Relationship of the Molecular Structure and Transport Properties of Imide-Based Lithium Salts of "Acetonitrile/Water-in-Salt" Electrolytes

XY Liu and SC Lee and S Seifert and RE Winans and Y Z and T Li, CHEMISTRY OF MATERIALS, 35, 6415-6422 (2023).

DOI: 10.1021/acs.chemmater.3c01148

"Water-in-salt" (WIS) electrolytes exhibitexcellentsafety and electrochemical performance. However, they possess highconcentrations, relatively low diffusion coefficient, and high viscosity."Acetonitrile/water in salt" (AWIS) electrolytes canovercome the disadvantages of WIS electrolytes. Under relatively lowconcentrations, AWIS electrolytes show good electrochemical performancecomparable to WIS electrolytes and low conductivity. Herein, we investigatethe relationship between the solvation structures and the transportproperties using small-angle X-ray scattering and molecular dynamicssimulation. We observed two solvation behaviors of AWIS: anions dissolvedin acetonitrile forming small acetonitrile/anion clusters and additionalwater further dissolving the small acetonitrile/anion clusters. Theintroduction of acetonitrile weakens the water-solute interactionand enhances the cation-anion interaction, which results inan enhanced dynamical slowdown as the concentration increases. Thiswork provides molecular-level understanding of the connection betweentwo- stage solvation structures and transport properties for imide- basedlithium salt solutions.

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