Study On The Preparation And Electrochemical Performance Of Fiber Based Carbon Materials

Supercapacitors are a new type of energy storage equipment,with long service life,high power density,fast charge and discharge advantages,so they are widely used in electronic equipment,new energy vehicles and other fields.Plant fiber based carbon material has the characteristics of renewable,degradable,low cost and easy to process,which makes it an ideal electrode material precursor.However,the capacitance and energy density of fiber based carbon material is low.With the increasing demand for energy storage equipment,supercapacitors with low capacitance and low energy density can hardly meet the demand of people.Therefore,two approaches are designed in this paper to improve the electrochemical performance of fiber based electrode materials.Firstly,lignin nanoparticles(LNPs)were loaded onto the fiber surface by solventantisolvent method,and then carbonized to obtain LNPs/ fiber based carbon material.The effect of lignin addition on the electrochemical properties of electrode materials was investigated.The experimental results show that the specific capacitance of the composites increases first and then decreases with the increase of lignin content.When the mass ratio of LNPs to fiber was 1:10,the specific capacitance of the fiber material was the highest,which was 7.88 F/g at the current density of 0.5 A/g.The specific capacitance of all loaded LNPs was higher than that of unloaded LNPs(0.6 F/g),which proved that LNPs had an effect on improving the electrochemical performance of fiber based carbon materials.Secondly,LNPs/ fiber based carbon materials was activated by KOH to obtain LNPs/fiber porous carbon.The effect of activation conditions on the electrochemical properties of the composite was investigated.The experimental results show that when the mass ratio of precursor to KOH is 1:8,the specific capacitance is 351.13 F/g,which is higher than that of fiber activated carbon without LNPs(306.5 F/g).At the same time,after 10000 constant current charge and discharge tests,the specific capacitance can still maintain 95%.Subsequently,PANI/ fiber based active carbon composites were prepared by loading nanocluster polyaniline(PANI)on the surface of fiber based activated carbon materials.The effect of aniline(AN)concentration on the electrochemical properties of the composites was investigated.The results show that when the concentration of AN is 0.07 mol/L,the specific capacitance of the composite is 452.0 F/g,and the capacitance can remain 86% after 10000 constant current charge-discharge tests.Finally,LNPs/ fiber based porous carbon and PANI/ fiber based active carbon were used as electrodes to fabricate asymmetric supercapacitors.The experimental results show that the energy density of the assembled supercapacitor can reach 27.18 Wh/kg at 350 W/kg and12.08 Wh/kg at 7000 W/kg.After 10000 charge and discharge tests,the capacitance retention rate is up to 89%.