Large specific gravimetric/volumetric energy density, environmental benignity and safe low working voltage. All of these points have been used to describe the lithium sulfur (Li-S) battery in the past, but often times it is short cycle life and poor capacity retention that is associated with the Li-S battery. In order to realize the full potential of the Li-S battery in society today, many obstacles must be overcome. In a typical Li-S cell with an organic liquid electrolyte sulfur is reduced by lithium during discharge and subsequent lithium polysulfide species (Li2Sx where x, 2 < x < 8) are formed. These species are readily soluble in typical organic electrolytes and can lead to low Coulombic efficiency and most challenging: active mass loss. Through the loss of active mass, rapid capacity fading occurs over long-term cell cycling. Overcoming the loss of active mass and stabilizing cell capacity at high rates is pivotal to the realization of practical Li-S cells. In this thesis, four separate concepts and materials were studied and prepared with the aim to improve the Li-S batteries capacity, cycle life and capacity retention.

Large specific gravimetric/volumetric energy density, environmental benignity and safe low working voltage. All of these points have been used to describe the lithium sulfur (Li-S) battery in the past, but often times it is short cycle life and poor capacity retention that is associated with the Li-S battery. In order to realize the full potential of the Li-S battery in society today, many obstacles must be overcome. In a typical Li-S cell with an organic liquid electrolyte sulfur is reduced by lithium during discharge and subsequent lithium polysulfide species (Li2Sx where x, 2 < x < 8) are formed. These species are readily soluble in typical organic electrolytes and can lead to low Coulombic efficiency and most challenging: active mass loss. Through the loss of active mass, rapid capacity fading occurs over long-term cell cycling. Overcoming the loss of active mass and stabilizing cell capacity at high rates is pivotal to the realization of practical Li-S cells. In this thesis, four separate concepts and materials were studied and prepared with the aim to improve the Li-S batteries capacity, cycle life and capacity retention.

In this study it was proposed to investigate the use of 3D metal oxides (specifically titanium oxides) as potential electrode materials for lithium ion batteries. Three different approaches were taken: mesoporous materials to increase the surface area and improve the capacity; nanocrystalline materials to increase the surface area and to investigate any changes that may occur using nanocrystals; and microporous materials that are more open, allowing rapid diffusion of lithium and higher capacities. Of the three categories of materials studies, mesoporous TiO2 was the least promising with low reversible capacities (20 mAh??g-1) due to densification resulting in a loss of surface area. In nanocrystalline rutile an irreversible phase change occurred upon initial intercalation, however after this intercalation occurred reversibly in a single phase mechanism giving capacities of 100 mAh??g-1. A trend in intercalation potential was observed with crystallite size that was related to the ability of the structure to relax and accept lithium. Doping of rutile yielded no real improvement. Brookite gave only low capacities from a single phase intercalation mechanism. TiO2 films produced by a novel electrochemical technique showed that while amorphous films give greater capacities, more crystalline (anatase) films give greater reversibility. Overall, microporous titanosilicates showed the most promise with sitinakite giving a reversible capacity of 80 mAh??g-1 after twenty cycles or double this when dried. The intercalation was found to occur by two steps that generate large changes in crystallite size explaining the capacity fade witnessed. While doping did not improve the performance, cation exchange has proven beneficial. The remaining titanosilicates did not perform as well as sitinakite, however a trend was observed in the intercalation potentials with the wavenumber of the Ti-O Raman stretch. This was due to the covalent nature of the bonding. Upon reduction an electron is added to the bond meaning the energy of the bond determines intercalation potential. Overall, most promise was shown by the microporous titanosilicates. The capacities of sitinakite after drying, are comparable to those of the "zero strain" material Li4Ti5O12. Investigation of the titanosilicates and their ion-exchanged derivatives is a promising path for new lithium-ion battery electrode materials.

Thesis (Ph. D.)--Virginia Polytechnic Institute, 1964. / Vita. Abstract. Includes bibliographical references (leaves 43-44). Also available via the Internet.

Thesis (Ph.D.)--Tufts University, 1999. / Adviser: Terry Haas. Submitted to the Dept. of Chemistry. Includes bibliographical references. Access restricted to members of the Tufts University community. Also available via the World Wide Web;

Thesis (Ph.D.) -- McMaster University, 1997 / Includes bibliographical references Also available via World Wide Web.

Zugl.: Innsbruck, Univ., Diss., 2007

Thesis (M.Eng.(Hons.))--University of Wollongong, 2003. / Typescript. Includes bibliographical references: leaf 99-106.

Freiburg i. Br., Univ., Diss., 2008.

Thesis (Ph.D.) - University of St Andrews, December 2007.