Method of preparing positive active material for rechargeable lithium battery

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

• mixing a nickel compound, a cobalt compound, and optionally a metal compound to obtain a first mixture;
• subjecting the first mixture to a co-precipitation reaction to obtain a first resulting product, washing with water, filtering and drying the first resulting product to prepare a transition metal hydroxide precursor represented by Chemical Formula 1A,
• NixCoyM1-x-y(OH)2, [Chemical Formula 1A]
• wherein M is at least one selected from Mn, Ni, Co, Al, Fe, V, Ti, Mg, Zr, B, F, and Cr, 0.3≤x≤1, 0≤y≤0.7, and 0.3≤x+y≤1;
• subjecting the transition metal hydroxide precursor to a primary heat treatment at about 400° C. to about 600° C. for about 0.5 hour to about 20 hours to prepare a transition metal composite oxide precursor;
• and
• preparing a dehydrated lithium salt by:
• drying a hydrated lithium salt having an average particle diameter (D50) of about 400 μm to 600 μm to obtain a resultant, and
• pulverizing the resultant to have an average particle diameter (D50) of about 3 μm to 30 μm to generate the dehydrated lithium salt;
• mixing the transition metal composite oxide precursor and the dehydrated lithium salt to obtain a second mixture;
• and
• performing a secondary heat treatment on the second mixture to prepare a nickel-based lithium transition metal oxide.