The present inventors have conducted intensive studies and various experiments, and as described below, they found that when a positive electrode active material particle includes a core containing lithium cobalt oxide represented by Li_1+xCo_1?xO₂ (?0.03≤x≤0.1); and a coating layer containing boron (B) and fluorine (F), which is coated on the surface of the core, surface stability of the positive electrode active material particle may be improved, side reactions on the surface of the positive electrode active material may be reduced, and high-temperature lifetime characteristic may be improved, thereby completing the present invention.

Accordingly, a positive electrode active material particle for secondary batteries according to the present invention is characterized by including a core containing lithium cobalt oxide represented by the following Chemical Formula 1; and a coating layer containing boron (B) and fluorine (F), which is coated on the surface of the core:
Li_1+xCo_1?xO₂??(1)

wherein ?0.03≤x≤0.1.

As described above, when the coating layer containing boron and fluorine is included, although electrolyte salts are decomposed, decomposition products react with boron or fluorine on the surface of the positive electrode active material particle to be converted into less reactive materials, thereby suppressing side reactions such as electrolyte decomposition on the surface of the positive electrode active material particle.

In a specific embodiment, in the coating layer, boron and fluorine may exist in a state in which they are chemically bonded with lithium.