Abstract: Provided is a nonaqueous electrolyte secondary battery porous layer which is capable of improving a capacity maintenance ratio shown when a nonaqueous electrolyte secondary battery is repeatedly subjected to a charge-discharge cycle. The nonaqueous electrolyte secondary battery porous layer contains at least one type of a resin having an amide bond, and an aspect ratio of a pore therein is not less than 1.0 and not more than 2.2.

Abstract: Provided is a nonaqueous electrolyte secondary battery functional layer that has an improved cycle characteristic when an electrode with a great change in volume is used. A nonaqueous electrolyte secondary battery functional layer in accordance with an embodiment of the disclosure is configured such that an area ratio of pores each having a cross-sectional area of not less than 0.1 ?m2 is not less than 30% by area with respect to all pores present in a cross section of the nonaqueous electrolyte secondary battery functional layer.

Abstract: Provided is a nonaqueous electrolyte secondary battery separator capable of satisfactorily maintaining ion permeability even after being compressed. The nonaqueous electrolyte secondary battery separator includes a polyolefin porous film in which an average of inclination angles of major axes of voids extracted from a two-dimensional image of a cross section of the polyolefin porous film is not less than 7.0, the inclination angles being calculated from respective circumscribed rectangles of the voids, the two-dimensional image being obtained by use of SEM, and the cross section being formed by cutting the polyolefin porous film (i) along a straight line that passes a center of a surface of the polyolefin porous film and is parallel to an MD or a TD and (ii) in a direction perpendicular to the surface.