Effect of Nb5+ doping on LiNi0.5Co0.25Mn0.25O2 cathode material

Li (Ni0.5Co0.25Mn0.25)1−xNbxO2 (x = 0, 0.005, 0.01, 0.02, 0.03) cathode material was synthesized by co-precipitation. X-ray diffraction spectroscopy (XRD) and scanning electron microscopy (SEM) were used to analyze the crystal structure characteristics and morphology of the powder. The charge and discharge test, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) were used to study the electrochemical properties of the battery in detail. XRD results show that Nb5+ substitution does not destroy the crystal structure, but it can enlarge the interplanar spacing, which is beneficial to the diffusion of lithium ions. The electrochemical properties of the material Li (Ni0.5Co0.25Mn0.25)0.99Nb0.01O2 are the best. The discharge specific capacity is 204.6, 186.0, 163.5, 141.6 mAh/g at 0.1C, 0.2C, 0.5C, and 1.0C, respectively. And the discharge specific capacity is as high as 174.1 mAh/g when returning to 0.1C again. After circulating 45 cycles at 0.1C, the capacity retention rate was 89.08%.