High-capacity Zr-based AB2-type alloys as metal hydride battery anodes

This work focused on the structural and electrochemical properties of AB2-type Zr/Ti-based metal hydride anode alloys. The as-cast and annealed Ti0.24Zr0.76Ni1.1Mn0.7V0.2 alloys were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical characterization (EC). X-ray diffraction (XRD) results indicated the presence of homogenous C14 Laves phase in the annealed alloy, and the major C15 and C14 phases coexisted with the TiNi and Zr9Ni11 secondary phases in the as- cast alloy. SEM images showed the phase compositions in these alloys and confirmed the significant decrease in the secondary phases of the annealed alloy. During EC, the as-cast alloy showed better activation performance than the annealed alloy. This result was related to the catalytic effect of the Ti-/Zr-related secondary phases during electrochemical reactions. Annealing increased the maximum discharge capacity from similar to 350 mAh/g for the as-cast alloy to similar to 400 mAh/g for the annealed alloy during activation. The annealed alloy also showed considerable cycling stability and a slightly high discharge rate. We developed a C14-Laves phase metal hydride alloy showing a discharge capacity similar to 400 mAh/g at a 100 mA/g rate (C/4) suitable for electric vehicle (EV) application. (c) 2020 Published by Elsevier B.V.