Effect of electrolyte temperature on the pseudo-capacitive behavior of manganese oxide in N-butyl-N-methylpyrrolidinium-dicyanamide ionic liquid

The electrochemical behavior of anodically deposited Mn oxide in N-butyl-N-methylpyrrolidinium-dicyanamide (BMP-DCA) ionic liquid (IL) at various temperatures (30-80°C) is investigated. Cyclic voltammetry (CV) is used to evaluate the electrochemical performance of the Mn oxide. Surface morphology of the deposited oxide after charging/discharging is examined by scanning electron microscopy (SEM). The experimental data show that the Mn oxide electrode exhibits good pseudo-capacitance performance even at 80°C. In the ionic liquid studied, the specific capacitance increases with increasing BMP-DCA IL temperature. A specific capacitance of 93 F g^-1 in a potential window of 3 V is obtained at 80°C, which is about 50% higher than that obtained at 30°C. The experimental results also show that the capacitance-retained ratio of the oxide electrode increases with increasing temperature at a high potential sweep rate. Furthermore, the capacitance decline about 40% after 500 repeated charging/discharging cycles in BMP-DCA IL at 80°C is observed, which is better than that measured in an aqueous electrolyte.