Composition for gel polymer electrolyte and lithium secondary battery comprising the gel polymer electrolyte formed therefrom

1. A composition for a gel polymer electrolyte, the composition comprising an electrolyte salt, an organic solvent, an oligomer represented by Formula 1, a non-fluoride oxygen scavenger, and a polymerization initiator:

wherein, in Formula 1,

R is an aliphatic hydrocarbon group or an aromatic hydrocarbon group,

R′ and R″ are each independently hydrogen or an alkyl group having 1 to 3 carbon atoms,

n is an integer of 1 or 2,

m, z, and K are the numbers of repeating units,

m is an integer of 1 to 3,

z is an integer of 1 to 10,000, and

K is an integer of 1 to 100.

2. The composition for a gel polymer electrolyte of claim 1 , wherein, in the oligomer represented by Formula 1, R is the aliphatic hydrocarbon group comprising at least one selected from the group consisting of:

at least one alicyclic hydrocarbon group selected from the group consisting of a substituted or unsubstituted cycloalkylene group having 4 to 20 carbon atoms; a substituted or unsubstituted cycloalkylene group having 4 to 20 carbon atoms which contains an isocyanate group (NCO); a substituted or unsubstituted cycloalkenylene group having 4 to 20 carbon atoms; and a substituted or unsubstituted heterocycloalkylene group having 2 to 20 carbon atoms, and

at least one linear hydrocarbon group selected from the group consisting of a substituted or unsubstituted alkylene group having 1 to 20 carbon atoms; a substituted or unsubstituted alkylene group having 1 to 20 carbon atoms which contains an isocyanate group (NCO); a substituted or unsubstituted alkoxylene group having 1 to 20 carbon atoms; a substituted or unsubstituted alkenylene group having 2 to 20 carbon atoms; and a substituted or unsubstituted alkynylene group having 2 to 20 carbon atoms.

3. The composition for a gel polymer electrolyte of claim 1 , wherein, in the oligomer represented by Formula 1, R is the aromatic hydrocarbon group comprising at least one selected from the group consisting of a substituted or unsubstituted arylene group having 6 to 20 carbon atoms; and a substituted or unsubstituted heteroarylene group having 4 to 20 carbon atoms.

4. The composition for a gel polymer electrolyte of claim 1 , wherein the oligomer represented by Formula 1 comprises at least one selected from the group consisting of compounds represented by Formulae 1a to 1c;

wherein, in Formula 1a,

z1 and K1 are the numbers of repeating units,

z1 is an integer of 1 to 500, and

K1 is an integer of 1 to 30;

in Formula 1b,

z2 and K2 are the numbers of repeating units,

z2 is an integer of 1 to 500, and

K2 is an integer of 1 to 30;

wherein, in Formula 1c,

z3 and K3 are the numbers of repeating units,

z3 is an integer of 1 to 500, and

K3 is an integer of 1 to 30.

5. The composition for a gel polymer electrolyte of claim 1 , wherein the oligomer represented by Formula 1 is included in an amount of 0.5 wt % to 25 wt % based on a total weight of the composition for a gel polymer electrolyte.

6. The composition for a gel polymer electrolyte of claim 1 , wherein the non-fluoride oxygen scavenger comprises at least one of a trisalkylsilylphosphite-based compound; and a trisarylsilylphosphite-based compound.

7. The composition for a gel polymer electrolyte of claim 6 , wherein the non-fluoride oxygen scavenger comprises at least one selected from the group consisting of tris(methylsilyl) phosphite, tris(ethylsilyl) phosphite, tris(propylsilyl) phosphite, tris (butylsilyl) phosphite, and trisphenylsilyl phosphite.

8. The composition for a gel polymer electrolyte of claim 1 , wherein the non-fluoride oxygen scavenger is included in an amount of 0.5 wt % to 15 wt % based on a total weight of the composition for a gel polymer electrolyte.

9. The composition for a gel polymer electrolyte of claim 8 , wherein the non-fluoride oxygen scavenger is included in an amount of 0.5 wt % to 10 wt % based on the total weight of the composition for a gel polymer electrolyte.

10. A gel polymer electrolyte prepared by polymerizing the composition for a gel polymer electrolyte of claim 1 .

11. A lithium secondary battery comprising a positive electrode, a negative electrode, and a gel polymer electrolyte disposed between the positive electrode and the negative electrode, wherein the gel polymer electrolyte comprises the gel polymer electrolyte of claim 10 .

12. The composition for a gel polymer electrolyte of claim 1 , wherein a weight-average molecular weight (Mw) of the oligomer represented by Formula 1 is in a range of 1,000 g/mol to 20,000 g/mol.

13. The composition for a gel polymer electrolyte of claim 1 , wherein a weight-average molecular weight (Mw) of the oligomer represented by Formula 1 is in a range of 1,000 g/mol to 10,000 g/mol.

14. The composition for a gel polymer electrolyte of claim 1 , wherein the non-fluoride oxygen scavenger is included in an amount of 0.5 wt % to 7 wt % based on a total weight of the composition for a gel polymer electrolyte.

15. The composition for a gel polymer electrolyte of claim 1 , wherein the polymerization initiator comprises one selected from the group consisting of benzoyl peroxide, acetyl peroxide, dilauryl peroxide, di-tert-butyl peroxide, t-butylperoxy-2-ethyl-hexanoate, cumyl hydroperoxide, and hydrogen peroxide.

16. The composition for a gel polymer electrolyte of claim 1 , wherein the polymerization initiator comprises at least one selected from the group consisting of azo compound selected from the group consisting of 2,2′-azobis(2-cyanobutane), 2,2′-azobis(methylbutyronitrile), 2,2′-azobis(iso-butyronitrile) (AIBN), and 2,2′-azobis(dimethylvaleronitrile) (AMVN).

17. The composition for a gel polymer electrolyte of claim 1 , further comprising a multifunctional (meth)acrylate-based compound having at least one acrylate group.

18. The composition for a gel polymer electrolyte of claim 1 , wherein the organic solvent comprises ether-based solvent, an ester-based solvent, or an amide-based solvent or a mixture thereof.