Sacrificial agent for reducing ash content of graphite product as well as preparation method and application of sacrificial agent
By adsorbing ash by spherical or spherical sacrificing agents prepared with porous carbon materials in continuous graphitization furnaces, the problem of excessive ash in continuous graphitization furnaces is solved, and product quality improvement and cost reduction are achieved.
Patent Information
- Application Number
- CN202410184382.1
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-02-19
- Publication Date
- 2025-08-19
AI Technical Summary
During the operation of continuous graphitization furnace, the problem of product ash content exceeding the standard leads to product quality decline and safety hazards, which are difficult to effectively solve in the existing technology.
The porous carbon material with a large specific surface area and strong adsorption capacity is used to prepare spherical or spherical sacrificial agent, and enters the continuous graphitization furnace with the raw materials to adsorb the ash in the preheated section, and the ash in the high-temperature reaction zone is vaporized and deposited on the sacrificial agent, and separated by a screening device to achieve recycling.
It significantly reduces the ash content of continuous graphitization products, improves product quality, and the sacrificial agent can be recycled, reduces production costs, and is suitable for large-scale applications.
Smart Images
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Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of negative electrode materials, and particularly relates to a sacrificial agent for reducing the ash content of a continuous graphitization product and a continuous graphitization method. Background Art
[0002] With the widespread application of lithium-ion batteries in various fields, particularly electric vehicles and electronic products, the consumer market has placed more stringent demands on the energy density and safety performance of lithium-ion batteries. As a crucial component of lithium-ion batteries, the performance of anode materials is crucial to the overall performance of the entire battery system. Currently, the most common anode materials used in lithium-ion batteries are graphite and silicon-based materials. Graphite, with its advantages of low price, good cycle stability, and excellent processing properties, accounts for over 95% of the anode material market. Graphite used in anode materials is primarily divided into natural graphite and artificial graphite. Artificial graphite, due to its stable structure, low ash content, and few surface defects, accounts for approximately 88% of the graphite anode material market.
[0003] For artificial graphite products, in addition to specific capacity and initial efficiency, ash content is also an extremely important control indicator, generally controlled below 0.10%. A higher ash content will lead to a decrease in the capacity and compaction density of artificial graphite, and poor processing performance. At the same time, ash can induce uncontrollable side reactions during the charge and discharge process, which in severe cases may cause safety accidents in lithium-ion batteries.
[0004] The ash content of artificial graphite primarily comes from the raw materials, which are typically coke byproducts from refining plants, such as petroleum coke. These raw materials inherently contain a certain amount of ash, and the amount is uncontrollable. Generally speaking, the artificial graphite industry addresses the high ash content in raw materials by vaporizing the inorganic salts or oxides in the raw materials at high temperatures during graphitization, followed by cooling, adsorption, or deposition through insulation, thereby reducing the ash content. However, this method is only applicable to traditional intermittent graphitization equipment, such as Acheson furnaces or box furnaces, because they use intermittent production and have insulation in the cooling zone to adsorb or deposit ash impurities, which then needs to be replaced.
[0005] Compared with traditional intermittent graphitization equipment, continuous graphitization furnaces have the characteristics of low energy consumption, small footprint, good environmental protection, and good product consistency, and have gradually become one of the main improvement directions in the artificial graphite negative electrode industry. However, for continuous graphite furnaces, due to their inherent heat preservation capabilities, no insulation materials are used. The raw materials are directly discharged after passing through the preheating zone, high-temperature reaction zone and cooling zone. Therefore, the ash gasified in the high-temperature reaction zone can only be discharged with the volatile matter through the induced draft fan. However, due to the low temperature of the preheating section, part of the ash will be directly cooled, adsorbed, or deposited on the surface of the unreacted raw materials, resulting in the continuous accumulation and increase of the raw material ash content, and the product ash content exceeds the standard.
[0006] Therefore, how to solve the problem of excessive ash content in products during the operation of continuous graphitization furnaces, so as to improve product quality while maintaining the advantages of continuous graphitization, has become an important improvement direction for the innovation of continuous graphitization equipment and the successful industrialization. Summary of the Invention
[0007] Against this technical background, the present invention proposes a template sacrificial method to reduce the ash content of continuous graphitization products. The present invention uses porous carbon materials with large specific surface area and strong adsorption capacity to prepare spherical or quasi-spherical sacrificial agents through granulation, which enter the continuous graphitization furnace together with the raw materials. Since the sacrificial agent has a smaller angle of repose, a larger specific surface area, and a stronger adsorption capacity, it can cover more of the cavity area in the preheating section. When the ash in the high-temperature reaction zone is gasified and discharged to the preheating section, it will preferentially be adsorbed or deposited on the sacrificial agent, thereby reducing the accumulation of ash in the raw material. At the same time, since the size of the sacrificial agent is smaller than that of the raw material, the sacrificial agent coming out with the finished product can be separated by a screening device at the outlet, and the sacrificial agent material is hard carbon, which is not easily graphitized at high temperatures and can be recycled.
[0008] In one aspect, the present invention provides a sacrificial agent for reducing the ash content of a continuous graphitization product, wherein the sacrificial agent is composed of a porous carbon material and a binder.
[0009] Furthermore, the porous carbon material is a hard carbon material, preferably one or more of biomass-based hard carbon, resin-based hard carbon, and organic polymer-based pyrolytic hard carbon.
[0010] Furthermore, the porous carbon material has a specific surface area BET of ≥ 1000 m 2 / g.
[0011] Furthermore, the binder is mainly composed of three elements: C, H, and O, and includes one or more polysaccharides and monosaccharides, specifically one or more selected from starch, maltose, glucose, cellulose, fructose, and galactose.
[0012] On the other hand, the present invention also provides a method for preparing a sacrificial agent for reducing the ash content of a continuous graphitization product, comprising the following steps:
[0013] S1. Mixing the porous carbon material with the binder to obtain a mixture A;
[0014] S2. Injecting a solvent into the mixture A obtained in S1 and mixing to obtain a mixture B;
[0015] S3. The mixture B obtained in S2 is granulated by a granulating device to obtain granulated material C;
[0016] S4. The granulated material C obtained in S3 is dried by a drying device to obtain a sacrificial agent D.
[0017] Furthermore, in step S1, the mass ratio of the porous carbon material to the binder is 100:(0.5-10), more preferably 100:(2-5).
[0018] Furthermore, the solvent in step S2 is preferably water or a mixed solution containing water, such as an ethanol-water mixed solution, an acetone-water mixed solution, or a methanol-water mixed solution.
[0019] Furthermore, the mass ratio of the porous carbon material to the solvent in step S2 is preferably 100:(20-60), and more preferably 100:(30-50).
[0020] Furthermore, the granulation equipment in step S3 is one or more of a double-roll granulation equipment, an extrusion double-roll combination granulation equipment, a pot-type granulation equipment and a disk-type granulation equipment.
[0021] Furthermore, the C morphology of the granulated material in step S3 is preferably one or more of spherical and quasi-spherical.
[0022] Furthermore, the maximum particle size of the granulated material C in step S3 is 2 to 7 mm.
[0023] Furthermore, the drying equipment in step S4 is one or more of a belt drying equipment, a box drying equipment, and a disc drying equipment.
[0024] Furthermore, in step S4, the drying temperature is 50-200° C., and the drying time is 60-180 min.
[0025] In another aspect, the present invention provides a method for continuous graphitization, comprising the following steps:
[0026] S1. Putting a certain mass ratio of raw material E and sacrificial agent D into a continuous graphitization furnace;
[0027] S2. The raw material E and the sacrificial agent D are sequentially passed through a high-temperature reaction zone and a cooling zone to obtain a sacrificial agent D and a finished product F; the finished graphite product is obtained by separation through a screening device, and the collected sacrificial agent can be reused.
[0028] Furthermore, the raw material E is preferably one or more of petroleum coke, pitch coke, oil-based needle coke, and coal-based needle coke.
[0029] Furthermore, in step S1, the mass ratio of the raw material E to the sacrificial agent D is preferably 100:(0.1-1.2), and more preferably 100:(0.5-1.0).
[0030] Furthermore, the particle size of the raw material E in step S1 is preferably in the range of 12 to 50 mm, more preferably 12 to 28 mm.
[0031] Furthermore, the temperature of the high temperature reaction zone in step S2 is preferably 2800-3100°C.
[0032] Furthermore, in step S2, the temperature of the material after passing through the cooling zone is preferably ≤60°C.
[0033] Furthermore, the aperture range of the screening device in step S2 is 8 to 11 mm.
[0034] The beneficial effects of the present invention are:
[0035] 1. The sacrificial agent provided by the present invention can meet the requirements of continuous graphitization process production and significantly reduce the ash content of the product on the basis of achieving continuous graphitization;
[0036] 2. The sacrificial agent provided by the present invention has a simple preparation process and is composed of porous carbon material. It has the characteristics of stronger adsorption capacity and smaller repose angle, and can preferentially adsorb or deposit ash in the preheating stage;
[0037] 3. The sacrificial agent provided by the present invention is composed of hard carbon material, which is not easily graphitized at high temperatures, and can be recycled a certain number of times, with good economic efficiency;
[0038] 4. The sacrificial agent provided by the present invention has a significant particle size difference from the finished product, allowing for good separation without affecting the quality of the finished product. The method of the present invention has a simple process flow, effectively controls the ash content of the continuous graphitization product, and improves product quality. Furthermore, the sacrificial agent can be recycled, resulting in low production costs and suitability for large-scale applications. BRIEF DESCRIPTION OF THE DRAWINGS
[0039] Figure 1 This is a SEM image of the finished product F obtained in Example 1 of the present invention.
[0040] Figure 2 This is an SEM image of the finished product F prepared in Comparative Example 1 of the present invention.
[0041] Figure 3 This is a process diagram of continuous graphitization of the present invention. DETAILED DESCRIPTION
[0042] The present invention will be further described below with reference to the examples, but the present invention is not limited to the following examples.
[0043] Raw materials and sources:
[0044] The bio-based carbon black material in this article was purchased from Fujian Xinsen's ultra-pure powdered activated carbon series, and the specific surface area can be customized.
[0045] The epoxy resin-based hard carbon material and polyaniline pyrolysis hard carbon material in this article are homemade materials. The high-temperature pyrolysis method in an inert atmosphere is adopted. The epoxy resin and polyaniline are added into a tubular furnace, and the temperature is raised to 1200℃ at a heating rate of 5℃ / min for carbonization for 5 hours. After natural cooling, they are taken out. Nitrogen atmosphere is used throughout the heating process. The carbon powder after being taken out is alkaline washed with 15% concentration NaOH for 45 minutes and then dried to obtain a porous carbon material with high specific surface area.
[0046] The starch and glucose in this article were purchased from Henan Jinhan Environmental Protection Technology Co., Ltd. 2101 series, and maltose was purchased from Shandong Pingju Biotechnology Co., Ltd. Pingzhiju series.
[0047] The raw materials mentioned in this article, such as petroleum coke and needle coke, were purchased from Weifang Fumei New Energy Co., Ltd.
[0048] Test method:
[0049] The ash content test in this article was carried out in accordance with the national standard GB / T 24533-2019 "Graphite Anode Materials for Lithium-ion Batteries", and the testing equipment was the Kejing box furnace KSL-1000X.
[0050] The electrochemical performance test in this article was carried out in accordance with the national standard GB / T 24533-2019 "Graphite Anode Materials for Lithium-ion Batteries", and the test equipment was the new VELCRO battery cell tester CT-4000Q.
[0051] The powder compaction density test in this article was carried out in accordance with the national standard GB / T 24533-2019 "Graphite Anode Materials for Lithium-ion Batteries", and the testing equipment was the Sansi Powder Compaction Density Meter UTM7305.
[0052] Example 1:
[0053] S1, using 1Kg specific surface area BET of 1000m 2 / g of Fujian Xinsen ultrapure powdered activated carbon bio-based carbon black material was fully mixed with 30g of starch to obtain a mixture A;
[0054] S2. Add 0.4 kg of water to mixture A and mix thoroughly to obtain mixture B;
[0055] S3, the mixed material B is passed through a double-roll granulation device to prepare spherical granules C with a particle size of 5 mm;
[0056] S4, drying the granulated material C through a belt drying device to obtain a sacrificial agent D, the drying temperature is 150° C., and the drying time is 120 min;
[0057] S5. Put 1 kg of sacrificial agent D and 200 kg of petroleum coke with a minimum particle size of 16 mm into a continuous graphitization furnace;
[0058] S6. After the high temperature reaction at 3000°C and cooling to 50°C, the sacrificial agent D and the finished product F are separated through a screening device with an aperture of 10 mm at the discharge port. The collected sacrificial agent can be reused.
[0059] Example 2:
[0060] S1, using 1 kg, the specific surface area BET is 1200m 2 / g of high-temperature pyrolysis homemade epoxy resin-based hard carbon material was fully mixed with 20g of maltose to obtain a mixture A;
[0061] S2. Inject 0.5 kg of a 1:1 ethanol-water mixed solution into mixture A and mix thoroughly to obtain mixture B;
[0062] S3, the mixture B is passed through a pot-type granulation equipment to prepare spherical granules C with a particle size of 7 mm;
[0063] S4, drying the granulated material C in a box-type drying equipment to obtain a sacrificial agent D, the drying temperature is 90° C., and the drying time is 150 min;
[0064] S5. 1 kg of sacrificial agent D and 333 kg of pitch coke with a minimum particle size of 20 mm are placed into a continuous graphitization furnace;
[0065] S6. After the high temperature reaction at 3100°C and cooling to 60°C, the sacrificial agent D and the finished product F are separated through a screening device with an aperture of 11 mm at the discharge port. The collected sacrificial agent can be reused.
[0066] Example 3:
[0067] S1, using 1 kg, the specific surface area BET is 1500m 2 / g of the self-made polyaniline pyrolysis hard carbon material was fully mixed with 50g of glucose to obtain a mixture A;
[0068] S2. Inject 0.3 kg of a 0.4:0.6 mixed solution of acetone and water into mixture A and mix thoroughly to obtain mixture B;
[0069] S3, the mixture B is passed through a disc granulation device to prepare spherical granules C with a particle size of 3 mm;
[0070] S4, drying the granulated material C through a disc drying device to obtain a sacrificial agent D, the drying temperature is 50 ° C, and the drying time is 180 min;
[0071] S5. 1 kg of sacrificial agent D and 125 kg of oil-based needle coke with a minimum particle size of 12 mm are placed into a continuous graphitization furnace;
[0072] S6. After the high temperature reaction at 2800°C and cooling to 40°C, the sacrificial agent D and the finished product F are separated through a screening device with an aperture of 8 mm at the discharge port. The collected sacrificial agent can be reused.
[0073] Example 4:
[0074] S1, using 1 kg, the specific surface area BET is 1400m 2 / g of Fujian Xinsen ultrapure powdered activated carbon bio-based carbon black material was fully mixed with 35g of starch to obtain a mixture A;
[0075] S2. Add 0.45 kg of water to mixture A and mix thoroughly to obtain mixture B;
[0076] S3, the mixture B is passed through an extrusion roller combined granulation equipment to prepare spherical granules C with a maximum particle size of 6 mm;
[0077] S4, drying the granulated material C through a belt drying device to obtain a sacrificial agent D, the drying temperature is 200 ° C, and the drying time is 60 min;
[0078] S5. Put 1 kg of sacrificial agent D and 1000 kg of coal-based needle coke with a minimum particle size of 18 mm into a continuous graphitization furnace;
[0079] S6. After the high temperature reaction at 2900°C and cooling to 30°C, the sacrificial agent D and the finished product F are separated through a screening device with an aperture of 10 mm at the discharge port. The collected sacrificial agent can be reused.
[0080] Comparative Example 1:
[0081] S1. Put petroleum coke with a minimum particle size of 16 mm into a continuous graphitization furnace;
[0082] S2. After a high temperature reaction at 3000°C and cooling to 50°C, a graphite product F is obtained.
[0083] Comparative Example 2:
[0084] S1. Put pitch coke with a minimum particle size of 20 mm into a continuous graphitization furnace;
[0085] S2, through high temperature reaction at 3100°C and cooling to 60°C to obtain graphite product F. Comparative Example 3:
[0086] S1. Put oil-based needle coke with a minimum particle size of 12 mm into a continuous graphitization furnace;
[0087] S2, through high temperature reaction at 2800°C and cooling to 40°C to obtain graphite product F. Comparative Example 4:
[0088] S1. Coal-based needle coke with a minimum particle size of 18 mm is placed into a continuous graphitization furnace;
[0089] S2. After a high temperature reaction at 2900°C and cooling to 30°C, a graphite product F is obtained.
[0090] Table 1
[0091]
[0092]
[0093] Table 1 compares the performance indicators of the finished products prepared in Examples 1 to 4 of the present invention and Comparative Examples 1 to 4. As can be seen from the table, the ash content of the finished graphite products obtained using the method provided by the present invention is significantly reduced, meeting the required indicators. Furthermore, the finished products also exhibit a certain degree of improvement in electrochemical performance and compaction performance.
[0094] contrast Figure 2 and Figure 3 From the SEM images, we can see that the micromorphology of the graphite products obtained by the two schemes is basically the same, which shows that the process of using sacrificial agents to reduce ash content will not affect the morphology of the graphite products.
Claims
1. A sacrificial agent for reducing the ash content of a continuous graphitization product, characterized in that: The sacrificial agent consists of a porous carbon material and a binder.
2. The sacrificial agent according to claim 1, wherein The porous carbon material is a hard carbon material, preferably one or more of biomass-based hard carbon, resin-based hard carbon, and organic polymer-based pyrolytic hard carbon. Preferably, the porous carbon material has a specific surface area BET of ≥1000 m 2 / g; and / or, the binder is mainly composed of three elements: C, H, and O, including one or more polysaccharides and monosaccharides, specifically selected from one or more of starch, maltose, glucose, cellulose, fructose, and galactose.
3. The method for preparing a sacrificial agent for reducing the ash content of a continuous graphitization product according to claim 1 or 2, comprising the following steps: S1. Mixing the porous carbon material with the binder to obtain a mixture A; S2. Injecting a solvent into the mixture A obtained in S1 and mixing to obtain a mixture B; S3. The mixture B obtained in S2 is granulated by a granulating device to obtain granulated material C; S4. The granulated material C obtained in S3 is dried by a drying device to obtain a sacrificial agent D.
4. The preparation method according to claim 3, wherein The mass ratio of the porous carbon material to the binder in step S1 is 100:(0.5-10), more preferably 100:(2-5); and / or, the mass ratio of the porous carbon material to the solvent in step S2 is preferably 100:(20-60), more preferably 100:(30-50); and / or, the solvent in step S2 is preferably water or a mixed solution containing water, such as an ethanol-water mixed solution, an acetone-water mixed solution, or a methanol-water mixed solution.
5. The preparation method according to claim 3 or 4, characterized in that The morphology of the granules C in step S3 is preferably one or more of spherical and quasi-spherical; and / or the maximum particle size of the granules C is 2 to 7 mm; and / or the drying temperature in step S4 is 50 to 200° C. and the drying time is 60 to 180 min.
6. A method for continuous graphitization, comprising the following steps: S1. Putting a certain mass ratio of raw material E and sacrificial agent D into a continuous graphitization furnace; S2. The raw material E and the sacrificial agent D are sequentially passed through a high-temperature reaction zone and a cooling zone to obtain a sacrificial agent D and a finished product F; and the sacrificial agent D and the finished graphite product F are separated by a screening device. The collected sacrificial agent can be reused, and the sacrificial agent D is selected from the sacrificial agent according to claim 1 or 2 or the sacrificial agent prepared by the preparation method according to any one of claims 3 to 5.
7. The method according to claim 6, wherein The raw material E is preferably one or more of petroleum coke, pitch coke, oil-based needle coke, and coal-based needle coke.
8. The method according to claim 6 or 7, wherein: The mass ratio of the raw material E to the sacrificial agent D in step S1 is preferably 100:(0.1-1.2), more preferably 100:(0.5-1.0); and / or the particle size range of the raw material E in step S1 is preferably 12-50 mm, more preferably 12-28 mm.
9. The method according to any one of claims 6 to 8, wherein: The temperature of the high-temperature reaction zone in step S2 is preferably 2800-3100° C.; and / or, the temperature of the material after passing through the cooling zone in step S2 is preferably ≤60° C.; and / or, the aperture range of the screening device in step S2 is 8-11 mm.