NbSe₂ Meets C₂N: A 2D‐2D Heterostructure Catalysts as Multifunctional Polysulfide Mediator in Ultra‐Long‐Life Lithium–Sulfur Batteries

The shuttle effect and sluggish conversion kinetics of lithium polysulfides (LiPS) hamper the practical application of lithium–sulfur batteries (LSBs). Toward overcoming these limitations, herein an in situ grown C 2 N@NbSe 2 heterostructure is presented with remarkable specific surface area, as a Li–S catalyst and LiPS absorber. Density functional theory (DFT) calculations and experimental results comprehensively demonstrate that C 2 N@NbSe 2 is characterized by a suitable electronic structure and charge rearrangement that strongly accelerates the LiPS electrocatalytic conversion. In addition, heterostructured C 2 N@NbSe 2 strongly interacts with LiPS species, confining them at the cathode. As a result, LSBs cathodes based on C 2 N@NbSe 2 /S exhibit a high initial capacity of 1545 mAh g −1 at 0.1 C. Even more excitingly, C 2 N@NbSe 2 /S cathodes are characterized by impressive cycling stability with only 0.012% capacity decay per cycle after 2000 cycles at 3 C. Even at a sulfur loading of 5.6 mg cm −2 , a high areal capacity of 5.65 mAh cm −2 is delivered. These results demonstrate that C 2 N@NbSe 2 heterostructures can act as multifunctional polysulfide mediators to chemically adsorb LiPS, accelerate Li‐ion diffusion, chemically catalyze LiPS conversion, and lower the energy barrier for Li 2 S precipitation/decomposition, realizing the “adsorption‐diffusion‐conversion” of polysulfides.