Method for preparing bio-based aramid coated lithium battery separator for ternary lithium battery

Abstract

This invention discloses a method for preparing a bio-based aramid-coated lithium battery separator for ternary lithium batteries, belonging to the field of battery separator processing technology. This invention addresses the technical problem in existing technologies where aramid itself has low conductivity and porosity, and coating an aramid solution onto a base membrane reduces the porosity and electrical performance of the base membrane. The method for preparing a bio-based aramid-coated lithium battery separator for ternary lithium batteries includes the following steps: washing the surface of seaweed with clean water, draining it, and cutting it into small segments to obtain seaweed segments; subjecting the seaweed segments to heat treatment and modification treatment sequentially to obtain modified biocarbon; adding 4,4'-diacyl chloride diphenyl ether, 2,5-bis(allyloxy)terephthaloyl chloride, and N-methylpyrrolidone to a three-necked flask and stirring, while lowering the temperature of the three-necked flask to -20±2℃. This invention, by coating the exterior of the PE separator, not only effectively improves the porosity and mechanical properties of the separator but also enhances its electrical performance.

Description

Technical Field

[0001] This invention relates to the field of battery separator processing technology, specifically to a method for preparing a bio-based aramid-coated lithium battery separator for ternary lithium batteries. Background Technology

[0002] Ternary lithium batteries refer to lithium batteries that use ternary cathode materials such as lithium nickel cobalt manganese oxide or lithium nickel cobalt aluminum oxide. Ternary lithium batteries are safer than lithium cobalt oxide batteries. With the booming development of new energy vehicles, the battery separator industry has expanded and technology has developed, leading to a demand for ternary lithium batteries with larger capacity and higher power. Polyolefin films such as PE or PP are used as base films. When overcharged or heated, they block the conduction of current through closed pores. Coating the surface of the base film can effectively improve the wettability and heat resistance of the base film to the electrolyte.

[0003] Aramid refers to aromatic polyamide, also known as poly(p- / m-phenylene isophthalamide). It has excellent properties such as high strength, high modulus, high temperature resistance, and flame retardancy. Aramid coating on a base film can effectively improve the heat resistance of the base film. However, aramid itself has low electrical conductivity and porosity. Coating an aramid solution on a base film will reduce the porosity and electrical properties of the base film.

[0004] To address this technical deficiency, a solution is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing a bio-based aramid-coated lithium battery separator for ternary lithium batteries, which solves the technical problem that the conductivity and porosity of aramid itself are low in the prior art, and that coating the aramid solution onto the base film will reduce the porosity and electrical performance of the base film.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] The preparation method of bio-based aramid coated lithium battery separator for ternary lithium batteries includes the following steps:

[0008] S1. Wash the seaweed with clean water, drain it and cut it into small pieces to obtain seaweed segments. Then, heat-treat and modify the seaweed segments to obtain modified biochar.

[0009] S2. Add 4,4'-diphenyl ether dichlorodichlorodiphenyl ether, 2,5-bis(allyloxy)terephthaloyl chloride and N-methylpyrrolidone to a three-necked flask and stir. Lower the temperature of the three-necked flask to -20±2℃ and add 3,3'-dimethylbenzidine dropwise to the three-necked flask using a constant pressure dropping funnel. After the addition is complete, keep the reaction at the temperature for 30-50 min. Raise the temperature of the three-necked flask to 185-195℃ and react for 6-8 h. Post-treatment yields modified aramid.

[0010] The synthesis reaction principle of modified aramid is as follows:

[0011]

[0012] S3. Add potassium hydroxide, purified water, N,N-dimethylformamide, and modified aramid to a three-necked flask. Raise the temperature of the three-necked flask to 75-85℃ and stir until the system is dissolved. Add modified biochar and hexadecyltrimethylammonium bromide to the three-necked flask, stir evenly, and then ultrasonically disperse for 3-5 hours to obtain the modified aramid coating.

[0013] S4. Use a coating machine to coat the modified aramid coating onto the PE separator, immerse it in the curing solution, and remove it after the coating has cured. After washing with water, transfer it to a drying oven and set the drying oven temperature to 65-75℃ for vacuum drying until constant weight to obtain the battery separator.

[0014] Furthermore, the heat treatment operation of the seaweed segment includes: transferring the seaweed segment to a tube furnace under nitrogen protection, raising the temperature of the tube furnace to 800-850℃, holding it at that temperature for 2-3 hours, and then processing it to obtain biochar; the post-processing operation includes: after the heat treatment is completed, removing the seaweed segment from the tube furnace, grinding it to obtain a black powder, soaking it in dilute hydrochloric acid, ultrasonically treating it for 20-30 minutes, filtering it, washing the filter cake with purified water until neutral, filtering it again, and then transferring it to a drying oven at a temperature of 95-105℃ to dry it with forced air until constant weight to obtain biochar.

[0015] Furthermore, the modification process includes:

[0016] A1. Add oxalic acid, ammonium metavanadate and purified water to a three-necked flask and stir to dissolve. Add biochar to the three-necked flask and sonicate for 40-60 minutes. Then transfer the three-necked flask to an iron stand with mechanical stirring. While stirring, add starch to the three-necked flask. Raise the temperature of the flask to 90-95℃ and stir until the system becomes a paste. Post-processing yields gelatinized biochar.

[0017] A2. Transfer the gelatinized biochar to a nitrogen-protected tube furnace, raise the temperature of the tube furnace to 650-750℃, hold for 2-3 hours, and then lower to room temperature to obtain modified biochar.

[0018] Furthermore, the weight ratio of oxalic acid, ammonium metavanadate, purified water, biochar, and starch is 2:1:120:15:2, and the post-processing operation includes: transferring the paste-like reaction system to a freeze dryer at a temperature of -20°C and freeze-drying for 40 hours to obtain gelatinized biochar.

[0019] Furthermore, in step S2, the molar ratio of 4,4'-diacyl chloride diphenyl ether, 2,5-bis(allyloxy)terephthaloyl chloride, and 3,3'-dimethylbenzidine is 1:1:2, and the amount of N-methylpyrrolidone used is 5 times the weight of 4,4'-diacyl chloride diphenyl ether. The post-treatment operation includes: after the reaction is completed, the temperature of the three-necked flask is lowered to room temperature, purified water is added to the three-necked flask, the mixture is stirred for 30-50 minutes, filtered, the filter cake is washed with purified water and then transferred to a drying oven at a temperature of 70-80℃ for vacuum drying to constant weight to obtain modified aramid.

[0020] Furthermore, in step S3, the weight ratio of potassium hydroxide, purified water, N,N-dimethylformamide, modified aramid, modified biochar, and hexadecyltrimethylammonium bromide is 1:2:30:8:2:0.5.

[0021] Furthermore, the curing solution is prepared by mixing N,N-dimethylformamide and purified water in a weight ratio of 1:3.

[0022] The present invention has the following beneficial effects:

[0023] 1. In preparing biochar, this invention selects iodine-rich seaweed as raw material and calcines it to produce biochar with a porous structure. Iodine in the biochar enriches the electrochemical active sites on the biochar, improving the electrostatic interaction of the biochar and thus enhancing the adsorption performance of lithium and reducing the occurrence of shuttle phenomenon. The biochar is soaked in oxalic acid and ammonium metavanadate solution, allowing the ammonium metavanadate to adhere to the biochar. After adding nitrogen-containing phosphate starch, the nitrogen-containing phosphate starch acts as an adhesive coating, promoting the cross-linking of ammonium metavanadate and biochar. Under high-temperature calcination, the nitrogen-containing phosphate starch and ammonium metavanadate decompose to generate modified biochar doped with nitrogen and vanadium pentoxide, which increases the porosity of the modified carbon. Vanadium pentoxide is anchored on the biochar in the form of nanoparticles, effectively improving the conductivity of the modified biochar, thereby improving the electrical strength of the battery separator. The nitrogen doping on the modified biochar effectively reduces the surface polarity of the modified biochar, improving the adsorption effect of lithium and further improving the electrical strength.

[0024] 2. In the preparation of modified aramid in this invention, 4,4'-diacyl chloride diphenyl ether, 2,5-bis(allyloxy) terephthaloyl chloride and 3,3'-dimethylbenzidine react to form a cross-linked structure with amide bonds. Under high temperature, a Claisen rearrangement reaction occurs to generate modified aramid with a long straight chain structure. The modified aramid contains abundant aromatic rings, which effectively improves its heat resistance and mechanical properties. The modified aramid and modified biochar are ultrasonically dispersed under the condition of hexadecyltrimethylammonium bromide as a pore-forming agent, which promotes the dispersion of hexadecyltrimethylammonium bromide in the modified aramid solution. This results in a coating layer with high porosity formed by coating the modified aramid coating on the PE separator, which is conducive to the migration of lithium ions and thus improves the electrical strength of the battery separator. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 The image shown is an electron microscope image of biochar in Example 1 of this invention.

[0027] Figure 2 This is an electron microscope image of the modified biochar in Example 1 of the present invention. Detailed Implementation

[0028] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1

[0030] This embodiment provides a method for preparing a bio-based aramid-coated lithium battery separator for ternary lithium batteries, including the following steps:

[0031] S1. Preparation of biochar

[0032] Wash the seaweed with clean water, drain it, and cut it into small pieces to obtain seaweed segments. Transfer the seaweed segments to a tube furnace under nitrogen protection. Raise the temperature of the tube furnace to 800℃ and keep it at that temperature for 2 hours. Then, lower the temperature of the tube furnace to room temperature, remove the seaweed segments from the tube furnace, grind them to obtain a black powder, soak them in dilute hydrochloric acid, sonicate them for 20 minutes, filter them, wash the filter cake with purified water until neutral, filter it again, and then transfer it to a drying oven at 95℃ and dry it with forced air until constant weight to obtain biochar.

[0033] S2, Biochar Modification

[0034] Weigh out 100g of oxalic acid, 50g of ammonium metavanadate, and 600g of purified water and add them to a three-necked flask. Stir and dissolve the dissolved oxalic acid. Add 75g of biochar to the three-necked flask and sonicate for 40 minutes. Then transfer the three-necked flask to an iron stand with a mechanical stirrer. While stirring, add 20g of nitrogen-containing phosphate starch to the three-necked flask. Raise the temperature of the flask to 90℃ and stir until the system becomes a paste. Transfer the paste-like reaction system to a freeze dryer at -20℃ and freeze dry for 40 hours to obtain gelatinized biochar.

[0035] The gelatinized biochar was transferred to a nitrogen-protected tubular furnace, where the temperature was raised to 650°C and held for 2 hours. The furnace was then cooled to room temperature and pulverized to obtain modified biochar.

[0036] S3, Preparation of modified aramid fibers

[0037] Weigh out 39.5 g of 4,4'-diphenyl ether chloride, 31.5 g of 2,5-bis(allyloxy)terephthaloyl chloride, and 197.5 g of N-methylpyrrolidone and add them to a three-necked flask. Stir the mixture and lower the temperature of the three-necked flask to -22°C. Using a constant pressure dropping funnel, add 42.5 g of 3,3'-dimethylbenzidine dropwise to the three-necked flask. After the addition is complete, maintain the temperature for 30 min. Then, raise the temperature of the three-necked flask to 185°C and react for 6 h. Lower the temperature of the three-necked flask to room temperature and add 592.5 g of purified water. Stir for 30 min, filter, wash the filter cake with purified water, and transfer it to a drying oven at 70°C to dry under vacuum until constant weight to obtain modified aramid.

[0038] S4. Preparation of modified aramid coatings

[0039] Weigh out 10g of potassium hydroxide, 20g of purified water, 300g of N,N-dimethylformamide, and 80g of modified aramid by weight and add them to a three-necked flask. Raise the temperature of the three-necked flask to 75℃ and stir until the system is dissolved. Add 20g of modified biochar and 5g of hexadecyltrimethylammonium bromide to the three-necked flask, stir evenly, and then ultrasonically disperse for 3 hours to obtain the modified aramid coating.

[0040] S5, Coating and Molding

[0041] N,N-dimethylformamide and purified water were mixed evenly at a weight ratio of 1:3 to prepare a curing solution;

[0042] The modified aramid coating is applied to the PE separator using a coating machine. The separator is then immersed in a curing solution. After the coating has cured, it is removed, washed with water, and transferred to a drying oven. The drying oven is set to 65°C and vacuum dried to constant weight, forming a coating layer with a thickness of 2-3 μm on the surface of the PE separator, thus obtaining the battery separator.

[0043] Example 2

[0044] This embodiment provides a method for preparing a bio-based aramid-coated lithium battery separator for ternary lithium batteries, including the following steps:

[0045] S1. Preparation of biochar

[0046] Wash the seaweed with clean water, drain it, and cut it into small pieces to obtain seaweed segments. Transfer the seaweed segments to a tube furnace under nitrogen protection. Raise the temperature of the tube furnace to 825°C and hold it at that temperature for 2.5 hours. Then, lower the temperature of the tube furnace to room temperature, remove the seaweed segments from the tube furnace, grind them to obtain a black powder, soak them in dilute hydrochloric acid, sonicate them for 25 minutes, filter them, wash the filter cake with purified water until neutral, filter it again, and then transfer it to a drying oven at 100°C and dry it with forced air until constant weight to obtain biochar.

[0047] S2, Biochar Modification

[0048] Weigh out 100g of oxalic acid, 50g of ammonium metavanadate, and 600g of purified water and add them to a three-necked flask. Stir and dissolve the dissolved substances. Add 75g of biochar to the three-necked flask and sonicate for 50 minutes. Then transfer the three-necked flask to an iron stand with a mechanical stirrer. While stirring, add 20g of nitrogen-containing phosphate starch to the three-necked flask. Raise the temperature of the flask to 93℃ and stir until the system becomes a paste. Transfer the paste-like reaction system to a freeze dryer at -20℃ and freeze-dry for 40 hours to obtain gelatinized biochar.

[0049] The gelatinized biochar was transferred to a nitrogen-protected tubular furnace, where the temperature was raised to 700°C and held for 2.5 hours. The furnace was then cooled to room temperature and pulverized to obtain modified biochar.

[0050] S3, Preparation of modified aramid fibers

[0051] Weigh out 39.5 g of 4,4'-diphenyl ether chloride, 31.5 g of 2,5-bis(allyloxy)terephthaloyl chloride, and 197.5 g of N-methylpyrrolidone and add them to a three-necked flask. Stir the mixture and lower the temperature of the three-necked flask to -20°C. Using a constant pressure dropping funnel, add 42.5 g of 3,3'-dimethylbenzidine dropwise to the three-necked flask. After the addition is complete, maintain the temperature for 40 min. Then, raise the temperature of the three-necked flask to 190°C and react for 7 h. Lower the temperature of the three-necked flask to room temperature and add 592.5 g of purified water. Stir for 40 min, filter, wash the filter cake with purified water, and transfer it to a drying oven at 75°C to vacuum dry to constant weight to obtain modified aramid.

[0052] S4. Preparation of modified aramid coatings

[0053] Weigh out 10g of potassium hydroxide, 20g of purified water, 300g of N,N-dimethylformamide, and 80g of modified aramid by weight and add them to a three-necked flask. Raise the temperature of the three-necked flask to 80℃ and stir until the system is dissolved. Add 20g of modified biochar and 5g of hexadecyltrimethylammonium bromide to the three-necked flask, stir evenly, and then ultrasonically disperse for 4 hours to obtain the modified aramid coating.

[0054] S5, Coating and Molding

[0055] N,N-dimethylformamide and purified water were mixed evenly at a weight ratio of 1:3 to prepare a curing solution;

[0056] The modified aramid coating is applied to the PE separator using a coating machine. The separator is then immersed in a curing solution. After the coating has cured, it is removed, washed with water, and transferred to a drying oven. The drying oven is set to 70°C and vacuum dried to constant weight, forming a coating layer with a thickness of 2-3 μm on the surface of the PE separator, thus obtaining the battery separator.

[0057] Example 3

[0058] This embodiment provides a method for preparing a bio-based aramid-coated lithium battery separator for ternary lithium batteries, including the following steps:

[0059] S1. Preparation of biochar

[0060] Wash the seaweed with clean water, drain it, and cut it into small pieces to obtain seaweed segments. Transfer the seaweed segments to a tube furnace under nitrogen protection. Raise the temperature of the tube furnace to 850°C and keep it at that temperature for 3 hours. Then, lower the temperature of the tube furnace to room temperature, remove the seaweed segments from the tube furnace, grind them to obtain a black powder, soak them in dilute hydrochloric acid, sonicate them for 30 minutes, filter them, wash the filter cake with purified water until neutral, filter it again, and then transfer it to a drying oven at 105°C and dry it with forced air until constant weight to obtain biochar.

[0061] S2, Biochar Modification

[0062] Weigh out 100g of oxalic acid, 50g of ammonium metavanadate, and 600g of purified water and add them to a three-necked flask. Stir and dissolve the dissolved substances. Add 75g of biochar to the three-necked flask and sonicate for 60 minutes. Then, transfer the three-necked flask to an iron stand with a mechanical stirrer. While stirring, add 20g of nitrogen-containing phosphate starch to the three-necked flask. Raise the temperature of the flask to 95℃ and stir until the system becomes a paste. Transfer the paste-like reaction system to a freeze dryer at -20℃ and freeze-dry for 40 hours to obtain gelatinized biochar.

[0063] The gelatinized biochar was transferred to a nitrogen-protected tube furnace, where the temperature was raised to 750°C and held for 3 hours. The temperature was then lowered to room temperature and pulverized to obtain modified biochar.

[0064] S3, Preparation of modified aramid fibers

[0065] Weigh out 39.5 g of 4,4'-diphenyl ether chloride, 31.5 g of 2,5-bis(allyloxy)terephthaloyl chloride, and 197.5 g of N-methylpyrrolidone and add them to a three-necked flask. Stir the mixture and lower the temperature of the three-necked flask to -22°C. Using a constant pressure dropping funnel, add 42.5 g of 3,3'-dimethylbenzidine dropwise to the three-necked flask. After the addition is complete, maintain the temperature for 50 min. Then, raise the temperature of the three-necked flask to 195°C and react for 8 h. Lower the temperature of the three-necked flask to room temperature and add 592.5 g of purified water. Stir for 50 min, filter, wash the filter cake with purified water, and transfer it to a drying oven at 80°C to dry under vacuum until constant weight to obtain modified aramid.

[0066] S4. Preparation of modified aramid coatings

[0067] Weigh out 10g of potassium hydroxide, 20g of purified water, 300g of N,N-dimethylformamide, and 80g of modified aramid by weight and add them to a three-necked flask. Raise the temperature of the three-necked flask to 85℃ and stir until the system is dissolved. Add 20g of modified biochar and 5g of hexadecyltrimethylammonium bromide to the three-necked flask, stir evenly, and then ultrasonically disperse for 5 hours to obtain the modified aramid coating.

[0068] S5, Coating and Molding

[0069] N,N-dimethylformamide and purified water were mixed evenly at a weight ratio of 1:3 to prepare a curing solution;

[0070] The modified aramid coating is applied to the PE separator using a coating machine. The separator is then immersed in a curing solution. After the coating has cured, it is removed, washed with water, and transferred to a drying oven. The drying oven is set to 75°C and vacuum dried to constant weight, forming a coating layer with a thickness of 2-3 μm on the surface of the PE separator, thus obtaining the battery separator.

[0071] Comparative Example 1

[0072] The difference between this comparative example and Example 3 is that step S2 is omitted, and biochar is used instead of modified biochar in an equal amount to participate in the reaction in step S4.

[0073] Comparative Example 2

[0074] The difference between this comparative example and Example 3 is that no porogen was added in step S4.

[0075] Comparative Example 3

[0076] The battery separator in this comparative example is a PE separator without modified aramid coating.

[0077] Performance testing:

[0078] The porosity, physical properties, and electrical properties of the battery separators prepared by Examples 1-3 and Comparative Examples 1-3 were tested according to standard GB / T 36363-2018 "Polyolefin Separators for Lithium-ion Batteries". The specific test results are shown in the table below:

[0079]

[0080] Data Analysis:

[0081] Comparative Example 3 served as a blank test group. Analysis and comparison of the data from Examples 1-3 and Comparative Example 3 show that the battery separator of the present invention not only effectively improves its porosity and physical properties, but also increases the minimum electrical strength of the battery separator. (See attached description.) Figure 1 It can be seen that the prepared biochar has abundant pores, and as indicated in the instruction manual... Figure 2 It can be seen that by modifying biochar, a large number of vanadium pentoxide nanocrystals are formed on its surface;

[0082] Comparative Example 3 was a blank test group. Comparison of data from Comparative Example 1 with Examples 1-3 and Comparative Example 3 shows that the present invention effectively improves the porosity and minimum electrical strength of the battery separator by modifying biochar.

[0083] Comparative Example 3 was a blank test group. Comparison of the data of Comparative Example 2 with Examples 1-3 and Comparative Example 3 shows that the present invention can effectively improve the porosity of the battery separator by adding hexadecyltrimethylammonium bromide as a pore-forming agent. Furthermore, the addition of hexadecyltrimethylammonium bromide and the modification of biochar can have a synergistic effect, further improving the porosity of the battery separator.

[0084] The above description is merely an example and illustration of the structure of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the structure of the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

[0085] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0086] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing a bio-based aramid-coated lithium battery separator for ternary lithium batteries, characterized in that, Includes the following steps: S1. Wash the seaweed with clean water, drain it and cut it into small pieces to obtain seaweed segments. Then, heat-treat and modify the seaweed segments to obtain modified biochar. S2. Add 4,4'-diphenyl ether dichlorodichlorodiphenyl ether, 2,5-bis(allyloxy)terephthaloyl chloride and N-methylpyrrolidone to a three-necked flask and stir. Lower the temperature of the three-necked flask to -20±2℃ and add 3,3'-dimethylbenzidine dropwise to the three-necked flask using a constant pressure dropping funnel. After the addition is complete, keep the reaction at the temperature for 30-50 min. Raise the temperature of the three-necked flask to 185-195℃ and react for 6-8 h. Post-treatment yields modified aramid. S3. Add potassium hydroxide, purified water, N,N-dimethylformamide, and modified aramid to a three-necked flask. Raise the temperature of the three-necked flask to 75-85℃ and stir until the system is dissolved. Add modified biochar and hexadecyltrimethylammonium bromide to the three-necked flask, stir evenly, and then ultrasonically disperse for 3-5 hours to obtain the modified aramid coating. S4. Use a coating machine to coat the modified aramid coating onto the PE separator, immerse it in the curing solution, and remove it after the coating has cured. After washing with water, transfer it to a drying oven and set the drying oven temperature to 65-75℃ for vacuum drying until constant weight to obtain the battery separator. The heat treatment operation of the seaweed segment includes: transferring the seaweed segment into a tube furnace under nitrogen protection, raising the temperature of the tube furnace to 800-850℃, holding it at that temperature for 2-3 hours, and then processing it to obtain biochar. The modification process includes: A1. Add oxalic acid, ammonium metavanadate and purified water to a three-necked flask and stir to dissolve. Add biochar to the three-necked flask and sonicate for 40-60 minutes. Then transfer the three-necked flask to an iron stand with mechanical stirring. While stirring, add starch to the three-necked flask. Raise the temperature of the flask to 90-95℃ and stir until the system becomes a paste. Post-processing yields gelatinized biochar. A2. Transfer the gelatinized biochar to a nitrogen-protected tube furnace, raise the temperature of the tube furnace to 650-750℃, hold for 2-3 hours, and then lower to room temperature to obtain modified biochar.

2. The method for preparing a bio-based aramid-coated lithium battery separator for ternary lithium batteries according to claim 1, characterized in that, The weight ratio of oxalic acid, ammonium metavanadate, purified water, biochar, and starch is 2:1:120:15:

2.

3. The method for preparing a bio-based aramid-coated lithium battery separator for ternary lithium batteries according to claim 1, characterized in that, In step S2, the molar ratio of 4,4'-diacyl chloride diphenyl ether, 2,5-bis(allyloxy)terephthaloyl chloride and 3,3'-dimethylbenzidine is 1:1:2, and the amount of N-methylpyrrolidone used is 5 times the weight of 4,4'-diacyl chloride diphenyl ether.

4. The method for preparing a bio-based aramid-coated lithium battery separator for ternary lithium batteries according to claim 1, characterized in that, In step S3, the weight ratio of potassium hydroxide, purified water, N,N-dimethylformamide, modified aramid, modified biochar, and hexadecyltrimethylammonium bromide is 1:2:30:8:2:0.

5.

5. The method for preparing a bio-based aramid-coated lithium battery separator for ternary lithium batteries according to claim 1, characterized in that, The curing solution is prepared by mixing N,N-dimethylformamide and purified water in a weight ratio of 1:3.

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