. . . "C. which is the upper limit of temperatures at which cellsare usually used.FIG. 2 is a sectional view showing a button-shaped cell embodying this invention and having a thickness of 2.5 mm and desired diameter.FIGS. 3a and 3b are a sectional view and a plan view showing a flat-shaped cell which is another embodiment of this invention and measuring 1.5 mm in thickness, 52 mm in length and 25 mm in" . .