Cathode active material for secondary battery, method of manufacturing the same, and cathode for lithium secondary battery including the cathode active material

Abstract

The present invention relates to a cathode active material including a lithium-containing transition metal oxide and two or more metal composite oxide layers selected from the group consisting of Chemical Formulae 1 to 3 which are coated on the surface of the lithium-containing transition metal oxide, a method of manufacturing the same, and a cathode for a secondary battery including the cathode active material, M(C 2 H 5 O 2 ) n   [Chemical Formula 1] M(C 6 H (8-n) O 7 )  [Chemical Formula 2] M(C 6 H (8-n) O 7 )(C 2 H 5 O 2 )  [Chemical Formula 3] (where M, as a metal desorbed from a metal precursor, represents at least one metal selected from the group consisting of Mg, Ca, Sr, Ba, Y, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ir, Ni, Zn, Al, Ga, In, Si, Ge, Sn, La, and Ce, and n is an integer between 1 and 4).

1 . A cathode active material comprising:
 a lithium-containing transition metal oxide; and   two or more metal composite oxide layers selected from the group consisting of Chemical Formulae 1 to 3 which are coated on a surface of the lithium-containing transition metal oxide:
   M(C 2 H 5 O 2 ) n   [Chemical Formula 1]
 
   M(C 6 H (8-n) O 7 )  [Chemical Formula 2]
 
   M(C 6 H (8-n) O 7 )(C 2 H 5 O 2 )  [Chemical Formula 3]
 
   (where M, as a metal desorbed from a metal precursor, represents at least one metal selected from the group consisting of magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), yttrium (Y), titanium (Ti), zirconium (Zr), vanadium (V), niobium (Nb), tantalum (Ta), chromium (Cr), molybdenum (Mo), tungsten (W), manganese (Mn), iron (Fe), cobalt (Co), iridium (Ir), nickel (Ni), zinc (Zn), aluminum (Al), gallium (Ga), indium (In), silicon (Si), germanium (Ge), tin (Sn), lanthanum (La), and cerium (Ce), and n is an integer between 1 and 4).   
     
     
         2 . The cathode active material of  claim 1 , wherein the lithium-containing transition metal oxide comprises one selected from the group consisting of LiMO 2  (M=Co, Mn, Ni, Ni 1/3 Co 1/3 Mn 1/3 , Cr, or V), LiMO 4  (M=CoMn, NiV, CoV, CoP, FeP, MnP, NiP, or Mn 2 ), Li(Ni a Co b Mn c )O 2  (0<a<1, 0<b<1, 0<c<1, a+b+c=1), LiNi 1-y Co y O 2 , LiCo 1-y Mn y O 2 , LiNi 1-y Mn y O 2  (O≦=y≦1), Li(Ni a Mn b Co c )O 4  (0<a<2, 0<b<2, 0<c<2, a+b+c=2), LiMn 2-z Ni z O 4 , LiMn 2-z Co z O 4  (O<z<2), and LiV 3 O 6 . 
     
     
         3 . The cathode active material of  claim 1 , wherein
 the lithium-containing transition metal oxide is LiCoO 2 , LiMnO 2 , LiCuO 2 , LiMn 2 O 4 , LiNi 1/3 Mn 1/3 Co 1/3 O 2 , LiNi 0.6 Mn 0.2 Co 0.2 O 2 , LiCoPO 4 , or LiFePO 4 .   
     
     
         4 . The cathode active material of  claim 1 , wherein the two or more metal composite oxide layers are formed in a single layer structure, in which two or more metal composite oxides are uniformly mixed, or a multilayer structure having two or more layers in which two or more metal composite oxide layers are sequentially stacked. 
     
     
         5 . The cathode active material of  claim 1 , wherein a total thickness of the two or more metal composite oxide layers is in a range of 5 nm to 500 nm. 
     
     
         6 . The cathode active material of  claim 1 , wherein an amount of metal in the two or more metal composite oxide layers is in a range of 0.01 wt % to 10 wt % based on a total weight of the lithium-containing transition metal oxide. 
     
     
         7 . The cathode active material of  claim 1 , wherein the two or more metal composite oxide layers comprise a composite oxide of at least one metal selected from the group consisting of Mg, Ca, Sr, Ba, Y, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ir, Ni, Zn, Al, Ga, In, Si, Ge, Sn, La, and Ce. 
     
     
         8 . A method of manufacturing a cathode active material that comprises a metal composite oxide coating layer, the method comprising steps of:
 a first step of preparing a metal glycolate solution by performing two-steps heating process;   a second step of mixing lithium-containing transition metal oxide particles and the metal glycolate solution and stirring in a paste state;   a third step of drying the paste-state mixture; and a fourth step of performing a heat treatment on the dried mixture.   
     
     
         9 . The method of  claim 8 , wherein the metal glycolate solution is prepared by:
 preparing a mixed solution in which a metal precursor and a chelating agent are dispersed in a glycol-based solvent;   performing primary heating on the mixed solution; and   performing secondary heating on the mixed solution.   
     
     
         10 . The method of  claim 9 , wherein the metal glycolate solution comprises a single material selected from the group consisting of aluminum glycolate, zirconium glycolate, titanium glycolate, calcium glycolate, and manganese glycolate, or a mixture of two or more thereof. 
     
     
         11 . The method of  claim 9 , wherein the performing of the primary heating is performed in a temperature range of 150° C. to 300° C. for 1 hour to 48 hours. 
     
     
         12 . The method of  claim 9 , wherein the performing of the secondary heating is performed in a temperature range of 150° C. to 300° C. for 1 hour to 5 hours. 
     
     
         13 . The method of  claim 9 , wherein the performing of the primary heating and the performing of the secondary heating are performed in an inert gas atmosphere. 
     
     
         14 . The method of  claim 8 , wherein the drying (the third step) is performed in a temperature range of 100° C. to 200° C. for 1 hour to 4 hours. 
     
     
         15 . The method of  claim 8 , wherein the performing of the heat treatment (the fourth step) is performed in a temperature range of 200° C. to 1,200° C. for 1 hour to 3 hours. 
     
     
         16 . A cathode for a secondary battery comprising:
 a cathode collector; and   the cathode active material of  claim 1  coated on the cathode collector.   
     
     
         17 . A lithium secondary battery comprising:
 the cathode of  claim 16 ;   an anode;   a separator disposed between the cathode and the anode; and   a lithium salt-containing non-aqueous electrolyte solution.