Lithium cobalt oxide is a leading cathode material for 3C electronic products because of its high bulk energy density, excellent rate capacity and good cycle performance. The existing gram capacity of lithium cobalt oxide material in practical application is approximately 65% of the theoretical capacity, and this material has a potential for further development. In this paper, a lithium ion cobalt oxide cathode material was coated with lithium ion conductor material LiAlSiO₄ by a sol–gel method. The effects of LiAlSiO₄ and heat treatment temperature on the structure, morphology and electrochemical properties of the material were investigated. The results show that during the heat treatment, Al³⁺ enters the LiCoO₂ lattice to form a solid solution LiCo_1–xAl_xO₂, and an inert coating layer is formed on the surface of the lithium cobalt oxide particles LiAlSiO₄ coating, effectively improving the cycle and rate performance of the lithium cobalt oxide material at a high voltage. The optimum overall performance of the lithium cobalt oxide material coated with LiAlSiO₄ can be obtained at a heat treatment temperature of 600 ℃ . In a voltage range of 2.75–4.55 V, the specific discharge capacity at room temperature at 0.5 C rate is 209.3 mA·h/g, and the discharge specific capacity after 50 cycles is 201.6 mA·h/g (at a capacity retention rate of 96.3%), and the specific capacity is 160.0 mA·h/g at 8 C.