Electrolyte for lithium secondary battery and lithium secondary battery including the same

1. An electrolyte for a secondary battery, the electrolyte comprising:

a lithium salt;

a nonaqueous organic solvent; and

a cyclic fluorophosphonate compound represented by the following Chemical Formula 1:

wherein

R 1 and R 2 are independently of each other hydrogen, C1-C10alkyl, halogen, C1-C10alkoxy, C3-C10cycloalkyl, or C6-C20aryl, and the alkyl, alkoxy, cycloalkyl, or aryl may be further substituted by one or more selected from the group consisting of C1-C10alkyl, halogen, haloC1-C10alkyl, C1-C10alkoxy, C1-C10alkoxyC1-C10alkyl, C3-C10cycloalkyl, and C6-C20aryl;

A is —(CR a R b ) m —, C3-C10cycloalkylene, or C6-C20arylene, and the cycloalkylene or arylene may be further substituted by one or more selected from the group consisting of C1-C10alkyl, halogen, haloC1-C10alkyl, C1-C10alkoxy, C1-C10alkoxyC1-C10alkyl, C3-C10cycloalkyl, and C6-C20aryl;

R a and R b are independently of each other hydrogen, C1-C10alkyl, halogen, C1-C10alkoxy, C3-C10cycloalkyl, or C6-C20aryl, and the alkyl, alkoxy, cycloalkyl, or aryl may be further substituted by one or more selected from the group consisting of C1-C10alkyl, halogen, haloC1-C10alkyl, C1-C10alkoxy, C1-C10alkoxyC1-C10alkyl, C3-C10cycloalkyl, and C6-C20aryl; and

m is an integer of 1 to 5.

2. The electrolyte for a secondary battery of claim 1 , wherein the cyclic fluorophosphonate compound is a cyclic fluorophosphonate compound represented by the following Chemical Formula 2 or Chemical Formula 3:

wherein

R 11 , R 12 , R 13 , and R 14 are independently of one another hydrogen, C1-C10alkyl, or halogen, and the alkyl may be further substituted by one or more selected from the group consisting of halogen, C1-C10alkoxy, C3-C10cycloalkyl, and C6-C20aryl;

L 1 is —(CR c R d ) n —;

R c and R d are independently of each other hydrogen, C1-C10alkyl, or halogen, and the alkyl may be further substituted by one or more selected from the group consisting of halogen, C1-C10alkoxy, C3-C10cycloalkyl, and C6-C20aryl; and

n is an integer of 0 to 3, and p is an integer of 1 to 3.

3. The electrolyte for a secondary battery of claim 1 , wherein the cyclic fluorophosphonate compound is a cyclic fluorophosphonate compound represented by the following Chemical Formula 4:

wherein

R 11 to R 16 are independently of one another hydrogen, C1-C7alkyl, halogen, or C1-C7alkoxyC1-C7alkyl.

4. The electrolyte for a secondary battery of claim 1 , wherein the cyclic fluorophosphonate compound is one or more selected from the following structures:

5. The electrolyte for a secondary battery of claim 1 , wherein the cyclic fluorophosphonate compound is comprised at 0.1 to 5.0 wt %, based on a total weight of the electrolyte.

6. The electrolyte for a secondary battery of claim 1 , further comprising: one or two or more additives selected from the group consisting of oxalatoborate-based compounds, oxalatophosphate-based compounds, fluorine-substituted carbonate-based compounds, vinylidene carbonate-based compounds, and sulfinyl group-containing compounds.

7. The electrolyte for a secondary battery of claim 1 , wherein the nonaqueous organic solvent is selected from the group consisting of cyclic carbonate-based solvents, linear carbonate-based solvents, and mixed solvents thereof.

8. The electrolyte for a secondary battery of claim 7 , wherein the nonaqueous organic solvent has a mixed volume ratio of a linear carbonate solvent to a cyclic carbonate solvent of 1:1 to 9:1.

9. A lithium secondary battery comprising: a cathode, an anode, and the electrolyte for a secondary battery of claim 1 .

10. The lithium secondary battery of claim 9 , wherein the cathode includes a composite metal oxide of at least one transition metal selected from the group consisting of cobalt, manganese, and nickel with lithium as a cathode active material.

11. The lithium secondary battery of claim 10 , wherein the cathode active material is a lithium-nickel-cobalt-manganese-based composite oxide.

12. The lithium secondary battery of claim 11 , wherein the lithium-nickel-cobalt-manganese-based composite oxide is Li x (Ni a Co b Mn c )O 2 (0.5<x<1.3, 0<a<1, 0<b<1, 0<c<1, and a+b+c=1), Li x (Ni a Co b Mn c )O 4 (0.5<x<1.3, 0<a<2, 0<b<2, 0<c<2, and a+b+c=2), or a mixture thereof.

13. The electrolyte for a secondary battery of claim 6 , wherein the additive is comprised at 0.1 to 10.0 wt %, based on the total weight of the electrolyte.

14. The electrolyte for a secondary battery of claim 6 , wherein the sulfinyl group-containing compound is one or two or more selected from the group consisting of sulfone-based compounds, sulfite-based compounds, sulfonate-based compounds, sultone-based compounds, and sulfate-based compounds.

15. The electrolyte for a secondary battery of claim 1 , further comprising: two or more additives selected from the group consisting of fluorine-substituted carbonate-based compounds, vinylidene carbonate-based compounds, sultone-based compounds, and sulfate-based compounds.