Amphiphilic Carborane-Based Covalent Organic Frameworks as Efficient Polysulfide Nano-Trappers for Lithium-Sulfur Batteries

Lithium-sulfur batteries (LSBs) have been considered as one of the most promising energy storage systems because of their high theoretical energy density. However, the "shuttle effect" caused by polysulfide results in poor cycling stability and low electrochemical properties, which strongly impedes the practical application of LSBs. Herein, a kind of amphiphilic carborane-based covalent organic framework (CB-COF) is synthesized and treated as nano-trappers for polysulfide. The microporous CB-COFs show high-temperature resistance and excellent chemical stability. Both experimental results and theoretical calculation indicate the strong adsorption ability of CB-COF for polysulfides. Such an ability makes CB-COF a candidate separator material for LSBs, which efficiently suppresses the "shuttle effect," leading to a high-rate capacity (314 mA h g(-1) after 1000 cycles at 2.5 C) and an ultra-long cycling life (after 1000 cycles with a very low decay rate of 0.0395% per cycle at 1 C) of LSBs.