Delocalized Isoelectronic Heterostructured FeCoOxSy Catalysts with Tunable Electron Density for Accelerated Sulfur Redox Kinetics in Li‐S batteries

High interconversion energy barriers, depressive reaction kinetics of sulfur species, and sluggish Li + transport inhibit the wide development of high‐energy‐density lithium sulfur (Li−S) batteries. Herein, differing from random mixture of selected catalysts, the composite catalyst with outer delocalized isoelectronic heterostructure (DIHC) is proposed and optimized, enhancing the catalytic efficiency for decreasing related energy barriers. As a proof‐of‐content, the FeCoO x S y composites with different degrees of sulfurization are fabricated by regulating atoms ratio between O and S. The relationship of catalytic efficiency and principal mechanism in DIHCs are deeply understood from electrochemical experiments to in situ/operando spectral spectroscopies i.e., Raman, XRD and UV/Vis. Consequently, the polysulfide conversion and Li 2 S precipitation/dissolution experiments strongly demonstrate the volcano‐like catalytic efficiency of various DIHCs. Furthermore, the FeCoO x S y ‐decorated cell delivers the high performance (1413 mAh g −1 at 0.1 A g −1 ). Under the low electrolyte/sulfur ratio, the high loading cell stabilizes the areal capacity of 6.67 mAh cm −2 at 0.2 A g −1 . Impressively, even resting for about 17 days for possible polysulfide shuttling, the high‐mass‐loading FeCoO x S y ‐decorated cell stabilizes the same capacity, showing the practical application of the DIHCs in improving catalytic efficiency and reaching high electrochemical performance.