| abstract |
A lithium ion polymer secondary battery is a laminate of a positive-electrode sheet of a positive-electrode collector foil provided with an active material thereon, a negative-electrode sheet of a negative-electrode collector foil provided with another active material thereon, and a polymer electrolyte layer interposed between the positive-electrode sheet and the negative-electrode sheet. One of the positive-electrode sheet and the negative-electrode sheet is a strip and is fan-folded at least one time so that the positive-electrode sheet is provided on the surface of the active material on the sheet. The other one of the positive-electrode sheet and the negative-electrode sheet consists of a plurality of sheet segments having an area which is the same as the area of each flat portion of the fan-folded sheet. The sheet segments are interposed between the flat portions of the fan-folded sheet so that the polymer electrolyte layer is in contact with the surfaces of the active materials. The battery exhibits a large discharge capacity and improved discharge capacity characteristics after a number of discharge-charge cycles and does not cause internal short-circuiting. |