Cathode active material and lithium secondary battery containing them
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 mixture of a lithium/manganese spinel oxide having a substitution of a manganese (Mn) site with a certain metal ion and a lithium/nickel/cobalt/manganese composite oxide, as a cathode active material.
1. A cathode active material for a lithium secondary battery, comprising a mixture of a lithium/manganese spinel oxide represented by Formula I and a lithium/nickel/cobalt/manganese oxide represented by Formula II:
Li 1+x Mn 2-y M y O 4 (I)
Li 1+z Ni b Mn c Co 1−(b+c) O 2 (II)
wherein, M is a metal having an oxidation number of 2 to 3;
0<x≦0.2;
0<y≦0.2;
0.1≦z≦0.1;
0.45≦b≦65;
0.2≦c≦0.4; and
0.65≦b+c≦0.85
wherein the mixing ratio of the lithium/manganese spinel oxide of Formula I to the lithium/nickel/cobalt/manganese composite oxide of Formula II is in the range of 10:90 to 90:10 (w/w); and
wherein the cathode active material exhibits the life characteristics that the capacity at 300 cycles is more than 80% relative to the initial capacity.
2. The cathode active material according to claim 1 , wherein M in Formula I is aluminum (Al), magnesium (Mg) or both of them.
3. The cathode active material according to claim 1 , wherein the value of y is in the range of 0.01 to 0.2.
4. A lithium secondary battery comprising a cathode active material of claim 1 .