Covalent organic frameworks with conductive EDOT unit for superior lithium−sulfur batteries

Abstract

3,4-ethylenedioxythiophene (EDOT) unit featuring electron donor and self-structuring properties, has been considered as the conducting polymers resources for organic electronic devices. However, construction of covalent organic frameworks (COFs) with EDOT building blocks has not been reported. Herein, a novel conductive EDOT-based COF (EDOT-Por-COF) with enhanced chemical interaction and conductivity was synthesized as the electrocatalysts accelerating the conversion kinetics of soluble polysulfides. The corresponding EDOT-Por-COF with electron-rich conjugated microenvironment generates higher sulfur affinity and polysulfides catalytic activity, which is further verified by experimental data and density functional theory (DFT) calculations. The introduction of an electron-rich surrounding environment alleviates the tendency of charge loss at Co sites and guarantees an optimized electronic structure around the Co sites, thus improving the adsorption strength and electron transfer between the Co sites and polysulfides, contributing to an improved catalytic capability on polysulfides. As a result, the assembled cell displays a ultrahigh discharge capacity of 1585.9 mAh g⁻¹ at 0.1 C, a low the capacity decay rate of 0.031 % per cycle for 2000 cycles at 1 C and a high rate capacity of 763.9 mAh g⁻¹ at 5 C. This work supports a new insight into electrocatalyst structural regulation to boost the electrochemical performance of Li–S batteries.