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Impact of technological parameters on electrochemical properties of negative electrode in lithium-ion battery
Živčic, Samuel ; Máca, Josef (referee) ; Libich, Jiří (advisor)
This bachelor thesis deals with the issue of li-ion batteries and consists of two main parts. The first part of the thesis deals with a theory. It describes the functionality of electrochemical cells, especially li-ion cells. Operational principle of the cell is discussed, with the main focus given on negative electrode (anode) and the material it consists of, the natural graphite, mainly his electrochemical properties. Last chapter of theory describes expected impact of technological parameters on electrochemical properties of negative electrode. The second part of the thesis is the practical part. First, it describes procedure of making electrodes in laboratory and afterwards it provides an explanation of used measuring methods, steps taken during the measurement, and the results of the measurements. At the end of the thesis, the influence of pressure and layer thickness on electrochemical properties of natural graphite and on capacitive and current characteristics of negative electrode is evaluated.
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Low energy excitations in oriented graphite by THz magneto-optical spectroscopy
Dubský, Jan ; Kunc, Jan (referee) ; Vrba, Radimír (advisor)
This master’s thesis deals with the modelling of electronic properties of graphite crystal, which are measurable using a spectrometer based on high frequency electron paramagnetic resonance (HFEPR for short) located in laboratories of CEITEC BUT. This is especially the band structure of graphite and its Landau levels. The theoretical part of the thesis describes key effects and connections from quantum mechanics and definitions of important terms from solid state physics, which are used to describe the crystalline structure of graphite and its electronic properties. Furthermore, the project describes the HFEPR spectrometer and its functional principle. In the practical part of the thesis, there are numerical models of the band structure of graphite and of its Landau levels and description of the preparation of a graphite sample for measurement. At the end of the practical part there is the analysis of measurements results, namely the cyclotron resonance and Shubnikov-de Haas oscillations, thanks to which it is possible to determine physical parameters of the sample, such as effective mass of charge carriers and fundamental frequency.
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Infuence of Technological Parameters on Electrochemical Properties of Negative Electrode in Lithium-ion Cell
Kaňa, Michal ; Máca, Josef (referee) ; Libich, Jiří (advisor)
This diploma thesis deals with lithium-ion batteries. It is focused on negative electrode on grafit based. The goal of this thesis is to show the problematics of lithium-ion batteries together with possibilities for improvement of their basic parametres as capacity and current elektricity loadability. The first part is focused on the description of functionality of lithiumion battery. The second part is practical and it is focused on production of negative electrodes from natural graphite 280H which has different thickness and compression pressure. The third part describes preparation of negative electrodes from natural graphite 280H and also includes results of measurement. In the last part are different types of negative electrodes from natural graphite 280H compared and evaluated including the determination of conclusions. This comparison and evaluation based on obtained data.
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Effect of flexural loading on electrical properties of alkali-activated slag composites
Šimko, Lukáš ; Kusák, Ivo (referee) ; Rovnaník, Pavel (advisor)
Ordinary concrete is the most commonly used building material, but nowadays the requirements for low energy consumption, durability of structures together with their easy diagnostics as well as ecological production raises. This thesis deals with cement and aluminosilicate composites with content of conductive fillers, which allows to monitor the change in electrical properties, most commonly electrical resistance in dependence on mechanical stress. In the experimental part of the thesis, test beams were produced based on alkali-activated slag with content of carbon nanotubes, graphite powder, carbon black and carbon fibre. The beams were subjected to flexural loading in a three-point bending configuration and the shift in electrical resistance was monitored.
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Negative electrode materials for lithium-ion batteries
Šikuda, Milan ; Vondrák, Jiří (referee) ; Libich, Jiří (advisor)
This theses deal with a study of basic functional principles of cells. It is focused on carbon materials, which are the basic for negative electrode masses of lithium-ion accumulators. The aim of this work is understanding principle lithium-ion accumulator, get an overview about the most widespread materials currently using for negative electrode materials with measuring their characteristics. Then compare characteristics of carbon materials with alternatives materials for negative electrode on the base of silicon. First part of the work is devoted of principle functionality lithium-ion accumulators together with description of galvanostatics and potentiostatics measuring methods. Practical part deals with preparation and measuring negative electrode masses characteristics.
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Carbon Based Materials
Hrazdíra, Matěj ; Čelko, Ladislav (referee) ; Klakurková, Lenka (advisor)
The proposed bachelor thesis deals with carbon based materials. First of all, an overview of its allotropic modifications including newly discovered forms, conditions of their existence and also their basic properties is shown. Further the extraction of carbon materials is briefly introduced. In the next chapters, forms of carbon are classified and particularly described individually with respect to manufacturing technologies and further applications. Individual chapters are dedicated to synthetic carbon and graphite, carbon fibers and carbon fiber reinforced composites. Manufacturing processes of synthetic carbon and graphite, involving possible precursors, are described in detail together with their use in various engineering applications. The following part is dedicated to carbon fibers, in particular to the manufacturing process based on the precursor used including surface treatment and sizing. Additionally the use of virgin carbon fibers is also described. The last part is focused on carbon fiber reinforced composites. Firstly possible distributions of carbon fibers in a matrix are described. Then the technology of manufacturing, properties and use of single composites according to the matrix material are expounded.
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Biomimetic polymer/graphene layered nanocomposites
Dostalík, Petr ; Ondreáš, František (referee) ; Zbončák, Marek (advisor)
This batchelot thesis deals with preparation of biomimetic polymer/graphene layered nanocomposites. In order to prepare nanocomposites, it was first necessary to prepare a suitable graphene material. The Tour-Marcan method was chosen for its preparation, in which the effect of oxidation time on the structure of the resulting graphene/graphite oxide was investigated. From the result of structural analysis was evaluated, that after 4 hours of oxidation structure of graphite was intercalated, oxygen groups were formed (mainly expoxy groups) and inter-layer spacing increased to form graphite oxide (GO). Extension of oxidation time did not lead to major changes in struture of GO. Nanocomposites were prepareted by solution-casting method. The polar polymer – polyvinyl alcohol (PVAl) was used as a matrix with assumption of strong interaction between GO a PVAl. In order to promote GO intercalation, an ultrasonic dispersant was used in the process of nanocomposite preparation, the effect of which was manifested by an increase in the inter-layer GO distance in nanocomposites. It has been observed that the inter-layer spacing of GO and PVA1 is affected by the concentration of the individual components in the nanocomposites, suggesting a possible modification of the PVA1 crystalline structure. Structural analysis revealed that GO layers in composite were oriented in one direction.
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Lithium-ion battery: Negative electrode materials based on graphite
Vencelides, Lukáš ; Máca, Josef (referee) ; Libich, Jiří (advisor)
This bachelor‘s thesis deals with the isuess related to the lithium-ion batteries. The history of development of lithium-ion batteries, current commercially available and developed types are described in the thesis. The thesis deals in detail with the description of the characteristics and operating principle of lithium-ion accumulators with emphasis on negative electrode and negative electrode materials. The goal of the thesis is technological and electrochemical characterization of graphite negative electrode materials. Two types of natural graphite are used in the thesis, both are potenti-galvanistically analyzed from the point of view of capacitance and current characteristics.
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Study of the influence of fillers and external conditions on the resistivity of cement composites
Kejda, Dalibor ; Melichar, Jindřich (referee) ; Černý, Vít (advisor)
The progress of new materials is important for the construction industry. Modern materials include cement composites with reduced resistivity. This is achieved by adding suitable electrically conductive fillers. If there is enough of these fillers, the so-called percolation threshold occurs. Suitable fillers (Condufit C4 and Supragraphite C300) have been proposed. Recipes have been designed to be before and after the percolation threshold. The tests were performed on beams measuring 40x40x160 mm with built-in electrodes for measuring their resistivity. The aim of the work was the research of influencing external conditions on cement composites. The effect of temperature was verified. The lowest values of resistivity were evaluated at temperatures of 50 ° C and the resistivity increased with decreasing temperature. The effect of humidity on the resistivity was then verified. Reference samples and samples with a smaller proportion of graphite powder showed larger differences in resistivities with increasing humidity. The samples above the percolation threshold were not much affected by increasing humidity. Finally, the effect of loading on the resistivity of the samples was verified. Almost all samples with increasing compressive stress showed an increasing value of resistivity.
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Calandering of li-ion electrodes and its impact on the final capacity of lithium-ion cell
Svoboda, Lukáš ; Kazda, Tomáš (referee) ; Čech, Ondřej (advisor)
There is an effort to produce lithium-ion batteries with maximal density of energy, or higher capacity of cell with the same size. Calendaring of electrodes is important part of manufacturing of batteries. Its parameters, mainly the pressure of calendaring and with it related the final compression ratio of electrode layers, affect parameters of battery significantly. It is the process of pressing electrode material coated on current collector with certain pressure and it reduces its porosity and thickness. The aim of this bachelor thesis is determination of suitable level of calendaring that increases specific capacity, but does not reduce its cyclability.
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