Over the last 30 years it has been demonstrated that conductivity in ion-conducting materials occurs via a number of different processes including: (a) the migration of ions between coordination sites [2-5]; and (b) the diffusion of conformational states of the host matrix (segmental motion). [2-5]. In ion-conducting membranes the long-range charge migration is often correlated with the dielectric relaxation modes of the polymeric chains; the latter are typically associated with the fluctuation of: a) the main backbone chain bearing permanent dipole moments; b) side chains; or c) functional groups involved in ion-dipole interactions. The key technique to investigate the interplay between structure and conductivity of ion-conducting materials is Broadband Electrical Spectroscopy (BES).
Here we present several case studies of AEMs paying particular attention to their thermal stability and the thermomechanical properties. BES is then adopted to study the electrical response of each material in terms of polarizations and relaxation phenomena. The results allow us to: (a) suggest a comprehensive model capable to rationalize the long-range charge transfer mechanism in AEMs; and (b) clarify how the chemical composition and nanostructure of the materials is influencing the coordination of mobile species.
The authors thank the StrategicProject “From materials for Membrane electrode Assemblies to electric Energy conversion and SToRAge devices” (MAESTRA) of the University of Padova for funding this activity.
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