Electrolyte for lithium-sulfur battery, and lithium-sulfur battery comprising same

1. A liquid electrolyte for a lithium-sulfur battery comprising:

a lithium salt; and

a non-aqueous solvent,

wherein the non-aqueous solvent comprises a linear ether and a cyclic ether comprising one oxygen in a ring structure,

wherein in the linear ether, a bond dissociation energy of a C—O bond when receiving one electron is greater than −19.9 kcal/mol when calculating using a DFT M06-2X method,

wherein a volume ratio of the cyclic ether and the linear ether is from 30:70 to 70:30,

wherein the cyclic ether is tetrahydrofuran or tetrahydropyran unsubstituted or substituted with a C1 to C4 alkyl group or alkoxy group.

2. The liquid electrolyte for a lithium-sulfur battery of claim 1 , wherein the linear ether is represented by the following Chemical Formula 1:

R 1 —O—R 2   [Chemical Formula 1]

in Chemical Formula 1,

R 1 and R 2 are the same as or different from each other, and each independently a C1 to C6 alkyl group unsubstituted or substituted with one or more fluorine, a C6 to C12 aryl group unsubstituted or substituted with one or more fluorine, or a C7 to C13 arylalkyl group unsubstituted or substituted with one or more fluorine.

3. The liquid electrolyte for a lithium-sulfur battery of claim 2 , wherein R 1 and R 2 are the same as or different from each other, and each independently a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a sec-butyl group, a t-butyl group, a pentyl group or a hexyl group.

4. The liquid electrolyte for a lithium-sulfur battery of claim 1 , wherein the linear ether is one or more types selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, diisobutyl ether, dipentyl ether, dihexyl ether, ethylmethyl ether, methylpropyl ether, butylmethyl ether, ethylpropyl ether, butylpropyl ether, phenylmethyl ether, diphenyl ether, dibenzyl ether, bis(fluoromethyl)ether, 2-fluoromethyl ether, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, bis(2,2,2-trifluoroethyl)ether, propyl-1,1,2,2-tetrafluoroethyl ether, isopropyl-1,1,2,2-tetrafluoroethyl ether, 1,1,2,2-tetrafluoroethylisobutyl ether, 1,1,2,3,3,3-hexafluoropropylethyl ether, 1H, 1H,2′ H,3H-decafluorodipropyl ether and 1H,1H,2′H-perfluorodipropyl ether.

5. The liquid electrolyte for a lithium-sulfur battery of claim 1 , wherein the cyclic ether is one or more types selected form the group consisting of tetrahydrofuran, 2-methyltetrahydrofuran, 3-methyltetrahydrofuran, 2,3-dimethyltetrahydrofuran, 2,4-dimethyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, 2-methoxytetrahydrofuran, 3-methoxytetrahydrofuran, 2,5-dimethoxytetrahydrofuran, 2-ethoxytetrahydrofuran, 3-ethoxytetrahydrofuran, tetrahydropyran, 2-methyltetrahydropyran, 3-methyltetrahydropyran and 4-methyltetrahydropyran.

6. The liquid electrolyte for a lithium-sulfur battery of claim 1 , wherein the lithium salt includes one type selected from the group consisting of LiCl, LiBr, LiI, LiClO 4 , LiBF 4 , LiB 10 Cl 10 , LiPF 6 , LiCF 3 SO 3 , LiCF 3 CO 2 , LiC 4 BO 8 , LiAsF 6 , LiSbF 6 , LiAlCl 4 , CH 3 SO 3 Li, CF 3 SO 3 Li, (CF 3 SO 2 ) 2 NLi, (C 2 F 5 SO 2 ) 2 NLi, (SO 2 F) 2 NLi, (CF 3 SO 2 ) 3 CLi, chloroborane lithium, lower aliphatic carboxylic acid lithium, lithium tetraphenylborate, lithium imide and combinations thereof.

7. The liquid electrolyte for a lithium-sulfur battery of claim 1 , wherein the lithium salt is included in a concentration of 0.1 M to 4.0 M.

8. The liquid electrolyte for a lithium-sulfur battery of claim 1 , further comprising an additive having N—O bonds in a molecule.

9. The liquid electrolyte for a lithium-sulfur battery of claim 8 , wherein the additive is one or more types selected from the group consisting of lithium nitrate, potassium nitrate, cesium nitrate, barium nitrate, ammonium nitrate, lithium nitrite, potassium nitrite, cesium nitrite, ammonium nitrite, methyl nitrate, dialkyl imidazolium nitrate, guanidine nitrate, imidazolium nitrate, pyridinium nitrate, ethyl nitrite, propyl nitrite, butyl nitrite, pentyl nitrite, octyl nitrite, nitromethane, nitropropane, nitrobutane, nitrobenzene, dinitrobenzene, nitropyridine, dinitropyridine, nitrotoluene, dinitrotoluene, pyridine N-oxide, alkylpyridine N-oxide and tetramethylpiperidinyloxyl.

10. The liquid electrolyte for a lithium-sulfur battery of claim 8 , wherein the additive is included in 0.01% by weight to 10% by weight with respect to 100% by weight of the liquid electrolyte.

11. A lithium-sulfur battery comprising the liquid electrolyte of claim 1 .