NOVELTY - A separator (1) has a base material (2), and a layer (3) formed on surface(s) of base material. The layer contains resin material and particles chosen from e.g. strontium titanate, barium sulfate, porous aluminosilicate, phyllosilicate, lithium oxide, lithium phosphate, lithium fluoride, aluminum hydroxide, graphite, carbon nanotube, diamond, yttrium oxide, titanium oxide, magnesium oxide, zirconium oxide, silicon oxide, and aluminum nitride. The separator has heat capacity per unit area of 0.0001 J/Kcm2 or more, and a heat capacity per unit volume of 3.0 J/Kcm3 or less.    USE - Separator is used for battery e.g. square-shaped nonaqueous electrolyte battery and laminate film-type nonaqueous electrolyte battery for battery pack, electric vehicle, electrical power system, electrical storage apparatus and electronic device (all claimed). Uses include but are not limited to mobile telephone, video camera and notebook-type personal computer, and hybrid vehicle.    ADVANTAGE - The separator provides battery having excellent cycle characteristics. The layer contained in the separator has excellent heat resistance and oxidation resistance. The heat generated in the anode is transmitted to the positive electrode, and generation of thermal decomposition reaction by positive electrode is suppressed.    DETAILED DESCRIPTION - A separator has a base material, and a layer formed on surface(s) of base material. The layer contains resin material and particles chosen from strontium titanate, barium sulfate, porous aluminosilicate, phyllosilicate, lithium oxide, lithium phosphate, lithium fluoride, aluminum hydroxide, graphite, carbon nanotube, diamond, Boehmite, yttrium oxide, titanium oxide, magnesium oxide, zirconium oxide, silicon oxide, zinc oxide, aluminum nitride, boron nitride, silicon nitride, titanium nitride, silicon carbide, boron carbide, and barium titanate. The separator has heat capacity per unit area of 0.0001 J/Kcm2 or more, and a heat capacity per unit volume of 3.0 J/Kcm3 or less. INDEPENDENT CLAIMS are included for the following:    (1) battery;    (2) battery pack;    (3) electronic device;    (4) electric vehicle;    (5) electrical storage apparatus; and    (6) electric power system.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of separator. (Drawing includes non-English language text)    Separator (1)    Base material (2)    Layer (3)