Dual confining polysulfides by growing NiCo2S4 nanosheets on porous carbon nanoboxes to accelerate redox kinetics for efficient lithium-sulfur batteries

Abstract

It is of particular significance to develop functional materials to regulate the polysulfide shuttling and promote the polysulfide conversion for lithium-sulfur (Li-S) batteries. Herein, we demonstrate the dual confinement of polysulfides on a composite host featuring NiCo2S4 nanosheets grown on porous carbon nanoboxes (CNB). The porous CNBs provide huge cavity for efficient accommodation of sulfur and physical confinement of soluble polysulfides. Meanwhile, the surface-grown NiCo2S4 nanosheets show strong chemical entrappment of polysulfides, and good catalytic effect on the polysulfide conversion. By virtue of the above dual effect on confining polysulfides, the sulfur cathode based on NiCo2S4/CNB host shows a high reversible capacity of 635.6 mAh g−1 at 5 C. Excellent cycle stability with a low capacity decay rate of 0.15% per cycle can be realized with a high sulfur loading of 4.8 mg cm−2 and an electrolyte/sulfur (E/S) ratio of 15 μL mgS−1. Moreover, the S/NiCo2S4/CNB cathode delivers a reversible capacity of 637 mAh g−1 at 1 C with a low E/S ratio of 3 μL mgS−1, as well as a good cycle stability. This work provide an effective strategy for fabricating sulfur hosts that enable a physical/chemical dual confinement of polysulfides for high-performance Li-S batteries.