A rechargeable battery using a hydrogen-absorbing alloy anode and nickel oxyhydroxide cathode.
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The nickel-metal hydride battery uses a nickel oxyhydroxide cathode and a hydrogen-absorbing metal alloy anode in potassium hydroxide electrolyte. Hydrogen is stored reversibly in the alloy during charging and released during discharge, giving about 1.2 V per cell. It replaced the toxic nickel-cadmium cell because it avoids cadmium and offers higher capacity. It has a higher self-discharge rate and lower energy density than lithium-ion cells. It was widely used in early hybrid vehicles and in rechargeable AA batteries.
Key ideas: NiMH cell: NiOOH cathode, metal hydride alloy anode (LaNi5 type) absorbing hydrogen, KOH electrolyte, 1.2 V nominal. Discharge: MH + OH- giving M + H2O + e- (anode) and NiOOH + H2O + e- giving Ni(OH)2 + OH- (cathode). Energy density is about 60 to 120 Wh/kg, higher than NiCd, and no toxic Cd.
Common mistakes and connections: Mistakes: mixing with NiCd (memory effect is much weaker in NiMH) and charging with the wrong charger. Self-discharge is relatively high; low-self-discharge versions exist. Hybrid cars such as Prius use it. Hydrogen is stored in the metal lattice, linking it to fuel cells and hydrogen storage.
A NiMH cell stores hydrogen in a metal alloy anode and releases it on discharge, giving about 1.2 V per cell with no toxic cadmium. The interactive lesson shows this as a live animation or chart.
A rechargeable AA NiMH cell provides about 1.2 V, slightly less than a fresh alkaline cell.
A rechargeable battery using a hydrogen-absorbing alloy anode and nickel oxyhydroxide cathode.
Nickel-Metal Hydride Battery is a advanced topic in Acids, Bases & Electrochemistry. It builds on beginner and intermediate topics, so review those first if needed.
Study these earlier topics in Acids, Bases & Electrochemistry first: Alkaline Battery, Lead-Acid Battery, Lithium-Ion Battery.
The next topics in Acids, Bases & Electrochemistry are Fuel Cells and Solid-State Batteries.
Yes. The interactive lesson includes a self-check question on Nickel-Metal Hydride Battery, and the Acids, Bases & Electrochemistry quiz draws on every topic in this area.
Nickel-Metal Hydride Battery is topic 72 of 105 in Acids, Bases & Electrochemistry.