Cell

A method of forming a package, comprising:

• presenting two laminate edge portions of the package, each of which includes a foil layer between first and second resin layers such that the respective first resin layers face each other and the respective second resin layers face away from each other and such that edges of the edge portions are in registration;
• and
• welding together the respective first resin layers at a position spaced apart from the edges while not welding the respective first resin layers at the edges such that, given a thickness of each laminate edge portion before being subjected to heat and compression is represented by t, a thickness of the laminate portions at the position is represented by t1, and a thickness of the laminate portions at the edges thereof is represented by t2, then t1<2t2,
• wherein,
• the edge portions include the edges of the laminate film from which electrode terminals extend such that portions of the electrode terminals are exposed beyond the edges with respect to the laminate film, and
• the edge portion is between the sealing portion and the exposed portions of the electrode terminals.