New applications of lithium ion batteries in hybrid electric vehicles require high electrochemical performance such as improved power density. High crystalline submicron-size LiNi0.5Mn1.5O4 with high capacity and high rate capability was explored in this work through a low-temperature solid-state reaction route. Samples were characterized by thermal gravimetric analysis (TGA), X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and cell measurements. It is found that LiNi0.5Mn1.5O4 thus obtained has a cubic spinel structure, which can be indexed in a space group of Fd3m with a disordering distribution of Ni. The particle size is about 200nm. Electrochemical tests demonstrated that the as-prepared LiNi0.5Mn1.5O4 possesses high capacity and excellent rate capability. When discharged at a rate as high as of 8C, the as-prepared LiNi0.5Mn1.5O4 powders can still deliver a capacity of 110mAhg−1, which shows to be a potential cathode material for high power batteries.