Cobalt-nickel layered double hydroxides (CoxNi1-x LDHs) were deposited onto stainless steel electrodes by the potentiostatic deposition method at -1.0 V vs. Ag/AgCl using various molar ratios of Co(NO3)(2) and Ni(NO3)(2) in distilled water. Their structure and surface morphology were studied by using X-ray diffraction analysis, energy dispersive X-ray spectroscopy and scanning electron microscopy. A network of CoxNi1-x LDH nanosheets was obtained. The nature of the cyclic voltammetry and charge-discharge curves suggested that the CoxNi1-x LDHs exist in the form of solid solutions. The capacitive characteristics of the CoxNi1-x LDHs in 1 M KOH electrolyte showed that Co0.72Ni0.28 LDHs had the highest specific capacitance value, 2104 F g(-1), which is also the highest yet reported value for oxide materials in general. (c) 2007 Elsevier B.V. All rights reserved.