Synthesis, characterization, and electrochemical properties of lithium-based fluorosulfate nanoparticles as cathode for lithium-ion batteries

Lithium-based fluorosulfate nanoparticles were synthesized by a simple and fast solid state reaction from the precursors FeSO4∙7H2O and LiF ground by high energy ball milling. Through the introduction of excess of LiF, relatively pure LiFeSO4F phase with polycrystalline structure was obtained. The structure, morphology, and element valence state were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectra (XPS). The results demonstrate uniformly distributed particles and larger particles consisted of single crystalline structure, besides the valence states for different elements were analyzed and Fe2+ was confirmed. The cyclic voltammograms (CV) and charge-discharge cycling performances were employed to characterize electrochemical properties of prepared cathode material. It is very interesting that double redox peaks appeared reversibly. Meanwhile, it exhibited a relatively higher first-discharge capacity of 115 mAh/g at 0.05C and it still maintained above 60 mAh/g capacity after experiencing 30 times cycles at final 2C rate.