Advancing post-Li metal-sulfur batteries: In situ Raman and FTIR studies of electrocatalytic mechanisms

Abstract

Post‑lithium metal‑sulfur batteries, especially magnesium‑sulfur (MgS) and aluminum‑sulfur (AlS), have emerged as promising candidates for next-generation energy storage due to their high theoretical energy density, low cost, and material abundance. Despite these advantages, their practical deployment is hindered by sluggish sulfur/sulfide conversion kinetics, dendrite growth at the anode surface, and the polysulfide shuttle effect. Recent advances in electrocatalyst design, such as transition metal compounds, single-atom catalysts, and composite materials have shown significant potential to accelerate conversion reactions and suppress polysulfide migration. In situ and operando spectroscopic techniques, including Raman and Fourier-transform infrared (FTIR) spectroscopy, provide real-time insights into polysulfide bonding evolution and catalyst functionality while maintaining battery operating conditions. Complementary density functional theory (DFT) calculations further elucidate adsorption energies, charge transfer, and Gibbs free energy profiles, guiding rational catalyst design. This review summarizes the advantage of combining in situ spectroscopy with electrochemical characterization techniques and the recent progress in in situ Raman and FTIR studies of electrocatalytic mechanisms in MgS and AlS batteries.