Boron Vacancy Engineering in 2D WB-Based MBene Catalysts for Optimizing Lithium Polysulfide Reactions

The shuttle effect of lithium polysulfides (LiPSs) and the slow conversion kinetics of sulfur have been hindering the commercial development of lithium-sulfur (Li-S) batteries. Herein, WB-V_B based 2Dl MBene catalyst containing B vacancies is successfully prepared by a one-step room temperature F-free etching method. Both W and B atoms in this catalyst can interact with LiPSs simultaneously, effectively inhibiting the diffusion of soluble LiPSs. B-vacancy construction not only provides more exposure of active site W, but also improves the d band center, which is conducive to the rapid adsorption and Li-S reaction kinetics. More importantly, its mechanism for catalyzing LiPS reaction is characterized by in situ X-ray absorption spectroscopy. The results show that the reversible capacity is as high as 1485 mAh g^-1 at 0.2 C, and 664 mAh g^-1 even at 4 C. Furthermore, an outstanding capacity of 4.15 mAh cm^-2 under high load of 4.36 mg cm^-2 has remarkable cyclic stability.