Electrochemical Energy Storage Device

An electrochemical energy storage device comprises: a cover plate (4), comprising a lead-out bar (41) and a fixing plate (42), wherein the lead-out bar (41) is a conductor, the fixing plate (42) is an insulator, and the lead-out bar (41) vertically passes through the fixing plate (42) and is fixed thereon; a housing (9), which is cylindrical and is provided with an opening at at least one end thereof, wherein the insulating fixing plate (42) and the opening of the housing (9) are connected in a sealed manner by means of a sealing ring (2); and a rolled core (7), provided in an inner cavity of the housing (9), wherein the rolled core (7) is conductively connected to the lead-out bar (41) by means of an upper connecting piece (6), and is conductively connected to another lead-out end of the housing (9) by means of a lower connecting piece (8); and the device further comprises: a welding ring (1), conductively connected to the housing (9) by means of welding, and a welding bar (3), conductively connected to the lead-out bar (41) of the cover plate (4) by means of welding, wherein the welding ring (1) and the welding bar (3) are provided on the same side of the housing (9). The upper connecting piece (6) and the lower connecting piece (8) respectively lead out the positive electrode and the negative electrode of the electrochemical energy storage device, and lead the positive electrode and the negative electrode to the outside. The device is led out at two ends, has a low internal resistance, and can be tin-soldered, thereby facilitating the assembly of modules.