Capacity degradation study of AB4-type La-Y-Mg-Ni superlattice structure hydrogen storage alloy

In this study, an AB 4 -type La 2.5 Y 0.5 MgNi 14 alloy is synthesized by partially substituting La with Y in La-Mg-Ni alloys. The structure, hydrogen storage, and electrochemical properties of the alloys are systematically studied to elucidate capacity degradation mechanisms. The maximum hydrogen storage capacity of all alloys is approximately 1.4 wt%, with reversible hydrogen storage improving as the Y content increases. The AB 4 -type La-Y-Mg-Ni alloy exhibits excellent cycling stability in both hydrogen storage and electrochemical cycling. After 500 electrochemical cycles, its capacity retention is significantly higher than that of other alloys studied. The discharge capacity of all alloys reaches ∼230 mAh g −1 at a current density of 1000 mA g −1 . The AB 4 -type La-Y-Mg-Ni alloy demonstrates superior resistance to pulverization and corrosion. These findings suggest that optimizing Y content and synthesizing high stability AB 4 -type structures can enhance the cycle performance of Re-Mg-Ni-based alloys, making them suitable for long-life Ni/MH battery applications. • La/Y ratio optimization induces phase transition to form AB 4 superlattice structure. • Three alloys retain >90 % capacity after 20 hydrogen storage cycles. • Ex situ characterization reveals reversible structural transformation in AB 4 hydrides. • Multiphase synergy and phase boundaries enhance kinetic performance. • AB 4 -type La-Y-Mg-Ni alloy exhibits excellent pulverization and corrosion resistance.