Mechanoelectrical Conversion in Highly Ionic Conductive Solid-State Polymer Electrolyte Membranes

A novel phenomenon of mechanoelectrical conversion in a flexible solid-state polymer electrolyte membrane (PEM) is presented, hereafter denoted as flexoelectric effect. The flexoelectric coefficient (approximate to 323 mu Cm-1), that is, a measure of the converted mechanoelectrical energy, is the highest among all flexoelectric materials hitherto reported. It is proposed in this work that the flexoelectricity in PEMs operates based on electrical energy generation driven by ion polarization/depolarization across the PEM subjected to a pressure gradient during bending. Of particular interest is the phenomenon of polarity switching during bending, that is, reversal of the polarization direction with increasing succinonitrile (SCN) concentration (i.e., 10-20 wt%). The size disparity between the solvated cations and anions is attributed as the key factor in determining the polarization direction, which is responsible for the polarity switching. Of particular importance is that the present flexoelectric PEM itself is a key component of the solid-state lithium ion battery and thus their integration opens up a new avenue for energy harvesting and storage devices.