Ionic Liquid Electrolyte Technologies for High-Temperature Lithium Battery Systems

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Commercial lithium-ion batteries (LIBs) face operational temperature limitations, typically below 60 °C, due to safety concerns and degradation issues associated with conventional organic electrolytes and unstable lithium salts.
• High-temperature applications demand advanced energy storage solutions that can reliably operate under extreme thermal conditions, exceeding the capabilities of current LIB technology.

Purpose of the Study:

• To develop and evaluate novel electrolyte formulations for high-temperature LIBs using safer ionic liquids (ILs).
• To investigate the thermal stability, ion transport properties, and electrochemical performance of selected IL-based electrolytes at elevated temperatures.

Main Methods:

• Synthesis and characterization of ionic liquids based on tetrabutylphosphonium and 1-ethyl-3-methyl-imidazolium cations with per(fluoroalkylsulfonyl)imide anions.
• Evaluation of thermal behavior, ionic conductivity, and electrochemical stability window (anodic stability) at temperatures up to 100 °C.
• Performance testing of Li/LiFePO4 cells at 100 °C using the developed IL electrolytes.

Main Results:

• Ionic liquids demonstrated remarkable thermal robustness exceeding 150 °C and anodic stability above 4.5 V at 100 °C.
• Conductivity measurements showed significant ion transport properties between 10⁻³ and 10⁻² S cm⁻¹ at 100 °C.
• Li/LiFePO4 cells cycled at 100 °C delivered over 94% of theoretical capacity at 0.5C, indicating promising performance.

Conclusions:

• The studied ionic liquid electrolytes exhibit excellent thermal stability and electrochemical performance suitable for high-temperature LIB applications.
• These advanced electrolyte formulations represent a promising alternative to conventional electrolytes for demanding energy storage systems operating at elevated temperatures.