Structure and electrochemical properties of (La _1-xDy _x) _0.8Mg _0.2Ni _3.4Al _0.1 (x = 0.0-0.20) hydrogen storage alloys

The structure and electrochemical characteristics of (La _1-xDy _x) _0.8Mg _0.2Ni _3.4Al _0.1 (x = 0-0.20) hydrogen storage alloys have been investigated. Dysprosium was adopted as a partial substitution element for lanthanum in order to improve electrochemical properties. The XRD, SEM and EDX results showed that the alloys were composed of (La, Mg) ₂Ni ₇, LaNi ₅ and (La, Mg)Ni ₂ phases. The introduction of Dy promoted the formation of (La, Mg) ₂Ni ₇ phase which possesses high hydrogen storage capacity, and controlling dysprosium content at 0.05 can obtain the maximum (La, Mg) ₂Ni ₇ phase abundance in the alloys. The maximum discharge capacity was heightened from 382.5 to 390.2 mAh/g, which was ascribed to (La, Mg) ₂Ni ₇ phase abundance increasing from 54.8% to a maximum (60.5%). Also, the biggest discharge capacity retention remained 82.7% after 100 cycles at discharge current density of 300 mA/g.