Binary Solvent-Induced Microheterogeneous Structural Stability and Ion Pairing Thermodynamics of Fluorinated Li-Ion Battery Electrolyte.

Classical molecular dynamics simulations are performed to examine the structure and transport properties of fluorinated electrolytes containing trifluoropropylene carbonate (TFPC) and ethyl methyl carbonate (EMC) solvent of 1 M LiPF₆ solution at different temperatures. Structural analysis employing radial distribution function (RDF), coordination number (CN), and spatial distribution function (SDF) calculation is carried out. This work presents both qualitative and quantitative information on different interactions from the structural analysis. Ion-cluster analysis reveals the presence of different microstructures in the solution. The stability of microstructures is studied using the potential of mean force (PMF) calculation. The solvent-separated ion pairs (SSIPs) are more stable than contact ion pairs (CIPs). We quantified the heterogeneity in dynamics by calculating non-Gaussian parameters. Ionic conductivities are calculated using the current autocorrelation function and compared with experiments for all temperatures. The calculated ion cages' lifetime and relaxation time determine which ion-ion/solvent interactions are the most and least lived at different temperatures. The most robust interaction for Li⁺-EMC is found. The correlation between conductivity and lifetime is found at all studied temperatures. The outcome revealed by the current work will help us understand the underlying mechanism of ionic transport and the atomistic details of solvation structure.