PURPOSE: To improve the reliability of preservation at high and low temps., to reduce thickness and cost and to obtain high mass productivity by constituting a part of a package with a material having flexibility.

CONSTITUTION: A sheet 10 consisting of a resin which has flexibility and is highly resistant to chemicals and heat is adhered to a glass substrate 3 by means of an epoxy adhesive agent 12 via a frame 11. A resin plate of 0.05W0.5mm thickness which has flexibility, is highly resistant to chemicals and heat, and permits adhesion by an epoxy adhesive resin 12 is preferable for the sheet 10, for which, for example, bakelite, fiber-reinforced heat resistant bakelite, epoxy resins, and fiber-reinforced epoxy resins are used. The sheet 10 plays the role of cushion by deforming with the expansion or shrinkage of an electrolyte 7. It is equally well to constitute a package 13 with a bakelite plate which is reduced of the thickness in the parts other than the frame part and to adhere such package to the glass substrate by means of the adhesive agent.