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 RuP 2 -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 ).