Cathode active material for lithium secondary battery and lithium secondary battery including the same

A method of manufacturing a cathode active material for a lithium secondary battery comprising:

• preparing a preliminary lithium-transition metal composite oxide particle;
• mixing the preliminary lithium-transition metal composite oxide particle with a sulfonyl-based compound aqueous solution including the sulfonyl-based compound represented by Structural Formula 1 below;
• and
• performing a drying and a heat treatment on the mixed preliminary lithium-transition metal composite oxide particle and the sulfonyl-based compound aqueous solution, to prepare a lithium-transition metal composite oxide particle comprising a plurality of primary particles and a lithium-sulfur-containing portion formed between the primary particles,
• wherein a sulfur content in the lithium-transition metal composite oxide particle measured through a carbon-sulfur (CS) analyzer is 2,000 to 7,000 ppm based on a total weight of the lithium-transition metal composite oxide particle:
• (In Structural Formula 1, n is 0≤n<3, R1 and R2 are O−, NH2, NH3+, OH, or a hydrocarbon group having 1 to 3 carbon atoms that can be substituted with a substituent, and the substituent includes a halogen, cyano group, hydroxyl group, phosphoric acid group, carboxyl group or a salt thereof).