Structure and electrochemical characteristics of melted composite Ti0.10Zr0.15V0.35Cr0.10Ni0.30–LaNi5 hydrogen storage alloys

The structure and electrochemical characteristics of melted composite Ti0.10Zr0.15V0.35Cr0.10Ni0.30 + x% LaNi5 (x = 0, 1, 5 and 10) hydrogen storage alloys have been investigated systematically. XRD shows that the matrix phase structure of V-based solid solution phase with a BCC structure and C14 Laves phase with hexagonal structure is not changed after adding LaNi5 alloy. However, the amount of the secondary phase increases with increasing LaNi5 content. Field emission scanning electron microscopy–energy dispersive spectroscopy (FESEM–EDS) shows that the C14 Laves phase contains more Zr and the white lard phase has a composition close to (Zr, Ti)(V, Cr, Ni, La)2. The electrochemical measurements show that the hysteresis effect decreases dramatically with increasing x. The activation performance, the low temperature dischargeability, high rate dischargeability and cyclic stability of composite alloy electrodes increase greatly with increasing x. The maximum discharge capacity first increases as x increases from 0 to 5 and then decreases when x increases further from 5 to 10. The improvement of the electrochemical characteristics caused by adding LaNi5 seems to be related to formation of the secondary phase.