Covalent Organic Frameworks as the Coating Layer of Ceramic Separator for High-Efficiency Lithium–Sulfur Batteries

Covalent organic frameworks (COFs) have been proven to be an efficient host material for trapping sulfur in lithium–sulfur batteries. However, the potential application as the coating layer of the separator has not been well-addressed yet. Here, we synthesized an imine-based COF, DMTA-COF, which exhibited an AB-stacking mode and had a pore size of 0.56 nm. For the first time, we applied this nanoporous COF as the coating layer of the ceramic separator; the corresponding cell gave an initial discharge capacity up to 1415 mA h/g, and 1000 mA h/g remained after 100 cycles at 0.5 C. The performance is much better than that of the pristine ceramic separator and the super-P coated ceramic separator, demonstrating that the nanopores in the composite separator can effectively block the polysulfide across the separator, thus reducing the “shuttle” effect and the loss of active materials. This study provides a new design strategy for separators in lithium–sulfur batteries.