Covalent organic frameworks integrated MXene as selective "ion-sieving" heterostructure catalyst for kinetics-reinforced Li-S batteries

The paramount target in advancing high-efficiency lithium-sulfur (Li-S) batteries lies in hindering polysulfides shuttling and enhancing redox kinetics. Herein, the covalent organic frameworks (designated as TBCOF) are grafted in-situ on the surface of MXene to achieve MXene@TBCOF heterostructure at ambient temperature, modulating the kinetics behavior of ions owing to its unparalleled ionic sieving functionality. The resultant compound possesses a gradient (non-conductive/ conductive) electric field effect, well-defined porous architecture, and abundant sulfophilic/lithiophilic sites, enriching the chemical space of 0D-2D heterostructures. By harnessing the multiple-in-one characteristics of MXene@TBCOF heterostructure, the formed electron-bridge of integrated conductive MXene in heterostructures prohibits the accumulation of TBCOF and MXene, serving as a versatile accelerator for the polysulfides bidirectional evolution, as comprehensively evidenced by theoretical analysis and pouch cells. Therefore, the batteries equipped with MXene@TBCOF functional separator acquire a brilliant cyclicity at a current density of 1C (with capacity decaying rate of merely 0.0191 % per cycle) during 1500 cycles. Impressively, even with a sulfur loading up to 9.31 mg cm(-2), the batteries exhibit a superior area capacity of 7.14 mAh cm(-2) after enduring 90 cycles. This work proposes an innovative one-step synthesis strategy to construct catalytic "ion-sieving" heterostructure via covalent coupling for practical Li-S batteries.