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Influence of Strain and Interfaces on the Properties of Ion Conducting Thin Films for micro-Solid-Oxide-Fuel-Cells

Applicant Lippert Thomas
Number 147190
Funding scheme Project funding (Div. I-III)
Research institution Paul Scherrer Institut
Institution of higher education Paul Scherrer Institute - PSI
Main discipline Material Sciences
Start/End 01.05.2013 - 28.02.2017
Approved amount 442'335.00
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All Disciplines (4)

Discipline
Material Sciences
Inorganic Chemistry
Physical Chemistry
Condensed Matter Physics

Keywords (6)

strain ; thin films; interfaces; micro solid oxide fuel cells; ion conductors; pulsed laser deposition

Lay Summary (German)

Lead
Die Zukunft unserer Gesellschaft benötigt eine nachhaltige Energieversorgung. Festoxid-Brennstoffzellen (engl. SOFC) verfügen über ein grosses Potential für stationäre und mobile Energieversorgung. Die Erforschung von Dünnfilmen kann einen wichtigen Beitrag zur Verbesserung der Herstellung und Effizienz dieser Geräte leisten.
Lay summary

Miniaturisierte SOFCs, die mittels Abscheideverfahren für Dünnfilme hergestellt werden, werden momentan intensiv als möglicher Ersatz für Batterien in mobilen Geräten erforscht. Ein wichtiger Aspekt, um die Marktreife dieser Technologie voranzubringen, ist das Herzstück der SOFC, die Elektrolytmembran, welche zuverlässig mit den erforderlichen physikalischen Eigenschaften herzustellen sein muss. Die physikalischen Eigenschaften von Nanometer dünnen Filmen und ihren Grenzflächen unterscheiden sich oftmals markant von denen ihrer makroskopischen Pendants. Im Fall einiger Elektrolytmaterialien für SOFCs wurde der experimentelle Nachweis erbracht, dass stark erhöhte elektrische Leitfähigkeiten mit Hilfe einer entsprechenden Anpassung der Grenzflächen zwischen den Dünnfilmen und anderen Materialien erzielt werden können. Weiterhin kann die notwendige mechanische Stabilität der Membranen durch neuartige Mikrostrukturen verbessert werden.

Dieses Forschungsprojekt setzt sich als Ziel, künstlich geschaffene Nanostrukturen herzustellen und zu analysieren, um der Ursache für die erhöhte Leitfähigkeit dieser Dünnfilme auf den Grund zu gehen. Eine Steigerung um mehr als zwei Grössenordnungen wurde berichtet, was einen eindrucksvollen potentiellen Effekt auf die Effizienz der SOFCs hat.

Äusserst kontroverse Ergebnisse bezüglich der gesteigerten Leitfähigkeit lassen sich in der Wissenschaftsliteratur finden. Zudem wurde noch keine mechanisch stabile Mikrostruktur identifiziert, welche die Herstellung und Verwendung entsprechender Geräte zuverlässig gewährleistet. Von diesem Forschungsprojekt erwarten wir uns einen wichtigen Beitrag zum Verständnis der Physik in diesen Materialien. Dieses Interesse ist selbstverständlich nicht nur rein akademischer Natur, da die zu erwartenden Ergebnisse von grundlegender Bedeutung für die Konstruktion und Herstellung energiefreundlicher Energielieferanten darstellen, und somit deren Markteintritt ermöglichen können.


Direct link to Lay Summary Last update: 11.04.2013

Responsible applicant and co-applicants

Employees

Publications

Publication
Zigzag or spiral-shaped nanostructures improve mechanical stability in yttria-stabilized zirconia membranes for micro-energy conversion devices
Shi Yanuo, Fluri Aline, Garbayo Inigo, Schwiedrzik J. Jakob, Michler Johann, Pergolesi Daniele, Lippert Thomas, Rupp Jennifer Lilia Marguerite (2019), Zigzag or spiral-shaped nanostructures improve mechanical stability in yttria-stabilized zirconia membranes for micro-energy conversion devices, in Nano Energy, 59, 674-682.
Anisotropic Proton and Oxygen Ion Conductivity in Epitaxial Ba 2 In 2 O 5 Thin Films
Fluri Aline, Gilardi Elisa, Karlsson Maths, Roddatis Vladimir, Bettinelli Marco, Castelli Ivano E., Lippert Thomas, Pergolesi Daniele (2017), Anisotropic Proton and Oxygen Ion Conductivity in Epitaxial Ba 2 In 2 O 5 Thin Films, in The Journal of Physical Chemistry C, 121(40), 21797-21805.
Micro-solid state energy conversion membranes: influence of doping and strain on oxygen ion transport and near order for electrolytes
Shi Yanuo, Garbayo Iñigo, Muralt Paul, Marguerite Rupp Jennifer Lilia (2017), Micro-solid state energy conversion membranes: influence of doping and strain on oxygen ion transport and near order for electrolytes, in J. Mater. Chem. A, 5(8), 3900-3908.
In situ stress observation in oxide films and how tensile stress influences oxygen ion conduction
Fluri Aline, Pergolesi Daniele, Roddatis Vladimir, Wokaun Alexander, Lippert Thomas (2016), In situ stress observation in oxide films and how tensile stress influences oxygen ion conduction, in Nature Communications, 10692.
The effect of mechanical twisting on oxygen ionic transport in solid-state energy conversion membranes
Shi Yanuo, Bork Alexander Hansen, Schweiger Sebastian, Rupp Jennifer Lilia Marguerite (2015), The effect of mechanical twisting on oxygen ionic transport in solid-state energy conversion membranes, in Nature Materials, 14(7), 721-727.

Collaboration

Group / person Country
Types of collaboration
Professor H. Tuller, Department of Material Science and Engineering, MIT United States of America (North America)
- in-depth/constructive exchanges on approaches, methods or results
Solid State Chemistry, Paul Scherrer Institut, Professor K. Conder Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
ETH Zurich, High Energy Physics, Dr. M. Döbeli Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
Fuel Cell and Solid State Chemistry Department, Risoe Danish Technical University, Dr. N. Pryds Denmark (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
Professor B. Ylidiz, Nuclear Science and Engineering, MIT United States of America (North America)
- in-depth/constructive exchanges on approaches, methods or results
Professor D. Poulikakos, Institute of Energy Technology, ETH Zurich Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
ECS Conference on Electrochemical Energy Conversion & Storage with SOFC-XIV Talk given at a conference Role of Lattice Strain vs. Solid Solution Doping on Atomistic near Order and Oxygen Ionic Transport for Ceria-based Micro-Energy Conversion Membranes 26.07.2015 Glasgow, Schottland, Great Britain and Northern Ireland Shi Yanuo; Rupp Jennifer;
E-MRS Spring Meeting 2014 Talk given at a conference Impact of Strain State and Buckling on the Ionic Transport of Free-Standing Membrane vs. Self-Supported Pt-Gd0.2Ce0.8O1.9-x-Pt Micro-Electrode Structures 26.05.2014 Lille, France Rupp Jennifer; Shi Yanuo;


Awards

Title Year
ETH medal doctoral thesis 2018

Associated projects

Number Title Start Funding scheme
126783 Single crystalline films of ion conductors 01.11.2009 Project funding (Div. I-III)
134577 Negative ions: the overlooked species in thin film growth by pulsed laser deposition 01.04.2011 Project funding (Div. I-III)
155986 Beyond von-Neuman computing - Materials Functionalization and Integration of Three-dimensionally stacked Multiterminal Memristive Oxides Replacing Existing Transistors for Neuromorphic Computing 01.06.2015 Temporary Backup Schemes
142176 Small band-gap nanostructured perovskite materials for photovoltaic and photocatalytic hydrogen generation applications 01.01.2013 Romanian-Swiss Research Programme (RSRP)
152553 Positive or negative? Selecting the charge state of ions during pulsed laser deposition of thin films 01.07.2014 Project funding (Div. I-III)
159198 The search for low temperature super protonic conductivity 01.09.2015 Project funding (Div. I-III)
172708 Laser interaction with materials for thin film deposition: From fundamentals to functional films 01.08.2017 Project funding (Div. I-III)
172708 Laser interaction with materials for thin film deposition: From fundamentals to functional films 01.08.2017 Project funding (Div. I-III)

Abstract

A solid oxide fuel cell (SOFC) is an electrochemical device that converts chemical energy (normally hydrogen containing) into electric energy and consists of two electrodes and an oxygen ion conducting oxide as electrolyte. State-of-the-art oxygen-ion conducting oxides in SOFCs are doped CeO2 or Y2O3 stabilized ZrO2 (YSZ). Existing SOFC systems operate at rather high temperatures (above 900°C) in order to achieve suitable ionic conductivity across the electrolyte material, which imply severe restrictions (material specifications) and are therefore the most important drawback of this technology. The application of thin films of the electrolyte, allows a significant reduction of the ohmic losses across the ionic conductor promising lower operating temperatures, increased lifetimes, and a wider range of eligible materials. Thin film deposition technologies are therefore the key for these type of developments and play also the key role in the fabrication of micro solid oxide fuel cells (µSOFC) prototypes. Such micro-fuel cells exhibit a free-standing fuel cell membrane integrated on a substrate (e.g. Si wafer) with an active total fuel cell thickness of less than 1 micron (for anode-electrolyte-cathode thin films) producing power in the hundreds mW to several W range. One important part of the µSOFC is the ion conducting oxide layer, but a review of the available data shows that the key numbers, i.e. the conductivity and activation energy of conduction, for a given material, such as YSZ scatter over several orders of magnitude (for conductivity). There are many possible origins for the large scatter of the data, but it is very important to understand the reason for variations in the properties, which would allow to create improved ion conducting structures for µSOFCs. Within this project two likely origins of increased conductivity in thin films will be tested, i.e. the role of hetero-interfaces which induces strain and homo-interfaces which may be described as grain boundaries, including interfaces with a high number of defects and misfit dislocations. These two effects will be studied by growing heterolayer superlattices (with a varying number of layers, but also single layers) with a high control of the interface near order and chemistry (using RHEED) and quantitative overall strain (using the optical strain monitor at PSI, which can by used during PLD together with RHEED). For the second approach, i.e. the homointerfaces, special thin film microstructures, i.e. zigzag or even helicoidal structures, will be prepared by the variable-angle pulsed laser deposition process. The properties, especially electric conductivity, of these thin films will be characterized in detail by various electrochemical methods (e.g. impedance combined with optical monitoring) and secondary ion mass spectrometry using 18O2. These characterizations (in plane and cross plane) will be performed for the thin film structures on various substrates, as well as on free standing membranes, which will be prepared by selectively etching the substrate underneath the electrolyte film. The characterization of the properties (electrochemical, but also mechanical) is of key importance for the performance and design of µSOFCs and whether it is possible to engineer ion conductors with optimized properties for micro devices.
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