Theoretical Design of Na-Rich Antiperovskites as Cathode Material for Sodium-Ion Batteries

Sodium-ion batteries (SIBs) have emerged as a promising alternative to lithium-ion batteries, driven by the natural abundance, low cost, nonflammability, and broad geographic availability of sodium. In this study, we investigate the electrochemical properties of Na 2 TMSO (TM: 3d transition metals) antiperovskites as potential cathode materials for SIBs, using Li 2 FeSO as a model system. Density functional theory calculations are employed to evaluate the phase stability, ion transport, and structural integrity of these materials. Interestingly, we find that, except for Na 2 FeSO and Na 2 CuSO, all compounds exhibit high formation energies above the convex hull ( E Hull ), indicating metastability at 0 K. A trend of decreasing unit cell volume is observed across the series from Ti 2+ to Cu 2+ . All pristine compounds adopt structures featuring trans -TMS 4 O 2 octahedra, where compression along the z -axis results in reduced D 4 h symmetry. The computed band gaps (∼3 eV) fall within the range typical of sodium cathode materials. On-the-fly machine learning molecular dynamics simulations suggest that these materials undergo local structural change under dynamic conditions. Upon desodiation, structural stability diminishes, particularly for Na 2 MnSO and Na 2 FeSO. Cell voltages, calculated for desodiation of 37.5%, are within 3.5 V vs Na/Na + . Finally, ab initio molecular dynamics simulations reveal high Na + ion diffusivity, with diffusion barriers around 0.3 eV, comparable to state-of-the-art materials such as Na 2 TiSO, Na 2 FeSO, and Na 2 NiSO, highlighting the potential of these antiperovskites as promising cathode candidates for next-generation SIBs.