Phase Structures and Electrochemical Properties of V2.1TiNi0.4Zrx (x=0−0.06) Hydrogen Storage Electrode Alloys

The phase structures and electrochemical properties of the V2.1TiNi0.4Zrx (x=0-0.06) hydrogen storage electrode alloys have been investigated. It is found that all the alloys consist of a main phase of V-based solid solution with a bcc structure and a secondary phase with a three-dimensional network structure. The secondary phase precipitates along the grain boundaries of the main phase. For the alloys with Zr content x≤0.02, the secondary phase is the TiNi-based phase. As x reaches 0.04, the secondary phase changes into the C14-type Laves phase. Moreover, both the unit cell of the main phase and the secondary phase expand with increasing Zr content. Electrochemical measurements show that the activation behavior and maximum discharge capacities of the Zr-added alloy are better than those of the V2.1TiNi0.4 alloy. As the Zr content in the alloy increases, its high-rate dischargeability is improved significantly, but its cycle stability degrades gradually. For the alloy with the Zr content of x=0.04, the best overall electrochemical performance is obtained.