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

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.