APPARATUS FOR ULTRASONIC WELDING AND SECONDARY BATTERY HAVING AN ELECTRODE STRUCTURE WITH IMPROVED STRENGTH

摘要

The present invention relates to an apparatus for ultrasonic welding for improving the welding strength between an electrode tap and an electrode lead which comprise a secondary battery, and to a secondary battery which is welded by the apparatus for ultrasonic welding so as to improve the strength of a welded area. The secondary battery according to the present invention comprises: an electrode assembly on which a positive electrode plate having a positive tap, a negative electrode plate having a negative tap, and a separator are alternately stacked; an exterior pouch material for receiving the electrode assembly; a positive electrode lead welded and electrically connected to the positive electrode tap; and a negative electrode lead welded and electrically connected to the negative tap. A welded point of a welded surface between the negative electrode lead and the negative electrode tap has a density greater than that of a welded point of a welded surface between the positive electrode lead and the positive electrode tap.