Designing Temperature-Insensitive Solvated Electrolytes for Low-Temperature Lithium Metal Batteries

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Lithium metal batteries (LMBs) suffer from poor low-temperature performance due to sluggish interfacial charge transfer and parasitic reactions.
• The high electronegativity of oxygen donor solvents in electrolytes exacerbates these issues, limiting reversibility and kinetics.

Purpose of the Study:

• To develop a novel electrolyte strategy for enhancing the low-temperature performance of LMBs.
• To address the challenges of interfacial instability and slow ion transport in cold conditions.

Main Methods:

• Introduction of a nonsolvating cosolvent to reduce the electronegativity of ether solvents.
• Design of an anion-aggregated electrolyte with a temperature-insensitive solvation structure for Li+ ions.
• Testing of LiFePO4||Li cells and pouch cells at various temperatures.

Main Results:

• The new electrolyte significantly accelerates Li+ desolvation and improves interfacial stability.
• High average Coulombic efficiency was achieved for lithium metal anodes at room temperature and -20 °C.
• LiFePO4||Li cells demonstrated 100% capacity retention over 150 cycles across a temperature range.
• Practical 1 Ah pouch cells maintained significant capacity at -20 °C (81%) and -40 °C (61%).

Conclusions:

• Electronegativity regulation of solvation structures offers a viable approach for developing advanced low-temperature electrolytes.
• The developed anion-aggregated electrolyte enables stable and efficient operation of lithium metal batteries at sub-zero temperatures.
• This strategy provides a new pathway for overcoming critical barriers in cold-weather energy storage applications.