Fluorine-Free Electrolytes for Lithium Metal Batteries: Challenges and Opportunities in Solvation Structure and Interphase Design

Electrolyte design has emerged as a key strategy to overcome performance and safety challenges in lithium metal batteries. In this Perspective, we examine the recent movement toward fluorinated electrolyte solvents for high performance lithium metal batteries. We highlight the state-of-the-art understanding of the role of fluorine in modifying solvent properties and influencing electrolyte reactivity and further discuss the role of fluorinated species in the interphases at both the anode and cathode. In light of risks associated with per- and polyfluoroalkyl substances (PFAS), we propose that a deeper understanding of the role of fluorine in electrolytes and interphases is essential to eventually design fluorine-free molecules for high performance batteries and discuss areas for further research.