High-conductivity 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 high-conductivity carbon aerogel as well as a preparation method and application thereof. The preparation method comprises the following steps: (1) crushing a biomass raw material, and uniformly mixing the crushed biomass raw material with an organic solvent to obtain a biomass suspension; (2) adding a conductive additive into the suspension, and stirring to obtain high-conductivity carbon aerosol; and (3) drying the high-conductivity carbon aerosol, and carbonizing to obtain the high-conductivity carbon aerogel. According to the method, renewable biomass resources are fully utilized, the cost is reduced, the environmental pollution is reduced, the prepared carbon aerogel has excellent physical and chemical properties, and 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 particularly relates to a highly conductive carbon aerogel, a preparation method thereof, and an application thereof. Background Art

[0002] As a material with characteristics such as high specific surface area, low density, good electrical conductivity, and thermal stability, carbon aerogels are widely used in fields such as electrochemical energy storage, catalyst carriers, and adsorption materials. However, the preparation of traditional carbon aerogels mostly relies on fossil fuels, which not only increases costs but also is not conducive to environmental protection. Therefore, finding sustainable and low-cost biomass raw materials for preparing carbon aerogels has become the focus of research.

[0003] CN 110817871 A discloses a preparation method and application of nitrogen-doped graphene-based carbon aerogel microspheres, including the following steps: mixing resorcinol, formaldehyde, catalyst anhydrous sodium carbonate, graphene oxide, melamine, and deionized water for reaction to obtain a reaction solution; adding the reaction solution to a surfactant and stirring to obtain a uniformly dispersed reddish-brown emulsion; subjecting the reddish-brown emulsion to a sol-gel reaction, then aging with an acetone solution containing trifluoroacetic acid, soaking with acetone, and drying under normal pressure to obtain an organic aerogel; carbonizing to obtain graphene-based carbon aerogel microspheres; activating with KOH to obtain spherical carbon aerogels; activating with CO2; the carbon aerogel microspheres prepared by this method have a moderate particle size, high packing density and porosity, high effective specific surface area, excellent electrical conductivity, and good wettability with the electrolyte. This technical solution has a complex process, with activation after carbonization, and there is still room for improvement.

[0004] CN 1248250 C discloses a preparation method of a high specific capacitance electrode material. This method uses petroleum coke or pitch coke as raw materials and KOH as an activator to prepare high specific surface area powdered activated carbon, and uses phenolic resin and furfural to form a propanol solution according to a weight ratio, reacts to form an alcohol gel, dries in supercritical petroleum ether to form a phenolic aerogel, and carbonizes the aerogel to produce a carbon aerogel; mixing the two evenly to obtain a high specific capacitance electrode material. The electrode material prepared by this method has a specific capacitance as high as 330 F / g at room temperature. This electrode material has the advantages of simple preparation method, high specific capacitance, and good electrical conductivity, providing a good prospect for the large-scale application of electric double layer capacitor technology. However, it cannot be applied to the field of new energy batteries.

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

[0006] The object of the present invention is to address the deficiencies of existing carbon aerogel preparation methods and obtain a carbon aerogel with excellent physical and chemical properties through carbonization, thereby expanding the application fields of carbon aerogels. The detailed technical solution of the present invention is described as follows.

[0007] The present invention protects a method for preparing a highly conductive carbon aerogel, which is characterized by comprising the following steps:

[0008] (1) After crushing the biomass raw material, it is mixed uniformly with an organic solvent to obtain a biomass suspension;

[0009] (2) The suspension is added with a conductive additive and stirred to obtain a highly conductive carbon aerosol;

[0010] (3) The highly conductive carbon aerosol is dried and then carbonized to obtain a highly conductive carbon aerogel.

[0011] Preferably, in step (1), an inorganic acid is further added. Specifically, after the biomass powder is mixed uniformly with the solvent, the inorganic acid is added and dissolved under acidic conditions.

[0012] Preferably, the solvent includes at least one of phenol and p-cresol.

[0013] Preferably, the mass ratio of the biomass raw material to the solvent is 1:(2 - 10), and the mass ratio of the biomass raw material to the inorganic acid is 10:(1 - 2).

[0014] Preferably, in step (3), the carbonization is carried out under a protective atmosphere, the carbonization temperature is 800 - 1000 °C, and the carbonization time is 2 - 4 h.

[0015] Preferably, in step (2), the conductive additive includes any one of graphene and carbon nanotubes (CNTs).

[0016] Preferably, the inorganic acid includes at least one of sulfuric acid, hydrochloric acid, and nitric acid.

[0017] Preferably, the biomass raw material includes any one of rice husks, corn straws, and wood wastes.

[0018] The present invention also protects a highly conductive carbon aerogel prepared by the preparation method described above.

[0019] The present invention also protects the application of the highly conductive carbon aerogel in electrochemical energy storage and solid-state batteries.

[0020] The first inventive point of the present invention is to prepare highly conductive carbon aerogels by innovatively selecting biomass precursors. Agricultural and forestry wastes rich in cellulose / lignin (such as rice husks, corn straws) are used, and a three-dimensional cross-linked network is formed by the natural structure-directing effect. An in-situ activation technique is adopted to retain the components with a high carbonization rate, and highly connected pores are retained after carbonization.

[0021] The second inventive point of the present invention is to introduce graphene or carbon nanotube composites during the carbonization process, and a three-dimensional conductive path is formed through π-π stacking. The conductivity is 5 times that of pure biomass carbon aerogels.

[0022] Therefore, the beneficial effects of the present invention are as follows:

[0023] (1) The process of the present invention significantly increases the contact area between biomass and organic solvents, thereby greatly improving the efficiency of biomass conversion into liquefied liquids. Compared with biomass raw materials that have not been pulverized, this method can more quickly and completely dissolve and liquefy biomass, and can also ensure the quality stability of the final product.

[0024] (2) The present invention is applicable to various combinations of biomass raw materials and organic solvents, overcomes the dependence limitations of traditional methods on specific types of biomass or solvents, broadens the effective utilization rate and application fields of biomass resources. The whole process conforms to the principles of green chemistry and helps to promote sustainable development. This process can not only improve production efficiency and reduce costs, but also further enhance economic benefits and social benefits due to the improvement of product quality and the reduction of waste emissions. Description of the Drawings

[0025] Figure 1 It is a graph of the conductivity and specific surface area of the highly conductive biomass-based carbon aerogel electrode material in the examples. Detailed Embodiments

[0026] The following further describes the detailed embodiments of the present invention with reference to the drawings:

[0027] Examples

[0028] Example 1

[0029] 1. Pulverize rice husks to 200 mesh, mix them with phenol at a mass ratio of 1:5, add sulfuric acid (rice husks:sulfuric acid = 10:1.5), and stir at 80 °C for 2 h to obtain a uniform suspension.

[0030] 2. Add graphene (20% of the mass of rice husks), ultrasonically disperse for 1 h and then stir for 3 h.

[0031] 3. Freeze-dry for 24 h and carbonize at 900 °C for 3 h under N2 protection.

[0032] After testing, the specific surface area of this carbon aerogel is 690 m2 / g, with a conductivity of 192 S / m and a porosity of 91%.

[0033] Example 2

[0034] 1. After crushing corn straw, it is mixed with p-cresol at a ratio of 1:8, and nitric acid is added (straw:nitric acid = 10:1), and the reaction is carried out at 70 °C for 3 h.

[0035] 2. Add CNTs (15% of the straw mass) and mechanically stir for 4 h.

[0036] 3. After supercritical CO2 drying, carbonize at 1000 °C for 2 h under an Ar atmosphere.

[0037] After testing, the specific surface area of this carbon aerogel is 820 m 2 / g, with a conductivity of 226 S / m and a porosity of 95%.

[0038] Example 3

[0039] 1. Wood waste is mixed with phenol / p-cresol (1:1) at a ratio of 1:10, and hydrochloric acid is added (waste:hydrochloric acid = 10:2), and hydrolysis is carried out at 90 °C for 4 h.

[0040] 2. Add graphene (10%) and CNTs (10%) simultaneously, and perform ultrasonic-stirring composite treatment for 5 h.

[0041] 3. After vacuum drying, carbonize at 800 °C for 4 h under N2 protection.

[0042] After testing, the specific surface area of this carbon aerogel is 780 m 2 / g, with a conductivity of 258 S / m and a porosity of 89%.

[0043] Example 4

[0044] 1. Rice husk is mixed with phenol at a ratio of 1:3, and sulfuric acid is added (rice husk:sulfuric acid = 10:1), and the reaction is carried out at 60 °C for 5 h.

[0045] 2. Add graphene (5%) and CNTs (5%), and stir for 6 h.

[0046] 3. After freeze-drying, carbonize at 950 °C for 2.5 h under an Ar / H2 mixed atmosphere.

[0047] After testing, the specific surface area of this carbon aerogel is 975 m 2 / g, with a conductivity of 288 S / m and a porosity of 93%.

[0048] Example 5

[0049] 1. Mix corn straw and p-cresol in a ratio of 1:6, with nitric acid / sulfuric acid (1:1, straw:acid = 10:1.8), and react at 75 °C for 2 h.

[0050] 2. Add CNTs (20%) and stir at high speed with shear for 2 h.

[0051] 3. After microwave drying, carbonize at 850 °C under N2 for 3.5 h.

[0052] After testing, the specific surface area of the carbon aerogel is 775 m 2 / g, the conductivity is 250 S / m, and the porosity is 92%.

[0053] The relevant information and test performance data of the above-prepared carbon aerogel composite material are shown in Table 1.

[0054] Table 1

[0055] Parameter Example 1 Example 2 Example 3 Example 4 Example 5 Raw material Rice husk Corn straw Wood waste Rice husk Corn straw Add conductive agent Graphene CNTs Graphene + CNTs Graphene + CNTs CNTs Carbonization temperature / time 900℃ / 3h 1000℃ / 2h 800℃ / 4h 950℃ / 2.5h 850℃ / 3.5h <![CDATA[Specific surface area (m 2 / g)]]> 690 820 780 975 775 Conductivity (S / m) 192 226 258 288 250 Porosity (%) 91 95 89 93 92

[0056] Figure 1 It is the graph of the conductivity and specific surface area of the highly conductive biomass-based carbon aerogel electrode material in the embodiment. From the data analysis, it can be obtained that the change trend of the conductivity of the highly conductive biomass-based carbon aerogel electrode material is that with the addition of the conductive agent, the conductivity increases significantly, and it has a relatively high conductivity.

[0057] The results show that the material has excellent physical and chemical properties, a relatively high carbonization temperature, and the obtained material has a relatively high specific surface area; using low-cost biomass raw materials as the carbon source, the conductivity is significantly improved.

[0058] According to the disclosure and teachings of the above specification, those skilled in the art to which the present invention pertains can 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 some modifications and changes to the invention should also fall within the protection scope of the claims of the present invention. In addition, although some specific terms are used in this specification, these terms are only for convenience of description and do not constitute any limitation to the present invention.

Claims

1. A preparation method of a highly conductive carbon aerogel, characterized in that, It includes the following steps: (1) After crushing the biomass raw material, it is mixed evenly with a solvent to obtain a biomass suspension; (2) The suspension is added with a conductive additive and stirred to obtain a highly conductive carbon aerosol; (3) After drying the highly conductive carbon aerosol, carbonization is carried out to obtain a highly conductive carbon aerogel.

2. The preparation method according to claim 1, wherein, In step (1), an inorganic acid is also added. Specifically, after the biomass powder is mixed evenly with the solvent, the inorganic acid is added and dissolved under acidic conditions.

3. The preparation method according to claim 2, wherein, The solvent includes at least one of phenol and p-cresol.

4. The preparation method according to claim 2, characterized in that, The mass ratio of the biomass raw material to the solvent is 1:(2 - 10), and the mass ratio of the biomass raw material to the inorganic acid is 10:(1 - 2).

5. The preparation method according to claim 1, characterized in that, In step (3), carbonization is carried out under a protective atmosphere, the carbonization temperature is 800 - 1000 °C, and the carbonization time is 2 - 4 h.

6. The preparation method according to claim 1, characterized in that, In step (2), the conductive additive includes any one of graphene and carbon nanotubes.

7. The preparation method according to claim 2, characterized in that, The inorganic acid includes at least one of sulfuric acid, hydrochloric acid, and nitric acid.

8. The preparation method according to claim 1, characterized in that, The biomass raw material includes any one of rice husks, corn straws, and wood wastes.

9. A highly conductive carbon aerogel, characterized in that, Prepared by the preparation method according to any one of claims 1 - 8.

10. Application of the highly conductive carbon aerogel according to claim 9 in electrochemical energy storage and solid-state batteries.

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