Cathode active material for lithium secondary battery, process for preparing the same and reactor for use in the same process

A method for preparing a composite cathode active material for a lithium secondary battery, the method comprising:

• producing a first lithium metal composite oxide by (a) precipitating a first metal composite hydroxide from a first mixture of a first metal precursor, a first aqueous ammonia solution and a first basic solution, and (b) mixing and reacting the first metal composite hydroxide with a first lithium precursor to form the first lithium metal composite oxide;
• producing a second lithium metal composite oxide by (a) precipitating a second metal composite hydroxide from a second mixture of a second metal precursor, a second aqueous ammonia solution and a second basic solution, and (b) mixing and reacting the second metal composite hydroxide with a second lithium precursor to form the second lithium metal composite oxide;
• and
• mixing the first and second lithium metal composite oxides in a ratio of 20:80 parts by weight, respectively, to form a composite cathode active material for a lithium secondary battery;
• wherein
• the first lithium metal composite oxide has a mean particle diameter that is greater than 60% but less than 90% of a mean particle diameter of the second lithium metal composite oxide;
• the first and second lithium metal composite oxides comprise a primary particle having a particle diameter distribution between about 0.1 μm and about 0.2 μm, and a secondary particle having a mean particle diameter distribution between about 10 μm and about 20 μm when the primary particles are aggregated to form the secondary particles;
• and
• the first lithium metal composite oxide has a formula
• LiNi1−x′−yCOx′M′yO2Pz;
• the second lithium metal composite oxide has a formula selected from the group consisting of
• Li1+δ[NixMnx−y/2Co1−2x−zMyNz]O2−aPa
• and
• Li1+δ[NixMnx+yCo1−2(x+y)My]O2−aPa;
• M is selected from the group consisting of Mg, Zn, Ca, Sr, Cu and Zr;
• M′ is selected from the group consisting of Al, Mg, Zr and Ti;
• N is selected from the group consisting of Fe, Al, Ga, In, Cr, Ge and Sn;
• P is selected from the group consisting of F and S;
• δ has a value such that -1/10≦δ≦1/10;
• x has a value such that 0.2≦x≦0.4;
• x′ has a value such that 0.1≦x′≦0.3;
• y has a value such that 0≦y≦1/10;
• z has a value such that 0≦z≦1/10;
• and
• a has a value such that 0≦a≦0.3.