Patent ID: 8741460

Claim:
A lithium ion secondary battery comprising an electrode wound body including: a positive electrode plate in which a positive current collector is partially applied with a positive-electrode material mixture layer and has a positive-electrode uncoated portion on one end side in which the positive-electrode material mixture layer is not applied, and a remaining portion is a positive-electrode coated portion applied with the positive-electrode material mixture layer; a negative electrode plate in which a negative current collector is partially applied with a negative-electrode material mixture layer and has a negative-electrode uncoated portion on one end side in which the negative-electrode material mixture layer is not applied, and a remaining portion is a negative-electrode coated portion applied with the negative-electrode material mixture layer; and a separator for insulating the positive electrode plate and the negative electrode plate, the positive electrode plate, the negative electrode plate, and the separator being wound in a flat form so that the positive-electrode uncoated portion and the negative-electrode uncoated portion protrude in opposite directions to each other, and the electrode wound body being sealed together with an electrolyte in a battery case, wherein the lithium ion secondary battery includes: a positive terminal connected to the positive-electrode uncoated portion; and a negative terminal connected to the negative-electrode uncoated portion; wherein the battery case has a flat rectangular shape in which one surface is a lid portion and two of surfaces excepting the lid portion are flat surfaces having a larger area than the other surfaces; wherein the positive terminal and the negative terminal are placed to penetrate through the lid portion to partially protrude outside; wherein assuming that a length of the electrode wound body in a winding axis direction is W, a size of the electrode wound body in a direction perpendicular to the winding axis direction and parallel to the flat surfaces is H, and a distance between a farthest position in a connecting range of at least one of the positive terminal and the negative terminal, in which the terminal is connected to the uncoated portion, from the lid portion and an edge of the electrode wound body on a side of the lid portion is X, the values W, H, and X are determined so that a point defined in a plane (X/H, H/W) by a value (X/H) and a value (H/W) is located in a triangular region defined by joining three points, (0.50, 0.70), (0.32, 0.40), and (0.70, 0.40) in the same plane; and wherein a battery capacity is 3 to 30 Ah, X/H is 0.3 to 0.4 or 0.6 to 0.7, and the value H is in a range of 40 mm≦H≦90 mm.