LiMn2O4 spinel phase having a single crystal structure with the grain sizes of 20–30nm is synthesized at lower temperature of 500°C after a ball-milling promoted solid-state reaction. The interplanar spacing of LiMn2O4 is calculated to be ca. 0.47nm, which is corresponding to the same orientation of atomic plane (111). TG, SEM, XRD and TEM are used to measure the process of the heat treatment and microstructure of synthesized LiMn2O4. The high rate discharge capability is improved due to the strong interaction of nanomaterials with lithium ion occurred mostly at the surface rather than bulk. The improvement of the high rate discharge capability of electrodes is confirmed further by comparing electrochemical reaction activity and diffusion property of the electrode with nanostructure. However, the cyclic performance of LiMn2O4 spinel phase with nanostructure declined rapidly to a certain extent.