The recent growth of 3D printing has opened the scope for designing microstructures for solid oxide fuel cell (SOFC) electrodes with improved power density and lifetime. This technique can introduce structural modifications of the electrode/electrolyte interface at a scale which is larger than the particle size but smaller than the cell size, such as the insertion of dense electrolyte pillars in the order of 5-100 um. This study presents some guidelines and sets the minimum requirements for the rational design of 3D printed electrodes based on an electrochemical numerical model and approximated analytical solutions for functional layers with negligible electronic resistance. Results show that this structural modification enhances the power density only when the effective ionic conductivity factor keff of the composite electrode is smaller than 0.5. The maximum performance improvement can be straightforwardly predicted analytically as a function of keff only. A design study on a wide range of pillar shapes indicates that improvements in electrochemical performance are achieved by any chosen structural modification capable to provide ionic conduction farther from the electrolyte up to a characteristic thickness (typically ~10-40 um) without removing electrochemically active volume at the electrolyte interface. The best performance improvements are reached in the limit of thin (< ~2 um) and long (> ~80 um) pillars when the composite electrode domain is optimised for maximum three-phase boundary (TPB) density, pointing towards the design of scaffold electrodes with well-defined geometry and fractal structures.

Guidelines and numerical analysis for the rational design of 3D manufactured solid oxide fuel cell electrodes

Bertei A
Investigation
;
2016-01-01

Abstract

The recent growth of 3D printing has opened the scope for designing microstructures for solid oxide fuel cell (SOFC) electrodes with improved power density and lifetime. This technique can introduce structural modifications of the electrode/electrolyte interface at a scale which is larger than the particle size but smaller than the cell size, such as the insertion of dense electrolyte pillars in the order of 5-100 um. This study presents some guidelines and sets the minimum requirements for the rational design of 3D printed electrodes based on an electrochemical numerical model and approximated analytical solutions for functional layers with negligible electronic resistance. Results show that this structural modification enhances the power density only when the effective ionic conductivity factor keff of the composite electrode is smaller than 0.5. The maximum performance improvement can be straightforwardly predicted analytically as a function of keff only. A design study on a wide range of pillar shapes indicates that improvements in electrochemical performance are achieved by any chosen structural modification capable to provide ionic conduction farther from the electrolyte up to a characteristic thickness (typically ~10-40 um) without removing electrochemically active volume at the electrolyte interface. The best performance improvements are reached in the limit of thin (< ~2 um) and long (> ~80 um) pillars when the composite electrode domain is optimised for maximum three-phase boundary (TPB) density, pointing towards the design of scaffold electrodes with well-defined geometry and fractal structures.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11568/885352
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