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Microstructure of Electrodeposited Lithium Metal Electrodes in Reservoir-Free Solid-State Batteries
(2026) Becker, Juri Jonathan Erwin
The transition towards renewable energy sources and the electrification of transportation are essential drivers for the development of advanced energy storage solutions with high energy and power densities. Conventional lithium-ion batteries based on liquid electrolytes have become the dominant technology for portable electronics and electric vehicles. However, they are rapidly approaching their theoretical physicochemical limits in terms of energy density. Solid-state batteries comprising lithium metal electrodes and inorganic solid electrolytes promise substantial improvements over conventional lithium-ion batteries, offering the potential to overcome current safety concerns, mitigate flammability risks inherent to liquid electrolytes, and increase both energy as well as power density. A critical obstacle in implementing lithium metal electrodes remains the maintenance of the electrode|solid electrolyte interface during cell operation, which can lead to morphological instabilities during both charge and discharge. Furthermore, the storage of lithium metal and cell manufacturing must take place under inert gas atmospheres, which is costly. Otherwise, contact with atmospheric components such as moisture (H2O), oxygen (O2), and nitrogen (N2) leads to the formation of resistive passivation layers on the surface, which impede cell performance. To address these challenges, reservoir-free cell concepts are being intensively explored. In these configurations, the lithium metal electrode is electrodeposited only during the initial charging step, with lithium sourced from the lithiated positive electrode. This approach substantially simplifies cell fabrication, as no lithium metal needs to be handled during assembly. However, electrodeposition is likewise associated with new morphological instabilities, and fundamental differences in microstructure and chemistry between conventionally produced and electrodeposited lithium remain insufficiently understood. This dissertation focuses on the chemical and microstructural characterization of electrodeposited lithium, using reservoir-free model systems comprising steel|Li6PS5Cl interfaces. Chemical analysis revealed an exceptionally high purity compared to commercial lithium foils. Microstructural analysis on millimeter-sized cross-sections, based on electron backscatter diffraction, uncovered a dynamic evolution of the resulting lithium grain structure during both electrodeposition and subsequent electrodissolution cycles. Finally, interlayer materials were introduced as an effective measure to control the resulting lithium microstructure. Overall, the results presented in this dissertation significantly expand the understanding of electrodeposited lithium layers both in terms of their purity as well as their microstructure. Latter depends on electrodeposition parameters, cycling history, and current collector modifications. These insights aim to optimize the performance of reservoir-free cells and enable the development of advanced solid-state batteries.
Preparation, Characterization and Testing of an Electrochemical Pumping System for Modifying the Nonstoichiometry of Cerium Oxide CeO2-x
(2026) Rink, Florian
Cerium oxide is considered a promising catalyst for HCl oxidation reaction. In this context, it has been found that the oxidation state of cerium oxide (CeO2-x, 0 ≤ x ≤ 0.5) influences the corresponding catalytic activity. For a more detailed investigation, however, a system would be desirable that allows the controlled modification of this. In this work, a respective approach is presented. Based on the Pt/YSZ electrode system, an electrochemical pumping system was devised that allows the oxidation state modification of a CeO2-x(111) film. The cerium oxide films were prepared by pulsed laser deposition and characterized by scanning electron microscopy, X-ray diffraction, Raman spectroscopy and X-ray photoelectron spectroscopy. Beyond that, electrochemical measurements were conducted on various (CeO2-x/)Pt/YSZ/Pt systems. Here, impedance spectroscopy, cyclic voltammetry and potentiostatic polarization experiments revealed effects caused by the cerium oxide film, indicating thereby the working principle of the pumping system. Ultimately, the working principle could be proven using an operando setup that allowed X-ray photoelectron spectroscopy measurements at high temperatures and after applying electric potentials. By this, oxidation as well as reduction of the cerium oxide film could be verified.
Sustainable insect feed in shrimp aquaculture: Challenges and opportunities in research and practical implementation
(2026) Barth, Annalena
Aquaculture is a growing global food production sector that aims to meet the increasing demand for human dietary protein. Crustaceans are an important part of aquaculture, particularly the Pacific white shrimp (PWS; Penaeus vannamei). Shrimp farming often has a large ecological footprint, partly due to the fishmeal content in commercial aquafeed. An opportunity to improve sustainability and move towards a circular economy would be replacing fishmeal in aquafeeds with insects, such as the black soldier fly larvae (BSF; Hermetia illucens), reared on plant by-products. However, limited data is available on the effects of novel plant by-products on the growth performance of BSF larvae and in turn on shrimp. Research into BSF-based feed is in its infancy, and the few existing studies show inconsistent results regarding shrimp growth performance. Although some of these discrepancies can be attributed to the properties of the insect feed used, other unknown factors are probably influencing the results. Therefore, this dissertation aims to assess challenges and opportunities in using insects as a sustainable feed in shrimp aquaculture research and practice. It covers key sustainability concerns, enhances the consistency and reproducibility of feeding trials, and offers a comprehensive view of practical application within the context of a circular economy. This dissertation demonstrates that BSF larvae are a promising, sustainable source of protein for shrimp farming. BSF larvae can efficiently convert plant by-products into high-quality protein. Feeding trials show that replacing up to 50% of fishmeal-based compound feed with BSF larvae achieves excellent feed conversion rates. However, the use of BSF meal in compound feed in industrial aquaculture offers greater potential. Furthermore, compliance with reporting guidelines and transparency will be essential for reproducibility and food safety when using insects as feed in the future. The implementation of circular economy concepts remains largely theoretical and depends on optimised rearing systems, increased inclusion rates, industrial scalability and economic profitability. Even though there are still challenges regarding scalability, regulation and consumer acceptance, BSF-based feed has great potential for commercial shrimp farming.
Nachweis und molekulare Charakterisierung pathogener und antibiotikaresistenter Bakterien isoliert aus legal und illegal in die Europäische Union importierten Lebensmitteln tierischer Herkunft
(2025) Rinn, Nicola Susan
Der Import von tierischen Lebensmitteln aus Drittländern spielt für die EU eine große Rolle. Insbesondere Rindfleisch wird jährlich in großen Mengen in die EU eingeführt. Ebenso werden illegal Lebensmittel tierischer Herkunft über den internationalen Reiseverkehr eingeführt. Über die Charakteristika von Bakterienisolaten aus tierischen Erzeugnissen, die in die EU eingeführt werden, ist dabei bisher wenig bekannt. Diese Arbeit umfasst die Erhebung des mikrobiologischen Status von aus Drittländern in die EU importierten Rindfleischproben (n = 100) sowie von illegal über den Flugverkehr eingeführten Lebensmitteln tierischer Herkunft (n = 100) mittels einer Bewertung anhand der mikrobiologischen Grenzwerte auf EU-Ebene bzw. der Warnwerte der Deutschen Gesellschaft für Hygiene und Mikrobiologie (DGHM). Ein Schwerpunkt lag auf der molekularen Charakterisierung der Isolate einschließlich des Nachweises von Virulenz-assoziierten Faktoren. Um eine Aussage über das Vorkommen von Resistenzen bei den Isolaten zu treffen, wurden zudem antimikrobielle Empfindlichkeitstestungen durchgeführt und die Isolate auf das Vorliegen von Resistenzgenen untersucht. Ziel war es, zu evaluieren, inwiefern Lebensmittelimporte zur Verbreitung pathogener bzw. virulenter und/oder multiresistenter sowie in der EU für gewöhnlich nicht vorkommender Genotypen beitragen können.
Olfactory Landmark Information in Wayfinding: Implicit and Explicit Processing of Sensory Information in Spatial Orientation
(2025) Schwarz, Mira
Human navigation research has long been dominated by a vision-centered perspective, often neglecting the role of other sensory modalities, particularly olfaction. Across two empirical studies and a state-of- the-art review, this dissertation examines how visual and olfactory cues guide human wayfinding. The first study shows that switching between visual and olfactory landmark information leads to switching costs, reflected in longer decision times and reduced wayfinding accuracy. These results diverge from earlier findings of absent switching costs between auditory and visual landmarks, suggesting that odors and images are initially processed in separate cognitive systems and require cognitively demanding cross-modal translation. The second study demonstrates that olfactory landmarks can support navigation even without explicit recognition. Across two testing times one month apart, wayfinding performance in a virtual maze was highest when olfactory cues were processed implicitly, whereas performance with visual landmarks was higher when processed explicitly. These results suggest distinct implicit mechanisms in the olfactory system and highlight the importance of non-conscious contributions to navigation. The third publication is a review article on the sense of smell in human navigation, summarizing empirical findings, challenging the misconception that humans have a poor sense of smell, and outlining why this ability has been largely overlooked. Together, the studies provide converging evidence that olfactory cues can meaningfully support human wayfinding, largely through implicit processes. Based on these insights, the dissertation proposes a Multimodal Integrative Model distinguishing implicit from explicit processes across visual and olfactory modalities, highlighting their joint role in flexible multimodal navigation.