Cerium oxide embedded bilayer separator enabling fast polysulfide conversion for high-performance lithium-sulfur batteries

[Display omitted] •A facile strategy to prepare the functional asymmetric bilayer separator.•The bilayer separator shows synergistic absorption-electrocatalysis behavior for LiPS.•The integrated Li-S cell achieves a low capacity decay rate of 0.04% per cycle.•The asymmetric separator could effectively depress the self-discharge issue. Lithium sulfur (Li-S) batteries are considered as a promising candidate for next generation energy storage. However, the practical implementation of Li-S batteries is seriously hampered by the notorious shuttling of polysulfides. Current research mostly focuses on modifying polyolefin-based separators for immobilization of polysulfides. Herein we report a facile and efficient approach for fabrication of a functional bilayer separator based on 0D (nanocrystals)/1D (nanofibers) composite mats. The top layer comprises CeO2 nanocrystals spatially besieged by carbon nanofibers, serving as electrocatalysts to accelerate the reduction of polysulfides, meanwhile, acting as a dual-conductive upper current collector and a polysulfide inhibitor. The support layer maintains the structural integrity of the separator and allows the safe operation of Li-S batteries at high temperature. Consequently, the Li-S batteries with the bilayer separators exhibit a high initial reversible capacity of 1359 mA h g−1 at 0.2 C, high rate capability, superior cycling stability (with a capacity decay rate of 0.04% per cycle at 0.5 C over 300 cycles), and ultralow self-discharge.