Boosting the Performance of Lithium-Sulfur Batteries with PY−DHBD−COF-Enhanced Separators

Abstract

Lithium–sulfur batteries (LSBs) hold promise for use in next-generation high-energy-density energy storage systems. However, the commercial application of LSBs is hindered by the shuttle effect of polysulfides. In this study, we synthesized a covalent organic framework material (PY−DHBD−COF) and employed it to modify the separators of LSBs in order to buffer the shuttle effect of polysulfides. A modified separator, involving PY−DHBD−COF coating of the commercial Celgard 2500 PP separator, is prepared via a vacuum-assisted self-assembly method. The PY−DHBD−COF features hydroxyl and imine bonds, which can adsorb lithium polysulfides (LiPSs) and buffer the shuttle effect. The PY−DHBD−COF coating exhibits a thin thickness and oriented nanochannels, facilitating electrolyte wetting and Li+ transport. As a result, the LSBs with PY−DHBD−COF-modified separators exhibit a high specific capacity of 373 mAh g−1 at 4 C with only 0.005% capacity decay per cycle after 450 cycles at 2 C, demonstrating an excellent cycling performance.