Synergistically Enhanced Hydrogen Storage Kinetics and Cycling Stability by Secondary Phase in TiCrVNbFe High-Entropy Alloy

High-entropy alloys (HEAs) have garnered significant attention for their high hydrogen storage capacity, yet their hydrogen uptake kinetics and cycling stability require further improvement. In this study, adding 3 at.% Mn to the body-centered cubic (BCC) V₃₀Ti₂₅Cr₂₉Fe₆Nb₁₀ HEA induced the formation of a minor second phase. This enhanced hydrogen diffusion, reducing the time required for the alloy to reach 90% maximum hydrogen uptake by 23% (from 157 s to 121 s). Moreover, Mn addition reduced the pressure hysteresis factor from 1.84 to 1.39, which effectively lowered the thermodynamic barrier for hydrogen desorption and raised the reversible hydrogen storage capacity from 2.01 wt. to 2.06 wt.%. Furthermore, the incorporation of Mn significantly improved the cycling stability of the alloy, elevating the capacity retention rate after 20 hydrogen absorption and desorption cycles from 81.75% to 93.20%, an enhancement of 14%. These findings provide an effective strategy for developing high-performance hydrogen storage alloys.