PURPOSE: To prevent short-circuit between a positive plate edge and a negative plate edge or terminal even when the positive plate is swollen, by covering the positive plate with a separator with a reverse U-shaped cross section while its terminal protruding side is a bag-shaped bottom.

CONSTITUTION: A separator 3 which covers a positive plate 1 shall have a reverse U-shaped cross section wherein the protruding side of the positive terminal 5 is a bag-shaped bottom so that the distance from the top of this bag-shaped bottom to the distance from the top of this bag-shaped bottom to the positive plate 1' is 2∼ 3mm, the electrode them in a vortex form. A slit 4 is provided in order to project a t erminal 5 from the separator 3 with reverse U-shaped cross section wherein the positive plate protruding side is a bag-shaped bottom.