A nickel–metal hydride battery, abbreviated NiMH or Ni–MH, is a rechargeable battery. Its chemical reactions are similar to the nickel-cadmium cell (NiCd). NiMH uses positive electrodes of nickel oxyhydroxide (NiOOH), like the NiCd. However, the negative electrodes use a hydrogen-absorbing alloy instead of cadmium, offering a practical application of nickel-hydrogen battery chemistry. A NiMH battery can have two to three times the capacity of an equivalent size NiCd, and its energy density can approach that of a lithium-ion cell.
