Influence of Electrolyte Concentration and Temperature on the Capacitance of Activated Carbon

The influences of electrolyte concentration and temperature on the capacitive behavior of activated carbon (AC) were investigated by cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge/discharge measurements. The performance of a symmetric capacitor was characterized in 0.1, 0.5, 1.0, and 6.0 mol . L-1 KOH solution. We found that the high electrolyte concentration led to high capacitance, low internal resistance, and a narrow voltage window. The capacitance and internal resistance were found to be linearly dependent on the logarithm of KOH concentration. AC supercapacitor performance was investigated at 20, 40 and 80 degrees C, respectively. We found that elevated temperatures are favorable for an increase in capacitance and for a decrease in internal resistance. However, elevated temperatures increase the capacitance fading rate during long charge/discharge cycling tests.