Method for manufacturing separator including porous coating layers, separator manufactured by the method and electrochemical device including the separator
View Patent ↗Disclosed is a method for manufacturing a separator. The method includes (S1) preparing a slurry containing inorganic particles dispersed therein and a solution of a binder polymer in a solvent, and coating the slurry on at least one surface of a porous substrate to form a first porous coating layer, and (S2) electroprocessing a polymer solution on the outer surface of the first porous coating layer to form a second porous coating layer. The first porous coating layer formed on at least one surface of the porous substrate is composed of a highly thermally stable inorganic material to suppress short-circuiting between an anode and a cathode even when an electrochemical device is overheated. The second porous coating layer formed by electroprocessing improves the bindability of the separator to other base materials of the electrodes.
1. A method for manufacturing a separator, comprising
(S1) preparing a slurry containing inorganic particles dispersed therein and a solution of a binder polymer in a solvent, and coating the slurry on at least one surface of a porous substrate to form a first porous coating layer, and
(S2) electroprocessing a polymer solution on the outer surface of the first porous coating layer to form a second porous coating layer, wherein air permeability of the separator after forming the first porous coating layer and after forming the second porous coating layer remains substantially constant, and,
wherein the polymer solution consists of 1) a polymer in a solvent or 2) a molten solution of a polymer.
2. The method according to claim 1 , wherein the porous substrate is made of a polyolefin.
3. The method according to claim 2 , wherein the polyolefin is selected from the group consisting of polyethylene, polypropylene, polybutylene and polypentene.
4. The method according to claim 1 , wherein the inorganic particles are selected from the group consisting of inorganic particles having a dielectric constant of 5 or above, inorganic particles having the ability to transport lithium ions, and mixtures thereof.
5. The method according to claim 4 , wherein the inorganic particles having a dielectric constant of 5 or above are selected from the group consisting of BaTiO 3 , Pb(Zr x ,Ti 1-x )O 3 (PZT, 0<x<1) , Pb 1-x La x Zr 1-y Ti y O 3 (PLZT, 0<x<1, 0<y<1) , (1-x) Pb(Mg 1/3 Nb 2/3 ) O 3 -xPbTiO 3 (PMN-PT, 0<x<1) hafnia (HfO 2 ) SrTiO 3 , SnO 2 , CeO 2 , MgO, NiO, CaO, ZnO, ZrO 2 , SiO 2 , Y 2 O 3 , Al 2 O 3 , SiC, TiO 2 particles, and mixtures thereof.
6. The method according to claim 4 , wherein the inorganic particles having the ability to transport lithium ions are selected from the group consisting of 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 type 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 type glass (Li x Si y S z , 0<x<3, 0<y<2, 0<z<4), P 2 S 5 type glass (Li x P y S z , 0<x<3, 0<y<3, 0<z<7) particles, and mixtures thereof.
7. The method according to claim 1 , wherein the binder polymer is selected from the group consisting of polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethyl methacrylate, polybutyl acrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, polyvinyl alcohol, polyethylene-co-vinyl acetate, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose, compounds having a molecular weight of 10,000 g/mol or lower, and mixtures thereof.
8. The method according to claim 1 , wherein the polymer solution is prepared by melting at least one polymer selected from the group consisting of polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethyl methacrylate, polybutyl acrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, polyvinyl alcohol, polyethylene-co-vinyl acetate, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose and compounds having a molecular weight of 10,000 g/mol or lower, or dissolving the polymer in a solvent.
9. The method according to claim 1 , wherein the electroprocessing is electrospinning or electrospraying.
10. A separator comprising
(a) a first porous coating layer formed on at least one surface of a porous substrate and composed of a mixture of inorganic particles and a binder polymer, and
(b) a second porous coating layer formed by electroprocessing a polymer solution on the outer surface of the first porous coating layer, wherein air permeability of the separator after forming the first porous coating layer and after forming the second porous coating layer remains substantially constant, and,
wherein the polymer solution consists of 1) a polymer in a solvent or 2) a molten solution of a polymer.
11. The separator according to claim 10 , wherein the porous substrate is made of a polyolefin.
12. The separator according to claim 11 , wherein the polyolefin is selected from the group consisting of polyethylene, polypropylene, polybutylene and polypentene.
13. The separator according to claim 10 , wherein the porous substrate has a thickness of 5 to 50 μm, a pore size of 0.01 to 50 μm and a porosity of 10 to 95%.
14. The separator according to claim 10 , wherein the inorganic particles have an average particle diameter of 0.001 to 10 μm.
15. The separator according to claim 10 , wherein the inorganic particles are selected from the group consisting of inorganic particles having a dielectric constant of 5 or above, inorganic particles having the ability to transport lithium ions, and mixtures thereof.
16. The separator according to claim 15 , wherein the inorganic particles having a dielectric constant of 5 or above are selected from the group consisting of BaTiO 3 , Pb(Zr x ,Ti 1-x )O 3 (PZT, 0<x<1) , Pb 1-x La x Zr 1-y Ti y O 3 (PLZT, 0<x<1, 0<y<1) , (1-x) Pb (Mg 1/3 Nb 2/3 ) O 3 -xPbTiO 3 (PMN-PT, 0<x<1) , hafnia (HfO 2 ) SrTiO 3 , SnO 2 , CeO 2 , MgO, NiO, CaO, ZnO, ZrO 2 , SiO 2 , Y 2 O 3 , Al 2 O 3 , SiC, TiO 2 particles, and mixtures thereof.
17. The separator according to claim 15 , wherein the inorganic particles having the ability to transport lithium ions are selected from the group consisting of 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 type 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 type glass (Li x Si y S z , 0<x<3, 0<y<2, 0<z<4), P 2 S 5 type glass (Li x P y S z , 0<x<3, 0<y<3, 0<z<7) particles, and mixtures thereof.
18. The separator according to claim 10 , wherein the binder polymer is selected from the group consisting of polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethyl methacrylate, polybutyl acrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, polyvinyl alcohol, polyethylene-co-vinyl acetate, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose, compounds having a molecular weight of 10,000 g/mol or lower, and mixtures thereof.
19. The separator according to claim 10 , wherein the polymer solution is prepared by melting at least one polymer selected from the group consisting of polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethyl methacrylate, polybutyl acrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, polyvinyl alcohol, polyethylene-co-vinyl acetate, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose and compounds having a molecular weight of 10,000 g/mol or lower, or dissolving the polymer in a solvent.
20. The separator according to claim 10 , wherein the electroprocessing is electrospinning or electrospraying.
21. The separator according to claim 10 , wherein the second porous coating layer has a thickness of 0.001 to 5 μm, a pore size of 0.01 to 50 μm and a porosity of 1 to 90%.
22. An electrochemical device comprising a cathode, an anode and the separator according to claim 10 interposed between the cathode and the anode.
23. The electrochemical device according to claim 22 , wherein the electrochemical device is a lithium secondary battery.