Nickel metal hydride cell (NiMH)
The active components of a rechargeable NiMH battery in the charged state consist of nickel hydroxide (NiOOH) in the positive electrode and a hydrogen storing metal alloy (MH) in the negative electrode as well as an alkaline electrolyte.
The advantage compared to rechargeable NiCd batteries is the higher energy density per volume and weight. The substitution of cadmium is mostly used to create a positive image but in view of the recycling situation today this does not offer any lasting benefits. In several applications rechargeable NiMH batteries have replaced the rechargeable NiCd batteries.
The disadvantages are a higher sensitivity to high temperature, leading eventually to shorter service life (as in the case of high rate charge for power tools for example), greater temperature dependence and a higher cost.