Atom-Dominated Relay Catalysis of High-Entropy MXene Promotes Cascade Polysulfide Conversion for Lithium-Sulfur Batteries

To address the challenges in Li-S batteries, i.e. the shuttle effect and lithium dendrite formation, a high-entropy MXene (HE-MXene) of TiVNbMoC3 with four size-compatible transition metal elements uniformly dispersed in its M-layer is designed as sulfur host and separator modification layer. Through theoretical analysis and experimental investigations, the synergistic engineering of the multi-active centers within the HE-MXene is revealed, which provides high configuration compatibility with lithium polysulfides and optimizes the d-band center. Furthermore, the HE-MXene delivers an atom-dominated relay catalysis effect of Ti, V, Nb and Mo sites throughout the ordered multistep sulfur redox reactions, providing new opportunities for enabling a cascade of trapping-catalysis-conversion towards polysulfides and continuously mitigating the shuttle effect in Li-S chemistry. Moreover, the homogeneous electric field distribution and resilient lattice configuration are facilitated by the HE-MXene on the separator, promoting uniform lithium nucleation and deposition on lithium anode. Leveraging these unique properties, Li-S batteries incorporating the HE-MXene demonstrate a high areal capacity of 4.92 mAh cm-2 at 0.2 C after 100 cycles. This study not only introduces the HE-MXene as a solution for shuttle-free sulfur cathodes and dendrite-free lithium anodes, but also provides valuable insights for the rational design of advanced electrocatalysts at the atomic level.