LiMn1.5Ni0.5O4 materials coated with AlPO4 are prepared by a sol–gel method with citric acid to improve their electrochemical performance; the physical and electrochemical properties are characterized by various analytical techniques. The coated AlPO4 layer completely covers the surfaces of the LiMn1.5Ni0.5O4 particles and the thickness of the coated layer is ∼15nm. 1wt.% AlPO4-coated LiMn1.5Ni0.5O4 has much lower surface and charge-transfer resistances and shows a higher lithium diffusion rate in comparison with the pristine sample. The modified material demonstrates dramatically enhanced electrochemical reversibility and stability under elevated temperature conditions. This is because the coated AlPO4 layer reduces the contact area between the electrode and electrolyte and suppresses the formation of undesirable solid electrolyte interface films.