Highly Electronegative Element-Rich COF Modified Separator Achieves High-Performance of Lithium–Sulfur Batteries

In this work, a covalent organic framework (COF) containing high electronegativity (TTBT-COF) was prepared to improve the separator of commercial Celgard lithium–sulfur batteries (LSBs). The LSBs with a TTBT-COF separator had a high initial capacity of 1033 mAh g–1 at 0.1 C and remained at 530 mAh g–1 after 500 cycles at 1 C. The average capacity attenuation rate per cycle is 0.057%. In addition, they exhibit a high initial capacity of 616 mAh g–1 at 2 C. The TTBT-COF improved separator can significantly inhibit the shuttle effect of polysulfides, thereby improving the cycle stability and coulomb efficiency of the battery, providing another strategy for the construction of high-performance LSBs.