Effect of Ni content on the structural and electrochemical properties of Mg_1.9Cu_0.1Ni_χ alloys

Mg-based alloys, Mg_1.9Cu_0.1Ni_χ (χ = 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 χ = 1.8, compared with 435 mAhg^-1 for χ = 2.1. As to capacity degradation, 66.7 % of initial capacity was lost after 15 cycles for χ = 1.8, while only 47.2% for χ = 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 O 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. © J. New. Mat. Electrochem. Systems.