CATHODE ACTIVE MATERIAL AND LITHIUM SECONDARY BATTERY COMPRISING THE SAME
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.