Preparation method for regulating micro-pore structure of hard carbon negative electrode material and application

Abstract

The application relates to a preparation method and application of a hard carbon negative electrode material micro-pore structure regulator. The preparation method comprises the following steps: placing a hard carbon precursor material in a closed reactor to perform a preliminary reaction to obtain a pre-product, wherein the filling degree of the hard carbon precursor material in the closed reactor is greater than or equal to 40%; when the filling degree is 40%, the temperature of the preliminary reaction is 350 DEG C-450 DEG C, and when the filling degree increases by 5%, the temperature of the preliminary reaction is relatively reduced by 20 DEG C-25 DEG C; and the pre-product is sequentially subjected to a first carbonization treatment and a second carbonization treatment under a protective atmosphere to obtain a hard carbon negative electrode material. The application provides a simpler preparation method, and the prepared hard carbon negative electrode material has rich closed nano-pore structure, so that the sodium storage performance of the negative electrode material is improved.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery energy storage technology, and in particular to a method for preparing and applying a hard carbon anode material with controlled micropore structure. Background Technology

[0002] Sodium-ion batteries have shown broad application prospects in the energy storage field due to their advantages such as low cost, low temperature operation, and good rate performance. Hard carbon, with its interlocking layered structure and pores formed by the disordered stacking of some carbon layers, can store sodium ions at low potentials, making it the primary choice for anode materials in sodium-ion batteries. However, the microstructure of hard carbon is very complex, composed of a large number of graphite microcrystals and amorphous nanodomains. + These graphite microcrystals cannot form stable compounds, resulting in poor sodium storage performance and low specific capacity, which greatly limits their commercial application.

[0003] To improve the sodium storage performance of hard carbon, structural defects can be created to provide more sodium adsorption sites in the high-pressure region (>0.1V), thereby increasing the ramp capacity and ultimately the total capacity of the hard carbon. However, this reduces the initial coulombic efficiency of the hard carbon. In the low-pressure region (<0.1V), sodium ions, in addition to intercalating in the graphite microcrystalline layer, also form a large number of quasi-metallic clusters by filling closed nanopores, which greatly improves the sodium storage performance of hard carbon in the plateau stage. Therefore, precisely controlling the pore structure to form more closed nanopore structures is beneficial for preparing hard carbon anodes with large plateau capacities. However, traditional template methods and chemical activation methods require acid-base washing to remove templates and impurities, which not only causes the hard carbon structure to collapse but also increases the preparation cost due to the complexity of subsequent processing. Summary of the Invention

[0004] Based on this, it is necessary to provide a preparation method and application for regulating the micropore structure of hard carbon anode materials to address the above problems. This invention proposes a simpler preparation method that enables the prepared hard carbon anode material to have a rich closed pore structure, thereby improving the sodium storage performance of the anode material.

[0005] A method for preparing a hard carbon anode material with controlled micropore structure includes the following steps:

[0006] Hard carbon precursor material is placed in a closed reactor for preliminary reaction to obtain a pre-product. The hard carbon precursor material is filled to a degree greater than or equal to 40% in the closed reactor. When the filling degree is 40%, the temperature of the preliminary reaction is 350℃-450℃. For every 5% increase in filling degree, the temperature of the preliminary reaction decreases by 20℃-25℃.

[0007] Under a protective atmosphere, the preproduct is subjected to a first carbonization treatment and a second carbonization treatment in sequence to obtain a hard carbon anode material.

[0008] In one embodiment, the hard carbon precursor material is filled to a density of 50%-90% in the closed reactor.

[0009] In one embodiment, the change in the fill degree of the reactants before and after the reaction in the closed reactor is 5%-10%.

[0010] In one embodiment, the hard carbon precursor material includes at least one of sugar-based materials, bio-based materials, and resin-based materials.

[0011] In one embodiment, the initial reaction temperature is 150℃-500℃, the heating rate is 1℃ / min-10℃ / min, and the holding time is 60min-600min.

[0012] In one embodiment, the temperature of the first carbonization treatment is 500℃-700℃, the heating rate is 1℃ / min-10℃ / min, and the holding time is less than or equal to 180min.

[0013] In one embodiment, the temperature of the second carbonization treatment is 1000℃-1500℃, the heating rate is 1℃ / min-5℃ / min, and the holding time is less than or equal to 180min.

[0014] A hard carbon anode material prepared by the method described above for controlling the micropore structure of hard carbon anode materials, wherein the volume of the closed nanopores in the hard carbon anode material is 0.1 cm³. 3 / g-0.5cm 3 / g.

[0015] In one embodiment, the volume of the closed nanopores in the hard carbon anode material is 0.15 cm³. 3 / g-0.4cm 3 / g.

[0016] A hard carbon anode material as described above is used in sodium-ion batteries.

[0017] The preparation method of this invention involves a preliminary reaction of a hard carbon precursor material with a filling degree of 40% or higher in a closed reactor without liquid. This causes the hard carbon precursor material to expand under restricted conditions and decompose, releasing gases such as carbon dioxide, methane, carbon monoxide, hydrogen, ammonia, and water vapor. The filling degree of the hard carbon precursor material in the closed reactor and the temperature of the preliminary reaction are synergistically controlled to create a specific high-pressure environment in the limited reaction space. This restricts the expansion of the precursor, causing local contraction and shrinkage between molecular layers. This promotes the formation of abundant closed pore structures, thereby precisely controlling the microstructure of the hard carbon material. Furthermore, the concentrated high-pressure gas molecules can create cavities between the restricted molecular layers through thermal motion, which is beneficial for the material to generate more micropores and closed nanopore structures during the later carbonization process, thereby improving the sodium storage performance of the hard carbon material. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a scanning electron microscope image of the hard carbon anode material prepared in Example 3 of the present invention;

[0020] Figure 2 This is a scanning electron microscope image of the hard carbon anode material prepared in Example 5 of the present invention;

[0021] Figure 3 This is a scanning electron microscope image of the hard carbon anode material prepared in Example 7 of the present invention;

[0022] Figure 4 This is a scanning electron microscope image of the hard carbon anode material prepared in Comparative Example 1 of the present invention.

[0023] Figure 5 This is a scanning electron microscope image of the hard carbon anode material prepared in Comparative Example 2 of the present invention.

[0024] Figure 6 This is a scanning electron microscope image of the hard carbon anode material prepared in Comparative Example 3 of the present invention.

[0025] Figure 7 The first charge-discharge curve of a sodium-ion battery prepared using the hard carbon anode material of Example 3 of this invention is shown.

[0026] Figure 8 The first charge-discharge curve of a sodium-ion battery prepared using the hard carbon anode material of Example 5 of this invention is shown.

[0027] Figure 9 The first charge-discharge curve of a sodium-ion battery prepared using the hard carbon anode material of Example 7 of this invention is shown.

[0028] Figure 10 The first charge-discharge curve of a sodium-ion battery prepared using the hard carbon anode material of Comparative Example 1 of this invention is shown.

[0029] Figure 11 The first charge-discharge curve of a sodium-ion battery prepared using the hard carbon anode material of Comparative Example 2 of this invention is shown.

[0030] Figure 12 The image shows the first charge-discharge curve of a sodium-ion battery prepared using the hard carbon anode material of Comparative Example 3 of this invention. Detailed Implementation

[0031] To facilitate understanding of the present invention, it will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. Rather, these embodiments or examples are provided to make the disclosure of the present invention more thorough and complete.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments or examples only and is not intended to limit the invention. The optional scope of the term "and / or" as used herein includes any one of two or more of the related listed items, as well as any and all combinations of the related listed items, including any two related listed items, any more related listed items, or a combination of all related listed items.

[0033] This invention provides a method for preparing a hard carbon anode material with controlled micropore structure, comprising the following steps:

[0034] S1, the hard carbon precursor material is placed in a closed reactor for preliminary reaction to obtain a pre-product, wherein the hard carbon precursor material is filled to a degree greater than or equal to 40% in the closed reactor, and when the filling degree is 40%, the temperature of the preliminary reaction is 350℃-450℃, and for every 5% increase in the filling degree, the temperature of the preliminary reaction decreases by 20℃-25℃.

[0035] S2, under a protective atmosphere, the preproduct is subjected to a first carbonization treatment and a second carbonization treatment in sequence to obtain the hard carbon anode material.

[0036] During the carbonization of hard carbon precursor materials, pyrolysis occurs, leading to structural reorganization and gas generation. This alters the distance between molecules / atoms, increasing internal stress and causing volume expansion. This results in an open porous structure, which is detrimental to sodium ion storage. Traditional hydrothermal / solvothermal methods, using liquid solvents such as ethanol and water, can increase the cross-linking degree between raw material molecules, mitigating volume expansion to some extent. However, the vaporization of these liquids generates gases that overflow into the precursor material, forming open porous structures, which are also unfavorable for sodium ion storage.

[0037] This invention involves a preliminary reaction of a hard carbon precursor material with a filling density of 40% or higher in a closed reactor. Upon heating, the precursor material expands and decomposes, releasing gases (carbon dioxide, methane, carbon monoxide, hydrogen, ammonia, and water vapor, etc.). However, due to space constraints, the expansion of the precursor is limited, leading to localized contraction at both the macroscopic and microscopic levels. Furthermore, under high temperature and pressure, the molecular layers of the precursor further contract, thus regulating the microstructure of the material. Simultaneously, the concentrated high-pressure gas molecules, through thermal motion, can create cavities between the confined molecular layers. This results in a tendency for the material to develop more micropores and closed nanopore structures during subsequent carbonization, which is beneficial for improving the sodium storage performance of the hard carbon material.

[0038] In step S1, preferably, the hard carbon precursor material is filled to 50%-90% in the closed reactor, including any one of 50%, 60%, 70%, 80%, 90%, or any range between two.

[0039] Preferably, the change in the fill degree of the reactants before and after the reaction in the closed reactor is 5%-10%, including any one of 5%, 6%, 7%, 8%, 9%, 10%, or any range between two.

[0040] In one embodiment, the hard carbon precursor material includes, but is not limited to, at least one of sugar materials, bio-based materials, and resin-based materials. Specifically, the sugar material is preferably starch, the bio-based material is preferably biomass coconut shell powder, and the resin-based material is preferably synthetic formaldehyde-resorcinol phenolic resin powder.

[0041] In one embodiment, the initial reaction temperature is 150℃-500℃, the heating rate is 1℃ / min-10℃ / min, and the holding time is 60min-600min.

[0042] In one embodiment, after the preliminary reaction, a particle size screening step is further included to make the particle size of the preproduct 2μm-80μm.

[0043] In step S2, the preproduct with a specific preset pore structure is subjected to a two-step carbonization treatment. Preferably, the temperature of the second carbonization treatment is higher than that of the first carbonization treatment, which is more conducive to promoting the preset pore structure to form more closed nanopore structures during the gradual carbonization process, thereby improving the sodium storage performance of the hard carbon material.

[0044] In one embodiment, the temperature of the first carbonization treatment is 500℃-700℃, the heating rate is 1℃ / min-10℃ / min, and the holding time is less than or equal to 180min.

[0045] In one embodiment, after the first carbonization treatment, a particle size screening step is further included to make the particle size of the product 2μm-50μm.

[0046] In one embodiment, the temperature of the second carbonization treatment is 1000℃-1500℃, the heating rate is 1℃ / min-5℃ / min, and the holding time is less than or equal to 180min.

[0047] In one embodiment, the protective atmosphere includes, but is not limited to, at least one of nitrogen and argon.

[0048] This invention provides a hard carbon anode material prepared by the method described above for controlling the micropore structure of hard carbon anode materials, wherein the volume of the closed nanopores in the hard carbon anode material is 0.1 cm³. 3 / g-0.5cm 3 / g, preferably 0.15cm 3 / g-0.4cm 3 / g.

[0049] The present invention also provides a hard carbon anode material as described above for use in a sodium-ion battery. It is understood that the sodium-ion battery includes a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the negative electrode uses the aforementioned hard carbon anode material as the active material.

[0050] It should be noted that this invention does not limit the preparation method of the negative electrode sheet; conventional processes can be used. For example, the above-mentioned hard carbon negative electrode material, conductive agent, and binder are mixed in a mass ratio of 80:10:10-94:3:3 to form a slurry, which is then coated onto the current collector and dried. The conductive agent includes conductive carbon black, acetylene black, graphite powder, Ketjen black, etc., with conductive carbon black being preferred. The binder includes, but is not limited to, at least one of sodium carboxymethyl cellulose, sodium alginate, and polyvinylidene fluoride, with sodium carboxymethyl cellulose being preferred. Water is preferred as the solvent used to prepare the slurry. The current collector includes copper foil or aluminum foil, and the drying temperature is 60℃-120℃, with a drying time of 1h-20h.

[0051] Specifically, the electrolyte includes a sodium salt and a non-aqueous solvent. The sodium salt includes, but is not limited to, at least one of NaPF6 and NaClO4, preferably NaPF6. The non-aqueous solvent includes, but is not limited to, at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate and diethyl carbonate, preferably a mixture of diethyl carbonate and ethylene carbonate.

[0052] The following specific embodiments will further illustrate the preparation method and application of the modified hard carbon anode material microstructure. However, those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified, specific conditions in the embodiments were performed under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0053] Example 1

[0054] Starch was used as a precursor material for hard carbon. It was placed in a high-pressure reactor and the starch filling degree in the reactor was controlled to be 40%. The reactor was sealed and heated to 450℃ at a heating rate of 5℃ / min. After holding at the temperature for 300min, it was cooled to room temperature. The resulting material was passed through a 100-mesh sieve to obtain the pretreated product.

[0055] The pretreated product was heated to 500℃ for 120 min at a heating rate of 5℃ / min under a nitrogen protective atmosphere, then cooled to room temperature and ground through a 400-mesh sieve. Then, under a nitrogen protective atmosphere, the temperature was further increased to 1400℃ for 120 min at a heating rate of 2℃ / min, and then cooled to room temperature to obtain the regulated hard carbon anode material.

[0056] Example 2

[0057] Starch was used as a precursor material for hard carbon. It was placed in a high-pressure reactor and the starch filling degree in the high-pressure reactor was controlled to be 70%. The reactor was sealed and heated to 300℃ at a heating rate of 5℃ / min. After holding at the temperature for 300min, it was cooled to room temperature. The resulting material was passed through a 100-mesh sieve to obtain the pretreated product.

[0058] The pretreated product was heated to 500℃ for 120 min at a heating rate of 10℃ / min under a nitrogen protective atmosphere, then cooled to room temperature and ground through a 400-mesh sieve. Then, under a nitrogen protective atmosphere, the temperature was further increased to 1400℃ for 120 min at a heating rate of 2℃ / min, and then cooled to room temperature to obtain the regulated hard carbon anode material.

[0059] Example 3

[0060] Starch was used as a precursor material for hard carbon. It was placed in a high-pressure reactor and the starch filling degree in the high-pressure reactor was controlled to be 100%. The reactor was sealed and heated to 200℃ at a heating rate of 5℃ / min. After holding at the temperature for 300min, it was cooled to room temperature. The resulting material was passed through a 100-mesh sieve to obtain the pretreated product.

[0061] The pretreated product was heated to 500℃ for 120 min at a heating rate of 10℃ / min under a nitrogen protective atmosphere, then cooled to room temperature and ground through a 400-mesh sieve. Then, under a nitrogen protective atmosphere, the temperature was further increased to 1400℃ for 120 min at a heating rate of 2℃ / min, and then cooled to room temperature to obtain the regulated hard carbon anode material.

[0062] Example 4

[0063] Biomass coconut shell powder was used as a hard carbon precursor material and placed in a high-pressure reactor. The filling degree of biomass coconut shell powder in the high-pressure reactor was controlled to be 60%. The reactor was sealed and heated to 400℃ at a heating rate of 5℃ / min and held for 300min. After cooling to room temperature, the resulting material was passed through a 100-mesh sieve to obtain the pretreated product.

[0064] The pretreated product was heated to 600℃ for 120 min at a heating rate of 10℃ / min under a nitrogen protective atmosphere, then cooled to room temperature and ground through a 400-mesh sieve. Then, under a nitrogen protective atmosphere, the temperature was further increased to 1400℃ for 120 min at a heating rate of 2℃ / min, and then cooled to room temperature to obtain the regulated hard carbon anode material.

[0065] Example 5

[0066] Biomass coconut shell powder was used as a hard carbon precursor material and placed in a high-pressure reactor. The filling degree of biomass coconut shell powder in the high-pressure reactor was controlled to be 80%. The reactor was sealed and heated to 300℃ at a heating rate of 5℃ / min and held for 300min. After cooling to room temperature, the resulting material was passed through a 100-mesh sieve to obtain the pretreated product.

[0067] The pretreated product was heated to 600℃ for 120 min at a heating rate of 10℃ / min under a nitrogen protective atmosphere, then cooled to room temperature and ground through a 400-mesh sieve. Then, under a nitrogen protective atmosphere, the temperature was further increased to 1400℃ for 120 min at a heating rate of 2℃ / min, and then cooled to room temperature to obtain the regulated hard carbon anode material.

[0068] Example 6

[0069] Phenolic resin powder was used as a hard carbon precursor material and placed in a high-pressure reactor. The filling degree of phenolic resin powder in the high-pressure reactor was controlled to be 60%. The reactor was sealed and heated to 380℃ at a heating rate of 5℃ / min. After holding at the temperature for 300min, the temperature was cooled to room temperature. The resulting material was passed through a 100-mesh sieve to obtain the pretreated product.

[0070] The pretreated product was heated to 700℃ for 120 min at a heating rate of 10℃ / min under a nitrogen protective atmosphere, then cooled to room temperature and ground through a 400-mesh sieve. Then, under a nitrogen protective atmosphere, the temperature was further increased to 1400℃ for 120 min at a heating rate of 2℃ / min, and then cooled to room temperature to obtain the regulated hard carbon anode material.

[0071] Example 7

[0072] Phenolic resin powder was used as a hard carbon precursor material and placed in a high-pressure reactor. The filling degree of phenolic resin powder in the high-pressure reactor was controlled to be 90%. The reactor was sealed and heated to 250°C at a heating rate of 5°C / min and held for 300 min. After cooling to room temperature, the resulting material was passed through a 100-mesh sieve to obtain the pretreated product.

[0073] The pretreated product was heated to 700℃ for 120 min at a heating rate of 10℃ / min under a nitrogen protective atmosphere, then cooled to room temperature and ground through a 400-mesh sieve. Then, under a nitrogen protective atmosphere, the temperature was further increased to 1400℃ for 120 min at a heating rate of 2℃ / min, and then cooled to room temperature to obtain the regulated hard carbon anode material.

[0074] Comparative Example 1

[0075] The difference between Comparative Example 1 and Example 3 is that the starch was placed in a crucible, heated to 200°C at a heating rate of 5°C / min and held for 300 min, then cooled to room temperature, and the resulting material was passed through a 100-mesh sieve to obtain the pretreated product.

[0076] The pretreated product was heated to 500℃ for 120 min at a heating rate of 5℃ / min under a nitrogen protective atmosphere, then cooled to room temperature and ground through a 400-mesh sieve. Then, under a nitrogen protective atmosphere, the temperature was further increased to 1400℃ at a heating rate of 2℃ / min and held for 120 min, then cooled to room temperature to obtain the hard carbon anode material.

[0077] Comparative Example 2

[0078] The difference between Comparative Example 2 and Example 5 is that the biomass coconut shell powder was placed in a crucible, heated to 300°C at a heating rate of 5°C / min and held for 300 min, then cooled to room temperature, and the resulting material was passed through a 100-mesh sieve to obtain the pretreated product.

[0079] The pretreated product was heated to 600℃ for 120 min at a heating rate of 5℃ / min under a nitrogen protective atmosphere, then cooled to room temperature and ground through a 400-mesh sieve. Then, under a nitrogen protective atmosphere, the temperature was further increased to 1400℃ for 120 min at a heating rate of 2℃ / min, and then cooled to room temperature to obtain the hard carbon anode material.

[0080] Comparative Example 3

[0081] The difference between Comparative Example 3 and Example 7 is that the phenolic resin powder was placed in a crucible, heated to 250°C at a heating rate of 5°C / min and held for 300 min, then cooled to room temperature, and the resulting material was passed through a 100-mesh sieve to obtain the pretreated product.

[0082] The pretreated product was heated to 700℃ for 120 min at a heating rate of 5℃ / min under a nitrogen protective atmosphere, then cooled to room temperature and ground through a 400-mesh sieve. Then, under a nitrogen protective atmosphere, the temperature was further increased to 1400℃ at a heating rate of 2℃ / min and held for 120 min, then cooled to room temperature to obtain the hard carbon anode material.

[0083] Comparative Example 4

[0084] The difference between Comparative Example 4 and Example 3 is that the starch filling degree in the high-pressure reactor is 20%. After heating to 500°C at a heating rate of 5°C / min and holding for 300min, the mixture is cooled to room temperature, and the resulting material is passed through a 100-mesh sieve to obtain the pretreated product.

[0085] The pretreated product was heated to 500℃ for 120 min at a heating rate of 5℃ / min under a nitrogen protective atmosphere, then cooled to room temperature and ground through a 400-mesh sieve. Then, under a nitrogen protective atmosphere, the temperature was further increased to 1400℃ at a heating rate of 2℃ / min and held for 120 min, then cooled to room temperature to obtain the hard carbon anode material.

[0086] The porous hard carbon anode materials prepared in Examples 3, 5, and 7 and Comparative Examples 1, 2, and 3 were characterized in morphology, and the results are as follows: Figure 1-6 As shown in Table 1, the porous hard carbon anode materials prepared in Examples 1-7 and Comparative Examples 1-4 were subjected to true density and performance tests. The test results are shown in Table 1 and 2. Figure 7-12 As shown.

[0087] (1) The volume of the closed nanopores can be calculated by measuring the true density of hard carbon using the formula:

[0088]

[0089] Among them, 2.26cm 3 / g represents the true density of ideal graphite.

[0090] (2) Performance Testing: Weigh 450 mg of hard carbon anode material, 25 mg of conductive carbon black, and 20 mg of carboxymethyl cellulose. Add an appropriate amount of deionized water and ball mill for 2 hours using a planetary ball mill. Coat the ball-milled slurry onto the current collector, vacuum dry at 80°C for 12 hours, and then cut it into anode sheets with a diameter of 12 mm. Use metallic sodium as the counter electrode and reference electrode. Select glass fiber membrane as the separator. Use 1 mol / L NaPF6 as the electrolyte and a mixed solution of diethyl carbonate and ethylene carbonate (volume ratio 1:1) as the solvent. Assemble coin cells in a glove box under an argon atmosphere. Perform electrochemical performance testing on the prepared coin cells using the Xinwei Battery Testing System. The charge / discharge voltage range is 0–2 V, the current density is 0.5 C, and 1 C = 100 mA / g.

[0091] Table 1

[0092]

[0093] The above examples demonstrate that the porous hard carbon anode material prepared by the method provided by this invention can give sodium-ion batteries better electrochemical performance.

[0094] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0095] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a hard carbon anode material with controlled micropore structure, characterized in that, Includes the following steps: Hard carbon precursor material is placed in a closed reactor for preliminary reaction to obtain a pre-product. The hard carbon precursor material is filled to a degree greater than or equal to 40% in the closed reactor. When the filling degree is 40%, the temperature of the preliminary reaction is 350℃-450℃. For every 5% increase in filling degree, the temperature of the preliminary reaction decreases by 20℃-25℃. Under a protective atmosphere, the preproduct was subjected to a first carbonization treatment and a second carbonization treatment sequentially to obtain a hard carbon anode material, wherein the volume of the closed nanopores in the hard carbon anode material is 0.1 cm³. 3 / g-0.5cm 3 / g.

2. The preparation method for regulating the micropore structure of hard carbon anode material according to claim 1, characterized in that, The hard carbon precursor material is filled to a density of 50%-90% in the closed reactor.

3. The preparation method for regulating the micropore structure of hard carbon anode material according to claim 1, characterized in that, The change in the fill degree of the reactants before and after the reaction in a closed reactor is 5%-10%.

4. The method for preparing a hard carbon anode material with controlled micropore structure according to any one of claims 1-3, characterized in that, The hard carbon precursor material includes at least one of sugar-based materials, bio-based materials, and resin-based materials.

5. The method for preparing a hard carbon anode material with controlled micropore structure according to any one of claims 1-3, characterized in that, The initial reaction temperature is 150℃-500℃, the heating rate is 1℃ / min-10℃ / min, and the holding time is 60min-600min.

6. The method for preparing a hard carbon anode material with controlled micropore structure according to any one of claims 1-3, characterized in that, The temperature of the first carbonization treatment is 500℃-700℃, the heating rate is 1℃ / min-10℃ / min, and the holding time is less than or equal to 180min.

7. The method for preparing a hard carbon anode material with controlled micropore structure according to any one of claims 1-3, characterized in that, The second carbonization treatment is carried out at a temperature of 1000℃-1500℃, with a heating rate of 1℃ / min-5℃ / min and a holding time of less than or equal to 180min.

8. A hard carbon anode material prepared by the method for controlling the micropore structure of the hard carbon anode material as described in any one of claims 1-7, characterized in that, The volume of the closed nanopores in the prepared hard carbon anode material is 0.1 cm³. 3 / g-0.5cm 3 / g.

9. The hard carbon anode material according to claim 8, characterized in that, The volume of the closed nanopores in the hard carbon anode material is 0.15 cm³. 3 / g-0.4cm 3 / g.

10. A hard carbon anode material as described in claim 8 or 9 for use in a sodium-ion battery.

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