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Adding salt to expand voltage window of humid ionic liquids
Ming Chen1, Jiedu Wu2, Ting Ye1
1State Key Laboratory of Coal Combustion, School of Energy and Power Engineering, Huazhong University of Science and Technology (HUST), 430074, Wuhan, China.
Nature Communications
|November 17, 2020
Summary
Adding lithium salt to humid ionic liquids pushes water away from electrodes. Remaining water binds to lithium ions, preventing water electrolysis and widening electrochemical windows for better electrolyte performance.
Area of Science:
- Electrochemistry
- Materials Science
- Computational Chemistry
Background:
- Humid hydrophobic ionic liquids are crucial electrolytes.
- Water presence narrows their electrochemical windows.
- Electrolysis involving surface-adsorbed water is the cause.
Purpose of the Study:
- Investigate the effect of adding lithium salt to humid ionic liquids.
- Understand the impact on water adsorbed on electrode surfaces.
- Develop a method to protect ionic liquid electrolytes.
Main Methods:
- Molecular dynamics simulations.
- Cyclic voltammetry measurements.
Main Results:
- Lithium salt addition displaces most water from electrode surfaces.
- Remaining water molecules bind strongly to Li+ ions, reducing their activity.
- This Li+-water interaction inhibits water electrolysis.
- Electrochemical windows of humid ionic liquids are enlarged.
Conclusions:
- Lithium salt addition is a practical approach to prevent electrochemical performance degradation in humid ionic liquids.
- The mechanism involves Li+-water complexation and surface water re-arrangement.
- This strategy enhances the stability and utility of ionic liquids as electrolytes.
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