Fabrication of NaCl aqueous electrolyte electric double layer capacitor as practical device and dependence of cell performance on pore structure of activated carbon

Abstract

Abstract In this study, electric double layer capacitor (EDLC) cells were fabricated as laminate type by using NaCl aqueous solution, which should be relatively safe electrolyte against environments and biological objects, for the investigation of the performance from a practical point of view. The capacitance value of the cell depended on the kind of activated carbon for EDLC electrode. The capacitance values of the cell fabricated from the best activated carbon were ca. 1.45 F at 0.1-1 mA of discharging current value and at 1.2 V of charging voltage. The capacitance value should be equivalent to commercial EDLCs although the charging voltage is smaller. The relationship between the properties related to pores of activated carbon and the capacitance value was examined. The enumerated values obtained from the Dubinin-Astakhov (DA) method for the activated carbons of this study were between 1 and 2, which could indicate that the micropore distribution of the activated carbons used in this study was heterogeneous. The capacitance value was found to be strongly related to the micropore volume calculated by the DA method from the adsorption isotherm of CO2 at 298 K. That is, the micropore volume estimated from the DA method should be used as the indicator for the selection of high-performance activated carbon for electrode of EDLC containing NaCl aqueous solution electrolyte.