Binary complex systems have been prepared based on acetamide with lithium bis(trifluoromethane sulfone)imide [LiN(SO2CF3)(2), LiTFSI], lithium triflate (LiCF3SO3), and lithium perchlorate (LiClO4), respectively. Due to their superior physicochemical properties, such as wide liquid-phase range and high ionic conductivity, they can be practically useful electrolytes for electrochemical capacitors. We prepared electric double-layer capacitors (EDLCs) composed of activated carbon electrode and the above three complex systems based on acetamide as the electrolytes and evaluated the electrochemical performances of the EDLCs with cyclic voltammetry (CV), ac impedance spectroscopy, and galvanostatic charge/discharge, etc. The EDLCs with these components show better electrochemical properties in specific capacitance and cycling performances at ambient and elevated (80 degrees C) temperatures. Considering that the complex electrolytes possess a number of excellent properties such as negligible vapor pressure and high thermal stability, the results demonstrate that these electrolytes are promising electrolyte candidates for the EDLCs and especially for those requiring high safety and stability. (C) 2007 The Electrochemical Society.