Structural study, computational analysis and structure-property correlations in anion conducting electrolytes for Solid Oxide Fuel Cells

Abstract

A combined experimental and theoretical approach has been used in order to investigate the local structural features that have an influence on ionic conductivity of IT-SOFC (Intermediate Temperature Solid Oxide Fuel Cell) electrolytes, in order to link the properties of these materials with their atomic and electronic structure. Doped delta-Bi2O3 and LaGaO3 electrolytes for AC-SOFC applications have been studied as model compounds for oxygen-ion diffusion in fluorite-like and perovskite-like materials, due to their incredibly high anion conductivity. A combined X-Ray Absorption Spectroscopy (XAS) and Density Functional Theory (DFT) study has been carried out with the aim to unveil the role of the dopants on the short range structure of these materials, to probe the preferential association of vacancies with both dopant and regular site cations, and to highlight the preferential oxygen-ion diffusion paths. This could help to define criteria for the design of new materials with improved properties. The influence of the electrode-electrolyte interface on the overall fuel cell ionic conductivity has been also addressed. To this aim, a novel protocol to evaluate electrode-electrolyte compatibility through Scanning X-Ray Microscopy (SXM) has been developed and cation interdiffusion has been successfully probed at the interface between some electrolyte-cathode couples.