1,2-bis(2,2-difluoroethoxy)ethane

F4DEE (1,2-bis(2,2-difluoroethoxy)ethane) is a high-purity, linear fluorinated ether solvent designed specifically for advanced battery applications. Synthesized as a fluorinated derivative of diethoxyethane, F4DEE exhibits exceptional electrochemical properties that make it highly valuable in electrolyte formulation for battery research and development. F4DEE features a unique molecular structure characterized by its fluorinated ethoxy groups. This structure enables effective solvation of lithium salts, such as lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium bis(fluorosulfonyl)imide (LiFSI), at concentrations exceeding 1 M. The compound exhibits excellent oxidative stability and anodic stability, making F4DEE an ideal solvent for formulating electrolytes in lithium metal batteries and other next-generation energy storage applications.

F4DEE is primarily used in the formulation of electrolytes for lithium metal batteries (LMBs) and lithium-sulfur (Li-S) batteries. In LMBs, it serves as an effective solvent for advanced lithium salts like LiFSI, enhancing electrochemical performance by providing high ionic conductivity and promoting the formation of a stable solid electrolyte interphase (SEI) on the lithium metal anode. This stable SEI mitigates dendritic lithium growth and electrolyte decomposition, improving battery longevity, safety, and overall efficiency.
In Li-S batteries, F4DEE plays a crucial role in optimizing the solubility of lithium polysulfide (LiPS) intermediates. Electrolytes formulated with F4DEE achieve a moderate LiPS solubility range (50 to 200 mM [S]), which effectively balances the shuttling effect and Li-S reaction kinetics. This balance leads to significant improvements in cycling stability, capacity retention, and calendar life compared to performance using conventional ether-based electrolytes. Additionally, these electrolytes exhibit excellent performance under lean electrolyte conditions and higher temperatures.
With its high boiling point and reduced flammability compared to conventional carbonate and ether solvents, F4DEE enhances the thermal stability and safety profile of energy storage systems. This makes it particularly attractive for demanding applications in electric vehicles, portable electronics, and other high-performance devices. F4DEE′s exceptional oxidative stability also opens up possibilities for developing high-voltage batteries, extending the potential of energy storage technologies. Furthermore, as a co-solvent in localized high-concentration electrolytes (LHCEs), F4DEE balances electrolyte viscosity and ionic conductivity, optimizing battery performance by combining the advantages of high-concentration electrolytes with improved wettability and cost-effectiveness.