an electrode assembly comprising a first electrode, a second electrode, and a separator between the first electrode and the second electrode;

a case having an opening and housing the electrode assembly, the opening being located at a top of the case that is opposite a bottom of the case along a first direction;

a cap assembly sealing the opening of the case; and

a second electrode tab extending from the second electrode,

wherein the cap assembly comprises:

a cap plate bonded to the case and covering the opening, the cap plate having a terminal hole;

a terminal plate bonded to the cap plate; and

a thermal fusion member between the terminal plate and the cap plate and thermally fused with the terminal plate and the cap plate,

wherein, along the first direction, an uppermost surface of the terminal plate is located at a height greater than an uppermost surface of the thermal fusion member,

the terminal plate is electrically connected to the second electrode through the second electrode tab, the terminal plate and the second electrode tab are connected through the terminal hole, and the thermal fusion member is entirely on an upper surface of the cap plate facing in the first direction and is entirely outside the terminal hole in a second direction crossing the first direction so as not to overlap the terminal hole in the first direction, and

the terminal plate completely covers the thermal fusion member in the first direction.