Cathode active material, method for preparing the same, and lithium secondary batteries including the same

The present invention relates to a cathode active material for a lithium secondary battery, a method for preparing the same, and a lithium secondary battery including the same. Provided is a cathode active material composed of a lithium-excess lithium metal composite compound including LiMnOhaving a layered structure, and doped with a fluoro compound, wherein an FWHM (half value width) value is within a range from 0.164 degree to 0.185 degree.