Lithium secondary battery and battery system including the same

A battery system, comprising:

• a plurality of battery cells, each of which comprises:
• a pouch comprising:
• a first pouch case comprising a first peripheral portion and a first conductive unit formed at the first peripheral portion;
• and
• a second pouch case comprising a second peripheral portion and a second conductive unit formed at the second peripheral portion, the second pouch case being sealed with the first pouch case;
• and
• an electrode assembly accommodated in the pouch;
• and
• a power supply applying a current to the first conductive unit or the second conductive unit from an outside of at least one battery cell of the plurality of battery cells,
• wherein the first conductive unit and the second conductive unit are in contact with each other to form an electric circuit along the first peripheral portion or the second peripheral portion, and the current is circulated through the electric circuit,
• wherein the first conductive unit comprises two or more first conductive patterns spaced apart from each other, and the second conductive unit comprises two or more second conductive patterns spaced apart from each other,
• wherein at least a portion of the first conductive patterns and at least a portion of the second conductive patterns are electrically connected to each other.