Safety of sodium-sulfur (Na/S) batteries for electric vehicles begins with cell safety. Cell safety has been an important part of Na/S research and is based on three general principles: (1) minimize the quantity of sodium immediately available for reaction if the beta'-alumina fails, (2) separate the bulk of cell reactants and restrict the flow of bulk sodium to the reaction site, and (3) protect the outer cell case against corrosion by sodium polysulfides at elevated temperatures (for a sodium-core cell). The principal mechanisms of Na/S cell failure include cracking of the electrolyte, degradation of the glass seal, corrosion of the container, and breaching of the metal-to-ceramic seals. Operating factors that impact these failure mechanisms included number of electrical and thermal cycles, time at operating temperature, depth of discharge, and cycling regime. Both failure testing and life testing of cells have shown that the chemical and thermal risks implicit in the presence of sodium, sulfur, and sodium polysulfides have been satisfactorily mitigated by engineering and design at the cell level. Although cell safety has been established through life and failure testing, the electrical, thermal, and mechanical environment at the battery level imposes additional safety questions and requirements. Failure testing of prototype Na/S batteries has shown that they can withstand extreme conditions to which they may be exposed.
Environmental, health, and safety issues of sodium-sulfur batteries for electric and hybrid vehicles: cell and battery safety
Umgebungs-, Gesundheits- und Sicherheitsaspekte beim Einsatz von Natrium-Schwefel-Batterien in Elektro- und Hybridfahrzeugen: Zellen- und Batterie-Sicherheit
1993
7 Seiten, 1 Tabelle, 10 Quellen
Conference paper
English
Safety considerations for sodium-sulfur batteries for electric vehicles
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