Abstract: Rare earth (RE)-based hydrogen storage alloys with superlattice structure, recognized for their high hydrogen storage capacity and safety, are considered crucial materials to overcome the hydrogen storage and transportation bottleneck. This review summarized and discussed the key challenge of synthesizing RE-based single-phase superlattice alloys with high performance. First, it is demonstrated through detailed case studies how strategic A- and B-side substitutions in RE-based superlattice alloys effectively optimize phase composition, abundance, and subunit volume mismatch. Subsequently, the functionality and limitations of primary preparing methods, including melting, melt spinning, powder sintering, and mechanical alloying, are elucidated. Furthermore, the principles and procedures of two essential post-processing techniques, annealing and quenching, essential for single-phase formation, are discussed in depth. At last, significant challenges facing the efficient synthesis of high-performance RE-based superlattice alloys are critically analyzed, encompassing unclear synergistic mechanisms in multi-element substitution, narrow annealing/quenching temperature windows for single-phase synthesis, and uncertain phase transformation mechanisms during annealing. Accordingly, Potential solutions to mitigate these challenges are proposed. In conclusion, this review presents an integrated process flow for developing high-performance RE-based superlattice alloys, spanning rational composition design, preparation, and tailored post-processing.

Key words: Hydrogen storage materials, Rare earth-based alloys, Superlattice structures, Phase-structural modulation, Single-phase synthesis