Composite cathode active material having improved power characteristics, and secondary battery, battery module, and battery pack including the same

1. A composite cathode active material comprising:

a layered lithium manganese oxide represented by Chemical Formula 1 shown below; and

a lithium-containing metal oxide represented by Chemical Formula 3 shown below,

a [Li 2 MnO 3 ].(1 −a )[LiM 1 O 2 ]  Chemical Formula 1

wherein, 0<a<1 and M 1 is one or more metals selected from the group consisting of manganese (Mn), nickel (Ni), cobalt (Co), iron (Fe), chromium (Cr), vanadium (V), copper (Cu), zinc (Zn), titanium (Ti), aluminum (Al), magnesium (Mg), and boron (B); and

Li(Ni x Co y Al z )O 2   Chemical Formula 3

wherein, x, y, and z are each independently selected from a range of 0<x, y, z<1, and x+y+z=1.

2. The composite cathode active material of claim 1 , wherein a mixing ratio of the layered lithium manganese oxide represented by Chemical Formula 1 and the lithium-containing metal oxide represented by Chemical Formula 3 is in a weight ratio ranging from 99:1 to 50:50.

3. The composite cathode active material of claim 1 , wherein M 1 in Chemical Formula 1 of the layered lithium manganese oxide includes Mn, Ni, and Co.

4. The composite cathode active material of claim 1 , wherein x, y, and z in Chemical Formula 3 are in ranges of 0.45 to 0.90, 0.05 to 0.35, and 0.005 to 0.20, respectively.

5. The composite cathode active material of claim 1 , further comprising one or more selected from the group consisting of lithium cobalt oxide; lithium nickel oxide; lithium manganese oxide; lithium cobalt-nickel oxide; lithium cobalt-manganese oxide; lithium manganese-nickel oxide; lithium cobalt-nickel-manganese oxide; and oxides having one or more other elements selected from the group consisting of Al, Mg, Ni, Co, Fe, Cr, V, Ti, Cu, B, calcium (Ca), Zn, zirconium (Zr), niobium (Nb), molybdenum (Mo), strontium (Sr), antimony (Sb), tungsten (W), and bismuth (Bi) substituted or doped therein.

6. A secondary battery comprising the composite cathode active material of claim 1 .

7. A battery module comprising the secondary battery of claim 6 .

8. A battery pack comprising the battery module of claim 7 .

9. The battery pack of claim 8 , wherein the battery pack is used as a power source of one or more medium and large sized devices selected from the group consisting of an electric vehicle (EV) including an electric car, a hybrid electric vehicle (HEV), and a plug-in hybrid electric vehicle (PHEV); an electric bike; an electric scooter; an electric golf cart; an electric truck; and an electric commercial vehicle.