Three-dimensional composite solid electrolyte with high interface stability and preparation method thereof

Abstract

The invention belongs to the technical field of solid-state lithium batteries, and discloses a three-dimensional composite solid-state electrolyte with high interface stability, which is characterized in that a bionic hierarchical pore inorganic skeleton and a polymer electrolyte form a dynamic covalent bond network through a covalent reaction of surface active groups, and the bionic hierarchical pore inorganic skeleton is subjected to a sol-gel reaction to form the three-dimensional composite solid-state electrolyte with high interface stability. The polymer electrolyte is prepared from the following raw materials in parts by weight: 80 to 90 parts of polymer matrix, 5 to 8 parts of lithium salt, 1 to 3 parts of organic solvent and 10 to 15 parts of modified chitosan nanofiber. The modified chitosan nanofiber is obtained through acid activation, plasma activation, alkali loading of Li and freeze drying, and by adding the modified chitosan nanofiber, the ion migration efficiency in the charging and discharging process of the battery is remarkably improved, the interface contact impedance is reduced, the self-repairing efficiency is improved, the ion transmission performance of electrolyte is recovered, and the service life of the battery is prolonged.

Description

Technical Field

[0001] This invention belongs to the field of solid-state lithium battery technology, specifically relating to a three-dimensional composite solid electrolyte with high interface stability and its preparation method. Background Technology

[0002] Solid-state batteries have become the core development direction of next-generation power batteries due to their advantages such as high energy density and strong safety. However, the performance bottleneck of solid electrolytes restricts their industrialization process: inorganic solid electrolytes have high ionic conductivity, but are rigid and brittle, and are prone to cracking when in contact with electrodes. They also have high interfacial impedance and are prone to side reactions with the positive electrode. Polymer solid electrolytes have good flexibility, but have low room temperature ionic conductivity and insufficient mechanical strength, making it difficult to suppress lithium dendrites. Existing composite solid electrolytes, which are made by physically mixing inorganic phases and polymers, have problems such as inorganic phase agglomeration, discontinuous conductive pathways, and interfaces that rely solely on physical adsorption. During cycling, the interfaces are prone to separation, impedance increases sharply, and performance improvement is limited.

[0003] Furthermore, existing technologies struggle to precisely control the electrolyte's microstructure, resulting in complex preparation processes and significant challenges in large-scale production. This invention addresses these issues by providing a high-performance composite solid-state electrolyte and its preparation method through structural innovation and process optimization. Summary of the Invention

[0004] To address the shortcomings mentioned in the background art, the present invention aims to provide a three-dimensional composite solid electrolyte with high interfacial stability and its preparation method. By adding modified chitosan nanofibers, an additional lithium-ion source is provided for the electrolyte. Combined with the continuous network pathways formed by its nanoscale fiber structure, and the hierarchical structure of macropores, mesopores, and micropores of the biomimetic multi-level porous inorganic framework, a multi-scale ion transport channel is synergistically constructed. This significantly enhances the ion migration efficiency during battery charging and discharging, effectively inhibits the growth and penetration of lithium dendrites, reduces the risk of short circuits during battery cycling, reduces inorganic phase aggregation, improves the wettability of the organic-inorganic interface, reduces interfacial contact impedance, promotes the recombination of broken dynamic covalent bonds, enhances self-repair efficiency, restores the integrity and ion transport performance of the electrolyte, and extends battery life.

[0005] The objective of this invention can be achieved through the following technical solutions: A three-dimensional composite solid electrolyte with high interfacial stability is characterized by comprising a biomimetic hierarchical porous inorganic framework, a polymer electrolyte, and a dynamic covalent bond network; the biomimetic hierarchical porous inorganic framework has a hierarchical pore structure of macropores, mesopores, and micropores, and contains active groups on its surface; the polymer electrolyte comprises a polymer matrix containing dynamic covalent bonds; the dynamic covalent bond network is formed by a covalent reaction between the surface active groups of the biomimetic hierarchical porous inorganic framework and the dynamic covalent bonds of the polymer electrolyte; the polymer electrolyte comprises the following raw materials in parts by weight: 80-90 parts polymer matrix, 5-8 parts lithium salt, 1-3 parts organic solvent, and 10-15 parts modified chitosan nanofibers.

[0006] More preferably, the raw materials for the biomimetic hierarchical porous inorganic framework include an inorganic precursor, a template agent, and a pore-forming agent; the inorganic precursor is one or two of tetraethyl orthosilicate and aluminum isopropoxide; the template agent is one or two of block copolymers P123 and F127; the pore-forming agent is one or two of glucose and starch; and the dynamic covalent network is formed by one or two of polyacrylate, polyphosphazene, and epoxy resin through a covalent reaction.

[0007] More preferably, the polymer matrix containing dynamic covalent bonds is one or two of polyvinylidene fluoride-hexafluoropropylene, polyethylene oxide, and polyacrylonitrile; the lithium salt is one or two of lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate, and lithium nitrate; and the organic solvent is one or two of propylene carbonate, ethylene carbonate, and dimethyl carbonate.

[0008] More preferably, the method for preparing modified chitosan nanofibers includes the following steps: A1. Take chitosan nanofibers and ultrasonically disperse them for 30-40 minutes. Heat them to 30-40℃ and stir. Slowly add 15-20wt% HCl solution and stir for 1-2 hours. Then, pass Ar plasma through them for 10-15 minutes and continue stirring for 1-2 hours. A2. Wash the chitosan nanofibers by centrifugation with ethanol 3-5 times at a speed of 5000-7000 r / min for 7-9 min. Freeze the centrifuged wet chitosan nanofibers at -40 to -50℃ for 2-4 h to form uniform ice crystals. Dry them under vacuum of 0.1-0.2 Pa for 12-14 h. A3. Disperse dried chitosan nanofibers in ethanol, heat to 50-60℃ and stir for 10-15 min, add 10-15 wt% LiOH solution in 3 portions, stir for 2-3 h, cool and neutralize pH 7-8 with glacial acetic acid, centrifuge and wash 3-5 times, freeze at -40--50℃ for 2-4 h, and vacuum dry at 0.1-0.2 Pa for 12-14 h to obtain modified chitosan nanofibers.

[0009] More preferably, the ultrasonic dispersion power in A1 is 300W and the frequency is 40kHz.

[0010] More preferably, the method for preparing a three-dimensional composite solid electrolyte with high interfacial stability includes the following steps: S1. Mix the inorganic precursor, template agent, and pore-forming agent in a mass ratio of 2:2:1, add solvent to form a homogeneous solution, and carry out a sol-gel reaction at 30~50℃ for 24~48h to form a wet gel. Freeze-dry the wet gel to obtain a dry gel. Heat the dry gel to 600~800℃ in air at a heating rate of 2~5℃ / min and hold for 3~5h for high-temperature sintering to obtain a biomimetic hierarchical porous inorganic framework. S2. Mix the polymer matrix containing dynamic covalent bonds, lithium salt, and organic solvent in a mass ratio of 4:2:1, and stir at 50~70℃ for 8~12h to obtain a homogeneous polymer electrolyte solution. S3. Immerse the biomimetic hierarchical porous inorganic framework in a polymer electrolyte solution and impregnate it under vacuum conditions of 0.01~0.05MPa for 1~2h. Then, heat the impregnated sample at 80~100℃ for 2~4h to initiate a covalent reaction and form a dynamic covalent bond network. Finally, vacuum dry it at 60~70℃ for 12~14h to remove the organic solvent and obtain a three-dimensional composite solid electrolyte.

[0011] More preferably, in step S1, the freeze-drying temperature is -40~-60℃ and the time is 24~36h.

[0012] More preferably, in step S2, the mass ratio of the polymer matrix containing dynamic covalent bonds, the lithium salt, and the organic solvent is 8:2:1.

[0013] The beneficial effects of this invention are: After being loaded with Li⁺, modified chitosan nanofibers form stable Li⁺ adsorption sites on their surface. Through the coordination of Li⁺ and the hydroxyl groups of the chitosan molecular chains, lithium ions are anchored and released in a controlled manner, increasing the concentration of free lithium ions in the electrolyte. This, combined with the pore structure of the biomimetic hierarchical porous inorganic framework, forms a fiber-pore mass transfer pathway, significantly improving ionic conductivity. The chitosan nanofibers themselves possess a high-strength molecular chain structure, and after freeze-drying, the nanofiber morphology is preserved. When uniformly dispersed in the polymer electrolyte, they inhibit local deformation of the polymer matrix during lithium dendrite growth. Simultaneously, the Li⁺ on the fiber surface can regulate lithium ion deposition behavior, guiding lithium dendrites to grow uniformly along the fiber direction and avoiding puncture problems caused by excessive local dendrite growth.

[0014] Ar plasma treatment further introduces active free radicals and oxygen-containing functional groups, significantly increasing the density of active sites on the fiber surface. Simultaneously, it forms hydrogen bond bridges with the silanol or aluminol hydroxyl groups on the surface of the biomimetic hierarchical porous inorganic framework, reducing physical defects at the organic-inorganic interface and lowering the probability of interfacial charge accumulation and side reactions. The amino and hydroxyl groups on the surface of the modified chitosan nanofibers can act as a dynamic covalent bond network. When the electrolyte is damaged, they react with reversible dynamic covalent bonds in the polymer matrix, accelerating the recoupling of broken bonds. At the same time, the network structure of the nanofibers restricts excessive molecular chain migration, improving the orientation of dynamic covalent bond recombination and enhancing self-repair efficiency and post-repair structural stability. Detailed Implementation

[0015] 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.

[0016] Example 1: A method for preparing modified chitosan nanofibers, comprising the following steps: A1. Take 10g of chitosan nanofibers, disperse them ultrasonically for 35min, heat to 30~40℃ and stir, slowly add 200mL of 15wt%HCl solution, stir for 1.5h, then pass Ar plasma through for 10min, and continue stirring for another 1.5h. A2. Wash the chitosan nanofibers four times by centrifugation with 500 mL of ethanol at a speed of 6000 r / min for 8 min. Freeze the centrifuged wet chitosan nanofibers at -45℃ for 3 h to allow the water to form uniform ice crystals. Dry them under a vacuum of 0.15 Pa for 13 h. A3. Disperse the dried chitosan nanofibers in 200 mL of ethanol, heat to 55 °C and stir for 10 min, add 30 mL of 15 wt% LiOH solution in 3 portions, stir for 2.5 h, cool and neutralize pH 7 with 4 mL of glacial acetic acid, centrifuge and wash 4 times, freeze at -45 °C for 3 h, and vacuum dry at 0.15 Pa for 13 h to obtain modified chitosan nanofibers.

[0017] Example 2: A three-dimensional composite solid electrolyte with high interfacial stability, comprising the following raw materials in parts by weight: It is composed of a biomimetic hierarchical porous inorganic framework, a polymer electrolyte, and a dynamic covalent bond network. The biomimetic hierarchical porous inorganic framework has a hierarchical pore structure of macropores, mesopores, and micropores, and contains active groups on its surface. The polymer electrolyte contains a polymer matrix containing dynamic covalent bonds. The dynamic covalent bond network is formed by a covalent reaction between the surface active groups of the biomimetic hierarchical porous inorganic framework and the dynamic covalent bonds of the polymer electrolyte. The polymer electrolyte comprises the following raw materials in parts by weight: 90 parts of polyvinylidene fluoride-hexafluoropropylene, 5 parts of lithium bis(trifluoromethanesulfonylimide), 3 parts of propylene carbonate, and 10 parts of modified chitosan nanofibers, wherein the modified chitosan nanofibers are prepared in Example 1.

[0018] The above preparation method includes the following steps: S1. Mix the inorganic precursor, template agent, and pore-forming agent in a mass ratio of 2:2:1, add solvent to form a homogeneous solution, and carry out a sol-gel reaction at 50°C for 24 hours to form a wet gel. Freeze-dry the wet gel to obtain a dry gel. Heat the dry gel to 600°C in air at a heating rate of 5°C / min and hold for 5 hours for high-temperature sintering to obtain a biomimetic hierarchical porous inorganic framework. S2. Mix the polymer matrix containing dynamic covalent bonds, lithium salt, and organic solvent in a mass ratio of 4:2:1, and stir at 50°C for 12 hours to obtain a homogeneous polymer electrolyte solution. S3. Immerse the biomimetic hierarchical porous inorganic framework in a polymer electrolyte solution and impregnate it under a vacuum of 0.01 MPa for 2 hours. Then, heat the impregnated sample at 80°C for 4 hours to initiate a covalent reaction and form a dynamic covalent bond network. Finally, vacuum dry it at 60°C for 14 hours to remove the organic solvent and obtain a three-dimensional composite solid electrolyte.

[0019] Example 3: A three-dimensional composite solid electrolyte with high interfacial stability, comprising the following raw materials in parts by weight: It is composed of a biomimetic hierarchical porous inorganic framework, a polymer electrolyte, and a dynamic covalent bond network. The biomimetic hierarchical porous inorganic framework has a hierarchical pore structure of macropores, mesopores, and micropores, and contains active groups on its surface. The polymer electrolyte contains a polymer matrix with dynamic covalent bonds. The dynamic covalent bond network is formed by a covalent reaction between the surface active groups of the biomimetic hierarchical porous inorganic framework and the dynamic covalent bonds of the polymer electrolyte. The polymer electrolyte comprises the following raw materials in parts by weight: 85 parts of polyethylene oxide, 7 parts of lithium hexafluorophosphate, 2 parts of ethylene carbonate, and 13 parts of modified chitosan nanofibers, wherein the modified chitosan nanofibers are prepared in Example 1.

[0020] The above preparation method includes the following steps: S1. Mix the inorganic precursor, template agent, and pore-forming agent in a mass ratio of 2:2:1, add solvent to form a homogeneous solution, and carry out a sol-gel reaction at 40°C for 30 hours to form a wet gel. Freeze-dry the wet gel to obtain a dry gel. Heat the dry gel to 700°C in air at a heating rate of 3°C / min and hold for 4 hours for high-temperature sintering to obtain a biomimetic hierarchical porous inorganic framework. S2. Mix the polymer matrix containing dynamic covalent bonds, lithium salt, and organic solvent in a mass ratio of 4:2:1, and stir at 60°C for 10 hours to obtain a homogeneous polymer electrolyte solution. S3. Immerse the biomimetic hierarchical porous inorganic framework into the polymer electrolyte solution and impregnate it under a vacuum of 0.03 MPa for 1.5 h. Then heat the impregnated sample at 90 °C for 3 h to initiate a covalent reaction and form a dynamic covalent bond network. Finally, vacuum dry it at 65 °C for 13 h to remove the organic solvent and obtain a three-dimensional composite solid electrolyte.

[0021] Example 4: A three-dimensional composite solid electrolyte with high interfacial stability, comprising the following raw materials in parts by weight: It is composed of a biomimetic hierarchical porous inorganic framework, a polymer electrolyte, and a dynamic covalent bond network. The biomimetic hierarchical porous inorganic framework has a hierarchical pore structure of macropores, mesopores, and micropores, and contains active groups on its surface. The polymer electrolyte contains a polymer matrix containing dynamic covalent bonds. The dynamic covalent bond network is formed by a covalent reaction between the surface active groups of the biomimetic hierarchical porous inorganic framework and the dynamic covalent bonds of the polymer electrolyte. The polymer electrolyte includes the following raw materials in parts by weight: 80 parts polyacrylonitrile, 8 parts lithium nitrate, 1 part dimethyl carbonate, and 15 parts modified chitosan nanofibers.

[0022] The above preparation method includes the following steps: S1. Mix the inorganic precursor, template agent, and pore-forming agent in a mass ratio of 2:2:1, add solvent to form a homogeneous solution, and carry out a sol-gel reaction at 30°C for 48 hours to form a wet gel. Freeze-dry the wet gel to obtain a dry gel. Heat the dry gel to 800°C in air at a heating rate of 2°C / min and hold for 3 hours for high-temperature sintering to obtain a biomimetic hierarchical porous inorganic framework. S2. Mix the polymer matrix containing dynamic covalent bonds, lithium salt, and organic solvent in a mass ratio of 4:2:1, and stir at 70°C for 8 hours to obtain a homogeneous polymer electrolyte solution. S3. Immerse the biomimetic hierarchical porous inorganic framework in a polymer electrolyte solution and impregnate it for 1 hour under a vacuum of 0.05 MPa. Then, heat the impregnated sample at 100°C for 2 hours to initiate a covalent reaction and form a dynamic covalent bond network. Finally, vacuum dry it at 70°C for 12 hours to remove the organic solvent and obtain a three-dimensional composite solid electrolyte.

[0023] Comparative Example 1: A three-dimensional composite solid electrolyte with high interfacial stability, with the same composition and preparation as in Example 4, except that no modified chitosan nanofibers were added.

[0024] Performance testing Ionic conductivity was tested according to GB / T39864-2021. The three-dimensional composite solid electrolyte was cut into circular pieces with a diameter of 10~15mm and a thickness of 0.1~0.5mm. The surface was cleaned with anhydrous ethanol and then vacuum dried for 2h. Electrochemical impedance was tested according to AC impedance spectroscopy. The three-dimensional composite solid electrolyte was cut into circular pieces with a diameter of 10~15mm and a thickness of 0.1~0.5mm. After cleaning the surface with anhydrous ethanol, it was dried under vacuum of 0.1~0.2Pa for 12~14h to remove residual solvent and moisture.

[0025] Table 1. Test results of three-dimensional composite solid electrolyte with high interfacial stability

[0026] As shown in Table 1, the ionic conductivity of Examples 2-4 is significantly higher than that of Comparative Example 1. This is attributed to the additional lithium-ion source provided by the modified chitosan nanofibers after Li⁺ loading, and the fiber and pore mass transfer channels formed by their nano-network structure and biomimetic hierarchical porous inorganic framework, which reduces ion migration resistance. Among them, Example 4 shows the most significant improvement, meeting the requirements of high-rate charge-discharge for ion transport efficiency. The electrochemical impedance of Examples 2-4 is lower than that of Comparative Example 1, indicating that the active groups such as hydroxyl and amino groups on the surface of the modified chitosan nanofibers improve the wettability of the organic-inorganic interface through hydrogen bonding and weak covalent interactions, reducing interfacial contact defects.

[0027] The initial electrochemical impedance of Examples 2-4 was lower than that of Comparative Example 1, indicating that the active groups such as hydroxyl and amino groups on the surface of the modified chitosan nanofibers can undergo hydrogen bonding or weak covalent interactions with the active groups on the surface of the polymer matrix and inorganic framework, improving interfacial wettability and reducing contact defects. Among them, Example 4 showed the most significant improvement. Comparative Example 1 showed the most significant increase in impedance after 1000 cycles. Due to the lack of interfacial bridging effect of modified chitosan nanofibers, the organic and inorganic phases were only physically adsorbed and bound together, which easily separated during cycling, leading to a sharp increase in impedance. The increase in impedance of Examples 2-4 was relatively smaller. The modified chitosan nanofibers stabilized the interfacial structure and suppressed side reactions through the synergistic effect of active groups and dynamic covalent bond network, significantly improving long-term cycling stability.

[0028] 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.

[0029] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A three-dimensional composite solid electrolyte with high interfacial stability, characterized in that, The system comprises a biomimetic hierarchical porous inorganic framework, a polymer electrolyte, and a dynamic covalent bond network. The biomimetic hierarchical porous inorganic framework has a hierarchical pore structure of macropores, mesopores, and micropores, and its surface contains active groups. The polymer electrolyte comprises a polymer matrix containing dynamic covalent bonds. The dynamic covalent bond network is formed through a covalent reaction between the surface active groups of the biomimetic hierarchical porous inorganic framework and the dynamic covalent bonds of the polymer electrolyte. The polymer electrolyte comprises the following raw materials in parts by weight: 80-90 parts polymer matrix, 5-8 parts lithium salt, 1-3 parts organic solvent, and 10-15 parts modified chitosan nanofibers. The modified chitosan nanofibers were obtained by acid activation, plasma activation, alkali loading of Li⁺, and freeze drying.

2. The three-dimensional composite solid electrolyte according to claim 1, characterized in that, The raw materials of the biomimetic hierarchical porous inorganic framework include an inorganic precursor, a template agent, and a pore-forming agent; the inorganic precursor is one or two of tetraethyl orthosilicate and aluminum isopropoxide; the template agent is one or two of block copolymers P123 and F127; the pore-forming agent is one or two of glucose and starch; and the dynamic covalent network is formed by one or two of polyacrylate, polyphosphazene, and epoxy resin through a covalent reaction.

3. The three-dimensional composite solid electrolyte according to claim 1, characterized in that, The polymer matrix containing dynamic covalent bonds is one or two of polyvinylidene fluoride-hexafluoropropylene, polyethylene oxide, and polyacrylonitrile; the lithium salt is one or two of lithium bis(trifluoromethanesulfonyl)imide, lithium hexafluorophosphate, and lithium nitrate; and the organic solvent is one or two of propylene carbonate, ethylene carbonate, and dimethyl carbonate.

4. The three-dimensional composite solid electrolyte according to claim 1, characterized in that, The preparation method of modified chitosan nanofibers includes the following steps: A1. Take chitosan nanofibers and ultrasonically disperse them for 30-40 minutes. Heat them to 30-40℃ and stir. Slowly add 15-20wt% HCl solution and stir for 1-2 hours. Then, pass Ar plasma through them for 10-15 minutes and continue stirring for 1-2 hours. A2. Wash the chitosan nanofibers by centrifugation with ethanol 3-5 times at a speed of 5000-7000 r / min for 7-9 min. Freeze the centrifuged wet chitosan nanofibers at -40 to -50℃ for 2-4 h to form uniform ice crystals. Dry them under vacuum of 0.1-0.2 Pa for 12-14 h. A3. Disperse dried chitosan nanofibers in ethanol, heat to 50-60℃ and stir for 10-15 min, add 10-15 wt% LiOH solution in 3 portions, stir for 2-3 h, cool and neutralize pH 7-8 with glacial acetic acid, centrifuge and wash 3-5 times, freeze at -40--50℃ for 2-4 h, and vacuum dry at 0.1-0.2 Pa for 12-14 h to obtain modified chitosan nanofibers.

5. The three-dimensional composite solid electrolyte according to claim 4, characterized in that, In A1, the ultrasonic dispersion power is 300W and the frequency is 40kHz.

6. A method for preparing a three-dimensional composite solid electrolyte with high interfacial stability as described in any one of claims 1 to 5, characterized in that, Includes the following steps: S1. Mix the inorganic precursor, template agent, and pore-forming agent in a mass ratio of 2:2:1, add solvent to form a homogeneous solution, and carry out a sol-gel reaction at 30~50℃ for 24~48h to form a wet gel. Freeze-dry the wet gel to obtain a dry gel. Heat the dry gel to 600~800℃ in air at a heating rate of 2~5℃ / min and hold for 3~5h for high-temperature sintering to obtain a biomimetic hierarchical porous inorganic framework. S2. Mix the polymer matrix containing dynamic covalent bonds, lithium salt, and organic solvent in a mass ratio of 4:2:1, and stir at 50~70℃ for 8~12h to obtain a homogeneous polymer electrolyte solution. S3. Immerse the biomimetic hierarchical porous inorganic framework in a polymer electrolyte solution and impregnate it under vacuum conditions of 0.01~0.05MPa for 1~2h. Then, heat the impregnated sample at 80~100℃ for 2~4h to initiate a covalent reaction and form a dynamic covalent bond network. Finally, vacuum dry it at 60~70℃ for 12~14h to remove the organic solvent and obtain a three-dimensional composite solid electrolyte.

7. The method for preparing the three-dimensional composite solid electrolyte with high interfacial stability according to claim 6, characterized in that, In step S1, the freeze-drying temperature is -40~-60℃ and the time is 24~36h.

8. The method for preparing the three-dimensional composite solid electrolyte with high interfacial stability according to claim 6, characterized in that, In step S2, the mass ratio of the polymer matrix containing dynamic covalent bonds, lithium salt, and organic solvent is 8:2:1.

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