High Quality Content by WIKIPEDIA articles! A nickel–metal hydride battery, abbreviated NiMH or Ni-MH, is a type of rechargeable battery. It is very similar to the nickel–cadmium cell (NiCd). NiMH use positive electrodes of nickel oxyhydroxide (NiOOH), like the NiCd, but the negative electrodes use a hydrogen-absorbing alloy instead of cadmium, being in essence 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 their energy density approaches that of a lithium-ion cell.