Battery and ultrasonic bonding method for battery

A battery comprising:

• a container;
• an electrode group being housed in the container and including a positive electrode and a negative electrode;
• a plurality of current collecting tabs being extended from any one of the positive electrode and the negative electrode of the electrode group, being located at an edge of the electrode group, and having a metallic foil overlapped with one another;
• a clip plate configured such that the metallic foil of at least one of the current collecting tabs can be inserted;
• a lead bonded to the clip plate at an ultrasonic bonding portion by ultrasonic bonding;
• a lid configured to close an opening portion of the container;
• and
• an external terminal provided on the lid and connected to the at least one current collecting tab via the lead, wherein
• the lead has a middle portion where a gradual increase of a cross-sectional area of the lead occurs between the lid and a center of the edge of the electrode group,
• the current collecting tabs include a planar surface opposing the lead,
• a thickness of the lead increases in a direction substantially perpendicular to the planar surface,
• a front end portion connects the lead to the external terminal, and
• the cross-sectional area of the lead is substantially constant from the middle portion to the front end portion.