Composite separator for secondary battery and lithium secondary battery including the same

1. A composite separator for a secondary battery comprising:

a porous substrate; and

a coating layer formed on the porous substrate, by thermally curing an aqueous slurry including inorganic particles, first binder particles, a second binder, and a thermal curing agent,

wherein the first binder particles contain a copolymer of a monomer mixture including 30 to 50 wt % of acrylamide-based monomer, 20 to 40 wt % of a vinyl cyanide-based monomer, 5 to 20 wt % of an acrylic monomer having a carboxyl group, and 5 to 20 wt % of an acrylic monomer having a hydroxyl group, based on a total amount of the first binder particles,

wherein the first binder particles have a glass transition temperature of 150 to 200° C.

2. The composite separator for the secondary battery of claim 1 , wherein the inorganic particles and the first binder particles have an average particle diameter of 10 nm to 2 μm.

3. The composite separator for the secondary battery of claim 1 , wherein the second binder is any one or a mixture of two or more selected from the group consisting of cellulose-based compounds and polyvinyl alcohol-based compounds.

4. The composite separator for the secondary battery of claim 1 , wherein the thermal curing agent is any one or a mixture of two or more selected from the group consisting of compounds including any one or two or more functional groups selected from an epoxy group and an oxazoline group.

5. The composite separator for the secondary battery of claim 1 , wherein the composite separator for a secondary battery has thermal shrinkage at 160° C. of 3% or less, and a melt fracture temperature of 400° C. or more.

6. A lithium secondary battery comprising the composite separator for the secondary battery of claim 1 .