Cathode active material and lithium secondary battery comprising the same
View Patent ↗Disclosed is a cathode active material (and secondary battery comprising the same) comprising a combination of a lithium manganese composite oxide having a spinel structure represented by the following Formula 1 with a lithium nickel composite oxide represented by the following Formula 2, the cathode active 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 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, and Li 1+y′ Ni z′ M′ 1−z′ O 2−z″ A′ z″ ( 2) wherein 0≦y′≦0.1, 0.5<z′≦0.9, and 0≦z″<0.2; M′ is at least one selected from the group consisting of elements stable for 6-coordination, including Mn, Co, Mg and Al; and A′ is at least one monovalent or bivalent anion.
1. A cathode active material comprising
a combination of a lithium manganese composite oxide having a spinel structure represented by the following Formula 3 with a lithium nickel composite oxide represented by the following Formula 2, wherein the oxide of Formula 3 is mixed with the oxide of Formula 2 in a weight ratio of 50:50 to 99:1, the cathode active material having a potential region (potential plateau) at 3.0 to 4.8V upon initial charge:
Li x Ni y Mn 2−y O 4 Formula 3
wherein 0.9≦x≦1.2, and 0.4≦y≦0.5, and
Li 1+y′ Ni z′ M′ 1−z′ O 2−z″ A′ z″ Formula 2
wherein 0≦y′≦0.1, 0.5<z′≦0.9, and 0≦z″<0.2;
M′ is at least one selected from the group consisting of elements stable for 6-coordination; and
A′ is at least one monovalent or bivalent anion.
2. The cathode active material according to claim 1 , wherein the oxide of Formula 3 is LiNi 0.5 Mn 1.5 O 4 or LiNi 0.4 Mn 1.6 O 4 .
3. The cathode active material according to claim 1 , wherein the oxide of Formula 2 is represented by the following Formula 4:
LiNi a Mn b Co c O 2 Formula 4
wherein 0.5<a≦0.9, 0<b≦0.5, 0<c≦0.5, a+b+c=1, and c≦b.
4. The cathode active material according to claim 1 , wherein the oxide of Formula 3 is provided as a secondary particle formed of agglomerated primary particles, wherein the secondary particle has a mean particle diameter (D50) of 2 to 30 μm.
5. The cathode active material according to claim 1 , wherein the oxide of Formula 3 is mixed with the oxide of Formula 2 in a weight ratio of 80:20 to 95:5.
6. A secondary battery comprising the cathode active material according to claim 1 .
7. The secondary battery according to claim 6 , 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 Formula 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.
8. The secondary battery according to claim 7 , wherein the lithium metal oxide is represented by the following Formula 6:
Li a Ti b O 4 Formula 6
wherein 0.5≦a≦3 and 1≦b≦2.5.
9. The secondary battery according to claim 8 , wherein the lithium metal oxide is Li 1.33 Ti 1.67 O 4 or LiTi 2 O 4 .
10. The secondary battery according to claim 6 , wherein the secondary battery is a lithium secondary battery.