Heat resistant layer composition, lithium secondary battery separator comprising heat resistant layer formed therefrom, and lithium secondary battery comprising same
The present invention relates to a heat resistant layer composition, a heat resistant layer formed therefrom, and a separator for a lithium secondary battery, and a lithium secondary battery including same, wherein the heat resistant layer composition includes an acrylic copolymer including a first structural unit derived from (meth)acrylamide, and a second structural unit including at least one of a structural unit derived from (meth)acrylic acid or a (meth)acrylate, a structural unit derived from (meth)acrylonitrile, and a structural unit derived from (meth)acrylamidosulfonic acid or a salt thereof; a cross-linking agent including at least one functional group of an aldehyde group, an epoxy group, an amide group, an imide group, an amine group, and a silane-based group; and a solvent.
1. A separator for a lithium secondary battery, comprising
a porous substrate; and
a heat resistant layer on at least one surface of the porous substrate, wherein a ratio of a thickness of the heat resistant layer relative to a thickness of the porous substrate is 0.05 to 0.5,
wherein the heat resistant layer is formed from a heat resistant layer composition, comprising
an acrylic copolymer comprising
a first structural unit derived from (meth)acrylamide, and
a second structural unit including at least one selected from a structural unit derived from (meth)acrylonitrile, a structural unit derived from (meth)acrylamidosulfonic acid or a salt thereof, and a structural unit derived from (meth)acrylic acid or a (meth)acrylate;
a cross-linking agent including glyoxal; and
a solvent,
wherein the cross-linking agent is included in an amount of 15 to 20 parts by weight based on 100 parts by weight of the acrylic copolymer.
2. The separator of claim 1 , wherein the first structural unit is included in an amount of 55 mol % to 95 mol % based on 100 mol % of the acrylic copolymer, and the second structural unit is included in an amount of 5 mol % to 45 mol % based on 100 mol % of the acrylic copolymer.
3. The separator of claim 1 , wherein the second structural unit comprises at least one of a structural unit derived from (meth)acrylic acid or a (meth)acrylate and a structural unit derived from (meth)acrylamidosulfonic acid or a salt thereof.
4. The separator of claim 1 , wherein the second structural unit comprises at least one of a structural unit derived from (meth)acrylonitrile and a structural unit derived from (meth)acrylamidosulfonic acid or a salt thereof.
5. The separator of claim 1 , wherein
the first structural unit derived from (meth)acrylamide is represented by Chemical Formula 1, and
the structural unit derived from (meth)acrylic acid or a (meth)acrylate is represented by one of Chemical Formula 2, Chemical Formula 3, and a combination thereof, and
the structural unit derived from (meth)acrylonitrile is represented by Chemical Formula 4, and
the structural unit derived from (meth)acrylamidosulfonic acid or a salt thereof is represented by one of Chemical Formula 5, Chemical Formula 6, Chemical Formula 7, and a combination thereof:
wherein, in Chemical Formula 1 to Chemical Formula 7,
R 1 to R 7 are independently hydrogen or a C1 to C6 alkyl group,
R 8 is a substituted or unsubstituted C1 to C20 alkyl group,
L 1 to L 5 are 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,
a, b, c, d, and e are independently one of integers of 0 to 2, and
M is an alkali metal.
6. The separator of claim 1 , wherein a weight average molecular weight of the acrylic copolymer is 300,000 to 950,000.
7. The separator of claim 1 , wherein
the heat resistant layer further comprises inorganic particles.
8. The separator of claim 7 , wherein the acrylic copolymer: inorganic particle are included in a weight ratio of 1:20 to 1:40.
9. The separator of claim 7 , wherein the inorganic particles comprise Al 2 O 3 , SiO 2 , TiO 2 , SnO 2 , CeO 2 , MgO, NiO, CaO, GaO, ZnO, ZrO 2 , Y 2 O 3 , SrTiO 3 , BaTiO 3 , Mg(OH) 2 , boehmite, or a combination thereof.
10. The separator of claim 1 , wherein the thickness of the heat resistant layer is 1 μm to 10 μm.
11. A lithium secondary battery, comprising
a positive electrode; a negative electrode; and the separator for a lithium secondary battery of claim 1 between the positive electrode and the negative electrode.