THESIS
2016
xvi, 144 pages : illustrations ; 30 cm
Abstract
Oxide ionic conductors have found applications across many fields, including solid
oxide fuel cells (SOFCs) and solid-state batteries. While these oxides have many differences,
they often share similar conduction mechanisms. This dissertation will first study O ion
conductors with applications in SOFCs and then extend to Li solid electrolytes for batteries. O
ion conduction is one of the processes enabling the operation of SOFCs. It is therefore vital to
understand the O diffusion and its coupling with the oxygen catalysis at the active sites of the
materials that allows for O diffusion. In our study, oxygen transport properties are calculated
from molecular simulations, while the catalytic activity is assessed thanks to computational
descriptors. On the other hand, recent prog...[
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Oxide ionic conductors have found applications across many fields, including solid
oxide fuel cells (SOFCs) and solid-state batteries. While these oxides have many differences,
they often share similar conduction mechanisms. This dissertation will first study O ion
conductors with applications in SOFCs and then extend to Li solid electrolytes for batteries. O
ion conduction is one of the processes enabling the operation of SOFCs. It is therefore vital to
understand the O diffusion and its coupling with the oxygen catalysis at the active sites of the
materials that allows for O diffusion. In our study, oxygen transport properties are calculated
from molecular simulations, while the catalytic activity is assessed thanks to computational
descriptors. On the other hand, recent progress in the Li battery community has shown growing
interest in applying Li-conducting oxide ceramic material as the electrolytes in order to increase
the safety, boost the energy density, and extend the lifetime of the battery. In this dissertation,
several O ion conducting and Li ion conducting oxides are studied from primarily a
computational point of view and some experiments are carried out to support computational
findings. First, a series of BaFeO
3 derivatives are studied. Their ability to conduct O ions and
catalyze oxygen reduction at high temperature is assessed. Our results show remarkable
potential for inexpensive Fe-based materials as SOFC cathodes and open new possibilities for
catalysts design. Based on molecular dynamics simulations, we develop a data-mining
framework to analyze the diffusion patterns. We further extend this approach to study Li ion
diffusion in Li
7La
3Zr
2O
12. Hopping between different sites is determined to be the basic
principle underpinning ionic transport in both types of conductors. This work puts forward a
perspective of combining computational design with data science and experiments for the
analysis of functional materials.
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