The present invention relates to a lithium secondary battery having improved output characteristics, as well as to a high-capacity mixture of positive electrode active material and to a lithium secondary battery comprising the material, in which a sudden voltage drop caused by the difference of operating voltages among mixed lithium-transition metal oxides is prevented, in order to achieve a uniform profile over the entirety of the SOC region and improved output characteristics at a low voltage. Particularly, the lithium secondary battery according to the present invention satisfies the required output characteristics, capacity, safety, etc. when used as a power source for medium or large devices such as an electric vehicle or the like.