An in-situ thermal polymerizable environment-friendly eutectic cellulose quasi-solid electrolyte and a preparation method thereof

Abstract

The application belongs to the technical field of material synthesis, and discloses an environmentally-friendly eutectic cellulose quasi-solid electrolyte capable of in-situ thermal polymerization and a preparation method thereof, which comprises the following steps: forming a deep eutectic electrolyte by mixing a metal sodium salt and 1,2-dimethyl imidazole according to different molar ratios; preparing a double bond functionalized modified cellulose derivative through an addition reaction in an organic solvent system; dissolving the double bond modified cellulose derivative in the deep eutectic electrolyte to prepare a precursor solution; and finally constructing a quasi-solid electrolyte in-situ in a battery through a thermal polymerization method. The application provides an environmentally-friendly eutectic cellulose quasi-solid electrolyte, which provides a new idea for solving the safety hidden danger of new energy vehicles.

Description

Technical Field

[0001] This invention belongs to the field of materials synthesis technology and relates to an environmentally friendly eutectic cellulose quasi-solid electrolyte that can be thermally polymerized in situ and its preparation method. Background Technology

[0002] Traditional organic electrolytes are volatile, flammable, and prone to leakage, posing a safety hazard in new energy vehicles during accidents or severe impacts, as they can cause battery short circuits and further combustion or explosions. Currently, both academia and industry have proposed solid-state electrolytes as a solution. However, solid-state electrolytes suffer from serious interfacial contact problems. Developing quasi-solid-state electrolytes has become a practically feasible strategy, but these are mainly composed of organic solvents and polymer segments, raising concerns about flammability and environmental pollution during post-processing. Summary of the Invention

[0003] Objective: In order to overcome the shortcomings of the existing technology and solve the problems of flammability and environmental pollution of quasi-solid electrolytes, this invention provides an environmentally friendly eutectic cellulose quasi-solid electrolyte that can be thermally polymerized in situ and its preparation method.

[0004] Technical solution: The technical solution adopted in this invention is as follows: According to a first aspect of the present invention, a method for preparing a eutectic cellulose quasi-solid electrolyte is provided, comprising: 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.

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

[0006] In some embodiments, in step (a), the molar ratio of 1,2-dimethylimidazole to sodium in the sodium metal salt is 4 to 15; preferably 8 to 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-methylpyrrolidone (NMP), and dimethylacetamide (DMAc); Correspondingly, in step (b), the cellulose derivative is dissolved in an organic solvent at 40–80 °C.

[0008] In some embodiments, in step (b), the catalyst is dibutyltin dilaurate or tetrabutyltin dilaurate; In some embodiments, in step (b), the double bond modifying monomer is ethyl isocyanate methacrylate; In some embodiments, in step (b), the reaction temperature of the addition reaction is 25~40°C.

[0009] In some embodiments, step (b) further includes, after the reaction preparation of the double bond modified cellulose derivative, collecting the product by precipitation 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 in the deep eutectic electrolyte 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), azobisisoheptanenitrile (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, the heat treatment time in step (d) is 12-36 hours.

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

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

[0014] Deep eutectic electrolytes are green solvents similar to ionic liquids, exhibiting low volatility, excellent flame retardancy, high ionic conductivity, and a wide electrochemical window. Cellulose, a biodegradable polymer material, possesses numerous hydroxyl groups and other functional groups on its derivative segments that promote ion transport. The rigid polysaccharide network of cellulose complements the dynamic ion coordination structure of the deep eutectic electrolyte, endowing it with excellent mechanical strength while maintaining the dynamic stability of the electrode / electrolyte interface. The organic combination of deep eutectic electrolytes and cellulose materials not only solves the drawbacks of conventional organic quasi-solid-state electrolytes, such as flammability and environmental pollution, but also synergistically improves the performance of quasi-solid-state electrolytes. This multi-scale synergistic design is expected to overcome the traditional triangular contradiction of "high safety-high performance-sustainability" in solid-state electrolytes, providing a revolutionary solution for next-generation energy storage devices.

[0015] Beneficial Effects: This invention provides an environmentally friendly eutectic cellulose quasi-solid-state electrolyte capable of in-situ thermal polymerization and its preparation method. A deep eutectic electrolyte is formed by mixing sodium metal salt and 1,2-dimethylimidazole in different molar ratios; a double-bond functionalized cellulose derivative is prepared via an 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; finally, the quasi-solid-state electrolyte is constructed in-situ inside the battery via thermal polymerization. This invention effectively solves the problems of flammability and environmental pollution associated with traditional quasi-solid-state electrolytes, providing a new approach for designing environmentally friendly, high-performance quasi-solid-state electrolytes. It has broad application prospects in addressing safety hazards in new energy vehicles, specifically in the following aspects: An environmentally friendly eutectic cellulose quasi-solid electrolyte that can be thermally polymerized has been invented, achieving an organic combination of environmental protection, high safety, and high performance.

[0016] A general method for modifying polymer segments with double bonds is provided, which improves the application potential of biodegradable polymers such as cellulose in solid electrolytes. Attached Figure Description

[0017] Figure 1 The 1H NMR spectrum of the double-bond modified cellulose acetate obtained in Example 1; Figure 2 The 1H NMR spectrum of the double-bond modified ethyl cellulose obtained in Example 2; Figure 3 The 1H NMR spectrum of the double-bond modified cyanoethyl cellulose prepared in Example 3; Figure 4 The application of the eutectic cellulose quasi-solid-state electrolyte prepared in the three examples in sodium solid-state batteries (the positive electrode is sodium vanadium phosphate and the negative electrode is sodium metal) shows that the discharge specific capacity of the three examples is basically not reduced under 100 cycles, which demonstrates the excellent performance of the eutectic cellulose quasi-solid-state electrolyte.

[0018] Figure 5 This is a schematic diagram showing the flame retardant performance test results of a commercial electrolyte and the eutectic cellulose quasi-solid electrolyte prepared in Example 1. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0020] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0021] For the purposes of this specification and the appended claims, unless otherwise stated, all expressions, percentages, or proportions, and other numerical values ​​used in this specification and the appended claims, are to be understood to be modified by the term "about" in all cases. Furthermore, all scopes disclosed herein include their endpoints and can be combined independently.

[0022] Example 1: A method for preparing an environmentally friendly eutectic cellulose quasi-solid-state electrolyte that can be thermally polymerized in situ, comprising: (1) Preparation of deep eutectic electrolyte: In a glove box filled with high-concentration argon gas, 5 mol of sodium perchlorate and 40 mol of 1,2-dimethylimidazole were added to a sample vial. After vigorous stirring at 85 ºC for 6 h, a transparent, light yellow deep eutectic electrolyte was obtained and cooled to room temperature for later use.

[0023] (2) Preparation of double bond modified cellulose derivatives: 2 g of cellulose acetate was dissolved in 30 mL of anhydrous DMF at 70°C. Then, 5 drops of dibutyltin dilaurate were added as a catalyst. The temperature was lowered to 40°C, and 1.5 g of isocyanate methacrylate was added dropwise with vigorous stirring. After the addition was complete, stirring was continued for 12 h. After the reaction was complete, the solution was poured into 400 mL of deionized water. The flocculent product was collected by centrifugation, washed three times with deionized water, and then freeze-dried for 48 h to obtain double-bond modified cellulose acetate. Figure 1 This is the 1H NMR spectrum of the double-bond modified cellulose acetate sample in Example 1 of this embodiment.

[0024] (3) Fabrication of thermally in-situ eutectic cellulose solid-state batteries: 50 mg of double-bond modified cellulose acetate was dissolved in 2 g of deep eutectic electrolyte at 50°C to prepare a 2.5 wt% cellulose acetate solution. Then, 0.01 wt% thermal initiator AIBN and 15 mg crosslinking agent methylenebisacrylamide were added and stirred for 5 min to obtain a precursor solution. The precursor solution was injected into the button cell and the cell was encapsulated and heat-treated at 70°C to obtain a solid-state battery based on eutectic cellulose quasi-solid-state electrolyte.

[0025] Example 2: A method for preparing an environmentally friendly eutectic cellulose quasi-solid-state electrolyte that can be thermally polymerized in situ, comprising: (1) Preparation of deep eutectic electrolyte: The deep eutectic electrolyte was prepared according to the steps in Example 1.

[0026] (2) Preparation of double bond modified cellulose derivatives: 2 g of ethyl cellulose was dissolved in 30 mL of anhydrous DMF at 70°C. Then, 5 drops of dibutyltin dilaurate were added as a catalyst. The system was cooled to 40°C, and 1.5 g of isocyanate methacrylate was added dropwise under vigorous stirring. After the addition was complete, stirring was continued for 12 h. After the reaction was complete, the solution was poured into 400 mL of deionized water, and the flocculent product was collected by centrifugation. The product was washed three times with deionized water and then freeze-dried for 48 h to obtain double-bond modified ethyl cellulose. Figure 2 This is the 1H NMR spectrum of the double-bond modified ethyl cellulose sample in Example 2 of this study.

[0027] (3) Fabrication of thermally in-situ eutectic cellulose solid-state batteries: 50 mg of double-bond modified ethyl cellulose was dissolved in 2 g of deep eutectic electrolyte at 50°C to prepare a 2.5 wt% ethyl cellulose solution. Then, 0.01 wt% thermal initiator AIBN and 15 mg crosslinking agent methylenebisacrylamide were added and stirred for 5 min to obtain a precursor solution. The precursor solution was injected into the button cell and the cell was encapsulated and heat-treated at 70°C to obtain a solid-state battery based on eutectic cellulose quasi-solid-state electrolyte.

[0028] Example 3: A method for preparing an environmentally friendly eutectic cellulose quasi-solid-state electrolyte that can be thermally polymerized in situ, comprising:

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

[0030] (2) Preparation of double bond modified cellulose derivatives: 2 g of cyanoethyl cellulose was dissolved in 30 mL of anhydrous DMF at 70°C. Then, 5 drops of dibutyltin dilaurate were added as a catalyst. After cooling the system to 40°C, 1.5 g of isocyanoethyl methacrylate was added dropwise under vigorous stirring. Stirring continued for 12 h after the addition was complete. After the reaction was complete, the solution was poured into 400 mL of deionized water. The flocculent product was collected by centrifugation, washed three times with deionized water, and then freeze-dried for 48 h to obtain double-bond modified cyanoethyl cellulose. Figure 3 This is the 1H NMR spectrum of the double-bond modified cyanoethyl cellulose sample in Example 3 of this study.

[0031] (3) Fabrication of thermally in-situ eutectic cellulose solid-state batteries: 50 mg of double-bond modified cyanoethyl cellulose was dissolved in 2 g of deep eutectic electrolyte at 50°C to prepare a 2.5 wt% cyanoethyl cellulose solution. Then, 0.01 wt% of thermal initiator AIBN and 15 mg of crosslinking agent methylenebisacrylamide were added and stirred for 5 min to obtain a precursor solution. The precursor solution was injected into the inside of a button cell, and after the cell was encapsulated, it was heat-treated at 70°C to obtain a solid-state battery based on eutectic cellulose quasi-solid-state electrolyte.

[0032] from Figures 1 to 3 The 1H NMR spectrum shows the NMR peaks of the carbon-carbon double bond, indicating that a double-bond modified cellulose derivative was prepared through a simple addition reaction. This can realize cross-linking polymerization and broaden the application of cellulose in solid electrolytes.

[0033] Figure 4 The application of the eutectic cellulose quasi-solid-state electrolyte prepared in the three examples in sodium solid-state batteries (the positive electrode is sodium vanadium phosphate and the negative electrode is sodium metal) shows that the discharge specific capacity of the three examples is basically not reduced under 100 cycles, which demonstrates the excellent performance of the eutectic cellulose quasi-solid-state electrolyte.

[0034] Figure 5 The flame retardant properties of commercial electrolyte and eutectic cellulose quasi-solid electrolyte were tested. The commercial electrolyte was ignited upon contact with a flame, while the eutectic cellulose quasi-solid electrolyte exhibited good flame retardant properties, indicating its good safety.

[0035] This invention proposes a method for preparing a eutectic cellulose quasi-solid electrolyte, which mainly combines a deep eutectic electrolyte with a double-bond modified cellulose derivative and forms a flame-retardant and environmentally friendly quasi-solid electrolyte through thermal in-situ polymerization. This method can effectively solve the problems and defects of commercial electrolytes and traditional organic quasi-solid electrolytes, thereby improving the safety of new energy vehicles.

[0036] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

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 to 15. 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, 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%; And / or, in step (c), the dissolution temperature of the double bond modified cellulose derivative in the deep eutectic electrolyte is 25~60°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; 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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