Abstract: To obtain a separator for a nonaqueous electrolyte battery that has an excellent nonaqueous electrolyte permeability into an electrode and an excellent electrolyte retentivity of the electrode and achieves a large capacity, a high energy density and a good high-temperature charge characteristic. A separator 3 used for a nonaqueous electrolyte battery is formed by disposing a porous layer 2 made of inorganic fine particles and a resin binder on a porous separator substrate 1, the resin binder is made of at least one resin selected from the group consisting of polyimide resins, polyamide resins and polyamideimide resins and the molecular chain of the resin has a halogen atom content of 10% to 30% by weight, and the content of the resin binder in the porous layer is 5% by weight or more.

Abstract: The present invention provides a composite porous membrane suited for a separator for a battery having excellent ion permeability, low pore blocking temperature, and high membrane breakage temperature by compositing resin porous membranes having different melting points (or softening points) without using a termocompression bonding method or a method of directly applying a solution to the substrate by using a composite porous membrane containing a porous membrane A of a resin having a melting point of 150° C. or less and a porous membrane B of a resin having a glass transition temperature of more than 150° C. integrated with the porous membrane A, wherein both a superficial side of the porous membrane B and an interfacial side with the porous membrane A of the porous membrane B have a three-dimensional network structure.