Study On Preparation And Performance Of Electrode Materials In Supercapacitors

Electrochemical capacitor is an efficient energy storage device with theadvantages of high specific capacitance, long cycling life, wider worktemperatures and free service. The performance of super capacitors dependson the electrode materials. Activated carbon was the earliest material used insupercapacitors because of its characteristics of low cost, easy to prepare andelectrochemical stabilities. Manganese dioxide is a new material with highspecific capacitance for the positive electrode of asymmetric capacitor.Conductive additives such as acetylene black and carbon nanofibres can alsoaffect the performance of supercapacitors’ electrode. Graphite nanoplateletshave been paid much attention recently due to excellent electrical conductiveproperties and unique two dimensional nanostructure.In this paper, the low cost carbon electrode was prepared by NaOHchemical activation of petroleum coke for the first time, and then assembledto button capacitors. The effect of the weight ratio of NaOH/coke on thestructure and capacitance performance of the electrode materials forsupercapacitors was investigated by constant current discharge, cyclicvoltammetry and electrochemical impedance spectroscopy measurement. Thepetroleum coke based activated carbon prepared under2.5:1weight ratio ofNaOH/coke had specific surface areas over929m²/g and specific capacitanceabout119F/g in1M ET4NBF₄/PC electrolyte. The power stabilities ofpetroleum coke based activated carbon were also improved when the ratio was3:1.Graphite nanoplatelets were prepared from expanded graphite worm viaultrasonic treatment which was used as conductive additives later. Threecarbon materials with different dimensions were selected as conductiveadditives to apply for the electrodes of supercapacitors. The electrodes wereinvestigated by SEM and various electrochemical tests. The composite electrode with both acetylene black and graphite nanoplatelets showedexcellent discharge properties at different current densities. The“plane-to-point” conducting mode was the key factor for the high propertiesof supercapacitor.Designed and assembled the asymmetric capacitors with manganesedioxide electrode and activated carbon electrode. Certain problems in theproduct processes of the asymmetric capacitors were solved. And thecapacitance performance of asymmetric capacitors was in accordance withdesigned capacitance.