SQUARE-TYPE SECONDARY BATTERY AND METHOD FOR MANUFACTURING SAME

A rectangular secondary battery includes an electrode body, a rectangular battery case housing the electrode body, a sealing plate, a current collector extending on an end side of the sealing plate in a longitudinal direction thereof and joined, by ultrasonic welding, to an end of a positive electrode plate or a negative electrode plate, and an external terminal provided outside the sealing plate and connected to the current collector. The sealing plate has a gas discharge valve ruptured when the internal gas pressure of the battery case has reached a predetermined value or greater, and a thin portion formed between the external terminal and the gas discharge valve and formed thicker than the gas discharge valve.