Ion dynamics and charge transport in ultrathin films of polymerized ionic liquids

University Of Tennessee Knoxville, Knoxville TN

Investigators

Abstract

NON-TECHNICAL SUMMARY: The rising energy needs of the modern society continue to provide a significant impetus for extensive research and development in energy storage devices. Polymer electrolytes play a key role in these devices. This project will employ specialized electrical experiments to gain deeper understanding of the impact of the confinement of the molecules within extrememly thin films and their interactions with surfaces on their electrical and mechanical properties. This fundamental understanding will be useful in guiding the design of novel functional polymer electrolytes with desirable properties for sustainable technologies, including polymerized ionic liquids for portable batteries, solar cells, fuel cells, actuators, field-effect transistors, and electrochromic devices. The information regarding the interplay between molecular structure, polymer/substrate interactions, ion transport and dynamics in thin films of polymerized ionic liquids gained from this work will be beneficial not only within the field of ionic liquids but also to the polymer science and engineering scientific communities. An important component of this project also involves several integrated educational activities. The project will contribute to training and education of specialists in polymer nanotechnology and materials science through active involvement of graduate and undergraduate students in this research. This integrated research/educational program also emphasizes work with underrepresented groups and outreach to K-12 students. TECHNICAL SUMMARY: Polymerized ionic liquids are a novel class of functional polymers that combine the unique physicochemical properties of molecular ionic liquids (e.g. wide electrochemical windows, negligible vapor pressures, and ionic conduction) with the outstanding mechanical characteristics of polymers. These materials are promising for a variety of applications including dye-sensitized solar cells, portable batteries, actuators, field-effect transistors and electrochromic devices. Many of these technologies involve the use of polymerized ionic liquids confined in one dimension as thin films. However, fundamental understanding of the impact of one-dimensional nanoscale confinement on ion transport and dynamics in polymerized ionic liquids is still very limited. The main goal of this research is to unravel the mechanisms controlling charge transport and ion dynamics in ultrathin films of polymerized ionic liquids. The project will focus on: (i) investigating the impact of film thickness on ion conduction and dynamics in polymerized ionic liquids, (ii) unraveling the role of the polymer/substrate interactions on ion transport and dynamics, and (iii) investigating the role of chemical composition/structure on ion dynamics and charge transport in thin films of polymerized ionic liquids. The research will primarialy utilize broadband dielectric spectroscopy measurements of thin polymer films using a recently developed electrode configuration featuring silica nanostructures and an air gap. The detailed fundamental understanding of the impact of one-dimensional confinement on ion transport and dynamics gained in these studies will provide a firm scientific basis for design of more efficient polymer electrolytes suitable for potential use in electrochemical power sources and devices.