With the rapid development of portable electronics, hybrid-electric and electric cars, there is great interest in utilization of sulfur as cathodes for rechargeable lithium batteries. Lithium/sulfur batteries implement inexpensive, the earth-abundant elements at the cathode while offering up to a five-fold increase in energy density compared with the present Li-ion batteries. However, electrically insulating character of sulfur and solubility of intermediate polysulfides in organic liquid electrolytes, which causes rapid capacity loss upon repeated cycling, restrict the practical application of Li/S batteries. In this thesis, the gel polymer and solid polymer electrolytes were synthesized and applied in Li/S batteries. A gel polymer electrolyte (GPE) was formed by trapping 1 M lithium bistrifluoromethane-sulfonamide (LiTFSI) in tetraethylene glycol dimethyl ether (TEGDME) electrolyte in a poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF-HFP) /poly(methylmethacrylate) (PMMA) polymer matrix. The electrochemical properties of the resulting GPE were investigated in lithium/sulfur battery. The gel polymer battery exhibited a high specific capacity of 753.8 mAh gˉ¹ at the initial cycle, stable reversible cycling and a capacity retention about 80% over 40 cycles along with a high Coulombic efficiency. Comparative studies conducted with the 1 M LiTFSI liquid electrolyte cell demonstrated that a cell with liquid electrolyte has remarkably low capacity retention and Coulombic efficiency compared with the GPE cell. In the further studies, a solid polymer electrolyte (SPE) based on poly- (ethylene-oxide)/nanoclay composite was prepared and used to assemble an all-solid-state lithium/sulfur battery. The ionic conductivity of the optimized electrolyte has achieved about 3.22×10ˉ¹ mS cmˉ¹ at 60 °C. The Li/S cell with this SPE delivered an initial discharge capacity of 998 mAh gˉ¹ when operated at 60 °C, and retained a reversible capacity of 634 mAh gˉ¹ after 100 cycles. These studies has revealed that the electrochemical performance of lithium/sulfur cells, including charge-discharge cyclability and Coulombic efficiency, can be significantly improved by replacing liquid electrolytes with solid polymer and gel polymer electrolytes, which reduce the polysulfide shuttle effect and could protect the lithium anode from the deposition of the electrochemical reaction, leading to higher sulfur utilization in the cell.

Undesired reactions in Li-ion batteries, which lead to capacity loss, can consume or produce charge at either the positive or negative electrode. For example, the formation and repair of the solid electrolyte interphase consumes Li+ and e- at the negative electrode. Electrolyte oxidation at the positive electrode allows extra electrons (with corresponding electrolyte decomposition products) to be extracted at the electrode compared to the number which could be extracted in the absence of electrolyte oxidation. High purity electrolytes, various electrolyte additives, electrode coatings and special electrode materials are known to improve cycle life and therefore must impact coulombic efficiency. Careful measurements of coulombic efficiency are needed to quantify the impact of different battery materials on cell life time in only a few charge-discharge cycles and in a relatively short time. In order to make an impact on Li-ion cells for automotive and energy storage applications, where thousands of charge-discharge cycles are required, coulombic efficiency must be measured to an accuracy and precision of at least 0.01%. An instrument designed to make high-precision coulombic efficiency measurements on Li ion batteries is described in this thesis. Such measurements can be used to detect the influence of different electrode materials, voltage ranges, cell temperature, etc. on the performance of a cell. The effects of cycle induced and time-related capacity loss can be probed using experiments carried out at different C-rates. Precision differential voltage and capacity measurements can also be used to identify the different failure mechanisms that occur in full cells.

Lithium-ion batteries have been used extensively over the past two decades in the portable consumer electronics industry. More recently, Li-ion batteries have become candidates for much larger-scale applications such as electric vehicles and energy grid storage, which impose much more stringent requirements on batteries, especially in terms of cell lifetime. In order to develop batteries with improved lifetimes, a means of quickly and accurately evaluating battery life is required. The use of coulombic efficiency (CE) is an important tool in this regard, which provides a way to quantify parasitic reactions occurring within the cell. As more stable battery chemistries are developed, the rates of parasitic reactions occurring in the cell become reduced, and differences in CE among cells become increasingly smaller. In order to resolve these differences, charger systems must be developed which can measure CE with increased precision and accuracy. This thesis investigates various ways to improve the precision and accuracy of CE measurements. Using the high-precision charger (HPC) at Dalhousie University (built in 2009) as a starting point, a new prototype charger was built with several modifications to the design of the existing HPC. The effect of each of these modifications is investigated in detail to provide a blueprint for the development of next-generation charger systems. This prototype charger shows greatly improved precision and accuracy, with CE results that are approximately four times more precise than those of the existing HPC and over an order of magnitude more precise than high-end commercially available charger systems

Electric Vehicles (EVs) have gained acceptance as low or zero emission means of transportation. This thesis deals with the design of a battery cell testing platform and Lithium-Ion (Li-Ion) battery modeling for EVs. A novel regenerative cell testing platform is developed for cell cycling applications. A 300 W - 5 V cell cycler consisting of a buck and a boost converter is designed. Furthermore, a novel battery modeling approach is proposed to accurately predict the battery performance by dynamically updating the model parameters based on the battery temperature and State of Charge (SOC). The comparison between the experimental and the model simulation results of an automotive cell under real-world drive-cycle illustrates 96.5% accuracy of the model. In addition, the model can be utilized to assess the long-term impact of battery impedance on performance of EVs under real-world drive-cycles.

Electric Vehicles (EVs) have gained acceptance as low or zero emission means of transportation. This thesis deals with the design of a battery cell testing platform and Lithium-Ion (Li-Ion) battery modeling for EVs. A novel regenerative cell testing platform is developed for cell cycling applications. A 300 W - 5 V cell cycler consisting of a buck and a boost converter is designed. Furthermore, a novel battery modeling approach is proposed to accurately predict the battery performance by dynamically updating the model parameters based on the battery temperature and State of Charge (SOC). The comparison between the experimental and the model simulation results of an automotive cell under real-world drive-cycle illustrates 96.5% accuracy of the model. In addition, the model can be utilized to assess the long-term impact of battery impedance on performance of EVs under real-world drive-cycles.

The present study was designed to assess the role of response time on the Category Test of the Halstead-Reitan Neuropsychological Test Battery (HRNB). The intent was to define the underlying constructs of the Category Test more particularly, the speed of performance by examining response time to individual slides of the Category Test.Seventy-two normal adult volunteers were administered the complete HRNB. Average response times were computed for correct (CRT), incorrect (IRT), and total (TRT) scores on the Category Test. The efficacy of using response measures (CRT, IRT, and TRT) to predict Category performance was examined in the context of other HRNB variables that loaded factorially with the Category Test, more specifically: TPT-time, memory, and location, Trails B, WAIS-R Block Design, and WAIS-R Object Assembly.A step-wise multiple regression analysis was computed using the above HRNB and response time measures to predict Category error scores. Results from this analysis indicated that TPT-location, TRT, and IRT contributed significantly (p<.05) in the prediction of Category scores. Approximately 15% of the variability in Category scores was explained by a measure of spatial memory (TPT-location) and an additional 15% was accounted for by psycho-motor speed (TRT and IRT). The significant contribution of response time in defining the underlying construct of the Category Test was discussed in terms of possible implications for enhancing the neuropsychological significance of the Category Test.

Zinc air batteries are among the most promising energy storage devices due to their high energy density, low cost and environmental friendliness. The low mass and cost of zinc air batteries is a result of traditional active materials replacement with a thin gas diffusion layer which allows the battery to use the oxygen directly from the air. Despite the environmental and electronic advantages offered by this system, challenges related to drying the electrolyte and catalyst, determining a high activity bifictional catalyst, and ensuring durability of the gas diffusion layer need to be optimized during the fabrication of rechargeable zinc-air batteries. To date, platinum on carbon (Pt/C) provides the best electrochemical catalytic activity in acidic and alkaline electrolytes. However, the difficult acquisition and high cost of this catalyst mandates investigation into a new composition or synthesis of a bifunctional catalyst. A number of non-precious metal catalyst have been introduced for zinc-air batteries. Nevertheless, their catalytic activities and durability are still too low for commercial rechargeable zinc-air batteries. Thus, it is very important to synthesize a highly active bifunctional catalyst with good durability for long term charge and discharge use. In this study, it is proposed that a manganese-based perovskite oxide nanoparticle combined with nitrogen doped carbon nanotubes willshow promising electrochemical activity with remarkable cycle stability as a bifunctional catalyst for zinc-air batteries. In the first part of this work, nano-sized LaMnO3 and LaMn0.9Co0.1O3 were prepared to research the effectiveness of Co doping into LaMnO3 and its effect on electrochemical catalytic activities. To prepare LaMnO3 and LaMn0.9Co0.1O3, a hydrothermal reaction method was applied to synthesize nanoparticles which can increase the activity of perovskite type oxides. The result shows that while perovskite oxides replacing 10 wt. % of Mn doped with Co metal did not iv change its crystalline structure, the oxygen evolution reaction (OER) performance was increased by 600%. In the second part, a core-corona structured bifunctional catalyst (CCBC) was synthesized by combining LaMn0.9Co0.1O3 nanoparticles with nitrogen doped carbon nanotubes (NCNT). NCNT was chosen because of its large surface area and high catalytic activity for ORR. SEM and TEM analysis show that metal oxide nanoparticles were surrounded with nanotubes. Based on the electrochemical performances, ORR and OER activity is attributed to NCNT and the metal oxide core, respectively, complementing the activities of each other. Furthermore, its unique morphology introduces synergetic activity especially for OER. Electrochemical test results show that the onset potential was enhanced from -0.2 V (in LaMnO3 and LaMn0.9Co0.1O3) to -0.09 V (in CCBC) and the half wave potential was improved from -0.38 V to -0.19 V. In the third part, a single cell zinc-air battery test was performed using CCBC as the bifunctional catalyst for the air electrode. These results were compared with battery performance against a high-performance and expensive Pt/C based air catalyst. The results show that the battery containing catalytic CCBC consumes less energy during charge/discharge. The single cell long-term durability performance was compared, further proving that CCBC provides a more suitable catalyst for zinc-air battery than Pt/C.

This thesis was devised as a fundamental study of the Li-S system by the use of 7Li Magic Angle Spinning (MAS) Nuclear Magnetic Resonance (NMR), X-ray Absorption Near- Edge Structure (XANES), and Non-Resonant Inelastic X-ray Scattering (NRIXS). The first part of this thesis reports the first evidence of a stable solid-phase intermediate between elemental sulfur (α-S8) and Li2S, Li2S6, which can be used to understand deeper Li-S battery. The second part of this thesis is based on operando XANES measurements made in the Argonne Photon Source (APS).Linear combination fit (LCF) analyses are performed to interpret the data; and, noticeably, the distinction between short-chain and long-chain polysulfides can be made due to the use of proper reference materials. The results reveal the first detailed observation of typical sulfur redox chemistry upon cycling, showing how sulfur fraction (under-utilization) and sulfide precipitation impact capacity. It also gives new insights into the differences between the charge and discharge mechanisms, resulting in the hysteresis of the cycling profile. Operando XANEs were also performed on het-treated material, which exhibits a particular electrochemical signature, which has never explained. After a preliminary electrochemical study by potentiodynamic cycling with galvanostatic acceleration (PCGA), operando XANES measurements at the sulfur K-edge are performed on heat-treated PCNS. Noticeably, the difference in the XANES signatures of the pristine and the recharged state shows the irreversible process that occurs during the first discharges. At last, electrolytes are investigated by the compilation of quantitative physico-chemical parameters – viscosity, ionic conductivity, and solubility of Li2S and Li2S6 – on novel class of solvents that are glymes with non-polar groups and acetonitrile (ACN) complexed with LiTFSI. 1,1,2,2-Tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (HFE) is chosen to decrease their viscosities. (ACN)2:LiTFSI attracts particular attention because of the particularly low Li2Sn solubility and. Its good electrochemical performance when mixed with 50 vol% HFE. Operando XANES proves the formation of polysulfides in this electrolyte, although constrains imposed by this novel electrolyte to the XANES experiment complicate the data analysis. The low energy feature evolution shows a more progressive mechanism involved in this electrolyte, which could be linked to the particularly low Li2Sn solubility

Lithium-ion batteries designed for use in heavy-duty hybrid vehicles are continuously improved in terms of performance and longevity, but they still have limitations that need to be considered when developing new hybrid vehicles.                The aim of this thesis has been to study and evaluate potential test and analysis methods suitable for being used in the design process when maximizing lifetime and utilization of batteries in heavy-duty hybrid vehicles. A concept for battery cell cycling on vehicles has been evaluated. The work included development of test equipment, verification of hardware and software as well as an extended period of validation on heavy-duty trucks. The work showed that the concept has great potential for evaluating strategies for battery usage in hybrid vehicles, but is less useful for accelerated aging of battery cells.                             Battery cells encapsulated in flexible packaging material have been investigated with respect to the durability of the encapsulation in a demanding heavy-duty hybrid truck environment. No effect on water intrusion was detected after vibration and temperature cycling of the battery cells.                    Aging of commercial battery cells of the type lithium manganese oxide - lithium cobalt oxide / lithium titanium oxide (LMO-LCO/LTO) was investigated with different electrochemical methods to gain a deeper understanding of the origin of performance deterioration, and to understand the consequences of aging from a vehicle manufacturer's perspective. The investigation revealed that both capacity loss and impedance rise were largely linked to the positive electrode for this type of battery chemistry.                           Postmortem analysis of material from cycle-aged and calendar-aged battery cells of the type LMO-LCO/LTO and LiFePO4/graphite was performed to reveal details about aging mechanisms for those cell chemistries. Analysis of cycle-aged LMO-LCO/LTO cells revealed traces of manganese in the negative electrode and that the positive electrode exhibited the most severe aging. Analysis of cycle-aged LFP/graphite cells revealed traces of iron in the negative electrode and that the negative electrode exhibited the most severe aging. / Litiumjonbatterier anpassade för användning i tunga hybridfordon förbättras kontinuerligt med avseende på prestanda och livslängd men har fortfarande begränsningar som måste beaktas vid utveckling av nya hybridfordon.                 Syftet med denna avhandling har varit att studera och utvärdera potentiella prov- och analysmetoder lämpliga för användning i arbetet med att maximera livslängd och utnyttjandegrad av batterier i tunga hybridfordon.                               Ett koncept för battericykling på fordon har utvärderats. Arbetet innefattade utveckling av testutrustning, verifiering av hårdvara och mjukvara samt en längre periods validering på lastbilar. Arbetet har visat att konceptet har stor potential för utvärdering av strategier för användandet av batterier i hybridfordon, men är mindre användbar för åldring av batterier.                                Batterier kapslade i flexibelt förpackningsmaterial har undersökts med avseende på kapslingens hållbarhet i en krävande hybridlastbilsmiljö. Ingen påverkan på fuktinträngning kunde påvisas efter vibration och temperaturcykling av de testade battericellerna.                     Åldring av kommersiella battericeller av typen litiummanganoxid - litiumkoboltoxid/litiumtitanoxid (LMO-LCO/LTO) undersöktes med olika elektrokemiska metoder för att få en djupare förståelse för prestandaförändringens ursprung och för att förstå konsekvenserna av åldrandet ur en fordonstillverkares användarperspektiv. Undersökningen visade att både kapacitetsförlust och impedanshöjning till största delen var kopplat till den positiva elektroden för denna batterityp.                  Post-mortem analys av material från cyklade och kalenderåldrade kommersiella battericeller av typen LMO-LCO/LTO och LiFePO4/grafit utfördes för att avslöja detaljer kring åldringsmekanismerna för dessa cellkemier. Vid analys av cyklade LMO-LCO/LTO celler påvisades mangan i den negativa elektroden samt uppvisade den positiva elektroden kraftigast åldring. Vid analys av cyklade LFP/grafit celler påvisades järn i den negativa elektroden samt uppvisade den negativa elektroden kraftigast åldring. / <p>QC 20140520</p>

South Africa has faced tremendous changes over the past decade, which has had a huge impact on the working environment. Organisations are compelled to address the societal disparities between various cultural groups. However, previously disadvantaged groups have had to face inequalities of the education system in the past, such as a lack of qualified teachers (especially in the natural sciences), and poor educational books and facilities. This has often resulted in poor grade 12 results. Social responsibility and social investment programmes are an attempt to rectify these inequalities. The objective of this research was to investigate the validity of the current selection battery of the Youth Foundation Training Programme (YFTP) in terms of academic performance of the students on the bridging programme. A correlational design was used in this research in order to investigate predictive validity whereby data on the assessment procedure was collected at about the time applicants were hired. The scores obtained from the Advanced Progressive Matrices (APM), which forms part of the Raven's Progressive Matrices as well as the indices of the Potential Index Battery (PIB) tests, acted as the independent variables, while the Matric results of the participants served as the criterion measure ofthe dependent variable. The data was analysed using the Statistical Package for Social Sciences (SPSS) software programme by means of correlations and regression analyses. The results showed that although the current selection battery used for the bridging students does indeed have some value, it only appears to be a poor predictor of the Matric results. Individually, the SpEEx tests used in the battery evidently were not good predictors of the Matric results, while the respective beta weights of the individual instruments did confirm that the APM was the strongest predictor. Limitations were identified and recommendations for further research were discussed. / Thesis (M.A. (Industrial Psychology))--North-West University, Potchefstroom Campus, 2007.