High-strength lithium battery diaphragm and preparation process thereof

Abstract

The invention discloses a high-strength lithium battery diaphragm and a preparation process thereof, and belongs to the technical field of lithium battery diaphragms.The preparation process comprises the following steps that under the nitrogen atmosphere, dianhydride and diamine are subjected to a condensation reaction to obtain a polyamide acid oligomer; the preparation method comprises the following steps: cross-linking a polyamide acid oligomer and polysiloxane borane to form gel, then carrying out imidization by using an imidization reagent, and carrying out room temperature aging and supercritical carbon dioxide drying to obtain the high-strength lithium battery diaphragm. The polysiloxyborane is prepared from 6-aminopyridine boric acid and a silane coupling agent through hydrolytic condensation. According to the high-strength polyimide-based lithium battery diaphragm, polyimide is taken as a resin matrix, and a polysiloxyborane (Si-O-B-O) chain segment is introduced into a polymer network through molecular structure design, so that the mechanical property and the electrochemical stability of the diaphragm are remarkably improved.

Description

Technical Field

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

[0002] The primary function of the separator is to separate the positive and negative electrodes of the battery, preventing short circuits caused by contact between the electrodes, while allowing electrolyte ions to pass through, ensuring the normal charging and discharging process of the battery. The separator material is non-conductive, and its physicochemical properties have a crucial impact on battery performance. Different types of batteries use different separator materials. For lithium-ion batteries, since the electrolyte is an organic solvent system, the separator material needs to be resistant to organic solvents. Traditional lithium-ion battery separators typically use high-strength, thin-film polyolefin porous membranes, such as polyethylene (PE) and polypropylene (PP).

[0003] With the continuous development of lithium battery technology, especially in fields requiring high performance and high safety such as electric vehicles and energy storage systems, the performance requirements for separators are becoming increasingly stringent. While traditional polyolefin separators possess good mechanical strength and chemical stability, their shortcomings are gradually becoming apparent under extreme conditions. For example, polyolefin separators are prone to melting or shrinkage at high temperatures (above 160°C), leading to direct contact between the positive and negative electrodes inside the battery, potentially causing short circuits or even fires and explosions. Furthermore, polyolefin separators have low porosity and poor electrolyte wettability, making it difficult to meet the ion transport efficiency requirements of high-energy-density battery systems.

[0004] To overcome these shortcomings, polyimide (PI), as a high-performance polymer material, has been gradually introduced into the field of battery separators. Polyimide is composed of aromatic heterocyclic polymers containing imide groups (—CO—NH—CO—), and its molecular chain contains numerous aromatic heterocyclic structures, which endow polyimide with high rigidity and stability. Polyimide possesses excellent mechanical properties, high-temperature resistance (can be used for extended periods above 300℃), and chemical stability, enabling it to maintain the structural integrity of the separator under extreme conditions, thereby significantly improving battery safety. Furthermore, polyimide separators also exhibit excellent dielectric properties and anti-aging properties, effectively extending battery life.

[0005] However, despite the excellent performance of polyimide separators in terms of high temperature resistance and mechanical strength, some challenges remain in practical applications. Polyimide materials themselves have poor wettability to electrolytes, making it difficult for the electrolyte to fully penetrate the separator, thus reducing ionic conductivity and resulting in poor electrochemical performance of the battery separator.

[0006] Currently, to improve the performance of polyimide membranes, the pore structure and electrolyte wettability of the membrane can be optimized by introducing crosslinking agents or compounding with other materials (such as ceramic particles, nanofibers, etc.); surface modification techniques (such as plasma treatment, chemical grafting, etc.) can be used to improve the surface wettability of the membrane. These methods have improved the performance of polyimide membranes to some extent, but further research and optimization are still needed. Summary of the Invention

[0007] The purpose of this invention is to provide a high-strength lithium battery separator and its preparation process to solve the problem of poor electrochemical performance of polyimide lithium battery separators.

[0008] The objective of this invention can be achieved through the following technical solutions: The first aspect of this application provides a process for preparing a high-strength lithium battery separator, comprising the following steps: Under a nitrogen atmosphere, dianhydride and diamine undergo a condensation reaction to obtain polyamic acid oligomers; the polyamic acid oligomers and polysiloxane are crosslinked to form a gel, which is then imidized with an imidizing agent, aged at room temperature, and dried with supercritical carbon dioxide to obtain a high-strength lithium battery separator; the polysiloxane is prepared by hydrolysis and condensation of 6-aminopyridineboronic acid and a silane coupling agent.

[0009] In some possible implementations, the dianhydride and diamine are in a molar ratio of 1.1-1.2:1; The ratio of dianhydride to polysiloxane is 10 mmol: 0.18-0.2 g.

[0010] In some possible implementations, the temperature of the condensation reaction is 0-5°C, and the time of the condensation reaction is 8-24 hours.

[0011] In some possible implementations, the dianhydride is an aromatic dianhydride; the diamine is an aromatic diamine.

[0012] In some possible implementations, the aromatic dianhydride is at least one of 3,3',4,4'-biphenyltetracarboxylic dianhydride and 3,3',4,4'-benzophenonetetracarboxylic dianhydride; The aromatic diamine is at least one of 2,2'-dimethylbenzidine, 4,4-diaminodiphenyl ether, and p-phenylenediamine.

[0013] In some possible implementations, the imidizing agent includes a catalyst and a dehydrating agent, wherein the catalyst is triethylamine and the dehydrating agent is acetic acid.

[0014] In some possible implementations, the molar ratio of 6-aminopyridineboronic acid to silane coupling agent is 1.2-1.8:1.

[0015] In some possible implementations, the general structural formula of the silane coupling agent is denoted as R. n SiX （4-n） In the formula, R is a non-hydrolyzable organic functional group selected from alkyl, alkenyl, and amino groups; X is a hydrolyzable group selected from alkoxy groups.

[0016] In some possible implementations, 6-aminopyridineboronic acid and a silane coupling agent are dissolved separately, and then the silane coupling agent is added dropwise to 6-aminopyridineboronic acid under nitrogen protection. The mixture is heated to 78-80°C and refluxed to obtain polysiloxane.

[0017] The second aspect of this application provides a high-strength lithium battery separator, which is prepared by the above-described preparation process.

[0018] The beneficial effects of this invention are: This invention prepares a high-strength polyimide-based lithium battery separator, which uses polyimide as the resin matrix and introduces polysiloxane (Si-OBO) segments into the polymer network through molecular structure design, which significantly improves the mechanical properties and electrochemical stability of the separator.

[0019] Among them, polysiloxane is prepared by hydrolysis-condensation polymerization of 6-aminopyridineboronic acid (6-APBA) and a silane coupling agent. 6-APBA SP 2 Boron-containing groups can interact with lithium salt anions (such as PF6) in the electrolyte through Lewis acid-base interactions. - TFSI - Coordination effectively reduces anion mobility, thereby increasing the lithium-ion transference number (t). + ); nitrogen atom of the pyridine ring (SP 2 The lone pair electrons exhibit a strong electron-withdrawing effect, which can optimize the interfacial charge distribution of the separator, suppress polarization, and further improve electrochemical stability. The flexible structure of Si-OBO can also alleviate volume deformation during charge and discharge, improving cycle life. This separator combines high mechanical strength, excellent ionic conductivity, and high-temperature dimensional stability, making it suitable for high-energy-density lithium-ion battery systems. Detailed Implementation

[0020] 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.

[0021] Obviously, the following description is merely some examples or embodiments of this application. Those skilled in the art can apply this application to other similar scenarios without any inventive effort. Furthermore, it is understood that although the effort involved in such development may be complex and lengthy, for those skilled in the art related to the content disclosed in this application, any changes to design, manufacturing, or production based on the technical content disclosed in this application are merely conventional technical means and should not be construed as insufficient disclosure of the content of this application.

[0022] However, there may be instances where unnecessary detailed descriptions are omitted. For example, detailed descriptions of well-known matters or repetitive descriptions of essentially the same structure may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the following description is provided to enable those skilled in the art to fully understand this application and is not intended to limit the subject matter of the claims.

[0023] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions, and all technical features and optional technical features of this application can be combined to form new technical solutions.

[0024] The first aspect of this application provides a process for preparing a high-strength lithium battery separator, comprising the following steps: Under a nitrogen atmosphere, dianhydride and diamine undergo a condensation reaction to obtain polyamic acid oligomers. The polyamic acid oligomers and polysiloxanes are crosslinked to form a gel, which is then imidized with an imidizing agent. After room temperature aging and supercritical carbon dioxide drying, a high-strength lithium battery separator is obtained. The polysiloxane is prepared by hydrolysis-condensation of 6-aminopyridineboronic acid and a silane coupling agent. The silane coupling agent hydrolyzes to form silanol groups, which then undergo dehydration-condensation with the boronol groups on 6-aminopyridineboronic acid. 6-aminopyridineboronic acid can also undergo self-condensation under heating conditions to release water, generating a Si-OBO main chain structure of polysiloxane. The introduction of the Si-OBO segment enhances the thermal stability of the separator. The amino group of 6-aminopyridineboronic acid can participate in the synthesis of polyimide. As a polar group, it can improve the wettability of the separator. In addition, 6-aminopyridineboronic acid contains not only boron groups but also pyridine groups, which can improve conductivity and lithium-ion transference number. Furthermore, the heat resistance and polarity of the pyridine ring can be used to enhance the thermal dimensional stability and electrolyte wettability of the lithium battery separator, thereby improving the electrochemical performance of the lithium battery separator.

[0025] In some specific embodiments, the dianhydride and diamine are used in a molar ratio of 1.1-1.2:1; The ratio of dianhydride to polysiloxane is 10 mmol: 0.18-0.2 g.

[0026] In some specific embodiments, during the preparation of polyamic acid oligomers, the total mass concentration of dianhydride and diamine in the synthesis system is 8% to 11%.

[0027] In some specific embodiments, the temperature of the condensation reaction is 0-5°C, and the time of the condensation reaction is 8-24 hours.

[0028] In some specific embodiments, the dianhydride is an aromatic dianhydride; the diamine is an aromatic diamine.

[0029] In some specific embodiments, the aromatic dianhydride is at least one of 3,3',4,4'-biphenyltetracarboxylic dianhydride and 3,3',4,4'-benzophenonetetracarboxylic dianhydride; The aromatic diamine is at least one of 2,2'-dimethylbenzidine, 4,4-diaminodiphenyl ether, and p-phenylenediamine.

[0030] In some specific embodiments, the imidizing agent includes a catalyst and a dehydrating agent, wherein the catalyst is triethylamine and the dehydrating agent is acetic acid. The molar ratio of triethylamine to acetic acid is 0.8:1; the molar ratio of acetic acid to dianhydride is 4-5:1; because the monomer raw material in this invention contains a pyridine structure, the amount of triethylamine can be appropriately reduced.

[0031] In some specific embodiments, the molar ratio of 6-aminopyridineboronic acid to silane coupling agent is 1.2-1.8:1.

[0032] In some specific embodiments, the general structural formula of the silane coupling agent is denoted as R. n SiX （4-n） In the formula, R is a non-hydrolyzable organic functional group selected from alkyl, alkenyl, amino, preferably methyl, ethyl and vinyl; X is a hydrolyzable group selected from alkoxy, preferably methoxy and ethoxy.

[0033] In some specific embodiments, the polysiloxane is prepared by the following steps: After dissolving 6-aminopyridineboronic acid and silane coupling agent in solvents, the silane coupling agent was added dropwise to 6-aminopyridineboronic acid under nitrogen protection. The temperature was raised to 78-80℃ and refluxed for 8 hours. After the reaction was completed, the solvent was removed by rotary evaporation to obtain polysiloxane.

[0034] The second aspect of this application provides a high-strength lithium battery separator, which is prepared by the above steps.

[0035] The following is a detailed description with reference to specific examples.

[0036] Example 1

[0037] This embodiment provides a process for preparing a high-strength lithium battery separator, including the following steps: Under a nitrogen atmosphere, 2,2'-dimethylbenzidine and 4,4-diaminodiphenyl ether were dissolved in N-methylpyrrolidone and then added to 3,3',4,4'-biphenyltetracarboxylic dianhydride. The mixture underwent a condensation reaction at 0°C for 12 hours to obtain a polyamic acid oligomer. The dianhydride was 3,3',4,4'-biphenyltetracarboxylic dianhydride; the diamine was 2,2'-dimethylbenzidine and 4,4-diaminodiphenyl ether in a molar ratio of 1:1; the molar ratio of dianhydride to diamine was 1.1:1; and the total amount of dianhydride and diamine used was 8% of the mass concentration of N-methylpyrrolidone. 6-Aminopyridineboronic acid and 1,2-dichloroethane were mixed and dissolved by heating to obtain a mixture. A silane coupling agent and 1,2-dichloroethane were mixed and added dropwise to the mixture. The mixture was heated to 80°C and refluxed. After the reaction was complete, 1,2-dichloroethane was removed by rotary evaporation to obtain polysiloxane. The silane coupling agent was triethoxyethylsilane; the molar ratio of 6-aminopyridineboronic acid to the silane coupling agent was 1.2:1.

[0038] Polysiloxane was added to polyamic acid oligomers, and after stirring for 5 min, acetic anhydride and triethylamine were added and stirred for another 5 min. The mixture was then coated with a doctor blade to a thickness of approximately 100 μm. After aging at room temperature for 24 h, the membrane was successively immersed and washed in 75 V% NMP acetone solution, 25 V% NMP acetone solution, and pure acetone. It was then dried using supercritical carbon dioxide at 60 °C and 15 MPa for 8 h to obtain a high-strength lithium-ion battery separator. The molar ratio of acetic anhydride to polysiloxane was 10 mmol:0.18 g; the molar ratio of triethylamine to acetic acid was 0.8:1; and the molar ratio of acetic acid to acetic anhydride was 4:1.

[0039] Example 2

[0040] The difference between this embodiment and Example 1 lies in the process of preparing polysiloxane: In the preparation of polysiloxaborane, the silane coupling agent is methyltriethoxysilane; the remaining raw materials and preparation process are the same as in Example 1.

[0041] Specifically, 6-aminopyridineboronic acid and 1,2-dichloroethane are mixed and heated to dissolve, yielding a mixture. A silane coupling agent and 1,2-dichloroethane are then mixed and added dropwise to the mixture. The mixture is heated to 80°C and refluxed. After the reaction is complete, 1,2-dichloroethane is removed by rotary evaporation to obtain polysiloxane. The silane coupling agent is methyltriethoxysilane; the molar ratio of 6-aminopyridineboronic acid to the silane coupling agent is 1.2:1.

[0042] Example 3

[0043] The difference between this embodiment and Example 1 is that the process for preparing polysiloxane is different; the other raw materials and preparation process are the same as in Example 1.

[0044] Specifically, 6-aminopyridineboronic acid and 1,2-dichloroethane are mixed and heated to dissolve, yielding a mixture. A silane coupling agent and 1,2-dichloroethane are then mixed and added dropwise to the mixture. The mixture is heated to 80°C and refluxed. After the reaction is complete, 1,2-dichloroethane is removed by rotary evaporation to obtain polysiloxane. The silane coupling agent is triethoxyethylsilane; the molar ratio of 6-aminopyridineboronic acid to the silane coupling agent is 1.4:1.

[0045] Example 4

[0046] The difference between this embodiment and Example 1 is that the process for preparing polysiloxane is different; the other raw materials and preparation process are the same as in Example 1.

[0047] Specifically, 6-aminopyridineboronic acid and 1,2-dichloroethane are mixed and heated to dissolve, yielding a mixture. A silane coupling agent and 1,2-dichloroethane are then mixed and added dropwise to the mixture. The mixture is heated to 80°C and refluxed. After the reaction is complete, 1,2-dichloroethane is removed by rotary evaporation to obtain polysiloxane. The silane coupling agent is triethoxyethylsilane; the molar ratio of 6-aminopyridineboronic acid to the silane coupling agent is 1.6:1.

[0048] Example 5

[0049] The difference between this embodiment and Example 1 is that the process for preparing polysiloxane is different; the other raw materials and preparation process are the same as in Example 1.

[0050] Specifically, 6-aminopyridineboronic acid and 1,2-dichloroethane are mixed and heated to dissolve, yielding a mixture. A silane coupling agent and 1,2-dichloroethane are then mixed and added dropwise to the mixture. The mixture is heated to 80°C and refluxed. After the reaction is complete, 1,2-dichloroethane is removed by rotary evaporation to obtain polysiloxane. The silane coupling agent is triethoxyethylsilane; the molar ratio of 6-aminopyridineboronic acid to the silane coupling agent is 1.8:1.

[0051] Example 6

[0052] The difference between this embodiment and Example 1 is that the amount of polysiloxane added is different; the other raw materials and preparation process are the same as in Example 1.

[0053] Under a nitrogen atmosphere, 2,2'-dimethylbenzidine and 4,4-diaminodiphenyl ether were dissolved in N-methylpyrrolidone and then added to 3,3',4,4'-biphenyltetracarboxylic dianhydride. The mixture underwent a condensation reaction at 0°C for 12 hours to obtain a polyamic acid oligomer. The dianhydride was 3,3',4,4'-biphenyltetracarboxylic dianhydride; the diamine was 2,2'-dimethylbenzidine and 4,4-diaminodiphenyl ether in a molar ratio of 1:1; the molar ratio of dianhydride to diamine was 1.1:1; and the total amount of dianhydride and diamine used was 8% of the mass concentration of N-methylpyrrolidone. 6-Aminopyridineboronic acid and 1,2-dichloroethane were mixed and dissolved by heating to obtain a mixture. A silane coupling agent and 1,2-dichloroethane were mixed and added dropwise to the mixture. The mixture was heated to 80°C and refluxed. After the reaction was complete, 1,2-dichloroethane was removed by rotary evaporation to obtain polysiloxane. The silane coupling agent was triethoxyethylsilane; the molar ratio of 6-aminopyridineboronic acid to the silane coupling agent was 1.2:1.

[0054] Polysiloxane was added to polyamic acid oligomers, and after stirring for 5 min, acetic anhydride and triethylamine were added and stirred for 10 min. The mixture was then coated with a doctor blade to a thickness of approximately 100 μm. After aging at room temperature for 24 h, the membrane was successively immersed and washed in 75 V% NMP acetone solution, 25 V% NMP acetone solution, and pure acetone. It was then dried using supercritical carbon dioxide at 60 °C and 15 MPa for 8 h to obtain a high-strength lithium battery separator. The molar ratio of acetic anhydride to polysiloxane was 10 mmol:0.2 g; the molar ratio of triethylamine to acetic acid was 0.8:1; and the molar ratio of acetic acid to acetic anhydride was 4:1.

[0055] Example 7

[0056] This embodiment provides a process for preparing a high-strength lithium battery separator, including the following steps: Under a nitrogen atmosphere, 4,4-diaminodiphenyl ether was dissolved in N-methylpyrrolidone and then 3,3',4,4'-biphenyltetracarboxylic dianhydride was added. The condensation reaction was carried out at 0°C for 12 hours to obtain a polyamic acid oligomer. The dianhydride was 3,3',4,4'-biphenyltetracarboxylic dianhydride; the diamine was 4,4-diaminodiphenyl ether; the molar ratio of dianhydride to diamine was 1.1:1; and the total amount of dianhydride and diamine used was 8% of the mass concentration of N-methylpyrrolidone. 6-Aminopyridineboronic acid and 1,2-dichloroethane were mixed and dissolved by heating to obtain a mixture. A silane coupling agent and 1,2-dichloroethane were mixed and added dropwise to the mixture. The mixture was heated to 80°C and refluxed. After the reaction was complete, 1,2-dichloroethane was removed by rotary evaporation to obtain polysiloxane. The silane coupling agent was triethoxyethylsilane; the molar ratio of 6-aminopyridineboronic acid to the silane coupling agent was 1.2:1.

[0057] Polysiloxane was added to polyamic acid oligomers, and after stirring for 5 min, acetic anhydride and triethylamine were added and stirred for another 5 min. The mixture was then coated with a doctor blade to a thickness of approximately 100 μm. After aging at room temperature for 24 h, the membrane was successively immersed and washed in 75 V% NMP acetone solution, 25 V% NMP acetone solution, and pure acetone. It was then dried using supercritical carbon dioxide at 60 °C and 15 MPa for 8 h to obtain a high-strength lithium-ion battery separator. The molar ratio of acetic anhydride to polysiloxane was 10 mmol:0.18 g; the molar ratio of triethylamine to acetic acid was 0.8:1; and the molar ratio of acetic acid to acetic anhydride was 4:1.

[0058] Example 8

[0059] This embodiment provides a process for preparing a high-strength lithium battery separator, including the following steps: Under a nitrogen atmosphere, 2,2'-dimethylbenzidine and 4,4-diaminodiphenyl ether were dissolved in N-methylpyrrolidone and then added to 3,3',4,4'-biphenyltetracarboxylic dianhydride. The mixture underwent a condensation reaction at 0°C for 12 hours to obtain a polyamic acid oligomer. The dianhydride was 3,3',4,4'-biphenyltetracarboxylic dianhydride; the diamine was 2,2'-dimethylbenzidine and 4,4-diaminodiphenyl ether in a molar ratio of 1:1; the molar ratio of dianhydride to diamine was 1.2:1; and the total amount of dianhydride and diamine used was 11% of the mass concentration of N-methylpyrrolidone. 6-Aminopyridineboronic acid and 1,2-dichloroethane were mixed and dissolved by heating to obtain a mixture. A silane coupling agent and 1,2-dichloroethane were mixed and added dropwise to the mixture. The mixture was heated to 80°C and refluxed. After the reaction was complete, 1,2-dichloroethane was removed by rotary evaporation to obtain polysiloxane. The silane coupling agent was triethoxyethylsilane; the molar ratio of 6-aminopyridineboronic acid to the silane coupling agent was 1.2:1.

[0060] Polysiloxane was added to polyamic acid oligomers, and after stirring for 5-10 min, acetic anhydride and triethylamine were added and stirred for another 5-10 min. The mixture was then coated with a doctor blade to a thickness of approximately 100 μm. After aging at room temperature for 24 h, the membrane was sequentially immersed and washed in 75 V% NMP acetone solution, 25 V% NMP acetone solution, and pure acetone. It was then dried using supercritical carbon dioxide at 60 °C and 15 MPa for 8 h to obtain a high-strength lithium battery separator. The molar ratio of acetic anhydride to polysiloxane was 10 mmol:0.18 g; the molar ratio of triethylamine to acetic acid was 0.8:1; and the molar ratio of acetic acid to acetic anhydride was 5:1. Comparative Example 1 The difference between this comparative example and Example 1 lies in the amount of polysiloxane added; the remaining raw materials and preparation process are the same as in Example 1. Specifically: Polysiloxane was added to polyamic acid oligomers, and after stirring for 5 min, acetic anhydride and triethylamine were added and stirred for another 5 min. The mixture was then coated with a doctor blade to a thickness of approximately 100 μm. After aging at room temperature for 24 h, the membrane was successively immersed and washed in 75 V% NMP acetone solution, 25 V% NMP acetone solution, and pure acetone. It was then dried using supercritical carbon dioxide at 60 °C and 15 MPa for 8 h to obtain a high-strength lithium-ion battery separator. The molar ratio of acetic anhydride to polysiloxane was 10 mmol:0.18 g; the molar ratio of triethylamine to acetic acid was 0.8:1; and the molar ratio of acetic acid to acetic anhydride was 4:1.

[0061] Comparative Example 2

[0062] The difference between this comparative example and Example 1 is the use of a different polysiloxane; all other raw materials and preparation processes remain the same as in Example 1. Specifically: Polysiloxane is prepared by the following steps: Phenylated boric acid and 1,2-dichloroethane were mixed and heated to dissolve, yielding a mixture. A silane coupling agent and 1,2-dichloroethane were mixed and added dropwise to the mixture. The mixture was heated to 80°C and refluxed. After the reaction was complete, the 1,2-dichloroethane was removed by rotary evaporation to obtain polysiloxane. The silane coupling agent was triethoxyethylsilane; the molar ratio of phenylboronic acid to the silane coupling agent was 1.2:1.

[0063] Comparative Example 3

[0064] The difference between this comparative example and Example 1 is that the polysiloxane is replaced with other raw materials containing multiple amino groups. In this comparative example, 1,3,5-triaminobenzene is selected. Specifically: 1,3,5-Triaminobenzene was added to polyamic acid oligomers, and after stirring for 5 min, acetic anhydride and triethylamine were added and stirred for another 5 min. The mixture was then coated with a doctor blade to a thickness of approximately 100 μm. After aging at room temperature for 24 h, the membrane was successively immersed and washed in 75 V% NMP acetone solution, 25 V% NMP acetone solution, and pure acetone. Supercritical carbon dioxide drying was then performed at 60 °C and 15 MPa for 8 h to obtain a high-strength lithium battery separator. The molar ratio of dianhydride to 1,3,5-triaminobenzene was 10 mmol:0.18 g; the molar ratio of triethylamine to acetic acid was 0.8:1; and the molar ratio of acetic acid to dianhydride was 4:1.

[0065] Mechanical properties were tested on the diaphragm samples prepared in Examples 1-8 and Comparative Examples 1-3: diaphragm samples with a length of 10 cm and a width of 1 cm were prepared, and the tensile rate of the tensile machine was controlled at 20 mm / min. The tensile strength and elongation at break of the diaphragms were analyzed. The results are shown in Table 1. Table 1

[0066] The ionic conductivity and ion transference number of the membrane samples prepared in Example 1 and Comparative Examples 1-3 were tested, and the results are shown in Table 2 below: Table 2

[0067] According to the test results, the battery separator prepared by this invention has high strength, maintains the excellent mechanical properties of polyimide battery separators, and effectively improves the migration ability and conductivity of lithium ions.

[0068] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0069] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A process for preparing a high-strength lithium battery separator, characterized in that, Includes the following steps: Under a nitrogen atmosphere, dianhydride and diamine undergo a condensation reaction to obtain polyamic acid oligomers; the polyamic acid oligomers and polysiloxane are crosslinked to form a gel, which is then imidized with an imidizing agent, aged at room temperature, and dried with supercritical carbon dioxide to obtain a high-strength lithium battery separator; the polysiloxane is prepared by hydrolysis and condensation of 6-aminopyridineboronic acid and a silane coupling agent.

2. The preparation process of a high-strength lithium battery separator according to claim 1, characterized in that, The dianhydride and diamine are mixed in a molar ratio of 1.1-1.2:1; The ratio of dianhydride to polysiloxane is 10 mmol: 0.18-0.2 g.

3. The preparation process of a high-strength lithium battery separator according to claim 1, characterized in that, The condensation reaction is carried out at a temperature of 0-5℃ for 8-24 hours.

4. The preparation process of a high-strength lithium battery separator according to claim 1, characterized in that, The dianhydride is an aromatic dianhydride; the diamine is an aromatic diamine.

5. The preparation process of a high-strength lithium battery separator according to claim 1, characterized in that, The aromatic dianhydride is at least one of 3,3',4,4'-biphenyltetracarboxylic dianhydride and 3,3',4,4'-benzophenonetetracarboxylic dianhydride; The aromatic diamine is at least one of 2,2'-dimethylbenzidine, 4,4-diaminodiphenyl ether, and p-phenylenediamine.

6. The preparation process of a high-strength lithium battery separator according to claim 1, characterized in that, Imine reagents include triethylamine and acetic acid.

7. The preparation process of a high-strength lithium battery separator according to claim 1, characterized in that, The molar ratio of 6-aminopyridineboronic acid to silane coupling agent is 1.2-1.8:

1.

8. The preparation process of a high-strength lithium battery separator according to claim 1, characterized in that, The general structural formula of the silane coupling agent is denoted as R. n SiX （4-n） In the formula, R is a non-hydrolyzable organic functional group selected from alkyl, alkenyl, and amino groups; X is a hydrolyzable group selected from alkoxy groups.

9. The preparation process of a high-strength lithium battery separator according to claim 1, characterized in that, After dissolving 6-aminopyridineboronic acid and silane coupling agent separately, the silane coupling agent was added dropwise to 6-aminopyridineboronic acid under nitrogen protection, and the temperature was raised to 78-80℃ and refluxed to obtain polysiloxane.

10. A high-strength lithium battery separator, characterized in that, Prepared by the preparation process described in any one of claims 1-9.

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