TY - THES A1 - Hofmann, Michael T1 - Overcoming Obstacles in the Aqueous Processing of Nickel-rich Layered Oxide Cathode Materials T1 - Überwindung von Hindernissen bei der wässrigen Verarbeitung von nickelreichen Schichtoxid-Kathodenmaterialien N2 - The implementation of a water-based cathode manufacturing process is attractive, given the prospect of improved sustainability of future lithium-ion batteries. However, the sensitivity of many cathode materials to water poses a huge challenge. Within the scope of this work, a correlation between the water sensitivity of cathode materials from the class of layered oxides and their elemental composition was identified. In particular for the cathode material LiNi0.8Co0.15Al0.05O2 (NCA), the processes taking place in aqueous medium were clarified in detail. Based on this knowledge, the surface of NCA particles could be specifically modified, which led to a reduced water sensitivity. As a result, the electrochemical performance of cells with water-based NCA cathodes was significantly improved and a remarkable long-term cycling performance was achieved. The present work contributes to a deeper understanding of the water sensitivity of cathode materials and at the same time presents a promising approach to overcome this obstacle. Consequently, this work advances the successful widespread realization of water-based cathode manufacturing. N2 - Die Nachhaltigkeit zukünftiger Lithium-Ionen-Batterien kann durch die Implementierung eines wasserbasierten Herstellungsverfahrens für Kathoden verbessert werden. Die Wasserempfindlichkeit vieler Kathodenmaterialien stellt hierbei jedoch eine große Herausforderung dar. Im Rahmen dieser Arbeit wurde ein Zusammenhang zwischen der Wasserempfindlichkeit von Kathodenmaterialien der Klasse der Schichtoxide und deren Elementzusammensetzung hergestellt. Insbesondere für das extrem wasserempfindliche Kathodenmaterial LiNi0.8Co0.15Al0.05O2 (NCA) wurden die im wässrigen Medium ablaufenden Prozesse detailliert aufgeklärt. Auf Basis dieser Erkenntnisse konnte die Oberfläche von NCA-Partikeln gezielt modifiziert und damit die Wasserempfindlichkeit reduziert werden. Infolgedessen konnte die elektrochemische Performance von Zellen mit wasserbasierten NCA-Kathoden signifikant verbessert und eine bemerkenswerte Langzeitperformance erzielt werden. Die vorliegende Arbeit trägt somit zu einem tieferen Verständnis der Wasserempfindlichkeit von Kathodenmaterialien bei und liefert zugleich einen vielversprechenden Ansatz, um diese zu minimieren. So wird die erfolgreiche Realisierung der wässrigen Kathodenherstellung vorangetrieben. KW - Elektrochemie KW - Kathode KW - Lithium-Ionen-Akkumulator KW - cathode material KW - aqueous processing KW - lithium-ion battery KW - layered oxides Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-273787 ER - TY - JOUR A1 - Hofmann, Julian A1 - Fayez, Shaimaa A1 - Scheiner, Matthias A1 - Hoffmann, Matthias A1 - Oerter, Sabrina A1 - Appelt‐Menzel, Antje A1 - Maher, Pamela A1 - Maurice, Tangui A1 - Bringmann, Gerhard A1 - Decker, Michael T1 - Sterubin: Enantioresolution and Configurational Stability, Enantiomeric Purity in Nature, and Neuroprotective Activity in Vitro and in Vivo JF - Chemistry – A European Journal N2 - Alzheimer′s disease (AD) is a neurological disorder with still no preventive or curative treatment. Flavonoids are phytochemicals with potential therapeutic value. Previous studies described the flavanone sterubin isolated from the Californian plant Eriodictyon californicum as a potent neuroprotectant in several in vitro assays. Herein, the resolution of synthetic racemic sterubin (1) into its two enantiomers, (R)‐1 and (S)‐1, is described, which has been performed on a chiral chromatographic phase, and their stereochemical assignment online by HPLC‐ECD coupling. (R)‐1 and (S)‐1 showed comparable neuroprotection in vitro with no significant differences. While the pure stereoisomers were configurationally stable in methanol, fast racemization was observed in the presence of culture medium. We also established the occurrence of extracted sterubin as its pure (S)‐enantiomer. Moreover, the activity of sterubin (1) was investigated for the first time in vivo, in an AD mouse model. Sterubin (1) showed a significant positive impact on short‐ and long‐term memory at low dosages. KW - Alzheimer′s disease KW - chiral resolution KW - circular dichroism KW - Eriodictyon californicum KW - flavonoids KW - sterubin Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-215993 VL - 26 IS - 32 SP - 7299 EP - 7308 ER - TY - JOUR A1 - Figel, Benedikt A1 - Brinkmann, Leonie A1 - Buff, Christine A1 - Heitmann, Carina Y. A1 - Hofmann, David A1 - Bruchmann, Maximilian A1 - Becker, Michael P. I. A1 - Herrmann, Martin J. A1 - Straube, Thomas T1 - Phasic amygdala and BNST activation during the anticipation of temporally unpredictable social observation in social anxiety disorder patients JF - NeuroImage: Clinical N2 - Anticipation of potentially threatening social situations is a key process in social anxiety disorder (SAD). In other anxiety disorders, recent research of neural correlates of anticipation of temporally unpredictable threat suggests a temporally dissociable involvement of amygdala and bed nucleus of the stria terminalis (BNST) with phasic amygdala responses and sustained BNST activation. However, the temporal profile of amygdala and BNST responses during temporal unpredictability of threat has not been investigated in patients suffering from SAD. We used functional magnetic resonance imaging (fMRI) to investigate neural activation in the central nucleus of the amygdala (CeA) and the BNST during anticipation of temporally unpredictable aversive (video camera observation) relative to neutral (no camera observation) events in SAD patients compared to healthy controls (HC). For the analysis of fMRI data, we applied two regressors (phasic/sustained) within the same model to detect temporally dissociable brain responses. The aversive condition induced increased anxiety in patients compared to HC. SAD patients compared to HC showed increased phasic activation in the CeA and the BNST for anticipation of aversive relative to neutral events. SAD patients as well as HC showed sustained activity alterations in the BNST for aversive relative to neutral anticipation. No differential activity during sustained threat anticipation in SAD patients compared to HC was found. Taken together, our study reveals both CeA and BNST involvement during threat anticipation in SAD patients. The present results point towards potentially SAD-specific threat processing marked by elevated phasic but not sustained CeA and BNST responses when compared to HC. KW - FMRI KW - threat anticipation KW - social anxiety disorder KW - bed nucleus of stria terminalis KW - amygdala Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-228071 VL - 22 ER -