Adding salt to expand voltage window of humid ionic liquids

Ming Chen, Jiedu Wu, Ting Ye, Jinyu Ye, Sheng Bi, Jiawei Yan, Bingwei Mao, Guang Feng

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Received Date: 12th February 20

Humid hydrophobic ionic liquids, widely used as electrolytes, have narrowed electrochemical windows, because their water, absorbed on the electrode surface, gets involved in electrolysis. In this work, we performed molecular dynamics simulations to explore effects of adding Li-salt in humid ionic liquids on the water adsorbed on the electrode surface. Results reveal that most of water molecules are pushed away from both cathode and anode, by adding salt. The water remained on the electrode is almost bound with Li+, which has significantly lowered activity. The Li+-bonding and re-arrangement of the surface-adsorbed water both facilitate the inhibition of water electrolysis, and thus prevent the reduction of electrochemical windows of humid hydrophobic ionic liquids. This finding is testified by cyclic voltammetry measurements where salt-in-humid ionic liquids exhibit enhanced electrochemical windows. Our work provides the underlying mechanism and a simple but practical approach for protection of humid ionic liquids from performance degradation.

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This is an abstract of a preprint hosted on an independent third party site. It has not been peer reviewed but is currently under consideration at Nature Communications.

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