Metal–Organic Framework Decorated Polymer Nanofiber Composite Separator for Physiochemically Shielding Polysulfides in Stable Lithium–Sulfur Batteries

Lithium–sulfur (Li–S) batteries have attracted numerous attention owing to their overwhelming theoretical capacity. However, the dissolution and shuttle effect of lithium polysulfides (LiPSs) have seriously limited the development of Li–S batteries. Herein, we rationally designed a dual-engineered nanofibrous composite separator with a Janus structure to both physically and chemically block LiPS shuttling in Li–S batteries. The separator, consisting of a cross-linked poly(vinyl alcohol)/poly(acrylic acid) (CPP) composite nanofiber matrix and the electrosprayed poly(vinyl alcohol) (PVA)/zeolitic imidazolate framework-8 (ZIF-8) layer on the cathode side, is fabricated through a facile electrospinning–electrospray coupling approach and signed as CPP@PVA/ZIF-8. The intrinsic narrow size and opened Lewis acid sites of ZIF-8 both confine free transport of LiPS anions. Meanwhile, the cross-linked CPP layer with abundant electronegative groups (−COOH) can shield the LiPS shuttle while ensuring the integrity of the flexible separator. Benefiting from the unique Janus structure, the CPP@PVA/ZIF-8 separator demonstrates a high initial capacity of 1125 mAh g–1 at a good coulombic efficiency of 98% over 300 cycles at 0.1 C. This work not only establishes a combined strategy to immobilize LiPSs but also provides novel interfacial engineering modification ideas for the development of high-performance separators in Li–S batteries.