Development of Molten Salt Electrolyte for Molten Salt Batteries (Na-Zn)

Abstract

The demand for efficient and sustainable energy storage technologies has intensified in recent years due to the growing need for clean and renewable energy sources, as well as the rapid expansion of electric vehicles and portable electronics. Batteries, as versatile electrochemical energy storage devices, play a pivotal role in addressing this need. Liquid metal batteries (LMBs) represent an innovative class of energy storage devices with potential applications in large-scale energy storage systems as they provide high scalability, have the potential for long cycle life and offer high energy density making them attractive for storing large amounts of energy. Sodium-based LMBs operating at elevated temperatures to maintain the liquid state of components are currently under development by the EU-funded SOLSTICE project. The elevated temperature is necessary for efficient ion transport and to avoid solidification of materials. In this thesis, the molten salt electrolyte of sodium-based LMBs was developed to overcome the challenges of high melting point of the electrolyte and high sodium solubility in the electrolyte. Chloride salts of strontium (Sr) and potassium (K) in addition to sodium chloride were considered for investigation to identify salt compositions best suited to overcome the challenges mentioned above. Initially, simulations were carried out in FactSage to recognize the eutectic compositions of the electrolyte mixture. The melting behaviour of the most promising salt composition was analysed using differential scanning calorimetry (DSC). Moreover, the solubility of electrodes in the selected electrolyte mixture was examined to study its effect on self-discharge of the battery.