Abstract
Na-S(NAS) battery cell are comprised of a negative sodium electrode and a positive sulfur electrode separated by a solid electrolyte made of beta-alumina and housed in a cylindrical aluminum container.
High Cr-Fe alloy surface coatings are applied on the inner walls of cylindrical aluminum containers by atmospheric plasma spraying to prevent a sulfide corrosion. Methods used for applying these coatings and methods used for evaluating polished surfaces were studied. Just after a high Cr-Fe alloy coating is sprayed, the surface contains a considerable amount of unmelted alloy particles and black fine fumes of Cr oxides. This situation causes excessive electric resistance during battery charge and discharge.
Therefore, an automatic polishing method for high Cr-Fe alloy containers using a rotating brush made from piano wire was developed. As a result, most of the fumes on the coatings were eliminated, and by polishing the uneven coating surface, the new metallic surface is revealed.
This makes it possible to control the amount of electric resistance inside the battery.
Also, through a study of polished surface evaluation methods, it was confirmed that it is possible to measure the average amount of contact resistance for sprayed coating surfaces before and after polishing using a surface quality (SQ) meter.
