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.

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.

This thesis deals with a study of lithium-ion batteries. It is focused into negative electrode materials and electrolytes. In this thesis is presented synthesis, electrochemical properties, possibilities to improving negative electrode materials as LTO (Lithium Titanate Oxid) and graphite. These electrode materials were investigated with respect to their compatibility at electrolytes with carbonate solvents, Sulfolane and DMF (DiMethylFormamide) in detail. The main aim of this thesis is to characterize electrode materials and electrolyte properties depending on wide range of temperatures and their comparison for the purpose of achievement of the best solution. The thesis is divided into two main parts. The theoretical part of thesis describes composition, process of synthesis and analysis of lithium-ion cell. Practical part contains measuring and evaluating of charge-discharge and irreversible capacity characteristics related to variety of environmental temperatures.

The dissertation thesis deals with investigation of electrode materials for Lithium-ion batteries. The main aim of investigation was focused to materials for negative electrode of Litihum-ion batteries. These negative electrode materials operate on intercalation principle. Object of interest are carbonaceous materials, especially their graphite forms. Graphite plays host role in lithium ion – graphite interactions that provides LiC6 compound. As a result of that investigation can be considered improving of graphite materials from stability, irreversible capacity and other parameters points of view. This kind of investigation takes an important part in field of elementary investigation work engaged to the next generation of Lithium-ion batteries. The work also describes the fire safety issue of Lithium-ion batteries along with compatibility of negative electrode materials and aprotic electrolytes.

The diploma thesis is focused on the dependence of heat storage on thermal conductivity, which is characterized by the thermal conductivity coefficient. Two basic materials were chosen for the measurements – universal plaster mixture and gypsum plaster. The thermal conductivity of the materials was increased by adding milled graphite powder, which conducts the heat very well. The taken samples were then examined for differences in the behaviour in the non-stationary thermal field and thermal-technical parameters – the specific heat capacity and the thermal conductivity coefficient – were determined.

In the diploma thesis the charge transfer reaction on thin layer N,N',N'',N'''-tetramethyl-tetra-3,4-pyridinoporphyrazinocobalt mediator is studied. The mediator is deposited on electrode surface formed by basal plane of highly ordered pyrolytic graphite. The modified electrode, which displays electrocatalytic activity to oxidation of propylene, has been characterized by cyclic voltammetry, backscattering spectroscopy and atomic force microscopy.

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.

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.

Bei der Herstellung von dickwandigem GJS treten zahlreiche ungeklärte Effekte durch die sehr langsamen Abkühlungs- und Erstarrungsgeschwindigkeiten auf. Bisherige Untersuchungsmethoden ermöglichen keine definierte Temperaturführung analog zum realen Bauteil und benötigen trotzdem große Schmelzemengen und einen hohen Trennaufwand für die Probenherstellung. Das Ziel der Arbeit bestand in der Entwicklung einer Versuchsmethode zur experimentellen Simulation extrem langer Abkühl- und Erstarrungszeiten von GJS. Die Verwendung einer geeigneten Abdeckung der Schmelze zur Minimierung des Mg-Abbrandes und eines druckfesten Kaltwandofens inkl. dynamischer Temperatursteuerung ermöglichte reproduzierbare Versuche zur Einstellung verschiedener Gefügezustände durch Variation der Abkühlregime und des Impfzustandes. Es gelang, Chunkygrafit und Grafitflotation gezielt herzustellen und dadurch die Entstehungsmechanismen wissenschaftlich zu untersuchen. Ein Chunkygrafit-Index-Diagramm konnte erarbeitet werden.

Electroconductive composites are modern materials that are commonly used in many industries such as the construction industry among others. For example these materials can be useful as sensors for monitoring changes in constructions. The aim of this thesis is the research of electrically conductive silicate composite based on secondary raw materials. The design of this composite is based on the development of its own mixtures and experimental verification of the effect of the structure. The introduction part consists of a detailed analysis of 15 materials. Samples of the 5 fine and 2 coarse electrically conductive fillers were tested. Composite with filler Condufit C4 was selected as representative for type of fine fillers. Composite with filler Supragraphite C300 was selected as representative for type of coarse fillers. The selection of the composites was based on the impedance of the fabricated composites with these fillers. Subsequently, the individual components of the primary mixture were substituted. The cement was replaced by high-temperature fly ash in the amount of 20, 30, and 40 %, the aggregate of a similar fraction was replaced by steel sawdust, and the primary electrically conductive fillers were replaced by secondary ones in the amount of 30 and 50 %. All proposed replacements reduced the impedance of the composite. The most effective replacement for impedance reduction was replacement with waste graphite (up to 92 % reduction), which also slightly improved the mechanical properties of the composite. The result of this thesis is an optimized electrically conductive composite based on secondary raw materials with a fine type of filler with 30 % replacement by waste graphite "odpad vysavač"which achieves an impedance of 5 ohms. The partial goal of this thesis is a verification of the influence of moisture on the impedance of composites. Results are significantly affected by moisture when using the coarse type of filler, when using the fine type are not.