Ionic liquids based on l-ethyl-3-methylimidazolium cation $(EMI^+)$ and inorganic or organic anions containing fluorine atoms were applied to electrolyte materials for double-layer capacitors. The double-layer capacitors composed of a pair of activated carbon electrodes and an ionic liquid selected from $EMIBF_4,; EMINbF_6,;EMITaF_6,;EMICF_3SO_3,;EMI(CF_3SO_2)_2N,;and;EMI(C_2F_5SO_2)_2N$ showed inferior low-temperature characteristics to those of a conventional nonaqueous electrolyte based on propylene carbonate (PC) solvent. On the other hand, the capacitor using $EMIF{cdot}2.3HF$ showed excellent low-temperature characteristics due to its high conductivity at low temperatures, however, it had a lower working voltage $(~2V)$ than the conventional nonaqueous counterpart $(~3V)$.