Effect of surface modification of TiV 2.1Ni 0.3 by ball-milling with MgNi on charge–discharge cycle performance

Abstract

Charge–discharge cycle performance of TiV 2.1Ni 0.3 alloy was markedly improved by surface modification with MgNi alloy using a ball-milling method. For the purpose of clarifying the effect of the surface modification, the change in the surface structure before and after the charge–discharge measurement was investigated by X-ray photoelectron spectroscopy (XPS). As a result, it was found that the mutual diffusion layer was formed after ball-milling for 3 h and it could work as a barrier against the deep corrosion of the components. This is thought to be responsible for the improvement of the charge–discharge cycle performance. However, the extension of the mutual diffusion layer by ball-milling for longer duration led to the acceleration of the corrosion, resulting in the formation of the thick oxide layers, probably due to the decrease in surface concentration of the Mg and Ni components and to the increase in those of the Ti and V components, causing the deterioration of the charge–discharge cycle performance.