Tailoring Coordination Micro‐Environments in Metal‐Based Molecular Complexes to Homogeneously Catalyze Li─S Battery Reactions

ABSTRACT The performance of lithium‐sulfur (Li─S) batteries is severely constrained by fatal polysulfide shuttling, sluggish sulfur redox kinetics, and uncontrollable lithium deposition. Organic metal‐based molecules have recently emerged as a novel type of promoters capable of modulating sulfur and lithium species evolution through either heterogeneous or homogeneous mechanisms to respond these issues. Herein, homogeneous metal‐based phenanthroline molecular catalysts are developed by tailoring coordination micro‐environments within electrolyte. By altering metal center type, the Co‐based complex in the electrolyte (Co‐ETL) shows an identical coordination geometry of Co–N 4 , whereas the Fe‐based complex in the electrolyte (Fe‐ETL) exhibits dual Fe─N 2 /Fe─N 4 coordination structures. Specifically, the Fe─N 2 coordination enhances adsorption of sulfur and lithium species, whereas the Fe─N 4 coordination promotes lithium atom diffusion more efficiently. Such a rational functionality division remarkably enhance the homogeneous optimization activity of the Fe‐ETL toward the kinetically favorable sulfur cathode reactions and improved lithium anode stability. Therefore, the battery demonstrates stable cycling at 5.0 C over 500 cycles with a low degradation of 0.03% per cycle. Even under a sulfur loading of 7.1 mg cm −2 , the battery delivers a remarkable initial areal capacity of 6.4 mA h cm −2 and maintains a favorable cycling stability.