Mo2N–W2N Heterostructures Embedded in Spherical Carbon Superstructure as Highly Efficient Polysulfide Electrocatalysts for Stable Room‐Temperature Na–S Batteries

Room‐temperature sodium–sulfur (RT Na–S) batteries are highly desirable for a sustainable large‐scale energy‐storage system due to their high energy density and low cost. Nevertheless, practical applications of RT Na–S batteries are still prevented by the shuttle effect of sodium polysulfides (NaPS), slow reaction kinetics of S, and incomplete conversion process of NaPS. Here, Mo2N–W2N heterostructures embedded in a spherical carbon superstructure (Mo2N–W2N@PC) are designed to efficiently suppress the “polysulfide shuttle” and promote NaPS redox reactions. The designed Mo2N–W2N@PC heterostructure with abundant heterointerfaces, high conductivity, and porosity can facilitate electron/ion diffusion and provide high catalytic activity for efficient NaPS conversion. The obtained Na–S battery delivers high reversible capacity with superior long‐term cyclability (517 mAh g−1 at 1 A g−1 after 400 cycles) and unprecedented rate capability (417 mAh g−1 at 2 A g−1). Furthermore, the electrocatalysis mechanism is revealed by combining in situ X‐ray diffraction (XRD), ex situ X‐ray photoelectron spectroscopy (XPS), UV–vis spectra, and precipitation experiments. This work demonstrates a novel heterostructure design strategy that enables high‐performance Na–S batteries. Mo2N–W2N heterostructures embedded in a spherical carbon superstructure (Mo2N–W2N@PC) are designed as the S hosts for room‐temperature sodium–sulfur (RT Na–S) batteries. The Mo2N–W2N@PC can efficiently suppress the polysulfide shuttling, promote redox reactions, and catalyze the fast conversion of sodium polysulfides.