(637a) Coupling High Ionic Conductivity and High Electrochemical Stability in Fluorinated Ethers for Lithium-Based Batteries.

The development of next generation batteries with energy densities much higher than lithium-ion is predicated on the use of lithium metal as an anode and high voltage electrodes as the cathode. Ether solvents are highly ionically conductive and can support high lithium metal deposition and stripping efficiencies, but unfortunately have low oxidative stability (< 4 V vs Li/Li⁺). In contrast, hydrofluoroethers have improved oxidative stabilities, but do not dissolve any salt and hence do not support ion transport. A conventional approach of mixing hydrofluoroethers with ether solvents does not lead to a combination of both desired properties. In this work, we show that a covalent approach of attaching a fluorinated functional group with ether functional groups allows for the combination of high ionic conductivity and high oxidative stability. We use nuclear magnetic resonance and molecular dynamics to study the ion transport behavior. Finally, we explore these electrolytes with NMC 811 electrodes and show that they can support at least 100 cycles. Our rational approach for electrolyte design can be utilized in other battery chemistries.