All-Cyclic-Solvent Electrolyte Design Enables Ultra-Low-Temperature and Fast-Charging Sodium-Ion Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Chemical Engineering

Background:

• Conventional sodium-ion battery (SIB) electrolytes face challenges like solvent crystallization and slow ion transport at low temperatures.
• Current electrolytes often use mixed cyclic and linear carbonates, limiting SIB performance in cold conditions.

Purpose of the Study:

• To develop a low-cost, all-cyclic-solvent electrolyte for SIBs.
• To enhance Na+ transport and suppress crystallization for improved low-temperature performance and fast charging.

Main Methods:

• Systematically reconstructing Na+ solvation structure by introducing cyclic ethers (THF, CPME) into cyclic carbonates (PC, EC).
• Investigating competitive coordination between high-polarity and low-polarity cyclic ethers to create an anion-rich solvation environment.
• Evaluating electrolyte properties including ionic conductivity, freezing point, and interfacial stability.

Main Results:

• Achieved an ultralow freezing point (< -130°C) and high ionic conductivity.
• Demonstrated ultra-fast charging (89.9 mAh g-1 at 50C) and excellent low-temperature performance (57% capacity retention at -70°C).
• Exhibited ultra-long cycling stability (>10000 cycles) and validated practical applicability in 26700 cylindrical cells.

Conclusions:

• The developed all-cyclic-solvent electrolyte overcomes critical low-temperature limitations of SIBs.
• This strategy offers a universal approach for low-cost, fast-charging, and ultralow-temperature SIBs.
• The electrolyte design ensures high safety under various abuse conditions.