Unique Octupolar 2D‐Polymer Frameworks as Mixed Conductors and Metal‐Free Catalysts for Dual‐Promoted Li and S Electrochemistry: Multi‐regulation Role of Ethoxylation Chemistry

Abstract

AbstractHere, we for the first time introduce ethoxylation chemistry to develop a new octupolar cyano‐vinylene‐linked 2D polymer framework (Cyano‐OCF‐EO) capable of acting as efficient mixed electron/ion conductors and metal‐free sulfur evolution catalysts for dual‐promoted Li and S electrochemistry. Our strategy creates a unique interconnected network of strongly‐coupled donor 3‐(acceptor‐core) octupoles in Cyano‐OCF‐EO, affording enhanced intramolecular charge transfer, substantial active sites and crowded open channels. This enables Cyano‐OCF‐EO as a new versatile separator modifier, which endows the modified separator with superior catalytic activity for sulfur conversion and rapid Li ion conduction with the high Li+ transference number up to 0.94. Thus, the incorporation of Cyano‐OCF‐EO can concurrently regulate sulfur redox reactions and Li‐ion flux in Li−S cells, attaining boosted bidirectional redox kinetics, inhibited polysulfide shuttle and dendrite‐free Li anodes. The Cyano‐OCF‐EO‐involved Li−S cell is endowed with excellent overall electrochemical performance especially large areal capacity of 7.5 mAh cm−2 at high sulfur loading of 8.7 mg cm−2. Mechanistic studies unveil the dominant multi‐promoting effect of the triethoxylation on electron and ion conduction, polysulfide adsorption and catalytic conversion as well as previously‐unexplored −CN/C−O dual‐site synergistic effect for enhanced polysulfide adsorption and reduced energy barrier toward Li2S conversion.