Interconnecting current collectors comprising polymer bases

Described herein are electrochemical cells fabricated with current collectors comprising polymer bases and metal layers and methods of interconnecting these current collectors or, more specifically, interconnecting their metal layers. For example, a current collector, positioned between two other current collectors, can have an opening allowing these two other current collectors to form a direct interface. This interface not only directly interconnects the metal layers on these two current collectors but also indirectly interconnects the two metal layers of the middle current collector, which are positioned on the opposite sides of the polymer base of this current collector. In some examples, the metal layers of current collectors are reinforced by external metal foils that help to maintain continuity and/or repair any discontinuities in the metal layers when these metal layers are welded together. For example, welding may push portions of the polymer bases away from the weld zone.