Application of Low-Viscosity Ionic Liquid to the Electrolyte of Double-Layer Capacitors

TLDR: In this article, the performance of a double-layer capacitor (DLC) composed of activated carbon electrodes and 1--ethyl-3-methylimidazolium fluoride (EMIF).

Abstract: The performance of a double-layer capacitor (DLC) composed of activated carbon electrodes and 1--ethyl-3-methylimidazolium fluoride (EMIF).2.3HF, which has extremely high conductivity with low viscosity, was examined and compared with those using the popular ionic liquid EMIBF 4 , conventional aqueous electrolyte 35 wt % H 2 SO 4 , and nonaqueous electrolyte 1 M Et 3 MeNBF 4 /propylene carbonate. The DLC using EMIF.2.3HF showed an intermediate capacitance and internal resistance between the aqueous and nonaqueous electrolyte systems due to its intermediate double-layer capacitance and electrolytic conductivity. EMIF.2.3HF afforded much higher capacitance than EMIBF 4 even at low temperatures, however, it had a lower decomposition voltage (∼2 V), resulting in lower energy density. The capacitance of EMIF.2.3HF was extremely dependent on the applied voltage.