Electrochemical hydrogen storage properties of ball-milled NdMg₁₂ alloy with Ni powders

The electrochemical characteristics of the ball-milled NdMg₁₂ alloys with Ni powders were investigated. The first discharge capacity of the ball-milled sample was improved from 770 to 1200 mAh/g when the Ni content in the alloy was increased from 150 to 200 wt%. Furthermore, the first discharge capacity of the ball-milled NdMg₁₂ + 200 wt % Ni composite was very close to that of the ball-milled PrMg₁₂ + 200 wt % Ni composite. However, the high rate dischargeability of the former was not as good as that of the latter. Further analysis by electrochemical impedance spectroscopy (EIS) technique reveals a larger reaction resistance in the ball-milled NdMg₁₂ + 200 wt % Ni composite, probably due to the formation of Nd oxide or Nd (OH)₃ film on the surface of alloy. Larger reaction resistance resulted in the lower high rate dischargeability of this sample. In addition, the ball-milled NdMg₁₂ + 200 wt % Ni composite exhibited better cycle performance due to the existence of the corrosion resistant Nd oxide or Nd (OH)₃ film. © 2007 International Association for Hydrogen Energy.