Surface modification of Li1.20Mn0.54Ni0.13Co0.13O2 cathode materials with SmF3 and the improved electrochemical properties

The Li1.20Mn0.54Ni0.13Co0.13O2 cathode materials with the different SmF3 coating contents were successfully synthesized through the typical wet chemical method. The X-ray diffractometer, scanning electron microscopy, transmission electron microscope, X-ray photoelectron spectroscopy and galvanostatic charge–discharge tests were adopted to investigate the influence of SmF3 layer on the crystal structural, morphology and electrochemical properties of Li1.20Mn0.54Ni0.13Co0.13O2. The results showed that the cathode materials were successfully coated with SmF3 without changing its micro-structure. Besides, the electrochemical tests results demonstrated that electrochemical properties of Li1.20Mn0.54Ni0.13Co0.13O2 were significantly enhanced after applying the SmF3 coating. The specific discharge capacity of the 2 wt% SmF3 coated Li1.20Mn0.54Ni0.13Co0.13O2 is 30.4 mAh g−1 higher than that of pristine one at 0.5C rate. Meanwhile, the 2 wt% SmF3 coated Li1.20Mn0.54Ni0.13Co0.13O2 delivered an outstanding cycle stability with a high capacity retention of 91.4% after 100 cycles, while the pristine one showed the less discharge capacity and a low capacity retention of 85.2%. The enhanced electrochemical properties could be ascribed to the SmF3 coating layer, which not only stabilizes the cathode structure by restricting the side reaction between cathodes materials with electrolyte, but also relieves the increase of impedance for Li+ migration across the electrode/electrolyte interface during cycling.