Welding method and welding apparatus for secondary battery, and monitoring method and monitoring apparatus for secondary battery welding process

A welding apparatus for a secondary battery, wherein when an electrode assembly having a center hole is seated on a lower can, an electrode tab of the electrode assembly is welded to an inner bottom surface of the lower can by the welding apparatus, the welding apparatus comprising:

• a jig which comprises a seating portion that has a disk shape and an insertion portion that has a pipe shape extending from a lower surface of the seating portion, the insertion portion having a diameter enabling entry into the center hole of the electrode assembly and the seating portion having a larger diameter than a diameter of an upper end of the insertion portion proximal to the seating portion;
• and
• a laser irradiation apparatus configured to emit a laser beam into a hole of the insertion portion,
• wherein, when the electrode assembly is seated on the lower can such that the electrode tab is placed within the center hole, the laser irradiation apparatus is configured to perform welding as the laser beam is emitted to a contact point between the inner bottom surface of the lower can and the electrode tab after passing through the hole of the insertion portion of the jig.