Cathode active material for secondary battery, manufacturing method therefor, and secondary battery including same

The present invention provides a cathode active material for a secondary battery and a secondary battery including the same, the cathode active material comprising: a core; a shell positioned to encompass the core; and a buffer layer positioned between the core and the shell, and including pores and three-dimensional network structures for connecting the core and the shell, wherein the three-dimensional network structures in the core, the shell, and the buffer layer respectively and independently comprise a lithium nickel manganese cobalt-based complex metal oxide, and have a BET specific surface area of 0.2m 2 /g to 0.5m 2 /g, a porosity of 30 volume% or less, and an average particle size (D 50 ) of 8μm to 15μm, and thus a specific surface area, an average particle diameter, and a porosity of active material particles are controlled together, along with a specific structure, such that the degradation of an active material, occurring because of a rolling process, is minimized when an electrode is manufactured, and reactivity with an electrolyte is maximized. Furthermore, since particles for forming the shell have an oriented crystalline structure by which lithium ions can be easily intercalated and deintercalated, an output characteristic and a lifespan characteristic of a secondary battery can be improved.