Well-defined metal-N4 sites coordinated defective carbon as efficient electrocatalysts for high performance lithium–sulfur batteries

Abstract

The practical application of lithium–sulfur batteries has been limited by the detrimental shuttling behavior and sluggish conversion kinetics of lithium polysulfides (LiPSs), especially under high sulfur loading and lean electrolyte dosage. Although experimental and theoretical studies show that introducing defect and Fe–N4 site in carbon materials is the desirable strategy to expedite LiPSs conversion, the synergetic effect between them for sulfur redox chemistry is hardly explored. Herein, derived from a well-define Fe–N4 macrocyclic pristine iron phthalocyanine molecules (FePc) coordinated on the defective carbon nanosheets (FePc-DC), the marriage and synergetic effect between defective carbon and FePc molecules can induce remarkable Fe center electron delocalization and regulate the local electron redistribution between FePc-DC interfaces, thus brings improved LiPSs adsorption ability and conversion reaction rate. Meanwhile, the robust two-dimensional flake texture with large surface area and abundant porosity ensures robust physical confinement and fast electron/ion transfer. Attributed to such unique features, the lithium–sulfur batteries with FePc-DC cathode delivers good electrochemical performance with high areal capacity of 5.53 mAh/cm2 under high sulfur mass loading of 4.9 mg/cm2 and low electrolyte/sulfur ratio of 6.5 μL/mg, demonstrating great potential in advanced Li–S batteries.