According to one embodiment of the present invention, a battery assembly comprises: a battery module comprising a plurality of unit batteries; an exterior case for housing the battery module in an internal space; and a heat-dissipating film which is inserted between the plurality of unit batteries and fitted tightly against each of the plurality of unit batteries, and is attached to the inside surface of the exterior case; and the heat-dissipating film comprises: first and second heat-dissipating layers which are formed of a thermally conductive material and discharge the heat of the unit batteries; and an adhesive layer which is formed between the first and second heat-dissipating layers and adheres the first and second heat-dissipating layers.