Electrochemical hydrogen storage of ball-milled CeMg12 and PrMg12 alloys with Ni powders

The structure and electrochemical hydrogen storage properties of the ball-milled CeMg12 and PrMg12 alloys with Ni powder in the range of 150 and 200 wt.%, respectively, were investigated. It was found that the first discharge capacities of the ball-milled samples with 200 wt.% Ni were obviously larger than those of the samples with 150 wt.% Ni. In addition, discharge capacities of the ball-milled PrMg12 with Ni powders were larger than those of the ball-milled CeMg12 with the equivalent amount of Ni powders. The ball-milled PrMg12 + 200 wt.% Ni composite has the highest initial discharge capacity (1204 mAh/g) among these samples, although the cycle performance was not satisfactory as electrode materials in the practical applications of Ni/MH batteries at the current stage. The high rate dischargeability of the ball-milled PrMg12 + 200 wt.% Ni is better than that of the ball-milled CeMg12 + 200 wt.% Ni. The reason is that the CeO2 membrane causes the increase of the electrochemical reaction resistance in the ball-milled CeMg12 with Ni powders as analyzed by electrochemical impedance spectra (EIS). The lower reaction resistance and Warburg impedance contribute to the higher discharge capacity of the ball-milled PrMg12 + 200 wt.% Ni.