PNNL

Abstract

Aqueous electrolytes composed of 0.1 M Zn(TFSI)2 and acetonitrile (ACN) additive were studied using combined experimental and simulation techniques. The electrolyte was found electrochemically stable when the ACN V% is higher than 74.4. In addition, it was found that the ionic conductivity of the mixed solvent electrolytes changes as a function of ACN composition and a maximum was observed at 91.7 V% of ACN although the salt concentration is the same. This behavior was qualitatively reproduced by molecular dynamics (MD) simulations. Detailed analyses based on experiments and MD simulations show that, at high ACN composition, the water network existing in the high water composition solutions breaks. As a result, the screening effect of the solvent weakens and the correlation among ions increases, which causes the decrease in ionic conductivity at high ACN V%. The studys provide fundamental understanding of this complex mixed solvent electrolyte system.