Patent ID: 8435669

Claim:
An electro-chemical device comprising: a package including a metal film; a battery element sealed within the package; resin layers disposed at least on the inside of a seal part of the package; and a lead extending in a length direction from the battery element to the outside of the package through between, in a thickness direction perpendicular to the length direction, the resin layers at the seal part of the package, wherein the lead has a thickness Z 1 in the thickness direction and an upper surface and a lower surface in the thickness direction, and the resin layers have a total thickness Z 2 in the thickness direction; the lower surface of the lead defines a curve in a cross-section containing the thickness direction and a width direction perpendicular to both the length direction and the thickness direction, the curve including a portion that unidirectionally curves toward the upper surface, the portion having two end points that define therebetween a straight line having a length L 1 , the portion having a top point between the two end points, the top point having a maximum distance L 2 from the straight line; and the lead satisfies the relationship of; 30%≦ Z 1 /Z 2≦60%, and 0 <R< 2% where R=L 2 /L 1 .