Electronic structure adjustment of lithium sulfide by a single-atom copper catalyst toward high-rate lithium-sulfur batteries

•Developing a novel approach for enhancing catalytic efficiency toward Li2S deposition/dissolution by insulator-to-metal transition of Li2S.•Single-copper was screened out among single-atom catalysts to endow insulator-to-metal transition of Li2S.•Rapidly charge transfer on metallic Li2S nuclei leads to a morphology of spherical clusters other than conventional lateral film by continuous 3D nucleation & growth.•The catalytic efficiency of Li2S-covered catalytic sites is considerably enhanced, resulting in remarkable rate performance of Li-S batteries under high sulfur loading.