Battery module having structure capable of absorbing swelling, and battery pack and vehicle comprising same

A battery module comprising:

• a cell stack comprising a plurality of battery cells;
• a first end plate and a second end plate covering a top surface and a bottom surface, respectively, of the cell stack;
• at least one first upper reinforcing plate and at least one second upper reinforcing plate located on the first end plate and extending from a first side and a second side of the first end plate, respectively, in a longitudinal direction of the first end plate toward a central portion of the first end plate;
• at least one first lower reinforcing plate and at least one second lower reinforcing plate located on the second end plate and extending from a first side and a second side of the second end plate, respectively, in a longitudinal direction of the second end plate toward a central portion of the second end plate;
• a first fastening bolt located on a first side of the cell stack in a longitudinal direction of the cell stack, and passing through the at least one first upper reinforcing plate, the first end plate, the second end plate, and the at least one first lower reinforcing plate;
• and
• a second fastening bolt located on a second side of the cell stack in the longitudinal direction of the cell stack, and passing through the at least one second upper reinforcing plate, the first end plate, the second end plate, and the at least one second lower reinforcing plate wherein each of the first fastening bolt and the second fastening bolt comprises an upper bolt and a lower bolt that are spaced apart from each other, wherein the battery module further comprises a pressure relief coupler connecting the upper bolt to the lower bolt of each of the first fastening bolt and the second fastening bolt, wherein the pressure relief coupler comprises:
• a first main hinge coupled to the upper bolt;
• a second main hinge coupled to the lower bolt;
• and a first connection bar fastened between the first main hinge and the second main hinge.