An energy storage module (100, 200) comprising: 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, each of the battery cells comprising a vent; a plurality of insulation spacers (130, 230), at least one of the insulation spacers (130, 230) being between the long side surfaces of each adjacent pair of the battery cells, each of the insulation spacers (130, 230) comprising a heat-insulating first sheet (131a, 231a) and a plurality of flame-retardant second sheets (131b, 231b) respectively adhered to opposite surfaces of the first sheet (131a, 231a) by an adhesion member (131c, 231c); a cover member (110, 210) comprising an internal receiving space configured to accommodate the battery cells and the insulation spacers (130, 230); a top plate (140, 240) coupled to a top of the cover member (110, 210), the top plate (140, 240) comprising ducts (141, 241) respectively corresponding to the vents of the battery cells and having fire extinguishing agent openings (143, 243) respectively corresponding to the insulation spacers (130, 230); a top cover (160, 260) coupled to a top of the top plate (140, 240) and having discharge openings (161, 261) respectively corresponding to the ducts (141, 241); and an extinguisher sheet (150, 250) between the top cover (160, 260) and the top plate (140, 240), the extinguisher sheet (150, 250) being configured to emit a fire extinguishing agent at a temperature exceeding a reference temperature, and wherein the long side surfaces of adjacent ones of the battery cells are spaced apart from each other by a first distance, and wherein a thickness of each of the insulation spacers (130, 230) is less than 50% of the first distance. 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, each of the battery cells comprising a vent; a plurality of insulation spacers (130, 230), at least one of the insulation spacers (130, 230) being between the long side surfaces of each adjacent pair of the battery cells, each of the insulation spacers (130, 230) comprising a heat-insulating first sheet (131a, 231a) and a plurality of flame-retardant second sheets (131b, 231b) respectively adhered to opposite surfaces of the first sheet (131a, 231a) by an adhesion member (131c, 231c); a cover member (110, 210) comprising an internal receiving space configured to accommodate the battery cells and the insulation spacers (130, 230); a top plate (140, 240) coupled to a top of the cover member (110, 210), the top plate (140, 240) comprising ducts (141, 241) respectively corresponding to the vents of the battery cells and having fire extinguishing agent openings (143, 243) respectively corresponding to the insulation spacers (130, 230); a top cover (160, 260) coupled to a top of the top plate (140, 240) and having discharge openings (161, 261) respectively corresponding to the ducts (141, 241); and an extinguisher sheet (150, 250) between the top cover (160, 260) and the top plate (140, 240), the extinguisher sheet (150, 250) being configured to emit a fire extinguishing agent at a temperature exceeding a reference temperature, and wherein the long side surfaces of adjacent ones of the battery cells are spaced apart from each other by a first distance, and wherein a thickness of each of the insulation spacers (130, 230) is less than 50% of the first distance.