Sodium-sulfur battery, and a battery system using same

A sodium-sulfur battery as claimed in claim 11, wherein said carbides in said Co base alloy have a spherical shape, a particle diameter of utmost 5 μm, and an area ratio of 20˜80%.

A sodium-sulfur battery comprising:

• a cell container for a positive electrode, composed of
• materials in plate shape and pipe-shape, said materials (1) being a Co base alloy, which contains Cr, Ni, C, and W or Mo, and
• (2) having carbides containing at least one of W, Mo, and Cr, which are precipitated in said alloy.

A sodium-sulfur battery comprising

• a cell container for positive electrode, composed of materials in plate-shape and pipes which are made of a Co base alloy, which contains (1) Cr and C, or (2) Cr, Ni, C, and W or Mo, wherein at least Cr carbide having utmost 5 μm in diameter is precipitated by heating at 500˜1000° C. for 10 hours as an aging heat treatment.