A method of forming a package is provided and includes providing two laminate edge portions of the package, each of which includes a foil layer between first and second resin layers; and welding together the respective first resin layers at a first position spaced apart from the edges while not welding the respective first resin layers at the edges, wherein the edge portions include edges from which electrode terminals extend such that portions of the electrode terminals are exposed beyond the edges, and wherein the edge portions are between a sealing portion and exposed portions of positive and negative electrode terminals.