Electrolyte additive and electrolyte and lithium rechargeable battery including same

1. An additive for a rechargeable lithium battery electrolyte, comprising an aromatic compound having an isothiocyanate group (—NCS);

wherein the aromatic compound is selected from phenyl isothiocyanate, 4-nitrophenyl isothiocyanate, trifluoromethyl phenyl isothiocyanate, 4-cyanophenyl isothiocyanate, 4-methoxyphenyl isothiocyanate, 4-fluorophenyl isothiocyanate, 4-methylphenyl isothiocyanate, 2-fluoro-5-(trifluoromethyl)phenyl isothiocyanate, 4-methyl-3-(trifluoromethyl)phenyl isothiocyanate, 4-fluoro-3-(trifluoromethyl)phenyl isothiocyanate, 3,5-bis(trifluoromethyl)phenyl isothiocyanate, and 1,4-phenylene diisothiocyanate.

2. The additive for a rechargeable lithium battery electrolyte of claim 1 , wherein the aromatic compound is represented by the following Chemical Formula 1:

wherein,

R 1 , R 2 , R 3 , R 4 , and R 5 are independently, hydrogen, substituted or unsubstituted C 1 to C 30 alkyl group, —OR 6 , —CN, —NO 2 , —F, —NCS, —CF 3 , —COR 7 , —COOR 8 , wherein R 6 to R 8 are independently a substituted or unsubstituted C 1 to C 30 alkyl group.

3. The additive for a rechargeable lithium battery electrolyte of claim 1 , wherein the aromatic compound is represented by at least one of the following chemical formulas:

4. An electrolyte for a rechargeable lithium battery, comprising:

a non-aqueous organic solvent,

a lithium salt, and

an aromatic compound having an isothiocyanate group (—NCS);

wherein the aromatic compound is selected from phenyl isothiocyanate, 4-nitrophenyl isothiocyanate, trifluoromethyl phenyl isothiocyanate, 4-cyanophenyl isothiocyanate, 4-methoxyphenyl isothiocyanate, 4-fluorophenyl isothiocyanate, 4-methylphenyl isothiocyanate, 2-fluoro-5-(trifluoromethyl)phenyl isothiocyanate, 4-methyl-3-(trifluoromethyl)phenyl isothiocyanate, 4-fluoro-3-(trifluoromethyl)phenyl isothiocyanate, 3,5-bis(trifluoromethyl)phenyl isothiocyanate, and 1,4-phenylene diisothiocyanate.

5. The electrolyte for a rechargeable lithium battery of claim 4 , wherein the aromatic compound is represented by the following Chemical Formula 1:

wherein,

R 1 , R 2 , R 3 , R 4 , and R 5 are independently, hydrogen, substituted or unsubstituted C1 to C30 alkyl group, −OR 6 , —CN, —NO 2 , —F, —NCS, —CF 3 , —COR 7 , —COOR 8 , wherein R 6 to R 8 are independently a substituted or unsubstituted C1 to C30 alkyl group.

6. The electrolyte for a rechargeable lithium battery of claim 4 , wherein the aromatic compound is included in an amount of about 0.01 wt % to about 5 wt % based on the total amount of the rechargeable lithium battery electrolyte.

7. The electrolyte for a rechargeable lithium battery of claim 4 , wherein the aromatic compound is included in an amount of about 0.01 wt % to about 1 wt % based on the total amount of the rechargeable lithium battery electrolyte.

8. The electrolyte for a rechargeable lithium battery of claim 4 , wherein the lithium salt comprises at least one selected from LiPF 6 , LiBF 4 , LiSbF 6 , LiAsF 6 , LiC 4 F 9 SO 3 , LiClO 4 , LiAlO 2 , LiAlCl 4 , LiN(C x F 2x+1 SO 2 )(C y F 2y+1 SO 2 ) (wherein, x and y are natural numbers), LiCl, LiI, LiB(C 2 O 4 ) 2 (lithium bis(oxalato) borate; LiBOB), and a combination thereof.

9. The electrolyte for a rechargeable lithium battery of claim 4 , wherein the aromatic compound is represented by at least one of the following chemical formulas:

10. A rechargeable lithium battery, comprising:

a positive electrode,

a negative electrode, and

an electrolyte comprising:

a non-aqueous organic solvent,

a lithium salt, and

an aromatic compound having an isothiocyanate group (—NCS);

wherein the aromatic compound is selected from phenyl isothiocyanate, 4-nitrophenyl isothiocyanate, trifluoromethyl phenyl isothiocyanate, 4-cyanophenyl isothiocyanate, 4-methoxyphenyl isothiocyanate, 4-fluorophenyl isothiocyanate, 4-methylphenyl isothiocyanate, 2-fluoro-5-(trifluoromethyl)phenyl isothiocyanate, 4-methyl-3-(trifluoromethyl)phenyl isothiocyanate, 4-fluoro-3-(trifluoromethyl)phenyl isothiocyanate, 3,5-bis(trifluoromethyl)phenyl isothiocyanate, and 1,4-phenylene diisothiocyanate.

11. The rechargeable lithium battery of claim 10 , wherein the rechargeable lithium battery further comprises a solid electrolyte interface (SEI) film that is positioned on at least one surface of the positive electrode and the negative electrode and formed by electrical reduction and polymerization reaction of the aromatic compound.

12. The rechargeable lithium battery of claim 10 , wherein the aromatic compound is represented by the following Chemical Formula 1:

wherein,

R 1 , R 2 , R 3 , R 4 , and R 5 are independently, hydrogen, substituted or unsubstituted C 1 to C 30 alkyl group, —OR 6 , —CN, —NO 2 , —F, —NCS, —CF 3 , —COR 7 , —COOR 8 , wherein R 6 to R 8 are independently a substituted or unsubstituted C1 to C30 alkyl group.

13. The rechargeable lithium battery of claim 10 , wherein the aromatic compound is included in an amount of about 0.01 wt % to about 5 wt % based on the total amount of the rechargeable lithium battery electrolyte.

14. The rechargeable lithium battery of claim 10 , wherein the aromatic compound is included in an amount of about 0.01 wt % to about 1 wt % based on the total amount of the rechargeable lithium battery electrolyte.

15. The rechargeable lithium battery of claim 10 , wherein the lithium salt comprises at least one selected from LiPF 6 , LiBF 4 , LiSbF 6 , LiAsF 6 , LiC 4 F 9 SO 3 , LiClO 4 , LiAlO 2 , LiAlCl 4 , LiN(C x F 2x+1 SO 2 )(C y F 2y+1 SO 2 ) (wherein, x and y are natural numbers), LiCl, LiI, LiB(C 2 O 4 ) 2 (lithium bis(oxalato) borate; LiBOB), and a combination thereof.

16. The rechargeable lithium battery of claim 10 , wherein the aromatic compound is represented by at least one of the following chemical formulas: