Secondary battery which detects displacement of gas discharge part to prevent battery cell swelling, system for charging secondary battery, and method for manufacturing secondary battery

1. A secondary battery, comprising:

a battery case having a sealing part about a periphery of the battery case;

a gas discharging part which is positioned in the sealing part that seals an electrode assembly, and induces a discharge of gas, the gas discharging part having a first edge and a second edge; and

a detecting part which detects a displacement generated in the gas discharging part and generates an electric signal, the detecting part being on the sealing part and between the first edge and the second edge of the gas discharging part,

wherein the gas discharging part induces the discharge of gas by weakening bonding force compared to other attachment portions of the sealing part.

2. The secondary battery of claim 1 , wherein the gas discharging part is thicker than other attachment portions of the sealing part by weakly performing thermo-compression on two sheets of material forming the battery case compared to other attachment portions of the sealing part.

3. The secondary battery of claim 1 , wherein the detecting part is a strain gauge.

4. The secondary battery of claim 1 , wherein the detecting part is a piezoelectric element.

5. A system for charging a secondary battery, the system comprising:

a battery case having a sealing part about a periphery of the battery case;

a gas discharging part which is positioned at one end of the sealing part that seals an electrode assembly, and induces a discharge of gas, the gas discharging part having a first edge and a second edge;

a detecting part which detects a displacement generated in the gas discharging part and generates an electric signal, the detecting part being on the sealing part and between the first edge and the second edge of the gas discharging part; and

a control unit which receives the electric signal generated by the detecting part and controls charging of the secondary battery.

6. The system of claim 5 , wherein the gas discharging part induces the discharge of gas by weakening bonding force compared to other attachment portions of the sealing part.

7. The system of claim 6 , wherein the gas discharging part is thicker than other attachment portions of the sealing part by weakly performing thermo-compression on two sheets of material forming the battery case compared to other attachment portions of the sealing part.

8. The system of claim 5 , wherein the detecting part is a strain gauge.

9. The system of claim 5 , wherein the detecting part is a piezoelectric element.

10. The system of claim 5 , wherein the control unit adjusts the quantity of current flowing in a charging electrode of the secondary battery according to the electric signal generated in the detecting part.

11. The system of claim 5 , wherein the control unit blocks a charging current according to the electric signal generated in the detecting part.

12. A method of manufacturing a secondary battery, the method comprising:

accommodating an electrode assembly in a battery case;

sealing the battery case at a sealing part extending about the periphery of the battery case;

forming a gas discharging part, which is thicker than other attachment portions, at one end of a sealing part that seals the battery case by weakly performing thermo-compression compared to other attachment portions of the sealing part, the gas discharging part having a first edge and a second edge; and

placing a detecting part which detects a displacement generated in the gas discharging part and generates an electric signal on the sealing part and between the first edge and the second edge of the gas discharging part.