Secondary battery having electrode with self cutting part to be destructed on application of over-current

1. A plate-shaped secondary battery for middle- or large-sized battery pack, the secondary battery, comprising:

a sheet-shaped battery case having a sealing part and including a metal layer and a resin layer; and

an electrode assembly, which can be charged and discharged, the electrode assembly mounted with an electrolyte in the sheet-shaped battery case in a sealed state, and having electrode terminals, the electrode terminals including a cathode terminal having an exposed portion protruding outside the sealing part of the battery case,

wherein at least one of the electrode terminals is provided at a position spaced a predetermined distance from the sealing part with a self cutting part having a vertical sectional area less than a vertical sectional area of a remaining part of the at least one electrode terminal such that the self cutting part can break first when overcurrent flows in electrode assembly, and the self cutting part is located outside the battery case such that the battery case and sealing part are located between the self cutting part and the electrode assembly,

wherein the self cutting part is formed in the cathode terminal,

wherein thin resin film-shaped sealing members are attached to coupling regions between the battery case and the electrode terminals,

wherein an endothermic layer having high latent heat during a change of phase is formed only on the exposed portion of the cathode terminal between the sealing part and the self cutting part,

wherein the predetermined distance is defined as a distance at which the self cutting part can break before heat generated from the self cutting part is transmitted to the sealing part of the battery case, such that the sealing part is separated, when the overcurrent flows in the electrode assembly, and

wherein the battery case is made of a laminate sheet including the metal layer and the resin layer.

2. The secondary battery according to claim 1 ,

wherein the battery case is constructed in a structure in which the electrode assembly is mounted in a one-unit sheet member having one or more surfaces integrally formed and opening regions of the one-unit sheet member are bonded to each other such that the one-unit sheet member is sealed.

3. The secondary battery according to claim 1 , wherein the secondary battery is a pouch-shaped battery.

4. The secondary battery according to claim 1 , wherein the secondary battery is a lithium ion battery or a lithium polymer battery.

5. The secondary battery according to claim 1 , wherein the vertical sectional area of the self cutting part is equivalent to 30 to 90% of the vertical sectional area of the remaining part of the at least one electrode terminal.

6. The secondary battery according to claim 1 , wherein the self cutting part is selected from the group consisting of a first structure in which a width of the at least one electrode terminal is reduced, a second structure in which a thickness of the at least one electrode terminal is reduced, a third structure in which at least one through-hole is formed in the at least one electrode terminal, and combinations thereof.

7. The secondary battery according to claim 6 , wherein the self cutting part is constructed in the third structure in which at least one through-hole is formed in the at least one electrode terminal.

8. The secondary battery according to claim 6 , wherein the self cutting part is constructed in the first structure in which the width of the at least one electrode terminal is reduced by forming a depression in at least one side of the at least one electrode terminal.

9. The secondary battery according to claim 8 , wherein the depression is a notch-shaped depression.

10. A middle- or large-sized battery pack including a plurality of secondary batteries, wherein each secondary battery is the secondary battery according to claim 1 .

11. The battery pack according to claim 10 , wherein the plurality of the secondary batteries are at least partially or entirely connected in series with each other.

12. The secondary battery according to claim 1 , wherein the battery case is constructed in a structure in which the electrode assembly is mounted between a completed separated two-unit sheet member and contact regions of edges of the two-unit sheet member are bonded to each other such that the two-unit sheet member is sealed.

13. The secondary battery according to claim 1 , wherein an anode terminal is made from a material having a higher melting point than the cathode terminal.

14. The secondary battery according to claim 13 , wherein the anode terminal is made from copper.

15. The secondary battery according to claim 1 , wherein the sealing members protrude outwardly from the battery case, and

wherein the endothermic layer contacts the sealing member of the cathode terminal.