A battery separator, method of making the same, and battery

Abstract

The application provides a battery diaphragm, a preparation method thereof and a battery. The battery diaphragm is prepared by the following steps: preparing a spinning solution by mixing modified bamboo fiber powder and PET chips, electrospinning to obtain a PET fiber film, finishing the PET fiber film with hexanediamine solution and sulfonated finishing liquid in sequence, and washing, drying to obtain the battery diaphragm. The modified bamboo fiber powder is prepared by the following steps: oxidizing bamboo fiber powder with sodium periodate, and then reacting with an aminated DOPO flame retardant. The aminated DOPO flame retardant is prepared by the following steps: reacting 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide with diethyl maleate, and then reacting with isophorone diamine. The battery diaphragm provided by the application has excellent flame retardant performance and high ion conductivity.

Description

Technical Field

[0001] This invention relates to the field of battery separator technology, specifically to a battery separator, its preparation method, and a battery. Background Technology

[0002] Battery separators, located inside the battery, serve several functions, including preventing direct contact between the positive and negative electrodes, controlling the rate and extent of short-circuit reactions, and allowing lithium ions to pass while blocking electrons. While traditional polyolefin battery separators are inexpensive, they suffer from drawbacks such as poor heat resistance, poor electrolyte wettability, flammability, and low strength, making them unsuitable for most applications.

[0003] This application uses high-strength, heat-resistant PET as raw material to prepare battery separators via electrospinning. Compared to traditional polyolefin battery separators, it exhibits higher mechanical strength and thermal stability. However, PET battery separators still suffer from flammability and poor electrolyte wettability. To address this deficiency, this application employs chemical modification and process optimization, using bamboo fiber powder as a biomass raw material and loading it with a DOPO-type flame retardant during the PET spinning process. This not only improves the flame retardant properties of the battery separator but also allows the bamboo fiber powder to act as a reinforcing rib, further enhancing the mechanical strength of the battery separator. Furthermore, by introducing a large number of highly polar sulfonic acid groups onto the surface of the PET fiber membrane, the wettability between the battery separator and the electrolyte is improved, further enhancing the ionic conductivity of the battery separator. Summary of the Invention

[0004] The purpose of this invention is to provide a battery separator, its preparation method, and a battery, in order to solve the problems existing in the prior art.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: A battery separator is obtained by preparing a spinning solution from modified bamboo fiber powder and PET chips, electrospinning to obtain a PET fiber membrane, and then treating the PET fiber membrane with hexamethylenediamine solution and sulfonation finishing solution in sequence, followed by washing and drying.

[0006] Furthermore, the modified bamboo fiber powder is prepared by reacting pre-modified bamboo fiber powder and aminated DOPO flame retardant with a Schiff base reaction. The pre-modified bamboo fiber powder is obtained by oxidizing bamboo fiber powder with sodium periodate.

[0007] Furthermore, the aminated DOPO flame retardant is prepared by reacting DOPO diethyl ester and isophorone diamine; The DOPO diethyl ester is prepared by reacting 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide with diethyl maleate.

[0008] A method for preparing a battery separator includes the following preparation steps: (1) Weigh DOPO diethyl ester and isophorone diamine at a molar ratio of 1:(6~8); mix DOPO diethyl ester and tetrahydrofuran at a mass ratio of 1:(8~10), heat to 63~65℃ under nitrogen protection, add isophorone diamine dropwise at a uniform rate over 1h, continue the reaction for 4~5h after the addition is complete, cool to room temperature, filter, wash with tetrahydrofuran, and vacuum dry at 50~60℃ for 16~18h to obtain aminated DOPO flame retardant; (2) Bamboo fiber powder, sodium periodate, isopropanol and distilled water are mixed evenly in a mass ratio of 1:(1.2~1.4):(0.6~0.8):(16~20), stirred and reacted at 40~50℃ for 6~8h under light-proof conditions, filtered, washed with distilled water, and vacuum dried at 50~60℃ for 8~10h to obtain pre-modified bamboo fiber powder; pre-modified bamboo fiber powder, aminated DOPO flame retardant and N,N-dimethylformamide are mixed in a mass ratio of 1:(0.5~0.6):(14~18), stirred and reacted at 60~70℃ for 5~6h, filtered, washed with N,N-dimethylformamide, and vacuum dried at 50~60℃ for 20~24h to obtain modified bamboo fiber powder; (3) Dissolve PET chips in a mixed solvent to prepare a PET solution with a mass fraction of 10%~12%; add 10%~14% of modified bamboo fiber powder by mass of PET chips, mix evenly to obtain a spinning solution; perform electrospinning on the spinning solution to obtain a PET fiber film. (4) Immerse the PET fiber membrane in a hexamethylenediamine solution with a bath ratio of 1:20 for 15-25 minutes, roll it with a roll-off rate of 60%-70%, heat it at 160°C for 10 minutes, wash it with water, and dry it at 60°C for 1 hour to obtain a pretreated PET fiber membrane; immerse the pretreated PET fiber membrane in a sulfonation finishing solution with a bath ratio of 1:20, keep it at 70-80°C for 8-10 hours, take it out, wash it with water, and dry it at 100°C to obtain a battery separator.

[0009] Furthermore, the preparation process of DOPO-based diethyl ester in step (1) is as follows: 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and diethyl maleate are weighed in a molar ratio of 1:1; 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 1,2-dichloroethane are mixed in a mass ratio of 1:(5~6) to prepare a DOPO solution; diethyl maleate, potassium carbonate, and 1,2-dichloroethane are mixed in a mass ratio of 1:(0.2~0.4):(5~6), placed in a reflux condenser, heated to 90~100℃ under nitrogen protection, and DOPO solution is added dropwise at a uniform rate over 30 min. After the addition is complete, the reaction is stirred for 3~4 h, cooled to room temperature, washed with saturated sodium bicarbonate, dried with anhydrous magnesium sulfate, filtered, and the filtrate is evaporated under reduced pressure to obtain DOPO-based diethyl ester.

[0010] Furthermore, the reaction mechanism of the DOPO diethyl ester is as follows: .

[0011] Furthermore, the mixed solvent in step (3) is obtained by mixing trifluoroacetic acid and dichloromethane in a volume ratio of 3:2.

[0012] Furthermore, the hexamethylenediamine solution in step (4) is prepared by dissolving 1,6-hexamethylenediamine in distilled water to form a hexamethylenediamine solution with a mass fraction of 2% to 3%.

[0013] Furthermore, the sulfonation finishing solution in step (4) is prepared by mixing 1,3-propanesulfonate lactone and isopropanol in a mass ratio of 1:(40~50).

[0014] This application also provides a battery, wherein the battery separator is prepared according to the above-described battery separator preparation method.

[0015] The beneficial effects of this invention are: Effect 1: DOPO diethyl ester is prepared by reacting 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide with diethyl maleate; then, DOPO diethyl ester is reacted with excess isophorone diamine, and the ester group is exchanged for an amide group to obtain an amino-modified DOPO flame retardant.

[0016] Effect 2: Bamboo fiber powder is oxidized with sodium periodate to introduce aldehyde groups into the bamboo fiber powder, and then reacted with an amino-modified DOPO flame retardant through a Schiff base reaction, loading the DOPO flame retardant onto the bamboo fiber powder in the form of chemical bonds. Bamboo fiber has a high fixed carbon content and good char-forming properties, so it can be used as a carbon source for polymer flame retardancy. Loading the DOPO flame retardant through the Schiff base reaction increases phosphorus and nitrogen elements, which can achieve a synergistic effect and give the battery separator excellent flame retardant properties.

[0017] Effect 3: Treating the surface of PET fiber membrane with 1,6-hexanediamine can introduce amino groups into the surface of the PET fiber membrane. The amino groups then undergo a ring-opening reaction with 1,3-propanesulfonate lactone, introducing a large number of highly polar sulfonic acid groups into the surface of the PET fiber membrane. This can effectively enhance the membrane's wettability to the electrolyte, thereby improving ion conduction performance. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] In the following examples and comparative examples Raw material information: PET chips: Dongguan Xingwang Plastic Raw Materials Co., Ltd. Bamboo fiber powder: Hydrogen peroxide and acetic acid with a mass fraction of 30% were mixed at a mass ratio of 1:1 to prepare a treatment solution; bamboo powder with a particle size of 200 mesh and the treatment solution were mixed at a mass ratio of 1:10, treated at 80℃ for 6 hours, washed with distilled water, and vacuum dried at 50℃ for 24 hours to obtain bamboo fiber powder for the experiment. Mixed solvent: Trifluoroacetic acid and dichloromethane are mixed in a volume ratio of 3:2 to obtain a mixed solvent.

[0020] Electrospinning process parameters: spinning voltage 18.5kV, receiving distance 15cm, liquid pushing speed 0.9mL / h, ambient temperature 26℃, humidity 35%.

[0021] Example 1 This embodiment provides a method for preparing a battery separator, including the following preparation steps: (1) Weigh 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and diethyl maleate in a molar ratio of 1:1; mix 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 1,2-dichloroethane in a mass ratio of 1:5 to prepare a DOPO solution; mix diethyl maleate, potassium carbonate and 1,2-dichloroethane in a mass ratio of 1:0.2:5, place in a reflux condenser, and under nitrogen protection, heat to 90°C. Add the DOPO solution dropwise at a uniform rate over 30 minutes. After the addition is complete, continue... The reaction was stirred for another 4 hours, cooled to room temperature, washed with saturated sodium bicarbonate, dried over anhydrous magnesium sulfate, filtered, and the filtrate was evaporated under reduced pressure to obtain DOPO diethyl ester. DOPO diethyl ester and isophorone diamine were weighed in a molar ratio of 1:6. DOPO diethyl ester and tetrahydrofuran were mixed evenly in a mass ratio of 1:8. Under nitrogen protection, the mixture was heated to 63°C, and isophorone diamine was added dropwise at a uniform rate over 1 hour. After the addition was complete, the reaction was continued for 5 hours, cooled to room temperature, filtered, washed with tetrahydrofuran, and dried under vacuum at 50°C for 18 hours to obtain the amino-modified DOPO flame retardant. (2) Bamboo fiber powder, sodium periodate, isopropanol and distilled water were mixed evenly in a mass ratio of 1:1.2:0.6:16. The mixture was stirred and reacted at 40°C for 8 hours under dark conditions. The mixture was then filtered, washed with distilled water, and dried under vacuum at 50°C for 10 hours to obtain pre-modified bamboo fiber powder. Pre-modified bamboo fiber powder, amino-modified DOPO flame retardant and N,N-dimethylformamide were mixed in a mass ratio of 1:0.5:14. The mixture was stirred and reacted at 60°C for 6 hours. The mixture was then filtered, washed with N,N-dimethylformamide, and dried under vacuum at 50°C for 24 hours to obtain modified bamboo fiber powder. (3) Dissolve PET chips in a mixed solvent to prepare a PET solution with a mass fraction of 10%; add modified bamboo fiber powder with a mass of 10% of PET chips, mix evenly to obtain a spinning solution; perform electrospinning on the spinning solution to obtain a PET fiber film. (4) Dissolve 1,6-hexanediamine in distilled water to prepare a hexanediamine solution with a mass fraction of 2%; mix 1,3-propanesulfonate lactone and isopropanol in a mass ratio of 1:40 to prepare a sulfonation finishing solution; immerse the PET fiber membrane in the hexanediamine solution with a bath ratio of 1:20 for 15 min, roll it with a roll-off rate of 60%, heat it at 160℃ for 10 min, wash it with water, and dry it at 60℃ for 1 h to obtain a pretreated PET fiber membrane; immerse the pretreated PET fiber membrane in the sulfonation finishing solution with a bath ratio of 1:20, keep it at 70℃ for 10 h, take it out, wash it with water, and dry it at 100℃ to obtain a battery separator.

[0022] Example 2 This embodiment provides a method for preparing a battery separator, including the following preparation steps: (1) Weigh 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and diethyl maleate in a molar ratio of 1:1; mix 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 1,2-dichloroethane in a mass ratio of 1:5.5 to prepare a DOPO solution; mix diethyl maleate, potassium carbonate and 1,2-dichloroethane in a mass ratio of 1:0.3:5.5, place in a reflux condenser, and under nitrogen protection, heat to 95°C. Add the DOPO solution dropwise at a uniform rate over 30 minutes. After the addition is complete, continue... The reaction was stirred for another 3.5 h, cooled to room temperature, washed with saturated sodium bicarbonate, dried over anhydrous magnesium sulfate, filtered, and the filtrate was evaporated under reduced pressure to obtain DOPO diethyl ester. DOPO diethyl ester and isophorone diamine were weighed in a molar ratio of 1:7. DOPO diethyl ester and tetrahydrofuran were mixed evenly in a mass ratio of 1:9. Under nitrogen protection, the mixture was heated to 64 °C, and isophorone diamine was added dropwise at a uniform rate over 1 h. After the addition was complete, the reaction was continued for 4.5 h, cooled to room temperature, filtered, washed with tetrahydrofuran, and dried under vacuum at 55 °C for 17 h to obtain the aminated DOPO flame retardant. (2) Bamboo fiber powder, sodium periodate, isopropanol and distilled water were mixed evenly in a mass ratio of 1:1.3:0.7:18. The mixture was stirred and reacted at 45°C for 7 hours under dark conditions. The mixture was then filtered, washed with distilled water, and dried under vacuum at 55°C for 9 hours to obtain pre-modified bamboo fiber powder. Pre-modified bamboo fiber powder, amino-modified DOPO flame retardant and N,N-dimethylformamide were mixed in a mass ratio of 1:0.55:16. The mixture was stirred and reacted at 65°C for 5.5 hours. The mixture was then filtered, washed with N,N-dimethylformamide, and dried under vacuum at 55°C for 22 hours to obtain modified bamboo fiber powder. (3) Dissolve PET chips in a mixed solvent to prepare a PET solution with a mass fraction of 11%; add modified bamboo fiber powder at a mass of 12% of the PET chips, mix evenly to obtain a spinning solution; perform electrospinning on the spinning solution to obtain a PET fiber film. (4) Dissolve 1,6-hexanediamine in distilled water to prepare a hexanediamine solution with a mass fraction of 2.5%; mix 1,3-propanesulfonate lactone and isopropanol in a mass ratio of 1:45 to prepare a sulfonation finishing solution; immerse the PET fiber membrane in the hexanediamine solution with a bath ratio of 1:20 for 20 min, roll it with a roll-off rate of 65%, heat it at 160℃ for 10 min, wash it with water, and dry it at 60℃ for 1 h to obtain a pretreated PET fiber membrane; immerse the pretreated PET fiber membrane in the sulfonation finishing solution with a bath ratio of 1:20, keep it at 75℃ for 9 h, take it out, wash it with water, and dry it at 100℃ to obtain a battery separator.

[0023] Example 3 This embodiment provides a method for preparing a battery separator, including the following preparation steps: (1) Weigh 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and diethyl maleate in a molar ratio of 1:1; mix 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 1,2-dichloroethane in a mass ratio of 1:6 to prepare a DOPO solution; mix diethyl maleate, potassium carbonate and 1,2-dichloroethane in a mass ratio of 1:0.4:6, place in a reflux condenser, and under nitrogen protection, heat to 100°C. Add the DOPO solution dropwise at a uniform rate over 30 minutes. After the addition is complete, continue... The reaction was stirred for another 3 hours, cooled to room temperature, washed with saturated sodium bicarbonate, dried over anhydrous magnesium sulfate, filtered, and the filtrate was evaporated under reduced pressure to obtain DOPO diethyl ester. DOPO diethyl ester and isophorone diamine were weighed at a molar ratio of 1:8. DOPO diethyl ester and tetrahydrofuran were mixed evenly at a mass ratio of 1:10. Under nitrogen protection, the mixture was heated to 65°C, and isophorone diamine was added dropwise at a uniform rate over 1 hour. After the addition was complete, the reaction was continued for 4 hours, cooled to room temperature, filtered, washed with tetrahydrofuran, and dried under vacuum at 60°C for 16 hours to obtain the amino-modified DOPO flame retardant. (2) Bamboo fiber powder, sodium periodate, isopropanol and distilled water were mixed evenly in a mass ratio of 1:1.4:0.8:20. The mixture was stirred and reacted at 50°C for 6 hours under dark conditions. The mixture was then filtered, washed with distilled water, and dried under vacuum at 60°C for 8 hours to obtain pre-modified bamboo fiber powder. Pre-modified bamboo fiber powder, amino-modified DOPO flame retardant and N,N-dimethylformamide were mixed in a mass ratio of 1:0.6:18. The mixture was stirred and reacted at 70°C for 5 hours. The mixture was then filtered, washed with N,N-dimethylformamide, and dried under vacuum at 60°C for 20 hours to obtain modified bamboo fiber powder. (3) Dissolve PET chips in a mixed solvent to prepare a PET solution with a mass fraction of 12%; add modified bamboo fiber powder at a mass of 14% of the PET chips, mix evenly to obtain a spinning solution; perform electrospinning on the spinning solution to obtain a PET fiber film. (4) Dissolve 1,6-hexanediamine in distilled water to prepare a hexanediamine solution with a mass fraction of 3%; mix 1,3-propanesulfonate lactone and isopropanol in a mass ratio of 1:50 to prepare a sulfonation finishing solution; immerse the PET fiber membrane in the hexanediamine solution with a bath ratio of 1:20 for 25 min, roll it with a roll-off rate of 70%, heat it at 160℃ for 10 min, wash it with water, and dry it at 60℃ for 1 h to obtain a pretreated PET fiber membrane; immerse the pretreated PET fiber membrane in the sulfonation finishing solution with a bath ratio of 1:20, keep it at 80℃ for 8 h, take it out, wash it with water, and dry it at 100℃ to obtain a battery separator.

[0024] Comparative Example 1 This embodiment provides a method for preparing a battery separator. The specific implementation method is the same as that in embodiment 2. The difference from embodiment 2 is that steps (1) and (2) are not performed. In step (3), "modified bamboo fiber powder" is replaced with "bamboo fiber powder".

[0025] Comparative Example 2 This embodiment provides a method for preparing a battery separator. The specific implementation method is the same as that in embodiment 2. The difference from embodiment 2 is that step (4) is not performed, and the "PET fiber membrane" in step (3) is used as the "battery separator".

[0026] Performance testing Flame retardant performance: The diaphragm was cut into samples with a length × width of 10cm × 2mm, and the limiting oxygen index of the samples was tested in the HC-2 oxygen index tester.

[0027] Ion conductivity: The electrochemical impedance spectroscopy (AC impedance method) was used to measure the electrochemical impedance curve of the lithium battery using a Shanghai Chenhua CH660D electrochemical workstation. The impedance of the lithium battery separator was obtained by Zview fitting. Specific procedures: The battery separator was cut into circular pieces. Stainless steel sheets were used as electrodes. Before use, the battery casing and stainless steel sheets were dried in an 80℃ oven. The CR2032 button cell was assembled in a glove box. The assembly sequence was: positive electrode casing, stainless steel sheet, battery separator, electrolyte, stainless steel sheet, spring contact, negative electrode casing. The electrolyte was a 1M LiPF6 EC / DMC (v / v=1:1) solution. Ion conductivity α The calculation formula is as follows, where d is the diaphragm thickness, A is the effective contact area of ​​the electrode, and Ra is the diaphragm impedance.

[0028] The test results for the above tests are recorded in Table 1; Table 1 Comparing the experimental data in Table 1, it can be concluded that by loading DOPO-type flame retardants onto bamboo fiber powder through Schiff base reaction and increasing phosphorus and nitrogen elements, the present application can achieve a synergistic effect and improve the flame retardant performance of battery separators.

[0029] This application sequentially treats the PET fiber membrane with 1,6-hexanediamine and 1,3-propanesulfonate lactone, introducing a large number of highly polar sulfonic acid groups onto the surface of the PET fiber membrane, effectively enhancing the membrane's wettability to the electrolyte, thereby improving ion conduction performance.

[0030] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the technical solutions are intended to be included within the present invention.

Claims

1. A method for preparing a battery separator, characterized in that, The preparation steps include the following: (1) Weigh DOPO diethyl ester and isophorone diamine at a molar ratio of 1:(6~8); mix DOPO diethyl ester and tetrahydrofuran at a mass ratio of 1:(8~10), heat to 63~65℃ under nitrogen protection, add isophorone diamine dropwise at a uniform rate over 1h, continue the reaction for 4~5h after the addition is complete, cool to room temperature, filter, wash with tetrahydrofuran, and vacuum dry at 50~60℃ for 16~18h to obtain aminated DOPO flame retardant; (2) Bamboo fiber powder, sodium periodate, isopropanol and distilled water are mixed evenly in a mass ratio of 1:(1.2~1.4):(0.6~0.8):(16~20), stirred and reacted at 40~50℃ for 6~8h under light-proof conditions, filtered, washed with distilled water, and vacuum dried at 50~60℃ for 8~10h to obtain pre-modified bamboo fiber powder; pre-modified bamboo fiber powder, aminated DOPO flame retardant and N,N-dimethylformamide are mixed in a mass ratio of 1:(0.5~0.6):(14~18), stirred and reacted at 60~70℃ for 5~6h, filtered, washed with N,N-dimethylformamide, and vacuum dried at 50~60℃ for 20~24h to obtain modified bamboo fiber powder; (3) Dissolve PET chips in a mixed solvent to prepare a PET solution with a mass fraction of 10%~12%; add 10%~14% of modified bamboo fiber powder by mass of PET chips, mix evenly to obtain a spinning solution; perform electrospinning on the spinning solution to obtain a PET fiber film. (4) Immerse the PET fiber membrane in a hexamethylenediamine solution with a bath ratio of 1:20 for 15-25 min, roll it with a roll-off rate of 60%-70%, heat it at 160℃ for 10 min, wash it with water, and dry it at 60℃ for 1 h to obtain a pretreated PET fiber membrane; Immerse the pretreated PET fiber membrane in a sulfonation finishing solution with a bath ratio of 1:20, keep it at 70-80℃ for 8-10 h, take it out, wash it with water, and dry it at 100℃ to obtain a battery separator. The preparation process of DOPO-based diethyl ester in step (1) is as follows: 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and diethyl maleate are weighed in a molar ratio of 1:1; 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 1,2-dichloroethane are mixed in a mass ratio of 1:(5~6) to prepare a DOPO solution; diethyl maleate, potassium carbonate and 1,2-dichloroethane are mixed in a mass ratio of 1:(0.2~0.4):(5~6), placed in a reflux condenser, heated to 90~100℃ under nitrogen protection, and DOPO solution is added dropwise at a uniform rate over 30 min. After the addition is complete, the reaction is stirred for 3~4 h, cooled to room temperature, washed with saturated sodium bicarbonate, dried with anhydrous magnesium sulfate, filtered, and the filtrate is evaporated under reduced pressure to obtain DOPO-based diethyl ester. The sulfonation finishing solution in step (4) is prepared by mixing 1,3-propanesulfonate lactone and isopropanol in a mass ratio of 1:(40~50).

2. The method for preparing a battery separator as described in claim 1, characterized in that, The reaction mechanism of the DOPO-based diethyl ester is as follows: 。 3. The method for preparing a battery separator as described in claim 1, characterized in that, The mixed solvent in step (3) is obtained by mixing trifluoroacetic acid and dichloromethane in a volume ratio of 3:

2.

4. The method for preparing a battery separator as described in claim 1, characterized in that, The hexamethylenediamine solution in step (4) is prepared by dissolving 1,6-hexamethylenediamine in distilled water to form a hexamethylenediamine solution with a mass fraction of 2% to 3%.

5. A battery separator, characterized in that, The battery separator is prepared by the method for preparing the battery separator according to any one of claims 1 to 4.

6. A battery, characterized in that, The battery separator of the battery is prepared by the method of preparing the battery separator according to any one of claims 1 to 4.

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