Supercapacitors using singlewalled carbon nanotube electrodes

We have investigated the key factors determining the performance of supercapacitors using singlewalled carbon nanotube (SWNT) electrodes. Several parameters of compositions of the binder, annealing temperature, type of current collectors, charging time and discharging current density are optimized for the best performance of the energy density and power density. We find a maximum specific capacitance of 180 F/g and a measured power density of 20 kW/kg at the energy density of 7 Wh/kg in a solution of 7.5 N KOH. The specific surface area and the specific capacitance increase with increasing annealing temperatures of the sample. It was found that most of the BET surface area of the SWNT electrode contributed to the theoretically estimated specific capacitance. Minimization of the contact resistance is independent of the specific capacitance but directly related to the maximum of the power density.