Modification of LiNi0.5Co0.2Mn0.3O2 with a NaAlO2 coating produces a cathode with increased long-term cycling performance at a high voltage cutoff

A long-lived cycling property is an important factor for the extensive use of the lithium-ion batteries. In this study, a NaAlO2 layer was initially coated on the LiNi0.5Co0.2Mn0.3O2 surface. Electrochemical tests indicate that the coated surface achieves better cycling stability and a higher capacity at 25 °C. In addition, the 1 wt % NaAlO2-coated sample exhibits the best performance, and it also exhibits a discharge specific capacity of 189.6 mAh∙g−1 at 0.1C in the first cycle. After 800 cycles at 1C, the capacity retention of the 1 wt % NaAlO2-coated sample is approximately 73.31%, a value that is 21.26% higher than the pristine sample. The electrochemical impedance spectroscopy (EIS) analysis reveals a decrease in the LiNi0.5Co0.2Mn0.3O2 charge transfer impedance and a significant increase in lithium ion diffusion after the application of the NaAlO2 coating. The high ion diffusion coefficient and low charge transfer impedance are conducive to the better rate performance of NaAlO2-coated LiNi0.5Co0.2Mn0.3O2.