Kinetic properties of La2Mg17–x wt.% Ni (x = 0–200) hydrogen storage alloys prepared by ball milling

•Addition of Ni on La2Mg17 and ball milling process form an amorphous.•Unstable hydrides were obtained via the addition of Ni.•The maximum hydrogen capacity of La2Mg17–50 wt.% Ni reached to 5.13 wt.% at 300 °C.•Electrochemical discharge capacity increase 54 times under addition of 200 wt.%Ni.

The as-cast La2Mg17 with different amount of Ni powders were mixed through ball milling to produce a new type of La2Mg17–x wt.% Ni (x = 50, 100, 150, 200) alloy. The microstructures of the alloys were characterized by XRD technique, the results show that the crystal structure transfers to amorphous one with the increasing amount of Ni powders. La2Mg17–50 wt.% Ni alloy reaches the highest hydrogen absorption capacity of 5.13 wt.% at 300 °C under 2 MPa hydrogen pressure due to its amorphous structure. Furthermore, La2Mg17–50 wt.% Ni alloy expresses fast hydriding kinetics and absorbs 4.99 wt.% hydrogen gas in 200 s. The hydrogen desorption ability described as discharge capacity during electrochemical reaction is fade next to La2Mg17–200 wt.% Ni alloy, attributed to the less Mg2NiH4 with lower enthalpies and easier to release H2. The maximum discharge capacity of La2Mg17–200 wt.% Ni alloy reaches to exciting 980.90 mAh/g, while the La2Mg17 alloy is only 18.10 mAh/g with inconspicuous improvement of cycle stability. These dramatic difference in electrochemical performance reflect the consequence of sluggish dehydriding process of La2Mg17–50 and 100 wt.% Ni alloys again. Whereas La2Mg17–200 wt.% Ni alloy has lower resistance both on alloy surface and in the bulk.