This paper describes a novel simple redox process for synthesizing monodispersed MnO2 powders and preparation of spherical LiNi0.5Mn1.5O4 cathode materials by molten salt synthesis (MSS) method. Monodispersed MnO2 powders have been synthesized by using potassium permanganate and manganese sulfate as the starting materials. By using this redox method, it was found that monodispersed MnO2 powders with average particle size ∼5μm can be easily obtained. Resultant MnO2 and LiOH, Ni(OH)2 was then used to synthesis LiNi0.5Mn1.5O4 cathode materials with retention of spherical particle shape by MSS method. The discharge capacity was 129mAhg−1 in the first cycle and 127mAhg−1 after 50 cycles under an optimal synthesis condition for 12h at 800°C.