Current breaking structure of battery system

A current breaking structure of a battery system includes lead wires, which extend from a plurality of battery cells connected in parallel with each other. The lead wires are bonded to one of two faces of an outer busbar that connect a battery module to outside, in which the one of the two faces is faced to an interior of a battery module, such that upon battery cell expansion, the lead wires are entirely broken by the outer busbar. Accordingly, in case where overcharge occurs in a pouch type lithium ion battery, i.e., in a high-voltage battery having battery cells in parallel connection and then serial connection, connecting structure is broken effectively, thus preventing in advance overcharge-related safety accident.