Carbon-Coated Si Nanoparticles Anchored between Reduced Graphene Oxides as an Extremely Reversible Anode Material for High Energy-Density Li-Ion Battery

Improving the lithium (Li) storage properties of silicon (Si)-based anode materials is of great significance for the realization of advanced Li-ion batteries. The major challenge is to make Si-based anode materials maintain electronic conduction and structural integrity during cycling. Novel carbon-coated Si nanoparticles (NPs)/reduced graphene oxides (rGO) composites are synthesized through simple solution mixing and layer-by-layer assembly between polydopamine-coated Si NPs and graphene oxide nanosheets by filtration, followed by a thermal reduction. The anodic properties of this composite demonstrate the potency of the novel hybrid design based on two dimensional materials for extremely reversible energy conversion and storage. A high capacity and an extremely stable cycle life are simultaneously realized with carbon-coated Si/rGO composite, which has a sandwich structure. The unprecedented electrochemical performance of this composite can be ascribed to the synergistic effect of polydopamine and rGO. The polydopamine layer forms strong hydrogen bonding with rGO through chemical cross-linking, thus firmly anchoring Si NPs on rGO sheets to prevent the aggregation of Si NPs and their electronic contact loss. Finally, its structural feature with stacked rGO clipping carbon-coated Si NPs inside it enables to keep the overall electrode highly conductive and mechanically robust, thus maintaining its initial capacity even with extended cycling.