Recent advances in Na/S cell development — a review

This paper describes recent progress in the development of sodium/ sulfur batteries. Ceramic beta alumina electrolyte tubes with high conductivity and long life are being fabricated. Sulfur utilization is increased to 80%. Improvements are outlined which have been made in finding corrosion resistant casing materials and in cell design. Experimental cells with a weight of 1.1 kg and a capacity of 90 Wh have been built and successfully tested. Ninety-six of these cells have been electrically connected and enclosed in a conventional thermal insulation. The energy density of this non-optimized battery was 36 Wh/kg at the 2.5 hour discharge rate. Optimization with respect to weight will result in batteries with an energy density of more than 100 Wh/kg. Further improvements in cycle life are necessary for the practical application of these batteries.