Elektroliti na osnovi fluoriranih topil v akumulatorjih s kovinskimi litijevimi in magnezijevimi anodami

The transition from fossil fuels to sustainable energy sources requires substantial advancements in large-scale energy storage technologies. Sustainable and safe batteries are essential to enable this transition. Among various options, rechargeable metal anode-based batteries, particularly those using Li and Mg metal anodes, have attracted significant attention in both academic and industrial research due to their potential to achieve higher energy densities compared to systems employing carbon-based anodes. However, the practical realization of long-lasting and reliable Li and Mg metal batteries is hindered by critical challenges associated with the highly reactive, ionically non-blocking, and mechanically unstable interfaces and interphases formed at the metal electrodes and strategies to address or overcome these issues. These issues are strongly influenced by the nature of the electrolyte and its interaction with these metallic anodes. In this context, electrolyte engineering has emerged as a promising strategy to overcome such limitations. This thesis focuses on the development of liquid electrolytes aimed at addressing these challenges, with particular emphasis on fluorinated solvents. Fluorinated solvent-based electrolytes have demonstrated potential in enhancing oxidative stability, improving low-temperature performance, and stabilizing interfaces/interphases in both Li and Mg metal batteries. The research presented in this dissertation is organized into two main parts. The first part investigates the design and characterization of fluorinated electrolytes for Li metal batteries. We aimed to understand the Li+ transport in these electrolytes using various techniques to determine the Li+ transport number. Furthermore, we employed electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy, and scanning transmission electron microscopy to analyze the interfaces and interphases in high-voltage Li metal batteries. Motivated by the success of these electrolytes in Li batteries, the second part extends this investigation to Mg metal batteries. The fluorinated electrolytes demonstrated improved performance of Mg metal anode in high-voltage Mg battery configuration. Operando EIS was used to probe the interfacial electrochemical processes at the Mg metal surface, and insights into performance enhancements were obtained by integrating microscopy and chemical analyses. Finally, we explored the application of the fluorinated solvent-based electrolytes in Mg-S batteries, identifying key factors that may guide the rational design of advanced electrolytes for future Mg-S batteries.