Gelled Electrolyte Containing Phosphonium Ionic Liquids for Lithium-Ion Batteries

Area of Science:

• Materials Science
• Electrochemistry
• Polymer Chemistry

Background:

• Developing advanced electrolytes is crucial for enhancing lithium-ion battery performance.
• Ionic liquids offer unique properties but require suitable host matrices for practical applications.

Purpose of the Study:

• To synthesize and characterize novel gelled electrolytes based on phosphonium ionic liquids within an epoxy host network.
• To investigate the influence of these electrolytes on epoxy polymerization kinetics and final material properties.
• To evaluate the electrochemical performance of the prepared gelled electrolytes for lithium-ion battery applications.

Main Methods:

• Preparation of gelled electrolytes by mixing phosphonium ionic liquid (trihexyl(tetradecyl)phosphonium bis(trifluoromethane)sulfonimide) with a lithium salt and an epoxy prepolymer/amine hardener system.
• Characterization of thermal, thermo-mechanical, transport, and electrochemical properties.
• Assembly and testing of lithium-ion cells (Li|LiFePO₄) to assess cycle stability.

Main Results:

• Gelled electrolytes exhibit excellent thermal stability (>300 °C) and good thermo-mechanical properties.
• Achieved an ionic conductivity of 0.13 mS·cm⁻¹ at 100 °C.
• Demonstrated electrochemical stability of 3.95 V vs. Li⁰/Li⁺.
• Assembled Li|LiFePO₄ cells showed stable cycling performance over 30 cycles.

Conclusions:

• The developed gelled electrolytes, incorporating phosphonium ionic liquids in an epoxy network, present a promising alternative for advanced lithium-ion batteries.
• The study highlights the significant impact of electrolyte composition on polymerization kinetics and final material properties.
• These electrolytes offer a favorable combination of thermal stability, mechanical integrity, and electrochemical performance.