Patent ID: 8778524

Claim:
An electrochemical device comprising: (a) a composite separator comprising a porous substrate, a first porous coating layer coated on one surface of the porous substrate and composed of a mixture comprising inorganic particles and a binder polymer, and a second porous coating layer coated on the other surface of the porous substrate and composed of a mixture comprising inorganic particles and a binder polymer, wherein the first porous coating layer is thicker than the second porous coating layer; (b) an anode disposed to face the first porous coating layer; and (c) a cathode disposed to face the second porous coating layer, wherein the thicknesses of the first and second porous coating layers satisfy the following relationship 1: 0.11≦( T 1 −T 2 )/ T tot ≦0.56 wherein T 1 and T 2 represent the thicknesses of the first and second porous coating layers, respectively, and T tot represents the total thickness of the first and second porous coating layers, and wherein the total thickness of the first and second porous coating layers is from 1.0 to 20.0 μm, wherein the binder polymers are each independently selected from the group consisting of polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethyl methacrylate, polybutyl acrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, polyethylene-co-vinyl acetate, polyethylene oxide, polyarylate, cyanoethylpullulan, cyanoethyl polyvinyl alcohol, cyanoethyl sucrose, pullulan, and mixtures of two or more kinds thereof, and wherein the inorganic particles are each independently selected from the group consisting of BaTiO 3 , Pb(Zr,Ti)O 3 (PZT), Pb 1-x La x Zr 1-y Ti y O 3 (PLZT, 0<x<1, 0<y<1), Pb(Mg 1/3 Nb 2/3 )O 3 —PbTiO 3 (PMN-PT), hafnia (HfO 2 ), SrTiO 3 , SnO 2 , CeO 2 , NiO, CaO, ZnO, Y 2 O 3 , Al 2 O 3 , TiO 2 , SiC, Li 3 PO 4 , Li x Ti y (PO 4 ) 3 (0<x<2, 0<y<3), Li x Al y Ti z (PO 4 ) 3 (0<x<2, 0<y<1, 0<z<3), (LiAllTiP) x O y (0<x<4, 0<y<13), (Li x La y TiO 3 , 0<x<2, 0<y<3), Li x Ge y P z S w (0<x<4, 0<y<1, 0<z<1, 0<w<5), Li x N y (0<x<4, 0<y<2), Li x Si y S z (0<x<3, 0<y<2, 0<z<4), Li x P y S z (0<x<3, 0<y<3, 0<z<7), and mixtures of two or more kinds thereof.