What's in a Used Lead Acid Battery
Lead acid batteries are made up of plates of lead and separate plates of lead dioxide, which are submerged into an electrolyte solution of about 35% sulphuric acid and 65% water. This causes a chemical reaction that releases electrons allowing them to flow through conductors to produce electricity.
As the battery discharges, the acid of the electrolyte reacts with the materials of the plates charging their surface to lead sulphate. When the battery is recharged, the chemical reaction is reversed and the lead sulphate reforms into lead oxide and lead. With the plates restored to their original condition, the process may now be repeated.