Dual Role of Ti3C2Tx MXene in Li–S Batteries: Cathode Additive and Separator Modifier for Enhanced Performance

Lithium-sulfur batteries (LSBs) are one of the most promising energy storage technologies. However, their commercialization is limited by the shuttle effect and slow reaction kinetics. Strategies to overcome such limitations have commonly focused on modifying sulfur hosts and separators with carbonaceous materials; however, the effectiveness of these strategies is often limited. In the present study, a novel approach, that involves the concurrent utilization of a pristine Ti-based MXene material as both a sulfur-host cathode and a modified separator is proposed. The modification of the separator enhances the ionic conductivity, porosity, and wettability and completely inhibits the diffusion of lithium polysulfides. The advanced computational, kinetic, and electrochemical studies demonstrate that the synergistic effect improves Li-ion diffusion and reaction kinetics and decreases polarization, translating into improved electrochemical performance of LSBs, including capacity retention values close to 85% at a rate of 5C, ultra-long cycling performance of 1000 cycles at 0.5C, and areal capacity values above 6 mAh cm-2; remarkably, these results are obtained at an ultra-high loading of 9 mg cm-2. Overall, this study demonstrates the possibility of achieving high energy density combined with extended cycle life in lithium-sulfur batteries through the synergistic implementation of Ti3C2Tx MXene as a bifunctional cathode and separator material.