Cathode active material including lithium transition metal phosphate particles, preparation method thereof, and lithium secondary battery including the same

A cathode active material comprising lithium transition metal phosphate particles represented by Chemical Formula 1,

• wherein the lithium transition metal phosphate particles comprise:
• a first secondary particle formed by agglomeration of two or more first primary particles;
• and
• a second secondary particle formed by agglomeration of two or more second primary particles,
• wherein the second secondary particle is included in the first secondary particle, and a porous portion is included between the first primary particles and the second primary particles, and
• wherein the cathode active material further comprises a carbon coating layer on the first primary particles and the second primary particles,
• Li1+aM11-xM2x(PO4-b)Xb Chemical Formula 1
• wherein M1 represents at least one element selected from the group consisting of iron (Fe), manganese (Mn), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), and magnesium (Mg);
• M2 represents at least one element selected from Groups 2 to 15 elements excluding M1;
• X represents at least one element selected from the group consisting of fluorine (F), sulfur (S), and nitrogen (N);
• and
• −0.5≦a≦+0.5, 0≦x≦0.5, and 0≦b≦0.1.