An oxazole-linked donor–acceptor covalent organic framework as an efficient electrocatalyst for lithium–sulfur batteries

Abstract

Covalent organic frameworks (COFs) with ordered channels and light weight are regarded as promising separator modifications for lithium–sulfur (Li–S) batteries. However, they typically suffer from stability issues and limited electrocatalytic activity, resulting in unsatisfactory battery performance. Herein, a donor–acceptor (D–A) COF (BTT-DABD) featuring oxazole linkages is developed through a one-step solvothermal route and then coated on a commercial separator, acting as an efficient electrocatalyst for Li–S batteries. Note that BTT-DABD exerts better chemical stability than its traditional imine-linked counterpart (BTT-DA). Moreover, the heterocyclic structure of oxazole linkage not only regulates the electronic structure of active N sites to enhance the chemical affinity for polysulfides but also gives rise to extended π-conjugation and enhanced D–A interaction to facilitate electron transport along the framework, thus endowing BTT-DABD with excellent electrocatalytic activity in the bidirectional sulfur redox processes. The assembled Li–S batteries using BTT-DABD separator exhibit an impressive electrochemical performance, including high incipient discharge capacity (1383 mA h g⁻¹ at 0.1C), outstanding rate capability (674 mA h g⁻¹ at 5C), and excellent long-term cycling performance (decay rate of 0.061% per cycle over 500 cycles at 3C). This work provides novel insights into the rational design of COF-based electrocatalysts for advanced Li–S batteries.