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 AB(2) 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 AB(2) alloy with a composition of Ti10Zr27Cr8Mn15Co5Ni35 was identified and compared to vanadium-containing AB(2) 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 AB(2) phases. (C) 2011 Elsevier B.V. All rights reserved.