Patent ID: 8263256

Claim:
A cell comprising: a cell element including (a) a positive electrode having a belt-shaped metal foil and reaction layers provided on two surfaces thereof, (b) a negative electrode having a belt-shaped metal foil and reaction layers provided on two surfaces thereof, and (c) an electrolyte; a laminate film enclosing the cell element, the laminate film having a sealing portion and being composed of (a) an exterior resin layer, (b) an interior resin layer, and (c) a metal layer provided between the exterior resin layer and the interior resin layer, the sealing portion being thermal welded on a part of the laminate film apart from an edge portion thereof to form a thermal welded portion for sealing the cell; electrode terminals electrically connected to the cell element and extending outside through the sealing portion; and sealant between the laminate film and the electrode terminals, wherein, a portion A of the laminate film, remote from an edge of the laminate film, is thermal welded, and a portion B at the edge portion of the laminate film is not thermal welded, portion B increases in thickness along a lengthwise direction of the electrode terminals proceeding from the portion A to the edge of the laminate film, a thickness of the sealant on the electrode terminals is less at said portion A than said portion B, the edge of the laminate film on the electrode terminals is not thermal welded such that the edge of the laminate film is thicker than said portion A, a thickness t 2 of the laminate film at the edge thereof is larger than a thickness t 1 of the thermal welded portion, and when the thickness of the laminate film and the thickness of the interior resin layer are represented by t and p, respectively, the following equations are satisfied: t× 2- p× 2+5< t 1 < t× 2-5 (μm) and t 1 < t× 2≦ t 2 (μm).