Electric Field-Insensitive Solvation Chemistry Stabilizes High-Voltage Lithium Metal Batteries

Area of Science:

• Electrochemistry
• Materials Science
• Battery Technology

Background:

• Ether-based electrolytes are crucial for lithium metal batteries (LMBs).
• Electrolyte oxidation at high voltages limits LMB performance.
• Understanding and controlling solvent coordination at interfaces is key.

Purpose of the Study:

• To enhance the anodic stability of ether-based electrolytes for high-voltage LMBs.
• To develop a strategy for decoupling solvation dynamics from interfacial electric fields.
• To investigate the role of solvent-diluent interactions in electrolyte stability.

Main Methods:

• Identification of solvophilic diluents (SPDs) with strong solvent interaction energies (>3.3 kcal mol⁻¹).
• Design of electrolytes using diethylene glycol dimethyl ether (DEGDME) and SPDs to anchor solvent molecules.
• Characterization of electrolyte properties, including dipole moment reduction and electric field insensitivity.
• Electrochemical testing of Li||LiNi$_{0.8}$Co$_{0.1}$Mn$_{0.1}$O$_{2}$ cells at 4.7 V.

Main Results:

• Reinforced solvent-diluent interactions maintained Li⁺-solvent coordination integrity.
• Reduced uncoordinated solvents and decreased DEGDME dipole moment (<2.47 D).
• Achieved outstanding anodic stability with 80% capacity retention after 168 cycles in a 4.7 V-class cell.
• Demonstrated improved cycle life compared to conventional electrolytes.

Conclusions:

• Stabilizing solvation dynamics via strong solvent-diluent interactions enhances electrolyte anodic stability.
• Electric field-insensitive solvation environments are critical for high-voltage LMBs.
• This work provides a mechanistic framework for designing stable electrolytes for advanced energy storage.