Write a note on lead storage cell (battery).

(N/A) The most important secondary cell is the lead storage battery. It can be recharged after its discharge.
Construction:
Anode: It consists of a grid of lead packed with spongy lead $(Pb)$.
Cathode: $A$ grid of lead packed with lead dioxide $(PbO_2)$.
Electrolyte: $A$ $38\%$ solution of sulphuric acid $(H_2SO_4)$ is used as an electrolyte.
(Density: initial $1.25$ to $1.30 \ g \ mL^{-1}$)
Discharging reaction of the cell:
When the cell is in working condition,the following reactions are carried out:
Anode: Oxidation of $Pb$ into $PbSO_4$.
$(i) \ Pb_{(s)} + SO_{4(aq)}^{2-} \rightarrow PbSO_{4(s)} + 2e^{-}$
Cathode: Reduction of $PbO_2$ into $PbSO_4$.
$(ii) \ PbO_{2(s)} + SO_{4(aq)}^{2-} + 4H^+_{(aq)} + 2e^- \rightarrow PbSO_{4(s)} + 2H_2O_{(l)}$
Overall reaction: Adding $(i)$ and $(ii)$ gives the overall reaction of the lead storage cell:
$(iii) \ Pb_{(s)} + PbO_{2(s)} + 2H_2SO_{4(aq)} \rightarrow 2PbSO_{4(s)} + 2H_2O_{(l)}$