Zwitterionic covalent organic framework as a multifunctional separators for high performance lithium-sulfur batteries

Covalent organic frameworks (COFs) are considered as a class of potential energy storage and catalytic materials. In this paper, a COF containing hydrogen sulfite (HSO 3 − -ETB-COF) is prepared by anion exchange strategy and uses as a modified separator of lithium-sulfur batteries. The cells assembled from the HSO 3 − -ETB-COF modified intermediate layer have higher ionic conductivity (2.8 mS⋅cm −1 ) thanks to the charged hydrogen sulfite group in the structure. In addition, the modified intermediate layer based on HSO 3 − -ETB-COF can not only inhibit the shuttle of polysulfides, but also promote the diffusion of Li  +  through electrostatic interaction. The HSO 3 − -ETB-COF battery also shows excellent electrochemical performance, with an initial specific capacity of 1000 mAh g −1 at 1C and a specific capacity of 754.6 mAh g −1 after 500 cycles.