Electrolyte for lithium ion secondary battery and lithium ion secondary battery comprising the same

1. An electrolyte for a lithium ion secondary battery comprising:

a non-aqueous organic solvent; and

a lithium salt, which is at least one selected from the group consisting of LiPF 6 , LiBF 4 , LiSbF 6 , LiAsF 6 , LiClO 4 , LiCF 3 SO 3 , LiC 4 F 9 SO 3 , LiAlO 4 , LiAlCl 4 , LiN(C p F 2p+1 SO 2 )(C q F 2q+1 SO 2 ) (where p and q are natural numbers), LiCl and LiI; and

additives comprising difluoro oxalato borate (DFOB) represented by a chemical formula 1 below and fluoro ethylene carbonate (FEC)

2. The electrolyte of claim 1 , wherein the non-aqueous organic solvent is at least one selected from the group consisting of a carbonate, an ester, an ether and a ketone.

3. The electrolyte of claim 2 , wherein the carbonate is at least one selected from the group consisting of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, ethylmethyl carbonate, ethylene carbonate, propylene carbonate, butylene carbonate and pentylene carbonate.

4. The electrolyte of claim 2 , wherein the ester is at least one selected from the group consisting of n-methyl acetate, n-ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, γ-butyrolactone, decanolide, valerolactone, mevalonolactone and caprolactone.

5. The electrolyte of claim 2 , wherein the ether is at least one selected from the group consisting of dibutyl ether, tetraglyme, diglyme, dimethoxy ethane, 2-methyltetrahydrofuran and tetrahydrofuran.

6. The electrolyte of claim 2 , wherein the ketone is at least one selected from the group consisting of cyclohexanone and polymethylvinyl ketone.

7. A lithium ion secondary battery, comprising:

a cathode including a cathode active material that can reversibly intercalate and deintercalate lithium;

an anode including an anode active material that can reversibly intercalate and deintercalate lithium; and

the electrolyte of claim 1 .

8. A lithium ion secondary battery, comprising:

a cathode including a cathode active material that can reversibly intercalate and deintercalate lithium;

an anode including an anode active material that can reversibly intercalate and deintercalate lithium; and

the electrolyte of claim 2 .

9. A lithium ion secondary battery, comprising:

a cathode including a cathode active material that can reversibly intercalate and deintercalate lithium;

an anode including an anode active material that can reversibly intercalate and deintercalate lithium; and

the electrolyte of claim 3 .

10. A lithium ion secondary battery, comprising:

a cathode including a cathode active material that can reversibly intercalate and deintercalate lithium;

an anode including an anode active material that can reversibly intercalate and deintercalate lithium; and

the electrolyte of claim 4 .

11. A lithium ion secondary battery, comprising:

a cathode including a cathode active material that can reversibly intercalate and deintercalate lithium;

an anode including an anode active material that can reversibly intercalate and deintercalate lithium; and

the electrolyte of claim 5 .

12. A lithium ion secondary battery, comprising:

a cathode including a cathode active material that can reversibly intercalate and deintercalate lithium;

an anode including an anode active material that can reversibly intercalate and deintercalate lithium; and

the electrolyte of claim 6 .

13. A method of making a lithium ion secondary battery, the method comprising:

providing an electrolyte comprising:

a non-aqueous organic solvent;

a lithium salt, which is at least one selected from the group consisting of LiPF 6 , LiBF 4 , LiSbF 6 , LiAsF 6 , LiClO 4 , LiCF 3 SO 3 , LiC 4 F 9 SO 3 , LiAlO 4 , LiAlCl 4 , LiN(C p F 2p+1 SO 2 )(C q F 2q+1 SO 2 ) (where p and q are natural numbers), LiCl and LiI, and;

additives comprising difluoro oxalato borate (DFOB) and fluoro ethylene carbonate (FEC), the difluoro oxalate being represented by Chemical Formula 1:

providing a battery can including an electrode assembly, which comprises:

a cathode including a cathode active material that can reversibly intercalate and deintercalate lithium, and

an anode including an anode active material that can reversibly intercalate and deintercalate lithium;

containing the electrolyte in the battery can to form a lithium ion secondary battery; and

charging the lithium ion secondary battery or exposing the lithium ion secondary battery to a temperature of 60° C. or greater.