TiMn-based AB₂-type alloys have emerged as promising candidates for large-scale hydrogen storage applications due to their high theoretical capacity, room-temperature reversibility, and cost-effectiveness. However, their practical deployment has been hindered by sluggish activation kinetics and insufficient cyclic stability. This study addresses these limitations through strategic Ni substitution at Fe sites in the B-side sublattice, guided by first-principles calculations and experimentally validated via vacuum arc melting. The optimized Ti_0.65Zr_0.35Cr_0.85Mn_0.95Fe_0.196Ni_0.004 alloy demonstrates exceptional hydrogen storage performance, attributed to the charge redistribution among all constituent atoms in the alloy, which is induced by the strong electronegativity of Ni. Crucially, this study demonstrates that optimizing hydrogen storage performance requires a dual consideration of electronic interactions and volumetric effects. The Ni-substituted alloy achieves unprecedented cyclic stability, retaining 1.91 wt.% capacity (100% retention) over 100 cycles at 318 K under 5.5 MPa H₂ pressure, and maintaining 99.46% capacity after 1000 cycles, which the highest reported durability for TiMn-based AB₂-type systems. Mechanistic analysis reveals that Ni substitution significantly enhances structural resilience by effectively suppressing lattice pulverization and mitigating cyclic stress-induced degradation, thereby maintaining a well-preserved micron-scale architecture throughout cycling. These findings provide transformative insights for designing high-capacity and long-lifespan AB₂-type alloys.

High density and safe storage of hydrogen are the preconditions for the large-scale application of hydrogen energy. Herein, the hydrogen storage properties of Ti_0.6Zr_0.4Cr_0.6Mn_1.4 alloys are systematically studied by introducing Y element instead of Ti element through vacuum arc melting. After the partial substitution of Y, a second phase of rare earth oxide is added in addition to the main suction hydrogen phase, C14 Laves phase. Thanks to the unique properties of rare earth elements, the partial substitution of Y can not only improve the activation properties and plateau pressure of the alloys, but also increase the effective hydrogen storage capacity of the alloys. The comprehensive properties of hydrogen storage alloys are improved by multidimensional regulation of rare earth elements. Among them, Ti_0.552Y_0.048Zr_0.4Cr_0.6Mn_1.4 has the best comprehensive performance. The alloy can absorb hydrogen without activation at room temperature and 5 MPa, with a maximum hydrogen storage capacity of 1.98 wt.%. At the same time, it reduces the stability of the hydride and the enthalpy change value, making it easier to release hydrogen. Through theoretical analysis and first-principle simulation, the results show that the substitution of Y element reduces the migration energy barrier of hydrogen and the structural stability of the system, which is conducive to hydrogen evolution. The alloy has superior durability compared to the original alloy, and the capacity retention rate was 96.79% after 100 hydrogen absorption/desorption cycles.