Rubber-coated lithium battery separator and method of making the same

Abstract

This invention discloses a rubber-coated lithium-ion battery separator and its preparation method. The rubber-coated lithium-ion battery separator comprises a base film and a coating applied to the base film. The coating is obtained by applying a rubber coating slurry, and the coating comprises hydrogenated nitrile butadiene rubber (HNBR), polyacrylonitrile (PAB), and polyimide (PI). The rubber coating slurry of this invention introduces HNBR, giving the rubber-coated lithium-ion battery separator higher adhesion; the introduction of PIB gives the rubber-coated lithium-ion battery separator higher temperature resistance; this invention also innovatively introduces PIB, and the good compatibility between PIB and HNBR brings uniformly distributed pores to the separator. It is the first time that PIB has been found to have a dense and uniformly distributed pore-forming function in oil-based coated separators, improving the separator's air permeability.

Description

Technical Field

[0001] This invention belongs to the field of battery separator technology, specifically relating to a rubber-coated lithium battery separator and its preparation method. Background Technology

[0002] Lithium-ion battery separators are a crucial component of lithium-ion batteries, significantly impacting overall battery safety and performance. Currently, China's domestic production of lithium-ion battery separators is accelerating, with significant progress achieved. China ranks among the world's leading countries in market share and production capacity. Therefore, to further increase the domestic production rate in the high-end market, continued research efforts on lithium-ion battery separators are necessary. Separators play two main roles in lithium-ion batteries: First, the separator material needs to possess good insulation and sufficient strength to prevent direct contact between the positive and negative electrodes within the battery. It must also effectively prevent short circuits caused by punctures from burrs or dendrites, and ensure minimal dimensional changes under sudden high-temperature conditions, thus guaranteeing battery safety. Second, the porous structure of the separator provides excellent migration channels for lithium ions, ensuring stable and efficient battery operation.

[0003] One of the main performance degradation mechanisms of lithium-ion batteries is triggered by the dissolution of transition metal (especially manganese) cations in the positive electrode active material. These ions electromigrate and deposit on the negative electrode surface. The deposited manganese (transition metal) causes catalytic decomposition of solvent molecules and simultaneous consumption of electrochemically active lithium, leading to surface film growth, gas emission, graphite particle shedding, and overall battery performance degradation. The ability to capture transition metal ions and enhance battery life is a crucial performance characteristic of lithium-ion battery separators; therefore, developing separators with high safety and ion-capturing capabilities is of great significance. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a rubber-coated lithium battery separator.

[0005] Another object of the present invention is to provide a method for preparing the above-mentioned rubber-coated lithium battery separator.

[0006] Another object of the present invention is to provide a rubber coating slurry.

[0007] Another object of the present invention is to provide a method for preparing the above-mentioned rubber coating slurry.

[0008] The objective of this invention is achieved through the following technical solution.

[0009] A rubber-coated lithium battery separator includes: a base film and a coating applied to the base film. The coating is obtained by applying a rubber coating slurry. The coating includes: hydrogenated nitrile butadiene rubber (HNBR), polyacrylonitrile and polyimide (PI). The ratio of hydrogenated nitrile butadiene rubber (HNBR), polyacrylonitrile and polyimide (PI) by mass parts is (0.5-10):(1-8):(6-12).

[0010] In the above technical solution, the preferred ratio of hydrogenated nitrile butadiene rubber (HNBR), polyacrylonitrile and polyimide (PI) by mass parts is (1.8-2.2):(2.6-3.5):(8-11.5).

[0011] In the above technical solution, the ratio of hydrogenated nitrile butadiene rubber (HNBR), polyacrylonitrile and polyimide (PI) by mass parts is preferably 2:(1.8-5):(4-20), more preferably 2:(2-4):(4-18), and even more preferably 2:(2-4):(8-15).

[0012] The preparation method of the above-mentioned rubber-coated lithium battery separator includes: coating a rubber coating slurry onto a base film to obtain a rubber-coated lithium battery separator precursor; extracting the rubber-coated lithium battery separator precursor and dehydrating it to obtain the rubber-coated lithium battery separator.

[0013] In the above technical solution, the extraction uses an extractant solution, and the rubber-coated lithium battery separator precursor is sequentially passed through an extractant solution with an extractant concentration decreasing from high to low. The extractant solution is N-methylpyrrolidone (NMP).

[0014] In the above technical solution, the extractants with extractant concentrations from high to low are, in order, a first extractant, a second extractant, a third extractant, and a fourth extractant. The first, second, and third extractants are each mixtures of extractant and water, and the fourth extractant is water. The concentration of extractant in the first extractant is 65–80 wt%, the concentration of extractant in the second extractant is 40–60 wt%, and the concentration of extractant in the third extractant is 20–40 wt%.

[0015] In the above technical solution, the dehydration treatment is to dry at 50-60°C for 6-12 minutes.

[0016] A rubber coating slurry includes: hydrogenated nitrile butadiene rubber (HNBR), polyacrylonitrile and polyimide (PI), wherein, by mass parts, the ratio of hydrogenated nitrile butadiene rubber (HNBR), polyacrylonitrile and polyimide (PI) in the rubber coating slurry is (0.5-10):(1-8):(6-12).

[0017] In the above technical solution, the rubber coating slurry further includes a solvent, wherein the solvent is a single-component solvent and / or a multi-component solvent, wherein:

[0018] The single-component solvent is N-methylpyrrolidone;

[0019] The multi-component solvent includes solvent 1 and solvent 2. Solvent 1 is one or a mixture of tetrahydrofuran, methyl isobutyl ketone, and dimethylformamide. Solvent 2 is one or a mixture of dimethyl sulfoxide and acetonitrile.

[0020] A method for preparing a rubber coating slurry includes: mixing a first solution, a second solution, and a third solution until homogeneous to obtain a rubber coating slurry, wherein the first solution comprises hydrogenated nitrile butadiene rubber (HNBR) and a first solvent, the second solution comprises polyacrylonitrile and a second solvent, and the third solution comprises polyimide (PI) and a third solvent. The ratio of hydrogenated nitrile butadiene rubber (HNBR), polyacrylonitrile, and polyimide (PI) by mass parts is (0.5–10):(1–8):(6–12), the ratio of hydrogenated nitrile butadiene rubber (HNBR) to the first solvent by mass parts is (5–15):(85–95), and the ratio of the first solvent, the second solvent, and the third solvent by mass parts is (5–25):(15–45):(30–80).

[0021] In the above technical solution, the first solvent is one or a mixture of several of N-methylpyrrolidone (NMP), tetrahydrofuran, methyl isobutyl ketone and dimethylformamide.

[0022] In the above technical solution, the second solvent is one or a mixture of several of N-methylpyrrolidone (NMP), tetrahydrofuran, methyl isobutyl ketone and dimethylformamide.

[0023] In the above technical solution, the third solvent is one or a mixture of several of N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), and acetonitrile.

[0024] In the above technical solution, the first solvent, the second solvent, and the third solvent may be the same or different.

[0025] In the above technical solution, the ratio of hydrogenated nitrile butadiene rubber (HNBR) to the first solvent by mass parts is (5-15):(85-95).

[0026] In the above technical solution, the first solution, the second solution and the third solution are mixed and stirred at a stirring speed of 300-500 r / min for 0.5-2 h until homogeneous.

[0027] In the above technical solution, the method for preparing the first solution is as follows: hydrogenated nitrile butadiene rubber (HNBR) is dissolved in a first solvent to obtain the first solution.

[0028] In the method for preparing the first solution, the method for dissolving hydrogenated nitrile butadiene rubber (HNBR) in the first solvent is as follows: stirring at 350-400 r / min for 12-16 h at 30-45 °C.

[0029] In the above technical solution, the method for preparing the second solution is as follows: dissolve polyacrylonitrile in a second solvent to obtain the second solution.

[0030] In the method for preparing the second solution, the method for dissolving polyacrylonitrile in the second solvent is as follows: stirring at 350-400 r / min for 3-5 h at 30-45 °C.

[0031] In the above technical solution, the method for preparing the third solution is as follows: In a nitrogen or inert gas atmosphere, the first part of the third solvent and the diamine are mixed until homogeneous, and then the dianhydride and the second part of the third solvent are added sequentially. The mixture undergoes a polycondensation reaction at room temperature and under stirring for 20-26 hours to generate polyimide acid. Toluene is added, and the mixture undergoes an imidization reaction at 160-195°C and under stirring for 8-16 hours. The mixture is then cooled to room temperature to obtain the third solution. The third solvent is composed of the first part of the third solvent and the second part of the third solvent. By mass fraction, the ratio of the third solvent, diamine, dianhydride and toluene is (200-250):(11-15):(33-36):(21-26).

[0032] In the method for preparing the third solution, the ratio of the first part of the third solvent to the second part of the third solvent, by mass parts, is (80-150):(100-200).

[0033] In the method for preparing the third solution, the diamine is 4,4'-diaminodiphenyl ether, and the dianhydride is 4,4'-bisphenol A type diether dianhydride.

[0034] In the above technical solution, the organic solvents all need to be dehydrated before use, and the organic solvents are any one of the first solvent, the second solvent, and the third solvent.

[0035] In the above technical solution, the water removal method is as follows: the molecular sieve is dried at 150℃~230℃ for 2~4 hours, and the dried molecular sieve is added to the organic solvent and left to stand for 2~6 hours. The ratio of the dried molecular sieve to the organic solvent is (85~92):(8~15) by mass.

[0036] Application of rubber-coated lithium battery separators in lithium-ion batteries.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] 1. The rubber coating slurry of the present invention introduces HNBR, which gives the rubber-coated lithium battery separator high adhesion; the introduction of PI gives the rubber-coated lithium battery separator high temperature resistance; the present invention also innovatively introduces polyacrylonitrile, and the good compatibility between polyacrylonitrile and HNBR brings uniformly distributed pores to the separator. It is the first time that polyacrylonitrile has a dense and uniformly distributed pore-forming function in oil-based coated separators, which improves the air permeability of the separator.

[0039] 2. The rubber-coated lithium battery separator of the present invention has a good transition metal ion capture effect;

[0040] 3. This invention has high repeatability and is simple to operate. Attached Figure Description

[0041] Figure 1 SEM image of the membrane prepared in Example 5;

[0042] Figure 2 SEM image of the membrane prepared in Comparative Example 5. Detailed Implementation

[0043] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0044] The sources of the pharmaceuticals involved in the following examples and comparative examples are as follows:

[0045] Hydrogenated nitrile butadiene rubber (HNBR), purity 99.5%;

[0046] Polyacrylonitrile (powder), purity 99.9%, molecular weight 200,000;

[0047] N-methylpyrrolidone (NMP), purity 99.5%;

[0048] 4,4'-Diaminodiphenyl ether, purity 99%;

[0049] 4,4'-Bisphenol A type diether dianhydride, purity 98%;

[0050] Toluene, 99.5% purity

[0051] Positive electrode (ternary positive electrode, ternary material is LiN) i0.8 Co 0.2 O2);

[0052] Negative electrode sheet (graphite negative electrode).

[0053] The models and manufacturers of the equipment involved in the following embodiments and comparative examples are as follows:

[0054] Scanning electron microscope, Sigma 300, Carl Zeiss GmbH, Germany;

[0055] Asahi Seiko (Japan) breathability meter, model EH01-551MR;

[0056] Japanese Shimadzu stretching machine, model AGS-X(100N);

[0057] Electrochemical workstation, CHI660E, Shanghai Chenhua Instrument Co., Ltd.;

[0058] Withstand voltage insulation analyzer, AN9636HS, Qingdao Aino Intelligent Instrument Co., Ltd.;

[0059] In the following embodiments, the first solvent, the second solvent, and the third solvent all need to be dehydrated before use.

[0060] The method for removing water with the first solvent is as follows: the molecular sieve is dried at 200℃ for 3 hours, the dried molecular sieve is added to the first solvent, and it is left to stand for 4 hours. The ratio of molecular sieve to first solvent by mass is 90:10. The molecular sieve is hydrated aluminosilicate.

[0061] The methods for removing water with the second and third solvents are the same as those for removing water with the first solvent.

[0062] In the following embodiments, the base film is a polyethylene film with a thickness of 9 μm.

[0063] Diaphragm adhesion test method: The diaphragm is cut into a shape of 25mm × 60mm and attached to the diaphragm with tape. The force required to tear the tape and diaphragm apart using a Shimadzu stretching machine is the diaphragm adhesion force. The diaphragm is one of the diaphragms prepared in Examples 5-8 and Comparative Examples 5-8.

[0064] Battery electrode adhesion test method: The separator is cut into a shape of 25mm × 150mm, and the battery electrode is cut into a shape of 25mm × 60mm. The separator and the battery electrode are stacked together and hot-pressed using a battery electrode press. The hot-pressing pressure is 1000KG, the hot-pressing temperature is 80℃, and the hot-pressing time is 1s. The battery electrode and the separator are then torn apart using a Shimadzu stretching machine. The force used is the battery electrode adhesion force. The battery electrode is either a positive electrode (the resulting battery electrode adhesion force is the positive electrode adhesion force) or a negative electrode (the resulting battery electrode adhesion force is the negative electrode adhesion force). The separator is one of the separators prepared in Examples 5-8 and Comparative Examples 5-8.

[0065] Examples 1-4

[0066] A method for preparing a rubber coating slurry includes: mixing a first solution, a second solution, and a third solution, and stirring at a stirring speed of 400 r / min for 1 h until homogeneous to obtain a rubber coating slurry. The first solution is a mixture of hydrogenated nitrile butadiene rubber (HNBR) and a first solvent; the second solution is a mixture of polyacrylonitrile and a second solvent; and the third solution comprises polyimide (PI) and a third solvent. The ratio of hydrogenated nitrile butadiene rubber (HNBR), polyacrylonitrile, and polyimide (PI) by mass is X; the ratio of hydrogenated nitrile butadiene rubber (HNBR) to the first solvent by mass is 10:90; the first solvent is N-methylpyrrolidone (NMP); the second solvent is N-methylpyrrolidone (NMP); the third solvent is N-methylpyrrolidone (NMP); and the ratio of the first solvent, the second solvent, and the third solvent by mass is Y. The values ​​of X and Y are shown in Table 1.

[0067] The method for preparing the first solution (hydrogenated nitrile butadiene rubber solution) is as follows: granular hydrogenated nitrile butadiene rubber (HNBR) and a first solvent are mixed and stirred at 380 r / min for 14 h at 35°C to dissolve the hydrogenated nitrile butadiene rubber (HNBR) in the first solvent, thereby obtaining the first solution.

[0068] The method for preparing the second solution (polyacrylonitrile solution) is as follows: powdered polyacrylonitrile and the second solvent are mixed and stirred at 380 r / min for 4 h at 35 °C to dissolve the polyacrylonitrile in the second solvent, thereby obtaining the second solution.

[0069] The method for preparing the third solution is as follows: Under a nitrogen atmosphere, the first part of the third solvent and the diamine are mixed and stirred for 10 minutes until homogeneous. Then, the dianhydride and the second part of the third solvent are added sequentially, and the polycondensation reaction is carried out at room temperature and under stirring for 24 hours to obtain polyimide acid. Toluene is added, and the imidization reaction is carried out at 180°C and under stirring for 9 hours. After cooling to room temperature, the third solution is obtained. The first part of the third solvent and the second part of the third solvent constitute the third solvent. By mass parts, the ratio of the third solvent, diamine, dianhydride and toluene is 210:13.6356:35.4373:24.7. By mass parts, the ratio of the first part of the third solvent and the second part of the third solvent is 100:126. The diamine is 4,4'-diaminodiphenyl ether, and the dianhydride is 4,4'-bisphenol A type diether dianhydride.

[0070] Table 1

[0071] Example X Y Example 1 2：3：10 18：27：66.9 Example 2 1：3：12 9：27：79.3 Example 3 2：2：12 18：18：79.3 Example 4 2.5：4.5：6 22.5：40.5：33.15

[0072] Comparative Example 1

[0073] A method for preparing a coating slurry includes: mixing a first solution prepared in Example 1, solvent A, and a third solution prepared in Example 1, stirring until homogeneous to obtain a coating slurry. The ratio of hydrogenated nitrile butadiene rubber (HNBR), solvent A, and polyimide (PI) in the first solution to that in the third solution is 1.5:30:10 by mass, and solvent A is N-methylpyrrolidone (NMP).

[0074] Comparative Example 2

[0075] A method for preparing a coating slurry includes: mixing a first solution prepared in Example 1, a second solution prepared in Example 1, and solvent B, and stirring until homogeneous to obtain a coating slurry. The ratio of hydrogenated nitrile rubber (HNBR) in the first solution, polyacrylonitrile in the second solution, and solvent B, by mass parts, is 1.5:3:50, and solvent B is N-methylpyrrolidone (NMP).

[0076] Comparative Example 3

[0077] A method for preparing a coating slurry includes: mixing solvent C, a second solution prepared in Example 1, and a third solution prepared in Example 1, stirring until homogeneous to obtain a coating slurry, wherein the ratio of solvent C, polyacrylonitrile in the second solution, and polyimide (PI) in the third solution is 20:2:10 by mass, and solvent C is N-methylpyrrolidone (NMP).

[0078] Comparative Example 4

[0079] A method for preparing a coating slurry is basically the same as that in Example 1, “A method for preparing a rubber coating slurry”, except that the first solution is different. In this comparative example, the method for preparing the first solution (SBR solution) is as follows: granular styrene-butadiene rubber (SBR) and a first solvent are mixed and stirred at 380 r / min for 14 h at 35°C to dissolve the styrene-butadiene rubber (SBR) in the first solvent to obtain the first solution. The ratio of styrene-butadiene rubber (SBR) to the first solvent is 10:90 by mass.

[0080] Examples 5-8 and Comparative Examples 5-8

[0081] A method for preparing a diaphragm involves coating a slurry onto a base membrane to obtain a diaphragm precursor, extracting the diaphragm precursor (using NMP), and drying it in an oven at 55°C for 8 minutes for dehydration to obtain the diaphragm. The extraction uses an extractant solution, and the diaphragm precursor is sequentially passed through extractants with decreasing extractant concentrations. The extractant is N-methylpyrrolidone (NMP). The extractants with decreasing extractant concentrations are, in order, a first extractant, a second extractant, a third extractant, and a fourth extractant. The first, second, and third extractants are each mixtures of the extractant and deionized water, while the fourth extractant is deionized water. The extractant concentration in the first extractant is 80 wt%, in the second extractant is 50 wt%, and in the third extractant is 30 wt%. The slurry is one of the rubber coating slurries prepared in Examples 1 to 4 and the coating slurries prepared in Comparative Examples 1 to 4. The separators (rubber-coated lithium battery separators) of Examples 5 to 8 were obtained sequentially from Examples 1 to 4, and the separators of Comparative Examples 5 to 8 were obtained sequentially from Comparative Examples 1 to 4, as shown in Table 2.

[0082] Table 2

[0083]

[0084]

[0085] The membrane adhesion, positive electrode adhesion, and negative electrode adhesion of the membranes prepared in Examples 5-8 and Comparative Examples 5-8 are shown in Table 3.

[0086] Table 3

[0087]

[0088] As shown in Table 3, the membrane adhesion, positive electrode adhesion, and negative electrode adhesion of the membrane prepared with slurry containing HNBR are much greater than those of the membrane prepared with slurry without HNBR. The performance of the membrane prepared with slurry containing HNBR is higher than that of the membrane prepared with slurry containing SBR. The membrane prepared with the rubber-coated slurry of Example 1 has the highest adhesion.

[0089] The diaphragms prepared in Examples 5-8 and Comparative Examples 5-8 were subjected to air permeability tests, breakdown voltage tests, thermal shrinkage tests, and ionic conductivity tests. The air permeability value, breakdown voltage, thermal shrinkage rate, and ionic conductivity were obtained sequentially. Specifically, the diaphragm was placed on an Asahi Seiko air permeability analyzer (Japan) and tested at 10 points evenly (one point every 10 cm). The average value of these 10 points was taken as the air permeability value. The diaphragm was laid flat on the test conductive plate of a withstand voltage insulation analyzer, and 50 breakdown points were tested. The average value of these 50 breakdown points was taken as the breakdown voltage. The diaphragm was cut into 4cm × 6cm pieces, and its area change was measured in a 150℃ oven for 1 hour to obtain the thermal shrinkage rate (measuring heat resistance stability). The ionic conductivity was obtained by AC impedance method at room temperature and 100% RH. The test results are shown in Table 4.

[0090] Table 4

[0091]

[0092] As shown in Table 4, adding polyacrylonitrile to the slurry can reduce the air permeability of the diaphragm. The introduction of PI can effectively improve the breakdown voltage and heat shrinkage performance of the diaphragm, making the diaphragm more stable in use. The diaphragms prepared in Examples 5 to 8 also have good ionic conductivity.

[0093] SEM images of the membranes prepared in Comparative Example 5 and Example 5 were obtained by microscopic scanning. Figure 2 It can be seen that the membrane prepared using slurry without added polyacrylonitrile does not form pores, therefore its air permeability is quite high. Figure 1 SEM images showed that the membrane prepared in Example 5 left many micropores, demonstrating the role of polyacrylonitrile. Therefore, polyacrylonitrile has a certain pore-forming function.

[0094] The membranes prepared in Example 5, Comparative Example 7, and Comparative Example 8 were tested for their ability to capture transition metal ions (iron, nickel, and manganese ions). The membranes prepared in Example 5, Comparative Example 7, and Comparative Example 8 were cut into three pieces of the same size. The three membranes of the same example or comparative example were used as a sample. The content of transition metal ions in the three membranes of each sample was tested by ICP and the average value was calculated, as shown in Table 5, "Elemental content before immersion".

[0095] Three cut membrane pieces from each sample were immersed for one day in an electrolyte containing 500 ppm of transition metal ions. The electrolytes used for immersion in the membranes were: one containing 500 ppm of iron ions, one containing 500 ppm of nickel ions, and one containing 500 ppm of manganese ions. Each membrane was immersed in only one electrolyte. After immersion, the membranes were removed and subjected to ICP testing to determine the content of transition metal ions. The test results are shown in Table 5, “Elemental Content After Immersion.” The electrolyte was LiPF6 with a concentration of 1.0 M. The electrolyte solvents were ethyl carbonate, methyl carbonate, and dimethyl carbonate, with a volume ratio of 1:1:1.

[0096] Table 5

[0097]

[0098] ICP testing of the diaphragm revealed that hydrogenated nitrile butadiene rubber (NBR) exhibits a high capture effect on nickel, manganese, and iron ions, demonstrating superior capture ability compared to styrene-butadiene rubber (SBR).

[0099] Compared with Comparative Examples 5-8, Comparative Example 5 has a very high air permeability and cannot be used; the membrane prepared in Comparative Example 6 has poor heat shrinkage; the adhesive force of the membrane prepared in Comparative Example 7 mainly comes from PI, and PI can only provide low adhesive force, so the adhesive force of Comparative Example 7 is relatively poor; compared with Comparative Example 8, the membrane prepared in Example 5 has better adhesive force, while the air permeability is lower than that of Comparative Example 8.

[0100] Ion capture experiments further demonstrated that the membrane prepared in Example 5 had a superior ion capture effect compared to Comparative Example 8. Through comparison of the examples and the comparative examples, the membrane prepared by hydrogenated nitrile rubber, polyacrylonitrile and polyimide in a better ratio had excellent performance. To a certain extent, the three components played a synergistic role in constructing a correspondingly superior lithium battery membrane.

[0101] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. A rubber-coated lithium battery separator, characterized by, It comprises: a base film and a coating layer coated on the base film, the coating layer comprising: hydrogenated nitrile rubber, polyacrylonitrile and polyimide, the ratio of hydrogenated nitrile rubber, polyacrylonitrile and polyimide being (0.5-10):(1-8):(6-12) by mass fraction; the preparation method of the rubber coating lithium battery separator comprises: coating a rubber coating slurry on a base film to obtain a rubber coating lithium battery separator precursor, extracting the rubber coating lithium battery separator precursor, dehydrating to obtain a rubber coating lithium battery separator, and the dehydration treatment is drying at 50-60℃.

2. The rubber-coated lithium battery separator of claim 1, wherein, Drying at 50-60℃ for 6-12min.

3. The rubber-coated lithium battery separator of claim 1, wherein, The rubber coating slurry comprises: hydrogenated nitrile rubber, polyacrylonitrile and polyimide, and the ratio of hydrogenated nitrile rubber, polyacrylonitrile and polyimide in the rubber coating slurry is (0.5-10):(1-8):(6-12) by mass fraction.

4. The rubber-coated lithium battery separator of claim 3, wherein, The rubber coating slurry further comprises a solvent, which is a single-component solvent and / or a multi-component solvent, wherein: The single-component solvent is N-methyl pyrrolidone; The multi-component solvent comprises solvent 1 and solvent 2, the solvent 1 is a mixture of one or more of tetrahydrofuran, methyl isobutyl ketone and dimethylformamide, and the solvent 2 is a mixture of one or both of dimethyl sulfoxide and acetonitrile.

5. The rubber-coated lithium battery separator of claim 1, wherein, The method for preparing the rubber coating slurry comprises: mixing a first solution, a second solution and a third solution uniformly to obtain the rubber coating slurry, wherein the first solution comprises: hydrogenated nitrile rubber and a first solvent, the second solution comprises: polyacrylonitrile and a second solvent, and the third solution comprises: polyimide and a third solvent, the ratio of hydrogenated nitrile rubber, polyacrylonitrile and polyimide being (0.5-10):(1-8):(6-12) by mass fraction, the ratio of hydrogenated nitrile rubber and the first solvent being (5-15):(85-95) by mass fraction, and the ratio of the first solvent, the second solvent and the third solvent being (5-25):(15-45):(30-80) by mass fraction.

6. The rubber-coated lithium battery separator of claim 5, wherein, The first solvent is a mixture of one or more of N-methyl pyrrolidone, tetrahydrofuran, methyl isobutyl ketone and dimethylformamide.

7. The rubber-coated lithium battery separator of claim 5, wherein, The second solvent is a mixture of one or more of N-methyl pyrrolidone, tetrahydrofuran, methyl isobutyl ketone and dimethylformamide.

8. The rubber-coated lithium battery separator of claim 5, wherein, The third solvent is a mixture of one or more of N-methyl pyrrolidone, dimethyl sulfoxide and acetonitrile.

9. The method of claim 1-8, wherein the rubber-coated lithium battery separator is prepared by the steps of: It comprises: coating a rubber coating slurry on a base film to obtain a rubber coating lithium battery separator precursor, extracting the rubber coating lithium battery separator precursor, dehydrating to obtain a rubber coating lithium battery separator, and the dehydration treatment is drying at 50-60℃.

10. The rubber coating lithium battery separator according to any one of claims 1-8 for use in a lithium ion battery.

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