Lead storage battery are secondary storage cells which can be recharged after use by passing current through it in the opposite direction and can be used again. The cell reactions when the battery is in use are as follows:

Anode: Pb(s) + SO₄^2–(aq) → PbSO₄(s) + 2e^–

Cathode: PbO₂(s) + SO₄^2–(aq) + 4H⁺(aq) + 2e^–→ PbSO₄(s) + 2H₂O(l)

When the battery is charged, the reactions are reversed and PbSO₄(s) on the anode and cathode is converted to Pb and PbO₂. From the anodic reaction, it is seen that the reverse is reduction. The correct option is (i).