Write short note on lead storage battery.

Explanation

In the lead-storage cell, anode is made up of number of plates joined in parallel sequence. Each plate is a grid of lead filled with spongy lead. Cathode also consists of equal number of plates connected in parallel sequence. Each plate is a grid of lead packed with lead dioxide. The arrangement is shown in the figure. These plates are separated by thin fibre glass sheets.
The whole arrangement is suspended in dilute `H_(2)SO_(4)`, taken in a hard rubber vessel. Here, `H_(2)SO_(4)` acts as electrolyte. The electrode reactions taking place during discharging are as follows :
At anode : `Pb(s)+SO_(4)^(2-)(aq)rarrPbSO_(4)(s)+2e^(-)` (Oxidation)
At cathode : `PbO_(2)(s)+SO_(4)^(2-)(aq)+4H^(+)(aq)+2e^(-)rarrPbSO_(4)(s)+2H_(2)O(l)` (Reduction)
Overall cell reaction : `Pb(s)+PbO_(2)(s)+4H^(+)(aq)+2SO_(4)^(2-)(aq)rarr2PbSO_(4)(s)+2H_(2)O(l)`
Thus, during discharging, `H_(2)SO_(4)` is used up.
During recharging, the cell is operated like an electrolytic cell. The electrode reaction are the reverse of discharging
`PbSO_(4)(s)+2e^(-)rarrPb(s)+SO_(4)^(2-)(aq)` (Reduction)
`PbSO_(4)(s)+2H_(2)O(l)rarrPbO_(2)(s)+SO_(4)^(2-)(aq)+4H^(+)2e^(-)` (Oxidation)
Overall cell reaction : `2PbSO_(4)(s)+2H_(2)O(l)rarrPb(s)+PbO_(2)(s)+4H^(+)(aq)+2SO_(4)^(2-)(aq)`.
`Pb(s)+PbO_(2)(s)+4H^(+)(aq)+2SO_(4)^(2-)(aq)underset("Charging")overset(("Discharging"))iff2PbSO_(4)(s)+2H_(2)O(l)`.