A series of Mg-doped LiCoO2 cathode materials are prepared by a solid-state reaction with a titanate coating for use in lithium ion batteries. The detailed structures of the materials are thoroughly characterized by experimental techniques including scanning electron microscopy, transmission electron microscopy, X-ray diffraction, electron energy loss spectroscopy, and electron probe microanalysis. The coating layer, which is characterized as a spinel phase of Mg2TiO4, plays the important role of a protective layer to prevent detrimental side reactions. Hence, the coated materials exhibit much improved cycling ability, excellent C-rate capability, and high upper cut-off voltages owing to the Mg doping. Mg ions in the coating layer are relocated from the bulk region of the active material and have a beneficial effect that enhances battery performance. This work provides an informative guide for the development of novel high-voltage cathode materials.