Corrosion behavior of Zn in electrolyte during the charge and discharge process and its influence on the electrochemical performance of zinc doped Mg2Ni1-xZnx rapidly quenched alloys

Abstract

In the electrochemical process, a continuous passivation layer of Mg(OH)2 is formed on the surface of Mg2Ni alloy particles and prevents the penetration of hydrogen atoms, which have a negative impact on the discharge capacity. In this work, Mg2Ni1-xZnx (x = 0, 0.17, or 0.33) rapid quenching alloys were prepared by partially replacing Ni with Zn in order to modify the surface of the alloy with the corrosiveness of Zn in alkaline solution. The microstructure results indicate that Zn doping promotes the corrosion of Mg2Ni alloy in the electrolyte, and many corrosion holes are formed on the surface after the electrochemical process. With the increase of Zn, the charge-transfer reaction resistance (Rct) and polarization resistance (Rp) of the alloy electrode increase from 306.24 and 366.41 mΩ to 508.76 and 526.57 mΩ, respectively, and the corrosion current density (Io) decreases from 70.08 to 48.77 mA/g. The appropriate amount of Zn atoms increases the discharge capacity, and the highest value can reach 92.94 mAh/g at x = 0.33. This reveals that corrosion holes are formed on the surface of Zn-doped alloys during the electrochemical process and destroy the continuity of the passivation layer on the Mg2Ni surface, which facilitate the penetration of hydrogen atoms.