A coal-based hard carbon material with ash content regulated by elements, its preparation method and application

Abstract

This invention discloses a coal-based hard carbon material with ash element regulation, its preparation method, and its application, relating to the field of electrochemical technology. The invention involves crushing and sieving raw coal to remove particulate impurities, obtaining coal powder. Then, the coal powder is treated sequentially with hydrochloric acid and sodium hydroxide solutions to remove acid-soluble and alkali-soluble ash, resulting in purified coal powder. Finally, the purified coal powder is placed in a CaCl2 solution for doping modification, followed by carbonization treatment to obtain the coal-based hard carbon material. This invention improves the structure of the coal-based hard carbon material by regulating the type and concentration of ash elements in the coal, thereby increasing the initial coulombic efficiency and reversible specific capacity of sodium-ion batteries. Specifically, the sodium-ion battery constructed using the coal-based hard carbon material prepared by this invention exhibits an initial coulombic efficiency of 89.94% and a reversible specific capacity of 332.10 mAh / g.

Description

Technical Field

[0001] This invention relates to the field of electrochemical technology, and in particular to a coal-based hard carbon material with ash content controlled by elements, its preparation method, and its application. Background Technology

[0002] Sodium-ion batteries (SIBs) have shown great promise in large-scale energy storage due to the abundance of sodium resources, low cost, and good safety. The anode material is a key component affecting the energy density, rate performance, and cycle life of SIBs. Among them, hard carbon, with its unique disordered layer structure, tunable interlayer spacing, and multi-level sodium storage structure composed of graphite-like microregions and closed pores, can achieve high reversible sodium storage capacity, making it one of the most promising anode materials for SIBs. However, traditional hard carbon materials still suffer from low initial coulombic efficiency, insufficient rate performance, and limited cycle stability, which severely restricts the commercial application of sodium-ion batteries.

[0003] Hard carbon materials are primarily produced by the high-temperature carbonization of raw materials such as coal. Coal, with its high carbon residue, low cost, and well-developed directional structure, is considered an important precursor for hard carbon material preparation. However, coal, as a complex natural carbon resource, contains not only organic carbon structures but also a certain proportion of inorganic mineral components (i.e., ash elements). Studies have shown that metallic elements in ash may play an important role in thermochemical conversion processes. For example, some metallic elements can catalyze the formation of carbon microcrystalline structures and regulate carbon interlayer spacing; metal oxides may remain in the carbon matrix after carbonization, thereby altering the electronic structure of the material and providing additional sodium storage active sites. Therefore, effective regulation of ash elements in coal is of great significance for further improving the sodium storage performance of coal-based hard carbon anode materials.

[0004] In the prior art, CN113381013A discloses a method for obtaining a coal-based hard carbon anode material for sodium-ion batteries by deashing, carbonizing, and cooling raw coal. CN121493947A discloses a method for obtaining a purified coal-based hard carbon material with an ash content of <1% and an iron content of <100ppm by sequentially deashing raw coal with caustic soda and mixed acids (hydrochloric acid and hydrofluoric acid). Deashing can effectively remove ash from coal, thereby improving the energy density and safety of the battery. However, some components in the ash may be beneficial to improving sodium storage performance, and excessive removal of ash may reduce the first-efficiency and reversible capacity of the hard carbon anode material. CN120328556A discloses a coal-based porous carbon based on trace salt-induced activation. The preparation method is as follows: Huaidong coal is mixed with trace salts (carbonates or bicarbonates of Na, K, Ca, and Mg), and then carbonized under an inert atmosphere to obtain carbonization products; finally, after activation treatment, coal-based porous carbon is obtained. This patent utilizes metal salts to activate and create pores, forming an open-pore structure. However, for hard carbon anode materials used in sodium-ion batteries, closed pores are key to improving sodium storage capacity and initial coulombic efficiency.

[0005] The Zhundong Coalfield is one of my country's largest integrated coalfields, rich in coal reserves and characterized by low ash fusion point and high volatile matter content. Unlike most coal types, whose ash composition is dominated by silicon and aluminum, Zhundong coal is often rich in metallic elements such as calcium and iron. This unique ash characteristic provides a new research opportunity for the structural control of coal-based hard carbon materials. Therefore, using Zhundong coal as raw material, regulating the structure of coal-based hard carbon by controlling the metallic elements in the coal is crucial for optimizing the microstructure of hard carbon and improving its sodium storage capacity. Summary of the Invention

[0006] To address the aforementioned limitations of existing technologies, the present invention aims to provide a coal-based hard carbon material with ash element regulation, its preparation method, and its applications. The present invention involves pulverizing and sieving raw coal to remove particulate impurities, obtaining coal powder. Then, the coal powder is treated sequentially with hydrochloric acid and sodium hydroxide solutions to remove acid-soluble and alkali-soluble ash, respectively, resulting in purified coal powder. Finally, the purified coal powder is placed in a CaCl2 solution for doping modification, followed by carbonization treatment to obtain the coal-based hard carbon material. By regulating the type and concentration of ash elements in coal, the present invention can improve the structure of the coal-based hard carbon material, thereby increasing the initial coulombic efficiency and reversible specific capacity of sodium-ion batteries. Specifically, the sodium-ion battery constructed using the coal-based hard carbon material prepared by the present invention exhibits an initial coulombic efficiency of 89.94% and a reversible specific capacity of 332.10 mAh / g.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing a coal-based hard carbon material with ash content controlled by elements, comprising the following steps: (1) After the raw coal is crushed and sieved, coal powder is obtained; the coal powder is placed in hydrochloric acid for acid dissolution treatment, and after washing and drying, intermediate coal powder is obtained; the intermediate coal powder is added to sodium hydroxide solution, heated for alkaline dissolution treatment, and purified to obtain purified coal powder; wherein, the material-liquid ratio of coal powder to hydrochloric acid is 1g: (8-12)mL, and the material-liquid ratio of intermediate coal powder to sodium hydroxide solution is 1g: (8-12)mL; (2) The purified coal powder is placed in a metal salt solution and stirred to obtain doped modified coal powder; the doped modified coal powder is placed in an inert atmosphere for carbonization treatment, and after washing, coal-based hard carbon material is obtained; the ratio of purified coal powder to metal salt solution is 2g:(30-60)mL, and the carbonization temperature is 1100-1300℃. The metal salt solution is a CaCl2 solution.

[0008] Preferably, in step (1), the raw coal is Zhundong coal.

[0009] Preferably, in step (1), the sieving process is to pass through a 100-400 mesh sieve.

[0010] Preferably, in step (1), the volume fraction of hydrochloric acid is 5%-15%.

[0011] Preferably, in step (1), the acid dissolution treatment time is 4-8 hours.

[0012] Preferably, in step (1), the drying temperature is 60-100℃ and the drying time is 8-12h.

[0013] Preferably, in step (1), the concentration of the sodium hydroxide solution is 4-8 mol / L.

[0014] Preferably, in step (1), the heating temperature is 40-80℃ and the alkali dissolution treatment time is 4-8h.

[0015] Preferably, in step (1), purification includes washing and drying, wherein the drying temperature is 60-100℃ and the drying time is 8-12h.

[0016] Preferably, in step (2), the concentration of the metal salt solution is 0.02-0.06 mol / L.

[0017] Preferably, in step (2), the stirring time is 4-8 hours.

[0018] Preferably, in step (2), the inert atmosphere is an argon atmosphere.

[0019] Preferably, in step (2), the carbonization time is 1.5-2.5h.

[0020] As a preferred option, in step (2), the washing process is performed by sequentially washing the carbonized product with hydrochloric acid and deionized water at a volume fraction of 5%-15%.

[0021] In a second aspect, the present invention provides a coal-based hard carbon material with ash content regulated by the above-described preparation method.

[0022] A third aspect of the present invention provides the application of the above-mentioned coal-based hard carbon material with ash content regulated by elements in the preparation of anode materials for sodium-ion batteries.

[0023] Preferably, the sodium-ion battery anode material is prepared by: mixing the above-mentioned coal-based hard carbon material, conductive agent and binder to obtain a mixture; adding the mixture to a solvent for homogenization to obtain a slurry; coating the slurry onto a substrate and drying to obtain the sodium-ion battery anode material.

[0024] Furthermore, the conductive agent is one or more of Super P, KB, CNTs, and conductive graphite; the binder is one or more of polyvinylidene fluoride, PTFE, sodium carboxymethyl cellulose, or sodium alginate; and the solvent is N-methylpyrrolidone.

[0025] Furthermore, the mass ratio of coal-based hard carbon material, conductive agent, and binder is (7-10):1:1, and the material-to-liquid ratio of mixture and solvent is 1g:(2-4)mL.

[0026] Furthermore, the substrate is aluminum foil with a coating amount of 0.8-1.5 g / cm³. 2 .

[0027] Furthermore, the drying temperature is 60-90℃ and the drying time is 8-12h.

[0028] The beneficial effects of this invention are: This invention involves crushing and sieving raw coal to remove particulate impurities, obtaining coal powder; then treating the coal powder sequentially with hydrochloric acid and sodium hydroxide solution to remove acid-soluble ash and alkali-soluble ash from the coal, respectively, to obtain purified coal powder; finally, the purified coal powder is placed in CaCl2 solution for doping modification, and then carbonized to obtain coal-based hard carbon material.

[0029] This invention improves the structure of coal-based hard carbon materials by controlling the types and concentrations of ash elements in coal, thereby increasing the initial coulombic efficiency and reversible specific capacity of sodium-ion batteries. Specifically, the sodium-ion battery constructed using the coal-based hard carbon material prepared by this invention exhibits an initial coulombic efficiency of 89.94% and a reversible specific capacity of 332.10 mAh / g.

[0030] Furthermore, the preparation method of the coal-based hard carbon material of the present invention is simple to operate, has a short process flow, and is highly safe, which is of great significance for the development of high-performance sodium-ion batteries for large-scale energy storage. Attached Figure Description

[0031] Figure 1 Small-angle X-ray scattering (SAXS) curves of coal-based hard carbon materials prepared in Example 1 and Comparative Examples 1-3; Figure 2 Constant current charge-discharge curves of coal-based hard carbon materials prepared in Example 1 and Comparative Examples 1-3; Figure 3 Bar charts showing the electrochemical performance of coal-based hard carbon materials prepared in Examples 1 and Comparative Examples 1-3; Figure 4 Constant current charge-discharge curves of coal-based hard carbon materials prepared in Comparative Examples 4-5. Detailed Implementation

[0032] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0033] Currently, electrolyte modification or chemical pre-sodiumization strategies are commonly used to improve the initial coulombic efficiency of hard carbon anodes. Among these, ester-based electrolyte modification, although commercially available, reduces the specific capacity and rate performance of the material, thus limiting solvent selection. While chemical pre-sodiumization can effectively compensate for active sodium loss, it requires the use of aromatic compounds such as naphthalene and biphenyl, whose residues can increase electrode polarization and reduce battery life.

[0034] Based on this, the present invention provides a coal-based hard carbon material with ash element regulation. The preparation method is as follows: raw coal is crushed and sieved to remove particulate impurities, yielding coal powder; then, the coal powder is treated sequentially with hydrochloric acid and sodium hydroxide solution to remove acid-soluble and alkali-soluble ash from the coal, respectively, yielding purified coal powder; finally, the purified coal powder is placed in a metal salt solution (CaCl2 solution) for doping modification, followed by carbonization treatment to obtain the coal-based hard carbon material. The above-mentioned coal-based hard carbon material, conductive agent, and binder are mixed and coated onto a substrate to obtain a sodium-ion battery anode material; and a sodium-ion battery is constructed using this sodium-ion battery anode material, metallic sodium, and NaPF6 / G2 solution (electrolyte).

[0035] The applicant investigated the effects of different types and concentrations of metal salts on the microstructure and electrochemical performance of coal-based hard carbon materials through experiments. Details are as follows: Regarding the types of ash elements: During the experiment, CaCl2 solution, MgCl2 solution, and FeCl3 solution were selected as metal salt solutions to explore the effects of different metal salt types on the microstructure and electrochemical performance of coal-based hard carbon materials. Ca reduced the degree of defects, increased the size of microcrystalline graphite domains, and increased the number of closed pores; Mg increased the degree of defects, reduced the thickness of microcrystalline graphite domains, slowed down the effective transport of sodium ions, and reduced the number of closed pores; Fe, although it could reduce the degree of defects, led to a transformation towards graphitized carbon, with a significant increase in microcrystalline graphite domains, which is also a manifestation of graphitization. Combined with the electrochemical performance test results, only the introduction of Ca had a positive effect on the structure and performance of the material; the microstructure and electrochemical performance of coal-based hard carbon with added Mg or Fe salts showed a downward trend.

[0036] Regarding ash element concentration: Studies have found that both excessively high and low ash element concentrations are detrimental to improving the structure and electrochemical performance of coal-based hard carbon materials. This application controls the ash element concentration in coal-based hard carbon materials by controlling the ratio of purified coal powder to metal salt (CaCl2). Specifically, excessively high ash element concentrations lead to insufficient defects in the hard carbon material, increased graphitization, and larger microcrystalline graphite domains. Electrochemically, this manifests as reduced initial efficiency and decreased capacity, especially a significant decrease in the plateau region capacity. Conversely, if the concentration is too low, the elements are unable to function effectively, failing to improve the hard carbon structure, and electrochemical performance cannot be effectively improved.

[0037] This invention uses hydrochloric acid and sodium hydroxide solution to treat impurities in Zhundong coal raw materials, removing all impurities from the coal powder. Then, CaCl2 solution is used for ion doping control, achieving effective regulation of the type and concentration of metal elements. The doped Ca... 2+ During heat treatment, defect sites in hard carbon anodes can be effectively repaired, significantly reducing defect concentration; furthermore, Ca... 2+ The pore structure generated by regulation provides additional sodium storage sites for the hard carbon anode, reducing the number of inaccessible active sites and Na during SEI formation. + The consumption of sodium ions enhances the sodium ion storage capacity, allowing sodium ions to be used to the maximum extent for electrochemical insertion / extraction reactions. This fundamentally reduces irreversible capacity loss during the first charge / discharge process, thereby improving the battery's first coulombic efficiency.

[0038] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0039] The experimental materials used in the embodiments of this invention are all conventional experimental materials in the art and can be purchased through commercial channels.

[0040] In this invention, Xinjiang Zhundong coal is used as the raw coal to prepare coal-based hard carbon materials. Xinjiang Huaidong coal was purchased from Guoneng Xinjiang Zhundong Energy Co., Ltd.

[0041] Example 1: (1) After crushing the raw coal, pass it through a 200-mesh sieve to obtain coal powder; place 10g of coal powder in 100mL of 10% hydrochloric acid and stir for 6h for acid dissolution treatment, wash with water until neutral, and dry at 80℃ for 10h to obtain intermediate coal powder; mix 10g of intermediate coal powder with 100mL of 6mol / L sodium hydroxide solution, heat to 60℃ and stir for 6h for alkali dissolution treatment, wash with water until neutral, and dry at 80℃ for 10h again to obtain purified coal powder; (2) Take 2g of purified coal powder and place it in 50mL of 0.04mol / L CaCl2 solution and stir for 6h to obtain doped modified coal powder; place the above doped modified coal powder under argon atmosphere and heat it to 1200℃ at a heating rate of 5℃ / min, and keep it at the temperature for 2h for carbonization treatment. After the carbonization treatment is completed, wash the carbonization product with 10% hydrochloric acid and deionized water in sequence, and dry it to obtain coal-based hard carbon material, denoted as Ca-HC-0.04.

[0042] Example 2: (1) After crushing the raw coal, pass it through a 100-mesh sieve to obtain coal powder; place 10g of coal powder in 80mL of 5% hydrochloric acid and stir for 4h for acid dissolution treatment, wash with water until neutral, and dry at 60℃ for 8h to obtain intermediate coal powder; mix 10g of intermediate coal powder with 80mL of 4mol / L sodium hydroxide solution, heat to 40℃ and stir for 4h for alkali dissolution treatment, wash with water until neutral, and dry at 60℃ for 8h again to obtain purified coal powder; (2) Take 2g of purified coal powder and place it in 30mL of 0.02mol / L CaCl2 solution and stir for 4h to obtain doped modified coal powder; place the above doped modified coal powder under argon atmosphere and heat it to 1100℃ at a heating rate of 5℃ / min, and keep it at the temperature for 1.5h for carbonization treatment. After the carbonization treatment is completed, wash the carbonization product with 10% hydrochloric acid and deionized water in sequence, and dry it to obtain coal-based hard carbon material.

[0043] Example 3: (1) After crushing the raw coal, pass it through a 400-mesh sieve to obtain coal powder; place 10g of coal powder in 120mL of 15% hydrochloric acid and stir for 8h for acid dissolution treatment, wash with water until neutral, and dry at 100℃ for 12h to obtain intermediate coal powder; mix 10g of intermediate coal powder with 120mL of 8mol / L sodium hydroxide solution, heat to 80℃ and stir for 8h for alkali dissolution treatment, wash with water until neutral, and dry at 100℃ for 12h again to obtain purified coal powder; (2) Take 2g of purified coal powder and place it in 60mL of 0.06mol / L CaCl2 solution and stir for 8h to obtain doped modified coal powder; place the above doped modified coal powder under argon atmosphere and heat it to 1300℃ at a heating rate of 5℃ / min, and keep it at the temperature for 2.5h for carbonization treatment. After the carbonization treatment is completed, wash the carbonization product with 10% hydrochloric acid and deionized water in sequence, and dry it to obtain coal-based hard carbon material.

[0044] Comparative Example 1: The difference between this comparative example and Example 1 is that no metal salt was added for doping modification. The specific steps are as follows: Purified coal powder was prepared according to the method in Example 1. The purified coal powder was placed in an argon atmosphere and heated to 1200°C at a heating rate of 5°C / min. The temperature was maintained for 2 hours for carbonization treatment. After carbonization treatment, the carbonization product was washed with 10% hydrochloric acid and deionized water in sequence and dried to obtain coal-based hard carbon material, denoted as HC.

[0045] Comparative Example 2: The difference between this comparative example and Example 1 is that MgCl2 solution is used as the metal salt solution. The specific steps are as follows: Purified coal powder was prepared according to the method in step (1) of Example 1; then 2g of purified coal powder was placed in 50mL of 0.04mol / L MgCl2 solution and stirred for 6h to obtain doped modified coal powder; the above doped modified coal powder was placed in an argon atmosphere and heated to 1200℃ at a heating rate of 5℃ / min, and held for 2h for carbonization treatment. After the carbonization treatment was completed, the carbonization product was washed with 10% hydrochloric acid and deionized water in sequence, and dried to obtain coal-based hard carbon material, denoted as Mg-HC-0.04.

[0046] Comparative Example 3: The difference between this comparative example and Example 1 is that FeCl3 solution is used as the metal salt solution. The specific steps are as follows: Purified coal powder was prepared according to the method in step (1) of Example 1; then 2g of purified coal powder was placed in 50mL of FeCl3 solution with a concentration of 0.04mol / L and stirred for 6h to obtain doped modified coal powder; the above doped modified coal powder was placed under an argon atmosphere and heated to 1200℃ at a heating rate of 5℃ / min, and held for 2h for carbonization treatment. After the carbonization treatment was completed, the carbonization product was washed with hydrochloric acid with a volume fraction of 10% and deionized water in sequence, and dried to obtain coal-based hard carbon material, denoted as Fe-HC-0.04.

[0047] Comparative Example 4: The difference between this comparative example and Example 1 is that the ash element concentration is too high, i.e., the ratio of purified coal powder to CaCl2 is controlled at 2g:0.0005mol. The specific steps are as follows: Purified coal powder was prepared according to the method in Example 1. 2g of purified coal powder was placed in 95mL of 0.04mol / L CaCl2 solution and stirred for 6h to obtain doped modified coal powder. The doped modified coal powder was placed under an argon atmosphere and heated to 1200℃ at a heating rate of 5℃ / min. The temperature was maintained for 2h for carbonization treatment. After the carbonization treatment, the carbonization product was washed with 10% hydrochloric acid and deionized water in sequence and dried to obtain coal-based hard carbon material, denoted as Ca-HC-H.

[0048] Comparative Example 5: The difference between this comparative example and Example 1 is that the ash element concentration is too low, specifically, the ratio of purified coal powder to CaCl2 is controlled at 2g:0.0038mol. The specific steps are as follows: Purified coal powder was prepared according to the method in Example 1. 2g of purified coal powder was placed in 12.5mL of 0.04mol / L CaCl2 solution and stirred for 6h to obtain doped modified coal powder. The doped modified coal powder was placed under an argon atmosphere and heated to 1200℃ at a heating rate of 5℃ / min, and held for 2h for carbonization treatment. After carbonization treatment, the carbonization product was washed sequentially with 10% hydrochloric acid and deionized water, and dried to obtain coal-based hard carbon material, denoted as Ca-HC-L.

[0049] Experimental Example 1: Ash Content The coal powder and purified coal powder obtained in step (1) of Example 1 were subjected to ICP detection using ICP-OES: Agilent 5110, and the element content W (%) was calculated. The results are shown in Tables 1-2.

[0050] The formula for calculating the element content W (%) is as follows: ; ; In the formula, W represents the percentage content of the element, %; C x C0 is the final concentration of the element being measured, in mg / kg; f is the element concentration in the test solution, in mg / kg; f is the dilution factor, with a value of 1; V0 is the volume of the sample after digestion and reconstitution, in mL; m is the mass of the sample used, in g.

[0051] Table 1. Elemental content of coal powder before ash removal Table 2. Element content of purified coal powder after ash removal As can be seen from Tables 1 and 2, acid dissolution and alkali dissolution treatments of coal powder with hydrochloric acid and sodium hydroxide, respectively, can effectively remove the ash content from the coal powder.

[0052] Experimental Example 2: Structural Characterization Small-angle X-ray scattering (SAXS) tests were performed on the coal-based hard carbon materials prepared in Example 1 and Comparative Examples 1-3. The results are as follows: Figure 1 As shown.

[0053] Depend on Figure 1 It can be seen that the Ca-HC-0.04 prepared in Example 1 has a specific temperature range of Q=0.1 Å. -1 The highest intensity value was observed at this time, indicating the presence of numerous closed pore structures in Ca-HC-0.04, which facilitates the reversible storage of sodium ions.

[0054] Experimental Example 3: Electrochemical Performance Sodium-ion anode materials were prepared using the coal-based hard carbon materials obtained in Example 1 and Comparative Examples 1-5, and their electrochemical performance was tested. The specific steps are as follows: (1) The coal-based hard carbon material, Super P (conductive agent) and CMC (binder) prepared in Example 1 and Comparative Examples 1-5 were mixed at a mass ratio of 7.5:1:1 to obtain a mixture; the mixture and N-methylpyrrolidone were mixed at a material-liquid ratio of 1g:3mL and homogenized to obtain a slurry; The slurry is coated onto the aluminum foil (substrate) at a coating weight of 1.2 g / m². 2 The material was dried at 75°C for 10 hours to obtain sodium-ion battery anode material. (2) A sodium-ion battery was constructed using the above-mentioned sodium-ion battery anode material, 1.0M sodium hexafluorophosphate / diethylene glycol dimethyl ether solution and metallic sodium.

[0055] The assembled sodium-ion battery was subjected to constant current charge-discharge testing at room temperature using a LAND CT2001A workstation. The electrochemical performance of the sodium-ion battery anode material was tested at a voltage window of 0.01-1.5 V and a current density of 50 mA / g.

[0056] First, the electrochemical performance of the original coal-based hard carbon material and coal-based hard carbon materials with the same ash concentration but different ash elements were compared. The results are as follows: Figure 2 and Figure 3 As shown. By Figures 2-3It can be seen that the initial charge-discharge capacities of Ca-HC-0.04, Mg-HC-0.04, Fe-HC-0.04, and HC are 327.06 / 377.07 mAh / g, 248.95 / 317.02 mAh / g, 237.51 / 306.13 mAh / g, and 269.82 / 330.65 mAh / g, respectively, with corresponding initial coulombic efficiencies of 89.94%, 78.51%, 77.61%, and 79.6%. These results indicate that, compared to the original coal-based hard carbon materials, Ca... 2+ The introduction of [a specific ingredient] can effectively enhance capacity and first-efficiency, while Mg [a specific ingredient]... 2+ and Fe 2+ The introduction of Ca-HC-0.04 disrupted the hard carbon structure, reducing its first-efficiency and reversible capacity. Furthermore, the plateau capacity of Ca-HC-0.04 increased to 199.94 mAh / g, significantly higher than that of Mg-HC-0.04, Fe-HC-0.04, and HC (152.87, 138.71, and 145.64 mAh / g, respectively), indicating that Ca... 2+ Catalysis can enhance the capacity of the plateau region, which is consistent with the SAXS test results.

[0057] Furthermore, the effect of ash element concentration on the electrochemical performance of coal-based hard carbon materials was investigated, and the results are as follows: Figure 4 As shown. By Figure 4 It can be seen that the initial charge-discharge capacities of Ca-HC-H and Ca-HC-L are 269.1 / 318.04 mAh / g and 275.1 / 325.7 mAh / g, respectively, with corresponding initial coulombic efficiencies of 84.6% and 84.5%. These results indicate that both increasing and decreasing the ash content have a negative impact on the material, with 0.04 M being the optimal concentration.

[0058] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for preparing coal-based hard carbon materials with ash content controlled by elements, characterized in that, Includes the following steps: (1) After the raw coal is crushed and sieved, coal powder is obtained; the coal powder is placed in hydrochloric acid for acid dissolution treatment, and after washing and drying, intermediate coal powder is obtained; the intermediate coal powder is added to sodium hydroxide solution, heated for alkaline dissolution treatment, and purified to obtain purified coal powder; wherein, the material-liquid ratio of coal powder to hydrochloric acid is 1g:(8-12)mL, and the material-liquid ratio of intermediate coal powder to sodium hydroxide solution is 1g:(8-12)mL; (2) The purified coal powder is placed in a metal salt solution and stirred to obtain doped modified coal powder; the doped modified coal powder is placed in an inert atmosphere for carbonization treatment, and after soaking and washing treatment, coal-based hard carbon material is obtained; wherein, the ratio of purified coal powder to metal salt is 2g: (30-60)mL, and the carbonization temperature is 1100-1300℃. The metal salt solution is a CaCl2 solution with a concentration of 0.02-0.06 mol / L; the stirring time is 4-8 h.

2. The preparation method of coal-based hard carbon material with ash element regulation as described in claim 1, characterized in that, In step (1), the volume fraction of hydrochloric acid is 5%-15%, and the acid dissolution treatment time is 4-8 hours.

3. The preparation method of coal-based hard carbon material with ash element regulation as described in claim 1, characterized in that, In step (1), the concentration of sodium hydroxide solution is 4-8 mol / L; the heating temperature is 40-80℃; and the alkali dissolution treatment time is 4-8h.

4. The preparation method of coal-based hard carbon material with ash element regulation as described in claim 1, characterized in that, In step (2), the inert atmosphere is argon; the carbonization time is 1.5-2.5h.

5. The coal-based hard carbon material with ash element regulation prepared by the preparation method according to any one of claims 1-4.

6. The application of the coal-based hard carbon material with ash element regulation as described in claim 5 in the preparation of sodium-ion battery anode materials.

7. The application as described in claim 6, characterized in that, The preparation method of the sodium-ion battery anode material is as follows: After mixing the coal-based hard carbon material, conductive agent and binder as described in claim 5, a mixture is obtained. The mixture is then added to a solvent for homogenization to obtain a slurry. The slurry is coated onto a substrate and dried to obtain a sodium-ion battery anode material.

8. The application as described in claim 7, characterized in that, The conductive agent is one or more of Super P, KB, CNTs, and conductive graphite; the binder is one or more of polyvinylidene fluoride, PTFE, sodium carboxymethyl cellulose, or sodium alginate; and the solvent is N-methylpyrrolidone.

9. The application as described in claim 7, characterized in that, The mass ratio of coal-based hard carbon material, conductive agent, and binder is (7-10):1:1; the material-to-liquid ratio of the mixture and solvent is 1g:(2-4)mL; the substrate is aluminum foil, and the coating amount is 0.8-1.5 g / cm³. 2 .

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