结构有序的Si/void/C/graphene纳米复合结构的制备及储锂性能

采用简单的超声、冷冻干燥和热还原相结合的自组装方法，设计和构建了纳米硅核/间隙/无定形碳壳层/石墨烯（Si/void/C/graphene） 三维有序纳米复合结构。在该结构中，纳米硅核与碳壳层之间的空隙有效避免了硅的巨大体积膨胀对碳层的破坏，大幅度提高了锂离子电池的循环稳定性；将Si/void/C纳米结构嵌入在石墨烯层与层之间，利用石墨烯卓越的导电性和柔韧性，进一步缓冲了硅材料的体积效应和提高了复合材料的导电性能。该复合材料在4200 mA·h·g^-1（1 C）电流密度下循环1000次后比容量仍高达1603 mA·h·g^-1；在67 A·g^-1（16 C）的高倍率下，比容量仍有310 mA·h·g^-1，显示出了在锂离子电池负极材料领域的巨大应用潜力。

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.