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 NaAlO 2 layer was initially coated on the LiNi 0.5 Co 0.2 Mn 0.3 O 2 surface. Electrochemical tests indicate that the coated surface achieves better cycling stability and a higher capacity at 25 °C. In addition, the 1 wt % NaAlO 2 -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 % NaAlO 2 -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 LiNi 0.5 Co 0.2 Mn 0.3 O 2 charge transfer impedance and a significant increase in lithium ion diffusion after the application of the NaAlO 2 coating. The high ion diffusion coefficient and low charge transfer impedance are conducive to the better rate performance of NaAlO 2 -coated LiNi 0.5 Co 0.2 Mn 0.3 O 2 .