Environment-friendly eutectic cellulose quasi-solid electrolyte capable of being thermally polymerized in situ and preparation method of environment-friendly eutectic cellulose quasi-solid electrolyte

Abstract

The invention belongs to the technical field of material synthesis, and discloses an environment-friendly eutectic cellulose quasi-solid electrolyte capable of in-situ thermal polymerization and a preparation method thereof, and the method comprises the following steps: mixing a metal sodium salt and 1, 2-dimethylimidazole according to different molar ratios to form a deep eutectic electrolyte; carrying out addition reaction in an organic solvent system to prepare a double-bond functional modified cellulose derivative; the preparation method comprises the following steps: dissolving a double-bond modified cellulose derivative in a deep eutectic electrolyte to prepare a precursor solution, and finally constructing the quasi-solid electrolyte in situ in the battery in a thermal polymerization manner. The environment-friendly eutectic cellulose quasi-solid electrolyte provided by the invention provides a new thought for solving the potential safety hazard of a new energy automobile.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of material synthesis, and relates to an environmentally-friendly eutectic cellulose quasi-solid electrolyte capable of in-situ thermal polymerization and a preparation method thereof. BACKGROUND

[0002] Traditional organic electrolyte has the characteristics of being volatile, flammable and easy to leak, so that new energy vehicles have safety hazards such as further combustion or explosion caused by battery short circuit under the condition of vehicle accident or severe impact. At present, the academic and enterprise circles have proposed the solution strategy of solid electrolyte, but the solid electrolyte has a serious interface contact problem, and the development of quasi-solid electrolyte becomes a practical strategy, but the quasi-solid electrolyte is mainly composed of organic solvent and polymer chain segment, and faces the problems of flammability and environmental pollution in the post-processing process. SUMMARY

[0003] The purpose is to overcome the deficiencies in the prior art, solve the problems of flammability and environmental pollution of the quasi-solid electrolyte, and provide an environmentally-friendly eutectic cellulose quasi-solid electrolyte capable of in-situ thermal polymerization and a preparation method thereof.

[0004] The technical scheme adopted by the present application is as follows: According to a first aspect of the present application, a preparation method of a eutectic cellulose quasi-solid electrolyte is provided, comprising: Step (a), mixing a metal sodium salt and 1, 2-dimethylimidazole under heating conditions to form a deep eutectic electrolyte; Step (b), dissolving a cellulose derivative in an organic solvent, adding a double bond modified monomer under the conditions of a catalyst and argon, and preparing a double bond modified cellulose derivative through an addition reaction; Step (c), dissolving the double bond modified cellulose derivative in the deep eutectic electrolyte, and adding a thermal initiator and a crosslinking agent to obtain a precursor solution; Step (d), injecting the precursor solution into the inside of a battery, and forming a quasi-solid electrolyte through heat treatment.

[0005] In some embodiments, in step (a), the metal sodium salt is selected from at least one of sodium perchlorate, sodium trifluoromethane sulfonate and sodium difluoro oxalate borate.

[0006] In some embodiments, in step (a), the molar ratio of 1, 2-dimethylimidazole to sodium in the metal sodium salt is 4-15; preferably 8-10; In some embodiments, in step (a), the heating temperature is 60-100°C.

[0007] In some embodiments, in step (b), the cellulose derivative is selected from at least one of cellulose acetate, ethyl cellulose and cyanoethyl cellulose; In some embodiments, the concentration of the cellulose derivative solution is 5-10 wt%; In some embodiments, in step (b), the organic solvent is selected from at least one of N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), N-methyl pyrrolidone (NMP), dimethylacetamide (DMAc); Correspondingly, in step (b), the cellulose derivative is dissolved in the organic solvent at 40-80 °C.

[0008] In some embodiments, in step (b), the catalyst is dibutyl tin dilaurate or tetrabutyl tin; In some embodiments, in step (b), the double bond modified monomer is isocyanatoethyl methacrylate; In some embodiments, in step (b), the reaction temperature of the addition reaction is 25-40 °C.

[0009] In some embodiments, in step (b), after the double bond modified cellulose derivative is prepared by the reaction, the method further comprises: collecting the product by a precipitation method, and freeze-drying to obtain the double bond modified cellulose derivative.

[0010] In some embodiments, in step (c), the concentration of the double bond modified cellulose derivative in the precursor solution is 1-10 wt%, preferably 2.5-5 wt%; In some embodiments, in step (c), the dissolution temperature of the double bond modified cellulose derivative dissolved in the deep eutectic solvent is 25-60 °C, preferably 50 °C; In some embodiments, in step (c), the thermal initiator is selected from at least one of azobisisobutyronitrile (AIBN), azobisisoheptyl nitrile (ABVN), and benzoyl peroxide (BPO); And / or, in step (c), the crosslinking agent is selected from at least one of methylene bisacrylamide, polyethylene glycol diacrylate, and pentaerythritol tetraacrylate.

[0011] In some embodiments, in step (d), the heat treatment temperature is 60-120 °C, preferably 70-90 °C; In some embodiments, in step (d), the heat treatment time is 12-36 hours.

[0012] According to a second aspect of the present application, a eutectic cellulose quasi-solid-state electrolyte is provided, which is prepared by the preparation method.

[0013] According to a third aspect of the present application, the eutectic cellulose quasi-solid-state electrolyte is applied in a new energy battery.

[0014] Deep eutectic solvents are green solvents similar to ionic liquids, which have low volatility, excellent flame retardant properties, high ionic conductivity and wide electrochemical window. Cellulose is a biodegradable polymer material, and the large number of hydroxyl groups and other functional groups on the cellulose derivative segment promote ion transmission. The rigid polysaccharide chain network of cellulose and the dynamic ion coordination structure of deep eutectic solvents form a complement, which not only gives the electrolyte excellent mechanical strength, but also maintains the dynamic stability of the electrode / electrolyte interface. The organic combination of deep eutectic solvents and cellulose materials not only solves the problems of flammability and environmental pollution of conventional organic quasi-solid electrolytes, but also synergistically improves the performance of quasi-solid electrolytes. This multi-scale collaborative design is expected to break through the traditional solid-state electrolyte 'high safety-high performance-sustainable' triangular contradiction, and provide an innovative solution for the next generation of energy storage devices.

[0015] Beneficial effects: The application provides an environmentally friendly eutectic cellulose quasi-solid electrolyte capable of in-situ thermal polymerization and a preparation method thereof. A deep eutectic electrolyte is formed by mixing a metal sodium salt with 1,2-dimethylimidazole according to different molar ratios; a double bond functionalized modified cellulose derivative is prepared by addition reaction in an organic solvent system; the double bond modified cellulose derivative is dissolved in the deep eutectic electrolyte to prepare a precursor solution, and finally a quasi-solid electrolyte is constructed in-situ inside the battery by thermal polymerization. The application effectively solves the problems of flammability and environmental pollution of traditional quasi-solid electrolytes, provides a new idea for designing environmentally friendly high-performance quasi-solid electrolytes, and has broad application prospects in solving the safety hazards of new energy vehicles, specifically in the following aspects: An environmentally friendly eutectic cellulose quasi-solid electrolyte capable of thermal polymerization is invented, realizing the organic combination of environmental protection, high safety and high performance.

[0016] A method for providing a general double bond modified polymer segment is provided, which improves the application potential of degradable polymers such as cellulose in solid-state electrolytes. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 NMR spectrum of the double bond modified cellulose acetate prepared in Example 1; Figure 2 NMR spectrum of the double bond modified ethyl cellulose prepared in Example 2; Figure 3 NMR spectrum of the double bond modified cyanoethyl cellulose prepared in Example 3; Figure 4 Application of the eutectic cellulose quasi-solid electrolyte prepared in the three examples in sodium solid-state batteries (positive electrode: sodium vanadium phosphate, negative electrode: sodium metal), it can be seen that the discharge specific capacity of the three examples has no attenuation under the condition of 100 cycles, indicating the excellent performance of the eutectic cellulose quasi-solid electrolyte.

[0018] Figure 5 The results of the flame retardant performance test of the eutectic cellulose quasi-solid electrolyte prepared in Example 1 are shown in the following table. DETAILED DESCRIPTION

[0019] The application will be further described below in conjunction with the accompanying drawings and examples.

[0020] The endpoints of the ranges and any values disclosed herein are not limited to the precise values stated. The endpoints of the ranges and any values are understood to be approximate values. The exact numerical values of the endpoints of the ranges and any values are understood to be approximations. It is intended to include all values between the upper and lower ends of the ranges and any values described, and are understood to include amounts that are reasonably approximated.

[0021] For purposes of this description and appended claims, unless otherwise indicated, all numbers expressing amounts, percentages or ratios, and other numerical values used in the description and claims herein are to be understood as being modified in all instances by the term "about". Furthermore, all ranges disclosed herein are intended to include the endpoints and independent combinations of the ranges with one another.

[0022] Example 1: A preparation method of an environmentally friendly eutectic cellulose quasi-solid electrolyte capable of in-situ thermal polymerization, comprising: (1) Preparation of deep eutectic electrolyte: In a high-concentration argon glove box, 5 mol of sodium perchlorate and 40 mol of 1,2-dimethylimidazole were added to a sample bottle. After being stirred vigorously at 85 °C for 6 h, a transparent light yellow deep eutectic electrolyte was obtained, which was cooled to room temperature for use.

[0023] (2) Preparation of double bond modified cellulose derivative: 2 g of cellulose acetate was dissolved in 30 mL of anhydrous DMF at 70 °C, followed by the addition of 5 drops of dibutyltin dilaurate as a catalyst. After the system was reduced to 40 °C, 1.5 g of isocyanatoethyl methacrylate was added dropwise under vigorous stirring. After the addition was completed, the stirring was continued for 12 h. After the reaction was completed, the above solution was poured into 400 mL of deionized water, the flocculent product was collected by centrifugation, and washed with deionized water three times, and then freeze-dried for 48 h to obtain the double bond modified cellulose acetate. Figure 1 The nuclear magnetic resonance spectrum of the double bond modified cellulose acetate of the sample of this example 1.

[0024] (3) Preparation of a thermal in-situ eutectic cellulose solid-state battery: Dissolve 50 mg of double bond modified cellulose acetate in 2 g of deep eutectic electrolyte at 50 °C to prepare a 2.5 wt% cellulose acetate solution, then add 0.01 wt% thermal initiator AIBN and 15 mg of crosslinking agent methylene bisacrylamide, stir for 5 min to obtain a precursor solution, inject the precursor solution into the inside of a button cell, and heat treat at 70 °C after packaging the cell to obtain a solid-state battery based on eutectic cellulose quasi-solid electrolyte.

[0025] Example 2: A preparation method of an environmentally friendly eutectic cellulose quasi-solid electrolyte capable of in-situ thermal polymerization, comprising: (1) Preparation of deep eutectic electrolyte: Prepare the deep eutectic electrolyte according to the steps in Example 1.

[0026] (2) Preparation of double bond modified cellulose derivative: Dissolve 2 g of ethyl cellulose in 30 mL of anhydrous DMF at 70 °C, then add 5 drops of dibutyltin dilaurate as a catalyst, reduce the system to 40 °C, and then add isocyanatoethyl methacrylate 1.5 g dropwise under vigorous stirring. After the addition is complete, continue stirring for 12 h. After the reaction is complete, pour the above solution into 400 mL of deionized water, centrifuge to collect the flocculent product, and wash with deionized water three times, then freeze-dry for 48 h to obtain double bond modified ethyl cellulose. Figure 2 The nuclear magnetic resonance hydrogen spectrum of the double bond modified ethyl cellulose sample in this example 2.

[0027] (3) Preparation of thermal in-situ eutectic cellulose solid-state battery: Dissolve 50 mg of double bond modified ethyl cellulose in 2 g of deep eutectic electrolyte at 50 °C to prepare a 2.5 wt% ethyl cellulose solution, then add 0.01 wt% thermal initiator AIBN and 15 mg of crosslinking agent methylene bisacrylamide, stir for 5 min to obtain a precursor solution, inject the precursor solution into the inside of a button cell, and heat treat at 70 °C after packaging the cell to obtain a solid-state battery based on eutectic cellulose quasi-solid electrolyte.

[0028] Example 3: A preparation method of an environmentally friendly eutectic cellulose quasi-solid electrolyte capable of in-situ thermal polymerization, comprising:

[0029] (1) Preparation of deep eutectic electrolyte: Prepare the deep eutectic electrolyte according to the steps in Example 1.

[0030] (2) Preparation of double bond modified cellulose derivative: Dissolve 2 g of cyanoethyl cellulose in 30 mL of anhydrous DMF at 70°C, then add 5 drops of dibutyltin dilaurate as a catalyst, and then add isocyanatoethyl methacrylate 1.5 g dropwise under vigorous stirring after the system is reduced to 40°C. Continue stirring for 12 h after the addition is complete. After the reaction is complete, pour the solution into 400 mL of deionized water, centrifuge to collect the flocculent product, and then wash three times with deionized water, and then freeze-dry for 48 h to obtain cyanoethyl cellulose modified with a double bond. Figure 3 The nuclear magnetic resonance spectrum of the cyanoethyl cellulose modified with a double bond for the sample of Example 3 is shown in the following figure.

[0031] (3) Preparation of a thermal in-situ eutectic cellulose solid-state battery: Dissolve 50 mg of cyanoethyl cellulose modified with a double bond in 2 g of a deep eutectic electrolyte at 50°C to obtain a 2.5 wt% cyanoethyl cellulose solution, then add 0.01 wt% of a thermal initiator AIBN and 15 mg of a crosslinking agent methylene bisacrylamide, and stir for 5 min to obtain a precursor solution. Pour the precursor solution into a coin cell, and then heat treat the cell at 70°C after packaging to obtain a solid-state battery based on a eutectic cellulose quasi-solid-state electrolyte.

[0032] From Figures 1 to 3 The nuclear magnetic resonance spectrum of the cyanoethyl cellulose modified with a double bond for the sample of Example 3 is shown in the following figure.

[0033] Figure 4 The application of the eutectic cellulose quasi-solid-state electrolyte prepared in the three examples in a sodium solid-state battery (positive electrode: sodium vanadium phosphate, negative electrode: sodium metal) can be seen. The discharge specific capacity of the three examples is basically not attenuated under 100 cycles, indicating the excellent performance of the eutectic cellulose quasi-solid-state electrolyte.

[0034] Figure 5 The flame retardant performance test of the commercial electrolyte and the eutectic cellulose quasi-solid-state electrolyte shows that the commercial electrolyte is ignited after being contacted with a flame, while the eutectic cellulose quasi-solid-state electrolyte shows good flame retardant performance, indicating that it has good safety.

[0035] The present application proposes a preparation method of a eutectic cellulose quasi-solid-state electrolyte, which mainly combines a deep eutectic electrolyte with a double-bond-modified cellulose derivative to form a flame-retardant and environmentally friendly quasi-solid-state electrolyte through thermal in-situ polymerization, thereby effectively solving the problems and defects of commercial electrolytes and traditional organic quasi-solid-state electrolytes, and improving the safety of new energy vehicles.

[0036] The above merely describes the preferred embodiments of the present application, and it should be pointed out that, for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present application, and these improvements and modifications should also be considered as the protection scope of the present application.

Claims

1. A method for preparing a eutectic cellulose quasi-solid electrolyte, characterized in that, include: Step (a): Mix the sodium metal salt with 1,2-dimethylimidazole under heating conditions to form a deep eutectic electrolyte; Step (b): Dissolve the cellulose derivative in an organic solvent, add a double bond modified monomer under the conditions of catalyst and argon, and prepare the double bond modified cellulose derivative by addition reaction; Step (c): Dissolve the double bond modified cellulose derivative in a deep eutectic electrolyte and add a thermal initiator and a crosslinking agent to obtain a precursor solution; Step (d): Inject the precursor solution into the battery and form a quasi-solid electrolyte through heat treatment.

2. The preparation method according to claim 1, characterized in that, In step (a), the sodium metal salt is selected from at least one of sodium perchlorate, sodium trifluoromethanesulfonate, and sodium difluorooxalate borate.

3. The preparation method according to claim 1, characterized in that, In step (a), the molar ratio of 1,2-dimethylimidazole to sodium in the sodium metal salt is 4~15; preferably 8~10. And / or, in step (a), the heating temperature is 60~100°C.

4. The preparation method according to claim 1, characterized in that, In step (b), the cellulose derivative is selected from at least one of cellulose acetate, ethyl cellulose, and cyanoethyl cellulose; And / or, the concentration of the cellulose derivative solution is 5-10 wt%; And / or, in step (b), the organic solvent is selected from at least one of N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, and dimethylacetamide; And / or, in step (b), the cellulose derivative is dissolved in an organic solvent at 40–80 °C.

5. The preparation method according to claim 1, characterized in that, In step (b), the catalyst is dibutyltin dilaurate or tetrabutyltin dilaurate; And / or, in step (b), the double bond modifying monomer is ethyl isocyanate methacrylate; And / or, in step (b), the reaction temperature of the addition reaction is 25~40°C.

6. The preparation method according to claim 1, characterized in that, In step (b), after the double bond modified cellulose derivative is prepared by reaction, the product is collected by precipitation and freeze-dried to obtain the double bond modified cellulose derivative.

7. The preparation method according to claim 1, characterized in that, In step (c), the concentration of the double-bond modified cellulose derivative in the precursor solution is 1-10 wt%, preferably 2.5-5 wt%. And / or, in step (c), the dissolution temperature of the double bond modified cellulose derivative in the deep eutectic electrolyte is 25~60°C, preferably 50°C; And / or, in step (c), the thermal initiator is selected from at least one of azobisisobutyronitrile, azobisisoheptanenitrile, and benzoyl peroxide; And / or, in step (c), the crosslinking agent is selected from at least one of methylene bisacrylamide, polyethylene glycol diacrylate, and pentaerythritol tetraacrylate.

8. The preparation method according to claim 1, characterized in that, In step (d), the heat treatment temperature is 60-120 °C, preferably 70-90 °C; And / or, in step (d), the heat treatment time is 12-36 hours.

9. A eutectic cellulose quasi-solid-state electrolyte, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.

10. The application of the eutectic cellulose quasi-solid-state electrolyte as described in claim 9 in new energy batteries.

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