Electrolytic solution for lithium secondary battery, and lithium secondary battery comprising same

1. An electrolytic solution for a secondary battery, comprising:

a lithium salt;

a non-aqueous organic solvent; and

a difluorophosphite compound of the following Formula 1:

A -OPF 2   [Formula 1]

in Formula 1,

A is a substituted or unsubstituted C1-C10 alkyl or C3-C10 cycloalkyl,

wherein the substituted C1-C10 alkyl and C3-C10 cycloalkyl are substituted with C1-C10 alkoxy or C1-C10 alkoxy-C1-C10 alkoxy.

2. The electrolytic solution of claim 1 , wherein in Formula 1, A is C2-C8 alkyl, C2-C8 alkyl substituted with H—(CH 2 CH 2 O) m −, or C3-C7 cycloalkyl, and

m is an integer of 1 or 2.

3. The electrolytic solution of claim 1 , wherein the difluorophosphite compound of Formula 1 is represented by the following Formula 2,

in Formula 2,

R is hydrogen or H—(CH 2 CH 2 O) m —,

n is an integer of 2 to 8, and m is an integer of 1 or 2.

4. The electrolytic solution of claim 1 , wherein the difluorophosphite compound of Formula 1 is represented by the following Formula 3,

in Formula 3,

p is an integer of 1 to 3.

5. The electrolytic solution of claim 1 , wherein the difluorophosphite compound is one or more selected from the following compounds.

6. The electrolytic solution of claim 1 , wherein the difluorophosphite compound is contained in an amount of 0.1 to 5 wt % with respect to a total weight of the electrolytic solution.

7. The electrolytic solution of claim 1 , further comprising one or two or more additional additives selected from 1,3-propane sultone (PS), lithium bis(oxalato)borate (LiBOB), lithium difluoro bis(oxalato)phosphate (LiDFBOP), and ethylene sulfate (ESA).

8. The electrolytic solution of claim 7 , wherein the additional additive is contained in an amount of 0.1 to 10.0 wt % with respect to a total weight of the electrolytic solution.

9. A lithium secondary battery comprising:

a cathode containing a nickel-cobalt-manganese-based cathode active material, an anode, a separator interposed between the cathode and the anode, and the electrolytic solution of claim 1 .

10. The lithium secondary battery of claim 9 , wherein the cathode active material includes Li x1 (Ni a1 Co b1 Mn c1 )O 2 , Li x2 (Ni a2 Co b2 Mn c2 )O 4 , or a mixture therof where 0.5<x1<1.3, 0<a1<1, 0<b1<1, 0<c1<1, and a1+b1+c1=1; 0.5<x2<1.3, 0<a2<2, 0<b2<2, 0<c2<2, and a2+b2+c2=2).

11. The lithium secondary battery of claim 10 , wherein the cathode active material is Li x1 (Ni a1 Co b1 Mn c1 )O 2 where 0.90≤x1≤1.10, 0.3≤a1≤0.9, 0.05≤b1≤0.5, 0.05≤c1≤0.5, and a1+b1+c1=1.

12. The lithium secondary battery of claim 11 , wherein the cathode active material is Li(Ni a1 Co b1 Mn c1 )O 2 where 0.3≤a1≤0.9, 0.05≤b1≤0.5, 0.05≤c1≤0.5, and a1+b1+c1=1.

13. A lithium secondary battery comprising:

a cathode containing a nickel-cobalt-manganese-based cathode active material, an anode, a separator interposed between the cathode and the anode, and the electrolytic solution of claim 1 .