Surface modification and characterization of LiNi0.8Co0.2O2

The harmful interactions between the positive active materials and the electrolyte in lithium secondary batteries hurt the performance of the cathode materials and the batteries. A Li2O-2B2O3 glass film was coated on the LiNi0.8Co0.2O2 cathode material surface by mixing LiNi0.8Co0.2O2, LiOH&middotH2O and H3BO3 with a molar ratio of 100:1:2 and heating the mixture at 500°C for 10 h. The structures of the coated and uncoated LiNi0.8Co0.2O2 were investigated by X-ray photoelectron spectrometry (XPS), scanning electron microscope (SEM), and X-ray-diffractometer (XRD). It was shown that the surface modification effectively reduced the harmful interactions between the LiNi0.8Co0.2O2 and the electrolyte. The surface modified LiNi0.8Co0.2O2 cathode material had increased actual specific capacity, stabilized cycling performance and reduced self-discharge. Surface modification is an effective way to improve the properties of the positive active materials for lithium secondary batteries.