Electrochemical Properties of a 4.7 V-Class LiNi0.5Mn1.5O4 Positive Electrode Material for High Power Li-Ion Battery

The LiNi0.5Mn1.5O4 cathode material for high power lithium-ion battery is successfully synthesized by sol–gel method. The structure, the morphology and the electrochemical characteristics of the compound are studied by X-ray diffraction (XRD), a field emission scanning electron microscope (FE-SEM), cyclic voltammogram (CV) and charge–discharge techniques, respectively. The results indicate that LiNi0.5Mn1.5O4 sample has cubic spinel structure and its particles crystallized well with submicro size. There are a higher voltage plateau around 4.7 V and a lower voltage plateau above 4 V at 3.3–5.0 V in the charge–discharge curves of LiNi0.5Mn1.5O4, corresponding to two redox peaks of Ni2+/Ni4+ and Mn3+/Mn4+ of its CV respectively. The LiNi0.5Mn1.5O4 with ordered Fd3m space group has 150.57 mAh g−1 initial charge capacity and 139.57 mAh g−1 initial discharge capacity, showing excellent electrochemical performance. A short arc at more high frequency zone from 4.4 V potential emerges in electrochemical impedance spectroscopy (EIS), attributing to oxidative decomposition of the electrolyte at high voltage. The equivalent circuit selected could fit the EIS experiment data very well.