Mit der Entwicklung der Weltwirtschaft steigt der Energieverbrauch weiterhin stark an. Darüber hinaus reduzieren sich die nicht erneuerbaren Energiequellen, wie Öl, Erdgas und Kohle und die Umweltverschmutzung wird größer. Daher soll die Energienutzung in eine neue, erneuerbare und umweltfreundliche Richtung gehen. Die Arbeit hat zum Ziel innovative, wässrige Akkumulatoren zu entwickeln. Im Allgemeinen können wässrige Akkumulatoren gemäß der Elektrolyte in drei verschiedenen Kategorien eingeteilt werden. Es gibt feste, organische und wässrige Elektrolyte einschließlich saurer, alkalischer und neutraler. In Bezug auf metallbasierte negative Elektroden können sie auch als Lithiumbatterie, Natriumbatterie sowie Magnesiumbatterie etc. bezeichnet werden. Daher werden im ersten Kapitel einige typische Akkumulatoren, wie die Lithiumionenbatterien, Daniell-Element, Weston-Zelle, Nickel-Cadmium-Batterie und Bleibatterie vorgestellt. Im Vergleich zu organischen Elektrolyten wurden wässrige Akkumulatoren aufgrund ihrer billigen, leichten und sicheren Bauweise in den letzten Jahren umfassend untersucht. Zusätzlich dazu ist die ionische Leitfähigkeit von wässrigen Elektrolyten um zwei Größenordnungen höher als die von organischen Elektrolyten. Dies garantiert eine hohe Entladungsrate für wässrige wiederaufladbare Batterien. Somit bieten wiederaufladbare Batterien potentielle Anwendungen in der Energiespeicherung und -umwandlung. Allerdings verursachen starke Säuren oder Basen, die als Elektrolyte für sekundäre Batterien eingesetzt werden, eine starke Korrosion. Somit wären neutrale wässrige Elektrolyten (oder Elektrolytlösungen) mit einem pH-Wert in der Nähe von sieben, wie zum Beispiel schwach basisch oder sauer, die beste Wahl für wässrige Akkumulatoren. Aktive Elektrodenmaterialien der Batterien, die hochgiftige Schwermetalle wie Blei, Quecksilber und Cadmium enthalten, belasten die Umwelt. Um die Menge an Schwermetallen und Säure (oder Basen) zu verringern, sowie die spezifische Kapazität von Batterien zu erhöhen, untersucht diese Dissertation vor allem die elektrochemische Leistung der PbSO4/0,5M Li2SO4/LiMn2O4-Zelle, der Cd/0,5M Li2SO4+10mM Cd(Ac)2/LiCoO2-Zelle und von C/Cu/CNT-Gemischen als negative Materialien in 0,5 M K2CO3–Elektrolyt-Halbzellen. Die zugehörigen experimentellen Ergebnisse werden wie folgt zusammengefaßt: Im Kapitel 3 wurde eine säurefreie Bleibatterie auf Basis des LiMn2O4-Spinells als positive Elektrode, PbSO4 als negativer Elektrode und der wässrigen Lösung von 0,5 M Li2SO4 als Elektrolyt zusammengesetzt. Die spezifische Kapazität auf Basis von LiMn2O4 beträgt 128 mA•h•g-1 und die durchschnittliche Entladungsspannung beträgt 1,3 V. Die berechnete Energiedichte ist 68 W•h•kg-1, bezogen auf die praktischen Kapazitäten der beiden Elektroden. Diese Ergebnisse zeigen, dass die positive Elektrode der Bleibatterie (PbO2) vollständig durch umweltfreundliches und billiges LiMn2O4 ersetzt werden kann, wodurch 50 % des Bleis eingespart werden können. Außerdem wird Schwefelsäure nicht benötigt. Kapitel 4 zeigt eine wässrige wiederaufladbare Lithiumionenbatterie, die metallisches Cadmium als negative Elektrode, LiCoO2-Nanopartikel als positive Elektrode und eine wässrige, neutrale Lösung von 0,5 M Li2SO4 und 10 mM Cd(Ac)2 als Elektrolyt enthält. Die durchschnittliche Entladungsspannung beträgt 1,2 V und die spezifische Entladungskapazität beträgt 107 mA•h•g-1 auf Basis von LiCoO2. Die berechnete Energiedichte beträgt 72 W•h•kg-1, bezogen auf die praktischen Kapazitäten der beiden Elektroden. Wie bereits oben beschrieben demonstrieren die Ergebnisse, dass 100 % von Quecksilber und der alkalischen Elektrolyt im Vergleich zur Weston-Zelle bzw. der Ni-Cd-Batterie, eingespart werden können. Kapitel 5 zeigt einen Verbundwerkstoff von Kupfer, das auf der Oberfläche von CNTs durch eine Redoxreaktion zwischen Kupferacetat und Ethylenglykol, zur Verwendung als negative Elektrode bei hohen Strömen in der Energiespeicherung, hergestellt wurde. Der so hergestellte C/Cu/CNT-Verbundwerkstoff zeigt ein besseres Geschwindigkeitsverhalten und eine höhere Kapazität ebenso wie eine exzellente Zyklusstabilität in wässrigen 0,5 M K2CO3-Lösungen im Vergleich zu einfachem Kupfer. Die Kohlenstoffbeschichtung kann die Auflösung von Kupfercarbonatkomplexen verhindern, die Elektrodenleitfähigkeit erhöhen und die Oberflächenchemie des aktiven Materials verbessern. / With the economic development of the world, energy consumption continues to rise sharply. Moreover, non-renewable energy sources including fossil oil, natural gas and coal are declining gradually and environmental pollution is becoming more severe. Hence, energy usage should go into a new direction of development that is renewable and environmental-friendly. This thesis aims to explore innovative aqueous rechargeable batteries. Generally, rechargeable batteries could be classified into three categories according to the different electrolytes. There are solid electrolytes, organic electrolytes and aqueous electrolytes including acidic, alkaline and neutral. In terms of metal-based negative electrodes, they also could be named lithium battery, sodium battery as well as magnesium battery etc. Therefore, some typical rechargeable batteries are introduced in Chapter 1, such as lithium ion batteries, Daniell-type cell, Weston cell, Ni-Cd battery and lead-acid battery. Compared to organic electrolytes, aqueous rechargeable batteries have been investigated broadly in recent years because they are inexpensive, easy to construct and safe. Additionally, the ionic conductivity of aqueous electrolytes is higher than that of organic electrolytes by about two orders of magnitude. Furthermore, it ensures high rate capability for aqueous rechargeable battery. Consequently, aqueous rechargeable batteries present potential applications in energy storage and conversion. However, strong acid or alkaline, which is used as the electrolyte for secondary batteries, will cause serious corrosion. Thus, neutral aqueous electrolyte (or pH value of electrolyte solution close to 7 such as weak alkaline and acid) would be the best choice for aqueous rechargeable battery. In addition, the electrode active materials of batteries containing highly toxic heavy metals such as Pb, Hg and Cd, pollute the environment. As a result, in order to reduce the amount of heavy metals and acid (or alkaline) as well as increase the specific capacity of batteries, this dissertation mainly studies the electrochemical performance of PbSO4/0.5M Li2SO4/LiMn2O4 full battery, Cd/0.5M Li2SO4+10 mM Cd(Ac)2/LiCoO2 full battery and C/Cu/CNT composites as negative material in 0.5 M K2CO3 electrolyte as half cell. The related experimental results are as follows: In Chapter 3, an acid-free lead battery was assembled based on spinel LiMn2O4 as the positive electrode, PbSO4 as the negative electrode, and 0.5 M Li2SO4 aqueous solution as the electrolyte. Its specific capacity based on the LiMn2O4 is 128 mA•h•g-1 and the average discharge voltage is 1.3 V. The calculated energy density is 68 W•h•kg-1 based on the practical capacities of the two electrodes. These results show that the positive electrode of the lead acid battery (PbO2) can be totally replaced by the environmentally friendly and cheap LiMn2O4, which implies that 50 % of Pb can be saved. In addition, H2SO4 is not needed. Chapter 4 shows an aqueous rechargeable lithium ion battery using metallic Cd as the negative electrode, LiCoO2 nanoparticles as the positive electrode, and an aqueous neutral solution of 0.5 M Li2SO4 and 10 mM Cd(Ac)2 as the electrolyte. Its average discharge voltage is 1.2 V and the specific discharge capacity is 107 mA•h•g-1 based on the LiCoO2 . In addition, the calculated energy density based on the capacities of the electrodes is 72 W•h•kg-1. As described above, the results demonstrate that 100 % of Hg and alkaline electrolyte can be saved compared with the Weston cell and the Ni-Cd battery, respectively. The work reported in Chapter 5 deals with a composite of copper grown on the surface of CNTs as prepared by a redox reaction between copper acetate and ethylene glycol for use as negative electrode at high currents in energy storage. The as-prepared C/Cu/CNTs composite exhibits better rate behavior and higher capacity as well as excellent cycling stability in aqueous 0.5 M K2CO3 solution compared to the unsupported copper. The carbon coating can effectively prevent the dissolution of copper carbonate complexes, increase the electrode conductivity, improve the surface chemistry of the active material and protect the electrode from direct contact with electrolyte solution.

Stainless steel bipolar plates are a possible replacement for graphite and composite bipolar plates in fuel cells. However, due to a native oxide layer they exhibit a high interfacial contact resistance (ICR) which lowers the performance. Conductive coatings like gold are a possible solution because they can reduce the contact resistance of metallic bipolar plates. We investigate the pulsed cathodic arc technique for deposition of carbon-based thin films on austenitic stainless steel 316L as cost-efficient alternative. Different types of coatings were prepared by varying the layer structure and processing parameters. Potentiodynamic polarization tests and ICR measurements were conducted to evaluate the performance of the films as conductive and corrosion resistant coatings. It was found that the corrosion resistance of coated austenitic steel samples is improved by both coatings and that measured ICR-values are well below the DOE 2020 target of 10 mΩ/cm2.

One of the major challenges in earth sciences and mineral exploration has been to determine with high accuracy and at a fast rate the elemental composition as well as the general chemistry of a rock sample. Many analytical techniques e.g., scanning electron microscopy (SEM) have been employed in the past with a certain degree of success, but their analyses usually require a lengthy sample preparation and time-consuming measurements which produce results at a much slower rate than techniques whichrequire less or do not require any sample preparation at all. SEM images the surface of a sample by scanning it with a high-energy beam of electrons in a raster scan pattern, where the primary electron beam produced under very low air pressure vacuum scans across the sample by striking it, and a variation of signals produce an image of the surface, or its elemental composition together with energy dispersive X-rays. Alternatively, laser induced breakdown spectrometry (LIBS) and multi energy X-ray transmission (ME-XRT) are non-contact measurement scanning techniques, capable of producing faster results than SEM-EDS which makes them suitable for real time measurements and analyses as they do not slow down the pace of a project being carried out. LIBS is a spectroscopic technique used to characterize and detect materials where a highly energetic laser pulse is focused onto the surfaces of solids, liquids or gases resulting in atomic and molecular species to emit light at specific wavelengths which is collected with a spectrometer and analysed using a computer. Comparably, ME-XRT is a sensor-based sorting technique involving the planar projection of X-ray attenuation of a particle stream, distributed on a fast conveyor belt, where they are scanned and evaluated while passing and an image is recorded by a line scan detector.      Eleven rock samples were analysed in this study. They include four rock type samples: granite, basalt, sandstone, and gneiss, all obtained from Luleå University of Technology (LTU) sample storage and seven ore type samples which include a porphyry Cu sulphide ore, a porphyry Cu oxide ore, a porphyry Cu-Au-Ag ore, an apatite iron ore (AIO), an iron-oxide copper gold ore (IOCG), an orogenic gold ore and a volcanogenic massive sulphide ore (VMS).       The SEM results give a semi-quantitative elemental composition of the rocks, which may be usedto discriminate mineralisation. Energy dispersive X-ray spectroscopy (EDS) maps may be used to identifygeological features and secondary electron (SE) images may be used to understand the topography of the rock samples. The SEM has a low penetration depth rate but produces moderate to high accuracy resultsdepending on the settings and calibrations. It requires a lengthy sample preparation, and its analytical time is often too long for routine industrial application. LIBS results also provide rock elemental compositions similar to the SEM, which may be quantitative if the same spectrometer is used for all elements and calibrated against a standard. It also produces element maps similar to the SEM-EDS maps. LIBS analyses yield high accuracy results but at a low penetration depth. There are no standard calibrations for the LIBS measurements, which limits quantification. LIBS measurements do not require any form of sample preparation. ME-XRT analyses result in rock chemical data portraying a light material fraction (aluminium-like) and a heavy material fraction (iron-like) which may be used to distinguish different rock samples based on the closeness of their effective atomic number Zeff to that of aluminium and iron respectively. It’s analysis also produces low-resolution images of the analysed rock samples. The image resolution is too low to allow interpretation of the data in the context of the structures and textures in the rock samples. It has a higher penetration depth than LIBS and SEM-EDS producing more volumetric data but with a lower accuracy in terms of the amount of information obtained. Only two elements are used for ME-XRT calibration measurements, if many elements of varying atomic numbers could be used, it would have the ability to provide a more reliable data. Samples must have a maximum and minimum thickness; thus, sample preparation is required to regulate the rock thickness.      SEM and LIBS provide element compositions of minerals and element distribution maps required by geologist in their daily activities during exploration and mining. This information can be considered the most useful obtained from all three techniques. However, LIBS analyses are faster, and its maps are of higher quality even at the same resolution as the SEM-EDS. This makes the LIBS preferable for real time measurements and analyses. Geological activities like drill core logging, mine mapping and sampling for grade control all require fast results for project continuity and LIBS is suitable for this purpose as it can keep up with the pace of these activities. SEM analytical technique provides semi-quantitative data which is more accurate than the LIBS data and thus, preferable for usage in research institutions and universities.ME-XRT can reveal information on the internal structures or different rock sample compositions. This makes it a suitable technique in distinguishing ore from waste material especially in iron ore mining and processing where the iron needs to be separated from the siliceous waste and sorting is also required prior to beneficiation to avoid equipment destruction by abrasive quartz. LIBS and ME-XRT analytical techniques complement each other in terms of analytical capabilities as LIBS has a low penetration depthrate but high accuracy results while the ME-XRT has a high penetration depth rate but low accuracy results. They are both fast scanning techniques that can be used for real time measurements and analyses and if their analytical prowess can be improved, the combination of these two fast analytical techniques may enable us to obtain high quality data and may as well be what is needed by geologists in the future.

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