Abstract: A heat-resistant separator contains a porous film, a polymeric fibrous layer adhesively bonded to the surface of the porous film, and an adhesive binder layer located between the porous film and the fibrous layer and covering at least a portion of the surface of the porous film. The fibrous layer contains fibers manufactured of a polyimide wherein the fibers of a form of polyimide comprise fibers with a majority of fibers having diameters in the range of 1-3000 nm. In one of the embodiment the binder layer contains sodium carboxymethylcellulose, and the amount of adhesive present between the porous film and the fibrous web in the final product is within the range of 0.30 grams per square meter of covered surface of porous film to 0.90 grams per square meter of covered surface of porous film.