A hard carbon anode material for sodium-ion batteries derived from wood waste, its preparation method and application

Abstract

This invention discloses a hard carbon anode material for sodium-ion batteries derived from wood waste, its preparation method, and its application. Waste wood derived from mulberry trees is washed, dried, pulverized, and then transferred to a muffle furnace. In an air atmosphere, it is heated to a pyrolysis temperature of 250-350 °C for carbonization. After cooling, a pre-carbonized material is obtained. The pre-carbonized material is pretreated using a hydrothermal method or a template method. The pretreated product is transferred to an atmosphere furnace and, under the protection of an inert gas, heated to a pyrolysis temperature of 1300-1500 °C for high-temperature carbonization. After carbonization, it is cooled to obtain a high-temperature carbonized product. This high-temperature carbonized product undergoes post-processing to obtain the hard carbon anode material derived from wood waste. The hard carbon material prepared by this invention through hydrothermal and template pretreatment has suitable interlayer spacing and pore structure, effectively reducing the defect concentration, reducing irreversible capacity loss, improving the reversible capacity, and exhibiting excellent cycle performance.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion battery electrode material preparation, and specifically relates to a hard carbon anode material for sodium-ion batteries derived from wood waste, its preparation method, and its application. Background Technology

[0002] Currently, sodium-ion batteries exhibit multiple advantages in terms of resource availability, electrochemical performance, and safety characteristics. Among various sodium-ion battery anode materials, carbon-based materials have become a focus of research and application due to their comprehensive advantages such as abundant resources, low cost, excellent conductivity, and structural stability. Although traditional graphite has been commercialized on a large scale in lithium-ion batteries, its relatively small interlayer spacing makes it difficult to achieve efficient sodium ion insertion and extraction during charge and discharge, resulting in significantly insufficient reversible capacity when used as a sodium-ion battery anode, thus rendering it unsuitable. Compared to graphite, hard carbon has a disordered microcrystalline structure and a larger interlayer spacing, which can effectively accommodate the insertion and extraction of larger-radius sodium ions. Due to its abundant resources, high capacity, and good cycle stability, hard carbon is considered a highly promising anode material for sodium-ion batteries. Among them, biomass-derived hard carbon materials have a unique microstructure and significant advantages in terms of abundant resources, renewability, sustainability, and cost-effectiveness. In recent years, biomass-derived hard carbon materials have attracted increasing attention from researchers and have shown broad application prospects in the field of sodium-ion battery energy storage.

[0003] In existing research on hard carbon materials, pyrolysis under an inert atmosphere is a common process for treating biomass carbon. Temperatures exceeding 1000℃ are typically required to obtain structurally ordered hard carbon. However, the complex composition, generally low electrical conductivity, and low degree of graphitization of biomass itself limit its electrochemical performance. To overcome these inherent drawbacks, pretreatment of biomass is necessary. In recent years, researchers have developed various methods to improve the porous structure, increase sodium storage sites, and expand interlayer spacing, thereby modifying biomass.

[0004] Modification methods for biomass-derived carbon-based materials include pyrolysis, chemical activation, hydrothermal methods, and template methods. Zhu et al. used H3PO4 as an activator and horse chestnut leaves as raw material to synthesize p-doped porous carbon (PC) via chemical activation. PC-3 exhibits stable and rapid sodium ion storage performance. (The last sentence appears to be incomplete and requires further context.) -1 At the current density, the reversible capacity is 310.4 mAh•g. -1 , in 2 A•g −1 After 200 cycles at a current density, the capacity is 226.2 mAh•g. -1However, this chemical activation method also has drawbacks. It causes excessive binding of sodium ions in the micropores, significantly reducing the initial efficiency; strong alkalis corrode the equipment, limiting mass production. Cao Xinxin et al. placed an appropriate amount of sisal into a reaction vessel containing different acids for hydrothermal reaction, followed by high-temperature carbonization to obtain sisal hard carbon anode material. The prepared sisal hard carbon material exhibited high plateau capacity and excellent long-cycle stability. However, this hydrothermal method with added acid causes excessive oxygen defects, and the residual acid washing cost is high. Zhang Yawei et al. used calcium carbonate as a template and groundwood lignin powder as raw material, utilizing a template method supplemented with unique process parameters to prepare hard carbon products with low surface area and large interlayer spacing. This achieved fine-tuning of the nanoscale pore size and precise control of the pore size distribution of the hard carbon material, increasing the plateau capacity from 131.2 mAh•g. -1 Increased to 239.47 mAh•g -1 .

[0005] Existing modification methods generally fail to synergistically achieve high sodium storage capacity, high initial coulombic efficiency, and excellent long-cycle stability. Although they can significantly improve the electrochemical performance of materials, problems such as insufficient capacity and low initial coulombic efficiency still exist. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a hard carbon anode material for sodium-ion batteries derived from wood waste, its preparation method and application, which modifies biomass raw materials to improve the electrochemical performance of the material.

[0007] To solve the above technical problems, according to one aspect of the present invention, a method for preparing a hard carbon anode material for a wood waste-derived sodium-ion battery is provided, comprising: Step 1: Wash and dry the waste wood derived from mulberry wood to obtain waste wood precursor; Step 2: After crushing the waste wood precursor, transfer it to a muffle furnace and carbonize it in an air atmosphere at a pyrolysis temperature of 250-350 ℃. After cooling, obtain the pre-carbonized material. Step 3: Pre-treat the pre-carbonized material using a hydrothermal method or a template method; The hydrothermal method involves mixing pre-carbonized materials with deionized water and carrying out a hydrothermal reaction at a temperature of 160℃-220℃ to obtain a pretreated product. The template method involves mixing pre-carbonized material with magnesium gluconate, then adding deionized water and stirring. After drying, the mixture is transferred to an atmosphere furnace and heated to a low-temperature carbonization temperature of 550℃-650℃ under inert gas protection to obtain the pretreated product. Step 4: Transfer the pretreated product to an atmosphere furnace and heat it to the pyrolysis temperature of 1300-1500 ℃ under the protection of inert gas for high-temperature carbonization. After carbonization, cool it down to obtain the high-temperature carbonized product. Step 5: Soak the high-temperature carbonization product in an acidic solution, then wash it with deionized water and ethanol until neutral. Dry, grind, and sieve the obtained product to obtain the wood waste-derived hard carbon anode material.

[0008] In a preferred embodiment, in step two, the heating rate of the muffle furnace is 5 °C / min, and the pyrolysis temperature is 300 °C.

[0009] In a preferred embodiment, in step three, the ratio of pre-carbonized material to deionized water in the hydrothermal method is 1 g / 10 mL.

[0010] In a preferred embodiment, in step three, the mass ratio of the pre-carbonized material to magnesium gluconate in the template method is 2:1-2:3.

[0011] In a preferred embodiment, in step three, the product obtained after the reaction is completed is cooled down, placed in an acidic solution for immersion, then washed with deionized water and ethanol until neutral, and dried to obtain the pretreated product.

[0012] In a preferred embodiment, in step four, the heating rate is 5°C / min and the pyrolysis temperature is 1400°C.

[0013] In a preferred embodiment, in step five, the acidic solution is a 1 mol / L dilute hydrochloric acid solution, and the soaking time is 12 hours.

[0014] According to another aspect of the present invention, a hard carbon anode material for sodium-ion batteries derived from wood waste is provided, obtained by any of the above methods.

[0015] According to another aspect of the present invention, the application of the above-described wood waste-derived sodium-ion battery hard carbon anode material in the preparation of carbon-based anode materials for sodium-ion batteries is provided.

[0016] According to another aspect of the invention, a sodium-ion battery is provided, comprising a sodium-ion battery carbon-based anode material prepared from the aforementioned wood waste-derived sodium-ion battery hard carbon anode material.

[0017] This invention uses mulberry wood as a precursor, which is low-cost, environmentally friendly, and suitable for large-scale production. The hard carbon material prepared by this invention through hydrothermal and template pretreatment has suitable interlayer spacing and pore structure, effectively reducing the defect concentration, minimizing irreversible capacity loss, improving reversible capacity, and exhibiting excellent cycling performance. Attached Figure Description

[0018] Figure 1 This is a SEM image of the biomass-derived hard carbon material prepared in Comparative Example 1; Figure 2 Here is a SEM image of the biomass-derived hard carbon material prepared in Example 3; Figure 3 The images show the XRD patterns of the biomass-derived hard carbon materials prepared in Comparative Example 1 and Example 3. Figure 4 The first charge-discharge curves of the biomass-derived hard carbon materials prepared in Comparative Example 1 and Example 3 are shown. Figure 5 This is a rate performance curve of the biomass-derived hard carbon materials prepared in Comparative Example 1 and Example 3; Figure 6 The graphs show the cycling performance of the biomass-derived hard carbon materials prepared in Comparative Example 1 and Example 3. Figure 7 This is the cyclic voltammogram of the biomass-derived hard carbon material prepared in Comparative Example 1; Figure 8 This is a cyclic voltammogram of the biomass-derived hard carbon material prepared in Example 3. Detailed Implementation

[0019] Mulberry trees are mainly used for silkworm rearing or fruit harvesting, but in actual production, pruned branches are usually discarded or burned, generating a large amount of waste every year. Based on this, a typical embodiment of the present invention provides a method for preparing hard carbon anode materials for sodium-ion batteries derived from wood waste, improving performance by treating the pre-carbonized products through different pretreatment methods.

[0020] Step 1, Material Pretreatment Waste wood derived from mulberry trees is washed and dried to obtain waste wood precursors.

[0021] More specifically, waste wood is placed in deionized water for ultrasonic washing to remove surface dust and impurities. The washed material is then placed in a forced-air drying oven for drying. The temperature of the forced-air drying oven is preferably 80°C, and the drying time is 12 hours.

[0022] Step 2, Pre-carbonization treatment Waste wood precursors are crushed and transferred to a muffle furnace, where they are heated to a pyrolysis temperature of 250-350℃ in an air atmosphere for carbonization. After cooling, pre-carbonized materials are obtained.

[0023] In this step, in some preferred embodiments, the pyrolysis temperature can be selected as 250℃, 280℃, 300℃, 320℃, or 350℃.

[0024] In a further preferred embodiment, the heating rate of the muffle furnace is 5°C / min, the pyrolysis temperature is 300°C, and the holding time is 2 hours.

[0025] Step 3, Modification Treatment In this step, the pre-carbonized material is pretreated using a hydrothermal method or a template method.

[0026] The solvent used in the hydrothermal method is deionized water. The pre-carbonized material is mixed with deionized water and subjected to a hydrothermal reaction to obtain the pretreated product.

[0027] In a further preferred embodiment, the ratio of pre-carbonized material to deionized water is 1 g / 10 mL.

[0028] The hydrothermal reaction temperature is 160℃-220℃. In some preferred embodiments, the hydrothermal reaction temperature can be selected as 160℃, 180℃, 200℃, or 220℃, and the heat preservation time is preferably 10h.

[0029] In some preferred embodiments, after the hydrothermal reaction is completed, the product is washed with deionized water and ethanol, and then placed in a forced-air drying oven and dried at 80°C for 12 hours to obtain the pretreated product.

[0030] The template method involves mixing pre-carbonized material with magnesium gluconate, then adding deionized water and stirring. After drying, the mixture is transferred to an atmosphere furnace and carbonized at low temperature under inert gas protection to obtain a pretreated product.

[0031] In this step, the preferred mass ratio of the pre-carbonized material to magnesium gluconate is 2:1 to 2:3, for example: 2:1, 2:2, 2:3.

[0032] The drying process is carried out in an oven, specifically at 80°C in some concrete embodiments. The inert gas is preferably argon.

[0033] The temperature for low-temperature carbonization is 550℃-650℃. In some preferred embodiments, the temperature for low-temperature carbonization can be selected as 550℃, 600℃, or 650℃.

[0034] In some preferred embodiments, after the low-temperature carbonization reaction is completed, the product is cooled and placed in an acidic solution for immersion. It is then washed with deionized water and ethanol until neutral, and dried to obtain the pretreated product. The acidic solution is preferably a 1 mol / L dilute hydrochloric acid solution.

[0035] Step 4, High-temperature carbonization The pretreated product is transferred to an atmosphere furnace and heated to the pyrolysis temperature of 1300-1500 ℃ under the protection of inert gas for high-temperature carbonization. After carbonization, the product is cooled to obtain the high-temperature carbonized product.

[0036] Argon is the preferred inert gas for high-temperature carbonization.

[0037] In this step, in some preferred embodiments, the pyrolysis temperature can be selected as 1300℃, 1350℃, 1400℃, 1450℃, or 1500℃.

[0038] In a further preferred embodiment, the heating rate is 5℃ / min, the pyrolysis temperature is 1400℃, the holding time is 2h, and the cooling rate is 5℃ / min.

[0039] Step 5, Post-processing The high-temperature carbonization product was soaked in an acidic solution, then washed with deionized water and ethanol until neutral. The resulting product was dried, ground, and sieved to obtain a hard carbon anode material derived from wood waste.

[0040] The product was dried in a forced-air drying oven at 80°C for 12 hours. The preferred acidic solution was a 1 mol / L dilute hydrochloric acid solution, and the soaking time was 12 hours.

[0041] The wood waste-derived sodium-ion battery hard carbon anode material obtained through the above embodiments can be used to prepare hard carbon anode sheets for sodium-ion batteries. The process involves grinding and mixing the wood waste-derived sodium-ion battery hard carbon anode material with acetylene black and polyvinylidene fluoride at a mass ratio of 8:1:1, adding N-methylpyrrolidone and stirring to obtain a uniformly mixed electrode slurry. The slurry is then uniformly coated onto copper foil using a coating machine, placed in a vacuum drying oven for 12 hours, and then formed into a disc electrode using a die-cutting machine to obtain a hard carbon material electrode sheet. The prepared hard carbon material anode sheet can be further used to prepare sodium-ion batteries.

[0042] The technical solutions claimed in this invention will be further described below through some embodiments. However, the embodiments and comparative examples are for explaining the implementation schemes of this invention and do not exceed the scope of the subject matter of this invention. The scope of protection of this invention is not limited by the embodiments. Unless otherwise specified, the materials and reagents used in this invention can be obtained from commercially available products in the art.

[0043] Example 1 The mulberry wood was ultrasonically washed with deionized water for 2 hours to remove surface dust and impurities. After washing, it was dried in a forced-air drying oven at 80°C for 12 hours.

[0044] The dried mulberry wood was placed in a pulverizer and pulverized. After pulverization, it was transferred to a muffle furnace and heated to 300°C at a heating rate of 5°C / min under air atmosphere. The temperature was then maintained for 2 hours. After natural cooling, the pre-carbonized material was obtained.

[0045] The pre-carbonized material and deionized water were placed in a hydrothermal reactor at a mass-volume ratio of 1 g / 10 mL and kept at 160 °C for 10 h. The mixture was then washed with deionized water and ethanol until the supernatant was clear. The resulting product was placed in a forced-air drying oven and dried at 80 °C for 12 h to obtain the pretreated product.

[0046] The pretreated product was placed in a tube furnace and heated from room temperature to 1400°C at a rate of 5°C / min under the protection of inert argon gas. The temperature was held for 2 hours and then cooled to room temperature at a rate of 5°C / min.

[0047] After cooling, the material was soaked in a 1 mol / L dilute hydrochloric acid solution for 12 hours, then washed with deionized water and ethanol until neutral. The resulting product was placed in a forced-air drying oven and dried at 80℃ for 12 hours. After drying, the material was ground and sieved to obtain mulberry wood-derived hard carbon anode material.

[0048] Example 2 The mulberry wood was ultrasonically washed with deionized water for 2 hours to remove surface dust and impurities. After washing, it was dried in a forced-air drying oven at 80°C for 12 hours.

[0049] The dried mulberry wood was placed in a pulverizer and pulverized. After pulverization, it was transferred to a muffle furnace and heated to 300°C at a heating rate of 5°C / min under air atmosphere. The temperature was then maintained for 2 hours. After natural cooling, the pre-carbonized material was obtained.

[0050] The pre-carbonized material and deionized water were placed in a hydrothermal reactor at a mass-volume ratio of 1 g / 10 mL and kept at 180 °C for 10 h. The mixture was then washed with deionized water and ethanol until the supernatant was clear. The resulting product was placed in a forced-air drying oven and dried at 80 °C for 12 h to obtain the pretreated product.

[0051] The pretreated product was placed in a tube furnace and heated from room temperature to 1400℃ at a heating rate of 5℃ / min under the protection of inert argon gas. The temperature was held for 2 hours and then cooled to room temperature at a cooling rate of 5℃ / min.

[0052] After cooling, the material was soaked in a 1 mol / L dilute hydrochloric acid solution for 12 hours, then washed with deionized water and ethanol until neutral. The resulting product was placed in a forced-air drying oven and dried at 80℃ for 12 hours. After drying, the material was ground and sieved to obtain mulberry wood-derived hard carbon anode material.

[0053] Example 3 The mulberry wood was ultrasonically washed with deionized water for 2 hours to remove surface dust and impurities. After washing, it was dried in a forced-air drying oven at 80°C for 12 hours.

[0054] The dried mulberry wood was placed in a pulverizer and pulverized. After pulverization, it was transferred to a muffle furnace and heated to 300°C at a heating rate of 5°C / min under air atmosphere. The temperature was then maintained for 2 hours. After natural cooling, the pre-carbonized material was obtained.

[0055] The pre-carbonized material and deionized water were placed in a hydrothermal reactor at a mass-volume ratio of 1 g / 10 mL and kept at 200 °C for 10 h. Then, the mixture was washed with deionized water and ethanol until the supernatant was clear. The resulting product was placed in a forced-air drying oven and dried at 80 °C for 12 h to obtain the pretreated product.

[0056] The pretreated product was placed in a tube furnace and heated from room temperature to 1400℃ at a heating rate of 5℃ / min under the protection of inert argon gas. The temperature was held for 2 hours and then cooled to room temperature at a cooling rate of 5℃ / min.

[0057] After cooling, the material was soaked in a 1 mol / L dilute hydrochloric acid solution for 12 hours, then washed with deionized water and ethanol until neutral. The resulting product was placed in a forced-air drying oven and dried at 80℃ for 12 hours. After drying, the material was ground and sieved to obtain mulberry wood-derived hard carbon anode material.

[0058] Example 4 The mulberry wood was ultrasonically washed with deionized water for 2 hours to remove surface dust and impurities. After washing, it was dried in a forced-air drying oven at 80°C for 12 hours.

[0059] The dried mulberry wood was placed in a pulverizer and pulverized. After pulverization, it was transferred to a muffle furnace and heated to 300°C at a heating rate of 5°C / min under air atmosphere. The temperature was then maintained for 2 hours. After natural cooling, the pre-carbonized material was obtained.

[0060] The pre-carbonized material and deionized water were placed in a hydrothermal reactor at a mass-volume ratio of 1 g / 10 mL and kept at 220 °C for 10 h. The mixture was then washed with deionized water and ethanol until the supernatant was clear. The resulting product was placed in a forced-air drying oven and dried at 80 °C for 12 h to obtain the pretreated product.

[0061] The pretreated product was placed in a tube furnace and heated from room temperature to 1400°C at a rate of 5°C / min under the protection of inert argon gas. The temperature was held for 2 hours and then cooled to room temperature at a rate of 5°C / min.

[0062] After cooling, the material was soaked in a 1 mol / L dilute hydrochloric acid solution for 12 hours, then washed with deionized water and ethanol until neutral. The resulting product was placed in a forced-air drying oven and dried at 80℃ for 12 hours. After drying, the material was ground and sieved to obtain mulberry wood-derived hard carbon anode material.

[0063] Example 5 The mulberry wood was ultrasonically washed with deionized water for 2 hours to remove surface dust and impurities. After washing, it was dried in a forced-air drying oven at 80°C for 12 hours.

[0064] The dried mulberry wood was placed in a pulverizer and pulverized. After pulverization, it was transferred to a muffle furnace and heated to 300°C at a heating rate of 5°C / min under air atmosphere. The temperature was then maintained for 2 hours. After natural cooling, the pre-carbonized material was obtained.

[0065] The pre-carbonized material was mixed with magnesium gluconate at a mass ratio of 2:1, and 20 ml of deionized water was added. The mixture was stirred for 12 h, then dried in an 80 °C oven. The mixture was then placed in a tube furnace and heated from room temperature to 600 °C at a rate of 5 °C / min under the protection of inert argon gas, held at that temperature for 2 h, and then cooled to room temperature at a rate of 5 °C / min. After cooling, the mixture was soaked in a 1 mol / L dilute hydrochloric acid solution for 12 h, then washed with deionized water and ethanol until neutral. The resulting product was then placed in a forced-air drying oven and dried at 80 °C for 12 h to obtain the pretreated product.

[0066] The pretreated product was placed in a tube furnace and heated from room temperature to 1400°C at a rate of 5°C / min under the protection of inert argon gas. The temperature was held for 2 hours and then cooled to room temperature at a rate of 5°C / min.

[0067] After cooling, the material was soaked in a 1 mol / L dilute hydrochloric acid solution for 12 hours, then washed with deionized water and ethanol until neutral. The resulting product was placed in a forced-air drying oven and dried at 80℃ for 12 hours. After drying, the material was ground and sieved to obtain mulberry wood-derived hard carbon anode material.

[0068] Example 6 The mulberry wood was ultrasonically washed with deionized water for 2 hours to remove surface dust and impurities. After washing, it was dried in a forced-air drying oven at 80°C for 12 hours.

[0069] The dried mulberry wood was placed in a pulverizer and pulverized. After pulverization, it was transferred to a muffle furnace and heated to 300°C at a heating rate of 5°C / min under air atmosphere. The temperature was then maintained for 2 hours. After natural cooling, the pre-carbonized material was obtained.

[0070] The pre-carbonized material was mixed with magnesium gluconate at a mass ratio of 2:2, and 20 ml of deionized water was added and stirred for 12 h. The mixture was then dried in an 80 °C oven and placed in a tube furnace under the protection of inert argon gas. The temperature was increased from room temperature to 600 °C at a rate of 5 °C / min and held for 2 h. The mixture was then cooled to room temperature at a rate of 5 °C / min. After cooling, the mixture was immersed in a 1 mol / L dilute hydrochloric acid solution for 12 h, followed by washing with deionized water and ethanol until neutral. The resulting product was then placed in a forced-air drying oven and dried at 80 °C for 12 h to obtain the pretreated product.

[0071] The pretreated product was placed in a tube furnace and heated from room temperature to 1400°C at a rate of 5°C / min under the protection of inert argon gas. The temperature was held for 2 hours and then cooled to room temperature at a rate of 5°C / min.

[0072] After cooling, the material was soaked in a 1 mol / L dilute hydrochloric acid solution for 12 hours, then washed with deionized water and ethanol until neutral. The resulting product was placed in a forced-air drying oven and dried at 80℃ for 12 hours. After drying, the material was ground and sieved to obtain mulberry wood-derived hard carbon anode material.

[0073] Example 7 The mulberry wood was ultrasonically washed with deionized water for 2 hours to remove surface dust and impurities. After washing, it was dried in a forced-air drying oven at 80°C for 12 hours.

[0074] The dried mulberry wood was placed in a pulverizer and pulverized. After pulverization, it was transferred to a muffle furnace and heated to 300°C at a heating rate of 5°C / min under air atmosphere. The temperature was then maintained for 2 hours. After natural cooling, the pre-carbonized material was obtained.

[0075] The pre-carbonized material was mixed with magnesium gluconate at a mass ratio of 2:3, and 20 ml of deionized water was added. The mixture was stirred for 12 h, then dried in an oven at 80 °C. The mixture was then placed in a tube furnace and heated from room temperature to 600 °C at a rate of 5 °C / min under the protection of inert argon gas, held at that temperature for 2 h, and then cooled to room temperature at a rate of 5 °C / min. After cooling, the mixture was immersed in a 1 mol / L dilute hydrochloric acid solution for 12 h, then washed with deionized water and ethanol until neutral. The resulting product was then placed in a forced-air drying oven and dried at 80 °C for 12 h to obtain the pretreated product.

[0076] The pretreated product was placed in a tube furnace and heated from room temperature to 1400°C at a rate of 5°C / min under the protection of inert argon gas. The temperature was held for 2 hours and then cooled to room temperature at a rate of 5°C / min.

[0077] After cooling, the material was soaked in a 1 mol / L dilute hydrochloric acid solution for 12 hours, then washed with deionized water and ethanol until neutral. The resulting product was placed in a forced-air drying oven and dried at 80℃ for 12 hours. After drying, the material was ground and sieved to obtain mulberry wood-derived hard carbon anode material.

[0078] Comparative Example 1 The mulberry wood was ultrasonically washed with deionized water for 2 hours to remove surface dust and impurities. After washing, it was dried in a forced-air drying oven at 80°C for 12 hours.

[0079] The dried mulberry wood was crushed in a pulverizer and then transferred to a muffle furnace. Under an air atmosphere, the temperature was raised to 300℃ at a heating rate of 5℃ / min and held for 2 hours. After natural cooling, the pre-carbonized material was obtained.

[0080] The pre-carbonized material was placed in a tube furnace and heated from room temperature to 1400℃ at a heating rate of 5℃ / min under the protection of inert argon gas. The temperature was held for 2 hours and then cooled to room temperature at a cooling rate of 5℃ / min.

[0081] After cooling, the material was soaked in a 1 mol / L dilute hydrochloric acid solution for 12 h, then washed with deionized water and ethanol until neutral. The resulting product was placed in a forced-air drying oven and dried at 80℃ for 12 h. After drying, the material was ground and sieved to obtain mulberry wood-derived hard carbon anode material.

[0082] The mulberry wood-derived hard carbon anode materials obtained in each embodiment and Comparative Example 1 were ground and mixed with acetylene black and polyvinylidene fluoride at a mass ratio of 8:1:1. N-methylpyrrolidone was added and stirred to obtain a uniformly mixed electrode slurry. The battery slurry was uniformly coated onto copper foil using a coating machine and placed in a vacuum drying oven for 12 h of vacuum drying. Then, it was prepared into a circular electrode with a diameter of 12 mm using a punching machine to obtain a hard carbon material electrode sheet.

[0083] The electrode sheet obtained above was used as the negative electrode, a glass fiber (Whitman, GF / D) disc with a diameter of 19 mm was used as the separator, and a sodium metal sheet with a diameter of 12 mm and a thickness of 0.2 mm was used as the counter electrode and reference electrode. The electrolyte was a 1 mol / L sodium perchlorate / ethylene carbonate / dimethyl carbonate solution. The sodium-ion battery was assembled in a glove box filled with high-purity argon gas according to the construction of a CR2016 standard coin cell. The battery was charged and discharged on a battery test platform at a current density of 20 mA / g (0.1C).

[0084] Table 1. Main parameters and electrochemical performance of Examples 1-7 and Comparative Example 1

[0085] As can be seen from Table 1, Examples 1-7, which underwent pretreatment using the hydrothermal or template method, outperformed Comparative Example 1, which was untreated, in terms of initial coulombic efficiency and initial reversible specific capacity.

[0086] Figure 1 , 2 The images shown are SEM images of Comparative Example 1 and Example 3, respectively. It can be seen that the hard carbon material of Example 3 exhibits a richer pore structure after hydrothermal treatment, providing abundant sodium ion active sites, which is beneficial for sodium ion storage and can effectively improve reversible capacity. Figure 3In the XRD patterns shown, Comparative Example 1 and Example 3 both show characteristic peaks near 23° and 43°, which correspond to the diffraction of the (002) and (100) crystal planes, respectively, indicating that the materials are both amorphous carbon materials. Figure 4 The figures show the charge-discharge curves of Comparative Example 1 and Example 3 at a current density of 20 mA / g. Example 3 shows an initial coulombic efficiency of 70.05% and a current density of 323.7 mAh•g. -1 The initial reversible specific capacity; Figure 5 The rate performance graph shown indicates that the material in Example 3 exhibits better rate performance; Figure 6 The graph shows the cycling performance of Comparative Example 1 and Example 3 at 200 mA / g. After 50 cycles, the charging capacity of Comparative Example 1 is 165.2 mAh•g. -1 The capacity retention rate was 92.08%, and the charging capacity in Example 3 was 254.6 mAh•g. -1 The capacity retention rate was 93.06%. Figure 7 , 8 The figures show the cyclic voltammetry curves of Comparative Example 1 and Example 3 at a scan rate of 0.1 mV / s, respectively. Compared with Comparative Example 1, Example 3 shows better overlap in the second and third cycles, indicating that it has higher sodium ion insertion / extraction reversibility. The smallest irreversible peak area proves that it has the highest ICE.

[0087] The above-described embodiments are merely preferred embodiments of the present invention, illustrating the basic principles and features of the present invention. The present invention is not limited to the specific implementation methods described above. All improvements and optimizations made within the scope of the methods disclosed in the present invention are within the protection scope of the present invention.

Claims

1. A method for preparing a hard carbon anode material for sodium-ion batteries derived from wood waste, characterized in that, include: Step 1: Wash and dry the waste wood derived from mulberry wood to obtain waste wood precursor; Step 2: After crushing the waste wood precursor, transfer it to a muffle furnace and carbonize it in an air atmosphere at a pyrolysis temperature of 250-350 ℃. After cooling, obtain the pre-carbonized material. Step 3: Pre-treat the pre-carbonized material using a hydrothermal method or a template method; The hydrothermal method involves mixing pre-carbonized materials with deionized water and carrying out a hydrothermal reaction at a temperature of 160℃-220℃ to obtain a pretreated product. The template method involves mixing pre-carbonized material with magnesium gluconate, then adding deionized water and stirring. After drying, the mixture is transferred to an atmosphere furnace and heated to a low-temperature carbonization temperature of 550℃-650℃ under inert gas protection to obtain the pretreated product. Step 4: Transfer the pretreated product to an atmosphere furnace and heat it to the pyrolysis temperature of 1300-1500 ℃ under the protection of inert gas for high-temperature carbonization. After carbonization, cool it down to obtain the high-temperature carbonized product. Step 5: Soak the high-temperature carbonization product in an acidic solution, then wash it with deionized water and ethanol until neutral. Dry, grind, and sieve the obtained product to obtain the wood waste-derived hard carbon anode material.

2. The method for preparing the hard carbon anode material for sodium-ion batteries derived from wood waste according to claim 1, characterized in that: In step two, the heating rate of the muffle furnace is 5 ℃ / min, and the pyrolysis temperature is 300℃.

3. The method for preparing the hard carbon anode material for sodium-ion batteries derived from wood waste according to claim 1 or 2, characterized in that: In step three, the ratio of pre-carbonized material to deionized water in the hydrothermal method is 1 g / 10 mL.

4. The method for preparing the hard carbon anode material for sodium-ion batteries derived from wood waste according to claim 1 or 2, characterized in that: In step three, the mass ratio of the pre-carbonized material to magnesium gluconate in the template method is 2:1-2:

3.

5. The method for preparing the hard carbon anode material for sodium-ion batteries derived from wood waste according to claim 4, characterized in that: In step three, after the reaction is complete, the product is cooled and placed in an acidic solution for immersion. Then, it is washed with deionized water and ethanol until neutral, and dried to obtain the pretreated product.

6. The method for preparing the hard carbon anode material for sodium-ion batteries derived from wood waste according to claim 1 or 5, characterized in that: In step four, the heating rate is 5℃ / min and the pyrolysis temperature is 1400℃.

7. The method for preparing the hard carbon anode material for sodium-ion batteries derived from wood waste according to claim 6, characterized in that: In step five, the acidic solution is a 1 mol / L dilute hydrochloric acid solution, and the soaking time is 12 hours.

8. A hard carbon anode material for sodium-ion batteries derived from wood waste, obtained by any one of claims 1-7.

9. The application of the wood waste-derived sodium-ion battery hard carbon anode material of claim 8 in the preparation of carbon-based anode materials for sodium-ion batteries.

10. A sodium-ion battery, characterized in that: This includes carbon-based anode materials for sodium-ion batteries prepared from the wood waste-derived hard carbon anode material for sodium-ion batteries as described in claim 8.

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