A designed asymmetric hybrid electrochemical capacitor was presented where NiO and Ru0.35V0.65O2 as the positive and negative electrode, respectively, both stored charge through reversible faradic pseudocapacitive reactions of the anions (OH-) with electroactive materials. And the two electrodes had been individually tested in 1 M KOH aqueous electrolyte to define the adequate balance of the active materials in the hybrid system as well as the working voltage of the capacitor based on them. The electrochemical tests demonstrated that the maximum specific capacitance and energy density of the asymmetric hybrid electrochemical capacitor were 102.6 Fg(-1) and 41.2 Wh kg(-1), respectively, delivered at a current density of 7.5 A cm(-2). And the specific energy density decreased to 23.0 Wh kg(-1) when the specific power density increased up to 1416.7 W kg(-1). The hybrid electrochemical capacitor also exhibited a good electrochemical stability with 83.5% of the initial capacitance over consecutive 1500 cycle numbers. (C) 2007 Elsevier B.V. All rights reserved.