Method for manufacturing positive active material, and positive active material and lithium secondary battery using same

A method for preparing a positive electrode active material comprising:

• (a) preparing a coating composition including a precursor of metal-phosphorous-oxynitride;
• (b) forming a precursor layer on a positive electrode active material with the coating composition of (a) using a solution process;
• and
• (c) forming a metal-phosphorous-oxynitride protective layer on the positive electrode active material by heat treating the positive electrode active material having the precursor layer formed thereon,
• wherein the precursor of metal-phosphorous-oxynitride is prepared by a reaction of a compound comprising a phosphorous-nitrogen bond with a metal salt compound,
• wherein the compound comprising the phosphorous-nitrogen bond comprises at least one selected from the compounds represented by the following Chemical Formulae 1 to 3:
• wherein each X1 is the same or different from each other and each independently is OR1, F, Cl, Br or I, wherein R1 is an alkyl group having 1 to 5 carbon atoms;
• wherein R2 and R3 are the same or different from each other and each independently is an alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 20 carbon atoms;
• wherein each X2 is the same or different from each other and each independently is R4, OR5, NR6R7, F, Cl, Br or I, wherein R4 to R7 are the same or different from each other, and each independently is an alkyl group having 1 to 10 carbon atoms or an aryl group having 6 to 20 carbon atoms and
• n is an integer of 100 to 100,000.