Pyrite film synthesized for lithium-ion batteries

Iron sulfide films were prepared on gold substrates by sulfurizing the iron oxide films previously deposited through a sol–gel technique. The crystal structure and the morphology have been characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD patterns have demonstrated that the iron sulfide film synthesized at 350 °C is pyrite. Energy dispersive spectroscopy (EDAX) showed that the S/Fe ratio is 1.9. The film was shown by chemical analysis to contain about 138.4 μg cm−2 pyrite. A thin-film battery was characterized by charge–discharge measurements and cyclic voltammograms. The results of the charge–discharge measurements showed that 48% of the iron formed in the first discharging process could not be oxidized to Fe(II) in the subsequent charging process at room temperature, which results in the main loss of reverse capacity. The film electrode of pyrite has a reversible capacity of 291 mAh g−1 at room temperature.