Design, preparation, and lithium-storage properties of ordered Si/void/C/graphene nanocomposites

An ordered three-dimensional Si/void/C/graphene nanostructure composite was constructed by a simple self-assembly method combined with ultrasonication, freeze-drying, and thermal reduction. In this novel nanostructure, Si nanoparticles are completely sealed inside carbon shells with rationally designed void spaces between the Si nanoparticles and the carbon shell, which are in turn embedded in layers of graphene sheets. The well-defined void space allows the Si particles to expand freely without breaking the outer carbon shell. Meanwhile, the graphene layers further reinforce the Si/void/C structure and thus enhance the electrical conductivity of silicon anode material and substantially increase the electrochemical performance of silicon anode material. This novel ordered structure delivers a long-term stability of 1603 mA·h·g^-1 over 1000 cycles at a high current density of 4200 mA·g^-1 (1 C), and an excellent rate capability of 310 mA·h·g^-1 at 67 A·g^-1 (16 C), thus exhibiting great potential as an anode composite structure for durable high-rate lithium ion batteries.