Electrochemical behaviors of a V–Ni amorphous binary alloy

Abstract

A novel V–Ni amorphous binary alloy prepared by ball-milling was characterized with electrochemistry and X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis. The alloy was found to exhibit a good activation property and a durable cycling stability. It was attributed to the amorphous structure of the alloy with a high defect density and the extra energy accumulating during mechanical alloying. In the present paper, the dissolution of V on the cyclic stability of V–Ni alloy was first studied. In the present experiment the V–Ni amorphous alloy shows no capacity decay even after 50 cycles, and the capacity decay for the V–Ti–Ni alloy is mainly due to the formation of a TiO2 layer instead of the dissolution of V. The effect of the structural features of the amorphous alloys on the capacity of the alloy was studied next. The discharge capacity is found to be contributed to mainly the protons stored in the V4 and V3Ni tetrahedral interstices. By using a constant current discharge technique, the average hydrogen diffusion coefficient in the amorphous solid solution is determined to be 3.77×10−11 cm2 s−1, and is a function of the state of the charge in the V–Ni alloy.