Preparation method and application of coal-based derived hard carbon material capable of effectively coordinating sodium storage in platform region and slope region

Abstract

A method for preparing and applying a coal-derived hard carbon material that effectively coordinates sodium storage in platform and slope regions. The method involves: heat-treating 1-10 parts by weight of a coal sample to 1000-1500℃ and holding for 1-3 hours to obtain a one-step carbonized hard carbon powder; mixing 1-5 parts by weight of the one-step carbonized hard carbon powder, 1-20 parts by weight of a dopant source, and 1-20 parts by weight of a pore-forming agent in an aqueous solution for 1-3 hours, and drying to obtain powder B; and then heat-treating powder B to 500-100℃. By holding the material at 0℃ for 1-3 hours, a two-step carbonization-assisted heteroatom-doped coal-based derived hard carbon material is obtained. The prepared two-step carbonization-assisted heteroatom-doped coal-based derived hard carbon material can be used to prepare electrode sheets, sodium-ion button half-cells, or sodium-ion button full cells. This invention, through two-step carbonization-assisted heteroatom doping, can coordinate the electrochemical sodium storage capacity of the plateau region and the slope region, so that it also has excellent electrochemical performance. At the same time, the introduction of two-step carbonization achieves high heteroatom doping and improves the doping efficiency of heteroatoms.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion battery anode material technology, specifically relating to a method for preparing and applying a coal-based derived hard carbon material that effectively coordinates sodium storage in the plateau and slope regions. Background Technology

[0002] Renewable energy sources such as solar, wind, and tidal power have been discovered, but these are intermittent and dispersed, necessitating the development of efficient, low-cost energy storage systems. The advent of rechargeable batteries has solved this problem. Lithium-ion batteries (LIBs) are widely popular due to their large capacity (twice that of nickel-cadmium batteries), high operating voltage (three times that of nickel-cadmium and nickel-metal hydride batteries), high energy density, small size, and pollution-free operation. They are already widely used in various mobile electronic devices and electric vehicles, dominating the market. However, lithium resources comprise only 0.0065% of the Earth's crust, and their uneven global distribution makes extraction difficult. Since Sony commercialized LIBs in 1991, lithium resources have been continuously depleted, and high demand coupled with low lithium content has led to a continuous rise in lithium prices. Compared to lithium, sodium resources are more abundant and cheaper. Therefore, developing sodium-ion batteries (SIBs) to partially replace LIBs is particularly important.

[0003] A series of studies have revealed a wide variety of suitable cathode materials for SIBs, exhibiting excellent electrochemical performance. Common cathode materials include metal oxides (NaXMO2), polyanionic compounds (NaFePO4 is commonly found in SIBs), and Prussian blue and its analogues. However, the anode material for SIBs remains a significant challenge. Research has shown that graphite, which demonstrates excellent performance in LIBs, exhibits electrochemical inertness in NIBs, with a capacity of only 33 mA hg. -1 This could be because of Na. + ionic radius Greater than Li + A large ionic radius results in slow ion diffusion. Therefore, finding an electrode material with high specific capacity, long cycle life, and high safety is key to the development of SIBs.

[0004] Patent application CN202111673684.8 discloses a coal-based carbon anode material, its preparation method and application, and batteries containing it. A coal-based hard carbon anode is obtained by pulverizing coal and modifying it with volatile organic compounds through heat treatment. However, the difficulty in processing and high cost of organic compounds increase the cost of the reaction and raise safety concerns, hindering commercial development.

[0005] Patent application CN202311399859.X discloses a coal-based hard carbon material, its preparation method, and its application. A coal-based hard carbon anode is prepared by combining oxidative crosslinking and high-temperature carbonization. However, due to the uncontrollable reaction during the oxidative crosslinking process and the different physical and chemical structures of different coal samples, reproducibility is poor, failing to meet the requirements for industrial applications. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, the present invention aims to provide a method for preparing and applying a coal-derived hard carbon material that effectively coordinates sodium storage in the plateau and slope regions. By using two-step carbonization to assist heteroatom doping, the electrochemical sodium storage capacity in the plateau and slope regions can be coordinated, so that it can have excellent electrochemical performance at the same time. At the same time, the introduction of two-step carbonization can achieve high heteroatom doping and improve the doping efficiency of heteroatoms.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] A method for preparing coal-derived hard carbon materials that effectively coordinate sodium storage in platform and slope regions includes the following steps:

[0009] S1: By weight, 1 to 10 parts of coal sample are heat-treated, heated to 1000-1500℃ and held for 1-3 hours to obtain hard carbon powder A after one-step carbonization;

[0010] S2: By weight, 1-5 parts of hard carbon powder A obtained in step S1 after one-step carbonization, 1-20 parts of dopant source and 1-20 parts of pore-forming agent are mixed in an aqueous solution for 1-3 hours and dried to obtain powder B.

[0011] S3: By weight, the powder B obtained in step S2 is heat-treated to 500-1000℃ and held for 1-3 hours to obtain a two-step carbonization-assisted heteroatom-doped coal-based derived hard carbon material.

[0012] The coal sample in step S1 is a mixture of one, two or more of lignite, bituminous coal, anthracite, coal coke, coal gangue or coal tar pitch in any proportion; the coal sample is a mixture of one, two or more of 300 mesh, 400 mesh or 500 mesh in any proportion.

[0013] The heat treatment atmosphere in steps S1 and S3 is argon or nitrogen.

[0014] The dopant source in step S2 is one, two or more of formamide, urea, melamine acid, thiourea or phytic acid in any proportion; the pore-forming agent is one, two or more of calcium carbonate, magnesium oxide, sodium chloride, silicon dioxide or potassium permanganate in any proportion.

[0015] An application of a coal-derived hard carbon material that effectively coordinates sodium storage in platform and slope regions can be used to prepare electrode sheets, sodium-ion button half-cells, or sodium-ion button full-cells.

[0016] The electrode sheet comprises a two-step carbonization-assisted heteroatom-doped coal-based hard carbon material, Ketjen black, and polyvinylidene fluoride. By weight, the ratio of the two-step carbonization-assisted heteroatom-doped coal-based hard carbon material to Ketjen black to polyvinylidene fluoride is (1-9): (0.1-9): (0.1-9). The two-step carbonization-assisted heteroatom-doped coal-based hard carbon material, Ketjen black, and polyvinylidene fluoride obtained in step S3 are uniformly mixed in N-methylpyrrolidone and ground to obtain a negative electrode slurry. The negative electrode slurry is coated on a current collector and vacuum dried. After being sliced ​​by a slicing machine, an electrode sheet loaded with hard carbon is obtained.

[0017] The obtained electrode sheet, sodium source and electrolyte are packaged by a packaging machine to obtain a sodium-ion button cell; the obtained electrode sheet and sodium vanadium phosphate are packaged by a packaging machine to obtain a sodium-ion button cell.

[0018] The current collector is aluminum foil, copper foil, carbon-coated aluminum foil, or carbon-coated copper foil; the electrode cutting size of the cutting machine is 10mm, 14mm, or 19mm.

[0019] The electrolyte comprises: by weight, 1 to 3 parts of sodium salt uniformly dispersed in 1 to 10 parts of electrolyte solvent, and stirred for 1 to 5 hours to obtain the electrolyte; the sodium source is sodium block or sodium sheet.

[0020] The sodium salt is one, two or more of sodium hexafluorophosphate, sodium perchlorate or sodium bis(trifluoromethanesulfonyl)imide in any proportion;

[0021] The electrolyte solvent is one, two, or a mixture of two or more of dimethyl carbonate, ethylene carbonate, propylene carbonate, diethyl carbonate, diethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether in any proportion.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] 1. In step S1 of this invention, a coal-based hard carbon material with a pseudo-graphite phase as the main component is successfully synthesized through a one-step carbonization process, which further promotes the insertion and extraction of sodium ions between carbon layers.

[0024] 2. Step S2 of the present invention promotes the generation of defect sites on the surface of carbon materials by combining heteroatom doping on the basis of one-step carbonization, thereby facilitating the adsorption process of sodium ions in the slope region.

[0025] 3. Step S3 of this invention prepares a coal-based hard carbon material with a high "plateau region-slope region" through two-step carbonization pyrolysis and effective reconstruction of heteroatoms, which significantly improves the specific capacity and electrochemical performance of coal-based hard carbon.

[0026] In summary, the novel coal-derived hard carbon material prepared by introducing a two-step carbonization combined with heteroatom doping method in the product of this invention achieves the unification of the plateau region and the slope region. The resulting hard carbon material has excellent electrochemical performance, providing a new method for preparing sodium-ion batteries with cost and performance in harmony. Attached Figure Description

[0027] Figure 1 This is a rate performance curve of a two-step carbonization-assisted N-doped coal-based carbon material prepared under different implementation conditions of the present invention, used as a negative electrode material for sodium-ion batteries. Detailed Implementation

[0028] The technical solutions adopted by the present invention will be described in detail below with reference to the embodiments and accompanying drawings.

[0029] Example 1

[0030] A method for preparing coal-derived hard carbon materials that effectively coordinate sodium storage in platform and slope regions includes the following steps:

[0031] S1: By weight, 3 parts of 400-mesh bituminous coal were placed in a tube furnace under an argon atmosphere for heat treatment. The temperature was raised to 1200℃ and held for 2 hours to obtain hard carbon powder A after one-step carbonization.

[0032] S2: By weight, 1 part of hard carbon powder A obtained from step S1 after one-step carbonization, 5 parts of urea and 10 parts of sodium chloride are mixed in an aqueous solution for 2 hours and dried to obtain powder B.

[0033] S3: By weight, the powder B obtained in step S2 is placed in a tube furnace under an argon atmosphere for heat treatment, heated to 700°C and held for 2 hours to obtain a two-step carbonization-assisted heteroatom-doped coal-based derived hard carbon material.

[0034] An application of a coal-derived hard carbon material that effectively coordinates sodium storage in platform and slope regions can be used to prepare electrode sheets, sodium-ion button half-cells, or sodium-ion button full-cells.

[0035] The electrode sheet comprises a two-step carbonization-assisted heteroatom-doped coal-based hard carbon material, Ketjen black, and polyvinylidene fluoride. By weight, the ratio of the two-step carbonization-assisted heteroatom-doped coal-based hard carbon material to Ketjen black to polyvinylidene fluoride is 8:1:1. The two-step carbonization-assisted heteroatom-doped coal-based hard carbon material, Ketjen black, and polyvinylidene fluoride obtained in step S3 are uniformly mixed in N-methylpyrrolidone and ground to obtain a negative electrode slurry. The negative electrode slurry is coated on aluminum foil and vacuum dried. After being sliced ​​14 mm by a slicing machine, an electrode sheet loaded with hard carbon is obtained.

[0036] Electrode sheets, sodium sheets, and electrolyte are packaged together using a packaging machine to obtain sodium-ion button-type half-cells; electrode sheets and sodium vanadium phosphate are packaged together using a packaging machine to obtain sodium-ion button-type full-cells.

[0037] The electrolyte comprises: by weight, 1 part of sodium perchlorate is uniformly dispersed in a mixed electrolyte solvent of 3 parts of dimethyl carbonate and ethylene carbonate (v / v, 1:1), and the mixture is magnetically stirred for 3 hours to obtain the electrolyte for battery assembly.

[0038] Example 2

[0039] A method for preparing coal-derived hard carbon materials that effectively coordinate sodium storage in platform and slope regions includes the following steps:

[0040] S1: By weight, 5 parts of 300-mesh anthracite and coke were placed in a tube furnace under a nitrogen atmosphere for heat treatment. The temperature was raised to 1000℃ and held for 1 hour to obtain hard carbon powder A after one-step carbonization.

[0041] S2: By weight, mix 1 part of the one-step carbonized hard carbon powder A obtained in step S1 with 1 part of melamine-urea, then add 1 part of calcium carbonate and mix in an aqueous solution for 1 hour, and dry to obtain powder B.

[0042] S3: By weight, the powder B obtained in step S2 is placed in a tube furnace under a nitrogen atmosphere for heat treatment, heated to 500°C and held for 1 hour to obtain a two-step carbonization-assisted heteroatom-doped coal-based derived hard carbon material.

[0043] An application of a coal-derived hard carbon material that effectively coordinates sodium storage in platform and slope regions can be used to prepare electrode sheets, sodium-ion button half-cells, or sodium-ion button full-cells.

[0044] The electrode sheet comprises a two-step carbonization-assisted heteroatom-doped coal-based hard carbon material, Ketjen black, and polyvinylidene fluoride. By weight, the ratio of the two-step carbonization-assisted heteroatom-doped coal-based hard carbon material to Ketjen black to polyvinylidene fluoride is 7:2:1. The two-step carbonization-assisted heteroatom-doped coal-based hard carbon material, Ketjen black, and polyvinylidene fluoride obtained in step S3 are uniformly mixed in N-methylpyrrolidone and ground to obtain a negative electrode slurry. The negative electrode slurry is coated on a copper foil and vacuum dried. After being sliced ​​10 mm by a slicing machine, an electrode sheet loaded with hard carbon is obtained.

[0045] Electrode sheets, sodium blocks, and electrolytes are packaged using a packaging machine to obtain sodium-ion button-type half-cells; electrode sheets and sodium vanadium phosphate are packaged using a packaging machine to obtain sodium-ion button-type full-cells.

[0046] The electrolyte comprises: by weight, 1 part of sodium hexafluorophosphate is uniformly dispersed in a mixed electrolyte solvent of 1 part diethyl carbonate and ethylene carbonate (v / v, 1:1), and the mixture is magnetically stirred for 2 hours to obtain the electrolyte for battery assembly.

[0047] Example 3

[0048] A method for preparing coal-derived hard carbon materials that effectively coordinate sodium storage in platform and slope regions includes the following steps:

[0049] S1: By weight, 10 parts of 500-mesh lignite were placed in a tubular furnace under an argon atmosphere for heat treatment. The temperature was raised to 1500℃ and held for 3 hours to obtain hard carbon powder A after one-step carbonization.

[0050] S2: By weight, 5 parts of hard carbon powder A obtained from step S1 after one-step carbonization, 20 parts of thiourea, and 20 parts of magnesium oxide and silicon dioxide are mixed in an aqueous solution for 2 hours and dried to obtain powder B.

[0051] S3: By weight, the powder B obtained in step S2 is placed in a tube furnace under an argon atmosphere for heat treatment, heated to 1000℃ and held for 3 hours to obtain a two-step carbonization-assisted heteroatom-doped coal-based derived hard carbon material.

[0052] An application of a coal-derived hard carbon material that effectively coordinates sodium storage in platform and slope regions can be used to prepare electrode sheets, sodium-ion button half-cells, or sodium-ion button full-cells.

[0053] The electrode sheet comprises a two-step carbonization-assisted heteroatom-doped coal-based hard carbon material, Ketjen black, and polyvinylidene fluoride. By weight, the ratio of the two-step carbonization-assisted heteroatom-doped coal-based hard carbon material to Ketjen black to polyvinylidene fluoride is 8:0.5:1.5. The two-step carbonization-assisted heteroatom-doped coal-based hard carbon material, Ketjen black, and polyvinylidene fluoride obtained in step S3 are uniformly mixed in N-methylpyrrolidone and ground to obtain a negative electrode slurry. The negative electrode slurry is coated on carbon-coated aluminum foil and vacuum dried. After being sliced ​​to 19 mm by a slicing machine, an electrode sheet loaded with hard carbon is obtained.

[0054] Electrode sheets, sodium sheets, and electrolyte are packaged together using a packaging machine to obtain sodium-ion button-type half-cells; electrode sheets and sodium vanadium phosphate are packaged together using a packaging machine to obtain sodium-ion button-type full-cells.

[0055] The electrolyte comprises: by weight, 2 parts of sodium bis(trifluoromethanesulfonyl)imide are uniformly dispersed in a mixed electrolyte solvent of 10 parts of propylene carbonate and ethylene carbonate (v / v, 1:1), and the mixture is magnetically stirred for 3 hours to obtain the electrolyte for battery assembly.

[0056] Example 4

[0057] A method for preparing coal-derived hard carbon materials that effectively coordinate sodium storage in platform and slope regions includes the following steps:

[0058] S1: By weight, 8 parts of 300-mesh coal gangue were placed in a tube furnace under a nitrogen atmosphere for heat treatment. The temperature was raised to 1100℃ and held for 1 hour to obtain hard carbon powder A after one-step carbonization.

[0059] S2: By weight, mix 3 parts of the one-step carbonized hard carbon powder A obtained in step S1 with 15 parts of formamide, then add 8 parts of potassium permanganate in an aqueous solution and mix for 2 hours. After drying, obtain powder B.

[0060] S3: By weight, the powder B obtained in step S2 is placed in a tube furnace under a nitrogen atmosphere for heat treatment, heated to 700°C and held for 2 hours to obtain a two-step carbonization-assisted heteroatom-doped coal-based derived hard carbon material.

[0061] An application of a coal-derived hard carbon material that effectively coordinates sodium storage in platform and slope regions can be used to prepare electrode sheets, sodium-ion button half-cells, or sodium-ion button full-cells.

[0062] The electrode sheet comprises a two-step carbonization-assisted heteroatom-doped coal-based hard carbon material, Ketjen black, and polyvinylidene fluoride. By weight, the ratio of the two-step carbonization-assisted heteroatom-doped coal-based hard carbon material to Ketjen black to polyvinylidene fluoride is 9:0.5:0.5. The two-step carbonization-assisted heteroatom-doped coal-based hard carbon material, Ketjen black, and polyvinylidene fluoride obtained in step S3 are uniformly mixed in N-methylpyrrolidone and ground to obtain a negative electrode slurry. The negative electrode slurry is coated on a carbon-coated copper foil and vacuum dried. After being sliced ​​10 mm by a slicing machine, an electrode sheet loaded with hard carbon is obtained.

[0063] Electrode sheets, sodium blocks, and electrolytes are packaged using a packaging machine to obtain sodium-ion button-type half-cells; electrode sheets and sodium vanadium phosphate are packaged using a packaging machine to obtain sodium-ion button-type full-cells.

[0064] The electrolyte comprises: by weight, 3 parts of sodium perchlorate uniformly dispersed in 8 parts of diethylene glycol dimethyl ether, and magnetically stirred for 2 hours to obtain the electrolyte for battery assembly.

[0065] Example 5

[0066] A method for preparing coal-derived hard carbon materials that effectively coordinate sodium storage in platform and slope regions includes the following steps:

[0067] S1: By weight, 8 parts of 500-mesh coal tar pitch were placed in a tube furnace under a nitrogen atmosphere for heat treatment, heated to 1300℃ and held for 3 hours to obtain hard carbon powder A after one-step carbonization.

[0068] S2: By weight, 2 parts of hard carbon powder A obtained from step S1 after one-step carbonization, 5 parts of phytic acid and 12 parts of magnesium oxide are mixed in an aqueous solution for 2 hours and dried to obtain powder B.

[0069] S3: By weight, the powder B obtained in step S2 is placed in a tube furnace under a nitrogen atmosphere for heat treatment, heated to 600°C and held for 1 hour to obtain a two-step carbonization-assisted heteroatom-doped coal-based derived hard carbon material.

[0070] An application of a coal-derived hard carbon material that effectively coordinates sodium storage in platform and slope regions can be used to prepare electrode sheets, sodium-ion button half-cells, or sodium-ion button full-cells.

[0071] The electrode sheet comprises a two-step carbonization-assisted heteroatom-doped coal-based hard carbon material, Ketjen black, and polyvinylidene fluoride. By weight, the ratio of the two-step carbonization-assisted heteroatom-doped coal-based hard carbon material to Ketjen black to polyvinylidene fluoride is 9:0.5:0.5. The two-step carbonization-assisted heteroatom-doped coal-based hard carbon material, Ketjen black, and polyvinylidene fluoride obtained in step S3 are uniformly mixed in N-methylpyrrolidone and ground to obtain a negative electrode slurry. The negative electrode slurry is coated on aluminum foil and vacuum dried. After being sliced ​​14 mm by a slicing machine, an electrode sheet loaded with hard carbon is obtained.

[0072] Electrode sheets, sodium sheets, and electrolyte are packaged together using a packaging machine to obtain sodium-ion button-type half-cells; electrode sheets and sodium vanadium phosphate are packaged together using a packaging machine to obtain sodium-ion button-type full-cells.

[0073] The electrolyte comprises: 3 parts by weight of sodium bis(trifluoromethanesulfonyl)imide uniformly dispersed in 6 parts of tetraethylene glycol dimethyl ether, and magnetically stirred for 4 hours to obtain the electrolyte for battery assembly.

[0074] This invention provides a two-step carbonization-assisted heteroatom-doped coal-based hard carbon material preparation process, including electrolyte preparation and assembly of sodium-ion button half-cells and full cells. The coal-derived hard carbon is a novel coal-based hard carbon material obtained by two-step carbonization-assisted heteroatom doping of low-rank coal. The two-step carbonization process forms more graphite-like phases and expands the interlayer spacing, facilitating sodium ion insertion. The introduction of heteroatoms introduces external defect sites, enhancing sodium ion adsorption, thus obtaining a hard carbon material with excellent capacity in both plateau and slope regions. The electrolyte preparation provides the basis for wetting the positive and negative electrode materials and providing faster sodium ion and electron transport channels. The assembly of sodium-ion button half-cells and full cells, by controlling the mass ratio of the positive and negative electrodes, ensures that the electrodes have optimal specific capacity and cycle performance. This invention uses low-rank coal as a carbon precursor and, through reasonable modification methods, controls the carbon microcrystalline structure of the coal-derived hard carbon, further improving the electrochemical performance of the electrode material, enabling it to meet the application requirements of energy storage electronic devices, aerospace, and high-power industries in the future.

[0075] Table 1. Specific capacity and initial coulombic efficiency of a two-step carbonization-assisted N-doped coal-based carbon material prepared under different implementation conditions, used as a negative electrode material for sodium-ion batteries.

[0076]

[0077] In summary, compared with existing technologies, this invention successfully prepared a hard carbon anode with excellent plateau and slope capacity by introducing a two-step carbonization process and heteroatom doping, enabling simultaneous intercalation and adsorption of sodium ions. The two-step carbonization process induces a change in the carbon microcrystal configuration, expanding the carbon interlayer spacing, while the introduction of heteroatoms effectively improves defect sites. Due to these advantages, this invention exhibits superior electrochemical performance.

[0078] like Figure 1 The figure shows the cycling performance of the coal-based hard carbon material prepared in the examples. Example 5 exhibits superior rate performance, exceeding that of the other examples at any current density.

Claims

1. A method for preparing coal-derived hard carbon materials that effectively coordinate sodium storage in platform and slope regions, characterized in that: Includes the following steps: S1: By weight, 1 to 10 parts of coal sample are heat-treated, heated to 1000-1500℃ and held for 1-3 hours to obtain hard carbon powder A after one-step carbonization; S2: By weight, 1-5 parts of hard carbon powder A obtained in step S1 after one-step carbonization, 1-20 parts of dopant source and 1-20 parts of pore-forming agent are mixed in an aqueous solution for 1-3 hours and dried to obtain powder B. S3: By weight, the powder B obtained in step S2 is heat-treated to 500-1000℃ and held for 1-3 hours to obtain a two-step carbonization-assisted heteroatom-doped coal-based derived hard carbon material. The coal sample in step S1 is a mixture of one, two or more of lignite, bituminous coal, anthracite, coal coke, coal gangue or coal tar pitch in any proportion; the coal sample is a mixture of one, two or more of 300 mesh, 400 mesh or 500 mesh in any proportion. The dopant source in step S2 is one, two or more of formamide, urea, melamine acid, thiourea or phytic acid in any proportion; the pore-forming agent is one, two or more of calcium carbonate, magnesium oxide, sodium chloride, silicon dioxide or potassium permanganate in any proportion.

2. The method for preparing a coal-based derived hard carbon material for effectively coordinating sodium storage in platform and slope regions according to claim 1, characterized in that: The heat treatment atmosphere in steps S1 and S3 is argon or nitrogen.

3. The application of a coal-derived hard carbon material for effectively coordinating sodium storage in the platform and slope regions as described in any one of claims 1 to 2, characterized in that: It can be used to prepare electrode sheets, sodium-ion button half cells or sodium-ion button full cells.

4. The application of a coal-derived hard carbon material for effectively coordinating sodium storage in platform and slope areas as described in claim 3, characterized in that: The electrode sheet comprises a two-step carbonization-assisted heteroatom-doped coal-based hard carbon material, Ketjen black, and polyvinylidene fluoride. By weight, the ratio of the two-step carbonization-assisted heteroatom-doped coal-based hard carbon material to Ketjen black to polyvinylidene fluoride is (1-9):(0.1-9):(0.1-9). The two-step carbonization-assisted heteroatom-doped coal-based hard carbon material, Ketjen black, and polyvinylidene fluoride obtained in step S3 are uniformly mixed in N-methylpyrrolidone and ground to obtain a negative electrode slurry. The negative electrode slurry is coated on a current collector and vacuum dried. After being sliced ​​by a slicing machine, an electrode sheet loaded with hard carbon is obtained.

5. The application of a coal-derived hard carbon material for effectively coordinating sodium storage in platform and slope areas as described in claim 3 or 4, characterized in that: The obtained electrode sheet, sodium source and electrolyte are packaged by a packaging machine to obtain a sodium-ion button cell; the obtained electrode sheet and sodium vanadium phosphate are packaged by a packaging machine to obtain a sodium-ion button cell.

6. The application of a coal-based derived hard carbon material for effectively coordinating sodium storage in platform and slope areas as described in claim 4, characterized in that: The current collector is aluminum foil, copper foil, carbon-coated aluminum foil, or carbon-coated copper foil; the electrode cutting size of the cutting machine is 10mm, 14mm, or 19mm.

7. The application of a coal-based derived hard carbon material for effectively coordinating sodium storage in platform and slope areas as described in claim 5, characterized in that: The electrolyte comprises: by weight, 1-3 parts of sodium salt uniformly dispersed in 1-10 parts of electrolyte solvent, and stirred for 1-5 hours to obtain the electrolyte; the sodium source is sodium block or sodium sheet.

8. The application of a coal-derived hard carbon material for effectively coordinating sodium storage in platform and slope areas as described in claim 7, characterized in that: The sodium salt is one, two or more of sodium hexafluorophosphate, sodium perchlorate or sodium bis(trifluoromethanesulfonyl)imide in any proportion; The electrolyte solvent is one, two, or a mixture of two or more of dimethyl carbonate, ethylene carbonate, propylene carbonate, diethyl carbonate, diethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether in any proportion.

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