Inorganic/organic composite fluorinated interphase layers for stabilizing ether-based electrolyte in high-voltage lithium metal batteries

Abstract

Despite their superior reduction stability to Li metal compared with conventional carbonate electrolytes, ethers have been precluded from use in high-voltage batteries due to their limited oxidation stability (<4 V). Herein, this issue can be effectively addressed by the synergistic effect strategy based on dual salt and fluoroethylene carbonate (FEC) as a co-solvent, which forms a unique Li⁺ solvation structure with aggregated dual anions and induces more robust inorganic/organic composite fluorinated interphase layers. It is noted that this ether-based electrolyte presents an enlarged electrochemical window up to 4.6 V resulting from the enhanced oxidative stability by introducing FEC. Meanwhile, the interphase layers effectively improve the Li plating/stripping kinetics and interface stability. Besides, in situ FTIR, Raman spectra and theoretical calculations are used to confirm the solvation interactions. And the inorganic/organic composite fluorinated interphase layer component is verified by X-ray photoelectron spectroscopy (XPS) spectra. Using this ether-based electrolyte, the Li/Cu cells present colossal Li deposits with a high coulombic efficiency (≈98.95%). More significantly, the 4.4 V Li/LiCoO₂ battery exhibits excellent cycling stability with a capacity retention of 80% over 300 cycles. This work offers a promising approach to enable ether-based electrolytes for high-voltage Li metal batteries (LMBs).