EFFECT OF PARTIAL SUBSTITUTION IN TINI ON ITS STRUCTURAL AND ELECTROCHEMICAL HYDROGEN STORAGE PROPERTIES

TiNi is known to react with hydrogen to form a high solubility solid solution by electrochemical reaction in concentrated KOH, and thus this compound is a good candidate to be used in nickel-hydride batteries. In order to improve the absorption properties, several substitutions are proposed using a combination of thermodynamic and geometrical models. Among the (Ti1-x-yZrBx)Ni type compounds (where B = Al, Mo, Si, V), the silicon and vanadium containing alloys are single phase. The crystallographic structure of vanadium substituted alloy is cubic CsCl type with a cell parameter 1 % higher than TiNi. Concerning the vanadium containing alloy, the solid-gas capacity measured by the volumetric method is 35% higher than TiNi (0.95 H/M) and the reversible electrochemical capacity determined at constant potential is 40% higher (350 mAh/g).