ENERGY STORAGE SYSTEM

An energy storage system includes a battery module including a plurality of secondary battery cells and an electrode tab disposed on one or both sides; and a housing accommodating a module stack in which the plurality of battery modules are stacked, wherein the housing includes a first cover disposed to oppose at least one side surface of the module stack on which the electrode tab is disposed, and a second cover disposed to oppose at least one of the side surfaces of the module stack on which the electrode tab is not disposed, and wherein a flame passage is formed between the first cover and the module stack, and a cooling passage is formed between the second cover and the module stack.