Effect of Ni content on the structural and electrochemical properties of Mg1.9Cu0.1Niχ alloys

Mg-based alloys, Mg1.9Cu0.1Ni chi (chi = 1.8, 1.9, 2.0, 2.1), were fabricated through high-energy ball milling, and the effects of nickel content on the electrochemical characteristics have been investigated. A high discharge capacity of 490 mAhg(-1) was observed for chi = 1.8, compared with 435 mAhg(-1) for chi = 2.1. As to capacity degradation, 66.7 % of initial capacity was lost after 15 cycles for chi = 1.8, while only 47.2 % for chi = 2.1. Cyclic Voltammograms (CV) indicates that nickel can help maintain redox reaction current and consequently improve the cycle performance. The X-ray mapping analysis indicates that Mg, Ni, and Cu are uniformly distributed in the particles. The 0 content in the alloy electrodes after 15 cycles decreases with the increase of Ni content in the alloys, suggesting that Ni can efficiently suppress the formation of Mg(OH)(2). The linear polarization curves show that the exchange current density, namely the rate of hydriding/dehydriding, increases from 13 mAg-1 to 133 mAg(-1) when the nickel content varies from 1.8 to 2.1. This is also considered as a reason for the observed improved capacity stability.