The effect of ion exchange capacity on water uptake and ion transport in anion-conducting polyelectrolytes

Deconvoluting the relationship between material structure and properties including ionic conductivity, water uptake, and volume expansion, is the key to developing advanced electrochemical devices. One of the most fundamental challenges is to understand the role of ion exchange capacity in anion transport and water absorption at molecular level. In this work, we investigate bromide conducting thin films with different ion exchange capacities combining in situ RH generator-ellipsometer-QCM with electrochemical characterization on nano-fabricated interdigitated electrodes. Study shows ion exchange capacity decides different conductivity behaviors with respect to relative humidity. Solvation number and ion concentration are analyzed to provide insight into ion distribution and water molecule solvation structure. We conclude that the ion-to-ion distance and water solvation shell interaction are the underlying factors determining ion transport mechanisms. This work provides a strategy to design high-performance AEMs and paves the way for further ion transport studies.