Temperature-Robust Solvation Enabled by Solvent Interactions for Low-Temperature Sodium Metal Batteries

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Rechargeable metal batteries face challenges with organic electrolytes' temperature adaptability, particularly at low temperatures (LT).
• Traditional weakly solvation electrolytes (WSEs) exhibit temperature-sensitive solvation structures, limiting their LT performance.
• Anion participation in solvation is crucial but often leads to instability with temperature fluctuations.

Purpose of the Study:

• To develop an innovative electrolyte with a temperature-robust solvation structure for improved LT performance in rechargeable metal batteries.
• To overcome the limitations of traditional electrolytes susceptible to temperature variations.
• To enhance ionic conductivity and prevent salt precipitation at sub-zero temperatures.

Main Methods:

• Designed a novel electrolyte blending strong and weak solvents with controlled anion participation.
• Investigated the interplay between solvent molecules and their effect on solvation structure stability.
• Tested the electrolyte's ionic conductivity and electrochemical performance in Na3V2(PO4)3||Na cells at LT.

Main Results:

• Achieved an ionic conductivity of 3.12 mS cm⁻¹ at -40 °C.
• Demonstrated high reversible capacity (95.9 mAh g⁻¹ at -40 °C, 87.6% of room temperature capacity).
• Exhibited stable cycling performance: 3400 cycles with 98.2% retention at -20 °C (5 C) and 600 cycles with 96.1% retention at -40 °C (1 C).

Conclusions:

• The developed electrolyte exhibits excellent LT performance due to its temperature-robust solvation structure.
• Competitive coordination between solvents enhances ionic conductivity and prevents salt precipitation.
• Provides a new strategy for designing advanced LT electrolytes for energy storage applications.