Tomography-based analysis of battery, electrolyser and fuel cell microstructures

Hochschulschrift

Abstract: In this thesis, it is shown how imaging by X-ray tomography (Xt) and focused ion beam / scanning electron microscopy tomography (FIB/SEMt), image processing, and subsequent calculations can be used to quantify morphological-, transport- and degradation parameters in porous structures used in energy devices. The investigated features range from approximately 300 micrometres to approximately 10 nanometres. A special focus lies on the role of the porous carbon and binder domains (CBD), as they are used in PEM electrolysers, PEM fuel cells, lithium ion batteries and many more energy devices. During this thesis, there were several challenges that were identified and partially overcome, such as:1) The CBD cannot be reliably segmented using Xt, if the investigated electrode contains heavy metal atoms, e.g. Co. A solution is presented, via a statistical modelling approach where the CBD is virtually inserted in the active material framework from X-ray tomography. This approach also provided understanding as to how changes in CBD morphology influence e.g. Li-ion transport in such electrodes.2) It was unclear how the three-dimensional morphology of lithium sulphur electrodes changes when the battery is cycled. It is shown in this thesis that Xt can be used to quantify such morpho-logical changes and that not only the sulphur particles do change size, distribution and form with increased cycling, but that the morphology of the CBD changes as well. When using three-dimensional carbon paper as a current collector, the CBD clogs the top of the current collector. This partially clogged surface than acts as a barrier to sulphur, increasing sulphur retention in the electrode.3) Mechanical stress during lithiation of Silicon electrodes changes the electrodes morphology. It is shown that these stresses have caused a partial contact loss of single Si particles to the CBD or the ionically conducting electrolyte phase. The high image contrast between pore, CBD and silicon particles have allowed for a deeper analysis of the battery, finding that particles which have less than 40% of their surface area still covered by CBD do not experience lithiation related fracturing.4) There were no studies on the three-dimensional morphology of an interface between a catalyst layer (CL) and a micro porous layer (MPL) in a fuel cell in their application relevant state. By using a combination of FIB/SEMt and ALD, such an interface was reconstructed and it was shown that its morphology represents a transitional region, rather than a barrier between the CL and the MPL

Object Details

• Location: Deutsche Nationalbibliothek Frankfurt am Main
• Extent: Online-Ressource
• Language: Englisch
• Notes: IN COPYRIGHT http://rightsstatements.org/page/InC/1.0 rs ; Albert-Ludwigs-Universität Freiburg, Dissertation, 2016

Classification and Topics

• Classification: Elektrotechnik, Elektronik
• Keyword: Tomografie ; Lithium-Ionen-Akkumulator ; Alterung ; Mikrostruktur

Contributors, Places and Time

• Event: Veröffentlichung
• (where): Freiburg
• (who): Universität
• (when): 2016
• Creator: Zielke, Lukas
• Contributor: Zengerle, Roland ; Technische Fakultät ; Albert-Ludwigs-Universität Freiburg

Further information

• DOI: 10.6094/UNIFR/12205
• URN: urn:nbn:de:bsz:25-freidok-122055
• Rights: Der Zugriff auf das Objekt ist unbeschränkt möglich.
• Last update: 25.03.2025, 1:55 PM CET