Synthesis of LiNi0.5Mn1.5O4 cathode material with improved electrochemical performances through a modified solid-state method

Abstract

High voltage LiNi0.5Mn1.5O4 cathode material was prepared by a modified solid-state method. For comparison, the LiNi0.5Mn1.5O4 sample was also prepared by a traditional solid-state method. The structure, morphology and electrochemical properties were investigated by X-ray diffraction (XRD), scanning-electron microscopy (SEM), Fourier transformation infrared spectroscopy (FT-IR), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge/discharge test in detail. XRD and SEM results show that the LiNi0.5Mn1.5O4 cathode material prepared by modified solid-state method has Fd-3m space group without impurity phase Li1−xNixO and relatively homogenous particle size distribution with smaller particle size. Especially, the primary particles are in the chamfered polyhedral morphology, totally different from the octahedral particle morphology prepared by traditional solid-state method. FT-IR and CV results show that the material prepared by modified solid-state method has lower cation disordering degree and lower Mn3+ content, which are advantageous to the cycling stability. EIS analysis indicates that the material prepared by modified solid-state method has lower charge transfer resistance and higher lithium ion diffusion coefficient, leading to its better electrochemical kinetics. The LiNi0.5Mn1.5O4 cathode material prepared by modified solid-state method exhibits discharge specific capacity of 122.9mAhg−1 at 10C rate and capacity retention rate of 97.4% after 100cycles at 1C rate, much higher than 103.3mAhg−1 and 89.0% of the material prepared by traditional solid-state method.