Method for manufacturing a porous nanoweb

Abstract

Disclosed is a porous nanoweb including first and second nanofilaments, which facilitates to perform heat resistance simultaneously with a shutdown function for preventing a battery explosion caused by an abnormal heat generation, and to realize small thickness and easy control of porosity, wherein, if the porous nanoweb is used as a battery separator for a secondary battery, it allow the good battery efficiency and good safety owing to the low resistance, the porous nanoweb comprising the first nanofilament having a melting temperature not more than 200° C.; and the second nanofilament having a melting temperature not less than 210° C.

What is claimed is: 
     
         1 . A porous nanoweb for a separator disposed between an anode and a cathode of a secondary battery, the porous nanoweb comprising:
 a first polymer having a melting temperature not more than 200° C.; and   a second polymer having a melting temperature not less than 210° C.   
     
     
         2 . The porous nanoweb of  claim 1 , wherein the porous nanoweb comprises a first nanofilament formed of the first polymer and a second nanofilament formed of the second polymer. 
     
     
         3 . The porous nanoweb of  claim 2 , wherein the first and second nanofilaments have an average diameter of 0.005-5 μm, and the porous nanoweb has a thickness of 1-30 μm and a porosity of 40-90%. 
     
     
         4 . The porous nanoweb of  claim 2 , wherein the first and second nanofilaments constitute a single nanoweb. 
     
     
         5 . The porous nanoweb of  claim 2 , wherein the porous nanoweb comprises a first sub-nanoweb comprising the first nanofilament and a second sub-nanoweb comprising the second nanofilament. 
     
     
         6 . The porous nanoweb of  claim 1 , wherein the porous nanoweb comprises a composite nanofilament, and
 wherein the composite nanofilament comprises:   a core formed of the second polymer; and   a sheath surrounding the core, the sheath being formed of the first polymer.   
     
     
         7 . The porous nanoweb of  claim 1 , wherein the first polymer is polyurethane, polyethylene, polypropylene, copolymer thereof, or mixture thereof, and
 wherein the second polymer is polyimide.   
     
     
         8 . The porous nanoweb of  claim 1 , wherein a content of the second polymer in the porous nanoweb is 50-90% by weight.