Positive electrode active material, preparation method thereof, positive electrode, rechargeable lithium batteries and all-solid-state rechargeable batteries

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

• forming a first mixture by mixing a first positive electrode active material precursor including secondary particles including a nickel-cobalt-aluminum composite hydroxide, wherein the secondary particles are formed by agglomerating a plurality of primary particles and at least a portion of the primary particles is oriented radially, with a second positive electrode active material precursor including secondary particles including a nickel-cobalt-manganese composite hydroxide, wherein the secondary particles are formed by agglomerating a plurality of primary particles, and a lithium raw material;
• performing a first heat treatment on the first mixture to obtain a preliminary positive electrode active material, wherein an average particle diameter of the first positive electrode active material precursor is larger than an average particle diameter of the second positive electrode active material precursor;
• forming a second mixture by dry mixing the preliminary positive electrode active material and a zirconium raw material;
• and
• performing a second heat treatment on the second mixture to obtain a final positive electrode active material.