Spherical LiNi0.5Mn1.5O4 material with a core–shell structure is synthesized by a urea-assisted hydrothermal method followed by heat treatment with LiOH at high temperature. After the process of hydrothermal treatment, the carbonate precursor with a concentration gradient is produced, in a single spherical particle, the content of Ni in the surface is higher than that in the center while Mn has a reversal trend. LiNi0.5Mn1.5O4 synthesized through the hydrothermal route has a great improvement in cycling stability at elevated temperature and rate capability. The capacity retention can maintain at 95% after 30 cycles at 55 °C. Furthermore, it can deliver a discharge capacity of 118 mAh g−1 at a high rate of 10 C at room temperature. Such excellent electrochemical properties of LiNi0.5Mn1.5O4 can be ascribed to its unique core–shell structure and nano-size particle.