Method of making a battery cell including clamping, tapering, trimming and ultrasonic welding of electrode foils

A method for manufacturing a battery cell having electrode foils protruding from a cell pouch includes positioning the cell pouch in a fixture such that distal end sections of the foils extend outward from the fixture. The method includes clamping the distal end sections in a curvilinear guide clamp to cause the distal end sections to taper into an electrode foil stack, and then translating the clamp a predetermined distance toward the fixture to displace the distal end sections by the predetermined distance. The method also includes trimming the distal end sections using a trim tool, positioning a sonotrode and an anvil adjacent opposite surfaces of the stack, and ultrasonically welding the stack to a conductive lead tab using the sonotrode to thereby form a welded joint within the battery cell. The sonotrode may be multi-sided with different knurl patterns for performing different welding processes.