Homogeneous/Heterogeneous Catalyst Design for Lithium–Sulfur Batteries via Phase Separation

ABSTRACT The dual regulation of sulfur redox kinetics and lithium deposition behavior represents a pivotal breakthrough toward overcoming the performance limitations of lithium–sulfur (Li–S) batteries. Metal‐based organic molecules provide an ideal solution for rationalizing the electrolyte electrochemistry in Li–S system, featuring both nitrogen‐rich properties and active metal centers. Herein, we leverage the solubility of iron phthalocyanine chloride (FePcCl) in the electrolyte to induce phase separation. The dissolved portion (FePcCl solute) functions as a homogeneous catalyst (Fe‐Hom), whilst the insoluble fraction is uniformly loaded onto carbon spheres to act as a heterogeneous catalyst (Fe‐Het). The homogeneous/heterogeneous synergistic catalyst system (Fe‐Syg), developed through precise phase‐separation engineering, enables the coexistence of mobile and immobilized active sites. This synergy maximizes the working activity of Fe‐Syg beyond the limitations of single‐phase catalysts, simultaneously regulating sulfur conversion kinetics and lithium plating/stripping behavior toward high‐efficiency and robust electrodes. As a result, the Li–S batteries incorporating Fe‐Syg demonstrate favorable rate capability and operational lifespan under various conditions. Remarkably, a pouch cell assembled with a lean electrolyte dosage of 3.5 µL mg −1 achieves a favorable energy density of 364.8 Wh kg −1 and maintains stable cycling for 40 cycles.