Anchoring Polysulfides and Accelerating Redox Reaction Enabled by Fe-Based Compounds in Lithium-Sulfur Batteries

The synergetic mechanism of chemisorption and catalysis play an important role in developing high-performance lithium-sulfur (Li-S) batteries. Herein, a 3D lather-like porous carbon framework containing Fe-based compounds (including Fe3C, Fe3O4, and Fe2O3), named FeCFeOC, is designed as the sulfur host and the interlayer on separator. Due to the strong chemisorption and catalytic ability of FeCFeOC composite, the soluble lithium polysulfides (LiPSs) are first adsorbed and anchored on the surface of the FeCFeOC composite and then are catalyzed to accelerate their conversion reaction. In addition, the FexOy in Fe-based compounds can spontaneously react with LiPSs to form magnetic FeSx species with a larger size, further blocking the penetration of LiPSs cross the separator. As a result, the assembled Li-S cells show excellent long-term stability (748 mAh g(-1) over 500 cycles at 1.0 C, and approximate to 0.036% decay per cycle for 1000 cycles at 3.0 C), a superb rate capability with 659 mAh g(-1) at 5.0 C, and lower electrochemical polarization. This work introduces a feasible strategy to anchor and accelerate the conversion of LiPSs by designing the multifunctional Fe-based compounds with high chemisorption and catalytic activity, which advances the large-scale application of high-performance Li-S batteries.