Nickel-Cadmium (NICAD) Battery

A nickel – cadmium battery is a type of alkaline storage battery. This is also a rechargeable battery. In a $Ni$ – $Cad$ cell, the anode is a cadmium electrode and the cathode is nickel oxide $(NiO 2)$ . The electrolyte is a solution of $KOH$ . The electrode and electrolytes are enclosed in a sealed container.

It is represented as:

Cd | Cd(OH)₂ || KOH |NiO₂ | Ni

Discharging:

The NICAD battery operates when, cadmium is oxidised to $Cd 2+$ ions and insoluble $Cd(OH) 2$ is formed. $Ni 2+$ ions then combine with $OH -$ ions to form $Ni(OH) 2$ .

At Anode : Cd_(s) + 2OH^–_(aq)⇌ Cd(OH)_2(s) + 2e^–

At Cathode:

2NiO 2(s) + 2H 2 O (1) +2e - ⇌ 2Ni(OH) 2(s) +2OH - (aq)

Overall cell reaction :

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2NiO 2(s) +Cd (s) + 2H 2 O (1) ⇌ Cd(OH) 2(s) + 2Ni(OH) 2(s) + Energy

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Here the reaction products formed are solids which adhere to the electrode surface. Hence, a direct current through the cell can readily reverse the reaction.

Recharging the battery

The recharging process is similar to lead storage battery. When the current is passed in the opposite direction, the electrode reaction gets reversed. So, $Cd$ gets deposited in the anode and $NiO 2$ in the cathode.

The net reaction during charging is :

Energy

Cd(OH) 2 (s) + Ni(OH) 2 (s) \to Cd(s) + NiO 2 (s) + 2H 2 O

Advantages and disadvantages of nickel-cadmium battery

Advantages	Disadvantages
1. It has longer life.	1. It is very expensive.
2. It has relatively high rates of discharge and recharge	2. Cadmium is highly toxic
3. It has ability to operate in low temperature.	–
4. It is compact and lighter and used in high current applications.	–

Uses:

It is used in industrial trucks, emergency power applications and communication equipments.
It is used in electronic calculators, etc.
Due to low temperature performance it is widely used in aircraft and space satellites.

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