A Fully Methylated Cyclic Ether Solvent Enables Graphite Anode Cycling at Low Temperatures

Area of Science:

• Electrochemistry
• Materials Science
• Energy Storage

Background:

• Lithium-ion batteries (LIBs) face significant capacity loss and polarization at low temperatures.
• This is due to high Li+ desolvation energy barriers and slow Li+ transfer across the solid electrolyte interface (SEI).

Purpose of the Study:

• To design an electrolyte that stabilizes the graphite anode interface and enhances reaction kinetics at low temperatures.
• To achieve improved low-temperature performance in LIBs through electrolyte engineering.

Main Methods:

• Developed a highly ionic conductive electrolyte using 2,2,4,4,5,5-hexamethyl-1,3-dioxolane (HMD) and fluoroethylene carbonate (FEC).
• Investigated the electrolyte's solvation structure and its effect on Li+ desolvation and SEI formation.
• Tested the performance of Li||graphite cells with the new electrolyte under low-temperature conditions.

Main Results:

• The HMD-based electrolyte formed an anion-dominated solvation structure, accelerating Li+ desolvation.
• A LiF-rich SEI layer was formed, preventing solvent co-intercalation and improving ion migration.
• Cells with the new electrolyte showed 93.8% capacity retention over 227 cycles and 81% retention after 200 cycles at -20 °C, outperforming conventional electrolytes.

Conclusions:

• Anion-dominated solvation electrolytes offer a promising strategy for low-temperature LIBs.
• The designed HMD/FEC electrolyte significantly enhances graphite anode performance under cold conditions.
• This work provides valuable insights for designing advanced electrolytes for low-temperature energy storage applications.