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 (≈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).