Non-aqueous electrolyte and lithium secondary battery using the same

1. A lithium secondary battery, comprising:

an electrolyte assembly comprising a cathode, an anode, and a separator interposed therebetween; and

a non-aqueous electrolyte solution consisting of an electrolyte salt, an organic solvent, a sulfur-containing compound, and pyrimidine,

wherein the organic solvent consists of a non-fluorinated solvent and a fluorinated solvent, wherein the amount of fluorine (F) present in the organic solvent is in the range of 0.9 to 45.2 wt %,

wherein the non-fluorinated solvent includes a mixture of cyclic carbonate and an ester,

wherein the ester is selected from the group consisting of methyl propionate, ethyl propionate, and a mixture thereof,

wherein the cyclic carbonate is selected from the group consisting of ethylene carbonate, propylene carbonate, and mixtures thereof,

wherein the fluorinated solvent includes fluoroethylene carbonate and optionally at least one selected from the group consisting of 2-(trifluoromethyl)-3-ethoxydodecafluorohexane, ethyl heptafluorobutyrate, and mixtures thereof,

wherein the sulfur-containing compound is 1,3 propane sultone,

wherein the sulfur-containing compound is present in an amount of 0.5 to 3 parts by weight based on 100 parts of the organic solvent, wherein the anode comprises a carbon-based material as an active material; and

a polymerizable film present on a surface of the anode, wherein the polymerizable film is formed by a reaction of the pyrimidine with the anode,

wherein the pyrimidine is present in an amount of 0.5 to 3 parts by weight based on 100 parts of the organic solvent prior to formation of the polymerizable film.

2. The lithium secondary battery according to claim 1 , wherein the electrolyte salt is a lithium salt.

3. The lithium secondary battery according to claim 2 , wherein the lithium salt has an anion selected from the group consisting of F − , Cl − , Br − , I − , NO 3 − , N(CN) 2 − , BF 4 − , ClO 4 − , PF 6 − , (CF 3 ) 2 PF 4 − , (CF 2 ) 3 PF 3 − , (CF 3 ) 4 PF 2 − , (CF 3 ) 5 PF − , (CF 3 ) 6 P − , CF 3 SO 3 − , CF 3 CF 2 SO 3 − , (CF 3 SO 2 ) 2 N − , (FSO 2 ) 2 N − , CF 3 CF 2 (CF 3 )CO − , (CF 3 SO 2 ) 2 CH − , (SF 5 ) 3 C − , (CF 3 SO 2 ) 3 C − , CF 3 (CF 2 ) 7 SO 3 − , CF 3 CO 2 − , CH 3 CO 2 − , SCH − and (CF 3 CF 2 SO 2 ) 2 N − .

4. The lithium secondary battery according to claim 1 , wherein the cathode has a cathode layer comprising a lithium-containing oxide.

5. The lithium secondary battery according to claim 4 , wherein the lithium-containing oxide is a lithium-containing transition metal oxide.

6. The lithium secondary battery according to claim 5 , wherein the lithium-containing transition metal oxide is selected from the group consisting of LiNiO 2 , LiMnO 2 , LiMn 2 O 4 , Li(Ni a Co b Mn c )O 2 (0<a<1, 0<b<1, 0<c<1, a+b+c=1), LiNi 1-y Co y O 2 , LiCo 1-y Mn y O 2 , LiNi 1-y Mn y O 2 (0<y<1), Li(Ni a Co b Mn c )O 4 (0<a<2, 0<b<2, 0<c<2, a+b+c=2), LiMn 2-z Ni z O 4 , LiMn 2-z Co z O 4 (0<z<2), LiCoPO 4 , LiFePO 4 and a mixture thereof.