Well-defined LiNi0.5Mn1.5O4 powder has been synthesized by ethylene glycol (EG)-assisted oxalic acid co-precipitation method. The structure and physicochemical properties of this as-prepared powder were investigated by powder X-ray diffraction (XRD), Raman spectra (RS), scanning electron microscopy (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and galvanostatic charge–discharge test in detail. XRD shows impurity phase of LiyNi1-yO due to the oxygen loss reaction at high temperatures. SEM indicates that LiNi0.5Mn1.5O4 synthesized by EG-assisted method has a uniform and narrow size distribution under 1μm. RS confirms that both samples have Fd-3m space group. EIS and CV test exhibit that LiNi0.5Mn1.5O4 electrode synthesized by EG-assisted method has lower potential polarization, smaller charge transfer resistance, higher reversibility and larger lithium ion diffusion coefficient than the one obtained by ammonium hydroxide co-precipitation method. Galvanostatic charge–discharge test reveals that LiNi0.5Mn1.5O4 synthesized by EG-assisted method shows higher discharge capacity than that the one synthesized by ammonium hydroxide co-precipitation method at each rate.