Revealing the Charge Transport Mechanism in Polymerized Ionic Liquids: Insight from High Pressure Conductivity Studies

Polymerized ionic liquids (polylLs), composed mostly of organic ions covalently bonded to the polymer backbone and free counterions, are considered as ideal electrolytes for various electrochemical devices, including fuel cells, supercapacitors, and batteries. Despite large structural diversity of these systems, all of them reveal a universal but poorly understood feature: a charge transport faster than the segmental dynamics. To address this issue, we studied three novel polymer electrolyte membranes for fuel cells as well as four single-ion conductors, including highly conductive siloxane-based polyIL. Our ambient and high pressure studies revealed fundamental differences in the conducting properties of the examined systems. We demonstrate that the proposed methodology is a powerful tool to identify the charge transport mechanism in polylLs in general and thereby contribute to unraveling the microscopic nature of the decoupling phenomenon in these materials.