Construction of highly active interfacial structures based on Fe3+/Fe2+ dynamically regulated MoS2 to promote polysulfides catalytic conversion for lithium‑sulfur batteries

Efficient catalytic processes can reduce the potential barrier to sulfur conversion and accelerate the "solid-liquid-solid" conversion process so as to inhibit the "shuttle effect" which enhance electrochemical performances of lithium‑sulfur batteries. In this paper, a nanoflower-like Fe3+/Fe2+@MoS2/S composite is successfully designed as sulfur-wrapped matrix via a facile hydrothermal method. The interconversion of Fe2+ and Fe3+ during the redox reaction can induce dynamic structural changes in the MoS2 catalyst and construct a highly active interfacial structure so as to promote the catalytic conversion of polysulfides and effectively limit the "shuttle effect". In addition, Fe doping strategy can also modulate the favorable phase transition (2H → 1T) of the molybdenum disulfide matrix to further improve the catalytic activity. It is noteworthy that the interconversion of Fe2+ and Fe3+ occurs during the redox process accompanied by lithium-ion integration and disengagement phenomena. This provides additional specific capacity for Fe3+/Fe2+@MoS2/S composite cathode, resulting in a rather high initial discharge specific capacity of 1900 mAh·g−1 at 0.1C current rate and carry out a 500 time charge and discharge cycles at 0.5C current rate with only 0.13 % single capacity decay rate.