Encapsulated within graphene shell silicon nanoparticles anchored on vertically aligned graphene trees as lithium ion battery anodes

Silicon has been regarded as one of the most promising anode material for the next generation lithium ion battery. Unfortunately, the structure damage caused by the volume change of silicon and the continual interfacial reaction due to the electrolyte remain two major challenges. Here, we design a novel kind of in-situ growth binder-free silicon-based anodes. The adaptable silicon nanoparticles were encapsulated in graphene nanosheets (SiNPs@GNS). Simultaneously, the SiNPs@GNS composites anchored on vertically aligned graphene trees with loose intersecting leaves (GrTr). In the resulting samples, the GNS shells, as adaptable sealed wraps, could synergistically accommodate the volume change of the wrapped SiNPs, thus effectively avoiding the direct contact between encapsulated silicon and the electrolyte and enabling the interfacial and structural stabilization of encapsulated SiNPs during cycling. The GrTrs directly grown on current collector act as supporters of SiNPs, which ensure their dispersion uniformity and supply three dimensional short transportation paths for both Li ions and electrons. The in-situ growth of SiNPs@GNS-GrTr composites were proximately used as anodes in LIBs without adhesives and other complex brushing processes of the active material. The composite material exhibits a high capacity (1528 mAh g(-1) at 150 mA/g), relatively good cycle stability (88.6% after 50 cycles), and fast charge/discharge rate (412 mAh g(-1) at 8 A/g). The uniquely designed structure of the composites, which provide an ultra-thin, flexible GNS shell to accommodate the changes in volume, introduces large efficient areas, good conductivity, three dimensional transportation paths for both Li ions and electrons, and contributes to its excellent performance. (C) 2014 Elsevier Ltd. All rights reserved.