Separator for secondary battery and lithium secondary battery comprising same

1. A separator for a secondary battery, comprising

a porous substrate and a heat-resistant layer disposed on at least one surface of the porous substrate,

wherein the heat-resistant layer comprises an acrylic heat-resistant binder, an adhering binder, and a filler,

the acrylic heat-resistant binder comprises a structural unit derived from (meth)acrylate or (meth)acrylic acid, a cyano group-containing structural unit, and a sulfonate group-containing a structural unit, and

the adhering binder is represented by Chemical Formula 9:

R 15 is independently hydrogen or C1 to C10 alkyl group,

M 1 is an alkali metal, and

a mole ratio of the o:p:q is 94:1:5 to 79:1:20.

2. The separator of claim 1 , wherein the structural unit derived from (meth)acrylate or (meth)acrylic acid is represented by Chemical Formula 1, Chemical Formula 2, Chemical Formula 3, or a combination thereof:

wherein, in Chemical Formula 1 to Chemical Formula 3,

R 1 , R 2 , and R 3 are each independently hydrogen or a methyl group,

wherein, in Chemical Formula 2,

M is an alkali metal.

3. The separator of claim 1 , wherein the cyano group-containing structural unit is represented by Chemical Formula 4:

wherein, in Chemical Formula 4,

R 4 is hydrogen or a C1 to C1 alkyl group,

L 1 is —C(═O)—, —C(═O)O—, —OC(═O)—, —O—, or —C(═O)NH—,

x is an integer ranging from 0 to 2,

L 2 is a substituted or unsubstituted C1 to C10 alkylene group, a substituted or unsubstituted C3 to C20 cycloalkylene group, a substituted or unsubstituted C6 to C20 arylene group or a substituted or unsubstituted C3 to C20 heterocyclic group, and

y is an integer ranging from 0 to 2.

4. The separator of claim 1 , wherein the sulfonate group-containing structural unit is represented by Chemical Formula 5, Chemical Formula 6, Chemical Formula 7, or a combination thereof:

wherein, in Chemical Formula 5 to Chemical Formula 7,

R 5 , R 6 , and R 7 are each independently hydrogen or a C1 to C3 alkyl group,

L 3 , L 5 , and L 7 are each independently —C(═O)—, —C(═O)O—, —OC(═O)—, —O—, or —C(═O)NH—,

L 4 , L 6 , and L 8 are each independently a substituted or unsubstituted C1 to C10 alkylene group, a substituted or unsubstituted C3 to C20 cycloalkylene group, a substituted or unsubstituted C6 to C20 arylene group, or a substituted or unsubstituted C3 to C20 heterocyclic group, and

a, b, c, d, e, and f are each independently an integer ranging from 0 to 2,

wherein, in Chemical Formula 6,

M′ is an alkali metal.

5. The separator of claim 1 , wherein

the acrylic heat-resistant binder comprises

20 mol % to 60 mol % of the structural unit derived from (meth)acrylate or (meth)acrylic acid;

30 mol % to 75 mol % of the cyano group-containing structural unit; and

0.1 mol % to 20 mol % of the sulfonate group-containing structural unit.

6. The separator of claim 1 , wherein a weight average molecular weight of the acrylic heat-resistant binder is 200,000 g/mol to 700,000 g/mol.

7. The separator of claim 1 , wherein a glass transition temperature of the acrylic heat-resistant binder is 200° C. to 280° C.

8. The separator of claim 1 , wherein the acrylic heat-resistant binder further comprises an alkali metal.

9. The separator of claim 1 , wherein the mole ratio of the o:p:q is 89:1:10 to 84:1:15.

10. The separator of claim 1 , wherein a weight average molecular weight of the adhering binder is 50,000 g/mol to 1,000,000 g/mol.

11. The separator of claim 1 , wherein the acrylic heat-resistant binder and the adhering binder are included in a weight ratio of 2:8 to 8:2.

12. A lithium secondary battery, comprising

a positive electrode,

a negative electrode, and

the separator for the secondary battery according to claim 1 disposed between the positive electrode and the negative electrode.