Transformation from hollow carbon octahedra to compressed octahedra and their use in lithium-ion batteries

Hollow carbon octahedra with an average size of 300 nm and a shell thickness of 2.5 nm were prepared by a reaction starting from ferrocene and Mg(CH3COO)2·4H2O at 700 °C for 10 h. They became compressed and turned into deflated balloon-like octahedra when the reaction time was increased to 16 h. It was proposed that the gas pressure generated during the reaction process induced the transformation from broken carbon hollow octahedra into deflated balloon-like compressed octahedra. X-ray powder diffraction and Raman spectroscopy indicate that the as-obtained carbon products possess a graphitic structure and high-resolution transmission electron microscopy images indicate that they have low crystallinity. Their application as an electrode shows reversible capacity of 353 mAh g−1 after 100 cycles in the charge/discharge experiments of secondary lithium ion batteries.