Single atom catalysts adsorbed on reduced monolayers for enhanced kinetics in Al-S batteries

Rechargeable aluminum-sulfur (Al-S) batteries have attracted significant attention as potential next-generation energy storage devices due to their safety, the natural abundance of the elemental components, and high theoretical energy density. However, their utilization is hindered by sluggish reaction kinetics and poor reversibility. Introducing single-atom catalysts (SACs) can promote redox processes at the cathode and help in mitigating the shuttle effect of Al polysulfides (Al₂S_x). While the electrochemical, thermodynamic, and thermal stabilities of SACs (Co, Fe, Ir, Ni, Pt, and Rh) have been explored in previous studies, this work focuses on their potential role in enhancing reaction kinetics in Al-S batteries. Our calculations indicate that SACs-based substrates exhibit more robust binding energies for capturing Al₂S_x than the bare surfaces. Additionally, SACs lower the free energies associated with the rate-determining step during discharging and exhibit lower decomposition barriers during charging. Moreover, the interaction of soluble Al₂S_x with the electrolyte reveals that SAC supported polysulfides are less likely to dissolve in the electrolyte than their pristine counterparts. The analysis of the underlying mechanisms of the interaction of molecules and the Co@ substrate reveals the ability of this substrate to accommodate large volume changes and support a sulfur loading up to 53.37 wt% during the charging and discharging cycles, without causing fractures. The mechanism driving this enhanced performance is extensively investigated through charge transfer, bond strength, and d-band center analyses. Our findings present an effective strategy for designing SACs substrates to improve the electrochemical performance of Al-S cathodes.