Thesis (Ph. D.)--Northeastern University, 2008. / Title from title page (viewed June 24, 2009). Graduate School of Engineering, Dept. of Electrical and Computer Engineering. Includes bibliographical references (p. 205-213).

Thesis (B.S.)--University of Missouri, School of Mines and Metallurgy, 1925. / The entire thesis text is included in file. Typescript. Illustrated by author. Title from title screen of thesis/dissertation PDF file (viewed September 15, 2009) Includes bibliographical references (p. 13) and index (p. 14).

Thesis (PH. D.)--Columbia University, 1941. / Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Dissertation (Ph.D.)--University of Toledo, 2005. / Typescript. "A dissertation [submitted] as partial fulfillment of the requirements of the Doctor of Philosophy degree in Engineering." Bibliography: leaves 61-63.

Thesis (Ph.D.) - University of St Andrews, June 2009. / Restricted until 1st June 2011.

LiNi₀.₅Mn₁.₅O₄ thin films have been grown by pulsed laser deposition (PLD) on stainless steel (SS) substrates. The crystallinity and structure of thin films were investigated by X-ray diffraction (XRD). Microstructure and surface morphology of the thin films were examined using a field-emission scanning electron microscope (FESEM). The electrochemical properties of the thin films were studied with cyclic voltammetry (CV) and galvanostatic charge-discharge in the potential range between 3.0 and 4.9 V. The electrochemical behavior of LiNi₀.₅Mn₁.₅O₄ thin films showed reversible capacity above 4.7 V and good cycle performance up to 50 cycles. / Singapore-MIT Alliance (SMA)

Ce travail consiste en l’étude par RMN multinoyaux de matériauxparamagnétiques d’électrodes positives pour batteries Li ou Na-ion. La RMN du solidepermet une caractérisation de l’environnement local du noyau sondé grâce à l’exploitationdes interactions hyperfines dues à la présence d’une certaine densité d’électrons célibataires(déplacement de contact de Fermi) sur ce noyau (densité transférée selon des mécanismesplus ou moins complexes). Les matériaux étudiés sont des fluoro ou oxy phosphates devanadium de formules générales AVPO4X (A= Li ou Na; X = F, OH, ou OF) (structure typeTavorite), et Na3V2(PO4)2F1-xOx. Tous ces matériaux ont été caractérisés par RMN du 7Li ou23Na, 31P et 19F combiné à des calculs DFT, afin de mieux comprendre les structure etstructure électroniques locales. Notamment, ces études nous ont permis de mettre enévidence la présence de défauts dans certains matériaux et donc de discuter leur impact surles propriétés électrochimiques. L’utilisation de la méthode PAW nous a permis de modéliserdes défauts dilués dans des supermaille. Ensuite, l’impact de ces défauts sur la structurelocale a été étudié afin d’envisager les mécanismes de transfert de spin possibles etreproduire leur déplacements de RMN. / Paramagnetic materials for positive electrodes for Li or Na-ion batteries havebeen studied by multinuclear NMR. The local environment of the probed nucleus can becharacterized by solid state NMR making use of hyperfine interactions due to transfer ofsome electron spin density (Fermi contact shift) on this nucleus, via more or less complexmechanisms. The materials studied are vanadium fluoro or oxy phosphates of generalformulas AVPO4X (A= Li or Na; X = F, OH, or OF) belonging to the Tavorite family and theNa3V2(PO4)2F1-xOx . All these materials have been characterized by 7Li or 23Na, 31P and 19F,combined with DFT calculations to better understand local electronic structures andstructures. In particular, these studies have enabled us to highlight the presence of defects incertain materials and to discuss their impact on the electrochemical properties. The use ofthe PAW method allowed us to model diluted defects in large supercells, to calculate theFermi contact shifts of the surrounding nuclei and to study the mechanisms of electron spintransfer. This allowed us to better understand the nature of defects in materials.For some systems, the mechanisms related to the intercalation or deintercalation of Li+ orNa+ ions have also been studied by NMR.

Le cœur de technologie d'une batterie réside principalement dans les matériaux actifs des électrodes, qui est fondamental pour pouvoir stocker une grande quantité de charge et garantir une bonne durée de vie. Le dioxyde d'étain (SnO₂) a été étudié en tant que matériau d'anode dans les batteries Li-ion (LIB) et Na-ion (NIB), en raison de sa capacité spécifique élevée et sa bonne tenue en régimes de puissance élevés. Cependant, lors du processus de charge/décharge, ce matériau souffre d'une grande expansion volumique qui entraîne une mauvaise cyclabilité, ce qui empêche la mise en oeuvre de SnO₂ dans des accumulateurs commerciaux. Aussi, pour contourner ces problèmes, des solutions pour surmonter les limites de SnO₂ en tant qu'anode dans LIB / NIB seront présentées dans cette thèse. La partie initiale de la thèse est dédié à la production de SnO₂ et de RGO (oxyde de graphène réduit)/SnO₂ par pyrolyse laser puis à sa mise en oeuvre en tant qu'anode. La deuxième partie s'attarde à étudier l'effet du dopage de l'azote sur les performances et permet de démontrer l'effet positif sur le SnO₂ dans les LIB, mais un effet néfaste sur les NIB. La partie finale de la thèse étudie l'effet de l'ingénierie matricielle à travers la production d'un composé ZnSnO₃. Enfin, les résultats obtenus sont comparés avec l'état de l'art et permettent de mettre en perspectives ces travaux. / The heart of battery technology lies primarily in the electrode material, which is fundamental to how much charge can be stored and how long the battery can be cycled. Tin dioxide (SnO₂) has received tremendous attention as an anode material in both Li-ion (LIB) and Na-ion (NIB) batteries, owing to benefits such as high specific capacity and rate capability. However, large volume expansion accompanying charging/discharging process results in poor cycleability that hinders the utilization of SnO₂ in commercial batteries. To this end, engineering solutions to surmount the limitations facing SnO₂ as an anode in LIB/NIB will be presented in this thesis. The initial part of the thesis focuses on producing SnO₂ and rGO (reduced graphene oxide)/SnO₂ through laser pyrolysis and its application as an anode. The following segment studies the effect of nitrogen doping, where it was found to have a positive effect on SnO₂ in LIB, but a detrimental effect in NIB. The final part of the thesis investigates the effect of matrix engineering through the production of a ZnSnO₃ compound. Finally, the obtained results will be compared and to understand the implications that they may possess.

>Magister Scientiae - MSc / Spinel lithium manganese oxide (LiMn2O4), for its low cost, easy preparation and nontoxicity, is regarded as a promising cathode material for lithium-ion batteries. However, a key problem prohibiting it from large scale commercialization is its severe capacity fading during cycling. The improvement of electrochemical cycling stability is greatly attributed to the suppression of Jahn-Teller distortion (Robertson et al., 1997) at the surface of the spinel LiMn2O4 particles. These side reactions result in Mn2+ dissolution mainly at the surface of the cathode during cycling, therefore surface modification of the cathode is deemed an effective way to reduce side reactions. The utilization of a nanocomposite which comprises of metallic Cu and Au were of interest because their oxidation gives rise to a variety of catalytically active configurations which advances the electrochemical property of Li-ion battery. In this research study, an experimental strategy based on doping the LiMn2O4 with small amounts of Cu-Au nanocomposite cations for substituting the Mn3+ ions, responsible for disproportionation, was employed in order to increase conductivity, improve structural stability and cycle life during successive charge and discharge cycles. The spinel cathode material was synthesized by coprecipitation method from a reaction of lithium hydroxide and manganese acetate using 1:2 ratio. The Cu-Au nanocomposite was synthesized via a chemical reduction method using copper acetate and gold acetate in a 1:3 ratio. Powder samples of LiMxMn2O4 (M = Cu-Au nanocomposite) was prepared from a mixture of stoichiometric amounts of Cu-Au nanocomposite and LiMn2O4 precursor. The novel LiMxMn2O4 material has a larger surface area which increases the Li+ diffusion coefficient and reduces the volumetric changes and lattice stresses caused by repeated Li+ insertion and expulsion. Structural and morphological sample analysis revealed that the modified cathode material have good crystallinity and well dispersed particles. These results corroborated the electrochemical behaviour of LiMxMn2O4 examined by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The diffusion coefficients for LiMn2O4 and LiMxMn2-xO4 obtained are 1.90 x10-3 cm2 / s and 6.09 x10-3 cm2 / s respectively which proved that the Cu-Au nanocomposite with energy band gap of 2.28 eV, effectively improved the electrochemical property. The charge / discharge value obtained from integrating the area under the curve of the oxidation peak and reduction peak for LiMxMn2-xO4 was 263.16 and 153.61 mAh / g compared to 239.16 mAh / g and 120 mAh / g for LiMn2O4. It is demonstrated that the presence of Cu-Au nanocomposite reduced side reactions and effectively improved the electrochemical performance of LiMn2O4.

Cette étude s’inscrit dans le cadre de la recherche de nouveaux matériaux anodiques à forte capacité pour accumulateurs à ion lithium. Il y est décrit, la synthèse de systèmes graphite-étain obtenus par réduction, en présence de graphite à des taux variables, des chlorures d’étain SnCl2 et SnCl4, par les hydrures alcalins NaH et LiH activés par un alcoolate. Les nanomatériaux préparés présentent des capacités réversibles stables en cyclage, assez proches de celles calculées à partir des teneurs en métal déterminées par analyse élémentaire. Cependant, on peut noter des différences importantes entre les valeurs et l’évolution en cyclage des capacités irréversibles selon l’hydrure ou le mélange d’hydrure utilisé(s). Avec l’hydrure de sodium NaH, la capacité irréversible, très élevée au premier cycle, s’annule pratiquement dès le deuxième cycle ; avec l’hydrure de lithium LiH, cette capacité irréversible, bien que plus faible au premier cycle, donne une valeur résiduelle récurrente aux cycles suivants. Il a finalement été montré que l’utilisation du mélange des deux hydrures NaH/LiH permet de préserver les avantages des deux systèmes précédents et d’obtenir des matériaux combinant de manière synergique leurs propriétés. / This study is devoted to the development of new anodic materials with high capacities for lithium-ion batteries. The synthesis of graphite-tin systems obtained by reduction, in the presence of graphite at various rates, of the tin Chlorides SnCl2 and SnCl4, by the alkoxide-activated alkaline hydrides ( sodium hydride or lithium hydride) is described. The nanomaterials prepared have stable reversible capacities in cycling, close to those calculated from the amounts of metal given by elemental analysis. However, important differences between the values and the evolution in cycling of the irreversible capacities depending on the hydride or the mixture of hydride used were observed. With sodium hydride, the irreversible capacity, very high during the first cycle, is practically cancelled at the second cycle; with lithium hydride, this irreversible capacity, although lower to the first cycle, gives a recurring residual value at the following cycles. The use of the NaH/LiH allowed to preserve the advantages of the two preceding systems and to synergistically combine their properties.