Surfactant carbonization to synthesize pseudocubic α-Fe2O3/C nanocomposite and its electrochemical performance in lithium-ion batteries

Highlights: → First time to propose surfactant carbonization method to synthesize nanocomposites. → Oleic groups convert to carbon at 300 deg. C for 2 h under Ar. → Pseudocubic α-Fe2O3 nanoparticle coated by a carbon layer of 1-2 nm. → An improved cycling and rate performance after carbon coating. - Abstract: Pseudocubic α-Fe2O3/C nanocomposites with sizes of 30-35 nm were synthesized via in situ carbonization of surfactants under Ar atmosphere using oleic acid-capped α-Fe2O3 nanoparticles as precursors. The transformation from oleic groups to carbon was evidenced in detail by Fourier transform infrared spectroscopy, elemental analysis and thermogravimetric analysis. The high resolution transmission electron microscope further confirmed that a thin carbon layer of 1-2 nm in thickness tightly coated α-Fe2O3 nanocrystals. Compared with bare α-Fe2O3 nanoparticles, α-Fe2O3/C composites exhibited excellent cycling performance (a reversible capacity of 688 mAh/g after 50 cycles at 0.2 C rate) and rate capability (370 mAh/g after 20 cycles at 2 C) as anode materials for lithium-ion batteries. The remarkably improved electrochemical performance of α-Fe2O3/C nanocomposites was attributed to in situ carbon coating, which prevented nanoparticle aggregation, increased electronic conductivity and stabilized solid electrolyte interface (SEI) films.