Structure and electrochemical properties of (La1−xDyx)0.8Mg0.2Ni3.4Al0.1 (x = 0.0–0.20) hydrogen storage alloys

The structure and electrochemical characteristics of (La1−xDyx)0.8Mg0.2Ni3.4Al0.1 (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)2Ni7, LaNi5 and (La, Mg)Ni2 phases. The introduction of Dy promoted the formation of (La, Mg)2Ni7 phase which possesses high hydrogen storage capacity, and controlling dysprosium content at 0.05 can obtain the maximum (La, Mg)2Ni7 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)2Ni7 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.

► Dysprosium as an alloying element promotes (La, Mg)2Ni7 phase formation.
► The increase of (La, Mg)2Ni7 phase is helpful for heightening discharge capacity.
► The maximum discharge capacity reaches up to 390.2 mAh/g.
► The cyclic stability remains 82.7% after 100 cycles.