Effects of surface modifications of the LMNi3.9Co0.6Mn0.3Al0.2 alloy in a KOH/NaBH4 solution upon its electrode characteristics within a Ni-MH secondary battery

This study examined the effects of surface modifications of the LMNi3.9Co0.6Mn0.3Al0.2 (LM; Lanthanum rich misch metal) alloy in KOH solutions, both with and without NaBH4, on its electrode characteristics in a nickel-metal-hydride (Ni-MH) secondary battery at low and ambient temperatures. The activation behavior, discharge capacity, rate capability, and electrochemical catalytic activity of the alloy were significantly improved by surface treatment with a KOH/NaBH4 solution. This phenomenon is attributable to the alkaline treatment's removal of the oxide film and corrosion products on the surface of the alloy that can hinder surface activation, as well as its formation of a nickel- and cobalt-rich layer that exhibits high catalytic activity on the surface. (C) 2008 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.