The benzotriazinyl radical is a highly stable organic radical that is known to possess fast and reversible oxidation and reduction electrochemical processes. Such properties make it an ideal candidate for use as an anodic or cathodic charge storage material in a new class of high-power secondary batteries known as organic radical batteries. Towards this application, several new benzotriazinyl radical derivatives were synthesized and fully characterized using electronic absorption, EPR, and IR spectroscopy as well as elemental analysis and mass spectrometry. The electrochemical properties of the radicals were studied using cyclic voltammetry. The introduction of electron donating groups onto the structure of the radical was found to result in cathodic shifts in both of the electrochemical processes, without loss of reversibility. It was also found that in some cases functional groups led to the destabilization of the radical to a known chemical oxidation pathway that resulted in the formation of closed-shell iminoquinone compounds. These materials demonstrated good multi-electron accepting properties, undergoing two reversible one-electron reduction processes. Synthetic methodologies were developed for the preparation of two new classes of benzotriazinyl biradicals. One class used an expansion of a known benzotriazinyl radical synthesis to prepare a m-phenylene-bridged biradical, while the other class used microwave-assisted synthesis to prepare biradicals bridged by electron accepting aromatic diimides. Spectroscopic studies of both classes of biradical showed electronic isolation of the two radicals within each molecule, consistent with computational predictions. This resulted in minimal perturbation of the electrochemistry of these compounds from that of typical benzotriazinyl radicals. The solid state properties of a selection of benzotriazinyl radical derivatives were studied. Structural information obtained through single crystal X-ray diffraction studies showed significant intermolecular π-π and hydrogen bonding interactions. These solid state interactions were found to provide pathways for magnetic exchange, as determined using SQUID magnetometry. Additionally, preliminary conductivity studies indicated semiconducting behaviour in the compounds that were studied, warranting further studies. Anionic polymerization of a vinyl-functionalized benzotriazinyl radical was investigated as a method for the synthesis of a pendant benzotriazinyl polyradical with a saturated backbone. The electrochemistry of the putative polymer was identical to the monomer, maintaining reversibility of both the oxidation and reduction processes and verifying that the polymer could be used as an anodic or cathodic charge storage material. SQUID magnetometry was used to estimate a polymer spin content to be ~ 44 %. / Graduate / 0485

Thesis (Ph.D.) - University of St Andrews, April 2007. / Restricted until 20th April 2008.

Thesis (Ph. D.)--University of Hong Kong, 2007. / Title proper from title frame. Also available in printed format.

Proefschrift - Utrecht.

This standard establishes criteria for design analysis for quality and establishes criteria for reliability of rechargeable Li-Ion and Li-Ion polymer batteries for mobile telephone applications. Also included in the standard are battery pack electrical and mechanical construction, packaging technologies, pack and cell level charge and discharge controls, and overall system considerations. / "IEEE Std 1725-2006." "Approved 30 March 2006, IEEE-SA Standards Board." "Published 18 April 2006."--P. [ii]. "SH95526 ; SS95526"--P. [ii] Includes bibliographical references.

The synthesis, characterisation and performance of lithium manganese oxide spinels have been studied in terms of their application as cathode materials in rechargeable lithium batteries. A new air stable synthesis based on a solution route has been proposed. Powder X-ray diffraction demonstrates that formation of single phase spinel is possible at temperatures as low as 200 &deg;C. Chemical analysis indicates that the compositions of the spinels prepared by the new solution route depend on the firing temperature. A temperature of 200 &deg;C gives a composition of LiMn2O4.1 and the oxygen content decreases with increasing firing temperature, reaching LiMn2O4 .02 at 600 &deg;C and LiMn2O4 at 800 &deg;C. TEM indicates that the solution based spinels possess small particle sizes, less than 1 ?m. All these characteristics differ markedly from the highly stoichiometric and crystalline spinel prepared by traditional solid state reaction over 800 &deg;C. Electrochemical cells based on the new spinel cathodes were constructed and subjected to galvanostatical cycling at a high discharge rate of C/2 for 300 cycles (charging at C/4). The material fired at 200 &deg;C exhibits excellent performance at 3 V cells. An initial capacity of around 140 mAhg-1 is obtained, very close to the theoretical capacity (148 mAhg-1 ) expected for LiMn2O4 . An enhancement of capacity retention by nearly 50 % after 300 cycles is obtained if < 1 wt % of carbon is added to the solution during synthesis. After 300 cycles, 64 % of the initial capacity remains. The spinel prepared by the solution route and fired at 600 &deg;C gives excellent performance in 4 V cells. An initial capacity of 120 mAhg-1 is obtained and around 75 % of capacity remains after 300 cycles. Ex-situ X-ray diffraction and electrochemical studies such as ac impedance and cyclic voltammetry including the use of microelectrodes were carried out to understand self-discharge and capacity loss on cycling. Spinel dissolution in the electrolyte as well as layer formed on the electrode surface may play an important part in the cycle life of the 4 V spinel cathode. The capacity loss in the 3 V cells arises from incomplete reversibility of the phase transition between cubic and tetragonal spinel which accompanies each cycle.

Philosophiae Doctor - PhD / Lithium ion cathode systems based on composites of lithium iron phosphate (LiFePO₄), iron-cobalt-derivatised carbon nanotubes (FeCo-CNT) and polyaniline (PA) nanomaterials were developed. The FeCo-functionalised CNTs were obtained through in-situ reductive precipitation of iron (II) sulfate heptahydrate (FeSO₄.7H₂O) and cobalt (II) chloride hexahydrate (CoCl₂.6H₂O) within a CNT suspension via sodium borohydrate (NaBH₄) reduction protocol. Results from high Resolution Transmission Electron Microscopy (HRTEM) and Scanning Electron Microscopy (SEM) showed the successful attachment FeCo nanoclusters at the ends and walls of the CNTs. The nanoclusters provided viable routes for the facile transfer of electrons during lithium ion deinsertion/insertion in the 3-D nanonetwork formed between the CNTs and adjacent LiFePO₄ particles.

An open electrolytic cell has been designed and constructed for use in a dry environment. This was used to investigate the passivation processes concerned with both the lithium and the carbon (SO2) electrodes. A.c. impedance techniques have been used in both two and three terminal cell systems in order to study the kinetics of the electrode processes. Effects of temperature, state-of-charge and reverse cell operation have been studied. Computer simulations were made of the growth of crystals on a flat (Li) surface and the resulting growth transients connecting current and time were derived. This model was extended to simulate the porous carbon (SO2) electrode and the utilisation of the carbon as a function of the depth of reaction penetration into the electrode is devised for both potentiostatic and galvanostatic discharging.

In the introduction of this thesis thermodynamic and electrochemical studies on macrocyclic ligands related to those ligands investigated in this thesis are reviewed. A brief account on the progress made and the problems encountered in lithium battery technology are also presented. Thermodynamic parameters of complexation (Gibbs energies, DeltacG&deg;, enthalpies, DeltacH&deg;, and entropies, DeltacS&deg; of lithium (hexafluoroarsenate, tetrafluoroborate and trifluoromethanesulfonate) and crown ethers (1-aza-12-crown-4 and 15-crown-5) in acetonitrile and propylene carbonate and (4'-aminobenzo-15-crown-5 and 4'-nitrobenzo-15-crown-5) in acetonitrile at 298.15 K derived from calorimetric studies are presented. As far as 1-aza-12-crown-4 and 15-crown-5 are concerned the complexation processes are found to be enthalpy controlled. However, the stability (in enthalpic terms) of 15-crown-5 and lithium is slightly higher than that observed for the same cation and 1-aza-12-crown-4 in both solvents. Based on the stability of lithium-crown ether complexes, six lithium coronand salts were isolated and their thermochemical behaviour in dipolar aprotic media investigated. Comparison of solution enthalpies of these salts relative to those containing the free cation shows that while the former are endothermic, the latter are exothermic. This was taken as an indication that the lithium coronand cation is less solvated than the free cation. This statement was corroborated by the significant increase on the conductivity observed by the addition of crown ethers to lithium salts in propylene carbonate. From complexation and solution data for 15-crown-5 and 1-aza-12-crown-4 and lithium, enthalpies for the coordination, process in which the reactants and the product are in their pure physical state were calculated. These data combined with solution enthalpies for 15-crown-5, the un-complexed and complexed lithium salts were used to derive the enthalpy of complexation of 15-crown-5 and lithium in tetrahydrofuran, a solvent of low permittivity.

Polypropylene has proven to be the ideal material for the outer shell of the lead acid batteries. Due to its mold-ability and inert properties the material provides a capsule for the functioning components of the lead acid battery and can withstand a variety conditions encountered during its application, such as impact shock resistance, high and low temperatures and acid resistance. Polypropylene has however become of great concern with regards to environmental pollution since it is generally resistant to normal conditions of degradation and can only be properly disposed of by incineration. This factor has encouraged the industry to find ways to regenerate spent polypropylene. A good example of such a process is the recycling of lead acid batteries. This allows not only for the regeneration of lead, but also for the recycling of polypropylene in the manufacturing of battery cases. There are some cost advantages in using recycled polypropylene. However it does have its disadvantages in that the material does start to deteriorate after multiple processes. A common practice amongst battery manufacturers is to add virgin polypropylene to the recycled material in order to ensure performance consistency. The comparative study investigated the use of various ratios of virgin and recycled PP in the manufacturing of lead acid battery cases and their influence on the physical properties and performance of the final material. The degradation of PP was also investigated as the material was subjected to multiple manufacturing processes where the influence of stabilizers was further considered. A common technique of PP analysis such as MFI was shown to be an effective technique to maintain good quality control. The study further showed that it is important that the material grade of PP used in the manufacturing of the battery case and lid is compatible in order to allow for effective heating sealing of the two components. Polypropylene has a waxy surface finish and it is generally difficult to label or write on. Labels tend to fall off in application and make it difficult to maintain a track record of the manufactured batteries with time. This study showed successfully that a laser activated dye can be added to the PP without influencing its color or its performance. This allows for successful labeling of battery cases by various bar coding writers that can trace the battery through its manufacturing process. Lead acid batteries are often operated outside the specified temperature range that is determined by battery manufacturers resulting in premature failure. These failures can occur within the warranty period of the battery and result in illicit claims since the monitoring of the batteries in its application was not possible. A suitable temperature monitoring device was designed that would be incorporated into the vent cap or lid of the battery case. The device contained temperature sensitive indicators that would undergo a permanent color change at specified temperatures thereby giving the battery manufacturer an indication as to the maximum temperature the battery was exposed to.