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

1. A lithium secondary battery having a thickness increase rate of 1% to 15% after 30 days at 60° C. and comprising:

an anode comprising an anode active material capable of intercalating and deintercalating lithium ions;

a cathode comprising a cathode active material capable of intercalating and deintercalating lithium ions;

a separator preventing a short circuit between the anode and the cathode; and

an electrolyte comprising a lithium salt, a non-aqueous organic solvent, and a boron derivative represented by the following Chemical Formula 2, 4 or 5:

wherein in Chemical Formula 2 each of R 1 and R 2 is independently hydrogen, cyano, hydroxyl, halogen, halo(C1-C10)alkyl, (C1-C10)alkyl, (C1-C10)alkoxy, (C1-C10)alkoxycarbonyl, or (C6-C12)aryl,

wherein each of o and p is independently an integer of 1 to 4,

wherein, when o is 2 or more, the two or more R 1 are the same as or different from each other, and

wherein, when p is 2 or more, the two or more R 2 are the same as or different from each other,

wherein in Chemical Formula 4 each of R 11 to R 18 is independently hydrogen, or (C1-C10)alkoxycarbonyl, and at least one of R 11 to R 18 is (C1-C10)alkoxycarbonyl,

wherein in Chemical Formula 5 each of R 11 to R 22 is independently hydrogen, halo(C1-C10) alkyl, (C1-C10) alkyl, or (C1-C10)alkoxycarbonyl, and

wherein the boron derivative excludes the material represented by Chemical Formula 5 of which all of R 11 to R 22 are (C1-C10) alkyl.

2. The lithium secondary battery of claim 1 , wherein each of R 1 and R 2 is independently hydrogen or (C1-C10) alkyl.

3. The lithium secondary battery of claim 1 , wherein the boron derivative is selected from the group consisting of the following structures:

4. The lithium secondary battery of claim 1 , wherein the content of the boron derivative is 0.1 wt % to 5 wt % based on the total weight of the electrolyte.

5. The lithium secondary battery of claim 1 , wherein the electrolyte further comprises:

a first additive selected from the group consisting of oxalatoborate based compounds, carbonate based compounds substituted with fluorine, vinylidene carbonate based compounds, sulfinyl group-containing compounds, and a combination thereof.

6. The lithium secondary battery of claim 5 , wherein the electrolyte further comprises:

a second additive selected from the group consisting of lithium difluoro(oxalate)borate (LiFOB), lithium bis(oxalate)borate (LiB(C 2 O 4 ) 2 , LiBOB), fluoroethylene carbonate (FEC), vinylene carbonate (VC), vinyl ethylene carbonate (VEC), divinyl sulfone, ethylene sulfite, propylene sulfite, diallyl sulfonate, ethane sultone, propane sultone (PS), butane sultone, ethene sultone, butene sultone, propene sultone (PRS), and a combination thereof.

7. The lithium secondary battery of claim 5 , wherein the content of the first additive is 0.1 wt % to 5.0 wt % based on the total weight of the electrolyte.

8. The lithium secondary battery of claim 1 , wherein the non-aqueous organic solvent is selected from the group consisting of cyclic carbonate-based solvent, linear carbonate-based solvent, and a combination thereof.

9. The lithium secondary battery of claim 8 , wherein the cyclic carbonate-based solvent includes a compound selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, vinyl ethylene carbonate, fluoroethylene carbonate, and a mixture thereof, and

wherein the linear carbonate-based solvent includes a compound selected from the group consisting of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, ethyl propyl carbonate, and a mixture thereof.

10. The lithium secondary battery of claim 8 , wherein the non-aqueous organic solvent is a mixture of the linear carbonate-based solvent and the cyclic carbonate-based solvent, and

wherein the mixed volume ratio of the linear carbonate-based solvent:the cyclic carbonate-based solvent is 1 to 9:1.

11. The lithium secondary battery of claim 1 , wherein the lithium salt is 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 9 SO 3 , LiSCN, LiAlO 2 , LiAlCl 4 , LiCl, LiI, LiB(C 2 O 4 ) 2 , and a combination thereof.

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

13. An electrolyte for a lithium secondary battery, the electrolyte comprising a lithium salt, a non-aqueous solvent and a boron derivative represented by the following Chemical Formulas:

wherein in Chemical Formula 2 each of R 1 and R 2 is independently hydrogen, cyano, hydroxyl, halogen, halo(C1-C10)alkyl, (C1-C10)alkyl, (C1-C10)alkoxy, (C1-C10)alkoxycarbonyl, or (C6-C12)aryl,

wherein each of o and p is independently an integer of 1 to 4,

wherein, when o is 2 or more, the two or more R 1 are the same as or different from each other,

wherein, when p is 2 or more, the two or more R 2 are the same as or different from each other,

wherein in Chemical Formula 4 each of R 11 to R 18 is independently hydrogen, or (C1-C10)alkoxycarbonyl, and at least one of R 11 to R 18 is (C1-C10)alkoxycarbonyl,

wherein in Chemical Formula 5 each of R 11 to R 22 is independently hydrogen, halo(C1-C10) alkyl, (C1-C10) alkyl, or (C1-C10)alkoxycarbonyl, and

wherein the boron derivative excludes the material represented by Chemical Formula 5 of which all of R 11 to R 22 are (C1-C10) alkyl.

14. The electrolyte of claim 13 , wherein each of R 1 and R 2 is independently hydrogen or (C1-C10)alkyl.