A PHOTOCURRENT IMAGING STUDY OF THE DISTRIBUTION OF LEAD MONOXIDE IN CORROSION LAYERS ON LEAD-ACID-BATTERY GRIDS

It is widely believed that alpha-PbO is a principal contributor to pre mature capacity loss in lead/acid batteries via the formation of a res istive 'barrier' layer in the corrosion zone of the positive grid. Whi le batteries employing Pb-Ca grids are more prone to capacity loss tha n those using Pb-Sb grids, a definitive relationship of such behaviour with alpha-PbO distribution on either of these two alloys has yet to be demonstrated. In the work reported here, ex situ scanning laser ima ging has been used to reveal the distribution of the alpha-PbO phase a cross paste/corrosion layer/grid transverse sections of cycled Pb-Ca g rids. The technique has been successfully extended to in situ measurem ents of localized photocurrent at potentials that correspond to the en vironment of the positive plate in a lead/acid battery. It has been de monstrated that alpha-PbO films can be mapped at a resolution that pro vides an intimate insight into their influence on battery operation.