Lithium secondary battery

1. A lithium secondary battery, comprising:

a cathode electrode comprising a cathode active material containing lithium-metal oxide;

an anode electrode; and

a separation film installed between the cathode electrode and the anode electrode, the separation film comprising a base film and a ceramic coating layer formed on at least one surface of the base film,

wherein the lithium-metal oxide is represented by Formula 1 below,

Li x M1 a M2 b M3 c O y   [Formula 1]

wherein M1, M2 and M3 are selected from the group consisting of Ni, Co, Mn, Na, Mg, Ca, Ti, V, Cr, Cu, Zn, Ge, Sr, Ag, Ba, Zr, Nb, Mo, Al, Ga and B, and

0<x≤1.1, 2≤y≤2.02, 0<a<1, 0<b<1, 0<c<1, and 0<a+b+c≤1; and

the cathode active material having regions comprised of:

a core part within 0.1 μm radius from a center of the cathode active material;

a surface part within 0.1 μm from an outmost portion of the cathode active material; and

an intermediate region between the core part and the surface part, the intermediate region comprising a concentration gradient region wherein M1 and M3 have a concentration gradient in a direction from the core part to the surface part and a non-concentration gradient region wherein M1 and M3 do not have a concentration gradient in a direction from the core part to the surface part; and

wherein M2 has a constant concentration throughout the cathode active material from the core part to the surface part.

2. The lithium secondary battery according to claim 1 , wherein the concentration of M3 is increased within the concentration gradient region in the direction from the core part to the surface part, and the concentration of M1 is decreased within the concentration gradient region in the direction from the core part to the surface part.

3. The lithium secondary battery according to claim 2 , wherein the concentrations of M3 and M1 are constant within the core part and the surface part and the surface part.

4. The lithium secondary battery according to claim 2 , wherein the M1, M2 and M3 are Ni, Co and Mn, respectively.

5. The lithium secondary battery according to claim 2 , wherein the M1 is Ni, and 0.6≤a≤0.95 and 0.05≤b+c≤0.4.

6. The lithium secondary battery according to claim 2 , wherein the M1 is Ni, and 0.7≤a≤0.9 and 0.1≤b+c≤0.3.

7. The lithium secondary battery according to claim 1 , wherein the ceramic coating layer includes ceramic powders having an average particle diameter of 0.01 to 2.0 μm.

8. The lithium secondary battery according to claim 1 , wherein the ceramic coating layer includes the ceramic powders in an amount of 80 to 97% by weight to a total weight of the coating layer.

9. The lithium secondary battery according to claim 1 , wherein the ceramic coating layer includes metal oxide containing at least one metal selected from the group consisting of aluminum (Al), titanium (Ti), zirconium (Zr), barium (Ba), magnesium (Mg), boron (B), yttrium (Y), zinc (Zn), calcium (Ca), nickel (Ni), silicon (Si), lead (Pb), strontium (Sr), tin (Sn) and cesium (Ce), as the ceramic powders.

10. The lithium secondary battery according to claim 1 , wherein the ceramic coating layer includes at least one selected from the group consisting of Al 2 O 3 , TiO 2 , ZrO2, Y 2 O 3 , ZnO, CaO, NiO, MgO, SiO 2 , SiC, Al(OH) 3 , AlO(OH), BaTiO 3 , PbTiO 3 , PZT, PLZT, PMN-PT, HfO 2 , SrTiO 3 , SnO 3 and CeO 2 , as the ceramic powders.

11. The lithium secondary battery according to claim 1 , wherein the ceramic coating layer formed on the one surface of the separation film has a thickness of 1 to 10 μm.

12. The lithium secondary battery according to claim 1 , wherein the ceramic coating layer has a sum of total thickness of 2 to 20 μm.

13. The lithium secondary battery according to claim 1 , wherein the non-concentration gradient region comprises a first non-concentration gradient region between the core part and the concentration gradient region and a second non-concentration gradient region between the concentration gradient region and the surface part.

14. The lithium secondary battery according to claim 1 , wherein the intermediate region comprises the non-concentration gradient region between the core part and the concentration gradient region.

15. A lithium secondary battery, comprising:

a cathode electrode comprising a cathode active material, the cathode electrode having a core part and a surface part;

an anode electrode; and

a separation film installed between the cathode electrode and the anode electrode, the separation film comprising a base film and a ceramic coating layer formed on at least one surface of the base film,

wherein the cathode active material consists of one or more lithium-metal oxides containing Ni, Co and Mn, and at least one of said one or more lithium metal oxides includes a compound represented by Formula 1 and includes a concentration gradient region between the core part and the surface part:

Li x M1 a M2 b M3 c O y   [Formula 1]

0<x<1.1, 2<y<2.02, 0<a<1, 0<b<1, 0<c<1, and 0<a+b+c<1,

wherein M3 is Mn and a concentration of M3 continuously increases in the concentration gradient region in a direction from the core part to the surface part;

M1 is Ni and a concentration of M1 continuously decreases in the concentration gradient region in a direction from the core part to the surface part; and

M2 is Co and a concentration of M2 is constant from the core part to the surface part;

the core part within 0.1 μm radius from a center of the cathode active material; and

the surface part within 0.1 μm from an outmost portion of the cathode active material.

16. The lithium secondary battery according to claim 15 , wherein the compound represented by Formula 1 further includes non-concentration gradient regions between the core part and the concentration gradient region, and between the concentration gradient region and the surface part, and M1 and M3 do not have a concentration gradient in the non-concentration gradient regions.

17. The lithium secondary battery according to claim 15 , wherein 0.7≤a≤0.9 and 0.1≤b+c≤0.3.