|
|
Composite electrode materials for lithium-ion batteries based on LiFePO4 prepared using GAC method
Vilhelm, Ondřej ; Neoral, Jiří (referee) ; Čech, Ondřej (advisor)
Presented work investigates the problem of secondary lithium-ion cells and the different available cathode materials. We have prepared samples of LiFePO4 with the addition of different kinds of carbon materials such as Super P, Vulcan and expanded graphite. We have always created the sample with and without surfactant. Developed samples were compared by measuring electrochemical methods (cyclic voltammetry, charge and discharge cycles and impedance spectroscopy). We also modeled the three-point cell for measuring electrochemical electrode materials.
|
|
|
Influence of Mn ionts in nickel hydroxide on behavour electrodes
Cirkovský, Jaroslav ; Vrbický, Jiří (referee) ; Sedlaříková, Marie (advisor)
The aim of my diploma thesis was to explore the influence of manganese ions put into nickel nitrate structure. The attention was focused mainly on the stabilization of nickel nitrate a modification, which could not change into b modification. The theoretical part of my thesis focused on applied materials, kinds of acumulators, basic parameters of acumulators and the description of chosen methods of measurement employed. It contained the electrodeposition, the impedance spectroscopy and the cyclic voltammetry. The task of the experimental part was to measure the effect of manganese ions put into potassium hydroxide structure. Proportions of Ni (nickel nitrate) : Mn (manganese nitrate) 10:0, 7:3, 5:5, 6:1 and 6:4 were blended for the measurement. By means of the electrodeposition, there was a thin layer of nickel hydroxide with an admixture of manganese ions from nickel nitrate and manganese nitrate dilution put on the nickel plate. After the spread of the thin layer on the nickel plate, the measurement by the method of cyclic voltammetry followed. The next task consisted in trying to add KOH (potassium hydroxide) anionic and cationic surfactant into the dilution.
|
|
|
Aprotic electrolytes for supercapacitors
Musílek, Václav ; Knotek, Tomáš (referee) ; Dvořák, Petr (advisor)
This master´s thesis deals different types of the aprotic electrolytes for supercapacitors and investigates by impedance spectroscopy to conductivity and method cyclic voltametry to measure dimension potential windows. Used aprotic solvents: propylencarbonate, dimethylsulfoxide, N, N dimethylformamide, ethylencarbonate, dimethylcarbonate, diethylcarbonate and acetonitrile. In the aprotic solvents were appended salts: LiClO4, NaClO4, KClO4, LiBF4, LiPF6, TEABF4 and TMABF4. From these compounds were prepared solutions with the different molar concentrations.
|
|
|
Study of optoelectrical properties of organic semiconductor thin film layers of phtalocyanines
Miklíková, Zdeňka ; Vala, Martin (referee) ; Zmeškal, Oldřich (advisor)
Diploma thesis is focused on the study of optoelectric properties of thin layers of organic materials based on phthalocyanines, which can be used as an active layer of photovoltaic cells. Especially are studied the properties of the thin active layers of PdPc and PdPc + IL on the glass or ceramic substrates with aluminium contact, which are prepared by material printing here. On the prepared samples were first measured current-voltage characteristics in the dark and in the light and then were measured impedance spectrums in the dark. The received results will be used to improve the properties and structures of photovoltaic cells.
|
|
|
Study of optoelectrical properties of organic semiconductor thin film layers
Pospíšil, Jan ; Weiter, Martin (referee) ; Zmeškal, Oldřich (advisor)
The thesis is focused on the study of electric and dielectric properties of thin film organic materials that can be used as an active layer of photovoltaic cells. Primarily were studied the properties of the layers on the glass substrates, which consist of a thin active layer of phthalocyanines. On the samples were first measured current-voltage characteristics (in the dark and during the exposure) and the basic parameters of the photovoltaic conversion were determined. Finally were measured frequency dependencies (impedance spectra, in the dark and during the exposure) and the parameters of a model of the structure with organic semiconductor were determined. The obtained results will be used to optimize the properties of photovoltaic cells.
|
|
|
Study of electrical and dielectric properties of ionic liquids
Maráčková, Lucie ; Nešpůrek, Stanislav (referee) ; Zmeškal, Oldřich (advisor)
This bachelor´s thesis is focused on a study of electrical and dielectric properties of ionic liquids in the form of solution and thin layers. The values of breakdown voltage have been determined from current-voltage characteristics in solutions. Frequency dependencies have been also observed and used for calculation of values of parallel conductivity and capacity of ionic liquid. It was found that solutions is contained by model with one parallel combination of conductivity and capacity. Thin layers have been created by mixing up PEDOT:PSS with two ionic liquids: 1-butyl-3- methylimidazolium trifluoromethanesulfonate and 1-ethyl-3-methylimidazolium tetrafluoroborate. These layers have created electrochemical battery as is evident from current-voltage characteristics. Frequency dependencies are more complex, a model contained two or respectively three parallel conductivities and capacities which have been influenced by PEDOT:PSS and by ionic liquids characteristics.
|
|
|
Study of electrical and dielectric properties of thin polymer films
Miklíková, Zdeňka ; Novák, Vítězslav (referee) ; Zmeškal, Oldřich (advisor)
The thesis is focused on the study of electric and dielectric properties of thin-film organic materials that can be used as an active layer of photovoltaic cells. Primarily were studied the properties of the layers on the glass substrate, which consist of a thin active layer of mixture ZnPc/PCBM with Al or Au contact. On the selected samples were first measured current-voltage characteristics in the dark and during the exposure then on the selected samples were measured frequency dependences (impedance spectra) in the dark and finally on the selected samples were measured relaxation characteristics (transient response analysis – current dependences on time at constant voltage) in the dark. The measured data for transient measurement were evaluated using the methods of fractal analysis in HarFA. The results will be used to optimize the properties of photovoltaic cells.
|
|
|
Study of electrical properties of thin polymer films
Pospíšil, Jan ; Vala, Martin (referee) ; Zmeškal, Oldřich (advisor)
The thesis is focused on the study of electric and dielectric properties of thin-film organic materials that can be used as an active layer of photovoltaic cells. Primarily were studied the properties of the layers on the PET or glass substrate, which consist of a thin active layer of polymethylphenylsilane (PMPSi) or derivatives of diketopyrrolpyrrole (DPP). On a selected sample were first measured current-voltage characteristics and current dependences on time at constant voltage (relaxation characteristics). Finally were measured frequency dependences (impedance spectra) and their relaxation characteristics too. The measured data were evaluated using the methods of fractal analysis in HarFA. The results will be used to optimize the properties of photovoltaic cells.
|
|
|
Measurement and modeling of real impedance results in dependence on the position the sensing electrodes
Haňka, J.
Content of this work is aimed to solutions of issues created due experimental measurement impedance properties of dielectric materials by sensitive impedance spectroscopy analysis. To this purpose should be created mathematical model by suitable simulation software, which should be able to simulate impedance changes in dependence of electrodes position. The work deals with description of complex impedance system behavior and response to electrodes position changes.
|
|
|
Electrochemistry as a Tool for an Enzyme Characterization
Gál, M. ; Krahulec, J. ; Jiríčková, K. ; Sokolová, Romana ; Híveš, J.
Basic biochemical properties such as Michaelis constant (KM) and turnover number (kcat) of enzyme enteropeptidase was measured by electrochemical impedance spectroscopy. Both values determined by impedance measurements are in good agreement with those obtained by traditional spectroscopic techniques. Therefore one can suppose that electrochemical methods might be successful for such measurements also in the case where usual ones (UV-Vis, fluorescence spectroscopy) are not able to determine these enzyme characteristics.
|
guest ::
