The Effect of Host Incompatibility and Polarity Contrast on Ion Transport in Ternary Polymer-Polymer-Salt Blend Electrolytes

Conventional lithium-ion battery electrolytes are typically formed by blending high polarity and high mobility small-molecule components. These electrolytes tend to have ionic conductivities higher than those formed from either component alone. This is hypothesized to arise from a molecular-level synergy between miscible components. In short, molecular simulations have suggested that lithium ion solvation is dominated by the high polarity component. The solvated ions are then able to diffuse through a medium dominated by the high mobility component.

We hypothesize that similar effects can be seen in miscible polymeric blend electrolytes (PBEs) containing a high polarity and high mobility component. We have previously shown that increasing host polarity both improves solvation strength and slows dynamics. We thus investigate the role of changing the polarity of the nominally high polarity polymer on ionic conduction. Further, we study the influence of PBE miscibility on transport by varying the bare interaction parameter between polymer hosts. As hypothesized, we find that ionic conduction can be improved with increased miscibility and at intermediate levels of polarity contrast. We preliminarily investigate the effect of host molecular weight contrast on ionic transport.