Structural and Functional Optimization of Lithium-Sulfur Battery Separators by Sulfur-Containing of Covalent Organic Frameworks

Abstract

The polysulfide shuttle effect and growth of lithium dendrites are major challenges for the development of high-performance lithium-sulfur (Li-S) batteries. In this work, a thiazole-based covalent organic framework (TTT-COF) is designed to modify the separators and provide an efficient strategy to tackle these challenges. A series of chemical structural analyses and electrochemical tests reveal that the modification of the linkages in TTT-COF enhances π-electron delocalization, with the active sites predominantly activated by the introduced adjacent heteroatoms via electronic effects. This not only facilitates the electrocatalytic conversion of polysulfides but also enhances lithium-ion (Li⁺)/electron migration, thus alleviating the formation of lithium dendrites. The experimental results demonstrate that the modified battery exhibits an initial specific capacity of 987.3 mA h g⁻¹ at a current density of 1.0 C, with a specific capacity decay rate of just 0.082% per cycle after 800 cycles.