Function mechanism of Fe in improving cycle stability and plateau characteristics of AB5-type hydrogen storage alloys.

Rare-earth AB 5 -type alloys have great application potential in solid-state hydrogen storage. To further improve their plateau characteristics and cycling life, the effects of Fe on the long-term hydrogen storage properties of LaNi 5- x Fe x (x = 0, 0.5, 1) alloys are studied, and the function mechanisms are revealed. Fe induces a (Fe,Ni) phase layer with good ductility around LaNi 5 main phase, which plays a buffer role to relieve the microstrain during hydrogen absorption/desorption, thus stabilizing the crystal structure and improving the cycling performance. Further, Fe with larger atomic radius than Ni relieves the compression from 12 o to 6 m site of the LaNi 5 phase, and suppresses the plateau splitting phenomenon, resulting in a single and long hydrogen absorption/desorption plateau throughout 1000 cycles. This study promotes the understanding and application of cheap and effective Fe in improving the hydrogen storage properties of AB 5 -type alloys during long-term cycling. [Display omitted] • Long-term H 2 storage properties of LaNi 5- x Fe x alloys during 1000 cycles are studied. • (Fe,Ni) phase layer is induced by Fe addition. • (Fe,Ni) phase with good ductility decreases microstrain of H 2 absorption/desorption. • Fe addition relieves the stress of 6 m to 12 o sites, and suppresses plateau splitting. • Appropriate amount of Fe stabilizes crystal structure and increases capacity retention. [ABSTRACT FROM AUTHOR]