Cathode active material and lithium secondary battery containing the same
View Patent ↗Provided is a non-aqueous electrolyte-based, high-power lithium secondary battery having a long service life and superior safety at both room temperature and high temperature, even after repeated high-current charging and discharging. The battery comprises a cathode active material composed of a mixture of lithium/manganese spinel oxide and lithium/nickel/cobalt/manganese composite oxide wherein the cathode active material exhibits the life characteristics that the capacity at 300 cycles is more than 70% relative to the initial capacity, in the provision of satisfying the condition (i) regarding the particle size and the condition (ii) regarding the mixing ratio.
1. A cathode active material for a lithium secondary battery, comprising a mixture of:
(a) a lithium/manganese spinel oxide represented by Formula I or Formula III, and
(b) a lithium/nickel/cobalt/manganese composite oxide represented by Formula II,
wherein the cathode active material exhibits the life characteristics that the capacity at 300 cycles is more than 70% relative to the initial capacity, in the provision that the below conditions (i) and (ii) are satisfied,
(i) the lithium/manganese spinel oxide of Formula I or Formula III has an average particle diameter of 15 μm or more, and the lithium/nickel/cobalt/manganese composite oxide of Formula II have an average particle diameter of 9 to 17 μm; and
(ii) the mixing ratio of the lithium/manganese spinel oxide: lithium/nickel/cobalt/manganese composite oxide is in the range of 10:90 to 90:10 (w/w);
Li 1+x Mn 2 O 4 (I);
Li 1+y Ni b Mn c Co 1−(b+c) O 2 (II);
Li 1+x Mn 2−z M z O 4 (III);
wherein, M is a metal having an oxidation number of 2 or 3,
0≦x≦0.2,
0≦y≦0.1,
0.01≦z≦0.2;
0.2≦b≦0.7,
0.2≦c≦0.7, and
b+c<1;
wherein an oxide unit of the lithium/manganese spinel oxide of Formula I or Formula III has a particle diameter of 0.2 to 12 μm and a surface area of 0.1 to 1.0 m 2 /g.
2. The cathode active material according to claim 1 , wherein the capacity at 300 cycles is more than 80% relative to the initial capacity.
3. The cathode active material according to claim 1 , wherein the lithium/nickel/cobalt/manganese composite oxide of Formula II is Li 1+z Ni 1/3 Co 1/3 Mn 1/3 O 2 .
4. The cathode active material according to claim 1 , wherein the lithium/nickel/cobalt/manganese composite oxide of Formula II Li 1+z Ni 0.4 Mn 0.4 Co 0.2 O 2 .
5. The cathode active material according to claim 1 , wherein the lithium/manganese spinel oxide of Formula I or Formula III has an average particle diameter of 15 to 30 μm.
6. The cathode active material according to claim 1 , wherein the mixing ratio is in the range of 10:90 to 70:30.
7. The cathode active material according to claim 1 , wherein M in the Formula III is aluminum (Al), magnesium (Mg) or both.
8. The cathode active material according to claim 1 , wherein the value of z is in the range of 0.01 to 0.2.
9. A lithium secondary battery comprising the cathode active material of claim 1 .
10. A cathode active material for a lithium secondary battery, comprising a mixture of:
(a) a lithium/manganese spinel oxide of Formula III, and
(b) a lithium/nickel/cobalt/manganese composite oxide of Formula II,
wherein the cathode active material exhibits the life characteristics that the capacity at 300 cycles is more than 70% relative to the initial capacity, in the provision that the below conditions (i) and (ii) are satisfied,
(i) the lithium/manganese spinel oxide of Formula III has an average particle diameter of 15 μm or more;
(ii) the mixing ratio of the lithium/manganese spinel oxide: the lithium/nickel/cobalt/manganese composite oxide is in the range of 10:90 to 70:30 (w/w),
Li 1+y Ni b Mn c Co 1−(b+c) O 2 (II)
Li 1+x Mn 2−z M z O 4 (III)
wherein,
M is aluminum (Al), magnesium (Mg) or both,
0≦x≦0.2,
0≦y≦0.1,
0.01≦z≦0.2;
0.2≦b≦0.7,
0.2≦c≦0.7, and
b+c<1;
wherein an oxide unit of the lithim/manganese spinel oxide of Formula III has a particle diamter of 0.2 to 12 μm and a surface area of 0 . 1 to 1 . 0 m 2 /g.
11. The cathode active material according to claim 10 , wherein the lithium/nickel/cobalt/manganese composite oxide of Formula II has an average particle diameter of 9 μm to 17 μm.
12. The cathode active material according to claim 10 , wherein the capacity at 300 cycles is more than 80% relative to the initial capacity.
13. The cathode active material according to claim 10 , wherein the lithium/nickel/cobalt/manganese composite oxide of Formula II is Li 1+z Ni 1/3 Co 1/3 Mn 1/3 O 2 .
14. The cathode active material according to claim 10 , wherein the lithium/nickel/cobalt/manganese composite oxide of Formula II Li 1+z Ni 0.4 Mn 0.4 Co 0.2 O 2 .
15. The cathode active material according to claim 10 , wherein the lithium/manganese spinel oxide of Formula III has an average particle diameter of 15 to 30 μm.
16. A lithium secondary battery comprising the cathode active material of claim 10 .