Cathode active material and lithium secondary battery comprising the same

Abstract

Disclosed is a cathode active material (and a secondary battery having the same) comprising a combination of lithium manganese composite oxide with a spinel structure of Formula 1 and an oxide of Formula 2, the material having a broad potential region at 3.0 to 4.8V upon initial charge: Li x M y Mn 2-y O 4-z A z   (1) wherein 0.9≦x≦1.2, 0 <y<2, and 0≦z<0.2; M is at least one element of Al, Mg, Ni, Co, Fe, Cr, V, Ti, Cu, B, Ca, Zn, Zr, Nb, Mo, Sr, Sb, W, Ti or Bi; and A is at least one monovalent or bivalent anion, y′Li 2 M′O 3 .(1−y′)LiM″O 2-z′ A′ z′   (2) 0<y′<1 and 0≦z′<0.2; M′ is at least one element of Mn, Sn or Zr having an oxidation number of +4; M″ is at least one element of Period I or II transition metals and A′ is at least one monovalent or bivalent anion.

1 . A cathode active material comprising a combination of lithium manganese composite oxide with a spinel structure represented by the following Formula 1 and a specific oxide represented by the following Formula 2, the cathode active material having a broad potential region (potential plateau) at 3.0 to 4.8V upon initial charge:
   Li x M y Mn 2-y O 4-z A z    (1)
   wherein 0.9≦x≦1.2, 0<y<2, and 0≦z<0.2;   M is at least one element selected from the group consisting of Al, Mg, Ni, Co, Fe, Cr, V, Ti, Cu, B, Ca, Zn, Zr, Nb, Mo, Sr, Sb, W, Ti and Bi; and   A is at least one monovalent or bivalent anion,
   y′Li 2 M′O 3 .(1−y′)LiM″O 2-z′ A′ z′   (2)
 
   0<y′<1 and 0≦z′<0.2;   M′ is at least one element selected form the group consisting of Mn, Sn and Zr having an oxidation number of +4;   M″ is at least one element selected from the group consisting of Period I and II transition metals, including Ni, Mn and Co, which have a 6-coordination structure and are stable in a layered structure; and   A′ is at least one monovalent or bivalent anion.   
     
     
         2 . The cathode active material according to  claim 1 , wherein the oxide of Formula 1 is represented by the following Formula 3:
   Li x Ni y Mn 2-y O 4    (3)
   wherein 0.9≦x≦1.2, and 0.4≦y≦ 0 . 5 .   
     
     
         3 . The cathode active material according to  claim 2 , wherein the oxide of Formula 3 is LiNi 0.5 Mn 1.5 O 4  or LiNi 0.4 Mn 1.6 O 4.    
     
     
         4 . The cathode active material according to  claim 1 , wherein the oxide of Formula 2 is represented by the following Formula 4:
   z′Li 2 MnO 3 .(1−z′)LiM″O 2    (4)
   wherein 0.5<z′<1, and M″ is at least one element selected from the group consisting of Period I and II transition metals, including Ni, Mn and Co, which have 6-coordination structure and are stable in a layered structure.   
     
     
         5 . The cathode active material according to  claim 1 , wherein the secondary particle of the oxide of Formula 1 has a mean particle diameter (D50) of 2 to 30 μm. 
     
     
         6 . The cathode active material according to  claim 1 , wherein the oxide of Formula 2 is a composite with a layered structure or a solid solution with a layered structure. 
     
     
         7 . The cathode active material according to  claim 1 , wherein the oxide of Formula 1 is mixed with the oxide of Formula 2 in a weight ratio of 50:50 to 99:1. 
     
     
         8 . The cathode active material according to  claim 7 , wherein the oxide of Formula 1 is mixed with the oxide of Formula 2 in a weight ratio of 80:20 to 95:5. 
     
     
         9 . The cathode active material according to  claim 7 , wherein the oxide of Formula 1 is mixed with the oxide of Formula 2 in a weight ratio of 80:20 to 90:10. 
     
     
         10 . A secondary battery comprising the cathode active material according to  claim 1 . 
     
     
         11 . The secondary battery according to  claim 10 , wherein the secondary battery comprises a lithium metal oxide represented by the following Formula 5 as an anode active material:
   Li a M′ b O 4-c A c    (5)
   wherein M′ is at least one element selected from the group consisting of Ti, Sn, Cu, Pb, Sb, Zn, Fe, In, Al and Zr;   a and b are determined according to an oxidation number of M′ within ranges of 0.1≦a≦4 and 0.2≦b≦ 4 ;   c is determined according to an oxidation number of A within a range of 0≦c<0.2; and   A is at least one monovalent or bivalent anion.   
     
     
         12 . The secondary battery according to  claim 11 , wherein the lithium metal oxide is represented by the following Formula 6:
   Li a Ti b O 4    (6)
   wherein 0.5≦a≦3 and 1≦b≦2.5.   
     
     
         13 . The secondary battery according to  claim 12 , wherein the lithium metal oxide is Li 1.33 Ti 1.67 O 4  or LiTi 2 O 4.    
     
     
         14 . The secondary battery according to  claim 10 , wherein the secondary battery is a lithium secondary battery. 
     
     
         15 . A battery module comprising the secondary battery according to  claim 10  as a unit battery. 
     
     
         16 . A battery pack comprising the battery module according to  claim 15 . 
     
     
         17 . A device comprising the battery pack according to  claim 16 . 
     
     
         18 . The device according to  claim 17 , wherein the device is an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle or a power storage system.