A battery cell, comprising: an electrode assembly; a battery case having a case body for accommodating the electrode assembly and a case terrace extending from the case body; a pair of electrode leads configured to protrude out of the battery case and electrically connected to the electrode assembly; and an overcharge cut-off unit provided in the case terrace to prevent overcharge of the battery cell; wherein the overcharge cut-off unit includes: a cut-off unit body provided between the pair of electrode leads adapted to emit an overcharge cut-off gas; at least one detection sensor provided to at least one side of the cut-off unit body and disposed close to the pair of electrode leads to detect a temperature of the pair of electrode leads or a voltage of the battery cell; 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 to break the at least one capsule 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, 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, characterized in that the cut-off unit body has at least one gas outlet which protrudes toward the case body and guides the nitrogen gas to be emitted toward the case body. an electrode assembly; a battery case having a case body for accommodating the electrode assembly and a case terrace extending from the case body; a pair of electrode leads configured to protrude out of the battery case and electrically connected to the electrode assembly; and an overcharge cut-off unit provided in the case terrace to prevent overcharge of the battery cell; wherein the overcharge cut-off unit includes: a cut-off unit body provided between the pair of electrode leads adapted to emit an overcharge cut-off gas; at least one detection sensor provided to at least one side of the cut-off unit body and disposed close to the pair of electrode leads to detect a temperature of the pair of electrode leads or a voltage of the battery cell; 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 to break the at least one capsule 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, 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, characterized in that the cut-off unit body has at least one gas outlet which protrudes toward the case body and guides the nitrogen gas to be emitted toward the case body. a cut-off unit body provided between the pair of electrode leads adapted to emit an overcharge cut-off gas; at least one detection sensor provided to at least one side of the cut-off unit body and disposed close to the pair of electrode leads to detect a temperature of the pair of electrode leads or a voltage of the battery cell; 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 to break the at least one capsule 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, 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, characterized in that the cut-off unit body has at least one gas outlet which protrudes toward the case body and guides the nitrogen gas to be emitted toward the case body.