A Band-Matching Descriptor Breaks Scaling Relations for Sulfur Electrocatalysts

A predictive descriptor is crucial for the rational design of catalysts that enable fast and reversible sulfur redox in lithium-sulfur (Li-S) batteries. Although several descriptors have been proposed, most remain constrained by the conventional adsorption-activity trade-off and the associated volcano-type behavior. Here, we uncover that the catalytic activity of widely used transition-metal sulfides is dictated by the d/p band-matching ratio between metal centers and surface sulfur atoms, thereby going beyond this limitation. By tuning the band-matching ratio, which modulates the interaction between lithium polysulfides and the catalyst surface, a linear correlation with the overpotentials of both sulfur reduction and evolution reactions is established, accelerating the sulfur conversion kinetics. NbS₂, with a band-matching ratio of 99.2%, delivers a minimal bifunctional overpotential of 0.70 V (the sum of sulfur reduction reaction (SRR) and sulfur evolution reaction (SER) overpotentials), 4-fold lower than that of WS₂ (2.85 V, with a band-matching ratio of 46.0%). The Li-S battery that delivers a high initial areal capacity of 10.98 mAh cm^-2 with the NbS₂ catalyst exhibits an exceptionally high retention of 90.29% after 100 cycles, surpassing most of the reports. This work establishes band matching as a general principle for sulfur electrocatalysis, providing a predictive design rule that transcends classical scaling relations for metal-sulfur batteries.