Iron Carbide Dispersed on Nitrogen-Doped Graphene-like Carbon Nanosheets for Fast Conversion of Polysulfides in Li–S Batteries

The lithium–sulfur (Li–S) battery has drawn tremendous interest because of its superior theoretical specific capacity, while the shuttle effect of lithium polysulfides (LPSs) has greatly hindered its application. Herein, MOF-derived Fe3C compounded with the nitrogen-doped graphene-like carbon nanosheet, Fe3C/NG, was prepared and applied to realize a stable long cycle of Li–S batteries. With the catalytic and conductive Fe3C nanoparticles distributed on the conductive nitrogen-doped graphene-like carbon nanosheets, the Fe3C/NG composite could quickly adsorb and catalyze LPSs under a high current density or large sulfur loading, thus achieving high rate performance for the cell. Even at a current density of 6 C, the Li–S cell with the Fe3C/NG-coated separator can still have a specific capacity of 954.5 mA h/g at the first cycle, and maintain 439.9 mA h/g after 500 stable cycles. Meanwhile, when the cell has a high sulfur loading of 6.5 mg/cm2, a stable specific capacity of 6.0 mA h/cm2 could still be maintained at 0.1 C. Such a lightweight separator coating with excellent catalytic performance and conductivity can provide a good example for the search of catalytic coatings for the high-performance Li–S battery.