Abstract >> In the present study, Ni and TaF5 were chosen as additives to enhance the hydriding and dehydriding rates of Mg. A sample with a composition of 80 wt% Mg + 14 wt% Ni + 6 wt% TaF5 (named 80Mg+14Ni+6TaF5) was prepared by high-energy ball milling in hydrogen. Its hydriding and dehydriding properties were then examined. At the fourth cycle, the activated sample absorbed 3.88 wt% H for 2.5 min, 4.74 wt% H for 5 min, and 5.75 wt% H for 60 min at 593 K under 12 bar H2. 80Mg+14Ni+6TaF5 had an effective hydrogen-storage capacity (the quantity of hydrogen absorbed for 60 min) of about 5.8 wt%. The sample desorbed 1.42 wt% H for 5 min, 3.42 wt% H for 15 min, and 5.09 wt% H for 60 min at 593 K under 1.0 bar H2. Line scanning results by EDS for 80Mg+14Ni+6TaF5 before and after cycling showed that the peaks of Ta and F appeared at different positions, indicating that the TaF5 in 80Mg+14Ni+6TaF5 was decomposed