All-bamboo carbon aerogel as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of carbon aerogel, and particularly relates to full-bamboo carbon aerogel as well as a preparation method and application thereof. The preparation method comprises the following steps: (1) mechanically crushing bamboo wood, removing lignin and hemicellulose, and reserving a cellulose skeleton structure to obtain a primary bamboo wood product; (2) carbonizing the bamboo primary product to form a porous bamboo carbon matrix; and (3) forming a graded porous structure from the porous bamboo carbon matrix by a chemical activation method, and cleaning and drying the graded porous structure to obtain the bamboo carbon aerogel. Through step-by-step carbonization and activation, the porous bamboo carbon matrix is formed through carbonization, and then a hierarchical porous structure is constructed and pore distribution is optimized through a chemical activation method, so that the conductivity and the electrochemical performance of the carbon aerogel are remarkably improved, the interface resistance in the solid-state battery is effectively reduced, the cost is reduced, the environmental pollution is reduced, and the solid-state battery is suitable for large-scale popularization and application. The application field of the carbon aerogel is expanded.

Description

Technical Field

[0001] The present invention belongs to the technical field of carbon aerogels, and in particular relates to a full-bamboo carbon aerogel and a preparation method and application thereof. Background Art

[0002] Carbon aerogels, a material with high specific surface area, low density, good conductivity, and thermal stability, are widely used in electrochemical energy storage, catalyst supports, adsorption materials, and other fields. However, the production of traditional carbon aerogels relies heavily on fossil fuels, which not only increases costs but also poses environmental risks. Therefore, finding sustainable, low-cost biomass feedstocks to produce carbon aerogels has become a research priority.

[0003] CN 102430369 A discloses a method for preparing a bamboo charcoal / carbon aerogel composite material, comprising the following steps: mixing resorcinol and formaldehyde, dissolving them in water, and stirring to obtain a mixed solution A; adding bamboo charcoal to the mixed solution A and sealing; first allowing the mixed solution to stand at room temperature, then allowing it to stand at 70-80°C, and filtering to obtain a mixture B; first soaking the mixture B in a trifluoroacetic acid solution with a mass concentration of 0.4-0.6%, then removing it and soaking it in acetone, and drying it; and finally placing the dried mixture in a nitrogen atmosphere furnace and maintaining it at 800-1000°C for 1-3 hours to obtain the bamboo charcoal / carbon aerogel composite material. This composite material can be widely used in industries such as air purification, sewage treatment, toxic wastewater treatment, chemical catalyst carriers, automobile exhaust purification, sugar and wine making, and food refining. However, this technical solution has complex procedures and requires activation after carbonization, leaving room for improvement.

[0004] CN 110665442 A discloses a composite activated carbon aerogel, its preparation method, and its application. This method uses cellulose pulp and carbon nanotubes as raw materials, with the weight ratio of cellulose pulp to carbon nanotubes being 8-10:5. Using cellulose as the carbon aerogel matrix allows for the recycling of agricultural waste, reducing environmental pollution and resource waste. However, it cannot be applied to the field of new energy batteries.

[0005] Therefore, the prior art still requires a method for preparing carbon aerogel with simple preparation process and reliable product quality. Summary of the Invention

[0006] The present invention aims to address the shortcomings of existing carbon aerogel preparation methods by obtaining a carbon aerogel with excellent physical and chemical properties through carbonization, thereby expanding the application field of carbon aerogel. The detailed technical solution of the present invention is described below.

[0007] The present invention provides a method for preparing a full bamboo carbon aerogel, comprising the following steps: (1) Mechanically crushing the bamboo to remove lignin and hemicellulose, retaining the cellulose skeleton structure to obtain the primary bamboo product; (2) Carbonizing the primary bamboo material to form a porous bamboo carbon matrix; (3) The porous bamboo carbon matrix is ​​chemically activated to form a hierarchical porous structure, and the hierarchical porous structure is cleaned and dried to obtain bamboo carbon aerogel.

[0008] Preferably, the chemical activation method in step (3) is to treat the porous bamboo carbon substrate with a chemical activator at 500-900° C. for 1-3 hours.

[0009] Preferably, the chemical activator comprises at least one of KOH, ZnCl2 and H3PO4.

[0010] Preferably, the carbonization in step (2) is carried out under a protective atmosphere, the carbonization temperature is 300-500°C or 800-1200°C, the carbonization time is 2h-4h, and the heating rate is 5-10°C / min.

[0011] Preferably, the drying in step (3) is freeze drying or supercritical carbon dioxide drying.

[0012] Preferably, in step (1), the bamboo is mechanically crushed into 100-200 mesh powder, and lignin and hemicellulose are removed by adding acid or alkali.

[0013] Preferably, the bamboo material in step (1) includes any one of moso bamboo, arrow bamboo and square bamboo.

[0014] The present invention also provides a full bamboo carbon aerogel, which is prepared by any of the above preparation methods.

[0015] The present invention also discloses an application of all-bamboo carbon aerogel in electrochemical energy storage.

[0016] Preferably, the method comprises preparing a composite electrolyte membrane and a negative electrode material; Preferably, the composite electrolyte membrane is prepared by compounding the all-bamboo carbon aerogel with a solid electrolyte material, and preparing the composite electrolyte membrane by a sol-gel method, a hot pressing method or an impregnation-sintering method; Preferably, the preparation of the positive electrode material comprises depositing sulfur or lithium iron phosphate on the surface of the bamboo charcoal aerogel and stabilizing the interface by carbon coating to form the positive electrode material; Preferably, the negative electrode material is prepared by using the whole bamboo carbon aerogel as a lithium metal negative electrode host, and injecting lithium metal into the pores of the bamboo carbon aerogel by a molten lithium infusion method to form a lithium-carbon composite negative electrode.

[0017] The first invention point of the present invention is to use whole bamboo (Moso bamboo, Arrow bamboo, Square bamboo, etc.) as the only raw material, through mechanical crushing (100-200 mesh) and selective removal of lignin and hemicellulose, retaining the cellulose skeleton structure, to achieve green and efficient utilization of biomass resources.

[0018] The second key feature of this invention is the step-by-step carbonization and activation process: First, carbonization at low temperatures (300-500°C) or high temperatures (800-1200°C) forms a porous bamboo carbon matrix. Chemical activation (KOH / ZnCl2 / H3PO4, 500-900°C) creates a hierarchical porous structure and optimizes pore distribution. A specific heating rate (5-10°C / min) and protective atmosphere are used to control the carbonization process and ensure structural stability.

[0019] It can efficiently adsorb pollutants in wastewater, and achieve rapid separation and recovery under the action of an external magnetic field. It can efficiently adsorb pollutants in wastewater, and achieve rapid separation and recovery under the action of an external magnetic field. Drying technology: freeze drying or CO2 supercritical drying is used to avoid pore collapse and maintain a high specific surface area of ​​the aerogel.

[0020] The third inventive point of the present invention is to obtain carbon aerogel with excellent physical and chemical properties through all-bamboo derivation and hierarchical porous structure design, which has high porosity, light weight and conductivity, and expands the application boundaries of traditional carbon aerogel.

[0021] Therefore, the beneficial effects of the present invention are: (1) The present invention uses step-by-step carbonization and activation to first carbonize a porous bamboo carbon matrix, and then constructs a hierarchical porous structure through chemical activation to optimize the pore distribution, significantly improving the conductivity and electrochemical properties of the carbon aerogel, effectively reducing the interfacial resistance in the solid-state battery, and improving the integrity of the solid-state battery.

[0022] (2) The method of the present invention is simple and easy to implement, and the raw materials are widely available, thus having good prospects for industrialization. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the flow chart of the preparation of all-bamboo carbon aerogel.

[0024] Figure 2 This is a test chart of battery specific capacity and cycle number using the sulfur-loaded positive electrode prepared in Example 2. DETAILED DESCRIPTION

[0025] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings: Example Example 1

[0026] Bamboo carbon aerogel is prepared by the following method: 1. Mechanically crush the bamboo into 200 mesh powder; 2. Remove lignin and hemicellulose through acid and alkali treatment, retaining the cellulose skeleton structure; 3. Under nitrogen protection, heat to 800℃ at a heating rate of 5℃ / min for carbonization treatment for 2 hours; 4. The porous bamboo carbon matrix was treated with KOH as a chemical activator at 700 °C for 2 h and then freeze-dried to obtain the full bamboo carbon aerogel.

[0027] Application Example 1: Application of Bamboo Carbon Aerogel in Composite Electrolyte Membrane 1. Grind the prepared bamboo carbon aerogel and pass it through a 200-mesh sieve; 2. Mix with Li6PS5Cl precursor in a mass ratio of 3:7 to form a uniform suspension in ethanol; 3. After ultrasonic dispersion, pour into mold and freeze-dry to form a film; 4. Dry at 60℃ under nitrogen atmosphere for 4h to obtain composite electrolyte membrane.

[0028] The room temperature ionic conductivity of the composite electrolyte membrane was tested to be 2.2 × 10 -3 S / cm, thermal stability>180°C, cycle stability (Li / electrolyte membrane / Li symmetric battery, 100 cycles) with no significant impedance growth.

[0029] In summary, the all-bamboo carbon aerogel was composited with the solid electrolyte Li6PS5Cl, and the sol-gel method was used to construct a three-dimensional ion transport network structure to improve the ionic conductivity and interface stability.

[0030] Example 2: All-bamboo carbon aerogel used as positive electrode material - sulfur-loaded positive electrode Bamboo carbon aerogel is prepared by the following method: 1. Mechanically crush the bamboo into 150 mesh powder; 2. Use acid treatment to remove lignin and hemicellulose while maintaining the cellulose skeleton; 3. Under nitrogen protection, heat to 1000℃ at a heating rate of 8℃ / min for carbonization treatment for 3 hours; 4. The porous bamboo carbon matrix was treated at 600℃ for 2h using ZnCl2 as a chemical activator and then dried using supercritical carbon dioxide to obtain carbon aerogel.

[0031] Application Example 2: All-bamboo carbon aerogel used as positive electrode material - sulfur-loaded positive electrode 1. Place the bamboo carbon aerogel in sulfur powder and heat it at 155℃ for 12 hours under argon protection; 2. After cooling, the surface is coated with a thin carbon layer (glucose carbon is deposited by CVD method); 3. Prepare the positive electrode sheet and assemble it into a CR2032 button battery.

[0032] After testing, such as Figure 2 As shown, the button cell has a specific capacity (0.1C) of 1280 mAh / g, a capacity retention rate of 92% (after 50 cycles), and a Coulombic efficiency (stable cycling) of >98%. Therefore, using all-bamboo carbon aerogel as a matrix, elemental sulfur is loaded via a melt diffusion method and then carbon-coated to improve sulfur utilization and active material retention. Example 3

[0033] Bamboo carbon aerogel is prepared by the following method: 1. Square bamboo was selected as raw material and mechanically crushed to 100 mesh; 2. Alkali treatment to remove lignin and hemicellulose; 3. Under argon protection, heat to 1200℃ at a heating rate of 10℃ / min for carbonization treatment for 4 hours; 4. H3PO4 was selected as the chemical activator, and the porous bamboo carbon matrix was treated at 800℃ for 3 hours. After that, freeze-drying technology was used to complete the drying to obtain the full bamboo carbon aerogel.

[0034] Application Example 3: Bamboo Carbon Aerogel as Negative Electrode Material - Lithium Metal Host 1. Cut and shape the prepared bamboo carbon aerogel; 2. Under argon protection, metallic lithium is injected into the aerogel pores by molten lithium infusion method; 3. Assemble into a symmetrical battery (Li@bamboo carbon aerogel || Li@bamboo carbon aerogel) and test stability.

[0035] After testing, the deposition / stripping coulombic efficiency of the battery (1mA / cm 2 )>99.2% (100 cycles), cycle life (1mA / cm 2 , 1mAh / cm 2 ) for more than 1,000 cycles while maintaining voltage stability (<50mV fluctuation) and a volume expansion rate of <5%. Therefore, utilizing the hierarchical porous structure of all-bamboo carbon aerogel as a three-dimensional host skeleton for the lithium metal anode can inhibit lithium dendrite growth and mitigate volume expansion. Example 4

[0036] Bamboo carbon aerogel is prepared by the following method: 1. Use bamboo as raw material and crush it mechanically to 150 mesh; 2. Removal of non-cellulosic components by acid treatment; 3. Carbonize the sample by heating it to 900°C at a heating rate of 7°C / min in a nitrogen atmosphere for 3 hours. 4. Using KOH as a chemical activator, the porous bamboo carbon substrate was treated at 650°C for 2 hours and freeze-dried to obtain the final bamboo carbon aerogel. Application Example 4: Bamboo Carbon Aerogel as Supercapacitor Electrode Material 1. Press the purified bamboo carbon aerogel into a film; 2. Use 6 mol / L KOH aqueous solution as the electrolyte; 3. Test the electrochemical performance in a three-electrode system.

[0037] Testing has shown that the electrode material has a specific capacitance (1A / g) of 186 F / g, a power density (energy density 10Wh / kg) of 15 kW / kg, and a cycle life (5,000 cycles) retention rate of >95%. Therefore, all-bamboo carbon aerogel has great potential for application in electric double-layer capacitors, with excellent specific capacitance and power density.

[0038] In summary, the all-bamboo carbon aerogel provided by this invention is suitable for use as a key component in solid-state batteries, such as an electrolyte carrier, a lithium metal anode host, or a cathode current collector, significantly improving the battery's energy density, cycling stability, and safety. The entire process requires strict control of carbonization temperature, activator ratio, doping conditions, and composite process parameters to ensure the material's high performance in solid-state batteries.

[0039] Based on the disclosure and teachings of the above description, those skilled in the art may also make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments disclosed and described above, and any modifications and variations of the invention should also fall within the scope of protection of the claims of the present invention. In addition, although certain specific terms are used in this description, these terms are for convenience of description only and do not constitute any limitation to the present invention.

Claims

1. A method for preparing a bamboo carbon aerogel, characterized in that: The following steps are involved: (1) Mechanically crushing the bamboo to remove lignin and hemicellulose, retaining the cellulose skeleton structure to obtain the primary bamboo product; (2) Carbonizing the primary bamboo material to form a porous bamboo carbon matrix; (3) The porous bamboo carbon matrix is ​​chemically activated to form a hierarchical porous structure, and the hierarchical porous structure is cleaned and dried to obtain bamboo carbon aerogel.

2. The preparation method according to claim 1, characterized in that The chemical activation method in step (3) is specifically to treat the porous bamboo carbon substrate with a chemical activator at 500-900° C. for 1-3 hours.

3. The preparation method according to claim 2, characterized in that The chemical activator includes at least one of KOH, ZnCl2 and H3PO4.

4. The preparation method according to claim 1, characterized in that In step (2), carbonization is carried out under a protective atmosphere, the carbonization temperature is 300-500°C or 800-1200°C, the carbonization time is 2h-4h, and the heating rate is 5-10°C / min.

5. The preparation method according to claim 1, characterized in that The drying in step (3) is freeze drying or supercritical carbon dioxide drying.

6. The preparation method according to claim 1, characterized in that In step (1), the bamboo material is mechanically crushed into 100-200 mesh powder, and lignin and hemicellulose are removed by adding acid or alkali.

7. The preparation method according to claim 1, characterized in that The bamboo material in step (1) includes any one of moso bamboo, arrow bamboo and square bamboo.

8. A bamboo carbon aerogel, characterized in that: It is prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the all-bamboo carbon aerogel according to claim 8 in electrochemical energy storage.

10. The use of the bamboo carbon aerogel in electrochemical energy storage according to claim 8, characterized in that: Including the preparation of composite electrolyte membranes, positive electrode materials and negative electrode materials; Preferably, the composite electrolyte membrane is prepared by compounding the all-bamboo carbon aerogel with a solid electrolyte material, and preparing the composite electrolyte membrane by a sol-gel method, a hot pressing method or an impregnation-sintering method; Preferably, the preparation of the positive electrode material comprises depositing sulfur or lithium iron phosphate on the surface of the bamboo charcoal aerogel and stabilizing the interface by carbon coating to form the positive electrode material; Preferably, the negative electrode material is prepared by using the whole bamboo carbon aerogel as a lithium metal negative electrode host, and injecting lithium metal into the pores of the bamboo carbon aerogel by a molten lithium infusion method to form a lithium-carbon composite negative electrode.

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