A biomass-based supercapacitor electrode material and preparation method thereof

Abstract

The present invention relates to the field of capacitor technology, specifically to a biomass-based supercapacitor electrode material and a preparation method thereof, comprising nitrogen-doped biomass-based carbon; and a multinary metal sulfide distributed on the surface and internal pore walls of the biomass-based carbon, wherein the multinary metal sulfide is Zn-Mo-CdS. The electrode material prepared by the present invention has an extremely high specific capacitance value, a high capacitance retention rate, and exhibits good cycle stability.

Description

Technical Field

[0001] The present invention relates to the technical field of capacitors, and in particular to an electrode material for a biomass-based supercapacitor and a preparation method thereof. Background Art

[0002] In recent years, carbon materials have become the most important supercapacitor electrode materials due to their advantages such as good chemical stability, high specific surface area, excellent conductivity, diverse forms, and wide operating temperature range.

[0003] When carbon materials are used as electrode materials for supercapacitors, since they only exhibit double-layer capacitance properties, achieving high specific capacity often requires them to have a large specific surface area. Porous carbon has abundant pores and a large specific surface area, making it very suitable as an electrode material for supercapacitors. However, even so, the specific capacity of carbon materials is still too low, and their electrochemical performance needs to be improved. Therefore, in order to improve the capacitance performance of carbon materials, in addition to morphological optimization, structural modification is also required. Heteroatom doping and compounding with pseudocapacitive materials are two commonly used methods. Summary of the Invention

[0004] Purpose of the invention: In response to the above technical problems, the present invention proposes a biomass-based supercapacitor electrode material and a preparation method thereof.

[0005] The technical solutions adopted are as follows:

[0006] A biomass-based supercapacitor electrode material comprising nitrogen-doped biomass-based carbon;

[0007] and multinary metal sulfides distributed on the surface and internal pore walls of the biomass-based carbon.

[0008] Furthermore, the multinary metal sulfide is Zn-Mo-CdS.

[0009] Furthermore, the preparation method of the nitrogen-doped biomass-based carbon is as follows:

[0010] The biomass raw materials and organic amines are mixed in a weight ratio of 10-30:1, heated to 600-800°C in an inert atmosphere, carbonized for 1-4 hours, then acid washed, washed with water and dried.

[0011] Furthermore, the biomass raw material is any one or more combinations of corn cobs, walnut shells, peanut shells, coconut shells, rice straw, and wheat straw.

[0012] Furthermore, the organic amine includes aliphatic amine and alcohol amine, and the weight ratio of the aliphatic amine to the alcohol amine is 1-5:1-5.

[0013] Furthermore, the fatty amine is any one or more combinations of diethylamine, triethylamine, and ethylenediamine.

[0014] Furthermore, the alcoholamine is any one or more combinations of monoethanolamine, diethanolamine, and triethanolamine.

[0015] Furthermore, the heating rate is 1-10°C / min.

[0016] The present invention also provides a method for preparing a biomass-based supercapacitor electrode material:

[0017] Zinc acetate, ammonium molybdate and cadmium acetate are dissolved in water to obtain a solution, and nitrogen-doped biomass-based carbon is added and dispersed by ultrasonic oscillation. Sodium sulfide solution is added dropwise under stirring conditions, and stirring is continued for more than 12 hours. The temperature is raised to 150-170°C for hydrothermal reaction for more than 12 hours. After cooling to room temperature, the product is collected, washed and dried.

[0018] Furthermore, it is characterized in that the molar ratio of zinc acetate, ammonium molybdate and cadmium acetate is 1:1:5-10.

[0019] Beneficial effects of the present invention:

[0020] The present invention provides an electrode material for a biomass-based supercapacitor. The material uses a combination of aliphatic amines and alcohol amines as a nitrogen source to introduce nitrogen into biomass-based carbon, thereby changing the charge density and surface physical and chemical properties of the carbon material, providing more active sites, and endowing the electrode material with excellent electrochemical performance. Furthermore, comparative tests show that the nitrogen-doping effect of the triethylamine and triethanolamine combination is superior to that of urea. This may be because triethylamine and triethanolamine not only serve as nitrogen sources but also react with acidic impurities and oxygen-containing functional groups in the biomass raw material to generate gas or water-soluble compounds and reduce the oxygen content of the carbon material, thereby regulating the chemical properties of the biomass-based carbon and improving the electrochemical performance.

[0021] Composite biomass-based carbon and metal sulfide is a better choice to improve the electrochemical performance of electrode materials, which can achieve the complementary advantages of the two. On the one hand, biomass-based carbon provides a certain double-layer capacitance and improves the conductivity of metal sulfide. Moreover, the porous structure provides sufficient space for the adsorption, desorption and rapid transfer of electrolyte ions, so that the electrolyte can quickly penetrate into the electrode material to reach more electrochemical active sites, thereby improving the utilization rate of metal sulfide. On the other hand, it protects the structure of metal sulfide from being destroyed and improves the cycle stability. Metal sulfide provides high energy density, thereby obtaining an electrode material with excellent performance. Compared with single metal sulfide, the multi-metal sulfide used in the present invention can better meet the energy storage needs of supercapacitors, utilize the synergistic effect between metal ions, provide more active sites for the reaction, and have more superior redox performance and higher conductivity.

[0022] After testing, the electrode material prepared by the present invention has an extremely high specific capacitance value, a high capacitance retention rate, and exhibits good cycle stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the SEM image of the electrode material prepared in Example 1. DETAILED DESCRIPTION

[0024] Unless otherwise specified, the following examples and comparative examples were conducted in parallel, using the same processing steps and parameters.

[0025] Example 1:

[0026] A method for preparing electrode materials for biomass-based supercapacitors:

[0027] The coconut shell was dried and crushed into 80 mesh powder and dried to a moisture content of ≤5% as a biomass raw material. Corn cob powder, triethylamine and triethanolamine with a weight ratio of 20:0.5:0.5 were mixed, heated to 800°C at a rate of 5°C / min under an argon atmosphere, kept warm for 2 hours, washed with 0.1mol / L hydrochloric acid to remove impurities, and then washed with deionized water to neutrality. Finally, it was dried at 80°C for 10 hours to obtain nitrogen-doped biomass-based carbon. 1.83g zinc acetate (10mmol), 1.96g ammonium molybdate (10mmol) and 18.44g cadmium acetate (80mmol) were dissolved in 500ml deionized water to obtain a solution, and then 100g nitrogen-doped biomass-based carbon was added, ultrasonically dispersed for 30min, and 55ml was added dropwise under stirring. 2 mol / L sodium sulfide solution, continue stirring for 15 h, heat to 160 ° C for hydrothermal reaction for 24 h, cool to room temperature, collect the product, wash with deionized water and anhydrous ethanol several times, and then dry at 80 ° C for 10 h.

[0028] Example 2:

[0029] A method for preparing electrode materials for biomass-based supercapacitors:

[0030] The walnut shells were dried and crushed into 80 mesh powder and dried to a moisture content of ≤5% as biomass raw materials. Corn cob powder, triethylamine and triethanolamine in a weight ratio of 30:0.5:0.5 were mixed and heated to 800°C at a rate of 10°C / min under an argon atmosphere. After carbonization for 4 hours, the mixture was washed with 0.1mol / L hydrochloric acid to remove impurities and then washed with deionized water to neutrality. Finally, it was dried at 80°C for 10 hours to obtain nitrogen-doped biomass-based carbon. 1.83g zinc acetate (10mmol), 1.96g ammonium molybdate (10mmol) and 18.44g cadmium acetate (80mmol) were dissolved in 500ml deionized water to obtain a solution. 100g nitrogen-doped biomass-based carbon was added, ultrasonically dispersed for 30min, and 55ml was added dropwise under stirring. 2 mol / L sodium sulfide solution, continue stirring for 15 h, heat to 170 ° C for hydrothermal reaction for 24 h, cool to room temperature, collect the product, wash with deionized water and anhydrous ethanol several times, and then dry at 80 ° C for 10 h.

[0031] Example 3:

[0032] A method for preparing electrode materials for biomass-based supercapacitors:

[0033] The corn cob was dried and crushed into 80 mesh powder and dried to a moisture content of ≤5% as a biomass raw material. The corn cob powder, triethylamine and triethanolamine with a weight ratio of 25:0.5:0.5 were mixed, and the temperature was raised to 700°C at a rate of 1°C / min under an argon atmosphere. After being kept warm and carbonized for 2 hours, it was washed with 0.1mol / L hydrochloric acid to remove impurities, and then washed with deionized water to neutrality. Finally, it was dried at 80°C for 10 hours to obtain nitrogen-doped biomass-based carbon. 1.83g zinc acetate (10mmol), 1.96g ammonium molybdate (10mmol) and 18.44g cadmium acetate (80mmol) were dissolved in 500ml deionized water to obtain a solution, and then 100g nitrogen-doped biomass-based carbon was added, ultrasonically dispersed for 30min, and 55ml was added dropwise under stirring. 2 mol / L sodium sulfide solution, continue stirring for 15 h, heat to 150 ° C for hydrothermal reaction for 24 h, cool to room temperature, collect the product, wash with deionized water and anhydrous ethanol several times, and then dry at 80 ° C for 10 h.

[0034] Comparative Example 1:

[0035] The same as Example 1, except that triethylamine and triethanolamine are replaced by equal weights of urea.

[0036] Comparative Example 2:

[0037] The same as Example 1, except that triethylamine was replaced by triethanolamine of equal weight.

[0038] Comparative Example 3:

[0039] The same as Example 1, except that triethanolamine was replaced by equal weight of triethylamine.

[0040] Comparative Example 4:

[0041] The method is basically the same as Example 1, except that only 100 mmol of zinc acetate is added, and ammonium molybdate and cadmium acetate are not added.

[0042] Comparative Example 5:

[0043] The process is basically the same as Example 1, except that only 100 mmol of ammonium molybdate is added, and zinc acetate and cadmium acetate are not added.

[0044] Comparative Example 6:

[0045] The process is substantially the same as Example 1, except that only 100 mmol of cadmium acetate is added, and zinc acetate and ammonium molybdate are not added.

[0046] Performance testing:

[0047] Electrochemical performance tests were performed on the electrode materials prepared in Examples 1-3 and Comparative Examples 1-6 using a three-electrode system.

[0048] The working electrode is prepared by dissolving the electrode material, acetylene black, and polytetrafluoroethylene in an 8:1:1 mass ratio in ethanol, grinding and mixing, and coating it on a 1 cm × 1 cm nickel foam. After drying and compaction, it is made into a three-electrode system with a saturated calomel electrode as the reference electrode, a platinum sheet as the counter electrode, and 1 mol / L H2SO4 as the electrolyte. The specific capacitance of the three-electrode system at a current density of 1 A / g and the capacitance retention after 10,000 cycles are tested using a CH1760D electrochemical workstation. The test results are shown in Table 1:

[0049] Table 1:

[0050]

[0051] As can be seen from Table 1 above, the electrode material prepared by the present invention has an extremely high specific capacitance value and a high capacitance retention rate, showing good cycle stability;

[0052] By comparing the data of Example 1 with that of Comparative Example 1, it can be seen that the nitrogen doping effect of the triethylamine and triethanolamine composition of the present invention is better than that of urea;

[0053] By comparing the data of Example 1 with Comparative Examples 2 and 3, it can be seen that the nitrogen doping effect of the triethylamine and triethanolamine combination is better than that of single triethylamine or triethanolamine, so that the combination improves the electrochemical performance of the electrode material more significantly;

[0054] By comparing the data of Example 1 with Comparative Examples 4, 5, and 6, it can be seen that the introduction of multi-metal sulfides improves the electrochemical performance of the electrode material better than that of single metal sulfides.

[0055] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A biomass-based supercapacitor electrode material, characterized in that: including nitrogen-doped biomass-based carbon; and multinary metal sulfides distributed on the surface and internal pore walls of the biomass-based carbon; The multinary metal sulfide is Zn-Mo-CdS; The preparation method of the nitrogen-doped biomass-based carbon is as follows: Mix the biomass raw materials and organic amine in a weight ratio of 10-30:1, heat to 600-800℃ under an inert atmosphere, carbonize for 1-4 hours, then acid wash, wash with water and dry. The organic amine includes aliphatic amine and alcohol amine, and the weight ratio of the aliphatic amine to the alcohol amine is 1-5:1-5; The fatty amine is any one or more combinations of diethylamine, triethylamine, and ethylenediamine; The alcoholamine is any one or more combinations of monoethanolamine, diethanolamine and triethanolamine.

2. The biomass-based supercapacitor electrode material according to claim 1, wherein The biomass raw material is any one or more combinations of corn cobs, walnut shells, peanut shells, coconut shells, rice straw, and wheat straw.

3. The biomass-based supercapacitor electrode material according to claim 1, wherein The heating rate is 1-10℃ / min.

4. A method for preparing a biomass-based supercapacitor electrode material according to any one of claims 1 to 3, characterized in that: Zinc acetate, ammonium molybdate and cadmium acetate are dissolved in water to obtain a solution, and nitrogen-doped biomass-based carbon is added and dispersed by ultrasonic oscillation. Sodium sulfide solution is added dropwise under stirring conditions, and stirring is continued for more than 12 hours. The temperature is raised to 150-170°C for hydrothermal reaction for more than 12 hours. After cooling to room temperature, the product is collected, washed and dried.

5. The method for preparing a biomass-based supercapacitor electrode material according to claim 4, wherein: The molar ratio of the zinc acetate, ammonium molybdate and cadmium acetate is 1:1:5-10.

Images