oa High Performance Metal Hydride Alloy for Rechargeable Battery Technology

Nickel metal hydride (NiMH) rechargeable battery technology is currently the major competitor to well-established nickel cadmium (NiCad) technology. Due to new legislation in the European Union and elsewhere, NiCad cells are gradually being replaced to reduce the use of toxic cadmium, and NiMH cells are predicted to be a reliable alternative. NiMH batteries provide a higher energy density and are environmentally more acceptable than NiCad cells. In addition they have a low memory effect, allowing easy charging and discharging. However, current NiMH technology has limitations, particularly when cells are rapidly charged/discharged, and the lifetime of a cell is ~ 500 cycles, compared to ~ 1000 cycles for NiCad. Here, we report advances enabling rapid charging/discharging to be achieved by the modification of the surface of the metal hydride alloy with platinum group metals. This enhances the rates of sorption of hydrogen within the alloy, and the alloy is shown to be stable in air. An overview of NiMH battery technology is presented and developments resulting in high performance cells are described.