Chain-like Structures Facilitate Li+ Transport in Concentrated Aqueous Electrolytes: Insights from Ultrafast Infrared Spectroscopy and Molecular Dynamics Simulations

Highly concentrated aqueous electrolytes have attractedattentiondue to their unique applications in lithium ion batteries (LIBs).However, the solvation structure and transport mechanism of Li+ cations at concentrated concentrations remain largely unexplored.To address this gap in knowledge, we employ ultrafast infrared spectroscopyand molecular dynamics (MD) simulations to reveal the dynamic andspatial structural heterogeneity in aqueous lithium chloride (LiCl)solutions. The coupling between the reorientation dynamics of theextrinsic probe and the macroscopic viscosity in aqueous LiCl solutionswas analyzed using the Stokes-Einstein-Debye (SED) equations.MD simulations reveal that the Cl- and Li+ form chain-like structures through electrostatic interactions, supportingthe vehicular migration of Li+ through the chain-like structure.The concentration dependent conductivity of the LiCl solution is wellreproduced, where Li(H2O)(2) (+) and Li(H2O)(3) (+) are the dominant species that contributeto the conduction of Li+. This study is expected to establishcorrelations between ion pair structures and macroscopic properties.