Battery cell

1. A battery cell, comprising:

an electrode assembly;

a battery case having a first sheet and a second sheet forming a case body for accommodating the electrode assembly, the first sheet and second sheet sealed together to form a case terrace extending from the case body;

a pair of electrode leads configured to protrude out of the battery case and being electrically connected to the electrode assembly; and

an overcharge cut-off unit provided between the first sheet and second sheet of the case terrace to prevent overcharging of the battery cell, wherein the overcharge cut-off unit includes:

a cut-off unit body provided between the pair of electrode leads and being configured to emit an overcharge cut-off gas out of the cut-off unit body when the pair of electrode leads has a temperature over a predetermined temperature or when the battery cell has a voltage over a predetermined voltage;

at least one detection sensor provided to at least one side of the cut-off unit body and configured to detect a temperature of the pair of electrode leads or a voltage of the battery cell; and

at least one gas outlet protruding toward the case body and configured to guide the overcharge cut-off gas into the case body.

2. The battery cell according to claim 1 , wherein the overcharge cut-off unit further includes:

at least one capsule provided in the cut-off unit body and filled with sodium azide; and

a burst trigger connected to the at least one detection sensor and being configured to break the at least one capsule when the temperature of the pair of electrode leads is over the predetermined temperature or when the voltage of the battery cell is over the predetermined voltage.

3. The battery cell according to claim 2 , wherein the overcharge cut-off gas is a nitrogen gas, and

wherein the cut-off unit body is filled with iron oxide that is capable of reacting with the sodium azide to generate the nitrogen gas.

4. The battery cell according to claim 1 , wherein the overcharge cut-off unit includes at least one cover film provided at the at least one gas outlet, the at least one cover film being configured to open when the overcharge cut-off gas is emitted.

5. The battery cell according to claim 1 , wherein the at least one detection sensor is a temperature sensor or a voltage sensor.

6. The battery cell according to claim 1 , wherein the battery cell is a pouch-type secondary battery.

7. The battery cell according to claim 1 , wherein the at least one detection sensor is electrically connected to the pair of electrode leads.

8. The battery cell according to claim 1 , wherein the cut-off body further comprises a first component and a second component, and

wherein the first component is sodium azide, the second component is iron oxide and the overcharge cut-off gas is nitrogen gas.

9. The battery cell according to claim 1 , wherein the at least one detection sensor is a pair of detection sensors, the pair of detection sensors extending from opposite sides of the cut-off body.

10. The battery cell according to claim 9 , wherein each of the pair of detection sensors attaches to a respective capsule provided in the cut-off unit body, each capsule filled with a first component, and

wherein the cut-off unit body is filled with a second component configured to react with the first component to generate the overcharge cut-off gas.

11. The battery cell according to claim 9 , wherein the overcharge cut-off unit further includes:

at least one capsule provided in the cut-off unit body and filled with a first component; and

a burst trigger connected to the at least one detection sensor and being configured to break the at least one capsule when the temperature of the pair of electrode leads is over the predetermined temperature or when the voltage of the battery cell is over the predetermined voltage.

12. The battery cell according to claim 11 , wherein the cut-off unit body is filled with a second component configured to react with the first component to generate the overcharge cut-off gas.