Towards better understanding of atomic-scale ion migration processes in solid oxide electrolytes

Jacob Tarver (NIST/MML/MSED/Functional Polymers)

Polymers bearing ion-containing pendent groups, known as ionomers, are sought for energy applications due to their potential to serve as mechanically-robust electrolyte membranes capable of single-ion transport in batteries and fuel cells. Above the glass transition temperature of these materials, strong electrostatic interactions induce the aggregation of ionic clusters, the morphology of which has been shown to be controlled by the frequency of the ionic moiety along the polymer backbone and by the nature of the counter-ion. The mobility of the counter-ion is directly coupled to the mobility of the polymer host, and as a consequence, the dynamics of ion transport is strongly influenced by the structure of the ionic aggregate. This talk will discuss the use of quasielastic neutron scattering to characterize a set of precisely defined ionomers in which the frequency of an acrylic acid group's placement along a polyethylene backbone, and the extent of its neutralization to lithium acrylate, is rigidly controlled. At nanosecond timescales a single relaxation process is observed; measurements of picosecond dynamics reveal two additional processes. By following the thermal dependence of these processes, the roles that the distance between acrylate groups and that the extent of neutralization play on influencing dynamics is probed.

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