Method of preparing cathode active material precursor for lithium rechargeable battery, cathode active material precursor for lithium rechargeable battery prepared thereby, and cathode active material formed using the cathode active material precursor

A method of preparing a cathode active material precursor for a lithium rechargeable battery, the method comprising:

• preparing a metallic salt aqueous solution for formation of a core part and a metallic salt aqueous solution for formation of a shell part that include nickel, cobalt, and manganese as metallic salts;
• providing a first chelating agent, a first alkaline aqueous solution, the metallic salt aqueous solution for the formation of the core part, and the metallic salt aqueous solution for the formation of the shell part into a reactor while changing a mixing ratio of the metallic salt aqueous solution for the formation of the core part and the metallic salt aqueous solution for the formation of the shell part, thereby forming a concentration gradient part of which concentrations of metallic salts are gradually changed;
• providing a second chelating agent, a second alkaline aqueous solution, the metallic salt aqueous solution for the formation of the core part, and the metallic salt aqueous solution for the formation of the shell part into the reactor while mixing the metallic salt aqueous solution for the formation of the core part and the metallic salt aqueous solution for the formation of the shell part at a fixed ratio, thereby forming a shell part having a fixed concentration;
• and
• drying and heating a formed precipitate to prepare an active material precursor,
• wherein a concentration of a specific metallic salt of the concentration gradient part in a contact portion of the concentration gradient part and the shell part is denoted by “MC”, and a concentration of the specific metallic salt of the shell part in the contact portion of the concentration gradient part and the shell part is denoted by “MS”, and
• wherein the MC and the MS satisfy a relation formula MC≠MS.