Positive electrode active material, method for manufacturing the same, and secondary battery

An object is to provide a method for manufacturing a positive electrode active material that achieves high powder properties and high load resistance (e.g., rate performance and output resistance) when used in a lithium-ion secondary battery, within a short manufacturing cycle time and at low cost. To perform heat treatment at temperatures lower than the melting point of magnesium fluorine, lithium fluoride is mixed to melt magnesium fluorine and modify the surface of lithium cobalt oxide powder. By mixing lithium fluoride, magnesium fluorine can be melted at a temperature lower than its melting point, and a positive electrode active material is formed utilizing this eutectic phenomenon.