A method for producing artificial graphite negative electrode material by using graphitization box furnace

Abstract

The application discloses a method for producing artificial graphite negative electrode material by adopting graphitization compartment type furnace, and comprises the following steps: S1. A plurality of graphite trapezoidal electrode blocks are spliced and assembled into middle electrodes connected with two ends of conductive electrodes, and the splicing positions of the adjacent two graphite trapezoidal electrode blocks are supported by graphite pad blocks; S2. Artificial graphite negative electrode material is loaded; S3. Graphite felt and top cover plate are sequentially laid on the surface of the artificial graphite negative electrode material; S4. Fine heat preservation material and coarse heat preservation material are alternately laid on the upper surface of the top cover plate in the horizontal direction; S5. Electricity is supplied; S6. After the electricity supply is completed, the top of the coarse heat preservation material in step S4 is covered by fine heat preservation material; and S7. Cooling and furnace discharge are carried out. The specific surface area of the negative electrode material produced by the compartment type furnace can reach the level of Acheson furnace, and the quality is more excellent. Meanwhile, the graphite trapezoidal electrode blocks are adopted, so that the space utilization rate can be effectively improved, and the loading capacity of the negative electrode material is improved.

Description

Technical Field

[0001] This invention belongs to the field of artificial graphite technology, specifically relating to a method for producing artificial graphite anode materials using a graphitization chamber furnace. Background Technology

[0002] Currently, the two most widely used graphitization equipment for artificial graphite anode materials are crucible furnaces and box furnaces.

[0003] Among them, the traditional process of box-type furnaces, such as Figures 1-2 As shown, the furnace core space is divided into several equal-volume chambers by graphite plates. The negative electrode material is placed directly into the enclosed small chamber space, and after filling, it is covered with insulation material on the top layer. Compared with crucible furnaces, the effective volume of the chamber furnace is increased, the production capacity is increased by about 100%, and the energy consumption per unit of product is reduced by about 40-50%. However, this structure uses more vertical graphite plates, and graphite plates themselves are prone to ablation and wear. When the current flows through the graphite plates in the furnace, the current density is unevenly distributed, resulting in uneven heating of the overall material, poor consistency, and irregular discharge of volatiles, leading to localized furnace spraying. The specific surface area of ​​the product is also 25-40% higher than that of crucible furnaces. Specific surface area is one of the important physicochemical properties of anode materials. Excessive specific surface area not only leads to agglomeration and streaking during the homogenization and coating of the electrode, but also increases the side reactions between the anode material and the electrolyte during the battery charging and discharging process, resulting in the consumption of more electrolyte, the generation of more SEM films, and an increase in the loss of initial cycle capacity. In addition, more binder is required during homogenization, which leads to an increase in interfacial electrochemical impedance. Summary of the Invention

[0004] The purpose of this invention is to provide a method for producing artificial graphite anode materials using a graphitization box furnace to overcome the shortcomings of the prior art, which can reduce the specific gravity of the material produced by the box furnace to the level of the Atchison crucible furnace.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A method for producing artificial graphite anode material using a graphitization chamber furnace, wherein the graphitization chamber furnace comprises an open chamber consisting of conductive end walls at both ends, graphite plates on both sides, and a graphite plate at the bottom. Conductive electrodes are symmetrically arranged on the conductive end walls at both ends, with one end of each conductive electrode extending into the chamber and the other end located outside the chamber for connection to a power supply device. The method includes the following steps:

[0007] S1. Inside the compartment, multiple graphite trapezoidal electrode blocks are spliced ​​together to form an intermediate electrode that connects the conductive electrodes at both ends, and graphite pads are used to support the splicing of two adjacent graphite trapezoidal electrode blocks.

[0008] S2. Inside the compartment, artificial graphite negative electrode material is filled around the graphite trapezoidal electrode block and the graphite pad block;

[0009] S3. Graphite felt and a top cover plate are sequentially laid on the surface of the artificial graphite negative electrode material;

[0010] S4. Fine insulation material and coarse insulation material are alternately laid on the upper surface of the top cover plate in the horizontal direction;

[0011] S5. Power is supplied to bring the furnace temperature to the graphitization temperature;

[0012] S6. After power supply is completed, cover the top of the coarse insulation material described in step S4 with fine insulation material;

[0013] S7. Cooling, and the graphitized anode material is obtained upon removal from the furnace.

[0014] Preferably, there are multiple sets of conductive electrodes and intermediate electrodes.

[0015] Preferably, in step S2, when filling the artificial graphite negative electrode material, it is filled layer by layer, and the filling height is slightly lower than the graphite plates on both sides.

[0016] Preferably, the fine insulation material has a particle size of 7-9 μm, and the coarse insulation material has a particle size of 10-12 mm.

[0017] Preferably, the width of the fine insulation material laying area is 5 to 8 meters, and the width of the coarse insulation material laying area is 30 to 60 mm.

[0018] Preferably, in steps S5 and S6, when a fire occurs, fine insulating material is used to cover and extinguish it.

[0019] Preferably, in step S7, the material is first naturally cooled for 7 to 10 days, and then cooled with cooling water. The material is removed from the furnace when the temperature of the fine insulation material is <50°C.

[0020] Preferably, in step S7, during the natural cooling and cooling water cooling stages, if cracks or overheating occur in the insulation material, yellow mud is applied for repair.

[0021] Preferably, the artificial graphite negative electrode material on the surface is discarded after the furnace is removed from the furnace.

[0022] Preferably, the graphitization chamber furnace further includes a refractory wall located outside the bottom graphite plate and the two side graphite plates, and carbon black is filled between the bottom graphite plate, the two side graphite plates and the refractory wall.

[0023] The carbon black filling height between the graphite plates on both sides and the fire-resistant wall is lower than that between the graphite plates on both sides, and fine thermal insulation material is filled above the carbon black between the graphite plates on both sides and the fire-resistant wall.

[0024] By employing the graphitization chamber furnace provided in this application, and through optimized production processes such as using graphite felt, alternating between fine and coarse insulation materials on the top cover plate, and covering the coarse insulation material with fine insulation material after power supply, volatile matter can be effectively guided out, preventing localized high positive pressure that could lead to furnace blowouts or fires. This improves the heating uniformity of the negative electrode material, isolates internal and external air circulation, and reduces the probability and proportion of oxidation of the negative electrode powder material inside the furnace. As a result, the specific surface area of ​​the negative electrode material produced by this chamber furnace reaches the level of an Atchison furnace, resulting in superior quality. Simultaneously, the use of graphite trapezoidal electrode blocks effectively improves space utilization, thereby increasing the loading capacity of the negative electrode material. Attached Figure Description

[0025] Figure 1 This is a front view schematic diagram of a typical box-type furnace in the prior art;

[0026] Figure 2 yes Figure 1 Top view;

[0027] Figure 3 This is a schematic diagram of the main structure of the box-type furnace provided in this application;

[0028] Figure 4 yes Figure 3 Side view.

[0029] Among them, 1-conductive end wall; 2-fire-resistant wall; 3-conductive electrode; 4-small compartment; 5-insulation material; 6-negative electrode material; 7-graphite plates on both sides; 8-top cover plate; 9-bottom graphite plate; 10-graphite trapezoidal electrode block; 11-graphite pad block; 12-fine insulation material; 13-coarse insulation material; 14-graphite felt; 15-carbon black. Detailed Implementation

[0030] This invention provides a method for producing artificial graphite anode materials using a graphitization chamber furnace, wherein the graphitization chamber furnace is as follows: Figures 3-4 As shown, the device includes an open compartment consisting of conductive end walls 1 at both ends, graphite plates 7 on both sides, and a graphite plate 9 at the bottom. Conductive electrodes 3 are symmetrically arranged on the conductive end walls at both ends. One end of the conductive electrode extends into the compartment, and the other end is located outside the compartment for connection with the power supply device.

[0031] The method includes the following steps:

[0032] S1. Inside the compartment, multiple graphite trapezoidal electrode blocks 10 are assembled to form an intermediate electrode connecting the conductive electrodes at both ends. Graphite pads 11 support the joints of adjacent graphite trapezoidal electrode blocks to prevent instability. The thickness of the graphite trapezoidal electrode blocks is preferably no less than 110mm. After power is supplied, the graphite trapezoidal electrode blocks and graphite pads conduct electricity and generate heat. This application uses multiple graphite trapezoidal electrode blocks assembled to form a long electrode, which prevents the problem of easy breakage when directly using long graphite electrodes. Moreover, compared to using rectangular blocks, the use of trapezoidal electrode blocks provides both downward gravity and upward reaction force on the contact slope of adjacent trapezoidal electrode blocks, resulting in a more secure joint. Multiple sets of conductive electrodes and intermediate electrodes can be configured, such as... Figure 3 and 4 As shown, there are two sets, which are beneficial to improving the heating uniformity of the negative electrode material. Replacing the large-space-consuming graphite plates forming small compartments in existing box furnaces with graphite trapezoidal electrode blocks and graphite pads can make the current density more balanced throughout the furnace, the heating of the negative electrode material more uniform, improve the consistency of the negative electrode material processed in the box furnace, and increase the loading capacity of the negative electrode material.

[0033] S2. Inside the compartment, artificial graphite negative electrode material 6 is filled around the graphite trapezoidal electrode and graphite pad. During filling, a layer of material with a height of about 100mm can be formed at the bottom first, and then filled layer by layer upwards, and the material is compacted with a vibrating rod. The filling height is slightly lower than the graphite plates on both sides (preferably 50mm lower than the upper edge of the graphite plates on both sides) to allow space for laying graphite felt and top cover plate.

[0034] S3. Graphite felt 14 and top cover plate 8 are sequentially laid on the surface of artificial graphite negative electrode material; the function of graphite felt is to leave space for the discharge of volatiles, and the thickness is preferably 2-3mm; the function of top cover plate is to separate the insulation material from the negative electrode material, and the material is preferably carbon plate or graphite plate, with a thickness of 40-50mm.

[0035] Graphite felt has a much lower density than graphite plates, typically 0.1–0.2 g / cm³. 3 (The density of graphite is 2-2.3 g / cm³) 3 It has high porosity, good air permeability, and is a flexible material with low ash content, so no impurities will be introduced. When volatiles are discharged upwards, the porous structure of the graphite felt can act as a buffer zone when they reach the top of the compartment, allowing the volatiles to diffuse to both sides until they are discharged from the gaps in the top cover plate (graphite plate / carbon plate).

[0036] Carbon plates refer to non-graphite carbon materials. Their corrosion resistance, high temperature resistance, and flexural strength are generally lower than those of graphite plates. When setting up graphite felt, carbon plates can be used as the top cover.

[0037] S4. Fine insulation material 12 and coarse insulation material 13 are alternately laid horizontally on the upper surface of the top cover plate; wherein, the particle size of the fine insulation material is preferably 7-9 μm, and the particle size of the coarse insulation material is 10-12 mm. By setting insulation materials with different particle sizes, the fine insulation material has a small particle size and small interparticle pores, which can play a good role in heat preservation; the coarse insulation material has a large particle size and large interparticle pores, which can guide the volatile matter and gas to escape, prevent local positive pressure from causing furnace blowout or fire, and also improve the heating uniformity of the negative electrode material. Preferably, the width of the fine insulation material laying area is 5-8 meters, and the width of the coarse insulation material laying area is 30-60 mm.

[0038] S5. Power supply, the power supply process generally lasts for 18 to 24 hours, and the graphitization temperature is about 3000℃;

[0039] When the conductive electrode is energized, the intermediate electrode and the graphite pad formed by splicing graphite trapezoidal electrode blocks also conduct electricity and generate heat. At the same time, the negative electrode material is graphite material, which also generates heat. During the process of temperature rise, the negative electrode material gradually undergoes lattice rearrangement to complete graphitization. This process is accompanied by the volatilization and release of volatiles such as hydrocarbons and sulfides.

[0040] In the event of a fire during power supply, fine insulating material is used to cover and extinguish the fire. The purpose of extinguishing the fire is to prevent the fire from causing high negative pressure in the vicinity, which would cause volatiles in the furnace to quickly converge towards the fire, creating negative pressure in various areas. This would cause air to break through the surface material and quickly diffuse into the depths of the furnace, oxidizing the material inside the chamber.

[0041] S6. After power is supplied, cover the top of the coarse insulation material from step S4 with fine insulation material. The optimal thickness is 10-30mm to block external air and prevent oxidation of the materials inside the compartment. If a fire occurs during this process, it must also be extinguished using fine insulation material.

[0042] S7. Cooling, and the graphitized anode material is obtained upon removal from the furnace.

[0043] Specifically, the cooling process begins with natural cooling for 7 to 10 days. During this period, no auxiliary cooling is required, as the temperature difference between the furnace and the environment will create a relatively fast cooling rate. Afterward, cooling water is poured onto the fine insulation material to assist in cooling.

[0044] The standard for the amount of cooling water poured at one time is that it should not form a water flow on the surface of the insulation material. Water should be poured by moving the crane, with small or multiple water flows being the best. The time interval between two waterings should not exceed the time it takes for the temperature to return to high temperature. It is best to water again as soon as the temperature returns to high temperature after watering is completed and measured with a handheld infrared thermometer.

[0045] During the natural cooling and cooling water cooling stages, when cracks appear or fires occur in the hard shell of the insulation material, yellow clay is applied for repair. The main components of yellow clay are alumina and iron oxide. It is characterized by its high viscosity, which can effectively repair cracks, isolate internal and external air, and prevent the material from oxidizing.

[0046] Preferably, the fine insulation material is discharged from the furnace when its temperature is below 50°C. Upon discharge, the hard shells of the fine and coarse insulation materials are first removed, followed by the top cover and graphite felt. The top 10mm layer of artificial graphite negative electrode material is then removed and discarded. The remaining negative electrode material is conveyed to the discharge hopper using a negative pressure suction method. The reason for removing the approximately 10mm layer of material is that this portion inevitably comes into contact with air, and its specific surface area is about twice that of the lower layer.

[0047] The graphite plates on both sides and the bottom should have a certain flexural strength and a thickness of not less than 50mm.

[0048] As those skilled in the art will understand, the graphitized box furnace has refractory walls 2 on the outside of the bottom graphite plate, the side graphite plates, and the conductive end wall. Insulating material is filled between the side graphite plates and the refractory walls.

[0049] Graphitized coke is preferred for both fine and coarse insulation materials. Since graphitized coke is prone to erosion and loss after high-temperature graphitization and requires replacement, this application fills the space between the graphite plates on both sides and the refractory wall with carbon black 15, while filling the space above with fine insulation material. Carbon black is also filled between the bottom graphite plate and the refractory wall. Compared to ordinary graphitized coke, carbon black has greater strength. Placed below the bottom graphite plate and on the outer sides of the graphite plates, it provides better insulation and support for the graphite plates. Moreover, due to its high strength, carbon black generally does not need to be replaced even after multiple graphitization treatments.

[0050] After graphitization, another set of negative pressure suction pipes is used to transport the fine insulation material from both sides and the top to a screening machine for screening. Coke particles with a particle size greater than 4mm are collected and mixed with coarse insulation material at a ratio of 1:5 for continued use. The powder under screening is discarded, and some insulation material is recycled, saving production costs.

[0051] Using the box furnace provided in this application, after the previous graphitization is completed, the graphite plate and carbon black have low erosion and wear, and do not need to be replaced or reassembled. The intermediate electrode, which is spliced ​​from graphite trapezoidal electrode blocks, will be disturbed during the extraction of negative electrode material, which may lead to poor contact and requires reassembly.

[0052] By employing the graphitization chamber furnace provided in this application, and through optimized production processes such as using graphite felt, alternating between fine and coarse insulation materials on the top cover plate, and covering the coarse insulation material with fine insulation material after power supply, volatile matter can be effectively guided out, preventing localized high positive pressure that could lead to furnace blowouts or fires. This improves the heating uniformity of the negative electrode material, isolates internal and external air circulation, and reduces the probability and proportion of oxidation of the negative electrode powder material inside the furnace. As a result, the specific surface area of ​​the negative electrode material produced by this chamber furnace reaches the level of an Atchison furnace, resulting in superior quality. Simultaneously, the use of graphite trapezoidal electrode blocks effectively improves space utilization, thereby increasing the loading capacity of the negative electrode material.

[0053] Table 1 shows the performance test data of the anode materials obtained using different graphitization furnaces and production processes, as detailed below:

[0054] Table 1

[0055]

[0056] As can be seen from Table 1, regardless of whether the anode material is produced using secondary petroleum coke particles or single needle coke particles, the tap density and specific surface area of ​​the anode material produced by the box furnace provided in this application are superior to those of traditional box furnaces and can reach the level of Atchison furnaces. At the same time, the single furnace charge is significantly greater than that of Atchison furnaces.

[0057] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if these modifications and modifications of the invention fall within the scope of the claims and their equivalents, the invention is also intended to include these modifications and modifications.

Claims

1. A method for producing artificial graphite anode material using a graphitization chamber furnace, wherein the graphitization chamber furnace comprises an open chamber consisting of conductive end walls at both ends, graphite plates on both sides, and a graphite plate at the bottom; conductive electrodes are symmetrically arranged on the conductive end walls at both ends; one end of each conductive electrode extends into the chamber, and the other end is located outside the chamber for connection to a power supply device, characterized in that... The method includes the following steps: S1. Inside the compartment, multiple graphite trapezoidal electrode blocks are spliced ​​together to form an intermediate electrode that connects the conductive electrodes at both ends, and graphite pads are used to support the splicing of two adjacent graphite trapezoidal electrode blocks. S2. Inside the compartment, artificial graphite negative electrode material is filled around the graphite trapezoidal electrode block and the graphite pad block; S3. Graphite felt and a top cover plate are sequentially laid on the surface of the artificial graphite negative electrode material; S4. Fine insulation material and coarse insulation material are alternately laid on the upper surface of the top cover plate in the horizontal direction; the particle size of the fine insulation material is 7~9μm, and the particle size of the coarse insulation material is 10~12mm. S5. Power is supplied to bring the furnace temperature to the graphitization temperature; S6. After power supply is completed, cover the top of the coarse insulation material described in step S4 with fine insulation material; S7. Cooling, and the graphitized negative electrode material is obtained upon removal from the furnace; Step S7: First, allow natural cooling for 7-10 days, then use cooling water for assisted cooling. When the temperature of the fine insulation material is <50℃, it is taken out of the furnace. The graphitized box furnace also includes refractory walls located outside the bottom graphite plate and the two side graphite plates. Carbon black is filled between the bottom graphite plate, the two side graphite plates and the refractory walls. The carbon black filling height between the two side graphite plates and the refractory walls is lower than that between the two side graphite plates. The fine insulating material is filled above the carbon black between the two side graphite plates and the refractory walls.

2. The method for producing artificial graphite anode materials using a graphitization chamber furnace as described in claim 1, characterized in that, The conductive electrodes and the intermediate electrodes are in multiple sets.

3. The method for producing artificial graphite anode materials using a graphitization chamber furnace as described in claim 1, characterized in that, When filling the artificial graphite negative electrode material in step S2, it is filled layer by layer, and the filling height is slightly lower than the graphite plates on both sides.

4. The method for producing artificial graphite anode materials using a graphitization chamber furnace as described in claim 1, characterized in that, The width of the area where the fine insulation material is laid is 5 to 8 meters, and the width of the area where the coarse insulation material is laid is 30 to 60 mm.

5. The method for producing artificial graphite anode materials using a graphitization chamber furnace as described in claim 1, characterized in that, In steps S5 and S6, when a fire occurs, fine insulating material is used to cover and extinguish it.

6. The method for producing artificial graphite anode materials using a graphitization chamber furnace as described in claim 1, characterized in that, In step S7, during the natural cooling and cooling water cooling stages, if cracks or overheating occur in the insulation material, yellow mud is applied for repair.

7. The method for producing artificial graphite anode materials using a graphitization chamber furnace as described in claim 1, characterized in that, After being removed from the furnace, the artificial graphite anode material on the surface is discarded.

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