The preparation and electrochemical study of LiNi0.6Co0.2Mn0.2O2 cathode material for lithium-ion battery

Abstract

To improve the cycling performance of nickel-rich layered LiNi0.6Co0.2Mn0.2O2 material, many methods have been studied to reduce cation mixing degree, improve layered structure and modify particle morphology, including doping elements, coating metal oxides and morphology control (spherical, nanoflower, core–shell structure, etc.). In this paper, a new gradient calcination process through four-step temperature gradients is applied to synthesize LiNi0.6Co0.2Mn0.2O2 material. The LiNi0.6Co0.2Mn0.2O2 material synthesized by gradient calcination shows more excellent electrochemical performance than traditional method. The XRD results indicate that the LiNi0.6Co0.2Mn0.2O2 material produced by four-step calcination shows lower cation mixing degree and better crystallinity. In addition, the LiNi0.6Co0.2Mn0.2O2 cathode produced by gradient calcination presents the highest initial capacity (177.9 mAh g−1) and a retention of 82.07% after 100 cycles at 0.2C. And the material shows the best electrochemical properties when the final temperature in these steps is 820 °C. Our results explain the reason why the thermal stability and electrochemical performance could be improved by gradient calcination from the aspect of material crystallinity, crystal defects, cation mixing degree and the completeness of the layered structure.