Electrode assembly with hybrid weld

An electric storage battery including a jelly roll type electrode assembly having a mandrel. The mandrel includes a positive portion, negative portion and removable portion. The mandrel has two faces with grooves dimensioned to accommodate positive and negative feedthrough pins. Electrodes are welded to the mandrel using an ultrasonic weld to the face on which the electrodes are attached. An additional weld is made to at least one ultrasonic weld using a through-mandrel laser weld, incident on the opposite face from which the ultrasonic weld. The laser melts the mandrel such that molten mandrel material fills the area under the foil at the area of the ultrasonic weld, the surface area of the foil being significantly increased by knurls formed by ultrasonic welding. Electrodes are wrapped around the mandrel using the removable portion to wind the mandrel. The mandrel allows tighter wrapping of the jelly roll assembly increasing battery miniaturization.