The effects of temperature on the electrochemical performance of sodium-nickel chloride batteries

Sodium-nickel chloride (ZEBRA) batteries are typically operated at relatively high temperatures ((3)300 degrees C) to achieve adequate electrochemical performance. In the present study, the effects of operating temperature on the electrochemical performance of planar-type Na/NiCl2 batteries were investigated to evaluate the feasibility of battery operation at low temperatures (200 pound degrees C). The planar-type cell was able to be cycled at C/3 rate at as low as 175 degrees C despite higher cell polarization. Overall, low operating temperature resulted in a considerable improvement in the stability of cell performance. Cell degradation was negligible at 175 degrees C, while 55% increase in end-of-charge polarization was observed at 280 degrees C after 60 cycles. SEM analysis indicated that the degradation at higher temperatures was related to the particle growth of both nickel and sodium chloride. The cells tested at lower temperatures (200 pound degrees C), however, exhibited a sharp drop in voltage at the end of discharge due to the diffusion limitation, possibly caused by the limited ionic conductivity of catholyte or the poor wettability of sodium on the beta ''-Al2O3 solid electrolyte (BASE). Therefore, improvements in the ionic conductivity of catholyte and sodium wetting as well as reduction in the ohmic resistance of BASE are required to enhance the battery performance at low temperatures. Published by Elsevier B.V.