Separator for electrochemical device
The present disclosure provides a separator for an electrochemical device, comprising: a porous polymer film; and a porous coating layer formed on one or both surfaces of the porous polymer film and comprising at least one of inorganic particles and organic particles, and a binder polymer, wherein fibrils in the surface of the porous polymer film are entangled with the particles in the porous coating layer in the contact surface between the porous polymer film and the porous coating layer, and the separator has an air permeability of 100 to 800 sec/100 cc, an electrical resistance of 0.5 to 1.5Ω, and a heat-shrinkage rate of 8% or less in each of machine and transverse directions, and an electrochemical device having the same.
1. A separator for an electrochemical device, prepared by the steps comprising:
coating a slurry for a porous coating layer on a first and/or a second surface of a porous polymer film; and
heat-setting the porous polymer film with the slurry coated thereon,
wherein the porous coating layer formed on the first and/or the second surface of the porous polymer film comprises at least one of inorganic particles and organic particles, and a binder polymer,
wherein the second surface is opposite to the first surface,
wherein fibrils in the first and/or second surface of the porous polymer film having the porous coating layer formed thereon are entangled with the particles in the porous coating layer by 10 to 200 nm in a thickness direction from the first and/or second surface, respectively, of the porous polymer film, and
wherein the porous coating layer, and the separator has an air permeability of 100 to 800 sec/100 cc, an electrical resistance of 0.5 to 1.5Ω, and a heat-shrinkage rate of 8% or less in each of machine and transverse directions.
2. The separator of claim 1 , which has a tensile strength of 1,500 to 2,500 kg/cm 2 , and a puncture strength of 480 to 1,000 kgf.
3. The separator of claim 1 , wherein the porous coating layer has a peeling force to the porous polymer film of no less than 5,000 gf/cm.
4. The separator of claim 1 , wherein the porous polymer film is a porous polyolefin film.
5. The separator of claim 4 , wherein the porous polyolefin film is selected from polyethylene; polypropylene; polybutylene; polypentene; polyhexene; polyoctene; a copolymer of at least one of ethylene, propylene, butene, pentene, 4-methylpentene, hexene and octene; and a mixture thereof.
6. The separator of claim 1 , wherein the porous polymer film has a thickness of 5 to 50 μm, a pore size of 0.01 to 50 and a porosity of 10 to 95%.
7. The separator of claim 1 , wherein the binder polymer is any one selected from the group consisting of polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethylmethacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, carboxyl methyl cellulose, acrylonitrile-styrene-butadiene copolymer, polyimide, and a mixture thereof.
8. The separator of claim 1 , wherein the porous coating layer comprises the inorganic particles, wherein the inorganic particles are inorganic particles having a dielectric constant of 5 or higher, inorganic particles having the ability to transport lithium ions, or a mixture thereof.
9. The separator of claim 8 , wherein the inorganic particles having a dielectric constant of 5 or higher are selected from BaTiO 3 , Pb(Mg 1/3 Nb 2/3 )O 3 —PbTiO 3 (PMN-PT), hafnia (HfO 2 ), SrTiO 3 , SnO 2 , CeO 2 , MgO, NiO, CaO, ZnO, ZrO 2 , Y 2 O 3 , Al 2 O 3 , TiO 2 , SiC and a mixture thereof.
10. The separator of claim 8 , wherein the inorganic particles having the ability to transport lithium ions are selected from lithium phosphate (Li 3 PO 4 ), lithium titanium phosphate (Li x Ti y (PO 4 ) 3 , 0<x<2, 0<y<3), lithium aluminum titanium phosphate (Li x Al y Ti z (PO 4 ) 3 , 0<x<2, 0<y<1, 0<z<3), (LiAlTiP) x O y glass (0<x<4, 0<y<13), lithium lanthanum titanate (Li x La y TiO 3 , 0<x<2, 0<y<3), lithium germanium thiophosphate (Li x Ge y P z S w , 0<x<4, 0<y<1, 0<z<1, 0<w<5), lithium nitride (Li x N y , 0<x<4, 0<y<2), SiS 2 glass (Li x Si y S z , 0<x<3, 0<y<2, 0<z<4), P 2 S 5 glass (Li x P y S z , 0<x<3, 0<y<3, 0<z<7), and a mixture thereof.
11. The separator of claim 1 , wherein the porous coating layer comprises the organic particles, wherein the organic particles are selected from polystyrene, polyethylene, polyimide, melamine resins, phenolic resins, cellulose, cellulose modifiers, polypropylene, polyester, polyphenylene sulfide, polyaramid, polyamideimide, polyimide, a copolymer of butyl acrylate and ethyl methacrylate, and a mixture thereof.
12. The separator of claim 1 , wherein the inorganic particles and the organic particles have an average diameter of 0.001 to 10 μm.
13. The separator of claim 1 , wherein the porous polymer film has the structure that a plurality of fibrils are disposed in parallel with the surface of the film and are laminated in layers, and the fibrils disposed on one surface of the film where the porous coating layer is formed may have a diameter smaller than that of the fibrils disposed in a center of the film in the thickness direction thereof.
14. The separator of claim 1 , wherein the fibrils disposed on the first and/or second surface of the film where the porous coating layer is formed have a diameter being 2 to 4 times smaller than that of the fibrils disposed in a center of the film in the thickness direction thereof.
15. The separator of claim 1 , wherein the fibrils disposed on the first and/or second surface of the film where the porous coating layer is formed have a diameter of 0.01 to 0.04 μm, and the fibrils disposed in a center of the film in the thickness direction thereof have a diameter of 0.04 to 0.08 μm.
16. The separator of claim 1 , wherein the porous polymer film has a porous coating layer formed on only the first or second surface thereof, and fibrils disposed on one surface of the film where the porous coating layer is formed have a diameter smaller than that of fibrils disposed on the first or second surface of the film where the porous coating layer is not formed.
17. The separator of claim 16 , wherein the fibrils disposed on the first or second surface of the film where the porous coating layer is formed has a diameter being 2 to 7 times smaller than that of the fibrils disposed on the first or second surface of the film where the porous coating layer is not formed.
18. The separator of claim 16 , wherein the fibrils disposed on the first or second surface of the film where the porous coating layer is formed have a diameter of 0.01 to 0.07 μm, and the fibrils disposed on the first or second surface of the film where the porous coating layer is not formed have a diameter of 0.07 to 0.14 μm.
19. The separator of claim 1 , wherein the binder polymer is present on a surface of adjacent particles to connect the adjacent particles with each other and form a porous structure, and the binder polymer has a size of 10 to 100 nm.
20. An electrochemical device, comprising a cathode, an anode, and the separator of claim 1 interposed between the cathode and the anode.
21. The electrochemical device according to claim 20 , which is a lithium secondary battery.