Preparation method and application of hard carbon negative electrode material
By employing steps such as esterification modification, alkaline treatment, acid treatment, and carbon dioxide etching, the preparation process of hard carbon anode materials has been simplified, improving their yield and electrochemical performance, and solving the problems of complex processes and high costs in existing technologies.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- WUHAN BISIDI BATTERY MATERIAL CO LTD
- Filing Date
- 2024-03-29
- Publication Date
- 2026-07-31
AI Technical Summary
Existing hard carbon anode materials have complex preparation processes, high costs, and problems such as environmental pollution and high energy consumption, while their electrochemical performance improvement is limited.
The process employs esterification modification, alkaline treatment, acid treatment, precursor modification, carbon dioxide etching, and coating carbonization. Esterification modification increases the amorphous carbon structure and regulates SEI film formation. Combined with alkaline and acid treatment, it improves the processability and closed porosity of hard carbon materials and reduces the sodium ion deposition barrier.
The preparation process was simplified, the yield and electrochemical performance of hard carbon anode materials were improved, the cost was reduced, and good electrochemical performance was achieved.
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Figure CN118306967B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of battery materials technology, and specifically relates to a method for preparing and applying a hard carbon anode material. Background Technology
[0002] Hard carbon is a commonly used anode material in sodium-ion batteries, possessing advantages such as suitable operating voltage, low cost, and suitability for large-scale production. However, to further improve the energy density of sodium-ion batteries, the electrochemical performance of hard carbon anode materials needs further enhancement. Furthermore, current research suggests that the theoretical low-cost advantage of hard carbon anode materials has not yet materialized. As the industrialization of sodium batteries progresses, new market demands for even lower-cost hard carbon anode materials have emerged. Hard carbon, as a type of carbon that is difficult to graphitize, is considered the most suitable anode material for sodium-ion batteries due to its randomly distributed vortex structure, large interlayer spacing (exceeding 0.37 nm), and closed nanopores. Generally, hard carbon is synthesized through the high-temperature carbonization of thermosetting precursors. During the pyrolysis of the precursor, the carbon layers readily form a vortex-like and disordered microstructure composed of surface defects, nanopores, voids, and graphite domains.
[0003] To create more closed pores in hard carbon, chemical activators such as ZnO, MgO, K2CO3, KOH, and ZnAc2 are typically added to the carbon precursor. While these reported hard carbons can effectively improve the capacity of low potential plateaus, these etching reagents are expensive and mostly corrosive. Removing them involves complex and time-consuming acid dissolution processes, inevitably causing environmental pollution, high energy consumption, and complex production processes.
[0004] Therefore, there is an urgent need for a new preparation process to prepare hard carbon anode materials, which is not only simple to prepare, but also produces hard carbon anode materials with good electrochemical performance. Summary of the Invention
[0005] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, the present invention proposes a method for preparing and applying a hard carbon anode material. The preparation method described in this invention is relatively simple and can increase the yield of the anode material while improving the closed-pore content, thereby enhancing the electrochemical performance of the anode material.
[0006] This invention provides a novel method for preparing hard carbon anode materials. The method includes esterification modification, alkaline treatment, acid treatment, precursor modification, carbon dioxide etching, and coating carbonization. Esterification modification increases the amorphous carbon structure tendency of biomass, resulting in larger amorphous carbon structures, inducing void structures, and regulating SEI film formation. Further alkaline and acid treatments based on esterification modification increase the yield and electrochemical performance of the final hard carbon anode material, while also increasing the amount of closed pores. Adding a pre-sintering process (i.e., a first sintering, which removes most volatiles and improves the surface processability of the hard carbon material, facilitating sufficient carbon dioxide etching) before etching the closed pores enhances the surface processability of the hard carbon and creates closed pores within the hard carbon, reducing the deposition barrier for sodium ions. This allows inexpensive biomass raw materials to exhibit high electrochemical performance without complex processing.
[0007] The first aspect of the present invention provides a method for preparing a hard carbon anode material.
[0008] Specifically, a method for preparing a hard carbon anode material includes the following steps:
[0009] Biological raw materials and esterifying agents are mixed and reacted to obtain esterified materials;
[0010] The esterified material is immersed in an alkaline solution and subjected to repeated microwave and ultrasonic treatments to obtain an alkaline-treated sample.
[0011] The alkaline-treated sample was immersed in an acid solution to obtain a precursor;
[0012] In a protective gas atmosphere, the precursor is sintered and pulverized for the first time to obtain the modified precursor material.
[0013] In a carbon dioxide atmosphere, the precursor modified material is sintered for the second time and pulverized for the second time to obtain carbon dioxide etchant.
[0014] The carbon dioxide etchant is mixed with a coating agent and sintered for the third time in a protective gas atmosphere to obtain the hard carbon anode material.
[0015] Preferably, the biological raw material is selected from one or more of polysaccharide precursors or biomass, wherein the polysaccharide precursor is selected from one or more of starch, sucrose, cellulose, etc., and the biomass is selected from one or more of coconut shell, lotus leaf stalk, peanut shell, lignin, fruit shell, rice husk, straw, corn cob, etc.
[0016] Preferably, the esterifying agent is selected from at least one of maleic anhydride, citric acid, malic acid, and oxalic acid.
[0017] Preferably, the D50 particle size of the biological raw material is no more than 18 μm, more preferably no more than 15 μm, for example, the D50 particle size is 1-15 μm.
[0018] Preferably, the mass ratio of the biological raw material to the esterifying agent is (60-99):(1-40), more preferably (80-95):(5-20), and even more preferably (85-95):(5-15).
[0019] Preferably, the temperature of the mixing reaction is 80-200℃, and more preferably 120-180℃.
[0020] Preferably, the mixing reaction takes 1-8 hours, more preferably 2-6 hours.
[0021] Preferably, the mixing reaction is carried out under air, nitrogen, or vacuum.
[0022] Preferably, the alkaline solution includes at least one of sodium hydroxide solution and potassium hydroxide solution.
[0023] Preferably, the concentration of the alkaline solution is 0.05-0.5 mol / L, and more preferably 0.1-0.2 mol / L.
[0024] Preferably, after microwave treatment for 20-30 seconds, ultrasonic treatment is performed for 8-10 minutes, and then the microwave treatment for 20-30 seconds and ultrasonic treatment for 8-10 minutes are repeated 2-5 times. Alternating between microwave and ultrasonic treatments ensures more thorough soaking. The specific treatment time and number of treatments can be adjusted as needed.
[0025] Preferably, the acid solution contains an oxidizing acid; more preferably, the acid solution is a mixed solution of phosphoric acid and perchloric acid. The mixed solution of phosphoric acid and perchloric acid can both reduce the ash content of the precursor and oxidize the carbon skeleton, introducing oxygen heteroatoms and improving the electrochemical performance and first coulombic efficiency (ICE) of the material.
[0026] Preferably, the total concentration of the acid solution is 0.5-1.5 mol / L, and more preferably 0.5-1.0 mol / L.
[0027] Preferably, the molar ratio of phosphoric acid to perchloric acid in the acid solution is 1:(0.5-1.2), more preferably 1:1.
[0028] Preferably, the protective gas is selected from at least one of argon, nitrogen, a hydrogen-argon mixture, and helium. Alternatively, a vacuum atmosphere can be used instead of a protective gas atmosphere.
[0029] Preferably, the temperature of the first sintering is 480-850℃, more preferably 500-850℃. During the first sintering process, oxygen-containing functional groups and bound water of the precursor can be removed, allowing the structure to rearrange further and avoiding the decrease in initial coulombic efficiency caused by excessive formation of SEI film (solid electrolyte interface film) due to excessive micropores and specific surface area.
[0030] Preferably, the first sintering time is 0.5-3 hours, and more preferably 1-3 hours.
[0031] Preferably, the first pulverization is performed to reduce the particle size of the precursor modified material to D. 50 The size is 3-15 μm, more preferably 5-15 μm, and even more preferably 8-10 μm.
[0032] Preferably, the temperature of the second sintering is 480-850℃, more preferably 500-850℃. During the second sintering process, CO2 gas etches the precursor modified material that has been pre-carbonized (i.e., undergone the first sintering treatment), and a large number of open micropores are generated in the activated carbon matrix of the precursor modified material through the reaction (CO2+C→2CO).
[0033] Preferably, the second sintering time is 0.5-3 hours, and more preferably 1-3 hours.
[0034] Preferably, the second pulverization is performed to reduce the particle size of the carbon dioxide etchant to D. 50 The size is 3-15 μm, more preferably 5-15 μm, and even more preferably 8-10 μm.
[0035] Preferably, the coating agent includes at least one of asphalt and phenolic resin.
[0036] Preferably, the mass ratio of the carbon dioxide etchant to the coating agent is (90-98):(2-10), and more preferably (92-95):(5-8).
[0037] Preferably, the temperature of the third sintering is 650-1400℃, more preferably 700-1400℃. During the third sintering process, the high temperature completely transforms the open holes formed during the etching process into closed pores, which is beneficial to improving the electrochemical performance of the hard carbon anode material.
[0038] Preferably, the third sintering time is 0.5-3 hours, and more preferably 1-3 hours.
[0039] A second aspect of the present invention provides a hard carbon anode material.
[0040] A hard carbon anode material is prepared by the above-described method.
[0041] A third aspect of the present invention provides an application of a hard carbon anode material.
[0042] A sodium-ion battery includes a negative electrode, said negative electrode comprising the aforementioned hard carbon negative electrode material.
[0043] Compared with the prior art, the beneficial effects of the present invention are as follows:
[0044] This invention provides a novel method for preparing hard carbon anode materials. The method includes esterification modification, alkaline treatment, acid treatment, precursor modification, carbon dioxide etching, and coating carbonization. Esterification modification increases the amorphous carbon structure tendency of biomass, resulting in larger structures, inducing void structures, and regulating SEI film formation. Further alkaline and acid treatments based on esterification modification facilitate thorough precursor modification. The first sintering in precursor modification removes most volatiles, improving the processability of the hard carbon material surface. Sufficient carbon dioxide etching allows the hard carbon anode material prepared after coating carbonization to increase both the closed-pore content (carbon dioxide etching increases the open-pore content of the precursor modified material; after coating and sintering, the open pores close and shrink, increasing the closed-pore content) and yield, thus improving its electrochemical performance. This method allows inexpensive bio-raw materials to exhibit high electrochemical performance without complex processing. This invention utilizes a combination of esterification modification, alkaline treatment, acid treatment, precursor modification, carbon dioxide etching, and coating carbonization processes to achieve a hard carbon anode material with excellent electrochemical performance. Attached Figure Description
[0045] Figure 1 This is a charge-discharge curve of a coin cell assembled from hard carbon negative electrode material according to Embodiment 1 of the present invention. Detailed Implementation
[0046] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.
[0047] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are available from conventional commercial sources or can be obtained by existing known methods.
[0048] In this application, "at least one" and "one or more" can both be understood as a combination of one or more.
[0049] Example 1: Preparation of hard carbon anode material
[0050] A method for preparing a hard carbon anode material includes the following steps:
[0051] (1) Esterification modification: coconut shells (particle size D) 50 The mixture (14±1μm) with citric acid, with a mass concentration of 5% for citric acid and a mass concentration of 95% for coconut shell, was subjected to an esterification reaction at 120℃ for 4 hours to obtain the esterified material.
[0052] (2) Alkali treatment: Immerse the esterified material obtained in step (1) in 0.1 mol / L sodium hydroxide solution, microwave for 30 seconds and sonicate for 10 minutes, and then repeat the microwave treatment for 30 seconds and sonication for 10 minutes twice to obtain the alkali-treated sample.
[0053] (3) Acid treatment: The alkaline-treated sample obtained in step (2) is immersed in an acid solution with a total concentration of 1 mol / L. The acid solution consists of phosphoric acid, perchloric acid and water. The molar ratio of phosphoric acid to perchloric acid is 1:1. The acid treatment time is 30 minutes to obtain the precursor.
[0054] (4) Precursor modification: In a nitrogen atmosphere, the precursor from step (3) is sintered for the first time at a temperature of 800°C for 2 hours, and then pulverized to D. 50 The thickness was 10μm ± 1μm, resulting in a precursor modified material;
[0055] (5) Carbon dioxide etching: In a carbon dioxide atmosphere, the precursor modified material obtained in step (4) is subjected to a second sintering at a temperature of 800°C for 1 hour, and then pulverized to D. 50 The thickness was 10μm ± 1μm, resulting in a carbon dioxide etchant.
[0056] (6) Coating carbonization: The carbon dioxide etchant obtained in step (5) is mixed with the coating agent asphalt. The mass ratio of carbon dioxide etchant to coating agent asphalt is 95:5. The third sintering is carried out in a nitrogen atmosphere. The temperature of the third sintering is 1250℃ and the time of the third sintering is 1.5 hours to obtain hard carbon anode material.
[0057] Example 2: Preparation of hard carbon anode material
[0058] A method for preparing a hard carbon anode material includes the following steps:
[0059] (1) Esterification modification: coconut shells (particle size D) 50 The mixture (14±1μm) was mixed with citric acid, the mass concentration of citric acid was 5%, and the mass concentration of coconut shell was 95%. The mixture underwent an esterification reaction at 125℃ for 4 hours to obtain the esterified material.
[0060] (2) Alkali treatment: Immerse the esterified material obtained in step (1) in a 0.2 mol / L sodium hydroxide solution, microwave for 30 seconds and sonicate for 10 minutes, and then repeat the microwave treatment for 30 seconds and sonication for 10 minutes twice to obtain an alkali-treated sample.
[0061] (3) Acid treatment: The alkaline-treated sample obtained in step (2) is immersed in an acid solution with a total concentration of 1 mol / L. The acid solution consists of phosphoric acid, perchloric acid and water. The molar ratio of phosphoric acid to perchloric acid is 1:1. The acid treatment time is 30 minutes to obtain the precursor.
[0062] (4) Precursor modification: In a nitrogen atmosphere, the precursor from step (3) is subjected to a first sintering at a temperature of 650°C for 2 hours, and then pulverized to D. 50 The thickness was 10μm ± 1μm, resulting in a precursor modified material;
[0063] (5) Carbon dioxide etching: In a carbon dioxide atmosphere, the precursor modified material obtained in step (4) is subjected to a second sintering at a temperature of 650°C for 2 hours, and then pulverized to D. 50 The thickness was 10μm ± 1μm, resulting in a carbon dioxide etchant.
[0064] (6) Coating carbonization: The carbon dioxide etchant obtained in step (5) is mixed with the coating agent phenolic resin. The mass ratio of carbon dioxide etchant to coating agent phenolic resin is 95:5. The third sintering is carried out in a nitrogen atmosphere. The temperature of the third sintering is 1450℃ and the time of the third sintering is 1.5 hours to obtain hard carbon anode material.
[0065] Example 3: Preparation of hard carbon anode material
[0066] A method for preparing a hard carbon anode material includes the following steps:
[0067] (1) Esterification modification: coconut shells (particle size D) 50 The mixture (13±1μm) was mixed with citric acid, the mass concentration of citric acid was 8%, and the mass concentration of coconut shell was 92%. The mixture was subjected to an esterification reaction at 130℃ for 4 hours to obtain the esterified material.
[0068] (2) Alkali treatment: Immerse the esterified material obtained in step (1) in a 0.3 mol / L sodium hydroxide solution, microwave for 25 seconds, sonicate for 8 minutes, and then repeat the microwave treatment for 30 seconds and sonication for 10 minutes 3 times to obtain an alkali-treated sample.
[0069] (3) Acid treatment: The alkaline-treated sample obtained in step (2) is immersed in an acid solution with a total concentration of 0.8 mol / L. The acid solution consists of phosphoric acid, perchloric acid and water. The molar ratio of phosphoric acid to perchloric acid is 1:1.2. The acid treatment time is 30 minutes to obtain the precursor.
[0070] (4) Precursor modification: In a nitrogen atmosphere, the precursor from step (3) is subjected to a first sintering at a temperature of 750°C for 2 hours, and then pulverized to D. 50 The thickness was 10μm ± 1μm, resulting in a precursor modified material;
[0071] (5) Carbon dioxide etching: In a carbon dioxide atmosphere, the precursor modified material obtained in step (4) is subjected to a second sintering at a temperature of 750°C for 2 hours, and then pulverized to D. 50 The thickness was 10μm ± 1μm, resulting in a carbon dioxide etchant.
[0072] (6) Coating carbonization: The carbon dioxide etchant obtained in step (5) is mixed with the coating agent phenolic resin. The mass ratio of carbon dioxide etchant to coating agent phenolic resin is 95:5. The third sintering is carried out in a nitrogen atmosphere. The temperature of the third sintering is 1250℃ and the time of the third sintering is 1.5 hours to obtain hard carbon anode material.
[0073] Comparative Example 1
[0074] Compared with Example 1, the only difference in Comparative Example 1 is that the precursor modification treatment was not performed; the rest of the process was the same as in Example 1.
[0075] Comparative Example 2
[0076] Compared with Example 1, the only difference in Comparative Example 2 is that no alkaline treatment is performed; the rest of the process is the same as in Example 1.
[0077] Comparative Example 3
[0078] Compared with Example 1, the only difference in Comparative Example 3 is that no acid treatment was performed; the rest of the process was the same as in Example 1.
[0079] Comparative Example 4
[0080] Compared with Example 1, the only difference in Comparative Example 4 is that esterification modification was not performed; the rest of the process was the same as in Example 1.
[0081] Product effectiveness test
[0082] The hard carbon anode material prepared in the above examples and comparative examples was mixed with conductive carbon Super-P and PVDF (polyvinylidene fluoride) at a mass ratio of 94:3:3. Then, using N-methylpyrrolidone (NMP) as a solvent, the mixture was thoroughly mixed and coated onto aluminum foil, which was then dried in a vacuum oven at 102°C. After rolling, the foil was cut into circular electrode sheets with a diameter of 8 mm. Sodium sheets were used as the anode, and the electrolyte was NaPF6 ester electrolyte (model NP-001). A glass fiber separator was used, and the batteries were assembled into button cells in an argon-filled glove box. The charge-discharge performance of the seven sodium-ion batteries prepared was tested using a Xinwei battery testing system. The testing method employed constant current and constant voltage discharge and constant current charging, with charge-discharge tests conducted at a current density of 0.1C. The discharge cutoff voltage was 0V, and the charging cutoff voltage was 2.5V. The test results are shown in Table 1.
[0083] Table 1
[0084]
[0085]
[0086] As can be seen from Table 1, the hard carbon anode materials prepared in Examples 1-3 of this invention have higher specific charging capacity compared to Comparative Examples 1-4, especially Example 1, which has the best specific charging capacity and first-cycle charge-discharge efficiency. This demonstrates that precursor modification, alkaline treatment, acid treatment, and esterification modification all have a significant impact on the electrical properties of hard carbon anode materials during their preparation.
[0087] Figure 1 This is a charge-discharge curve of a coin cell assembled from hard carbon anode material according to Embodiment 1 of the present invention. Figure 1 It can be seen that the coin cell assembled from the hard carbon anode material in Example 1 has good electrical performance.
[0088] Furthermore, the yield of the hard carbon anode material prepared in Example 1 of this invention was 62%, while the yield of Comparative Example 2 was 49%. The yield of the hard carbon anode material in other examples was 60-62%, while the yield of other comparative examples was 49-51%.
Claims
1. A method for preparing a hard carbon anode material, characterized in that, Includes the following steps: Biological raw materials and esterifying agents are mixed and reacted to obtain esterified materials; The esterified material is immersed in an alkaline solution and subjected to repeated microwave and ultrasonic treatments to obtain an alkaline-treated sample. The alkaline-treated sample is immersed in an acid solution to obtain a precursor; the total concentration of the acid solution is 0.5-1.5 mol / L, and the acid solution is a mixed solution of phosphoric acid and perchloric acid, wherein the molar ratio of phosphoric acid to perchloric acid in the acid solution is 1:(0.5-1.2). In a protective gas atmosphere, the precursor is sintered for the first time to obtain the modified precursor material; the temperature of the first sintering is 650-800℃ and the time of the first sintering is 0.5-3 hours. In a carbon dioxide atmosphere, the precursor modified material is sintered a second time to obtain a carbon dioxide etchant; the temperature of the second sintering is 480-850℃, and the time of the first sintering is 0.5-3 hours. The carbon dioxide etchant is mixed with a coating agent and sintered for the third time in a protective gas atmosphere to obtain the hard carbon anode material; the temperature of the third sintering is 650-1400℃ and the time of the third sintering is 0.5-3 hours.
2. The method for preparing the hard carbon anode material according to claim 1, characterized in that, The esterifying agent is selected from at least one of maleic anhydride, citric acid, malic acid, and oxalic acid; And / or, the biological raw material is selected from one or more of polysaccharide precursors or biomass, wherein the polysaccharide precursor is selected from one or more of starch, sucrose, and cellulose, and the biomass is selected from one or more of coconut shell, lotus leaf stalk, peanut shell, lignin, fruit shell, rice husk, straw, and corn cob; And / or, the mass ratio of the biological raw material to the esterifying agent is (60-99):(1-40); and / or, the D90of the biological feedstock is less than 1000 μm 50 particle size is no more than 18 μm; The temperature of the mixing reaction is 80-200℃; And / or, the mixing reaction time is 1-8 hours.
3. The method for preparing the hard carbon anode material according to claim 1, characterized in that, The alkaline solution includes at least one of sodium hydroxide solution and potassium hydroxide solution; And / or, the concentration of the alkaline solution is 0.05-0.5 mol / L.
4. The method for preparing the hard carbon anode material according to claim 1, characterized in that, After microwave treatment for 20-30 seconds, ultrasonic treatment is performed for 8-10 minutes. Then, the microwave treatment for 20-30 seconds and ultrasonic treatment for 8-10 minutes are repeated 2-5 times.
5. The method for preparing the hard carbon anode material according to any one of claims 1-4, characterized in that, The protective gas is selected from at least one of argon, nitrogen, hydrogen-argon mixture, and helium; And / or, the first time after sintering also carried out the first time, the first time to the particle size D of the precursor modified material 50 3-15 μm; And / or, after the first sintering, a second pulverization is performed, the second pulverization reducing the particle size of the carbon dioxide etchant to D. 50 It is 3-15μm.
6. The method for preparing the hard carbon anode material according to any one of claims 1-4, characterized in that, The coating agent includes at least one of asphalt and phenolic resin; And / or, the mass ratio of the carbon dioxide etchant to the coating agent is (90-98):(2-10).
7. A hard carbon anode material, characterized in that, It is prepared by the preparation method according to any one of claims 1-6.
8. A sodium-ion battery, characterized in that, Includes a negative electrode, said negative electrode comprising the hard carbon negative electrode material of claim 7.