Method for manufacturing separator, separator manufactured by the method and method for manufacturing electrochemical device including the separator

Abstract

A method for manufacturing a separator includes (S1) preparing a porous substrate having pores, (S2) coating at least one surface of the porous substrate with a first solvent, (S3) coating the first solvent with a slurry containing inorganic particles dispersed therein and formed by dissolving a binder polymer in a second solvent, (S4) drying the first and second solvents simultaneously to form a porous organic-inorganic composite layer on the porous substrate. Since the phenomenon that the pores of the porous substrate are closing by the binder polymer is minimized, it is possible to prevent the resistance of the separator from increasing due to the formation of the porous organic-inorganic composite layer.

What is claimed is: 
     
         1 . A method for manufacturing a separator, comprising:
 (S1) preparing a porous substrate having pores;   (S2) coating at least one surface of the porous substrate with a composition consisting essentially of a first solvent;   (S3) coating the composition consisting essentially of the first solvent with a slurry containing inorganic particles dispersed therein and formed by dissolving a binder polymer in a second solvent; and   (S4) drying the first and second solvents simultaneously to form a porous organic-inorganic composite layer on the porous substrate,   wherein binder polymer in the second solvent is substantially prevented from entering the pores of the porous substrate in the manufactured separator.   
     
     
         2 . The method for manufacturing a separator according to  claim 1 ,
 wherein the binder polymer of the porous organic-inorganic composite layer is present on the surfaces of the inorganic particles in whole or in part as a coating layer,   wherein the inorganic particles fixedly connect to each other by the coating layer in an adhered state, and   wherein vacant spaces present among the inorganic particles form pores.   
     
     
         3 . The method for manufacturing a separator according to  claim 1 , wherein the porous substrate is a polyolefin-based porous film. 
     
     
         4 . The method for manufacturing a separator according to  claim 1 , wherein the porous substrate has a thickness of 1 to 100 μm. 
     
     
         5 . The method for manufacturing a separator according to  claim 1 , wherein the binder polymer has a solubility parameter of 15 to 45 MPa 1/2 . 
     
     
         6 . The method for manufacturing a separator according to  claim 1 , wherein the binder polymer is 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, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, carboxyl methyl cellulose, or their mixtures. 
     
     
         7 . The method for manufacturing a separator according to  claim 1 , wherein the first and second solvents are independently selected from the group consisting of acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylformamide, N-methyl-2-pyrrolidone (NMP), cyclohexane, water, or their mixtures. 
     
     
         8 . The method for manufacturing a separator according to  claim 7 , wherein the first and second solvents are the same kind of solvent. 
     
     
         9 . The method for manufacturing a separator according to  claim 1 , wherein the difference in solubility parameters between the binder polymer and the first solvent, between the binder polymer and the second solvent, and between the first solvent and the second solvent is 5.0 Mpa 0.5  or less, respectively. 
     
     
         10 . The method for manufacturing a separator according to  claim 1 , wherein the first solvent has a boiling point equal to or higher than that of the second solvent. 
     
     
         11 . The method for manufacturing a separator according to  claim 1 , wherein the average particle diameter of the inorganic particles is 0.001 to 10 μm. 
     
     
         12 . The method for manufacturing a separator according to  claim 1 , wherein the weight ratio of the inorganic particles to the binder polymers is 50:50 to 99:1. 
     
     
         13 . The method for manufacturing a separator according to  claim 1 , wherein the first solvent has a coating thickness of 10 to 250 μm. 
     
     
         14 . A separator manufactured by the method according to  claim 1 . 
     
     
         15 . An electrochemical device, comprising:
 a cathode;   an anode; and   a separator interposed between the cathode and the anode and formed according to the method for manufacturing a separator, defined in  claim 1 .   
     
     
         16 . The electrochemical device to  claim 15 , wherein the electrochemical device is a lithium secondary battery.