Engineering covalent organic frameworks to enhance interfacial lithium-ion flux redistribution in dendrite-free lithium–sulfur batteries

Abstract

The development of high-performance electrocatalysts that efficiently adsorb and rapidly convert polysulfides represents a pivotal approach to enhance the specific capacity and cycling life of lithium–sulfur (Li–S) batteries. Nevertheless, their performance remains hindered by the shuttling effect of LiPSs and the sluggish kinetics of redox reactions. Herein, the covalent organic frameworks (labeled as fBTTP-COF) are prepared via a Schiff-base condensation reaction at ambient temperature, circumventing the hazards associated with solvothermal methods. As a porous π-conjugated structural material, the ion-sieving architecture of fBTTP-COF not only exhibits rapid charge transfer and lithium-ion migration, but also boasts abundant anchoring sites on its π-conjugated backbone that can adsorb and facilitate the conversion of polysulfides. Benefiting from its superior catalytic performance, the batteries with fBTTP-COF modified separator deliver a splendid cycle stability with a minimal capacity decay rate of 0.037% during 700 cycles at 1C, and a superior areal capacity of 5.59 mA h cm⁻² at a high-sulfur loading of 5 mg cm⁻². Meanwhile, the Li//Li symmetric batteries enable steady lithium plating/stripping cycling stability over 483 h. This work offers a novel perspective for designing economically efficient catalysts to improve the cycling life of Li–S batteries.