Separator for electrochemical device
Disclosed is a separator for an electrochemical device including a porous polymer film, and a porous coating layer including at least one type of particles of inorganic particles and organic particles and binder polymer, the porous coating layer formed on one surface or both surfaces of the porous polymer film, wherein the porous polymer film has a structure in which multiple fibrils arranged parallel to the surface of the film are stacked in layers, and a diameter of the fibril disposed at the side of one surface of the film where the porous coating layer is formed is smaller than a diameter of the fibril disposed at a central part in a thickness-wise direction of the film, and an electrochemical device comprising the same.
1. A separator for an electrochemical device, comprising:
a porous polymer film; and
a porous coating layer including at least one type of particles of inorganic particles and organic particles and binder polymer, the porous coating layer formed on one surface or both surfaces of the porous polymer film,
wherein the porous polymer film has a structure in which multiple fibrils arranged parallel to the surface of the porous polymer film are stacked in layers, and a diameter of the fibril disposed at the side of one surface of the porous polymer film where the porous coating layer is formed is smaller than a diameter of the fibril disposed at a central part in a thickness-wise direction of the porous polymer film.
2. The separator for an electrochemical device according to claim 1 , wherein the diameter of the fibril disposed at the side of one surface of the porous polymer film where the porous coating layer is formed is smaller two to four times than the diameter of the fibril disposed at the central part in the thickness-wise direction of the porous polymer film.
3. The separator for an electrochemical device according to claim 1 , wherein the diameter of the fibril disposed at the side of one surface of the porous polymer film where the porous coating layer is formed is from 0.01 to 0.04 μm, and the diameter of the fibril disposed at the central part in the thickness-wise direction of the porous polymer film is from 0.04 to 0.08 μm.
4. The separator for an electrochemical device according to claim 1 , wherein the separator comprises a porous coating layer formed on only one surface of the porous polymer film, and a diameter of the fibril disposed at the side of one surface of the porous polymer film where the porous coating layer is formed is smaller than a diameter of the fibril disposed at the side of the other surface of the porous polymer film where the porous coating layer is not formed.
5. The separator for an electrochemical device according to claim 1 , wherein the diameter of the fibril disposed at the side of one surface of the porous polymer film where the porous coating layer is formed is smaller two to seven times than the diameter of the fibril disposed at the side of the other surface of the porous polymer film where the porous coating layer is not formed.
6. The separator for an electrochemical device according to claim 1 , wherein the diameter of the fibril disposed at the side of one surface of the porous polymer film where the porous coating layer is formed is from 0.01 to 0.07 μm, and the diameter of the fibril disposed at the side of the other surface of the porous polymer film where the porous coating layer is not formed is from 0.07 to 0.14 μm.
7. The separator for an electrochemical device according to claim 1 , wherein the binder polymer is disposed at an interface of adjacent particles and connects the particles to form a porous structure, and a particle diameter of the binder polymer is from 10 to 100 nm.
8. The separator for an electrochemical device according to claim 1 , wherein the porous polymer film is a porous polyolefin film.
9. The separator for an electrochemical device according to claim 8 , wherein the porous polyolefin film includes polyethylene; polypropylene; polybutylene; polypentene; polyhexene; polyoctene; copolymers of at least one of ethylene, propylene, butene, pentene, 4-methylpentene, hexene and octene, or mixtures thereof.
10. The separator for an electrochemical device according to claim 1 , wherein a thickness of the porous polymer film is from 5 to 50 μm, and a pore size and a porosity are from 0.01 to 50 μm and from 10 to 95%, respectively.
11. The separator for an electrochemical device according to claim 1 , wherein the binder polymer includes at least one selected from the group consisting of polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethylmethacrylate, polybutylacrylate, 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, and polyimide, or mixtures thereof.
12. The separator for an electrochemical device according to claim 1 , wherein the inorganic particles include inorganic particles having a dielectric constant greater than or equal to 5, inorganic particles capable of transporting lithium ions, or mixtures thereof.
13. The separator for an electrochemical device according to claim 12 , wherein the inorganic particles having a dielectric constant greater than or equal to 5 include BaTiO 3 , Pb(Zr,Ti)O 3 (PZT), Pb 1-x La x Zr 1-y Ti y O 3 (PLZT), PB(Mg 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, or mixtures thereof.
14. The separator for an electrochemical device according to claim 12 , wherein the inorganic particles capable of transporting lithium ions include 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 based 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 based glass (Li x Si y S z , 0<x<3, 0<y<2, 0<z<4), P 2 S 5 based glass (Li x P y S z , 0<x<3, 0<y<3, 0<z<7), or mixtures thereof.
15. The separator for an electrochemical device according to claim 1 , wherein the organic particles include polystyrene, polyethylene, polyimide, melamine-based resin, phenol-based resin, cellulose, modified cellulose, polypropylene, polyester, polyphenylene sulfide, polyaramide, polyamide imide, butylacrylate-ethylmethacrylate copolymers, or mixtures thereof.
16. The separator for an electrochemical device according to claim 1 , wherein each average grain diameter of the inorganic particles and the organic particles is independently from 0.001 to 10 μm.
17. An electrochemical device comprising a cathode, an anode, and a separator interposed between the cathode and the anode, wherein the separator is the separator for an electrochemical device according to claim 1 .
18. The electrochemical device according to claim 17 , wherein the electrochemical device is a lithium secondary battery.