Highly compacted porous carbon material and method for producing the same

Abstract

The application discloses a high-compaction porous carbon material preparation method, which sprays and granulates an organic carbon source and carbon nanotubes, realizes the integration of multiple processes such as dispersion, granulation and pre-solidification to prepare a high-compaction porous carbon precursor, greatly simplifies a process flow and improves the preparation stability of the material; in a one-time calcination process, three processes of solidification, carbonization and activation are integrated into a one-step process in three temperature intervals, thereby simplifying the process flow of a conventional alkali method for preparing the porous carbon; the introduction of high-strength carbon nanotubes can enhance the compression strength of the particles and improve the conductivity of the material, and is beneficial to improving the rate performance of the negative electrode material. The high-compaction porous carbon material has a clear spherical structure and a smooth and dense surface, and is beneficial to the subsequent limited deposition of nanosilicon during the preparation of silicon-carbon.

Description

Technical Field

[0001] This invention belongs to the field of porous carbon materials technology, and relates to high-pressure porous carbon materials, as well as a method for preparing the above-mentioned high-pressure porous carbon materials. Background Technology

[0002] Porous carbon materials have important applications in adsorption, hydrogen storage, supercapacitors, and lithium-ion battery anodes. As the energy density requirements of supercapacitors and lithium-ion batteries increase, especially during electrode fabrication, higher demands are placed on compaction density. However, porous carbon materials prepared by conventional methods exhibit irregular particle morphologies, and their carbon skeletons are relatively fragile, resulting in poor compaction resistance.

[0003] Current research on improving the compaction density of porous carbon materials mainly employs techniques such as using different carbon sources, including coke, biomass, and resins, to create pores through chemical alkali activation or physical methods (steam or carbon dioxide activation), and controlling the carbonization temperature. However, porous carbon materials prepared in this way still fall short of the technical requirements for porous carbon in anode materials, and the preparation process is complex. Especially for porous carbon materials using novel silicon-carbon anodes as a technical carrier, the skeletal strength of the porous carbon directly determines the compaction density of the silicon-carbon anode material, thus affecting the improvement of battery energy density and cycle performance. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing high-compaction porous carbon materials, which solves the problem of poor compaction density in the prior art.

[0005] The technical solution adopted in this invention is a method for preparing high-pressure porous carbon materials, comprising the following steps:

[0006] Step 1: Dissolve and disperse the resin, carbon nanotubes, and KOH separately in ethanol, then mix them to obtain a mixed slurry;

[0007] Step 2: Spray dry the mixed slurry to obtain a porous carbon precursor;

[0008] Step 3: Calcine the porous carbon precursor to obtain a black powder;

[0009] Step 4: Wash and dry the black powder to obtain porous carbon;

[0010] Step 5: After high-temperature purification of porous carbon, high-pressure compacted porous carbon material is obtained.

[0011] The invention is further characterized by:

[0012] In step 1, the mass ratio of resin, carbon nanotubes, and KOH is 1:0.001-0.1:0.5-3.

[0013] Resins include phenolic resins, epoxy resins, furfural resins, or urea-formaldehyde resins.

[0014] In step 2, during the spray drying process, the spray temperature is 150–200℃ and the atomizer frequency is 200–350 Hz.

[0015] In step 2, the spray drying process is protected by an inert atmosphere, which is either nitrogen or argon.

[0016] In step 3, during the calcination process, a three-stage heating program is adopted: first, the temperature is maintained at 0-200℃ for 1-4 hours; then, the temperature is increased to 400℃-500℃ and maintained for 1-4 hours; finally, the temperature is increased to 800-900℃ and maintained for 1-4 hours.

[0017] An inert atmosphere is used for protection during the calcination process in step 3.

[0018] Another objective of this invention is to provide a high-pressure porous carbon material and use it as a carrier for preparing silicon-carbon materials.

[0019] Another technical solution adopted in this invention is a high-pressure porous carbon material, which is prepared by the above-mentioned high-pressure porous carbon material preparation method.

[0020] The beneficial effects of this invention are as follows: The method for preparing high-pressure porous carbon materials of this invention integrates the organic carbon source and carbon nanotubes through spray granulation, achieving the fusion of dispersion, granulation, and pre-curing processes to prepare high-pressure porous carbon precursors, greatly simplifying the process flow and improving the stability of the material preparation. In a single calcination process, three temperature ranges are used to integrate the curing, carbonization, and activation processes into a single step, simplifying the conventional alkaline method for preparing porous carbon. The introduction of high-strength carbon nanotubes enhances the compressive strength of the particles and improves the electrical conductivity of the material, which is beneficial for improving the rate performance of the anode material. The high-pressure porous carbon material of this invention has a distinct spherical structure, a smooth and dense surface, and a high pore volume (0.6-1.0 cm³). 3 / g) and a surface area greater than 1500m 2 / g), with a microporous structure, micropores (<2nm) account for >97%, and have good compaction resistance and conductivity, which is very beneficial for the confined deposition of nano-silicon during the subsequent preparation of silicon-carbon. Attached Figure Description

[0021] Figure 1 These are morphology images of silicon-carbon anode materials obtained using traditional methods;

[0022] Figure 2 This is a roll forming diagram of silicon-carbon anode material obtained by traditional methods and then compounded with graphite.

[0023] Figure 3This is a microscopic SEM image of porous carbon material obtained by the high-pressure porous carbon material preparation method of the present invention;

[0024] Figure 4 This is a roll-pressing diagram of the silicon-carbon anode material prepared in Example 1 of the preparation method of high-pressure porous carbon material of the present invention after being compounded with graphite;

[0025] Figure 5 This is an electrochemical curve of the silicon-carbon anode material prepared in Example 1 of the preparation method of high-pressure porous carbon material of the present invention. Detailed Implementation

[0026] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0027] A method for preparing high-pressure porous carbon materials includes the following steps:

[0028] Step 1: Dissolve and disperse the resin, carbon nanotubes, and KOH in ethanol at a mass ratio of 1:0.001-0.1:0.5-3, then mix them in a stirred tank to obtain a mixed slurry; the resin includes phenolic resin, epoxy resin, furfural resin, or urea-formaldehyde resin.

[0029] Step 2: Spray dry the mixed slurry under an inert atmosphere. The spray temperature is 150-200℃ and the atomizer frequency is 200-350Hz to obtain a porous carbon precursor. The inert atmosphere is either nitrogen or argon.

[0030] Step 3: Calcine the porous carbon precursor under an inert atmosphere. Use a three-stage heating program: first, heat at 0-200℃ for 1-4 hours; then heat to 400℃-500℃ and heat for 1-4 hours; finally heat to 800-900℃ and heat for 1-4 hours to obtain a black powder.

[0031] Step 4: Wash the black powder with deionized water to remove residual alkali, and then dry it to obtain black powder.

[0032] Step 5: After high-temperature purification of the black powder, high-pressure porous carbon material is obtained.

[0033] High-pressure porous carbon material is prepared using the high-pressure porous carbon material preparation method described above.

[0034] Comparative Example

[0035] Conventional alkaline method for preparing porous carbon materials:

[0036] Step 1: Pre-carbonize the phenolic resin at a temperature of 500℃ to obtain a pre-carbonized material;

[0037] Step 2: After crushing the pre-carbonized material, mix it with KOH at a mass ratio of 1:2 to obtain a mixture.

[0038] Step 3: Place the mixture in an activation furnace and activate it at 850℃ for 2 hours;

[0039] Step 4: Place the activated mixture in a water washing tank, wash repeatedly until neutral, and then dry.

[0040] Step 5: Further purify the dried material at a high temperature of 800℃ to obtain porous carbon material.

[0041] Silicon-carbon materials prepared using the porous carbon materials obtained in this embodiment are as follows: Figure 1 As shown, it is an irregular porous carbon material with a distinctly irregular morphology. A schematic diagram of the rolling process after silicon-carbon material and graphite are shown below. Figure 2 As shown, under the same compaction density, particle breakage is more severe.

[0042] Example 1

[0043] Step 1: Dissolve and disperse phenolic resin, carbon nanotubes and KOH separately according to a mass ratio of 1:0.01:1.5, then mix them in a stirred tank and stir for 1 hour to obtain a mixed slurry;

[0044] Step 2: Spray drying granulation is used to spray dry the mixed slurry. An inert atmosphere is used during the process. The spray temperature is 160℃ and the atomizer frequency is 300HZ to obtain a porous carbon precursor.

[0045] Step 3: Calcine the porous carbon precursor under an inert atmosphere. First, heat it at 0-200℃ for 1 hour; then heat it to 400℃ and heat it for 1 hour; finally heat it to 800℃ and heat it for 2 hours to obtain a black powder.

[0046] Step 4: Wash the black powder with deionized water at a water-to-material ratio of 1:20, stir for 10 hours to remove residual alkali, and then dry to obtain porous carbon.

[0047] Step 5: After purifying the porous carbon at 800℃, high-pressure compacted porous carbon material is obtained.

[0048] The spherical porous carbon material obtained in this embodiment is as follows: Figure 3 As shown, it exhibits a distinct spherical structure, a dense surface, and a microporous structure, which provides a good carbon framework matrix for subsequent silicon deposition and avoids localized over-deposition of silicon. Figure 4As shown, the schematic diagram of the electrode sheet prepared by further depositing silicon using the spherical porous carbon material obtained in this embodiment and then combining it with graphite is shown. Under high compaction, it still maintains a good particle shape, and no obvious broken particles were found, indicating that the material has good compaction resistance. Figure 5 As shown in the figure, the charging curve exhibits a good charging performance with no obvious plateau, indicating that the deposited silicon nanoparticles are small in size and there is no significant enrichment of silicon nanoparticles. The capacity reaches 1930 mAh / g, with an initial efficiency of 93.5%, further demonstrating that porous carbon materials possess good conductivity, thus enabling the prepared silicon-carbon material to achieve a high initial efficiency.

[0049] Example 2

[0050] Step 1: Dissolve and disperse phenolic resin, carbon nanotubes and KOH separately according to a mass ratio of 1:0.01:2, then mix them in a stirred tank and stir for 1 hour to obtain a mixed slurry;

[0051] Step 2: Spray drying granulation is used to spray dry the mixed slurry. An inert atmosphere is used during the process. The spray temperature is 200℃ and the atomizer frequency is 300HZ to obtain a porous carbon precursor.

[0052] Step 3: Calcine the porous carbon precursor under an inert atmosphere. First, heat it at 0-200℃ for 2 hours; then heat it to 400℃ and heat it for 2 hours; finally heat it to 800℃ and heat it for 2 hours to obtain a black powder.

[0053] Step 4: Wash the black powder with deionized water at a water-to-material ratio of 1:20, stir for 10 hours to remove residual alkali, and then dry to obtain porous carbon.

[0054] Step 5: After purifying the porous carbon at 800℃, high-pressure compacted porous carbon material is obtained.

[0055] Example 3

[0056] Step 1: Dissolve and disperse phenolic resin, carbon nanotubes and KOH separately according to a mass ratio of 1:0.1:3, then mix them in a stirred tank and stir for 1 hour to obtain a mixed slurry;

[0057] Step 2: Spray drying granulation is used to spray dry the mixed slurry. An inert atmosphere is used during the process. The spray temperature is 200℃ and the atomizer frequency is 300HZ to obtain a porous carbon precursor.

[0058] Step 3: Calcining the porous carbon precursor under an inert atmosphere. First, hold at 0-200℃ for 4 hours; then continue heating to 400℃ and hold for 4 hours; finally, heat to 800℃ and hold for 4 hours to obtain a black powder.

[0059] Step 4: Wash the black powder with deionized water at a water-to-material ratio of 1:20, stir for 10 hours to remove residual alkali, and then dry to obtain porous carbon.

[0060] Step 5: After purifying the porous carbon at 800℃, high-pressure compacted porous carbon material is obtained.

[0061] The performance comparison of the high-pressure porous carbon materials obtained in the comparative examples and Examples 1-3 is shown in the table below:

[0062]

[0063] As can be seen from the table above, the high-pressure compaction porous carbon material obtained by the preparation method of the present invention has excellent compaction resistance and good electrical conductivity.

[0064] Through the above methods, the high-compaction porous carbon material preparation method of this invention integrates organic carbon source and carbon nanotubes through spray granulation, realizing the preparation of high-compaction porous carbon precursor by combining multiple processes such as dispersion, granulation, and pre-curing, greatly simplifying the process flow and improving the stability of material preparation. In the single calcination process, the three processes of curing, carbonization, and activation are integrated into a one-step process using three temperature ranges, simplifying the process flow of conventional alkaline method for preparing porous carbon. The introduction of high-strength carbon nanotubes enhances the compressive strength of the particles and improves the electrical conductivity of the material, which is beneficial to improving the rate performance of the anode material. The high-compaction porous carbon material of this invention has a distinct spherical structure, a smooth and dense surface, high pore volume (0.6-1.0 cm3 / g) and large specific surface area (>1500 m2 / g), and a microporous structure with micropores (<2nm) accounting for >97%. It has good compressive strength and electrical conductivity, which is very beneficial for the confined deposition of nano-silicon during the subsequent preparation of silicon-carbon.

Claims

1. A method for preparing high-pressure porous carbon materials, characterized in that, Includes the following steps: Step 1: Dissolve and disperse the resin, carbon nanotubes, and KOH separately in ethanol, then mix them to obtain a mixed slurry; Step 2: Spray dry the mixed slurry to obtain a porous carbon precursor; Step 3: Calcine the porous carbon precursor to obtain a black powder; Step 4: Wash and dry the black powder to obtain porous carbon; Step 5: The porous carbon is purified at high temperature to obtain a high-pressure compacted porous carbon material; The mass ratio of resin, carbon nanotubes, and KOH in step 1 is 1:0.001~0.1:0.5~3; In the spray drying process described in step 2, the spray temperature is 150~200℃ and the atomizer frequency is 200~350HZ; In the calcination process described in step 3, a three-stage heating program is adopted: first, the temperature is maintained at 0-200℃ for 1-4 hours; then, the temperature is increased to 400℃-500℃ and maintained for 1-4 hours; finally, the temperature is increased to 800-900℃ and maintained for 1-4 hours.

2. The method for preparing high-pressure porous carbon materials as described in claim 1, characterized in that, The resin includes phenolic resin, epoxy resin, furfural resin, or urea-formaldehyde resin.

3. The method for preparing high-pressure porous carbon materials as described in claim 1, characterized in that, The spray drying process described in step 2 is protected by an inert atmosphere, which is either nitrogen or argon.

4. The method for preparing high-pressure porous carbon materials as described in claim 1, characterized in that, An inert atmosphere is used for protection during the calcination process described in step 3.

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