Oxygen-Plasma-Treated Fe-N-C Catalysts with Dual Binding Sites for Enhanced Electrocatalytic Polysulfide Conversion in Lithium-Sulfur Batteries

Abstract

Enhanced polysulfide conversion kinetics is essential for realizing lithium-sulfur batteries with high energy density and rate performance and promising cyclability. The modification of the local atomic structure of MNx active sites in single-atom M-N-C catalysts was proposed to improve their electrocatalytic activity for demanding reactions by fine-tuning the interaction with reaction intermediates. Here, we demonstrate that engineering the binding geometry of lithium polysulfides (LiPSs) by introducing dual binding sites improves the LiPS conversion kinetics. We use mild oxygen plasma treatment to introduce oxygen species into the Fe-N-C catalyst. The plasma-treated Fe-N-C (pFeNG) catalyst with dual sulfiphilic (mononuclear iron) and lithiophilic (oxygen) binding sites has a lower polysulfide decomposition energy, especially for Li2S redox, which is known to be the most sluggish process. The pFeNG cathode shows significant improvement, especially at high C rates (916.3 mA h g(-1) at 5C), with promising cycling performance.