An electro-deposition method was used for the preparation of nano-structured lead dioxide. The lead dioxide films prepared were used as positive electrodes of lead acid batteries. Different parameters such as pulse time (t(on)), pulse height, and relaxation time (t(off)) were optimized to obtain higher capacity. Depend on the pulse conditions, a range of different morphologies of various porosities and connectivity was obtained. The resulting batteries were discharged to a cut off voltage of 1.75 V by a pulsed current method. The energy storage ability of the prepared lead acid batteries shows a close relation with the morphology of cathode materials. Maximum capacity was observed when pulse and relaxation time was equal to 0.1 and 5 s, respectively, at a current density of 25 mA cm(-2). A change in morphology of lead dioxide from aggregated globular structure to nanofiber was occurred. It was found that the high surface area as well as high connectivity between particles resulted in increased discharge capacity. Analysis of electrochemical impedance spectroscopy (EIS) data revealed that the charge transfer resistance is decreased by a change in morphology from bulk globular to nanofiber as the energy storage test showed. The time dependence of impedance behavior of a sample prepared at t(on) = 0.1 s and t(off) = 5 s at 25 mA cm(-2) was investigated and the results are discussed. (c) 2006 Elsevier Ltd. All rights reserved.