Low-temperature asphalt-coated foam carbon sib carbon-based negative electrode material and preparation method thereof

Abstract

The application discloses a low-temperature asphalt-coated foam carbon SIBs carbon-based negative electrode material and a preparation method thereof, and the method comprises the following steps: mixing a foam carbon precursor and a foaming agent, uniformly mixing, transferring into a crucible, and transferring into a tube furnace, and heating under an inert gas atmosphere to obtain foam carbon. Then, the prepared foam carbon and asphalt are fully mixed according to a certain proportion, and then transferred into a crucible and transferred into a tube furnace to obtain an asphalt-coated foam carbon negative electrode material after carbonization under an inert gas atmosphere. The novel asphalt-coated foam carbon negative electrode material prepared by the application greatly improves the sodium storage performance of the foam carbon, has high specific capacity and high initial coulomb efficiency, and can be used in low-speed electric vehicles, portable electronic devices and distributed energy storage fields.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery anode material technology, and in particular to a low-temperature pitch-coated foamed carbon sodium-ion battery (SIBs) anode material and its preparation method. Background Technology

[0002] With the continuous development of energy technology, the demand for large-scale, safe, and reliable clean energy storage equipment is constantly increasing. Sodium-ion batteries (SIBs) have become one of the hottest topics in the energy storage field and have attracted widespread attention. Because lithium resources are very limited in the Earth's crust, their high cost makes further commercial development difficult. Compared to lithium, sodium resources are abundant (approximately 440 times more abundant than lithium), inexpensive, and have a larger operating voltage window. Therefore, sodium-ion batteries are a highly promising next-generation electrochemical energy storage technology that can be mass-produced and commercialized. Currently, many countries and regions have formulated corresponding policies to promote the development and application of sodium-ion batteries.

[0003] Sodium-ion batteries (SIBs) have entered the early stages of commercialization, but have not yet achieved a breakthrough in industrialization. The main limiting factor lies in the availability of suitable anode materials. Traditional graphite has been proven unsuitable as an anode material for sodium-ion batteries. In contrast, amorphous carbon (including hard carbon and soft carbon) is favored due to its superior energy storage performance and low cost; among them, hard carbon has a high sodium storage capacity (up to 300 mAh g⁻¹). -1 Sodium-ion batteries have a certain slope and platform energy storage capacity, which can achieve a high energy density, but their carbon production rate is low and their economic efficiency is poor compared to soft carbon. Soft carbon has a relatively high carbon production rate and its precursors are widely available and economical, but its capacity is low, mainly consisting of slope capacity with virtually no energy storage platform, and its cycle life is poor. These factors have become the constraints on its development in sodium-ion batteries.

[0004] When carbon-based materials are used as anode materials in sodium-ion batteries, their charge-discharge curves exhibit a typical high-voltage range (≥0.5V) with a surface diffusion-controlled ramp and a low-voltage range (≤0.1V) with an intercalation-controlled plateau. The sodium storage mechanisms in these two regions differ. Currently, most commonly accepted mechanisms are the adsorption of sodium ions in the ramp region and the intercalation, micropore filling, and deposition of sodium ions in the plateau region. The sodium ion kinetics also differ between the two regions; the sodium ion kinetics in the plateau region are relatively slow, while the ramp region exhibits faster reaction kinetics. Summary of the Invention

[0005] The purpose of this invention is to provide a low-temperature asphalt-coated foamed carbon sodium-ion battery carbon-based anode material and its preparation method, addressing the existing technical problems of sodium-ion batteries (SIBs).

[0006] The technical solution of the present invention is as follows:

[0007] A method for preparing a low-temperature pitch-coated foamed carbon-sodium ion battery carbon-based anode material includes the following steps:

[0008] A1. The raw material, foamed carbon precursor, is pulverized by ball milling and then sieved.

[0009] A2. Remove impurities by acid washing / alkali washing of low-temperature asphalt, then wash with deionized water until neutral and dry to obtain pure low-temperature asphalt;

[0010] A3. Mix the foamed carbon precursor with the foaming agent, and after mixing evenly, transfer it into a crucible and then into a tube furnace.

[0011] A4. In an inert gas atmosphere, start the tubular furnace and heat it at a certain heating rate. After holding it at the predetermined temperature for a period of time, cool it down to room temperature at a certain cooling rate.

[0012] A5. Mix the prepared foamed carbon and low-temperature asphalt thoroughly in a certain proportion, then transfer it into a crucible and then into a tube furnace;

[0013] A6. Also under an inert gas atmosphere, start the tube furnace, heat it at a certain heating rate, hold it at the predetermined temperature for a period of time, then heat it to a higher temperature at a certain heating rate, hold it at the predetermined temperature for a period of time, and then cool it down to room temperature at a certain cooling rate.

[0014] A7. After the tube furnace has completely cooled down, remove the crucible, grind the carbonized material and sieve it to obtain low-temperature asphalt-coated foamed carbon anode material.

[0015] In the preparation method described above, the sieve mesh size is 50-300 mesh, and the foam carbon precursor is one or more of glucose, starch, diethylaminetetraacetic acid (EDTA), carboxymethyl cellulose (CMC), polystyrene (PS), polyurethane (PU), and phenolic resin (PF).

[0016] In the preparation method described above, in step A2 acid washing / alkali washing, the acid is one or more of oxalic acid, hydrochloric acid, sulfuric acid, hydrofluoric acid, and nitric acid, with a molar fraction of 0.05-2 mol / L, and the alkali is one or more of ammonium bicarbonate, ammonia, potassium hydroxide, and sodium hydroxide, with a molar fraction of 0.05-2 mol / L.

[0017] In the preparation method described above, the solvent in step A3 is one or more of ammonium carbonate, urea, ammonium chloride, ammonium sulfate, sodium bicarbonate, magnesium carbonate, and calcium carbonate.

[0018] The preparation method described herein involves a heating rate of 1-10℃ / min, a holding temperature of 45-1000℃, a holding time of 2-25h, and a cooling rate of 1-10℃ / min in the tube furnace.

[0019] In the preparation method described above, the ratio of foamed carbon to asphalt powder in step A5 is 1:0.5-5.

[0020] The preparation method described herein, wherein the negative electrode material obtained in step A6 has a low degree of surface amorphism, a high degree of internal amorphism, and is a carbon material with a large number of microporous structures.

[0021] Low-temperature asphalt-coated foamed carbon sodium-ion battery carbon-based anode material prepared according to any of the methods described.

[0022] This invention primarily addresses the problems of low initial coulombic efficiency and low sodium storage capacity (especially low plateau capacity) caused by the high porosity of foamed carbon. Furthermore, to meet the development trend in energy storage and the demand for sodium-ion battery anode materials, this invention provides a novel method for preparing a low-temperature asphalt-coated foamed carbon sodium-ion battery anode material.

[0023] This invention is the first to use low-temperature asphalt (such as 45℃ coal-based impregnating agent asphalt) to coat foamed carbon, achieving a comprehensive improvement effect by reducing the surface defect content and macropore content of foamed carbon and forming micropore and closed-pore structures. This is mainly reflected in: 1. Due to the high porosity and large specific surface area of ​​foamed carbon, its surface defect content is high, which adversely affects the initial coulombic efficiency. Coating with molten asphalt can reduce the surface defect concentration of foamed carbon and improve the initial coulombic efficiency; 2. Low-temperature asphalt melts when heated to a lower temperature. When fully mixed with foamed carbon, the molten asphalt fills the internal macropore structure of the foamed carbon, transforming the macropore structure into a micropore and closed-pore structure, thereby providing plateau capacity. By utilizing the combined effect of low-temperature asphalt inducing the transformation of the pore structure of foamed carbon and reducing the surface defect content, the sodium storage performance of foamed carbon is effectively improved.

[0024] The present invention has the following beneficial effects:

[0025] (1) Low-temperature asphalt coating can reduce the surface defect concentration of foamed carbon, especially the irreversible adsorption defect concentration of sodium ions, and reduce the sodium ion loss during the first charge and discharge, thereby improving the first coulombic efficiency.

[0026] (2) Low-temperature asphalt induces the transformation of the pore structure of foam carbon, forming micropores and closed-pore structures; and during the carbonization process after being coated by low-temperature asphalt, the foam carbon itself also has a secondary carbonization effect, thereby causing the internal carbon layer of the foam carbon to grow and form a partial closed-pore structure again to improve the platform capacity. Attached Figure Description

[0027] Figure 1 XRD (a) and Raman spectra (b) of foamed carbon (with glucose as a precursor) mixed with low-temperature asphalt at a ratio of 1:1 and carbonized at 600℃;

[0028] Figure 2 Raman spectra (a), constant current charge-discharge curve (b), and rate curve (c) of foamed carbon (glucose as precursor) mixed with low-temperature asphalt at a ratio of 1:2 and carbonized at 600℃.

[0029] Figure 3 The constant current charge-discharge curves (a), rate curves (b), and SEM images (c) of foamed carbon (starch as a precursor) mixed with low-temperature asphalt at a ratio of 1:1 and carbonized at 800℃ are shown.

[0030] Figure 4 Raman spectra (a) and XRD (b) of foamed carbon (with glucose as a precursor) mixed with low-temperature asphalt at a ratio of 1:1 and carbonized at 1000℃;

[0031] Figure 5 Raman spectra (a), SEM images (b), constant current charge-discharge curves (c), and rate curves (d) of foamed carbon (starch as a precursor) mixed with low-temperature asphalt at a ratio of 2:1 and carbonized at 1000℃.

[0032] Figure 6 Glucose as a precursor and ammonium chloride as a foaming agent, constant current charge-discharge curve (a) and SEM image after carbonization at 900℃; Detailed Implementation

[0033] The present invention will be described in detail below with reference to specific embodiments.

[0034] The preparation method of low-temperature asphalt-coated foamed sodium-carbon ion battery carbon-based anode material is carried out according to the following steps:

[0035] 1. The raw material foam carbon precursor is ball-milled and then passed through a 100-400 mesh sieve.

[0036] 2. Removal of ash from asphalt: The sieved asphalt is acid-washed / alkali-washed to remove impurities, then washed with deionized water until neutral and dried to obtain pure low-temperature asphalt.

[0037] 3. The foamed carbon precursor and the foaming agent are mixed evenly and then transferred to a crucible and then to a tube furnace.

[0038] IV. In an N2 atmosphere, start the tube furnace and heat it at a heating rate of 5℃ / min until it reaches 900℃. Hold the temperature for 2 hours and then cool it down to room temperature at a cooling rate of 2℃ / min.

[0039] 5. Mix the foamed carbon obtained in step 4 with the low-temperature asphalt obtained in step 2 in a certain proportion, then transfer the mixture to a crucible and then to a tube furnace.

[0040] VI. Under the same N2 atmosphere, start the tube furnace and heat it at a heating rate of 3℃ / min until it reaches 60℃ and holds for 0.5h. Then, heat it again at a heating rate of 2℃ / min until it reaches 600~1000℃ and holds for 1~12h. Finally, cool it down to room temperature at a cooling rate of 2℃ / min.

[0041] 7. After the tube furnace has completely cooled to room temperature, remove the crucible and pass the carbonized material through a 200-mesh sieve to obtain a novel low-temperature pitch-coated foamed carbon sodium-ion battery carbon-based anode material.

[0042] Naturally, the novel low-temperature asphalt-coated foamed sodium-ion battery carbon-based anode material can be prepared by the above method. If the novel low-temperature asphalt-coated foamed sodium-ion battery carbon-based anode material is prepared by other methods, it is also within the scope of disclosure and protection of the embodiments of the present invention.

[0043] Example 1: The preparation method of the novel low-temperature asphalt-coated foamed sodium-carbon ion battery carbon-based anode material of this embodiment is carried out according to the following steps:

[0044] 1. Glucose raw material is ball-milled and then passed through a 300-mesh sieve.

[0045] 2. Removal of ash from asphalt: The low-temperature asphalt is first pickled with hydrochloric acid for 12 hours, then pickled with hydrofluoric acid for 12 hours, then washed with deionized water until neutral, and dried to remove moisture to obtain pure low-temperature asphalt.

[0046] 3. Mix 2g of glucose with 2g of ammonium chloride, and after mixing evenly, transfer the mixture to a crucible and then to a tube furnace.

[0047] IV. In an N2 atmosphere, start the tube furnace and heat it at a heating rate of 5℃ / min until it reaches 900℃. Hold the temperature for 2 hours and then cool it down to room temperature at a cooling rate of 2℃ / min.

[0048] 5. Weigh 1g of the foamed carbon obtained in step 4 and 1g of the low-temperature asphalt obtained in step 2, mix them thoroughly, then transfer them into a crucible and transfer them into a tube furnace.

[0049] 6. In the same N2 atmosphere, start the tube furnace and heat it at a heating rate of 2℃ / min until it reaches 60℃ and holds for 0.5h. Then continue heating at a heating rate of 2℃ / min until it reaches 600℃ and holds for 2h. Finally, cool it down to room temperature at a cooling rate of 2℃ / min.

[0050] 7. After the tube furnace has completely cooled to room temperature, remove the crucible and pass the carbonized material through a 200-mesh sieve to obtain a novel low-temperature pitch-coated foamed carbon sodium-ion battery carbon-based anode material.

[0051] like Figure 1 As shown, after the foamed carbon and low-temperature asphalt are fully mixed, carbonization is carried out at 600℃. It can be seen that the (002) peak is lower than the typical soft carbon characteristic peak. This is because the carbonization temperature is lower, resulting in a lower degree of ordering of the graphite layer. It has certain advantages for sodium storage performance, but the first coulombic efficiency will be adversely affected.

[0052] Example 2: The preparation method of the novel low-temperature asphalt-coated foamed sodium-carbon ion battery carbon-based anode material of this embodiment is carried out according to the following steps:

[0053] 1. Glucose raw material is ball-milled and then passed through a 300-mesh sieve.

[0054] 2. Removal of ash from asphalt: The low-temperature asphalt is first pickled with hydrochloric acid for 12 hours, then pickled with hydrofluoric acid for 12 hours, then washed with deionized water until neutral, and dried to remove moisture to obtain pure low-temperature asphalt.

[0055] 3. Mix 2g of glucose with 2g of urea, and after mixing evenly, transfer the mixture to a crucible and then to a tube furnace.

[0056] IV. In an N2 atmosphere, start the tube furnace and heat it at a heating rate of 5℃ / min until it reaches 900℃. Hold the temperature for 2 hours and then cool it down to room temperature at a cooling rate of 2℃ / min.

[0057] 5. Weigh 1g of the foamed carbon obtained in step 4 and 2g of the low-temperature asphalt obtained in step 2, mix them thoroughly, then transfer them into a crucible and transfer them into a tube furnace.

[0058] 6. In the same N2 atmosphere, start the tube furnace and heat it at a heating rate of 2℃ / min until it reaches 60℃ and holds for 0.5h. Then continue heating at a heating rate of 2℃ / min until it reaches 600℃ and holds for 2h. Finally, cool it down to room temperature at a cooling rate of 2℃ / min.

[0059] 7. After the tube furnace has completely cooled to room temperature, remove the crucible and pass the carbonized material through a 200-mesh sieve to obtain a novel low-temperature pitch-coated foamed carbon sodium-ion battery carbon-based anode material.

[0060] like Figure 2 As shown, in the Raman spectrum at 1350 cm⁻¹ -1 and 1580cm -1Two peaks, D and G, appear respectively. The D peak represents amorphous or defective carbon materials, and its appearance is due to the interaction of photons and phonons, leading to a change in the lattice vibration mode. The G peak represents pure crystalline carbon materials. It is caused by the relative motion between sp^2 hybridized carbon atoms in the carbon material. 2g Vibration of the mode. With increased low-temperature bitumen content, the I-mode of the Raman spectrum... D / I G A significant decrease indicates an improvement in the degree of ordering of the graphite carbon layers in the material. (From...) Figure 2 (b) It can be seen that due to the increased degree of graphitization, some sodium storage active sites are lost, resulting in a decrease in the first-cycle discharge capacity compared to Implementation Case 3.

[0061] Example 3: The preparation method of the novel low-temperature asphalt-coated foamed sodium-carbon ion battery carbon-based anode material of this embodiment is carried out according to the following steps:

[0062] 1. Grind the raw starch into powder by ball milling and then pass it through a 300-mesh sieve.

[0063] 2. Removal of ash from asphalt: The low-temperature asphalt is first pickled with hydrochloric acid for 12 hours, then pickled with hydrofluoric acid for 12 hours, then washed with deionized water until neutral, and dried to remove moisture to obtain pure low-temperature asphalt.

[0064] 3. Mix 2g of starch with 2g of ammonium chloride (mass ratio 1:1), mix evenly, transfer to a crucible and then to a tube furnace.

[0065] IV. In an N2 atmosphere, start the tube furnace and heat it at a heating rate of 5℃ / min until it reaches 900℃. Hold the temperature for 2 hours and then cool it down to room temperature at a cooling rate of 2℃ / min.

[0066] 5. Weigh 1g of the foamed carbon obtained in step 4 and 1g of the low-temperature asphalt obtained in step 2, mix them thoroughly, then transfer them into a crucible and transfer them into a tube furnace.

[0067] 6. Under the same N2 atmosphere, start the tube furnace and heat at a heating rate of 2℃ / min until it reaches 60℃ and holds for 0.5h. Then continue heating at a heating rate of 2℃ / min until it reaches 800℃ and holds for 3h. Finally, cool it down to room temperature at a cooling rate of 2℃ / min.

[0068] 7. After the tube furnace has completely cooled to room temperature, remove the crucible and pass the carbonized material through a 200-mesh sieve to obtain a novel low-temperature pitch-coated foamed carbon sodium-ion battery carbon-based anode material.

[0069] like Figure 3As shown, the anode material obtained by uniformly mixing foamed carbon and low-temperature asphalt in a 1:1 ratio and carbonizing at 800℃ can achieve an initial discharge capacity of 427 mAh / g and an initial coulombic efficiency of over 80%. It has a capacity of 158 mAh / g at a current density of 2 A / g, and the capacity recovers to the initial value when the current recovers to 0.03 A / g, demonstrating good rate performance. The SEM images show that the coating effect of low-temperature asphalt can significantly reduce the porosity of the foamed carbon surface, making it smoother, which plays a positive role in improving the ICE (interval discharge capacity). In addition, the coating effect of low-temperature asphalt can change the pore structure of the foamed carbon surface, thereby generating a considerable number of closed pores and further improving the plateau capacity.

[0070] Example 4: The preparation method of the novel low-temperature asphalt-coated foamed sodium-carbon ion battery carbon-based anode material of this embodiment is carried out according to the following steps:

[0071] 1. Glucose raw material is ball-milled and then passed through a 300-mesh sieve.

[0072] 2. Removal of ash from asphalt: The low-temperature asphalt is first pickled with hydrochloric acid for 12 hours, then pickled with hydrofluoric acid for 12 hours, then washed with deionized water until neutral, and dried to remove moisture to obtain pure low-temperature asphalt.

[0073] 3. Mix 2g of glucose with 2g of ammonium chloride, and after mixing evenly, transfer the mixture to a crucible and then to a tube furnace.

[0074] IV. In an N2 atmosphere, start the tube furnace and heat it at a heating rate of 5℃ / min until it reaches 900℃. Hold the temperature for 2 hours and then cool it down to room temperature at a cooling rate of 2℃ / min.

[0075] 5. Weigh 1g of the foamed carbon obtained in step 4 and 1g of the low-temperature asphalt obtained in step 2, mix them thoroughly, then transfer them into a crucible and transfer them into a tube furnace.

[0076] 6. Under the same N2 atmosphere, start the tube furnace and heat at a heating rate of 2℃ / min until it reaches 60℃ and holds for 0.5h. Then continue heating at a heating rate of 2℃ / min until it reaches 1000℃ and holds for 5h. Finally, cool it down to room temperature at a cooling rate of 2℃ / min.

[0077] 7. After the tube furnace has completely cooled to room temperature, remove the crucible and pass the carbonized material through a 200-mesh sieve to obtain a novel low-temperature pitch-coated foamed carbon sodium-ion battery carbon-based anode material.

[0078] like Figure 4 As shown, after foamed carbon and low-temperature asphalt are thoroughly mixed, carbonization is carried out at 1000℃. Due to the increase in carbonization temperature, the degree of graphitization of the material is significantly improved, and the I in the Raman spectrum is significantly enhanced. D / IG The value further decreased, and the (002) peak in the XRD was sharper than that in Example 1, indicating poorer sodium storage performance.

[0079] Example 5: The preparation method of the novel low-temperature asphalt-coated foamed sodium-carbon ion battery carbon-based anode material of this embodiment is carried out according to the following steps:

[0080] 1. Grind the raw starch into powder by ball milling and then pass it through a 300-mesh sieve.

[0081] 2. Removal of ash from asphalt: The low-temperature asphalt is first pickled with hydrochloric acid for 12 hours, then pickled with hydrofluoric acid for 12 hours, then washed with deionized water until neutral, and dried to remove moisture to obtain pure low-temperature asphalt.

[0082] 3. Mix 2g of starch with 2g of urea, and after mixing evenly, transfer the mixture to a crucible and then to a tube furnace.

[0083] IV. In an N2 atmosphere, start the tube furnace and heat it at a heating rate of 5℃ / min until it reaches 900℃. Hold the temperature for 2 hours and then cool it down to room temperature at a cooling rate of 2℃ / min.

[0084] 5. Weigh 2g of the foamed carbon obtained in step 4 and 1g of the low-temperature asphalt obtained in step 2, mix them thoroughly, then transfer them into a crucible and transfer them into a tube furnace.

[0085] 6. Under the same N2 atmosphere, start the tube furnace and heat at a heating rate of 2℃ / min until it reaches 60℃ and holds for 0.5h. Then continue heating at a heating rate of 2℃ / min until it reaches 1000℃ and holds for 5h. Finally, cool it down to room temperature at a cooling rate of 2℃ / min.

[0086] 7. After the tube furnace has completely cooled to room temperature, remove the crucible and pass the carbonized material through a 200-mesh sieve to obtain a novel low-temperature pitch-coated foamed carbon sodium-ion battery carbon-based anode material.

[0087] like Figure 5 As shown, foamed carbon and low-temperature asphalt were uniformly mixed at a ratio of 2:1 and carbonized at 1000℃. As can be seen from the SEM image, due to the low content of low-temperature asphalt, the coating effect was greatly reduced, and a considerable number of open-cell structures existed, which had an adverse effect on the initial coulombic efficiency, which dropped to 67.1%. The rate performance was worse than that of Implementation Case 3.

[0088] Example 6: The preparation method of the novel low-temperature asphalt-coated foamed sodium-carbon ion battery carbon-based anode material of this embodiment is carried out according to the following steps:

[0089] First, the glucose is ball-milled and then passed through a 300-mesh sieve.

[0090] 2. Mix 2g of glucose with 2g of ammonium chloride, and after mixing evenly, transfer the mixture to a crucible and then to a tube furnace.

[0091] 3. In an N2 atmosphere, start the tube furnace and heat it at a heating rate of 5℃ / min until it reaches 900℃. Hold the temperature for 2 hours and then cool it down to room temperature at a cooling rate of 2℃ / min.

[0092] 4. After the tube furnace has completely cooled to room temperature, remove the crucible and pass the carbonized material through a 200-mesh sieve to obtain a novel low-temperature pitch-coated foamed carbon sodium-ion battery carbon-based anode material.

[0093] like Figure 6 As shown, compared with Implementation Case 3, the surface of pure foamed carbon has many open pores, a larger specific surface area, and a rougher surface with more defects. This also results in a very low initial coulombic efficiency of only about 43% when pure foamed carbon is used as the negative electrode material.

[0094] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for preparing a low-temperature pitch-coated foamed carbon SIBs carbon-based anode material, characterized in that, Includes the following steps: A1. The raw material, foamed carbon precursor, is pulverized by ball milling and then sieved. A2. Remove impurities by acid washing and / or alkali washing of low-temperature asphalt, then wash with deionized water until neutral and dry to obtain pure low-temperature asphalt. A3. Mix the foamed carbon precursor with the foaming agent, and after mixing evenly, transfer it into a crucible and then into a tube furnace. A4. In an inert gas atmosphere, start the tube furnace and heat it at a certain heating rate. After holding it at the predetermined temperature for a period of time, cool it down to room temperature at a certain cooling rate to obtain foamed carbon. A5. Mix the foamed carbon prepared in step A4 with the low-temperature asphalt prepared in step A2 in a certain proportion, then transfer the mixture into a crucible and then into a tube furnace. A6. Also under an inert gas atmosphere, start the tube furnace, heat it at a certain heating rate, hold it at the predetermined temperature for a period of time, then heat it to a higher temperature at a certain heating rate, hold it at the predetermined temperature for a period of time, and then cool it down to room temperature at a certain cooling rate. A7. After the tube furnace has completely cooled down, remove the crucible, grind the carbonized material and sieve it to obtain low-temperature asphalt-coated foamed carbon anode material.

2. The preparation method according to claim 1, characterized in that, In step A1, the sieve mesh size is 50-300 mesh.

3. The preparation method according to claim 1, characterized in that, In step A3, the foam carbon precursor is one or more of glucose, starch, diethylaminetetraacetic acid (EDTA), carboxymethyl cellulose (CMC), polystyrene (PS), polyurethane (PU), and phenolic resin (PF); the foaming agent is one or more of ammonium carbonate, urea, ammonium chloride, ammonium sulfate, sodium bicarbonate, magnesium carbonate, and calcium carbonate; the mass ratio of the precursor to the foaming agent is 1:0.5-3.

4. The preparation method according to claim 1, characterized in that, In step A3, starch and ammonium chloride are mixed in a mass ratio of 1:1, and after being mixed evenly, the mixture is transferred to a crucible and then to a tube furnace.

5. The preparation method according to claim 1, characterized in that, In step A2, the acid used for pickling and / or alkali washing is one or more of oxalic acid, hydrochloric acid, sulfuric acid, hydrofluoric acid, and nitric acid, with a molar fraction of 0.05-2 mol / L, and the alkali used is one or more of ammonia, potassium hydroxide, and sodium hydroxide, with a molar fraction of 0.05-2 mol / L.

6. The preparation method according to claim 1, characterized in that, In step A4, the temperature is increased at a rate of 1-10℃ / min, heated to 600-1000℃ and held for 1-2 hours, and then cooled to room temperature at a rate of 1-10℃ / min.

7. The preparation method according to claim 1, characterized in that, In step A4, the temperature is increased at a rate of 5°C / min, heated to 900°C and held for 2 hours, and then cooled to room temperature at a rate of 2°C / min.

8. The preparation method according to claim 1, characterized in that, In step A6, the temperature is increased at a rate of 1-10℃ / min to 45-60℃, held for 0.5-1h, then increased at a rate of 1-10℃ / min to 600-1000℃ and held for 3h, and then cooled to room temperature at a rate of 1-10℃ / min.

9. The preparation method according to claim 1, characterized in that, In step A5, the mass ratio of foamed carbon to asphalt powder is 1:0.5-5.

10. Low-temperature asphalt-coated foamed carbon sodium-ion battery carbon-based anode material prepared by any one of claims 1-9.

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