Effect of TiO2 coating on structure and electrochemical performance of LiNi0.6Co0.2Mn0.2O2 cathode material for lithium ion batteries

Abstract

Many efforts have been made to improve the electrochemical performance of Ni-rich cathode materials, such as metal ion doping, surface modification, and fabricating nanostructured materials. Here, to enhance the electrochemical performance of the LiNi_0.6Co_0.2Mn_0.2O₂ (NCM622) cathode, NCM622 was coated by TiO₂ layers through the sol-gel process. X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and electrochemical tests have been applied for material characterizations and electrochemical measurements. Compared with the pristine NCM622 electrode, the cycling stability and rate performance of the TiO₂-coated NCM622 electrodes are significantly improved. Among all TiO₂-coated NCM622, the NCM622 cathode with TiO₂ coating content of 0.5% demonstrats a highest capacity retention of 89.3% and a discharge capacity of 163.9 mAh g^− 1, in contrast to 80.9% and145 mAh g^− 1 for the pristine NCM622 electrode, after 100 cycles at 0.3 C between 3-4.3 V. Under the high cutoff voltage of 4.6 V, the 5 wt% TiO₂-coated. NCM electrode exhibit better electrochemical properties than bare NCM622 in terms of specific capacity and cyclability, similar to the results measured at a cut-off voltage of 4.3 V. The results prove that TiO₂ modification can lower the polarization of the material, effectively raising the cycling stability rate performance of the battery. It provides a reference path for the further progress of high capacity and stability ternary cathode materials.