Vanadium-based solid solution alloys with three-dimensional network structure for high capacity metal hydride electrodes

V-based alloys with a 3-D network structure of a TiNi phase provided high-capacity metal hydride electrodes for Ni-MH cells. The network of TiNi phase worked as a micro-current collector and electro-catalyst. It was shown that the micro-structure and chemical composition of the network phase remarkably influenced the electrochemical properties of the V-based alloys. The kinetics of the electrochemical reaction of V3TiNix depended mainly on the volume fraction of the TiNi phase. The cyclic 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 C14-Laves type phase containing Zr could not. By adding Co, Nb and Ta to a V-Ti-Ni alloy, the durability during charge-discharge cycles was remarkably improved.