Non-aqueous electrolyte lithium secondary battery

1. A lithium secondary battery comprising an anode made of carbon material capable of occluding or emitting lithium ions, a cathode made of lithium-containing oxide, a separator between the anode and the cathode, and a non-aqueous electrolyte,

wherein the non-aqueous electrolyte comprises:

a lithium salt; and

a non-linear carbonate-based mixed organic solvent consisting of (a) at least two cyclic carbonate compounds expressed by the following Chemical Formula 1 and (b) a propionate-based ester compound expressed by the following Chemical Formula 3, wherein (a) and (b) are mixed at a volume ratio (a:b) in the range from about 10:90 to about 70:30, and (c) a vinylene carbonate expressed by the following Chemical Formula 2,

wherein the cathode has a capacity density in the range from 3.5 to 5.5 mAh/cm 2 and a porosity in the range from 18 to 35%,

Chemical Formula 1

where R3 to R6 are independently any one selected from the group consisting of a hydrogen, fluorine, and an alkyl group having a carbon number of 1 to 4, respectively,

Chemical Formula 2

where R7 and R8 are independently a hydrogen or an alkyl group having a carbon number of 1 to 4, respectively, and

Chemical Formula 3

where R 1 is a CH 3 CH 2 group and R 2 is a linear or branched C 1-6 alkyl group, and R 1 and R 2 may be unsubstituted or substituted with at least one halogen, respectively,

wherein one of the at least two cyclic carbonate compounds is fluroethylene carbonate.

2. The lithium secondary battery according to claim 1 ,

wherein one of the at least two cyclic carbonate compounds is fluoroethylene carbonate, and another of the at least two cyclic carbonate compounds is selected from the group consisting of ethylene carbonate, propylene carbonate and butylenes carbonate.

3. The lithium secondary battery according to claim 1 , wherein the propionate-based ester compound expressed by the Chemical Formula 3 includes at least one compound selected from the group consisting of methyl propionate-based ester, ethyl propionate-based ester, propyl propionate-based ester, and butyl propionate-based ester.

4. The lithium secondary battery according to claim 1 , wherein the propionate-based ester compound is an ethyl propionate-based ester compound expressed by the following Chemical Formula 4

where at least one hydrogen is capable of being substituted with fluorine.

5. The lithium secondary battery according to claim 4 , wherein the ethyl propionate-based compound expressed by the Chemical Formula 4 is any one compound or a mixture of at least two compounds selected from the group consisting of ethyl propionate, ethyl 3-fluoropropanoate, ethyl 3,3-difluoropropanoate, ethyl 3,3,3-trifluoropropanoate, 2-fluoroethyl propionate, 2,2-difluoroethyl propionate, 2,2,2-trifluoroethyl propionate, 2,2,2-trifluoroethyl 3-fluoropropanoate, 2,2,2-trifluoroethyl 3,3-difluoropropanoate, and 2,2,2-trifluoroethyl 3,3,3-trifluoropropanoate.

6. The lithium secondary battery according to claim 1 , wherein the lithium salt is any one compound or a mixture of at least two compounds selected from the group consisting of LiPF 6 , LiBF 4 , LiSbF 6 , LiAsF 6 , LiClO 4 , LiN(C 2 F 5 SO 2 ) 2 , LiN(CF 3 SO 2 ) 2 , CF 3 SO 3 Li and LiC(CF 3 SO 2 ) 3 .

7. The lithium secondary battery according to claim 1 , wherein the non-aqueous electrolyte further includes an inhibitor between the anode and the propionate-based ester compound.

8. The lithium secondary battery according to claim 7 , wherein the inhibitor is selected from the group consisting of fluorinated ethylene carbonate, and vinylene carbonate.