Provided is a battery, and more particularly, a battery in which a cutting unit is formed in a seating groove so that the cutting unit and a sub battery module do not contact each other in a normal operation state, such that the battery may be stably driven, and a pouch of the sub battery module may be cut by the cutting unit only in an abnormal operation state such as over-charging, over-discharging, exposure to a high temperature, an electric short circuit, or the like, to prevent ignition or explosion in advance, such that safety may be improved.