A nano-structured CoAl double hydroxide with an average particle size of 60-70 nm was prepared by a chemical co-precipitation. It was used as a positive electrode for the asymmetric hybrid supercapacitor in combination with an active carbon negative electrode in KOH electrolyte solution. The electrochemical capacitance performance of this kind of hybrid supercapacitor was investigated by means of cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge-discharge tests. A specific capacitance of 77 F g(-1) with a specific energy density of 15.5 wh kg(-1) was obtained for the hybrid supercapacitor within the voltage range of 0.9-1.5 V. The supercapacitor also exhibits a good cycling performance and keep 90% of initial capacity over 1000 cycles. (c) 2005 Published by Elsevier B.V.