Prolonging cycling life of AB3-type superlattice alloys by adjusting hydrogen absorption/desorption behaviors of [A2B4] and [AB5] subunits.

AB 3 -type La-Mg-Ni-based hydrogen storage alloys are known for their high electrochemical hydrogen storage capacity. However, their practical application has been hindered by fast capacity degradation. Herein, we managed to improve their cycle life by synchronizing the hydrogen absorption/desorption behaviors of [A 2 B 4 ] and [AB 5 ] subunits based on a series of AB 3 -type single-phase La 0.60 R 0.12 Mg 0.28 Ni 3 (R = La, Pr, Nd, Gd) superlattice alloys. This is achieved by the preferable occupation of Pr, Nd and Gd in [A 2 B 4 ] subunits rather than [AB 5 ] subunits compared to La, which decreases the volume difference between [A 2 B 4 ] and [AB 5 ], significantly reducing the mismatch between [A 2 B 4 ] and [AB 5 ] during hydrogen absorption/desorption. Resultantly, the microstrain of the R = Gd alloy is only half that of the R = La alloy, leading to enhanced anti-pulverization and anti-oxidation/corrosion resistance, as well as an improved cycle stability. The S 100 of the R = Gd alloy is more than 15 % higher than the R = La alloy. Moreover, the plateau pressure is adjusted to a proper level, enabling an increase in the high-rate dischargeability (HRD 1500) from 53.6 % (R = La) to 66.4 % (R = Gd). This work provides impressive insights into developing high-performance superlattice hydrogen storage alloys. [Display omitted] • Single-phase AB 3 -type superlattice alloys with different RE elements are acquired. • V [A2B4] and V [AB5] are equalized by selective occupation of RE elements. • H 2 absorption/desorption of [A 2 B 4 ] and [AB 5 ] subunits are synchronized. • Not only is cycle stability greatly enhanced, but HRD is also improved. [ABSTRACT FROM AUTHOR]