Dry Synthesis of Sulfur-Terminated MXene as Multifunctional Catalyst for Stable Lithium-Sulfur Batteries

A multifunctional catalyst with enhanced polysulfide adsorption, rapid lithium diffusion, and exceptional catalytic activity is crucial for accelerating redox kinetics and effectively suppressing the shuttle effect in lithium-sulfur (Li-S) batteries. However, developing an efficient synthesis method for such catalysts remains challenging. Here, a sustainable, sulfur-terminated MXene is introduced via a completely dry molten salt process, which avoids the need for harsh acid treatment, byproduct removal, and extensive rinsing, typical in MXene syntheses. Theoretical calculations and electrochemical data confirm that this sulfur-terminated MXene serves as a powerful multifunctional catalyst, promoting rapid lithium diffusion, effective polysulfide adsorption, and superior catalytic performance, making it highly suitable for advanced separators in Li-S batteries. As a result, Li-S cells incorporating sulfur-terminated MXene separators demonstrate a high capacity of 665 mAh g^-1 after 500 cycles at 1 C, with a remarkably low-capacity decay rate of 0.05% per cycle. This study underscores the potential of precise surface termination control in MXenes to drive further advancements in Li-S battery technology.