Preparation method of composite porous carbon beneficial to silicon deposition

Abstract

The invention relates to a preparation method of composite porous carbon beneficial to silicon deposition. Comprising the following steps: S1, carrying out surface oxidation and acylating chlorination treatment on porous carbon fine powder to obtain acylating chlorinated porous carbon fine powder; s2, adding the acylating chlorination porous carbon fine powder and an amino compound into a solvent to obtain amide modified porous carbon fine powder; s3, soaking the amide-modified porous carbon fine powder in a catalyst aqueous solution to obtain catalyst-loaded porous carbon; s4, mixing the porous carbon loaded with the catalyst with a carbon source precursor solution, carrying out hydrothermal reaction, and freeze-drying to obtain a porous carbon composite precursor; and S5, carbonizing and activating the porous carbon composite carbon precursor to obtain the composite porous carbon beneficial to silicon deposition. The composite porous carbon prepared by the invention is beneficial to more and uniform deposition of silicon in pores of the core porous carbon fine powder, and has low powder resistivity.

Description

Technical Field

[0001] This invention belongs to the field of materials preparation, specifically a method for preparing composite porous carbon that is conducive to silicon deposition. Background Technology

[0002] Porous carbon is a core material for preparing silicon-carbon materials. Its key parameters—pore size, specific surface area, powder resistivity, and strength—significantly affect the material's capacity, initial efficiency, compaction density, and kinetics. However, currently, porous carbon suffers from numerous surface defects and high resistivity, leading to deviations in its initial efficiency and power performance. Although some researchers have attempted to improve the specific capacity and rate performance of porous carbon by adding activators or doping, the effects have been limited. Summary of the Invention

[0003] To improve the first-pass efficiency and power performance of porous carbon, this invention coats the surface of a porous carbon precursor with a polymer material and grows carbon nanotubes thereon. This reduces surface defects and free energy, thereby improving the first-pass efficiency and power performance. It also facilitates silicon deposition within the porous carbon and reduces gas generation.

[0004] A method for preparing composite porous carbon that facilitates silicon deposition, characterized by comprising the following steps: Step S1: Porous carbon fine powder and concentrated nitric acid were weighed at a mass ratio of 10:(50-200). The porous carbon fine powder was then added to concentrated nitric acid with a mass concentration of 10-68wt% and soaked at 80℃-150℃ for 1-6 hours. After filtration, oxidized porous carbon was obtained. Then, oxidized porous carbon and sulfoxide were weighed at a mass ratio of 10:10-50 and added to sulfoxide solvent. The reaction was carried out at 25℃-80℃ for 1-6 hours. After filtration, the mixture was vacuum dried to obtain acyl chloride porous carbon fine powder. Step S2: Weigh out the acyl chloride porous carbon fine powder and amino compound solution at a mass ratio of 100:100-500, add the acyl chloride porous carbon fine powder to the amino compound solution with a mass concentration of 1-10wt%, disperse evenly, filter, and vacuum dry to obtain amidated porous carbon fine powder. Step S3: Weigh out the aminated porous carbon fine powder and catalyst in a mass ratio of 100:1-5, then soak the aminated porous carbon fine powder in an aqueous solution of catalyst with a mass concentration of 0.5-2wt% for 24 hours to obtain porous carbon supported on catalyst. Step S4: After weighing the porous carbon supported on the catalyst and the carbon source solution at a mass ratio of 100:100-500, the porous carbon supported on the catalyst was mixed with a carbon source precursor solution with a mass concentration of 1-10 wt%, and then transferred to a high-pressure reactor. The mixture was reacted at a temperature of 100℃-200℃ and a pressure of 1-5 MPa for 1-6 hours, and then freeze-dried to obtain a porous carbon composite precursor. Step S5: The porous carbon composite carbon precursor is transferred to a tube furnace and heated to 700-1000℃ for carbonization for 1-6 hours. Then, the temperature is raised to 1200℃-1500℃, and carbon dioxide gas is introduced at a flow rate of 100-500 ml / min for activation for 30-300 minutes to obtain the composite porous carbon.

[0005] The porous carbon powder in step S1 has the following parameters: particle size D50 of 1-5µm and specific surface area of ​​2000-3000m². 2 / g, the proportion of micropores with a diameter of 5nm or less in porous carbon fine powder is 10-30%.

[0006] The amino compound in step S2 is one of aniline, melamine, urea, or dopamine.

[0007] The catalyst in step S3 is one of ferrocene, palladium acetate, stannous octoate, and dibutyltin diacetate.

[0008] In step S4, the carbon source is one of glucose, sucrose, maltose, fructose, or lactose.

[0009] Beneficial effects

[0010] 1. By carboxylating, acylated, and amidated porous carbon fine powder, organic compounds are coated onto the porous carbon surface to reduce defects. At the same time, carbon nanotubes are grown on the surface of the carbon as a substrate to improve electronic conductivity.

[0011] 2. By hydrothermal reaction, porous carbon supported on catalysts and carbon-based compounds are mixed to achieve the mixing of two different carbon source matrices, leveraging the advantages of both porous carbon powder and glycosidic materials. Specifically, the amino groups on the surface of amidated porous carbon powder interact with the metal free radicals in the organic catalyst, adsorbing onto the surface and altering the carbon arrangement of the porous carbon. This results in highly anisotropic porous carbon, increased tap density, and reduced impedance, yielding a porous carbon composite containing the catalyst. Carbon nanotubes can then be grown on this composite to obtain a particulate structure. Meanwhile, the glycosidic compounds, containing hydroxyl and carbonyl groups, undergo dehydration during the hydrothermal reaction to generate spherical structures. The two structures complement each other, increasing tap density and reducing impedance, thereby reducing expansion and initial efficiency.

[0012] 3. Activating it by introducing carbon dioxide gas increases pore volume and pore size, facilitating the deposition of nano-silicon. Attached Figure Description

[0013] Figure 1 The image shows a SEM image of the composite porous carbon prepared in Example 1. Detailed Implementation

[0014] Example 1

[0015] A method for preparing composite porous carbon that facilitates silicon deposition includes the following steps: Step S1: 10g of porous carbon fine powder was added to 100g of concentrated nitric acid with a mass concentration of 50wt% and soaked at 120℃ for 3h. The mixture was then filtered to obtain oxidized porous carbon. 10g of oxidized porous carbon was added to 30ml of thionyl chloride solvent and reacted at 50℃ for 3h. The filter residue was dried under vacuum at 80℃ for 24h to obtain fine powder of acyl chloride porous carbon. Step S2: 100g of acyl chloride porous carbon fine powder was added to 300g of aniline aqueous solution with a mass concentration of 5wt%, and the mixture was dispersed evenly. The filter residue obtained by filtration was vacuum dried at 80℃ for 24h to obtain amidated porous carbon fine powder. Step S3: 100g of amidated porous carbon fine powder was soaked in 300g of ferrocene aqueous solution with a mass concentration of 1wt% for 24h to obtain porous carbon with supported catalyst. Step S4: 100g of porous carbon supported on catalyst was mixed with 300g of glucose aqueous solution with a mass concentration of 5wt%, and then transferred to a high-pressure reactor. The mixture was reacted at 150℃ and 3MPa for 3h, and then freeze-dried at -40℃ for 48h to obtain a porous carbon composite precursor. Step S5: The porous carbon composite carbon precursor was transferred to a tube furnace and pre-carbonized at 800℃ for 3 hours. Then, the temperature was raised to 1300℃ and activated for 150 minutes by introducing carbon dioxide gas at a flow rate of 300 ml / min to obtain the composite porous carbon.

[0016] Example 2

[0017] A method for preparing composite porous carbon that facilitates silicon deposition includes the following steps: Step S1: 10g of porous carbon fine powder was added to 50g of concentrated nitric acid with a mass concentration of 68wt% and soaked at 80℃ for 6h. The mixture was then filtered to obtain oxidized porous carbon. 10g of oxidized porous carbon was added to 10ml of thionyl chloride solvent and reacted at 25℃ for 6h. After filtration, the filter residue was dried under vacuum at 80℃ for 24h to obtain fine powder of acyl chloride porous carbon. Step S2: 100g of acyl chloride porous carbon fine powder was added to 100g of melamine aqueous solvent with a mass concentration of 10wt%, and the mixture was dispersed evenly. The filter residue was dried under vacuum at 80℃ for 24h to obtain amidated porous carbon fine powder. Step S3: 100g of amidated porous carbon fine powder was soaked in 200g of an aqueous solution of 0.5wt% palladium acetate for 24h to obtain porous carbon with supported catalyst. Step S4: 100g of porous carbon supported on catalyst was mixed with 100g of sucrose aqueous solution with a mass concentration of 10wt%, and then transferred to a high-pressure reactor. The mixture was reacted at 100℃ and 5MPa for 6h, and then freeze-dried at -40℃ for 48h to obtain a porous carbon composite precursor. Step S5: The porous carbon composite carbon precursor was transferred to a tube furnace, heated to 700℃ for carbonization for 6 hours, and then heated to 1200℃. Carbon dioxide gas was introduced at a flow rate of 100 ml / min for activation for 300 minutes to obtain the composite porous carbon.

[0018] Example 3

[0019] A method for preparing composite porous carbon that facilitates silicon deposition includes the following steps: Step S1: 10g of porous carbon fine powder was added to 200g of concentrated nitric acid with a mass concentration of 10wt% and soaked at 150℃ for 1h. The mixture was then filtered to obtain oxidized porous carbon. 10g of oxidized porous carbon was added to 50g of thionyl chloride solvent and reacted at 80℃ for 1h. After filtration, it was vacuum dried at 80℃ for 24h to obtain fine powder of acyl chloride porous carbon. Step S2: 100g of acyl chloride porous carbon fine powder was added to 500g of dopamine aqueous solvent with a mass concentration of 1wt%, dispersed evenly, filtered, and the resulting filter residue was vacuum dried at 80℃ for 24h to obtain amidated porous carbon fine powder. Step S3: 100g of amidated porous carbon fine powder was soaked in 250g of aqueous solution with a mass concentration of 2wt% stannous octoate for 24h to obtain porous carbon with supported catalyst. Step S4: 100g of porous carbon supported on catalyst was mixed with 500g of maltose aqueous solution with a mass concentration of 1wt%, and then transferred to a high-pressure reactor. The mixture was reacted at 200℃ and 1MPa for 1h, and then freeze-dried at -40℃ for 48h to obtain a porous carbon composite precursor. Step S5: The porous carbon composite carbon precursor was transferred to a tube furnace, heated to 1000℃ for carbonization for 1 hour, and then heated to 1500℃. Carbon dioxide gas was introduced at a flow rate of 500 ml / min for activation for 30 minutes to obtain the composite porous carbon.

[0020] Comparative Example 1: Unlike Example 1, steps S1-S3 are omitted. In step S4, porous carbon is used to replace the porous carbon in the supported catalyst. Otherwise, the process is the same as in Example 1.

[0021] Comparative Example 2: Unlike Example 1, step S4 does not involve adding a glucose solution; otherwise, it is the same as Example 1.

[0022] Performance testing

[0023] 1. Scanning electron microscopy (SEM) test: SEM images of the composite porous carbon prepared in Example 1 are shown below. Figure 1 As shown, by Figure 1 As can be seen, the material exhibits a spherical structure with a uniform size distribution and a particle size between 2 and 8 μm.

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

[0025] 2.2 Button Cell Battery Performance Test: The composite porous carbon corresponding to Examples 1-3 and Comparative Examples 1-3 was used as the negative electrode material for lithium-ion batteries to prepare coin cells according to the following method: A binder, conductive agent, and solvent are added to each corresponding porous carbon, stirred to form a slurry, coated onto copper foil, and dried and rolled to obtain a negative electrode sheet. The binder used is LA136D, the conductive agent is SP (conductive carbon black), and the solvent is NMP. The ratio of metal-doped porous carbon:SP:LA136D: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.

[0026] Each coin cell was assembled in an argon-filled glove box, and then the following performance tests were performed: Electrochemical performance test: Specifically, the electrochemical performance was performed on a Wuhan Landian CT2001A battery tester, with a charge / discharge voltage range of 0.005V to 1.5V and a charge / discharge rate of 0.1C. The discharge specific capacity and initial efficiency of the corresponding coin cells were tested. At the same time, the room temperature charge DCR (50% SOC) and cycle performance (0.1C / 0.1C, 100 cycles) of the corresponding coin cells were tested. The diffusion coefficient of the material was also tested by GITT.

[0027] The test results are shown in Table 2.

[0028]

[0029] As can be seen from Table 1, the composite porous carbon prepared in Examples 1-3 is superior to that in Comparative Examples 1-2 in terms of powder compaction density and powder resistivity. The reason is that the examples graft amide groups onto the surface of porous carbon through chemical reaction, thereby increasing the density of the material, improving the powder compaction density and tap density. At the same time, the doping of sugar-based porous carbon achieves a reasonable particle size distribution and improves the tap density.

[0030]

[0031] As can be seen from Table 2, Examples 1-3 are superior to Comparative Examples 1-2 in terms of initial efficiency and its rate of return, as well as cycling performance. This is because the materials in the examples have low powder resistivity, which reduces polarization and improves initial efficiency. At the same time, the materials in the examples are doped with sugar-based porous carbon, which reduces expansion and improves cycling performance.

[0032] The applicant declares that the present invention is illustrated by the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing composite porous carbon that facilitates silicon deposition, characterized in that, Includes the following steps: Step S1: Porous carbon fine powder and concentrated nitric acid were weighed at a mass ratio of 10:(50-200). The porous carbon fine powder was then added to concentrated nitric acid with a mass concentration of 10-68wt% and soaked at 80℃-150℃ for 1-6 hours. After filtration, oxidized porous carbon was obtained. Then, oxidized porous carbon and sulfoxide were weighed at a mass ratio of 10:10-50 and added to sulfoxide solvent. The reaction was carried out at 25℃-80℃ for 1-6 hours. After filtration, the mixture was vacuum dried to obtain acyl chloride porous carbon fine powder. Step S2: Weigh out the acyl chloride porous carbon fine powder and amino compound solution at a mass ratio of 100:100-500, add the acyl chloride porous carbon fine powder to the amino compound solution with a mass concentration of 1-10wt%, disperse evenly, filter, and vacuum dry to obtain amidated porous carbon fine powder. Step S3: The amidated porous carbon fine powder and the catalyst were weighed at a mass ratio of 100:1-5. The amidated porous carbon fine powder was soaked in an aqueous solution of catalyst with a mass concentration of 0.5-2wt% for 24 hours to obtain porous carbon supported on catalyst. Step S4: After weighing the porous carbon supported on the catalyst and the carbon source solution at a mass ratio of 100:100-500, the porous carbon supported on the catalyst was mixed with a carbon source precursor solution with a mass concentration of 1-10 wt%, and then transferred to a high-pressure reactor. The mixture was reacted at a temperature of 100℃-200℃ and a pressure of 1-5 MPa for 1-6 hours, and then freeze-dried to obtain a porous carbon composite precursor. Step S5: The porous carbon composite carbon precursor is transferred to a tube furnace and heated to 700℃-1000℃ for carbonization for 1-6 hours. Then, the temperature is raised to 1200℃-1500℃, and carbon dioxide gas is introduced at a flow rate of 100-500 ml / min for activation for 30-300 minutes to obtain the composite porous carbon.

2. The method for preparing composite porous carbon favorable for silicon deposition according to claim 1, characterized in that, The porous carbon powder in step S1 has the following parameters: particle size D50 of 1-5µm and specific surface area of ​​2000-3000m². 2 / g, the proportion of micropores with a diameter of 5nm or less in porous carbon fine powder is 10-30%.

3. The method for preparing composite porous carbon favorable for silicon deposition according to claim 1, characterized in that, The amino compound in step S2 is one of aniline, melamine, urea, or dopamine.

4. The method for preparing composite porous carbon favorable for silicon deposition according to claim 1, characterized in that, The catalyst in step S3 is one of ferrocene, palladium acetate, stannous octoate, and dibutyltin diacetate.

5. The method for preparing composite porous carbon favorable for silicon deposition according to claim 1, characterized in that, In step S4, the carbon source is one of glucose, sucrose, maltose, fructose, or lactose.

Images