Nitrogen / carbon synergistically modified lignocellulose-based hard carbon material, preparation method and application
By synergistically modifying lignocellulose materials with urea and sugars, nitrogen-doped hard carbon materials were prepared, which solved the performance deficiencies of lignocellulose materials in sodium-ion batteries, improved the electrochemical performance and cycle stability of the batteries, and has good industrial application value.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HEFEI INSTITUTE OF PHYSICAL SCIENCE CHINESE ACADEMY OF SCIENCES
- Filing Date
- 2026-06-23
- Publication Date
- 2026-07-24
AI Technical Summary
Existing lignocellulose materials suffer from low initial coulombic efficiency, poor sodium storage capacity, and poor cycle stability during the preparation of carbon materials, which limits their application in sodium-ion batteries.
By introducing urea and sugars during hydrothermal treatment, nitrogen/carbon synergistic modification is achieved, optimizing the structure of carbon materials. High-temperature carbonization process is then used to prepare hard carbon materials with optimized nitrogen doping, thereby improving electrochemical performance.
It significantly improves the first-pass coulombic efficiency and rate performance of hard carbon anode materials for sodium-ion batteries, achieving a balance between material performance and economic benefits, and the process is simple and environmentally friendly.
Smart Images
Figure CN122444166A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the technical field of sodium-ion battery anode materials, specifically relating to a nitrogen / carbon synergistic modified lignocellulose-based hard carbon material, its preparation method, and its application. Background Technology
[0002] Sodium-ion batteries are considered a promising next-generation energy storage device due to the abundance, wide distribution, and low cost of sodium in the Earth's crust. Their electrochemical working principle is similar to that of lithium-ion batteries, and they have broad application prospects in large-scale grid energy storage, low-speed electric vehicles, and portable electronic devices. Hard carbon materials, with their core advantages such as adjustable interlayer spacing, moderate specific surface area, high sodium storage capacity, and excellent cycle stability, are currently one of the preferred technologies for sodium-ion battery anode materials.
[0003] Lignocellulose materials are mainly composed of three parts: cellulose, hemicellulose, and lignin. The mass percentages of cellulose, hemicellulose, and lignin are 30%-50%, 20%-40%, and 15%-25%, respectively. These three components interact through covalent and hydrogen bonds, forming a dense three-dimensional network structure. The high crystallinity of cellulose in lignocellulose materials, along with the coating and cross-linking effect of lignin on cellulose and hemicellulose, creates a natural anti-degradation barrier. While this structural characteristic endows plant cell walls with excellent mechanical strength and resilience, it also significantly increases the difficulty of processing lignocellulose materials during subsequent conversion and utilization, thus limiting their applications. Lignocellulose materials are widely found in plant-derived biomass such as wood, bamboo, crop straw, forestry processing residues, and agricultural processing byproducts. Among them, crop straw includes corn stalks, wheat straw, rice straw, etc., forestry processing residues include wood chips, sawdust, etc., and agricultural product processing by-products include rice husks, sugarcane bagasse, etc. These materials are usually treated as wastes in the production and processing process. The conventional treatment method is to burn them directly as fuel. However, they have problems such as low thermal efficiency and significant environmental pollution, making it difficult for them to truly meet the requirements of modern energy use for high efficiency, cleanliness, and sustainability.
[0004] In recent years, the preparation of hard carbon anode materials using lignocellulose as raw material has become a research hotspot and has been widely used in the preparation of anode materials for sodium-ion batteries. However, due to the disordered structure of cellulose, hemicellulose, and lignin in lignocellulose materials, uneven cross-linking, and the presence of ash impurities, a large number of defective structures are easily generated during pyrolysis and carbonization. This results in low initial coulombic efficiency, poor sodium storage capacity, rate performance, and cycle stability of the carbon materials prepared from them, which cannot meet the actual application requirements of sodium-ion batteries and limits their further application. Summary of the Invention
[0005] Addressing the current limitations of lignocellulose materials in carbon material preparation, this invention aims to provide a nitrogen / carbon synergistically modified lignocellulose-based hard carbon material, its preparation method, and applications. Using lignocellulose as a raw material, this invention simultaneously introduces urea and sugars during hydrothermal treatment. Leveraging the specific hydrothermal environment provided by urea, it promotes the decomposition of hemicellulose in the lignocellulose material, achieving uniform carbon source coating while simultaneously achieving mild nitrogen doping. Furthermore, by introducing sugars as a small-molecule carbon source, a dense, low-defect, uniform carbon shell can be uniformly coated onto the biomass surface. Finally, a high-temperature carbonization process is employed to prepare a nitrogen-doped hard carbon material, effectively improving the initial coulombic efficiency and rate performance. Ultimately, this yields a sodium-ion battery hard carbon anode material with excellent electrochemical performance, balancing material performance and economic benefits.
[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of this invention is to provide a method for preparing a nitrogen / carbon synergistic modified lignocellulose-based hard carbon material, comprising the following steps: The lignocellulosic material is prepared into a powder; preferably, the lignocellulosic material is at least one of wood, bamboo, crop straw, forestry processing residues, and agricultural product processing by-products. Further, the crop straw is at least one of corn stalks, wheat straw, and rice straw; the forestry processing residues are at least one of sawdust and wood chips; and the agricultural product processing by-products are at least one of rice husks, sugarcane bagasse, and peanut shells. Powdered materials, sugars, and urea are added to water and mixed evenly to obtain a mixture. The mass ratio of the powdered materials, sugars, and urea is (10-20):1:(1-3). Preferably, the mass ratio of the powdered materials, sugars, and urea is 20:1:1. Further, the sugars are small molecules such as glucose or sucrose, which are monosaccharides or disaccharides and have good water solubility in water. Under hydrothermal conditions, they can be evenly dispersed to achieve controllable carbonization, construct a uniform carbon shell, and achieve nitrogen-carbon synergistic modification. It should be noted that the sugars in this invention cannot be replaced by macromolecular polysaccharides such as starch, because macromolecular polysaccharides such as starch have poor water solubility and severe molecular chain entanglement, making it difficult to disperse evenly and affecting the carbon layer structure.
[0007] The mixture was heated to 160-180 ℃ for hydrothermal reaction for 8-12 h to obtain hydrothermal products; The hydrothermal product is washed with water until neutral, dried at 60-100 °C for 5-10 h, and then carbonized in a protective atmosphere to obtain the target product. Preferably, the carbonization temperature is 1300-1500 °C and the time is 1-5 h.
[0008] The second aspect of the present invention is to provide a nitrogen / carbon synergistic modified lignocellulose-based hard carbon material, which is prepared by the preparation method described in the first aspect above.
[0009] A third aspect of the present invention is to provide a sodium-ion battery, wherein the negative electrode of the sodium-ion battery is a nitrogen / carbon synergistic modified lignocellulose-based hard carbon material as described in the second aspect above.
[0010] The present invention has the following beneficial effects: This invention precisely controls the nitrogen doping amount of carbon materials through the synergistic modification effect of glucose and urea. On one hand, during the hydrothermal reaction, the ammonia produced by urea decomposition forms an alkaline environment in the water. This alkaline environment not only significantly reduces the activation energy of sugar dehydration carbonization, catalyzing its rapid hydrothermal carbonization and uniform deposition, but also selectively hydrolyzes unstable hemicellulose in lignocellulose, disrupting its original dense structure and providing more loading sites for glucose-derived hydrothermal carbon, effectively enhancing the interfacial bonding between the carbon shell and the lignocellulose matrix. Furthermore, the small-molecule sugars generated by the hydrolysis of hemicellulose under alkaline hydrothermal conditions can synergistically participate in hydrothermal carbonization with added glucose, jointly constructing a uniform and dense carbon shell layer, further optimizing the carbon layer structure and reducing material defects. This structure provides abundant sodium storage sites and effectively inhibits irreversible loss of active sodium, achieving a simultaneous increase in sodium storage capacity and initial coulombic efficiency. Furthermore, urea, as a cheap and environmentally friendly nitrogen source, can be used to in-situ dope nitrogen atoms into the carbon framework during the hydrothermal stage. Nitrogen-doped carbon shells significantly improve the electronic conductivity of the material, effectively enhancing rate performance, resulting in composite hard carbon anodes that possess high capacity, high initial coulombic efficiency, and excellent rate performance. On the other hand, this invention employs a one-step low-temperature hydrothermal process at 160-180 °C, unlike conventional high-temperature hydrothermal processes (>200 °C). Through a mild and controllable reaction environment, it achieves simultaneous and synergistic hydrolysis of hemicellulose, directional carbonization of glucose, and uniform nitrogen doping. This avoids the defects of excessive hydrolysis, carbon shell agglomeration, and uneven nitrogen doping at high temperatures, achieving precise synergistic control of structure and doping. This invention requires no large amounts of acid or alkali reagents, is simple in process, low in cost, environmentally friendly, and easy to scale up. Compared to existing technologies, batteries assembled from hard carbon materials prepared by this invention exhibit significantly improved electrochemical performance, possessing good industrial application value and industrialization prospects. Attached Figure Description
[0011] Figure 1 The image shows a scanning electron microscope image of the hard carbon material prepared at a carbonization temperature of 1400°C in Example 1. Figure 2 The X-ray diffraction pattern of the hard carbon material obtained by carbonization at 1400 °C in Example 1 is shown below. Figure 3The first charge-discharge curves of sodium-ion batteries assembled from hard carbon materials obtained at different carbonization temperatures in Example 1 are shown. Figure 4 The rate performance diagram shows the sodium-ion battery assembled from the hard carbon material obtained in Example 1 at a carbonization temperature of 1400 °C. Figure 5 The graph shows the long-cycle performance of a sodium-ion battery assembled from the hard carbon material obtained by carbonization at 1400 °C in Example 1. Figure 6 The first charge-discharge curves of sodium-ion batteries assembled with hard carbon materials obtained in Examples 1-3 and Comparative Example 5 at a carbonization temperature of 1400 °C are shown. Figure 7 The first charge-discharge curves of sodium-ion batteries assembled with hard carbon materials obtained in Example 1 and Comparative Examples 1-4 at a carbonization temperature of 1400 °C are shown. Detailed Implementation
[0012] The present invention will be further described below with reference to embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments are not intended to limit the present invention. In addition, unless otherwise specified, the preparation processes in the following embodiments are all conventional methods in the prior art, and therefore will not be described in detail.
[0013] Example 1 A method for preparing a nitrogen / carbon synergistic modified lignocellulose-based hard carbon material includes the following steps: (1) Prepare bamboo into powder and take bamboo powder that has passed through a 100-mesh sieve. Mix 2 g of bamboo powder, 0.1 g of glucose and 0.1 g of urea evenly, then add 60 mL of deionized water and stir for two hours to obtain a mixture; (2) Pour the precursor mixture into a high-pressure reactor with a 100 mL polytetrafluoroethylene liner and react at 160 °C for 10 h. (3) Wash the hydrothermal products with deionized water until the filtrate is neutral; (4) Place the washed product in a 90 ℃ forced-air drying oven and dry for 5 h; (5) The dried material was placed in a tube furnace and subjected to heat treatment at 1300 ℃, 1400 ℃ and 1500 ℃ respectively under an argon protective atmosphere. The heating rate was 10 ℃ / min and the heat treatment time was 2 h. After cooling, nitrogen / carbon synergistic modified lignocellulose-based hard carbon material was obtained.
[0014] Example 2 A method for preparing a nitrogen / carbon synergistic modified lignocellulose-based hard carbon material includes the following steps: (1) Prepare bamboo into powder and take bamboo powder that has passed through a 100-mesh sieve. Mix 2 g of bamboo powder, 0.1 g of glucose and 0.2 g of urea evenly, then add 60 mL of deionized water and stir for two hours to obtain a mixture; (2) Pour the precursor mixture into a high-pressure reactor with a 100 mL polytetrafluoroethylene liner and react at 160 °C for 10 h. (3) Wash the hydrothermal products with deionized water until the filtrate is neutral; (4) Place the washed product in a 90 ℃ forced-air drying oven and dry for 5 h; (5) The dried material was placed in a tube furnace and heat-treated at 1400 °C under an argon protective atmosphere. The heating rate was 10 °C / min and the heat treatment time was 2 h. After cooling, nitrogen / carbon synergistic modified lignocellulose-based hard carbon material was obtained.
[0015] Example 3 A method for preparing a nitrogen / carbon synergistic modified lignocellulose-based hard carbon material includes the following steps: (1) Prepare bamboo into powder and take bamboo powder that has passed through a 100-mesh sieve. Mix 2 g of bamboo powder, 0.1 g of glucose and 0.3 g of urea evenly, then add 60 mL of deionized water and stir for two hours to obtain a mixture; (2) Pour the precursor mixture into a high-pressure reactor with a 100 mL polytetrafluoroethylene liner and react at 160 °C for 10 h. (3) Wash the hydrothermal products with deionized water until the filtrate is neutral; (4) Place the washed product in a 90 ℃ forced-air drying oven and dry for 5 h; (5) The dried material was placed in a tube furnace and subjected to heat treatment at 1400 °C under an argon protective atmosphere. The heating rate was 10 °C / min and the heat treatment time was 2 h. After cooling, nitrogen / carbon synergistic modified lignocellulose-based hard carbon material was obtained.
[0016] Comparative Example 1 A method for preparing a lignocellulose-based hard carbon material includes the following steps: (1) Prepare bamboo into powder and take bamboo powder that has passed through a 100-mesh sieve. Mix 2 g of bamboo powder and 0.1 g of glucose evenly, then add 60 mL of deionized water and stir for two hours to obtain a mixture; (2) Pour the precursor mixture into a high-pressure reactor with a 100 mL polytetrafluoroethylene liner and react at 160 °C for 10 h. (3) Wash the hydrothermal products with deionized water until the filtrate is neutral; (4) Place the washed product in a 90 ℃ forced-air drying oven and dry for 5 h; (5) The dried material was placed in a tube furnace and subjected to heat treatment at 1400 °C under an argon protective atmosphere. The heating rate was 10 °C / min and the heat treatment time was 2 h. After cooling, the target product was obtained.
[0017] Comparative Example 2 A method for preparing a nitrogen-doped lignocellulose-based hard carbon material includes the following steps: (1) Prepare bamboo into powder and take bamboo powder that has passed through a 100-mesh sieve. Mix 2 g of bamboo powder and 0.1 g of urea evenly, then add 60 mL of deionized water and stir for two hours to obtain a mixture; (2) Pour the precursor mixture into a high-pressure reactor with a 100 mL polytetrafluoroethylene liner and react at 160 °C for 10 h. (3) Wash the hydrothermal products with deionized water until the filtrate is neutral; (4) Place the washed product in a 90 ℃ forced-air drying oven and dry for 5 h; (5) The dried material was placed in a tube furnace and subjected to heat treatment at 1400 °C under an argon protective atmosphere. The heating rate was 10 °C / min and the heat treatment time was 2 h. After cooling, the target product was obtained.
[0018] Comparative Example 3 Compared with Example 1, the only difference in this comparative example is the amount of glucose used, which is 0.4 g.
[0019] Comparative Example 4 Compared with Example 1, the difference in this comparative example is that glucose and urea are not added simultaneously, but at different times. The specific steps are as follows: (1) Prepare bamboo into powder and take bamboo powder that has passed through a 100-mesh sieve. Mix 2 g of bamboo powder and 0.1 g of glucose evenly, then add 60 mL of deionized water and stir for two hours to obtain a mixture; (2) Pour the precursor mixture into a high-pressure reactor with a 100 mL polytetrafluoroethylene liner and react at 160 °C for 10 h. (3) Wash the hydrothermal products with deionized water until the filtrate is neutral; (4) Dissolve 0.1 g of urea in water to obtain an aqueous urea solution; add the washed product from step 3 to the aqueous urea solution and mix well to obtain a suspension; place the suspension in a 90 ℃ forced-air oven and dry for 5 h; (5) The dried material from step 4 is placed in a tube furnace and subjected to heat treatment at 1400 °C under an argon protective atmosphere. The heating rate is 10 °C / min and the heat treatment time is 2 h. After cooling, the target product is obtained.
[0020] Comparative Example 5 A method for preparing a nitrogen / carbon synergistic modified lignocellulose-based hard carbon material includes the following steps: (1) Prepare bamboo into powder and take bamboo powder that has passed through a 100-mesh sieve. Mix 2 g of bamboo powder, 0.1 g of glucose and 0.4 g of urea evenly, then add 60 mL of deionized water and stir for two hours to obtain a mixture; (2) Pour the precursor mixture into a high-pressure reactor with a 100 mL polytetrafluoroethylene liner and react at 160 °C for 10 h. (3) Wash the hydrothermal products with deionized water until the filtrate is neutral; (4) Place the washed product in a 90 ℃ forced-air drying oven and dry for 5 h; (5) The dried material was placed in a tube furnace and heat-treated at 1400 °C under an argon protective atmosphere. The heating rate was 10 °C / min and the heat treatment time was 2 h. After cooling, nitrogen / carbon synergistic modified lignocellulose-based hard carbon material was obtained.
[0021] The materials prepared in the above embodiments and comparative examples were used as negative electrodes, and coin-type sodium-ion batteries were assembled with metallic sodium as the counter electrode. Electrochemical performance tests were conducted. The electrolyte in the battery consisted of a 1M NaPF6 solution, with diethylene glycol dimethyl ether as the solvent. The results are as follows: Figure 1 The image shows a scanning electron microscope image of the hard carbon material prepared at a carbonization temperature of 1400 °C in Example 1. As can be seen from the image, the synthesized material retains the long, micron-sized fibrous block structure of bamboo.
[0022] Figure 2 The figure shows the X-ray diffraction pattern of the hard carbon material obtained by carbonization at 1400 °C in Example 1. As can be seen from the figure, the hard carbon material synthesized by glucose-urea synergistic modification has two typical characteristic peaks of hard carbon materials, namely (002) at 23° and (100) at 44°.
[0023] Figure 3 The graph shows the first charge-discharge curves of sodium-ion batteries assembled from hard carbon materials obtained at different carbonization temperatures in Example 1. As can be seen from the graph, the hard carbon anode material synthesized at 1400 °C has a charge-discharge rate of 0.05 A g. -1 At the given current density, the initial discharge specific capacity is 362.79 mAh g. -1 The initial charge capacity is 321.19 mAh g. -1 It exhibits the highest initial coulombic efficiency of 88.5%, which is higher than 83.0% for hard carbon anode materials synthesized at 1300 °C and 88.3% for hard carbon anode materials synthesized at 1500 °C.
[0024] Figure 4 This is a graph showing the rate performance of a sodium-ion battery assembled with the hard carbon material obtained in Example 1 at a carbonization temperature of 1400 °C. The graph shows that the obtained hard carbon material achieves a rate performance of 5 A g / L at a carbonization temperature of 1400 °C. -1 It has a current density of 218.79 mAh g. -1 High specific capacity, even at 10 A g -1 It still has 150.03 mAh g⁻¹ even at high current densities. -1 It has a high specific capacity and excellent rate performance.
[0025] Figure 5 The graph shows the long-cycle performance of a sodium-ion battery assembled with the hard carbon material obtained in Example 1, carbonized at 1400 °C. The graph shows that the obtained hard carbon material achieves a long-cycle performance of 0.2 A g / L. -1 The initial discharge specific capacity at the given current density is 328.50 mAh g. -1 After 300 cycles, the discharge specific capacity still reaches 292.23 mAh g. -1 The capacity retention rate is as high as 89% after 300 cycles, demonstrating its excellent structural stability.
[0026] Figure 6 The graph shows the first charge-discharge curves of sodium-ion batteries assembled with hard carbon materials obtained in Examples 1-3 and Comparative Example 5 at a carbonization temperature of 1400 °C. As can be seen from the graph, the hard carbon material obtained in Example 1 exhibits the highest efficiency of 362.79 mAh g⁻¹. -1 The discharge specific capacity and initial coulombic efficiency are 88.5%. Increasing the amount of urea added will slightly decrease the initial coulombic efficiency of the product.
[0027] Figure 7 The figures show the first charge-discharge curves of sodium-ion batteries assembled with hard carbon materials obtained in Example 1 and Comparative Examples 1-4 at a carbonization temperature of 1400 °C. As can be seen from the figures, the hard carbon material obtained in Example 1 has the highest first coulombic efficiency of 88.5%, indicating that the synergistic effect of introducing appropriate amounts of glucose and urea is better than using glucose or urea alone, better than increasing the amount of glucose, and better than adding glucose and urea in steps.
[0028] Furthermore, the above embodiment 1 3 and Comparative Example 1 The assembled button cell battery has a capacitance of 0.05 A g. -1 The charge-discharge performance at the specified current density is shown in Table 1.
[0029] Table 1. Charge-discharge performance of batteries prepared in the examples and comparative examples.
[0030] As can be seen from Table 1, in Example 1 In the assembled coin cells, the first-cycle charge-discharge efficiency gradually decreased with increasing urea content. The maximum first-cycle charge-discharge capacity was achieved when the mass ratio of bamboo powder precursor powder, sugar, and urea was 20:1:1, with an efficiency of 88.50%, meeting the usage requirements and achieving the best results. (Comparative Example 1) In the assembled coin cells, the charging specific capacity and first-cycle charge-discharge efficiency of the cells obtained by adding glucose alone, adding urea alone, increasing the amount of glucose, adding glucose and urea in stages, and increasing the amount of urea all decreased compared to Example 1, demonstrating the superiority of the synergistic effect of the optimal ratio of glucose and urea.
[0031] The rate performance of the coin cells assembled in Example 1 above after carbonization at 1400 °C at high current densities of 1-10 A / g is shown in Table 2.
[0032] Table 2. Rate performance of the battery prepared in Example 1 after carbonization at 1400 °C at high current density.
[0033] Furthermore, as shown in Table 2, the rate performance of the battery prepared in Example 1 after carbonization at 1400 °C under high current density is [data missing]. (The last part, "1 A g," appears to be a separate, unrelated sentence fragment and is left untranslated.) -1 At high current density, the first-cycle discharge capacity reaches 266.74 mAh g. -1 Even at 10 Ag -1 At high current densities, the first-cycle discharge capacity can reach as high as 150.03 mAh g. -1 It exhibits excellent rate performance.
[0034] It should be noted that in other embodiments, the objective of this invention can be achieved when the experimental process meets the following conditions: For lignocellulosic materials, in addition to bamboo, at least one of the following can be selected: bamboo, crop straw, forestry processing residues, and agricultural product processing by-products. These lignocellulosic materials have similar composition and properties, and can achieve similar purposes.
[0035] The preferred temperature for the hydrothermal reaction is 160-180 ℃, specifically 160 ℃, 170 ℃, or 180 ℃; the preferred reaction time is 8-12 h, specifically 8 h, 10 h, or 12 h.
[0036] The preferred drying temperature is 60-100 ℃, specifically 60 ℃, 70 ℃, 80 ℃, 90 ℃ or 100 ℃; the preferred drying time is 5-10 h, specifically 5 h, 7 h, 8 h or 10 h.
[0037] The preferred carbonization time is 1-5 hours, specifically 1 hour, 2 hours, 3 hours, or 5 hours.
[0038] Those skilled in the art can make appropriate selections of the above process parameters according to actual needs, and all of them can achieve the purpose of this invention.
[0039] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.
Claims
1. A method for preparing a nitrogen / carbon synergistically modified lignocellulose-based hard carbon material, characterized in that, Includes the following steps, Lignocellulose materials are prepared into powder form; Powdered materials, sugars, and urea are added to water and mixed evenly to obtain a mixture; the mass ratio of the powdered materials, sugars, and urea is (10-20):1:(1-3); the sugars are monosaccharides or disaccharides; The mixture was heated to 160-180 °C to carry out a hydrothermal reaction, yielding the hydrothermal product. The hydrothermal product is washed with water until neutral, dried, and then carbonized in a protective atmosphere to obtain the target product.
2. The preparation method according to claim 1, characterized in that, The lignocellulose material is at least one of wood, bamboo, crop straw, forestry processing residues, and agricultural product processing by-products.
3. The preparation method according to claim 2, characterized in that, The crop straw is at least one of corn stalks, wheat straw, and rice straw; the forestry processing residue is at least one of wood chips and sawdust; and the agricultural product processing by-product is at least one of rice husks, sugarcane bagasse, and peanut shells.
4. The preparation method according to claim 1, characterized in that, The monosaccharide is glucose or fructose; the disaccharide is sucrose, maltose or lactose.
5. The preparation method according to claim 1, characterized in that, The hydrothermal reaction takes 8-12 hours.
6. The preparation method according to claim 1, characterized in that, The drying temperature is 60-100 °C, and the drying time is 5-10 h.
7. The preparation method according to claim 1, characterized in that, The carbonization temperature is 1300-1500 °C, and the time is 1-5 h.
8. The preparation method according to any one of claims 1 to 7, characterized in that, The mass ratio of the powdered material, sugar, and urea is 20:1:
1.
9. A nitrogen / carbon synergistic modified lignocellulose-based hard carbon material, characterized in that, It is prepared by the preparation method as described in any one of claims 1 to 8.
10. A sodium-ion battery, characterized in that, The negative electrode of the sodium-ion battery is the nitrogen / carbon synergistic modified lignocellulose-based hard carbon material as described in claim 9.