No description available.

In this thesis, high-voltage nitrile-based electrolytes for lithium ion batteries were investigated. The electrolytes were composed of nitrile, dinitrile, and vinylene carbonate (VC) as an additive. Scanning electron microscopy showed the change of surface morphology of electrodes. The chemical compositions of the solid electrolyte interface were characterized by high resolution X-ray photo electron spectroscopy (HR-XPS). We found that the optimal ratio of dinitrile to nitrile is 6 to 4 by volume in terms of electrochemical performances. 5wt% VC as the additive has the enhanced electrochemical performances. The oxidation potential of the nitrile-based electrolytes can reach to 5.7 V. The discharge capacity of the Li||LiFePO4 cell with the nitrile-based electrolyte is about 80 mAhg-1 at a charge/discharge rate of 5 C under 30 oC, and its discharge efficiency after 100 cycles still keeps 94.35%.

Thesis (Ph. D.)--Florida State University, 2002. / Advisor: Dr. Joseph B. Schlenoff, Florida State University, College of Arts and Sciences, Dept. of Chemistry. Title and description from dissertation home page (viewed Sept. 29, 2003). Includes bibliographical references.

The aim of this thesis is to develop a better understanding about the degradation mechanisms occurring within lithium-ion cells which eventually lead to their failure. An introduction to the components and operation of Li-ion cells is followed by proposed degradation mechanisms which limit the lifetime of cells. These mechanisms and how they can be identified from electrochemical testing are discussed. Electrolyte additives can be used to improve the safety of Li-ion cells or decrease the rate of cell degradation. Different types of additives and testing methods are discussed followed by an introduction to high precision coulometry which can be used to detect the impact of additives on cycling performance. The High Precision Charger that was constructed for this project is described and shown to meet the desired precision. The use of additives and different materials to extend lifetime of cells is shown to be detectable through the use of high precision coulometry. High precision coulometry proves to be a more efficient way of estimating the lifetime of cells under realistic conditions in a reasonably short amount of time. / MSc. Thesis

No description available.

x, 131 leaves : photos., graphs, tables ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physical and Inorganic Chemistry, 1979

Thesis (Ph.D.) -- University of Adelaide, Dept. of Physical and Inorganic Chemistry, 1979.

Th. 3e cycle--Électrochim.--Grenoble--I.N.P., 1982. N°: D3 126.

No description available.

The equilibrium constant for the dissociation of the BeF₄˭ ion in aqueous solutions of the ammonium salt has been computed by using the intensities of the fluorine nuclear magnetic resonance signals to indicate the concentrations of the three species at equilibrium. The simple dissociation may be represented as; BeF₄˭⇢ BeF₃¯+ F¯ (i) KE = 8.0 ± 0.9 x 10¯²moles (Kg)¯¹at 33°C. The equilibrium was measured over the temperature range 0-50°C but no appreciable temperature coefficient was observed. Variation of the concentration of BeF₂ solution allows the identification of further resonances, which have been associated with the unionized BeF₂ and a possible existence of a BeBeF₄ species. Chemical shift changes in the ⁹Be nuclear resonance positions are minimal. Some suggestions are made regarding the kinetics of fluorine exchange in reaction (i). The large changes in ¹¹B-¹⁹F coupling constant and ¹⁹F chemical shift of BF₄¯ ion at different concentration in aqueous and mixed solvents (acetone/water, dioxane/ water and D.M.S.O./water) have been interpreted in terms of changes in the hydrogen bonding of water to the BF₄¯ ion. The unique behavior of chemical shift and coupling constant in D.M.S.O./water has been explained by preferential solvation of BF₄¯ ion by the protolysis product of D.M.S.O. in water. The concentration dependence of the fluorine chemical shift of diamagnetic salts of fluoroanions of the type F¯, BF₄¯ and SiF₆˭ have been studies and the molal chemical shift has been correlated with the size and the charge of the cation. A displacement of the fluorine chemical shift to low field was observed for F¯, BF₄¯, BeF₄˭, PF₆¯ and SiF₆˭ aqueous solutions with paramagnetic cations Cu⁺⁺, Ni⁺⁺, Co⁺⁺, Fe⁺⁺, Fe⁺⁺⁺, Cr⁺⁺⁺ and Mn⁺⁺. These shifts are explained on the basis of ion-pair formation between cation and fluoroanion. The molar shifts have been interpreted in terms of a contact interaction between unpared electron and ¹⁹F nucleus. The contribution due to Pseudo contact shift, which arises due to anisotropy in g-factor is probably small. The changes in ¹⁹F line width with the concentration of paramagnetic ion have been discussed in the light of exchange between freee and ion-paired fluoro-anion. Further evidence regarding the ion-pair formation in f luoro-borates has been obtained from ¹¹B chemical shift and line width measurements. ¹⁹F N.M.R. spectra of HF₂¯ ion of Na⁺, K⁺ and NH₄⁺ cations have been studied, and the equilibrium constant for the reaction HF₂ ⇢ HF + F¯ (ii) have been measured for the potassium salt. Preliminary investigations of different gallium fluoride complex in mixtures of AgF and Ga(ClO₄)₃ have been made / Science, Faculty of / Chemistry, Department of / Graduate