Monofluorinated acetal electrolyte for high-performance lithium metal batteries

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Highly fluorinated ether electrolytes enhance lithium metal battery stability via SEI formation and oxidative stability.
• Challenges include sluggish ion transport and environmental concerns associated with high fluorination.

Purpose of the Study:

• To introduce and evaluate bis(2-fluoroethoxy)methane (F2DEM), a novel, less fluorinated ether electrolyte.
• To assess F2DEM's performance in lithium metal batteries compared to traditional electrolytes.

Main Methods:

• Electrochemical testing of Li||Cu half cells and anode-free LiFePO4 pouch cells.
• Comparative analysis with diethoxymethane (DEM) and F5DEE electrolytes.
• Mechanism investigation using XPS, SEM, cryo-EM, FIB, EIS, and GC.

Main Results:

• F2DEM demonstrates high coulombic efficiency and stable cycling, even under fast lithium plating.
• Lower overpotential and improved energy efficiency observed with F2DEM.
• Enhanced capacity retention in LiFePO4 cells and improved lithium deposition morphology with reduced dead lithium.

Conclusions:

• F2DEM offers a promising, less fluorinated electrolyte for stable and efficient lithium metal batteries.
• Its performance advantages are particularly evident under high-rate conditions and in practical cell configurations.