Sulfiphilic FeP/rGO as a highly efficient sulfur host for propelling redox kinetics toward stable lithium-sulfur battery

The sluggish redox kinetics and shuttling effect result in low sulfur utilization, large polarization and rapid capacity decay of lithium-sulfur batteries. Here, we develop iron phosphide nanoparticles/reduced graphene oxide composites (FeP/rGO) as sulfiphilic host materials, which not only immobilize the polysulfides but also facilitate the fast charge transport kinetics, contributing to the reduced polarization and effective adsorption-diffusion-conversion interface of polysulfides. Moreover, the superficial oxidation of FeP nanoparticles helps to enhance the catalytic effect, facilitating a higher coulombic efficiency. As a consequence, the optimized S@FeP/rGO exhibits a high initial capacity of 1467 mAh g(-1) at 0.1 C with a sulfur utilization of 87.7% and stable cycling stability with a capacity retention of 646 mAh g(-1) at 1 C after 500 cycles. Even with a high sulfur loading of 6.1 mg cm(-2), the cell can still deliver an initial capacity of 835 mAh g(-1) at 0.2 C. In addition, the modified separator using FeP/rGO composites also exhibits excellent electrochemical performance. The current work provides a proof-of-concept study and practical application of S@FeP/rGO positive electrode in the lithium-sulfur batteries. (C) 2020 Published by Elsevier Ltd.