Ediacaran phosphorites provide a principal record of the paleoenvironmental and paleoecological conditions of the oceans during Earth's second major oxygenation and the evolution of complex life. Although the fidelity of this record is high, diagenesis and metamorphism frequently alter or overprint primary minerals and structures, necessitating validation of results from mineralogical and geochemical analyses and determinations of fossil affinities. Therefore, it is imperative to unravel the complications of post-depositional alteration, and thus provide a strong foundation for environmental and biological interpretations, via an integrated sedimentological, stratigraphic, petrographic, and geochemical approach. Transmitted light, cathodoluminescence, and scanning electron microscope petrography in conjunction with Raman spectroscopic and X-ray diffraction analyses were employed to determine the origin of phosphorites from the early Ediacaran (632 – 614 Ma) Doushantuo Formation at the Wanjiagou section, near Zhangcunping, Hubei Province in South China. Results suggest granular phosphorites were deposited during one to two episodes of reworking of pristine phosphorite hardgrounds, which originated during redox-controlled and/or microbially-mediated phosphogenesis. Granular laminae were then cemented by a ferric iron-phosphate mineral, phosphosiderite. As a product of oxidative weathering and/or thermal stabilization of ferrous iron-phosphates (e.g., vivianite), this cement is suggestive of precipitation from ferruginous porewaters. This is the first direct evidence for iron-phosphate minerals in Ediacaran phosphorites and substantiates previous hypotheses of P burial beyond primary calcium phosphate. If accumulation and burial of phosphorites during this interval was rapid enough to have limited P availability and thus primary productivity, their formation may have governed oxygen production prior to the Neoproterozoic Oxygenation Event (NOE). Oxygenation of the oceans during the NOE and the appearance of complex, multicellular life are suspected to be causally linked within the Ediacaran. However, a fragmented fossil record with insufficient analogues and varied taphonomic modes leaves much of the Ediacaran fauna with uncertain taxonomic and phylogenetic affinities, leading to ambiguity regarding their life modes and environmental associations. Furthermore, demonstrating biogenicity is an often overlooked, yet fundamental component of Ediacaran fossil identification and interpretation, something that has particularly affected the morphologically simple discoidal group of fossils known colloquially as Aspidella. Petrographic observations supported by Raman and energy dispersive spectroscopy provide evidence that discoidal concretions from the Ediacaran Miaohe Member near Maxi, Hubei Province in South China are diagenetic in origin but superficially resemble Aspidella's morphology. Erosion of these syn-compactional concretions produced concentric rings on bedding planes caused by internally deformed laminae resulting in Aspidella pseudofossils. These results highlight the necessity for critical evaluation of the origin of discoidal structures observed in Ediacaran sedimentary successions. / Master of Science / Contemporary and ancient phosphorus-rich sedimentary deposits, known as phosphorites, precipitate within the oceans as a result of intricate chemical and biological interactions. The Ediacaran Period (635 – 539 million years ago) contains the first truly extensive occurrences of phosphorites in addition to a fossil record of the earliest animal organisms. Deposited after the end of Earth's last global glaciation, the origins of Ediacaran phosphorites are affiliated with these dramatic climatic and evolutionary transitions as well as the rise of atmospheric and oceanic oxygen concentrations to near modern levels. Deposition of phosphorites often occurs in low-oxygen oceanic environments and their formation constitutes the dominant mechanism by which phosphorus is removed from the phosphorus cycle on time scales greater than 1000 years. Therefore, phosphorite occurrences provide a record of phosphorus cycling, oxygen availability, and biological productivity. However, microscopic and chemical analyses of phosphorites from the Ediacaran Doushantuo Formation in South China demonstrate they are partially composed of phosphorus minerals that likely formed in non-oxygenated environments. The presence of these atypical phosphorus minerals has been previously hypothesized, with the implication that they further limited the availability of phosphorus for use by photosynthetic organisms. Such a limitation on photosynthesis would have resulted in decreased oxygen production and thus the formation of these phosphorites may explain the rate and trend of the change in oxygen concentrations observed during the Ediacaran. Ediacaran fossils also act as a proxy for environmental conditions of the ancient oceans through inferences about the preserved organisms' requirements for life. Although most fossils of this age are the first of their kind in terms of biological complexity, they are typically simple in terms of their morphology, making identification difficult. Furthermore, providing evidence that such simple structures actually represent a fossilized organism is often problematic due to the inability to compare them with modern organisms. Microscopic and chemical analyses of disc-shaped structures from the Ediacaran Miaohe Member in South China reveal that they are concretions that were not created by an organism, even though their morphology very closely resembles the Ediacaran fossil Aspidella. Identification of these concretions as pseudofossils suggests that close examination of fossils from Ediacaran rocks is necessary.

Lithium iron phosphate (LiFePO4) has been synthesized by hydrothermal synthesis using pyrrole as an efficient reducing agent. The oxidized Fe3+ in the system reacts with pyrrole that can form polypyrrole (PPy) to generate Fe2+. The PPy can also be a carbon source for further calcination. The observations of scanning electron microscope (SEM) and transmission electron microscope (TEM) show that the particle size of LiFePO4 is around 500 nm and a layer of carbon coats on LiFePO4. The chemical composition of the LiFePO4 was characterized by elemental analysis (EA) and inductively coupled plasma mass spectroscopy (ICP/MS). The results of TEM and X-ray diffraction (XRD) show the structure of LiFePO4 is orthorhombic olivine. Raman and X-ray photoelectron spectroscopy (XPS) results indicate that pyrrole as a reducing agent prevents the impurity of Fe3+ formation and the resulting polypyrrole plays a role as carbon source. The calcination of LiFePO4 greatly affects the energy density. In addition, the carbon contain in the LiFePO4 powder is controllable using the addition of Fe3+ to enhance the electrical conductivity. Moreover, the electrochemical results show the energy capacity of the hydrothermal LiFePO4 is 152 mAh g−1. The LiFePO4 has a better rate discharge capability compared with LiFePO4 synthesized with ascorbic acid as a reducing agent.

Lithium iron phosphate (LiFePO4) is prepared by hydrothermal process using Fe(III) as precursor and pyrrole as an efficient reducing agent. The Fe(III) precursor in the system reacts with pyrrole to generate polypyrrole (PPy) and reduce Fe(III) to Fe(II). The different molar ratio Fe(III) polymerize different content of PPy and PPy can also be a carbon source for further calcination. The structural and morphological properties of LiFePO4 powder were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and a transmission electron microscope (TEM). The XRD and TEM results demonstrate that LiFePO4 powder has an orthorhombic olivine-type structure with a space group of Pnma. The SEM and TEM results show that the particle size of LiFePO4 is around 200 nm and a layer of carbon coats on LiFePO4. The chemical composition of the LiFePO4 powder was characterized by elemental analysis (EA) and inductively coupled plasma/mass spectroscopy (ICP/MS). Raman and X-ray photoelectron spectroscopy (XPS) results indicate that pyrrole as a reducing agent reduces and prevents the formation of Fe(III) impurity and the resulting PPy plays a role as carbon source. Among the synthesized cathode materials, LiFePO4 synthesized using 5% molar ratio of Fe(III) and subsequent calcinations of 600 ¢XC shows the best electrochemical property with an discharge capacity of 160 mAhg−1 close to its theoretical capacity 170 mAh g−1 at 0.2 C rate. Using 10% molar ratio of Fe(III), and the discharge capacity of LiFePO4 at 10 C rate reaches 106 mAhg−1.

Increasing pressure from environmental, political and economic sources are driving the development of an electric vehicle powertrain. The advent of hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and battery electric vehicles (BEVs) bring significant technological and design challenges. The success of electric vehicle powertrains depends heavily on the robustness and longevity of the on-board energy storage system or battery. Currently, lithium-ion batteries are the most suitable technology for use in electrified vehicles. The majority of literature and commercially available battery performance data assumes a working environment that is at room temperature. However, an electrified vehicle battery will need to perform under a wide range of temperatures, including the extreme cold and hot environments. Battery performance changes significantly with temperature, so the effects of extreme temperature operation must be understood and accounted for in electrified vehicle design. In order to meet the aggressive development schedules of the automotive industry, electrified powertrain models are often employed. The development of a temperature-dependent battery model with an accompanying vehicle model would greatly enable model based design and rapid prototyping efforts. This paper empirically determines the performance characteristics of an A123 lithium iron-phosphate battery, re-parameterizes the battery model of a vehicle powertrain model, and estimates the electric range of the modeled vehicle at various temperatures. The battery and vehicle models will allow future development of cold-weather operational strategies. As expected the vehicle range is found to be far lower with a cold battery back. This effect is seen to be much more pronounced in the aggressive US06 drive cycle where the all-electric range was found to be 44% lower at -20°C than at 25°C. Also it was found that there was minimal impact of temperature on range above 25°C

This thesis investigates the high frequency discharging characteristics of the lithium iron phosphate battery. The investigation focuses on effects of the high-frequency current on the dischargeable capacity of the battery. Included are the current profiles of triangle, saw-tooth, and trapezoidal waves, which are produced from commonly used DC-DC converters. Experimental results show that the current with the higher frequency has less dischargeable capacity. On the other hand, the converter current resonating into and out from the battery results the additional losses. The possible reasons that affect the discharged capacities are explained by the equivalent circuit of the battery.

Increasing pressure from environmental, political and economic sources are driving the development of an electric vehicle powertrain. The advent of hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and battery electric vehicles (BEVs) bring significant technological and design challenges. The success of electric vehicle powertrains depends heavily on the robustness and longevity of the on-board energy storage system or battery. Currently, lithium-ion batteries are the most suitable technology for use in electrified vehicles. The majority of literature and commercially available battery performance data assumes a working environment that is at room temperature. However, an electrified vehicle battery will need to perform under a wide range of temperatures, including the extreme cold and hot environments. Battery performance changes significantly with temperature, so the effects of extreme temperature operation must be understood and accounted for in electrified vehicle design. In order to meet the aggressive development schedules of the automotive industry, electrified powertrain models are often employed. The development of a temperature-dependent battery model with an accompanying vehicle model would greatly enable model based design and rapid prototyping efforts. This paper empirically determines the performance characteristics of an A123 lithium iron-phosphate battery, re-parameterizes the battery model of a vehicle powertrain model, and estimates the electric range of the modeled vehicle at various temperatures. The battery and vehicle models will allow future development of cold-weather operational strategies. As expected the vehicle range is found to be far lower with a cold battery back. This effect is seen to be much more pronounced in the aggressive US06 drive cycle where the all-electric range was found to be 44% lower at -20°C than at 25°C. Also it was found that there was minimal impact of temperature on range above 25°C

abstract: There was a growing trend in the automotive market on the adoption of Hybrid Electric Vehicles (HEVs) for consumers to purchase. This was partially due to external pressures such as the effects of global warming, cost of petroleum, governmental regulations, and popularity of the vehicle type. HEV technology relied on a variety of factors which included the powertrain (PT) of the system, external driving conditions, and the type of driving pattern being driven. The core foundation for HEVs depended heavily on the battery pack and chemistry being adopted for the vehicle performance and operations. This paper focused on the effects of hot and arid temperatures on the performance of LiFePO4 (LFP) battery packs and presented a possible modeling method for overall performance. Lithium-ion battery (LIB) packs were subjected to room and high temperature settings while being cycled under a current profile created from a drive cycle. The Federal Urban Driving Schedule (FUDS) was selected and modified to simulate normal city driving situation using an electric only drive mode. Capacity and impedance fade of the LIB packs were monitored over the lifetime of the pack to determine the overall performance through the variables of energy and power fade. Regression analysis was done on the energy and power fade of the LIB pack to determine the duration life of LIB packs for HEV applications. This was done by comparing energy and power fade with the average lifetime mileage of a vehicle. The collected capacity and impedance data was used to create an electrical equivalent model (EEM). The model was produced through the process of a modified Randles circuit and the creation of the inverse constant phase element (ICPE). Results indicated the model had a potential for high fidelity as long as a sufficient amount of data was gathered. X-ray powder diffraction (XRD) and a scanning electron microscope (SEM) was performed on a fresh and cycled LFP battery. SEM results suggested a dramatic growth on LFP crystals with a reduction in carbon coating after cycling. XRD effects showed a slight uniformed strain and decrease in size of LFP olivine crystals after cycling. / Dissertation/Thesis / Masters Thesis Engineering 2016

<p>Li-ion batteries are not only a technology for the future, they are indeed already the technology of choice for today’s mobile phones, laptops and cordless power tools. Their ability to provide high energy densities inexpensively and in a way which conforms to modern environmental standards is constantly opening up new markets for these batteries. To be able to maintain this trend, it is imperative that all issues which relate safety to performance be studied in the greatest detail. The surface chemistry of the electrode-electrolyte interfaces is intrinsically crucial to Li-ion battery performance and safety. Unfortunately, the reactions occurring at these interfaces are still poorly understood. The aim of this thesis is therefore to increase our understanding of the surface chemistries and stability phenomena at the electrode-electrolyte interfaces for three novel Li-ion battery electrode materials.</p><p>Photoelectron spectroscopy has been used to study the surface chemistry of the anode material AlSb and the cathode materials LiFePO₄ and Li₂FeSiO₄. The cathode materials were both carbon-coated to improve inter-particle contact. The surface chemistry of these electrodes has been investigated in relation to their electrochemical performance and X-ray diffraction obtained structural results. Surface film formation and degradation reactions are also discussed.</p><p>For AlSb, it has been shown that most of the surface layer deposition occurs between 0.50 and 0.01 V <i>vs.</i> Li°/Li⁺ and that cycling performance improves when the lower cut-off potential of 0.50 V is used instead of 0.01 V. For both LiFePO₄ and Li₂FeSiO₄, the surface layer has been found to be very thin and does not provide complete surface coverage. Li₂CO₃ was also found on the surface of Li₂FeSiO₄ on exposure to air; this was found to disappear from the surface in a PC-based electrolyte. These results combine to give the promise of good long-term cycling with increased performance and safety for all three electrode materials studied.</p>

Hydrothermal synthesis is a widely used technique for the preparation of fine particles. It can be carried out in batch or flow systems, although most studies have used batch reactors below 200 C. More recently, however, continuous hydrothermal synthesis has been employed in near- and supercritical water to obtain metal oxide particles. This technique offers tremendous promise for control of particle characteristics due to the rapidly changing properties of water with temperature and pressure in the critical region. However, the role of temperature in this process is not completely understood. Moreover, agglomeration of particles remains a problem in both batch and continuous hydrothermal techniques. This work is concerned with the use of continuous hydrothermal synthesis at near-critical and supercritical conditions to obtain iron oxide and lithium iron phosphate nanoparticles. Factors that affect size, size-distribution, and morphology of nanoparticles were investigated and the results have been used to resolve differences in the literature concerning the effect of temperature on particle size. It was shown that agglomeration can be minimized by using a protective polymer coating and this appears to be an effective method to control particle size. The continuous hydrothermal technique was also extended to materials other than metal oxides by synthesizing lithium iron phosphate. Differences in the particle sizes obtained using the batch and continuous methods were shown to be due to the different mechanisms of particle formation in the two techniques. Better particle characteristics (size, size distribution and morphology) were obtained using the continuous hydrothermal technique than using the batch hydrothermal method. Iron oxide nanoparticles were also deposited on the surface and in the pores of activated carbon pellets in a batch reactor in order to minimize agglomeration of particles. The resulting iron oxide activated carbon nanocomposites exhibited significant catalytic performance in the oxidation of propanal. Therefore, the use of supercritical water to deposit metal oxide particles on hydrophobic surfaces offers promise for carbon-supported catalyst preparation without the use of toxic or noxious solvents.

Darbe yra pateikti ličio geležies fosfato baterijų iškrovimo prie įvairių temperatūrų proceso tyrimai. Išanalizuotos įvairių rūšių baterijos ir nustatytos tinkamiausios baterijos panaudojimui elektra varomame transporte. Mokslinių straipsnių analizė, leido nustatyti ličio geležies fosfato baterijų trūkumus ir pranašumus bei išanalizuoti jų savybes ir ypatumus. Suprojektuotas eksperimentinių tyrimo stendas, pateikta tyrimo metodika ir atlikti ličio geležies fosfato baterijų iškrovimo prie skirtingų temperatūrų tyrimai. Išanalizuoti eksperimentinių tyrimų rezultatai, pateiktos išvados ir rekomendacijos. / In this work a research of lithium iron phosphate batteries discharge process at different temperatures has been carried out. Different types of batteries have been analyzed and the most suitable battery type for electric transport is chosen. Scientific publication analysis allowed to identify the limitations of lithium iron phosphate batteries and to analyze the characteristics and peculiarities of this battery type. A battery testing stand has been designed, a research methodology has been presented and discharge tests of lithium iron phosphate batteries at normal and low temperatures have been performed. The results have been analyzed and findings together with recommendations have been presented.