Abstract: A sodium-sulfur storage battery comprises an alpha alumina ring, a sodium conductive solid electrolyte tube and solder glass jointing said ring and said tube together; and is characterized in that the alpha alumina ring is provided at its open end with a groove for collecting the solder glass, a width of said groove is in a range from 0.2 mm to 5 mm and a depth of said groove is in a range from 0.2 mm to 10 mm. A surface of the solder glass is formed at a position inner than an end surface of the alpha alumina ring. Said groove may have a section of a rectangular shape. An inside surface of said groove may have a section of a round shape or an oblique section.

Abstract: The present invention discloses a sodium-sulfur storage battery utilizing an inside of a sodium-ion conductive solid electrolyte tube as a negative chamber, comprising an .alpha.-alumina ring jointed with solder glass to an open end of said electrolyte tube, a flanged aluminum housing having a fine hole at its bottom incorporated in said solid electrolyte tube, a negative auxiliary cover thermo-compressively jointed through a flange of said aluminum housing to an upper surface of said .alpha.-alumina ring, and a negative cover provided with a negative current collector terminal welded to said negative auxiliary cover.

Abstract: The invention relates to multilayer heat insulators wherein gas-impermeable layers each made of a metal foil of one member selected from the group consisting of aluminum, nickel and stainless steel and gas-containing layers each made of at least one member selected from the group consisting of glass fiber, asbestos fiber, mineral fiber, ceramic fiber, carbon fiber, silica powder, alumina powder and zirconia powder in the form of wool, paper or mat are laminated alternately so that the same layers do not contact each other. The thickness of the gas-impermeable layer is 10 to 20 .mu.m, the thickness of the gas-containing layer is 0.3 to 1.8 mm and its porosity is 0.98 to 0.95 to make the thermal conductivity of this laminated multilayer heat insulator about 0.02 kcal/mh.degree. C. (200.degree. C.) so that the behavior of the contained gas may be as small as possible, the thermal conduction may be prevented and the heat insulating performance may be improved.