A Weak-Aggregation Electrolyte Enables Lithium-Ion Capacitors at Ultra-Low Temperature

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Extreme cold environments necessitate advanced energy storage devices (ESDs).
• Conventional electrolytes fail at ultra-low temperatures (-100°C) due to poor ion transport and interfacial instability.
• Existing ESDs struggle with performance degradation in sub-zero conditions.

Purpose of the Study:

• To design a novel electrolyte for stable and efficient electrochemical energy storage at ultra-low temperatures (ULT).
• To overcome the limitations of conventional electrolytes in extreme cold environments.
• To enable reliable operation of ESDs in demanding applications like space exploration and polar research.

Main Methods:

• Development of a weak-aggregation (AGG-w) electrolyte incorporating a unilaterally fluorinated motif.
• Molecular engineering to enhance steric hindrance and reconfigure molecular dipoles for improved solvent-anion interactions.
• Characterization of ion transport, interfacial kinetics, viscosity, and ionic conductivity at ULT.
• Testing of 1100 F pouch cells under extreme cold conditions (-40°C and -100°C).

Main Results:

• The AGG-w electrolyte demonstrates reconciled bulk-phase ion transport and interfacial kinetics at ULT.
• Enhanced solvent-anion cooperativity accelerates desolvation kinetics and reduces interfacial resistance.
• The electrolyte maintains low viscosity and high ionic conductivity at ULT.
• 1100 F pouch cells show 97.9% capacity retention after 7 months at -40°C and achieve discharge capability at -100°C.

Conclusions:

• Weak-interaction engineering provides a critical paradigm for designing advanced electrolytes.
• The AGG-w electrolyte establishes a generalizable strategy for high-performance electrochemistry in extreme conditions.
• This work enables the development of robust ESDs for satellites, research stations, and other extreme cold applications.