Study On Preparation Of Super Activated Carbon From Biomass And Ins Electrochemical Properties

Supercapacitors can be used as new renewable energy storage devices because of their high power density and fast charging and discharging.However,the power and energy density of supercapacitors should be further improved,which depends on the improvement of electrode materials.In this paper,aiming at the shortcomings of high price,low yield and uncontrollable pore size of electrode materials,a new idea of developing supercapacitor electrodes is proposed.Cotton is a rare and pure biomass in nature.Its main component is cellulose,and the interference of other impurities is less.In this paper,biomass was treated by high temperature carbonization,KNO3 oxidation and KOH activation,and biomass-based activated carbon materials were prepared.The structure,morphology and properties of the prepared carbon materials were improved by single factor test,combined with various test methods such as scanning electron microscopy,X-ray diffraction,nitrogen adsorption and desorption test,constant current charge-discharge,cyclic voltammetry and other electrochemical tests.The optimum conditions of carbonization,oxidation and activation were obtained by characterization.The porous biomass activated carbon material prepared by carbonization,oxidation and activation has the best performance.Its specific capacitance can reach 283 F g-1 when the current density is 1 A g-1.When the current density increases to 100 A g-1,the specific capacitance can reach 229 F g-1,with only 19.09%attenuation.In addition,it has excellent cycle performance.When the current density is 20,50 and 100 A g-1,the attenuation after 100,000 cycles is less,only 3.5%,4.1%and 5.8%.In this experiment,phosphate is used as carbonization promoter in the carbonization process,which can significantly improve the yield of biomass carbonization.The results show that the optimum conditions are as follows:When the optimum condition of using disodium hydrogen phosphate and the mass ratio of cotton is 6%,the carbonization yield is 23.18%,and the specific capacitance is 271.1 F g-1.When the optimum condition of using sodium dihydrogen phosphate and the mass ratio of cotton is 2%,the yield is 24.43%,and the specific capacitance is 272.4 F g-1.The yield is 25.11%and the specific capacitance is 271.4 F g-1 at 350?.Finally,the innovative method of producing carbon materials with adjustable specific surface area and controllable pore size and abundant pore structure is put forward.In the process of pore-making,viscose fiber method and impregnation method are used in this paper.The results showed that adding 0.4 g sodium silicate to the viscose made from 10 g raw cotton had the best performance.Compared with viscose,the specific surface area of activated carbon increased by 51.45%,the discharge specific capacitance increased from 142.2 F g-1 to 209.5 F g-1,and increased by 47.34%.There were a lot of pore structures on the surface of activated carbon prepared by impregnation method,and the performance was improved.The ratio of cotton to sodium silicate was increased.When the discharge capacitance is 4%,the specific capacitance increases from 273.6 F g-1 to 288 F g-1,an increase of 5.37%.