Energy storage device, the contact element for such an energy storage device and process for producing such an energy storage device

The electrochemical energy storage device, an energy storage cell (10) having an electrode stack and an enclosure; a current conductor (12) connected to the electrode stack of the energy storage cell (10) is electrically conductively connected and which is arranged an at least partially outside the enclosure of the energy storage cell (10) contact portion (12a); and a housing (16, 18) for receiving said energy storage cell (10) and of the current conductor (12). Further, a contact element (20) is provided comprising a first contact portion (20a) within the housing (16, 18) and with the contact portion (12a) of the current conductor (12) electrically conductively connected, preferably welded surface with ultrasound is and a second contact portion (20c) which is disposed at least partially outside the housing (16, 18),. The first contact portion (20a) of this contact element (20) has a compared to the second contact portion (20c) of the contact element (20) low material thickness in its direction of connection with the contact portion (12a) of the current conductor (12).