Effects of Co and Ti on the electrode properties of Mg3MnNi2 alloy by ball-milling process

Mg3MnNi2-x mol% M (M = Co, Ti; x = 0, 200) alloys are ball-milled for 30 min and their electrochemical hydrogen storage properties are investigated. X-ray diffraction studies show that Co and Ti facilitate the amorphization of Mg3MnNi2 alloy. The Co and Ti addition have been carried out for improvement of the anti-corrosion ability of the alloys. The electrochemical measurement indicates that the addition of Co and Ti can enhance the discharge capacity and cycle stability of the alloys. The maximum discharge capacities of ball-milled Mg3MnNi2, Mg3MnNi2-2Co and Mg3MnNi2-2Ti alloys are 206 mAhg(-1), 238 mAhg(-1) and 209 mAhg(-1), respectively. Although Mg3MnNi2-2Ti alloy has lower maximum discharge capacity, the capacity retaining rate of this alloy is much batter than those of Mg3MnNi2 and Mg3MnNi2-2Co alloys. Mg3MnNi2-2Ti alloy has kept 80% of its maximum discharge capacity at 10th cycle. Surface analyses indicate that the presence of Ti-oxide could retard the formation of corrosive reaction of the alloy surface. (C) 2012 Elsevier Ltd. All rights reserved.