The invention relates to a device for storing electric energy, in particular for the traction supply of a rail vehicle. It comprises a plurality of chargeable storage cells (10) having cell poles (12) that protrude from a cell surface (11), a cooling body (20) that is in thermal contact with the storage cells (10), and a plurality of bridge members (30), by way of which two of the plurality of storage cells (10) are in electric contact. According to the invention, at least some of the bridge members (30) contact the storage cells (10) on the sides thereof facing the cooling body (20). Furthermore, a bridge member (30) comprises a connecting web (31) having two recesses (32) and two connecting parts (33), each being introduced into one of the recesses (32), wherein each connecting part (33) is connected to a cell pole (12) of a storage cell (10) to be contacted. The connecting parts (33) are fixed non-rotatably and non-displaceably in the recesses (32) of the connecting web (31) by means of a releasable tensioning device (36, 37, 38). Thus the efficiency and service life of the energy storage device according to the invention can be increased by reducing the thermal resistance between the storage cells (10) and the cooling body (20).