Patent ID: 7252906

Claim:
A preparation method of positive active material for a lithium secondary battery comprising the steps of: a) preparing lithium metal complex oxide as core particles described by Formula 1; b) providing an overlayer material compound described by Formula 2 for forming a glass phase overlayer of non-crystalline oxide, which glass phase overlayer comprises C s O t as a network structure modifier and D z O w as a network structure maker, by dissolving: i) a compound selected from the group consisting of carbonate salt, nitrate salt, hydrate salt, acetate salt, citric acid salt, chloride, and an oxide of metal C described as Na, K, Mg, Sr, Ga, In, Li, Rb, and Al, and ii) a compound selected from the group consisting of carbonate salt, nitrate salt, hydrate salt, acetate salt, citric acid salt, chloride, and oxide of metal D described as Al, B, Si, Ge, Ti, and Pb; c) coating the lithium metal complex oxide of step a) with the overlayer material compound of step b), wherein said coating step is performed by making the core particles of step a) fluid in air and spraying the material of step b) on the core particles and drying the resultant material; and d) sintering the coated lithium metal complex oxide of step c), LiA 1−x B x O 2 [Formula 1] wherein, A is Co or Ni; B is selected from the group consisting of Al, B, Ni, Co, Ti, Sn, Mn, and Zr; and x is a real number of 0-0.5, C s O t .yD z O w [Formula 2] wherein, C is selected from the group consisting of Na, K, Mg, Sr, Ga, In, Li, Rb and Al; D is selected from the group consisting of Al, B, Si, Ge, Ti and Pb; y is a real number of 0.5-3; and s and t, and z and w are real numbers determined by an oxidation number of C and D, respectively.