Development of Molten Salt Electrolytes in Na-ZnCl2 All Liquid Battery for Electrical Grid Storage

Abstract

Energy is a major pillar for any development; however, it poses new challenges to the environment. For instance, conventional energy generation from fossil fuels brings the climate to a critical situation; in addition, nuclear energy generation cannot be a reliable choice due to high safety and environmental risk. The solution was provided through green renewable energy sources. However, their production cannot be adapted to energy consumption over different times, which brings the challenge of volatile energy to the front. The energy storage idea showed a promising solution for this problem. Energy can be stored with many different techniques and one of those that is showing a promising trend is electrochemical technology (batteries). They attracted the researchers’ attention as they are not limited to geographical limitations, but they can also be used for stationary and portable applications. In addition, they have different technologies and consequently different alternatives for one case they can provide limited or high energy densities. High energy density characteristics raised the importance of batteries as an innovative alternative to grid-scale energy storage. This path was proven with some practical applications. Therefore, (SOLSTICE) project- funded by the European Union’s research program -aspires to develop Sodium-Zinc Molten salt Battery (Na||Zn MSB) as a low-cost grid-scale electrical energy storage in accordance with the European green deal ambitious goals. This master thesis-in collaboration with the German Aerospace Centre (DLR) - aims to develop a molten salt electrolyte for Sodium-Zinc Molten salt high-temperature all liquid battery that can provide the best performance within the battery operating conditions. Chloride salts were pinpointed for this thesis due to their high thermal stability, low prices, and they can provide relatively low melting temperature salt mixtures. In this work, Calcium (Ca), Barium (Ba), strontium (Sr), Lithium (Li), and Potassium (K) chloride salts will be investigated in combination with Sodium chloride salt (NaCl) as the source of charge. For this purpose, the FactSage simulation will be utilized to investigate the phase diagrams for different chloride salt mixture combinations. FactSage simulation data for the promising candidate salt mixture will be emphasized by the Differential Scanning Calorimeter (DSC). The electrode solubility in the promising candidate salt mixture will be investigated also as one major reason for battery self-discharge.