Multifunctional electrospun nanofiber separators toward high-performance lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries have attracted increasing attention as promising energy storage systems owing to their exceptionally high theoretical energy density of 2600 Wh kg^-1 and the low cost of sulfur. However, their practical application is still limited by lithium polysulfides (LiPSs) dissolution and shuttling, sluggish sulfur redox kinetics, and inhomogeneous lithium deposition. In addition, conventional polypropylene/polyethylene separators often exhibit insufficient capability to regulate LiPSs migration and lithium deposition, which further deteriorates the electrochemical performance and safety of Li-S batteries. Electrospun nanofibers, featuring high porosity, interconnected structures, and tunable functionality, have emerged as attractive platforms for constructing advanced functional separators. This review summarizes the principles of electrospinning and highlights recent progress in electrospun nanofiber-based separators for Li-S batteries, including separator modification, interlayers, and free-standing nanofiber separators. Their multifunctional roles in suppressing polysulfide shuttling, enhancing ion transport, and stabilizing lithium deposition are discussed. Finally, the current challenges and future perspectives of electrospun nanofiber functionalized separators are outlined, providing insights for the development of safe and high-performance Li-S batteries.