NOVELTY - A non-aqueous electrolyte secondary battery (41) comprises an electrode assembly, a non-aqueous electrolyte, and a rectangular battery case for housing the electrode assembly and the non-aqueous electrolyte. The electrode assembly includes a positive electrode, a negative electrode, and a porous heat-resistant layer disposed between the positive and negative electrodes. The positive electrode includes a positive electrode active material layer and the negative electrode includes a negative electrode active material layer.    USE - Non-aqueous electrolyte secondary battery used as a power source for devices requiring a high output, particularly hybrid electric vehicles (HEVs) and electrically-powered tools.    ADVANTAGE - The secondary battery can avoid the forcing out of non-aqueous electrolyte from the electrode assembly, even under the environment where the size change in the battery case is unacceptable. It can maintain excellent cycle life characteristic and high reliability even when used as a power source for HEVs which require a high dimensional precision. The porosity of the porous heat-resistant layer can be obtained, for example, from the thickness of the porous heat-resistant layer, the true specific gravity of the nonconductive filler and the binder, and the weight ratio between the nonconductive filler and binder. The thickness of the porous heat-resistant layer can be obtained for example by cutting the porous heat-resistant layer and determining the thickness at 10 points at the cut surface with an electron microscope.    DETAILED DESCRIPTION - A non-aqueous electrolyte secondary battery (41) comprises an electrode assembly, a non-aqueous electrolyte, and a rectangular battery case for housing the electrode assembly and the non-aqueous electrolyte. The battery case has a thickness alpha , a width beta , and a height gamma satisfying a relation alpha less than beta greater than or equal to gamma . The electrode assembly includes a positive electrode, a negative electrode, and a porous heat-resistant layer disposed between the positive electrode and the negative electrode. The positive electrode includes a positive electrode active material layer and the negative electrode includes a negative electrode active material layer. A ratio of a pore volume in a predetermined area of the porous heat-resistant layer to a theoretical capacity of the battery is 0.18-1.117 ml/Ah. The predetermined area has the same area as the positive electrode active material layer. A porosity of the porous heat-resistant layer is 35-85%. The porous heat-resistant layer includes a porous sheet comprising a highly heat-resistant resin. A thickness of the porous heat-resistant layer is 2-20 mu m. An INDEPENDENT CLAIM is included for a battery module (40) comprising a stack (42) in which at least two non-aqueous electrolyte secondary batteries are stacked in at least a thickness direction; end plates (44, 45) placed at both ends of the stack; and at least two bridges (46) for binding the nonaqueous electrolyte secondary batteries.    DESCRIPTION OF DRAWING(S) - The drawing is a perspective view of a battery module.    Battery module (40)    Non-aqueous electrolyte secondary battery (41)    Stack (42)    End plates (44, 45)    Bridges (46)