LiNi0.5Mn1.5O4 was prepared by a spray drying and post-annealing process. The re-annealing treatment in O2 could not only decrease the Mn3+ content, but also increased the reversible capacity and significantly improve the rate capability compared to the untreated material. Moreover, the cyclic performance of the LiNi0.5Mn1.5O4 depends on both the cycling rate and operating temperature, which was ascribed to the difference between the phase transition rates between cubic I↔cubic II and cubic II↔cubic III.