POSITIVE ELECTRODE ACTIVE MATERIAL, PREPARATION METHOD THEREFOR, AND LITHIUM SECONDARY BATTERY COMPRISING SAME

The present invention relates to a positive electrode active material including a small-particle diameter lithium iron manganese phosphate-based oxide and a large-particle diameter lithium iron phosphate-based oxide, wherein the small-particle diameter lithium iron manganese phosphate-based oxide has an average particle diameter (D50) of 1 µm or less, the large-particle diameter lithium iron phosphate-based oxide has an average particle diameter (D50) of 4 µm to 10 µm, and the small-particle diameter lithium iron manganese phosphate-based oxide and the large-particle diameter lithium iron phosphate-based oxide are included in a weight ratio of 75:25 to 98:2.