Enhanced Electrochemical Properties of Surface Modified LiMn2O4by Li-Fe Composites for Rechargeable Lithium Ion Batteries

The surface modified LiMn2O4 materials with Li-Fe composites were prepared by a sol-gel method to improve the elec- trochemical performance of LiMn2O4 and were characterized by X-ray diffraction (XRD), X-ray photoelectron spec- troscopy (XPS), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), and transmission electron microscopy (TEM)-EDS. XRD results indicate that all the samples (modified and pristine samples) have cubic spinel structures, and XRD, XPS, and TEM-EDS data reveal the formation of Li(LixFexMn2-2x)O4 solid solution on the sur- face of particles. For the electrochemical properties, the modified material demonstrated dramatically enhanced reversibility and stability even at elevated temperature. These improvements are attributed to the formation of the solid solution, and thus-formed solid solution phase on the surface of LiMn2O4 particle reduces the dissolution of Mn ion and suppresses the Jahn-Teller effect.