Lithium-sulfur (Li-S) batteries with exceptional theoretical capacities and environmentally friendly characteristics have been investigated as next-generation energy storage devices. However, the dissolution and diffusion of polysulfide result in a rapid capacity degeneration, which hinders their practical application. Here, poly(ionic liquid) (PIL)-based core-shell structured nanofibers, poly(pyrrole)@poly(ionic liquid)-polyacrylonitrile (PPy@PIL-PAN), were prepared via electrospinning and followed by a surface polymerization of pyrrole. The as-prepared PPy@PIL-PAN nanofibers were implemented as a functional interlayer for Li-S batteries, and it is found that the cationic poly(ionic liquid) framework could selectively adsorb polysulfide species in the electrolytes, contributing to effective shuttle inhibition as well as stable sulfur electrochemistry. Moreover, this work sheds light on an efficient approach to improving the performance of Li-S batteries by using PIL-based functional interlayers.