Secondary battery with improved life characteristics

1. An electrode assembly comprising a cathode, an anode, and a separator interposed between the cathode and the anode,

wherein the cathode comprises a cathode active material capable of being applied at a high voltage, and

the separator comprises a porous substrate and a porous coating layer formed on only one surface of the porous substrate and comprising inorganic particles and an organic binder polymer, and has pores whose longest diameter ranges from 10 nm to 5 μm,

wherein the porous coating layer is formed in a thickness of 0.5 to 20 μm, and

wherein the porous coating layer is disposed to be faced with the anode.

2. The electrode assembly of claim 1 , wherein the cathode active material is any one selected from lithium oxides of formula (I) to (IV) and a mixture thereof:

Li x [Ni a Co b Mn c ]O 2   (I)

(0.95≦x≦1.05, 0≦a, b, c≦1, a+b+c=1, and a and c are not simultaneously 0),

Li[Li x Ni a Co b Mn c ]O 2   (II)

(0.05≦x≦0.6, and x+a+b+c=1),

Li x [Ni a Co b Mn c ]O 2   (III)

(0.95≦x≦1.05, 0<a, b, c≦1, a+b+c=1, and 0.4<c<1),

LiMn 2-x M x O 4   (IV)

(M is at least one element selected from the group consisting of Ni, Co, Fe and Al, and 0≦x≦2).

3. The electrode assembly of claim 1 , wherein the longest diameter of pores ranges from 50 to 500 nm.

4. The electrode assembly of claim 1 , wherein the separator has a Gurley value of 1 to 3000 sec/100 cc.

5. The electrode assembly of claim 1 , wherein the separator has a Gurley value of 50 to 2000 sec/100 cc.

6. The electrode assembly of claim 1 , wherein the porous substrate is a porous membrane obtained from a polyethylene resin, a polypropylene/polyethylene/polypropylene resin, or a polypropylene resin.

7. The electrode assembly of claim 1 , wherein the porous substrate is a non-woven fabric.

8. A secondary battery comprising the electrode assembly of claim 1 .

9. The secondary battery of claim 8 , which has an upper voltage of 4.3 to 5.0 V.