Ion Transport in Single-Ion Conducting Polymer Electrolytes for Lithium Batteries

Abstract

Electrochemical energy storage devices are increasingly desired for consumer vehicle electrification and renewable power utilization. Safety and performance of batteries is strongly dictated by the performance of the electrolyte. Polymer electrolytes offer advantages over liquid and inorganic solid-state electrolytes, as they are non-leakable and non-volatile, yet flexible. Single-ion conducting electrolytes that eliminate ion concentration gradients offer further advantages: greater electrochemical stability allowing for higher voltage cells, lower interfacial impedance, and higher theoretical charge/discharge rates. Single-ion conducting polymer electrolytes may simply be created by titration of an ionomer with the active ion – Li+ in a Li-ion battery, for example. Unfortunately, the drastically low ionic conductivity of single-ion conducting polymer electrolytes without added solvent has precluded their commercial application thus far. Improved understanding of lithium ion transport mechanisms is critical for the development of high performance electrolytes. Our efforts in this area are focused on understanding ion states and ion transport in two distinct classes of single-ion conducting polymers. The first class of materials of interest are polyethers with highly dissociable tethered anions, where the research focus is to understand ion-pair dissociation and ion states that contribute to conduction. The second class of materials of interest are ionomers with solely non-polar polymer components, where we aim to understand ion transport through ionic domains.