Method for preparing hard carbon from xylose residue and application thereof

Abstract

This invention discloses a method for preparing hard carbon from xylose residue and its application, belonging to the field of biochemical technology. The method includes the following steps: removing impurities from the xylose residue to obtain intermediate 1; the impurity removal process includes mixing the xylose residue with a removal liquid and then filtering by pressure; mixing intermediate 1 with a crosslinking agent and then performing crosslinking treatment in an air atmosphere to obtain intermediate 2; pre-carbonizing intermediate 2 in a reaction atmosphere to obtain intermediate 3; and carbonizing intermediate 3 in an argon atmosphere to obtain hard carbon material. This invention, through refined process control, successfully establishes a technological chain from "xylose residue - high-performance hard carbon - high-performance sodium-ion battery." The prepared hard carbon material exhibits significant advantages in key indicators such as capacity, initial efficiency, cycle life, and compaction density, demonstrating strong potential for industrial application.

Description

Technical Field

[0001] This invention belongs to the field of biochemical technology, specifically relating to a method and application for preparing hard carbon using xylose residue as raw material. Background Technology

[0002] Xylose residue is a solid byproduct produced by hydrolyzing agricultural and forestry waste such as corn cobs with dilute acid to extract xylose (or xylitol). It is widely used in the food, pharmaceutical, and chemical industries. However, current methods of xylose residue disposal are not ideal: firstly, direct dumping easily leads to rotting and mold growth, polluting the environment; secondly, incineration produces CO2 and PM2.5, failing to meet green and low-carbon requirements; and thirdly, traditional composting or landfilling wastes carbon resources and increases the environmental burden. Therefore, efficient and clean utilization of xylose residue has become a common challenge in the industry.

[0003] With the rapid development of the sodium-ion battery industry, the research and application of biomass-based hard carbon materials have attracted increasing attention. Xylitol residue, a major solid waste product from the deep processing of corn cobs to produce xylitol, is rich in cellulose and hemicellulose, has a high fixed carbon content and low ash content, making it an ideal hard carbon precursor. Existing technologies have attempted to prepare hard carbon anodes from xylitol residue through a simple pyrolysis carbonization process, thus serving as a material for sodium-ion batteries. However, the direct preparation of hard carbon from xylose residue also faces technical challenges: First, there is the problem of acid residue, which can corrode equipment and affect electrochemical performance, requiring efficient removal or neutralization. Second, there are inorganic impurities, such as K, Ca, Mg, and Si enriched in corn cobs, which remain in the residue and form salts after carbonization, affecting the purity and interfacial stability of the material. Third, the lignocellulose structure is partially dense, and although acid hydrolysis destroys some of the structure, the interaction between cellulose and lignin remains strong, leading to insufficient development of closed-cell structures after direct carbonization. Fourth, there is the issue of carbonization process adaptability: the pyrolysis behavior of xylose residue differs from that of conventional biomass, and parameters such as carbonization temperature and heating rate have a decisive impact on the microcrystalline structure and electrochemical performance, but systematic research is currently limited, and the structure-activity relationship needs further exploration. Summary of the Invention

[0004] Based on the above-mentioned technical problems, this invention proposes a method for preparing hard charcoal using xylose residue as raw material and its application.

[0005] The technical solution adopted in this invention is: A method for preparing hard charcoal using xylose residue as raw material includes the following steps: S1 Impurity Removal Process: The xylose residue is subjected to impurity removal process to obtain intermediate 1; the impurity removal process includes stirring and mixing the xylose residue with the impurity removal liquid and then pressing and filtering. S2 Crosslinking treatment: After mixing intermediate 1 obtained in step S1 with the crosslinking agent evenly, crosslinking treatment is carried out in an air atmosphere to obtain intermediate 2; S3 Pre-carbonization treatment: Intermediate 2 obtained in step S2 is pre-carbonized under a reaction atmosphere to obtain intermediate 3; S4 Carbonization treatment: The intermediate 3 obtained in step S3 is carbonized under an argon atmosphere to obtain hard carbon material.

[0006] The aforementioned xylose residue is a solid byproduct produced after extracting xylose or xylitol from agricultural and forestry waste such as corn cobs.

[0007] Preferably, in step S1: the impurity removal solution is selected from one or more of water, acid, and alkali; the concentration of the acid is 0.5-1.5 mol / L, and the concentration of the alkali is 0.5-1.5 mol / L; the stirring, mixing, and pressure filtration steps are repeated 2-5 times. The above steps are to reduce the ash content and / or hemicellulose content in the xylose residue.

[0008] The intermediate 1 obtained above contains 85-95 wt% cellulose and lignin, and 0.5-7 wt% hemicellulose.

[0009] Preferably, in step S2, the crosslinking agent is selected from one or more of citric acid, maleic anhydride, urea, phenol, terephthalic acid, trimesic acid, phosphoric acid, ammonium dihydrogen phosphate, and diammonium hydrogen phosphate.

[0010] Preferably, in step S2, the amount of crosslinking agent added is 0.5-15 wt% of the weight of xylose residue, preferably 10-15 wt%.

[0011] Preferably, the specific steps of the crosslinking treatment in step S2 are as follows: heating to 90-250°C at a heating rate of 4-6°C / min, holding the reaction at that temperature for 1.5-2.5 hours, and then cooling to room temperature to obtain intermediate 2.

[0012] Preferably, the specific steps of the pre-carbonization treatment in step S3 are as follows: heating to 270-350°C at a heating rate of 1-6°C / min, holding the temperature for 1.5-2.5h, then heating to 650-750°C at a heating rate of 1-6°C / min, holding the temperature for 1.5-2.5h, and cooling to room temperature to obtain intermediate 3.

[0013] Preferably, in step S3, the reaction atmosphere is selected from one or more of air, nitrogen, argon, carbon dioxide, ammonia, and water vapor.

[0014] Preferably, the specific steps of the carbonization process in step S4 are as follows: heating to 1100-1600℃, preferably 1250-1350℃, at a heating rate of 1-3℃ / min, holding for 4-6 hours, and cooling to room temperature to obtain hard carbon material.

[0015] Preferably, in step S4: the intermediate 3 is mixed with a coating agent and then carbonized. The coating agent is selected from one or more of asphalt, phenolic resin, sucrose and glucose. The amount of coating agent added is 0.01 to 15 wt% of the weight of the intermediate 3, preferably 2 to 6 wt%.

[0016] The application of a hard carbon material prepared by the above-described method of preparing hard carbon from xylose residue in the preparation of sodium-ion batteries.

[0017] The beneficial effects of this invention are as follows: This invention, through refined process control, successfully establishes a technological chain from "xylose residue - high-performance hard carbon - high-performance sodium-ion battery." The prepared hard carbon material exhibits significant advantages in key indicators such as capacity, initial efficiency, cycle life, and compaction density, demonstrating strong potential for industrial application. Specifically: (1) The hard carbon material prepared by the present invention has the following excellent characteristics: ash content is 0.01-0.99wt%, average particle size D50 is 2-13μm, specific surface area is 0.8-9m² / g, compaction density is 0.85-1.25g / cm³, reversible specific capacity in sodium-ion batteries is 295-468mAh / g, initial coulombic efficiency is 80%-96%, and capacity retention rate after 1000 cycles in sodium-ion batteries is ≥93%.

[0018] (2) By introducing a cross-linking process, the present invention utilizes a cross-linking agent to cross-link with cellulose, forming more closed pores during carbonization, thereby effectively improving the sodium storage capacity.

[0019] (3) The present invention constructs a uniform carbon coating layer on the surface of hard carbon by liquid phase coating (asphalt, phenolic resin, etc.), which effectively seals the open pores on the surface of the material. This not only reduces the excessive wetting of the active material by the electrolyte, but also inhibits the excessive growth of the solid electrolyte interface (SEI) film, and significantly reduces irreversible capacity loss.

[0020] (4) The present invention has significant advantages in selecting xylose residue as a hard char precursor: First, the composition is highly consistent; as a standardized acid hydrolysis byproduct, xylose residue has an extremely low hemicellulose content (about 1.6%), and the sum of cellulose and lignin exceeds 84%; the chemical composition variation of xylose residue is lower than that of the original biomass, which is conducive to batch stability in industrial production.

[0021] Secondly, the composition is ideal. Hemicellulose in xylose residue is a disadvantageous component in hard carbon, reducing the initial coulombic efficiency. Cellulose, on the other hand, forms an ordered carbon skeleton to improve capacity, and lignin, rich in defect sites, is conducive to sodium ion adsorption, both of which are beneficial for sodium ion storage. The "low hemicellulose-high cellulose-high lignin" composition of xylose residue makes it an ideal precursor for hard carbon.

[0022] Third, the output is large and the cost is extremely low; xylose residue is almost zero cost as waste, and its conversion into hard carbon anode material can significantly reduce production costs, which is in line with the low-cost direction of sodium-ion batteries. Attached Figure Description

[0023] Figure 1 Comparison of infrared spectra of intermediate 2 in Example 1 of the present invention and xylose residue raw material; Figure 2 A comparison of the infrared spectra of intermediate 2 in Example 4 of the present invention and xylose residue raw material; Figure 3 A comparison chart of the charge-discharge sodium storage performance of the hard carbon products of Example 1 and Comparative Example 1 of this invention. Detailed Implementation

[0024] The present invention will be further described below with reference to specific embodiments. Unless otherwise specified, all chemical reagents used in the embodiments of the present invention are obtained through conventional commercial means.

[0025] Example 1 Step 1: Disperse 1 kg of xylose residue into 5 L of 1 M hydrochloric acid solution, stir and acid wash for 2 h, and obtain filter residue by pressure filtration; rinse with water until the pH of the filtrate is 6-7; transfer the filter residue to an oven and dry at 80 °C for 10 h to obtain intermediate 1.

[0026] Step 2: Mix intermediate 1 with 100g of citric acid evenly, transfer to a rotary tube furnace, heat to 150℃ in air at a heating rate of 5℃ / min, hold for 2h to carry out cross-linking reaction, and cool to room temperature to obtain intermediate 2.

[0027] Step 3: Transfer intermediate 2 to a tube furnace and heat it to 280°C in an air atmosphere at a heating rate of 5°C / min, hold it at that temperature for 2 hours, then switch to an argon atmosphere and heat it to 700°C at a heating rate of 5°C / min, hold it at that temperature for 2 hours, and then cool it to room temperature to obtain intermediate 3.

[0028] Step 4: Take 500g of intermediate 3 and crush it to an average particle size D50=7μm. Mix it evenly with 20g of medium-temperature asphalt, put it into a ceramic boat, transfer it to a tube furnace, heat it to 1300℃ at 2℃ / min under an argon atmosphere, keep it at that temperature for 5h, and cool it to room temperature to obtain sample 1.

[0029] Example 2 Step 1: Disperse 1 kg of xylose residue into 5 L of deionized water, stir for 2 h, and obtain filter residue by pressure filtration; rinse with water until the pH of the filtrate is 6-7; transfer the filter residue to an oven and dry at 110℃ for 10 h to obtain intermediate 1.

[0030] Step 2: Same as Example 1.

[0031] Step 3: Transfer intermediate 2 to a tube furnace and heat it to 280°C in air at a heating rate of 5°C / min, hold for 2 hours, then switch to argon atmosphere and heat it to 700°C at a heating rate of 5°C / min, hold for 2 hours, cool to room temperature, disperse the pre-carbonized product in 5L of 1M hydrochloric acid solution, stir and acid wash for 2 hours, obtain filter residue by pressure filtration, wash with water until the pH of the filtrate is 6-7, transfer the filter residue to an oven and dry at 80°C for 10 hours to obtain intermediate 3.

[0032] Step 4: Same as Example 1, to obtain Sample 2.

[0033] Example 3 Step 1: Disperse 1 kg of xylose residue into 5 L of 1 M NaOH solution, stir and wash with alkali for 2 h; filter by pressure to obtain filter residue; rinse with water until the pH of the filtrate is 6-7; disperse the filter residue into 5 L of 1 M hydrochloric acid solution, stir and wash with acid for 2 h, filter by pressure to obtain filter residue; rinse with water until the pH of the filtrate is 6-7; transfer the filter residue to an oven and dry at 110℃ for 10 h to obtain intermediate 1.

[0034] Step 2: Same as Example 1.

[0035] Step 3: Same as Example 1.

[0036] Step 4: Same as in Example 1, to obtain Sample 3.

[0037] Example 4 Step 1: Same as Example 3.

[0038] Step 2: Replace citric acid with an equal amount of maleic anhydride, and the rest is the same as in Example 1.

[0039] Step 3: Same as Example 1.

[0040] Step 4: Same as in Example 1, to obtain Sample 4.

[0041] Example 5 Step 1: Same as Example 3.

[0042] Step 2: Replace citric acid with an equal amount of diammonium hydrogen phosphate, and the rest is the same as in Example 1.

[0043] Step 3: Same as Example 1.

[0044] Step 4: Same as in Example 1, to obtain Sample 5.

[0045] Example 6 Step 1: Same as Example 3.

[0046] Step 2: Same as Example 1.

[0047] Step 3: Same as Example 1.

[0048] Step 4: Change the carbonization temperature to 1100℃, and the rest is the same as in Example 1, to obtain Sample 6.

[0049] Example 7 Step 1: Same as Example 3.

[0050] Step 2: Same as Example 1.

[0051] Step 3: Same as Example 1.

[0052] Step 4: Change the carbonization temperature to 1600℃, and the rest is the same as in Example 1, to obtain Sample 7.

[0053] Example 8 Step 1: Same as Example 3.

[0054] Step 2: Same as Example 1.

[0055] Step 3: Same as Example 1.

[0056] Step 4: Replace the coating agent with an equal amount of phenolic resin, and the rest is the same as in Example 1, to obtain Sample 8.

[0057] Example 9 Step 1: Same as Example 3.

[0058] Step 2: Same as Example 1.

[0059] Step 3: Transfer intermediate 2 to a tube furnace and heat it to 280°C in an air atmosphere at a heating rate of 5°C / min, and hold it for 2 hours; then switch to an argon atmosphere and heat it to 700°C at a heating rate of 5°C / min. Replace the atmosphere with a CO2 / Ar mixture with a volume ratio of 1:4, hold it for 2 hours, and then cool it to room temperature to obtain intermediate 3.

[0060] Step 4: Same as in Example 1, to obtain Sample 9.

[0061] Example 10 Step 1: Same as Example 3.

[0062] Step 2: Same as Example 1.

[0063] Step 3: Transfer intermediate 2 to a tube furnace and heat it to 280°C in an air atmosphere at a heating rate of 5°C / min, and hold it for 2 hours; then switch to an argon atmosphere and heat it to 700°C at a heating rate of 5°C / min. Replace the atmosphere with NH3, hold it for 2 hours, and then cool it to room temperature to obtain intermediate 3; NH3 is used as an activation medium here, and at 700°C, NH3 reacts with the carbonization product to form pores.

[0064] Step 4: Same as in Example 1, to obtain sample 10.

[0065] Example 11 Step 1: Same as Example 3.

[0066] Step 2: Same as Example 1.

[0067] Step 3: Transfer intermediate 2 to a tube furnace and heat it to 280°C in an air atmosphere at a heating rate of 5°C / min, and hold for 2 hours; then switch to an argon atmosphere and heat it to 700°C at a heating rate of 5°C / min. Replace the atmosphere with a mixture of H2O / Ar with a volume ratio of 1:4, hold for 2 hours, and then cool to room temperature to obtain intermediate 3; water vapor is used as the activation medium here, and at 700°C, water vapor reacts with the carbonization products to form pores.

[0068] Step 4: Same as in Example 1, to obtain Implementation Sample 11.

[0069] Example 12 Step 1: Same as Example 3.

[0070] Step 2: Same as Example 1.

[0071] Step 3: Same as Example 2.

[0072] Step 4: Replace the coating agent with an equal amount of phenolic resin, and the rest is the same as in Example 1, to obtain Sample 12.

[0073] Example 13 Step 1: Same as Example 3.

[0074] Step 2: Same as Example 1.

[0075] Step 3: Same as Example 2.

[0076] Step 4: Without adding a coating agent, the rest is the same as in Example 1, to obtain Sample 13.

[0077] Comparative Example 1 Step 1: Place 1 kg of xylose residue in a porcelain boat, transfer it to a muffle furnace, heat it to 280°C at 5°C / min in an air atmosphere, hold it at that temperature for 2 hours, and cool it to room temperature to obtain intermediate 1.

[0078] Step 2: Transfer the ceramic boat to a tube furnace, heat it to 700℃ at 2℃ / min in an argon atmosphere, hold it at that temperature for 2 hours, and then cool it to room temperature to obtain intermediate 2.

[0079] Step 3: Take 500g of intermediate 2 and crush it to an average particle size D50=7μm. Place it in a ceramic boat and transfer it to a tube furnace. In an argon atmosphere, heat it to 1300℃ at 2℃ / min, hold it for 5h, and cool it to room temperature to obtain control sample 1.

[0080] Comparative Example 2 Step 1: Place 1 kg of xylose residue in a porcelain boat, transfer it to a muffle furnace, heat it to 280°C at 5°C / min in an air atmosphere, hold it at that temperature for 2 hours, and cool it to room temperature to obtain intermediate 1.

[0081] Step 2: Transfer the ceramic boat to a tube furnace, heat it to 700℃ at 2℃ / min in an argon atmosphere, hold it at that temperature for 2 hours, and then cool it to room temperature to obtain intermediate 2.

[0082] Step 3: Take 500g of intermediate 2 and crush it to an average particle size D50=7μm. Mix it evenly with 20g of medium-temperature asphalt, put it into a ceramic boat, transfer it to a tube furnace, heat it to 1300℃ at 2℃ / min under an argon atmosphere, keep it at that temperature for 5h, and cool it to room temperature to obtain control sample 2.

[0083] Comparative Example 3 Step 1: Place 1 kg of xylose residue in a porcelain boat, transfer it to a muffle furnace, heat it to 280°C at 5°C / min in an air atmosphere, hold it at that temperature for 2 hours, and cool it to room temperature to obtain intermediate 1.

[0084] Step 2: Transfer the ceramic boat containing intermediate 1 to a tube furnace, change the atmosphere to NH3, raise the temperature to 700℃ at 2℃ / min, hold for 2h, and then cool to room temperature to obtain intermediate 2.

[0085] Step 3: Take 500g of intermediate 2 and crush it to an average particle size D50=7μm. Mix it evenly with 20g of medium-temperature asphalt, put it into a ceramic boat, transfer it to a tube furnace, heat it to 1300℃ at 2℃ / min under an argon atmosphere, keep it at that temperature for 5h, and cool it to room temperature to obtain control sample 3.

[0086] Ash content, electrochemical properties, specific surface area, and compaction density were tested on the hard carbon samples obtained in Examples 1-13 and Comparative Examples 1-3. The contents of cellulose, hemicellulose, and lignin components in intermediate 1 obtained after impurity removal in Examples 1-13 were determined. The test results are shown in Table 1. The test standards are as follows: (1) Ash content The determination was carried out in accordance with the provisions of GB / T 1429-2025 "Analytical Methods for Carbon Materials Industry".

[0087] (2) Electrochemical performance: capacity, first-efficiency (first coulombic efficiency) and retention rate after 1000 cycles The determination was carried out in accordance with the provisions of GB / T 43114-2023 "Hard Carbon".

[0088] (3) Specific surface area The determination shall be carried out in accordance with the provisions of GB / T19587.

[0089] (4) Compacted density The determination was carried out in accordance with the provisions of GB / T 24533-2019 "Graphite Anode Materials for Lithium-ion Batteries".

[0090] (5) Determination of the content of cellulose, hemicellulose and lignin components The fiber content was tested using a FIWE fiber content analyzer based on the Van der Waals washing method.

[0091] The principle of Fan's washing is as follows: Neutral detergents are used to dissolve fats, sugars, proteins, and other substances within biomass cells. These substances are collectively called neutral detergent dissolved substances (NDS), and the remaining insoluble components are neutral detergent fibers (NDF). The NDS and hemicellulose in biomass cells are dissolved in an acidic detergent to obtain acid detergent fiber (ADF). The difference between neutral detergent fiber and acid detergent fiber is the hemicellulose content. Acid-washed fiber can be washed with 72% concentrated sulfuric acid to obtain acid-washed lignin (ADL). The difference between acid-washed fiber (ADF) and acid-washed lignin (ADL) is the cellulose content. Acid-washed lignin (ADL) is then ashed at 575℃ for 2 hours. The ash residue is the content of acid-insoluble ash (ASH) in the biomass, while the components that escape during the ashing process are lignin.

[0092] Preparation of neutral detergent: Accurately weigh 18.6g of disodium ethylenediaminetetraacetate and 6.8g of sodium borate into a beaker, add a small amount of distilled water and heat to dissolve. Then add 30g of sodium dodecyl sulfate and 10mL of ethylenediether ethanol. Next, weigh 4.56g of anhydrous disodium hydrogen phosphate into another beaker, add a small amount of distilled water and heat to dissolve. Pour the solution into the first beaker and dilute to 1000mL in a volumetric flask. Shake well and set aside.

[0093] Preparation of acidic detergent: Measure approximately 27.87 mL of concentrated sulfuric acid and slowly add it to a beaker containing 500 mL of distilled water. After the beaker cools, pour the liquid into a volumetric flask and bring the volume to 1000 mL. Weigh 20 g of hexadecanetrimethylammonium bromide and dissolve it in the above 1000 mL sulfuric acid solution. Shake well and set aside. The formulas for calculating the mass percentage of hemicellulose, cellulose, and lignin are as follows: Hemicellulose mass percentage (HC) = (NDF - ADF) × 100%; Cellulose mass percentage (C) = (ADF - ADL) × 100%; Lignin mass percentage (L) = (ADL - ASH) × 100%.

[0094] Table 1 Test Results

[0095] As can be seen from the test results in Table 1, the performance of the samples obtained in Comparative Example 1, Comparative Example 2, and Comparative Example 3 was worse than that of Examples 1-12 because Comparative Example 1 lacked the steps of impurity removal, crosslinking, and coating.

[0096] Example 13 lacks a coating process. Compared with Examples 1-12, the resulting sample has a lower ash content, but other properties are worse.

[0097] The main difference between Examples 9-11 and other examples is that in step 3, the reaction atmosphere was changed to a mixture of CO2 / Ar and a mixture of NH3 and H2O / Ar, respectively. The resulting samples had higher sodium storage capacity and cycle stability, mainly because the above reaction atmosphere can promote the carbonization product reaction and pore formation, thereby providing more sodium storage sites and improving sodium storage capacity and cycle stability.

[0098] In Examples 6 and 7, the carbonization temperature was replaced with 1100℃ and 1600℃ respectively. The sodium storage capacity of the resulting samples was low. This shows that the carbonization temperature needs to be set within a reasonable range. Setting it too low or too high will have an adverse effect on the sodium storage capacity.

[0099] Compared with other examples, Example 2 performed a second impurity removal treatment on the pre-carbonized product in step 3, but the performance of the obtained sample was not significantly improved. This indicates that the impurity removal treatment only needs to be completed in step 1, that is, it is best to remove impurities before crosslinking and pre-carbonization.

[0100] Compared with Example 1, Example 3 underwent two impurity removal processes in step 1. The ash content of the sample obtained in Example 3 decreased significantly compared with that in Example 1, indicating that performing more than two impurity removal processes in step 1 would be more effective.

[0101] The intermediate 2 obtained in Examples 1 and 4 was compared with xylose residue raw material by infrared spectrum analysis.

[0102] like Figure 1 As shown, by comparing the infrared spectra of xylose residue and intermediate 2 of Example 1, it can be found that by adding citric acid to crosslink the cellulose in xylose residue, the -OH peak of cellulose is significantly reduced, while the C=O peak and COC peak, which are generated by crosslinking esterification, are significantly enhanced, indicating that the cellulose in xylose residue has undergone crosslinking esterification reaction with the crosslinking agent citric acid.

[0103] like Figure 2As shown, by comparing the infrared spectra of xylose residue and intermediate 2 of Example 4, it can be found that by adding maleic anhydride to crosslink with cellulose in xylose residue, the -OH peak of cellulose is significantly reduced, while the C=O peak and COC peak generated by crosslinking esterification are significantly enhanced, indicating that cellulose in xylose residue has undergone a significant crosslinking esterification reaction with the crosslinking agent maleic anhydride.

[0104] The sodium storage performance of the hard carbon products obtained in Example 1 and Comparative Example 1 was tested by charge-discharge testing.

[0105] like Figure 3 As shown, a comparison of the charge-discharge sodium storage performance of the hard carbon products of Example 1 and Comparative Example 1 reveals that the sodium storage performance of the hard carbon products obtained in Example 1 is significantly improved through the synergistic effects of impurity removal, cross-linking, and coating.

[0106] For any parts not mentioned in the above embodiments, existing technologies can be adopted or referenced.

[0107] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the above embodiments. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should be protected by the present invention.

Claims

1. A method for preparing hard carbon using xylose residue as a raw material, characterized by, Includes the following steps: S1 Impurity Removal Process: The xylose residue is subjected to impurity removal process to obtain intermediate 1; the impurity removal process includes stirring and mixing the xylose residue with the impurity removal liquid and then pressing and filtering. S2 Crosslinking treatment: After mixing intermediate 1 obtained in step S1 with the crosslinking agent evenly, crosslinking treatment is carried out in an air atmosphere to obtain intermediate 2; S3 Pre-carbonization treatment: Intermediate 2 obtained in step S2 is pre-carbonized under a reaction atmosphere to obtain intermediate 3; S4 Carbonization treatment: The intermediate 3 obtained in step S3 is carbonized under an argon atmosphere to obtain hard carbon material.

2. The method of claim 1, wherein the method of preparing hard carbon using wood residue as a raw material is characterized by, In step S1: the impurity removal solution is selected from one or more of water, acid and alkali; the concentration of the acid is 0.5-1.5 mol / L and the concentration of the alkali is 0.5-1.5 mol / L; the stirring and filtration steps are repeated 2-5 times.

3. The method of claim 1, wherein the method of preparing hard carbon using wood residue as a raw material is characterized by, In step S2: the crosslinking agent is selected from one or more of citric acid, maleic anhydride, urea, phenol, terephthalic acid, trimesic acid, phosphoric acid, ammonium dihydrogen phosphate and diammonium hydrogen phosphate.

4. The method of claim 1, wherein the method of preparing hard carbon using wood residue as a raw material is characterized by, In step S2: the amount of crosslinking agent added is 0.5-15 wt% of the weight of xylose residue.

5. The method of claim 1, wherein the method of preparing hard carbon using wood residue as a raw material is characterized by, The specific steps of the crosslinking treatment in step S2 are as follows: heat to 90-250℃ at a heating rate of 4-6℃ / min, keep the reaction at this temperature for 1.5-2.5h, and then cool to room temperature to obtain intermediate 2.

6. The method for preparing hard charcoal using xylose residue as raw material according to claim 1, characterized in that, The specific steps of the pre-carbonization treatment in step S3 are as follows: heat to 270-350℃ at a heating rate of 1-6℃ / min, hold for 1.5-2.5h, then heat to 650-750℃ at a heating rate of 1-6℃ / min, hold for 1.5-2.5h, and cool to room temperature to obtain intermediate 3.

7. The method of claim 1, wherein the wood residue is xylose residue. In step S3: the reaction atmosphere is selected from one or more of air, nitrogen, argon, carbon dioxide, ammonia and water vapor.

8. The method of claim 1, wherein the wood residue is xylose residue. The specific steps of carbonization treatment in step S4 are as follows: heat to 1100-1600℃ at a heating rate of 1-3℃ / min, hold for 4-6 hours, and cool to room temperature to obtain hard carbon material.

9. The method of claim 1, wherein the wood residue is xylose residue. In step S4: the intermediate 3 is mixed with a coating agent and then carbonized. The coating agent is selected from one or more of asphalt, phenolic resin, sucrose and glucose. The amount of coating agent added is 0.01~15wt% of the weight of the intermediate 3.

10. The application of the hard carbon material prepared by the method for preparing hard carbon using xylose residue as raw material as described in any one of claims 1-9 in the preparation of sodium-ion batteries.

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