Si nanoparticles encapsulated in elastic hollow carbon fibres for Li-ion battery anodes with high structural stability.

Silicon has a large specific capacity which is an order of magnitude beyond that of conventional graphite, making it a promising anode material for lithium ion batteries. However, the large volume changes (∼ 300%) during cycling caused material pulverization and instability of the solid-electrolyte interphase resulting in poor cyclability which prevented its commercial application. Here, we have prepared a novel one-dimensional core-shell nanostructure in which the Si nanoparticles have been confined within hollow carbon nanofibres. Such a unique nanostructure exhibits high conductivity and facile ion transport, and the uniform pores within the particles which are generated during magnesiothermic reduction can serve as a buffer zone to accommodate the large volume changes of Si during electrochemical lithiation. Owing to these advantages, the composite shows high rate performance and good cycling stability. The optimum design of the core-shell nanostructure shows promise for the synthesis of a variety of high-performance electrode materials.