Preparation method of hard carbon material and application of hard carbon material in sodium-ion battery

Abstract

The invention provides a preparation method of a hard carbon material and application of the hard carbon material in a sodium-ion battery. The preparation method comprises the following steps: mixing petroleum coke powder with carbonate powder, and carrying out ball milling, acid pickling and high-temperature treatment to obtain the hard carbon material. According to the invention, carbonate is introduced as a grinding aid, the destructive effect of a ball milling process on an aromatic structure in petroleum coke is enhanced, graphitization is delayed, carbon layer spacing is increased, carbon layers are promoted to be stacked randomly to form a large number of closed pores, then carbon dioxide generated by thermal decomposition of carbonate can be utilized to activate petroleum coke to generate micropores, the surface activity defect concentration is increased, and the performance of petroleum coke is improved. Finally, the petroleum coke-based hard carbon material with rich sodium storage sites is obtained. The obtained hard carbon material is used as the negative electrode of the sodium-ion battery, and the reversible sodium storage capacity and the rate capability are effectively improved. The adopted raw materials are good in conductivity, the cost is low, the preparation process is simple, convenient and safe, and the method is suitable for large-scale application.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemical energy storage. Specifically, it relates to a preparation method of hard carbon materials and their application in sodium-ion batteries. Background Art

[0002] Sodium-ion batteries have developed rapidly in recent years due to their abundant raw material reserves and significant cost advantages. However, restricted by thermodynamic factors, sodium ions are difficult to effectively intercalate / deintercalate in graphite anodes like lithium ions, resulting in poor sodium storage performance of traditional graphite anode materials. Therefore, developing sodium-ion battery anode materials with both low cost and high performance has become the focus of current research. Among them, carbon materials are regarded as the most promising sodium-ion battery anode materials due to their high intrinsic conductivity, chemical stability, highly adjustable structure, and abundant sodium storage sites.

[0003] Currently, the research and development of carbon-based anode materials for sodium-ion batteries mainly focus on the hard carbon system and have made significant progress. Hard carbon usually comes from the high-temperature pyrolysis of thermosetting precursors, such as biomass, thermosetting resins, and organic macromolecules. Petroleum coke, as a by-product of the petroleum industry, has the advantages of high carbon content, low cost, and good conductivity. However, as a precursor for carbon anode materials in sodium-ion batteries, the macromolecular aromatic structure in petroleum coke often forms highly graphitized soft carbon with a narrow interlayer spacing during pyrolysis, resulting in poor sodium storage performance. To address the above problems, researchers have carried out various modifications. A Chinese invention patent (publication number: CN117923459A) provides a nitrogen / sulfur co-doped petroleum coke-based porous carbon. Although the porous structure shortens the diffusion distance of sodium ions and improves the rate performance to a certain extent, it only has a sodium storage capacity of 92.5 mAh g -1 at 1 A g -1 ; another patent (publication number: CN118083943A) prepared a petroleum coke-based core-shell structured carbon material through the combined strategy of KOH activation and pitch coating for use as a sodium-ion battery anode material, which showed a sodium storage capacity of 221 mAh g -1 at 40 mA g -1 . Although the above modification strategies can improve the sodium storage performance to a certain extent, the materials have a high degree of graphitization and a small carbon layer spacing, which hinders the effective intercalation and diffusion process of sodium ions, thus restricting the improvement of the sodium storage capacity and rate performance of the materials. Therefore, there is an urgent need to develop a preparation method to improve the sodium storage performance of petroleum coke-based carbon materials to meet the requirements of large-scale energy storage for high-performance sodium-ion batteries. Summary of the Invention

[0004] In view of the deficiencies of the prior art, the present invention provides a method for preparing hard carbon materials and their application in sodium-ion batteries. Based on highly conductive and low-cost petroleum coke, the present invention has developed a method for preparing a hard carbon negative electrode for sodium-ion batteries. By introducing carbonate as a grinding aid, this method enhances the destructive effect of the ball milling process on the aromatic structure in petroleum coke, delays graphitization, increases the carbon layer spacing, promotes the random stacking of carbon layers to form a large number of closed pores, and effectively improves the sodium storage capacity of the petroleum coke-based hard carbon material. Secondly, the carbon dioxide generated by the thermal decomposition of carbonate can be used to activate petroleum coke to generate micropores, increase the concentration of surface active defects, and improve the rate performance of the petroleum coke-based hard carbon material.

[0005] The technical solution of the present invention is as follows:

[0006] A method for preparing a hard carbon material, comprising the following steps:

[0007] (1) Mix petroleum coke and carbonate and ball mill to obtain a mixture, and perform acid washing on the mixture to obtain a hard carbon precursor;

[0008] (2) Perform high-temperature carbonization on the hard carbon precursor to obtain a hard carbon material.

[0009] The petroleum coke is one or more of low-sulfur petroleum coke, medium-sulfur petroleum coke, and high-sulfur petroleum coke.

[0010] The Mohs hardness of the carbonate is greater than 3. Further, the carbonate includes one or more of calcium carbonate, magnesium carbonate, and zinc carbonate.

[0011] The mass ratio of the carbonate to the petroleum coke is (0.25 - 3):1.

[0012] Before the petroleum coke in step (1) is mixed and ball milled with the carbonate, it is first crushed to 100 - 200 mesh.

[0013] The ball milling is carried out in a closed high-energy ball milling tank.

[0014] The ball milling speed is 400 - 900 rpm, and the ball milling time is 0.5 - 3 h.

[0015] The acid solution in the acid washing includes one or more of hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, and acetic acid solutions, and the concentration of the acid solution is 0.1 - 10 mol / L -1 .

[0016] Before step (1) is acid washed, it further includes pre-carbonizing the mixture in an inert atmosphere.

[0017] The pre-carbonization temperature is 750 - 900 °C, and the pre-carbonization time is 1 - 4 h. Further, the heating rate is 1 - 5 °C / min -1 .

[0018] The temperature of the high-temperature carbonization is 1000 - 1500 °C, and the time of the high-temperature carbonization is 1 - 4 h. Further, the heating rate of the high-temperature carbonization is 1 - 5 °C / min -1 .

[0019] The process of pre-carbonization or high-temperature carbonization is carried out in an inert atmosphere.

[0020] The inert atmosphere is argon and / or nitrogen.

[0021] The present invention also provides an application of the hard carbon material in a sodium-ion battery, and the hard carbon material is used as the negative electrode of the sodium-ion battery.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] 1. The present invention uses inexpensive and highly conductive petroleum coke as a precursor to prepare a hard carbon negative electrode material for a sodium-ion battery, which is conducive to the high-value utilization of petroleum coke.

[0024] 2. By introducing carbonate as a grinding aid, the present invention enhances the destructive effect of ball milling on the macromolecular aromatic structure of petroleum coke, delays graphitization, increases the carbon layer spacing, and promotes the random stacking of carbon layers to form a large number of closed pores. This unique microstructure is beneficial to improving the sodium storage capacity of the material. The sodium storage capacity of the petroleum coke-based hard carbon material prepared based on the present invention used as the negative electrode of a sodium-ion battery reaches 263.2 mA h / g -1 .

[0025] 3. The carbon dioxide generated by the thermal decomposition of carbonate is used to activate petroleum coke to generate micropores, obtaining a hard carbon material with a high surface activity defect concentration, improving the rate performance of the petroleum coke-based hard carbon material, and having a sodium storage capacity of 90.1 mA h / g at a current density of 2 A / g -1 The carbon dioxide generated by the thermal decomposition of carbonate is used to activate petroleum coke to generate micropores, obtaining a hard carbon material with a high surface activity defect concentration, improving the rate performance of the petroleum coke-based hard carbon material, and having a sodium storage capacity of 90.1 mA h / g at a current density of 2 A / g -1 of the sodium storage capacity.

[0026] 4. The method for preparing hard carbon according to the present invention has a simple process, is safe and reliable, and is suitable for large-scale application. Description of the Drawings

[0027] Figure 1 is the XRD pattern of the petroleum coke-based hard carbon materials prepared in Examples 1 - 3 and Comparative Example 2.

[0028] Figure 2 is the XRD pattern of the petroleum coke-based soft carbon material prepared in Comparative Example 1.

[0029] Figure 3 is the TEM image of the petroleum coke-based hard carbon material prepared in Example 1.

[0030] Figure 4It is the TEM image of the petroleum coke-based soft carbon material prepared in Comparative Example 1.

[0031] Figure 5 It is the galvanostatic charge-discharge curve of the petroleum coke-based hard carbon material prepared in Example 1 during the first charge-discharge process.

[0032] Figure 6 It is the galvanostatic charge-discharge curve of the petroleum coke-based soft carbon material prepared in Comparative Example 1 during the first charge-discharge process.

[0033] Figure 7 It is the nitrogen adsorption isotherm diagram of the petroleum coke-based hard carbon materials prepared in Comparative Examples 1-2 and Examples 1-3.

[0034] Figure 8 It is the nitrogen adsorption isotherm diagram of the petroleum coke-based hard carbon material prepared in Example 11. Detailed Embodiments

[0035] The present invention is described in detail by the following representative examples, but the present invention is not limited to these examples.

[0036] Comparative Example 1

[0037] Take 1 g of petroleum coke powder and place it in a tubular carbonization furnace. Under an argon atmosphere, heat it to 1500 °C at a heating rate of 3 °C / min -1 and hold it at this temperature for 2 h. Then cool it to 1000 °C at a cooling rate of 2 °C / min -1 and then cool it naturally to room temperature to obtain a soft carbon material.

[0038] Use the carbon material prepared in Comparative Example 1 as the negative electrode for a sodium-ion battery. The specific steps are as follows: First, grind the carbon material and CNTs evenly, then mix them with the SA+PEO binder in a mass ratio of 8:1:1 evenly, add an appropriate amount of pure water and stir to form a uniform slurry. Then coat the slurry on a copper foil current collector and transfer it to a 100 °C vacuum drying oven for drying for 12 h. After drying, cut it into a circular piece with a diameter of 12 mm as the electrode piece for standby. The battery assembly is carried out in a glove box filled with an argon atmosphere. Use a sodium metal sheet as the counter electrode, a commercial electrolyte NP-004 as the electrolyte, and a glass fiber membrane as the separator. The prepared electrode piece is used as the negative electrode, and it is assembled into a CR2032 button battery in the order of negative electrode shell, negative electrode piece, separator, electrolyte, sodium metal sheet, gasket, spring, and positive electrode shell from bottom to top. After standing at room temperature for 12 h, use a Neware CT4008 (Shenzhen, China) battery testing device to conduct a galvanostatic charge-discharge test, where the voltage range is 0.01-3 V.

[0039] The test results are shown in Table 1 and Figure 6 as follows.

[0040] Comparative Example 2

[0041] Take 5 g of petroleum coke powder and place it in a high-energy ball milling jar. Ball mill it at 800 rpm for 1 h. Take out 1 g of the ball-milled petroleum coke powder and place it in a tubular carbonization furnace. Under an argon atmosphere, heat it at a heating rate of 3 °C / min -1 to 1500 °C and hold for 2 h. Then, cool it at a cooling rate of 2 °C / min -1 to 1000 °C, and finally cool it naturally to room temperature to obtain the hard carbon material.

[0042] The battery assembly and electrochemical performance test are the same as those in Comparative Example 1.

[0043] The test results are shown in Table 1.

[0044] Table 1 Electrochemical performance of the materials in Comparative Example 1 and Comparative Example 2

[0045]

[0046] Examples 1 - 3

[0047] This example provides a preparation method for a petroleum coke-based hard carbon material. The specific operation steps are as follows:

[0048] According to the different mass ratios of calcium carbonate to petroleum coke shown in Table 2, take petroleum coke powder and calcium carbonate and place them in a ball milling jar. Ball mill them at 800 rpm for 1 h to obtain a mixture of petroleum coke and calcium carbonate. Wash away the calcium carbonate with a 0.5 mol / L -1 hydrochloric acid solution and filter it until neutral. Dry it in a blast drying oven at 50 °C for 12 h to obtain the hard carbon precursor. Place the obtained hard carbon precursor in a tubular carbonization furnace. Under an argon atmosphere, heat it at a heating rate of 3 °C / min -1 to 1500 °C and hold for 2 h. Then, cool it at a cooling rate of 2 °C / min -1 to 1000 °C, and finally cool it naturally to room temperature to obtain the hard carbon material.

[0049] The battery assembly and electrochemical performance test are the same as those in Comparative Example 1.

[0050] The test results are shown in Table 2 and Figure 5 as follows.

[0051] Table 2 Comparison of the electrochemical performance of the hard carbon materials obtained with different mass ratios of calcium carbonate to petroleum coke

[0052]

[0053] It can be seen from Examples 1-3 and Comparative Example 2 that the hard carbon materials obtained by calcium carbonate-assisted ball milling have higher sodium storage capacity, which is attributed to the fact that calcium carbonate enhances the destructive effect of the ball milling process on the aromatic structure in petroleum coke, delays graphitization, and increases the carbon layer spacing ( Figure 1 ), promotes the random stacking of carbon layers to form a large number of closed pores ( Figure 3 ), and increases the sodium storage capacity; in addition, the defects generated form open pores at high temperatures ( Figure 7 ), which can shorten the sodium ion diffusion path and improve the rate performance of the battery.

[0054] Examples 4-6

[0055] This example provides a preparation method for petroleum coke-based hard carbon materials, and the specific operation steps are as follows:

[0056] Take 2.5 g of petroleum coke powder and 2.5 g of calcium carbonate and place them in a ball milling jar. Ball mill at 800 rpm according to different ball milling times shown in Table 3 to obtain a mixture of petroleum coke and calcium carbonate. Wash away the calcium carbonate with 0.5 mol L -1 hydrochloric acid solution and filter until neutral, and dry in a blast drying oven at 50 °C for 12 h to obtain a hard carbon precursor. Place the obtained hard carbon precursor in a tubular carbonization furnace, and under an argon atmosphere, heat it to 1500 °C at a heating rate of 3 °C min -1 , and keep it at this temperature for 2 h, then cool it to 1000 °C at a cooling rate of 2 °C min -1 , and finally cool it naturally to room temperature to obtain the hard carbon material.

[0057] The battery assembly and electrochemical performance test are the same as in Comparative Example 1.

[0058] The test results are shown in Table 3.

[0059] Table 3 Comparison of electrochemical performance of hard carbon materials obtained at different ball milling times

[0060]

[0061] It can be seen from Example 1, Examples 4-6 and Comparative Example 2 that the performance of the hard carbon materials obtained by using calcium carbonate as a grinding aid and ball milling for 0.5-3 h is improved.

[0062] Examples 7-8

[0063] This example provides a preparation method for petroleum coke-based hard carbon materials, and the specific operation steps are as follows:

[0064] According to the types of carbonates shown in Table 4, take 2.5 g of petroleum coke powder and 2.5 g of carbonate and place them in a ball milling jar. Ball mill at 800 rpm for 1 h to obtain a mixture of petroleum coke and carbonate. Wash away the carbonate with 0.5 mol L -1Wash away the carbonate with hydrochloric acid solution and filter by suction until neutral, then dry in a blast drying oven at 50 °C for 12 h to obtain the hard carbon precursor. Place the obtained hard carbon precursor in a tubular carbonization furnace, and under an argon atmosphere, heat it to 1500 °C at a heating rate of 3 °C min -1 and keep it at this temperature for 2 h, then cool it to 1000 °C at a cooling rate of 2 °C min -1 , and finally cool it naturally to room temperature to obtain the hard carbon material.

[0065] The battery assembly and electrochemical performance test are the same as in Comparative Example 1.

[0066] The test results are shown in Table 4.

[0067] Table 4 Comparison of the electrochemical performance of hard carbon materials obtained from different carbonates

[0068]

[0069] It can be seen from Example 1 and Examples 7 - 8 that the method provided by the present invention has wide applicability to different carbonates, can all damage the aromatic structure in petroleum coke, delay graphitization, increase the carbon layer spacing, increase the closed pore volume, and improve the sodium storage capacity of petroleum coke-based hard carbon materials.

[0070] Examples 9 - 10

[0071] This example provides a preparation method of a petroleum coke-based hard carbon material, and the specific operation steps are as follows:

[0072] Take 2.5 g of petroleum coke powder and 2.5 g of calcium carbonate and place them in a ball milling tank, ball mill for 1 h at 800 rpm to obtain a mixture of petroleum coke and calcium carbonate. Wash away the calcium carbonate with 0.5 mol L -1 hydrochloric acid solution and filter by suction until neutral, then dry in a blast drying oven at 50 °C for 12 h to obtain the hard carbon precursor. Place the obtained hard carbon precursor in a tubular carbonization furnace, and under an argon atmosphere, heat it to the temperature shown in Table 5 at a heating rate of 3 °C min -1 and keep it at this temperature for 2 h, then cool it to 1000 °C at a cooling rate of 2 °C min -1 , and finally cool it naturally to room temperature to obtain the hard carbon material.

[0073] The battery assembly and electrochemical performance test are the same as in Comparative Example 1.

[0074] The test results are shown in Table 5.

[0075] Table 5 Comparison of the electrochemical performance of hard carbon materials obtained at different carbonization temperatures

[0076]

[0077] As can be seen from Example 1 and Examples 9-10, high-temperature carbonization can drive the deep pyrolysis and structural rearrangement of the carbon skeleton, making the internal pores close more effectively, increasing the closed-pore volume, providing more stable storage sites for sodium ions, and thus improving the sodium storage capacity.

[0078] Example 11

[0079] This example provides a preparation method for a petroleum coke-based hard carbon material, and the specific operation steps are as follows:

[0080] Take 1 g of petroleum coke powder and 3 g of calcium carbonate and place them in a ball milling jar. Ball mill for 1 h at 800 rpm to obtain a mixture of petroleum coke and calcium carbonate. Place the above-obtained mixture in a tubular furnace under an argon atmosphere and heat it to 750 °C at a heating rate of 3 °C / min -1 and keep it at this temperature for 2 h, then cool it to room temperature. Wash away calcium oxide with a 0.5 mol / L -1 hydrochloric acid solution and filter it until neutral, and dry it in a blast drying oven at 50 °C for 12 h to obtain a hard carbon precursor. Place 1 g of the obtained hard carbon precursor in a tubular carbonization furnace, and under an argon atmosphere, heat it to 1500 °C at a heating rate of 3 °C / min -1 and keep it at this temperature for 2 h, then cool it to 1000 °C at a cooling rate of 5 °C / min -1 and finally cool it to room temperature naturally to obtain a hard carbon material.

[0081] The battery assembly and electrochemical performance test are the same as in Comparative Example 1.

[0082] The test results are shown in Table 6.

[0083] Table 6 Electrochemical performance of the hard carbon material obtained in Example 11

[0084]

[0085] As can be seen from Example 2 and Example 11, the carbon dioxide generated by the thermal decomposition of calcium carbonate during the pre-carbonization process is used to activate petroleum coke to generate more micropores ( Figure 8 ), increasing the surface active defect concentration, enhancing the sodium ion diffusion kinetics, and improving the rate performance of the petroleum coke-based hard carbon material.

[0086] The microcrystalline structures of Examples 1-3 and Comparative Examples 1-2 were characterized by XRD, and the test results are as Figure 1 、 Figure 2 shown. By introducing carbonate as a grinding aid, the destructive effect of the ball milling process on the aromatic structure in petroleum coke is enhanced, graphitization is delayed, the carbon layer spacing increases, which is beneficial to improving the sodium storage capacity.

[0087] The microstructures of Example 1 and Comparative Example 1 were characterized by TEM, and the test results are as Figure 3 、Figure 4 As shown. The sample of Comparative Example 1 exhibited typical lamellar order, while the image of Example 1 showed a disordered turbostratic structure, indicating that the carbonate-assisted ball milling process could disrupt the aromatic structure in petroleum coke, delay graphitization, promote the random stacking of carbon layers to form closed pores, facilitate the sodium ion insertion and filling processes, and effectively improve the sodium storage capacity of the petroleum coke-based hard carbon material.

[0088] The above has made a detailed description of the present invention, aiming to enable those skilled in this field to understand the content of the present invention and implement it. However, it cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for preparing a hard carbon material, characterized in that: It includes the following steps: S1 Mix petroleum coke with carbonate and ball-mill to obtain a mixture, and pickle the mixture to obtain a hard carbon precursor; S2 Subject the hard carbon precursor to high-temperature carbonization to obtain a hard carbon material.

2. The preparation method of a hard carbon material according to claim 1, characterized in that: The petroleum coke is one or more of low-sulfur petroleum coke, medium-sulfur petroleum coke, and high-sulfur petroleum coke.

3. The preparation method of a hard carbon material according to claim 1, characterized in that: The Mohs hardness of the carbonate is greater than 3.

4. The preparation method of a hard carbon material according to claim 3, characterized in that: The carbonate includes one or more of calcium carbonate, magnesium carbonate, and zinc carbonate.

5. The preparation method of a hard carbon material according to claim 1, characterized in that: The mass ratio of the carbonate to the petroleum coke is (0.25 - 3):

1.

6. The preparation method of a hard carbon material according to claim 1, wherein: Before mixing with the carbonate for ball-milling, the petroleum coke in step S1 is first crushed to 100 - 200 mesh; the ball-milling speed is 400 - 900 rpm, and the ball-milling time is 0.5 - 3 h.

7. The preparation method of a hard carbon material according to claim 1, characterized in that: Before pickling in step S1, it also includes pre-carbonizing the mixture under an inert atmosphere.

8. The preparation method of a hard carbon material according to claim 7, characterized in that: The pre-carbonization temperature is 750 - 900 °C, and the pre-carbonization time is 1 - 4 h.

9. The preparation method of a hard carbon material according to claim 1, characterized in that: The temperature of the high-temperature carbonization in step S2 is 1000 - 1500 °C, and the high-temperature carbonization time is 1 - 4 h.

10. Application of the hard carbon material obtained by the method according to any one of claims 1-9 in a sodium ion battery, characterized in that: The hard carbon material is used as the negative electrode of a sodium-ion battery.

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