Investigation on the structure and electrochemical properties of AB3-type La–Mg–Ni–Co-based hydrogen storage composites

Abstract

The La 0.7 Mg 0.3 Ni 2.75 Co 0.75 and Ti 0.17 Zr 0.08 V 0.35 Cr 0.1 Ni 0.3 alloys were prepared by vacuum magnetic levitation melting and the La–Mg–Ni–Co-based composites containing Ti 0.17 Zr 0.08 V 0.35 Cr 0.1 Ni 0.3 with different weight ratios (5, 10, 15 and 20%) were successfully synthesized by ball milling method. The XRD analyses showed that all these composites mainly consisted of the (La, Mg)Ni 3 phase with the rhombohedral PuNi 3 -type structure and the LaNi 5 phase with the hexagonal CaCu 5 -type structure, the cell volumes of the (La, Mg)Ni 3 phase increased with the increasing Ti 0.17 Zr 0.08 V 0.35 Cr 0.1 Ni 0.3 weight ratio, while the cell volumes of LaNi 5 phase decreased. The electrochemical measurements showed that the maximum discharge capacity of the composites decreased, and the cycling life improved distinctly with increasing Ti 0.17 Zr 0.08 V 0.35 Cr 0.1 Ni 0.3 weight ratio, which can be ascribed to the improved anti-corrosion performance of composite electrode in KOH solution. However, the electrochemical impedance spectroscopy (EIS) and anodic polarization (AP) measurements showed that the kinetics of composite electrodes was retarded with the increase of Ti 0.17 Zr 0.08 V 0.35 Cr 0.1 Ni 0.3 amount. These results suggest that the formation of composite with Ti 0.17 Zr 0.08 V 0.35 Cr 0.1 Ni 0.3 alloy is a promising strategy for improving the cyclic life of AB 3 -type La–Mg–Ni–Co-based alloy.