A device stores electric energy, in particular for the traction supply of a rail vehicle. The device has a plurality of chargeable storage cells with cell poles, a cooling body that is in thermal contact with the storage cells, and a plurality of bridge members, by way of which two of the plurality of storage cells are in electric contact. Accordingly, at least some of the bridge members contact the storage cells on the sides thereof facing the cooling body. A bridge member contains a connecting web having two recesses and two connecting parts, each being introduced into one of the recesses. Each connecting part is connected to a cell pole of a storage cell to be contacted. The connecting parts are fixed non-rotatably and non-displaceably in a connecting web by a releasable tensioning device. Thus the efficiency and service life of the energy storage device can be increased by reducing the thermal resistance between the storage cells and the cooling body.