A low-temperature benzyl alcohol/benzyl mercaptan synthesis of iron oxysulfide/iron oxide composite materials for electrodes in Li-ion batteries

A low-temperature reaction of benzyl alcohol/benzyl mercaptan with iron(III) acetylacetonate was used to synthetize micron and submicron-sized materials composed of one-pot mixture of iron oxysulfide and iron oxide. The final compound as well as reference materials greigite and magnetite were investigated by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) spectroscopy. The crystal structure, chemical composition, and morphology of the particles of the iron oxysulfide/iron oxide composite were compared to the ones of the references, iron sulfide and iron oxide. The materials showed clear differences both in reduction and oxidation when they were cycled between 0.1–3.0 V or 1.0–3.0 V vs. Li+/Li. In all cases, electrochemical properties of the iron oxysulfide/iron oxide mixture make out to the ones of two reference materials. The in situ XRD investigation of greigite nanoplatelets confirmed that a topotactic reaction occurs between 3.0 and 1.0 V vs. Li+/Li, followed by a conversion reaction at potentials negative to 1.0 V vs. Li+/Li during the first lithiation.