Inverse-vulcanization of vinyl functionalized covalent organic frameworks as efficient cathode materials for Li–S batteries

Abstract

Covalent organic frameworks (COFs) are an emerging class of crystalline porous materials featuring pre-designable structures and tailor-made functions. Herein, a mesoporous imine COF with densely arranged reactive vinyl groups (COF-V) was inverse-vulcanized with sulfur and used as a cathode material for Li–S batteries. Owing to the synergetic chemical covalent binding with the vinyl groups and physical confinement by the mesoporous channels, the shuttle effect of polysulfides could be efficiently suppressed. As a result, the inverse-vulcanized S-COF-V cathode demonstrated a high initial capacity of 1400 mA h g⁻¹ which retained 959 mA h g⁻¹ after 100 cycles at 0.2C and can be further cycled 1000 times at 1C with a low fading rate of 0.057% per cycle. These results are among the best performances of reported COF-based sulfur cathodes. Our findings provide a new approach to develop efficient cathode materials for Li–S batteries.