Separator for secondary battery, manufacturing method therefor, and lithium secondary battery comprising separator
A method for manufacturing a separator for a secondary battery, and a lithium secondary battery comprising same. A separator for a lithium secondary battery, and a lithium secondary battery comprising same, the separator having excellent heat resistance, adhesive strength, air permeability and high-temperature shrinkage characteristics, which are significantly improved, and having an inorganic particle layer formed on one surface or both surfaces of a porous substrate layer, the inorganic particle layer being prepared from a slurry comprising inorganic particles and a condensation-suppressed silane-based hydrocondensate having excellent binding force between organic and inorganic materials.
1. A separator comprising:
a porous substrate and an inorganic particle layer formed on one or both surfaces of the porous substrate,
wherein the inorganic particle layer includes inorganic particles, and a hydrocondensate of a silane compound, the hydrocondensate comprises one or more of, dimer form, trimer form, tetramer form and pentamer form, and
the separator has a heat resistance so that, when two types of specimens with a width of 5 mm and a length of 15 mm, with one having a length direction in a machine direction (MD) and the other having a length direction in a transverse direction (TD), are prepared from the separator,
when both ends of each specimen are hooked to a metal jig and mounted in a thermomechanical analyzer (TMA) chamber, and when each specimen is pulled with a force of 0.015 N in the downward direction while heated at 5° C./min,
the specimens are not broken in both the MD and TD until after a temperature of 180° C. is reached.
2. The separator of claim 1 , wherein the separator has a heat shrinkage rate of 3% or less, when evaluated after 150° C. for 60 minutes.
3. The separator of claim 1 , wherein the separator has a heat shrinkage rate of 2% or less, when evaluated after 150° C. for 60 minutes.
4. The separator of claim 1 , wherein the hydrocondensate of the silane compound is hydrolyzed and condensation-suppressed by formation in an acidic atmosphere, wherein the acid component is carbonic acid prepared by bubbling carbon dioxide, or an organic acid.
5. The separator of claim 1 , wherein the porous substrate comprises a polyolefin-based porous substrate and has a porosity ranging from 30 to 70%.
6. The separator of claim 1 , wherein the porous substrate is hydrophilically surface-treated.
7. The separator of claim 1 , wherein the silane compound is represented by the following Chemical Formula 1:
A a Si(OR) b Chemical Formula 1
wherein A is a C1-C10 alkyl group having a hydrogen group, a hydroxyl group, or a polar functional group, R is independent of each other hydrogen or C1-C5 alkyl group, a is 0 to 2, b is 2 to 4, and a+b is 4.
8. The separator of claim 7 , wherein the polar functional group is selected from one or more groups of an amino group, an epoxy group, a carboxylic acid group, a hydroxyl group, an amide group, a thiol group, and an aldehyde group, or is a reactive group which reacts with the groups.
9. The separator of claim 1 , wherein the inorganic particles comprise a metal hydroxide.
10. The separator of claim 1 , wherein the inorganic particles and the hydrocondensate of the silane compound are present in a weight ratio ranging from 70 to 99.9:30 to 0.1.
11. The separator of claim 1 , wherein the separator has an air permeability change (ΔG) satisfying the following Equation 1:
Δ G=G 1 −G 2 ≤40 Equation 1
wherein
G 1 is a Gurley permeability of the separator including the inorganic particle layer,
G 2 is a Gurley permeability of the porous substrate itself, and
the Gurley permeability is measured in accordance with ASTM D726 and has a unit of see/100 cc.
12. A secondary battery comprising: the separator of claim 1 , a negative electrode, and a positive electrode.