Positive active material for a lithium secondary battery with higher performance and preparation method of the same

Abstract

Disclosed is a positive active material for a lithium secondary battery and a preparation method of the same that can improve cycle-life characteristics and storage characteristics at a high temperature by improving structural safety characteristics and electrochemical characteristics, by forming an overlayer comprising an oxide glass phase on the surface of the positive active material, and a lithium secondary battery comprising the positive active material.

1 . A positive active material for a lithium secondary battery comprising: 
 a) a lithium metal complex oxide described by the following Formula 1; and    b) a glass phase overlayer of a non-crystalline oxide described by the following Formula 2 coated on the a) lithium metal complex 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;      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, Y, Ga, In, Pb, Li and Rb;    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 respectively variable to an oxidation number of C and D.    
   
   
       2 . The positive active material of  claim 1 , wherein b) the glass phase overlayer of non-crystalline oxide is 0.01 to 10% based on the mole of a) the lithium metal complex oxide.  
   
   
       3 . 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) preparing a homogeneous complex solution by mixing: 
 i) a compound selected from the group consisting of carbonate salt of C, nitrate salt of C, hydrate salt of C, acetate salt of C, citric acid salt of C, chloride of C, and an oxide of C, wherein C is selected from the group consisting of Na, K, Mg, Sr, Y, Ga, In, Pb, Li and Rb, and  
 ii) a compound selected from the group consisting of carbonate salt of D, nitrate salt of D, hydrate salt of D, acetate salt of D, citric acid salt of D, chloride of D, and oxide of D, wherein D is selected from the group consisting of Al, B, Si, Ge, Ti and Pb,  
 with water or alcohol;  
   c) adding the lithium metal complex oxide prepared by a) step into the homogeneous complex solution prepared by b) step to prepare a slurry, and evaporating the water or alcohol from the slurry to prepare a coated lithium metal complex oxide;    d) sintering the coated lithium metal complex oxide of the c) step at 300 to 900° C. for 10 minute to 30 hours in the air at a flow rate of 0.05 to 2.0 l/gH or complex air having over 10 vol % of oxygen to prepare a positive active material comprising a lithium metal complex oxide described by the following Formula 1, and a glass phase overlayer of a non-crystalline oxide described by the following Formula 2 coated on the lithium metal complex oxide of the following Formula 1:      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, Y, Ga, In, Pb, Li and Rb;    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 respectively variable to an oxidation number of C and D.    
   
   
       4 . The preparation method of  claim 3 , wherein the core particles of a) is prepared by heat treating a mixture of: 
 i) a lithium compound;    ii) a compound selected from the group consisting of carbonate salt of A, nitrate salt of A, hydrate salt of A, acetate salt of A, citric acid salt of A, chloride of A, and an oxide of A, wherein A is Co or Ni; and    iii) a compound comprising metal B, wherein B is selected from the group consisting of Al, B, Ni, Co, Ti, Sn, Mn and Zr,    wherein the heat treating is proceeded at 400 to 900° C. for 1 to 20 hours in air or complex air comprising over 10 vol % of oxygen.    
   
   
       5 . The preparation method of  claim 4 , wherein the lithium compound is selected from the group consisting of LiOH, LiOH.H 2 O, LiCH 3 COO, Li 2 CO 3 , Li 2 SO 4  and LiNO 3 .  
   
   
       6 . The preparation method of  claim 3 , wherein the coated glass phase overlayer of non-crystalline oxide is 0.01 to 10% based on the core particles of lithium metal complex oxide.  
   
   
       7 . A lithium secondary battery comprising the positive active material of  claim 1.