<P> Lead -- acid batteries lose the ability to accept a charge when discharged for too long due to sulfation , the crystallization of lead sulfate . They generate electricity through a double sulfate chemical reaction . Lead and lead dioxide , the active materials on the battery 's plates , react with sulfuric acid in the electrolyte to form lead sulfate . The lead sulfate first forms in a finely divided , amorphous state , and easily reverts to lead , lead dioxide and sulfuric acid when the battery recharges . As batteries cycle through numerous discharges and charges , some lead sulfate is not recombined into electrolyte and slowly converts to a stable crystalline form that no longer dissolves on recharging . Thus , not all the lead is returned to the battery plates , and the amount of usable active material necessary for electricity generation declines over time . </P>
what are the active materials of a lead acid battery
Lead and lead dioxide