An energy storage module includes: a plurality of battery cells arranged in a first direction such that long side surfaces of adjacent ones of the battery cells face one another; a plurality of insulation spacers, at least one of the insulation spacers being between each adjacent pair of the battery cells, each of the insulation spacers including a heat-insulating first sheet and a plurality of flame-retardant second sheets respectively adhered to opposite surfaces of the first sheet by an adhesion member; a cover member including an internal receiving space configured to accommodate the battery cells and the insulation spacers; a top plate coupled to the cover member, the top plate including ducts respectively corresponding to vents of the battery cells and having fire extinguishing agent openings respectively corresponding to the insulation spacers; a top cover coupled to the top plate and having discharge openings respectively corresponding to the ducts; and an extinguisher sheet between the top cover and the top plate.