Synergetic effect of spatially separated dual co-catalyst for accelerating multiple conversion reaction in advanced lithium sulfur batteries

The enhanced chemical immobilization and catalytic conversion of polysulfides (LiPS) intermediates are considered a promising solution to improve the electrochemical performance in lithium-sulfur batteries. However, the role of catalysts on catalytic mechanism of distinctive selectivity is still not understood and overlooked. Herein, a dual-functional strategy, composed of Fe3O4 nanoparticles/hierarchical porous carbon (Fe3O4/HPC) cathode and FeP/HPC modified separator, is proposed to improve anchoring and catalyzing of LiPS, ensure uniform Li2S deposition and reduce the dead sulfur. The systematic theoretical calculation reveals that the Fe3O4 has the stronger binding energy with LiPS (Li2S4 and Li2S6) due to the Fe-S bonds and Li-O bonds. The variations in the catalytic performance of Fe3O4 and FeP are due to the shifts of p band center. Especially, Fe3O4 and FeP tend to selectively catalyze the solid-liquid reaction and liquid-liquid-solid conversion, respectively. Thus, the synergistic effects of dual-catalysts in spatial separation help to achieve excellent cycling stability with an ultralow capacity decay rate of 0.083% over 1000 cycles at 1 C. Even with a high areal sulfur loading of 5.73 mg cm−2 and a cruel current density of 0.01 C, the cells can still keep a low shuttle factor of 0.08, demonstrating the effective inhibition of shuttle effect. This work offers novel insights for designing a dual-functional structure in lithium-sulfur batteries.