Two-dimensional salen-based covalent organic frameworks with highly electronegative groups as separators for high stability lithium–sulfur batteries

Abstract

Covalent organic frameworks (COFs), with their abundant nitrogen and oxygen heteroatoms, have been developed for the inhibition of lithium polysulfide (LiPSs) shuttling in lithium–sulfur batteries (Li–S batteries). In this paper, we introduce the synthesis of Salen-TAPT-COF, which is rich in N and O atoms, under solvothermal conditions. Its ordered pore structure and large specific surface area are natural chemical channels and physical barriers to accelerate Li⁺ diffusion, while effectively inhibiting LiPSs shuttling. Therefore, we prepared a modified separator (Salen-TAPT-COF/PP) using Salen-TAPT-COF and applied it to Li–S batteries. The experimental results show that the performance of the battery modified with Salen-TAPT-COF is significantly improved. At a rate of 0.1 C, the initial discharge capacity of the Salen-TAPT-COF-modified battery can reach 1169.9 mA h g⁻¹, and when the rate is increased to 2 C, the capacity of the battery can still be stabilized at 641.4 mA h g⁻¹. XPS results also show the interaction of Salen-TAPT-COF with LiPSs.