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.