Asphalt-based hard carbon, preparation method thereof and sodium ion battery negative electrode material

Abstract

The invention discloses asphalt-based hard carbon, a preparation method thereof and a sodium-ion battery negative electrode material, and relates to the technical field of sodium-ion batteries. The preparation method of the asphalt-based hard carbon comprises the following steps: S1, mixing an asphalt precursor, a sulfur source and a cross-linking agent, and performing cross-linking vulcanization treatment at a first temperature to obtain a primary product; s2, performing carbonization treatment on the primary product at a second temperature to obtain asphalt-based hard carbon; the sulfur source is any one of elemental sulfur, thiourea, dimethyl sulfide and sulfide, or any two of elemental sulfur, concentrated sulfuric acid, thiourea, dimethyl sulfide and sulfide. By adopting the method, the type of the sulfur source is controlled, and the sulfur source and the cross-linking agent are added, so that the reversible capacity and the rate capability of the asphalt-based negative electrode material can be effectively improved, and the application field of the asphalt-based negative electrode material is widened.

Description

Technical Field

[0001] This application relates to the field of sodium-ion battery technology, and more specifically, to an asphalt-based hard carbon, its preparation method, and a sodium-ion battery anode material. Background Technology

[0002] Fossil fuels, such as coal, oil, and natural gas, have long been the mainstay of global energy supply, supporting all aspects of industrial development and human life. However, the finite nature of fossil fuels and the severe environmental impact of their extraction and use have prompted the energy sector to seek more sustainable alternatives. Renewable energy sources, however, are limited by the natural environment, exhibiting randomness, volatility, and intermittency, making it impossible to maintain stable power output. Therefore, developing efficient and convenient large-scale energy storage technologies has become a major technical challenge in the utilization and development of renewable energy. Lithium-ion batteries, among electrochemical energy storage technologies, are considered one of the most promising technologies due to their high energy density, long lifespan, and environmental friendliness. However, the limited reserves and uneven distribution of lithium resources restrict the development of lithium-ion batteries for large-scale energy storage. Sodium-ion batteries, a type of secondary battery that uses sodium ions as a metal ion carrier, operate on a similar principle to lithium-ion batteries. They offer advantages such as abundant sodium resources, low price, high safety, excellent high and low temperature performance, and compatibility with existing lithium-ion battery devices.

[0003] Because sodium ions are larger than lithium ions, graphite, a commonly used anode material in lithium-ion batteries, has limited ability to insert and extract sodium ions. Hard carbon materials, on the other hand, have large interlayer spacing and good conductivity, resulting in high sodium storage capacity, making them suitable as anode materials for sodium-ion batteries. However, their precursors are usually quite expensive, making them unsuitable for large-scale production.

[0004] Asphalt, with its high yield, low cost, and high carbon production rate, is an excellent precursor for preparing carbon materials for sodium-ion battery anodes. However, its carbon materials exhibit soft carbon properties, resulting in low reversible capacity and poor rate performance. Therefore, how to modify asphalt to produce carbon materials with a hard carbon structure and further improve their reversible capacity and rate performance is a problem worthy of research. Summary of the Invention

[0005] The main objective of this application is to provide a pitch-based hard carbon, its preparation method, and a sodium-ion battery anode material, in order to solve the problems of low reversible capacity and poor rate performance of pitch-based hard carbon in the prior art.

[0006] To achieve the above objectives, according to a first aspect of this application, a method for preparing pitch-based hard carbon is provided, comprising the following steps:

[0007] S1, mix asphalt precursor, sulfur source and crosslinking agent, and perform crosslinking vulcanization treatment at the first temperature to obtain primary product;

[0008] S2, the primary product is carbonized at a second temperature to obtain pitch-based hard carbon;

[0009] The sulfur source can be any one of elemental sulfur, thiourea, dimethyl sulfide, or sulfides, or any two of elemental sulfur, concentrated sulfuric acid, thiourea, dimethyl sulfide, or sulfides.

[0010] Furthermore, the sulfur source can be any two of elemental sulfur, concentrated sulfuric acid, thiourea, dimethyl sulfide, or sulfides.

[0011] Furthermore, the sulfide is at least one of boron sulfide, zinc sulfide, and sodium sulfide.

[0012] Furthermore, the sulfur source is a mixture of concentrated sulfuric acid and elemental sulfur, wherein the mass ratio of concentrated sulfuric acid to elemental sulfur in the mixture is 1:(1~5).

[0013] Furthermore, the crosslinking agent is at least one of benzyl dimethyl alcohol, terephthalaldehyde, benzaldehyde, and paraformaldehyde.

[0014] Furthermore, the crosslinking agent is a compound of terephthalic acid and benzaldehyde, wherein the mass ratio of terephthalic acid to benzaldehyde in the compound is (1~5):1.

[0015] Furthermore, the mass ratio of the asphalt precursor, sulfur source, and crosslinking agent is 1:(1~9):(1~9).

[0016] Furthermore, the first temperature is 100℃~500℃, and the crosslinking vulcanization treatment time is 0.5h~48h; the second temperature is 1200℃~1600℃, and the carbonization treatment time is 0.5h~48h. The crosslinking vulcanization treatment and the carbonization treatment are carried out independently under nitrogen or inert atmosphere.

[0017] Furthermore, the asphalt precursor is at least one of coal tar pitch, petroleum pitch, coal liquefaction pitch, ethylene tar pitch, and natural pitch.

[0018] According to a second aspect of this application, a pitch-based hard carbon is provided, which is prepared by the preparation method of the first aspect of this application.

[0019] According to a third aspect of this application, a sodium-ion battery anode material is provided, comprising pitch-based hard carbon according to the second aspect of this application.

[0020] By applying the technical solution of this application and performing cross-linking vulcanization treatment, a more complex network structure is formed between asphalt molecules, increasing the porosity and carbon interlayer spacing of the material, thereby significantly improving the sodium storage capacity. Adding a sulfur source also helps to form more active sites suitable for sodium ion storage, while the cross-linking agent promotes the stability and conductivity of the material structure, enabling the prepared hard carbon material to exhibit superior reversible capacity and rate performance in sodium-ion battery applications. Furthermore, compared with traditional asphalt-based hard carbon preparation methods such as oxidative pyrolysis and template pyrolysis, this method is simpler, has better performance, and is more cost-effective. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0022] As described in the background section of this application, existing technologies suffer from low reversible capacity and poor rate performance in carbon materials prepared from pitch. To address these technical problems, this application provides a method for preparing pitch-based hard carbon in a typical embodiment, comprising the following steps:

[0023] S1, mix asphalt precursor, sulfur source and crosslinking agent, and perform crosslinking vulcanization treatment at the first temperature to obtain primary product;

[0024] S2, the primary product is carbonized at a second temperature to obtain pitch-based hard carbon;

[0025] The sulfur source can be any one of elemental sulfur, thiourea, dimethyl sulfide, or sulfides, or any two of elemental sulfur, concentrated sulfuric acid, thiourea, dimethyl sulfide, or sulfides.

[0026] Cross-linking and vulcanization treatment creates a more complex and looser network structure within the asphalt molecules, which increases the interlayer spacing of asphalt-based hard carbon materials. This provides more space for sodium ion insertion, significantly improving sodium storage capacity. Furthermore, cross-linking and vulcanization treatment generates more micropores and mesopores in the carbon material, increasing the specific surface area and improving the diffusion rate and electrochemical reactivity of sodium ions, thus enhancing the rate performance of asphalt-based hard carbon materials. In addition, the introduction of sulfur can form sulfur-containing functional groups or defects after carbonization, providing additional active sites for sodium ion storage, thereby improving the material's sodium storage performance and cycle stability. The aforementioned sulfur sources promote pore formation, providing more space and pathways for sodium ion insertion and extraction, thus improving the material's sodium storage capacity and rate performance.

[0027] In some embodiments, the sulfur source is any two of elemental sulfur, concentrated sulfuric acid, thiourea, dimethyl sulfide, and sulfides. The sulfide can be boron sulfide, zinc sulfide, sodium sulfide, etc., and is not specifically limited here.

[0028] Different sulfur sources can produce different chemical reactions with asphalt and crosslinking agents during the crosslinking and vulcanization process, forming intermediates with specific properties. When two sulfur sources are used in combination, they can work synergistically to promote the formation of larger carbon interlayer spacing and more complex pore structures in carbon materials, providing a more suitable environment for the insertion and extraction of sodium ions, and significantly improving the sodium storage capacity and rate performance of carbon materials.

[0029] In some embodiments, the sulfur source is a mixture of concentrated sulfuric acid and elemental sulfur, wherein the mass ratio of concentrated sulfuric acid to elemental sulfur in the mixture is 1:(1~5).

[0030] In the description of this application, concentrated sulfuric acid is a sulfuric acid solution with a mass fraction of 95%~98% H2SO4. Concentrated sulfuric acid acts as a catalyst, which is beneficial to promoting the cross-linking reaction and also has the effect of sulfur doping. Elemental sulfur has the effect of cross-linking and also has the effect of sulfur doping. Combining concentrated sulfuric acid and elemental sulfur can synergistically improve the preparation rate, enhance the sodium storage capacity and rate performance of pitch-based hard carbon, and compared with conventional preparation methods that use concentrated sulfuric acid as a sulfur source, the amount of concentrated sulfuric acid used is less and the experimental safety is relatively high.

[0031] In some embodiments, the crosslinking agent is at least one of benzyl dimethyl alcohol, terephthalaldehyde, benzaldehyde, and paraformaldehyde.

[0032] The aforementioned crosslinking agent can chemically react with molecules in the asphalt precursor to form covalent bonds, thereby constructing a three-dimensional network structure. This helps enhance the structural stability of asphalt-based hard carbon, reduce shrinkage and structural collapse during heat treatment, and improve the material's mechanical strength. Furthermore, the crosslinking agent and the sulfur source can jointly promote the formation of a conductive network within the material, improving the electronic conductivity of the asphalt-based hard carbon. Good conductivity is a key factor in ensuring battery rate performance and cycle stability.

[0033] Specifically, but not limitingly, paraformaldehyde with a degree of polymerization of 8–100, or 8–20, reacts more readily with functional groups in the asphalt precursor to form uniform and widely distributed crosslinking points. This helps establish a dense crosslinked network structure in the primary product, promoting pore formation. When the degree of polymerization is 20–100, it helps construct a more complex three-dimensional network, enhancing the material's mechanical strength and stability. When the degree of polymerization meets these requirements, asphalt-based hard carbon exhibits both good stability and sodium storage capacity.

[0034] In some embodiments, the crosslinking agent is a mixture of terephthalic acid and benzaldehyde, wherein the mass ratio of terephthalic acid to benzaldehyde in the mixture is (1~5):1.

[0035] When the crosslinking agent is a mixture of terephthalic acid and benzaldehyde, on the one hand, the excellent crosslinking properties of terephthalic acid are utilized to link asphalt molecules together, forming a crosslinked network structure with good sodium storage capacity and electronic conductivity; on the other hand, the micropore-forming property of benzaldehyde during high-temperature pyrolysis is utilized to regulate the microstructure of asphalt-based hard carbon, resulting in better rate performance. By selecting a mixture of terephthalic acid and benzaldehyde and controlling their mass ratio, the sodium storage capacity and rate performance of asphalt-based hard carbon can be synergistically improved, while also ensuring good stability.

[0036] In some embodiments, the mass ratio of the asphalt precursor, sulfur source and crosslinking agent is 1:(1~9):(1~9).

[0037] Precisely controlling the mass ratio of asphalt precursor, sulfur source, and crosslinking agent helps improve product purity and ensures sufficient and appropriate vulcanization and crosslinking reactions, thereby forming asphalt-based hard carbon with large interlayer spacing and rich pore structure, significantly improving sodium storage capacity and rate performance. Furthermore, controlling the mass ratio of the three components within the aforementioned range helps improve the mechanical strength and thermal stability of the primary product, ensuring its structural integrity during carbonization, thus improving the stability of the asphalt-based hard carbon; furthermore, the mass ratio of asphalt precursor, sulfur source, and crosslinking agent is 1:(2~6):(3~8).

[0038] In some embodiments, the first temperature is 100°C to 500°C, and the crosslinking vulcanization treatment time is 0.5h to 48h; the second temperature is 1200°C to 1600°C, and the carbonization treatment time is 0.5h to 48h. The crosslinking vulcanization treatment and the carbonization treatment are each carried out independently under nitrogen or an inert atmosphere.

[0039] Crosslinking vulcanization under the above conditions ensures a thorough and uniform reaction between the sulfur source, asphalt precursor, and crosslinking agent. It also creates uniformly distributed active sites, which are beneficial for sodium ion storage. Carbonization under these conditions ensures the complete conversion of primary products into carbon, while simultaneously increasing the interlayer spacing of carbon layers, forming a stable carbon structure, and enhancing the mechanical strength and thermal stability of asphalt-based hard carbon.

[0040] Typical, but not limited, inert atmospheres include at least one of helium and argon.

[0041] Typically, but not limitingly, the heating rates for crosslinking vulcanization and carbonization are each independently 0.1℃ / min to 10℃ / min, and the heating rates can be adjusted according to the preparation efficiency.

[0042] In some embodiments, the asphalt precursor is at least one of coal tar pitch, petroleum pitch, coal liquefaction pitch, ethylene tar pitch, and natural pitch.

[0043] In another typical embodiment of this application, an asphalt-based hard carbon is provided, prepared by the method described in the above embodiments. This asphalt-based material should possess good sodium storage performance, exhibiting a high sodium storage capacity and good rate capability.

[0044] In another typical embodiment of this application, a sodium-ion battery anode material is provided, which includes the pitch-based hard carbon described in the above embodiments of this application. Because the pitch-based hard carbon has excellent sodium storage performance, sodium-ion batteries made with this sodium-ion battery anode material have high energy density and rate performance.

[0045] The present application will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed in the present application.

[0046] Information on some materials used in the examples and comparative examples is as follows:

[0047] Coal tar pitch: medium-temperature pitch, manufactured by Xinno Lixing (Huanghua City) Group Co., Ltd.

[0048] Coal liquefaction bitumen: China Shenhua Coal-to-Oil Chemical Co., Ltd., coal liquefaction bitumen;

[0049] Petroleum asphalt: China National Petroleum Corporation (CNPC), modified asphalt;

[0050] Natural asphalt: Xi'an Zhongli Asphalt Co., Ltd., natural heavy traffic asphalt NNB-70;

[0051] Ethylene tar pitch: Liaoning Runxing New Materials Co., Ltd., 90# ethylene tar coated pitch;

[0052] Paraformaldehyde A: Degree of polymerization is 8-20;

[0053] Concentrated sulfuric acid: a sulfuric acid solution with a H2SO4 mass fraction of 98%.

[0054] Example 1

[0055] One embodiment of the bitumen-based hard carbon of this application, the preparation method of the bitumen-based hard carbon in this embodiment is as follows:

[0056] S1, weigh 2.5g coal tar pitch, 2.5g coal liquefaction pitch, 5g elemental sulfur, 5g sodium sulfide, and 15g terephthalaldehyde, and ball mill them together for 5 hours to ensure uniform mixing; under argon protection, load the mixed material into a stainless steel sealed autoclave, heat it to 280℃ at a rate of 3℃ / min, and hold it at that temperature for 3 hours to obtain the primary product;

[0057] S2, the primary product is ground to 200 mesh, heated to 1400℃ at a rate of 3℃ / min under argon atmosphere, and held at the temperature for 3h to obtain pitch-based hard carbon.

[0058] Example 2

[0059] One embodiment of the bitumen-based hard carbon of this application, the preparation method of the bitumen-based hard carbon in this embodiment is as follows:

[0060] S1, weigh 2.5g coal liquefaction pitch, 2.5g petroleum pitch, 20g sodium sulfide and 35g paraformaldehyde, and ball mill the four together for 5 hours to make them uniform; under argon protection, put the mixed material into a stainless steel sealed autoclave, heat it to 350℃ at a rate of 5℃ / min, and keep it at the temperature for 2 hours to obtain the primary product.

[0061] S2, the primary product is ground to 200 mesh, heated to 1300℃ at a rate of 4℃ / min under argon atmosphere, and held at the temperature for 7h to obtain pitch-based hard carbon.

[0062] Example 3

[0063] One embodiment of the bitumen-based hard carbon of this application, the preparation method of the bitumen-based hard carbon in this embodiment is as follows:

[0064] S1. Weigh 5g of natural asphalt, 5g of thiourea, 10g of terephthalaldehyde, and 10g of paraformaldehyde. Ball mill the four materials together for 5 hours to ensure uniform mixing. Under argon protection, load the mixed material into a stainless steel sealed autoclave and heat it to 400℃ at a rate of 4℃ / min. Hold the temperature for 4 hours to obtain the primary product.

[0065] S2, the primary product is ground to 200 mesh, heated to 1500℃ at a rate of 3℃ / min under argon atmosphere, and held at the temperature for 4h to obtain pitch-based hard carbon.

[0066] Example 4

[0067] One embodiment of the bitumen-based hard carbon of this application, the preparation method of the bitumen-based hard carbon in this embodiment is as follows:

[0068] S1, weigh 2.5g natural asphalt, 2.5g petroleum asphalt, 20g elemental sulfur, and 40g terephthalic acid, and ball mill them together for 5 hours to ensure uniform mixing; under argon protection, load the mixed material into a stainless steel sealed autoclave, heat it to 200℃ at a rate of 7℃ / min, and hold it at that temperature for 2 hours to obtain the primary product.

[0069] S2, the primary product is ground to 200 mesh, heated to 1250℃ at a rate of 2℃ / min under argon atmosphere, and held at the temperature for 8h to obtain pitch-based hard carbon.

[0070] Example 5

[0071] One embodiment of the bitumen-based hard carbon of this application, the preparation method of the bitumen-based hard carbon in this embodiment is as follows:

[0072] S1, weigh 2.5g of petroleum asphalt, 2.5g of ethylene tar pitch, 2.5g of elemental sulfur, 2.5g of thiourea, and 15g of terephthalic acid, and ball mill them together for 5 hours to ensure uniform mixing; under argon protection, load the mixed material into a stainless steel sealed autoclave, heat it to 300℃ at a rate of 2℃ / min, and hold it at that temperature for 12 hours to obtain the primary product;

[0073] S2, the primary product is ground to 200 mesh, heated to 1400℃ at a rate of 7℃ / min under argon atmosphere, and held at the temperature for 16h to obtain pitch-based hard carbon.

[0074] Example 6

[0075] One embodiment of the bitumen-based hard carbon of this application, the preparation method of the bitumen-based hard carbon in this embodiment is as follows:

[0076] S1, weigh 2.5g of petroleum asphalt, 2.5g of coal tar pitch, 15g of elemental sulfur, 15g of thiourea, and 40g of paraformaldehyde, and ball mill them together for 5 hours to ensure uniform mixing; under argon protection, load the mixed material into a stainless steel sealed autoclave, heat it to 400℃ at a rate of 5℃ / min, and hold it at that temperature for 16 hours to obtain the primary product;

[0077] S2, the primary product is ground to 200 mesh, heated to 1600℃ at a rate of 5℃ / min under argon atmosphere, and held at the temperature for 12h to obtain pitch-based hard carbon.

[0078] Example 7

[0079] One embodiment of the asphalt-based hard carbon of this application differs from that of Example 2 only in that the raw materials in S1 are: 5g petroleum asphalt, 20g elemental sulfur, and 35g terephthalic acid.

[0080] Example 8

[0081] One embodiment of the asphalt-based hard carbon of this application differs from that of Example 2 only in that the raw materials in S1 are: 5g petroleum asphalt, 5g concentrated sulfuric acid, 15g elemental sulfur, and 35g terephthalic acid.

[0082] Example 9

[0083] One embodiment of the asphalt-based hard carbon of this application differs from that of Example 2 only in that the raw materials in S1 are: 5g petroleum asphalt, 10g concentrated sulfuric acid, 10g elemental sulfur, and 35g terephthalic acid.

[0084] Example 10

[0085] One embodiment of the asphalt-based hard carbon of this application differs from that of Example 2 only in that the raw materials in S1 are: 5g petroleum asphalt, 3g concentrated sulfuric acid, 17g elemental sulfur, and 35g terephthalic acid.

[0086] Example 11

[0087] One embodiment of the asphalt-based hard carbon of this application differs from that of Example 2 only in that the raw materials in S1 are: 5g petroleum asphalt, 14g concentrated sulfuric acid, 6g elemental sulfur, and 35g terephthalic acid.

[0088] Example 12

[0089] One embodiment of the asphalt-based hard carbon of this application differs from that of Example 8 only in that the raw materials in S1 are: 5g petroleum asphalt, 5g concentrated sulfuric acid, 15g elemental sulfur, and 35g benzaldehyde.

[0090] Example 13

[0091] One embodiment of the asphalt-based hard carbon of this application differs from that of Example 8 only in that the raw materials in S1 are: 5g petroleum asphalt, 5g concentrated sulfuric acid, 15g elemental sulfur, and 35g terephthalaldehyde.

[0092] Example 14

[0093] One embodiment of the asphalt-based hard carbon of this application differs from that of Example 8 only in that the raw materials in S1 are: 5g petroleum asphalt, 5g concentrated sulfuric acid, 15g elemental sulfur, 25g terephthalic acid, and 10g benzaldehyde.

[0094] Example 15

[0095] One embodiment of the asphalt-based hard carbon of this application differs from that of Example 8 only in that the raw materials in S1 are: 5g petroleum asphalt, 5g concentrated sulfuric acid, 15g elemental sulfur, 20g terephthalic acid, and 15g benzaldehyde.

[0096] Example 16

[0097] One embodiment of the asphalt-based hard carbon of this application differs from that of Example 8 only in that the raw materials in S1 are: 5g petroleum asphalt, 5g concentrated sulfuric acid, 15g elemental sulfur, 28g terephthalic acid, and 7g benzaldehyde.

[0098] Example 17

[0099] One embodiment of the asphalt-based hard carbon of this application differs from that of Example 8 only in that the raw materials in S1 are: 5g petroleum asphalt, 5g concentrated sulfuric acid, 15g elemental sulfur, 15g terephthalic acid, and 10g benzaldehyde.

[0100] Comparative Example 1

[0101] A pitch-based hard carbon, the preparation method of which differs from that of Example 5 only in that the raw materials in S1 are: 2.5g petroleum pitch, 2.5g ethylene tar pitch, 5g concentrated sulfuric acid, and 15g terephthalic acid.

[0102] Comparative Example 2

[0103] A pitch-based hard carbon, the preparation method of which differs from that of Example 5 only in that the raw materials in S1 are: 2.5g petroleum pitch, 2.5g ethylene tar pitch, and 20g elemental sulfur.

[0104] Comparative Example 3

[0105] A pitch-based hard carbon, the preparation method of which differs from that of Example 5 only in that the raw materials in S1 are: 2.5g petroleum pitch, 2.5g ethylene tar pitch, and 20g terephthalic acid.

[0106] Performance testing:

[0107] Preparation of sodium-ion battery electrode sheets: Asphalt-based hard carbon, conductive carbon black, and PVDF were weighed at a mass ratio of 8:1:1 and ground into a uniform slurry in a mortar using NMP as a dispersant. The slurry was coated onto carbon-coated aluminum foil, then dried in a vacuum oven at 80°C for 12 h, and finally cut into electrode sheets with a diameter of 14.5 mm.

[0108] Assembly of sodium-ion half-cells: Assembly was carried out in an argon-filled glove box. The battery casing model was CR2032. The sodium salt in the electrolyte was NaClO4 with a concentration of 1M. The electrolyte was a mixture of EC, DMC, and FEC, with a volume ratio of EC to DMC of 1:1. The total mass fraction of EC and DMC was 100%, and the mass fraction of FEC was 5%. A Whatman GF / D glass fiber membrane was used as the separator. A sodium sheet with a diameter of 15.6 mm was used as the counter electrode in the half-cell.

[0109] Testing: Constant current charge / discharge testing involves charging or discharging the battery at a set fixed current density within a specific voltage range. The Wuhan Landian CT3001A battery tester was used for constant current charge / discharge testing. The test voltage range for sodium-ion half-cells is 0-2.5V.

[0110] Table 1

[0111]

[0112] The test results above show that the pitch-based hard carbon in the embodiments of the present invention has good electrochemical performance, high reversible specific capacity, and good rate performance. In Comparative Example 1, concentrated sulfuric acid was used as the sulfur source only, and its reversible specific capacity was significantly reduced. In Comparative Examples 2 and 3, only a sulfur source and a crosslinking agent were added, respectively, and the electrochemical performance of the resulting pitch-based hard carbon was significantly worse than that of the embodiments.

[0113] In addition, comparing the performance test results of Examples 7 to 11, it can be seen that when the sulfur source is a mixture of concentrated sulfuric acid and elemental sulfur, and the mass ratio of the two is 1: (1 to 5), pitch-based hard carbon has better electrochemical performance.

[0114] Comparing the performance test results of Examples 8 and 14-16, it can be seen that when the crosslinking agent is a mixture of terephthalic acid and benzaldehyde, the prepared pitch-based hard carbon has better electrochemical performance.

[0115] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing pitch-based hard carbon, characterized in that, Includes the following steps: S1, mix asphalt precursor, sulfur source and crosslinking agent, and perform crosslinking vulcanization treatment at the first temperature to obtain primary product; S2, the primary product is carbonized at a second temperature to obtain the pitch-based hard carbon; The sulfur source is any one of elemental sulfur, thiourea, dimethyl sulfide, or sulfides, or any two of elemental sulfur, concentrated sulfuric acid, thiourea, dimethyl sulfide, or sulfides.

2. The method for preparing pitch-based hard carbon according to claim 1, characterized in that, The sulfur source is any two of the following: elemental sulfur, concentrated sulfuric acid, thiourea, dimethyl sulfide, and sulfide; and / or, the sulfide is at least one of boron sulfide, zinc sulfide, and sodium sulfide.

3. The method for preparing pitch-based hard carbon according to claim 2, characterized in that, The sulfur source is a compound of concentrated sulfuric acid and elemental sulfur, wherein the mass ratio of concentrated sulfuric acid to elemental sulfur in the compound is 1:(1~5).

4. The method for preparing pitch-based hard carbon according to any one of claims 1 to 3, characterized in that, The crosslinking agent is at least one of benzyl dimethyl alcohol, terephthalaldehyde, benzaldehyde, and paraformaldehyde.

5. The method for preparing pitch-based hard carbon according to claim 4, characterized in that, The crosslinking agent is a compound of terephthalic acid and benzaldehyde, wherein the mass ratio of terephthalic acid to benzaldehyde in the compound is (1~5):

1.

6. The method for preparing pitch-based hard carbon according to claim 1, characterized in that, The mass ratio of the asphalt precursor, the sulfur source and the crosslinking agent is 1:(1~9):(1~9).

7. The method for preparing pitch-based hard carbon according to claim 1, characterized in that, The first temperature is 100℃~500℃, and the crosslinking vulcanization treatment time is 0.5h~48h; the second temperature is 1200℃~1600℃, and the carbonization treatment time is 0.5h~48h; the crosslinking vulcanization treatment and the carbonization treatment are each carried out independently under nitrogen or inert atmosphere.

8. The method for preparing pitch-based hard carbon according to claim 1, characterized in that, The asphalt precursor is at least one of coal tar pitch, petroleum pitch, coal liquefaction pitch, ethylene tar pitch, and natural pitch.

9. A pitch-based hard carbon fiber, characterized in that, Prepared by the preparation method according to any one of claims 1 to 8.

10. A sodium-ion battery anode material, characterized in that, Includes the bitumen-based hard carbon as described in claim 9.

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