The dry cell, useful as it is, cannot be recharged and used again. This is because the products of the electrode reactions diffuse away, and the reactions cannot be reversed simply by passing an external charging current through the cell.

The lead storage battery, shown at the right, has the great advantage that the products of each electrode reaction adhere to the electrode. When a reverse current is passed through the storage battery, the products are reconverted to reactants, energy is stored, and the battery is ready to deliver electrical energy again.

The anode is a spongy lead screen, and the cathode is a screen impregnated with lead dioxide. Both are immersed in the same sulfuric acid solution. Lead is oxidized to Pb²⁺ ions at the anode, and these ions immediately form insoluble lead sulfate, which sticks to the anode:

At the cathode, lead oxide with Pb in the +4 oxidation state is reduced to more Pb2+ ions, which also stick to the cathode as PbSO4:

The overall cell reaction therefore is