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

1. An electrolyte for a secondary battery, comprising:

a lithium salt;

a nonaqueous organic solvent;

a cyclic phosphate compound represented by the following Chemical Formula 2:

wherein R 1 to R 6 and R′ and R″ are independently of one another hydrogen or C1-C7 alkyl; L 2 is —(CR 7 R 8 ) n —; R 7 and Rs are independently of each other hydrogen or C1-C7 alkyl; and n is an integer of 1 to 3; and

a sulfinyl group-containing compound, wherein the sulfinyl group-containing compound is selected from the group consisting of one or more sulfone compound(s), sulfite compound(s), sulfonate compound(s), sultone compound(s), sulfate compound(s), and combination(s) thereof.

2. The electrolyte for a secondary battery of claim 1 , wherein

R 1 to R 6 , R′, and R″ are independently of one another hydrogen or C1-C4 alkyl;

L 2 is —CR 7 R 8 —; and

R 7 and R 8 are independently of each other C1-C4 alkyl.

3. The electrolyte for a secondary battery of claim 1 , wherein the cyclic phosphate compound is any one selected from the following structures:

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

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

6. The electrolyte for a secondary battery of claim 5 , further comprising: any one or two or more additives selected from the group consisting of lithium difluoro(oxalato)borate, lithium bis(oxalato)borate, lithium tetrafluoro(oxalato)phosphate, lithium difluoro bis(oxalato)phosphate, fluoroethylene carbonate, difluoroethylene carbonate, fluorodimethyl carbonate, fluoroethylmethyl carbonate, vinylene carbonate, and vinyl ethylene carbonate.

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

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

9. The electrolyte for a secondary battery of claim 8 , wherein the cyclic carbonate is selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, vinylethylene carbonate, fluoroethylene carbonate, and a mixture thereof, and the linear carbonate is selected from the group consisting of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethylmethyl carbonate, methylpropyl carbonate, methylisopropyl carbonate, ethylpropyl carbonate, and a mixture thereof.

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

11. The electrolyte for a secondary battery of claim 1 , wherein the lithium salt is one or two or more selected from the group consisting of LiPF 6 , LiBF 4 , LiClO 4 , LiSbF 6 , LiAsF 6 , LiN(SO 2 C 2 F 5 ) 2 , LiN(CF 3 SO 2 ) 2 , LiN(SO 3 C 2 F 5 ) 2 , LiN(SO 2 F) 2 , LiCF 3 SO 3 , LiC 4 F 9 SO 3 , LiC 6 H 5 SO 3 , LiSCN, LiAlO 2 , LiAlCl 4 , LiN(C x F 2x+1 SO 2 )(C y F 2y+1 SO 2 ) (wherein x and y are independently of each other a natural number), LiCl, LiI, and LiB(C 2 O 4 ) 2 .

12. The electrolyte for a secondary battery of claim 1 , wherein the lithium salt is present at a concentration of 0.1 to 2.0 M.

13. The electrolyte for a secondary battery of claim 1 , wherein the sulfinyl group-containing compound is selected from the group consisting of dimethyl sulfone, diethyl sulfone, ethyl methyl sulfone, methyl vinyl sulfone, divinyl sulfone, ethylene sulfite, methyl ethylene sulfite, ethyl ethylene sulfite, 4,5-dimethyl ethylene sulfite, 4,5-diethyl ethylene sulfite, propylene sulfite, 4,5-dimethyl propylene sulfite, 4,5-diethyl propylene sulfite, 4,6-dimethyl propylene sulfite, 4,6-diethyl propylene sulfite, 1,3-butylene glycol sulfite, methyl methanesulfonate, ethyl methanesulfonate, methyl ethanesulfonate, propyl methanesulfonate, methyl propanesulfonate, ethyl propanesulfonate, vinyl methanesulfonate, allyl methanesulfonate, vinyl benzenesulfonate, allyl prop-2-enesulfonate, ethanesultone, 1,3-propanesultone, 1,4-butanesultone, ethenesultone, 1,3-propenesultone, 3-fluoro-1,3-propanesultone, 1,4-butenesultone, ethylene sulfate, propylene sulfate, 2,3-butylene sulfate, 1,3-propylene sulfate, 1,3-butylene sulfate, and combination(s) thereof.

14. The electrolyte for a secondary battery of claim 1 , wherein the sulfinyl group-containing compound is a sultone compound represented by the following Chemical Formula F:

wherein

represents a single bond or a double bond;

R m to R o are independently of each other hydrogen, a halogen, C1-C10 alkyl, C2-C10 alkenyl, halo C1-C10 alkyl, halo C2-C10 alkenyl, or C6-C12 aryl; and n is an integer of 0 to 3.

15. The electrolyte for a secondary battery of claim 1 , wherein the sulfinyl group-containing compound is a sultone compound selected from the group consisting of ethane sultone, 1,3-propane sultone (PS), 1,4-butane sultone (BS), ethene sultone, 1,3-propene sultone (PES), 3-fluoro-1,3-propane sultone (FPS), 1,4-butene sultone, and combination(s) thereof.

16. The electrolyte for a secondary battery of claim 1 , wherein the sulfinyl group-containing compound is 1,3-propane sultone.

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