Accelerating Liquid‐Solid Phase Polysulfide Conversion with Triphasic MoN _Cubic ‐Co‐MoN _Hexagonal Heterostructures for High‐Performance Li/Na‐S Batteries

ABSTRACT Lithium‐sulfur (Li‐S) batteries represent an attractive next‐generation energy storage technology owing to their high theoretical energy density. Simultaneously, room‐temperature sodium‐sulfur (RT Na‐S) batteries have emerged as promising candidates for large‐scale energy storage due to the low cost and high abundance of sodium resources. Nevertheless, their practical deployments are severely limited by the notorious polysulfide shuttle effect, sluggish reaction kinetics, and low sulfur utilization. And the liquid‐solid conversion is a critical bottleneck, as it represents 75% of the maximum theoretical value. To address this, we report a novel catalyst comprising cobalt‐doped molybdenum nitride, a triphasic porous heterostructured MoN _Cubic ‐Co‐MoN _Hexagonal (MoN _C ‐Co‐MoN _H ). This integrated catalyst operates with high efficiency, as it capitalizes on the inherent synergy between its constituents to regulate the kinetics of polysulfide adsorption, diffusion, and conversion. The electrochemical investigations, spectroscopic analysis, and theoretical calculations demonstrate that the MoN _C ‐Co‐MoN _H significantly enhances the efficiency of the conversion from Li ₂ S ₄ to Li ₂ S, and reduces the energy barriers for both Li ₂ S nucleation/decomposition. Accordingly, Li‐S batteries incorporating the MoN _C ‐Co‐MoN _H catalyst deliver a combination of high capacity (1557.4 mAh g ⁻¹ at 0.1 C, 93% sulfur utilization), excellent rate capability, and long‐term cycling stability. Impressively, this heterostructure also confers exceptional electrochemical properties to RT Na‐S batteries.