Preparation method and application of petroleum coke-based porous carbon composite material

Abstract

The invention discloses a preparation method and application of a petroleum coke-based porous carbon composite material. The preparation method comprises the following steps: carrying out oxidation treatment on petroleum coke, mixing the obtained material with a cross-linking agent, carrying out pyrolysis at a temperature of 400-800 DEG C for 1-6 h, introducing an activation gas at a temperature of 900-1100 DEG C for activation for 60-600 min, stopping introducing the activation gas, introducing a lithium source gas and a heteroatom gas for co-doping, and carrying out drying to obtain the lithium ion battery positive electrode material. The multi-element doped petroleum coke-based porous carbon is obtained. According to the obtained material, the diffusion rate of the material is improved and the defects are reduced by doping a lithium source and heteroatom gas, the petroleum coke is prevented from forming a carbon layer structure with high anisotropy through the cross-linking agent, a porous structure is favorably formed, and the pore volume and the pore diameter are increased. The obtained material has the advantages of high silicon deposition amount, high initial efficiency and the like when applied to a silicon-carbon material.

Description

Technical Field

[0001] This invention belongs to the field of materials preparation, specifically a method for preparing petroleum coke-based porous carbon composite materials and their applications. Background Technology

[0002] Porous carbon is a key material in the preparation of silicon-carbon materials, and its performance, such as power, initial efficiency, and expansion, plays a crucial role. Currently, the raw materials used for preparing porous carbon mainly include biomass and resins, but each has its own problems. Biomass porous carbon suffers from poor consistency, and its large internal pores are not conducive to uniform silicon deposition. Resin-based silicon-carbon, while having advantages in expansion and initial efficiency, is relatively expensive and has poor power performance. Petroleum coke, as a novel raw material for preparing porous carbon, has advantages such as wide availability, high consistency, and moderate power performance. However, its compaction density, power discharge, and initial efficiency still have shortcomings, requiring optimization and improvement. Existing technology involves uniformly mixing pulverized petroleum coke with an activator, performing high-temperature activation treatment, acid washing, and drying to obtain petroleum coke-based porous carbon materials with high surface area, high conductivity, and high tap density. Although this improves pore size and volume, power performance remains poor, compaction density is low, and initial efficiency needs further improvement. Summary of the Invention

[0003] To improve the power performance, compaction density, and first-pass efficiency of silicon-carbon materials, this invention uses petroleum coke as raw material for oxidative crosslinking and activation, and reduces defects by introducing lithium source gas and heteroatom doping, thereby improving the first-pass efficiency and power performance.

[0004] A method for preparing a petroleum coke-based porous carbon composite material, characterized by comprising the following steps: Petroleum coke was transferred to a tubular furnace at a mass ratio of petroleum coke to crosslinking agent of 100:10-30. Oxygen was introduced at a flow rate of 100-500 L / h at a temperature of 150℃-250℃ to oxidize the petroleum coke for 1-3 hours, resulting in oxidized petroleum coke. The resulting oxidized petroleum coke material was then mixed with the crosslinking agent and pyrolyzed at a temperature of 400℃-800℃ for 1-6 hours. Activation was then carried out at a temperature of 900℃-1100℃ with an activation gas flow rate of 50-200 ml / min for 60-600 minutes. After stopping the activation gas flow, lithium source gas and heteroatom gas were introduced at a volume ratio of 1:1 and a flow rate of 10-100 ml / min for 30-300 minutes for co-doping, resulting in multi-element doped petroleum coke-based porous carbon.

[0005] The crosslinking agent is one of benzoyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, and dioctyl peroxide.

[0006] The activating gas is one of carbon dioxide, water vapor, or air.

[0007] The lithium source gas is formed by gasifying lithium tert-butoxide, lithium hydride, lithium acetate, lithium lactate, lithium oxalate, lithium oxalate, and lithium benzoate; the heteroatom gas is one of ammonia, sulfur dioxide, hydrogen sulfide, hydrogen boroide, phosphine, and hydrogen chloride.

[0008] A petroleum coke-based porous carbon composite material is applied to silicon-carbon materials.

[0009] Beneficial effects

[0010] 1. Petroleum coke precursor is used, and its surface is oxidized to generate free radicals such as hydroxyl / carboxyl groups, which facilitate the combination with oxygen free radicals in the crosslinking agent to form a porous structure. Further activation with an activating gas increases the number of pores, facilitating the deposition of more active substances. Peroxide crosslinking agent is used as a chemical pore-forming agent, which has advantages such as high pore strength and small pore size, and avoids the introduction of impurities after pore formation by other pore-forming agents, thus preventing a decrease in material storage performance. Simultaneously, using petroleum coke as a precursor results in porous carbon with more ordered carbon orientation, as shown by XRD analysis, indicating low impedance and high compaction density.

[0011] 2. By introducing lithium source gas and heteroatom gas into the porous carbon prepared by the present invention for co-doping, the defects on the surface of the porous carbon are reduced and the first-pass efficiency is improved. Furthermore, the co-doping of lithium and heteroatom gases can improve the electronic and ionic conductivity of the porous carbon, thereby improving its rate performance and diffusion coefficient. Attached Figure Description

[0012] Figure 1 The images show the XRD patterns of the petroleum coke-based porous carbon prepared in Example 1 and Comparative Example 3. Detailed Implementation

[0013] Example 1

[0014] A method for preparing a petroleum coke-based porous carbon composite material includes the following steps: 100g of petroleum coke was transferred to a tubular furnace and oxidized at 200℃ for 2 hours by introducing oxygen at a flow rate of 300L / h to obtain oxidized petroleum coke. Then, the obtained oxidized petroleum coke was mixed with 20g of benzoyl peroxide and pyrolyzed at 600℃ for 3 hours. After that, carbon dioxide gas was introduced at 1000℃ at a flow rate of 100ml / min for 120 minutes for activation. Then, the carbon dioxide gas was stopped, and lithium tert-butoxide gas and ammonia gas were introduced at a volume ratio of 1:1 and a flow rate of 50ml / min for 150 minutes for co-doping to obtain multi-element doped petroleum coke-based porous carbon.

[0015] Example 2

[0016] A method for preparing a petroleum coke-based porous carbon composite material includes the following steps: 100g of petroleum coke was transferred to a tubular furnace, and oxygen was introduced at a flow rate of 100L / h to oxidize the material at 150℃ for 3h to obtain oxidized petroleum coke. The resulting material was then mixed with 10g of dicumyl peroxide and pyrolyzed at 400℃ for 6h. After that, it was activated at 900℃ with steam gas introduced at a flow rate of 50ml / min for 600min. After that, the steam gas was stopped, and lithium hydride gas and hydrogen sulfide gas were introduced at a volume ratio of 1:1 and a flow rate of 10ml / min for 300min for co-doping to obtain multi-element doped petroleum coke-based porous carbon.

[0017] Example 3

[0018] A method for preparing a petroleum coke-based porous carbon composite material includes the following steps: 100g of petroleum coke was transferred to a tubular furnace and oxidized at 250℃ for 1 hour by introducing oxygen at a flow rate of 500L / h to obtain oxidized petroleum coke. The obtained material was then mixed with 30g of di-tert-butyl peroxide and pyrolyzed at 800℃ for 1 hour. The temperature was then raised to 1100℃ and activated by introducing air at a flow rate of 200ml / min for 60 minutes. After stopping the introduction of air, lithium acetate gas and hydrogen boroide gas were introduced at a volume ratio of 1:1 and a flow rate of 100ml / min for 30 minutes for co-doping to obtain multi-element doped petroleum coke-based porous carbon.

[0019] Comparative Example 1: Unlike Example 1, no benzoyl peroxide crosslinking agent was added; otherwise, it was the same as Example 1.

[0020] Comparative Example 2: Unlike Example 1, lithium tert-butoxide gas and ammonia gas were not introduced; otherwise, they were the same as in Example 1.

[0021] Comparative Example 3: The difference from Example 1 is that the petroleum coke in step S1 is replaced with phenolic resin, while the rest is the same as in Example 1.

[0022] Performance testing

[0023] 1) XRD test: The XRD patterns of the petroleum coke-based porous carbon and resin-based porous carbon materials prepared in Example 1 and Comparative Example 3 show that the (002) crystal plane peak of carbon is relatively sharp at 2θ=23.81°, which corresponds to the graphitization degree peak of the carbon material. The surface material has a high degree of order and low impedance.

[0024] 2) Physicochemical and button cell tests: 2.1 Physicochemical performance testing: The pore volume and pore size of the porous carbon materials obtained in Examples 1-3 and Comparative Examples 1-3 were tested according to the national standard GB / T-38949-2020 "Determination of Pore Size of Porous Membranes - Standard Particle Method". Their specific surface area and tap density were tested according to the national standard GB / T38823-2020 "Silicon Carbon". The powder resistivity of each porous carbon material was measured using a four-probe tester. The test results are shown in Table 1.

[0025]

[0026] As can be seen from Table 1, the materials in the examples have low powder resistivity and high pore volume. This is because lithium and heteroatoms are doped into the materials, which reduces defects on the porous carbon surface, improves the electronic and ionic conductivity of the materials, and reduces the powder resistivity. At the same time, crosslinking agents are doped into the petroleum coke, which forms a porous structure during the carbonization process, increasing the pore volume and pore size.

[0027] 2.2 Button Cell Battery Performance Test: The porous carbon materials corresponding to Examples 1-3 and Comparative Examples 1-3 were used as negative electrode materials for lithium-ion batteries to prepare coin cells according to the following method: A binder, conductive agent, and solvent are added to the corresponding porous carbon materials, stirred to form a slurry, coated onto copper foil, and dried and rolled to obtain a negative electrode sheet. The binder used is LA132, the conductive agent is SP (conductive carbon black), and the solvent is NMP. The ratio of porous carbon material: SP: LA132: NMP is 70g: 15g: 15g: 300mL. The electrolyte is a solution with LiPF6 as the electrolyte and a concentration of 1mol / L. The solvent is a mixture of EC and DEC with a volume ratio of 1:1. The lithium metal sheet is used as the counter electrode, and the separator is a polypropylene (PP) membrane.

[0028] Each button cell was assembled in an argon-filled glove box, and then the following performance tests were performed: Electrochemical performance testing: Electrochemical performance was specifically tested using the Wuhan Landian CT2001A battery tester. The charge / discharge voltage range was 0.005V to 2.0V, and the charge / discharge rate was 0.1C. The discharge specific capacity and initial efficiency of the corresponding coin cell were tested. At the same time, the room temperature charge DCR and the maximum compaction density of the electrode were tested, and the diffusion coefficient of the material was tested by GITT.

[0029] The test results are shown in Table 2.

[0030]

[0031] As can be seen from Table 2, Examples 1-3 have high specific capacity and high diffusion coefficient. This is because the crosslinking agent doped in the materials of Examples 1-3 forms a porous structure, which improves the diffusion coefficient and specific capacity of the materials. In addition, the surface doping with lithium and heteroatoms reduces the defects of the materials, reduces irreversible capacity, and improves the first efficiency.

[0032] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing a petroleum coke-based porous carbon composite material, characterized in that, Includes the following steps: Petroleum coke and crosslinking agent were mixed at a mass ratio of 100:10-30. The petroleum coke was transferred to a tubular furnace and oxidized for 1-3 hours at a temperature of 150℃-250℃ and a flow rate of 100-500 L / h to obtain oxidized petroleum coke. The resulting oxidized petroleum coke material was then mixed with the crosslinking agent and pyrolyzed at a temperature of 400℃-800℃ for 1-6 hours. After that, activation was carried out for 60-600 minutes at a temperature of 900℃-1100℃ and a flow rate of 50-200 ml / min. After that, the activation was stopped, and then lithium source gas and heteroatom gas were co-doped at a volume ratio of 1:1 and a flow rate of 10-100 ml / min for 30-300 minutes to obtain multi-element doped petroleum coke-based porous carbon.

2. The method for preparing a petroleum coke-based porous carbon composite material according to claim 1, characterized in that, The crosslinking agent is one of benzoyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, and dioctyl peroxide.

3. The method for preparing a petroleum coke-based porous carbon composite material according to claim 1, characterized in that, The activating gas is one of carbon dioxide, water vapor, or air.

4. The method for preparing a petroleum coke-based porous carbon composite material according to claim 1, characterized in that, The lithium source gas is generated by heating and vaporizing lithium tert-butoxide, lithium hydride, lithium acetate, lithium lactate, lithium oxalate, lithium oxalate, or lithium benzoate; the heteroatom gas is one of ammonia, sulfur dioxide, hydrogen sulfide, hydrogen boroide, phosphine, or hydrogen chloride.

5. The petroleum coke-based porous carbon composite material according to claims 1-4 is applied to silicon-carbon materials.

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