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 potassium compound aqueous solution;
• and
• performing a heat treatment on the mixed preliminary lithium-transition metal composite oxide particle and the potassium compound aqueous solution, to prepare a lithium-transition metal composite oxide particle comprising a plurality of primary particles and a lithium-potassium-containing portion formed between the primary particles.