VANADIUM-BASED SOLID-SOLUTION ALLOYS WITH 3-DIMENSIONAL NETWORK STRUCTURE FOR HIGH-CAPACITY METAL HYDRIDE ELECTRODES

V-based alloys with a 3-D network structure of a TiNi phase provided h igh-capacity metal hydride electrodes for Ni-MH cells. The network of TiNi phase worked as a micro-current collector and electro-catalyst. I t was shown that the micro-structure and chemical composition of the n etwork phase remarkably influenced the electrochemical properties of t he V-based alloys. The kinetics of the electrochemical reaction of V3T iNix depended mainly on the volume fraction of the TiNi phase. The cyc lic durability was improved by decreasing vanadium content in the TiNi phase by heat-treatment. A network of C14-Laves type phase containing Hf could improve the high rate capability, while a network phase of C 14-Laves type phase containing Zr could not. By adding Co, Nb and Ta t o a V-Ti-Ni alloy, the durability during charge-discharge cycles was r emarkably improved.