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Elektrofahrzeuge unterscheiden sich im Flamm- und Brandverhalten von Fahrzeugen mit Verbrennungsmotor. Insbesondere die Sicherheit der Traktionsbatterie stellt eine Herausforderung dar. Neben einer Beschädigung der Batteriezellen durch ein externes Schadereignis, beispielsweise ein Brand, verursacht durch einen Unfall mit einem kraftstoffbetriebenen Fahrzeug, kann die Batterie selbst durch internes Versagen zur Gefahrenquelle werden. Eine entsprechend wichtige Sicherheitsfunktion übernimmt daher das Batteriegehäuse. Um Gewicht und Kosten zu senken, werden Gehäuse aus faserverstärkten Kunststoffen entwickelt.

Conversion/alloy active materials, such as ZnO, are one of the most promising candidates to replace graphite anodes in lithium-ion batteries. Besides a high specific capacity (qZnO = 987 mAh g-1), ZnO offers a high lithium-ion diffusion and fast reaction kinetics, leading to a high-rate capability, which is required for the intended fast charging of battery electric vehicles. However, lithium-ion storage in ZnO is accompanied by the formation of lithium-rich solid electrolyte interphase (SEI) layers, immense volume expansion, and a large voltage hysteresis. Nonetheless, ZnO is appealing as an anode material for lithium-ion batteries and is investigated intensively. Surprisingly, the conclusions reported on the reaction mechanism are contradictory and the formation and composition of the SEI are addressed in only a few works. In this work, we investigate lithiation, delithiation, and SEI formation with ZnO in ether-based electrolytes for the first time reported in the literature. The combination of operando and ex situ experiments (cyclic voltammetry, X-ray photoelectron spectroscopy, X-ray diffraction, coupled gas chromatography and mass spectrometry, differential electrochemical mass spectrometry, and scanning electron microscopy) clarifies the misunderstanding of the reaction mechanism. We evidence that the conversion and alloy reaction take place simultaneously inside the bulk of the electrode. Furthermore, we show that a two-layered SEI is formed on the surface. The SEI is decomposed reversibly upon cycling. In the end, we address the issue of the volume expansion and associated capacity fading by incorporating ZnO into a mesoporous carbon network. This approach reduces the capacity fading and yields cells with a specific capacity of above 500 mAh g-1 after 150 cycles.

Li-S cells can have high gravimetric energy densities above 300 Wh kg−1 when the electrodes and cell components are optimized. Low electrolyte/sulfur mass ratios or more generallly, the relative amount of electrolyte in a Li-S cell have an especially high impact on the achievable gravimetric energy density. A negative side effect of low electrolyte/sulfur ratios are low cycle numbers due to electrolyte decomposition and the possibility that electrolyte becomes inaccessible at the lithium metal anode when the lithium becomes more and more porous during cycling. Electrode thickness measurements were performed during cycling for various cell chemistries such as lithium-sulfur (Li-S) with different cathode sulfur loadings and porosities, lithium-hard carbon (Li-HC), lithium-silicon (Li-Si), prelithiated HC-sulfur (LiHC-S), prelithiated Si-sulfur (LiSi-S) and Li-ion. The thickness measurements provided information about mechanical stress and irreversible thickness changes. The thickness measurements also helped to explain different electrolyte decomposition behavior and they can be used to discuss the impact of thickness changes on gas analysis. The electrolyte decomposition of the Li-S standard electrolyte based on lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in dimethoxyethane (DME): dioxolane (DIOX) with LiNO3 was examined by online mass spectrometry (MS) within Li-S, Li-HC, Li-Si, LiSi-S and LiHC-S cells. Several electrolyte decomposition products were verified by post-mortem gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) of Li-S cells with cycled electrolyte.

A new method for urea detection in surface and tap waters using LC-OCD-OND was developed. It could be shown that urea, ammonia and nitrate could be separated chromatographically from each other and from NOM (natural organic matter). A direct quantification at its specific retention time is possible using custom-made detectors for nitrogen and for organic carbon. Further, urea can be detected indirectly as urea is transformed to ammonia after enzymatic hydrolysis with urease. After sufficient contact time for complete hydrolysis to ammonia (about 320 minutes) urea concentration can be calculated on the basis of the additional ammonia measured by LC-OCD-OND. The limit of detection of urea as mass was determined as 4 ppb for natural waters and 1 ppb for deionised waters.

Li-S cells are attractive due to their high potential gravimetric energy density, but they achieve only low cycle numbers. A major reason for this is a continuous electrolyte decomposition during cycling. As low electrolyte/sulfur ratios are required for high gravimetric energy density, this electrolyte decomposition reduces the obtainable cycle number to below 50. It is therefore extremely important to evaluate, reduce or ideally prevent this electrolyte decomposition by utilizing new electrolyte (additives), separators and protection layers. Applying in-situ mass spectroscopy, the electrolyte decomposition has been characterized for Li-S cells with lithium metal anode, silicon anode and carbon anode with various electrolyte compositions, electrodes and cycling parameters. Electrolyte cracking leads to gaseous substances, some of which are created continuously while others show a maximum depending on the state of charge. Standard ether-based Li-S electrolytes (e.g. DME:DIOX) are unstable with Li metal anodes and will always limit the obtainable cycle number unless further protection devices are applied. The attached figure demonstrates specific gaseous substances created in a Li-S cell during cycling between 1.8-2.6 V at 0.6 mA/cm². Figure 1

Size-exclusion chromatography in combination with organic carbon detection (SEC-OCD) is an established method to separate the pool of NOM into major fractions of different sizes and chemical functions and to quantify these on the basis of organic carbon. One specific approach, also known as LC-OCD-OND, is based on the Grantzel thin-film UV-reactor. This approach is described with recent improvements in fraction assignation (humic substances, biopolymers, building blocks, low molecular weight organic acids and neutrals, hydrophobic organic carbon), the coupling of a novel organic nitrogen detector (OND), and an improved diagram for the characterisation of aquatic humic substances (HS-diagram). The diagram replaces the operational distinction between humic and fulvic acids by a continuum ranging from aquagenic fulvic acids to pedogenic humic acids.

The development of methods facilitating the detection of cyanobacterial blooms in drinking water reservoirs at an early stage is of great importance. Fluorescence spectroscopy could meet these requirements. The study contains the examination of possible correlations between the different maxima of a fluorescence excitation-emission matrix and the amount of produced and excreted toxins of a lab culture of Microcystis aeruginosa at different stages of growth. Various fluorescence signals (protein-like and humic-like substances, pigments) are suited for an estimation of cell density and actual intra- and extracellular toxin concentration. One signal at 315 nm/396 nm presumably originating from protein-like substances might be useful as a tool for the prediction of increasing cyanobacterial toxin concentrations. As the measurement of fluorescence matrices is still time consuming, synchronous scans with Δλ = 80 nm were tested as a potential alternative. They accurately depict the course of protein-like and humic-like fluorescence during the different stages of growth although especially the latter one is not captured at its maximum. However, due to insufficient separation of chlorophyll a and phycocyanin, the image of the matrix maxima by synchronous scans with Δλ = 80 nm can only be used with minor restrictions. Nevertheless, fluorescence spectroscopy seems to be a powerful tool for the evaluation of cyanobacterial blooms.