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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
Phase behaviour, transport properties, and interactions in Li-salt doped ionic liquids
Jagath Pitawala1, Jae-Kwang Kim, Per Jacobsson
1Department of Applied Physics, Chalmers University of Technology, Göteborg, Sweden.
Faraday Discussions
|March 30, 2012
Summary
Doping dicationic ionic liquids (DILs) with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) shows a lower impact on glass transition temperature and ionic conductivity compared to traditional ionic liquids. This is linked to a distinct Li-ion coordination environment.
Area of Science:
- Materials Science
- Electrochemistry
- Physical Chemistry
Background:
- Ionic liquids (ILs) are promising electrolytes for electrochemical applications.
- Dicationic ionic liquids (DILs) offer unique properties due to their dual cations.
- Understanding the effect of salt doping on DILs is crucial for electrolyte design.
Purpose of the Study:
- To investigate the influence of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) doping on the properties of dicationic ionic liquids (DILs).
- To compare the behavior of DILs with LiTFSI to traditional mono-cationic ionic liquids.
- To elucidate the relationship between Li-ion coordination, glass transition temperature (Tg), and ionic conductivity in DILs.
Main Methods:
- Synthesis and characterization of DILs with TFSI anions.
- Preparation of homogeneous DIL/LiTFSI mixtures across a wide concentration range.
- Measurement of glass transition temperature (Tg) and ionic conductivity.
- Raman spectroscopy to determine Li-ion coordination number.
Main Results:
- Increasing LiTFSI concentration increased Tg and decreased ionic conductivity in DILs.
- The influence of LiTFSI doping on Tg and conductivity was significantly lower in DILs compared to mono-cationic ILs.
- Lower average coordination number of TFSI anions around Li-ions was observed in DILs.
- Tg-scaled Arrhenius plots revealed consistent temperature dependence of ionic conductivity, indicating viscosity-dominated conduction.
Conclusions:
- DILs exhibit a more stable ionic environment upon salt doping compared to mono-cationic ILs.
- The local Li-ion environment plays a critical role in governing the glass transition and ionic conduction in IL/salt mixtures.
- DILs are promising candidates for electrolytes where stability against salt concentration variations is desired.
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