Chemistry > Electrochemistry > 17.0 Battery
Electrochemistry
1.0 Introduction
2.0 Conductors and Non-Conductors
3.0 Electrochemical Cells
4.0 Electrolysis and electrode Reactions
5.0 Electrochemical Cell
6.0 Electrode Potential
7.0 Nature of Electrodes
8.0 IUPAC Cell Representation and Convention
9.0 Standard Cell EMF and Standard Reduction Potential
10.0 Electropositive Character of Metals
11.0 Difference between EMF and potential difference
12.0 Nernst Equation
13.0 Laws of Electrolysis
14.0 Electromotive Force
15.0 Thermodynamics of the Cells
16.0 Concentration Cells
17.0 Battery
18.0 Fuel Cell
17.2 Secondary Cells
These are rechargeable batteries by passing current through them and can be used again and again. These are also called accumulators and storage cells.
Most common are lead accumulators and Nickel Cadmium accumulators.
Lead Storage Battery:
It is commonly used in automobiles and invertors. It consists of a lead anode and a grid of lead packed with lead dioxide $(PbO_2)$ as cathode. A $38\%$ solution of sulphuric acid is used as an electrolyte. The cell reactions when the battery is in use are:
At Anode: $$Pb + S{O_4}^{2 - }(aq) \to PbS{O_4}(s) + 2{e^ - }$$
At Cathode: $$Pb{O_2}(s) + S{O_4}^{2 - }(aq) + 4{H^ + }(aq) + 2{e^ - } \to PbS{O_4}(s) + 2{H_2}O(l)$$
Overall Reaction: $$Pb(s) + Pb{O_2}(s) + 2{H_2}S{O_4}(aq) \to 2PbS{O_4}(s) + 2{H_2}O(l)$$
On charging the battery, the reaction is reversed and $PbSO_4\ (s)$ on anode and cathode is converted into $Pb$ and $PbO_2$, respectively.
Nickel Cadmium Cell:
As compared to lead storage battery, it has longer life but it is more expensive to manufacture. The overall reaction during discharge is $$Cd(s) + 2Ni{(OH)_3}(s) \to CdO(s) + 2Ni{(OH)_2}(s) + {H_2}O(l)$$
