The ionic conductivity of the lithium ionic conductor, Li5La3Ta2O12, is studied in an attempt to better understand the intrinsic bulk ionic conductivity and extrinsic sample dependent contributions to the ionic conductivity, such as grain boundary effects and the electrode-electrolyte interface. To characterize the material, traditional AC impedance spectroscopy studies were performed as well novel in-situ nanoscale transport measurements. To perform the nanoscale measurements, higher quality samples were required and new synthesis techniques developed. The results of these new synthesis techniques was samples with higher densities, up to 96% of theoretical, and slightly higher room temperature ionic conductivity, 2x10^−5 S/cm. By combining the AC impedance spectroscopy results and in-situ nanoscale transport measurements from this study and prior reported results, as well as introducing models traditionally used to analyze supercapacitor systems, a new interpretation of the features seen in the AC impedance spectroscopy studies is presented. This new interpretation challenges the presence of Warburg Diffusion at low frequencies and the offers a new interpretation for the features that have been traditionally associated with grain boundary effects.

Lithium-ion batteries (LIBs) are the most commonly used type of rechargeable batteries with a global market estimated at $11 billion, which is predicted to grow to $60 billion by 2020. The global commercialization of Li-ion batteries is impeded by issues such as poor cycle life (5000 cycles achieved in some LIBs) in high energy and power density applications because of the rising internal resistance due to aging and safety concerns such as overcharge which ultimately leads to thermal runaway and explosions. A battery’s performance mainly depends on external factors such as electrode thickness and degree of compacting, and the type of conductive additive and electrolyte mixture used, and internal factors such as its internal temperature and state of charge. The performance suffers due to aging or erroneous mechanisms such as decomposition of the electrode or electrolyte material affecting the lifetime. In this thesis, an attempt is made to improve the lifetimes of the Li-ion batteries by incorporating suitable electrolyte additives, which were incorporated in the battery electrolyte to prevent overcharge. Also, several conductive electrode additives were incorporated as filler materials in an anode to explore the effects on its discharge capacities.

L'utilisation d'un électrolyte aqueux pour la technologie Li-ion devrait permettre des performances en termes de puissance et de coût tout en garantissant une sécurité de fonctionnement et un impact neutre vis-à-vis de l'environnement. Cette technologie utilise des composés d'insertion du lithium fonctionnant habituellement en milieu organique dont le choix doit être adapté à un électrolyte aqueux, présentant une fenêtre de stabilité électrochimique réduite. Le travail de thèse porte dans un premier temps sur la sélection des différents éléments constituant un accumulateur Li-ion aqueux: choix de l'électrolyte, des collecteurs de courant, des liants d'électrode et des matériaux d'électrode. Les performances électrochimiques en milieu aqueux de différents composés d'insertion du lithium ont été évaluées. Afin d'augmenter la fenêtre de stabilité électrochimique de l'électrolyte aqueux, la passivation des électrodes par réduction de sels de diazonium a été réalisée. L'influence de la nature des sels de diazonium et de l'épaisseur des films sur les performances électrochimiques des électrodes a été évaluée par diverses techniques, voltampérométrie et impédance électrochimique. Les résultats obtenus montrent l'impact positif des dépôts obtenus vis-à-vis de l'augmentation de la surtension de réduction de l'eau. Ces travaux ouvrent la voie à des perspectives prometteuses sur cette technologie Li-Ion aqueuse.

The work present in this thesis report introduces a novel non-destructive technique for experimentally measuring through thickness hygro-thermal strain of Nafion membranes though digital image correlation. An Optical Coherence Tomography (OCT) system was used to acquire images of a Nafion-TiO2 (titanium dioxide powder) composite membranes in a fuel cell like device. The proposed technique, commonly known as optical coherence elastography (OCE) makes use of the normalized correlation algorithm to calculate strain between two successive scans of different relative humidity step values. Different normalized correlation parameters were compared to measured results of PDMS-TiO2 phantoms in order to analyze accuracy. The effect of TiO2 on Nafion membranbes mechanical properties was further analysed by comparing the swelling behaviour of membranes with different concentrations. It has been found that Nafion undergoes approximately 25 – 30% more strain on the land section than on the channel section, regardless gas diffusion electrode (GDE) layer presence. Furthermore, it was shown that the overall strain on the material decrease by approximately 10% when GDE layers are present. Overall this work demonstrated how OCE is a viable technique for measuring through thickness strain distribution in Nafion composite membranes and has the potential to be implemented for non-destructive in situ measurements. / Graduate / 0548 / kellerv@uvic.ca

This study was designed to determine the impact of glycerol hyperhydration, compared with a placebo hyperhydration, on the run performance during an Olympic distance triathlon. Ten competitive triathletes (mean peak oxygen consumption, VO2 peak = 65.5 ± 5.5 ml.kg.-1min-1) undertook two simulated Olympic Distance Triathlons in 31° C and 61% relative humidity. The trials were split into two work phases: a fixed workload phase comprising a 18-20 min swim and a 60 min cycle and, a self regulated time trial run over 10 kilometres conducted on a treadmill. One hundred and fifty min prior each trial, either a glycerol solution (1 g.kg.-1 body mass (BM) in a 4% carbohydrate – electrolyte drink) or a placebo of equal volume of the 4% carbohydrate-electrolyte solution was ingested over one hour. The total fluid intake in each trial was 23 ml.kg.-1 BM. A randomised, double blind, cross over design was used. Due to either 1) the arduous nature of the trials 2) the side effects associated with the ingestion of glycerol 3) or the combination of the two aforementioned reasons, only five of the 10 subjects completed the final 10 km self regulated time trial for both treatments. Only the data obtained from these five subjects were reported in this study. Glycerol ingestion expanded body water over the placebo by 154 ml (26%). At 60 and 90 min after the start of drinking, urine output was significantly higher with glycerol than placebo treatment (216.4, 366.4 ml vs 81.0, 242.0 ml, respectively) but significantly higher at 120 min in the placebo (421.6 ml vs 131.2 ml). There were no significant differences in heart rate and rectal temperature during the swim and cycle phases. However, there were significant increases in heart rate (at 5, 10, 15, 25 and 30 min) and rectal temperature (at 5, 20 and 30 min) during the 10 km run in the glycerol trial. The mean 10 km run time for the placebo trial was 40 min 21 sec (± 2.9 min) while the glycerol trial was 39 min 22 sec (± 2.0 min). The mean difference of 2.1% in finishing time between trials was not significant. Three of the five subjects in the glycerol trial improved their 10 km time by 7.0, 2.4 and 2.7%, respectively. The finishing time for one subject did not change for both trials while another subject had deteriorated by 2.3% in the glycerol trial. In the glycerol treatment, five subjects complained of bloating and nausea while only one subject complained of feeling unwell in the placebo treatment. Data from this study have shown that glycerol hyperhydration did not significantly improve performance while plasma volume expansion and subsequent lower rectal temperature and lower heart rates were not evident. The exact mechanisms of how glycerol hyperhydration can improve performance warrant further investigation. / Masters in Applied Science

This study was designed to determine the impact of glycerol hyperhydration, compared with a placebo hyperhydration, on the run performance during an Olympic distance triathlon. Ten competitive triathletes (mean peak oxygen consumption, VO2 peak = 65.5 ± 5.5 ml.kg.-1min-1) undertook two simulated Olympic Distance Triathlons in 31° C and 61% relative humidity. The trials were split into two work phases: a fixed workload phase comprising a 18-20 min swim and a 60 min cycle and, a self regulated time trial run over 10 kilometres conducted on a treadmill. One hundred and fifty min prior each trial, either a glycerol solution (1 g.kg.-1 body mass (BM) in a 4% carbohydrate – electrolyte drink) or a placebo of equal volume of the 4% carbohydrate-electrolyte solution was ingested over one hour. The total fluid intake in each trial was 23 ml.kg.-1 BM. A randomised, double blind, cross over design was used. Due to either 1) the arduous nature of the trials 2) the side effects associated with the ingestion of glycerol 3) or the combination of the two aforementioned reasons, only five of the 10 subjects completed the final 10 km self regulated time trial for both treatments. Only the data obtained from these five subjects were reported in this study. Glycerol ingestion expanded body water over the placebo by 154 ml (26%). At 60 and 90 min after the start of drinking, urine output was significantly higher with glycerol than placebo treatment (216.4, 366.4 ml vs 81.0, 242.0 ml, respectively) but significantly higher at 120 min in the placebo (421.6 ml vs 131.2 ml). There were no significant differences in heart rate and rectal temperature during the swim and cycle phases. However, there were significant increases in heart rate (at 5, 10, 15, 25 and 30 min) and rectal temperature (at 5, 20 and 30 min) during the 10 km run in the glycerol trial. The mean 10 km run time for the placebo trial was 40 min 21 sec (± 2.9 min) while the glycerol trial was 39 min 22 sec (± 2.0 min). The mean difference of 2.1% in finishing time between trials was not significant. Three of the five subjects in the glycerol trial improved their 10 km time by 7.0, 2.4 and 2.7%, respectively. The finishing time for one subject did not change for both trials while another subject had deteriorated by 2.3% in the glycerol trial. In the glycerol treatment, five subjects complained of bloating and nausea while only one subject complained of feeling unwell in the placebo treatment. Data from this study have shown that glycerol hyperhydration did not significantly improve performance while plasma volume expansion and subsequent lower rectal temperature and lower heart rates were not evident. The exact mechanisms of how glycerol hyperhydration can improve performance warrant further investigation. / Masters in Applied Science

Electrochemical behavior of electrolytic manganese dioxide (EMD), chemically prepared battery grade manganese dioxide (BGM), titanium dioxide (TiO2), lithium iron phosphate (LiFePO4) and lithium manganese phosphate (LiMnPO4) in aqueous lithium hydroxide electrolyte has been investigated. These materials are commonly used as cathodes in non-aqueous electrolyte lithium batteries. The main aim of the work was to determine how the electroreduction/oxidation behavior of these materials in aqueous LiOH compares with that reported in the literature in non-aqueous electrolytes in connection with lithium batteries. An objective was to establish whether these materials could also be used to develop other battery systems using aqueous LiOH as electrolyte. The electrochemical characteristics of the above materials were investigated by subjecting them to slow scan cyclic voltammetry and determining the charge/discharge characteristics of Zn/cathode material-aqueous LiOH batteries. The products of electroreduction/oxidation were characterized by physical techniques using X-ray diffraction (XRD), scanning electron micrography (SEM), X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS), Thermogravimetric analysis (TG) and infra-red spectrometry (IR). The reduction of ã-MnO2 (EMD) in aqueous lithium hydroxide electrolyte is found to result in intercalation of Li+ into the host structure of ã-MnO2. The process was found to be reversible for many cycles. This is similar to what is known to occur for ã-MnO2 in non-aqueous electrolytes. The mechanism, however, differs from that for reduction/oxidation of ã-MnO2 in aqueous potassium hydroxide electrolyte. KOH electrolyte is used in the state-of-art aqueous alkaline Zn/MnO2 batteries. Alkaline batteries based on aqueous KOH as the electrolyte rely upon a mechanism other than K+ intercalation into MnO2. This mechanism is not reversible. This is explained in terms of the relative ionic sizes of Li+ and K+. The lithium-intercalated MnO2 lattice is stable because Li+ and Mn4+ are of approximately the same size and hence Li+ is accommodated nicely into the host lattice of MnO2. The K+ ion which has almost double the size of Li+ cannot be appropriately accommodated into the host structure and hence the K+ -intercalated MnO2 phase is not stable. Chemically prepared battery grade MnO2 (BGM) is found to undergo electroreduction/oxidation in aqueous LiOH via the same Li+ intercalation mechanism as for the EMD. While the Zn/BGM- aqueous LiOH cell discharges at a voltage higher than that for the Zn/EMD- aqueous LiOH cell under similar conditions, the rechargeability and the material utilization of the BGM cell is poorer. The cathodic behavior of TiO2 (anatase phase) in the presence of aqueous LiOH is not reversible. In addition to LiTiO2, Ti2O3 is also formed. The discharge voltage of the Zn/TiO2- aqueous LiOH cell and material utilization of the TiO2 as cathode are very low. Hence TiO2 is not suitable for use in any aqueous LiOH electrolyte battery. LiFePO4 (olivine-type structure) as a cathode undergoes electrooxidation in aqueous LiOH forming FePO4. However the subsequent reduction forms not only the original LiFePO4 but also Fe3O4. Thus the process is not completely reversible and hence LiFePO4 is not a suitable material for use as a cathode in aqueous battery systems. LiMnPO4 (olivine-type structure) undergoes reversible electrooxidation in aqueous LiOH forming MnPO4. The charge/discharge voltage profile of the Zn/MnPO4-aqueous LiOH cell, its coulombic efficiency and rechargeability are comparable to that of the cell using ã-MnO2. EMD and LiMnPO4 both have the potential for use in rechargeable batteries using aqueous LiOH as the electrolyte. Recommendations for further developmental work for such batteries are made.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2006. / Härtill 4 uppsatser.

Thesis (Ph. D.) -- University of Texas Southwestern Medical Center at Dallas, 2006. / Embargoed. Vita. Bibliography: 134-139.

Th. doct.-ing.--Électrochim., électrochim. anal.--Grenoble--I.N.P., 1980. N°: DI 164.