Wound electrochemical cell with a hollow core

An electrochemical cell having a spiral winding around a central core (100), wherein the central core is provided with longitudinal grooves (150) on its outer surface to facilitate electrolyte filing and accommodate overpressure. The core itself improves dissipation of heat generated along the center of the cell, and the hollow core design allows the cell core to have a larger radius, permitting the "jelly roll" winding to begin at a larger radius and thereby facilitate the initial turns of the winding by decreasing the amount of bending required of the electrode laminate at the beginning of the winding operation. The hollow core also provides mechanical support end-to-end. A pair of washers (134,136) are used at each end of the cell to sandwich current collection tabs (130) in a manner that improves electrical and thermal conductivity while also providing structural integrity.