Co-Al layered double hydroxides (LDHs) have been synthesized by a method involving separate nucleation and aging steps. The effects of varying thermal treatment and Co/Al mole ratio on their microscopic form, surface area, crystallinity, and electrochemical behavior have been investigated. Co-Al LDHs with Co/Al ratio of 2:1 retain a layered structure up to 160 degrees C, and the electrochemically active Co sites become increasingly exposed. The material obtained after heating at 160 degrees C exhibited supercapacitor behavior with a high specific capacitance of 684 F/g and a good working capacity at large specific current. This material may be a potential electrode material for supercapacitors. (c) 2005 The Electrochemical Society.