Calcination Temperature Effect on Citrate-Capped Iron Oxide Nanoparticles as Lithium-Storage Anode Materials

In this work, citrate-capped magnetites (cit-Fe3O4) are facilely synthesized according to a modified co-precipitation method, and the resulting cit-Fe3O4 underwent thermal calcination under N-2 flow for 2h. The calcined cit-Fe3O4 at 500 degrees C, so-called C-Fe3O4 (500 degrees C), exhibits the XRD patterns attributed mainly to the fcc crystalline phases of magnetite (Fe3O4). On the other hand, the calcined cit-Fe3O4 at 700 degrees C, so-called C-Fe2O3 (700 degrees C), exhibits the X-ray diffraction (XRD) patterns attributed mostly to hexagonal crystalline phases of hematite (-Fe2O3). The iron oxides calcined at different temperatures (500, 600, 700 degrees C) are employed as active anode materials for Li-ion batteries. After 80 cycles at the current rate of 0.1C, the C-Fe2O3 (700 degrees C) exhibits the higher reversible capacity by approximate to 200% than that of the C-Fe3O4 (500 degrees C). The improved reversible capacity of the C-Fe2O3 (700 degrees C) is attributed to the transformation of magnetite phases into hematite phases with higher crystallinity, which is more beneficial for faster transfer of charge carriers and structural stability.