Composite Solid Electrolyte for Low-Temperature Lithium Iron Phosphate Batteries and Its Preparation Method

Abstract

The present invention discloses a composite solid electrolyte applicable to low-temperature lithium iron phosphate batteries, which comprises 30wt% - 60wt% of NH2-MIL-125(Ti) and 40wt% - 70% of sPIM-1. Its preparation method includes the following steps: Step 1: Prepare NH2-MIL-125(Ti); Step 2: Prepare PIM-1; Step 3: Carry out sulfonation and sulfonyl chloride reaction on PIM-1; Step 4: Prepare the NH2-MIL-125(Ti) / PIM-1 composite solid electrolyte. The present invention can solve the problem of performance degradation of lithium iron phosphate batteries at low temperatures.

Description

Technical Field

[0001] The present invention relates to the technical field of new materials, and specifically refers to a composite solid electrolyte suitable for low-temperature lithium iron phosphate batteries and a preparation method thereof. Background Art

[0002] A lithium iron phosphate battery refers to a lithium-ion battery with lithium iron phosphate as the positive electrode and graphite as the negative electrode. Compared with other lithium-ion batteries, it has great advantages in safety performance and cycle life. The 1C charge-discharge cycle life can reach 2000 times, it will not explode when punctured, and it is not easy to catch fire and explode during overcharging. Thanks to these advantages of lithium iron phosphate batteries, lithium iron phosphate batteries are being used in more and more large-scale applications. However, the use of lithium iron phosphate batteries is restricted in low-temperature environments. In addition to the serious decline in discharge capacity, the battery cannot be charged at low temperatures. During low-temperature charging, the insertion and lithium plating reactions of lithium ions on the graphite electrode of the battery exist simultaneously and compete with each other. At low temperatures, the diffusion of lithium ions in graphite is inhibited, and the conductivity of the electrolyte decreases, resulting in a decrease in the insertion rate and making the lithium plating reaction more likely to occur on the graphite surface.

[0003] Using a solid electrolyte instead of a liquid electrolyte is considered the key to solving the performance degradation of lithium batteries at low temperatures. Solid electrolytes have the following advantages: First, the solid electrolyte has a high Li + transference number, and the concentration polarization problem in conventional liquid electrolytes can be solved in single-ion conductor solid electrolytes; second, the solid electrolyte has excellent electrochemical stability and heat resistance, which means a wider working potential window, a more stable interface with the electrode, and a wider working temperature range. Composite solid electrolytes are considered a feasible method for preparing high-performance electrolytes, which combine the advantages of polymers, inorganics, and even liquid electrolytes. These composite solid electrolytes are prepared by mixing at least two or more substance components together, such as composites of two ion conductors and a structural matrix with ion conductor substances. The former can combine polymers and inorganic electrolytes, while the latter usually consists of a liquid electrolyte wrapped in a solid porous matrix. However, existing composite solid electrolytes often use the method of physical doping, where inorganic electrolytes are simply blended and doped into the polymer matrix, resulting in limited doping amounts, poor compatibility between the inorganic electrolyte and the polymer, and easy generation of interfacial voids. Summary of the Invention

[0004] The purpose of the present invention is to provide a composite solid electrolyte suitable for low-temperature lithium iron phosphate batteries and a preparation method thereof, which can solve the problem of performance degradation of lithium iron phosphate batteries at low temperatures.

[0005] To achieve this purpose, the composite solid electrolyte designed by the present invention for low-temperature lithium iron phosphate batteries is characterized in that it comprises 30wt% - 60wt% of NH2-MIL-125(Ti) and 40wt% - 70% of sPIM-1. NH2-MIL-125(Ti) can improve the promotion effect of the composite solid electrolyte on lithium ion conductivity. NH2-MIL-125(Ti) can chemically crosslink with the modified sPIM-1, making the compatibility between NH2-MIL-125(Ti) and sPIM-1 better and increasing the mass fraction of NH2-MIL-125(Ti) in the composite solid electrolyte.

[0006] A preparation method of the above composite solid electrolyte comprises the following steps:

[0007] Step 1: Preparation of NH2-MIL-125(Ti). Add the organic ligand NH2-BDC (2-amino-1,4-benzenedicarboxylic acid) into the mixed solvent of MeOH (methanol) and DMF (N,N-dimethylformamide), stir to completely dissolve NH2-BDC, then add glacial acetic acid, and then add tetra-isopropyl titanate as the metal salt while maintaining the stirring state. Pour the reaction solution after completely dissolving tetra-isopropyl titanate into a polytetrafluoroethylene reaction kettle, place it in an oven for heating, and then cool it to room temperature. First, perform centrifugal separation on the reaction solution to obtain a solid, then further wash the obtained solid with DMF, and then wash it with absolute ethanol. Finally, place the obtained solid in a vacuum oven for drying to obtain the NH2-MIL-125(Ti) solid for use.

[0008] Step 2: Preparation of PIM-1. PIM-1 is composed of two monomers linked together, and its structural unit is as Figure 1 shown. During synthesis, the purified 2,3,5,6-tetrafluoroterephthalonitrile (TFTPN) and 5,5’,6,6’-tetrahydroxy-3,3,3’,3’-tetramethyl-1,1’-spirobiindane (TTSBI) are each dissolved in anhydrous DMF. After TTSBI and TFTPN are each completely dissolved, mix them together while maintaining the stirring state, add K2CO3 as the reaction catalyst, and carry out a reflux reaction. The whole reaction process is carried out under an inert gas atmosphere. After the reaction is completed and naturally cooled to room temperature, pour it into methanol to precipitate a yellow solid. Filter the collected yellow solid and dissolve it in CHCl3. Pour the CHCl3 solution containing the yellow solid into methanol to precipitate the yellow solid again. Finally, dry the precipitated product to obtain PIM-1.

[0009] Step 3: Sulfonation and sulfonyl chlorination reaction of PIM-1. PIM-1 was sulfonated. The obtained sulfonated PIM-1 was dissolved in DMF solvent and stirred to dissolve it completely to obtain a sulfonated PIM-1 solution. A certain amount of thionyl chloride was added to DMF for dilution, and then the diluted thionyl chloride was added dropwise to the sulfonated PIM-1 solution. The mixture was stirred at room temperature to obtain a yellow suspension, filtered, washed with methanol, and then washed with deionized water until neutral. It was dried in a vacuum oven at a working temperature of 393K to obtain a yellow solid sulfonyl chloride sPIM-1;

[0010] Step 4: Preparation of NH2-MIL-125(Ti) / PIM-1 composite solid electrolyte. The solid sulfonyl chloride sPIM-1 was dissolved in NMP (N-methylpyrrolidone) to obtain a yellow transparent solution. Under stirring, different mass fractions of NH2-MIL-125(Ti) and NaOH solution were added respectively and mixed well. The mixture was stirred at room temperature to obtain a pale yellow transparent film solution. The transparent film solution was evenly coated on the surface of a clean glass plate with a scraper. After standing for a period of time, after the solvent evaporated, the transparent film was peeled off with methanol, placed in a watch glass, soaked in a methanol environment and then taken out and dried in a vacuum oven at 363K. The finally obtained film was the composite solid electrolyte, which was stored in a dry environment for testing and characterization.

[0011] In the above technical solution, the specific process of sulfonating PIM-1 is as follows: First, 1.9 - 2.1 g of PIM-1 was dissolved in 99 - 101 ml of concentrated sulfuric acid and stirred to dissolve it completely. A certain amount of chlorosulfonic acid (volume ratio between 1:1 and 1:3) was added to 49 - 51 ml of concentrated sulfuric acid for dilution. The concentrated sulfuric acid diluted with chlorosulfonic acid was slowly added to the 99 - 101 ml concentrated sulfuric acid solution of PIM-1. Under continuous stirring, the reaction was carried out at room temperature for 11 - 13 h for a preset time and then transferred to a round-bottom flask with a working temperature of 363K for a reflux reaction for 2 - 4 h. The whole reaction process was carried out under a N2 atmosphere to obtain sulfonated PIM-1, and the sulfonated PIM-1 was washed with anhydrous methanol and deionized water. By modifying PIM-1 to obtain sPIM-1, a chemical cross-linking reaction between sPIM-1 and NH2-MIL-125(Ti) was achieved;

[0012] In step 1 of the above technical solution, 5-7 mmol of the organic ligand NH2-BDC is added to a mixed solvent of 24-26 ml of MeOH and 24-26 ml of DMF, stirred until completely dissolved, then 9-11 ml of glacial acetic acid is added, and then 2-4 mmol of the metal salt titanium tetraisopropoxide is added while maintaining the stirring state. The completely dissolved reaction solution is poured into a polytetrafluoroethylene reaction kettle, placed in an oven for heating, heated at a heating rate of 0.9-1.1 K per minute to 432-434 K, and kept warm for 47-49 h. Then it is cooled to room temperature at a cooling rate of 1.9-2.1 K per minute. The reaction kettle is taken out, the reaction solution is first centrifuged to obtain a pale yellow solid, and then the obtained solid is further washed three times with DMF and then three times with absolute ethanol. Finally, the obtained solid is placed in a vacuum oven at 393 K and dried for 11-13 h to obtain the NH2-MIL-125(Ti) solid, which is stored in a dry environment for use. NH2-MIL-125(Ti) with relatively high purity is obtained.

[0013] In step 2 of the above technical solution, 10.212 g (30 mmol) of TTSBI and 6.002 g (30 mmol) of TFTPN after purification treatment are each dissolved in 99-101 ml of anhydrous DMF. After TTSBI and TFTPN are each completely dissolved, they are mixed together while maintaining the stirring state, and 8.292 g (60 mmol) of K2CO3 is added as a reaction catalyst. A reflux reaction is carried out at 332-334 K for 47-49 h. The whole reaction process is carried out in an inert gas atmosphere, and the inert gas atmosphere is argon or nitrogen. The inert gas plays a role in protecting the reaction gas, isolating oxygen and moisture. After the reaction is completed and naturally cooled to room temperature, it is poured into methanol to precipitate a yellow solid. The collected yellow solid is dissolved in CHCl3, and the CHCl3 solution containing the yellow solid is poured into methanol to precipitate. Finally, the precipitated product is placed in a vacuum oven at 393 K and dried for 23-25 h to obtain PIM-1. PIM-1 with a relatively high yield is obtained.

[0014] In step 3 of the above technical solution, PIM-1 is sulfonated. 0.1-0.3 g of the sulfonated PIM-1 obtained after sulfonation treatment is dissolved in 4-6 ml of DMF solvent, stirred until fully dissolved, 1-3 ml of thionyl chloride is added to DMF for dilution, and then added dropwise to the sulfonated PIM-1 solution. Stirring reaction is carried out at room temperature for 23-25 h to obtain a yellow suspension. It is filtered, washed with methanol, and then washed with deionized water until neutral, and then placed in a vacuum oven at 393 K to dry to obtain a yellow solid sulfonyl chloride sPIM-1.

[0015] In step 4 of the above technical solution, 0.1-0.3 g of solid sulfonyl chloride sPIM-1 is dissolved in NMP (N-methylpyrrolidone) to obtain a yellow transparent solution. Under stirring, NH2-MIL-125(Ti) with a mass fraction of 10wt%, 20wt%, 30wt%, 40wt% and a NaOH solution with a concentration of 0.09-0.11 mol·L-1 are added respectively, and ultrasonic treatment is carried out for 40 min to fully mix them. The reaction is carried out for 71-73 h under stirring at room temperature to obtain a light yellow transparent film solution. The transparent film solution is evenly coated on the surface of a clean glass plate with a scraper. After standing for a period of time for the solvent to volatilize, the transparent film is peeled off with methanol, placed in a watch glass, soaked in a methanol environment for 23-25 h, and then taken out and dried in a vacuum oven at 363K. The finally obtained film is a composite solid electrolyte, which is stored in a dry environment for testing and characterization.

[0016] In the above technical solution, the concentration of NH2-BDC dissolved in methanol is 0.24 mmol / ml, and the concentration of the titanium metal salt is 0.12 mmol / ml. NH2-MIL-101(Ti) with smaller particle size is obtained.

[0017] In step 3 of the above technical solution, the concentration of PIM-1 dissolved in concentrated sulfuric acid is 20 g / L, the reaction temperature is 363K, the reaction time is 3 h, the concentration of sulfonated PIM-1 dissolved in DMF is 40 g / L, and the number of methanol washing times is 3-5 times.

[0018] The beneficial effects of the present invention:

[0019] The present invention provides a novel method for preparing a composite solid electrolyte: by modifying a polymer material and then linking an MOF material to the polymer material in a chemical cross-linking form, a composite solid electrolyte bonded in a chemical bond form is prepared.

[0020] (1) Utilizing the characteristics that the surface of the MOF material has abundant groups and the polymer material is easy to modify, a composite solid electrolyte cross-linked in a chemical bond form is prepared, greatly improving the compatibility between the MOF material and the polymer, and enabling the preparation of a composite solid electrolyte with a higher loading amount of filler particles;

[0021] (2) Benefiting from the fact that NH2-MIL-125(Ti) has a relatively large pore size, it can provide a fast channel for the diffusion of lithium ions when loaded in a polymer matrix, thereby improving the lithium ion conductivity;

[0022] (3) Since there are a large number of polar groups (-OH and -NH2) on the surface of the selected NH2-MIL-125(Ti) material, NH2-MIL-125(Ti) can preferentially adsorb lithium-ion molecules into its pores, resulting in a higher diffusion rate of lithium ions in the composite solid electrolyte. Description of the Drawings

[0023] Figure 1 It is a schematic diagram for the preparation of PIM-1.

[0024] Figure 2 It is the PXRD pattern of NH2-MIL-125(Ti) powder and NH2-MIL-123(Ti) / sPIM-1 composite solid electrolyte. The PXRD characterization results of NH2-MIL-125(Ti) particles and NH2-MIL-123(Ti) / sPIM-1 composite solid electrolyte are as Figure 2 shown. Obvious characteristic peaks of NH2-MIL-125(Ti) appear in the NH2-MIL-123(Ti) / sPIM-1 composite solid electrolyte, indicating that during the preparation process of the composite solid electrolyte, NH2-MIL-123(Ti) was successfully introduced into sPIM-1 and maintained the integrity of its own structure.

[0025] Figure 3 It is the FTTR pattern of PIM-1 film and 5wt% NH2-MIL-125(Ti) / sPIM-1 composite solid electrolyte. In order to verify that NH2-MIL-125(Ti) and sPIM-1 are combined in the form of chemical crosslinking, FTTR characterizations were performed on NH2-MIL-125(Ti) and 5wt% NH2-MIL-125(Ti) / sPIM-1-Cl composite solid electrolyte membranes respectively, and the results are as Figure 3 shown. When NH2-MIL-125(Ti) undergoes the Hinsberg reaction with the modified sPIM-1, the absorption peak (1374 cm -1 ) belonging to -SO2Cl in sPIM-1 completely disappears. At the same time, on the peak spectrum of the NH2-MIL-125(Ti) / sPIM-1 composite solid electrolyte, a new characteristic peak belonging to -SO2NH- appears at the position of 1174 cm -1 . This proves that NH2-MIL-125(Ti) has been linked to the molecular chain of sPIM-1 through chemical bonds.

[0026] Figure 4Cross-sectional views of the NH2-MIL-125(Ti) / sPIM-1 composite solid electrolyte: (a) 10 wt%, (b) 20 wt%. To facilitate further observation of the crosslinking of NH2-MIL-125(Ti) filler particles with sPIM and the distribution of NH2-MIL-125(Ti) filler particles in the sPIM-1 matrix, cross-sectional SEM characterizations were performed on the composite solid electrolytes with different loadings, and the results are as Figure 4 shown. The thickness of the prepared composite film is approximately 50 μm. Since NH2-MIL-125(Ti) is crosslinked and loaded on the sPIM-1 molecular chain, the NH2-MIL-125(Ti) particles are uniformly dispersed in the sPIM-1 matrix.

[0027] Figure 5 Comparison of discharge retention rates at -40 °C between a low-temperature battery based on the NH2-MIL-125(Ti) / sPIM-1 composite solid electrolyte and a conventional battery with a capacity of 16 Ah. When using commercial LFP, in a low-temperature environment, the ion diffusion rate in the commercial lithium iron phosphate electrolyte decreases severely, resulting in the attenuation of the cycling performance of lithium-ion batteries. As Figure 5 shown, the low-temperature performance of the lithium iron phosphate battery prepared based on the NH2-MIL-125(Ti) / sPIM-1 composite solid electrolyte is better than that of the commercial LFP battery. From the influencing factors of lithium-ion batteries, this is mainly because the NH2-MIL-125(Ti) / sPIM-1 composite solid electrolyte prepared in this work has a higher lithium-ion conductivity under low-temperature conditions during the charge and discharge process of lithium-ion batteries. Specific embodiments

[0028] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0029] Example 1

[0030] A composite solid electrolyte applicable to low-temperature lithium iron phosphate batteries, comprising 40 wt% NH2-MIL-125(Ti) and 60 wt% sPIM-1.

[0031] The preparation method of the composite solid electrolyte includes the following steps:

[0032] Step 1: Add 6 mmol of the organic ligand NH2-BDC into a mixed solvent of 25 ml of MeOH and 25 ml of DMF, stir to completely dissolve it, then add 10 ml of glacial acetic acid, and then add 3 mmol of the metal salt tetra-isopropyl titanate while maintaining the stirring state. Pour the completely dissolved reaction solution into a polytetrafluoroethylene reaction kettle, place it in an oven for heating, increase the temperature at a rate of 1 K per minute to 433 K, and keep it warm for 48 h. Then cool it to room temperature at a rate of 2 K per minute. Take out the reaction kettle, first centrifuge the reaction solution to obtain a pale yellow solid, then further wash the obtained solid three times with DMF, and then wash it three times with absolute ethanol. Finally, place the obtained solid in a vacuum oven at 393 K for drying for 12 h to obtain the NH2-MIL-125(Ti) solid, which is stored in a dry environment for use;

[0033] Step 2: Dissolve 10.212 g, 30 mmol of TTSBI and 6.002 g, 30 mmol of TFTPN respectively in 100 ml of anhydrous DMF after purification treatment. After TTSBI and TFTPN are completely dissolved respectively, mix them together while maintaining the stirring state, and add 8.292 g, 60 mmol of K2CO3 as the catalyst for the reaction. Ensure a reflux reaction at 333 K for 48 h. The whole reaction process is carried out under an inert gas atmosphere, and the inert gas atmosphere is argon or nitrogen. The inert gas plays a role in protecting the reaction gas, isolating oxygen and moisture. After the reaction is completed and naturally cooled to room temperature, pour it into methanol to precipitate a yellow solid. Filter and dissolve the collected yellow solid in CHCl3. Pour the CHCl3 containing the dissolved yellow solid into methanol to precipitate. Finally, place the precipitated product in a vacuum oven at 393 K for drying for 24 h to obtain PIM-1;

[0034] Step 3: Sulfonate PIM-1. Take out 0.2 g of the sulfonated PIM-1 obtained after sulfonation treatment and dissolve it in 5 ml of DMF solvent, stir to fully dissolve it to obtain a sulfonated PIM-1 solution. Take 2 ml of thionyl chloride and add it to DMF for dilution, and then gradually add the diluted thionyl chloride dropwise to the sulfonated PIM-1 solution. Stir and react at room temperature for 24 h to obtain a yellow suspension. Filter, wash with methanol, and then wash with deionized water until neutral. Place it in a vacuum oven at 393 K and dry to obtain a yellow solid sulfonyl chloride sPIM-1.

[0035] Step 4: Take 0.2 g of solid sulfonyl chloride sPIM-1 and dissolve it in NMP (N-methylpyrrolidone) to obtain a yellow transparent solution. Under stirring, add NH2-MIL-125(Ti) with mass fractions of 10 wt%, 20 wt%, 30 wt%, 40 wt% and 0.1 mol·L-1 NaOH solution respectively, and ultrasonicate for 40 min to make them fully mixed. Keep stirring at room temperature for 72 h to obtain a pale yellow transparent film solution. Use a spatula to evenly scrape the transparent film solution on the surface of a clean glass plate. After standing for a period of time for the solvent to evaporate, peel off the transparent film with methanol, put it into a petri dish, soak it in methanol environment for 24 h, then take it out and dry it in a vacuum oven at 363 K. The finally obtained film is a composite solid electrolyte, which is stored in a dry environment for testing and characterization.

[0036] The invention discloses a preparation method of a composite solid electrolyte for a low-temperature lithium iron phosphate battery, which + uses NH2-MIL-125(Ti) with selective adsorption effect on Li and a modified polymer of intrinsic microporosity (PIM-1) to prepare a new composite solid electrolyte combined in the form of chemical bonds through a chemical cross-linking method. Since PIM-1 and NH2-MIL-125(Ti) cannot directly undergo a chemical reaction, PIM-1 is first modified. A -SO2Cl functional group is added to the benzene ring structure of PIM-1 through sulfonation and sulfonyl chlorination to obtain sPIM-1. The -NH2 in NH2-MIL-125(Ti) can undergo a Hinsberg reaction with -SO2Cl, thus generating chemical cross-linking. On the one hand, there are a large number of polar functional groups (-OH and -NH2) in the structure of NH2-MIL-125(Ti), which can preferentially adsorb Li + . The patent is of great significance for solving the problem of capacity decay of lithium iron phosphate batteries at low temperatures, and will promote the use range of lithium iron phosphate batteries at low temperatures.

[0037] The present invention will +A novel composite solid electrolyte bonded by chemical bonds was prepared by chemically crosslinking NH2-MIL-125(Ti) with selective adsorption and a polymer of intrinsic microporosity (PIM-1). Since PIM-1 and NH2-MIL-125(Ti) cannot directly undergo a chemical reaction, PIM-1 was first modified. A -SO2Cl functional group was added to the benzene ring structure of PIM-1 through sulfonation and sulfonyl chlorination. The -NH2 in NH2-MIL-125(Ti) can undergo the Hinsberg reaction with -SO2Cl, resulting in chemical crosslinking. On the one hand, there are a large number of polar functional groups (-OH and -NH2) in the NH2-MIL-125(Ti) structure, which can preferentially adsorb Li + .

[0038] The content not detailed in this specification belongs to the prior art well-known to those skilled in the art.

Claims

1. A composite solid electrolyte applicable to low-temperature lithium iron phosphate batteries, characterized in that, It comprises 30 wt% to 60 wt% of NH2-MIL-125(Ti) and 40 wt% to 70 wt% of sPIM-1, and NH2-MIL-125(Ti) is chemically bonded to the molecular chain of sPIM-1.

2. A preparation method of a composite solid electrolyte applicable to a low-temperature lithium iron phosphate battery, characterized in that, It comprises the following steps: Step 1: Add the organic ligand NH2-BDC into the mixed solvent of MeOH and DMF, stir to completely dissolve it, then add glacial acetic acid, and then add tetra-isopropyl titanate as the metal salt and keep stirring. Pour the completely dissolved reaction solution into a polytetrafluoroethylene reaction kettle, place it in an oven for heating, and then cool it to room temperature. First, centrifuge the reaction solution to obtain a solid, then further wash the obtained solid with DMF, then wash it with absolute ethanol. Finally, dry the obtained solid to obtain the NH2-MIL-125(Ti) solid for use; Step 2: Dissolve the purified TTSBI and TFTPN in anhydrous DMF respectively. After TTSBI and TFTPN are completely dissolved respectively, mix them together and keep stirring. Add K2CO3 as the catalyst for the reaction, and carry out a reflux reaction. The whole reaction process is carried out under an inert gas atmosphere. After the reaction is completed and naturally cooled to room temperature, pour it into methanol to precipitate a solid. Filter and dissolve the collected solid in CHCl3. Pour the CHCl3 dissolved with this solid into methanol to precipitate. Finally, dry the precipitated product to obtain PIM-1; Step 3: Sulfonate PIM-1. Dissolve the obtained sulfonated PIM-1 in a DMF solvent to obtain a sulfonated PIM-1 solution. Take a certain amount of thionyl chloride and add it to DMF for dilution. Then add the diluted thionyl chloride dropwise to the sulfonated PIM-1 solution. Stir and react at room temperature to obtain a suspension. Filter, wash with methanol, and then wash with deionized water until neutral. Dry to obtain the solid sulfonyl chloride sPIM-1; Step 4: Take the solid sulfonyl chloride sPIM-1 and dissolve it in NMP to obtain a transparent solution. Under stirring, add NH2-MIL-125(Ti) and NaOH solution with different mass fractions respectively, mix well, and keep stirring at room temperature to react to obtain a transparent film solution. Spread the transparent film solution on the surface of a glass plate. After the solvent volatilizes, peel off the transparent film with methanol, put it into a petri dish, soak it in a methanol environment and then take it out and dry it. The finally obtained film is a composite solid electrolyte.

3. The preparation method of the composite solid electrolyte according to claim 2, wherein: The specific process of sulfonating PIM-1 is as follows: First, dissolve PIM-1 in concentrated sulfuric acid, add chlorosulfonic acid to the concentrated sulfuric acid for dilution, add the concentrated sulfuric acid diluted with chlorosulfonic acid to the concentrated sulfuric acid solution of PIM-1, react at room temperature for a preset time and then transfer it to a flask for reflux reaction. The whole reaction process is carried out under an N2 atmosphere to obtain sulfonated PIM-1, and wash the sulfonated PIM-1 with absolute methanol and deionized water.

4. The preparation method of the composite solid electrolyte according to claim 2, wherein: In the step 1, 5 to 7 mmol of the organic ligand NH2-BDC is added to a mixed solvent of 24 to 26 ml of MeOH and 24 to 26 ml of DMF, stirred to completely dissolve it, then 9 to 11 ml of glacial acetic acid is added, and then 2 to 4 mmol of the metal salt tetraisopropyl titanate is added and kept stirring, the completely dissolved reaction solution is poured into a polytetrafluoroethylene reactor, placed in an oven for heating, and the temperature is increased to 432 to 434 K at a rate of 0.9 to 1.1 K per minute, and kept warm for 47 to 49 hours, and then cooled to room temperature at a rate of 1.9 to 2.1 K per minute, the reaction solution is first centrifuged to obtain a solid, and then the obtained solid is further washed with DMF, and then washed with anhydrous ethanol, and finally, the obtained solid is dried to obtain NH2-MIL-125 (Ti) solid for standby use.

5. The preparation method of the composite solid electrolyte according to claim 2, wherein: In the step 2, 10.212 g, 30 mmol of TTSBI and 6.002 g, 30 mmol of TFTPN after purification are each dissolved in 99-101 ml of anhydrous DMF. After TTSBI and TFTPN are completely dissolved, they are mixed together and stirred, and 8.292 g, 60 mmol of K2CO3 is added as a catalyst for the reaction to ensure that the reflux reaction is carried out at 332-334 K for 47-49 hours. The entire reaction is carried out under an inert gas atmosphere. After the reaction is completed and naturally cooled to room temperature, it is poured into methanol to precipitate to obtain a yellow solid. The collected yellow solid is filtered and dissolved in CHCl3, and the CHCl3 dissolved with the yellow solid is poured into methanol for precipitation. Finally, the precipitated product is placed in a vacuum oven and dried to obtain PIM-1.

6. The preparation method of the composite solid electrolyte according to claim 2, wherein: In the step 3, PIM-1 is subjected to sulfonation treatment, 0.1-0.3 g of the sulfonated PIM-1 obtained by the sulfonation treatment is taken out and dissolved in 4-6 ml of DMF solvent, stirred to fully dissolve, 1-3 ml of dichlorothionyl is added to DMF for dilution, and then added dropwise to the sulfonated PIM-1 solution, stirred and reacted at room temperature for 23-25 hours to obtain a yellow suspension, filtered, washed with methanol, and then washed with deionized water until neutral, placed in a 393K vacuum oven, and dried to obtain a yellow solid sulfonyl chloride sPIM-1.

7. The preparation method of the composite solid electrolyte according to claim 2, characterized in that: In the step 4, 0.1-0.3 g of solid sulfonyl chloride sPIM-1 is dissolved in NMP to obtain a transparent solution, and 10 wt%, 20 wt%, 30 wt%, and 40 wt% of NH2-MIL-125 (Ti) and 0.09-0.11 mol·L-1 of NaOH solution are added respectively under stirring, and the mixture is fully mixed. The mixture is stirred at room temperature for 71-73 hours to obtain a transparent film solution, and the transparent film solution is scraped on the surface of a glass plate. After the solvent evaporates, the transparent film is peeled off with methanol, placed in a watch glass, soaked in a methanol environment for 23-25 hours, and then taken out and dried. The final film is a composite solid electrolyte.

8. The preparation method of the composite solid electrolyte according to claim 2, wherein: The concentration of NH2-BDC dissolved in methanol is 0.24 mmol / ml, and the concentration of the titanium metal salt is 0.12 mmol / ml.

9. The preparation method of the composite solid electrolyte according to claim 2, characterized in that: In the step 3, the concentration of PIM-1 dissolved in concentrated sulfuric acid is 20 g / L, the reaction temperature is 363 K, the reaction time is 3 h, the concentration of sulfonated PIM-1 dissolved in DMF is 40 g / L, and the number of times of methanol washing is 3 to 5 times.

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