Zwitterionic microporous polymer with selective ion transport for durable lithium-sulfur batteries

Abstract

Functional separator which facilitates the fast transport of Li+ but obstructs the permeation of polysulfides is highly required for durable lithium-sulfur (Li-S) batteries. Here, we report a facile approach to developing such functional separator by coating the commercial polypropylene separator with a unique solution-processable polymer featuring both intrinsic microporosity and ion-selective functionality. The polymer is designed with contorted and rigid backbones, which incorporates zwitterionic side chains with both sulfophilic and lithiophilic groups, to produce confined ionic channels for selective ion transport via the chemical interactions with lithium polysulfides. Therefore, when used in the cell configuration, the as-developed functional separator can not only allow the fast Li+ conduction but also obstruct the penetration of bulky polysulfides, thus resulting in obvious shuttle suppression as well as the resultant credible and stable sulfur electrochemistry. Thanks to these advantages, the Li-S batteries implementing the as-developed functional separator possess high cycling ability and decent rate performance.