Cyclized-polyacrylonitrile modified carbon nanofiber interlayers enabling strong trapping of polysulfides in lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries are seriously constrained by the diffusion and crossover of intermediary product polysulfides and their further reductions on the anode surface. Although carbon-based interlayers have been widely used to inhibit the detrimental shuttle effect in Li-S batteries, the weak physical adsorption of pure carbon materials for trapping polysulfides still leads to low recycle efficiency of active species and short cycle life for cells. Herein, we report a cyclized-polyacrylonitrile-cast carbon nanofiber (CP@CNF) film as an interlayer in Li-S batteries. By exploiting the CP@CNF interlayer, the batteries assembled with bare sulfur cathodes deliver superior rate capability and cycle stability. The reversible capacity could be maintained at 710 mA h g(-1) after 200 cycles at 0.3C and a capacity of 560 mA h g(-1) can be obtained even at a 2C rate. The improved performances are attributed to both the abundant pyridine groups in the cyclized polyacrylonitrile matrix, which can entrap polysulfides by strong interatomic attraction, and the three-dimensional porous conductive network composed of the carbon nanofiber skeleton and conjugated polymer matrix, giving rise to highly effective transfer pathways for electrons and ions.