The improvement of the hydrogenation properties of nickel-metal hydride battery alloy by surface modificaiton with platinum group metals (PGMs)

摘要

Because of their higher power densities, lowmemory effects and ore environmentally friendly constituents,Nickel Metal Hydride (NiMH) batteries gave become a strongcompetitor to NiCad batteries. The use of multicoponent alloyshas been found to improve cell lifetimes, while furtherimprovements to the cell performnace are obtained by surfacecoating or 'microencapsulation' technaiques with various metalsor metal oxides. In the present work, a technique of coatinghydride powders with one or more Platinum Group Metals (PGMs)has been developed, which enables the alloy to becharged/discharged rapidly with hydrogen with the additionaladvantage of being extremely resistant to deactivation. Thehydrogenation kinetics of the uncoated and PGM doped alloyswere assessed by gravimetric analysis, with periodic exposure tothe atmosphere in an attempt to deactivate the powders. It wasobserved that, in the solid-gas studies, the Ru and Pd/Ru coatedalloys were readily charged/discharged with hydrogen, even afterlong periods in air. Thus, the use of PGMs in this applicationrepresents a valuable advance both in the technology of NiMHbatteries and of hydrogen storage. 1999 Elsevier Science S.A. Allrights reserved.