One-step detonation-assisted synthesis of Fe₃O₄-Fe@BCNT composite towards high performance lithium-ion batteries

An Fe₃O₄-Fe@BCNT composite was successfully synthesized via detonation of a mixture of hexogen (C₃H₆N₆O₆) and ferrocene (C₁₀H₁₀Fe), in which bamboo-like carbon nanotubes encapsulating iron nanoparticles attached to Fe₃O₄ flakes (up to 58.1%) were formed. In the detonation process, hexogen was used to generate high temperature and high pressure, while ferrocene was used as a carbon source and catalyst. The recovered Fe₃O₄-Fe@BCNT composite was characterized by TEM, SEM, XRD, XPS, and Raman spectroscopy. The results indicate that multi-walled carbon tubes with a bamboo-like structure are formed, in which iron nanoparticles are encapsulated. The length of the multi-layered nanotubes (about 18-20 layers) is over 600 nm with diameters in the range of 20-30 nm. The content of Fe₃O₄ flakes dispersed into the carbon tubes is affected by the atomic ratio of C to Fe. In addition, the Fe₃O₄-Fe@BCNT composite exhibits excellent electrochemical performance as an anode material in Li-ion batteries. The charge-discharge coulombic efficiency is up to 81.1% in the first cycle. After 100 cycles, the discharge capacity steadily increases up to nearly 800 mA h g^-1 due to activation. The rate capability of the Fe₃O₄-Fe@BCNT composite is also excellent at current densities ranging from 100 to 2000 mA g^-1.