A negative electrode material, a preparation method thereof and a sodium ion battery

Abstract

The application provides a negative electrode material and a preparation method thereof and a sodium ion battery, relates to the technical field of sodium ion batteries, and the preparation method comprises the following steps: performing acid pickling and ash removal on coal powder to obtain ash-removed coal powder; the ash-removed coal powder is mixed and ground with alkali, and after heat treatment at 800-1400 DEG C under a protective atmosphere, acid pickling, and drying, a coal-based porous carbon material is obtained; the coal-based porous carbon material, melamine and a transition metal compound are mixed and ground, and after heat treatment at 800-1000 DEG C under a protective atmosphere, a negative electrode material is obtained. The preparation method of the negative electrode material provided by the application uses coal as raw material, optimizes sodium storage sites and graphite microcrystal layer spacing through alkali high-temperature activation, and is supplemented by surface high-temperature grafting treatment, so that the sodium storage performance of the coal-based negative electrode material is improved, higher sodium storage specific capacity and first cycle charge-discharge coulombic efficiency are obtained, the process is simple, the conditions are mild, controllability is strong, and the application is more conducive to industrialization promotion and application.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery technology, and more particularly to a negative electrode material, its preparation method, and a sodium-ion battery. Background Technology

[0002] In recent years, electrochemical energy storage technologies, represented by lithium-ion batteries (LIBs), have been applied to commercial production. However, many problems still exist in terms of safety, lifespan, low-temperature performance, and cost. Furthermore, with the widespread use of large-size lithium batteries, the demand for lithium is constantly increasing. Coupled with my country's low lithium reserves and reliance on imports, the shortage of lithium resources creates cost issues for LIBs, limiting their application in large-scale energy storage devices.

[0003] Sodium and lithium belong to the same group and have similar physicochemical properties. Sodium resources are widely distributed and inexpensive, not limited by resources or location. Sodium ions have a lower solvation energy than lithium ions, resulting in better interfacial ion diffusion capabilities. Their internal resistance is slightly higher than lithium-ion batteries, leading to less instantaneous heat generation and lower temperatures in safety tests such as short circuits, thus improving safety. They also exhibit excellent low-temperature performance, with copper-based oxide / coal-based carbon systems retaining over 88% of their capacity at -20℃. Furthermore, sodium-ion batteries (SIBs) often use inexpensive and abundant elements such as iron, manganese, and copper as cathode materials, and aluminum foil is used for both positive and negative current collectors, giving them a cost and material availability advantage over LIBs.

[0004] Currently, carbon-based sodium-ion battery anode materials mainly include natural graphite, graphene, soft carbon, and hard carbon. Among them, hard carbon has an amorphous carbon microstructure with long-range disorder and short-range order. This structural feature is conducive to ion or electron transport. Moreover, hard carbon materials have low raw material costs and simple preparation processes, making them promising candidates for application in sodium-ion batteries.

[0005] In recent years, some people have proposed using anthracite as a raw material to prepare hard carbon materials. Although anthracite has the characteristics of low price, high degree of carbonization, low volatile matter and ash content, and high fixed carbon content, and has obvious comprehensive cost advantages, the carbon materials obtained by high-temperature sintering of anthracite are amorphous soft carbon with a graphite microcrystalline interlayer spacing of less than 0.37 nm and low sodium storage capacity.

[0006] Therefore, how to improve the sodium storage capacity of coal-based carbon materials has become one of the focal points of attention for many forward-thinking R&D companies and researchers in the industry. Summary of the Invention

[0007] To address the problem of low sodium storage capacity in existing coal-based carbon materials, this invention provides a method for preparing a negative electrode material. This method employs alkaline high-temperature activation to optimize sodium storage sites and the spacing between graphite microcrystals, followed by surface high-temperature grafting treatment to improve the sodium storage performance of the coal-based negative electrode material, thus solving the problem of low sodium storage capacity in existing coal-based carbon materials.

[0008] The technical solution adopted by this invention to solve its technical problem is:

[0009] A method for preparing a negative electrode material includes the following steps:

[0010] S1: Acid washing and deashing of pulverized coal to obtain deashed pulverized coal;

[0011] S2: The deashed coal powder is mixed and ground with alkali, and then heat-treated at 800-1400℃ under a protective atmosphere. After acid washing and drying, coal-based porous carbon material is obtained.

[0012] S3: The coal-based porous carbon material, melamine, and transition metal compound are mixed and ground, and then heat-treated at 800-1000℃ under a protective atmosphere to obtain the negative electrode material.

[0013] Optionally, the amine source is melamine.

[0014] Optionally, the pulverized coal is selected from at least one of anthracite pulverized coal, bituminous coal pulverized coal, sub-bituminous coal pulverized coal, or lignite pulverized coal.

[0015] Optionally, the alkali is an alkali metal hydroxide.

[0016] Optionally, the alkali metal hydroxide is selected from at least one of sodium hydroxide and potassium hydroxide.

[0017] Optionally, the mass ratio of the deashed coal powder to the alkali in step S2 is (1-10):1.

[0018] Optionally, the transition metal compound is selected from at least one of iron salts, cobalt salts, and nickel salts.

[0019] Optionally, the mass ratio of the coal-based porous carbon material, the melamine, and the transition metal compound in step S3 is 1:(1-4):(0.1-1).

[0020] Another object of the present invention is to provide a negative electrode material, which is prepared by the negative electrode material preparation method described above.

[0021] Another object of the present invention is to provide a sodium-ion battery comprising the negative electrode material as described above.

[0022] The beneficial effects of this invention are:

[0023] The method for preparing the anode material provided by this invention uses coal as raw material, optimizes the sodium storage sites and the spacing between graphite microcrystals through alkaline high-temperature activation, and then supplements it with surface high-temperature grafting treatment, thereby improving the sodium storage performance of coal-based anode materials and obtaining higher sodium storage specific capacity and first-cycle charge-discharge coulombic efficiency; moreover, the process is simple, the conditions are mild, and the controllability is strong, which is more conducive to industrial promotion and application. Attached Figure Description

[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0025] Figure 1 These are the XRD diffraction patterns of the negative electrode materials prepared in Comparative Example 1 and Example 1 of this invention;

[0026] Figure 2 These are the Raman spectra of the negative electrode materials prepared in Comparative Example 1 and Example 1 of this invention;

[0027] Figure 3 This is a scanning electron microscope image of the negative electrode material prepared in Example 1 of the present invention;

[0028] Figure 4 This is a graph showing the first cycle of coin cell testing data for the negative electrode material prepared in Example 1 of this invention. Detailed Implementation

[0029] The present invention will now be described in further detail. The embodiments described below are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0030] To address the problem of low sodium storage capacity in existing coal-based carbon materials, this invention provides a method for preparing a negative electrode material, which includes the following steps:

[0031] S1: Acid washing and deashing of pulverized coal to obtain deashed pulverized coal;

[0032] S2: Deashed coal powder is mixed with alkali and ground, then heat-treated at 800-1400℃ under a protective atmosphere, followed by acid washing and drying to obtain a coal-based porous carbon material; the specific surface area of ​​this coal-based porous carbon material is 50-300 m². 2 / g.

[0033] In this invention, the preferred heating rate during the heat treatment step is 0.5–5 °C / min; the preferred heat treatment holding time is 2–6 h; the preferred drying temperature is 50–80 °C; the preferred acid solution for pickling in this step is hydrochloric acid; the preferred concentration of the hydrochloric acid is 0.1–2 mol / L; and the preferred grinding time is 0.4–2 h.

[0034] S3: Coal-based porous carbon material, amine source and transition metal compound are mixed and ground, and heat-treated at 800-1000℃ under a protective atmosphere to obtain carbon nanotube-grafted porous carbon material, i.e. negative electrode material.

[0035] In preferred step S3, the heating rate during heat treatment is 0.5–5 °C / min; the heat treatment holding time is 4–6 h.

[0036] Specifically, the present invention for acid washing and deashing of pulverized coal includes: acid washing of pulverized coal with acid solution, followed by multiple water washings and centrifugation until the washing solution is neutral; preferably, the mass ratio of pulverized coal to acid solution during the acid washing process is 1:(3-15), and the acid solution is selected from at least one of hydrochloric acid, nitric acid, sulfuric acid and hydrofluoric acid; and further preferably, the concentration of the acid solution is 1-12 mol / L, the acid washing temperature is 20-90℃, and the acid washing time is 1-6h.

[0037] To improve the sodium storage capacity, this invention involves mixing and grinding deashed coal powder with alkali, preferably for 0.4–2 hours. Then, under a protective atmosphere (preferably nitrogen or argon), the mixture is heat-treated (first heat treatment). During this heat treatment, high-temperature activation by the alkali optimizes the sodium storage sites and the interlayer spacing of the graphite microcrystals, thereby increasing the sodium storage capacity and yielding a coal-based porous carbon material. To further improve the electrochemical performance, this invention further mixes and grinds the coal-based porous carbon material, an amine source, and a transition metal compound, preferably for 0.4–2 hours. Then, under a protective atmosphere (preferably nitrogen or argon), a second heat treatment is performed, where high-temperature grafting is applied to the surface of the carbon material to generate carbon nanotubes in situ, resulting in a carbon nanotube-grafted porous carbon material, i.e., the anode material.

[0038] Because this invention generates carbon nanotubes in situ on coal-based porous carbon materials through high-temperature grafting, the carbon nanotubes are chemically bonded to the coal-based porous carbon materials. Compared with the method of directly introducing carbon nanotubes, the distribution of carbon nanotubes in the anode material is more uniform, and the bonding between them and the coal-based porous carbon materials is tighter, resulting in a more stable structure. This helps to increase the sodium storage capacity of the anode material, improve the first coulombic efficiency of the anode material, and enhance the uniformity and stability of its electrochemical performance.

[0039] Furthermore, the present invention introduces nitrogen-containing carbon nanotubes into the negative electrode material through an amine source, which uniformly coat the surface of coal-based porous carbon. This can form a closed-pore structure, increase sodium storage capacity, improve conductivity, and enhance rate performance.

[0040] The method for preparing the anode material provided by this invention uses coal as raw material, optimizes the sodium storage sites and the spacing between graphite microcrystals through alkaline high-temperature activation, and then supplements it with surface high-temperature grafting treatment, thereby improving the sodium storage performance of coal-based anode materials and obtaining higher sodium storage specific capacity and first-cycle charge-discharge coulombic efficiency; moreover, the process is simple, the conditions are mild, and the controllability is strong, which is more conducive to industrial promotion and application.

[0041] The preferred amine source in this invention is melamine, so as to introduce nitrogen-rich carbon nanotubes into the negative electrode material in situ during the secondary heat treatment process.

[0042] Furthermore, the present invention preferably uses pulverized coal with a D content of [missing information]. 50 The particle size is 10–20 μm.

[0043] The pulverized coal can be obtained from raw materials, i.e., coal blocks, through crushing, ball milling, and screening. Furthermore, the present invention preferably selects at least one of anthracite pulverized coal, bituminous coal pulverized coal, sub-bituminous coal pulverized coal, or lignite pulverized coal, so as to take advantage of the fact that the above raw materials are all low-rank coals with rich oxygen-containing functional groups on their surface, which can form chemical bonds with melamine, ensuring that melamine can be uniformly coated on the porous carbon surface of coal.

[0044] The alkali of the present invention is preferably an alkali metal hydroxide, and more preferably the alkali metal hydroxide is selected from at least one of sodium hydroxide and potassium hydroxide.

[0045] To balance the sodium storage capacity and economy of the anode material, the preferred mass ratio of deashed coal powder to alkali in step S2 of this invention is (1-10):1.

[0046] The present invention preferably selects the transition metal compound from at least one of iron salts, cobalt salts, and nickel salts, and further preferably selects ferric chloride as the iron salt, cobalt dichloride as the cobalt salt, and nickel dichloride as the nickel salt.

[0047] Furthermore, in order to balance the conductivity and economy of the negative electrode material, the preferred mass ratio of coal-based porous carbon material, melamine and transition metal compound in step S3 of this invention is 1:(1-4):(0.1-1).

[0048] Another object of the present invention is to provide a negative electrode material, which is prepared by the negative electrode material preparation method described above.

[0049] The negative electrode material provided by this invention uses coal as raw material. The sodium storage sites and the spacing between graphite microcrystals are optimized through alkaline high-temperature activation, and then the surface is treated with high-temperature grafting, thereby improving the sodium storage performance of coal-based negative electrode materials and obtaining higher sodium storage specific capacity and first-cycle charge-discharge coulombic efficiency. Moreover, the process is simple, the conditions are mild, and the controllability is strong, which is more conducive to industrial promotion and application.

[0050] Another object of the present invention is to provide a sodium-ion battery comprising the negative electrode material as described above.

[0051] The sodium-ion battery provided by this invention uses coal as the anode material. The sodium storage sites and the spacing between graphite microcrystals are optimized through alkaline high-temperature activation, and then the surface is treated with high-temperature grafting, thereby improving the sodium storage performance of the coal-based anode material and obtaining higher sodium storage specific capacity and first-cycle charge-discharge coulombic efficiency. Moreover, the process is simple, the conditions are mild, and the controllability is strong, which is more conducive to industrial promotion and application.

[0052] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0053] The specific surface area in the various embodiments and comparative examples of the present invention was measured using a BET specific surface area analyzer.

[0054] Example 1

[0055] This embodiment provides a method for preparing a negative electrode material, including the following steps:

[0056] S1: Using anthracite as raw material, D is obtained by sequentially crushing, ball milling, and screening. 50 Anthracite powder with a particle size of 15μm was acid-washed with 6mol / L hydrochloric acid at 50℃ for 3h, followed by multiple water washings and centrifugation until the washing liquid was neutral. After drying at 60℃, deashed coal powder was obtained. The mass ratio of anthracite powder to acid solution was 1:9.

[0057] S2: Deashed coal powder and sodium hydroxide were mixed and ground at a mass ratio of 5:1 for 1 hour. Under a nitrogen atmosphere, the mixture was heated to 1100℃ at a heating rate of 3℃ / min for 4 hours. After holding at this temperature for 4 hours, it was acid-washed with 1mol / L hydrochloric acid and then dried at 60℃ to obtain coal-based porous carbon material. The specific surface area of ​​this coal-based porous carbon material was measured to be 603 m². 2 / g;

[0058] S3: Coal-based porous carbon material, melamine and transition metal compound ferric chloride are mixed and ground at a mass ratio of 1:2:0.5 for 1 hour. Under a nitrogen atmosphere, the temperature is increased to 900℃ at a heating rate of 3℃ / min for heat treatment. The heat treatment holding time is 5 hours to obtain carbon nanotube-grafted porous carbon material, i.e., negative electrode material.

[0059] The performance of the negative electrode material prepared in this embodiment was tested, as detailed in the following figures. Figures 1-4 As shown.

[0060] Example 2

[0061] This embodiment provides a method for preparing a negative electrode material, including the following steps:

[0062] S1: Using lignite as raw material, D is obtained by sequentially crushing, ball milling, and screening. 50 Lignite powder with a particle size of 15 μm was acid-washed with 6 mol / L hydrochloric acid at 50°C for 3 h, followed by multiple water washings and centrifugation until the washing liquid was neutral. After drying at 60°C, deashed coal powder was obtained. The mass ratio of lignite powder to acid solution was 1:9.

[0063] S2: Deashed coal powder and potassium hydroxide were mixed and ground at a mass ratio of 10:1 for 1 hour. Under a nitrogen atmosphere, the mixture was heated to 1400℃ at a heating rate of 3℃ / min for 2 hours. After holding at this temperature for 2 hours, it was acid-washed with 1mol / L hydrochloric acid and then dried at 60℃ to obtain coal-based porous carbon material. The specific surface area of ​​this coal-based porous carbon material was measured to be 405 m². 2 / g;

[0064] S3: Coal-based porous carbon material, melamine and transition metal cobalt dichloride are mixed and ground for 1 hour at a mass ratio of 1:4:0.5. Under a nitrogen atmosphere, the temperature is increased to 1000℃ at a heating rate of 3℃ / min for heat treatment. The heat treatment holding time is 4 hours to obtain carbon nanotube-grafted porous carbon material, i.e., negative electrode material.

[0065] Example 3

[0066] This embodiment provides a method for preparing a negative electrode material, including the following steps:

[0067] S1: Using lignite as raw material, D is obtained by sequentially crushing, ball milling, and screening. 50 Lignite powder with a particle size of 15 μm was acid-washed with 6 mol / L hydrochloric acid at 50°C for 3 h, followed by multiple water washings and centrifugation until the washing liquid was neutral. After drying at 60°C, deashed coal powder was obtained. The mass ratio of lignite powder to acid solution was 1:9.

[0068] S2: Deashed coal powder and potassium hydroxide were mixed and ground at a mass ratio of 10:1 for 1 hour. Under a nitrogen atmosphere, the mixture was heated to 800℃ at a heating rate of 3℃ / min for heat treatment. After holding the heat treatment at this temperature for 6 hours, the mixture was acid-washed with 1mol / L hydrochloric acid and then dried at 60℃ to obtain coal-based porous carbon material. The specific surface area of ​​this coal-based porous carbon material was measured to be 407 m². 2 / g;

[0069] S3: Coal-based porous carbon material, melamine and transition metal nickel dichloride are mixed and ground for 1 hour at a mass ratio of 1:1:0.5. Under nitrogen atmosphere, the temperature is raised to 800℃ at a heating rate of 3℃ / min for heat treatment. The heat treatment holding time is 6 hours to obtain carbon nanotube-grafted porous carbon material, i.e., negative electrode material.

[0070] Comparative Example 1

[0071] This comparative example provides a method for preparing a negative electrode material, including the following steps:

[0072] S1: Using anthracite as raw material, D is obtained by sequentially crushing, ball milling, and screening. 50 Anthracite powder with a particle size of 15μm was acid-washed with 6mol / L hydrochloric acid at 50℃ for 3h, followed by multiple water washings and centrifugation until the washing liquid was neutral. After drying at 60℃, deashed coal powder was obtained. The mass ratio of anthracite powder to acid solution was 1:9.

[0073] S2: Deashed coal powder and sodium hydroxide were mixed and ground at a mass ratio of 5:1 for 1 hour. Under a nitrogen atmosphere, the mixture was heated to 1100℃ at a heating rate of 3℃ / min for heat treatment. After holding the heat treatment at this temperature for 4 hours, it was acid-washed with 1mol / L hydrochloric acid and then dried at 60℃ to obtain a coal-based porous carbon material, i.e., the negative electrode material. The specific surface area of ​​this coal-based porous carbon material was measured to be 603 m². 2 / g.

[0074] The performance of the anode material prepared in this comparative example was tested, as detailed in the following figures. Figures 1-2 As shown.

[0075] Comparative Example 2

[0076] This comparative example provides a method for preparing a negative electrode material, including the following steps:

[0077] S1: Using anthracite as raw material, D is obtained by sequentially crushing, ball milling, and screening. 50 Anthracite powder with a particle size of 15μm was acid-washed with 6mol / L hydrochloric acid at 50℃ for 3h, followed by multiple water washings and centrifugation until the washing liquid was neutral. After drying at 60℃, deashed coal powder was obtained. The mass ratio of anthracite powder to acid solution was 1:9.

[0078] S2: The deashed coal powder, melamine and transition metal compound ferric chloride were mixed and ground for 1 hour at a mass ratio of 1:2:0.5. The mixture was then heated to 900°C under a nitrogen atmosphere at a heating rate of 3°C / min for 5 hours to obtain the negative electrode material.

[0079] Comparative Example 3

[0080] This comparative example provides a method for preparing a negative electrode material, including the following steps:

[0081] S1: Using anthracite as raw material, D is obtained by sequentially crushing, ball milling, and screening. 50 Anthracite powder with a particle size of 15μm was acid-washed with 6mol / L hydrochloric acid at 50℃ for 3h, followed by multiple water washings and centrifugation until the washing liquid was neutral. After drying at 60℃, deashed coal powder was obtained. The mass ratio of anthracite powder to acid solution was 1:9.

[0082] S2: Deashed coal powder and sodium hydroxide were mixed and ground at a mass ratio of 5:1 for 1 hour. Under a nitrogen atmosphere, the mixture was heated to 1100℃ at a heating rate of 3℃ / min for 4 hours. After holding at this temperature for 4 hours, it was acid-washed with 1mol / L hydrochloric acid and then dried at 60℃ to obtain coal-based porous carbon material. The specific surface area of ​​this coal-based porous carbon material was measured to be 603 m². 2 / g;

[0083] S3: Mix and grind coal-based porous carbon materials and carbon nanotubes at a mass ratio of 1:2 for 1 hour to obtain the negative electrode material.

[0084] Comparative Example 4

[0085] This comparative example provides a method for preparing a negative electrode material, including the following steps:

[0086] S1: Using anthracite as raw material, D is obtained by sequentially crushing, ball milling, and screening. 50 Anthracite powder with a particle size of 15μm was acid-washed with 6mol / L hydrochloric acid at 50℃ for 3h, followed by multiple water washings and centrifugation until the washing liquid was neutral. After drying at 60℃, deashed coal powder was obtained. The mass ratio of anthracite powder to acid solution was 1:9.

[0087] S2: Deashed coal powder and sodium hydroxide were mixed and ground at a mass ratio of 5:1 for 1 hour. Under a nitrogen atmosphere, the mixture was heated to 1100℃ at a heating rate of 3℃ / min for 4 hours. After holding at this temperature for 4 hours, it was acid-washed with 1mol / L hydrochloric acid and then dried at 60℃ to obtain coal-based porous carbon material. The specific surface area of ​​this coal-based porous carbon material was measured to be 603 m². 2 / g;

[0088] S3: Coal-based porous carbon material and melamine are mixed and ground at a mass ratio of 1:2 for 1 hour. Under a nitrogen atmosphere, the temperature is increased to 900℃ at a heating rate of 3℃ / min for heat treatment. The heat treatment holding time is 5 hours to obtain the negative electrode material.

[0089] Comparative Example 5

[0090] This comparative example provides a method for preparing a negative electrode material, including the following steps:

[0091] S1: Using anthracite as raw material, D is obtained by sequentially crushing, ball milling, and screening. 50 Anthracite powder with a particle size of 15μm was acid-washed with 6mol / L hydrochloric acid at 50℃ for 3h, followed by multiple water washings and centrifugation until the washing liquid was neutral. After drying at 60℃, deashed coal powder was obtained. The mass ratio of anthracite powder to acid solution was 1:9.

[0092] S2: The deashed coal powder is heated to 1100℃ under a nitrogen atmosphere at a heating rate of 3℃ / min for heat treatment; after holding the heat treatment for 4 hours, coal-based carbon material is obtained.

[0093] S3: Coal-based carbon materials, melamine, and transition metal compound ferric chloride are mixed and ground at a mass ratio of 1:2:0.5 for 1 hour. Under a nitrogen atmosphere, the mixture is heated to 900℃ at a heating rate of 3℃ / min for heat treatment. The heat treatment is held for 5 hours to obtain porous carbon materials grafted with carbon nanotubes, i.e., anode materials.

[0094] Comparative Example 6

[0095] This comparative example provides a method for preparing a negative electrode material, including the following steps:

[0096] S1: Using sintered coal as raw material, it is successively crushed, ball-milled, and screened to obtain D. 50 Sintered coal powder with a particle size of 15μm was acid-washed with 6mol / L hydrochloric acid at 50℃ for 3h, followed by multiple water washings and centrifugation until the washing liquid was neutral. After drying at 60℃, deashed coal powder was obtained. The mass ratio of sintered coal powder to acid liquid was 1:9.

[0097] S2: Deashed coal powder and sodium hydroxide were mixed and ground at a mass ratio of 5:1 for 1 hour. Under a nitrogen atmosphere, the mixture was heated to 1100℃ at a heating rate of 3℃ / min for 4 hours. After holding at this temperature for 4 hours, it was acid-washed with 1mol / L hydrochloric acid and then dried at 60℃ to obtain coal-based porous carbon material. The specific surface area of ​​this coal-based porous carbon material was measured to be 301 m². 2 / g;

[0098] S3: Coal-based porous carbon material, melamine and transition metal compound ferric chloride are mixed and ground at a mass ratio of 1:2:0.5 for 1 hour. Under a nitrogen atmosphere, the temperature is increased to 900℃ at a heating rate of 3℃ / min for heat treatment. The heat treatment holding time is 5 hours to obtain carbon nanotube-grafted porous carbon material, i.e., negative electrode material.

[0099] The negative electrode materials prepared in the above embodiments and comparative examples were used to prepare coin cells according to the following method:

[0100] The electrode slurry was prepared with a ratio of negative electrode material: conductive agent SP: binder CMC = 80:10:10 (mass ratio). Appropriate amounts of ethanol and water were added to form the slurry, which was then coated to a thickness of 100 μm. After drying and pressing, the slurry was fabricated into an electrode sheet. Using metallic sodium as the counter electrode, a 1 mol / L NaPF6 DEC / EC (1:1) solution as the electrolyte, and a glass fiber filter paper membrane GF / C as the separator, a 2032 coin cell was assembled. The electrode was tested at 0.1 A g. -1 Its charge and discharge performance was tested at a current density.

[0101] The test results are shown in Table 1:

[0102] Table 1

[0103]

[0104] As can be seen from the above data, the embodiments of the present invention have the advantages of high anthracite coal yield and low pyrolysis temperature; the prepared anode materials all have high specific capacity values, and are anode materials with promising industrial applications.

[0105] Compared with Example 1, Comparative Example 1 did not graft carbon nanotubes onto the surface of coal-based porous carbon, resulting in a decrease in both capacity and rate performance of the prepared anode material.

[0106] Compared with Example 1, Comparative Example 2 did not use alkaline high-temperature activation to optimize sodium storage sites and graphite microcrystal spacing, resulting in a negative electrode material with low capacity and poor rate performance.

[0107] Compared with Example 1, Comparative Example 3 did not graft carbon nanotubes onto the surface of coal-based porous carbon, but instead directly physically mixed the prepared coal-based porous carbon with carbon nanotubes, resulting in a low capacity anode material.

[0108] Compared with Example 1, no transition metal compound was added in step S3 of Comparative Example 4, resulting in a negative electrode material with low capacity and poor rate performance.

[0109] Compared with Example 1, no alkali was added in step S2 of Comparative Example 5, resulting in a negative electrode material with low capacity and poor rate performance.

[0110] Compared with Example 1, Comparative Example 6, which uses sintered coal instead of anthracite, produces a negative electrode material with low capacity and poor rate performance.

[0111] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for preparing a negative electrode material, characterized in that, Includes the following steps: S1: Acid washing and deashing of pulverized coal to obtain deashed pulverized coal; S2: The deashed coal powder is mixed and ground with alkali, and then heat-treated at 800-1400℃ under a protective atmosphere. After acid washing and drying, coal-based porous carbon material is obtained. S3: The coal-based porous carbon material, amine source and transition metal compound are mixed and ground, and then heat-treated at 800-1000℃ under a protective atmosphere to obtain the negative electrode material.

2. The method for preparing the negative electrode material as described in claim 1, characterized in that, The amine source is melamine.

3. The method for preparing the negative electrode material as described in claim 1, characterized in that, The pulverized coal is selected from at least one of anthracite pulverized coal, bituminous coal pulverized coal, sub-bituminous coal pulverized coal, or lignite pulverized coal.

4. The method for preparing the negative electrode material as described in claim 1, characterized in that, The alkali is an alkali metal hydroxide.

5. The method for preparing the negative electrode material as described in claim 4, characterized in that, The alkali metal hydroxide is selected from at least one of sodium hydroxide and potassium hydroxide.

6. The method for preparing the negative electrode material as described in claim 1, characterized in that, In step S2, the mass ratio of the deashed coal powder to the alkali is (1-10):

1.

7. The method for preparing the negative electrode material as described in claim 1, characterized in that, The transition metal compound is selected from at least one of iron salts, cobalt salts, and nickel salts.

8. The method for preparing the negative electrode material as described in claim 1, characterized in that, In step S3, the mass ratio of the coal-based porous carbon material, the amine source, and the transition metal compound is 1:(1~4):(0.1~1).

9. A negative electrode material, characterized in that, The anode material is prepared by the method described in any one of claims 1-8.

10. A sodium-ion battery, characterized in that, Includes the negative electrode material as described in claim 9.

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