Abstract: A method for preparing a positive electrode active material precursor includes preparing a metal aqueous solution including a nickel raw material, a cobalt raw material, and a manganese raw material (step 1); adding the metal aqueous solution, an ammonium cation complex forming agent, and a basic aqueous solution into a reactor, co-precipitating the mixture at pH 11 to less than pH 12 to form nuclei of first positive electrode active material precursor particles and growing the nuclei (step 2); 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 that of step 2; and adjusting input amount of the basic aqueous solution to change the pH in the reactor to pH 11 to less than pH 12 (step 4). A positive electrode active material precursor prepared by the above preparation method has an improved packing density.

Abstract: A method for preparing a bimodal-type positive electrode active material precursor is provided. The method is capable of not only increasing productivity by preparing positive electrode active material precursors having small diameters and large diameters in a single reactor but also improving packing density per unit volume, a positive electrode active material precursor prepared by the preparation method and having improved packing density, and a positive electrode for a secondary battery and a lithium secondary battery including the same.