing, a clean beaker is taken and 1 g of the sample to be tested is added, 20 ml of deionized water is added, and ultrasonic treatment is performed 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.

[0256] The above prepared organic particles 1# to 10# satisfy the following characteristics: no melting point, glass transition temperature Tg g between 108℃ and 160℃.

[0257] Next, the above prepared organic particles are used in the isolation film to verify their influence on the performance of the isolation film and the secondary battery monomer.

[0258] A commercially available polyethylene microporous film with a thickness of 7 μm is used as a 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 .

[0259] 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 uniformly 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.

[0260] The negative electrode active material artificial graphite, the negative electrode conductive agent acetylene black, the negative electrode binder styrene-butadiene rubber (SBR), and the thickening agent sodium carboxymethyl cellulose are mixed in deionized water at a mass ratio of 96.0:1.4:1.5:1.1, and the mixture is stirred uniformly to prepare a negative electrode slurry; the negative electrode slurry is uniformly coated on the negative electrode current collector copper foil, and then dried, cold-pressed, and cut to obtain a negative electrode sheet.

[0261] At 25℃, ethylene carbonate (EC) and methyl ethyl carbonate (EMC) are mixed at a volume ratio of 3:7 to obtain a mixed solvent, and then LiPF6 and vinylene carbonate (VC) are dissolved in the above mixed solvent to obtain an electrolyte. The concentration of LiPF6 is 1 mol / L. The mass fraction of VC is 3% based on the mass of the electrolyte.

[0262] The positive electrode sheet, the isolation film, and the negative electrode sheet are stacked and wound in sequence, and then hot-pressed to form an electrode assembly; the electrode assembly is placed in a hard-shell outer package, and the above prepared electrolyte is added, and then the package is sealed, placed, formed, aged, and the like to obtain a secondary battery monomer.

[0263] Performance testing

[0264] (1) Test of heat shrinkage rate of isolation film

[0265] The heat shrinkage rate of the separator film can be tested according to GB / T 36363-2018.

[0266] The separator film was punched into a sample with a width of 50 mm and a length of 100 mm by a punch press, and 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.

[0267] 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 started. After reaching the set time (1 h in the present disclosure), the length and width of the separator film were measured, and the values were marked as a and b, respectively.

[0268] The heat shrinkage rate was calculated as follows: the longitudinal (MD) heat shrinkage rate = [(100-a) / 100]x100%, and the transverse (TD) heat shrinkage rate = [(50-b) / 50]x100%. The average value of 3 parallel samples was taken as the test result.

[0269] (2) Cycle performance test of the secondary battery cell

[0270] At 25℃, the secondary battery cell was charged at 1 / 3C constant current to 3.8V, then charged at 3.8V constant voltage to a current of 0.05C, and rested for 5 min, then discharged at 1 / 3C constant current to 2.0V, and the obtained discharge capacity was recorded as the initial capacity C0; the above charging and discharging steps were repeated, and the discharge capacity Cn of the secondary battery cell after the nth cycle was recorded at the same time, then the capacity retention rate Pn of the secondary battery cell after each cycle was (Cn / C0) x 100%. The cycle performance difference of the secondary battery cell can be reflected by the capacity retention rate after 500 cycles of the secondary battery cell.

[0271] Table 1

[0272]

[0273] From the above test results, it can be seen that the crosslinked styrene-based organic particles with a 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.

[0274] 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 technical idea 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, and other ways constructed by combining part of the components in the embodiments are also included in the scope of the present disclosure.

Claims

1. A crosslinked styrenic organic particle, characterized in that, The crosslinked styrene-based organic particles have a particle size distribution (Dv90-Dv10) / Dv50 of less than or equal to 3.

0.

2. The crosslinked styrenic organic particle according to claim 1, wherein The crosslinked styrene-based organic particles have a particle size distribution (Dv90-Dv10) / Dv50 of 0.8-2.

6.

3. The crosslinked styrenic organic particles according to any one of claims 1-2, characterized in that, The crosslinked styrene-based organic particles satisfy at least one of the following conditions (1) to (3): (1) The crosslinked styrene-based organic particles have a volume distribution particle size Dv10 of 40 nm-200 nm; (2) The crosslinked styrene-based organic particles have a volume distribution particle size Dv50 of 80 nm-300 nm; (3) The crosslinked styrene-based organic particles have a volume distribution particle size Dv90 of 100 nm-800 nm.

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

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

6. The crosslinked styrenic organic particles according to any one of claims 1 to 5, characterized in that, The crosslinked styrene-based organic particles include styrene or styrene derivative structural units and crosslinking structural units; Optionally, the styrene or styrene derivative structural units include 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 include 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 crosslinked styrenic organic particles according to any one of claims 1 to 6, characterized in that, The crosslinked styrenic organic particles have a glass transition temperature Tg g of 108°C to 160°C.

8. The crosslinked styrenic organic particle 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 crosslinked styrene-based organic particles according to any one of claims 1-8, wherein: The crosslinked styrene-based organic particles have no melting point.

10. The crosslinked styrene-based organic particles 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 crosslinked styrenic organic particles according to any one of claims 1 to 10, characterized in that, The crosslinked styrene-based organic particles do not have an oxidation peak in a voltage range of 2.5 V to 4.4 V in a cyclic voltammogram of the first cycle. 12.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 subjecting the pre-emulsion to an emulsion polymerization reaction under heating, inert gas protection, and stirring to obtain 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.

13. The method of claim 12, wherein, The maturation temperature of the emulsion polymerization reaction is 76-90℃; and / or, the maturation time of the emulsion polymerization reaction is 1-6h.

14. The method according to any one of claims 12-13, characterized in that, The emulsion polymerization reaction comprises the steps of: dropping the pre-emulsion into a reactor containing water under a first heating temperature, inert gas protection, and stirring, and then raising the temperature to a maturation temperature for a maturation reaction after a first time to obtain crosslinked styrene-based organic particles, Optionally, the first heating temperature is 55-70℃. Optionally, the first time is 3-6h.

15. The method according to any one of claims 12-14, characterized in that, 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 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 the total mass of the monomers, the crosslinking agent, and the oligomers being 100%. 16.The method of any one of claims 12-15, 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, tripropylene glycol diacrylate, N,N-methylenebisacrylamide, and N,N’-vinylbisacrylamide; and / or, the mass fraction of the crosslinking agent is 3-40% based on the total mass of the monomers, the crosslinking agent, and the oligomers being 100%; and / or, the monomers comprise one or more of styrene, 1-methyl-1-phenylethylene, 4-methylstyrene, 2-methylstyrene, 2,4-dimethylstyrene, and 2,5-dimethylstyrene. 17.The method of any one of claims 12-16, wherein: The emulsifier includes one or more of sodium dodecyl sulfate, sodium dodecyl benzene sulfonate, sodium polyacrylate, polyvinylpyrrolidone, polyvinyl alcohol, polyoxyethylene ether emulsifier, cellulose and derivatives thereof; and / or, The mass fraction of the emulsifier is 0.5%-5% based on the total mass of the monomer, the crosslinking agent and the oligomer.

18. The method according to any one of claims 12-17, characterized by, 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.

19. The method according to any one of claims 12-17, characterized in that, The pre-emulsion satisfies: the mass fraction of the crosslinking agent is greater than or equal to 3% and less than 12% based on 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) the mass fraction of the emulsifier is 1%-5%; (2) the emulsifier includes a polyoxyethylene ether emulsifier; (3) the mass fraction of the oligomer is 0.25%-7.5%.

20. A crosslinked styrenic organic particle emulsion, characterized in that, The crosslinked styrene-based organic particle of any one of claims 1-11, or obtained by the method of any one of claims 12-19.

21. A separator membrane comprising a porous base membrane and a coating on at least one side of the porous base membrane, characterized in that, The coating layer includes the crosslinked styrene-based organic particle of any one of claims 1-11, or the crosslinked styrene-based organic particle prepared by the method of any one of claims 12-19.

22. The separator according to claim 21, wherein The mass content of the crosslinked styrene-based organic particle in the coating layer is 50%-99% based on the total mass of the coating layer; and / or, The thickness of the coating layer is 0.5 μm-5 μm; and / or, The areal density of the coating is 0.5 g / m 2 - 5 g / m 2 .

23. The separator membrane according to any one of claims 21-22, wherein, The ratio of the volume distribution particle size Dv50 of the crosslinked styrene-based organic particle to the average pore diameter of the porous base film is greater than or equal to 1.

1.

24. A secondary battery cell characterized by comprising: The separator of any one of claims 21-23 is disposed between the positive electrode tab and the negative electrode tab.

25. A battery device, characterized by The secondary battery device includes a plurality of the secondary battery cells of claim 24.

26. An electrical device, comprising: The secondary battery device includes the secondary battery cell of claim 24 or the battery device of claim 25.

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