Preparation and characterization of activated carbons for supercapacitor under moderate temperature activation condition

Abstract：Activated carbons were prepared from Indonesia lignite under moderate temperature（400～580 ℃） activation condition with KOH as activation agent.The pore structure,crystallite structure and surface morphology of activated carbons were characterized by hypothermia nitrogen adsorption,X-ray diffraction（XRD）,scanning electron microscope（SEM）.The electrochemical characteristics of supercapacitor with activated carbons as electrodes were evaluated by galvanostatic charge-discharge and cyclic voltammetry.The results show that during the activation process of preparing coal-based activated carbons,the reaction between KOH and C begins from 400 ℃ to 460 ℃.With increasing of activation temperature,the specific surface area and total pore volume of activated carbons increase,the pore size distributions widens and the ratio of mesopore improves.The BET specific surface area,total pore volume and the ratio of mesopore of activated carbons（denoted as AC580） can reach 1 598 m2/g,0.828 cm3/g and 41.4% respectively when the activation temperature is 580 ℃.In 3 mol/L KOH electrolyte,the supercapacitor with AC580 as electrodes has excellent charge-discharge performance,exhibits a high specific capacitance of 369 F/g at a low current density of 50 mA/g and still remains 305 F/g even at a high current density of 2 500 mA/g,its leakage current is only 0.02 mA and has excellent cycling stability,the residual specific capacitance is beyond 92% after 1 000 cycles.The results have demonstrated that the activated carbons AC580 is a perfect electrode materials for supercapacitor.