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

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 Li₂S₄ to Li₂S, and reduces the energy barriers for both Li₂S 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.