Adsorption-catalysis synergy within pyrrolic-N-rich carbon nanosheets: Propelling electrochemical kinetics and shielding polysulfides for lithium-sulfur batteries

The practical applications of lithium-sulfur (Li-S) batteries are rather limited by the shuttle effect of lithium polysulfides (LiPSs) and sluggish redox reaction kinetics. Here, a kind of pyrrolic-N-rich carbon nanosheets (Npr- CNs) are prepared by introducing melamine cyanurate (MCA) into the carbonization process of polyacrylonitrile (PAN). As a mediator in Li-S batteries, hierarchical pores, dominant pyrrolic-N-doping, disorder/defective structures and unique electronic states endow Npr-CNs with synergistic adsorption-catalysis function for S species. Specifically, they can effectively inhibit LiPSs shuttle, catalyze the conversion of both liquid-phase LiPSs and solid-phase Li2S, reduce the charge transfer resistance and enhance Li-ions migration rate. Hence, it can make the Li-S batteries deliver excellent rate performance and cycling stability. The battery can reach ultrahigh discharge capacity of 932.0 mAh g-1 at the beginning under current density of 1C and even liberate a capacity as high as 1109.4 mAh g-1 at 0.2C with high sulfur loading of 3.8 mg cm-2.