Sulfonyl cellulose-based solid electrolyte as well as preparation method and application thereof

Abstract

The invention provides a sulfonyl cellulose-based solid electrolyte as well as a preparation method and application thereof. The preparation method of the solid electrolyte comprises the following steps: fully dispersing microcrystalline cellulose and lithium salt in an organic solvent to obtain a cellulose solution; adding triethylamine and toluenesulfonyl chloride, reacting, and then separating and purifying to obtain sulfonyl cellulose; the preparation method comprises the following steps: dissolving sulfonyl cellulose in dimethyl sulfoxide, adding lithium salt, and fully mixing and uniformly dispersing to obtain a solid electrolyte precursor solution; and drying to obtain the product. The preparation method is simple, conditions are mild, the yield is high, and large-scale preparation can be achieved; and the cellulose is low in cost, rich in natural resources, environment-friendly and more suitable for industrial production. The sulfonyl-modified cellulose is applied to preparation of the solid electrolyte, the obtained sulfonyl-cellulose-based solid electrolyte has high ionic conductivity and excellent interface contact and adhesion effects, and the overall performance, including cycling stability and coulombic efficiency, of a lithium battery is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemical energy storage, and in particular relates to a sulfonyl cellulose-based solid electrolyte and a preparation method and application thereof. Background Art

[0002] Cellulose, as one of the most abundant natural polymers in nature, has good biodegradability, renewability and mechanical properties. However, pure cellulose has limitations in certain high-performance material applications, such as strong interactions between its hydrogen bond network structure, poor solubility, difficulty in processing and poor material compatibility. Therefore, chemical modification of cellulose to obtain new materials with specific functionalities has become a research hotspot. Each glucose unit in cellulose carries free active hydroxyl groups at the C2, C3 and C6 positions, making it prone to chemical reactions involving these groups. Chemical modification, grafting a large number of functional groups, can significantly improve the solubility, processability, ionic conductivity and mechanical strength of cellulose, and is a key method to overcome the above-mentioned problems of pure cellulose.

[0003] With the development of lithium-ion battery technology, and the increasing demands for improved safety and energy density, traditional liquid electrolytes are unable to meet the demands of future high-performance batteries due to safety risks such as flammability and leakage. Solid-state electrolytes have attracted widespread attention due to their excellent thermal and electrochemical stability. An ideal solid-state electrolyte should possess high ionic conductivity, good mechanical strength, and chemical stability.

[0004] Effective chemical modification strategies can significantly improve the physicochemical properties of cellulose, such as increasing solubility, reducing hydrogen bonding interactions, and enhancing ionic conductivity. Based on these improvements, modified cellulose demonstrates tremendous potential for application in solid-state electrolytes. By rationally designing and synthesizing modified cellulose materials with specific structures and properties, the overall performance of solid-state electrolytes can be effectively enhanced, promoting their practical application in next-generation high-performance energy storage devices.

[0005] Although modified cellulose theoretically has the potential to become an excellent solid-state electrolyte material, its practical application still faces many challenges. For example, how to prepare modified cellulose with high ionic conductivity, good mechanical strength, and chemical stability for better application in solid-state electrolytes; how to efficiently carry out cellulose modification reactions to ensure product uniformity and controllability; how to balance the relationship between characteristic functional groups and other key material properties; and how to further optimize the material preparation process to reduce costs and environmental impact.

[0006] Chinese patent document CN 117996173 A discloses a cellulose derivative-based solid electrolyte, its preparation method, and application. The preparation method for the cellulose derivative-based solid electrolyte comprises the following steps: acylation reaction of cellulose with an acylating agent in an ionic liquid or a mixture of an ionic liquid and an organic solvent to obtain a cellulose derivative; adding the reaction solution to a precipitant to precipitate the cellulose derivative; dissolving the cellulose derivative and a lithium salt in a solvent to obtain an electrolyte solution, applying a doctor blade to form a film, and drying to obtain a cellulose derivative-based solid electrolyte. This invention improves lithium ion transport by expanding the chemical structure of the cellulose backbone and introducing and regulating effective functional groups, thereby enhancing ionic conductivity without compromising mechanical properties, improving the surface stability of the solid electrolyte, and improving the cycle performance and lifespan of solid-state batteries. However, in addition to the organic solvent, this invention also incorporates an ionic liquid and a plasticizer, which increases costs. The more complex solvent system further increases the constraints of modifying the cellulose and the difficulty of the reaction. Furthermore, the addition of the plasticizer indirectly reflects the limitations of using only a cellulose derivative matrix in solid electrolyte applications. Furthermore, the electrochemical performance of the solid electrolyte obtained by this invention needs to be further improved.

[0007] Therefore, developing a modified cellulose-based solid electrolyte with simple preparation method, low cost, high ionic conductivity and high electrochemical performance is of great significance for promoting the development of high-performance energy storage materials. Summary of the Invention

[0008] In view of the shortcomings of the prior art, the present invention provides a sulfonyl cellulose-based solid electrolyte and its preparation method and application. The present invention introduces sulfonyl groups into cellulose to prepare sulfonyl-modified cellulose. The preparation method of the present invention is simple, the conditions are mild, the yield is high, and it can be prepared on a large scale; and cellulose is low-cost, abundant in natural resources, and environmentally friendly, making it more suitable for industrial production. The sulfonyl-modified cellulose of the present invention is used to prepare solid electrolytes, and the obtained sulfonyl cellulose-based solid electrolyte has high ionic conductivity, excellent interface contact and adhesion effects, and improves the overall performance of lithium batteries, including cycle stability and coulombic efficiency.

[0009] The technical solutions of the present invention are as follows:

[0010] A method for preparing a sulfonyl cellulose-based solid electrolyte comprises the following steps:

[0011] S1. Fully dispersing microcrystalline cellulose (MCC) and lithium salt in an organic solvent to obtain a cellulose solution; adding triethylamine and toluenesulfonyl chloride, reacting, and then separating and purifying to obtain sulfonyl cellulose;

[0012] S2. Dissolve sulfonyl cellulose in dimethyl sulfoxide (DMSO), add lithium salt, mix thoroughly and disperse evenly to obtain a solid electrolyte precursor solution; and dry to obtain a sulfonyl cellulose-based solid electrolyte.

[0013] According to the preferred embodiment of the present invention, in step S1, the organic solvent is dimethylacetamide (DMAc).

[0014] Preferably, according to the present invention, in step S1, the lithium salt is lithium chloride (LiCl); and the mass ratio of the lithium salt to the microcrystalline cellulose is 1-2:1.

[0015] According to the preferred embodiment of the present invention, in step S1, the volume ratio of the mass of microcrystalline cellulose to the organic solvent is 1:20-40 g / mL, preferably 1:30 g / mL.

[0016] Preferably, according to the present invention, in step S1, microcrystalline cellulose and lithium salt are added to an organic solvent and stirred at 100° C.-130° C. for 12-24 hours to fully disperse them.

[0017] According to the preferred embodiment of the present invention, in step S1, the mass ratio of triethylamine to microcrystalline cellulose is 6-7 mL:4 g, preferably 6.5 mL:4 g; the mass ratio of toluenesulfonyl chloride to microcrystalline cellulose is 1-6:4, preferably 1.6115-5.3593:4.

[0018] According to the preferred embodiment of the present invention, in step S1, the reaction temperature is -5-5°C, the reaction time is 4-10 hours, and the reaction is carried out under stirring conditions.

[0019] According to a preferred embodiment of the present invention, in step S1, the separation and purification method is as follows: adding 0°C deionized water to the reaction solution to precipitate the polymer segments, washing with deionized water and ethanol alternately to remove the organic solvent and unreacted reagents, and drying to obtain sulfonyl cellulose.

[0020] According to the present invention, preferably, in step S2, the sulfonyl cellulose is a combination of sulfonyl celluloses prepared by using different ratios of microcrystalline cellulose (MCC) and toluenesulfonyl chloride; preferably, the sulfonyl cellulose is a combination of sulfonyl cellulose prepared by using a mass ratio of toluenesulfonyl chloride to microcrystalline cellulose of 2.1485:4 and sulfonyl cellulose prepared by using a mass ratio of toluenesulfonyl chloride to microcrystalline cellulose of 5.3593:4.

[0021] Preferably, according to the present invention, in step S2, the volume ratio of sulfonyl cellulose to dimethyl sulfoxide is 0.15-0.45:4-10 g / mL.

[0022] According to a preferred embodiment of the present invention, in step S2, the lithium salt is lithium bis(fluorosulfonyl)imide; and the mass ratio of the lithium salt to the sulfonyl cellulose is 1-2:1.

[0023] According to a preferred embodiment of the present invention, in step S2, the conditions for fully mixing and uniformly dispersing are as follows: stirring at 50-80° C. for 5-8 hours.

[0024] According to a preferred embodiment of the present invention, in step S2, the solid electrolyte precursor is dropwise coated onto a glass plate and dried to obtain a sulfonyl cellulose solid electrolyte.

[0025] According to the preferred embodiment of the present invention, in step S2, the drying temperature is 50-80°C.

[0026] A sulfonyl cellulose-based solid electrolyte is prepared by the above method.

[0027] Application of the above-mentioned sulfonyl cellulose-based solid electrolyte in solid-state lithium metal batteries.

[0028] The technical features and beneficial effects of the present invention are as follows:

[0029] 1. The present invention proposes an innovative chemical grafting modification method, which aims to carry out a precise substitution reaction on the hydroxyl groups on the active sites of cellulose. By cleverly grafting the characteristic functional group, the sulfonyl group, onto the cellulose molecular chain segment, the strong hydrogen bond interaction inherent in the hydrogen bond network structure inside the cellulose is effectively destroyed, thereby significantly reducing the crystallinity of the modified polymer and increasing the spacing between the molecular segments. When this sulfonyl-modified cellulose is used as a polymer matrix material for the electrolyte, it not only exhibits better solubility and processing convenience, but also provides the possibility for large-scale production. In particular, the introduced sulfonyl group can effectively increase the distance between the molecular chains, forming a high-speed channel that is conducive to the rapid transmission of lithium ions, thereby greatly improving the ionic conductivity of the electrolyte. In addition, by finely adjusting the amount of the modifying agent, the content of specific functional groups in the cellulose molecular chain can be precisely controlled, which provides flexibility for further optimizing the material properties. It is worth noting that when modified cellulose with different sulfonyl group contents are used to prepare electrolytes, these materials show significant differences in adhesion properties and ionic conductivity (the grafting concentration of the present invention can make the electrolyte have higher ionic conductivity and better interface contact and adhesion effects); this means that its ionic conductivity and adhesive interface contact can be controlled and regulated according to the content of the grafted characteristic functional groups; by adjusting the number of grafted groups, the contact effect between the electrolyte and the positive and negative electrode interfaces of the battery can be optimized, thereby effectively alleviating the problem of electrochemical performance degradation caused by interface degradation. Therefore, the electrolyte obtained by the method of the present invention not only improves the overall performance of the battery, but also opens up a new way to extend its service life. In short, the present invention provides a new direction with great potential for the development of efficient and stable lithium-ion batteries.

[0030] 2. The preparation method of the present invention is simple, has mild conditions, high yield, and can be prepared on a large scale. In addition, the cellulose matrix is ​​low-cost, abundant in natural resources, and environmentally friendly, making it more suitable for industrial production. The type of solvent involved in the preparation of the electrolyte of the present invention (dimethyl sulfoxide is used in the present invention) is relatively important; if it is not suitable, it will react violently with the lithium metal negative electrode of the battery, destroying the stability of the negative electrode side and producing various adverse byproducts, affecting the coulombic efficiency and cycle life of the battery.

[0031] 3. The sulfonyl cellulose-based solid electrolyte provided by the present invention has a high room temperature ionic conductivity (1.11×10 -3 S cm -1 ), excellent interfacial contact and adhesion, improving the overall performance of lithium batteries, with good cycle stability (capacity decay rate of 0.023% / cycle after 500 cycles) and coulombic efficiency. It also exhibits good performance in soft-pack batteries, significantly demonstrating its potential value in practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is the solid-state NMR spectra of microcrystalline cellulose and sulfonyl cellulose in Example 1;

[0033] Figure 2 is the X-ray diffraction pattern of microcrystalline cellulose and the sulfonyl cellulose in Examples 1-2 and 4-6;

[0034] Figure 3 is a nano-infrared (AFM-IR) spectrum of the solid electrolyte prepared in Example 1-3;

[0035] Figure 4 Graphs showing room temperature ionic conductivity, activation energy, and ion mobility of the solid electrolytes prepared in Examples 1-3;

[0036] Figure 5 is the cyclic voltage curve of the symmetrical battery assembled with the solid electrolyte prepared in Example 3;

[0037] Figure 6 is the cyclic voltage curve of the symmetrical battery assembled with the solid electrolyte prepared in Example 1;

[0038] Figure 7 is the cyclic voltage curve of the symmetrical battery assembled with the solid electrolyte prepared in Example 2;

[0039] Figure 8 The cycle stability of the soft pack battery assembled with the solid electrolyte prepared in Example 3;

[0040] Figure 9 The dynamic viscosity (a) and the interfacial adhesion level with the stainless steel plate (b) of the solid electrolyte prepared in Examples 1-3;

[0041] Figure 10 Cycling stability of lithium iron phosphate full batteries assembled with solid electrolytes prepared in Examples 1 and 3. DETAILED DESCRIPTION

[0042] The following will clearly and completely describe the concept and technical effects of the present invention in conjunction with the embodiments to fully understand the purpose, features and effects of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0043] Example 1

[0044] A method for preparing a sulfonyl cellulose-based solid electrolyte comprises the following steps:

[0045] S1. Add 4 g of microcrystalline cellulose (MCC) to 120 mL of dimethylacetamide (DMAc), add 7.2 g of LiCl, and stir at 100°C for 12 hours to obtain a transparent, viscous cellulose solution.

[0046] S2. After adding 6.5 mL of triethylamine solution to the above cellulose solution, 2.1485 g of toluenesulfonyl chloride was added, and the mixture was stirred at 0°C and reacted for 8 h to obtain a sulfonyl cellulose solution;

[0047] S3, performing a precipitation and purification reaction on the sulfonyl cellulose, adding 0° C. deionized water to the sulfonyl cellulose solution to precipitate polymer segments, and washing with deionized water and ethanol alternately to remove the organic solvent and unreacted reagents to obtain wet sulfonyl cellulose;

[0048] S4. The wet sulfonyl cellulose is placed in a 60° C. forced air drying oven for 12 hours to obtain sulfonyl cellulose (SC-2).

[0049] S5. Dissolve 0.3 g of sulfonyl cellulose in 4 mL of DMSO solution, add 0.3 g of lithium salt lithium bis(fluorosulfonyl)imide, and stir at 80° C. for 6 hours to obtain a solid electrolyte precursor solution.

[0050] S6. Apply the solid electrolyte precursor droplets onto a glass plate and dry them on a heating platform at 60° C. to obtain a sulfonyl cellulose-based solid electrolyte (LC-SC).

[0051] This embodiment also provides a method for preparing and assembling a solid-state lithium metal battery, comprising: a positive electrode and a negative electrode;

[0052] The positive electrode is prepared as follows: lithium iron phosphate, acetylene black, and PVDF are thoroughly ground and mixed in a mass ratio of 8:1:1. N-methylpyrrolidone is added and homogenized to form a viscous black slurry. This slurry is coated on aluminum foil and dried to obtain the positive electrode sheet. The negative electrode is a lithium metal sheet.

[0053] The solid-state lithium-lithium symmetrical battery is assembled in a glove box (with a water-oxygen concentration of <0.01 ppm) in the following order: negative electrode shell, spring, gasket, lithium metal sheet, sulfonyl cellulose-based solid electrolyte, lithium metal sheet, and positive electrode shell. After the battery is assembled, it is placed in a tablet press for battery packaging to obtain a solid-state lithium-lithium symmetrical battery.

[0054] The solid-state full battery is assembled in a glove box (with a water-oxygen concentration of <0.01 ppm) in the following order: negative electrode shell, spring, gasket, lithium metal sheet, sulfonyl cellulose-based solid electrolyte, positive electrode, and positive electrode shell. After the battery is assembled, it is placed in a tablet press for battery packaging to obtain a solid-state lithium metal battery.

[0055] Example 2

[0056] A method for preparing a sulfonyl cellulose-based solid electrolyte comprises the following steps:

[0057] S1. Add 4 g of microcrystalline cellulose (MCC) to 120 mL of dimethylacetamide (DMAc), add 7.2 g of LiCl, and stir at 100°C for 12 hours to obtain a transparent, viscous cellulose solution.

[0058] S2. After adding 6.5 mL of triethylamine solution to the above cellulose solution, 5.3593 g of toluenesulfonyl chloride was added, and the mixture was stirred at 0° C. and reacted for 8 hours to obtain a sulfonyl cellulose solution;

[0059] S3, performing a precipitation and purification reaction on the sulfonyl cellulose, adding 0° C. deionized water to the sulfonyl cellulose solution to precipitate polymer segments, and washing with deionized water and ethanol alternately to remove the organic solvent and unreacted reagents to obtain wet sulfonyl cellulose;

[0060] S4. The wet sulfonyl cellulose is placed in a 60° C. forced air drying oven for 12 hours to obtain sulfonyl cellulose (SC-5).

[0061] S5. Dissolve 0.3 g of sulfonyl cellulose in 4 mL of DMSO solution, add 0.3 g of lithium salt lithium bis(fluorosulfonyl)imide, and stir at 80° C. for 6 hours to obtain a solid electrolyte precursor solution.

[0062] S6. Apply the solid electrolyte precursor droplets onto a glass plate and dry them on a heating platform at 60° C. to obtain a sulfonyl cellulose-based solid electrolyte (HC-SC).

[0063] The assembly method of the solid-state lithium-lithium symmetrical battery and the solid-state full battery is the same as that in Example 1.

[0064] Example 3

[0065] A method for preparing a sulfonyl cellulose-based solid electrolyte comprises the following steps:

[0066] S1. Add 4 g of microcrystalline cellulose (MCC) to 120 mL of dimethylacetamide (DMAc), add 7.2 g of LiCl, and stir at 100°C for 12 hours to obtain a transparent, viscous cellulose solution.

[0067] S2. After adding 6.5 mL of triethylamine solution to the above cellulose solution, 2.1485 g of toluenesulfonyl chloride was added, and the mixture was stirred at 0° C. and reacted for 8 hours to obtain a sulfonyl cellulose solution; the sulfonyl cellulose was subjected to a precipitation and purification reaction, and 0° C. deionized water was added to the sulfonyl cellulose solution to precipitate polymer segments. The solution was washed alternately with deionized water and ethanol to remove the organic solvent and unreacted reagents to obtain wet sulfonyl cellulose; the wet sulfonyl cellulose was placed in a 60° C. air drying oven for 12 hours to obtain sulfonyl cellulose (SC-2).

[0068] S3. After adding 6.5 mL of triethylamine solution to the above cellulose solution, 5.3593 g of toluenesulfonyl chloride was added, and the mixture was stirred at 0°C and reacted for 8 hours to obtain a sulfonyl cellulose solution; the sulfonyl cellulose was subjected to a precipitation and purification reaction, and 0°C deionized water was added to the sulfonyl cellulose solution to precipitate polymer segments. The polymer segments were washed alternately with deionized water and ethanol to remove the organic solvent and unreacted reagents to obtain wet sulfonyl cellulose; the wet sulfonyl cellulose was placed in a 60°C forced air drying oven for 12 hours to obtain sulfonyl cellulose (SC-5).

[0069] S4. Dissolve 0.15 g of sulfonyl cellulose (SC-2) and 0.15 g of sulfonyl cellulose (SC-5) in 4 mL of DMSO solution, add 0.3 g of lithium salt lithium bis(fluorosulfonyl)imide, and stir at 80° C. for 6 hours to obtain a solid electrolyte precursor solution.

[0070] S5. The solid electrolyte precursor droplets were applied to a glass plate and dried on a heating platform at 60° C. to obtain a sulfonyl cellulose-based solid electrolyte (RMGC-SC).

[0071] The assembly method of the solid-state lithium-lithium symmetrical battery and the solid-state full battery is the same as that in Example 1.

[0072] Example 4

[0073] A method for preparing a sulfonyl cellulose-based solid electrolyte comprises the following steps:

[0074] S1. Add 4 g of microcrystalline cellulose (MCC) to 120 mL of dimethylacetamide (DMAc), add 7.2 g of LiCl, and stir at 100°C for 12 hours to obtain a transparent, viscous cellulose solution.

[0075] S2. After adding 6.5 mL of triethylamine solution to the above cellulose solution, 1.6115 g of toluenesulfonyl chloride was added, and the mixture was stirred at 0° C. and reacted for 8 hours to obtain a sulfonyl cellulose solution;

[0076] S3, performing a precipitation and purification reaction on the sulfonyl cellulose, adding 0° C. deionized water to the sulfonyl cellulose solution to precipitate polymer segments, and washing with deionized water and ethanol alternately to remove the organic solvent and unreacted reagents to obtain wet sulfonyl cellulose;

[0077] S4. The wet sulfonyl cellulose is placed in a 60° C. forced air drying oven for 12 hours to obtain sulfonyl cellulose (SC-1).

[0078] S5. Dissolve 0.3 g of sulfonyl cellulose in 4 mL of DMSO solution, add 0.3 g of lithium salt lithium bis(fluorosulfonyl)imide, and stir at 80° C. for 6 hours to obtain a solid electrolyte precursor solution.

[0079] S6. Apply the solid electrolyte precursor droplets onto a glass plate and dry them on a heating platform at 60° C. to obtain a sulfonyl cellulose-based solid electrolyte.

[0080] The assembly method of the solid-state lithium-lithium symmetrical battery and the solid-state full battery is the same as that in Example 1.

[0081] Example 5

[0082] A method for preparing a sulfonyl cellulose-based solid electrolyte comprises the following steps:

[0083] S1. Add 4 g of microcrystalline cellulose (MCC) to 120 mL of dimethylacetamide (DMAc), add 7.2 g of LiCl, and stir at 100°C for 12 hours to obtain a transparent, viscous cellulose solution.

[0084] S2. After adding 6.5 mL of triethylamine solution to the above cellulose solution, 3.2230 g of toluenesulfonyl chloride was added, and the mixture was stirred at 0° C. and reacted for 8 hours to obtain a sulfonyl cellulose solution;

[0085] S3, performing a precipitation and purification reaction on the sulfonyl cellulose, adding 0° C. deionized water to the sulfonyl cellulose solution to precipitate polymer segments, and washing with deionized water and ethanol alternately to remove the organic solvent and unreacted reagents to obtain wet sulfonyl cellulose;

[0086] S4. The wet sulfonyl cellulose is placed in a 60° C. forced air drying oven for 12 hours to obtain sulfonyl cellulose (SC-3).

[0087] S5. Dissolve 0.3 g of sulfonyl cellulose in 4 mL of DMSO solution, add 0.3 g of lithium salt lithium bis(fluorosulfonyl)imide, and stir at 80° C. for 6 hours to obtain a solid electrolyte precursor solution.

[0088] S6. Apply the solid electrolyte precursor droplets onto a glass plate and dry them on a heating platform at 60° C. to obtain a sulfonyl cellulose-based solid electrolyte.

[0089] The assembly method of the solid-state lithium-lithium symmetrical battery and the solid-state full battery is the same as that in Example 1.

[0090] Example 6

[0091] A method for preparing a sulfonyl cellulose-based solid electrolyte comprises the following steps:

[0092] S1. Add 4 g of microcrystalline cellulose (MCC) to 120 mL of dimethylacetamide (DMAc), add 7.2 g of LiCl, and stir at 100°C for 12 hours to obtain a transparent, viscous cellulose solution.

[0093] S2. After adding 6.5 mL of triethylamine solution to the above cellulose solution, 4.2850 g of toluenesulfonyl chloride was added, and the mixture was stirred at 0° C. and reacted for 8 hours to obtain a sulfonyl cellulose solution;

[0094] S3, performing a precipitation and purification reaction on the sulfonyl cellulose, adding 0° C. deionized water to the sulfonyl cellulose solution to precipitate polymer segments, and washing with deionized water and ethanol alternately to remove the organic solvent and unreacted reagents to obtain wet sulfonyl cellulose;

[0095] S4. The wet sulfonyl cellulose is placed in a 60° C. forced air drying oven for 12 hours to obtain sulfonyl cellulose (SC-4).

[0096] S5. Dissolve 0.3 g of sulfonyl cellulose in 4 mL of DMSO solution, add 0.3 g of lithium salt lithium bis(fluorosulfonyl)imide, and stir at 80° C. for 6 hours to obtain a solid electrolyte precursor solution.

[0097] S6. Apply the solid electrolyte precursor droplets onto a glass plate and dry them on a heating platform at 60° C. to obtain a sulfonyl cellulose-based solid electrolyte.

[0098] The assembly method of the solid-state lithium-lithium symmetrical battery and the solid-state full battery is the same as that in Example 1.

[0099] Example 7

[0100] A method for preparing a sulfonyl cellulose-based solid electrolyte comprises the following steps:

[0101] S1. Add 4 g of microcrystalline cellulose (MCC) to 120 mL of dimethylacetamide (DMAc), add 7.2 g of LiCl, and stir at 100°C for 12 hours to obtain a transparent, viscous cellulose solution.

[0102] S2. After adding 6.5 mL of triethylamine solution to the above cellulose solution, 2.1485 g of toluenesulfonyl chloride was added, and the mixture was stirred at 0° C. and reacted for 8 hours to obtain a sulfonyl cellulose solution; the sulfonyl cellulose was subjected to a precipitation and purification reaction, and 0° C. deionized water was added to the sulfonyl cellulose solution to precipitate polymer segments. The solution was washed alternately with deionized water and ethanol to remove the organic solvent and unreacted reagents to obtain wet sulfonyl cellulose; the wet sulfonyl cellulose was placed in a 60° C. air drying oven for 12 hours to obtain sulfonyl cellulose (SC-2).

[0103] S3. After adding 6.5 mL of triethylamine solution to the above cellulose solution, 5.3593 g of toluenesulfonyl chloride was added, and the mixture was stirred at 0°C and reacted for 8 hours to obtain a sulfonyl cellulose solution; the sulfonyl cellulose was subjected to a precipitation and purification reaction, and 0°C deionized water was added to the sulfonyl cellulose solution to precipitate polymer segments. The polymer segments were washed alternately with deionized water and ethanol to remove the organic solvent and unreacted reagents to obtain wet sulfonyl cellulose; the wet sulfonyl cellulose was placed in a 60°C forced air drying oven for 12 hours to obtain sulfonyl cellulose (SC-5).

[0104] S4. Dissolve 0.15 g of sulfonyl cellulose (SC-2) and 0.15 g of sulfonyl cellulose (SC-5) in 4 mL of DMSO solution, add 0.6 g of lithium salt lithium bis(fluorosulfonyl)imide, and stir at 80° C. for 6 hours to obtain a solid electrolyte precursor solution.

[0105] S5. Apply a drop of the solid electrolyte precursor onto a glass plate and dry it on a heating table at 60° C. to obtain a sulfonyl cellulose-based solid electrolyte.

[0106] The assembly method of the solid-state lithium-lithium symmetrical battery and the solid-state full battery is the same as that in Example 1.

[0107] Example 8

[0108] A method for preparing a sulfonyl cellulose-based solid electrolyte comprises the following steps:

[0109] S1. Add 4 g of microcrystalline cellulose (MCC) to 120 mL of dimethylacetamide (DMAc), add 7.2 g of LiCl, and stir at 100°C for 12 hours to obtain a transparent, viscous cellulose solution.

[0110] S2. After adding 6.5 mL of triethylamine solution to the above cellulose solution, 2.1485 g of toluenesulfonyl chloride was added, and the mixture was stirred at 0° C. and reacted for 8 hours to obtain a sulfonyl cellulose solution; the sulfonyl cellulose was subjected to a precipitation and purification reaction, and 0° C. deionized water was added to the sulfonyl cellulose solution to precipitate polymer segments. The solution was washed alternately with deionized water and ethanol to remove the organic solvent and unreacted reagents to obtain wet sulfonyl cellulose; the wet sulfonyl cellulose was placed in a 60° C. air drying oven for 12 hours to obtain sulfonyl cellulose (SC-2).

[0111] S3. After adding 6.5 mL of triethylamine solution to the above cellulose solution, 5.3593 g of toluenesulfonyl chloride was added, and the mixture was stirred at 0°C and reacted for 8 hours to obtain a sulfonyl cellulose solution; the sulfonyl cellulose was subjected to a precipitation and purification reaction, and 0°C deionized water was added to the sulfonyl cellulose solution to precipitate polymer segments. The polymer segments were washed alternately with deionized water and ethanol to remove the organic solvent and unreacted reagents to obtain wet sulfonyl cellulose; the wet sulfonyl cellulose was placed in a 60°C forced air drying oven for 12 hours to obtain sulfonyl cellulose (SC-5).

[0112] S4. Dissolve 0.15 g of sulfonyl cellulose (SC-2) and 0.15 g of sulfonyl cellulose (SC-5) in 4 mL of DMSO solution, add 0.6 g of lithium salt lithium bis(fluorosulfonyl)imide, and stir at 80° C. for 6 hours to obtain a solid electrolyte precursor solution.

[0113] S5. Apply a drop of the solid electrolyte precursor onto a glass plate and dry it on a heating table at 70° C. to obtain a sulfonyl cellulose-based solid electrolyte.

[0114] The assembly method of the solid-state lithium-lithium symmetrical battery and the solid-state full battery is the same as that in Example 1.

[0115] Test example

[0116] Figure 1 The solid-state properties of microcrystalline cellulose (MCC) and the sulfonyl-modified cellulose sample in Example 1 are shown. 13C nuclear magnetic resonance spectrum. Comparative analysis shows that in addition to retaining the characteristic peaks associated with the original MCC, the modified cellulose exhibits additional signal peaks in the chemical shift range of approximately 22 ppm and 125-140 ppm. These new chemical shifts correspond to the resonance absorption of the p-CH3 (para-methyl) and aromatic carbon atoms in the toluenesulfonyl group, respectively. These unique spectral features strongly confirm that the sulfonyl group has been successfully and stably grafted onto the cellulose molecular chain, thus giving the material the expected chemical and physical properties.

[0117] Figure 2 The X-ray diffraction (XRD) spectra of microcrystalline cellulose (MCC) and the cellulose modified with sulfonyl groups in Examples 1-2 and 4-6 show that microcrystalline cellulose exhibits significant crystalline characteristics, as reflected by its obvious diffraction peaks at 15.1°, 22.6° and 34.5°, corresponding to the (110), (020) and (040) crystal planes, respectively. However, after chemical grafting modification, a series of sulfonyl-modified cellulose samples showed a significant decrease in crystallinity, especially a significant decrease in the diffraction angle corresponding to the (020) crystal plane. This change not only intuitively reflects the destruction of the internal hydrogen bond network structure of cellulose due to the introduction of sulfonyl groups, but also indicates an increase in the distance between molecular chains, providing a smoother transmission path for lithium ions. Therefore, in this way, not only the conductivity of the cellulose-based electrolyte can be effectively improved, but also the interface contact performance between it and the battery electrode can be optimized, thereby improving the electrochemical stability and service life of the entire battery system.

[0118] Figure 3 The nano-infrared (AFM-IR) spectra of the solid electrolytes prepared in Examples 1-3 were used to characterize the number of sulfonyl functional groups in the samples and their spatial distribution. From the AFM height image of the solid electrolyte (RMGC-SC) prepared in Example 3, it was observed that the surface of the formed solid electrolyte membrane was relatively flat, which helped to form a good interface contact with different electrodes. The FTIR spectrum showed that the low grafting concentration sulfonyl cellulose-based solid electrolyte (LC-SC) prepared in Example 1 had a peak at 1358 cm -1 The modified cellulose-based solid electrolyte (RMGC-SC) with a rich microdomain concentration gradient exhibits a staggered distribution of high and low functional groups, effectively demonstrating the successful preparation of a sulfonyl cellulose solid electrolyte with a rich microdomain concentration gradient.

[0119] Figure 4 Figure 3 shows key electrochemical parameters such as ionic conductivity, activation energy, and ion transference number for the solid electrolytes prepared in Examples 1-3. Taking into account interfacial contact and adhesion properties, the sulfonyl cellulose solid electrolyte membrane with rich micro-domain concentration gradients prepared in Example 3 exhibits excellent ionic conductivity, activation energy, ion transference number, and interfacial contact properties.

[0120] The solid-state lithium-lithium symmetrical battery assembled with the electrolyte prepared in Example 3 was tested at a current density of 0.2 mA / cm 2 and a capacity of 0.2 mAh / cm 2 It has excellent cycle stability under the conditions of 1000h cycle, and its polarization voltage is only 120mV. Figure 5 However, the solid-state lithium-lithium symmetrical batteries assembled with the electrolytes prepared in Example 1 and Example 2 are prone to short circuit and significant increase in polarization voltage at the same current density and capacity, as shown in FIG. Figure 6 and Figure 7 shown.

[0121] The solid electrolyte prepared in Example 3 was assembled into a soft pack battery. The assembly method of the soft pack battery was as follows: in a glove box (water and oxygen values ​​were all less than 0.01 ppm), a 5×5 cm 2 The lithium iron phosphate positive electrode is placed at the bottom, and the upper layer is 6×6cm 2 sulfonyl cellulose solid electrolyte layer, and then laminated on 5×5cm 2 The lithium metal sheet was used to obtain the inner core of the soft pack battery. The core was transferred to a 8×8 cm 2 After adjusting the size of the aluminum-plastic film, the positive and negative electrode tabs are drawn out, and then packaged to obtain a solid-state soft-pack battery. Figure 8 As shown, it shows good cycle stability and good practical application value.

[0122] Figure 9 a is the kinetic adhesion value of the solid electrolytes prepared in Examples 1-3. It can be seen from the figure that HC-SC has the highest viscosity value, LC-SC has the lowest viscosity value, and RMGC-SC has a moderate viscosity value. Figure 9 b is the interfacial adhesion test between different electrolytes and stainless steel plates. As can be seen from the figure, LC-SC shows the smallest average peel strength of 13.85 N m within the displacement range of 15 mm. -1 , indicating a significant decrease in viscosity. In contrast, HC-SC, characterized by increased viscosity, showed a significantly higher average peel strength of 32.47 N m -1 Meanwhile, RMGC-SC is a composite material that embodies a balance of two extreme properties, showing a strength of 22.42 N m -1This test result strongly confirms the effectiveness of viscosity regulation in adjusting the adhesion properties of the electrolyte electrode interface, thus highlighting the key role of viscosity control in optimizing the overall performance of solid-state battery systems.

[0123] Figure 10 The cycling stability of lithium iron phosphate full cells assembled with the electrolyte membranes prepared in Examples 1 and 3. As can be seen from the figure, after 500 cycles, the capacity of the cell assembled with the electrolyte membrane prepared in Example 3 can still be maintained at 88.6%, i.e., the capacity decay rate is 0.023% / cycle after 500 cycles.

Claims

1. A method for preparing a sulfonyl cellulose-based solid electrolyte, comprising the steps of: S1. Fully dispersing microcrystalline cellulose (MCC) and lithium salt in an organic solvent to obtain a cellulose solution; adding triethylamine and toluenesulfonyl chloride, reacting, and then separating and purifying to obtain sulfonyl cellulose; S2. Dissolve sulfonyl cellulose in dimethyl sulfoxide (DMSO), add lithium salt, mix thoroughly and disperse evenly to obtain a solid electrolyte precursor solution; and dry to obtain a sulfonyl cellulose-based solid electrolyte.

2. The method for preparing a sulfonyl cellulose-based solid electrolyte according to claim 1, wherein: In step S1, one or more of the following conditions are included: i. The organic solvent is dimethylacetamide (DMAc); ii. The lithium salt is lithium chloride (LiCl); the mass ratio of the lithium salt to the microcrystalline cellulose is 1-2:1; iii. The mass ratio of microcrystalline cellulose to the volume ratio of the organic solvent is 1:20-40 g / mL, preferably 1:30 g / mL; iv. Add microcrystalline cellulose and lithium salt into the organic solvent and stir at 100-130°C for 12-24 hours to fully disperse them.

3. The method for preparing a sulfonyl cellulose-based solid electrolyte according to claim 1, characterized in that: In step S1, the volume ratio of triethylamine to microcrystalline cellulose is 6-7 mL:4 g, preferably 6.5 mL:4 g; the mass ratio of toluenesulfonyl chloride to microcrystalline cellulose is 1-6:4, preferably 1.6115-5.3593:

4.

4. The method for preparing a sulfonyl cellulose-based solid electrolyte according to claim 1, wherein: In step S1, the reaction temperature is -5-5°C, the reaction time is 4-10 hours, and the reaction is carried out under stirring conditions.

5. The method for preparing a sulfonyl cellulose-based solid electrolyte according to claim 1, wherein: In step S2, the sulfonyl cellulose is a combination of sulfonyl celluloses prepared by using different ratios of microcrystalline cellulose (MCC) and toluenesulfonyl chloride; preferably, the sulfonyl cellulose is a combination of sulfonyl cellulose prepared by using a mass ratio of toluenesulfonyl chloride to microcrystalline cellulose of 2.1485:4 and sulfonyl cellulose prepared by using a mass ratio of toluenesulfonyl chloride to microcrystalline cellulose of 5.3593:

4.

6. The method for preparing a sulfonyl cellulose-based solid electrolyte according to claim 1, wherein: In step S2, the mass ratio of sulfonyl cellulose to dimethyl sulfoxide is 0.15-0.45:4-10 g / mL.

7. The method for preparing a sulfonyl cellulose-based solid electrolyte according to claim 1, wherein: In step S2, the lithium salt is lithium bis(fluorosulfonyl)imide; and the mass ratio of the lithium salt to the sulfonyl cellulose is 1-2:

1.

8. The method for preparing a sulfonyl cellulose-based solid electrolyte according to claim 1, wherein: In step S2, one or more of the following conditions are included: i. The conditions for thorough mixing and uniform dispersion are as follows: stirring at 50-80℃ for 5-8 hours; ii. applying a drop of the solid electrolyte precursor onto a glass plate and drying it to obtain a sulfonyl cellulose solid electrolyte; iii. Drying temperature is 50-80℃.

9. A sulfonyl cellulose-based solid electrolyte, characterized in that: Prepared by the method according to any one of claims 1 to 8.

10. Use of the sulfonyl cellulose-based solid electrolyte according to claim 9 in a solid-state lithium metal battery.

Images