Localized Deep Eutectic Electrolytes for Durable 4.8 V Lithium Metal Batteries.

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Lithium-rich manganese-based oxide (LRMO) cathodes offer high energy density for advanced batteries.
• Conventional electrolytes struggle to form stable interfaces on LRMO cathodes and lithium metal anodes, limiting performance.
• Weak anion-solvent interactions in traditional electrolytes hinder robust interface formation.

Purpose of the Study:

• To design a novel electrolyte for lithium metal batteries that enhances interface stability and electrochemical performance.
• To overcome limitations of conventional electrolytes in supporting high-voltage LRMO cathodes and reactive lithium metal anodes.
• To enable higher energy density and longer cycle life in next-generation lithium metal batteries.

Main Methods:

• A localized deep eutectic electrolyte (LDEE) was engineered by incorporating a fluorinated ether diluent into a deep eutectic electrolyte (DEE).
• The diluent was shown to modify hydrogen bonding interactions, strengthening anion-solvent interactions and compacting solvation structures.
• Electrochemical performance and interface stability were evaluated in LRMO||Li metal batteries.

Main Results:

• The LDEE effectively suppressed parasitic reactions at the lithium anode and mitigated lattice-oxygen release from the LRMO cathode.
• Batteries utilizing LDEE maintained 80% capacity after 200 cycles within a 2-4.8 V voltage range.
• A 12.8 Ah LRMO||Li pouch cell demonstrated a high energy density of 616.2 Wh kg^-1 and passed safety tests.

Conclusions:

• The developed LDEE provides a viable strategy for achieving high energy density and long cycling stability in lithium metal batteries.
• Enhanced anion-solvent interactions and stabilized interfaces are key to the improved performance.
• This electrolyte design paves the way for next-generation high-performance energy storage systems.