Method for Preparing Positive Electrode Active Material Precursor for Lithium Secondary Battery

A method for preparing a positive electrode active material precursor, the method comprising:

• Step 1 of preparing a metal aqueous solution including a nickel raw material, a cobalt raw material, and a manganese raw material;
• Step 2 of adding the metal aqueous solution, an ammonium cation complex forming agent, and a basic aqueous solution into a reactor, co-precipitating a resulting mixture at pH 11 to less than pH 13 to form nuclei of first positive electrode active material precursor particles and growing the nuclei;
• Step 3 of adjusting input amount of the basic aqueous solution to increase the pH in the reactor to a range of 0.8 to 1.5 compared to the pH of the Step 2, thereby forming nuclei of second positive electrode active material precursor particles;
• and
• Step 4 of adjusting input amount of the basic aqueous solution to change the pH in the reactor to pH 11 to less than pH 12, thereby simultaneously growing the nuclei of first positive electrode active material precursor particles and the nuclei of second positive electrode active material precursor particles to prepare a positive electrode active material precursor of a bimodal type including the first positive electrode active material precursor particles and the second positive electrode active material precursor particles having different average particle diameters (D50).