Patent watch: SEPARATOR INCLUDING POROUS COATING LAYER AND ELECTROCHEMICAL DEVICE

Disclosed is a separator. The separator includes a planar non-woven fabric substrate having a plurality of pores, and a porous coating layer formed on at least one surface of the non-woven fabric substrate. The porous coating layer is composed of a mixture of filler particles and a binder polymer. The filler particles include conductive positive temperature coefficient (PTC) particles composed of a mixture of conductive particles and a low melting point resin having a melting point lower than that of the non-woven fabric substrate. Due to the presence of the conductive PTC particles, the porous coating layer can be imparted with a shutdown function against thermal runaway. In addition, the porous coating layer exhibits appropriate electrical conductivity. Therefore, the separator is suitable for use in a high-capacity electrochemical device.

Inventors: Pil-Kyu Park, Jong-Hun Kim, Soon-Ho Ahn, Je-Young Kim
Original Assignee: LG CHEM, LTD.

Application number: 13/173,902; Publication number: US 2011/0256443 A1; Filing date: Jun 30, 2011

PTC or conductive particles are made of at least one carbonaceous material selected from the group consisting of natural graphite, artificial graphite, carbon black and graphite; the filler particles have an average particle diameter of 0.001 to 10 μm and the conductive particles and the low melting point resin are present in a weight ratio of 50:50 to 90:10.

The binder polymer is selected from the group consisting of polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, polyethylene-co-vinyl acetate, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose, and mixtures thereof  and has a solubility parameter of 15 to 45 Mpa1/2.

The non-woven fabric substrate is composed of microfibers having an average diameter of 0.5 to 10 μm and have a melting point of at least 200° C with a pore size distribution in which at least 50% of the pores have a longest diameter of 0.1 to 70 μm. It may be composed of at least one polymer selected from the group consisting of polyester, polyacetal, polyamide, polycarbonate, polyimide, polyether ether ketone, polyethersulfone, polyphenylene oxide, polyphenylene sulfide and polyethylene naphthalate.

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