Heat-treatment effects of V-based solid solution alloy with TiNi-based network structure on hydrogen storage and electrode properties

Heat-treatment at 973-1473 K was conducted on a V3TiNi0.56 alloy which consisted of a V-based solid solution main phase for hydrogen storage and a TiNi-based secondary phase for electrochemical reaction. Heat-treatment at 1073 K was found to improve the durability during electrical charge-discharge cycles in Ni-MH cells because the corrosive vanadium content in the secondary phase was decreased by the heat-treatment. High-rate capability, however, was decreased by heat-treatment above 1273 K because of the increased grain size of the main phase and degradation of the TiNi-based network structure of the secondary phase.