Heterogeneous microstructures and dynamics of the Li-ion electrolyte with a fluorinated additive solvent from molecular dynamics simulations

Abstract

Electrolytes diluted with fluorinated solvents exhibit potential qualities for improved Li-ion battery performance. Tuning the characteristics and creating novel electrolytes for rechargeable batteries requires investigating the structure and Li-ion transport. In this study, we investigated the detailed structure and dynamics of an electrolyte containing lithium hexafluorophosphate (LiPF₆) in nonaqueous 3,3,3-trifluoropropylene carbonate (TFPC) in a wide range of temperatures (283.15–333.15 K) using classical molecular dynamics simulations. The analyzed results provide insights into the different microstructures, such as contact and solvent-separated ion pairs, and the effect of temperature on their existence in the electrolyte. The potential of mean force calculation shows the relative stability of microstructures consisting of ions and solvents. The diffusivity and conductivity were calculated to assess the ionic transport. The electrolyte's temperature-dependent transport properties and ion-cage dynamics have significance in understanding the atomistic details of a lithium-ion battery electrolyte. Overall, the dynamics of the electrolytes are facilitated by the balanced ion–ion and ion–solvent correlations with a vital contribution from electrostatic interactions. Our results indicate that the formation of microstructures in the fluorinated carbonate-based electrolyte shows appropriate dynamics to achieve the suitable diffusivity of the Li-ion battery electrolyte.