Cap Plate Coupled to Battery Can and Battery Cell Including the Same

A cap plate coupled to a battery can include: a main body that seals the battery can; a vent notch that is formed in the main body, and ruptures when a pressure inside the battery can exceeds a threshold value; and a rupture inducing portion that is formed in the main body while being spaced apart from the vent notch, and induces an occurrence of rupture of the vent notch at a predetermined location.