The positive active material according to one embodiment of the present invention includes a composite metal oxide of the following Formula 1, and a compound being capable of intercalating and deintercalating lithium having the composite metal oxide coated on the surface thereof. M.sub.1-xAlO.sub.2 [Chemical Formula 1]Wherein, in the above Formula 1, M is selected from the group consisting of an alkali metal, an alkaline-earth metal, and combinations thereof, and 0.03.ltoreq.x.ltoreq.0.95. The composite metal oxide increases impregnation of an electrolyte, improves lithium mobility, and decreases internal resistance of a rechargeable lithium battery, and thereby improves discharge capacity and cycle-life characteristics.