Self-Assembled Nanocomposite of Silicon Nanoparticles Encapsulated in Graphene through Electrostatic Attraction for Lithium-Ion Batteries

Substantial efforts have been devoted in the past decade to developing rechargeable lithium-ion batteries with high energy density and long cycle life for portable electronics, electric vehicles (EVs), and renewable energy storage. [ 1-11 ] The low theoretical capacity (372 mA h g - 1 ) of currently commercialized graphite cannot satisfy the demand of high energy density. Various anode materials with higher specifi c capacities have been proposed for lithium-ion batteries. Among these, silicon has attracted enormous attention owing to its low lithium-uptake potential and the highest theoretical capacity (4200 mA h g - 1 ). [ 12-16 ] However, the practical application of Si as an anode material is seriously hampered by the low intrinsic electric conductivity and large volume changes (greater than 300%) during lithium insertion and extraction from Si, resulting in dramatic pulverization of Si particles and electrical disconnection from the current collector, [ 17 ] and leading to rapid capacity fade upon cycling. To overcome these obstacles, fabrication of Si nano structures including nanowires, nanotubes, and hollow nanospheres and preparation of highconductivity carbon-coated Si nanocomposites have been well developed. [ 18-27 ] However, there is still a need for well-designed Si-based nanomaterials and their facile synthetic methods towards high-performance anode materials. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.