Electrolyte additives are generally used in commercial Li-ion cells to improve capacity retention and calendar life. Although it is apparent that electrolyte additives play an important role, the details of how they work are poorly understood. In order to be able to distinguish the effect of an additive on the positive or negative electrodes, an experimental method has been developed based on electrochemical impedance spectroscopy of symmetric cells constructed from electrodes of disassembled full cells similar to the method described by previous workers. This technique proved to be useful and showed that the effects of additives on both electrodes depend strongly on their concentration. It also showed that in some cases, when two additives are introduced in the same cell, both additives contribute to the formation of the surface layer of both electrodes. In other cases, each additive controls the formation of the surface layer of only one electrode.

Iron (oxyhydr)oxide (FeOOH) minerals play important roles in various natural, technological and societal settings. The widespread abundance of these minerals has prompted numerous studies on their surface reactivity in aqueous media. Surface charge development, one that namely takes place through the adsorption of potential determining ions (p.d.i.; H+, OH-) and coadsorption of counterions (e.g. Cl-, ClO4-, Na+), is particularly interesting in this regard. Mineral surface charge development is determined by numerous factors related to the interplay of mineral surface structure, particle morphology and counterion identity. In this thesis the interplay between these factors is resolved by monitoring charge development on submicron-sized synthetic iron oxyhydroxide particles of different structures and sizes in aqueous media with counteranions of contrasting charge-to-size ratio (i.e. NaCl, NaClO4). This work, which is summarized in an introductory chapter and detailed in five appendices, is focused on three types of synthetic lepidocrocite (ã- FeOOH) of different shapes and surface roughness, three types of goethite (á-FeOOH) of different levels of surface roughness, and finally akaganéite (â-FeOOH), a mineral representing unique ion exchange properties due to its hollandite-type structure. While charge development was chiefly monitored by high precisition potentiometric titrations, these efforts were supported by a range of techniques including electrolyte ion uptake by cryogenic X-ray photoelectron spectroscopy, particle imaging by (high resolution) transmission electron microscopy, porosity analysis by N2 adsorption/desorption, surface potential development by electrokinetics, as well as thermodynamic adsorption modeling. These efforts showed that lepidocrocite particles of contrasting morphology and surface roughness acquired highly comparable pH and ionic strength p.d.i. loadings. Equilibriation times required to develop these loadings were however altered when particles became aggregated by aging. Goethite particles of contrasting surface roughness also acquired incongruent p.d.i. loadings, which were predominantly explained by the different charge-neutralizing capabilities of these surfaces, some of which were related to pore size distributions controlling the entrance of ions of contrasting sizes. Such size exclusion effects were also noted for the case of akaganéite where its bulk 0.4×0.4 nm wide channels permitted chloride diffusion but blocked perchlorate. Charge development at goethite surfaces in binary mixtures of NaCl and NaClO4 solutions also showed that the larger size-to-charge ratio chloride ion exerted a strong effect on these results even when present as a minor species. Many of these aforementioned effects were also modeled using variable, counterion- and loading-specific, Stern layer capacitance values. The findings summarized in this thesis are providing a better understanding of surface processes occurring at iron oxyhydroxide surfaces. They should impact our ability in designing uses of such particles, for example, effective sorption in aquatic media, as well as to understand how they behave in natural systems.

Pressing demands for high power and high energy densities in novel electrical energy storage units have caused reconsiderations regarding both the choice of battery chemistry and design. Practical concerns originating in the conventional use of flammable liquid electrolytes have renewed the interests of using solvent-free polymer electrolytes (SPEs) as solid ionic conductors for safer batteries. In this thesis work, SPEs developed from two polymer host structures, polyethers and polycarbonates, have been investigated for all-solid-state Li- and Li-ion battery applications. In the first part, functional polyether-based polymer electrolytes, such as poly(propylene glycol) triamine based oligomer and poly(propylene oxide)-based acrylates, were investigated for 3D-microbattery applications. The amine end-groups were favorable for forming conformal electrolyte coatings onto 3D electrodes via self-assembly. In-situ polymerization methods such as UV-initiated and electro-initiated polymerization techniques also showed potential to deposit uniform and conformal polymer coatings with thicknesses down to nano-dimensions. Moreover, poly(trimethylene carbonate) (PTMC), an alternative to the commonly investigated polyether host materials, was synthesized for SPE applications and showed promising functionality as battery electrolyte. High-molecular-weight PTMC was first applied in LiFePO4-based batteries. By incorporating an oligomeric PTMC as an interfacial mediator, enhanced surface contacts at the electrode/SPE interfaces and obvious improvements in initial capacities were realized. In addition, room-temperature functionality of PTMC-based SPEs was explored through copolymerization of ε-caprolactone (CL) with TMC. Stable cycling performance at ambient temperatures was confirmed in P(TMC/CL)-based LiFePO4 half cells (e.g., around 80 and 150 mAh g-1 at 22 °C and 40 °C under C/20 rate, respectively). Through functionalization, hydroxyl-capped PTMC demonstrated good surface adhesion to metal oxides and was applied on non-planar electrodes. Ionic transport behavior in polycarbonate-SPEs was examined by both experimental and computational approaches. A coupling of Li ion transport with the polymer chain motions was demonstrated. The final part of this work has been focused on exploring the key characteristics of the electrode/SPE interfacial chemistry using PEO and PTMC host materials, respectively. X-ray photoelectron spectroscopy (XPS) was used to get insights on the compositions of the interphase layers in both graphite and LiFePO4 half cells.

The purpose of this study was to determine the: 1) knowledge, attitudes, and behaviors toward hydration and fluid replacement among collegiate football players at an NCAA Division I University, overall , and the relationship, if any, by position on the team, number of seasons played, and previous nutrition education; 2) relationship between the athletes’ hydration knowledge, attitudes and behaviors; 3) current sources of nutrition information likely to be used by the football players; and 4) players’ perception of the adequacy of, and barriers to, their fluid intake before, during, and after exercise. The players’ mean Hydration Knowledge Score was 14.2 ± 1.4 out of 17 (83.5%). Common misconceptions included: 60% thought water, rather than sports drinks, should be consumed when exercising for more than one hour; 54% did not believe sports drinks are better at restoring muscle glycogen than water; 47% believed salt tablets kept players from getting dehydrated; and 42% indicated thirst is the best indicator of dehydration. No differences were detected by number of seasons, position or previous nutrition education. / Department of Family and Consumer Sciences

Bubbles in water are stabilised against coalescence by the addition of salt. The white froth in seawater but not in freshwater is an example of salt-stabilised bubbles. A range of experiments have been carried out to investigate this simple phenomenon, which is not yet understood.¶ The process of thin film drainage between two colliding bubbles relates to surface science fields including hydrodynamic flow, surface forces, and interfacial rheology. Bubble coalescence inhibition also stands alongside the better known Hofmeister series as an intriguing example of ion specificity: While some electrolytes inhibit coalescence at around 0.1M, others show no effect. The coalescence inhibition of any single electrolyte depends on the combination of cation and anion present, rather than on any single ion.¶ The surfactant-free inhibition of bubble coalescence has been studied in several systems for the first time, including aqueous mixed electrolyte solutions; solutions of biologically relevant non-electrolytes urea and sugars; and electrolyte solutions in nonaqueous solvents methanol, formamide, propylene carbonate and dimethylsulfoxide. Complementary experimental approaches include studies of terminal rise velocities of single bubbles showing that the gas-solution interface is mobile; and measurement of thin film drainage in inhibiting and non-inhibiting electrolyte solution, using the microinterferometric thin film balance technique.¶ The consolidation of these experimental approaches shows that inhibiting electrolytes act on the non-equilibrium dynamic processes of thin film drainage and rupture between bubble surfaces – and not via a change in surface forces, or by ion effects on solvent structure. In addition, inhibition is driven by osmotic effects related to solute concentration gradients, and ion charge is not important.¶ A new model is presented for electrolyte inhibition of bubble coalescence via changes to surface rheology. It is suggested that thin film stabilisation over a lifetime of seconds, is caused by damping of transient deformations of film surfaces on a sub-millisecond timescale. This reduction in surface deformability retards film drainage and delays film rupture. It is proposed that inhibiting electrolyte solutions show a dilational surface viscosity, which in turn is driven by interfacial concentration gradients. Inhibiting electrolytes have two ions that accumulate at the surface or two ions that are surface excluded, while non-inhibiting electrolytes have more evenly distributed interfacial solute. Bubble coalescence is for the first time linked through this ion surface partitioning, to the ion specificity observed at biological interfaces and the wider realm of Hofmeister effects.¶

Thesis (Ph. D.)--University of Chicago, 1942. / Lithoprinted. Description based on print version record. Includes bibliographical references.

Thesis (Ph.D.(Chemistry))--University of Pretoria, 2000. / Includes abstracts in English and Afrikaans. Includes bibliographical references. Also available online.

The objective of the thesis is to research the physiological differences between picked genotypes of Capsicum annuum and the effect of lower temperatures in the beginning of ontogeny. Another objective is to find out how Capsicum annuum plants react to application of anti-stress agent Atonic and to determine the most appropriate physiological indicators of resistence to low temperatures. Capsicum annuum ranks among thermophilic crops for which the temperature optimum is of 22 - 25 °C during the day and 18 - 20 °C overnight. They are planted at the field station at the time when ground frost may occur. These can cause physiological changes in the plant or even cause her death. Three varieties were chosen for the experiment: Amy, Eva a Lydia. Plants were divided into a control group and treatment group. Both groups were further divided into two additional groups - with and without the application of Atonic in the beginning of vegetative growth (6th day of exposure to stress). Control group plants were grown at 20 °C and stressed plants were moved into a klimabox with temperature of 5 °C throughout the entire day. Such temperature may occur after planting the plants into an outdoor habitat. Proline content in leaves of Capsicum annuum and relative discharge of electrolyte was studied in two - day intervals. From the obtained results it can be concluded that the accumulation of proline was the highest for Lydia variety in a stressed scenario with the application of Atonic and the lowest proline content was found in in the Amy variety in a control group. Furthermore, it was discovered that the ontogeny of plants has an effect on the accumulation of proline and relative discharge of electrolyte from the beginning of the measurement. The absolute highest electrolyte discharge was measured in the Lydia variety in a stressed scenario and the lowest one was present in the Amy variety in a control group. These results confirm the hypothesis.

A procura por fontes de energia confiáveis para motores elétricos, levou a grande esforços de síntese de novos eletrólitos para uso em baterias de íon-Li, de modo a aliar eficiência e segurança. Líquidos iônicos têm sido largamente estudados para este propósito. Misturas do sal Li(CF3SO2)2N, LiTf2N, no líquido iônico (LI) formado pelo cátion 1-butil-2,3-dimetilimidazólio, BMMI, e o ânion (CF3SO2)2N-, bis(trifluorometanosulfonil)imideto, Tf2N, foram preparadas em diferentes concentrações. A adição do sal de lítio a este liquido iônico diminuiu a mobilidade de todas as espécies, especialmente o Li+. A condutividade estimada usando os dados de difusão (NMRPGSE), os dados da espectroscopia Raman e as simulações por Dinâmica Molecular sugerem a formação de agregados compostos por ânions Tf2N em torno do Li+, com os oxigênios do Tf2N direcionados para o cátion Li+. Estes agregados aumentam conforme aumenta a concentração de LiTf2N, contribuindo para a diminuição da condutividade. Para contornar este obstáculo, foram sintetizados líquidos iônicos contendo um átomo de oxigênio na estrutura do cátion, de modo a promover a competição com os oxigênios do Tf2N pelo cátion Li+, prevenindo Li+ de formar agregados de grande massa e melhorando sua difusividade. Os cations escolhidos foram o 1,2-dimetil-imidazólio e o N-metilmorfolino. Estes LI´s serão representados por [Et2OMMI][Tf2N] e [Et2OMor][Tf2N], respectivamente. Os resultados mostraram que [Et2OMMI][Tf2N] tem uma menor janela eletroquímica (3,8V) que [BMMI][Tf2N] (4,6V), mas o potencial de redução para ambos é igual, o que os torna resistentes à redução pelo lítio metálico. Estes dois LI´s tem quase a mesma densidade e a viscosidade de [Et2OMMI][Tf2N] é 20% menor que a de [BMMI][Tf2N]. Sendo menos viscoso, é esperado que [Et2OMMI][Tf2N] tenha uma maior condutividade. De fato, sua condutividade é 40% maior que a de [BMMI][Tf2N], o que sugere que o grupo éter adiciona alguma modificação estrutural ao sistema, mostrando que neste caso, as mudanças no transporte de carga não decorrem apenas em função da fluidez. Coeficientes de difusão de [Et2OMMI][Tf2N] são maiores que aqueles de [Et2OMor][Tf2N], mas um pouco menores que aqueles de [BMMI][Tf2N]. Também foram estudadas as mudanças nas propriedades físico-químicas em [BMMI][Tf2N] decorrentes da adição do gás SO2. Todas as propriedades de transporte tiveram aumento e uma diminuição na dinâmica de formação de pares iônicos foi sugerida pelos dados experimentais / The searching for reliable power sources for electrical engines has lead to great efforts in order to synthesize new electrolytes to be used in Li-ion batteries in order to make them powerful and safe. Ionic liquids have been widely studied for this purpose. Lithium salt solutions of Li(CF3SO2)2N, LiTf2N, in a room-temperature ionic liquid (RTIL), 1-butyl-2,3-dimethyl-imidazolium cation, BMMI, and the (CF3SO2)2N-, bis(trifluoromethanesulfonyl)imide anion, Tf2N, were prepared in different concentrations. The addition of a lithium salt to this RTIL decreases the mobility of all species, especially Li+. Estimated conductivities (NMR-PGSE), Raman spectroscopy and Molecular Dynamics Simulation data suggest the formation of aggregates formed by [Tf2N] anions around Li+, with [Tf2N]´s oxygen atoms pointing toward Li+. These aggregates increase as LiTf2N content is increased, thus contributing to diminish conductivity. To overcome this obstacle, it was synthesized ionic liquids with ether-function-containing cations, so, oxygen atom from the ether group could compete for Li+ against the oxygen atoms from [Tf2N], preventing Li+ to form high mass aggregates improving the Li+ diffusion process. The chosen cations were the 1,2-dimethyl-imidazolium and N-methylmorpholine. RTILs were represented by [Et2OMMI][Tf2N] and [Et2OMor][Tf2N], respectively. Results show that [Et2OMMI][Tf2N] has a lower electrochemical window (3,8V) than [BMMI][Tf2N] (4,6V), but their reduction potential is equal, which makes them resistant to reduction by metallic lithium. These two RTIL´s have almost the same density and the viscosity of [Et2OMMI][Tf2N] is 20% lower than that of [BMMI][Tf2N]. Being less viscous, it is expected that [Et2OMMI][Tf2N] had a higher conductivity. It has in fact a conductivity 40% higher than [BMMI][Tf2N], which suggests that the ether chain add some structural modification to the system, showing that in this case, changes in charge transport is not only a function of the fluidity. Diffusion coefficients of [Et2OMMI][Tf2N] are higher than those of [Et2OMor][Tf2N], but a little bit lower than those of [BMMI][Tf2N]. It was also addressed the physical property changes in [BMMI][Tf2N] with the increasing addition of SO2. All the transport properties have improved and a decrease in ionic pair formation was suggested by experiment data

abstract: Dye sensitized solar cells (DSSCs) are currently being explored as a cheaper alternative to the more common silicon (Si) solar cell technology. In addition to the cost advantages, DSSCs show good performance in low light conditions and are not sensitive to varying angles of incident light like traditional Si cells. One of the major challenges facing DSSCs is loss of the liquid electrolyte, through evaporation or leakage, which lowers stability and leads to increased degradation. Current research with solid-state and quasi-solid DSSCs has shown success regarding a reduction of electrolyte loss, but at a cost of lower conversion efficiency output. The research work presented in this paper focuses on the effects of using nanoclay material as a gelator in the electrolyte of the DSSC. The data showed that the quasi-solid cells are more stable than their liquid electrolyte counterparts, and achieved equal or better I-V characteristics. The quasi-solid cells were fabricated with a gel electrolyte that was prepared by adding 7 wt% of Nanoclay, Nanomer® (1.31PS, montmorillonite clay surface modified with 15-35% octadecylamine and 0.5-5 wt% aminopropyltriethoxysilane, Aldrich) to the iodide/triiodide liquid electrolyte, (Iodolyte AN-50, Solaronix). Various gel concentrations were tested in order to find the optimal ratio of nanoclay to liquid. The gel electrolyte made with 7 wt% nanoclay was more viscous, but still thin enough to allow injection with a standard syringe. Batches of cells were fabricated with both liquid and gel electrolyte and were evaluated at STC conditions (25°C, 100 mW/cm2) over time. The gel cells achieved efficiencies as high as 9.18% compared to 9.65% achieved by the liquid cells. After 10 days, the liquid cell decreased to 1.75%, less than 20% of its maximum efficiency. By contrast, the gel cell's efficiency increased for two weeks, and did not decrease to 20% of maximum efficiency until 45 days. After several measurements, the liquid cells showed visible signs of leakage through the sealant, whereas the gel cells did not. This resistance to leakage likely contributed to the improved performance of the quasi-solid cells over time, and is a significant advantage over liquid electrolyte DSSCs. / Dissertation/Thesis / M.S.Tech Engineering 2012