a cover member comprising an internal receiving space configured to accommodate battery cells arranged along a first direction and each comprising a vent;

a top plate coupled to a top of the cover member and comprising ducts respectively corresponding to the vents of the battery cells, the ducts spaced apart along the first direction and each defining a passage to discharge a gas from the vent of a corresponding battery cell of the battery cells;

a top cover coupled to a top portion of the top plate and comprising discharge holes passing through the top cover, located in an exhaust area, and corresponding to the ducts; and

an extinguisher sheet located between the top cover and the top plate along a height direction, and configured to emit a fire extinguishing agent, the extinguisher sheet comprising opening holes located to respectively correspond to the ducts, such that, in a plan view as viewed along the height direction, the extinguisher sheet is entirely outside peripheries of the ducts,

wherein the top cover comprises protrusion parts located on a bottom surface of the top cover, covering the exhaust area, and each surrounding an exterior of a corresponding duct of the ducts.