Microscopic examination of active materials from lead-acid cells

Abstract Sections of lead-acid battery plates in various states of formation, charge and discharge have been examined microscopically. The formation of both the positive and negative plates begins at the grid/active-material interface. The discharge of both plates begins on the surface and penetrates into the bulk of the active material. The utilisation of the active material is illustrated. α and β lead dioxide can be differentiated by their colours under the microscope by the use of an oil-immersion lens. The residual lead in the pasted positive plate is always converted to the α form. β lead dioxide is more easily discharged than the α modification but the latter holds the plate together and is necessary for a long cycle life.