Give the different types of Batteries and explain the construction and working of each type of battery.

(a) Primary battery: - It is an electrochemical cell which act as a source of electrical energy without being previously charged up by any electric current.
Eg:-Leclanche cell, dry cell, mercury cell etc. they cannot be used again and again because they become dead over a period of time, and they can’t be recharged.
(i) Leclanche cell:- This cell consists of carbon rod in a porous pot and enclosed with a mixture of carbon powder and MNO₂ acts as cathode. Amalgamated Zn rod acts as anode. Both elecrodes are dipped in 20% NH₄Cl solution in a glass pot. The chemical energy is converted into electrical energy. It does not maintain study current for long periods.
(ii) Dry cell:- Dry cell is the modification of leclanche cell. The dry cell is cyllindrical Zn vessel covered with a cardboard and it acts as negative electrode. A caron rod (graphite) placed at centre of the Zn vessel act as positive electrode and it is surrounded by a paste of carbon and MNO₂. the space between Zn vessel and a paste of C + MNO₂ is filled with another paste of NH₄Cl + ZnCl₂ and these two pastes are seperated by porous sheet. Here MNO₂ acts as cathode depolariser and facilitate the discharge of H⁺ ion

Electrode reactions:- At cathode 
${\mathrm{MnO}}_2+{\mathrm{NH}}_4^{+}+\mathrm{e}\to \mathrm{MnO}\left(\mathrm{OH}\right)+{\mathrm{NH}}_3$ At anode $\mathrm{Zn}\to {\mathrm{Zn}}^{+2}+2\mathrm{e}$
EMF of dry cell is 1.5V. These are used in clocks, transisters, torches etc.
(b Secondary Battery: - A chemical device in which electrical energy may be stored in the form of chemical energy (electrolysis) from an external source. When the external source of current is removed, and the cell is made to operate in the reserve direction is called secondary battery.
→Simply secondary cell is the storage cell of electrical energy in the form of chemical energy.
→ Secondary cell is mostly reversible cell and the reverse chemical reactions takes place during charging and discharging.
Eg:- Lead accumulator (acid storage battery), Edison battery (alkali stroage cell), Ni-Cd cell etc.,
(1) It is a reversible galvanic cell and used as storage battery (secondary cell)
(2) it is also called lead storage battery.
(3) It consists of two lead electrodes. Spongy lead acts as anode and lead coated with PbO₂ a c t s as cathode.
(4) The cell is represented as Pb / PbSO₄, H₂SO₄, PbSO₄₍₂₎ PbO_2(s) / pb
(5) 20% aqueous H₂SO₄ is used as an electrolyte.
(6) When the battery is in use (discharge), the follwing cell reactions are take place
(7) At anode:  ${\mathrm{Pb}}_{\left(\mathrm{s}\right)}+{\mathrm{SO}}_4^{-2}\to {\mathrm{PbSO}}_4+2{\mathrm{e}}^{-}$
At cathode:-
${\mathrm{PbO}}_{2\left(\mathrm{s}\right)}+{{\mathrm{SO}}_{4\left(\mathrm{aq}\right)}}^{-2}+4{\mathrm{H}}^{+}+2{\mathrm{e}}^{-}\to {\mathrm{PbSO}}_{4\left(\mathrm{s}\right)}+2{\mathrm{H}}_2{\mathrm{O}}_{\left(\mathrm{l}\right)}$
The overall cell is :-
${\mathrm{Pb}}_{\left(\mathrm{s}\right)}+{\mathrm{PbO}}_{2\left(\mathrm{s}\right)}+2{\mathrm{H}}_2{\mathrm{SO}}_{4\left(\mathrm{aq}\right)} \underset{\mathrm{charg} \mathrm{ing}}{\overset{\mathrm{disch} \arg \mathrm{e}}{\rightleftarrows }} 2{\mathrm{PbSO}}_{4\left(\mathrm{s}\right)}+2{\mathrm{H}}_2{\mathrm{O}}_{\left(1\right)}$
(8) On charging the battery, the electrode eactions are reversed.
(9) The voltage increases with increase in the concentration of the electrolyte. The voltage
varies from 1.88V (5% H₂SO₄) to 2.15V (40% H₂SO₄)
(10) It is used in inverters and automobile vehicles.