TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The inorganic particles are inorganic particles having lithium ion conductivity and inorganic particles having dielectric constant of 5 or more. The inorganic particles having dielectric constant of 5 or more are chosen from 17 compounds e.g. barium titanate, hafnium oxide, strontium titanate, tin oxide, cerium oxide, magnesium oxide, nickel oxide, calcium oxide, zinc oxide, zirconium oxide and silica. The inorganic particles having lithium ion conductivity are chosen from 9 compounds e.g. lithium phosphate, lithium-titanium phosphate (LixTiy(PO4)3, where x is more than 0 to less than 2 and y is more than 0 to less than 3), lithium-aluminum-titanium phosphate (LixAly'Tiz(PO4)3, y' is more than 0 to less than 2 and z is more than 0 to less than 3) and lithium-lanthanum titanate (LixLayTiO3).    TECHNOLOGY FOCUS - POLYMERS - Preferred Composition: The weight ratio of inorganic particles and binder polymer is 50:50-99:1. The content of the organic polymer (b) is 1-60 wt.%. The organic polymer (a) is chosen from 21 compounds e.g. polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethylmethacrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate and ethylene-vinyl acetate copolymer. The organic polymer (b) is rosin-based resin, terpene-based resin and/or petroleum-based resin. The rosin-based resin is chosen from abietic acid resin, levopimaric acid resin and neo-abietic acid resin. The terpene-based value is chosen from alpha -pinene, beta -pinene, dipentene, alpha -pinene phenol resin, dipentene phenol resin or bis-terpene-phenol resin. The petroleum-based resin is chosen from aliphatic 5C petroleum resin, aromatic 9C petroleum resin, petroleum resin copolymer and dicyclopentadiene-based resin. The porous substrate is polyolefin-based porous substrate chosen from polyethylene-based porous substrate, polypropylene-based porous substrate, polybutylene-based porous substrate and polymethylpentene-based porous substrate, and has thickness of 5-50 mu m, pore size of 0.01-50 mu m and porosity of 10-95%. Preferred Property: The organic/inorganic composite separator has average particle size of 0.001-10 mu m.