Structures and electrochemical characteristics of Ti 0.26Zr 0.07V 0.24Mn 0.1Ni 0.33Mo x ( x = 0–0.1) hydrogen storage alloys

Abstract

Microstructures and electrochemical properties of Ti 0.26Zr 0.07V 0.24Mn 0.1Ni 0.33Mo x ( x = 0, 0.025, 0.05, 0.075, 0.10) electrode alloys have been investigated. The results of XRD analysis show that the alloys are mainly composed of V-based solid solution phase with body centered cubic (bcc) structure and C14 Laves phase with hexagonal structure. The addition of Mo element can improve the activation characteristics, maximum discharge capacity and cyclic durability for the electrode alloys. The discharge capacity of the electrode alloys increases with changing x from 0.025 to 0.10 within temperature region from 303 to 343 K. The results show that the discharge property of Ti 0.26Zr 0.07V 0.24Mn 0.1Ni 0.33Mo 0.075 electrode alloy at high temperature is the best, and its maximum discharge capacity is 633 mAh g −1 at 343 K. However, the high-rate dischargeability decreases and the self-discharge rate increases for Ti 0.26Zr 0.07V 0.24Mn 0.1Ni 0.33Mo x ( x = 0–0.10) electrode alloys with increasing Mo content. Electrochemical impedance spectroscopy (EIS) shows that the charge-transfer resistance at the surface of the alloy electrodes increases obviously with increasing Mo content.