Improved electrochemical performance of Li1.2Ni0.2Mn0.6O2 cathode materials by ball milling and carbon coating

Li1.2Ni0.2Mn0.6O2 powders have been synthesized and then treated by ball milling and carbon coating to improve the electrochemical performance. The effect of ball milling and carbon coating on physical and electrochemical properties has been discussed through the characterizations of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM), electrochemical impedance spectroscopy (EIS), discharge capacity and rate tests. The first discharge capacity and rate capability exhibit a great improvement for carbon-coated Li1.2Ni0.2Mn0.6O2 than the pristine and ball-milled. The discharge capacities of carbon-coated cathode at 0.1 and 10 C are 253 and 130 mAhg− 1, while those of ball-milled cathode are 228 and 85 mAhg− 1, and those of pristine Li1.2Ni0.2Mn0.6O2 are only about 219 and 22 mAhg− 1. The capacity retention of carbon-coated electrode after 50 cycles is 97.8%, in compared with those of pristine and ball-milled are 95.3% and 92.8%, respectively. EIS results indicate that the charge transfer resistance (Rct) of pristine electrode has been decreased from 62 Ω to 35 Ω after ball milling and to 23 Ω after carbon coating, and the Rct of pristine Li1.2Ni0.2Mn0.6O2 increased faster than that of carbon-coated sample after cycles.