Effects of lithium addition in AB2 metal hydride alloy by solid-state diffusion

In this study, microstructures and electrochemical properties of a Zr-based AB(2)-type metal hydride alloy (Ti12.1Zr21.3V10.3Cr7.5Mn8.1Co0.8Ni31.7Al0.8) doped with 6 wt% LiH by solid-state diffusion at different temperatures were investigated and compared with those of the base alloy sintered at the same conditions. Structural study by x-ray diffraction analysis exhibited a lattice expansion in the main C14 phase of the Li-doped alloys with a relatively low sintering temperature, indicating that Li incorporated into the C14 Laves phase but was evaporated at higher sintering temperatures. Addition of Li deteriorated both the electrochemical capacity and activation easiness; however, it improved the high-rate discharge-ability (HRD). The benefit of Li addition on HRD can be associated with the increase in amount of metallic nickel clusters embedded in the surface oxide (estimated by the saturated magnetic susceptibility) and was a strong function of sintering temperature. As the sintering temperature increased, HRD increased due to the increase in amount of surface catalytic metallic nickel. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.