Energy storage in liquid metals and fused salts

Stationary electric energy storage systems can help balance temporal differences in electricity supply and demand. With the increasing use of volatile electricity sources, this task is becoming more important. Liquid metal and molten salt batteries are high-temperature storage devices and one option for stationary storage. They are based on the stable density stratification of a liquid alkali metal, a fused salt and a molten heavy metal. Mediated by the high operating temperature, which must be above the melting temperatures of the individual phases, interfacial reactions are rapid and transport processes are fast. High current and power densities can thus be reached. The completely liquid cell interior enables conceptually simple scalability at the cell level, which suggests favorable energy-related investment costs. Electrode and electrolyte layers possess thicknesses in the millimeter range and consist either of pure metals or a small number of components. Both properties will facilitate recycling considerably. The battery concept enables the use of abundant and cost effective active material combinations like Na-Zn. In contrast to most other battery systems, fluid mechanical processes, which are closely coupled to charge transport and transfer, are of relatively high importance. The talk will present selected physical phenomena in liquid metal batteries as well as discuss their possible role in a future energy system.