Abstract: Battery module for a propulsion battery system of an electrical vehicle, comprising a plurality of battery cells, arranged in a cooling volume for containing a cooling fluid for cooling the battery cells, and a plurality of wall elements defining the cooling volume. One of the wall elements (33) comprises an inner surface (110), oriented towards one of the battery cells, for contacting the cooling fluid, and an outer surface forming an exterior surface of the battery module. The inner surface is shaped to define a plurality of grooves (130) or a plurality of ridges for increasing the contact surface between the wall element and the cooling fluid, and for directing the flow of the cooling fluid in the cooling volume.