Question

What is an Edison accumulator? Give its construction and working.

Answer 1

Edison Accumulator:

1. The Nickel-Iron alkaline cell was developed by an American scientist Thomson A. Edison in 1909. Therefore it is also known as Edison-cell.

Construction:

1. The nickel-iron battery construction is shown.
2. Nickel-Iron cell has two plates.
3. The active material of the positive plate is $Ni{\left(OH\right)}_4$ and the negative plate is iron (Fe).
4. The electrolyte is a solution of potassium hydroxide (KOH) with a small addition of lithium hydrate (LiOH) which increases the capacity of the cell.

Edison accumulator Working Principle:

1. The specific gravity of the electrolyte is $1.2$.
2. The container is also made of nickel-plated iron.
3. Negative plates are connected to the container.
4. Since a small quantity of electrolyte is used, therefore, it is quite compact.
5. Since a single cell produces a very low amount of current and voltage, many cells are connected in series and parallel to increase the current and voltage rating of a nickel-iron battery respectively.
6. When the battery is fully charged, its positive plate is of Ni(OH)₄ and its negative plate is of iron (Fe). The electrolyte used is potassium hydroxide (KOH).

Edison Accumulator:

1. The Edison storage cell is represented as :

$Fe\left(s\right)/FeO\left(s\right)/KOH\left(aq\right)/N{i}_2{O}_3\left(s\right)/Ni\left(s\right)$

The half-cell reactions are:

$N{i}_2{O}_3\left(s\right)+H_{2}O\left(l\right)+2e^{-}\to 2NiO\left(s\right)+2O{H}^{-}$
$FeO\left(s\right)+H_{2}O\left(l\right)+2e^{-}\to Fe\left(s\right)+2O{H}^{-}$