Cerium fluoride coated layered oxide Li1.2Mn0.54Ni0.13Co0.13O2 as cathode materials with improved electrochemical performance for lithium ion batteries

Cerium fluoride (CeF3) coated lithium-rich layered Li1.2Mn0.54Ni0.13Co0.13O2 particles are synthesized using a facile chemical deposition route. The structural and electrochemical properties of pristine and CeF3-coated electrodes are investigated by X-ray diffraction (XRD), thermogravimetric-differential scanning calorimetry (TG-DSC), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), galvanostatic charge/discharge tests, electrochemical impedance spectra (EIS) and cyclic voltammetry (CV). The results indicate that the cathode particles are uniformly covered with a CeF3 layer (similar to 10 nm thick) after 2 wt.% CeF3 surface coating. The coated electrode shows an enhanced initial coulombic efficiency of 80.8% compared to 75.2% for the pristine electrode. Moreover, the coated electrode demonstrates better cyclic performance, which exhibits capacity retention of 91.7% after 50 cycles compared with only 82.1% for the pristine one. Furthermore, the CeF3-coated electrode delivers a superior high-rate capacity of 103.1 mAh g(-1) at 5C, higher than 82.2 mAh g(-1) for the pristine one. The remarkably improved cycling stability and high-rate capacity of the surface-modified electrode is ascribed to the presence of a stable and thin CeF3 coating layer which effectively reduces the damage of electrode structure and suppresses the increase of impedance during cycling by preventing direct contact of electrode with electrolyte. (C) 2014 Elsevier B.V. All rights reserved.