Lignin-based epoxy resin derived porous carbon composite electrode material

Abstract

The invention discloses a lignin-based epoxy resin derived porous carbon composite electrode material and a preparation method and application thereof, and belongs to the technical field of electronic materials. Sodium lignin sulfonate, hydroquinone and epichlorohydrin are used as main raw materials, m-phenylenediamine is added for polycondensation to prepare a lignin-based epoxy resin polymer, then lignin-based epoxy resin derived porous carbon is obtained through pre-carbonization and high-temperature pyrolysis, finally, the porous carbon adsorbs aniline and then is subjected to in-situ polymerization, and the lignin-based epoxy resin derivative porous carbon is obtained. The lignin-based epoxy resin derivative porous carbon composite electrode material is obtained. The lignin-based epoxy resin derived porous carbon has a hierarchical pore structure, the specific surface area reaches 2287.87 m / g, and the mass specific capacitance of the polyaniline-introduced composite electrode material reaches 497.7 F / g. The composite electrode material has excellent electrochemical performance, the preparation process is safe and easy to implement, the cost is low, and the application prospect is wide.

Description

Technical Field

[0001] The present invention belongs to the technical field of electronic materials, and particularly relates to a lignin-based epoxy resin-derived porous carbon composite electrode material, a preparation method thereof, and an application thereof. Background Art

[0002] Supercapacitor electrode materials are divided into electric double layer capacitor materials and pseudocapacitor materials. Among them, an electric double layer capacitor stores charges at the electrode-electrolyte interface through electrostatic adsorption to form an electric double layer, which only involves the physical process of adsorption / desorption on the electrode surface and does not involve redox reactions and volume changes inside the electrode. The mechanism of a pseudocapacitor can be divided into underpotential deposition, intercalation pseudocapacitance, oxidation reaction of transition metal oxides, and reversible electrochemical doping / dedoping in conductive polymer oxides.

[0003] Using a carbon-based material composite with a pseudocapacitor material such as a conductive polymer or a metal oxide as the electrode material of a supercapacitor can not only improve the specific capacitance and corrosion resistance of the electrode material, but also improve the structural stability of the conductive polymer after the carbon-based material and the conductive polymer are compounded. The main material of an electric double layer capacitor electrode is a carbon-based material, and the electric double layer capacitance of the carbon-based material depends on its structure, especially porosity and specific surface area. Injecting heteroatoms such as nitrogen, oxygen, boron, sulfur, and phosphorus into the lattice of the carbon-based material can, to a certain extent, affect porosity and specific surface area, and at the same time improve the chemical activity, wettability, and conductivity of the material. The main materials of a pseudocapacitor electrode are metal oxides and conductive polymers. Compared with metal oxides, conductive polymers have many advantages such as high specific capacitance, good flexibility, strong conductivity, light weight, and low cost, making them a new generation of capacitor electrode materials. Polyaniline has high stability, high processability, and highly adjustable electrochemical properties, which are deeply favored by researchers. However, the backbone structure of polyaniline is prone to being damaged during long-term charge and discharge cycles, resulting in low conductivity and poor cycle stability. Therefore, in-situ growth of aniline on the surface of a carbon skeleton with rich pores has become a new research direction. The rich pore structure of the carbon skeleton can effectively inhibit the volume change of polyaniline during charge and discharge, and can protect the structure of polyaniline to a certain extent, thereby improving the cycle stability of the electrode material. Summary of the Invention

[0004] The object of the present invention is to provide a preparation method of a lignin-based epoxy resin-derived porous carbon composite electrode material in view of the deficiencies of the prior art. In the present invention, sodium lignosulfonate and hydroquinone are polycondensed and crosslinked with epichlorohydrin under alkaline conditions, and then m-phenylenediamine is added for further crosslinking to synthesize a lignin-based epoxy resin polymer. Then, it is pre-carbonized in a nitrogen atmosphere, and then the pre-carbonized product and potassium hydroxide are mixed evenly and pyrolyzed at a high temperature in a nitrogen atmosphere to obtain lignin-based epoxy resin-derived porous carbon. Finally, polyaniline is loaded by the method of in-situ polymerization of adsorbed aniline to prepare a lignin-based epoxy resin-derived porous carbon composite electrode material.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A preparation method of a lignin-based epoxy resin-derived porous carbon composite electrode material, comprising the following steps:

[0007] (1) Preparation of lignin-based epoxy resin polymer: In a 40°C water bath, measure 10 mL of sodium hydroxide aqueous solution (mass fraction 15-30 wt%), add 3.2-7 mL of epichlorohydrin, and then add hydroquinone and sodium lignosulfonate successively (the total molar amount of sodium lignosulfonate and hydroquinone is 0.0511 mol, and the molar ratio is 1:4-1:7), stir until dissolved, then add 0.1-0.4 g of m-phenylenediamine, stop stirring after the solution gradually gels, and react for another 3 h after complete gelation. Filter the product, wash it with water, and dry it to obtain the lignin-based epoxy resin polymer;

[0008] (2) Pre-carbonization of lignin-based epoxy resin polymer: Place the lignin-based epoxy resin polymer prepared in step (1) in a tubular furnace and pyrolyze it at 400-500°C for 0.5-1.5 h in a nitrogen atmosphere. After pickling, washing with water, and drying the pyrolysis product, a lignin-based epoxy resin pre-carbonized product is obtained;

[0009] (3) Preparation of lignin-based epoxy resin-derived porous carbon: Grind and mix the lignin-based epoxy resin pre-carbonized product prepared in step (2) and potassium hydroxide in a mass ratio of 1:1-1:5 evenly with a mortar, and then place the mixture in a tubular furnace and pyrolyze it at 500-800°C in a nitrogen atmosphere. After pickling, washing with water, and drying the pyrolysis product, lignin-based epoxy resin-derived porous carbon is obtained;

[0010] (4) Lignin - based epoxy resin - derived porous carbon supported polyaniline: Stir and disperse the sodium lignosulfonate - based epoxy resin - derived porous carbon prepared in step (3) in a 1 mol / L hydrochloric acid solution at 0 - 5 °C, add aniline, and adsorb it at 0 - 5 °C for 2 h to obtain a mixed solution containing 0.05 - 0.2 mol / L aniline and 18.6 mg / mL lignin - based epoxy resin - derived porous carbon; separately dissolve a certain amount of ammonium persulfate (the molar ratio of aniline to ammonium persulfate used is 1:0.5 - 1:3) in an equal volume of 1 mol / L hydrochloric acid solution, cool its temperature to 0 - 5 °C, then add it to the mixed solution, and carry out in - situ polymerization at 0 - 5 °C for 12 h. The product is washed with water and dried to obtain the lignin - based epoxy resin - derived porous carbon composite electrode material.

[0011] The present invention also provides a lignin - based epoxy resin - derived porous carbon composite electrode material prepared by the above - mentioned preparation method.

[0012] The present invention also provides the application of the above - mentioned lignin - based epoxy resin - derived porous carbon composite electrode material in a supercapacitor.

[0013] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0014] 1. In the present invention, lignin - based epoxy resin polymer is used as a porous carbon precursor. Sodium lignosulfonate contains many phenolic hydroxyl groups, which play the role of a cross - linker in the reaction. At the same time, sodium lignosulfonate contains sulfur, and sulfur atom doping is introduced after carbonization. Therefore, the prepared porous carbon has a controllable porous structure, a high specific surface area, and excellent electrochemical properties.

[0015] 2. In the synthesis of lignin - based epoxy resin polymer in the present invention, m - phenylenediamine is added. m - phenylenediamine not only participates in the cross - linking reaction, making the polymer network structure more abundant and perfect, which is beneficial to the adsorption and penetration of aniline after carbonization, but also contains nitrogen. The doping of nitrogen atoms can enhance the wettability of the electrolyte to the carbon material and improve the electrochemical properties.

[0016] 3. The present invention conducts two - step pyrolysis on the lignin - based epoxy resin polymer. The first step is the pre - carbonization process, the purpose of which is to form a preliminary carbon skeleton structure, providing a basic framework for the subsequent activation step. At the same time, some gases generated during the pre - carbonization process can form an initial pore structure inside the material, and appropriate pretreatment can also make the precursor arranged orderly and improve the graphitization degree, thereby improving the electrochemical properties of the carbon material. The second step is the activation and pore - forming process, enabling the lignin - based epoxy resin - derived porous carbon after pyrolysis to form a multi - level pore structure mainly composed of micropores through the activation of KOH while retaining the main carbon skeleton structure. The richer the pore structure of the porous carbon, the more beneficial it is to the diffusion and polymerization of aniline, thereby improving the electrochemical properties of the composite material.

[0017] 4. The lignin-based epoxy resin-derived porous carbon composite electrode material of the present invention has excellent electrochemical performance, and the preparation process is safe, easy and low-cost, providing a new idea for the preparation of composite capacitor electrode materials. Description of the Drawings

[0018] Figure 1 Scanning electron microscope image of the lignin-based epoxy resin-derived porous carbon prepared in Example 1;

[0019] Figure 2 Scanning electron microscope image of the lignin-based epoxy resin-derived porous carbon composite electrode material prepared in Example 1;

[0020] Figure 3 Nitrogen adsorption-desorption isotherm curve of the lignin-based epoxy resin-derived porous carbon composite electrode material prepared in Example 1;

[0021] Figure 4 Pore size distribution diagram of the lignin-based epoxy resin-derived porous carbon composite electrode material prepared in Example 1;

[0022] Figure 5 Galvanostatic charge-discharge curves and corresponding mass specific capacitances of the lignin-based epoxy resin-derived porous carbon prepared in Example 1 and the lignin-based epoxy resin-derived porous carbon composite electrode materials prepared in Example 1, Comparative Example 1 and Comparative Example 2 at a current density of 1 A / g;

[0023] Figure 6 Galvanostatic charge-discharge curves and corresponding mass specific capacitances of the lignin-based epoxy resin-derived porous carbon composite electrode materials prepared in Examples 1-7 at a current density of 1 A / g;

[0024] Figure 7 Charge-discharge cycle stability diagram of the lignin-based epoxy resin-derived porous carbon composite electrode material prepared in Example 1 at a current density of 10 A / g. Detailed Embodiments

[0025] In order to make the content of the present invention easier to understand, the technical solutions of the present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited thereto.

[0026] Example 1

[0027] (1) Preparation of lignin-based epoxy resin polymer: In a 40 °C water bath, measure 10 mL of 25 wt% sodium hydroxide aqueous solution, add 4 mL of epichlorohydrin, then add hydroquinone and sodium lignosulfonate successively (the total molar amount of sodium lignosulfonate and hydroquinone is 0.0511 mol, and the molar ratio is 1:6), stir until dissolved, then add 0.2 g of m-phenylenediamine. Stop stirring after the solution gradually gels, and react for another 3 h after complete gelation. Filter the product, wash it with water, and dry it to obtain the lignin-based epoxy resin polymer;

[0028] (2) Pre-carbonization of lignin-based epoxy resin polymer: Place the lignin-based epoxy resin polymer prepared in step (1) in a tube furnace, and pyrolyze it at 500 °C for 1 h under a nitrogen atmosphere. After pickling, washing with water, and drying the pyrolysis product, obtain the lignin-based epoxy resin pre-carbonized product;

[0029] (3) Preparation of lignin-based epoxy resin-derived porous carbon: Grind and mix the lignin-based epoxy resin pre-carbonized product prepared in step (2) and potassium hydroxide evenly in a mortar at a mass ratio of 1:3. Then place the mixture in a tube furnace and pyrolyze it at 700 °C for 2 h under a nitrogen atmosphere. After pickling, washing with water, and drying the pyrolysis product, obtain the lignin-based epoxy resin-derived porous carbon;

[0030] (4) Loading of polyaniline on lignin-based epoxy resin-derived porous carbon: Take 0.149 g of the lignin-based epoxy resin-derived porous carbon prepared in step (3), stir and disperse it in 8 mL of 1 mol / L hydrochloric acid solution at 0 - 5 °C, add aniline to make the concentration of aniline 0.1 mol / L, and adsorb it at 0 - 5 °C for 2 h to obtain a mixed solution; dissolve ammonium persulfate in 8 mL of 1 mol / L hydrochloric acid solution to make the concentration of ammonium persulfate 0.15 mol / L. After cooling its temperature to 0 - 5 °C, add it to the mixed solution and carry out in-situ polymerization at 0 - 5 °C for 12 h. Wash and dry the product to obtain the lignin-based epoxy resin-derived porous carbon composite electrode material.

[0031] It can be seen from Figure 1 that the lignin-based epoxy resin-derived porous carbon prepared in Example 1 has an obvious pore structure, and there are abundant fine pores on its pore walls, with a developed hierarchical pore structure, and the specific surface area reaches 2287.87 m 2 / g. These pores are beneficial to the adsorption and penetration of aniline. And it can be seen from Figure 2 that the lignin-based epoxy resin-derived porous carbon composite electrode material still maintains an obvious pore structure. Among them, polyaniline is wrapped on the surface of the lignin-based epoxy resin-derived porous carbon and penetrates into it, with firm loading, which promotes the improvement of electrochemical performance.

[0032] It can be seen from Figure 3The nitrogen adsorption - desorption isotherm shows that the adsorption type of the lignin - based epoxy resin - derived porous carbon composite electrode material prepared in Example 1 is Type I, indicating that the material mainly consists of micropores. At the same time, an H4 - type hysteresis loop appears in the adsorption - desorption curve, indicating that the pore structure of the material has slit - like pores or a layered structure, and there may be both micropores and relatively narrow mesopores simultaneously. Figure 4 The pore size distribution diagram also shows that the lignin - based epoxy resin - derived porous carbon composite electrode material contains both micropores and mesopores, as well as a small amount of macropores. Figure 3 and Figure 4 Analysis shows that the lignin - based epoxy resin - derived porous carbon composite electrode material has a hierarchical pore structure, which is beneficial to the diffusion and adsorption of electrolyte ions and promotes the improvement of the electrochemical performance of the material.

[0033] Comparative Example 1

[0034] (1) Preparation of lignin - based epoxy resin polymer: In a 40 °C water bath, measure 10 mL of 25 wt% sodium hydroxide aqueous solution, add 4 mL of epichlorohydrin, then add hydroquinone and sodium lignosulfonate successively (the total molar amount of sodium lignosulfonate and hydroquinone is 0.0511 mol, and the molar ratio is 1:6), stir until dissolved. After the solution gradually gels, stop stirring. After complete gelation, react for another 3 h. Filter the product, wash it with water, and dry it to obtain the lignin - based epoxy resin polymer;

[0035] Steps (2), (3), and (4) are the same as those in Example 1.

[0036] Comparative Example 2

[0037] (1) Preparation of lignin - based epoxy resin polymer: In a 40 °C water bath, measure 10 mL of 25 wt% sodium hydroxide aqueous solution, add 4 mL of epichlorohydrin, then add hydroquinone and sodium lignosulfonate successively (the total molar amount of sodium lignosulfonate and hydroquinone is 0.0511 mol, and the molar ratio is 1:6), stir until dissolved, then add 0.2 g of m - phenylenediamine. After the solution gradually gels, stop stirring. After complete gelation, react for another 3 h. Filter the product, wash it with water, and dry it to obtain the lignin - based epoxy resin polymer;

[0038] (2) Preparation of lignin - based epoxy resin - derived porous carbon: Grind and mix the lignin - based epoxy resin polymer prepared in step (1) and potassium hydroxide evenly in a mortar at a mass ratio of 1:3. Then place the mixture in a tube furnace and pyrolyze it at 700 °C for 2 h under a nitrogen atmosphere. After pickling, washing with water, and drying the pyrolysis product, lignin - based epoxy resin - derived porous carbon is obtained;

[0039] (3) Polyaniline-supported on lignin-based epoxy resin-derived porous carbon: Take 0.149 g of the lignin-based epoxy resin-derived porous carbon prepared in step (2), stir and disperse it in 8 mL of 1 mol / L hydrochloric acid solution at 0 - 5 °C, add aniline to make the concentration of aniline 0.1 mol / L, adsorb for 2 h at 0 - 5 °C to obtain a mixed solution; dissolve ammonium persulfate in 8 mL of 1 mol / L hydrochloric acid solution to make the concentration of ammonium persulfate 0.15 mol / L, cool its temperature to 0 - 5 °C, then add it to the mixed solution, and carry out in-situ polymerization at 0 - 5 °C for 12 h. The product is washed with water and dried to obtain the lignin-based epoxy resin-derived porous carbon composite electrode material.

[0040] Example 2

[0041] (1) Preparation of lignin-based epoxy resin polymer: In a 40 °C water bath, measure 10 mL of 25 wt% sodium hydroxide solution, add 4 mL of epichlorohydrin, then add hydroquinone and sodium lignosulfonate successively (the total molar amount of sodium lignosulfonate and hydroquinone is 0.0511 mol, and the molar ratio is 1:4), stir until dissolved, then add 0.2 g of m-phenylenediamine. Stop stirring after the solution gradually gels, and react for another 3 h after complete gelation. Filter the product, wash it with water and dry it to obtain the lignin-based epoxy resin polymer.

[0042] (2) Pre-carbonization of lignin-based epoxy resin polymer: Place the lignin-based epoxy resin polymer prepared in step (1) in a tube furnace, carry out pyrolysis at 500 °C for 1 h under a nitrogen atmosphere. After pickling, washing with water and drying the pyrolysis product, obtain the lignin-based epoxy resin pre-carbonized product.

[0043] (3) Preparation of lignin-based epoxy resin-derived porous carbon: Grind and mix the lignin-based epoxy resin pre-carbonized product prepared in step (2) and potassium hydroxide evenly in a mortar at a mass ratio of 1:3, then place the mixture in a tube furnace, carry out high-temperature pyrolysis at 700 °C for 2 h under a nitrogen atmosphere. After pickling, washing with water and drying the pyrolysis product, obtain the lignin-based epoxy resin-derived porous carbon.

[0044] (4) Polyaniline-supported on lignin-based epoxy resin-derived porous carbon: Take 0.149 g of the lignin-based epoxy resin-derived porous carbon prepared in step (3), stir and disperse it in 8 mL of 1 mol / L hydrochloric acid solution at 0 - 5 °C, add aniline to make the concentration of aniline 0.1 mol / L, adsorb for 2 h at 0 - 5 °C to obtain a mixed solution; dissolve ammonium persulfate in 8 mL of 1 mol / L hydrochloric acid solution to make the concentration of ammonium persulfate 0.15 mol / L, cool its temperature to 0 - 5 °C, then add it to the mixed solution, and carry out in-situ polymerization at 0 - 5 °C for 12 h. The product is washed with water and dried to obtain the lignin-based epoxy resin-derived porous carbon composite electrode material.

[0045] Example 3

[0046] (1) Preparation of lignin-based epoxy resin polymer: In a 40 °C water bath, measure 10 mL of 25 wt% sodium hydroxide aqueous solution, add 4 mL of epichlorohydrin, then add hydroquinone and sodium lignosulfonate successively (the total molar amount of sodium lignosulfonate and hydroquinone is 0.0511 mol, and the molar ratio is 1:6), stir until dissolved, then add 0.4 g of m-phenylenediamine. Stop stirring after the solution gradually gels, and react for another 3 h after complete gelation. Filter the product, wash it with water, and dry it to obtain the lignin-based epoxy resin polymer;

[0047] (2) Pre-carbonization of lignin-based epoxy resin polymer: Place the lignin-based epoxy resin polymer prepared in step (1) in a tube furnace, and pyrolyze it at 500 °C for 1 h under a nitrogen atmosphere. After pickling, washing with water, and drying the pyrolysis product, obtain the lignin-based epoxy resin pre-carbonized product;

[0048] (3) Preparation of lignin-based epoxy resin-derived porous carbon: Grind and mix the lignin-based epoxy resin pre-carbonized product prepared in step (2) and potassium hydroxide evenly in a mortar at a mass ratio of 1:3. Then place the mixture in a tube furnace and pyrolyze it at 700 °C for 2 h under a nitrogen atmosphere. After pickling, washing with water, and drying the pyrolysis product, obtain the lignin-based epoxy resin-derived porous carbon;

[0049] (4) Loading of polyaniline on lignin-based epoxy resin-derived porous carbon: Take 0.149 g of the lignin-based epoxy resin-derived porous carbon prepared in step (3), stir and disperse it in 8 mL of 1 mol / L hydrochloric acid solution at 0 - 5 °C, add aniline to make the concentration of aniline 0.1 mol / L, and adsorb it at 0 - 5 °C for 2 h to obtain a mixed solution; Dissolve ammonium persulfate in 8 mL of 1 mol / L hydrochloric acid solution to make the concentration of ammonium persulfate 0.15 mol / L. After cooling its temperature to 0 - 5 °C, add it to the mixed solution and carry out in-situ polymerization at 0 - 5 °C for 12 h. Wash the product with water and dry it to obtain the lignin-based epoxy resin-derived porous carbon composite electrode material.

[0050] Example 4

[0051] (1) Preparation of lignin-based epoxy resin polymer: In a 40 °C water bath, measure 10 mL of 25 wt% sodium hydroxide aqueous solution, add 4 mL of epichlorohydrin, then add hydroquinone and sodium lignosulfonate successively (the total molar amount of sodium lignosulfonate and hydroquinone is 0.0511 mol, and the molar ratio is 1:6), stir until dissolved, then add 0.2 g of m-phenylenediamine. Stop stirring after the solution gradually gels, and react for another 3 h after complete gelation. Filter the product, wash it with water, and dry it to obtain the lignin-based epoxy resin polymer;

[0052] (2) Pre-carbonization of lignin-based epoxy resin polymer: The lignin-based epoxy resin polymer obtained in step (1) is placed in a tube furnace and pyrolyzed at 400 °C for 1 h under a nitrogen atmosphere. The pyrolysis product is washed with acid, washed with water, and dried to obtain a lignin-based epoxy resin pre-carbonized product;

[0053] (3) Preparation of lignin-based epoxy resin-derived porous carbon: The lignin-based epoxy resin pre-carbonized product obtained in step (2) and potassium hydroxide are ground and mixed evenly in a mortar at a mass ratio of 1:3. Then the mixture is placed in a tube furnace and pyrolyzed at 700 °C for 2 h under a nitrogen atmosphere. The pyrolysis product is washed with acid, washed with water, and dried to obtain lignin-based epoxy resin-derived porous carbon;

[0054] (4) Loading of polyaniline on lignin-based epoxy resin-derived porous carbon: Take 0.149 g of the lignin-based epoxy resin-derived porous carbon prepared in step (3) and stir it to disperse in 8 mL of 1 mol / L hydrochloric acid solution at 0-5 °C. Add aniline to make the concentration of aniline 0.1 mol / L, and adsorb it at 0-5 °C for 2 h to obtain a mixed solution. Another ammonium persulfate is dissolved in 8 mL of 1 mol / L hydrochloric acid solution to make the concentration of ammonium persulfate 0.15 mol / L. After cooling its temperature to 0-5 °C, it is added to the mixed solution and in-situ polymerized at 0-5 °C for 12 h. The product is washed with water and dried to obtain a lignin-based epoxy resin-derived porous carbon composite electrode material.

[0055] Example 5

[0056] (1) Preparation of lignin-based epoxy resin polymer: In a 40 °C water bath, measure 10 mL of 25 wt% sodium hydroxide aqueous solution, add 4 mL of epichlorohydrin, and then add hydroquinone and sodium lignosulfonate (the total molar amount of sodium lignosulfonate and hydroquinone is 0.0511 mol, and the molar ratio is 1:6) and stir until dissolved. Then add 0.2 g of m-phenylenediamine. Stop stirring after the solution gradually gels, and react for another 3 h after complete gelation. The product is filtered, washed with water, and dried to obtain a lignin-based epoxy resin polymer;

[0057] (2) Pre-carbonization of lignin-based epoxy resin polymer: The lignin-based epoxy resin polymer obtained in step (1) is placed in a tube furnace and pyrolyzed at 500 °C for 1 h under a nitrogen atmosphere. The pyrolysis product is washed with acid, washed with water, and dried to obtain a lignin-based epoxy resin pre-carbonized product;

[0058] (3) Preparation of lignin - based epoxy resin - derived porous carbon: The lignin - based epoxy resin pre - carbide obtained in step (2) and potassium hydroxide were ground and mixed evenly in a mortar at a mass ratio of 1:3, and then the mixture was placed in a tube furnace. Under a nitrogen atmosphere, high - temperature pyrolysis was carried out at 600 °C for 2 h. After pickling, washing with water, and drying, the lignin - based epoxy resin - derived porous carbon was obtained;

[0059] (4) Preparation of lignin - based epoxy resin - derived porous carbon loaded with polyaniline: Take 0.149 g of the lignin - based epoxy resin - derived porous carbon prepared in step (3) and stir - disperse it in 8 mL of 1 mol / L hydrochloric acid solution at 0 - 5 °C. Add aniline to make the concentration of aniline 0.1 mol / L, and adsorb at 0 - 5 °C for 2 h to obtain a mixed solution. Separately, dissolve ammonium persulfate in 8 mL of 1 mol / L hydrochloric acid solution to make the concentration of ammonium persulfate 0.15 mol / L. After cooling its temperature to 0 - 5 °C, add it to the mixed solution and carry out in - situ polymerization at 0 - 5 °C for 12 h. The product was washed with water and dried to obtain the lignin - based epoxy resin - derived porous carbon composite electrode material.

[0060] Example 6

[0061] (1) Preparation of lignin - based epoxy resin polymer: In a 40 °C water bath, measure 10 mL of 25 wt% sodium hydroxide aqueous solution, add 4 mL of epichlorohydrin, and then add hydroquinone and sodium lignosulfonate (the total molar amount of sodium lignosulfonate and hydroquinone is 0.0511 mol, and the molar ratio is 1:6) and stir until dissolved. Then add 0.2 g of m - phenylenediamine. Stop stirring after the solution gradually gels, and react for another 3 h after complete gelation. The product was filtered, washed with water, and dried to obtain the lignin - based epoxy resin polymer;

[0062] (2) Pre - carbonization of lignin - based epoxy resin polymer: Place the lignin - based epoxy resin polymer obtained in step (1) in a tube furnace. Under a nitrogen atmosphere, pyrolysis was carried out at 500 °C for 1 h. After pickling, washing with water, and drying, the lignin - based epoxy resin pre - carbide was obtained;

[0063] (3) Preparation of lignin - based epoxy resin - derived porous carbon: The lignin - based epoxy resin pre - carbide obtained in step (2) and potassium hydroxide were ground and mixed evenly in a mortar at a mass ratio of 1:1, and then the mixture was placed in a tube furnace. Under a nitrogen atmosphere, high - temperature pyrolysis was carried out at 700 °C for 2 h. After pickling, washing with water, and drying, the lignin - based epoxy resin - derived porous carbon was obtained;

[0064] (4) Polyaniline-supported on lignin-based epoxy resin-derived porous carbon: Take 0.149 g of the lignin-based epoxy resin-derived porous carbon prepared in step (3), stir and disperse it in 8 mL of 1 mol / L hydrochloric acid solution at 0 - 5 °C, add aniline to make the concentration of aniline 0.1 mol / L, and adsorb for 2 h at 0 - 5 °C to obtain a mixed solution; separately dissolve ammonium persulfate in 8 mL of 1 mol / L hydrochloric acid solution to make the concentration of ammonium persulfate 0.15 mol / L, cool its temperature to 0 - 5 °C, then add it to the mixed solution, and carry out in-situ polymerization at 0 - 5 °C for 12 h. The product is washed with water and dried to obtain the lignin-based epoxy resin-derived porous carbon composite electrode material.

[0065] Example 7

[0066] (1) Preparation of lignin-based epoxy resin polymer: In a 40 °C water bath, measure 10 mL of 25 wt% sodium hydroxide aqueous solution, add 4 mL of epichlorohydrin, then successively add hydroquinone and sodium lignosulfonate (the total molar amount of sodium lignosulfonate and hydroquinone is 0.0511 mol, and the molar ratio is 1:6), stir until dissolved, then add 0.2 g of m-phenylenediamine. Stop stirring after the solution gradually gels, and react for another 3 h after complete gelation. Filter the product, wash it with water and dry it to obtain the lignin-based epoxy resin polymer;

[0067] (2) Pre-carbonization of lignin-based epoxy resin polymer: Place the lignin-based epoxy resin polymer prepared in step (1) in a tubular furnace, and carry out pyrolysis at 500 °C for 1 h under a nitrogen atmosphere. The pyrolysis product is pickled, washed with water and dried to obtain the lignin-based epoxy resin pre-carbonized product;

[0068] (3) Preparation of lignin-based epoxy resin-derived porous carbon: Grind and mix the lignin-based epoxy resin pre-carbonized product prepared in step (2) and potassium hydroxide in a mass ratio of 1:3 evenly with a mortar, then place the mixture in a tubular furnace, and carry out high-temperature pyrolysis at 700 °C for 2 h under a nitrogen atmosphere. The pyrolysis product is pickled, washed with water and dried to obtain the lignin-based epoxy resin-derived porous carbon;

[0069] (4) Polyaniline-supported on lignin-based epoxy resin-derived porous carbon: Take 0.149 g of the lignin-based epoxy resin-derived porous carbon prepared in step (3), stir and disperse it in 8 mL of 1 mol / L hydrochloric acid solution at 0 - 5 °C, add aniline to make the concentration of aniline 0.1 mol / L, and adsorb for 2 h at 0 - 5 °C to obtain a mixed solution; separately dissolve ammonium persulfate in 8 mL of 1 mol / L hydrochloric acid solution to make the concentration of ammonium persulfate 0.3 mol / L, cool its temperature to 0 - 5 °C, then add it to the mixed solution, and carry out in-situ polymerization at 0 - 5 °C for 12 h. The product is washed with water and dried to obtain the lignin-based epoxy resin-derived porous carbon composite electrode material.

[0070] Application Example

[0071] The prepared lignin - based epoxy resin - derived porous carbon composite electrode material was measured for mass - specific capacitance by an electrochemical workstation. The specific measurement method is as follows:

[0072] First, the prepared lignin - based epoxy resin - derived porous carbon composite electrode material, acetylene black, and polytetrafluoroethylene emulsion were mixed in a mass ratio of 8:1:1, and 1 - 2 mL of absolute ethanol was added. After ultrasonic dispersion for 20 minutes, the uniformly mixed slurry was coated on one side of a 1 cm×1 cm hydrophilic carbon cloth (the hydrophilic carbon cloth was ultrasonically treated with acetone), pressed into an electrode sheet at 20 MPa, and vacuum - dried at 80 °C. The constant - current charge - discharge curve of the electrode was tested by an electrochemical workstation, and the mass - specific capacitance was calculated by the following formula:

[0073]

[0074] Among them, C m is the mass - specific capacitance, F / g; I is the discharge current, A; Δt is the discharge time, s; m is the mass of the active material on the electrode sheet, g; ΔV is the discharge voltage range, V.

[0075] Table 1 Pore structures of the lignin - based epoxy resin - derived porous carbon in Example 1, Comparative Example 1, and Comparative Example 2

[0076]

[0077]

[0078] Figure 5 The constant - current charge - discharge curves and the corresponding mass - specific capacitances of the lignin - based epoxy resin - derived porous carbon, lignin - based epoxy resin - derived porous carbon composite electrode material prepared in Example 1, lignin - based epoxy resin - derived porous carbon composite electrode material prepared in Comparative Example 1, and lignin - based epoxy resin - derived porous carbon composite electrode material prepared in Comparative Example 2 at a current density of 1 A / g. From Figure 5It can be seen that the mass specific capacitance of the lignin-based epoxy resin-derived porous carbon prepared in Example 1 is 330.5 F / g. The curve shows a good linear relationship and is in an isosceles triangle shape, indicating that this material mainly exhibits the characteristics of electric double-layer capacitance. The charge-discharge curve of the lignin-based epoxy resin-derived porous carbon composite electrode material in Example 1 is nearly symmetric, but there are inflection points, proving that due to the loading of polyaniline, the porous carbon composite electrode material has both the characteristics of electric double-layer capacitance and pseudocapacitance. The mass specific capacitance of the lignin-based epoxy resin-derived porous carbon composite electrode material in Example 1 is 497.7 F / g, while that of Comparative Example 1 is 416.1 F / g, and its mass specific capacitance is significantly lower than that of Example 1. From the analysis of the pore structure of the porous carbon in Table 1, it can be seen that the specific surface area and total pore volume of the lignin-based epoxy resin-derived porous carbon prepared in Example 1 are larger than those of Comparative Example 1. This is because m-phenylenediamine was added during the synthesis of the polymer in Example 1. m-Phenylenediamine continued to react with the remaining active groups in the reaction system, further cross-linking different molecular chains, making the network structure more abundant and perfect. Therefore, after carbonization, it is beneficial to the adsorption and penetration of aniline. At the same time, after introducing amino groups into the cross-linked network, it is equivalent to introducing nitrogen-containing structural units into the polymer chain. The doping of nitrogen atoms can enhance the wettability of the carbon material and promote the contact between the electrode material and the electrolyte. The mass specific capacitance of Comparative Example 2 is 382.8 F / g, and its mass specific capacitance is also significantly lower than that of Example 1. Combining the analysis of the pore structure of the porous carbon in Table 1, it can be seen that the specific surface area and total pore volume of Example 1 are 2287.9 m 2 / g and 1.208 cm 3 / / g, which are much higher than 1475.6 m 2 / g and 0.793 cm 3 / / g of Comparative Example 2. This is because Example 1 underwent pre-carbonization treatment, which can form a preliminary carbon skeleton structure for the polymer precursor and provide a basic framework for the subsequent activation step. At the same time, during the pre-carbonization process, some gases generated by the polymer can form an initial pore structure inside the material. In addition, appropriate pretreatment operations can also, to a certain extent, make the precursor arrange in an orderly manner, which is beneficial to improving the graphitization degree of the carbon material and enhancing the electrochemical performance of the carbon material. The richer the pore structure of the porous carbon, the more conducive it is to the diffusion and polymerization of aniline. Comparative Example 2 did not undergo pre-carbonization treatment, so the electrochemical performance of the synthesized composite material is not as good as that of Example 1.

[0079] Figure 6 Figure 12 shows the galvanostatic charge-discharge curves and the corresponding mass specific capacitances of the lignin-based epoxy resin-derived porous carbon composite electrode materials prepared in Examples 1-7 at a current density of 1 A / g. Figure 6It can be seen that the mass specific capacitance of the composite electrode material in Example 1 is 497.7 F / g. Compared with Example 1, in Example 2, the molar mass ratio of sodium lignosulfonate to hydroquinone is 1:4. Since the dosage of sodium lignosulfonate is relatively large and its structure is very complex with a large steric hindrance, this will cause the viscosity of the overall reaction system to be very high, resulting in a large difference in the crosslinking degree of different parts of the system. After carbonization, a large amount of gas generated by sodium lignosulfonate accumulates inside the material but cannot be discharged. When the internal pressure of the material is too high to bear, the pores collapse. The excessive accumulation of carbonaceous residues inside the material blocks the pore channels, which is not conducive to the diffusion and polymerization of aniline subsequently. Its mass specific capacitance drops from 497.7 F / g in Example 1 to 406.2 F / g. In Example 3, the dosage of m-phenylenediamine is increased, resulting in local overheating of the reaction, which is more likely to cause the rupture and rearrangement of molecular chains. Too many amino groups will also cause an increase in crosslinking active sites and too many crosslinking bonds, making the polymer structure and crosslinking network too dense. During the carbonization process, the connectivity of the pores is poor, which will also lead to a decrease in the specific surface area of the material, thus affecting the preparation of the composite electrode material, and its mass specific capacitance drops to 430.7 F / g. In Example 4, the pre-carbonization temperature is lowered. When the precursor is pyrolyzed, the initial pores formed inside the precursor are not rich enough. After activation with KOH, the further increase in the specific surface area is limited, and the mass specific capacitance of the composite electrode material drops to 374.7 F / g. In Example 5, the activation temperature is lowered, and the reaction between KOH and carbon is not sufficient, generating limited gas, resulting in a limited degree of KOH etching of the carbon skeleton and it is difficult to form a large number of pore structures. Therefore, the specific surface area of the material is relatively low, causing the mass specific capacitance of the composite electrode material to drop to 453.6 F / g. In Example 6, the mass ratio of the pre-carbonized material to the activator potassium hydroxide is only 1:1, and the dosage of KOH is insufficient, resulting in a limited etching effect on the carbon material, only producing limited pore expansion and pore formation on the basis of pre-carbonization. At this time, the specific surface area is small, and the mass specific capacitance of the composite electrode material drops to 400.0 F / g. In Example 7, the molar ratio of aniline to the oxidant ammonium persulfate is 1:3, and the mass specific capacitance of the composite material drops from 497.7 F / g to 417.0 F / g. The reason is that the oxidation of aniline is excessive, resulting in a decrease in conductivity and a decline in the electrochemical performance of the composite material.

[0080] Figure 7 Figure 4 is the charge-discharge cycle stability diagram of the lignin-based epoxy resin-derived porous carbon composite electrode material prepared in Example 1 at a current density of 10 A / g. Figure 7 It can be seen that after 3000 charge-discharge cycles, the capacitance retention rate of this material is 75.7%, indicating that it has good cycle stability.

[0081] The above are only the preferred embodiments of the present invention. All equivalent changes and modifications made according to the scope of the patent application of the present invention shall fall within the scope covered by the present invention.

Claims

1. A method for preparing a lignin-based epoxy resin-derived porous carbon composite electrode material, characterized in that: Sodium lignin sulfonate, hydroquinone and epichlorohydrin are used as main raw materials, and m-phenylenediamine is added for polycondensation to prepare a lignin-based epoxy resin polymer, which is then pre-carbonized and pyrolyzed at high temperature to obtain a lignin-based epoxy resin-derived porous carbon. Finally, the porous carbon is adsorbed with aniline and then in-situ polymerized to obtain the lignin-based epoxy resin-derived porous carbon composite electrode material.

2. The method according to claim 1, characterized in that: The following steps are involved: (1) Preparation of lignin-based epoxy resin polymer: epichlorohydrin, hydroquinone and sodium lignin sulfonate were added to a sodium hydroxide solution in a 40°C water bath, stirred until dissolved, and m-phenylenediamine was added. Stirring was stopped after the solution gradually gelled. After complete gelation, the reaction was continued for 3 h. The product was filtered, washed with water, and freeze-dried to obtain a lignin-based epoxy resin polymer. (2) Pre-carbonization of lignin-based epoxy resin polymer: pyrolyzing the lignin-based epoxy resin polymer obtained in step (1) under a nitrogen atmosphere, and washing the pyrolysis product with acid, water, and drying to obtain a lignin-based epoxy resin pre-carbonized product; (3) Preparation of lignin-based epoxy resin derived porous carbon: the lignin-based epoxy resin pre-carbonized product obtained in step (2) and potassium hydroxide are ground and mixed evenly, and pyrolyzed at high temperature under a nitrogen atmosphere. The pyrolysis product is acid-washed, washed with water, and dried to obtain lignin-based epoxy resin derived porous carbon; (4) Lignin-based epoxy resin-derived porous carbon loaded with polyaniline: The lignin-based epoxy resin-derived porous carbon obtained in step (3) is stirred and dispersed in a hydrochloric acid solution, and after the temperature is lowered to 0-5°C, aniline is added and adsorbed at 0-5°C for 2 h to obtain a mixed solution A. Ammonium persulfate is dissolved in a hydrochloric acid solution, and after the temperature is lowered to 0-5°C, it is added to the mixed solution A for in-situ polymerization. The product is washed with water and dried to obtain the lignin-based epoxy resin-derived porous carbon composite electrode material.

3. The method according to claim 2, characterized in that: In step (1), the mass fraction of the sodium hydroxide solution is 15-30%, and the amount used is 10 mL; the molar ratio of the sodium lignin sulfonate to hydroquinone is 1:4-1:7; the amount of epichlorohydrin used is 3.2-7 mL, and the amount of m-phenylenediamine added is 0.1-0.4 g.

4. The method according to claim 2, characterized in that: In step (2), the pyrolysis temperature is 400-500°C and the time is 0.5-1.5 h.

5. The method according to claim 2, characterized in that: In step (3), the mass ratio of the lignin-based epoxy resin pre-carbonized product to potassium hydroxide is 1:1-1:5; the high-temperature pyrolysis temperature is 500-800°C, and the time is 2 h.

6. The method according to claim 2, characterized in that: In step (4), the concentration of the hydrochloric acid solution is 1 mol / L; the concentration of aniline in the mixed solution A is 0.05-0.2 mol / L, and the concentration of the lignin-based epoxy resin-derived porous carbon is 18.6 mg / mL; the molar ratio of aniline to ammonium persulfate is 1:0.5-1:3; the temperature of the in-situ polymerization is 0-5°C, and the time is 12 h.

7. A lignin-based epoxy resin derived porous carbon composite electrode material prepared by the method according to any one of claims 1 to 6.

8. Use of the lignin-based epoxy resin-derived porous carbon composite electrode material prepared by the method according to any one of claims 1 to 6 in a supercapacitor.

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