Influence of magnesium content on structure and electrochemical properties of La1-x,MgxNi1.75Co2.05 hydrogen storage alloys

La(1-)xMg(x)Ni(1.7)5Co(2.05) (x=0.07, 0.08, 0.10, 0.13, 0.15) alloys were prepared by high -frequency inductive method, and then their structure and electrochemical properties were investigated systematically. The XRD analysis revealed that the alloys consisted of LaNi5 phase and La4MgNi19 (Ce5Co19 + Pr5Co19) phase, and the introduction of Mg could promote the formation of La4MgNi19 phase. The observation of microstructure showed that all the alloys processed dendritic structure, which was refined with the increase of x value. The electrochemical measurements showed that all the alloys could be activated within 2 cycles, and with increasing x, the maximum discharge capacity obviously increased from 254.00 mAh/g (x=0.07) to 351.51 mAh/g (x=0.15), but the cycling stability (S-80) decreased somehow from 78.4% to 73.9%. Meanwhile, the appropriate addition of Mg could improve the high-rate discharge capacity (HRD) of the alloy electrodes, which was mainly controlled by the electrochemical reaction rate on the surface of the alloys.