Nickel–metal hydride battery

A nickel–metal hydride battery is a type of rechargeable battery. The chemical reaction at the positive electrode is similar to that of the older nickel–cadmium cell (NiCd), with both using nickel oxide hydroxide, NiO(OH). However, the negative electrodes use a hydrogen-absorbing alloy instead of cadmium. NiMH batteries typically 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 batteries have almost entirely replaced NiCd.