Preparation method of cellulose-derived hard carbon negative electrode material based on ionic liquid treatment and application of cellulose-derived hard carbon negative electrode material in sodium-ion battery

Abstract

The invention belongs to the technical field of sodium ion battery negative electrode materials, and discloses a preparation method of a cellulose-derived hard carbon negative electrode material based on ionic liquid treatment and application of the cellulose-derived hard carbon negative electrode material in a sodium ion battery. The method comprises the following steps: firstly, pretreating cellulose by utilizing ionic liquid, and destroying the crystal structure of the cellulose and improving the reaction activity of the cellulose through the unique solubility and reaction activity of the ionic liquid; then, the pretreated cellulose is subjected to high-temperature carbonization in an inert atmosphere, and the hard carbon material with rich nanopores and excellent electrochemical performance is prepared. The hard carbon material is used as a sodium-ion battery negative electrode, and shows high specific capacity, excellent cycling stability and good rate capability. The hard carbon negative electrode material provided by the invention is simple in preparation process and suitable for large-scale production, and a new technical path is provided for development of a high-performance negative electrode material of a sodium-ion battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of negative electrode materials for sodium ion batteries, and relates to a preparation method of a cellulose-derived hard carbon negative electrode material based on ionic liquid treatment and an application thereof in sodium ion batteries. Background Art

[0002] With the rapid growth of global energy demand and the increasing depletion of fossil fuel resources, the development of efficient and sustainable energy storage technologies has become an urgent need of today's society. Sodium-ion batteries (SIBs) are considered to be one of the important candidate technologies in the field of large-scale energy storage due to their abundant sodium resources, low cost, and similar working principles to lithium-ion batteries. However, the development of sodium-ion batteries is limited by the performance of negative electrode materials. Traditional graphite negative electrode materials are difficult to meet the requirements of high capacity and long cycle life due to the difficulty of sodium ion embedding. Therefore, the development of new negative electrode materials suitable for sodium ion storage has become the focus of current research.

[0003] Hard carbon materials have become a hot topic in the research of negative electrode materials for sodium ion batteries because of their unique disordered structure and abundant nanopores, which can effectively store sodium ions and exhibit excellent electrochemical properties. In particular, hard carbon materials prepared with biomass as precursors are not only widely available and low-cost, but also have controllable microstructures and excellent electrochemical properties, showing great application potential. Cellulose, as an abundant natural biomass resource, has the advantages of being renewable, environmentally friendly and low-cost, and is an ideal precursor for the preparation of hard carbon materials. However, the traditional cellulose carbonization process has problems such as high reaction temperature, high energy consumption, and difficult to control product structure, which limits its application in sodium ion batteries.

[0004] In view of the above problems, the present invention proposes a method for preparing cellulose-derived hard carbon materials based on ionic liquid pretreatment. As a green solvent, ionic liquid has the advantages of low volatility, high thermal stability and designability, and has been widely used in the fields of biomass pretreatment and material synthesis. Pretreatment of cellulose with ionic liquid can effectively destroy the crystalline structure of cellulose and change its microscopic crystal arrangement, thereby improving its reaction activity. This pretreatment method can achieve precise control of the microstructure of hard carbon materials in the subsequent carbonization process, such as optimizing pore distribution, increasing defect sites and regulating the number of closed pores, thereby significantly improving the electrochemical properties of hard carbon materials.

[0005] At present, the research on the preparation of hard carbon negative electrode materials by treating cellulose with ionic liquids is still in its infancy, and its process optimization and performance regulation mechanism are still unclear. Therefore, it is of great scientific significance and practical value to develop a cellulose-derived hard carbon negative electrode material based on ionic liquid treatment and explore its application in sodium ion batteries. The present invention aims to prepare high-performance hard carbon negative electrode materials by optimizing the ionic liquid treatment process and carbonization conditions, and provide a new solution for the development of sodium ion batteries. Summary of the invention

[0006] The object of the present invention is to provide a cellulose-derived sodium ion battery hard carbon negative electrode material based on ionic liquid treatment.

[0007] The technical solution of the present invention:

[0008] A method for preparing a cellulose-derived hard carbon negative electrode material based on ionic liquid treatment, firstly pre-treating cellulose with ionic liquid, destroying the crystalline structure of cellulose and improving its reactivity through the unique solubility and reactivity of ionic liquid; then, carbonizing the pre-treated cellulose at high temperature under an inert atmosphere to prepare a hard carbon material with abundant nanopores and excellent electrochemical properties. The specific experimental process is as follows:

[0009] (1) adding cellulose to the ionic liquid, controlling the ratio of cellulose mass g to ionic liquid volume mL to be 6:24 to 100:24, placing the mixture in a 60 to 80° C. water bath, and continuously stirring on a magnetic stirrer for 8 h until the cellulose is completely dispersed in the ionic liquid, thereby obtaining a cellulose-ionic liquid mixture;

[0010] (2) transferring the uniformly dispersed cellulose-ionic liquid mixture into a quartz boat to ensure that the cellulose-ionic liquid mixture is evenly spread, and heating the mixture to 1400° C. at a rate of 5° C. / min in an Ar gas environment and maintaining the temperature for 1 h to obtain a carbonized hard carbon material;

[0011] (3) The carbonized hard carbon material is taken out, and repeatedly washed with a detergent to remove residual ionic liquid and other impurities. The washed material is dried in a vacuum drying oven at 80° C. for 12 hours to obtain a hard carbon negative electrode material HC-ILs-1400.

[0012] The detergent comprises hydrochloric acid solution and deionized water, and the hydrochloric acid solution and the deionized water are washed alternately. The molar concentration of the hydrochloric acid solution is 0.5-1.2M.

[0013] In step (1), the ionic liquid is 1-butyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium chloride or 1-butylpyridinium chloride.

[0014] The hard carbon negative electrode material obtained by the above preparation method is used as a negative electrode material for sodium ion batteries.

[0015] The beneficial effects of the present invention are as follows: by treating cellulose with ionic liquid, the crystalline structure of cellulose is effectively destroyed, and its reaction activity is improved, so that the hard carbon material obtained after carbonization has richer nanopores and higher specific surface area, thereby significantly improving the specific capacity and rate performance of the sodium ion battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 The charge and discharge curves of HC-ILs-1400 and HC-1400 materials prepared in Example 2 and Comparative Example 1.

[0017] Figure 2 Cyclic test curves of HC-ILs-1400 and HC-1400 materials prepared in Example 2 and Comparative Example 1.

[0018] Figure 3 The rate test curves of HC-ILs-1400 and HC-1400 materials prepared in Example 2 and Comparative Example 1. DETAILED DESCRIPTION

[0019] The specific implementation scheme of the present invention is further described below in conjunction with the accompanying drawings and technical solutions.

[0020] The following comparative examples and examples were tested by assembling a sodium ion battery system: the active material, conductive additive (Super P) and binder (PVDF) were mixed in a ratio of 8:1:1 to form a slurry, and then the slurry was scraped onto a copper foil. The copper foil was dried in a vacuum oven at 60°C for 12 hours and then cut into electrode sheets with a diameter of 10 mm. In an argon-filled glove box (H2O and O2 <0.1ppm), the electrode sheet, diaphragm (glass fiber filter GF / D) and metallic sodium were assembled into a CR2032 button cell. 1mol L -1 NaPF6 was dissolved in ethylene glycol dimethyl ether as the electrolyte. First, HC-ILs-1400 was pre-sodiumized by simple contact with a sodium sheet. The charge-discharge curves (GCD) and cycle performance were obtained on a LAND-CT2001A battery tester (Wuhan, China). Electrochemical impedance spectroscopy and cyclic voltammetry were performed by an electrochemical workstation (CHI660, China). All electrochemical tests were performed in the voltage range of 0.01–2.5 V and at room temperature (25 °C).

[0021] Example 1

[0022] Weigh 0.75g of cellulose powder and 3ml of ionic liquid (1-butyl-3-methylimidazole acetate), add cellulose to the ionic liquid, and magnetically stir in a 70℃ water bath for 8h until the cellulose is completely dispersed. Transfer the sample to a quartz boat, flatten it evenly, and put it into a tube furnace. Heat the tube furnace to 1400℃ at a heating rate of 5℃ / min and keep it at this temperature for 1h. After carbonization, cool it naturally to room temperature, take out the hard carbon material, wash it repeatedly with deionized water and hydrochloric acid solution, and vacuum dry it at 80℃ for 12h.

[0023] Example 2

[0024] Preparation of HC-ILs-1400 materials

[0025] The mass of the cellulose powder was 1.0 g, and the rest was the same as in Example 1.

[0026] Example 3

[0027] The mass of the cellulose powder is 1.25 g, and the rest is the same as in Example 1.

[0028] Example 4

[0029] Weigh 1.0 g of cellulose powder and 3 ml of ionic liquid (1-butyl-3-methylimidazolium chloride), add cellulose to the ionic liquid, and magnetically stir in a 70°C water bath for 8 hours until the cellulose is completely dispersed. Transfer the sample to a quartz boat, flatten it evenly, and put it into a tube furnace. Heat the tube furnace to 1400°C at a heating rate of 5°C / min and keep it at this temperature for 1 hour. After carbonization, cool it naturally to room temperature, take out the hard carbon material, wash it repeatedly with deionized water and hydrochloric acid solution, and vacuum dry it at 80°C for 12 hours.

[0030] Example 5

[0031] The type of ionic liquid was changed to 1-butylpyridinium chloride, and the rest was the same as in Implementation Example 4.

[0032] Comparative Example 1

[0033] Preparation of HC-1400 material

[0034] Weigh 2.0 g of cellulose powder, place it in a quartz boat, heat the tube furnace to 1400°C at a heating rate of 5°C / min, and maintain at this temperature for 1 hour. After carbonization, cool it naturally to room temperature, take out the hard carbon material, wash it repeatedly with deionized water and hydrochloric acid solution, and vacuum dry it at 80°C for 12 hours.

[0035] Comparative Example 2

[0036] Weigh 1.5 g of cellulose powder and 3 ml of ionic liquid (1-butyl-3-methylimidazole acetate), add cellulose to the ionic liquid, and magnetically stir in a 70°C water bath for 8 hours until the cellulose is completely dispersed. Transfer the sample to a quartz boat, flatten it evenly, and put it into a tube furnace. Heat the tube furnace to 1400°C at a heating rate of 5°C / min and keep it at this temperature for 1 hour. After carbonization, cool it naturally to room temperature, take out the hard carbon material, wash it repeatedly with deionized water and hydrochloric acid solution, and vacuum dry it at 80°C for 12 hours.

[0037] The test results of the embodiments and comparative examples are as follows:

[0038] As shown in Figure (1), at 0.025Ag -1 At the current density of 1.547 W, the first cycle charge capacity of HC-1400 is 261.62 mAh g -1 , while the first cycle charge capacity of HC-ILs-1400 is 285.6 mAh g -1 , that is, the first cycle charge capacity of HC-ILs-1400 is higher than that of HC-1400, which may be because the ionic liquid treatment of cellulose effectively destroys the hydrogen bond network and crystalline regions of cellulose, transforming it into an amorphous state, making it easier to form a porous structure during the carbonization process. This porous structure provides more sodium ion storage sites, significantly improving the first cycle charge capacity.

[0039] As shown in Figure (2), at 1Ag -1 After 200 cycles at a current density of , the capacity retention rate of HC-1400 was 72.48%, and the capacity retention rate of HC-ILs-1400 was 89.44%, indicating that HC-ILs-1400 has better cycle stability.

[0040] From Figure (3), we can see that at 0.025, 0.05, 0.1, 0.2, 0.5, 1, 2, 5Ag -1 Under these conditions, the specific capacities of HC-ILs-1400 are 314.5, 275.7, 253.8, 238.9, 213.8, 182.9, 121.8, and 53.5 mAh g -1 And it can be observed from Figure (3) that the rate of HC-ILs-1400 is significantly improved compared with HC-1400.

Claims

1. A method for preparing a cellulose-derived hard carbon negative electrode material based on ionic liquid treatment, characterized in that: Here are the steps: (1) adding cellulose to the ionic liquid, controlling the ratio of cellulose mass g to ionic liquid volume mL to be 6:24 to 100:24, placing the mixture in a 60 to 80° C. water bath, and continuously stirring on a magnetic stirrer for 8 h until the cellulose is completely dispersed in the ionic liquid, thereby obtaining a cellulose-ionic liquid mixture; (2) transferring the uniformly dispersed cellulose-ionic liquid mixture into a quartz boat to ensure that the cellulose-ionic liquid mixture is evenly spread, and heating the mixture to 1400° C. at a rate of 5° C. / min in an Ar gas environment and maintaining the temperature for 1 h to obtain a carbonized hard carbon material; (3) The carbonized hard carbon material is taken out, and repeatedly washed with a detergent to remove residual ionic liquid and other impurities. The washed material is dried in a vacuum drying oven at 80° C. for 12 hours to obtain a hard carbon negative electrode material HC-ILs-1400.

2. The preparation method according to claim 1, characterized in that: The detergent comprises hydrochloric acid solution and deionized water, and the hydrochloric acid solution and the deionized water are washed alternately. The molar concentration of the hydrochloric acid solution is 0.5-1.2M.

3. The preparation method according to claim 1, characterized in that: In step (1), the ionic liquid is 1-butyl-3-methylimidazolium acetate, 1-butyl-3-methylimidazolium chloride or 1-butylpyridinium chloride.

4. Use of the hard carbon negative electrode material obtained by the preparation method according to any one of claims 1 to 3 as a negative electrode material for sodium ion batteries.

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