Flexible MoNb Bimetallic MXene for High‐Performance Lithium‐Sulfur Batteries via Separator Modification

ABSTRACT

Lithium–sulfur batteries have attracted extensive interest owing to their exceptionally high theoretical energy density and environmental benignity. However, their practical performance remains severely constrained by intrinsic challenges, including the polysulfide shuttle effect and large volume expansion during cycling, which markedly compromise energy efficiency and fall far short of the requirements for commercialization. To address these challenges, we modify a commercial separator (PP) with a dual‐transition‐metal Mo ₂ Nb ₂ C ₃ MXene, whose surface terminations are precisely regulated via distinct etching strategies, thereby substantially enhancing the electrochemical performance of lithium–sulfur batteries. Compared with cells employing the pristine commercial separator, all PP@Mo ₂ Nb ₂ C ₃ ‐based cells deliver superior rate performance at a high current density of 3C. Notably, the PP@Mo ₂ Nb ₂ C ₃ ‐Cl cell retains a high discharge capacity of 589 mAh g ⁻¹ after 200 cycles, nearly doubling that of the cell with the commercial PP separator (307 mAh g ⁻¹ ). At all tested C‐rates, the PP@Mo ₂ Nb ₂ C ₃ ‐based cells delivered higher discharge capacities than those employing the commercial PP separator. Overall, modification of Celgard 2500 with the dual‐transition‐metal Mo ₂ Nb ₂ C ₃ MXene effectively suppresses the polysulfide shuttle, enhances sulfur utilization, and substantially prolongs the cycle life of lithium–sulfur batteries. This work provides valuable insights into the rational design and application of MXenes as functional modifiers for advanced lithium–sulfur batteries.