Flexible secondary battery
A flexible secondary battery includes: an electrode assembly including a first electrode layer, a second electrode layer, and a separator between the first electrode layer and the second electrode layer; a gasket having flexibility and surrounding edges of the electrode assembly; a first sealing sheet attached to a first surface of the gasket; and a second sealing sheet attached to a second surface of the gasket facing away from the first surface, wherein an uneven pattern is at a bendable area of the gasket.
1. A flexible secondary battery comprising:
an electrode assembly comprising a first electrode layer, a second electrode layer, and a separator between the first electrode layer and the second electrode layer;
a gasket having flexibility and surrounding edges of the electrode assembly;
a first sealing sheet attached to a first surface of the gasket; and
a second sealing sheet attached to a second surface of the gasket facing away from the first surface,
wherein an uneven pattern is at a bendable area of the gasket,
wherein the uneven pattern comprises a plurality of ridges that extend across at least one selected from a thickness and a width of the gasket, and
wherein a distance between adjacent ones of the ridges varies along the bendable area of the gasket.
2. The flexible secondary battery of claim 1 , wherein the uneven pattern is at at least one selected from the first surface, the second surface, and one pair of side surfaces of the gasket that couple the first surface and the second surface.
3. The flexible secondary battery of claim 1 , wherein at least one selected from the thickness and the width of the gasket varies at the bendable area along a longitudinal direction of the electrode assembly.
4. The flexible secondary battery of claim 3 , wherein the gasket has an average thickness of about 80% to about 120% of a thickness of the electrode assembly.
5. The flexible secondary battery of claim 1 , wherein the uneven pattern is formed to be denser at a central portion of the bendable area than at an outer portion of the bendable area.
6. The flexible secondary battery of claim 1 , wherein the uneven pattern has a wave shape.
7. The flexible secondary battery of claim 1 , wherein each of the first sealing sheet and the second sealing sheet comprises a first insulating layer, a metal layer, and a second insulating layer,
wherein the first insulating layer contacts the gasket, and the gasket and the first insulating layer comprise materials that are the same.
8. The flexible secondary battery of claim 1 , wherein the first electrode layer comprises:
a first active material unit, the first active material unit comprising a first metal current collector coated with a first active material, and
a first non-coated portion on which the first active material is not coated and to which a first electrode tab is attached, and
wherein the second electrode layer comprises:
a second active material unit, the second active material unit comprising a second metal current collector coated with a second active material, and
a second non-coated portion on which the second active material is not coated and to which a second electrode tab is attached.
9. The flexible secondary battery of claim 8 , wherein the first electrode tab and the second electrode tab protrude to the outside between the gasket and the first sealing sheet or between the gasket and the second sealing sheet.
10. The flexible secondary battery of claim 8 , wherein the gasket comprises a first lead electrode and a second lead electrode passing through one side of the gasket,
wherein the first lead electrode is attached to the first electrode tab and the second lead electrode is attached to the second electrode tab in an internal space of the gasket.
11. The flexible secondary battery of claim 1 , wherein the electrode assembly further comprises a fixing member fixing one end portion of each of the first electrode layer, the separator, and the second electrode layer together.