Sulfur Reduction Catalyst Design Inspired by Elemental Periodic Expansion Concept for Lithium–Sulfur Batteries

The key challenges facing the commercialization of lithium-sulfur (Li-S) batteries are shortening the lithium polysulfide (LiPS) intermediate existence time while accelerating solid-phase conversion reactions. Herein, inspired by highly efficient natural enzymes with Fe/N active sites for oxygen reduction reactions, we report a periodic expansion catalysis concept, i.e., Ru and P synergic stereoselectivity, for designing sulfur reduction reaction (SRR) catalysts. As a proof of concept, a RuP₂-configuration molecular catalyst was exploited to assemble an interlayer in Li-S batteries that adsorbs LiPSs, optimizes Li⁺ migration paths, and catalyzes SRRs. Comprehensive investigation identified the elimination of steric hindrance and strong electron orbital couplings between metallic d band and nonmetallic p band as the main contributing factors of PEC for the SRRs. As a result, the Li-S battery with ∼0.5 wt % catalyst additive showed enhanced cycling stability even under a high sulfur loading (6.5 mg cm⁻²) and low electrolyte/sulfur ratio (9 μL mg⁻¹).