A hard carbon material for pre-oxidizing a biomass precursor and a method for preparing the same
Patent Information
- Application Number
- CN202610987484.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-07-03
- Publication Date
- 2026-09-04
AI Technical Summary
[0004]为解决上述技术问题，本发明提供一种预氧化处理生物质前驱体的硬碳材料及其制备方法，旨在解决现有技术中生物质基硬碳材料电化学性能不佳的问题，且操作简单，易于放大
[0020] The hard carbon material obtained by pre-oxidizing biomass precursors according to this invention is inexpensive, simple to operate, and easy to scale up. Furthermore, this invention introduces more cross-linking bonds into the biomass precursor, extending the carbon layer and thus creating larger pores, which effectively inhibits graphitization. The hard carbon material obtained after pre-oxidizing the biomass precursor has a larger interlayer spacing, better mesoporous structure, and lower degree of graphitization, exhibiting higher specific capacity and better cycle stability when applied in sodium-ion batteries.
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Abstract
Description
Technical Field
[0001] This invention relates to a hard carbon material and its preparation method, specifically to a hard carbon material based on a pre-oxidized biomass precursor and its preparation method. Background Technology
[0002] With the continuous depletion of non-renewable energy and the increasing severity of environmental pollution, there is an urgent need to develop new energy technologies such as clean energy storage and conversion. Sodium-ion batteries have attracted widespread attention due to their abundant resources, low price, and environmental friendliness, and can serve as an important supplement to lithium-ion battery energy storage technology. However, due to the large radius of sodium ions and the thermodynamic instability of intercalation compounds formed by sodium and graphite, graphite anodes, commonly used in lithium-ion batteries, cannot serve as anode materials for sodium-ion batteries. Therefore, the large-scale application of sodium-ion batteries urgently requires suitable anode materials. Hard carbon materials, due to their high sodium storage capacity, low operating potential, and good cycle stability, are widely used as anode materials for sodium-ion batteries.
[0003] Hard carbon precursors are commonly derived from biomass, synthetic resins, and fossil-derived materials. Among these, biomass hard carbon precursors are particularly advantageous for the industrialization of sodium-ion battery anode materials due to their abundant resources, low cost, typically good pore structure eliminating the need for pore creation, simple synthesis routes, and environmental friendliness. However, direct high-temperature carbonization of biomass precursors can lead to the collapse and adhesion of porous structures, resulting in a more graphitized structure. This results in lower specific capacity and poorer cycle stability, significantly limiting the application of biomass-based hard carbon anode materials in sodium-ion batteries. Currently, most methods employ hydrothermal pre-oxidation to reduce the graphitization degree of hard carbon. However, the liquid-phase oxidants used (such as hydrogen peroxide, sodium perchlorate, potassium permanganate, and nitric acid) are corrosive and toxic, requiring high standards for experimental equipment and safety precautions. Some oxidants can even cause irreversible adverse environmental effects. Therefore, there is an urgent need to develop a safe and feasible method for reducing the graphitization degree of biomass hard carbon. Summary of the Invention
[0004] To address the aforementioned technical problems, this invention provides a hard carbon material based on a pre-oxidized biomass precursor and its preparation method, aiming to solve the problem of poor electrochemical performance of biomass-based hard carbon materials in the prior art. Furthermore, the method is simple to operate and easy to scale up.
[0005] To achieve the above objectives, the technical solution provided by the present invention is as follows:
[0006] A hard carbon material based on pre-oxidized biomass precursors, through acidification, low-temperature pre-air oxidation, and high-temperature carbonization, disrupts the hydrogen bond network of biomass under the action of oxygen, introduces more cross-links into the biomass precursor, extends the carbon layer, and thus bends to form channels with larger pore sizes, effectively inhibiting the degree of graphitization.
[0007] The method for preparing hard carbon materials from pre-oxidized biomass precursors as described above includes the following steps:
[0008] S1. After crushing and sieving the biomass precursor, stir it in an acidic solution at 60-90 °C for 1-6 hours, then filter, wash and dry to obtain the acidified biomass precursor.
[0009] S2. Place the acidified biomass precursor in an air atmosphere at 100~400 ℃ for low-temperature heat treatment for 4~12 hours. After the heat treatment, the pre-oxidized material is obtained.
[0010] S3. The above pre-oxidized material is subjected to high-temperature heat treatment under a protective gas at a certain gas flow rate. After the heat treatment is completed, hard carbon material is obtained.
[0011] Preferably, in S1, the biomass precursor is at least one of bamboo powder, coconut shell, walnut shell, macadamia nut shell, hazelnut shell, apricot shell, peanut shell, corn cob, corn stalk, sorghum stalk, sesame stalk, wheat straw, rice husk, sugarcane bagasse, eucalyptus wood, or starch; the biomass precursor is pulverized through a 100-150 mesh sieve.
[0012] Preferably, in S1, the biomass precursor is at least one of macadamia nut shells, walnut shells, corn stalks, rice husks, or sugarcane bagasse.
[0013] Preferably, in S1, the acidic solution is at least one of hydrochloric acid solution, sulfuric acid solution, or nitric acid solution; the concentration of the acidic solution is 0.5~2 mol / L; the filtration and washing are performed by suction filtration and washing with water; the drying is performed at 50~90 ℃ for 6~14 hours; and the mass ratio of the pulverized and sieved biomass precursor to the acidic solution is 1:1~1:2.
[0014] Preferably, in S2, the low-temperature treatment is performed at 300 °C for 6 hours; the heating rate of the low-temperature treatment is 1~10 °C / min.
[0015] Preferably, in S3, the protective gas is one or more of argon, nitrogen, or helium; and the specific gas flow rate is 60~100 mL / min.
[0016] Preferably, in S3, the high-temperature treatment is performed at 700~1400 ℃ for 1~6 hours; the heating rate of the high-temperature treatment is 1~10 ℃ / min.
[0017] The application of hard carbon materials with pre-oxidized biomass precursors in sodium-ion batteries, as described above.
[0018] Preferably, the hard carbon material of the pre-oxidized biomass precursor is used in the anode material of sodium-ion batteries.
[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0020] The hard carbon material obtained by pre-oxidizing biomass precursors according to this invention is inexpensive, simple to operate, and easy to scale up. Furthermore, this invention introduces more cross-linking bonds into the biomass precursor, extending the carbon layer and thus creating larger pores, which effectively inhibits graphitization. The hard carbon material obtained after pre-oxidizing the biomass precursor has a larger interlayer spacing, better mesoporous structure, and lower degree of graphitization, exhibiting higher specific capacity and better cycle stability when applied in sodium-ion batteries. Attached Figure Description
[0021] Figure 1 These are the XRD patterns of the hard carbon anode materials prepared in Example 3 and Comparative Example 1 of this invention;
[0022] Figure 2 The charge-discharge curves of the hard carbon anode materials prepared in Example 3 and Comparative Example 1 of this invention are shown below.
[0023] Figure 3 The cycling curves are those of the hard carbon anode materials prepared in Example 3 and Comparative Example 1 of this invention. Detailed Implementation
[0024] The following detailed description, in conjunction with the accompanying drawings, outlines specific embodiments. However, it should be understood that the scope of protection of this invention is not limited to these specific embodiments. Unless otherwise specified, all raw materials and reagents used in the examples are commercially available.
[0025] Example 1
[0026] A method for preparing hard carbon materials from pre-oxidized biomass precursors, comprising the following steps:
[0027] S1. After crushing and sieving the biomass precursor macadamia nut shells through a 100-mesh sieve, take 40 g of the macadamia nut shells and stir them in 40 g of 0.5 mol / L hydrochloric acid solution at 60 °C for 1 hour. Then filter and wash the macadamia nut shells with water until the water after washing is neutral. Dry them at 50 °C for 6 hours to obtain acidified macadamia nut shells.
[0028] S2. Place the acidified macadamia nut shells in an air atmosphere and maintain a heating rate of 1 ℃ / min. Perform low-temperature heat treatment at 100℃ for 4 h to obtain the pre-oxidized material.
[0029] S3. The above pre-oxidized material is subjected to high-temperature heat treatment at 700 °C for 1 hour under a helium atmosphere, maintaining a gas flow rate of 60 mL / min, to obtain hard carbon material of pre-oxidized biomass precursor.
[0030] Example 2
[0031] A method for preparing hard carbon materials from pre-oxidized biomass precursors, comprising the following steps:
[0032] S1. After crushing the biomass precursor walnut shells and sieving them through a 150-mesh sieve, take 40 g of the crushed walnut shells and stir them in 60 g of a 2 mol / L sulfuric acid solution at 90 °C for 6 hours. Then filter the solution and wash the walnut shells with water until the water is neutral. Dry the solution at 90 °C for 14 hours to obtain the acidified walnut shells.
[0033] S2. Place the acidified walnut shells in an air atmosphere, maintain a heating rate of 10 ℃ / min, and perform low-temperature heat treatment at 400 ℃ for 12 h to obtain pre-oxidized material;
[0034] S3. The above pre-oxidized material is subjected to high-temperature heat treatment at 900 °C for 6 hours under a nitrogen atmosphere, maintaining a gas flow rate of 100 mL / min, to obtain hard carbon material of pre-oxidized biomass precursor.
[0035] Example 3
[0036] A method for preparing hard carbon materials from pre-oxidized biomass precursors, comprising the following steps:
[0037] S1. After crushing and sieving the biomass precursor sugarcane bagasse through a 130-mesh sieve, take 40 g of the bagasse and stir it in 80 g of 1 mol / L hydrochloric acid solution at 70 °C for 6 hours. Then filter the bagasse and wash it with water until the water is neutral. Dry it at 60 °C for 6 hours to obtain acidified sugarcane bagasse.
[0038] S2. Place the acidified bagasse in an air atmosphere, maintain a heating rate of 5 ℃ / min, and perform low-temperature heat treatment at 300 ℃ for 6 h to obtain the pre-oxidized material;
[0039] S3. The above pre-oxidized material is subjected to high-temperature heat treatment at 1200 °C for 2 hours under an argon atmosphere, maintaining a gas flow rate of 80 mL / min, to obtain hard carbon material of pre-oxidized biomass precursor.
[0040] Example 4
[0041] A method for preparing hard carbon materials from pre-oxidized biomass precursors, comprising the following steps:
[0042] S1. After crushing and sieving the biomass precursor sugarcane bagasse through a 130-mesh sieve, take 40 g of the bagasse and stir it in 80 g of 1 mol / L hydrochloric acid solution at 70 °C for 6 hours. Then filter the bagasse and wash it with water until the water is neutral. Dry it at 60 °C for 6 hours to obtain acidified sugarcane bagasse.
[0043] S2. Place the acidified bagasse in an air atmosphere, maintain a heating rate of 5 ℃ / min, and perform low-temperature heat treatment at 300 ℃ for 6 h to obtain the pre-oxidized material;
[0044] S3. The above pre-oxidized material is subjected to high-temperature heat treatment at 1200 °C for 2 hours under a nitrogen atmosphere, maintaining a gas flow rate of 80 mL / min, to obtain hard carbon material of pre-oxidized biomass precursor.
[0045] Example 5
[0046] A method for preparing hard carbon materials from pre-oxidized biomass precursors, comprising the following steps:
[0047] S1. After crushing and sieving the biomass precursor corn stalks through a 120-mesh sieve, take 40 g of the crushed corn stalks and stir them in 70 g of 1 mol / L hydrochloric acid solution at 80 °C for 2 hours. Then filter the solution and wash the corn stalks with water until the water is neutral. Dry the solution at 80 °C for 10 hours to obtain the acidified corn stalks.
[0048] S2. Place the acidified corn stalks in an air atmosphere, maintain a heating rate of 3 ℃ / min, and perform low-temperature heat treatment at 200 ℃ for 10 h to obtain the pre-oxidized material.
[0049] S3. The above pre-oxidized material is subjected to high-temperature heat treatment at 1400 °C for 4 hours under an argon atmosphere, maintaining a gas flow rate of 70 mL / min, to obtain hard carbon material of pre-oxidized biomass precursor.
[0050] Example 6
[0051] A method for preparing hard carbon materials from pre-oxidized biomass precursors, comprising the following steps:
[0052] S1. After crushing the biomass precursor rice husks and sieving them through a 115-mesh sieve, take 40 g of the rice husks and stir them in 60 g of 1 mol / L hydrochloric acid solution at 60 °C for 3 hours. Then filter the solution and wash the rice husks with water until the water is neutral. Dry the rice husks at 70 °C for 8 hours to obtain acidified rice husks.
[0053] S2. Place the acidified rice husks in an air atmosphere, maintain a heating rate of 2 ℃ / min, and perform low-temperature heat treatment at 200 ℃ for 8 h to obtain the pre-oxidized material.
[0054] S3. The above pre-oxidized material is subjected to high-temperature heat treatment at 1300 °C for 4 hours under a nitrogen atmosphere, maintaining a gas flow rate of 90 mL / min, to obtain hard carbon material of pre-oxidized biomass precursor.
[0055] Comparative Example 1
[0056] A method for preparing biomass-based hard carbon anode material, comprising the following steps:
[0057] S2. The acidified sugarcane bagasse was placed under an argon protective atmosphere for low-temperature heat treatment. The heating rate was maintained at 5 ℃ / min, and the low-temperature heat treatment was carried out at 300 ℃ for 6 h to obtain the low-temperature heat-treated material.
[0058] The operation steps of S1 and S3 are the same as those in Example 3. After high-temperature heat treatment, hard carbon material is obtained.
[0059] Comparative Example 2
[0060] A method for preparing biomass-based hard carbon anode material, comprising the following steps:
[0061] S1. After crushing and sieving the biomass precursor sugarcane bagasse through a 130-mesh sieve, take 40 g of the bagasse and stir it in 80 g of a 1 mol / L sodium hydroxide solution at 70 °C for 6 hours. Then filter the bagasse and wash it with water until the water is neutral. Dry it at 60 °C for 6 hours to obtain the alkalized sugarcane bagasse.
[0062] Operations S2 and S3 are the same as in Example 3. After high-temperature heat treatment, hard carbon material is obtained.
[0063] Comparative Example 3
[0064] A method for preparing biomass-based hard carbon anode material, comprising the following steps:
[0065] S1. After crushing the biomass precursor sugarcane bagasse and sieving it through a 130-mesh sieve, take 40 g of the bagasse and stir it in an 80 g aqueous solution at 70 ℃ for 6 hours. Then filter it and wash the bagasse with water until the water after washing is neutral. Dry it at 60 ℃ for 6 hours to obtain the washed sugarcane bagasse.
[0066] Operations S2 and S3 are the same as in Example 3. After high-temperature heat treatment, hard carbon material is obtained.
[0067] The hard carbon materials obtained in Examples 1-6 and Comparative Examples 1-3 were used as active materials. A slurry was prepared by mixing the active material, conductive agent (SP), and binder (PVDF) at a mass ratio of 8:1:1. The black slurry was then coated onto copper foil using a 200 μm four-sided coating tool and dried in a vacuum drying oven at 100 °C for 12 h to obtain the negative electrode sheet. The negative electrode sheet was cut into 12 mm diameter discs using a cutting machine. A sodium metal sheet was used as the counter electrode, and Waterman glass fiber was used as the separator. The electrolyte was the commercial electrolyte KLD-NF12 (1M NaPF6, diethylene glycol dimethyl ether). A 2025 coin cell sodium-ion battery was assembled in an Ar protective glove box. Furthermore, the assembled 2025 coin cell battery was subjected to constant current charge-discharge tests at 50 mA / g and 100 mA / g on a Blue Battery testing system, with a test voltage range of 0.005–2 V.
[0068] The XRD patterns of the hard carbon materials prepared in Example 3 and Comparative Example 1 are as follows: Figure 1 As shown, it can be seen that the peak of the (002) crystal plane in Comparative Example 1 is around 24.5°, while the peak of the (002) crystal plane in Example 3 is around 21.4°. According to the Bragg equation, Example 3 has a larger interlayer spacing and a lower degree of graphitization, which is beneficial for the insertion and extraction of sodium ions.
[0069] The charge-discharge curves of the hard carbon materials prepared in Example 3 and Comparative Example 1 at a current density of 50 mA / g are shown below. Figure 2 As shown, Example 3 has a high specific capacity of 344.6 mAh / g, while the specific capacity of Comparative Example 1 is only 214.1 mAh / g. This indicates that the low-temperature air pre-oxidation treatment has a good inhibitory effect on the degree of graphitization. The larger interlayer spacing is conducive to the storage of sodium ions in hard carbon materials, which promotes the improvement of specific capacity.
[0070] Table 1 shows the discharge specific capacity and capacity retention of Examples 1-6 and Comparative Examples 1-3 after 500 cycles at a current density of 100 mA / g. The cycling curves for Example 3 and Comparative Example 1 are shown in Table 1. Figure 3 As shown, Example 3 exhibits a capacity retention of up to 83.5% after 500 cycles at a current density of 100 mA / g, while Comparative Example 1 shows only 37.1%. This indicates that the hard carbon material obtained after air pre-oxidation treatment has a larger interlayer spacing and a better mesoporous structure, which suppresses the collapse of the porous structure during cycling and demonstrates better cycling stability.
[0071] Table 1. Comparison of electrochemical performance at a current density of 100 mA / g
[0072] First-cycle discharge specific capacity mAh / g Discharge specific capacity mAh / g after 500 cycles Capacity retention Example 1 259.1 201.6 77.8% Example 2 267.5 215.6 80.6% Example 3 294.7 246.1 83.5% Example 4 288.0 238.2 82.7% Example 5 285.5 235.0 82.3% Example 6 268.4 211.8 78.9% Comparative Example 1 191.9 71.2 37.1% Comparative Example 2 252.2 185.6 73.6% Comparative Example 3 229.1 115.0 50.2%
[0073] Compared to Examples 3 and 4, high-temperature heat treatment in nitrogen may introduce nitrogen atom doping, etch the carbon layer, and introduce defect sites, while the hard carbon material heat-treated in an argon atmosphere maintains a good pore structure and fewer impurities, and has higher reversible specific capacity and capacity retention.
[0074] Compared with macadamia nut shells, walnut shells, corn stalks, and rice husks, sugarcane bagasse has the highest first-cycle discharge specific capacity and the best cycle stability. Overall, sugarcane bagasse is the first choice for preparing sodium-ion battery anode materials, followed by corn stalks.
[0075] Compared with Comparative Examples 2 and 3, the hydrochloric acid-treated hard carbon material effectively removes impurities, reduces side reactions, and improves reversible capacity and cycle stability compared with the sodium hydroxide and water-treated materials.
[0076] This invention obtains the target product through acidification, low-temperature pre-air oxidation, and high-temperature carbonization. The specific raw materials and the synergistic effect of acidification and low-temperature pre-air oxidation result in a biomass-based hard carbon anode material prepared using this method, exhibiting a larger interlayer spacing and a lower degree of graphitization. This prevents structural collapse during sodium ion insertion / extraction, improving the capacity retention of the material during long-term cycling. Furthermore, the larger interlayer spacing facilitates sodium ion storage within the hard carbon material, promoting an increase in specific capacity.
[0077] The foregoing description of specific exemplary embodiments of the invention is for illustrative and explanatory purposes. These descriptions are not intended to limit the invention to the precise forms disclosed, and it will be apparent that many changes and variations can be made in accordance with the foregoing teachings. The exemplary embodiments were chosen and described in order to explain the specific principles of the invention and its practical application, thereby enabling those skilled in the art to implement and utilize various different exemplary embodiments of the invention, as well as various different choices and variations. The scope of the invention is intended to be defined by the claims and their equivalents.
Claims
1. A hard carbon material based on pre-oxidized biomass precursors, characterized in that: Hard carbon materials from pre-oxidized biomass precursors were obtained through acidification, low-temperature pre-air oxidation, and high-temperature carbonization.
2. The method for preparing hard carbon material from pre-oxidized biomass precursors as described in claim 1, characterized in that, The following steps are included: S1. After crushing and sieving the biomass precursor, stir it in an acidic solution at 60-90 °C for 1-6 hours, then filter, wash and dry to obtain the acidified biomass precursor. S2. Place the acidified biomass precursor in an air atmosphere at 100~400 ℃ for low-temperature heat treatment for 4~12 hours. After the heat treatment, the pre-oxidized material is obtained. S3. The above pre-oxidized material is subjected to high-temperature heat treatment under a protective gas at a certain gas flow rate. After the heat treatment is completed, hard carbon material is obtained.
3. The method for preparing hard carbon material from pre-oxidized biomass precursors according to claim 2, characterized in that: In S1, the biomass precursor is at least one of bamboo powder, coconut shell, walnut shell, macadamia nut shell, hazelnut shell, apricot shell, peanut shell, corn cob, corn stalk, sorghum stalk, sesame stalk, wheat straw, rice husk, sugarcane bagasse, eucalyptus wood, or starch; the biomass precursor is pulverized through a 100-150 mesh sieve.
4. The method for preparing hard carbon material from pre-oxidized biomass precursors according to claim 2, characterized in that: In S1, the biomass precursor is at least one of macadamia nut shells, walnut shells, corn stalks, rice husks, or sugarcane bagasse.
5. The method for preparing hard carbon material from pre-oxidized biomass precursors according to claim 2, characterized in that: In S1, the acidic solution is at least one of hydrochloric acid solution, sulfuric acid solution, or nitric acid solution; the concentration of the acidic solution is 0.5~2 mol / L; the filtration and washing are performed by suction filtration and washing with water; the drying is performed at 50~90 ℃ for 6~14 hours; the mass ratio of the pulverized and sieved biomass precursor to the acidic solution is 1:1~1:
2.
6. The method for preparing hard carbon material from pre-oxidized biomass precursors according to claim 2, characterized in that: In S2, the low-temperature treatment is performed at 300 °C for 6 hours; the heating rate of the low-temperature treatment is 1~10 °C / min.
7. The method for preparing hard carbon material from pre-oxidized biomass precursors according to claim 2, characterized in that: In S3, the protective gas is one or more of argon, nitrogen, or helium; the specific gas flow rate is 60~100mL / min.
8. The method for preparing hard carbon material from pre-oxidized biomass precursors according to claim 2, characterized in that: In S3, the high-temperature treatment is performed at 700~1400 ℃ for 1~6 hours; the heating rate of the high-temperature treatment is 1~10 ℃ / min.
9. The application of the hard carbon material of the pre-oxidized biomass precursor as described in claim 1 or the hard carbon material of the pre-oxidized biomass precursor prepared by any of the methods of claims 2-8 in sodium-ion batteries.
10. The application of the hard carbon material of the pre-oxidized biomass precursor as described in claim 1 or the hard carbon material of the pre-oxidized biomass precursor prepared by any of the methods of claims 2-8 in the anode material of sodium-ion batteries.