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Synthesis of Ionic Liquid Based Electrolytes, Assembly of Li-ion Batteries, and Measurements of Performance at High Temperature
Published on: December 20, 2016
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Evaluating the contributions to conductivity in room temperature ionic liquids
Emily D Simonis1, G J Blanchard1
1Michigan State University, Department of Chemistry, 578 S. Shaw Lane, East Lansing, MI 48824, USA. blanchard@chemistry.msu.edu.
Physical Chemistry Chemical Physics : PCCP
|June 5, 2024
Summary
Room temperature ionic liquids exhibit conductivity beyond simple ion diffusion. This study reveals that ion diffusion accounts for about 50% of conductivity in BMIM TFSI, suggesting other mechanisms contribute to excess conductivity.
Area of Science:
- Physical Chemistry
- Materials Science
- Electrochemistry
Background:
- The Nernst-Einstein equation inadequately describes ionic liquid conductivity, as it only considers Brownian motion.
- Ionic liquids (ILs) possess unique properties making them suitable for various applications.
- Understanding charge transport mechanisms in ILs is crucial for optimizing their performance.
Purpose of the Study:
- To investigate the conductivity of 1-butyl-3-methylimidazolum bis(trifluoromethylsulfonyl) imide (BMIM TFSI).
- To compare the conductivity of BMIM TFSI with the diffusion coefficients of its ions across various length scales.
- To elucidate the mechanisms contributing to the observed conductivity in ionic liquids.
Main Methods:
- Utilized time-resolved fluorescence depolarization and fluorescence recovery after photobleaching (FRAP) techniques.
- Measured diffusion constants of cationic and anionic species in BMIM TFSI.
- Correlated ion diffusion data with the bulk conductivity of the ionic liquid.
Main Results:
- Demonstrated that diffusional contribution to molar conductivity in BMIM TFSI is approximately 50%.
- Identified a significant "excess" molar conductivity beyond that explained by ion diffusion.
- Provided experimental evidence for multiple charge transport mechanisms in ionic liquids.
Conclusions:
- Ion diffusion accounts for only half of the conductivity in BMIM TFSI.
- An additional, unidentified mechanism contributes to the "excess" conductivity in ionic liquids.
- Further research is needed to fully characterize the non-diffusional charge transport pathways in RTILs.
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