Physical and Electrochemical Properties of CuO-Coated Li[Ni_0.8Co_0.1Mn_0.1]O₂ Cathodes at Elevated Temperature for Lithium Ion Batteries

Herein, different amount of CuO are onto Li[Ni_0.8Co_0.1Mn_0.1]O₂ (NCM811) cathode active materials and characterized using X-ray diffraction (XRD), field emission-scanning electron microscopy (FE-SEM), and field emission-transmission electron microscopy (FE-TEM). A 2 wt.% CuO-coated NCM811 material has an obviously enhanced electrochemical behavior compared with the NCM811 material. In addition, the 2 wt.% CuO-coated NCM811 has the highest capacity retention values of 82.4 and 63.9% in current density of 150 and 200 mA g⁻¹, respectively. The capacity retention of pristine NCM811 material is 84.1%, whereas that of 2 wt.% CuO-coated NCM811 material is 90.4% after 80 cycles at 60 °C. According to electrochemical impedance spectra (EIS), the film resistance and the charge transfer resistance of CuO-coated material are lower than those of pristine NCM811. The reason behind the enhanced electrochemical behaviors of CuO-coated material is that the CuO prevents a direct contact of the cathode active material with electrolyte, suppressing a side reaction between the cathode material and unwanted-byproduct hydrofluoric (HF) acid.