Enhanced electrochemical properties of LiNi0.6Co0.2Mn0.2O2 cathode material by the diffusional Al2O3 coating layer

Abstract

The surface coating is a greatly effective approach to improve the electrochemical performance of the Ni-rich LiNi0.6Co0.2Mn0.2O2 cathode material. Herein, the traditional and diffusional Al2O3 coating ways are used to modify LiNi0.6Co0.2Mn0.2O2 cathode materials. Various analysis techniques, such as scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS) were used to characterize materials. The results show that a thin and homogeneous Al2O3 coating layer was prepared on diffusional surface coating compared with traditional surface coating with a thick and uneven Al2O3 coating layer. The diffusional coating material exhibits the optimized electrochemical performance, with retention of 99.5% after 100 cycles at 1 C, and excellent rate performance. The electrochemical impedance spectroscopy further confirms that the superior electrochemical performance of diffusional Al2O3 coating sample can be attributed to the high-quality coating layer which is formed by the interface reactions between Al2O3 particles and the surface of LiNi0.6Co0.2Mn0.2O2 cathode material during high-temperature calcination. The outstanding coating layer not only protects the active material from the attack of electrolyte but also shortens Li+ diffusion path effectively during charge/discharge process. Based on the above results, the diffusional Al2O3 coating is considered as an effective surface modification method to improve the electrochemical performance of LiNi0.6Co0.2Mn0.2O2 materials.