Lithium-ion battery separator, its preparation method and lithium-ion battery

Abstract

The present invention discloses a lithium-ion battery separator, a preparation method thereof, and a lithium-ion battery, relating to the technical field of lithium-ion batteries. The lithium-ion battery separator provided by the present invention is composed of a honeycomb polyamide and polymer particles filled in the polyamide. The honeycomb polyamide structure plays a role of skeleton support during the preparation of the separator and can also increase the film-breaking temperature. When the battery temperature rises, the polymer particles can absorb the electrolyte in the separator and expand, closing the honeycomb structure, thereby reducing the closed-pore temperature of the separator.

Description

Technical Field:

[0001] The present invention relates to the technical field of lithium-ion batteries, and particularly to a lithium-ion battery separator and its preparation method and a lithium-ion battery. Background Art:

[0002] In recent years, in order to achieve sustainable development and protect the ecological environment, lithium-ion battery technology has been widely applied. Electric vehicles equipped with lithium-ion power batteries have become increasingly popular. In 2021 alone, the sales volume of new energy vehicles in the Chinese market reached 3.3 million, and it still maintains a rapid growth momentum. In 2022, the European Union reached an agreement on the plan that "the carbon dioxide emissions of all passenger cars and light commercial vehicles sold in the EU market will be zero starting from 2035", which is equivalent to banning the sale of gasoline-powered vehicles and diesel-powered vehicles starting from 2035. At the same time, lithium-ion batteries are also widely used in the fields of 3C, energy storage, etc. These data indicate that lithium-ion batteries will play an increasingly important role in the next decade or even longer.

[0003] The separator is a core component of a lithium-ion battery, ensuring battery safety and related to electrochemical performance. The mainstream separator products on the market today are prepared from polyethylene (PE) or polypropylene (PP) as raw materials. The normal operating temperature of a lithium-ion battery is 0 - 60 °C. When the temperature gets out of control and reaches 130 - 140 °C, it will cause abnormalities or damage to other parts, resulting in certain losses.

[0004] Therefore, developing a separator material with a low closed-pore temperature and a high membrane-breaking temperature, effectively reducing the closed-pore temperature of the separator and at the same time increasing the membrane-breaking temperature of the separator, is of great significance for the development of lithium-ion batteries. Summary of the Invention:

[0005] In order to solve the problem that the lithium battery separator in the prior art is easily damaged at high temperatures (130 - 140 °C), resulting in poor safety of the lithium battery, the present invention will provide a lithium-ion battery separator and its preparation method and a lithium-ion battery.

[0006] To achieve the above object, one of the objects of the present invention is to provide a lithium-ion battery separator, comprising a honeycomb structure of polyamide and polymer particles filled in the honeycomb structure;

[0007] The polymer particles are selected from at least one of polyacrylate, polystyrene, styrene-acrylate copolymer, butadiene-styrene copolymer, ethylene-vinyl acetate copolymer, epoxy resin, polyurethane resin, phenolic resin, alkyd resin, polyacrylonitrile, and polycarbonate.

[0008] Another object of the present invention is to provide a method for preparing a lithium-ion battery separator, the method comprising:

[0009] Under stirring conditions, polyamide is dissolved in a solvent, and then polymer particles are added. After mixing evenly, it is coated on the surface of a base film, and a lithium-ion battery separator is obtained through solvent replacement;

[0010] Among them, the polymer particles are polymerized from at least one of vinyl monomers, amino monomers, hydroxyl monomers, aldehyde group monomers, carboxyl group monomers, acyl chloride monomers, siloxanes, and chlorosilanes.

[0011] The third object of the present invention is to provide a lithium battery separator prepared according to the foregoing method.

[0012] The fourth object of the present invention is to provide a lithium-ion battery, including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, and the separator is the foregoing lithium-ion battery separator.

[0013] The beneficial effects of the present invention are as follows: The lithium-ion battery separator provided by the present invention is composed of a honeycomb-like polyamide and polymer particles filled in the polyamide. Among them, the honeycomb-like polyamide structure plays a role of skeleton support in the process of preparing the separator and can also increase the breakdown temperature; when the battery temperature rises, the polymer particles can absorb the electrolyte in the separator and expand, closing the honeycomb structure, thereby reducing the closure temperature of the separator. Description of the drawings:

[0014] Figure 1 SEM image of the honeycomb structure film obtained as a blank example;

[0015] Figure 2 SEM image of the honeycomb structure film obtained in Example 1. Detailed implementation manners:

[0016] In order to make the technical means, creative features, achieved purposes, and functions of the present invention easy to understand, the present invention will be further described below in conjunction with specific embodiments and illustrations.

[0017] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0018] The present invention provides a lithium-ion battery separator, including a honeycomb-structured polyamide and polymer particles filled in the honeycomb structure;

[0019] The polymer particles are selected from at least one of polyacrylate, polystyrene, styrene-acrylate copolymer, butadiene-styrene copolymer, ethylene-vinyl acetate copolymer, epoxy resin, polyurethane resin, phenolic resin, alkyd resin, polyacrylonitrile, and polycarbonate.

[0020] Preferably, the thickness of the lithium-ion battery separator is 3 to 50 μm.

[0021] In the present invention, the dosage ratio of the polyamide to the polymer particles should be controlled within a reasonable range. The increase in the dosage of the polymer particles can, to a certain extent, reduce the closed pore temperature. However, if the dosage of the polymer particles is too large, the strength of the composite membrane will be reduced, and then the membrane rupture temperature will be lowered; when the dosage of the polymer microspheres is reduced, the closed pore temperature will correspondingly increase; while if the dosage of the polymer microspheres is too small, it cannot effectively prevent the electrolyte from flowing and ion transport after liquid absorption and swelling, and no closed pore will occur even when the temperature rises above the membrane rupture temperature. Under preferred conditions, the weight ratio of the polyamide to the polymer particles is 10:1 to 1:1; for example, it can be 10:1, 5:1, 4:1, 3:1, 2:1, 1:1, or any value within the range composed of any two of the above ratios.

[0022] In the present invention, the particle size of the polymer particles should be controlled within a specific range, so that there is enough space between the polymer particles and the honeycomb structure of the polyamide to accommodate the electrolyte, and at the same time, liquid absorption and swelling plugging of the pores can be achieved at high temperatures, so that the closed pore temperature of the composite membrane is the lowest. If the particle size of the polymer particles is too large, the number of microspheres will decrease under the same mass, and it cannot effectively prevent the electrolyte from flowing and ion transport after liquid absorption and swelling, and no closed pore will occur even when the temperature rises above the membrane rupture temperature. Preferably, the particle size of the polymer particles is 0.2 to 10 μm, for example, it can be 0.2 μm, 0.5 μm, 1 μm, 2 μm, 3 μm, 5 μm, 8 μm, 10 μm, or any value within the range composed of any two of the above values; preferably 0.5 to 5 μm.

[0023] The closed pore temperature of the lithium-ion battery separator provided by the present invention is not higher than 110 °C, and the membrane rupture temperature is not lower than 185 °C.

[0024] The present invention provides a method for preparing a lithium-ion battery separator, and the method includes:

[0025] Under stirring conditions, dissolve the polyamide in a solvent, then add the polymer particles, mix evenly and coat on the surface of the base film, and obtain the lithium-ion battery separator through solvent replacement;

[0026] Among them, the polymer particles are selected from at least one of polyacrylate, polystyrene, styrene-acrylate copolymer, butadiene-styrene copolymer, ethylene-vinyl acetate copolymer, epoxy resin, polyurethane resin, phenolic resin, alkyd resin, polyacrylonitrile, and polycarbonate.

[0027] In some preferred embodiments of the present invention, the method for preparing the polymer particles includes: mixing at least two monomers evenly in a solvent in the presence of a protective gas and under stirring conditions, and then reacting at -10 to 90 °C for 0.5 to 48 h in the presence of a polymerization catalyst and a stabilizer; after filtering, washing, and drying the reaction product, the polymer particles are obtained.

[0028] In the present invention, the stirring rate affects the particle size of the polymer particles. If the particle size is too large, the polymer will agglomerate and polymer microparticles cannot be obtained. Under preferred conditions, the stirring rate is 80 to 500 r / min.

[0029] In the present invention, the polymer particles can be obtained by copolymerization of at least two or more monomers, and the type of copolymerization can be condensation polymerization or addition polymerization. Specifically, the addition polymerization can be obtained by polymerizing monomers containing unsaturated bonds (such as monomers containing alkenyl groups and / or monomers containing alkynyl groups); the condensation polymerization can be at least one of esterification reaction, aldol condensation reaction, hydroxylamine condensation reaction, ammonia-aldehyde condensation reaction, and hydroxyl-hydroxyl condensation reaction. The types of the foregoing condensation reactions are all known to those skilled in the art, and will not be elaborated herein.

[0030] In the present invention, the monomer is selected from at least one of vinyl monomers, amino monomers, hydroxyl monomers, aldehyde monomers, carboxyl monomers, acyl chloride monomers, siloxanes, and chlorosilanes; further preferably, the monomer is selected from styrene, acrylic acid, acrylamide, methyl acrylate, methyl methacrylate, acrylonitrile, vinyl acetate, vinyl alcohol, vinyl alkyl ether, ethyl acrylate, butyl acrylate, ethyl methacrylate, butyl methacrylate, polyethylene glycol diacrylate, trimethylolpropane triacrylate, isobutyl acrylate, tert-butyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, decyl acrylate, 2-hydroxypropyl acrylate, 2-ethoxyethyl acrylate, trimethylolpropane trimethacrylate, 2-cyanoethyl acrylate, cyclohexyl acrylate, isobornyl acrylate, formaldehyde, ethylene oxide, o-xylenol, terephthalic acid, ethylene glycol, bisphenol A, carbonyl chloride, maleic anhydride, hexamethylenediamine, adipic acid, norbornene, caprolactam, formaldehyde, paraformaldehyde, melamine, dimethyldichlorosilane, propargyl methacrylate, allyl methacrylate, 1,3-butadiene, isoprene, chloroprene, divinylbenzene, hydroxypropyl methacrylate, hydroxyethyl acrylate, hydrogen-containing silicone oil-modified polymethyl methacrylate allyl ester, etc. Further, when the polymerization type is addition polymerization, the monomer contains monomer A having at least two unsaturated bonds. For example, the monomer A may be at least one of allyl methacrylate, divinylbenzene, butadiene, isoprene, chloroprene, etc.

[0031] In the above method, the particle size of the polymer particles is 0.2 - 10 μm, preferably 0.5 - 5 μm.

[0032] In the above method, the weight ratio of the polyamide to the polymer particles is 10:1 - 1:1.

[0033] In the present invention, the polymerization catalyst is selected from at least one of hydrochloric acid, sulfuric acid, nitric acid, trifluoromethanesulfonic acid, phosphoric acid, perchloric acid, chlorosulfonic acid, fluorosulfonic acid, trichloroacetic acid, trifluoroacetic acid, trifluoromethanesulfonic acid, boron trifluoride, aluminum chloride, titanium tetrachloride, tin tetrachloride, zinc chloride, antimony chloride, strongly acidic cation exchange resin, acid clay, alkali metal hydroxide, tetramethylammonium hydroxide, cumene hydroperoxide, tert-butyl hydroperoxide, dicumyl peroxide, di-tert-butyl peroxide, benzoyl peroxide, lauroyl peroxide, tert-butyl peroxybenzoate, tert-butyl peroxypivalate, diisopropyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, azobisisobutyronitrile, azobisisoheptonitrile, dimethyl azobisisobutyrate, azobis(2-methylpropionamidine) dihydrochloride, azoisobutyronitrile carboxamide, potassium persulfate, ammonium persulfate, hydrogen peroxide, sodium persulfate, ferrous chloride, cuprous chloride, sodium sulfite, alcohol, amine, oxalic acid, glucose, potassium sodium tartrate, ascorbic acid, hydrazine hydrate, ultraviolet light, X-ray, γ-ray, β-ray, α-ray, neutron ray, microwave, benzophenone, plasma, sodium, lithium, cesium, sodium naphthalene, potassium amide, n-butyllithium, tert-butyllithium, Grignard reagent, sodium methoxide, potassium methoxide, Ziegler-Natta initiator, metallocene initiator.

[0034] In the present invention, the stabilizer is selected from at least one of polyvinylpyrrolidone, polyvinyl alcohol, sorbitan monooleate, carboxylate, sorbitan monooleate, alkyl sulfonate, whey protein, monoglyceride fatty acid glycerol ester, α-olefin sulfonate, alkylbenzene sulfonate, phosphoric acid diester salt, sorbitan fatty acid ester, alkylphenol polyoxyethylene ether, alkylamide betaine, alkylcarboxy betaine, pentaerythritol fatty acid ester, phosphoric acid monoester salt, sucrose fatty acid ester, sulfobetaine, aluminum sol, silica sol, magnesium sol.

[0035] In the present invention, the solvent is selected from at least one of m-cresol, N-methylpyrrolidone, dimethylacetamide, N,N-dimethylformamide, dimethyl sulfoxide, water, methanol, ethanol, n-propanol, isopropanol, n-butanol, ethyl acetate, tetrahydrofuran, acetone, ether, methyl ethyl ketone, cyclopentanone, dichloromethane, chloroform, petroleum ether, n-hexane, hexamethyldisiloxane, toluene and xylene.

[0036] In the present invention, the honeycomb polyamide is obtained by a solvent replacement method, that is, the polyamide coating film is rinsed with deionized water and dried to obtain the honeycomb polyamide.

[0037] The present invention provides a lithium battery separator prepared by the foregoing method.

[0038] The present invention further provides a lithium ion battery, including a positive electrode, a negative electrode and a separator disposed between the positive electrode and the negative electrode, and the separator is the foregoing lithium ion battery separator.

[0039] The present invention will be described in detail below with reference to embodiments.

[0040] In the following embodiments, the test methods are as follows:

[0041] Closed pore temperature test: Cut the separator into circular pieces with a diameter of 3 cm, place them in a fixture, and drop in a sufficient amount of electrolyte; use an electrochemical workstation to perform internal resistance testing by the AC impedance method, and record the temperature value when the internal resistance is greater than 250 mΩ.

[0042] Film breakage temperature test: Cut the separator into circular pieces with a diameter of 3 cm, perform heat treatment in an oven, and record the film breakage temperature.

[0043] Blank example

[0044] (1) Preparation of polyamide: Pass argon into a four-necked flask, pour in 100 mL of dimethylacetamide, add 7.03 g of m-phenylenediamine and 13.02 g of 4,4'-diaminodiphenyl ether, cool down to -10 °C and add 26.65 g of isophthaloyl chloride. After the system returns to room temperature, disperse and mix calcium hydroxide powder with 20 mL of dimethylacetamide, add it to the flask and continue the reaction for 30 min. After washing with water, filtering, and drying, the product polyamide is obtained.

[0045] (2) Dissolve the polyamide in dimethylacetamide with a purity of 98% to obtain a composite material with a solid content of 10%. Prepare a coated film with a single-sided coating thickness of 20 μm on the base film, and obtain a honeycomb structure film by the method of rinsing with deionized water. Then peel the honeycomb structure film from the base film to obtain the lithium-ion battery separator.

[0046] Figure 1 SEM image of the honeycomb structure film obtained in the blank example. From Figure 1 it can be seen that the film obtained in the blank example has a honeycomb structure, and its overall thickness is about 20 μm.

[0047] Example 1

[0048] (1) The preparation of polyamide is the same as that in the blank example.

[0049] (2) Preparation method of PMMA microspheres: Add 100 g of deionized water, 1 g of OP-10, and 0.1 g of aluminum sol to a three-necked flask, add 8 g of methyl methacrylate, 4 g of butyl methacrylate, 2 g of benzoyl peroxide, and 2 g of allyl methacrylate. Keep it at 80 °C with a stirring speed of 300 r / min for 8 h. After filtration, washing, and drying, PMMA microspheres with a particle size of 2 μm are obtained.

[0050] (3) Mix polyamide and PMMA microspheres in a weight ratio of 2:1 in dimethylacetamide with a purity of 98% to obtain a composite material with a solid content of 10%. Prepare a coated film with a single-sided coating thickness of 20 μm on the base film, and obtain a honeycomb-structured film by rinsing with deionized water. Then peel the honeycomb-structured film from the base film to obtain a lithium-ion battery separator, and its performance parameters are shown in Table 1.

[0051] Figure 2 SEM image of the honeycomb-structured film obtained in Example 1. From Figure 2 it can be seen that the film obtained in Example 1 has a honeycomb structure, and a large number of polymer particles are filled in the honeycombs.

[0052] Examples 2 - 3 and Comparative Examples 1 - 2

[0053] According to the method of Example 1, the difference is that the dosage of allyl methacrylate is shown in Table 1, and its performance parameters are shown in Table 1.

[0054] Table 1

[0055]

[0056] It can be seen from Table 1 that in Examples 1 - 3 and Comparative Example 2, as the dosage of allyl methacrylate increases, the electrolyte stability of the polymer microspheres gradually increases, and the corresponding closed-pore temperature increases. When the dosage of allyl methacrylate reaches 5 g, due to the large cross-linking density of the polymer microspheres, the closed-pore temperature exceeds 140 °C.

[0057] When no allyl methacrylate is used in Comparative Example 1, due to the linear structure of the polymer, the solvent resistance performance is poor, and it dissolves in dimethylacetamide when preparing the polyamide and polymer microsphere solution, unable to play the role of liquid absorption and swelling to block pores. And because methyl methacrylate exists between the polyamide matrixes, phase separation of the composite film occurs, resulting in a decrease in the film-breaking temperature.

[0058] Examples 4 - 6 and Comparative Examples 3 - 4

[0059] According to the method of Example 1, the difference is that the dosages of methyl methacrylate and butyl methacrylate are shown in Table 2, and its performance parameters are shown in Table 2.

[0060] Table 2

[0061]

[0062] It can be seen from Table 2 that when the content of methyl methacrylate increases, the closed pore temperature of the composite membrane also increases; when the dosage of butyl methacrylate increases, the closed pore temperature of the composite membrane decreases. However, for Examples 4 and 5, with the increase of the dosage of butyl methacrylate, the solvent resistance performance becomes poor, and it is easy to absorb liquid and swell by itself after long-term immersion in the electrolyte.

[0063] When all methyl methacrylate is used, its film breaking temperature exceeds 110 °C; when all butyl methacrylate is used, since the polymer microspheres swell in dimethylacetamide and present a jelly-like state, it is impossible to prepare a composite membrane.

[0064] Examples 7-11 and Comparative Example 5

[0065] According to the method of Example 1, the difference is that the reaction stirring speed in step (2) is different, and the particle sizes of the obtained PMMA microspheres are also different, as shown in Table 3 specifically.

[0066] Table 3

[0067]

[0068]

[0069] It can be seen from Table 3 that:

[0070] In Examples 1 and 7-11, different reaction rotation speeds were used to obtain polymer particles with different particle sizes. When the particle size of the polymer particles is 1 μm, since the adaptability between the particle size and the pore size of the honeycomb polyamide membrane is the best, enough voids are left to accommodate the electrolyte and liquid absorption and swelling plugging of pores can be achieved at high temperatures, so the closed pore temperature of the composite membrane is the lowest.

[0071] When the particle size of the PMMA microspheres is too large, it will lead to an increase in the closed pore temperature. Especially when the particle size reaches 15 μm, the number of microspheres decreases under the same mass, and it is impossible to effectively prevent the electrolyte from flowing and ion transport after liquid absorption and swelling. Even when the temperature rises above the film breaking temperature, no closed pore will occur.

[0072] When the particle size of the PMMA microspheres is too small, it will lead to an increase in the closed pore temperature. The possible reason is that the specific surface area of small particles is large, which reduces the resistance of ion transport to a certain extent.

[0073] In the blank example, no polymer microspheres are added, and it is impossible to achieve a reduction in the closed pore temperature.

[0074] Examples 12-15 and Comparative Examples 6-7

[0075] According to the method of Example 1, the difference is that the weight ratio of polyamide to PMMA microspheres is as shown in Table 4.

[0076] Table 4

[0077]

[0078] It can be seen from Table 4 that when the amount of polymer microspheres increases, the closed-cell temperature can be reduced to a certain extent, which may be due to the presence of a large number of polymer particles, resulting in a decrease in the film rupture temperature; when the amount of polymer microspheres decreases, the closed-cell temperature increases accordingly, but when the weight ratio of polyamide to PMMA microspheres is 12:1, due to the small amount of polymer microspheres, it is impossible to effectively prevent the flow of electrolyte and ion transmission after liquid absorption and expansion, and the closed-cell will not occur when the temperature rises above the film rupture temperature. When the weight ratio of polyamide to PMMA microspheres is 1:2, no film can be formed.

[0079] Example 16

[0080] The method of Example 1 is followed, except that styrene butadiene copolymer microspheres are used instead of PMMA microspheres. The specific method is as follows:

[0081] (1) The preparation method of polyamide is the same as that of Example 1.

[0082] (2) Preparation method of styrene butadiene copolymer microspheres: 100 g of deionized water, 1 g of polyvinyl pyrrolidone, 0.1 g of aluminum sol, 10 g of styrene, 2 g of butadiene, 2 g of benzoyl peroxide, and 2 g of divinylbenzene were added to a three-necked flask, and the mixture was kept warm at a stirring speed of 300 r / min and a temperature of 80°C for 8 h. After filtration, washing, and drying, styrene butadiene copolymer microspheres with a particle size of 2 μm were obtained.

[0083] (3) Polyamide and styrene butadiene copolymer microspheres were mixed in a 98% pure dimethylacetamide at a weight ratio of 2:1 to obtain a composite material with a solid content of 10%. A coating film with a single-sided coating thickness of 20 μm was prepared on a base film, and a honeycomb structure film was obtained by eluting with deionized water. The honeycomb structure film was then peeled off from the base film to obtain a lithium ion battery separator. Its performance parameters are shown in Table 5.

[0084] Embodiment 17

[0085] The method of Example 1 is followed, except that styrene acrylate copolymer microspheres are used instead of PMMA microspheres. The specific method is as follows:

[0086] (1) The preparation method of polyamide is the same as that of Example 1;

[0087] (2) Preparation method of styrene acrylate copolymer microspheres: Add 100 g of deionized water, 1 g of polyvinylpyrrolidone, and 0.1 g of aluminum sol into a three-necked flask. Then add 8 g of styrene, 4 g of butyl acrylate, 2 g of benzoyl peroxide, and 2 g of divinylbenzene. Keep the mixture at 80 °C with a stirring speed of 300 r / min for 8 h. After suction filtration, washing, and drying, styrene acrylate copolymer microspheres with a particle size of 2 μm are obtained.

[0088] (3) Mix polyamide and styrene acrylate copolymer microspheres in a weight ratio of 2:1 in dimethylacetamide with a purity of 98% to obtain a composite material with a solid content of 10%. Prepare a coated film with a single-sided coating thickness of 20 μm on a base film. Use deionized water rinsing to obtain a honeycomb structure film, and then peel the honeycomb structure film from the base film to obtain a lithium-ion battery separator. Its performance parameters are shown in Table 5.

[0089] Table 5

[0090]

[0091] It can be seen from Table 5 that PMMA microspheres, styrene butadiene copolymer microspheres, and styrene acrylate copolymer microspheres can all reduce the closed pore temperature of the separator while increasing the breakdown temperature of the separator.

[0092] Comparative Example 8

[0093] According to the method of Example 1, the difference is that the coated film is not eluted. The specific method is as follows:

[0094] (1) The preparation of polyamide is the same as that in Example 1.

[0095] (2) The preparation of PMMA microspheres is the same as that in Example 1.

[0096] (3) Mix polyamide and PMMA microspheres in a weight ratio of 2:1 in dimethylacetamide with a purity of 98% to obtain a composite material C1 with a solid content of 10%. Prepare a coated film with a single-sided coating thickness of 20 μm on a base film, and then peel the film from the base film.

[0097] The sample obtained in this comparative example has no honeycomb structure and cannot achieve the function of lithium-ion transmission, so it cannot be used as a separator.

[0098] Comparative Example 9

[0099] A preparation method of a lithium battery separator, characterized in that

[0100] (1) The preparation of polyamide is the same as that in Example 1.

[0101] (2) The preparation of PMMA microspheres is the same as that in Example 1.

[0102] (3) Mix polyamide and PMMA microspheres A1 in a weight ratio of 2:1 in dimethylacetamide with a purity of 98% to obtain a composite material with a solid content of 20%. Then, using a polyimide separator as the substrate, coat the composite material on the surface of the substrate with a vacuum coater, controlling the coating thickness to be 20 μm; while coating, turn on the vacuum pump to adsorb the coating solution into the separator; finally, put the prepared composite separator into an oven and dry it at 70 °C for 2 h to obtain a lithium battery separator.

[0103] The closed pore temperature of the lithium battery separator obtained in this comparative example is 127 °C, and the membrane rupture temperature is 168 °C.

[0104] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of protection claimed by the present invention is defined by the appended claims and their equivalents.

Claims

1. A lithium-ion battery separator, characterized in that: the lithium-ion battery separator comprises a honeycomb structure of polyamide and polymer particles filled in the honeycomb structure; under stirring conditions, dissolve polyamide in dimethylacetamide, then add polymer particles, mix evenly and coat on the surface of the base film, and obtain the lithium-ion battery separator through solvent replacement; the polymer particles are obtained by polymerizing methyl methacrylate, butyl methacrylate and allyl methacrylate; the particle size of the polymer particles is 0.2 - 10 μm; the closed pore temperature of the lithium-ion battery separator is not higher than 110 °C, and the film rupture temperature is not lower than 185 °C.

2. The lithium-ion battery separator according to claim 1, characterized in that: the thickness of the lithium-ion battery separator is 3 - 50 μm.

3. The lithium-ion battery separator according to claim 1, characterized in that: the weight ratio of polyamide to polymer particles is 10:1 - 1:

1.

4. The lithium-ion battery separator according to claim 1, characterized in that: the particle size of the polymer particles is 0.5 - 5 μm.

5. A method for preparing the lithium-ion battery separator according to any one of claims 1 - 4, characterized in that, the method comprises: under stirring conditions, dissolve polyamide in dimethylacetamide, then add polymer particles, mix evenly and coat on the surface of the base film, and obtain the lithium-ion battery separator through solvent replacement; the polymer particles are obtained by polymerizing methyl methacrylate, butyl methacrylate and allyl methacrylate; the preparation method of the polymer particles comprises: under the presence of a protective gas and stirring conditions, mix the monomers evenly in a solvent, then in the presence of a polymerization catalyst and a stabilizer, react at -10 - 90 °C for 0.5 - 48 h; after filtering, washing and drying the reaction product, obtain the polymer particles, and the stirring rate is 80 - 500 r / min.

6. The method according to claim 5, characterized in that, the particle size of the polymer particles is 0.2 - 10 μm.

7. The method according to claim 6, characterized in that, the particle size of the polymer particles is 0.5 - 5 μm.

8. The method according to claim 5, characterized in that, the weight ratio of polyamide to polymer particles is 10:1 - 1:

1.

9. A lithium battery separator prepared by the method according to any one of claims 5 - 8.

10. A lithium-ion battery, comprising a positive electrode, a negative electrode and a separator disposed between the positive electrode and the negative electrode, and the separator is the lithium-ion battery separator according to any one of claims 1 - 4 and 9.

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