Selecting the Optimal Fluorinated Ether Co-Solvent for Lithium Metal Batteries

Area of Science:

• Electrochemistry
• Materials Science
• Organic Chemistry

Background:

• Fluorinated ethers (FEs) are explored as co-solvents to enhance lithium metal battery performance.
• Understanding the structure-property relationships of FEs is crucial for electrolyte design.

Purpose of the Study:

• To investigate the impact of FE co-solvent structure on the electrochemical performance of lithium metal batteries.
• To identify promising FE co-solvents for improved battery cycling and low-temperature operation.

Main Methods:

• Synthesized and characterized three FEs: FEE, TTE, and OFDEE.
• Evaluated electrolyte performance in Li||NMC622 cells using electrochemical techniques.
• Utilized FTIR, multi-dimensional NMR, and Sand's model to analyze structure-electrolyte-performance correlations.

Main Results:

• Electrolyte performance followed the order: FEE > TTE > OFDEE.
• FEE demonstrated excellent cycling stability and significantly improved low-temperature performance.
• Relative Sand's time correlated with electrolyte diffusion behavior and battery performance.

Conclusions:

• 1,1,2,2-tetrafluoro-1-(2,2,2-trifluoroethoxy)ethane (FEE) is a promising co-solvent for lithium metal batteries.
• FEE enhances low-temperature performance due to its non-solvating nature, low viscosity, and non-flammability.
• The LiPF6-FEC-DMC-FEE electrolyte enables stable lithium metal battery cycling across various temperatures.