Liquid-metal electrode to enable ultra-low temperature sodium-beta alumina batteries for renewable energy storage

Commercial sodium-sulphur or sodium-metal halide batteries typically need an operating temperature of 300-350°C, and one of the reasons is poor wettability of liquid sodium on the surface of beta alumina. Here we report an alloying strategy that can markedly improve the wetting, which allows the batteries to be operated at much lower temperatures. Our combined experimental and computational studies suggest that addition of caesium to sodium can markedly enhance the wettability. Single cells with Na-Cs alloy anodes exhibit great improvement in cycling life over those with pure sodium anodes at 175 and 150°C. The cells show good performance even at as low as 95°C. These results demonstrate that sodium-beta alumina batteries can be operated at much lower temperatures with successfully solving the wetting issue. This work also suggests a strategy to use liquid metals in advanced batteries that can avoid the intrinsic safety issues associated with dendrite formation. © 2014 Macmillan Publishers Limited. All rights reserved.