Porous artificial graphite as well as preparation method and application thereof
By adding pitch and urea to expanded graphite to form macropores, and then using hydroxide treatment to form an interconnected pore structure, the problem of poor rate performance of artificial graphite was solved, thus achieving a significant improvement in the high-efficiency electrochemical performance of lithium-ion batteries.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-30
- Publication Date
- 2026-03-31
AI Technical Summary
The poor rate performance of existing artificial graphite limits its application in lithium-ion batteries. Furthermore, the pores are easily removed during the graphitization process, making it difficult to effectively improve the diffusion rate and electrolyte contact area of the material.
Porous artificial graphite is prepared by adding asphalt and urea to expanded graphite to form macropores, and then treating it with hydroxides to form an interconnected pore structure, thus ensuring the stability of the pore structure during the graphitization process.
It significantly improves the lithium storage sites and electrolyte contact area of artificial graphite, thereby enhancing the rate performance of lithium-ion batteries.
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Abstract
Description
Technical Field
[0001] This invention relates to the field of negative electrode materials technology, and in particular to a porous artificial graphite, its preparation method, and its application. Background Technology
[0002] Artificial graphite possesses high capacity and stable cycle performance, making it a commonly used anode material for lithium-ion batteries. However, its poor rate performance limits its applications. Forming micropores within artificial graphite can improve the diffusion rate of lithium-ion battery materials, thereby mitigating its poor rate performance. Currently, artificial graphite is often obtained by creating pores in carbon materials followed by graphitization. However, during graphitization, carbon atoms rearrange, removing the already formed pores and thus failing to effectively improve the rate performance of artificial graphite. Summary of the Invention
[0003] Based on the technical problems existing in the background technology, the present invention proposes a porous artificial graphite, its preparation method and application. The porous artificial graphite prepared by the present invention has large pores on its surface and small pores inside. The two together form an interconnected pore structure, which can significantly improve the lithium storage sites, transport rate and electrolyte contact area of artificial graphite, thereby achieving a significant improvement in the rate performance of artificial graphite.
[0004] This invention proposes a method for preparing porous artificial graphite, comprising the following steps: soaking expanded graphite in a mixture containing asphalt and pore-forming agent 1, separating the solid and liquid, and drying to obtain intermediate 1; mixing intermediate 1, binder, and needle coke, granulating, carbonizing, and graphitizing to obtain intermediate 2; mixing intermediate 2 and pore-forming agent 2, heat-treating, washing, and drying to obtain porous artificial graphite.
[0005] Preferably, the pore-forming agent 1 is urea.
[0006] Preferably, the pore-forming agent 2 is a hydroxide.
[0007] The aforementioned hydroxides can be sodium hydroxide, etc.
[0008] Preferably, the binder is asphalt.
[0009] Preferably, the expanded graphite is ultrasonically treated in a mixture containing asphalt and pore-forming agent 1 for 1-2 hours, and then soaked in a vacuum at room temperature for 8-10 hours.
[0010] Preferably, the weight ratio of expanded graphite, asphalt, and pore-forming agent 1 is 5:5:0.3-0.5.
[0011] Preferably, the solvent for the mixture is benzene.
[0012] Preferably, the concentration of asphalt in the mixture is 0.05-0.15 g / ml.
[0013] Preferably, the weight ratio of intermediate 1, binder, and needle coke is 0.5-1.5:0.5-1.5:10.
[0014] Preferably, the weight ratio of intermediate 2 to pore-forming agent 2 is 1:2-3.
[0015] Preferably, carbonization, graphitization, and heat treatment are carried out in an inert gas atmosphere.
[0016] The inert gas mentioned above can be at least one of nitrogen, argon, and helium.
[0017] Preferably, carbonization is carried out at 1100-1200℃ for 7-9 hours.
[0018] Preferably, the heat treatment process is as follows: hold at 170-190℃ for 1-2 hours, and then raise the temperature to 880-920℃ and hold for 1-2 hours.
[0019] Preferably, the material is then acid-washed, water-washed, and dried to obtain artificial graphite.
[0020] Dilute hydrochloric acid can be used for pickling.
[0021] The present invention also proposes a porous artificial graphite, which is prepared according to the above method.
[0022] The present invention also proposes an application of the above-mentioned porous artificial graphite in lithium batteries.
[0023] This invention involves immersing expanded graphite in a mixture containing asphalt and urea, allowing the asphalt and urea to penetrate the interlayers of the expanded graphite. The mixture is then mixed with a binder and needle coke, granulated, and subsequently carbonized and graphitized. The asphalt penetrating the interlayers forms a layered graphite structure. Urea creates micropores in the interlayers and on the resulting layered graphite. Furthermore, the interlayer structure of the expanded graphite avoids the removal of these micropores during graphitization, thus improving the pore structure of the artificial graphite. Next, a hydroxide treatment is applied to the artificial graphite to create larger pores on its surface. The large pores on the surface and the small pores inside the artificial graphite interact to form an interconnected pore structure, significantly increasing the lithium storage sites, transport rate, and electrolyte contact area, thereby greatly improving the rate performance of the artificial graphite. Detailed Implementation
[0024] The technical solution of the present invention will be described in detail below through specific embodiments. However, it should be clearly stated that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention.
[0025] Example 1 A method for preparing porous artificial graphite includes the following steps: 5g of asphalt and 0.3g of urea were dissolved in 50ml of benzene to obtain a mixture. Then, 5g of expanded graphite was added, and the mixture was ultrasonically treated for 2 hours. Then, it was soaked in a vacuum at room temperature for 8 hours, filtered, and dried under reduced pressure to obtain intermediate 1. Mix 1.5g of intermediate 1, 0.5g of pitch, and 10g of needle coke thoroughly and granulate. Transfer the granules to a corundum crucible and heat under high-purity nitrogen (gas flow rate of 200). Under the protection of (ml / min), the temperature was raised to 1200℃ at a heating rate of 5℃ / min and carbonized for 7h. After natural cooling, it was transferred to a graphite crucible and graphitized under the protection of a high-purity argon atmosphere. The graphitization procedure was as follows: first, the temperature was raised to 250℃, then raised to 500℃ at a rate of 12.5℃ / min; then raised to 1000℃ at a rate of 10℃ / min and held for 1min; then raised to 1200℃ at a rate of 10℃ / min and held for 30min; then raised to 2200℃ at a rate of 10℃ / min and held for 30min; then raised to 2600℃ within 60min and held for 30min; then raised to 2800℃ within 60min; and finally raised to 2900℃ within 40min and held for 5h to obtain intermediate 2. Mix 5g of intermediate 2 and 15g of sodium hydroxide, and heat to 170℃ for 2h at a rate of 5℃ / min under nitrogen protection to remove moisture. Then heat to 880℃ at a rate of 10℃ / min and hold for 2h. Then cool naturally, wash with dilute hydrochloric acid and deionized water in sequence, and then dry thoroughly in a forced-air drying oven to obtain porous artificial graphite.
[0026] Example 2 A method for preparing porous artificial graphite includes the following steps: Dissolve 5g asphalt and 0.5g urea in 50ml benzene to obtain a mixture, then add 5g expanded graphite, sonicate for 1h, then soak at room temperature under vacuum for 10h, filter, and dry under reduced pressure to obtain intermediate 1. Mix 0.5g of intermediate 1, 1.5g of asphalt, and 10g of needle coke thoroughly and granulate. Transfer the granules to a corundum crucible and heat under high-purity nitrogen (gas flow rate of 200). Under the protection of (ml / min), the temperature was raised to 1100℃ at a heating rate of 5℃ / min and carbonized for 9h. After natural cooling, it was transferred to a graphite crucible and graphitized under the protection of a high-purity argon atmosphere. The graphitization procedure was as follows: first, the temperature was raised to 250℃, then raised to 500℃ at a rate of 12.5℃ / min; then raised to 1000℃ at a rate of 10℃ / min and held for 1min; then raised to 1200℃ at a rate of 10℃ / min and held for 30min; then raised to 2200℃ at a rate of 10℃ / min and held for 30min; then raised to 2600℃ within 60min and held for 30min; then raised to 2800℃ within 60min; and finally raised to 2900℃ within 40min and held for 5h to obtain intermediate 2. Mix 5g of intermediate 2 and 10g of sodium hydroxide, and heat to 190℃ for 1h at a rate of 5℃ / min under nitrogen protection to remove moisture. Then heat to 920℃ at a rate of 10℃ / min and hold for 1h. Then cool naturally, wash with dilute hydrochloric acid and deionized water in sequence, and then dry thoroughly in a forced-air drying oven to obtain porous artificial graphite.
[0027] Example 3
[0028] A method for preparing porous artificial graphite includes the following steps: 5g of asphalt and 0.4g of urea were dissolved in 50ml of benzene to obtain a mixture. Then, 5g of expanded graphite was added, and the mixture was ultrasonically treated for 1.5h. Then, it was soaked in a vacuum at room temperature for 9h, filtered, and dried under reduced pressure to obtain intermediate 1. Mix 1g of intermediate 1, 1g of asphalt, and 10g of needle coke, granulate, and transfer to an alumina crucible. Heat under high-purity nitrogen (gas flow rate 200...) Under the protection of (ml / min), the temperature was raised to 1150℃ at a heating rate of 5℃ / min and carbonized for 8 hours. After natural cooling, it was transferred to a graphite crucible and graphitized under the protection of a high-purity argon atmosphere. The graphitization procedure was as follows: first, the temperature was raised to 250℃, then raised to 500℃ at a rate of 12.5℃ / min; then raised to 1000℃ at a rate of 10℃ / min and held for 1 minute; then raised to 1200℃ at a rate of 10℃ / min and held for 30 minutes; then raised to 2200℃ at a rate of 10℃ / min and held for 30 minutes; then raised to 2600℃ within 60 minutes and held for 30 minutes; then raised to 2800℃ within 60 minutes; and finally raised to 2900℃ within 40 minutes and held for 5 hours to obtain intermediate 2. Mix 5g of intermediate 2 and 12g of sodium hydroxide, and heat to 180℃ at a rate of 5℃ / min under nitrogen protection and hold for 1.5h to remove moisture. Then heat to 900℃ at a rate of 10℃ / min and hold for 1.5h. Then cool naturally, wash with dilute hydrochloric acid and deionized water in sequence, and then dry thoroughly in a forced-air drying oven to obtain porous artificial graphite.
[0029] Comparative Example 1 A method for preparing porous artificial graphite includes the following steps: Without adding intermediate 1, 1g of asphalt and 10g of needle coke were directly mixed and granulated to prepare porous artificial graphite according to the method of Example 3.
[0030] Comparative Example 2 A method for preparing porous artificial graphite includes the following steps: Replace intermediate 1 with expanded graphite, and prepare porous artificial graphite according to the method of Example 3.
[0031] Comparative Example 3 A method for preparing porous artificial graphite includes the following steps: Intermediate 2 was prepared as porous artificial graphite according to the method of Example 3.
[0032] Comparative Example 4 A method for preparing porous artificial graphite includes the following steps: Replace “1g intermediate 1” with “0.5g expanded graphite, 0.5g asphalt, 0.04g urea” and prepare porous artificial graphite according to the method of Example 3.
[0033] The porous artificial graphite from Examples 1-3 and Comparative Examples 1-4 was thoroughly ground with acetylene black and polyvinylidene fluoride at a mass ratio of 8:1:1 in agate to ensure thorough mixing. The mixture was then transferred to a slurry preparation vessel, and an appropriate amount of N-methylpyrrolidone was added to prepare a slurry. The slurry was then evenly coated onto a copper foil current collector with a thickness of 0.2 mm. The slurry was then placed in a forced-air drying oven and dried at 100°C for 1 hour to remove moisture. The slurry was then transferred to a vacuum drying oven and dried under vacuum at 100°C for 10 hours to remove N-methylpyrrolidone. The slurry was then punched and cut into circular electrode sheets with a diameter of 14 mm. The weight was recorded and used as the negative electrode. The electrodes were then assembled into LIR2016 type button cells.
[0034] Rate performance testing was performed on each group of batteries. The testing conditions were: current density range of 0.5C-3C, 200 cycles at different current densities, and capacity testing. The results are shown in Table 1.
[0035] Table 1 Test Results
[0036] As can be seen from Table 1, the present invention has good rate performance. The porous artificial graphite described in the present invention can provide a higher ion transport rate and improve its rate performance.
[0037] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.
Claims
1. A method for preparing porous artificial graphite, characterized in that, The process includes the following steps: soaking expanded graphite in a mixture containing asphalt and pore-forming agent 1, separating the solid and liquid, drying to obtain intermediate 1; mixing intermediate 1, binder, and needle coke, granulating, carbonizing, and graphitizing to obtain intermediate 2; mixing intermediate 2 and pore-forming agent 2, heat-treating, then washing and drying to obtain porous artificial graphite.
2. The method for preparing porous artificial graphite according to claim 1, characterized in that, Pore-forming agent 1 is urea; preferably, pore-forming agent 2 is hydroxide; preferably, binder is asphalt.
3. The method for preparing porous artificial graphite according to claim 1 or 2, characterized in that, Expanded graphite is ultrasonically treated in a mixture containing asphalt and pore-forming agent 1 for 1-2 hours, and then soaked in a vacuum at room temperature for 8-10 hours; preferably, the weight ratio of expanded graphite, asphalt and pore-forming agent 1 is 5:5:0.3-0.
5.
4. The method for preparing porous artificial graphite according to any one of claims 1-3, characterized in that, The solvent for the mixture is benzene; preferably, the concentration of asphalt in the mixture is 0.05-0.15 g / ml.
5. The method for preparing porous artificial graphite according to any one of claims 1-4, characterized in that, The weight ratio of intermediate 1, binder, and needle coke is 0.5-1.5:0.5-1.5:10; preferably, the weight ratio of intermediate 2 and pore-forming agent 2 is 1:2-3.
6. The method for preparing porous artificial graphite according to any one of claims 1-5, characterized in that, Carbonization, graphitization, and heat treatment are carried out in an inert gas atmosphere; preferably, carbonization is carried out at 1100-1200℃ for 7-9 hours.
7. The method for preparing porous artificial graphite according to any one of claims 1-6, characterized in that, The heat treatment process is as follows: hold at 170-190℃ for 1-2 hours, then raise the temperature to 880-920℃ and hold for 1-2 hours.
8. The method for preparing porous artificial graphite according to any one of claims 1-7, characterized in that, Then, it is acid-washed, water-washed, and dried to obtain artificial graphite.
9. A porous artificial graphite, characterized in that, Porous artificial graphite is prepared according to the method described in any one of claims 1-8.
10. An application of porous artificial graphite as described in claim 9 in a lithium battery.