A COF-coated MOF framework polysulfide barrier design for enhanced performance in lithium-sulfur batteries

Abstract

The shuttle effect of lithium polysulfide (LiPS) and slow sulfur reaction kinetics is a key problem hindering the application of lithium-sulfur (Li-S) batteries. To address these problems, herein, a novel multifunctional sulfur cathode design strategy of coating microsporous covalent organic framework (COF) onto metal organic framework (MOF)-derived carbon/transition metal composite is developed. This strategy is proofed by coating a TpPa-1 COFs layer on the UIO-66-NH2-derived N-doped Co/Zr-NC, forming core-shell structured Co/Zr-NC@TpPa composite. The Co/Zr-NC core consists of Co nanoparticles and ZrO2 that offers effective sulfur trapping and catalysis effect for sulfur redox reaction, whereas the microsporous COF shell with polar functional groups further reduces the shuttling of LiPS. The S/Co/Zr-NC@TpPa cathode achieves an initial capacity of 792 mAh g−l at 1 C with 76.4% capacity retention after 500 cycles. More importantly, under the high sulfur loading of 5.10 mg cm−2, it has a high specific surface area capacity of 4.15 mAh cm−2 at 0.2 C. This study provides a promising alternative design strategy for the development of efficient sulfur host in Li-S batteries.