Nickel-Metal Hydride Battery

MH + NiOOH → M + Ni(OH)₂

Overview

NiMH batteries use a metal hydride anode (typically a rare earth/nickel alloy like AB₅ or AB₂) and nickel oxyhydroxide cathode in KOH electrolyte. Cell voltage is 1.2 V with energy density of 60–120 Wh/kg. They replaced NiCd batteries due to lack of toxic cadmium and higher capacity.

Everyday Example

Rechargeable AA batteries (Eneloop, etc.) and early hybrid cars like the Toyota Prius used NiMH technology.

Industrial Importance

NiMH batteries power millions of hybrid vehicles. Toyota's Prius used NiMH from 1997–2015 before transitioning to lithium-ion.

Properties

Type: Electrochemical
Reversible: Yes
Energy: Exothermic
ΔH: -120.0 kJ/mol

Related Reactions

Alkaline Battery Discharge Anodizing of Aluminum Cathodic Protection (Zinc Sacrificial Anode) Chlor-Alkali Electrolysis Chrome Electroplating Copper Electroplating Daniell Cell (Zinc-Copper Galvanic Cell) Electrochemical CO₂ Reduction to CO Electrochemical Machining (ECM) Electrolysis of Molten NaCl (Downs Process)

Frequently Asked Questions

What is the equation for Nickel-Metal Hydride Battery?

The balanced equation is: MH + NiOOH → M + Ni(OH)₂.

What type of reaction is Nickel-Metal Hydride Battery?

Nickel-Metal Hydride Battery is a electrochemical reaction. It is reversible under certain conditions.

Is Nickel-Metal Hydride Battery exothermic or endothermic?

Nickel-Metal Hydride Battery is exothermic (releases energy). The enthalpy change (ΔH) is -120.0 kJ/mol.