Atomic-Scale Dispersed Fe-based Catalysts Confined on Nitrogen Doped Graphene for Li-S Batteries: Polysulfides with Enhanced Conversion Efficiency.

Due to satisfactory theoretical energy density, lithium-sulfur batteries have been considered as a potential electrochemical energy storage device. Nonetheless, the inferior conversion efficiency of polysulfides in essence leads to fast capacity decay during discharge-charge cycle. Herein, we have successfully demonstrated that the conversion efficiency of lithium polysulfides was remarkably enhanced by employing a well-distributed atomic-scale Fe-based catalyst immobilized on nitrogen doped graphene (Fe@NG) as a coating of separator in lithium-sulfur batteries. Quantitative electrocatalytic efficiency of the conversion of lithium polysulfides was determined via cyclic voltammetry technique. It was also proven that the Fe-N X configuration with highly catalytic activity was quite beneficial to the conversion of lithium polysulfides. In addition, the adsorption and permeation experiment distinctly indicated that the strong anchoring effect, originated from the charge redistribution of N doping into the graphene matrix, inhibited the movement of lithium polysulfides. Thanks to these advantages, when the as-prepared Fe@NG catalyst was combined with polypropylene and served as a separator (Fe@NG/PP) in Li-S batteries, it delivered high initial capacity (1616 mAh g -1 at 0.1 C), excellent capacity retention (93% at 0.2 C, 70% at 2 C) and superb rate performance (820 mAh g -1 at 2 C).