Synthesis of cage-like silicon/carbon microspheres and their high-rate performance anode materials for lithium-ion batteries

The practical application of Si-based materials has been impeded by poor cycling stability. The cage-like silicon/carbon microspheres were fabricated via a series of procedures: the allometric nucleation, magnesiothermic reduction and selective etching. The microstructure, morphology and electrochemical performance for cage-like silicon/carbon microspheres were investigated by X-ray photoelectron spectra, scanning electron microscopy, transmission electron microscopy and galvanostatic charge-discharge tests. The cage-like carbon shell can effectively absorb the volume expansion and restrain the pulverization for silicon electrodes due to its excellent flexibility and toughness, and particular structure. The cage-like silicon/carbon microspheres reveal an outstanding charge capacity of 1926 mA h g−1 at 0.1 C, and still remain 1790 mA h g−1 after 200 cycles. They exhibit an excellent rate capacity of 916 mA h g−1 and capacity retention of 96% after 1000 cycles at 5 C. The design strategy of the cage-like carbon shell structure offers a novel path for improving the electrochemical performance of silicon-based materials.