Improvement of the first coulomb efficiency and rate performance of Li1.5Ni0.25Mn0.75O2.5 with spinel LiNi0.5Mn1.5O4 doping

Li1.1Ni0.25Mn0.75O2.3 and Li1.5Ni0.25Mn0.75O2.5 have been synthesized by co-precipitation method. The effect of the LiNi0.5Mn1.5O4 spinel structure on physical and electrochemical properties is discussed through the characterizations of X-ray diffraction (XRD), scanning electron microscopy, high-resolution transmission electron microscopy, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and electrochemical performance tests. The LiNi0.5Mn1.5O4 spinel structure is detected in the XRD pattern, TEM image, first discharge, and CV curves of the Li1.1Ni0.25Mn0.75O2.3 electrode. The rate, cyclic performance, and first coulomb efficiency of Li1.1Ni0.25Mn0.75O2.35 are higher than those of Li1.5Ni0.25Mn0.75O2.5. The first coulomb efficiencies of Li1.1Ni0.25Mn0.75O2.3 and Li1.5Ni0.25Mn0.75O2.5 are 86.2 and 74.7 %, and the capacity retentions are 98.7 and 94.1 % after 50 cycles, respectively. EIS results indicate that the charge-transfer reaction resistance of Li1.1Ni0.25Mn0.75O2.3 is lower than that of Li1.5Ni0.25Mn0.75O2.5, which is responsible for the better rate capacity of Li1.1Ni0.25Mn0.75O2.3.