Nickel-Cadmium Batteries

Nickel-Cadmium Batteries Points : Nickel-Cadmium Batteries Active material used for positive plate and the electrolyte used in nickel cadmium cells are the same as that used for nickel iron cell. For negative plate a mixture of cadmium and iron is used.

The number of positive plates used in nickel-cadmium cell is one more than the number of negative plates.

The working of nickel-cadmium cell is almost similar to nickel iron cell. When current passes through the cell, the electrolyte KOH breaks up into K and OH ions. During discharging the K ions move to anode and OW ions move to cathode. Following chemical changes take place when the cell is supplying current to the external circuit.

At Anode: Ni (OH)₂ + 2OH — Ni (OH)₄
and at Cathode: Cd + 2OH — Cd (OH)₂

When the cell is charged by connecting the anode to the positive terminal of supply and cathode with the negative terminal of supply the direction of current flow is opposite to that during discharging. Therefore, IC ions move to cathode and OH_- ions move to anode. Following chemical reactions take place during charging.

At Anode: Ni (OH)₂ + 2OH — Ni (OH)
At Cathode: Cd (OH)2 +2K — Cd + 2KOH

Nickel cadmium batteries are more suitable than nickel iron batteries for floating duties in conjunction with charging dynamo. Open circuit losses in these batteries are also low as compared to nickel iron batteries.