PbO2 anodic layers were formed by direct oxidation of lead electrodes galvanostatically (G) and potentiostatically (P), in attempt to study PbO2 as positive active material for lead-acid batteries. The structural and electrochemical properties of PbO2 anodic layers, prepared by the two methods, were examined and found to be different. Comparative studies indicated that PbO2-G electrode exhibited a longer discharge time, corresponding to a higher capacity, and a lower charge transfer resistance than that of PbO2-P. Through SEM observation it was established that the PbO2-G had a compact structure, while the PbO2-P surface showed a porous structure. Discharge capacity was related to the film structure and internal resistance of PbO2 layer. The compact structure with higher degree of interconnected particles lead to lower internal resistance thus higher capacity, and the porous surface layer would result in high transfer resistance and diminished capacity. It was concluded that preparation methods could controllably affect the structure of PbO2 films, which further played important roles in discharge capacity. (C) 2007 Elsevier Ltd. All rights reserved.