During the charging process, lead sulfate (PbSO4) is converted into lead dioxide (PbO2) at the positive plate and into spongy lead (Pb) at the negative plate. Conversely, during the discharging process, lead dioxide and spongy lead are converted back into lead sulfate.
The electrolyte in a lead acid battery is a solution of sulfuric acid (H2SO4) and water. During the charging process, the sulfuric acid is converted into water and oxygen gas. The water is then recombined with the oxygen gas to form sulfuric acid again during the discharging process.
