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The aim of this thesis is to develop a better understanding about the degradation mechanisms occurring within lithium-ion cells which eventually lead to their failure. An introduction to the components and operation of Li-ion cells is followed by proposed degradation mechanisms which limit the lifetime of cells. These mechanisms and how they can be identified from electrochemical testing are discussed. Electrolyte additives can be used to improve the safety of Li-ion cells or decrease the rate of cell degradation. Different types of additives and testing methods are discussed followed by an introduction to high precision coulometry which can be used to detect the impact of additives on cycling performance. The High Precision Charger that was constructed for this project is described and shown to meet the desired precision. The use of additives and different materials to extend lifetime of cells is shown to be detectable through the use of high precision coulometry. High precision coulometry proves to be a more efficient way of estimating the lifetime of cells under realistic conditions in a reasonably short amount of time. / MSc. Thesis

In order for battery manufacturers to have a sustainable business, the batteries they produce must be as safe as possible. For lithium-ion batteries, reducing the flammability of the electrolyte is considered to be one way to improve safety, which might be achieved by adding flame retardants to the electrolyte. On the other hand, sodium-ion batteries are attracting attention from academic researchers due to the abundance of sodium reserves compared to lithium reserves. However, there are virtually no studies about the safety of sodium-ion batteries. In this thesis, studies of these two issues will be reported. The reactivity of charged/discharged electrode materials for sodium-ion batteries in different solvents and electrolytes at elevated temperature was studied using Accelerating Rate Calorimetry (ARC). Hard carbon was studied as a negative electrode material for sodium-ion batteries. The reactivity of sodium-inserted hard carbon in solvents and electrolytes was investigated. Then, the reactivity of sodium-inserted hard carbon was compared to lithiated graphite. NaCrO2, NaxCoO2 and NaNi0.5Mn0.5O2 were studied as positive electrode materials for sodium-ion batteries. The electrochemical performance of these materials was investigated. The reactivity of charged NaCrO2, NaxCoO2 and NaNi0.5Mn0.5O2 in solvents and electrolytes was studied using ARC. Sodium bis(trifluoromethanesulfonyl)imide (NaTFSI) was studied as an electrolyte salt for sodium-ion batteries. The electrochemical performance of hard carbon and NaCrO2 in NaTFSI/PC electrolyte was studied. The reactivity of sodium-inserted hard carbon and deintercalated NaCrO2 in NaTFSI/PC electrolyte was also investigated. Triphenyl phosphate (TPP) was studied as a flame retardant additive for lithium-ion batteries. Its impact on electrochemical performance of negative electrode materials (petroleum coke and graphite) and positive electrode materials (LiNi1/3Mn1/3Co1/3O2 (NMC) and LiNi0.8Co0.15Al0.05O2 (NCA)) was studied using an automated storage test, symmetric cells and Electrochemical Impedance Spectroscopy (EIS). The reactivity of lithiated graphite, deintercalated NMC and NCA in electrolyte containing TPP was investigated using ARC. Finally, the flammability of electrolytes containing TPP was studied using a Self-Extinguishing Time (SET) test.

A library of 2-nitrobenzenesulfonyl (Ns) derivatives incorporating isotopic labels and a range of structural variations was prepared and characterized to investigate mass spectrometric fragmentation processes. Deprotonated Ns amino acids were formed readily by negative mode electrospray ionization. Collision induced dissociation experiments established precursor-product ion relationships and indicated a novel loss of an aryl ortho substituent (NO2, F, Cl or Br). In total, four distinct fragmentation pathways of Ns-alpha- and Ns-beta-amino acid anions were identified using isotopic labeling, structural variations of the Ns derivatives, and collision induced dissociation of ions generated in source. Overall, the observation of specific fragmentation pathways correlated with anion structure and ionization site. However, the observation of only one of four possible fragmentation processes in the mass spectrum of the Ns derivative of an amino dicarboxylic acid indicated that functional group interactions must also be considered in the interpretation and prediction of fragmentation processes.

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Ion channel regulation is key to the control of excitability and behaviour. In the bag cell neurons of Aplysia californica, a voltage- and Ca2+-dependent nonselective cation channel drives a ~30-minute afterdischarge, culminating in the release of egg-laying hormone. Using excised, inside-out single channel patch-clamp, this study tested the hypothesis that inositol 1,4,5-trisphosphate (IP3), which is produced during the afterdischarge, and channel-associated protein kinase C (PKC), which is activated throughout the afterdischarge, cause a left-shift (enhancement) in both the voltage- and Ca2+-dependence of the cation channel. Kinetic analysis of bag cell neuron cation channel voltage-dependence revealed that, with depolarization, the channel remained open longer and reopened more often. A cation channel subconductance was also observed, and found to be 13 pS vs. the typical 23 pS full-conductance. The cytoplasmic face of cation channel-containing patches was exposed to 1 mM ATP, as a phosphate source for channel-associated PKC, and/or 5 uM IP3. Apparent PKC-dependent phosphorylation left-shifted voltage-dependence by -3 mV, although this effect was more prominent at negative voltages (between -90 and -30 mV). Conversely, IP3 right-shifted voltage-dependence (change in V1/2 of 6 mV). Cation channel Ca2+-dependence was similar to that previously reported, with a control EC50 of 3-5 uM. This was right-shifted by PKC (EC50 = 30 uM) and even more so by IP3 (apparent EC50 = 20 M). PKC largely rescued the Ca2+ responsiveness in the presence of IP3 (EC50 = 20 uM). Unexpectedly, IP3 plus ATP resulted in an increase in channel unitary conductance at more positive voltages. The multi-faceted regulation of the bag cell neuron cation channel suggests sophisticated modulatory control. Upregulation, such as depolarization and the left-shift in voltage-dependence with PKC, would drive the afterdischarge, while counteracting effects, such as IP3 right-shifting voltage-dependence, as well as PKC and IP3 suppressing Ca2+-dependence, would simultaneously or subsequently attenuate the channel, thus preventing an interminable afterdischarge. / Thesis (Master, Physiology) -- Queen's University, 2008-08-26 13:20:16.528