Preparation method of graphite negative electrode material

Abstract

The present application belongs to the technical field of graphite negative electrode material preparation, and particularly relates to a preparation method of graphite negative electrode material, comprising the following steps: step one, low-temperature carbonization treatment: low-temperature carbonization treatment is performed on petroleum coke; step two, crushing: the petroleum coke after low-temperature carbonization treatment is cooled and then crushed and screened; and step three, graphitization treatment: graphite negative electrode material is obtained. The present application adopts ordinary petroleum coke as raw material, and through low-temperature carbonization-crushing-pulverization-graphitization (product), the low-temperature carbonization is heating treatment on ordinary petroleum coke, and the low-temperature carbonized material after heating treatment is cooled. The prepared negative electrode material has low cost, greatly improved performance, and the pre-carbonization process is omitted, so that the production cycle can be shortened and the production yield can be improved, and the cost performance is high in actual use.

Description

Technical Field

[0001] This invention belongs to the field of graphite anode material preparation technology, specifically relating to a method for preparing graphite anode materials. Background Technology

[0002] Anode materials are one of the key materials in lithium-ion batteries. Currently, commercially available lithium-ion battery anode materials are mainly carbon-based. They possess advantages such as high specific capacity (200–400 mAh / g), low electrode potential (<1.0V vsLi+ / Li), high cycle efficiency (>95%), and long cycle life. Carbon-based anode materials include mesophase carbon microspheres (MCMB), graphite, and amorphous carbon. Among these, graphite materials have high theoretical lithium intercalation capacity, good conductivity, and a well-developed layered structure, making them a focus of lithium battery research in recent years. Graphite materials can be divided into artificial graphite and natural graphite. Natural graphite has advantages such as large specific surface area, high specific capacity, and high initial efficiency. However, it is prone to solvent co-intercalation during charging and discharging, resulting in poor cycle performance. Furthermore, natural graphite is a non-renewable mineral resource, and its quality is significantly affected by cost control and product quality. Artificial graphite has a lower degree of graphitization than natural graphite, but it has advantages such as good rate performance, good compatibility with electrolytes, and good cycle stability, thus becoming a research hotspot in recent years.

[0003] The anode material market has been growing steadily in recent years, with major global manufacturers including companies from China, Japan, and South Korea. With the rapid development of electric vehicles, energy storage, and other fields, the market demand for anode materials will continue to grow. In the future, anode materials will develop towards high performance, low cost, and environmental friendliness. However, the current production of traditional artificial graphitized anode materials still requires a pre-carbonization process, which is not only time-consuming and labor-intensive but also increases production costs. Summary of the Invention

[0004] To address the problems in the prior art, this invention provides a method for preparing graphite anode materials, aiming to achieve low cost and high performance in the preparation of graphite anode materials.

[0005] The technical problem solved by this invention is achieved by the following technical solution:

[0006] The present invention aims to provide a method for preparing a graphite anode material, comprising the following steps:

[0007] Step 1: Low-temperature carbonization treatment: The petroleum coke is subjected to low-temperature carbonization treatment;

[0008] Step 2, Crushing: The petroleum coke after low-temperature carbonization is cooled down and then crushed and screened.

[0009] Step 3: Graphitization treatment: to obtain graphite anode material.

[0010] Furthermore, the low-temperature carbonization process involves a feed temperature of 600–800°C, with the temperature decreasing in stages through 6–8 low-temperature carbonization zones.

[0011] Furthermore, the cooling rate is 30–45 °C / h, and the low-temperature carbonization time is 32–38 h.

[0012] Furthermore, there is a preheating zone before the low-temperature carbonization zone. The low-temperature carbonization process is carried out in a low-temperature carbonization furnace. The furnace body is arranged from top to bottom as a preheating zone and 6 to 8 low-temperature carbonization zones. A feed hopper is provided above the preheating zone. A volatilization space is left between the feed hopper and the low-temperature carbonization furnace. Interconnected combustible gas channels are provided around the preheating zone and the low-temperature carbonization zone.

[0013] Furthermore, petroleum coke smaller than 50mm was selected as raw material for low-temperature carbonization treatment.

[0014] Furthermore, in step two, a jaw crusher is used for crushing, and the crushed low-temperature carbonized material is then crushed and screened by a ring roller mill to produce particles with a D50 size of 14-17 μm, thus obtaining low-temperature carbonized raw material powder.

[0015] Furthermore, the graphitization process involves taking the low-temperature carbonized raw material powder from step two, heat-treating it from 25°C through multiple stages to 3000°C, and then maintaining a constant temperature.

[0016] Furthermore, the graphitization process includes the following stages:

[0017] The heating rate of the first stage heat treatment is 45℃ / h to 60℃ / h; the temperature of the first stage heat treatment is 25℃ to 1200℃; and the treatment time of the first stage heating is 20h to 26h.

[0018] The heating rate for the second stage of heat treatment is 40℃ / h to 50℃ / h; the temperature for the second stage of heat treatment is 1200℃.

[0019] ~2200℃; the second stage of heating treatment lasts for 20h to 26h;

[0020] The heating rate for the final stage of graphitization is 55℃ / h to 80℃ / h; the graphitization temperature is 2200℃.

[0021] ~3000℃; the graphitization treatment time is 10h to 15h.

[0022] After the graphitization process reaches the final temperature, it is kept at a constant temperature for 12 to 17 hours.

[0023] Furthermore, the graphitization process is carried out in an Atchison graphitization crucible furnace or an Atchison graphitization box furnace.

[0024] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0025] 1. The present invention uses ordinary petroleum coke as raw material, and processes it through low-temperature carbonization → crushing → pulverization → graphitization (product). Low-temperature carbonization involves heating the ordinary petroleum coke and then cooling the carbonized material. The resulting anode material has low cost and significantly improved performance. It also eliminates the pre-carbonization process, which can shorten the production cycle and increase production output. It has a high cost-performance ratio in practical use.

[0026] 2. Compared to traditional methods of processing carbonaceous raw materials at temperatures typically between 1250 and 1380°C, the low-temperature carbonization furnace of this invention operates at 600–800°C, employing a stepped cooling method to remove moisture and most volatile components from the raw materials. Low-temperature carbonization removes a significant portion of the volatiles, thereby increasing the fixed carbon content of the raw materials. The removal of moisture through low-temperature carbonization facilitates crushing, screening, and grinding processes, improving product performance and increasing the density and mechanical strength of the raw materials. Carbon materials that have undergone low-temperature carbonization experience a significant volume reduction, increased density, and enhanced strength due to the removal of most volatiles, while also achieving better thermal stability.

[0027] 3. The preparation method of this invention can also improve the electrical conductivity of the raw materials. Low-temperature carbonization eliminates most of the volatiles, and the molecular structure also changes, reducing resistivity and improving the conductivity of the raw materials. The resistivity of the carbon raw materials after low-temperature carbonization is 700–1200 μΩ·m, and the volatile content is 4–6%; the resistivity of the carbon raw materials treated by conventional methods is 450–550 μΩ·m, and the volatile content is 0.3–0.6%.

[0028] 4. The low-temperature carbonization of this invention can be completed at a lower temperature and in a shorter time, reducing energy consumption and preparation costs. Furthermore, low-temperature carbonization improves the tap density of the anode material while retaining its high conductivity, high capacity, and long lifespan. This improves the production efficiency of graphitization and ensures product quality, resulting in higher charge / discharge capacity, charge / discharge efficiency, and cycle efficiency. It also optimizes the electrical properties of the graphite anode material. The loosening process ensures the anode material is in a loose state, preventing caking. This method can also shorten the anode material production cycle, reduce production costs, and increase the yield of the anode material.

[0029] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above contents, objectives, features and advantages of the present invention more obvious and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0030] Figure 1 This is a scanning electron microscope image of the graphite anode material of the present invention.

[0031] Figure 2 This is a schematic diagram of the structure of a low-temperature carbonization furnace.

[0032] 1-Feed hopper, 2-Volatile space, 3-Combustible gas channel, A-Preheating zone, B1-First low-temperature carbonization zone, B2-Second low-temperature carbonization zone, B3-Third low-temperature carbonization zone, B4-Fourth low-temperature carbonization zone, B5-Fifth low-temperature carbonization zone, B6-Sixth low-temperature carbonization zone, B7-Seventh low-temperature carbonization zone, B8-Eighth low-temperature carbonization zone. Detailed Implementation

[0033] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0034] In addition, unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be obtained by purchasing them from the market or prepared by existing methods.

[0035] This invention provides a low-cost, low-temperature carbonized graphite anode material for energy storage, comprising the following production steps:

[0036] 1. Low-temperature carbonization treatment: Low-temperature carbonization treatment of ordinary petroleum coke;

[0037] 2. Crushing: The ordinary petroleum coke after low-temperature carbonization is cooled down and then crushed and screened.

[0038] 3. Graphitization treatment: to obtain a low-cost, low-temperature carbonized energy storage anode material.

[0039] Low-temperature carbonization stage:

[0040] The low-temperature carbonization of ordinary petroleum coke is carried out in a low-temperature carbonization furnace. Based on material requirements, a dedicated loading device is preferred to transport the material to the feeding equipment. During feeding, large pieces larger than 50mm and impurities should be removed and piled up for crushing. The material is then crushed into fine particles by roller crushing in the feeding equipment. After crushing, it enters the distributing equipment via an elevator, which evenly distributes the material into each feed hopper. The material in each feed hopper is replenished according to the low-temperature carbonization frequency.

[0041] The tank of the low-temperature carbonization furnace is arranged from top to bottom as a preheating zone and 6-8 low-temperature carbonization zones. A feed hopper 1 is located above the preheating zone, with a volatile space 2 between the feed hopper 1 and the low-temperature carbonization furnace. Interconnected combustible gas channels 3 surround the preheating zone A and the low-temperature carbonization zones. The petroleum coke particles, after being crushed and impurity-removed, are first placed into the preheating zone A for preheating, and then sequentially pass through multiple low-temperature carbonization zones, preferably eight: the first low-temperature carbonization zone B1, the second low-temperature carbonization zone B2, the third low-temperature carbonization zone B3, the fourth low-temperature carbonization zone B4, and the fifth low-temperature carbonization zone B5. Low-temperature carbonization zones B4, B5, B6, B7, and B8 are used to obtain low-temperature carbonized petroleum coke. During the low-temperature carbonization process, the petroleum coke combustible gas generated by the petroleum coke particles enters the combustible gas channel 3 through the preheating zone A. The low-temperature carbonization temperature of each low-temperature carbonization zone is controlled by adjusting the combustion status of the petroleum coke combustible gas and controlling the material emission rate. The temperature can also be controlled by adjusting the amount of natural gas.

[0042] The low-temperature carbonization process for petroleum coke also includes the following steps: controlling the low-temperature carbonization temperature of the uppermost first low-temperature carbonization zone B1 within the maximum allowable low-temperature carbonization temperature range for petroleum coke; maintaining the low-temperature carbonization temperature of the second low-temperature carbonization zone B2, located downstream of the first low-temperature carbonization zone B1, within the maximum low-temperature carbonization temperature range but not higher than the low-temperature carbonization temperature of the first low-temperature carbonization zone B1; starting from the third low-temperature carbonization zone B3, the low-temperature carbonization temperature of each low-temperature carbonization zone gradually decreases relative to the low-temperature carbonization temperature of the adjacent upstream low-temperature carbonization zone; and in the most downstream low-temperature carbonization zone, the low-temperature carbonization temperature is reduced to the discharge temperature.

[0043] The material is carbonized at low temperature, with the temperature of the uppermost layer controlled at 600-800℃. The low temperature carbonization temperature is controlled in 6-8 low temperature carbonization zones with a temperature gradient of 30-45℃. The low temperature carbonization time is 32-38 hours. After low temperature carbonization, the material is discharged from the outlet of the last low temperature carbonization zone of the low temperature carbonization furnace and transferred to the next workshop.

[0044] broken

[0045] The material is crushed using a jaw crusher, and the crushed low-temperature carbonized material is then pulverized and screened, and then crushed by a ring roller mill. The particle size (D50) of the pulverized material is 14-17 μm, resulting in low-temperature carbonized raw material powder.

[0046] Graphitization stage:

[0047] 1. The heating rate of the first stage heat treatment is 45℃ / h~60℃ / h; the temperature of the first stage heat treatment is 25℃.

[0048] The temperature is ~1200℃, and the first stage of heating takes 20h to 26h.

[0049] 2. The heating rate of the second stage heat treatment is 40℃ / h~50℃ / h; the temperature of the second stage heat treatment is 1200℃~2200℃; and the treatment time of the second stage heating is 20h~26h.

[0050] 3. The heating rate of the final stage graphitization treatment is 55℃ / h~80℃ / h; the graphitization treatment temperature is 2200℃~3000℃; and the graphitization treatment time is 10h~15h.

[0051] 4. After the graphitization treatment reaches the final temperature, maintain the temperature for 12 to 17 hours.

[0052] The conditions and methods for graphitization are those commonly used in this field, generally carried out in an Atchison graphitization crucible furnace. This furnace type is mainly an improvement on the traditional electrode Atchison furnace graphitization furnace, with a graphite crucible serving as the carrier for the negative electrode material. The crucible contains the low-temperature carbonized negative electrode raw material. The furnace core is filled with a heating resistance material, and the outer layer is insulated with insulating material and furnace walls. When electricity is applied, the resistance material heats up to a high temperature of 2800–3000°C, indirectly heating the negative electrode material inside the crucible, ultimately achieving high-temperature graphitization of the negative electrode material.

[0053] Graphitization can also be performed in an Atchison graphitization box furnace. The box furnace fills the chamber with low-temperature carbonization material, inserts insulation material on the top and sides, and then graphitizes by supplying electricity. This type of furnace employs advanced sealing technology, allowing the graphite to rapidly heat up and reach its high-temperature state, thus achieving graphitization in a shorter time. The box furnace is simple and convenient to operate, has low requirements for environmental and equipment maintenance, and also boasts a long service life and low operating costs.

[0054] Example 1

[0055]

[0056] Example 2

[0057]

[0058]

[0059] Example 3

[0060]

[0061] The following equipment was used to test the performance of the graphite anode materials prepared in Examples 1-3.

[0062]

[0063] The performance parameters obtained from tests in Examples 1-3 are as follows:

[0064]

[0065] The results in the table above show that the initial capacity of the low-temperature carbonized anode materials in Examples 1-3 is 351-352 mAh / g, indicating that the low-temperature carbonized anode materials of the present invention have the advantage of high capacity when applied to full batteries; and the tap density values ​​of the low-temperature carbonized anode materials in Examples 1-3 are 1.11-1.17 g / cm³. 3 This demonstrates that the low-temperature carbonized negative electrode material of the present invention exhibits excellent cycle performance and a longer service life when applied to full batteries.

[0066] The sequence numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0067] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A method for preparing a graphite anode material, characterized in that, Includes the following steps: Step 1: Low-temperature carbonization treatment: The petroleum coke is subjected to low-temperature carbonization treatment; Step 2, Crushing: The petroleum coke after low-temperature carbonization is cooled down and then crushed and screened. Step 3: Graphitization treatment: to obtain graphite anode material; The low-temperature carbonization process involves feeding at a temperature of 600-800℃ and then gradually reducing the temperature in 6-8 low-temperature carbonization zones. The cooling gradient is 30~45℃, and the low-temperature carbonization time is 32h~38h; The graphitization process includes taking the low-temperature carbonized raw material powder from step two, heat-treating it from 25°C through multiple stages to 3000°C, and then maintaining a constant temperature. The graphitization process includes the following stages: The heating rate of the first stage heat treatment is 45℃ / h~60℃ / h; the temperature of the first stage heat treatment is 25℃~1200℃; and the treatment time of the first stage heating is 20h~26h. The heating rate of the second stage heat treatment is 40℃ / h~50℃ / h; the temperature of the second stage heat treatment is 1200℃~2200℃; and the treatment time of the second stage is 20h~26h. The heating rate for the final stage of graphitization treatment is 55℃ / h~80℃ / h; the graphitization temperature is 2200℃~3000℃; and the heating time for graphitization treatment is 10h~15h. After the graphitization process reaches the final temperature, it is kept at a constant temperature for 12 to 17 hours.

2. The method for preparing a graphite anode material as described in claim 1, characterized in that: There is a preheating zone before the low-temperature carbonization zone. The low-temperature carbonization process is carried out in the low-temperature carbonization furnace. The furnace body is arranged from top to bottom as a preheating zone and 6 to 8 low-temperature carbonization zones. A feed hopper is provided above the preheating zone. A volatilization space is left between the feed hopper and the low-temperature carbonization furnace. There are interconnected combustible gas channels around the preheating zone and the low-temperature carbonization zone.

3. The method for preparing a graphite anode material as described in claim 1, characterized in that: Petroleum coke smaller than 50mm was selected as raw material and subjected to low-temperature carbonization treatment.

4. The method for preparing a graphite anode material as described in claim 1, characterized in that: In step two, a jaw crusher is used for crushing. The crushed low-temperature carbonized material is then crushed and screened by a ring roller mill. The particle size (D50) is 14~17um, resulting in low-temperature carbonized raw material powder.

5. The method for preparing a graphite anode material as described in claim 1, characterized in that: The graphitization process is carried out in an Atchison graphitization crucible furnace or an Atchison graphitization box furnace.

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