Electrospun Fe-ZIF derived carbon nanofibers for boosting adsorption and redox kinetics of polysulfides in lithium–sulfur batteries†

Lithium–sulfur batteries (LSBs) have received attention as next-generation electrochemical power sources owing to their high theoretical capacities and energy densities. Despite these merits, LSBs face critical problems, such as the dissolution and shuttle effect of lithium polysulfides (LiPSs), during their operation. In this study, Fe-zeolitic imidazolate framework (Fe-ZIF)-derived carbon nanofibers (Fe/N-CNFs) were fabricated using electrospinning and in situ growth. In particular, for the doping with Fe and N, the increased electronic density of the doped structure at the Fermi level was confirmed through density of state calculations. Furthermore, according to density functional theory (DFT) calculations, the Fe/N-CNFs with FeN_x active sites exhibited improved chemical affinity between Fe and S and enhanced adsorption properties for LiPSs, suppressing the dissolution of LiPSs and promoting fast conversion reactions and enhanced sulfur redox kinetics. The cell assembled with the electrospun Fe/N-CNFs as the cathode with sulfur showed a retention of 78% at a high rate of 2.0C. The enhanced electrochemical performance and stability of the LSB with Fe/N-CNFs can be attributed to the high electrical conductivity and excellent conversion reaction of the LiPSs on the FeN_x active sites.