Nickel–metal hydride battery

A nickel–metal hydride battery (NiMH or Ni–MH) is a type of rechargeable battery. The chemical reaction at the positive electrode is similar to that of the nickel-cadmium cell (NiCd), with both using nickel oxide hydroxide (NiOOH). However, the negative electrodes use a hydrogen-absorbing alloy instead of cadmium. NiMH batteries can have two to three times the capacity of NiCd batteries of the same size, with significantly higher energy density, although only about half that of lithium-ion batteries.

"NiMH" redirects here. For other uses, see NIMH.
Not to be confused with nickel–hydrogen battery.

Nickel–metal hydride battery
Modern Ni–MH rechargeable cells
Specific energy0.22-0.43 MJ/kg (60–120 W·h/kg)
Energy density140–300 W·h/L
Specific power250–1,000 W/kg
Charge/discharge efficiency66%–92%
Self-discharge ratePer month:
  • 13.9–70.6% at room temperature
  • 36.4–97.8% at 45 °C (113 °F)
  • Low self-discharge: 0.08–2.9%
Cycle durability180–2000 cycles
Nominal cell voltage1.2 V

They are typically used as a substitute for similarly shaped non-rechargeable alkaline batteries, as they feature a slightly lower but generally compatible cell voltage and are less prone to leaking.

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