Energy-storage system for use in a vehicle, preferably for use in a hybrid vehicle, wherein the energy-storage system has the following: - a multiplicity of lithium-ion cells, each with a positive pole and a negative pole, wherein each of the lithium-ion cells is, without the cell housing, in the form of a Swiss-roll cell; - a housing with an interior space for receiving the lithium-ion cells, wherein the housing is at least regionally formed from plastic and has an opening, and wherein a barrier layer composed of metal and/or metal oxide is at least regionally arranged between the interior space and the inner surfaces, delimiting the interior space, of the housing, wherein the barrier layer is a layer which is impermeable to gases in ambient air and gases which arise in the interior space during operation of the energy-storage system and to moisture in the surroundings; and - a cover device composed of a metallic material which is designed to be weldable to the housing, wherein the cover device is weldable or welded to the housing in such a way that the opening of the housing is sealed or sealable, and wherein the cover device at least regionally forms an outer surface of the housing sealed in this way, characterized in that the housing has a connecting region which is designed to connect the housing to the cover device and along which the barrier layer is arranged, wherein the connecting region extends outwardly away from the housing in a perpendicular manner, specifically in such a way that the housing is welded or weldable to the cover device via the connecting region, and wherein the opening of the housing is hermetically sealable or sealed by way of the cover device with the aid of the barrier layer. wherein the energy-storage system has the following: - a multiplicity of lithium-ion cells, each with a positive pole and a negative pole, wherein each of the lithium-ion cells is, without the cell housing, in the form of a Swiss-roll cell; - a housing with an interior space for receiving the lithium-ion cells, wherein the housing is at least regionally formed from plastic and has an opening, and wherein a barrier layer composed of metal and/or metal oxide is at least regionally arranged between the interior space and the inner surfaces, delimiting the interior space, of the housing, wherein the barrier layer is a layer which is impermeable to gases in ambient air and gases which arise in the interior space during operation of the energy-storage system and to moisture in the surroundings; and - a cover device composed of a metallic material which is designed to be weldable to the housing, - a multiplicity of lithium-ion cells, each with a positive pole and a negative pole, wherein each of the lithium-ion cells is, without the cell housing, in the form of a Swiss-roll cell; - a housing with an interior space for receiving the lithium-ion cells, wherein the housing is at least regionally formed from plastic and has an opening, and wherein a barrier layer composed of metal and/or metal oxide is at least regionally arranged between the interior space and the inner surfaces, delimiting the interior space, of the housing, wherein the barrier layer is a layer which is impermeable to gases in ambient air and gases which arise in the interior space during operation of the energy-storage system and to moisture in the surroundings; and - a cover device composed of a metallic material which is designed to be weldable to the housing, wherein the cover device is weldable or welded to the housing in such a way that the opening of the housing is sealed or sealable, and wherein the cover device at least regionally forms an outer surface of the housing sealed in this way, characterized in that the housing has a connecting region which is designed to connect the housing to the cover device and along which the barrier layer is arranged, wherein the connecting region extends outwardly away from the housing in a perpendicular manner, specifically in such a way that the housing is welded or weldable to the cover device via the connecting region, and wherein the opening of the housing is hermetically sealable or sealed by way of the cover device with the aid of the barrier layer.