Modulating Interfacial Solvent Aggregation Chemistry to Enable Low-Temperature Sodium-Ion Battery.

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Sodium-ion batteries (SIBs) are promising for energy storage but struggle with performance at low temperatures.
• Interfacial dynamics, particularly solvent aggregation in the inner Helmholtz plane (IHP), hinder stable operation by forming sluggish solid-electrolyte interphases (SEIs).

Purpose of the Study:

• To investigate and overcome the limitations of SIBs operating at low temperatures.
• To develop a strategy for stabilizing the solid-electrolyte interphase (SEI) and improving Na+ diffusion kinetics at sub-zero temperatures.

Main Methods:

• Utilizing polarization interactions between solvent molecules and free radicals to break solvent aggregation.
• Employing trimethylsilyl trifluoromethanesulfonate (TMSOTF) as an electric double-layer regulator to modify interfacial properties.
• Testing commercial hard carbon anodes with TMSOTF-modified electrolytes at -40 °C.

Main Results:

• The proposed method effectively breaks solvent aggregation, reduces molecular polarity, and promotes interfacial restructuring.
• Formation of an inorganic-rich SEI layer, enhancing mass transfer and Na+ diffusion kinetics.
• SIBs with TMSOTF-based electrolytes demonstrated over 2400 cycles at -40 °C, significantly outperforming conventional electrolytes.

Conclusions:

• Leveraging orbital overlap and radical generation is a viable strategy for low-temperature SIB interfacial engineering.
• TMSOTF acts as an effective electric double-layer regulator, enabling stable SIB operation at extreme sub-zero temperatures.
• This research offers critical insights for designing advanced electrolytes for reliable cold-weather energy storage solutions.