Molecular\nStructure Optimization of Fluorinated Ether\nElectrolyte for All Temperature Fast Charging Lithium-Ion Battery

New electrolytes are needed to replace\ncommercial carbonate\nelectrolytes\nto enable a wider working temperature range, higher energy density,\nand faster charging of lithium-ion batteries (LIBs). Fluorinated diluents\nand solvents have shown promise in LIB electrolyte design, but most\nof them are considered per- and polyfluoroalkyl substances (PFAS)\nwith significant environmental and health concerns. In this work,\nwe design a family of non-PFAS, partially fluorinated ether solvents\nfor LIB electrolytes. Through rational molecular design, an optimized\nrate capability is achieved by low viscosity, weak lithium-ion solvation,\nand high ion diffusivity. The optimized electrolytes enable a longer\ncycle life and better rate capability (up to 6 C) than previously\nreported fluorinated ethers or commercial carbonate electrolyte in\ngraphite/LiNi<sub>0.8</sub>Mn<sub>0.1</sub>Co<sub>0.1</sub>O<sub>2</sub> (Gr/NMC811) full cells. In addition, they also show an extended\nworking temperature window with stable long-term cycling from 60 \nto −40 °C. This work shows a promising path to next generation\nbatteries capable of extreme conditions without introducing PFAS concerns.