Rechargeable lithium battery

1. A rechargeable lithium battery, comprising:

a negative electrode comprising:

a negative current collector;

a negative active material layer disposed on the negative current collector; and

a negative electrode functional layer disposed on the negative active material layer; and

a positive electrode comprising:

a positive current collector; and

a positive active material layer disposed on the positive current collector,

wherein the negative electrode functional layer comprises:

flake-shaped polyethylene particles,

wherein the positive active material layer comprises:

a first positive active material comprising at least one of a composite oxide of a metal selected from cobalt, manganese, nickel, and a combination thereof and lithium;

a second positive active material including a compound represented by Chemical Formula 1,

LiaFe1−x1Mx1 PO4

wherein, in Chemical Formula 1, 0.90≤a≤1.8, 0≤x1≤0.7, and M is Mn, Co, Ni, or a combination thereof; and

carbon nanotubes, which have an average length of 30 μm to about 100 μm,

wherein an aspect ratio of average length over average diameter of the carbon nanotubes is 1,000 to 5,400.

2. The rechargeable lithium battery of claim 1 , wherein the carbon nanotubes have an average diameter of about 1 nm to about 20 nm.

3. The rechargeable lithium battery of claim 1 , wherein the carbon nanotubes are included in an amount of about 0.1 wt % to about 2 wt % based on a total weight of the positive active material layer.

4. The rechargeable lithium battery of claim 1 , wherein the positive active material layer further comprises a positive electrode conductive material.

5. The rechargeable lithium battery of claim 4 , wherein the positive electrode conductive material is included in an amount of less than about 1 wt % based on a total weight of the positive active material layer.

6. The rechargeable lithium battery of claim 1 , wherein the first positive active material and the second positive active material are included in an amount of about 80 wt % to about 99 wt % based on a total weight of the positive active material layer.

7. The rechargeable lithium battery of claim 1 , wherein the first positive active material and second positive active material are included in a weight ratio of about 97:3 to about 80:20.

8. The rechargeable lithium battery of claim 1 , wherein the positive active material layer further comprises a positive electrode functional layer disposed on the positive active material layer.

9. The rechargeable lithium battery of claim 8 , wherein

the first positive active material is included in the positive active material layer, and

the second positive active material is included in at least one of the positive active material layer and the positive electrode functional layer.

10. The rechargeable lithium battery of claim 1 , wherein the first positive active material comprises one of LiCoO 2 , Li b M 1 1-y 1-z1M 2 y 1M 3 z 1O 2 (0.9≤b≤1.8, 0 ≤y1≤1, 0≤z1≤, 0 ≤y1+z1≤1, and M 1 , M 2 , and M 3 are independently a metal of Ni, Co, Mn, Al, Sr, Mg, or La), and a combination thereof.

11. The rechargeable lithium battery of claim 1 , wherein the second positive active material comprises LiFePO 4 .

12. The rechargeable lithium battery of claim 1 , wherein the flake-shaped polyethylene particles have an average particle size (D50) of about 1 μm to about 8 μm.

13. The rechargeable lithium battery of claim 1 , wherein a ratio of the long axis length relative to the short axis length of the flake-shaped polyethylene particles is about 1 to about 5.

14. The rechargeable lithium battery of claim 1 , wherein a thickness of the flake-shaped polyethylene particles is about 0.2 μm to about 4 μm.

15. The rechargeable lithium battery of claim 1 , wherein the negative electrode functional layer further comprises inorganic particles and a binder.

16. The rechargeable lithium battery of claim 15 , wherein a sum amount of the flake-shaped polyethylene particles and the inorganic particles over an amount of the binder ranges within a weight ratio of about 80:20 to about 99:1.

17. The rechargeable lithium battery of claim 15 , wherein the flake-shaped polyethylene particles over the inorganic particles range within a weight ratio of about 95:5 to about 10:90.

18. The rechargeable lithium battery of claim 1 , wherein the negative electrode functional layer has a thickness of 1 μm to about 10 μm.

19. A rechargeable lithium battery, comprising:

a negative electrode comprising:

a negative current collector;

a negative active material layer disposed on the negative current collector; and

a negative electrode functional layer disposed on the negative active material layer; and

a positive electrode comprising:

a positive current collector; and

a positive active material layer disposed on the positive current collector,

wherein the negative electrode functional layer comprises:

flake-shaped polyethylene particles,

wherein the positive active material layer comprises:

a first positive active material comprising at least one of a composite oxide of a metal selected from cobalt, manganese, nickel, and a combination thereof and lithium;

a second positive active material including a compound represented by Chemical Formula 1,

LiaFe1−x1Mx1PO4  Chemical Formula 1

wherein, in Chemical Formula 1, 0.90≤a≤1.8, 0x1≤ 0 . 7 , and M is Mn, Co, Ni, or a combination thereof; and

carbon nanotubes, which have an average length of 30 μm to about 100 μm,

wherein the positive active material layer further comprises a positive electrode conductive material, and

wherein the positive electrode conductive material is included in an amount of about 0.1 wt % to about 0.6 wt % based on a total weight of the positive active material layer.

20. The rechargeable lithium battery of claim 19 , wherein an aspect ratio of average length over average diameter of the carbon nanotubes is 1,000 to 5,400.