Cathode active material and lithium secondary battery comprising same

A positive active material for a lithium secondary battery, the positive active material comprising:

• a secondary particle comprising a group of a plurality of primary particles,
• wherein the primary particles comprise a first primary particles provided on a surface portion of the secondary particle, and the primary particle is made of lithium (Li), nickel (Ni), cobalt (Co), manganese (Mn), and tungsten (W), which is a doping element, and
• wherein the secondary particle has a chemical formula Lix(NiyM1−y−zWz)O2, wherein Mis Co and Mn, x is 0.9 to 1.2, y is 0.85 to 0.95, and z is 0.005 to 0.02,
• a concentration of W varies within the secondary particle,
• wherein the primary particle has a layered structure and comprises a spinel structure in a first region which is the end of the first primary particle, and
• wherein the first primary particle has a transverse section having a flake shape having a major axis and a minor axis, and the first region accounts for 0.5% to 4% of an average length of the major axis of the first primary particle.