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Study of intercalation properties of electrode materials based on naturla graphite
Bílek, Lukáš ; Máca, Josef (referee) ; Libich, Jiří (advisor)
This diploma thesis deals with the issue of lithium-ion accumulators. The thesis focuses on the negative electrode of lithium-ion accumulators made of natural graphite. The first part of this thesis points to the issue of electrochemical cells. In the theoretical part the thesis deals with the SEI layer, advantages, disadvantages, characteristics, operating principle and the use of lithium-ion accumulators. The practical part focuses on the electrochemical properties of negative electrode, especially the determination of the diffusion coefficient. Thesis also deals with electrochemical impedance spectroscopy (EIS) and its use in determining the equivalent replacement circuit and calculating the diffusion coefficient.
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Analysis of liquid electrolyte electrical parameters using impedance spectroscopy
Brabenec, Josef ; Pikula, Stanislav (referee) ; Havránek, Zdeněk (advisor)
The bachelor thesis deals with impedance spectroscopy of electrochemical systems, especially liquid electrolytes. The method of impedance spectroscopy is widely used to describe electrochemical cells, batteries and electrolytes for diagnostic purposes over a wide range of frequencies. This thesis presents the main types of impedance imaging in the complex and frequency domain, as well as basic information on the measurement methods used and the methods for impedance analysis. The main part of the thesis was the development of software for automated impedance measurements and estimation of equivalent circuit parameters using basic and specialized circuit elements. A workplace with fabricated electrodes for liquid electrolyte measurements was prepared for the application. The functionality of the application was verified by real measurements of different concentrations of water and salt solutions. The validity of the estimated equivalent circuit parameters was verified on measured simple circuits connected from basic circuit elements and was also verified using the commercially used ZView software.
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Testing of a Prototype Device Using Electrochemical Impedance Spectroscopy (EIS)
Zsigmond, András ; Jaššo, Kamil (referee) ; Libich, Jiří (advisor)
.Tato diplomová práce se zabývá elektrochemickými procesy v lítium-iontových bateriích. Pro charakterizaci různých elektrochemických procesů se používá metoda nazývaná elektrochemická impedanční spektroskopie (EIS). V prvních kapitolách jsou popsány různé typy baterií a jejich rozdíly. Práce také obsahuje popis experimentálního zařízení používaného pro EIS. Součástí práce je také porovnání experimentálního zařízení a zařízení od společnosti BioLogic Science Instruments.
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Impedance Measurement of Lead-acid Accumulator
Abraham, Pavel ; Dostál, Zdeněk (referee) ; Jareš, Petr (referee) ; Bača, Petr (advisor)
This dissertation deals with impedance measurements of lead-acid accumulator. Main aim was to study recent problems of impedance measurements of lead-acid accumulator and most importantly to extend difference method and also to interpret its results. The original DC difference method was developed earlier at our Power Sources Laboratory of Department of Electrical and Electronic Technology. The DC difference method and also the new AC difference method are both non-destructive, which means that experimental data can be obtained in situ. New method provides more accurate set of information because of its wide frequency range nature. Electrodes of lead-acid accumulator were analysed with special attention to collector / active mass double layer and to active mass itself. Various states and operation regimes were investigated. Obtained data contributed to better understanding of involved degradation mechanisms. Main aim of other experiment was to observe and interpret corrosion rates of electrode collector composed of various lead alloys. Last but not least charge and discharge regimes e.g. 100% deep of discharge regime, partial state of charge (PSoC) regime and pulse charge regime were analysed. BioLogic VSP was the device used for almost all experimental measurements. It takes a lot of effort to optimise VSP operation regime. Best operation regime of VSP for the difference method was suggested too.
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Modelling of lithium ion batteries using ECM
Langer, Lukáš ; Kazda, Tomáš (referee) ; Vyroubal, Petr (advisor)
The main aim of this paper are models of Li-Ion storage batteries made and simulated in ANSYS Fluent software. Various ways of simulations are discussed with main aim on ECM method and how its numerical model is computed. A process of getting information and required data from real battery to be compared with simulation results by EIS method is also discussed. These results are then compared with results from ANSYS Fluent.
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Impedance spectroscopy of organic conductors and semiconductors
Černošek, Michal ; Sedláček, Jiří (referee) ; Hubálek, Jaromír (advisor)
This thesis deals with organic materials and determining their electrical parameters. In the thesis are discussed methods of deposition of organic layers and their measurement. Described are the aspects, which are characteristic for organic materials. They will briefly mention some new components and commercial systems. Special attention is given to conducting polymers and determining their parameters. In the experimental part were measured VA and impedance characteristics of the conductive polymer PEDOT-PSS. The research was also about material degradation in time and effects of thickness on the electrical parameters.
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Electrolytes characterization based on mixtures of ionic liquids and aprotic solvents
Šašek, Martin ; Libich, Jiří (referee) ; Máca, Josef (advisor)
The thesis deals with liquid aprotic electrolytes based on mixtures of ionic liquid and solvent. EmimBF4, namely 1-ethyl-3-ethylimidazolium tetrafluoroborate, was used as the starting ionic liquid. A mixture of propylene carbonate, ethylene carbonate and dimethyl carbonate was used as solvents. Electrolytes were enriched with two electrolyte salts LiBF4 and NaBF4 from the resulting mixtures selected the most suitable electrolytes for Li-ion and Na-ion accumulators. Electrolytes were selected taking into account the required properties: the width of the potential window, the measured electrical conductivity and, last but not least, the safety.
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Hydrothermal synthesis and characterization of calcium phosphate-based coatings on AZ31 magnesium alloy
Knoflíčková, Lenka ; Doskočil, Leoš (referee) ; Buchtík, Martin (advisor)
The aim of this diploma thesis was to summarize all necessary knowledge needed for preparation of a quality CaP coating on AZ31 wrought magnesium alloys, and to implement its optimization for use in simulated body fluids. The theoretical part discusses biomaterials and their classification. Subsequently, the potential of magnesium alloys, their corrosion, and the possibility of surface treatment for in vivo applications are described in detail. The theoretical part concludes with the mechanism of deposition of CaP coatings on magnesium alloys and methods to evaluate their corrosion resistance. The experimental part includes the process of optimization of Mg alloy pretreatment and optimization of CaP coatings preparation, where the quality evaluation criteria were the appearance of the coating and its electrochemical and corrosion properties. These were evaluated by potentiodynamic tests. The microstructure and the chemical composition of deposited coating were observed and measured by optical and scanning electron microscopy. Long-term corrosion tests using electrochemical impedance spectroscopy (EIS) were performed on the optimized CaP coatings and these results were then compared with the corrosion properties of the uncoated AZ31 alloy.
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Organic matter impedance extraction and modeling
Vyplel, Vojtěch ; Balada, Radek (referee) ; Šotner, Roman (advisor)
This thesis addresses the problem of extracting impedance characteristics from organic materials. The aim was to explain the modelling of impedance characteristics using non-integer models of electronic circuits. Also to explain the principle of electro impedance spectroscopy, what is a constant phase element and the Cole model. Based on this knowledge, impedance characteristics were measured and analyzed and circuit models were developed. The resulting measured data are confronted with the theoretical knowledge.
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