High rate capability of hydrogen annealed iron oxide-single walled carbon nanotube hybrid films for lithium-ion batteries.

A facile and effective hydrogen annealing method has been demonstrated to synthesize iron oxide/SWNT hybrid films involving the thermal reduction of rhombohedral Fe2O3 to cubic Fe3O4 through the phase transformation while maintaining the morphological integrity of the films. The poor rate capability and cyclic stability of the original α-Fe2O3/SWNT hybrid films have been significantly improved by H2 annealing. The prepared iron oxide/SWNT hybrid films have a high capacity of 786 mA h g(-1) at a high current density of 4 A g(-1) with a prolonged lifetime. The enhancement of the electrochemical performance is attributed to the presence of highly conductive Fe3O4, accelerated charge-transfer kinetics, and the increased Li+ diffusivity confirmed by electrochemical impedance spectra and galvanostatic intermittent titration.