  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.
