Thesis (Ph.D.)--University of Wollongong, 2006. / Typescript. Includes bibliographical references: leaf 188-189.

Thesis (Ph.D.)--University of Wollongong, 2008. / Typescript. Includes bibliographical references: page 205-222.

Thesis (Ph. D.)--State University of New York at Binghamton, Department of Chemistry, 2008. / Includes bibliographical references.

Thesis (Ph. D.)--State University of New York at Binghamton, Department of Chemistry, 2004. / Includes bibliographical references.

Thesis (Ph.D.)--Ohio University, June, 2005. / Title from PDF t.p. Includes bibliographical references (p. 89-92)

Thesis (M. Sc. (Chemistry)) -- University of Limpopo, 2019 / Nano-architecture structures of LixTiO2 are very promising as anode materials for lithium rechargeable batteries due to their ability to accommodate more lithium atoms and its ability to withstand high temperatures at atomistic level through charging and discharging. In these studies, we investigated how nano-architectured structures of LixTiO2 behave at high temperatures through the process of amorphisation and recrystallisation. A computational method of molecular dynamics (MD) simulation was employed to recrystallise the amorphous LixTiO2 nano-architectures of bulk, nanosheet, nanoporous and nanosphere, where x depicts the fraction of lithium ions, i.e. 0.03, 0.04 and 0.07. The main objective of this study was to go beyond the previous inserted lithium atoms on TiO2 and understand the effects of concentrations, temperature, defect chemistry and charge storage properties/capacity on the overall lithium transport to improve lithium ion battery performance. Recrystallisation of all four nanostructures from amorphous precursors were successfully achieved and was followed by the cooling process towards 0 K and finally we heated all four nano-architectures at temperature intervals of 100 K up to 500 K. The variation of configuration energies as a function of time, was used to monitor the crystal growth of all nanostructures. Calculated Ti-O radial distribution function, were used to confirm the stability interaction after cooling. Calculated X-Ray Diffraction (XRD) spectra where used to characterise and compare their patterns at cooled and above high temperatures, using the model nanostructures, and they showed polymorphic nanostructures with LixTiO2 domains of both rutile and brookite in accord with experiment. Amorphisation and recrystallization showed good results in generating complex microstructures. In particular, bulk structures show few zigzag tunnels (indicative of micro twinning) with 0.03 Li but 0.04 Li and 0.07 Li show complex v patterns indicating a highly defected structure. While 0.03 and 0.04Li nanospheres show, zigzag and straight tunnels in accord with experiment, the one with 0.07 Li has melted. Lastly, nanoporous and nanosheet structures have pure straight and zigzag patterns that are well in accord with our XRD patterns at all concentrations of lithium atoms and temperatures. The lithium transport was analysed using diffusion coefficient, calculated as a function of temperature in order to confirm the mobility above the given temperatures. An increase in temperature shows an increase in diffusivity of lithium at all lithium concentrations in nanoporous and nanosheet structures. The same trend was observed in bulk but only with 0.03 and 0.07 Li ion concentrations. / National Research Foundation (NRF)

The newly emerging Stimulated Raman Scattering (SRS) Microscopy has been proved to be a powerful tool in biomedical research. This advanced imaging platform offers high spatiotemporal resolution and chemical specificity, which greatly empowers the label-free biomedical imaging and small molecule metabolite tracing. Throughout the research introduced in this thesis, we focus on the exploration of more applications of SRS microscopy beyond aforementioned. Particularly, this new expedition involves more chemistry and answered two major questions: what SRS can do for chemistry and what chemistry can do for SRS. Chapter 1 introduces the basics of SRS microscopy, such as the physical fundamentals and start-of-art instrumentations. Besides, this chapter discusses the design principles of vibrational reporters through a chemistry view. Chapter 2 introduces one of the major progresses of SRS microscopy beyond biomedical study. We use SRS microscopy to study the ion transportation and concentration polarization phenomena in lithium metal batteries (LMBs), with a strong focus in solid-state polymer electrolyte. A self-induced phase separation process over lithium metal electrode is observed and correlated with local lithium ion concentrations, which inspires a protection mechanism for durable LMB design. Chapter 3 discusses the use of SRS microscopy for in-vivo drug tracing in mammalian cells. A novel alkyne tag is incorporated into bio-engineered natural depsi-peptides and serves as Raman reporter. The mode-of-action of the labeled drug is visualized with SRS microscopy. Chapter 4 heavily focuses on the development of synthetic molecular probes for super-multiplexed optical imaging. We systematically synthesize a library of molecular probes based on 9-cyanopyronin, and their Raman features are characterized to build a model that correlates photophysical properties with structures. The Raman shifts of probes can be tuned with high precision. The multiplexing capability of the new library is demonstrated in labeling fixed and living cell samples.

Thesis (Ph.D. (Physics)) -- University of Limpopo, 2017 / Density functional theory (DFT) study is employed in order to investigate the surfaces of, β-MnO2, β-TiO2 and β-VO2 (β-MO2) which act as catalysts in Li/Na-air batteries. Adsorption and co-adsorption of metal (Li/Na) and oxygen on (110) β-MO2 surface is investigated, which is important in the discharging and charging of Li/Na– air batteries. Due of the size of the supercell, and assuming that oxygen atoms occupy bulk-like positions around the surface metal atoms, only five values of (gamma) Γ are possible if constraint to a maximum of 1 monolayer (ML) of adatoms or vacancies: Γ= 0 surface is the stoichiometric surface, Γ= 1, 2 are the partially and totally oxidised surfaces, and Γ=-1, -2 are the partially and totally reduced surfaces. The manganyl, titanyl and vanadyl terminated surface is not the only surface that can be formed with Γ= +2. Oxygen can be adsorbed also as peroxo species (O2)2-, with less electron transfer from the surface vanadium atoms to the adatoms than in the case of manganyl and titanyl formation. The redox properties of the (110) surfaces are investigated by calculating the relative surface free energies of the non-stoichiometric compositions as a function of oxygen chemical potential. Increasing the temperature and lowering the pressure (i.e. more reducing conditions) we find the stoichiometric surface reduces first partially and then entirely at higher temperatures. The lithium orientation between two bridging oxygen and in-plane oxygen (bbi) orientation is much more stable for the three metal oxides, thus lithium generally prefers to adsorb where it will be triply coordinated to two bridging oxygens and one in-plane oxygen atom. However, sodium prefers to orientate itself on the bridging oxygen on the surface, but a triple coordination on sodium is also favourable. Oxygen adsorption on Li/MO2 was simulated and it was found that in all ii the metal oxides (MnO2, TiO2 and VO2) the most stable orientation is the dissociated composition where there is an oxygen atom on the “bulk-like” positions on top of each of the M cations. The surface lithium peroxide for MO2 simulated produces clusters with oxygen - oxygen bond lengths that are comparable to the calculated bulk and monomer discharge products reported in literature. Adsorption of oxygen on Na/MO2 was investigated and it was observed that the catalysts used encourage formation of the discharge product reported in literature, i.e. NaO2. The surface NaO2 appears to have comparable bond lengths to the calculated bulk and monomer NaO2. / National Research Foundation, South African Research Chair Initiative of the Department of Science Technology and Department of Energy storage Programme

This dissertation explores the application of acoustics as a characterization technique for three anode materials in lithium-based battery systems. The first focus is on the formation process of anode-free lithium metal batteries, examining how various parameters and properties influence lithium metal plating and stripping dynamics. Across three interconnected chapters, the key finding is that higher current density on formation supports cycling performance. Graphite is the second anode material, with a special consideration of observing its staging behavior. This is done using resonance, a novel method for extracting acoustic features of battery systems where conventional “chirping” falls short. The third and last anode material is silicon. Paired with a solid-state electrolyte, its phasing dynamics, expansion, and pitting are observed in the chemomechanical domain. Chapter 2 examines how electrolyte composition and formation rate affect the performance of anode-free lithium metal batteries. A faster C/3 formation protocol achieves cycling performance and cell stiffness changes comparable to a slower C/10 formation step. Differences in acoustic metrics across electrolytes are linked to variations in gas formation, cell swelling, and lithium deposition morphology. NMC811 cathodes with a high-concentration ether electrolyte exhibit a tendency for significant gas formation, which is mitigated by using a localized high-concentration ether electrolyte and single-crystal NMC532. Chapter 3 introduces a novel acoustic apparatus capable of dual-mode, spatially resolved acoustic interrogation. Medium-frequency pitch/catch in parallel with high-frequency pulse/echo enables simultaneous tracking of cell-level and layer-level chemomechanical dynamics. The apparatus is applied on the same gas-prone system studied in Chapter 2 during formation to detect gas localization and plating/stripping dynamics. The findings reinforce the takeaway from Chapter 2 that fast formation may be beneficial for lithium metal batteries. Chapter 4 further investigates the effects of anode-free lithium-metal battery formation parameters, focusing on the interplay between temperature, stack pressure, and current density in multilayered cells. Accelerated-rate cycling is used to evaluate the impact of formation protocols on performance. Higher temperature, stack pressure, and C-rate are shown to improve lithium morphology after formation. Ultrasound transmission during cycling reveals that these improvements gained during formation lead to better mechanical behavior during cycling, although cathode dynamics and electrolyte side reactions complicate interpretation of electrochemical performance. Chapter 5 shifts the focus from lithium metal batteries to Li-ion batteries. There we introduce resonance—a method distinct from, yet related to, the chirping technique used in earlier chapters. Acoustic resonance is demonstrated as a viable tool for State-of-Charge (SoC) characterization at both the module level and at the cell level, particularly for challenging cell geometries such as cylindrical cells. By sweeping through frequencies approximately two orders of magnitude lower than previously reported, changes in spectral density and signal energy are linked to known electrochemical processes. Chapter 6 considers silicon. It is a coveted electrode material due to its high energy density but suffers from poor cycle life due to a threefold expansion during lithiation—and contraction with commensurate pitting on delithiation—which continually breaks and reforms the solid-electrolyte interphase. In this work, it is paired with an argyrodite solid-state electrolyte to approach silicon’s theoretical energy density. Through differential acoustic analysis, the two-phase lithiation and one-phase delithiation dynamics are observed for the first time in the chemomechanical domain. Peak broadening and shifting are related to increased cell impedance and heterogeneous lithiation.

Thesis (M.S.)--Mississippi State University. Department of Chemistry. / Title from title screen. Includes bibliographical references.