Intermolecular Attraction-Repulsion Forces Enable Self-Reinforcing Electrolytes for Wide-Temperature Sodium Metal...

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Stable performance of energy storage devices across wide temperature ranges is critical for applications in extreme environments.
• Simultaneously achieving high chemical stability and efficient ion transport at both high and low temperatures presents a significant challenge for electrolyte design.

Purpose of the Study:

• To develop a novel temperature-responsive electrolyte system that ensures stable electrochemical performance over a wide temperature range.
• To investigate the synergistic effects of dipole-dipole attraction and electrostatic repulsion between solvent molecules on electrolyte properties.

Main Methods:

• Engineered a novel electrolyte by combining cyclopentyl methyl ether (CPME) and tetrahydrofuran (THF) to enhance high-temperature stability via dipole-dipole attraction.
• Incorporated diethylene glycol dimethyl ether (DGM) to promote electrostatic repulsion, strengthening anion participation and improving low-temperature desolvation kinetics.
• Fabricated Na||Na3V2(PO4)3 (NVP) full cells and assembled a 420 mAh pouch cell to evaluate the electrolyte's performance across a wide temperature spectrum.

Main Results:

• The developed electrolyte demonstrated a stable Coulombic efficiency above 99.5% across the entire temperature range, reaching 99.9% at -20 °C and -40 °C.
• The Na||NVP full cell exhibited robust cycling stability, maintaining 97.2% capacity after 1200 cycles at -40 °C with a 2 C rate.
• The assembled pouch cell showed stable cycling performance at low temperatures, validating the electrolyte's practical applicability.

Conclusions:

• The proposed electrolyte system, through synergistic regulation of intermolecular forces, effectively addresses the challenge of wide-temperature-range stable operation.
• This approach offers a new strategy for designing advanced electrolytes by precisely controlling solvation structures via attractive and repulsive forces.
• The findings underscore the importance of molecular-level interactions in developing high-performance electrolytes for demanding energy storage applications.