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Published on: December 20, 2016
Cation electrochemical stability in chloroaluminate ionic liquids
Christopher M Lang1, Ketack Kim, Liezel Guerra
1School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332-0100, USA.
The Journal of Physical Chemistry. B
|July 21, 2006
Summary
The electrochemical stability of organic cations in ionic liquids was studied. Cyclic pyrrolidinium cations were less stable in chloroaluminate ionic liquids, forming insoluble deposits, unlike benzyl- and butyl-substituted cations.
Area of Science:
- Electrochemistry
- Materials Science
- Ionic Liquids
Background:
- Ionic liquids (ILs) are promising electrolytes for various electrochemical applications.
- Understanding the electrochemical stability of organic cations within ILs is crucial for designing stable electrochemical systems.
- Acetonitrile (ACN) and chloroaluminate ILs are common solvents/media for studying IL properties.
Purpose of the Study:
- To investigate the electrochemical stability of ten organic cations as solutes in acetonitrile (ACN).
- To compare the stability of specific salts (BenMe2EtNCl, 1-butyl-2-methyl pyrrolidinium chloride, and BuMe2ProNCl) in chloroaluminate ILs.
- To evaluate the suitability of these ILs for sodium-ion battery applications.
Main Methods:
- Electrochemical stability window determination for organic cations in ACN.
- Cyclic voltammetry and electrolysis of selected salts in chloroaluminate ILs.
- Mass spectrometry analysis before and after electrolysis to identify decomposition products.
- Melting point determination of specific ILs.
Main Results:
- Benzyl-substituted cations were more easily reduced than alkyl-substituted cations due to benzyl group leaving ability.
- In ACN, the cyclic pyrrolidinium salt (VI) exhibited the highest reduction potential, indicating greater stability.
- In chloroaluminate ILs, pyrrolidinium cations (VI and VII) were more easily reduced, forming insoluble black deposits, unlike salts III and VII which produced low-molecular-weight products.
- The IL of salt VII demonstrated superior stability in the presence of sodium, with higher Coulombic efficiency for sodium ion reduction (94.1%) compared to salt VI (87.2%).
Conclusions:
- Electrochemical stability of organic cations is influenced by their structure and the IL medium.
- Pyrrolidinium cations, while stable in ACN, decompose in chloroaluminate ILs, forming insoluble products and hindering sodium-ion cycling.
- Benzyl- and butyl-substituted cations are more suitable for sodium-ion applications in chloroaluminate ILs due to their decomposition pathways and stability.
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