Basawood-based porous carbon negative electrode material applied to sodium-ion battery and preparation method and application of Basawood-based porous carbon negative electrode material
The bamboo-based porous carbon materials address the issues of low capacity and stability in sodium ion batteries by employing a method that includes pre-carbonization and high-temperature carbonization, resulting in high efficiency and stability for sodium ion insertion and extraction.
Patent Information
- Application Number
- CN202510631169.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-16
- Publication Date
- 2025-07-15
AI Technical Summary
When existing biomass carbon materials are used in the negative electrode of sodium ion batteries, there are problems of low specific capacity and poor cycle stability, and the method of preparing heteroatom doped carbon materials is not yet mature.
Using Bassa wood as the raw material, pre-carbonization and high-temperature carbonization are performed by mixing with pore-forming agent/activator and nitrogen source to prepare porous carbon materials, combined with pickling and water washing to remove impurities, and form a Bassa wood-based porous carbon anode material with a natural pore structure.
It improves the first Coulomb efficiency and reversible specific capacity of sodium ion batteries, has excellent cycle stability and rate performance, is simple in process and low in cost, and is suitable for industrial production.
Smart Images
Figure CN120308959A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of sodium-ion battery electrode materials, and specifically relates to a balsa-based porous carbon anode material for sodium-ion batteries and a preparation method thereof. Background Art
[0002] Carbon-based materials have attracted much attention due to their rich resources, low cost, high conductivity, and high stability. Although traditional commercial graphite can be widely used in lithium-ion batteries, its small interlayer spacing is not conducive to the insertion and extraction of Na+ during charge and discharge, showing a low reversible capacity as the anode of sodium-ion batteries. At present, some carbonaceous materials such as hard carbon, carbon spheres, carbon nanofibers, and carbon nanotubes have been tried as anodes for SIBs. Among them, hard carbon is the most promising anode material for SIBs due to its large interlayer distance, low graphitization degree, and disordered structure. Biomass, as an abundant renewable energy source, is widely available and inexpensive. Many organic matters rich in carbohydrates, lignin, cellulose, and hemicellulose, including crop straws, municipal wastes, and industrial by-products, usually generate heat through direct combustion or conversion into other forms of fuel combustion. Converting various waste biomasses into carbon-based anode materials can not only reduce environmental pollution and relieve environmental pressure but also enhance their utilization value. In the past few years, the synthesis of carbon-based materials with excellent properties such as large specific surface area, controllable porosity, and high conductivity from biomass as anode materials for sodium-ion batteries has received increasing attention from researchers.
[0003] In the process of studying biomass carbon materials as anodes for sodium-ion batteries, there are problems of low specific capacity and poor cycle stability, which need to be improved. To further improve the electrochemical performance of biomass carbon materials, researchers in this field have carried out a large number of research works and confirmed that the electrochemical performance of carbon materials can be improved by doping heteroatoms. In recent years, carbon materials doped with elements such as nitrogen, boron, phosphorus, sulfur, and oxygen have also attracted extensive attention. So far, the methods for preparing heteroatom-doped carbon materials are still very challenging, and there is an urgent need to develop methods with high specific capacity, good cycle stability, and simpler preparation methods. Summary of the Invention
[0004] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a balsa-based porous carbon anode material for sodium-ion batteries, a preparation method thereof, and uses thereof.
[0005] Another object of the present invention is to provide the balsa-based porous carbon material obtained by the above preparation method.
[0006] The object of the present invention is achieved by the following technical solutions.
[0007] The object of the first aspect of the present invention is to provide a preparation method of a balsa-based porous carbon negative electrode material for sodium-ion batteries, comprising the following steps:
[0008] Step 1: Wash the balsa material with deionized water to remove impurities on the surface, and then dry and crush it to obtain a carbon source biomass material for preparing the porous carbon negative electrode material; the carbon source biomass material is a powder with a particle size of 100-400 mesh;
[0009] Step 2: Mix the carbon source biomass material obtained in Step 1 with a pore-forming agent / activating agent, grind it until uniform, and carry out pre-carbonization treatment at 100-300 °C for 6-20 h in an air atmosphere, and then cool it to room temperature to obtain a pre-carbonized product. Among them, the pore-forming agent / activating agent is one or a mixture of several of KOH, NaOH or K2C2O4;
[0010] In Step 2, the grinding time is 1-3 h.
[0011] In Step 2, the heating rate of the pre-carbonization treatment is 1-10 °C / min.
[0012] Step 3: Mix the pre-carbonized product described in Step 2 with a nitrogen source, grind it until uniform, and carry out high-temperature carbonization at 600-1000 °C for 1-10 h in an inert gas atmosphere, then cool it and grind it to obtain a carbon material.
[0013] In Step 3, the nitrogen source is one or a mixture of several of melamine, urea or ammonium chloride.
[0014] In Step 3, the heating rate of the high-temperature carbonization is 1-10 °C / min.
[0015] Step 4: Wash the carbon material described in Step 3 to neutrality to remove impurities in the carbon material, then carry out suction filtration and drying to obtain the porous carbon negative electrode material.
[0016] In Step 4, the washing to neutrality is first pickling and then water washing.
[0017] In the above technical solution, the pickling uses one or a mixture of several of HCl, H3PO4 or H2SO4.
[0018] The object of the second aspect of the present invention is to provide a sodium-ion battery carbon negative electrode material, which is the porous biomass carbon material obtained by the above preparation method.
[0019] For the third aspect of the present invention, an object is to provide a porous carbon material electrode sheet. Polyvinylidene fluoride is added to N-methylpyrrolidone and stirred evenly. The carbon anode material for sodium-ion battery of the present invention is mixed evenly with conductive carbon black and ground. After being mixed evenly, a carbon anode slurry for sodium-ion battery is obtained. The slurry is evenly coated on copper foil or aluminum foil by a coater and dried in a vacuum drying oven for 6-12 h, and then cut into electrode sheets with different diameters by a punching machine. The mass ratio of the carbon anode material for sodium-ion battery, conductive carbon black and polyvinylidene fluoride is 8:0.5-1.5:0.5-1.5.
[0020] For the fourth aspect of the present invention, an object is to provide a sodium-ion battery, which has the porous carbon material electrode sheet obtained by the above method.
[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0022] 1. Utilize the natural multi-level pore structure of balsa wood, which is beneficial to the insertion and extraction of sodium ions. The sodium-ion half-cell prepared based on balsa wood exhibits high initial Coulomb efficiency and reversible specific capacity. Its charge curve is of a plateau type and the plateau capacity accounts for a high proportion. At the same time, it has excellent cycle stability and rate performance.
[0023] 2. The pre-carbonization process can make the raw materials mix more fully and reduce the dehydration rate of the biomass carbon material, which is beneficial to the formation of a more uniform pore structure. In the high-temperature carbonization stage, the pore-forming agent / activator (NaOH) reacts with carbon, and the natural pore structure of balsa wood provides a basic framework for the pore-forming process. The two work together to synchronize pore formation and activation, thereby preparing a biomass porous carbon material. The preparation method of the present invention has a simple process and low cost, and is suitable for industrial mass production.
[0024] 3. Through structural regulation, the present invention introduces anions (O, N) to change the layer spacing, ion diffusion coefficient and conductivity of the biomass carbon anode material for sodium-ion battery, thereby improving its cycle stability. Description of the Drawings
[0025] Figure 1 XRD patterns of the biomass carbon anode materials for sodium-ion batteries prepared in Examples 1 to 3;
[0026] Figures 2 to 10 Successively are the charge-discharge curves of the sodium-ion half-cells prepared in Examples 1-9 at a current density of 30 mA g -1 ;
[0027] Figures 11 to 19 Successively are the cycle performance and Coulomb efficiency of the sodium-ion half-cells prepared in Examples 1-9 at a current density of 500 mA g -1 ;
[0028] Figure 20 The rate performance graph of the sodium-ion half-cell prepared in Example 1;
[0029] Figure 21 The isothermal adsorption curve graph of Example 1;
[0030] Figure 22 The pore size distribution curve graph of Example 1;
[0031] Figure 23 The cycle performance graph of the full cell prepared in Example 1. Detailed implementation manners
[0032] Next, in combination with the appendages of the embodiments of the present invention, the solutions in the embodiments of the present invention will be described. The described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.
[0033] The object of the present invention is to prepare a balsa-based porous carbon anode material for sodium-ion batteries. The porous carbon material prepared by the present invention exhibits excellent cycle performance and rate performance, and is a porous carbon anode material with good electrochemical performance.
[0034] The preparation method of the balsa-based porous carbon anode material for sodium-ion batteries provided by the present invention includes the following steps:
[0035] Step 1: Wash the balsa material with deionized water to remove impurities on the surface, and dry and crush it to obtain a carbon source biomass material for preparing the porous carbon anode material;
[0036] Step 2: Mix the carbon source biomass material obtained in Step 1 with a pore-forming agent / activator, and use a mortar to grind it to make all materials evenly mixed;
[0037] Step 3: Transfer the materials evenly mixed in Step 2 to a muffle furnace, and perform pre-carbonization treatment in an air atmosphere, and naturally cool to room temperature to obtain a pre-carbonized product;
[0038] Step 4: Mix the pre-carbonized product in Step 3 with a nitrogen source evenly and grind it. Then transfer the material to a high-temperature tube furnace and perform high-temperature carbonization in an inert gas atmosphere. After natural cooling, grind it to obtain a carbon material; the inert gas in the present invention is helium or argon.
[0039] Step 5: Wash the carbon material pyrolyzed in Step 4 with acid and then with water until it is neutral to remove impurities in the material, filter by suction and dry it to obtain the porous carbon anode material.
[0040] In some embodiments of the present invention, in step two, the pore-forming agent / activator used is one or more of KOH, NaOH, and K2C2O4, and it is ground in a mortar for 1-3 h. Among them, the dosage ratio of biomass to the pore-forming agent / activator is 3:1-3, and specifically, it can be selected as 3:1, 3:2, or 3:3.
[0041] In some embodiments of the present invention, in step three, the heating rate of the pre-carbonization treatment is 1-10 °C / min, the pyrolysis temperature is 100-300 °C, and the holding time is 6-20 h. Specifically, the heating rate can be selected as 1 °C / min, 2 °C / min, 3 °C / min, 4 °C / min, 5 °C / min, 6 °C / min, 7 °C / min, 8 °C / min, 9 °C / min, or 10 °C / min. The pyrolysis temperature can be selected as 100 °C, 200 °C, or 300 °C. The holding time can be selected as 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h, 19 h, or 20 h.
[0042] In some embodiments of the present invention, in step four, the heating rate of the high-temperature carbonization is 1-10 °C / min, the pyrolysis temperature is 600-1000 °C, and the holding time is 1-10 h. Specifically, the heating rate of the high-temperature carbonization can be selected as 1 °C / min, 2 °C / min, 3 °C / min, 4 °C / min, 5 °C / min, 6 °C / min, 7 °C / min, 8 °C / min, 9 °C / min, or 10 °C / min. The pyrolysis temperature can be selected as 600 °C, 700 °C, 800 °C, 900 °C, or 1000 °C. The holding time can be selected as 1 h, 2 h, 3 h, 4 h, 5 h, 6 h, 7 h, 8 h, 9 h, or 10 h.
[0043] In some embodiments of the present invention, in step five, the acid used in the pickling process is one or more of HCl, H3PO4, and H2SO4.
[0044] The following is further illustrated by specific examples.
[0045] The present invention provides a balsa wood-based porous carbon anode material for sodium-ion batteries and a preparation method thereof, including the following steps:
[0046] Example 1
[0047] Step one: Thoroughly wash the balsa wood material with deionized water to remove the impurities on the surface, and dry it, and then crush the plant biomass material using a wall breaker.
[0048] Step two: Mix the crushed balsa wood material with the pore-forming agent / activator NaOH evenly, and grind it in a mortar for 1 h to make all the materials mixed evenly.
[0049] Step 3: Transfer the well-mixed materials into a muffle furnace and conduct pre-carbonization treatment under an air atmosphere. The heating rate of the pre-carbonization treatment is 5 °C / min, the pyrolysis temperature is 200 °C, the holding time is 10 h, and then cool naturally to room temperature to obtain the pre-carbonized product.
[0050] Step 4: Mix the pre-carbonized product and the nitrogen source urea uniformly and grind them. Subsequently, transfer this material into a high-temperature tubular furnace and conduct high-temperature carbonization under an Ar atmosphere. The heating rate of the high-temperature carbonization is 5 °C / min, the pyrolysis temperature is 750 °C, the holding time is 1 h, and then cool naturally and grind.
[0051] Step 5: Wash the carbon material obtained by pyrolysis with hydrochloric acid and then with deionized water until neutral to remove the impurities present in the material, filter by suction and dry to obtain the porous carbon anode for sodium-ion batteries.
[0052] Example 2
[0053] Step 1: Thoroughly wash the plant biomass material with deionized water to remove the impurities present on the surface, and dry it. Then use a blender to crush the plant biomass material.
[0054] Step 2: Mix the crushed plant biomass material and the pore-forming agent / activator KOH uniformly and grind them with a mortar for 1 h to make all materials well-mixed.
[0055] Step 3: Transfer the well-mixed materials into a muffle furnace and conduct pre-carbonization treatment under an air atmosphere. The heating rate of the pre-carbonization treatment is 5 °C / min, the pyrolysis temperature is 200 °C, the holding time is 10 h, and then cool naturally to room temperature to obtain the pre-carbonized product.
[0056] Step 4: Mix the pre-carbonized product and the nitrogen source urea uniformly and grind them. Subsequently, transfer this material into a high-temperature tubular furnace and conduct high-temperature carbonization under an Ar atmosphere. The heating rate of the high-temperature carbonization is 5 °C / min, the pyrolysis temperature is 750 °C, the holding time is 1 h, and then cool naturally and grind.
[0057] Step 5: Wash the carbon material obtained by pyrolysis with hydrochloric acid and then with deionized water until neutral to remove the impurities present in the material, filter by suction and dry to obtain the porous carbon anode for sodium-ion batteries.
[0058] Example 3
[0059] Step 1: Thoroughly wash the plant biomass material with deionized water to remove the impurities present on the surface, and dry it. Then use a blender to crush the plant biomass material.
[0060] Step 2: Mix the crushed plant biomass material and the pore-forming agent / activator K2C2O4 uniformly and grind them with a mortar for 1 h to make all materials well-mixed.
[0061] Step 3: Transfer the uniformly mixed materials into a muffle furnace and conduct pre-carbonization treatment under an air atmosphere. The heating rate for pre-carbonization treatment is 5 °C / min, the pyrolysis temperature is 200 °C, the holding time is 10 h, and then naturally cool to room temperature to obtain the pre-carbonized product.
[0062] Step 4: Mix the pre-carbonized product and the nitrogen source urea uniformly and grind them. Then transfer this material into a high-temperature tube furnace and conduct high-temperature carbonization under an Ar gas atmosphere. The heating rate for high-temperature carbonization is 5 °C / min, the pyrolysis temperature is 750 °C, the holding time is 1 h, and then naturally cool and grind.
[0063] Step 5: Wash the carbon material obtained by pyrolysis with hydrochloric acid and deionized water until it is neutral to remove the impurities present in the material, then filter by suction and dry to obtain the porous carbon anode for sodium-ion batteries.
[0064] Example 4
[0065] Except that the pyrolysis temperature in Step 4 is 650 °C, other steps are the same as those in Example 1.
[0066] Example 5
[0067] Except that the pyrolysis temperature in Step 4 is 850 °C, other steps are the same as those in Example 1.
[0068] Example 6
[0069] Except that the pyrolysis temperature in Step 4 is 650 °C, other steps are the same as those in Example 2.
[0070] Example 7
[0071] Except that the pyrolysis temperature in Step 4 is 850 °C, other steps are the same as those in Example 2.
[0072] Example 8
[0073] Except that the pyrolysis temperature in Step 4 is 650 °C, other steps are the same as those in Example 3.
[0074] Example 9
[0075] Except that the pyrolysis temperature in Step 4 is 850 °C, other steps are the same as those in Example 3.
[0076] Example 10
[0077] The preparation process of the electrode sheet in this embodiment is as follows: Weigh the raw materials according to the mass ratio of sodium-ion battery carbon negative electrode material, conductive carbon black, and polyvinylidene fluoride of 8:1:1. Add polyvinylidene fluoride to N-methylpyrrolidone and stir evenly. Mix the sodium-ion porous carbon negative electrode and conductive carbon black evenly and grind them. Mix the two evenly to obtain the sodium-ion battery carbon negative electrode slurry. Use a coater to evenly coat the slurry on copper foil and dry it in a vacuum drying oven at 80 °C for 12 h. Use a punching machine to cut it into electrode sheets with a diameter of 12 mm.
[0078] In some embodiments of the present invention, the mass ratio of the sodium-ion battery carbon negative electrode material, conductive carbon black, and polyvinylidene fluoride is 8:0.5 - 1.5:0.5 - 1.5. Specifically, the mass ratio of the sodium-ion battery carbon negative electrode material, conductive carbon black, and polyvinylidene fluoride can be selected as 8:0.5:0.5, 8:1:1, 8:1.5:1.5, 8:0.5:1.5, 8:0.5:1, 8:1.5:0.5, 8:1.5:1, 8:1:0.5.
[0079] In some embodiments of the present invention, it is dried in a vacuum drying oven at 80 °C for 6 - 12 h. Specifically, 6 h, 7 h, 8 h, 9 h, 10 h, 11 h, 12 h can be selected.
[0080] In the present invention, the conductive carbon black can be acetylene black.
[0081] Example 11
[0082] This embodiment provides a sodium-ion battery half-cell. Compact the prepared electrode sheet using a tablet press. Select a glass fiber round sheet with a diameter of 19 mm as the separator. Use a mixture of sodium perchlorate (solute) and polycarbonate (solvent) as the electrolyte. The concentration of sodium perchlorate in the electrolyte is 1 mol / L. Use a sodium sheet as the counter electrode and assemble a CR 2032 button cell in a glove box with a high-purity argon atmosphere. Let it stand for 5 and perform charge and discharge tests on the battery at current densities of 30 mA / g and 1000 mA / g on a blue dot test platform.
[0083] As Figure 1 shown, the balsa wood-based porous carbon materials prepared in Examples 1 - 3 exhibit obvious (002) diffraction peaks and unobvious (100) diffraction peaks, indicating that the sodium-ion battery balsa wood-based porous carbon negative electrode materials prepared in Examples 1 - 3 have highly amorphous properties.
[0084] Figures 2 to 10 For the charge and discharge diagram of the sodium-ion half-cells prepared in Examples 1 - 9 at a current density of 30 mA / g -1 Current density, as Figures 2 to 10 can be seen, the first charge capacity of Example 1 can reach 242.1 mAh / g -1, the first charge capacity of Example 2 can reach 200 mAh / g -1 , the first charge capacity of Example 3 can reach 210 mAh / g -1 , the first charge capacity of Example 4 can reach 200 mAh / g -1 , the first charge capacity of Example 5 can reach 225 mAh / g -1 , the first charge capacity of Example 6 can reach 178 mAh / g -1 , the first charge capacity of Example 7 can reach 198.9 mAh / g -1 , the first charge capacity of Example 8 can reach 145 mAh / g -1 , the first charge capacity of Example 9 can reach 153 mAh / g -1 .
[0085] Figures 11 to 19 The figure shows the electrochemical cycling performance and Coulombic efficiency of the sodium-ion half-cells prepared in Examples 1-9 at a current density of 1000 mA / g -1 , the initial reversible specific capacity of Example 1 is 165 mAh / g -1 , and the reversible capacity after 500 cycles can still reach 160 mAh / g -1 , the initial reversible capacity of Example 2 is 132 mAh / g -1 , and the reversible capacity after 500 cycles can still reach 135 mAh / g -1 , the initial reversible capacity of Example 3 is 125.8 mAh / g -1 , and the reversible capacity after 500 cycles can still reach 120 mAh / g -1 , the initial reversible capacity of Example 4 is 131 mAh / g -1 , and the reversible capacity after 500 cycles can still reach 130 mAh / g -1 , the initial reversible capacity of Example 5 is 151.2 mAh / g -1 , and the reversible capacity after 500 cycles can still reach 150 mAh / g -1 , the initial reversible capacity of Example 6 is 112.3 mAh / g -1 , and the reversible capacity after 500 cycles can still reach 110 mAh / g -1 , the initial reversible capacity of Example 7 is 125.3 mAh / g -1 , and the reversible capacity after 500 cycles can still reach 125 mAh / g -1 , the initial reversible capacity of Example 8 is 99.8 mAh / g -1 , and the reversible capacity after 500 cycles can still reach 95 mAh / g -1 , the initial reversible capacity of Example 9 is 110 mAh / g -1 , and the reversible capacity after 500 cycles can still reach 115 mAh / g-1 .
[0086] Figure 20 This is the rate image of the sodium ion half-battery prepared in Example 1. At 0.05, 0.1, 0.2, 0.5 and 1 A / g, the specific reversible capacity of the sodium ion half-battery prepared in Example 1 is 268.6, 241.5, 218.2, 177.5, 151.2 mAh g, respectively. -1 When the current density is reversed from 1 A / g to 0.5 A / g, the capacity can be almost completely restored, indicating that the sodium ion half-battery prepared in Example 1 has good capacity reversibility and exhibits excellent rate performance.
[0087] Figure 21 The isothermal adsorption curve of Example 1 is a ring-shaped graph with a high specific surface area, which can be used for Na + Provide more active sites. When the ratio of equilibrium pressure (P) to saturated vapor pressure (P0) is in the middle and high range, the adsorption amount increases rapidly, and there is a small hysteresis loop, which is consistent with the characteristics of type IV isotherm.
[0088] Figure 22 : is the pore size distribution curve of Example 1. The pore distribution of Example 1 is mainly concentrated in the range of 2-15nm, indicating that the pores on the surface of the carbon material mainly exist in the form of mesopores, accompanied by a small amount of micropores. This pore structure dominated by mesopores is conducive to ion diffusion. Generally, micropores increase the contact area between the material and the electrolyte, reduce the diffusion resistance, and ensure a larger specific capacity and energy density, while mesopores can be used as ion channels to shorten the ion transmission distance and improve the rate performance of the battery.
[0089] Figure 23 The cycle performance diagram of the full battery of Example 1, the current density is 100mAg -1 The reversible capacity of the full battery is 99.8 mAh g -1 , the capacity still remains at 90.9% after 200 cycles.
[0090] The present invention is described above by way of example. It should be noted that, without departing from the core of the present invention, any simple deformation, modification or other equivalent replacement that can be made by those skilled in the art without inventive effort falls within the protection scope of the present invention.
Claims
1. A preparation method of a balsa wood-based porous carbon anode material for sodium-ion batteries, characterized in that, It includes the following steps: Step 1: Wash the balsa wood material with deionized water to remove the impurities on the surface, and then dry and crush it to obtain the carbon source biomass material for preparing the porous carbon negative electrode material; Step 2: Mix the carbon source biomass material obtained in Step 1 with the pore-forming agent / activator, and then grind it using a mortar to make all the materials evenly mixed; Step 3: Transfer the evenly mixed materials in Step 2 to a muffle furnace, and carry out pre-carbonization treatment in the air atmosphere, and naturally cool to room temperature to obtain the pre-carbonization product; Step 4: Mix the pre-carbonization product in Step 3 with the nitrogen source evenly and grind it. Then transfer the material to a high-temperature tube furnace and carry out high-temperature carbonization in an inert gas atmosphere. After natural cooling, grind it to obtain the carbon material; Step 5: Wash the carbon material obtained by pyrolysis in Step 4 with acid and then with water until it is neutral to remove the impurities in the material, filter it by suction and dry it to obtain the porous carbon negative electrode material.
2. The method according to claim 1, wherein: In Step 2, the pore-forming agent / activator used is one or more of KOH, NaOH, and K2C2O4, and grind it with a mortar for 1-3 h.
3. The method according to claim 1, wherein: In Step 3, the heating rate of the pre-carbonization treatment is 1-10 °C / min, the pyrolysis temperature is 100-300 °C, and the heat preservation time is 6-20 h.
4. The method according to claim 1, wherein: In Step 4, the heating rate of the high-temperature carbonization is 1-10 °C / min, the pyrolysis temperature is 600-1000 °C, and the heat preservation time is 1-10 h.
5. The method according to claim 1, wherein: In Step 5, the acid used in the acid washing process is one or more of HCl, H3PO4, and H2SO4.
6. A carbon negative electrode material for a sodium ion battery, characterized in that: It is prepared by the method according to any one of claims 1-5.
7. The sodium-ion battery carbon negative electrode material according to claim 6, wherein: The carbon negative electrode material is a porous carbon material with both microporous and mesoporous structures, and the specific surface area of the porous carbon is 100 - 800 m 2 g -1 .
8. A porous carbon material electrode sheet, characterized in that: Add polyvinylidene fluoride to N-methylpyrrolidone and stir evenly. Mix the sodium-ion battery carbon negative electrode material according to claim 6 or 7 with conductive carbon black evenly and grind it. After mixing evenly, obtain the sodium-ion battery carbon negative electrode slurry. Use a coater to evenly coat the slurry on copper foil or aluminum foil, and dry it in a vacuum drying oven at 80 °C for 6-12 h, and use a punching machine to cut it into electrode sheets with different diameters.
9. The porous carbon material electrode sheet according to claim 8, characterized in that: The mass ratio of the sodium-ion battery carbon negative electrode material, conductive carbon black, and polyvinylidene fluoride is 8:0.5-1.5:0.5-1.
5.
10. A sodium-ion battery, characterized in that: It includes the porous carbon material electrode sheet according to claim 8 or 9.