Lead-Acid storage battery is a secondary cell which can be recharged by passing current through it in the opposite direction.
Following is the overall chemical reaction operative during discharging of lead-acid battery:
Pb(s) + PbO2(s) + 2H2SO4(aq) → 2PbSO4(s) + 2H2O(l)
From above reaction, it can be seen that oxidation state of lead in PbO2 and PbSO4 is +4 and +2 respectively. Thus, upon discharging lead oxide is reduced to lead sulphate in lead-acid storage battery.
