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.