LaF3-coated Li[Li0.2Mn0.56Ni0.16Co0.08]O2 as cathode material with improved electrochemical performance for lithium ion batteries

Abstract

In this article, the pristine Li-rich layered oxide Li[Li_0.2Mn_0.56Ni_0.16Co_0.08]O₂ porous microspheres have been successfully synthesized using a urea combustion method and then coated with 1 wt% LaF₃ via a facile chemical precipitation route. The structures and morphologies of both pristine and LaF₃ coated Li_1.2Mn_0.54Ni_0.16Co_0.08O₂ were investigated by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HR-TEM). The results reveal that the obtained particles possesses the morphology of porous microspheres and a LaF₃ layer with a thickness of 5–8 nm coated on the surface of the Li[Li_0.2Mn_0.56Ni_0.16Co_0.08]O₂ particles. As lithium ion battery cathodes, the LaF₃ coated sample, compared with the pristine one, has shown a significantly improved electrochemical performance; the initial coulombic efficiency improves from 75.36% to 80.01% and the rate compatibility increased from 57.4 mA h g⁻¹ to an extremely high capacity of 153.5 mA h g⁻¹ at 5 C. Decreased electrochemical impedance spectroscopy (EIS) reveals that the enhanced electrochemical performance of the surface coating was attributed to the lower charge transfer resistance of the sample.