ELECTROLYTE SOLUTION FOR LITHIUM SECONDARY BATTERY AND LITHIUM SECONDARY BATTERY INCLUDING THE SAME

1 . An electrolyte solution for a lithium secondar battery, comprising:

an organic solvent;

a lithium salt; and

a fluorine-based additive in which a terminal difluoro-phosphite group (—OPF 2 ) is bonded to a branched saturated hydrocarbon group.

2 . The electrolyte solution for a lithium secondary battery according to claim 1 , wherein the fluorine-based additive comprises a compound represented by Chemical Formula 1 or Chemical Formula 2 below:

wherein, in Chemical Formulae 1 and 2, R 1 , R 2 , R 3 and R 4 are each independently a C1-C10 alkyl group.

3 . The electrolyte solution for a lithium secondary battery according to claim 2 , wherein R 1 in Chemical Formula 1 is a C4-C10 alkyl group, and R 2 , R 3 and R 4 are each independently a C1-C3 alkyl group.

4 . The electrolyte solution for a lithium secondary battery according to claim 2 , wherein the fluorine-based additive comprises a compound represented by Chemical Formula 1-1 or Chemical Formula 2-1:

.

5 . The electrolyte solution for a lithium secondary battery according to claim 1 , wherein the fluorine-based additive is included in an amount ranging from 0.1 wt% to 5.0 wt% based on a total weight of the electrolyte solution.

6 . The electrolyte solution for a lithium secondary battery according to claim 1 , wherein the fluorine-based additive is included in an amount ranging from 0.5 wt% to 2.0 wt% based on a total weight of the electrolyte solution.

7 . The electrolyte solution for a lithium secondary battery according to claim 1 , further comprising at least one auxiliary additive selected from the group consisting of a cyclic carbonate-based compound, a fluorine-substituted cyclic carbonate-based compounds, a sultone-based compound and a cyclic sulfate-based compound.

8 . The electrolyte solution for a lithium secondary battery according to claim 7 , wherein the auxiliary additive is included in an amount ranging from 0.01 wt% to 5 wt% based on a total weight of the electrolyte solution.

9 . The electrolyte for a lithium secondary battery according to claim 1 , wherein the organic solvent includes at least one selected from the group consisting of ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC) and diethyl carbonate (DEC).

10 . A lithium secondary battery, comprising:

an electrode assembly comprising a plurality of cathodes and anodes that are repeatedly stacked;

a case accommodating the electrode assembly; and

the electrolyte solution for a lithium secondary battery of claim 1 accommodated in the case together with the electrode assembly.