Nickel Metal Hydride Ni-MH accumulator

The Nickel Metal Hydride (Ni-MH) accumulator was developed in the 1970s to deal with the problem posed by the use of Cadmium in the Ni-Cd accumulator, and 

The negative electrode is a metal alloy capable of adsorbing and desorbing hydrogen. As with Ni-Cd accumulators, the positive electrode uses a nickel oxyhydroxide (NiOOH), which is reduced into nickel hydroxide (Ni(OH)2) during the course of the discharge. The electrolyte is also of the same type, i.e. an aqueous alkaline solution, comprising potassium hydroxide (KOH) or caustic soda (NaOH), with the possible addition of lithine (LiOH). 

The electrochemical reactions that occur at the electrodes are as follows  

Lifetime (number of cycles) 400-700 if the depth of discharge is 100% in each cycle 

The manufacturers of Ni-MH accumulators are Saft (France), Energizer (USA) for portable electronics, Panasonic (Japan) for the automobile industry and Varta/Johnson Controls (USA) [DEV 12], 

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