SEPARATOR AND BATTERY CELL

A separator and a battery cell. The separator is used for being wound together with an electrode sheet to form the battery cell. The separator comprises: a first section, a second section, and a third section that are sequentially arranged in the length direction of the separator, wherein the width of the first section is smaller than that of the second section, and/or the width of the third section is smaller than that of the second section. The separator is divided into regions having different widths, so that the width of a region located at the head and/or the tail of the separator is smaller than that of the middle position of the separator. The width of the head of the separator is narrowed, so that the contact area between the separator and a winding shaft can be reduced, thereby reducing a friction force between the surface of the separator and the winding shaft, and solving the problem that the separator is pulled out of the battery cell. The width of the tail of the separator is narrowed, so that th