Composite porous carbon material and preparation method thereof, and silicon-carbon negative electrode material and preparation method thereof

Abstract

The invention provides a composite porous carbon material and a preparation method thereof, and a silicon-carbon negative electrode material and a preparation method thereof, and belongs to the technical field of silicon-carbon negative electrode materials. Liquid resin, biomass carbon and carbon nanotubes are fully mixed in an organic solvent, a high-strength spherical porous carbon material is obtained through processes of spray drying, carbonization, activation and the like, and finally the silicon-carbon negative electrode material is obtained through silicon deposition and carbon coating. The resin coating, the carbon nanotubes and the spherical structure cooperate with one another, so that the strength of the porous carbon structure is greatly enhanced; the high-strength porous carbon base material can effectively relieve the problem of pore fracture caused by silicon expansion and high compaction of the pole piece, improve the first efficiency and slow down long-cycle capacity attenuation.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon-carbon negative electrode materials, and in particular to a composite porous carbon material and a preparation method thereof, and a silicon-carbon negative electrode material and a preparation method thereof. Background Art

[0002] With the booming market for portable electronics and electric vehicles, the demand for high-energy-density lithium-ion batteries continues to soar. Traditional graphite negative electrodes are limited in theoretical capacity (only 372mAh·g-1), and are unable to meet the market's urgent demand for higher energy density and longer-lasting battery life. In this context, the silicon negative electrode, with its excellent theoretical specific capacity (up to 4200mAh·g-1) and suitable operating voltage, stands out as a highly promising negative electrode material option. In addition, silicon is abundant in the earth's crust, low in cost and environmentally friendly. These characteristics have further promoted the silicon negative electrode to become the focus of current scientific research.

[0003] However, silicon anodes face significant challenges in practical application. Silicon undergoes a dramatic volume expansion (>300%) during the insertion and extraction of lithium ions, leading to cracking and fragmentation of silicon particles, which in turn can cause electrode disintegration, fracture, and electrical isolation. This dramatic volume change not only severely impairs the cycling stability of the silicon anode but also accelerates the consumption of electrolyte and lithium ions, reducing Coulombic efficiency.

[0004] As an innovative carbon material, porous carbon has been widely used as a substrate material for silicon-carbon deposition in recent years due to its unique pore structure. Patent CN117776183A introduces a method for preparing porous carbon and its derived silicon-carbon negative electrode materials. The method uses a biomass carbon source (such as coconut shell, straw, etc.) after heat treatment and carbonization, and then uses a chemical vapor deposition technology to use an organic carbon source to close the pores, thereby reducing the specific surface area of the porous carbon, making it more suitable for the preparation of silicon-carbon negative electrode materials. However, although the sealing of the small pores in this process helps to reduce the specific surface area, it also limits the deposition of silicon in the small pores, posing a challenge to achieving high silicon content deposition. In addition, the prepared biomass porous carbon is not strong enough to resist the volume expansion generated during the silicon lithium insertion process. The expansion of silicon lithium insertion in the pores can easily cause pore damage, which constitutes an obstacle to the development of high-strength, high-density silicon-carbon products. Summary of the Invention

[0005] The object of the present invention is to provide a composite porous carbon material and a preparation method thereof, a silicon-carbon negative electrode material and a preparation method thereof, so as to solve the above-mentioned technical problems.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides a method for preparing a composite porous carbon material, comprising the following steps:

[0008] S1, mixing resin, biomass carbon material, carbon nanotubes and organic solvent in proportion to obtain resin / biomass carbon mixed slurry;

[0009] S2, spray drying the resin / biomass carbon mixed slurry to obtain composite biomass carbon solid spherical particles;

[0010] S3. Carbonizing and activating the composite biomass carbon solid spherical particles in sequence under a protective atmosphere, and obtaining a composite porous carbon material after drying.

[0011] Furthermore, the resin comprises one or more of epoxy resin, phenolic resin, polyurethane resin, acrylic resin, polyester resin, melamine resin, furan resin and urea-formaldehyde resin;

[0012] The biomass carbon material comprises one or more of coconut shells, corn cobs, straw, bamboo, wood, bark, rice husks, seaweed, bagasse and nut shells;

[0013] The organic solvent comprises one or more of toluene, xylene, ethanol, propanol, acetone, cyclohexanone, ethylene glycol monoethyl ether, dichloromethane and N-methylpyrrolidone.

[0014] Furthermore, the mass ratio of the resin to the biomass carbon material is 1-5:1-10, the doping amount of the carbon nanotubes accounts for 0.1-0.5% of the sum of the mass of the resin and the biomass carbon material; and the solid content of the resin / biomass carbon mixed slurry is 5-80%.

[0015] Furthermore, the temperature of the atomization chamber during the spray drying is 60 to 220°C.

[0016] Furthermore, the carbonization temperature is 500-1200° C., and the carbonization time is 1-48 hours; and the protective atmosphere comprises one or more of nitrogen, helium, neon, argon, krypton and xenon.

[0017] Furthermore, the activation treatment includes physical activation and chemical activation, the physical activation is performed using water vapor or carbon dioxide; the chemical reagent for the chemical activation is one or more of potassium hydroxide, potassium bicarbonate, sodium bicarbonate, phosphoric acid and hydrochloric acid.

[0018] Furthermore, the drying temperature is 60 to 120° C., and the drying time is 2 to 36 hours.

[0019] Furthermore, the silicon deposition and carbon coating are performed under a protective atmosphere, and the protective atmosphere includes one or more of nitrogen, helium, neon, argon, krypton and xenon.

[0020] The invention also provides a composite porous carbon material.

[0021] The present invention also provides a method for preparing a silicon-carbon negative electrode material, comprising the following steps: placing the composite porous carbon material according to claim 6 in a vapor deposition furnace, introducing silicon source gas to perform silicon deposition, and finally introducing carbon source gas to perform carbon coating to seal the pores to prepare a silicon-carbon negative electrode material.

[0022] Furthermore, the silicon source gas includes one or more of monosilane, disilane, trisilane, butadienesilane and cyclopentasilane, and the gas flow rate of the silicon source gas is 0.2 to 10 L / min; the temperature of the silicon deposition is 400 to 1200°C, the heating rate is 1 to 10°C / min, and the silicon deposition time is 2 to 24 hours.

[0023] Furthermore, the carbon source gas includes one or more of methane, ethane, propane, ethylene, propylene, acetylene and propyne, and the gas flow rate of the carbon source gas is 0.2 to 10 L / min; the temperature of the carbon coating is 450 to 1100°C, the heating rate is 1 to 10°C / min, and the carbon coating time is 2 to 24 hours.

[0024] The present invention also provides a silicon-carbon negative electrode material, wherein the mass content of Si in the silicon-carbon negative electrode material is 10-90%, and the mass content of C is 10-90%.

[0025] Beneficial effects of the present invention:

[0026] 1. High Strength and High-Density Performance: The synergistic effect of resin coating, carbon nanotubes, and spherical structure significantly enhances the structural strength of the porous carbon material. This high-strength porous carbon substrate effectively mitigates silicon volume expansion during battery charge and discharge, reducing the risk of pore rupture and improving battery stability and safety. The spherical structure also provides strong support for the application of silicon-carbon anode materials under high-density conditions.

[0027] 2. High initial efficiency and long cycle performance: Thanks to the high-strength porous carbon substrate, the problem of silicon expansion is effectively alleviated, the SEI film is not too thick, and the initial efficiency of the battery is significantly improved. In addition, during the cycle process, the high-strength porous carbon substrate effectively inhibits direct exposure of silicon, thereby slowing the rate of capacity decay.

[0028] 3. Excellent electrical conductivity: The carbon nanotubes in the porous carbon are interwoven to form a highly efficient conductive grid. This grid not only improves the overall conductivity of the material, but also effectively alleviates the poor conductivity of silicon itself.

[0029] 4. High-rate performance: Using spherical particles as the building blocks of porous carbon significantly increases the material's specific surface area, thereby shortening the migration path of lithium ions and increasing their diffusion rate. The introduction of carbon nanotubes further enhances the material's electrical conductivity, significantly increasing the battery's reaction rate during charge and discharge, thereby enhancing the battery's rate performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a process flow chart of the preparation method of the present invention. DETAILED DESCRIPTION

[0031] The present invention provides a method for preparing a composite porous carbon material, comprising the following steps:

[0032] S1, mixing resin, biomass carbon material, carbon nanotubes and organic solvent in proportion to obtain resin / biomass carbon mixed slurry;

[0033] S2, spray drying the resin / biomass carbon mixed slurry to obtain composite biomass carbon solid spherical particles;

[0034] S3. Carbonizing and activating the composite biomass carbon solid spherical particles in sequence under a protective atmosphere, and obtaining a composite porous carbon material after drying.

[0035] In the present invention, in step S1, the resin tightly wraps the biomass carbon.

[0036] In the present invention, the step S2 further includes a step of recovering the evaporated solvent.

[0037] In the present invention, the resin comprises one or more of epoxy resin, phenolic resin, polyurethane resin, acrylic resin, polyester resin, melamine resin, furan resin and urea-formaldehyde resin, preferably one or more of epoxy resin, phenolic resin, polyurethane resin and acrylic resin.

[0038] In the present invention, the biomass carbon material comprises one or more of coconut shell, corn cob, straw, bamboo, wood, bark, rice husk, seaweed, bagasse and nut shell, preferably one or more of coconut shell, straw, bamboo and seaweed.

[0039] In the present invention, the organic solvent comprises one or more of toluene, xylene, ethanol, propanol, acetone, cyclohexanone, ethylene glycol monoethyl ether, dichloromethane and N-methylpyrrolidone, preferably one or more of toluene, ethanol, acetone and N-methylpyrrolidone.

[0040] In the present invention, the mass ratio of the resin and the biomass carbon material is 1-5:1-10, preferably 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 5:1; the doping amount of the carbon nanotubes accounts for 0.1-0.5% of the sum of the mass of the resin and the biomass carbon material, preferably 0.2-0.4%; the solid content of the resin / biomass carbon mixed slurry is 5-80%, preferably 10-70%, and more preferably 20-60%.

[0041] In the present invention, the temperature of the atomization chamber in the spray drying is 60 to 220°C, preferably 80 to 210°C.

[0042] In the present invention, the carbonization temperature is 500-1200° C., preferably 700-1100° C.; the carbonization time is 1-48 hours, preferably 2-24 hours; and the protective atmosphere comprises one or more of nitrogen, helium, neon, argon, krypton and xenon.

[0043] In the present invention, the activation treatment includes physical activation and chemical activation. The physical activation is performed using water vapor or carbon dioxide; the chemical reagent for the chemical activation is one or more of potassium hydroxide, potassium bicarbonate, sodium bicarbonate, phosphoric acid and hydrochloric acid.

[0044] In the present invention, the temperature of the chemical activation is 800-1200° C., preferably 900-1000° C.; the time of the chemical activation is 4-10 hours, preferably 6 hours.

[0045] In the present invention, the drying temperature is 60 to 120° C., preferably 80 to 110° C., and more preferably 90 to 100° C.; the drying time is 2 to 36 hours, preferably 10 to 30 hours.

[0046] The invention also provides a composite porous carbon material.

[0047] The present invention also provides a method for preparing a silicon-carbon negative electrode material, comprising the following steps: placing the composite porous carbon material according to claim 6 in a vapor deposition furnace, introducing silicon source gas to perform silicon deposition, and finally introducing carbon source gas to perform carbon coating to seal the pores to prepare a silicon-carbon negative electrode material.

[0048] In the present invention, the silicon deposition and carbon coating are carried out under a protective atmosphere, and the protective atmosphere includes one or more of nitrogen, helium, neon, argon, krypton and xenon;

[0049] The silicon source gas includes one or more of monosilane, disilane, trisilane, butasilane and cyclopentasilane, preferably monosilane; the gas flow rate of the silicon source gas is 0.2 to 10 L / min, preferably 1 to 9 L / min, and more preferably 2 to 8 L / min; the temperature of the silicon deposition is 400 to 1200°C, preferably 450 to 700°C; the heating rate is 1 to 10°C / min, preferably 2 to 8°C / min, and more preferably 4 to 6°C / min; the time of silicon deposition is 2 to 24 hours, preferably 5 to 20 hours.

[0050] In the present invention, the carbon source gas includes one or more of methane, ethane, propane, ethylene, propylene, acetylene and propyne, preferably methane, ethane or propane; the gas flow rate of the carbon source gas is 0.2 to 10 L / min, preferably 1 to 8 L / min, and more preferably 2 to 7 L / min; the temperature of the carbon coating is 450 to 1100°C, preferably 600 to 1000°C; the heating rate is 1 to 10°C / min, preferably 2 to 8°C / min; the carbon coating time is 2 to 24 hours, preferably 3 to 12 hours.

[0051] The present invention also provides a silicon-carbon negative electrode material, wherein the mass content of Si in the silicon-carbon negative electrode material is 10-90%, and the mass content of C is 10-90%.

[0052] The technical solutions provided by the present invention are described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0053] Example 1

[0054] S1. Add epoxy resin, coconut shell carbon material, carbon nanotubes and ethanol into a container, wherein the mass ratio of epoxy resin to coconut shell carbon material is 1:2, the carbon nanotubes account for 0.2% of the sum of the mass of epoxy resin and coconut shell carbon material, and the solid content is controlled at 20%; after thorough stirring and mixing, the epoxy resin tightly wraps the coconut shell carbon material;

[0055] S2, transporting the resin / coconut shell carbon material mixture obtained in S1 to an atomizing chamber for spray drying, and controlling the temperature of the atomizing chamber at 100° C. to obtain solid spherical particles of composite coconut shell carbon material;

[0056] S3, the composite coconut shell carbon material solid spherical particles obtained in S2 are placed in a carbonization furnace with a nitrogen protective atmosphere for carbonization, the carbonization temperature is 800 ° C, the carbonization furnace heating rate is controlled at 5 ° C / min, and the carbonization time is controlled at 6 hours; the carbonized material is fully mixed with potassium hydroxide in a ratio of 1:3 and placed in a rotary kiln, and the furnace temperature is raised to 900 ° C at 5 ° C / min under a nitrogen atmosphere and kept warm for 6 hours; the material is then dissolved in deionized water, filtered and rinsed with deionized water, and repeated 3 times to remove most of the alkali metals; further, the material is placed in 5 mol / L dilute hydrochloric acid and soaked for 8 hours, and then repeatedly rinsed with distilled water until the filtrate is neutral; further, the material is placed in a 120 ° C oven and dried for 12 hours to prepare a composite porous carbon material;

[0057] S4. Place the composite porous carbon material obtained in S3 in a vapor deposition furnace, raise the furnace temperature to 450°C at a rate of 5°C / min under a nitrogen atmosphere, and then introduce monosilane at a flow rate of 5L / min for silicon deposition, and the deposition time is 6 hours; further, raise the furnace temperature to 900°C at a rate of 5°C / min, and introduce acetylene gas for carbon coating, the acetylene gas flow rate is 5L / min, and the coating time is 6 hours; after the coating is completed, a modified high-strength silicon-carbon negative electrode material is obtained, with a silicon content of 52% and a carbon content of 48%.

[0058] Example 2

[0059] The only difference from Example 1 is that the coconut shell biomass carbon material in step S1 is replaced by bamboo biomass carbon material; the carbonization temperature in step S3 is 700°C and the carbonization time is 4 hours; the other conditions remain unchanged, and a modified high-strength silicon-carbon negative electrode material is prepared with a silicon content of 54% and a carbon content of 46%.

[0060] Example 3

[0061] The only difference from Example 1 is that in step S1, the epoxy resin is replaced by phenolic resin, and ethanol is replaced by toluene; in step S2, the atomization temperature is replaced by 130°C; and the other conditions remain unchanged, and a modified high-strength silicon-carbon negative electrode material is prepared with a silicon content of 50% and a carbon content of 50%.

[0062] Example 4

[0063] The only difference from Example 1 is that the ratio of epoxy resin to coconut shell biomass carbon material in step S1 is replaced with 1:10, and the carbonization time in step S3 is modified to 3 hours; the other conditions remain unchanged, and a modified high-strength silicon-carbon negative electrode material is prepared with a silicon content of 56% and a carbon content of 44%.

[0064] Example 5

[0065] The only difference from Example 1 is that in step S1, the coconut shell biomass carbon material is replaced by seaweed biomass carbon material, the epoxy resin is replaced by acrylic resin, the ethanol is replaced by acetone, and the atomization temperature is replaced by 80°C; the other conditions remain unchanged, and a modified high-strength silicon-carbon negative electrode material is prepared with a silicon content of 48% and a carbon content of 52%.

[0066] Comparative Example 1

[0067] The only difference from Example 1 is that no resin is added in step S1; the other conditions remain unchanged, and a silicon-carbon negative electrode material is prepared with a silicon content of 44% and a carbon content of 56%.

[0068] Comparative Example 2

[0069] The only difference from Example 1 is that no carbon nanotubes are added in step S1; the other conditions remain unchanged, and a silicon-carbon negative electrode material is prepared with a silicon content of 46% and a carbon content of 54%.

[0070] The modified high-strength silicon-carbon negative electrode materials obtained in Examples 1 to 6 and the silicon-carbon negative electrode materials obtained in Comparative Examples 1 to 2 were subjected to performance tests, and the results are shown in Table 1 below.

[0071] Table 1 Test results

[0072]

[0073] It can be seen from the above embodiments that the present invention provides a composite porous carbon material and a preparation method thereof, a silicon-carbon negative electrode material and a preparation method thereof. The present invention uses composite biomass to prepare high-strength porous carbon materials, and thereby realizes the development of high-strength silicon-carbon products. Specifically, liquid resin, biomass carbon and carbon nanotubes are fully mixed in an organic solvent, and a high-strength spherical porous carbon material is obtained after processes such as atomization drying, carbonization, and activation. Finally, silicon deposition and carbon coating are performed to obtain a silicon-carbon negative electrode material; the resin coating, carbon nanotubes and spherical structure work together to greatly enhance the strength of the porous carbon structure; the high-strength porous carbon substrate can effectively alleviate the problem of pore rupture caused by silicon expansion and high compaction of the electrode, improve the first effect, and slow down the long-cycle capacity attenuation.

[0074] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for preparing a composite porous carbon material, characterized in that: The following steps are involved: S1, mixing resin, biomass carbon material, carbon nanotubes and organic solvent in proportion to obtain resin / biomass carbon mixed slurry; S2, spray drying the resin / biomass carbon mixed slurry to obtain composite biomass carbon solid spherical particles; S3. Carbonizing and activating the composite biomass carbon solid spherical particles in sequence under a protective atmosphere, and obtaining a composite porous carbon material after drying.

2. The preparation method according to claim 1, characterized in that The resin comprises one or more of epoxy resin, phenolic resin, polyurethane resin, acrylic resin, polyester resin, melamine resin, furan resin and urea-formaldehyde resin; The biomass carbon material comprises one or more of coconut shells, corn cobs, straw, bamboo, wood, bark, rice husks, seaweed, bagasse and nut shells; The organic solvent comprises one or more of toluene, xylene, ethanol, propanol, acetone, cyclohexanone, ethylene glycol monoethyl ether, dichloromethane and N-methylpyrrolidone.

3. The preparation method according to claim 1 or 2, characterized in that The mass ratio of the resin to the biomass carbon material is 1-5:1-10, the doping amount of the carbon nanotubes accounts for 0.1-0.5% of the sum of the mass of the resin and the biomass carbon material; the solid content of the resin / biomass carbon mixed slurry is 5-80%; and the temperature of the atomization chamber in the spray drying is 60-220°C.

4. The preparation method according to claim 3, characterized in that The carbonization temperature is 500-1200° C., and the carbonization time is 1-48 hours. The protective atmosphere comprises one or more of nitrogen, helium, neon, argon, krypton, and xenon. The activation treatment includes physical activation and chemical activation. The physical activation is performed using water vapor or carbon dioxide. The chemical reagent for chemical activation is one or more of potassium hydroxide, potassium bicarbonate, sodium bicarbonate, phosphoric acid and hydrochloric acid. The drying temperature is 60-120° C., and the drying time is 2-36 hours.

5. The preparation method according to claim 4, characterized in that The silicon deposition and carbon coating are performed under a protective atmosphere, and the protective atmosphere includes one or more of nitrogen, helium, neon, argon, krypton and xenon.

6. A composite porous carbon material prepared by the preparation method according to any one of claims 1 to 5.

7. A method for preparing a silicon-carbon negative electrode material, characterized in that: The method comprises the following steps: placing the composite porous carbon material according to claim 6 in a vapor deposition furnace, introducing silicon source gas to perform silicon deposition, and finally introducing carbon source gas to perform carbon coating to seal the pores to prepare a silicon-carbon negative electrode material.

8. The preparation method according to claim 7, characterized in that The silicon source gas includes one or more of monosilane, disilane, trisilane, butasilane and cyclopentasilane, and the gas flow rate of the silicon source gas is 0.2 to 10 L / min; the temperature of the silicon deposition is 400 to 1200°C, the heating rate is 1 to 10°C / min, and the silicon deposition time is 2 to 24 hours.

9. The preparation method according to claim 8, characterized in that The carbon source gas includes one or more of methane, ethane, propane, ethylene, propylene, acetylene and propyne, and the gas flow rate of the carbon source gas is 0.2 to 10 L / min; the temperature of the carbon coating is 450 to 1100°C, the heating rate is 1 to 10°C / min, and the carbon coating time is 2 to 24 hours.

10. The silicon-carbon negative electrode material based on composite porous carbon prepared by the preparation method according to any one of claims 7 to 9, characterized in that: The mass content of Si in the silicon-carbon negative electrode material is 10-90%, and the mass content of C is 10-90%.

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