Durability of Solid Oxide Cells: an experimental and modelling investigation based on synchrotron X-ray nano-tomography characterization

This work aims at better understanding and quantifying the degradation of high temperature Solid Oxide Cells. An approach based on electrochemical tests, advanced post-test characterizations and multi-scale models has been used to investigate the links between the performances, the electrodes microstructure and their degradation upon operation. In that goal, long-term durability tests have been performed over few 1000h in different operating conditions. Electrode microstructures have been reconstructed by synchrotron X-ray nano-holotomography for the pristine and aged cells. It is worth noting that a special attention has been paid to improve both the protocol reliability for the tomographic experiments as well as the spatial resolution of the 3D reconstructed images. Thanks to the valuable 3D volumes, the Ni-YSZ microstructural properties of the H₂ electrode have been quantified for the fresh and the aged samples. Then, a physically-based model for Nickel particle agglomeration has been adjusted on the microstructural parameters obtained by the 3D analysis and implemented in an in-house multi-scale modelling framework. Beforehand, it has been necessary to enrich the available numerical tool with a specific module dedicated to the oxygen electrode made in Mixed Ionic Electronic Conducting materials. Once validated on polarisation curves, the completed model has been used to quantify the contribution of Nickel agglomeration on the experimental degradation rates (~30%) recorded in fuel cell and electrolysis modes.