Fluid dynamic aspects of large liquid metal batteries

Liquid metal batteries (LMBs) are currently discussed as a means to provide economic grid-scale energy storage. LMBs are all-liquid electrochemical cells, typically containing an alkali metal as the negative, and a metal or half metal as the positive electrode. Due to their different densities, both metals form distinct horizontal layers separated by a molten salt with a density in between those of both metals. The molten salt acts as the electrolyte. Evidently, LMBs need elevated temperatures to function. However, they have a number of distinct advantages as, to name a few, self-assembly, ease of construction and scalability, high current densities, and potentially very long cycle life.
Due to the completely liquid inventory and the high total cell currents, fluid dynamics plays an important role for the operation of LMBs. We will focus on the occurrence and prevention of fluid dynamic instabilities in LMBs, especially the current driven Tayler instability (TI). Since the density differences between negative electrode and molten salt are typically small, fluid dynamic instabilities can provoke mixing of electrode and electrolyte material leading to an internal shorting of the cell. Both experimental as well as numerical results will be presented and discussed in relation to cell design and choice of active materials.