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

Here, 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.

Multipolar Conjugated Polymer Framework Derived Ionic Sieves via Electronic Modulation for Long‐Life All‐Solid‐State Li Batteries

“…[42,43] Importantly, various donor (D) and acceptor (A) moieties can be readily encoded into vinylene-linked framework by customized design, forming multipolar conjugated structures consisting of three radial-symmetrical branches attached to a central core. [44] Such multipolar structures allow the sufficient release of innate strong polarity and enable marked intramolecular charge transfer (ICT), thus rendering a good platform to regulate the electronic structure by multipolar D-A effect for probing electronic structure-activity relation. However, the synthesis of such class of COF materials is still challenging owing to poor reversibility of carbon-carbon double bonds.…”

Cobalt/MXene‐derived TiO2 Heterostructure as a Functional Separator Coating to Trap Polysulfide and Accelerate Redox Kinetics for Reliable Lithium‐sulfur Battery

“…[5] Even so, the practical application of LiÀ S batteries has faced various challenges. [6][7][8] These obstacles include the low electrical conductivity of S, the discharge product Li 2 S, [9][10][11] and notable changes in volume during charging and discharging. [12,13] The growth of lithium dendrites is likely to lead to internal short circuits or even thermal runaway failure of the battery.…”

“…In addition, S is extremely abundant, non‐toxic, and extremely friendly to the environment [5] . Even so, the practical application of Li−S batteries has faced various challenges [6–8] . These obstacles include the low electrical conductivity of S, the discharge product Li 2 S, [9–11] and notable changes in volume during charging and discharging [12,13] .…”

Design of Wide‐Temperature Lithium‐Sulfur Batteries

“…Therefore, lithium‐sulfur (Li−S) batteries are the most attractive next‐generation rechargeable energy storage device. Despite these advantages of Li−S batteries, which currently provide long life under conventional conditions, wide‐temperature lithium batteries are one of the most advanced technologies on the market today [18–26] . The cooperation of lithium technology and wide temperature range makes this battery type suitable for various applications.…”