NiMH
Short for Nickel-Metal Hydride and also abbreviated as Ni-MH, NiMH is a rechargeable battery used primarily in portable computers.
Research of the NiMH system started in the seventies as a means for hydrogen storage for a Nickel Hydrogen battery. The metal hydride alloys were unstable in the cell environment and the desired performance characteristics could not be achieved. As a result, the development of the NiMH slowed down. New hydride alloys were developed in the 1980's that were stable enough for use in a cell. Since the late eighties, the NiMH has steadily improved, mainly in terms of energy density. Design engineers have indicated that the NiMH has a potential of higher energy densities.
Also see: Battery definitions, Li-Ion, Ni-Cad