Structural and Transport Properties of Battery Electrolytes at Sub-zero Temperatures

Abstract

Lithium-ion batteries (LIBs) have become a core portable energy storage technology due to their high energy density, longevity, and affordability. Nevertheless, their use in low-temperature environments is challenging due to significant Li-metal plating and dendrite growth, sluggish Li-ion desolvation kinetics, and suppressed Li-ion transport. In this study, we employ classical molecular dynamics simulations to provide a mechanistic understanding of the impact of temperature- and concentration-effects on the ionic conductivity of the prototypical battery electrolyte lithium hexafluorophosphate in ethylene carbonate (LiPF6/EC). We further investigate the interplay between temperature and ionic speciation via a graph-based clustering analysis that resolves species-specific ionic conductivity contributions. Using these findings, we formulate two fundamental design principles governing electrolyte performance: one for ambient temperature and another for low-temperature conditions. The modeling framework outlined in this work provides a foundation for identifying design principles that can be used to rationally improve the low-temperature performance of LIBs.