Preparation method and application of a biomass-derived hard carbon material

Abstract

The application belongs to the field of battery electrode materials, and discloses a preparation method and application of a biomass-derived hard carbon material. The preparation method of the biomass-derived hard carbon material comprises the following steps: (1) mixing choline chloride and urea, then performing ultrasonic treatment, and then heating and stirring to prepare EDS; (2) adding a biomass material into the EDS obtained in step (1), and then heating and stirring to perform reaction; (3) performing high-temperature carbonization on the reaction product obtained in step (2) after cleaning, filtering and drying, to obtain the biomass-derived hard carbon material. The application further provides a sodium ion battery and a lithium ion battery. Through EDS pretreatment, the application can effectively break the close fiber structure of bamboo powder, promote the dissolution and separation of biomass components, and make the hard carbon material obtained through subsequent carbonization have more excellent conductivity, so as to improve the electrochemical performance of the hard carbon material in lithium ion batteries and sodium ion batteries.

Description

Technical Field

[0001] This invention belongs to the field of battery electrode materials, and particularly relates to a method for preparing and applying a biomass-derived hard carbon material. Background Technology

[0002] Hard carbon materials, due to their high specific surface area, excellent electrical conductivity, and structural stability, have broad application prospects in energy storage fields such as lithium-ion batteries and supercapacitors. Traditional hard carbon preparation often uses fossil-based raw materials (such as pitch and resin) as precursors, and the pretreatment process often uses strong acids, strong alkalis, or toxic organic solvents (such as N-methylpyrrolidone), which not only consumes non-renewable resources but also generates a large amount of wastewater and waste residue, causing serious environmental pollution.

[0003] Bamboo, as a renewable biomass resource, is characterized by its short growth cycle, high yield, and rich fibrous structure, making it an ideal green precursor for hard carbon production. However, the dense fibrous structure of bamboo powder easily leads to uneven pore distribution and poor performance in hard carbon materials when directly carbonized, necessitating pretreatment to break down the fibrous structure. Existing pretreatment methods mostly rely on chemical reagents, which suffer from poor environmental friendliness and complex processes, making it difficult to meet the requirements of green production.

[0004] Eutectic solvents (EDS), as novel green solvents, are formed by mixing hydrogen bond donors and acceptors in a specific ratio. They possess advantages such as low vapor pressure, low toxicity, recyclability, and good biocompatibility, and have shown promising application potential in the field of material pretreatment. Using EDS for bamboo powder pretreatment can replace traditional toxic solvents. Some researchers have attempted to combine eutectic solvents with Lewis acid pretreatment, but compared to Lewis acid catalytic treatment, precarbonization treatment offers significant green and environmentally friendly advantages and precise structural control capabilities. Traditional Lewis acid treatment requires the introduction of chemical reagents, inevitably generating acidic or metal ion-containing waste liquids, increasing environmental treatment costs, and easily leaving residues that affect product purity. Simultaneously, Lewis acids easily induce excessive graphitization of the product, leading to shrinkage of interlayer spacing and a reduction in active sites in carbon materials. For example, the carbon anode material prepared in Chinese patent document CN117585665A suffers from high environmental treatment costs and excessive graphitization. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the background art above, and to provide a method for preparing and applying biomass-derived hard carbon materials.

[0006] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0007] A method for preparing biomass-derived hard carbon material includes the following steps: (1) EDS was prepared by mixing choline chloride and urea and then sonicating them, followed by heating and stirring. (2) Add the biomass material to the EDS obtained in step (1) and heat and stir to carry out the reaction; (3) The reaction product obtained in step (2) is washed, filtered, dried and then carbonized at high temperature to obtain biomass-derived hard carbon material.

[0008] In the above preparation method, preferably, in step (1), the molar ratio of choline chloride and urea is 1:1.5-2.5.

[0009] In the above preparation method, preferably, in step (1), the ultrasonic treatment time is 4-8h, the heating temperature is 80-100℃, and the stirring time is 0.5-2h.

[0010] In the above preparation method, preferably, in step (2), the mass ratio of biomass material to EDS is 1:5-10.

[0011] In the above preparation method, preferably, in step (2), the temperature after adding biomass material is 80-120℃ and the heating and stirring time is 2-6 h.

[0012] Preferably, in step (2), the biomass material is 50-100 mesh bamboo powder.

[0013] In the above preparation method, preferably, in step (3), the high-temperature carbonization is carried out in a nitrogen or argon atmosphere. The high-temperature carbonization adopts a two-stage sintering process: first, the temperature is raised to 400-600℃ at a heating rate of 2-5℃ / min and held for 1-2 hours; then, the temperature is raised to 800-1400℃ at a heating rate of 2-5℃ / min and held for 1-2 hours.

[0014] In the above preparation method, preferably, in step (3), the washing is done with deionized water until the washing solution is neutral, and the drying is done at 70-90℃ for 10-15 hours.

[0015] As a general inventive concept, the present invention also provides a sodium-ion battery comprising a biomass-derived hard carbon material prepared by the preparation method described above.

[0016] As a general inventive concept, the present invention also provides a lithium-ion battery comprising biomass-derived hard carbon material prepared by the above-described preparation method.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention uses bamboo powder, which grows rapidly and is widely available, as a carbon source, which completely replaces traditional non-renewable fossil-based raw materials such as petroleum asphalt and synthetic resins, greatly reducing dependence on non-renewable resources and conforming to the concept of sustainable development and circular economy.

[0018] (2) This invention uses choline chloride-urea eutectic solvent (EDS) as a pretreatment agent, replacing the highly corrosive and toxic concentrated acids, alkalis, or organic solvents used in traditional processes. EDS has advantages such as low vapor pressure, low toxicity, biodegradability, and recyclability, avoiding the use of toxic chemicals at the source, significantly reducing wastewater and waste residue emissions, and lowering environmental pollution and treatment costs. The choline chloride-urea eutectic solvent raw material is inexpensive, readily available, green, and non-toxic. Compared with other eutectic solvents, it has a lower melting point and better fluidity, exhibiting excellent dissolution and exfoliation effects on lignin and hemicellulose. It can gently etch to form rich pores without severely damaging the cellulose skeleton. This system does not contain metal ions, and the subsequent carbonization process will not introduce metal impurities, avoiding the adverse effects of residual metals on the electrochemical performance of hard carbon.

[0019] (3) The present invention can effectively break the dense fiber structure of bamboo powder through EDS pretreatment, promote the dissolution and separation of biomass components, and make the hard carbon material obtained by subsequent carbonization have better conductivity, thereby improving its electrochemical performance in lithium-ion batteries and sodium-ion batteries.

[0020] (4) The preparation and pretreatment process of EDS of the present invention is simple, requiring only heating and stirring, without the need for complex equipment or harsh conditions. The process flow is easy to control, and the solvent can be recycled and reused, reducing production costs and making it suitable for large-scale green manufacturing.

[0021] (5) The preparation process of the present invention does not require the introduction of chemical reagents and does not generate acid or metal ion-containing waste liquid, reducing environmental load and post-treatment costs, and solving the pollution defects of traditional Lewis acid process; and can precisely control the degree of graphitization of carbon materials, effectively suppressing the problems of interlayer shrinkage and reduction of active sites caused by excessive graphitization, avoiding the drawbacks of uncontrollable graphitization process mediated by Lewis acid, and improving the ion intercalation and diffusion efficiency of materials.

[0022] (6) This invention employs a two-stage sintering process. First, the bamboo powder raw material is fully thermally decomposed to remove volatiles, forming a stable primary porous carbon skeleton. Then, high-temperature sintering is used to complete the carbon skeleton structure reorganization and defect control. Two-stage sintering can effectively avoid problems such as pore collapse and structural inhomogeneity caused by one-step high-temperature sintering, significantly improving the specific surface area, pore structure stability and carbon layer disorder of hard carbon materials. At the same time, it reduces surface-active oxygen-containing groups, improves the initial coulombic efficiency and cycle stability, thereby improving the sodium storage performance of the material. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a scanning electron microscope (SEM) image of the biomass hard carbon sodium anode material prepared in Example 1 of the present invention.

[0025] Figure 2 The image shows the XRD pattern of the biomass hard carbon sodium anode material in Example 1 of this invention.

[0026] Figure 3 This is a cycle stability diagram of the biomass hard carbon sodium anode material in Example 1 of the present invention.

[0027] Figure 4 This is the first charge-discharge curve of the biomass hard carbon sodium electrode material in Example 1 of the present invention.

[0028] Figure 5 This is the first charge-discharge curve of the biomass hard carbon sodium electrode material in Example 2 of the present invention.

[0029] Figure 6 This is the first charge-discharge curve of the biomass hard carbon sodium anode material in Example 3 of the present invention.

[0030] Figure 7 This is the first charge-discharge curve of the biomass hard carbon sodium anode material in Example 4 of the present invention.

[0031] Figure 8 This is the first charge-discharge curve of the biomass hard carbon sodium anode material in Example 5 of the present invention.

[0032] Figure 9 This is a graph showing the initial charge-discharge curve of the biomass hard carbon sodium anode material in Comparative Example 1 of the present invention.

[0033] Figure 10 This is the initial charge-discharge curve of the biomass hard carbon sodium electrode material in Comparative Example 2 of the present invention. Detailed Implementation

[0034] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0035] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0036] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0037] Example 1: A method for preparing biomass-derived hard carbon material according to the present invention includes the following steps: (1) Preparation of EDS: Choline chloride and urea were mixed at a molar ratio of 1:2, sonicated for 6 hours, and then stirred at 80°C for 30 minutes to form a uniform and transparent choline chloride-urea EDS.

[0038] (2) Bamboo powder pretreatment: Take dry bamboo powder with a particle size of 60 mesh and a moisture content of 3%, add it to the EDS prepared in step (1) at a mass ratio of 1:8, and stir at 80℃ for 4 hours to obtain the pretreated bamboo powder system.

[0039] (3) Solid-liquid separation and drying: The pretreated bamboo powder system was filtered, the filter residue was collected, and it was washed 4 times with deionized water until the pH of the washing liquid was 7. Then it was dried at 70℃ for 12h to obtain pretreated bamboo powder.

[0040] (4) High-temperature carbonization: The pretreated bamboo powder is placed in a nitrogen atmosphere and heated to 500°C at a heating rate of 5°C / min. It is kept at this temperature for 2 hours, then heated to 900°C at a heating rate of 5°C / min. It is kept at this temperature for 2 hours and then cooled to obtain hard carbon material.

[0041] The SEM image of the hard carbon material obtained in this embodiment is as follows: Figure 1 As shown, the hard carbon material exhibits a dense and uniform porous structure. This is primarily due to the selective etching and component stripping effect of the choline chloride-urea eutectic solvent on the bamboo powder, as well as the permanent pores formed by the synergistic effect of volatile matter release and skeletal shrinkage during the two-stage carbonization process. The eutectic solvent effectively dissolves hemicellulose and lignin in the raw material, causing the cellulose skeleton to swell, loosen, and form numerous initial channels. During the subsequent two-stage carbonization process, the small molecule gases generated by pyrolysis continuously escape, further expanding the pores and stabilizing the pore structure, ultimately forming a dense, uniform, and regularly distributed pore morphology. Its XRD pattern is shown below. Figure 2As shown, the XRD pattern of the sample exhibits a significantly broadened diffraction peak at approximately 23° 2θ, corresponding to an interplanar spacing d = 0.3854 nm, which is attributed to the characteristic diffraction peak of the (002) crystal plane in hard carbon materials. Simultaneously, a weaker broadened diffraction peak appears near approximately 43° 2θ, corresponding to the characteristic diffraction peak of the (100) crystal plane in hard carbon materials. This indicates that the sample is predominantly amorphous, with the carbon layers exhibiting a disordered stacking structure and an interlayer spacing greater than that of graphite, which is beneficial for ion transport and insertion / extraction.

[0042] Assemble into a button battery: 0.16g of the biomass-derived hard carbon material powder prepared in this embodiment was used as the negative electrode material and mixed with conductive carbon black and binder (PVDF) in a mass ratio of 8:1:1. The resulting mixture was added to N-methylpyrrolidone solvent and stirred for 6 hours. Then, it was coated on copper foil and dried in a drying oven at 100°C for 12 hours to prepare the negative electrode sheet. Then, a sodium metal sheet was used as the counter electrode, NaPF6 Diglyme mixture was used as the electrolyte, and Whatman's GF / C type glass fiber separator was used as the separator to assemble a sodium-ion button battery.

[0043] The electrochemical performance of the sodium-ion button battery was tested. The biomass-derived hard carbon material of this embodiment exhibited an initial discharge specific capacity of 416.1 mAh / g, a charge specific capacity of 268.4 mAh / g, and an initial coulombic efficiency of 64.5% at a charge / discharge current of 100 mA / g. The initial charge / discharge curves are shown below. Figure 4 As shown, from Figure 4 It can be seen that the voltage hysteresis effect of the charging and discharging curves is small, and the cycle stability is as follows. Figure 3 As shown, from Figure 3 It can be seen that the performance of this material meets the requirements of sodium-ion batteries for long-term charge-discharge reliability and service life in different application scenarios.

[0044] Example 2: A method for preparing biomass-derived hard carbon material according to the present invention includes the following steps: (1) Preparation of EDS: Choline chloride and urea were mixed at a molar ratio of 1:2, sonicated for 6 hours, and then stirred at 80°C for 30 minutes to form a uniform and transparent choline chloride-urea EDS.

[0045] (2) Bamboo powder pretreatment: Take dry bamboo powder with a particle size of 60 mesh and a moisture content of 3%, add it to the EDS prepared in step (1) at a mass ratio of 1:8, and stir at 80℃ for 2 hours to obtain the pretreated bamboo powder system.

[0046] (3) Solid-liquid separation and drying: The pretreated bamboo powder system was filtered, the filter residue was collected, and it was washed 4 times with deionized water until the pH of the washing liquid was 7. Then it was dried at 70℃ for 12h to obtain pretreated bamboo powder.

[0047] (4) High-temperature carbonization: The pretreated bamboo powder is placed in a nitrogen atmosphere and heated to 500°C at a heating rate of 5°C / min, held for 2 hours, and then heated to 900°C at a heating rate of 5°C / min, held for 2 hours, and then cooled to obtain hard carbon material.

[0048] The biomass-derived hard carbon material prepared in this example was assembled into a button battery according to the method of Example 1. The electrochemical performance of the button battery was tested. The results showed that the biomass-derived hard carbon material of this example had an initial discharge specific capacity of 385.4 mAh / g, a charge specific capacity of 237.0 mAh / g, and an initial coulombic efficiency of 61.5% at a charge-discharge current of 100 mA / g. The initial charge-discharge curves are shown below. Figure 5 As shown, from Figure 5 It can be seen that the voltage hysteresis effect of the charging curve and the discharging curve is small.

[0049] Example 3: A method for preparing biomass-derived hard carbon material according to the present invention includes the following steps: (1) Preparation of EDS: Choline chloride and urea were mixed at a molar ratio of 1:2, sonicated for 6 hours, and then stirred at 80°C for 30 minutes to form a uniform and transparent choline chloride-urea EDS.

[0050] (2) Bamboo powder pretreatment: Take dry bamboo powder with a particle size of 60 mesh and a moisture content of 3%, add it to the EDS prepared in step (1) at a mass ratio of 1:8, and stir at 80℃ for 6 hours to obtain the pretreated bamboo powder system.

[0051] (3) Solid-liquid separation and drying: The pretreated bamboo powder system was filtered, the filter residue was collected, and it was washed 4 times with deionized water until the pH of the washing liquid was 7. Then it was dried at 70℃ for 12h to obtain pretreated bamboo powder.

[0052] (4) High-temperature carbonization: The pretreated bamboo powder is placed in a nitrogen atmosphere and heated to 500°C at a heating rate of 5°C / min. It is kept at this temperature for 2 hours, then heated to 900°C at a heating rate of 5°C / min. It is kept at this temperature for 2 hours and then cooled to obtain hard carbon material.

[0053] The biomass-derived hard carbon material prepared in this example was assembled into a button battery according to the method of Example 1. The electrochemical performance of the button battery was tested. The results showed that the biomass-derived hard carbon material of this example had an initial discharge specific capacity of 403.4 mAh / g, a charge specific capacity of 225.9.0 mAh / g, and an initial coulombic efficiency of 56.0% at a charge-discharge current of 100 mA / g. The initial charge-discharge curves are shown below. Figure 6 As shown, the voltage hysteresis effect of the charging and discharging curves is relatively small.

[0054] Example 4: A method for preparing biomass-derived hard carbon material according to the present invention includes the following steps: (1) Preparation of EDS: Choline chloride and urea were mixed at a molar ratio of 1:2, sonicated for 6 hours, and then stirred at 80°C for 30 minutes to form a uniform and transparent choline chloride-urea EDS.

[0055] (2) Bamboo powder pretreatment: Take dry bamboo powder with a particle size of 60 mesh and a moisture content of 3%, add it to the EDS prepared in step (1) at a mass ratio of 1:8, and stir at 80℃ for 4 hours to obtain the pretreated bamboo powder system.

[0056] (3) Solid-liquid separation and drying: The pretreated bamboo powder system was filtered, the filter residue was collected, and it was washed 4 times with deionized water until the pH of the washing liquid was 7. Then it was dried at 70℃ for 12 hours to obtain pretreated bamboo powder.

[0057] (4) High-temperature carbonization: The pretreated bamboo powder is placed in a nitrogen atmosphere and heated to 900°C at a heating rate of 5°C / min. The temperature is maintained for 2 hours and then cooled to obtain hard carbon material.

[0058] The biomass-derived hard carbon material prepared in this example was assembled into a button battery according to the method of Example 1. The electrochemical performance of the button battery was tested. The results showed that the biomass-derived hard carbon material prepared in this example had an initial discharge specific capacity of 294.8 mAh / g, a charge specific capacity of 158.8 mAh / g, and an initial coulombic efficiency of 53.9% at a charge-discharge current of 100 mA / g. The initial charge-discharge curves are shown below. Figure 7 As shown, the voltage hysteresis effect of the charging and discharging curves is relatively small.

[0059] Example 5: A method for preparing biomass-derived hard carbon material according to the present invention includes the following steps: (1) Preparation of EDS: Choline chloride and urea were mixed at a molar ratio of 1:2, sonicated for 6 hours, and then stirred at 80°C for 30 minutes to form a uniform and transparent choline chloride-urea EDS.

[0060] (2) Bamboo powder pretreatment: Take dry bamboo powder with a particle size of 60 mesh and a moisture content of 3%, add it to the above EDS at a mass ratio of 1:8, and stir at 80℃ for 4 hours to obtain a pretreated bamboo powder system.

[0061] (3) Solid-liquid separation and drying: The pretreated bamboo powder system was filtered, the filter residue was collected, and it was washed 4 times with deionized water until the pH of the washing liquid was 7. Then it was dried at 70℃ for 12 hours to obtain pretreated bamboo powder.

[0062] (4) High-temperature carbonization: The pretreated bamboo powder is placed in a nitrogen atmosphere and heated to 500°C at a heating rate of 5°C / min, and kept at that temperature for 2 hours. Then, it is heated to 1300°C at a heating rate of 5°C / min, and kept at that temperature for 2 hours. After cooling, hard carbon material is obtained.

[0063] The biomass-derived hard carbon material prepared in this example was assembled into a button battery according to the method of Example 1. The electrochemical performance of the button battery was tested. The results showed that the biomass-derived hard carbon material of this example had an initial discharge specific capacity of 401.1 mAh / g, a charge specific capacity of 256.0 mAh / g, and an initial coulombic efficiency of 53.8% at a charge-discharge current of 100 mA / g. The initial charge-discharge curves are shown below. Figure 8 As shown, the voltage hysteresis effect of the charging and discharging curves is relatively small.

[0064] Comparative Example 1: The preparation method of the biomass hard carbon sodium anode material in this comparative example includes the following steps: Dry bamboo powder with a particle size of 60 mesh and a moisture content of 3% was placed in a nitrogen atmosphere and heated to 500°C at a heating rate of 5°C / min, held for 2 hours, and then heated to 900°C at a heating rate of 5°C / min, held for 2 hours, and then cooled to obtain hard carbon material.

[0065] The biomass-derived hard carbon material prepared in this comparative example was assembled into a button battery according to the method of Example 1. The electrochemical performance of the button battery was tested. The results showed that the biomass-derived hard carbon material of this example had an initial discharge specific capacity of 196.3 mAh / g, a charge specific capacity of 103.6 mAh / g, and an initial coulombic efficiency of 52.8% at a charge-discharge current of 100 mA / g. The initial charge-discharge curves are shown below. Figure 9 As shown.

[0066] Comparative Example 2: The preparation method of the biomass hard carbon sodium anode material in this comparative example includes the following steps: (1) Preparation of EDS: Choline chloride and urea were mixed at a molar ratio of 1:2, sonicated for 6 hours, and then stirred at 80°C for 30 minutes to form a uniform and transparent choline chloride-urea EDS.

[0067] (2) Bamboo powder pretreatment: Take dry bamboo powder with a particle size of 60 mesh and a moisture content of 3%, add it to the EDS prepared in step (1) at a mass ratio of 1:8, and stir at 80℃ for 4 hours to obtain the pretreated bamboo powder system.

[0068] (3) Solid-liquid separation and drying: The pretreated bamboo powder system was filtered, the filter residue was collected, and it was washed 4 times with deionized water until the pH of the washing liquid was 7. Then it was dried at 70℃ for 12h to obtain pretreated bamboo powder.

[0069] (4) Lewis acid treatment: Weigh 1g of pretreated bamboo powder and 3g of copper chloride and mix them evenly with distilled water. Heat and stir at 80℃ for 12h, then wash with deionized water, centrifuge and separate. Place the precipitate in a forced-air drying oven and dry at 80℃ for 12h to obtain a cellulose / lignin composite precursor chelated with transition metal ions.

[0070] (5) High-temperature carbonization: The obtained cellulose / lignin composite precursor was placed in a nitrogen atmosphere and heated to 900℃ at a heating rate of 5℃ / min, held for 2h, and then cooled to obtain hard carbon material.

[0071] The biomass-derived hard carbon material prepared in this comparative example was assembled into a button battery according to the method of Example 1. The electrochemical performance of the button battery was tested. The results showed that the biomass-derived hard carbon material of this example had an initial discharge specific capacity of 372.4 mAh / g, a charge specific capacity of 200.6 mAh / g, and an initial coulombic efficiency of 53.8% at a charge-discharge current of 100 mA / g. The initial charge-discharge curves are shown below. Figure 10 As shown.

Claims

1. A method for preparing a biomass-derived hard carbon material, characterized in that, Includes the following steps: (1) EDS was prepared by mixing choline chloride and urea and then sonicating them, followed by heating and stirring. (2) Add the biomass material to the EDS obtained in step (1) and heat and stir to carry out the reaction; (3) The reaction product obtained in step (2) is washed, filtered, dried and then carbonized at high temperature to obtain biomass-derived hard carbon material.

2. The preparation method according to claim 1, characterized in that, In step (1), the molar ratio of choline chloride to urea is 1:1.5-2.

5.

3. The preparation method according to claim 1, characterized in that, In step (1), the ultrasonic treatment time is 4-8 hours, the heating temperature is 80-100℃, and the stirring time is 0.5-2 hours.

4. The preparation method according to claim 1, characterized in that, In step (2), the mass ratio of biomass material to EDS is 1:5-10.

5. The preparation method according to claim 1, characterized in that, In step (2), the temperature after adding biomass materials is 80-120℃, and the heating and stirring time is 2-6 h.

6. The preparation method according to claim 1, characterized in that, In step (2), the biomass material is bamboo powder of 50-100 mesh.

7. The preparation method according to claim 1, characterized in that, In step (3), the high-temperature carbonization is carried out in a nitrogen or argon atmosphere. The high-temperature carbonization adopts a two-stage sintering process: first, the temperature is raised to 400-600℃ at a heating rate of 2-5℃ / min and held for 1-2 hours; then, the temperature is raised to 800-1400℃ at a heating rate of 2-5℃ / min and held for 1-2 hours.

8. The preparation method according to claim 1, characterized in that, In step (3), the cleaning is performed using deionized water until the washing solution is neutral, and the drying is performed at 70-90℃ for 10-15 hours.

9. A sodium-ion battery, characterized in that, This includes biomass-derived hard carbon materials prepared by any one of the preparation methods described in claims 1 to 8.

10. A lithium-ion battery, characterized in that, This includes biomass-derived hard carbon materials prepared by any one of the preparation methods described in claims 1 to 8.

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