A preparation method of an anion coupling eutectic gel composite electrolyte

Abstract

An anion coupling eutectic gel composite electrolyte and a preparation method thereof belong to the technical field of polymer solid electrolytes. The anion coupling eutectic gel composite electrolyte comprises 85-93 wt% of a composite electrolyte and 7-15 wt% of a solvent, and the solvent is coupled in the composite electrolyte material in the form of a eutectic solvent; the composite electrolyte material comprises one-dimensional porous covalent organic framework material and polymer material at a mass ratio of 1:(8-15), the one-dimensional porous covalent organic framework material has a pore size of 2-4 nm and a specific surface area of 1300-1600 m 2 / g, and the surface has thiol and amine polar functional groups. The porous covalent organic framework material has abundant thiol and amine polar functional groups, can produce coupling effects on anions, solvents and other anion aggregates in the composite electrolyte, reduce lithium ion conduction resistance, and realize high lithium ion conductivity and high ion transference number of the eutectic gel composite electrolyte at room temperature.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of polymer solid electrolytes, and specifically relates to a preparation method for improving the lithium ion conductivity of a eutectic gel composite electrolyte through an anion coupling strategy. BACKGROUND

[0002] With the growing global demand for clean energy, lithium ion batteries play an increasingly important role in the field of energy storage. However, traditional liquid electrolytes have exposed many problems in high energy density and large-scale applications, such as flammability, risk of thermal runaway, and poor long cycle stability. Therefore, developing high-performance solid-state electrolytes has become an important way to solve these problems. Solid-state electrolytes not only effectively improve the safety of batteries, but also improve the energy density and cycle life of batteries.

[0003] In the research of solid-state electrolytes, polymer solid-state electrolytes have attracted much attention due to their excellent flexibility and process adaptability. However, existing polymer electrolytes have the problem of low ionic conductivity, especially at room temperature, which limits their application in actual batteries. In order to overcome this technical bottleneck, researchers try to improve the performance of polymer solid-state electrolytes by introducing high-conductivity inorganic fillers or designing composite structures with ion conduction function. Among them, eutectic gel composite electrolytes are considered as a promising solution.

[0004] Eutectic gel composite electrolytes can achieve high ionic conductivity and better mechanical stability by combining polymers, eutectic materials and liquid electrolytes. However, in the eutectic system, the strong interaction between solvated lithium ions and anions will hinder the transport of lithium ions, thereby limiting the overall ionic conductivity of the composite electrolyte. This limitation mainly comes from the formation of anion aggregates, which hinder the migration path of free lithium ions, thereby reducing the conduction efficiency of lithium ions in the electrolyte. Therefore, how to effectively regulate the anion aggregation phenomenon and release more mobile lithium ions is one of the key challenges in the research of eutectic gel composite electrolytes.

[0005] To solve this problem, researchers have proposed ion ceramic conductor materials as fillers to enhance the solvation and transport capacity of lithium ions; or by chemical modification to change the microstructure characteristics of the polymer matrix to regulate ion distribution; or by introducing porous materials to construct ion channels for polymer composite electrolytes. For example, our previous report “A method for preparing a high lithium ion transference number eutectic gel composite electrolyte membrane, CN202210875952.2” greatly improved the lithium ion transference number, but the problem of incompatibility between ion ceramic conductors and PVDF-based polymers is still prominent. In addition, this method still has the shortcomings of large amount of ceramic conductors and uneven dispersion. The patent “Preparation method of zwitterionic modified PVDF polymer electrolyte, CN202410984911.6” reported by Xiong Jie et al. significantly improves the ionic conductivity of the polymer electrolyte and the stability of the polymer structure. However, the zwitterionic material of pyridinium propane sulfonate may degrade or decrease in performance under charging and discharging conditions, thereby affecting the long-term stability of the electrolyte and the cycle life of the battery, increasing the uncontrollable risk of battery safety. The patent “Solid electrolyte composite membrane, preparation method and application thereof, CN202410301369.X” disclosed by Li et al. uses a porous metal organic framework (MOFs) material to composite with a polymer to construct a solid electrolyte composite membrane. However, MOFs materials have stability problems such as structural damage during charging and discharging, and the preparation process of MOFs is complex and the raw materials are expensive.

[0006] Porous covalent organic frameworks (COF) are an ideal choice due to their unique polar structure, large specific surface area, and high chemical stability. The porous polar framework of COF materials can effectively adsorb anion aggregates, thereby reducing the influence of anions on lithium ion migration. Some studies have reported the use of porous silica and zeolite inorganic materials to adsorb anions in the electrolyte, thereby improving the lithium ion transference efficiency. However, these inorganic materials have certain limitations in terms of flexibility design and interface stability. COF materials have greater potential in this field due to their designability and diversity. By adjusting the pore size, surface chemical properties, and polarity characteristics of COF, their anion adsorption capacity can be further optimized. For example, during preparation, anions such as halogen ions and sulfate ions are combined with these functional groups through chemical bonds or coordination bonds to form stable anion conjugates, further forming a more efficient and stable composite system with the polymer matrix. In addition, the ordered structure and good chemical stability of COF materials also make them exhibit excellent stability and durability during long-term cycling, meeting the practical application requirements. SUMMARY

[0007] The purpose of the present application is to solve the problem of anion inhibition of lithium ion conduction in the above-mentioned eutectic gel composite electrolyte, and a preparation method of anion-coupled eutectic gel composite electrolyte is proposed. The present application uses a structure-adjustable COF material for anion coupling, which can significantly improve the migration ability of lithium ions and improve the compatibility of the lithium metal interface.

[0008] To solve the above technical problems, the technical scheme adopted by the present application is as follows:

[0009] An anion-coupled eutectic gel composite electrolyte, comprising 85-93wt% of a composite electrolyte and 7-15wt% of a residual solvent, the residual solvent being coupled in the composite electrolyte material in the form of a eutectic solvent;

[0010] The composite electrolyte material comprises one-dimensional porous covalent organic framework material and polymer material in a mass ratio of 1:(8-15), the one-dimensional porous covalent organic framework material has a pore size of 2-4 nanometers, a specific surface area of 1300-1600m 2 / g, and a surface with thiol (-SH) and amine (-NH2) polar functional groups;

[0011] The thickness of the anion-coupled eutectic gel composite electrolyte is 30-60 microns, and there is no flowing liquid at all.

[0012] Further, the one-dimensional porous covalent organic framework material is prepared by the following steps:

[0013] (1) 1,3,5-triformylbenzene is added to a mixed solvent of acetonitrile and water, and ultrasonic mixing is performed to obtain a mixed solution A; wherein the mass concentration of 1,3,5-triformylbenzene in the mixed solution A is 1-3 mg / mL;

[0014] (2) 2,5-diamino-1,4-benzenedithiol dihydrochloride is added to deionized water, and stirring is performed at a speed of 300-600 r / min for 0.5-1 hour to obtain a mixed solution B; wherein the mass concentration of 2,5-diamino-1,4-benzenedithiol dihydrochloride in the mixed solution B is 3-7 mg / mL;

[0015] (3) The mixed solution A and the mixed solution B are mixed in a volume ratio of 1:1 to obtain a mixed solution C; ice acetic acid is added to the mixed solution C as a catalyst by dropwise adding and stirring, the stirring speed is controlled at 100-300 r / min, the stirring time is 20-60 min, after stirring, the mixture is left to react at room temperature for 24-96 hours, the precipitate is separated and washed by centrifugation with ethanol for 2-6 times; vacuum drying is performed at a temperature of 60-100°C for 1-2 hours in a vacuum environment to obtain the one-dimensional porous covalent organic framework material.

[0016] Further, the polymer is polyvinylidene fluoride-chlorotrifluoroethylene.

[0017] Further, the residual solvent is one or a mixture of two or more of N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, and acetonitrile.

[0018] A preparation method of an anion coupling co-crystal gel composite electrolyte, comprising the following steps:

[0019] S1. Raw material pretreatment:

[0020] The polyvinylidene fluoride-chlorotrifluoroethylene, 1,3,5-benzene tricarboxaldehyde ligand, 2,5-diamino-1,4-benzenediol disulfide hydrochloride ligand, and lithium salt are vacuum dried at 40-100°C for 0.5-4h;

[0021] S2. COF polar powder preparation:

[0022] 2.1. The 1,3,5-benzene tricarboxaldehyde after S1 treatment is added to a mixed solvent of acetonitrile and water, and ultrasonic mixing is uniformly carried out to obtain a mixed solution A; wherein the mass concentration of 1,3,5-benzene tricarboxaldehyde in the mixed solution A is 1-3 mg / mL;

[0023] 2.2. The 2,5-diamino-1,4-benzenediol disulfide hydrochloride after S1 treatment is added to deionized water, and stirred at a speed of 300-600 r / min for 0.5-1h to obtain a mixed solution B; wherein the mass concentration of 2,5-diamino-1,4-benzenediol disulfide hydrochloride in the mixed solution B is 3-7 mg / mL;

[0024] 2.3. The mixed solution A and the mixed solution B are mixed according to a volume ratio of 1:1 to obtain a mixed solution C; ice acetic acid is added to the mixed solution C as a catalyst in a manner of dropwise adding while stirring, the stirring speed is controlled at 100-300 r / min, the stirring time is 20-60 min, after the stirring is completed, the reaction is carried out at room temperature for 24-96h, the precipitate is separated and washed by ethanol for 2-6 times; vacuum drying is carried out at a temperature of 60-100°C for 1-2h to obtain a COF polar powder;

[0025] S3. Lithium salt / polymer slurry preparation:

[0026] The lithium salt after S1 treatment is added to a mixed solvent, heated and stirred under a water bath at 40-80°C, the stirring speed is 300-600 r / min, until a fully dissolved and uniformly dispersed state is reached; then the polyvinylidene fluoride-chlorotrifluoroethylene polymer after S1 treatment is added, uniform speed stirring is continuously carried out for 2-6h to form an ionic sol; 2-3 times of ultrasonic treatment for 5-30 min is carried out without interruption during the stirring process to remove bubbles.

[0027] S4. Preparation of COF / lithium salt / polymer slurry:

[0028] The COF polar powder obtained in S2 was weighed and added to the ionic sol obtained in S3 in three batches. After each batch of COF polar powder was added, the stirring time was 30 min. After the last batch of COF was added, the stirring time was 2-4 h. A COF / lithium salt / polymer mixed slurry was obtained.

[0029] S5. Preparation of anion-coupled co-crystal gel composite electrolyte:

[0030] The mixed slurry obtained in S4 was coated on a substrate by spin coating. The wet gel film was obtained by slowly and uniformly evaporating the solvent after standing for 12-48 h. The spin coating speed was 200-600 r / min. The anion-coupled co-crystal gel composite electrolyte film was obtained by vacuum drying at 60-100 °C for 24-72 h.

[0031] Preferably, the polyvinylidene fluoride-chlorotrifluoroethylene P(VDF-CTFE) in step S1 has a CTFE branch content of 6-25%. The purity of the 1,3,5-benzene tricarboxaldehyde ligand and the 2,5-diamino-1,4-benzenedithiol dihydrochloride ligand is greater than 99.9%.

[0032] Preferably, the lithium salt in step S1 is at least one of lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(o-benzenediol)borate, and lithium (fluorosulfonyl)trifluoromethylsulfonylimide.

[0033] Preferably, in step 2.1, the volume ratio of acetonitrile to water in the mixed solvent of acetonitrile and water is 1:(0.2-0.6), preferably 1:0.3. In step 2.3, the volume ratio of glacial acetic acid to the mixed solution C is (1-4):20, preferably 3:20.

[0034] Preferably, the mixed solvent in step S3 is one or a mixture of two or more of N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, and acetonitrile.

[0035] Preferably, in the ionic sol prepared in step S3, the mass content of the polymer is 5-20 wt%. In step S3, the mass ratio of the added polymer to lithium salt is (2-4):1.

[0036] Preferably, in step S4, the mass ratio of the weighed COF polar powder to the polymer in the ionic sol is 1:(8-15).

[0037] Compared with the prior art, the present application has the following beneficial effects:

[0038] The application provides a preparation method of an anion coupling eutectic gel composite electrolyte, and the preparation method is simple, and the porous covalent organic framework material is prepared without high temperature and high pressure and long reaction time, but only needs stirring, catalysis and standing reaction at room temperature, so that the one-dimensional porous covalent organic framework material is obtained; the prepared porous covalent organic framework material has rich thiol (-SH) and amine (-NH2) polar functional groups, and the thiol (-SH) and amine (-NH2) polar functional groups have coupling effects on anions, residual solvents and other anion aggregates in the composite electrolyte, so that the lithium ion conduction resistance is reduced, and high lithium ion conductivity (0.08-0.6 mS cm -1 ) and high ion transference number (0.24-0.5) of the eutectic gel composite electrolyte at room temperature are realized. In addition, the prepared eutectic gel composite electrolyte has good interface compatibility with positive and negative electrodes of a solid-state battery due to the strong adsorption of the thiol (-SH) and amine (-NH2) polar functional groups, and the high positive electrode load (8 mg cm -2 ) solid-state battery assembled by using the eutectic gel composite electrolyte can be stably cycled for 200 times at room temperature under a current density of 0.5 C, and the cycle stability of the solid-state battery is significantly improved. Therefore, the preparation method of the eutectic gel composite electrolyte film has the advantages of simple preparation condition, excellent electrolyte performance and good interface performance, and has great potential for large-scale production and industrialization in the future. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 A preparation method flow chart of an anion coupling eutectic gel composite electrolyte is provided in the application;

[0040] Figure 2 An optical picture of a COF polar powder prepared in step S2 of Example 1 is provided;

[0041] Figure 3 A Raman spectrum picture of the COF polar powder prepared in step S2 of Example 1 is provided;

[0042] Figure 4 A direct current polarization curve of the anion coupling eutectic gel composite electrolyte prepared in Example 1 is provided;

[0043] Figure 5 An alternating current impedance test picture of the anion coupling eutectic gel composite electrolyte prepared in Example 1 before and after a direct current polarization test is provided;

[0044] Figure 6 An ion conductivity test picture of the anion coupling eutectic gel composite electrolyte prepared in Example 1 is provided;

[0045] Figure 7 A solid-state battery cycle performance test picture of the anion coupling eutectic gel composite electrolyte prepared in Example 1 is provided. DETAILED DESCRIPTION

[0046] The application will be further described below in conjunction with the accompanying drawings and specific embodiments:

[0047] Example 1

[0048] A preparation method of an anion coupling co-crystal gel composite electrolyte, comprising the following steps:

[0049] S1, raw material processing: vacuum drying the raw materials of polyvinylidene fluoride-chlorotrifluoroethylene, trimesaldehyde ligand, 2,5-diamino-1,4-benzenedithiol dihydrochloride ligand and lithium salt at 40°C for 0.5h; wherein the content of chlorotrifluoroethylene branch in polyvinylidene fluoride-chlorotrifluoroethylene is 10%.

[0050] S2, COF polar powder preparation: 10mL of 2mg / mL 1,3,5-trimesaldehyde acetonitrile and water mixed solution was measured, stirred and ultrasonically treated for standby. 10mL of 4mg / mL 2,5-diamino-1,4-benzenedithiol dihydrochloride deionized water solution was weighed, and the stirring speed was controlled at 300r / min. After stirring for 0.5h, it was ready for use. After mixing the two solutions, 3mL of glacial acetic acid was added as a catalyst, and the stirring speed was controlled at 120r / min. The stirring time was 30min, and after stirring, it was placed at room temperature for 24h. The precipitate was washed twice by centrifugation with ethanol, and then vacuum dried at 60°C for 1h to obtain COF polar powder.

[0051] S3, lithium salt / polymer slurry preparation: the lithium salt obtained in step S1 was added to the mixed solvent under water bath heating condition and stirred, the water bath temperature was 60°C, and the stirring speed was 400r / min. When the lithium salt was fully dissolved and uniformly dispersed, polyvinylidene fluoride-chlorotrifluoroethylene polymer was added, and uniform stirring was continued for 3h to form an ionic sol. Ultrasonic treatment was carried out twice for 20min without interruption during stirring to remove bubbles.

[0052] S4, COF / lithium salt / polymer slurry preparation: the COF polar powder obtained in step S2 was weighed and added to the ionic sol obtained in step S3 in 3 batches. After adding each batch of COF polar powder, the stirring time interval was 30min. After stirring for 2h after adding the COF for the last time, a COF / lithium salt / polymer mixed slurry was obtained.

[0053] S5, Preparation of anion-coupled co-crystal gel composite electrolyte: Take 3 mL of the mixed slurry obtained in step S4 and drop it on a clean and flat glass plate. Spin coat it at a rotation speed of 300 r / min to make it uniformly coated on the substrate. Let it stand for 12-48 h to allow the solvent to slowly and uniformly evaporate. Obtain a wet gel film, and then vacuum dry it at 60°C for 48 h to obtain an anion-coupled co-crystal gel composite electrolyte film.

[0054] Example 2

[0055] Example 2 differs from Example 1 in that, in step S1, the vacuum drying temperature is 60°C, and the vacuum drying time is adjusted to 1 h; in the polyvinylidene fluoride-chlorotrifluoroethylene, the proportion of chlorotrifluoroethylene branches is 8%. The remaining steps are exactly the same as in Example 1.

[0056] Example 3

[0057] Example 3 differs from Example 2 in that, in step S1, the vacuum drying temperature is 80°C, and the vacuum drying time is adjusted to 4 h; in the polyvinylidene fluoride-chlorotrifluoroethylene, the proportion of chlorotrifluoroethylene branches is 16%. The remaining steps are exactly the same as in Example 2.

[0058] Example 4

[0059] Example 4 differs from Example 3 in that, in step S1, the vacuum drying temperature is 60°C, and the vacuum drying time is adjusted to 4 h; the amount of glacial acetic acid catalyst is 2 mL, the room temperature standing reaction time is 36 h, the number of centrifugal separation and washing times is 4, and the vacuum drying temperature is 60°C. The remaining steps are exactly the same as in Example 3.

[0060] Example 5

[0061] Example 5 differs from Example 4 in that, in step S3, the mixed solvent is N,N-dimethylacetamide and dimethyl sulfoxide in a volume ratio of 3:1, and the mass ratio of the added polymer and lithium salt is 4:1. The remaining steps are exactly the same as in Example 4.

[0062] Example 6

[0063] Example 6 differs from Example 5 in that, in step S3, the mixed solvent is N,N-dimethylacetamide, dimethyl sulfoxide, and N-methyl pyrrolidone in a volume ratio of 1:1:1, and the mass ratio of the added polymer and lithium salt is 3:1. The remaining steps are exactly the same as in Example 5.

[0064] Example 7

[0065] Example 7 differs from Example 6 in that, in step S4, the amount of COF is adjusted to 0.01 g. The remaining steps are exactly the same as in Example 6.

[0066] Example 8

[0067] Example 8 is different from Example 7 in that in step S5, 4 mL of the mixed slurry obtained in step S3 is dropped on a clean and flat glass plate, and the solvent is volatilized for 24 h, and vacuum drying is performed at 60℃ for 48 h. The remaining steps are exactly the same as those in Example 7.

[0068] Example 9

[0069] Example 9 is different from Example 8 in that in step S5, 5 mL of the mixed slurry obtained in step S3 is spin-coated on a clean and flat glass plate at a rotation speed of 400 r / min, the solvent is volatilized for 36 h, and vacuum drying is performed at 80℃ for 60 h. The remaining steps are exactly the same as those in Example 8.

[0070] Example 10

[0071] Example 10 is different from Example 9 in that in step S5, the rotation speed of the spin coater is 600 r / min, the solvent volatilization time is 48 h, the vacuum drying temperature is 100℃, and the drying time is 72 h. The remaining steps are exactly the same as those in Example 9.

[0072] The following table is the performance comparison information of Examples 1 to 10:

[0073]

[0074] In summary, the preparation method of the anion-coupled eutectic gel composite electrolyte provided by the application can further optimize the size and distribution of the pores of the anion-coupled polar functionalized COF material to adapt to the conduction requirements of specific ions; the large-batch preparation of the anion-coupled polar functionalized COF material is under room temperature preparation conditions, which is energy-saving and environmentally friendly; the functionalized groups such as thiol groups (-SH) and amine groups (-NH2) on the surface of the material not only enhance the chemical activity of the material, but also improve the interfacial compatibility of the eutectic gel composite electrolyte with the lithium metal negative electrode and the positive electrode material, and significantly improve the cycle stability of the battery.

[0075] Based on the above inventive information, those skilled in the art will realize that the examples described herein are to help the reader understand the principles of the application and should be understood as not limiting the protection scope of the application to such specific statements and examples. Those skilled in the art can make various other specific modifications and combinations according to the technical inspirations disclosed in the application without departing from the essence of the application, and these modifications and combinations are still within the protection scope of the application.

Claims

1. An anion-coupled eutectic gel composite electrolyte, characterized in that, It includes 85-93 wt% of a composite electrolyte and 7-15 wt% of a solvent, with the solvent coupled in the form of a eutectic solvent in the composite electrolyte material; Among them, the composite electrolyte material includes a one-dimensional porous covalent organic framework material and a polymer material with a mass ratio of 1:(8~15). The pore size of the one-dimensional porous covalent organic framework material is 2~4 nanometers, the specific surface area is 1300~1600m² / g, and the surface has thiol and amine polar functional groups. The composite electrolyte was prepared using the following method: S1. Raw material pretreatment: Polyvinylidene fluoride-trifluorochloroethylene, 1,3,5-pyromellitic methyl aldehyde ligand, 2,5-diamino-1,4-benzenedithiophenol dihydrochloride ligand and lithium salt were vacuum dried at 40℃~100℃ for 0.5h~4h. S2. Preparation of COF polar powder: 2.1 The 1,3,5-pyromellitic aldehyde treated with S1 was added to a mixed solvent of acetonitrile and water and ultrasonically mixed to obtain a mixture A; wherein the mass concentration of 1,3,5-pyromellitic aldehyde in the mixture A was 1~3 mg / mL. 2.2 Add the S1-treated 2,5-diamino-1,4-benzenedithiophenol dihydrochloride to deionized water and stir to mix evenly to obtain mixture B; wherein, in mixture B, the mass concentration of 2,5-diamino-1,4-benzenedithiophenol dihydrochloride is 3~7 mg / mL. 2.3 Mixing solution A and mixture B in a volume ratio of 1:1 to obtain mixture C; adding glacial acetic acid as a catalyst to mixture C, stirring, allowing the reaction to stand, centrifuging to obtain the product; drying the obtained product in a vacuum environment at a temperature of 60~100 ℃ to obtain COF polar powder; S3. Preparation of lithium salt / polymer slurry: The S1-treated lithium salt was added to the mixed solvent and stirred in a water bath at 40~80℃ until it was fully dissolved and evenly dispersed; then the S1-treated polyvinylidene fluoride-chlorotrifluoroethylene polymer was added and stirred to form an ionic sol. S4. Preparation of COF / lithium salt / polymer slurry: Weigh the COF polar powder obtained in S2 and add it to the ionic sol obtained in S3 in 3 batches. The stirring time after each batch of COF polar powder is added is 30 min. After the last addition of COF, stir for 2~4 h to obtain COF / lithium salt / polymer mixed slurry. S5. Preparation of anion-coupled eutectic gel composite electrolyte: The mixed slurry obtained from S4 was coated onto a substrate using a spin coating method and allowed to stand to obtain a wet gel film. Then, it was vacuum dried at 60℃~100℃ to obtain anion-coupled eutectic gel composite electrolyte membrane.

2. A method for preparing anion-coupled eutectic gel composite electrolyte, characterized in that, Includes the following steps: S1. Raw material pretreatment: Polyvinylidene fluoride-trifluorochloroethylene, 1,3,5-pyromellitic methyl aldehyde ligand, 2,5-diamino-1,4-benzenedithiophenol dihydrochloride ligand and lithium salt were vacuum dried at 40℃~100℃ for 0.5h~4h. S2. Preparation of COF polar powder: 2.1 The 1,3,5-pyromellitic aldehyde treated with S1 was added to a mixed solvent of acetonitrile and water and ultrasonically mixed to obtain a mixture A; wherein the mass concentration of 1,3,5-pyromellitic aldehyde in the mixture A was 1~3 mg / mL. 2.2 Add the S1-treated 2,5-diamino-1,4-benzenedithiophenol dihydrochloride to deionized water and stir to mix evenly to obtain mixture B; wherein, in mixture B, the mass concentration of 2,5-diamino-1,4-benzenedithiophenol dihydrochloride is 3~7 mg / mL. 2.3 Mixing solution A and mixture B in a volume ratio of 1:1 to obtain mixture C; adding glacial acetic acid as a catalyst to mixture C, stirring, allowing the reaction to stand, centrifuging to obtain the product; drying the obtained product in a vacuum environment at a temperature of 60~100 ℃ to obtain COF polar powder; S3. Preparation of lithium salt / polymer slurry: The S1-treated lithium salt was added to the mixed solvent and stirred in a water bath at 40~80℃ until it was fully dissolved and evenly dispersed; then the S1-treated polyvinylidene fluoride-chlorotrifluoroethylene polymer was added and stirred to form an ionic sol. S4. Preparation of COF / lithium salt / polymer slurry: Weigh the COF polar powder obtained in S2 and add it to the ionic sol obtained in S3 in 3 batches. The stirring time after each batch of COF polar powder is added is 30 min. After the last addition of COF, stir for 2~4 h to obtain COF / lithium salt / polymer mixed slurry. S5. Preparation of anion-coupled eutectic gel composite electrolyte: The mixed slurry obtained from S4 was coated onto a substrate using a spin coating method and allowed to stand to obtain a wet gel film. Then, it was vacuum dried at 60℃~100℃ to obtain anion-coupled eutectic gel composite electrolyte membrane.

3. The method for preparing the anion-coupled eutectic gel composite electrolyte according to claim 2, characterized in that, In step S1, the proportion of trifluorochloroethylene branches in polyvinylidene fluoride-chlorotrifluoroethylene is 6%~25%.

4. The method for preparing the anion-coupled eutectic gel composite electrolyte according to claim 2, characterized in that, The lithium salt in step S1 is at least one of lithium perchlorate, lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(catechol)borate, and lithium (fluorosulfonyl)trifluoromethylsulfonylimide.

5. The method for preparing the anion-coupled eutectic gel composite electrolyte according to claim 2, characterized in that, In step 2.1, the volume ratio of acetonitrile to water in the mixed solvent is 1:(0.2~0.6); in step 2.3, the volume ratio of glacial acetic acid added to mixed solution C is (1~4):

20.

6. The method for preparing the anion-coupled eutectic gel composite electrolyte according to claim 2, characterized in that, The mixed solvent in step S3 is one or a mixture of two or more of N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, dimethyl sulfoxide, and acetonitrile.

7. The method for preparing the anion-coupled eutectic gel composite electrolyte according to claim 2, characterized in that, In the ionic sol prepared in step S3, the polymer accounts for 5~20 wt% of the total mass.

8. The method for preparing the anion-coupled eutectic gel composite electrolyte according to claim 2, characterized in that, In step S3, the mass ratio of the added polymer to the lithium salt is (2~4):

1.

9. The method for preparing the anion-coupled eutectic gel composite electrolyte according to claim 2, characterized in that, In step S4, the mass ratio of COF polar powder to polymer is 1:(8~15).

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