A battery module comprising: a cell stack comprising a plurality of battery cells stacked in a vertical direction; and a protective case configured to receive the cell stack, wherein the protective case comprises a lower cover located under the cell stack, an upper cover located above the cell stack, and a pair of side covers located at sides of the cell stack, and wherein each of the side covers is provided at an inside thereof with a structure configured to prevent ejection of flare and spark, generated during swelling, to the outside of the protective case, characterized in that each side cover comprises: a vertical plate having a lower end located in close contact with the lower cover and an upper end located in close contact with the upper cover; and a pair of bent plates formed at opposite side ends of the vertical plate so as to be bent and/or curved in a predetermined shape and face each other, wherein the cell stack comprises: the plurality of battery cells stacked in the vertical direction; one or more shock absorption pads located on one or more of the upper part and the lower part of the stacked battery cells; a pressing layer located outside of the shock absorption pads to uniformly press all surfaces of the battery cells, which is located on at least one of an upper part and a lower part of the stacked battery cells; a busbar configured to allow positive electrode leads and negative electrode leads of the plurality of battery cells to be connected thereto; and a pair of busbar holders interposed between the positive electrode leads and the busbar and between the negative electrode leads and the busbar, respectively, wherein the pressing layer comprises a pressing pad and a reinforcement frame. a cell stack comprising a plurality of battery cells stacked in a vertical direction; and a protective case configured to receive the cell stack, wherein the protective case comprises a lower cover located under the cell stack, an upper cover located above the cell stack, and a pair of side covers located at sides of the cell stack, and wherein each of the side covers is provided at an inside thereof with a structure configured to prevent ejection of flare and spark, generated during swelling, to the outside of the protective case, a vertical plate having a lower end located in close contact with the lower cover and an upper end located in close contact with the upper cover; and a pair of bent plates formed at opposite side ends of the vertical plate so as to be bent and/or curved in a predetermined shape and face each other, wherein the cell stack comprises: the plurality of battery cells stacked in the vertical direction; one or more shock absorption pads located on one or more of the upper part and the lower part of the stacked battery cells; a pressing layer located outside of the shock absorption pads to uniformly press all surfaces of the battery cells, which is located on at least one of an upper part and a lower part of the stacked battery cells; a busbar configured to allow positive electrode leads and negative electrode leads of the plurality of battery cells to be connected thereto; and a pair of busbar holders interposed between the positive electrode leads and the busbar and between the negative electrode leads and the busbar, respectively, wherein the pressing layer comprises a pressing pad and a reinforcement frame. the plurality of battery cells stacked in the vertical direction; one or more shock absorption pads located on one or more of the upper part and the lower part of the stacked battery cells; a pressing layer located outside of the shock absorption pads to uniformly press all surfaces of the battery cells, which is located on at least one of an upper part and a lower part of the stacked battery cells; a busbar configured to allow positive electrode leads and negative electrode leads of the plurality of battery cells to be connected thereto; and a pair of busbar holders interposed between the positive electrode leads and the busbar and between the negative electrode leads and the busbar, respectively, wherein the pressing layer comprises a pressing pad and a reinforcement frame.