Molecular dynamics study of propylene carbonate based concentrated electrolyte solutions for lithium ion batteries

Abstract

Concentrated electrolytes have displayed enhanced thermal and reactive stabilities, thus enabling development of safer lithium ion batteries (LIBs). Computational studies of the concentrated electrolytes are required to get better understanding of the physical phenomena responsible for the enhanced properties. Motivated by the improved cycle life of the LIBs made of propylene carbonate (PC) based concentrated electrolytes, we probe PC-LiPF6 (lithium hexafluorophosphate) electrolyte system for a range of concentrations up to 4 mol/kg using molecular dynamics simulation. Structural and dynamic properties of the system are affected by the salt concentration. Electrolyte tend to form contact-ion-pairs and multi-ion complexes at high concentration, thereby impacting the transport properties such as diffusivity and ionic conductivity. The rate of formation and disintegration of multi-ion complexes increases with concentration. Change in the molecular structure of the solution, especially composition of the lithium ion coordination shell, explains the improved stability features of the concentrated electrolytes reported in literature.