A Molybdenum Carbide Mixcrystal Structure with Synergistic Catalytic Activity for Accelerating Sulfur Redox Reactions in Lithium–Sulfur Batteries

A single-component electrocatalyst with weak and unidirectional catalytic activity cannot realize high-performance Li-S batteries with rapid sulfur redox kinetics and restricted shuttling. In this work, a heterostructured mixcrystal electrocatalyst of MoC-Mo2C nanodot-embedded carbon sheet-assembled hollow architecture (MoC-Mo2C/CSHA) was constructed to modulate the reaction behaviors of sulfur species. In situ X-ray diffraction and in situ electrochemical impedance spectroscopy unveiled an enhanced catalytic activity of MoC-Mo2C/CSHA for the bidirectional conversions of sulfur species, and the ensuing theoretical study confirmed the synergistic catalytic effect of the MoC-Mo2C structure originating from the integration of two different components. Further postcycling characterization suggested the prevention of anodic side reactions and the suppression of the polysulfide shuttling phenomenon. Consequently, the assembled Li-S batteries demonstrated a high rate performance of 706 mAh g-1 at 3.0 C and good long-life cyclic stability lasting for 500 cycles at 1.0 and 2.0 C. Moreover, both coin cells under high sulfur loadings and pouch cells exhibited steady cyclic performance, with a maximum areal capacity of 5.09 mAh cm-2. This study showcases the extraordinary advantages of heterostructures serving as electrocatalysts and providing an efficient route to advance Li-S batteries into practical utilizations.