BiOI nanosheets-wrapped carbon fibers as efficient electrocatalyst for bidirectional polysulfide conversion in Li–S batteries

Abstract The lithium-sulfur (Li-S) batteries involve intricate electrochemical processes containing the formation and conversion of polysulfides, in which the shuttle effect and slow reaction kinetics impair its practical performance. Exploring new electrocatalyst with strong catalytic ability can greatly accelerate the conversion of polysulfides in Li-S batteries. Herein, BiOI/carbon fibers (BiOI/CFs) core–shell composite has been prepared by a facile electrospinning combined with solvothermal method and used as a promising electrocatalyst. The BiOI nanosheets are cross-linked to form a porous three-dimensional network on the surface of carbon fibers. This architecture not only has the advantage of large aspect ratio, but also has a high specific surface area, which provides abundant active sites and ensures high electron/ion transfer for the electrocatalysis of lithium polysulfides. As expected, BiOI/CFs electrode presents a superior bidirectional oxidation–reduction ability for polysulfides. The first-principles calculations also prove the strong interaction between BiOI and polysulfides. Due to these advantages, BiOI/CFs can effectively inhibit the shuttle effect of polysulfides, and possesses excellent electrochemical performance in Li-S batteries. The specific capacity of the BiOI/CFs-S electrode is stable at 1020 mAh g−1 after 200 cycles at 0.2C and 598 mAh g−1 after 1000 cycles at 5C. This work provides new insights for the development of high-performance electrocatalysts for polysulfide conversion.