MOF derived in-situ carbon-encapsulated Fe3O4@C to mediate polysulfides redox for ultrastable Lithium-sulfur batteries

In view of the low sulfur utilization and poor cycle stability of lithium-sulfur (Li-S) batteries, an effective strategy is widely used by introducing strong polar materials into the sulfur host. Herein, metal organic frameworks (MOFs) derived in-situ carbon encapsulated transition metal oxides (Fe3O4@C) is proposed to mediate the polysulfides redox reaction, based on rapid charge transfer behavior, strong interaction with the intermediates of sulfur reduction and high electrochemical activation for polysulfides transformation. As expected, together with the hierarchical porous structure inheriting from the MIL-53 template, the Fe3O4@C incorporated in the sulfur cathode contributes to the apparently enhanced specific capacity, improved rate performance as well as super high cycling stability (extremely low capacity fading of 0.002% per cycle over 300 cycles at 1 C). This work provides a concise yet effective strategy to design a sulfur cathode for application of Li-S batteries with high rate performance and super high cycling stability.