Pulsed laser deposited FeOF as negative electrodes for rechargeable Li batteries

FeOF thin film has been successfully fabricated by reactive pulsed laser deposition for the first time, and its electrochemical behavior was examined as a negative electrode active material in lithium-ion batteries. The electrochemical properties of the as-deposited FeOF thin film during the first charging and discharging have been investigated by the galvanostatic cycling and cyclic voltammetry measurements. By using ex situ X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and selected-area electron diffraction measurements (SAED), it can be found that FeOF was initially decomposed into Fe0, LiF, and Fe2O3 after discharging to 1.0 V. The newly formed Fe2O3 is then subsequently reduced into Li2O and Fe0 after further discharging to 0.01 V. In the subsequent cycle, the reduction peaks at 0.76 V and the oxidation–reduction peaks at 1.6 and 1.9 V could be attributed to the reversible decomposition and formation of Li2O with the conversion reaction of Fe2O3 into Fe.