Origin and Acceleration of Insoluble Li2S2−Li2S Reduction Catalysis in Ferromagnetic Atoms‐based Lithium‐Sulfur Battery Cathodes

Abstract Accelerating insoluble Li 2 S 2 −Li 2 S reduction catalysis to mitigate the shuttle effect has emerged as an innovative paradigm for high‐efficient lithium‐sulfur battery cathodes, such as single‐atom catalysts by offering high‐density active sites to realize in situ reaction with solid Li 2 S 2 . However, the profound origin of diverse single‐atom species on solid‐solid sulfur reduction catalysis and modulation principles remains ambiguous. Here we disclose the fundamental origin of Li 2 S 2 −Li 2 S reduction catalysis in ferromagnetic elements‐based single‐atom materials to be from their spin density and magnetic moments. The experimental and theoretical studies disclose that the Fe−N 4 ‐based cathodes exhibit the fastest deposition kinetics of Li 2 S (226 mAh g −1 ) and the lowest thermodynamic energy barriers (0.56 eV). We believe that the accelerated Li 2 S 2 −Li 2 S reduction catalysis enabled via spin polarization of ferromagnetic atoms provides practical opportunities towards long‐life batteries.