Artificial graphite and its preparation method and application

Abstract

This invention relates to the field of battery technology, specifically disclosing an artificial graphite, its preparation method, and its applications. The artificial graphite is in the form of primary particles, and the average particle size D of the artificial graphite is... v The micrometer diameter (50) is 8–13 μm, and the specific surface area is 0.9–1.35 m². 2 / g, tap density is 0.89~1.2 g / cm³ 3 The preparation method includes: grinding the raw materials to obtain graphite precursor powder; subjecting the graphite precursor powder to methane vapor-phase deposition, shaping, and graphitizing to obtain artificial graphite. This invention utilizes the thermal decomposition characteristics of methane under specific temperature and gas flow ratio conditions to precisely deposit the carbon elements produced by decomposition into the internal pores and surface microcracks of the ground graphite precursor. The artificial graphite possesses a unique microstructure where internal pores are effectively filled with carbon and surface microcracks are healed, resulting in a significantly reduced specific surface area, a markedly increased tap density, and a high degree of graphitization. When used as a negative electrode in lithium-ion batteries, it can reduce electrolyte consumption, improve initial coulombic efficiency, and increase electrode energy density.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to an artificial graphite, its preparation method, and its application. Background Technology

[0002] Artificial graphite has become the mainstream choice for lithium-ion battery anode materials due to its high conductivity, good layered structure, and stable cycle performance. Current artificial graphite preparation processes mainly include three core steps: grinding, shaping, and graphitization. First, raw materials such as petroleum coke and needle coke are crushed and ground to the target particle size; then, the particle morphology is optimized and sharp edges are reduced using shaping equipment; finally, high-temperature graphitization treatment is used to improve the degree of graphitization.

[0003] However, after the grinding process, a large number of micron-sized pores and surface microcracks are easily formed inside the graphite precursor particles. These defects lead to two major problems in the subsequent finished products: 1. High specific surface area (BET): Surface microcracks and pores increase the specific surface area of ​​particles, which can easily lead to excessive electrolyte consumption in battery applications and cause a decrease in the first coulombic efficiency; 2. Low tap density: Internal pores reduce the compactness of particle packing, which directly affects the energy density of the battery electrode.

[0004] In existing technologies, the repair of graphite defects is mostly focused on post-graphitization coating modification (such as coating asphalt). However, this method can only improve the surface properties of particles and cannot repair internal pore defects. Moreover, the additional coating layer will increase the process cost and may also introduce impurities. Summary of the Invention

[0005] Based on this, the purpose of this invention is to provide artificial graphite, its preparation method and application. The process improvement method, which introduces a CVD methane treatment process to repair defects in artificial graphite precursors and improve material performance, is particularly suitable for the preparation of artificial graphite for lithium-ion battery anodes where there are strict requirements for tap density and specific surface area.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: This invention provides an artificial graphite, which is a primary particle with an average particle size D. v The micrometer diameter (50) is 8–13 μm, and the specific surface area is 0.9–1.35 m². 2 / g, tap density is 0.89~1.2 g / cm³ 3 .

[0007] This invention utilizes methane vapor deposition to deposit graphite precursor powder. Taking advantage of the thermal decomposition characteristics of methane under specific temperature and gas flow ratio conditions, the carbon elements produced during decomposition are precisely deposited into the internal pores and surface microcracks of the milled graphite precursor, achieving defect filling from the inside out. The pore filling rate can reach over 80%. Simultaneously, the surface roughness of the particles is optimized, ultimately increasing the tap density and reducing the specific surface area of ​​the finished product. This artificial graphite possesses a unique microstructure where internal pores are effectively filled with carbon and surface microcracks are healed. This results in a significantly reduced specific surface area, a markedly increased tap density, and a high degree of graphitization. When used as a negative electrode in lithium-ion batteries, it can reduce electrolyte consumption, improve initial coulombic efficiency, and increase electrode energy density.

[0008] The present invention also provides a method for preparing artificial graphite, which includes the following steps: grinding raw materials to obtain graphite precursor powder; subjecting the graphite precursor powder to methane vapor phase deposition reaction, shaping, and graphitizing to obtain artificial graphite.

[0009] This invention adds a CVD methane vapor deposition process between the grinding and shaping processes in traditional artificial graphite manufacturing. By utilizing the thermal decomposition characteristics of methane under specific temperature and gas flow ratio conditions, the carbon elements produced by the decomposition are precisely deposited into the internal pores and surface microcracks of the graphite precursor after grinding, achieving defect filling from the inside out, with a pore filling rate of over 80%. At the same time, the surface roughness of the particles is optimized, ultimately improving the tap density of the finished product and reducing the specific surface area.

[0010] The CVD methane treatment process of this invention only needs to be added between grinding and shaping, without the need to modify existing graphitization furnaces, shaping machines and other equipment. The equipment investment cost is low and it is easy to promote industrialization.

[0011] As a further improvement to the above-mentioned scheme of the present invention, the methane vapor deposition reaction involves placing the graphite precursor powder into a chemical vapor deposition reactor and introducing methane and argon gas for reaction, wherein the volume ratio of methane to argon gas is 1:3-8. Using a methane to argon gas volume ratio of 1:3-8 for the reaction can effectively control the methane thermal decomposition rate and carbon deposition uniformity, avoiding excessive carbon deposition that could lead to particle agglomeration or surface roughness; simultaneously, both methane and argon are conventional industrial gases, with low raw material costs, making them suitable for large-scale production.

[0012] As a further improvement to the above-mentioned scheme of the present invention, the temperature of the methane vapor deposition reaction is 800-1200℃, and the time is 30-120 min. Reacting at 800-1200℃ for 30-120 min ensures that the methane is fully thermally decomposed and accurately fills the internal pores and microcracks of the precursor, without significantly extending the overall production cycle. This temperature range has good compatibility with conventional CVD equipment, moderate energy consumption, and facilitates process integration.

[0013] As a further improvement to the above-mentioned solution of the present invention, the chemical vapor deposition reactor is a continuous reactor, in which the graphite precursor powder is conveyed at a uniform speed of 0.5-1 m / min via a conveyor belt, and the reactor is maintained at atmospheric pressure. Using a continuous reactor in conjunction with uniform conveyor belt transport (0.5-1 m / min) enables continuous CVD processing of the precursor powder, ensuring that each powder particle is uniformly contacted with the reaction atmosphere, significantly improving production efficiency. The atmospheric pressure condition reduces equipment sealing requirements, further reducing equipment investment and operating costs, and facilitates seamless integration with upstream and downstream grinding and shaping processes, avoiding particle agglomeration caused by high pressure.

[0014] As a further improvement to the above-mentioned solution of the present invention, the raw material is petroleum coke and / or needle coke, and the grinding is carried out at a speed of 300-400 r / min for 2-3 hours. Using petroleum coke and / or needle coke as raw materials, combined with grinding at 300-400 r / min for 2-3 hours, precursor powder with moderate particle size and uniform distribution can be obtained, providing sufficient and controllable pores and microcrack interfaces for subsequent CVD methane deposition, thereby maximizing the defect filling effect.

[0015] As a further improvement to the above-described solution of the present invention, the D50 of the graphite precursor powder is 8-12 μm. Compared with the traditional process, the present invention reduces the specific surface area by 20% (from 1.5 μm) while maintaining the D50 of the graphite precursor powder at 10.5 μm. 2 / g decreased to 1.2 m 2 / g), tap density increased by 12.7% (from 1.02 g / cm³). 3 Increased to 1.15 g / cm³ 3 This effectively solves the problem of balancing low specific surface area and high tap rate, meeting the requirements for high energy density anode materials for lithium-ion batteries.

[0016] As a further improvement to the above-mentioned solution of the present invention, the shaping is performed in a shaping machine at a rotation speed of 200-300 r / min for 1-2 hours. Shaping (200-300 r / min, 1-2 hours) after CVD methane deposition can further optimize particle sphericity and surface morphology, eliminate possible slight adhesion or surface roughness, and ensure the stability of the electrochemical performance of the finished negative electrode material.

[0017] As a further improvement to the above-mentioned solution of the present invention, the graphitization is carried out in a graphitization furnace at 2200-2800℃ for 4-6 hours. Graphitization at 2200-2800℃ for 4-6 hours allows the precursor after CVD filling and repair to be fully converted into artificial graphite with a high degree of graphitization, while maintaining the dense structure after the internal pores are filled with carbon, ultimately obtaining a high-quality anode material with high tap density and low specific surface area.

[0018] This invention also provides an application of the aforementioned artificial graphite as a lithium battery anode material. When this artificial graphite is used as a lithium battery anode, its low specific surface area and high tap density can effectively reduce side reactions between the electrolyte and the anode, thereby improving the initial coulombic efficiency. Simultaneously, the higher tap density helps reduce electrode expansion and improves the battery's cycle performance, making it particularly suitable for high-end lithium-ion batteries with high requirements for cycle stability. Detailed Implementation

[0019] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0020] 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 description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0021] Example 1 This embodiment proposes an artificial graphite, the preparation method of which includes the following steps: S1. Raw material grinding and processing Petroleum coke raw material was fed into a ball mill and ground at 350 r / min for 2.5 h to obtain precursor powder with D50=10.5 μm.

[0022] S2.CVD Methane Deposition Process The obtained precursor powder was fed into a continuous CVD reactor for vapor deposition, with the specific parameters controlled as follows: Reaction atmosphere: Methane (CH4) is used as the carbon source gas, and argon (Ar) is used as the protective gas; gas flow ratio: the volume ratio of methane to argon is 1:3; Reaction temperature: 800℃; Reaction time: 60min; Pressure control: Maintain atmospheric pressure (1atm) inside the reactor to avoid particle agglomeration caused by high pressure; Material condition: The material is conveyed at a constant speed (0.8m / min) via a conveyor belt to ensure that each powder particle is in uniform contact with the reaction atmosphere.

[0023] S3. Plastic Surgery The graphite precursor powder treated with CVD methane was fed into a shaping machine and processed at 250 r / min for 1.5 h to smooth the particle surface and remove a small amount of carbon nanotubes or irregular carbon particles generated during the deposition process.

[0024] S4. High-temperature graphitization The shaped powder is fed into a graphitization furnace and kept at 2500℃ for 5 hours for high-temperature graphitization treatment, finally obtaining the finished artificial graphite product.

[0025] Example 2 The difference between this embodiment and Embodiment 1 is that the reaction temperature in the CVD methane deposition step of this embodiment is 1000℃.

[0026] Example 3 The difference between this embodiment and Example 1 is that the reaction temperature in the CVD methane deposition step of this embodiment is 1200℃.

[0027] Example 4 The difference between this embodiment and Embodiment 1 is that in the CVD methane deposition process of this embodiment, the volume ratio of methane to argon is 1:5.

[0028] Example 5 The difference between this embodiment and embodiment 4 is that the reaction temperature in the CVD methane deposition step of this embodiment is 1000℃.

[0029] Example 6 The difference between this embodiment and Example 4 is that the reaction temperature in the CVD methane deposition step of this embodiment is 1200℃.

[0030] Example 7 The difference between this embodiment and Embodiment 1 is that in the CVD methane deposition process of this embodiment, the volume ratio of methane to argon is 1:8.

[0031] Example 8 The difference between this embodiment and Example 7 is that the reaction temperature in the CVD methane deposition step of this embodiment is 1000℃.

[0032] Example 9 The difference between this embodiment and Embodiment 7 is that the reaction temperature in the CVD methane deposition step of this embodiment is 1200℃.

[0033] Comparative Example This comparative example presents an artificial graphite, the preparation method of which includes the following steps: S1. Raw material grinding and processing Petroleum coke raw material was fed into a ball mill and ground at 350 r / min for 2.5 h to obtain precursor powder with D50=10.5 μm.

[0034] S2. Plastic Surgery The precursor powder was fed into a shaping machine and processed at 250 r / min for 1.5 h to smooth the particle surface.

[0035] S3. High-temperature graphitization The shaped precursor powder is fed into a graphitization furnace and held at 2500℃ for 5 hours for high-temperature graphitization treatment, finally obtaining the finished artificial graphite product.

[0036] Test case The following tests were performed on the artificial graphite materials of Examples 1-9 and the comparative examples: Specific surface area (BET): Detected using liquid nitrogen adsorption method (BET multi-point method); Tap density: According to GB / T 5162-2021 "Graphite Anode Materials for Lithium-ion Batteries", the tap density was tested using a tap density meter (vibration frequency 300 times / min, vibration time 5min).

[0037] The test results are shown in Table 1.

[0038]

[0039] The results in Table 1 show that: Compared to the comparative examples, Examples 1-9 Based on the results of Examples 1-3, when the volume ratio of methane to argon in CVD methane deposition treatment is 1:3 and the reaction time is 60 min, the excess methane can easily lead to uneven carbon deposition on the surface. Therefore, at a gas flow ratio of 1:3, the deposition time should be appropriately shortened.

[0040] Based on the results of Examples 4-6, the optimal effect was achieved when the volume ratio of methane to argon in the CVD methane deposition treatment was 1:5 and the reaction time was 60 min, at a reaction temperature of 1000 °C.

[0041] Based on the results of Examples 7-9, when the volume ratio of methane to argon in CVD methane deposition treatment is 1:8 and the reaction time is 60 min, insufficient methane leads to inadequate filling of pores, and the deposition time should be appropriately extended.

[0042] 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.

[0043] 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. Artificial graphite, characterized by, The artificial graphite is primary particles, and the average particle diameter D v 50 is 8 to 13 μm, the specific surface area is 0.9 to 1.35 m 2 / g, and the tap density is 0.89 to 1.2 g / cm 3 .

2. The method of producing artificial graphite according to claim 1, characterized by, It includes the following steps: The raw materials are ground to obtain graphite precursor powder; the graphite precursor powder is subjected to methane vapor deposition reaction, shaped, and graphitized to obtain artificial graphite.

3. The method for producing artificial graphite according to claim 2, characterized by, The methane vapor deposition reaction involves placing the graphite precursor powder into a chemical vapor deposition reactor and introducing methane and argon gas for reaction, wherein the volume ratio of methane to argon gas is 1:3-8.

4. The method for producing artificial graphite according to claim 3, characterized by, The temperature of the methane vapor deposition reaction is 800-1200℃, and the time is 30-120 min.

5. The method of claim 3, wherein the method further comprises the step of: The chemical vapor deposition reactor is a continuous reactor, in which the graphite precursor powder is conveyed at a constant speed of 0.5-1 m / min via a conveyor belt, and the reactor is kept at atmospheric pressure.

6. The method of claim 2, wherein the artificial graphite is prepared by the steps of: The raw material is petroleum coke and / or needle coke, and the grinding is carried out at a speed of 300-400 r / min for 2-3 hours.

7. The method of claim 2, wherein the method further comprises the step of: The D50 of the graphite precursor powder is 8-12 μm.

8. The method of claim 2, wherein the artificial graphite is prepared by the steps of: The shaping process involves processing the material in a shaping machine at a rotation speed of 200-300 r / min for 1-2 hours. ​ 9. The method of claim 2, wherein the artificial graphite is prepared by the steps of: The graphitization process involves holding the material at 2200-2800℃ in a graphitization furnace for 4-6 hours. ​ 10. An application of the artificial graphite as described in claim 1 as a negative electrode material for lithium batteries.

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