Carbonate-type organic electrolytes were prepared using propylene carbonate (PC) and dimethyl
carbonate (DMC) as a solvent, quaternary ammonium salts, and by adding different
contents of 1-ethyl-3-methyl imidazolium tetrafluoroborate (EMImBF4). Cyclic voltammetry
and linear sweep voltammetry were performed to analyze conducting behaviors. The surface
characterizations were analyzed by scanning electron microscopy method and X-ray photoelectron
spectroscopy. From the experimental results, increasing the EMImBF4 content increased
the ionic conductivity and reduced bulk resistance and interfacial resistance. In particular,
after adding 15 vol% EMImBF4 in 0.2 M SBPBF4 PC/DMC electrolyte, the organic
electrolyte showed superior capacitance and interfacial resistance. However, when EMImBF4
content exceeded 15 vol%, the capacitance was saturated and the voltage range decreased.