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Analog switch for switched current circuits
Jahn, Michal ; Kledrowetz, Vilém (referee) ; Pavlík, Michal (advisor)
This bachelor’s deals with a design of analog switches using switched current technique and CMOS technology. The design of these switches was implemented and subsequently simulated in the CADENCE environment where the emphasis was on suppression of transient processes. It is a charge injection error and a clock-feedthrough error when charging the capacities of channel during switching on or opening.
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Natural Graphite as Negative Electrode Material for Lithium-Ion Batteries
Paulovics, Petr ; Jahn, Michal (referee) ; Libich, Jiří (advisor)
This bachelor thesis deals with an issue of lithium-ion batteries. It is focused on the negative (anode) electrode materials, dealing with the study of their electrochemical properties. The aim was to study the capacity characteristics of active electrode materials based on natural graphite. Mainly it was assessed the relationship morphology electrode material and the pressing pressure due to the electrochemical properties of the capacitive electrode. The first part of the thesis contains a theoretical introduction to the negative electrode materials with focuses on the composition and overall analysis of the lithium-ion cell. The second part is focuses on the manufacture, assembly and measurement of lithium-ion cells.
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Dielectric properties of liquid insulators
Jahn, Michal ; Starý, Jiří (referee) ; Špinka, Jiří (advisor)
This master‘s thesis deals with measurement of liquid dielectric materials (insulators). Above all, it is the different kinds of clean and drinking water, but also transformer oils. There was done theoretical information retrieval about the given topic in this project and on the basis of theory there were realized the relevant measurements of selected properties of liquid dielectric, such as permittivity, capacitance, loss number, conductivity, but also temperature dependence of these parameters. The measurements were realized with the help of product manufactured at the faculty FEKT VUT and with the help of measuring system AGILENT 16452A. The measured results were evaluated, graphically processed and compared.
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Gel polymer electrolytes with nanoparticles
Szotkowski, Radek ; Sedlaříková, Marie (referee) ; Jahn, Michal (advisor)
This master‘s thesis concerns gel polymer electrolytes formed on a methyl methacrylate base with selected types of nanoparticles. In the thesis are also analyzed the methods for measuring electrochemical properties. The practical portion deals with sample preparations of gel polymer electrolytes with different contents of alkaline salt in a solvent, creating gels with different nanoparticle content and comparing gel polymer electrolytes polymerized with heat and UV radiation. The thesis deals with the evaluation of these samples from the viewpoint of electrical conductivity and potential windows as well as thermal analysis of selected samples.
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Gel polymer electrolytes with fire retardands
Veselkova, Iuliia ; Jahn, Michal (referee) ; Sedlaříková, Marie (advisor)
This graduate work deals with the study and preparation of gel polymer electrolytes with flame retardants for lithium-ion batteries. The theoretical part describes the types of electrolytes, their features, benefits, how they differ and where they are used in detail. The basis of this section is gel electrolytes with flame retardants, to measure their electrical and electrochemical properties. The experimental part deals with the preparation of samples of gel electrolytes with different percentages of flame retardant, where varied species of flame retardants and measuring their electrical conductivity and potential windows. Impedance spectroscopy, cyclic voltammetry and dynamic-analytical thermal analysis were selected as measuring methods.
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Gel polymer electrolytes modified by ionic liquids with aprotic solvents
Pospíšilová, Michaela ; Sedlaříková, Marie (referee) ; Jahn, Michal (advisor)
This graduate thesis is focused on measuring the electrical conductivity of the gel polymeric electrolytes, their preparation and deals with the changes of the performance ratio of the individual substances in gel electrolyte The theoretical part deals with electrochemistry, gel electrolytes, the conductivity of electrolytes, gel electrolytes preparation, methods used to evaluate the measured results and on the properties of the ionic liquids. In the practical part is summarized the process of preparing gel electrolytes, the chemicals to prepare the gels with ionic liquids. The results are evaluated by using impedance technique and linear voltammetry, there are calculated the values of the electrical conductivity of the electrolyte and potential windows.
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New gel electrolytes
Sumka, Martin ; Jahn, Michal (referee) ; Sedlaříková, Marie (advisor)
This master´s thesis deals with the properties of gel polymer electrolytes, brief characteristics of other types of electrolytes and materials that are used for preparing polymer electrolytes. The thesis explains the use of the gel electrolytes in practice, the current conduction in the electrolytes and the properties of ionic liquids, and flame retardants. This thesis also focuses on methods of measurement of mechanical properties of gel polymer electrolytes. The practical part is focused on preparation of methacrylate gel electrolytes and their modifications with the use of flame retardant - triethyl phosphate (TEP) and ionic liquid - 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (Emim TFSI). In this part there are evaluations of their potential funcionality (potential window) and specific conductance conductivity using the method LSV (linear sweep voltammetry) and impedance spectroscopy. The practical part also includes a thermal analysis of selected samples by TGA, DTA and EGA methods.
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Gel Polymer Electrolytes for Electrochemical Power Sources
Jahn, Michal ; Bartušek, Karel (referee) ; Paidar,, Martin (referee) ; Sedlaříková, Marie (advisor)
Dissertation thesis is focused on study of gel polymer electrolytes for electrochemical power sources, but also for other application. The electrical, electrochemical, mechanical and optical properties of gel electrolyte samples were measured in this work. The main goal was to prepare samples with high specific conductivity and with largest possible potential windows. Thermal stability of some samples was also monitored using thermogravimetric analyzes. The optimization of the chemical composition, quantities and ratios of individual chemicals has been made. Comparison of thermal polymerization and UV polymerization was performed. In the first part of the work, aprotic solvents and their mixtures in combination with lithium and sodium salts and one ammonium salt were investigated. Another subject of research was various crosslinking agents with methacrylate-based monomers. The second part of the work investigated the effect of ionic liquids, phosphor base flame retardants and nanoparticles as additives to gel electrolytes. In the last part of the work, the influence of the magnetic and electric field on the polymerization of gel electrolytes containing nanoparticles and selected copolymers was studied. Finally, a Li-ion cell with a graphite anode, LiFePO4 cathode and selected gel electrolyte was assembled.
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Gel Polymer Electrolytes Based On MMA With Ionic Liquids
Jahn, Michal
Gel polymer electrolytes are perspective electrolytes for new types of Li-ion batteries today. The properties respectively advantages of these gels can be used also in other fields of electrochemistry. Very promising combination can be electrochemically stable polymers and ionic liquids, which are substances that consist of an organic cation and an inorganic or organic anion, with a melting point below 100 °C. Main advantages of ionic liquids are high ionic conductivity, inflammability and excellent electrochemical stability. These ionic liquids may be suitable for new lithiumion batteries and supercapacitors, especially where the required higher thermal stability. In this paper, I will present fundamental characteristics of gel polymer electrolytes with ionic liquids.
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