Microstructure Design of Metal Selenides for Sodium-Ion Battery Anodes

The advancement of sodium-ion batteries (SIBs) as next-generation energy storage systems is critically dependent on developing high-performance anode materials. Metal selenides have garnered significant attention as promising anode candidates due to their high theoretical capacities, yet their practical application is hampered by intrinsic issues such as large volume expansion, poor electrical conductivity, and structural pulverization during cycling. Engineering the microstructure of metal selenides offers a powerful avenue to overcome these limitations and unlock their full electrochemical potential. This review comprehensively summarizes recent progress in advanced microstructural engineering strategies for metal selenide anodes in SIBs, encompassing micro-morphology design (0D, 1D, 2D, 3D, and hierarchical architectures), heteroatom doping, defect engineering (vacancies, interstitials, grain boundaries), and heterostructure engineering (analogous and dissimilar interfaces). The fundamental principles, synthetic methodologies, and the profound impact of these strategies on modulating electronic structure, ion diffusion kinetics, active site density, and mechanical integrity are critically discussed. Emphasis is placed on how these tailored microstructures synergistically address the inherent challenges of metal selenides, leading to enhanced specific capacity, superior rate capability, and extended cycling stability. Finally, current challenges and future perspectives are outlined, aiming to inspire innovative design paradigms for high-performance, stable, and practical metal selenide anodes for advanced SIBs.