Atomistic Simulations of Ternary Polymer Electrolytes Containing Ionic Liquids: Ion Transport and Viscoelastic Behavior

Influence of the BMIMPF$_6$ ionic liquid on ion transport and viscoelastic properties of ternary polymer electrolytes containing polyethylene oxide solvated with LiPF$_6$ salt and the underlying mechanisms are investigated. By employing atomistic molecular dynamics and trajectory extended kinetic Monte Carlo simulation techniques, we observe enhanced ionic mobilities and conductivities of the PEOLiPF$_6$-BMIMPF$_6$ ternary electrolytes upon the addition ionic liquid into the PEOLiPF$_6$ binary electrolyte. The dispersion of the BMIMPF$_6$ ionic liquid into the PEOLiPF$_6$ electrolyte is found to (a) promote dissociation of existing LiPF$_6$ ion-pairs and (b) slightly accelerate the polymer segmental dynamics. Together, these effects are observed to collectively give rise to an increase in ionic mobilities and conductivities of the ternary polymer electrolyte. On the other hand, Rouse analysis reveals that the storage and loss modulus of the ternary polymer electrolytes are coupled to their ion conducting properties.