Phase Structure and Electrochemical Properties of RE-Mg Based Composite Hydrogen Storage Alloys

A new type of AB5-x%LaMg3（x=2, 3, 4, 5, 6, 7, 8）composite hydrogen storage alloys were prepared by sintering the powder mixtures of a commercial AB5 alloy and LaMg3 alloy. The phase structure and electrochemical characteristics of the composite hydrogen storage alloys were also studied. It is shown that AB5-x%LaMg3（x=2, 3, 4, 5, 6, 7, 8）composites have mult; phase structure. The matrix phase has CaCu5 structure, the second phase is LaNi3 phase. The maximum discharge capacity, discharge capacity at low temperature and HRD of AB5 alloy electrodes are greatly improved after the composite. The maximum discharge capacity of the composite electrodes increases from 325 mAh·g-1 for x=0 to 358 mAh·g-1 for x=5, and the HRD of the composites for x=5 at the current density of 1200 mA·g-130% of that of the alloy at 60 mA·g-1. The discharge capacity of AB5-x%LaMg3 composite alloy electrode at 233 K is up to 174 mAh·g-1. The improvement of the electrochemical characteristics of the composite electrodes seems to be related with formation of the LaNi3 second phase.