Compositional optimization of vanadium-free hypo-stoichiometric AB2 metal hydride alloy for Ni/MH battery application

In an effort to reduce raw material cost and improve the charge retention characteristic of nickel metal hydride batteries, the Ti, Zr, and Ni-contents in vanadium-free AB₂ metal hydride alloys were optimized according to their capacity, charge retention, activation, high-rate capability, low-temperature performance, and cycle stability. A multi-component hypo-stoichiometric AB₂ alloy with a composition of Ti₁₀Zr₂₇Cr₈Mn₁₅Co₅Ni₃₅ was identified and compared to vanadium-containing AB₂ metal hydride alloys. Vanadium-free alloys provided better charge retention performance but with a trade-off in cycle life. The gaseous and electrochemical storage properties were correlated to both the average composition and the stoichiometry of the main AB₂ phases.