Ionic liquid "ECOENG (TM) 110", a promising electrolyte for electrochemical devices, was investigated by impedance spectroscopy. Metallic electrodes (Pt, Cu, Ag, and Mo) as well as carbon were used for the electrochemical characterization. The dependences of the real and imaginary impedance, polarization resistance and electrochemical capacity of the double layer on the electrode potential were investigated using electrical equivalent circuits of R-1(QR(2)) and R-1[Q(R2W)] types. (C) 2010 Elsevier B.V. All rights reserved.