Supercapacitors with Polymer Electrolyte and Shochu Waste as Carbon Electrode

Electric double-layer capacitors (EDLCs) are high-speed chargeable/dischargeable devices. The commercialization of this technology is hindered by the unavailability of inexpensive electrode materials. In this study, we present low-cost activated carbon electrodes fabricated from used shochu waste, and analyze their surface and electrochemical characteristics for the first time. We then determine the optimal time and temperature required for the activation of the KOH-CO
2
double-step reactions. Additionally, the obtained shochu waste carbons (SWCs) are used as the carbon electrodes of EDLCs, whose half-cell capacitances are evaluated using cyclic voltammetry. Their electrolyte and charge transfer resistances are estimated by measuring the corresponding AC impedance under both non-aqueous and aqueous electrolytes. The withstand voltage of the aqueous electrolyte is approximately 1.2 V, which is the voltage at which the electrolysis of water occurs; however, it lacks sufficient energy density. Therefore, we added sodium polyacrylate to the electrolyte to gelatinize it and prevent electrolysis, thereby improving the withstand voltage up to 3.5 V and obtained an energy density of 4.6 Wh/kg.