Abstract
A NAS battery cell is comprised of a sodium negative electrode and a sulfur positive electrode separated by a solid electrolyte made of beta-alumina, housed within a cylindrical aluminum container. The container is exposed highly corrosive materials, but have to be designed to deliver 4500 charge/ discharge cycles over a 15-year operating life. Studies have shown that a plasma sprayed Fe-75Cr alloy coating provides an effective protection layer. The major challenge to implementing this technology was the development of methods to apply plasma spray coatings in high volume mass production of the cells. This paper describes the development of high speed plasma spray guns optimized for volume manufacturing conditions, and the quality and reliability of NAS cells using this technology demonstrated over a period of nine years in laboratory tests. In April 2002 TEPCO and NGK decided to launch commercial production of NAS batteries. By April 2003, NGK started operation of a new NAS battery manufacturing facility and plasma sprayed aluminum cell containers are now being produced at a rate of over 1300 per day.
