Rational Design of a Dual-Function Hybrid Cathode Substrate for Lithium-Sulfur Batteries

A unique 3D hybrid sponge with chemically coupled nickel disulfide-reduced graphene oxide (NiS2-RGO) framework is rationally developed as an effective polysulfide reservoir through a biomolecule-assisted self-assembly synthesis. An optimized amount of NiS2 (approximate to 18 wt%) with porous nanoflower-like morphology is uniformly in situ grown on the RGO substrate, providing abundant active sites to adsorb and localize polysulfides. The improved polysulfide adsorptivity from sulfiphilic NiS2 is confirmed by experimental data and first-principle calculations. Moreover, due to the chemical coupling between NiS2 and RGO formed during the in situ synthesis, the conductive RGO substrate offers a 3D electron pathway to facilitate charge transfer toward the NiS2-polysulfide adsorption interface, triggering a fast redox kinetics of polysulfide conversion and excellent rate performance (C/20-4C). Therefore, the self-assembled hybrid structure simultaneously promotes static polysulfide-trapping capability and dynamic polysulfide-conversion reversibility. As a result, the 3D porous sponge enables a high sulfur content (75 wt%) and a remarkably high sulfur loading (up to 21 mg cm(-2)) and areal capacity (up to 16 mAh cm(-2)), exceeding most of the reported values in the literature involving either RGO or metal sulfides/other metal compounds (sulfur content of <60 wt% and sulfur loading of <3 mg cm(-2)).