Question

What is a nickel metal hydride battery?

Answer 1

1. A nickel-metal hydride $\left(\mathrm{NiMH}\right)$ battery has an alkaline electrolyte which is Potassium hydroxide ($\mathrm{KOH}$).
2. It is a type of rechargeable battery.
3. The negative electrode (anode) consists of a metallic hydride compound, $\mathrm{M}$.
4. Positive electrode (cathode) is Nickel hydroxide or $\mathrm{Ni}{\left(\mathrm{OH}\right)}_2$.
5. The reactions occur from the left to the right direction during charging and right to left direction during discharge.
6. The reaction at the negative electrode is,
   ${\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)+\mathrm{M}\left(\mathrm{s}\right)+{\mathrm{e}}^{-}\underset{\mathrm{Discharge}}{\overset{\mathrm{Charging}}{\rightleftarrows }}{\mathrm{OH}}^{-}\left(\mathrm{aq}\right)+\mathrm{MH}\left(\mathrm{s}\right)$
7. The reaction at the positive electrode is,
   $$\begin{gathered} \mathrm{Ni}{\left(\mathrm{OH}\right)}_2\left(\mathrm{s}\right)+{\mathrm{OH}}^{-}\left(\mathrm{aq}\right)\underset{\mathrm{Discharge}}{\overset{\mathrm{Charging}}{\rightleftarrows }}\mathrm{NiO}\left(\mathrm{OH}\right)\left(\mathrm{s}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)+{\mathrm{e}}^{-} \\ \mathrm{Nickel}\mathrm{hydroxide}\mathrm{Nickel}\mathrm{oxyhydroxide} \end{gathered}$$
8. It is commonly used in laptops, phones, camcorders, or other electronic devices.
9. These batteries have a higher voltage than $\mathrm{Ni}-\mathrm{Cd}$ batteries.