Square secondary battery

A square secondary battery which stores an electrode group in a battery case thereof, with the electrode group soaked with an electrolyte, the square secondary battery comprising:

• a case surface portion in which an injection opening for injecting the electrolyte into the battery case is opened;
• a sealing cap disposed in facing relation to the case surface portion at a position to close the injection opening, the sealing cap being welded at an outer circumferential edge thereof to the case surface portion, thereby sealing the injection opening;
• a pressure sensitive adhesive member interposed between the sealing cap and the case surface portion for securing the sealing cap to the case surface portion;
• and a gas passage formed between the case surface portion and the sealing cap, the gas passage communicating the injection opening with a gap in a gas permeable manner, the gap is positioned between the battery case and the sealing cap and downstream of the pressure sensitive adhesive member,
• wherein the pressure sensitive adhesive member is formed of double-sided tape adhered on both surfaces of a substrate wherein the substrate comprises a gas permeable layer that forms the gas passage.