Biomass-based hard carbon material and preparation method thereof, and sodium ion battery

Abstract

The application belongs to the technical field of new energy materials, and provides a biomass-based hard carbon material, a preparation method thereof and a sodium ion battery. The biomass-based hard carbon material has an irregular block shape and a microporous structure on the surface. The size of the irregular block shape is 5-10 mu m. The pore diameter of the microporous structure is less than 1 mu m. The biomass-based hard carbon material has a microstructure characteristic of short-range order and long-range disorder. Compared with existing hard carbon materials, the biomass-based hard carbon material can realize rapid diffusion of sodium ions, and is beneficial to improving the rate performance of the hard carbon.

Description

Technical Field

[0001] This application belongs to the field of new energy materials technology, and in particular relates to a biomass-based hard carbon material and its preparation method, and a sodium-ion battery. Background Technology

[0002] As a main group element, sodium possesses similar physicochemical properties to lithium, and its abundant reserves and low cost have made sodium-ion batteries the best complement to lithium-ion batteries in large-scale energy storage in recent years. Hard carbon holds a similar position in sodium-ion battery anode materials as graphite in lithium-ion batteries; however, currently, high-performance hard carbon materials are mainly resin-based, whose high cost limits their commercialization. Biomass-based hard carbon, on the other hand, has broad commercial application prospects due to its widely available and inexpensive raw materials.

[0003] Currently, biomass-based hard carbon materials still suffer from low capacity and low initial coulombic efficiency. Due to the complex composition of biomass, the influence of each component on the carbon structure and performance is unclear. How to accurately modify the composition of biomass to control the pore structure and carbon layer spacing of the final carbon and improve the sodium storage performance of hard carbon has become a key issue. Summary of the Invention

[0004] In view of this, embodiments of this application provide a biomass-based hard carbon material, which aims to solve the problems of low capacity and low initial coulombic efficiency of existing biomass-based hard carbon materials.

[0005] The first aspect of this application provides a biomass-based hard carbon material, wherein the biomass-based hard carbon material has an irregular block shape and a microporous structure on its surface; wherein the size of the irregular block shape is 5-10 μm; and the pore diameter of the microporous structure is less than 1 μm.

[0006] The biomass-based hard carbon material has a microstructure characterized by short-range order and long-range disorder.

[0007] In one possible implementation of the first aspect, the biomass-based hard carbon material is prepared by using lignocellulose-containing biomass as a precursor, treating it with a 2%-10% hydrogen peroxide solution at a temperature of 25-80°C for 1-6 hours, controlling the pH of the solution to be 3-9, and then carbonizing it under an inert atmosphere after washing and drying.

[0008] A second aspect of this application provides a method for preparing the biomass-based hard carbon material described in the first aspect above, comprising:

[0009] The pretreated biomass containing lignocellulose was treated with 2%-10% hydrogen peroxide solution at 25-80℃ for 1-6 hours, and the pH of the solution was controlled at 3-9 to obtain the reaction solution.

[0010] After the reaction solution is filtered, the resulting powder is washed until neutral and then dried.

[0011] The dried powder is carbonized under an inert atmosphere to obtain biomass-based hard carbon anode material.

[0012] A third aspect of this application provides an electrode material, characterized in that the electrode material comprises a conductive additive, a binder, and the biomass-based hard carbon material described in the first aspect above.

[0013] A fourth aspect of this application provides a negative electrode sheet for a sodium-ion battery, the negative electrode sheet comprising a current collector, a conductive additive coated on the current collector, a binder, and the biomass-based hard carbon material described in the first aspect above.

[0014] A fifth aspect of this application provides a sodium-ion battery, the sodium-ion battery including the negative electrode sheet described in the fourth aspect above.

[0015] The beneficial effects of the embodiments in this application compared with the prior art are:

[0016] This application provides a biomass-based hard carbon material with short-range ordered and long-range disordered microstructure characteristics. Its morphology is an irregular block shape with microporous structure on the surface. The size of the irregular block is 5-10 μm, and the pore diameter of the microporous structure is less than 1 μm, which is much smaller than the pore diameter of existing hard carbon materials. Compared with existing hard carbon materials, this biomass-based hard carbon material can achieve rapid diffusion of sodium ions, which is beneficial to improving the rate performance of hard carbon.

[0017] Furthermore, this application also provides one method for preparing the aforementioned biomass-based hard carbon material, using widely available lignocellulose-containing biomass as raw material. The preparation process is simple and inexpensive. On one hand, by changing the pH, the selective oxidation of lignin and cellulose by hydrogen peroxide can be controlled, thereby controlling the pore structure of the hard carbon and directionally improving its plateau capacity and ramp capacity. On the other hand, by changing the reaction temperature, reaction time, and hydrogen peroxide concentration, the degree of oxidation can be controlled, thereby controlling the specific surface area of ​​the hard carbon and improving the initial coulombic efficiency.

[0018] Furthermore, the sodium-ion battery using the biomass-based hard carbon material provided in the embodiments of this application has high capacity and initial coulombic efficiency, and stable cycle performance. Attached Figure Description

[0019] Figure 1 This is a SEM image of the biomass-based hard carbon material provided in Example 2 of this application;

[0020] Figure 2The XRD pattern of the biomass-based hard carbon material provided in Example 2 of this application;

[0021] Figure 3 This is a SEM image of the biomass-based hard carbon material provided in Example 4 of this application;

[0022] Figure 4 The XRD pattern of the biomass-based hard carbon material provided in Example 4 of this application;

[0023] Figure 5 This is a SEM image of the biomass-based hard carbon material provided in Example 6 of this application;

[0024] Figure 6 The XRD pattern of the biomass-based hard carbon material provided in Example 6 of this application;

[0025] Figure 7 SEM image of the biomass-based hard carbon material provided in Comparative Example 1 of this application;

[0026] Figure 8 The image shows the XRD pattern of the biomass-based hard carbon material provided in Comparative Example 1 of this application. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0028] This application provides a biomass-based hard carbon material, which has an irregular blocky morphology and a microporous structure on its surface; wherein the size of the irregular blocky morphology is 5-10 μm; the pore diameter of the microporous structure is less than 1 μm; and the biomass-based hard carbon material has a microstructure characterized by short-range order and long-range disorder.

[0029] Optionally, the biomass-based hard carbon material uses lignocellulose-containing biomass as a precursor, is treated with 2%-10% hydrogen peroxide solution at 25-80℃ for 1-6 hours, controls the pH of the solution to be 3-9, and then carbonized under an inert atmosphere after washing and drying.

[0030] Optionally, the selection requirements for lignocellulose-containing biomass in this application are limited to biomass materials containing lignin and cellulose, such as one or more selected from bamboo, cork, coconut shell, walnut shell, poplar, apricot shell, lignin, cellulose, and tea oil shell. The selected biomass material is then dehulled and mechanically crushed; for example, bamboo powder can be obtained by drying and dehulling 2-3 year old bamboo, followed by mechanical crushing and passing through a 50-mesh sieve. Although this application uses bamboo as an example in specific embodiments, this should not be construed as limiting the scope of protection of this application. Those skilled in the art can also use one or more of other materials selected from cork, coconut shell, walnut shell, poplar, apricot shell, lignin, cellulose, and tea oil shell to replace bamboo and achieve the same effect.

[0031] This application also provides a method for preparing biomass-based hard carbon materials with high sodium storage capacity and high energy density, which has a simple preparation process, low cost, and adjustable platform capacity, including the following steps:

[0032] Step S1: Treat the pretreated biomass containing lignocellulose with a 2%-10% hydrogen peroxide solution at 25-80℃ for 1-6 hours, and control the pH of the solution to 3-9 to obtain the reaction solution.

[0033] In the embodiments of this application, pretreatment of biomass containing lignocellulose refers to removing impurities and sterilizing the biomass. As an example, the pretreatment method can be to crush the biomass into powder, pass it through a 50-mesh sieve, and then boil it in deionized water for 30 minutes.

[0034] In the embodiments of this application, pH conditions can be controlled by adding an acid or a base to the system solution. For example, the acid used to control pH can be selected from one or more of hydrochloric acid, sulfuric acid, acetic acid, citric acid, phosphoric acid, and nitric acid; the base used to control pH can be selected from one or more of potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, sodium bicarbonate, and potassium bicarbonate. It is worth noting that pH control is particularly critical, as changing the pH can control the selective oxidation of lignin and cellulose by hydrogen peroxide, thereby controlling the pore structure of hard carbon and directionally increasing its plateau capacity and slope capacity. Therefore, the pH is preferably controlled between 3 and 7, more preferably 3.

[0035] In this embodiment, the control of reaction temperature, reaction time, and hydrogen peroxide concentration is also crucial. By changing the reaction temperature, reaction time, and hydrogen peroxide concentration, the degree of oxidation can be controlled, thereby controlling the specific surface area of ​​hard carbon and improving the initial coulombic efficiency. Therefore, the reaction temperature is preferably controlled at 60-70°C, and since the temperature may fluctuate within ±5°C during the reaction, it is preferably controlled at 65±5°C; the reaction time is preferably controlled at 1-3 hours, more preferably 3 hours; and the concentration of the hydrogen peroxide solution is preferably controlled at 2%-6%, more preferably 6%.

[0036] Step S2: After the reaction solution is filtered, the resulting powder is washed until neutral and then dried.

[0037] Optionally, the above reaction solution is filtered, the powder is washed with deionized water until neutral, and then dried in an oven at 105°C until constant weight.

[0038] Step S3: The dried powder is carbonized under an inert atmosphere to obtain the biomass-based hard carbon anode material.

[0039] Optionally, the dried powder is placed in a tube furnace and protected with inert gas. It is then treated at 1100-1500℃ for 1-3 hours to carbonize the material. After cooling to room temperature, the carbon powder is crushed at high speed to obtain a biomass-based hard carbon material with an irregular blocky macroscopic morphology and a porous surface. The typical size of the irregular blocky material is 5-10 μm, and the pore diameter of the porous structure is less than 1 μm. This biomass-based hard carbon material has a microstructure characterized by short-range order and long-range disorder.

[0040] Optionally, the inert gas can be one or more of argon and nitrogen.

[0041] Optionally, the heating rate is 2 to 10 °C / min.

[0042] The carbonization temperature, time, and heating rate can all be set with reference to existing technology. Although the following specific embodiments use only a single parameter as an example, they should not be used to limit the scope of protection of this application. Those skilled in the art can adjust the setting of carbonization temperature, time, and heating rate according to existing technology.

[0043] The biomass-based hard carbon material provided in this application embodiment can be used to prepare electrode materials. Specifically, the electrode material includes conductive additives, binders, and the above-mentioned biomass-based hard carbon material.

[0044] The biomass-based hard carbon material provided in this application embodiment can be used to prepare the negative electrode sheet of sodium-ion battery, and further applied in sodium-ion secondary battery; specifically, the negative electrode sheet includes a current collector, a conductive additive coated on the current collector, a binder, and the above-mentioned biomass-based hard carbon material.

[0045] The selection of the conductive additives, binders, and current collectors can refer to existing technologies. For example, the conductive additives can be carbon materials, including one or more of carbon black, acetylene black, carbon fiber, conductive graphite, carbon nanotubes, and graphene; the binders can be one or more of polyvinylidene fluoride, sodium alginate, sodium polyacrylate, and sodium carboxymethyl cellulose; and the current collectors can be copper foil or aluminum foil.

[0046] The following detailed description of biomass-based hard carbon materials uses specific embodiments, as shown below. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods; and the materials and reagents used are commercially available unless otherwise specified.

[0047] Example 1

[0048] In this embodiment, the preparation method of biomass-based hard carbon material includes the following steps:

[0049] Step S110: Peel the bamboo sections, crush them into powder using a mechanical method, and pass them through a 50-mesh sieve.

[0050] Step S120: Transfer the bamboo powder to a beaker and boil it with deionized water for 30 minutes.

[0051] Step S130: Bamboo powder is treated with 2% hydrogen peroxide solution at 65±5℃ for 3 hours, and the pH of the reaction is controlled at 3 with 30% acetic acid solution.

[0052] Step S140: Filter the reaction solution from step S130, wash the bamboo powder with deionized water until neutral, and dry it in an oven at 105°C until constant weight.

[0053] Step S150: Place bamboo powder into a tube furnace, introduce inert gas for protection, and heat treat at 1300℃ for 3 hours with a heating rate of 2℃ / min to carbonize it.

[0054] Step S160: After cooling to room temperature, the material is crushed at high speed to obtain a biomass-based hard carbon material with an irregular block shape and a microporous structure on the surface.

[0055] Example 2

[0056] In this embodiment, the preparation method of biomass-based hard carbon material includes the following steps:

[0057] Step S110: Peel the bamboo sections, crush them into powder using a mechanical method, and pass them through a 50-mesh sieve.

[0058] Step S120: Transfer the bamboo powder to a beaker and boil it with deionized water for 30 minutes.

[0059] Step S130: Bamboo powder is treated with 6% hydrogen peroxide solution at 65±5℃ for 3 hours, and the pH of the reaction is controlled at 3 with 30% acetic acid solution.

[0060] Step S140: Filter the reaction solution from step S130, wash the bamboo powder with deionized water until neutral, and dry it in an oven at 105°C until constant weight.

[0061] Step S150: Place bamboo powder into a tube furnace, introduce inert gas for protection, and heat treat at 1300℃ for 3 hours with a heating rate of 2℃ / min to carbonize it.

[0062] Step S160: After cooling to room temperature, the material is crushed at high speed to obtain a biomass-based hard carbon material with an irregular block shape and a microporous structure on the surface.

[0063] Example 3

[0064] In this embodiment, the preparation method of biomass-based hard carbon material includes the following steps:

[0065] Step S110: Peel the bamboo sections, crush them into powder using a mechanical method, and pass them through a 50-mesh sieve.

[0066] Step S120: Transfer the bamboo powder to a beaker and boil it with deionized water for 30 minutes.

[0067] Step S130: Bamboo powder is treated with 10% hydrogen peroxide solution at 65±5℃ for 3 hours, and the pH of the reaction is controlled at 3 with 30% acetic acid solution.

[0068] Step S140: Filter the reaction solution from step S130, wash the bamboo powder with deionized water until neutral, and dry it in an oven at 105°C until constant weight.

[0069] Step S150: Place bamboo powder into a tube furnace, introduce inert gas for protection, and heat treat at 1300℃ for 3 hours with a heating rate of 2℃ / min to carbonize it.

[0070] Step S160: After cooling to room temperature, the material is crushed at high speed to obtain a biomass-based hard carbon material with an irregular block shape and a microporous structure on the surface.

[0071] Example 4

[0072] In this embodiment, the preparation method of biomass-based hard carbon material includes the following steps:

[0073] Step S110: Peel the bamboo sections, crush them into powder using a mechanical method, and pass them through a 50-mesh sieve.

[0074] Step S120: Transfer the bamboo powder to a beaker and boil it with deionized water for 30 minutes.

[0075] Step S130: Bamboo powder is treated with 6% hydrogen peroxide solution at 65±5℃ for 3h, and the pH of the reaction is controlled at 7 with 1mol / L sodium hydroxide solution.

[0076] Step S140: Filter the reaction solution from step S130, wash the bamboo powder with deionized water until neutral, and dry it in an oven at 105°C until constant weight.

[0077] Step S150: Place bamboo powder into a tube furnace, introduce inert gas for protection, and heat treat at 1300℃ for 3 hours with a heating rate of 2℃ / min to carbonize it.

[0078] Step S160: After cooling to room temperature, the material is crushed at high speed to obtain a biomass-based hard carbon material with an irregular block shape and a microporous structure on the surface.

[0079] Example 5

[0080] In this embodiment, the preparation method of biomass-based hard carbon material includes the following steps:

[0081] Step S110: Peel the bamboo sections, crush them into powder using a mechanical method, and pass them through a 50-mesh sieve.

[0082] Step S120: Transfer the bamboo powder to a beaker and boil it with deionized water for 30 minutes.

[0083] Step S130: Bamboo powder is treated with 6% hydrogen peroxide solution at 65±5℃ for 3h, and the pH of the reaction is controlled at 9 with 1mol / L sodium hydroxide solution.

[0084] Step S140: Filter the reaction solution from step S130, wash the bamboo powder with deionized water until neutral, and dry it in an oven at 105°C until constant weight.

[0085] Step S150: Place bamboo powder into a tube furnace, introduce inert gas for protection, and heat treat at 1300℃ for 3 hours with a heating rate of 2℃ / min to carbonize it.

[0086] Step S160: After cooling to room temperature, the material is crushed at high speed to obtain a biomass-based hard carbon material with an irregular block shape and a microporous structure on the surface.

[0087] Example 6

[0088] In this embodiment, the preparation method of biomass-based hard carbon material includes the following steps:

[0089] Step S110: Peel the bamboo sections, crush them into powder using a mechanical method, and pass them through a 50-mesh sieve.

[0090] Step S120: Transfer the bamboo powder to a beaker and boil it with deionized water for 30 minutes.

[0091] Step S130: Bamboo powder is treated with 6% hydrogen peroxide solution at 25±5℃ for 3 hours, and the pH of the reaction is controlled at 3 with 30% acetic acid solution.

[0092] Step S140: Filter the reaction solution from step S130, wash the bamboo powder with deionized water until neutral, and dry it in an oven at 105°C until constant weight.

[0093] Step S150: Place bamboo powder into a tube furnace, introduce inert gas for protection, and heat treat at 1300℃ for 3 hours with a heating rate of 2℃ / min to carbonize it.

[0094] Step S160: After cooling to room temperature, the material is crushed at high speed to obtain a biomass-based hard carbon material with an irregular block shape and a microporous structure on the surface.

[0095] Example 7

[0096] In this embodiment, the preparation method of biomass-based hard carbon material includes the following steps:

[0097] Step S110: Peel the bamboo sections, crush them into powder using a mechanical method, and pass them through a 50-mesh sieve.

[0098] Step S120: Transfer the bamboo powder to a beaker and boil it with deionized water for 30 minutes.

[0099] Step S130: Bamboo powder is treated with 6% hydrogen peroxide solution at 65±5℃ for 1 hour, and the pH of the reaction is controlled at 3 with 30% acetic acid solution.

[0100] Step S140: Filter the reaction solution from step S130, wash the bamboo powder with deionized water until neutral, and dry it in an oven at 105°C until constant weight.

[0101] Step S150: Place bamboo powder into a tube furnace, introduce inert gas for protection, and heat treat at 1300℃ for 3 hours with a heating rate of 2℃ / min to carbonize it.

[0102] Step S160: After cooling to room temperature, the material is crushed at high speed to obtain a biomass-based hard carbon material with an irregular block shape and a microporous structure on the surface.

[0103] Example 8

[0104] In this embodiment, the preparation method of biomass-based hard carbon material includes the following steps:

[0105] Step S110: Peel the bamboo sections, crush them into powder using a mechanical method, and pass them through a 50-mesh sieve.

[0106] Step S120: Transfer the bamboo powder to a beaker and boil it with deionized water for 30 minutes.

[0107] Step S130: Bamboo powder is treated with 6% hydrogen peroxide solution at 65±5℃ for 6 hours, and the pH of the reaction is controlled at 3 with 30% acetic acid solution.

[0108] Step S140: Filter the reaction solution from step S130, wash the bamboo powder with deionized water until neutral, and dry it in an oven at 105°C until constant weight.

[0109] Step S150: Place bamboo powder into a tube furnace, introduce inert gas for protection, and heat treat at 1300℃ for 3 hours with a heating rate of 2℃ / min to carbonize it.

[0110] Step S160: After cooling to room temperature, the material is crushed at high speed to obtain a biomass-based hard carbon material with an irregular block shape and a microporous structure on the surface.

[0111] Comparative Example 1

[0112] In this comparative example, the preparation method of biomass-based hard carbon material includes the following steps:

[0113] Boil the bamboo powder for 30 minutes and dry it in an oven at 105°C until constant weight. Place the bamboo powder in a tube furnace and heat it to 1300°C at a rate of 2°C / min under argon protection. Hold the temperature for 3 hours to allow it to decompose and carbonize. Allow the tube furnace to cool naturally to room temperature before removing the bamboo powder.

[0114] Comparative Example 2

[0115] In this comparative example, the preparation method of biomass-based hard carbon material includes the following steps:

[0116] Step S110: Peel the bamboo sections, crush them into powder using a mechanical method, and pass them through a 50-mesh sieve.

[0117] Step S120: Transfer the bamboo powder to a beaker and boil it with deionized water for 30 minutes.

[0118] Step S130: Treat bamboo powder with 6% hydrogen peroxide solution at 65±5℃ for 3h, and control the pH of the reaction at 12 with 1mol / L sodium hydroxide solution.

[0119] Step S140: Filter the reaction solution from step S130, wash the bamboo powder with deionized water until neutral, and dry it in an oven at 105°C until constant weight.

[0120] Step S150: Place bamboo powder into a tube furnace, introduce inert gas for protection, and heat treat at 1300℃ for 3 hours with a heating rate of 2℃ / min to carbonize it.

[0121] Step S160: After cooling to room temperature, the material is crushed at high speed to obtain a biomass-based hard carbon material with an irregular block shape and a microporous structure on the surface.

[0122] Comparative Example 3

[0123] In this comparative example, the preparation method of biomass-based hard carbon material includes the following steps:

[0124] Step S110: Peel the bamboo sections, crush them into powder using a mechanical method, and pass them through a 50-mesh sieve.

[0125] Step S120: Transfer the bamboo powder to a beaker and boil it with deionized water for 30 minutes.

[0126] Step S130: Bamboo powder is treated with 30% hydrogen peroxide solution at 65±5℃ for 3 hours, and the pH of the reaction is controlled at 3 with 30% acetic acid solution.

[0127] Step S140: Filter the reaction solution from step S130, wash the bamboo powder with deionized water until neutral, and dry it in an oven at 105°C until constant weight.

[0128] Step S150: Place bamboo powder into a tube furnace, introduce inert gas for protection, and heat treat at 1300℃ for 3 hours with a heating rate of 2℃ / min to carbonize it.

[0129] Step S160: After cooling to room temperature, the material is crushed at high speed to obtain a biomass-based hard carbon material with an irregular block shape and a microporous structure on the surface.

[0130] The microstructure and typical dimensions of the biomass-based hard carbon materials prepared in the above embodiments and comparative examples were observed using scanning electron microscopy (SEM). The carbon interlayer spacing of the hard carbon was measured by X-ray diffraction (XRD), the average pore diameter of the hard carbon was measured by small-angle X-ray scattering (SAXS), and the specific surface area of ​​the hard carbon was obtained based on BET theory through N2 desorption testing. The test results are shown in Table 1.

[0131] in, Figure 1-2 The images shown are SEM and XRD patterns of the biomass-based hard carbon material prepared in Example 2 above. Figure 3-4 The images shown are SEM and XRD patterns of the biomass-based hard carbon material prepared in Example 4 above. Figure 5-6 The images shown are SEM and XRD patterns of the biomass-based hard carbon material prepared in Example 6 above. Figure 7-8 The images shown are SEM and XRD patterns of the biomass-based hard carbon material prepared in Comparative Example 1.

[0132] Table 1

[0133]

[0134]

[0135] Furthermore, the biomass-based hard carbon materials prepared in each embodiment were used as negative electrode active materials for sodium-ion secondary batteries. According to a mass ratio of 92%:3%:1.5%:3.5%, 184 mg of the above-mentioned hard carbon powder, 6 mg of conductive carbon black, 6 mg of a 2% (w / w) carboxymethyl cellulose solution, and 17.5 mg of a 40% (w / w) styrene-butadiene rubber were weighed out, and an appropriate amount of deionized water was added. The mixture was stirred for 20 minutes until a uniform slurry was formed. This slurry was then uniformly coated onto the surface of a copper (Cu) foil using a 100 μm scraper. The slurry was dried in a 105°C forced-air drying oven for 2 hours. The Cu foil containing the active material was then cut into circular negative electrode sheets and transferred to a glove box for later use.

[0136] The simulated battery assembly was carried out in a MIKROUNA glove box filled with Ar atmosphere. A prepared carbon material electrode was used as the negative electrode, 1.0 mol / L NaPF6 in DME as the electrolyte, and a Na metal sheet as the counter electrode to assemble a 2016 coin cell. After resting for 12 hours, the battery underwent its first charge-discharge test at 0.1C, with a voltage range of 0–2V. Long-cycle testing was then conducted at 1C. The electrochemical performance test results are shown in Table 2.

[0137] Table 2

[0138]

[0139]

[0140] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of this patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

[0141] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A biomass-based hard carbon material, characterized in that, The biomass-based hard carbon material has an irregular blocky morphology with a microporous structure on its surface; wherein the size of the irregular blocky morphology is 5-10µm; the pore diameter of the microporous structure is less than 1µm; the biomass-based hard carbon material has a microstructure characterized by short-range order and long-range disorder; the biomass-based hard carbon material is produced by using lignocellulose-containing biomass as a precursor, treating it with 2%-6% hydrogen peroxide solution at 60-70℃ for 1-3 hours, controlling the pH of the solution to be 3-7, and then carbonizing it under an inert atmosphere after washing and drying.

2. A method for preparing the biomass-based hard carbon material according to claim 1, characterized in that, include: The pretreated biomass containing lignocellulose was treated with 2%-6% hydrogen peroxide solution at 60-70℃ for 1-3 hours, and the pH of the solution was controlled at 3-7 to obtain the reaction solution. After the reaction solution is filtered, the resulting powder is washed until neutral and then dried. The dried powder is carbonized under an inert atmosphere to obtain biomass-based hard carbon anode material.

3. The method for preparing biomass-based hard carbon anode material according to claim 2, characterized in that, The concentration of the hydrogen peroxide solution was 6%; the temperature was 65℃; the time was 3 hours; and the pH was 3.

4. An electrode material, characterized in that, The electrode material includes conductive additives, binders, and the biomass-based hard carbon material as described in claim 1.

5. A negative electrode sheet for a sodium-ion battery, characterized in that, The negative electrode sheet includes a current collector, a conductive additive coated on the current collector, a binder, and the biomass-based hard carbon material as described in claim 1.

6. A sodium-ion battery, characterized in that, The sodium-ion battery includes the negative electrode sheet as described in claim 5.

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