Method of preparing separator, separator prepared therefrom, and electrochemical device having the same

1. A method of preparing a separator, comprising:

mixing inorganic particles, a polymer binder, polymer fibers, and a solvent to form a dispersion;

forming a non-woven fabric web from the dispersion, wherein, in the non-woven fabric web, the inorganic particles are adhered to the polymer fibers by the polymer binder and are positioned in pores formed in gaps in the non-woven fabric web present between the polymer fibers; and

drying and compressing the non-woven fabric web to obtain a separator in the form of a non-woven fabric substrate, wherein the pores of the separator has an average pore size of 40 to 200 nm,

wherein the polymer binder is selected from the group consisting of polyvinylidene fluoride (PVDF), hexafluoro propylene (HFP), polyvinylidene fluoride-co-hexafluoro propylene, polyvinylidene fluoride-co-trichloro ethylene, styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), polymethyl methacrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinyl acetate, polyethylene oxide, polyarylate, 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, and

wherein the polymer fibers are selected from the group consisting of polyolefins, polyesters, polyacetals, polyamides, polycarbonates, polyimides, polyetherether ketone, polyether sulfone, polyphenylene oxide, polyphenylene sulfide and a mixture thereof.

2. The method according to claim 1 , wherein the dispersion further comprises a dispersant.

3. The method according to claim 2 , wherein the dispersant is selected from the group of consisting of polyvinylpyrrolidone, polyacrylic acid hydrazide, poly-N-vinyl-5-methoxazolidon, N-alkyl polyimine, polyvinylalcohol, N-acetyl polyimine, polyacrylamide, poly-L-lysinhydrobromide, polyacroleine, benzyl-dodecyl-dimethylammonium chloride, polyacrylic acid, polyethylenimine, 4-vinylpyridine, methylvinylketone, and an oligomer thereof.

4. The method according to claim 1 , wherein the dispersion is produced by dispersing the inorganic particles in the solvent to obtain an inorganic dispersion, and adding the polymer binder and the polymer fibers to the inorganic dispersion.

5. 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 higher, inorganic particles having the ability to transport lithium ions, and a mixture thereof.

6. The method according to claim 5 , wherein the inorganic particles having a dielectric constant of 5 or higher are selected from the group consisting of SrTiO 3 , SnO 2 , CeO 2 , MgO, NiO, CaO, ZnO, ZrO 2 , SiO 2 , Y 2 O 3 , Al 2 O 3 , AlOOH, Al(OH) 3 , TiO 2 , SiC, BaTiO 3 , Pb(Zr x , Ti 1-x )O 3 (PZT, 0<x<1), Pb 1-x La x Zr 1-y TiO 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), HfO 2 inorganic particles and a mixture thereof.

7. The method according to claim 5 , 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) inorganic particles, and a mixture thereof.

8. The method according to claim 1 , wherein the inorganic particles have an average diameter of 0.001 to 100 μm.

9. The method according to claim 1 , wherein the polymer fibers have an average thickness of 0.05 to 10 μm.

10. The method according to claim 1 , wherein the solvent is selected from the group consisting of acetone, methanol, ethanol, tetrahydrofuran, methylene chloride, chloroform, dimethylform amide, N-methyl-2-pyrrolidone (NMP), cyclohexane, water and a mixture thereof.

11. The method according to claim 1 , wherein the drying and compressing of the non-woven fabric web is carried out at a temperature of 60 to 150° C. for 30 seconds to 10 minutes.

12. The method according to claim 1 , which further comprises applying a slurry comprising inorganic particles, a polymer binder and a solvent on at least one surface of the non-woven fabric substrate, and drying the applied slurry to form a porous coating layer, after obtaining the non-woven fabric substrate.

13. A separator prepared by the method according to claim 1 .

14. An electrochemical device, comprising a cathode, an anode and a separator interposed between the cathode and the anode,

wherein the separator is defined in claim 13 .

15. The electrochemical device according to claim 14 , which is a lithium secondary battery.