Preparation method of hard carbon negative electrode material and hard carbon negative electrode sheet for sodium ion battery

Abstract

This invention discloses a method for preparing a hard carbon anode material for sodium-ion batteries. First, a porous hard carbon material is prepared. Then, a zeolite imidazole ester framework is grown in situ on the surface of the porous hard carbon material. After sulfidation, it is transformed into a hard carbon material coated with polydopamine, a carbon layer precursor. Finally, it is carbonized to obtain the final product. As an anode material for sodium-ion batteries, the carbon layer formed by the pyrolysis of dopamine hydrochloride greatly alleviates the volume expansion of the material and allows for more uniform dispersion of Co active sites. More importantly, the carbon-coated material significantly improves the cycle stability of the battery. This invention also discloses a method for preparing a hard carbon anode sheet for sodium-ion batteries. The hard carbon anode material and hard carbon anode sheet prepared by this invention improve the cycle stability and rate performance of the battery.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery technology, specifically to a hard carbon anode material for sodium-ion batteries and a method for preparing hard carbon anode sheets. Background Technology

[0002] Electrochemical energy storage has become a prominent technology for green energy utilization, and has been widely researched and applied since the commercialization of lithium-ion batteries. However, the increasing cost of lithium has made it urgent to find a new material to replace lithium-ion batteries. Sodium (Na) and lithium (Li) are in the same group and have similar chemical properties to lithium, therefore sodium-ion batteries (SIBs) are considered the best alternative to lithium-ion batteries. Furthermore, sodium is abundant and widely distributed in seawater, and its low charge-to-mass ratio, high stability, low solvation effect, and wide redox electrochemical window are beneficial for constructing stable battery systems. With the increasing applications and expanding scope, sodium-ion battery technology is gradually seeking ways to create richer and more sustainable systems, and developing suitable electrode materials is the core of this transformation.

[0003] Currently, sodium-ion battery anode materials are mainly classified into three categories according to their sodium ion storage mechanism: carbon-based materials; transition metal oxides, sulfides, phosphides, etc.; and alloy materials (Fe, Co, Ni, Mn, etc.). Among these three categories, materials based on conversion reactions have higher theoretical capacity and lower operating potential, and are considered the most promising anode materials.

[0004] Among them, carbon-based materials have the highest technological maturity and abundant resources, and are expected to be the first to achieve industrialization. However, compared with lithium-ion... Compared to the diameter of the sodium ion, the diameter of the sodium ion is... The relatively large size of the electrode leads to sluggish sodium-ion anode reaction kinetics and significant electrode volume expansion, limiting the application of traditional graphite carbon in sodium-ion batteries. Among carbon-based anode materials, hard carbon (HC) is a feasible sodium-ion intercalation anode material. Its disordered, stacked microcrystalline structure provides abundant sodium storage sites and a suitable ion storage and transport environment, which is not only conducive to absorbing more Na but also to Na intercalation and deintercalation. However, developing materials with high rate capability and cycle stability remains a challenge for current hard carbon anode active materials. Summary of the Invention

[0005] The purpose of this invention is to provide a hard carbon anode material for sodium-ion batteries that is a hybrid of transition metal sulfide and carbon material, and a method for preparing the hard carbon anode sheet. The prepared anode material improves the cycle stability and rate performance of the battery.

[0006] To achieve the above objectives, the solution of the present invention is:

[0007] A method for preparing a hard carbon anode material for sodium-ion batteries includes the following steps:

[0008] Step 1: Preparation of porous hard carbon materials:

[0009] First, the buckwheat hull powder is heated to 600-800℃ at a heating rate of 3-5℃ / min, and then kept at this temperature for 2-3 hours under protective gas to carry out pyrolysis, thereby obtaining carbon-based materials. After soaking and washing with KOH solution, porous hard carbon materials are obtained, denoted as Buckwheat Carbon.

[0010] Step 2: In-situ growth of the zeolite imidazole ester skeleton:

[0011] Then, the porous hard carbon material obtained in step 2 was ultrasonically dispersed in an ethanol solution of cobalt nitrate hexahydrate. 2-methylimidazole was added to the ultrasonic solution to generate a zeolite imidazole ester framework in situ on the surface of the porous hard carbon material, thus obtaining a hard carbon material with a zeolite imidazole ester framework, denoted as ZIF-67Drived Carbon.

[0012] Step 3, vulcanization:

[0013] Then, the ZIF-67Drived Carbon obtained in step 2 is mixed evenly with sulfur powder and placed in a tube furnace. Under the protection of protective gas, the temperature is raised to 600-900℃ at 3-5℃ / min and held for 2-3 hours. After cooling, a hybrid material of cobalt polysulfide and hard carbon is obtained, which is denoted as Co9S8 / C material.

[0014] Step 4: Generate carbon layer precursor:

[0015] Then, the Co9S8 / C material obtained in step 3 was ultrasonically dispersed in deionized water, and the solution was adjusted to weak alkalinity. Dopamine hydrochloride was added, and a polymerization reaction occurred on the surface of the hybrid material under stirring to generate polydopamine-coated material. After stirring for 1 to 4 hours, the material was centrifuged and dried at 60 to 80°C overnight to obtain the Co9S8 / C material coated with carbon layer precursor.

[0016] Step 5, Carbonization:

[0017] Finally, the Co9S8 / C material obtained in step 4 is placed in a tube furnace and heated to 600-900°C at a rate of 3-5°C / min under protective gas and held for 2-3 hours to obtain the hard carbon anode material for sodium-ion batteries, denoted as C-Co9S8 / C.

[0018] In step 1, the KOH solution soaking and washing process is as follows: the carbon-based material obtained by pyrolysis is dispersed in 100 mL of KOH solution with a mass concentration of 10%, stirred for 10 to 12 hours, centrifuged to obtain precipitate, and then the precipitate is washed repeatedly with dilute hydrochloric acid and anhydrous ethanol, and dried overnight at 60 to 80°C.

[0019] In step 2, the mass ratio of the porous hard carbon material to cobalt nitrate hexahydrate is 1 to 2:3, and the mass ratio of 2-methylimidazole to cobalt nitrate hexahydrate is 1.5 to 2:1.

[0020] In step 3, the mass ratio of ZIF-67Drived Carbon to sulfur powder is 3:1 to 3.

[0021] In step 4, the ratio of the Co9S8 / C material to deionized water is 0.5-1.5g:50-100mL.

[0022] In step 4, the pH of the solution is adjusted to 9.0 using 33% NaOH.

[0023] In step 4, the mass ratio of dopamine hydrochloride to Co9S8 / C material is 0.5 to 1:4.

[0024] The protective gas is nitrogen.

[0025] A method for preparing a hard carbon anode sheet for sodium-ion batteries includes the following steps: first, the hard carbon anode material for sodium-ion batteries, a conductive agent, and a binder are mixed into a slurry at a mass ratio of 8-9:0.5-1:0.5-1; then, the prepared slurry is uniformly coated onto a copper foil; and after vacuum drying at 80-100°C for 10-12 hours, the hard carbon anode sheet for sodium-ion batteries is obtained.

[0026] The conductive agent is carbon black, and the binder is polyvinylidene fluoride.

[0027] By adopting the above technical solution, the preparation method of hard carbon anode material for sodium-ion batteries of the present invention has the following beneficial effects:

[0028] 1. First, the in-situ generated zeolite imidazole ester skeleton will generate cobalt polysulfide after sulfidation, which is embedded in hard carbon material to obtain a hybrid material of cobalt polysulfide and hard carbon. The material of transition metal sulfide and carbon material hybrid is used as the negative electrode material for sodium-ion batteries. Studies have found that the hybridization of transition metal sulfide and carbon material can effectively prevent particle aggregation and limit volume expansion, which can optimize the battery electrode reaction kinetics, improve the reaction rate, reduce electrochemical impedance, improve battery capacity, and more importantly, improve battery cycle life.

[0029] 2. Secondly, polydopamine hydrochloride undergoes a polymerization reaction on the surface of the Co9S8 / C material to generate a carbon layer precursor polydopamine-coated material. After pyrolysis and carbonization, a carbon layer is formed. The carbon layer formed by pyrolysis greatly alleviates the volume expansion of the electrode material and enables the active sites of Co to be nano-sized and dispersed more uniformly. The carbon layer also makes the material more stable in cycling, and the larger specific surface area can fully contact the electrolyte, thereby improving the reaction rate.

[0030] 3. Finally, the test results of assembling the prepared hard carbon negative electrode sheet into a half cell showed that the battery has good stability, low resistance during charging and discharging, and can significantly improve the battery capacity.

[0031] Therefore, the present invention provides a method for preparing a hard carbon anode material and a hard carbon anode sheet for sodium-ion batteries that is a hybrid of transition metal sulfide and carbon material. The prepared anode material improves the cycle stability and rate performance of the battery. Attached Figure Description

[0032] Figure 1 SEM image of C-Co9S8 / C (3℃) prepared in Example 1;

[0033] Figure 2 The image shows the EDS (energy dispersive spectroscopy) spectrum of C-Co9S8 / C (3℃) prepared in Example 1.

[0034] Figure 3 TEM image of C-Co9S8 / C (3℃) prepared in Example 1;

[0035] Figure 4 The XRD pattern of C-Co9S8 / C (3℃) prepared in Example 1;

[0036] Figure 5 The graph shows a comparison of the cycling performance of C-Co9S8 / C prepared in Examples 1-3.

[0037] Figure 6 The graph shows the cycling performance of C-Co9S8 / C (3℃) prepared in Example 1 at a current density of 10A / g. Detailed Implementation

[0038] To further explain the technical solution of the present invention, the present invention will be described in detail below through specific embodiments.

[0039] 1. Preparation of hard carbon anode material for sodium-ion batteries

[0040] Example 1

[0041] A method for preparing a hard carbon anode material for sodium-ion batteries includes the following steps:

[0042] Step 1: Preparation of porous hard carbon materials:

[0043] First, the buckwheat hull powder is passed through a 200-mesh sieve, placed in a corundum ceramic boat and spread evenly. It is then placed in a tube furnace, and nitrogen is introduced as a protective gas. The furnace is heated to 600°C at a heating rate of 3°C / min and held at that temperature for 2 hours for pyrolysis. After cooling to room temperature, carbon-based materials are obtained.

[0044] The carbon-based material obtained by pyrolysis was then dispersed in 100 mL of 10% KOH solution and stirred for 12 hours. The precipitate was obtained by centrifugation. The precipitate was then washed repeatedly with dilute hydrochloric acid and anhydrous ethanol, and dried at 60°C overnight to obtain porous hard carbon material, denoted as Buckwheat Carbon.

[0045] Step 2: In-situ growth of the zeolite imidazole ester skeleton:

[0046] Then, the 0.5g porous hard carbon material obtained in step 2 was ultrasonically dispersed in 100mL of ethanol solution, and 1.46g of cobalt nitrate hexahydrate was added. After ultrasonication for 20 minutes, 2.19g of 2-methylimidazole was added to the ultrasonicated solution. After stirring at room temperature for 2 hours, the solution was centrifuged and dried at 60℃ to obtain a hard carbon material with a zeolite imidazole ester framework, denoted as ZIF-67DrivedCarbon.

[0047] Step 3, vulcanization:

[0048] Then, the ZIF-67Drived Carbon obtained in step 2 was mixed with sulfur powder at a mass ratio of 3:1 and placed in a tube furnace. Nitrogen gas was introduced as a protective gas and the temperature was raised to 600℃ at 3℃ / min and held for 2 hours. After cooling, a hybrid material of cobalt polysulfide and hard carbon was obtained, which was denoted as Co9S8 / C material (3℃).

[0049] Step 4: Generate carbon layer precursor:

[0050] Then, the 1.0 g Co9S8 / C material obtained in step 3 was ultrasonically dispersed in 100 mL of deionized water, and the pH of the solution was adjusted to 9.0 with 33% NaOH. Then, 0.25 g of dopamine hydrochloride was added, and the mixture was stirred vigorously for 15 min, then stirred for another hour. After centrifugation, the mixture was dried at 60 °C overnight to obtain the Co9S8 / C material coated with carbon layer precursor.

[0051] Step 5, Carbonization:

[0052] Finally, the Co9S8 / C material obtained in step 4 was placed in a corundum ceramic boat and spread out. It was then placed in a tube furnace, and nitrogen was introduced as a protective gas. The temperature was increased to 600°C at 3°C / min, held for 2 hours, and then cooled to room temperature to obtain a hard carbon anode material for sodium-ion batteries, denoted as C-Co9S8 / C (3°C).

[0053] Example 2

[0054] A method for preparing a hard carbon anode material for sodium-ion batteries includes the following steps:

[0055] Step 1: Preparation of porous hard carbon materials:

[0056] First, the buckwheat hull powder is passed through a 200-mesh sieve, placed in a corundum ceramic boat and spread evenly. It is then placed in a tube furnace, and nitrogen is introduced as a protective gas. The furnace is heated to 800°C at a heating rate of 4°C / min and held at that temperature for 2.5 hours for pyrolysis. After cooling to room temperature, carbon-based materials are obtained.

[0057] The carbon-based material obtained by pyrolysis was then dispersed in 100 mL of 10% KOH solution and stirred for 12 hours. The precipitate was obtained by centrifugation. The precipitate was then washed repeatedly with dilute hydrochloric acid and anhydrous ethanol, and dried at 80°C overnight to obtain porous hard carbon material, denoted as Buckwheat Carbon.

[0058] Step 2: In-situ growth of the zeolite imidazole ester skeleton:

[0059] Then, the 0.5g porous hard carbon material obtained in step 2 was ultrasonically dispersed in 100mL of ethanol solution, and 1.5g of cobalt nitrate hexahydrate was added. After ultrasonication for 20 minutes, 3.0g of 2-methylimidazole was added to the ultrasonicated solution. After stirring at room temperature for 2 hours, the solution was centrifuged and dried at 80℃ to obtain a hard carbon material with a zeolite imidazole ester framework, denoted as ZIF-67Drived Carbon.

[0060] Step 3, vulcanization:

[0061] Then, the ZIF-67Drived Carbon obtained in step 2 was mixed with sulfur powder at a mass ratio of 3:2 and placed in a tube furnace. Nitrogen gas was introduced as a protective gas and the temperature was raised to 800℃ at 4℃ / min and held for 2.5 hours. After cooling, a hybrid material of cobalt polysulfide and hard carbon was obtained, which was denoted as Co9S8 / C material (4℃).

[0062] Step 4: Generate carbon layer precursor:

[0063] Then, the 1.0 g Co9S8 / C material obtained in step 3 was ultrasonically dispersed in 100 mL of deionized water, and the pH of the solution was adjusted to 9.0 with 33% NaOH. 0.25 g of dopamine hydrochloride was added, and the mixture was stirred vigorously for 15 min, then stirred for another 1.5 hours. After centrifugation, the mixture was dried at 80 °C overnight to obtain Co9S8 / C coated with carbon layer precursor.

[0064] Step 5, Carbonization:

[0065] Finally, the carbon layer precursor obtained in step 4 was placed in a corundum ceramic boat and spread evenly. It was then placed in a tube furnace, and nitrogen was introduced as a protective gas. The temperature was increased to 800°C at 4°C / min, held for 2 hours, and then cooled to room temperature to obtain the hard carbon anode material for sodium-ion batteries, denoted as C-Co9S8 / C (4°C).

[0066] Example 3

[0067] A method for preparing a hard carbon anode material for sodium-ion batteries includes the following steps:

[0068] Step 1: Preparation of porous hard carbon materials:

[0069] First, the buckwheat hull powder is passed through a 200-mesh sieve, placed in a corundum ceramic boat and spread evenly. It is then placed in a tube furnace, and nitrogen is introduced as a protective gas. The furnace is heated to 800°C at a heating rate of 5°C / min and held at that temperature for 2 hours for pyrolysis. After cooling to room temperature, carbon-based materials are obtained.

[0070] The carbon-based material obtained by pyrolysis was then dispersed in 100 mL of 10% KOH solution and stirred for 10 hours. The precipitate was obtained by centrifugation. The precipitate was then washed repeatedly with dilute hydrochloric acid and anhydrous ethanol, and dried at 60°C overnight to obtain porous hard carbon material, denoted as Buckwheat Carbon.

[0071] Step 2: In-situ growth of zeolite imidazole ester skeleton:

[0072] Then, the 0.5g porous hard carbon material obtained in step 2 was ultrasonically dispersed in 100mL of ethanol solution, and 1.46g of cobalt nitrate hexahydrate was added. After ultrasonication for 20 minutes, 2.19g of 2-methylimidazole was added to the ultrasonicated solution. After stirring at room temperature for 2 hours, the solution was centrifuged and dried at 60℃ to obtain a hard carbon material with a zeolite imidazole ester framework, denoted as ZIF-67DrivedCarbon.

[0073] Step 3, vulcanization:

[0074] Then, the ZIF-67Drived Carbon obtained in step 2 was mixed with sulfur powder at a mass ratio of 1:1 and placed in a tube furnace. Nitrogen gas was introduced as a protective gas and the temperature was raised to 800℃ at 5℃ / min and held for 2 hours. After cooling, a hybrid material of cobalt polysulfide and hard carbon was obtained, which was denoted as Co9S8 / C material (5℃).

[0075] Step 4: Generate carbon layer precursor:

[0076] Then, the 0.5g Co9S8 / C material obtained in step 3 was ultrasonically dispersed in 50mL of deionized water, and the pH of the solution was adjusted to 9.0 with 33% NaOH. Then, 0.125g of dopamine hydrochloride was added, and the mixture was stirred vigorously for 15min, then stirred for 1.5h, centrifuged, and dried at 60℃ overnight to obtain the Co9S8 / C material coated with carbon layer precursor.

[0077] Step 5, Carbonization:

[0078] Finally, the Co9S8 / C material obtained in step 4 was placed in a corundum ceramic boat and spread out. It was then placed in a tube furnace, and nitrogen was introduced as a protective gas. The temperature was increased to 800°C at 5°C / min, held for 2 hours, and then cooled to room temperature to obtain a hard carbon anode material for sodium-ion batteries, denoted as C-Co9S8 / C (5°C).

[0079] Example 4

[0080] A method for preparing a hard carbon negative electrode sheet for sodium-ion batteries includes the following steps: first, a slurry is prepared by mixing hard carbon negative electrode material for sodium-ion batteries, conductive agent carbon black super P, and binder polyvinylidene fluoride in a mass ratio of 8:1:1; then, the prepared slurry is uniformly coated on copper foil; and after vacuum drying at 80°C for 12 hours, the hard carbon negative electrode sheet for sodium-ion batteries is obtained.

[0081] 2. Material Characterization

[0082] Figure 1 This is a SEM image of the C-Co9S8 / C material (3℃) prepared in Example 1. The white particles in the image are Co9S8, with a particle size of approximately 1 μm. Figure 2 The image shows the EDS diagram of the C-Co9S8 / C (3℃) material prepared in Example 1. It can be seen from the image that the distribution of Co, S, and N elements is relatively uniform.

[0083] Figure 3The image shows a TEM image of the C-Co9S8 / C material (3°C) prepared in Example 1. The image clearly shows the carbon layer boundary. The whiter carbon layer was obtained by the pyrolysis of polydopamine hydrochloride. The image also shows the 200 and 511 crystal planes of Co9S8, with interlayer spacings of 0.2437 nm and 0.1892 nm, respectively.

[0084] Figure 4 The image shows the XRD pattern of the material C-Co9S8 / C (3℃) prepared in Example 1. As can be seen from the image, there are two obvious characteristic peaks at 2θ = 29.888 and 2θ = 52.186, which correspond to the peak values ​​of the standard PDF card of Co9S8 (Joint Committee on Powder Diffraction Standards, JCPDS card number) 75-2023.

[0085] 3. Performance Testing

[0086] Figure 5 The graph shows a comparison of the cycle performance of the hard carbon anode materials prepared in Examples 1 to 3. It can be seen from the graph that the hard carbon anode material corresponding to Example 1 has the highest reversible capacity.

[0087] Figure 6 The figure shows the cycling performance of C-Co9S8 / C (3℃) prepared in Example 1 at a current density of 10A / g. As can be seen from the figure, the material can still provide a reversible capacity of 186.15mAh / g after 2000 cycles, and the capacity decay rate per cycle is 0.07%, indicating that the hard carbon anode material has good fast charging potential.

[0088] Therefore, the present invention provides a method for preparing a hard carbon anode material and a hard carbon anode sheet for sodium-ion batteries that is a hybrid of transition metal sulfide and carbon material. The prepared hard carbon anode material improves the cycle stability and rate performance of the battery.

[0089] The above embodiments and figures are not intended to limit the product form and style of the present invention. Any appropriate changes or modifications made by those skilled in the art should be considered as not departing from the patent scope of the present invention.

Claims

1. A method for preparing a hard carbon anode material for sodium-ion batteries, characterized in that: Includes the following steps: Step 1: Preparation of porous hard carbon materials: First, buckwheat hull powder is heated to 600-800℃ at a heating rate of 3-5℃ / min, and then kept at this temperature for 2-3 hours under protective gas to carry out pyrolysis, thereby obtaining carbon-based materials. After soaking and washing with KOH solution, porous hard carbon materials are obtained. Step 2: In-situ growth of zeolite imidazole ester skeleton: Then, the porous hard carbon material obtained in step 2 was ultrasonically dispersed in an ethanol solution of cobalt nitrate hexahydrate. 2-methylimidazole was added to the ultrasonic solution to generate a zeolite imidazole ester framework in situ on the surface of the porous hard carbon material, thus obtaining a hard carbon material with a zeolite imidazole ester framework. Step 3, vulcanization: Then, the hard carbon material with zeolite imidazole ester skeleton obtained in step 2 is mixed evenly with sulfur powder and placed in a tube furnace. Under the protection of protective gas, the temperature is raised to 600-900℃ at 3-5℃ / min and held for 2-3 hours. After cooling, a hybrid material of cobalt polysulfide and hard carbon is obtained. Step 4: Generate carbon layer precursor: Then, the hybrid material of cobalt polysulfide and hard carbon obtained in step 3 was ultrasonically dispersed in deionized water, and the solution was adjusted to weak alkalinity. Dopamine hydrochloride was then added, and a polymerization reaction occurred on the surface of the hybrid material under stirring to generate a polydopamine-coated material. After stirring for 1 to 4 hours, the material was centrifuged and dried at 60 to 80°C overnight to obtain a carbon layer precursor-coated hybrid material of cobalt polysulfide and hard carbon. Step 5, Carbonization: Finally, the hybrid material of cobalt polysulfide and hard carbon obtained in step 4 is placed in a tube furnace and heated to 600-900°C at a rate of 3-5°C / min under protective gas and held for 2-3 hours to obtain the hard carbon anode material for sodium-ion batteries.

2. The method for preparing a hard carbon anode material for sodium-ion batteries according to claim 1, characterized in that: In step 1, the KOH solution soaking and washing process is as follows: the carbon-based material obtained by pyrolysis is dispersed in 100 mL of KOH solution with a mass concentration of 10%, stirred for 10 to 12 hours, centrifuged to obtain precipitate, and then the precipitate is washed repeatedly with dilute hydrochloric acid and anhydrous ethanol, and dried overnight at 60 to 80°C.

3. The method for preparing a hard carbon anode material for sodium-ion batteries according to claim 1, characterized in that: In step 2, the mass ratio of the porous hard carbon material to cobalt nitrate hexahydrate is 1 to 2:3, and the mass ratio of 2-methylimidazole to cobalt nitrate hexahydrate is 1.5 to 2:

1.

4. The method for preparing a hard carbon anode material for sodium-ion batteries according to claim 1, characterized in that: In step 3, the mass ratio of the hard carbon material with the zeolite imidazole ester skeleton to sulfur powder is 3:1 to 3.

5. The method for preparing a hard carbon anode material for sodium-ion batteries according to claim 1, characterized in that: In step 4, the ratio of the cobalt polysulfide-hard carbon hybrid material to deionized water is 0.5-1.5g:50-100mL.

6. The method for preparing a hard carbon anode material for sodium-ion batteries according to claim 1, characterized in that: In step 4, the pH of the solution is adjusted to 9.0 using 33% NaOH.

7. The method for preparing a hard carbon anode material for sodium-ion batteries according to claim 1, characterized in that: In step 4, the mass ratio of the hybrid material of dopamine hydrochloride and cobalt polysulfide to hard carbon is 0.5 to 1:

4.

8. The method for preparing a hard carbon anode material for sodium-ion batteries according to claim 1, characterized in that: The protective gas is nitrogen.

9. A method for preparing a hard carbon negative electrode sheet for a sodium-ion battery, characterized in that: Includes the following steps: First, a slurry is prepared by mixing hard carbon anode material for sodium-ion batteries, conductive agent, and binder in a mass ratio of 8-9:0.5-1:0.5-1. Then, the prepared slurry is uniformly coated on copper foil and vacuum dried at 80-100°C for 10-12 hours to obtain the hard carbon anode sheet for sodium-ion batteries. The hard carbon anode material for sodium-ion batteries is prepared by the preparation method of hard carbon anode material for sodium-ion batteries as described in claim 1.

10. The method for preparing a hard carbon negative electrode sheet for a sodium-ion battery according to claim 9, characterized in that: The conductive agent is carbon black, and the binder is polyvinylidene fluoride.

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