Three-dimensional Covalent Organic Frameworks as Host Materials for Lithium-Sulfur Batteries

Two reported three-dimensional covalent organic frameworks (3D-COFs), COF-300 and COF-301, which have hierarchical porous structures and large pore volumes, were synthesized and employed as host materials for lithium-sulfur batteries. Owing to possessing excellent porosities as well as abundant hydroxyl groups in the pore walls, COF-301 can not only trap lithium polysulfides (PSs) via physical adsorption inside the pores, but also capture PSs by chemical interactions to relieve the shuttle effect. Interestingly, it is the first time that 3D-COFs were utilized as host materials for lithium-sulfur batteries as well as hydroxyl groups were introduced into COFs for improving the battery performance. As a result, COF-301@S as cathode material could reserve the capacity of 411.6 mA·h·g−1 after 500 cycles with only 0.081% fading per cycle at 0.5 C, exhibiting better battery performance compared with COF-300@S. This study not only expands the applications of 3D-COFs but also provides a new route for designing lithium-sulfur batteries.