The spinel LiNi0.5Mn1.5O4 powders with high crystallinity and well-developed octahedral morphology were synthesized by a ultrasonic spray pyrolysis method using citric acid as a polymeric agents. The LiNi0.5Mn1.5O4 powders were characterized by X-ray diffraction, scanning electron microscopy, and electrochemical testing. The LiNi0.5Mn1.5O4 material delivers a discharge capacity of more than 138mAhg−1 with excellent capacity retention of more than 97% after 50 cycles even at 55°C.