Nickel–metal hydride battery
Type of rechargeable battery / From Wikipedia, the free encyclopedia
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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.[6]
Specific energy | 0.22-0.43 MJ/kg (60–120 W·h/kg) |
---|---|
Energy density | 140–300 W·h/L |
Specific power | 250–1,000 W/kg |
Charge/discharge efficiency | 66%[1]–92%[2] |
Self-discharge rate | Per month:
|
Cycle durability | 180[4]–2000[5] cycles |
Nominal cell voltage | 1.2 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.[7][8]