(680e) Ion Transport Properties of Ultra-Thin Film Polymer Electrolytes
AIChE Annual Meeting
2018
2018 AIChE Annual Meeting
Materials Engineering and Sciences Division
Polymers for Energy Storage and Conversion
Thursday, November 1, 2018 - 1:45pm to 2:00pm
In this work, we report the fabrication, structure and ion transport characteristics of ultra-thin films through a model system of poly(ethylene oxide) PEO and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) blends as a function of salt concentration, temperature and film thickness. PEO-LiTFSI ultrathin films are fabricated on top of a grafted PEO brush layer to circumvent thin film dewetting effect on substrates. Ion transport measurements were successfully performed using electrochemical impedance spectroscopy on PEO-LiTFSI ultra-thin films fabricated on top of custom-designed nanofabricated interdigitated electrode (IDE) devices. The thin film conductivity is found to increase from r = 0.01 to 0.05 but reduces for r equal or larger than 0.05, consistent with the well-established Vogel-Tammann-Fulcher (VTF) model for ion transport. Importantly, thickness dependence study of ion transport shows a monotonic decrease in PEO-LiTFSI thin film conductivity fabricated on the grafted PEO brush upon decreasing film thickness from 250 nm to ca. 10 nm, and the effect is stronger at low salt concentrations. The decrease of ionic conductivity at thinner films originate from the increasing fraction of the immobilized layer near the polymer/substrate interface. Our results suggest that using thin film configuration is a promising strategy to probe morphological and interfacial effects on ion conducting mechanism of polymer electrolytes.