History
See also: History of the batteryThe first consumer grade NiMH cells for smaller applications appeared on the market in 1989, the culmination of over two decades of research and development.
The earliest pioneering work on NiMH batteries—essentially based on sintered Ti2Ni+TiNi+x alloys for the negative electrode and NiOOH-electrodes for the positives—was performed at the Battelle-Geneva Research Center starting after its invention in 1967. The development work was sponsored over nearly two decades by Daimler-Benz in Stuttgart, Germany, and by Volkswagen AG within the framework of Deutsche Automobilgesellschaft, now a subsidiary of Daimler AG. The batteries showed high specific energy up to 50 W·h/kg (180 kJ/kg), power density up to 1000 W/kg and a reasonable life of 500 charge cycles (at 100% depth of discharge). Patent applications were filed in European countries (priority: Switzerland), the United States, and Japan, and the patents transferred to Daimler-Benz.
Interest grew in the 1970s with the commercialisation of the nickel–hydrogen battery for satellite applications. Hydride technology promised an alternative much less bulky way to store the hydrogen. Research carried out by Philips Laboratories and France's CNRS developed new high-energy hybrid alloys incorporating rare earth metals for the negative electrode. However, these suffered from the instability of the alloys in alkaline electrolyte and consequently insufficient cycle life. In 1987, Willems and Buschow demonstrated a successful battery based on this approach (using a mixture of La0.8Nd0.2Ni2.5Co2.4Si0.1) which kept 84% of its charge capacity after 4000 charge-discharge cycles. More economically viable alloys using mischmetal instead of lanthanum were soon developed and modern NiMH cells are based on this design.
Ovonic Battery Co. in Michigan altered and improved the Ti-Ni alloy structure and composition according to their patent and licensed NiMH batteries to over 50 companies worldwide. Ovonic's NiMH variation consisted of special alloys with disordered alloy structure and specific multicomponent alloy compositions. Unfortunately, linked to their composition, the calendar and cycle life of such alloys always remains very low, and all NiMH batteries manufactured at the present time consist of AB5-type rare earth metal alloys.
Positive electrode development was done by Dr. Masahiko Oshitani from GS Yuasa Company, who was the first to develop high-energy paste electrode technology. The association of this high-energy electrode with high-energy hybrid alloys for the negative electrode led to the new environmentally friendly high-energy NiMH cell.
Currently, more than 2 million hybrid cars worldwide are running with NiMH batteries, Many of these batteries are manufactured by PEVE (Panasonic) and Sanyo.
In the EU and due to the Battery Directive, Nickel–metal hydride batteries have replaced Ni–Cd batteries for portable use by consumers.
Read more about this topic: Low Self-discharge Ni MH Battery
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