Li-ion batteries are currently the most efficient technology available for electrochemical energy storage. The technology has revolutionized the portable electronics market and is becoming a corner stone for large scale applications, such as electric vehicles. It is therefore important to develop materials in which the energy storage relies on abundant redox active species, such as iron. In this thesis, new iron based electrode materials for positive electrodes in Li-ion batteries were investigated. Lithium iron pyrophosphate (Li2FeP2O7) and two polymorphs of lithium iron sulphate fluoride (LiFeSO4F) were studied. For Li2FeP2O7, preferred oxidation of iron with different coordination numbers within the crystal structure was studied, and six-coordinated iron was found to be oxidized preferentially at lower potentials compared to five‑coordinated iron. Electrochemical cycling resulted in structural changes of Li2FeP2O7 through an increased Li-Fe mixing in the compound, forming a metastable state during battery operation. For tavorite LiFeSO4F, the influence of the amount of a conductive polymer (poly(3,4-ethylenedioxythiophene), or PEDOT) was studied. All the different amounts of PEDOT coating reduced the polarization significantly, but the trade-off between functionality and weight added also has to be considered. Additionally, the effect of densifying the electrodes to different degrees is reported, and was found to have a significant influence on the battery performance. Also triplite LiFeSO4F was coated with PEODT, and it was found that the electrochemical performance improved, but not to the same extent as for tavorite LiFeSO4F. The faster solid state transport of Li-ions in tavorite type LiFeSO4F possibly accounts for the difference in electrochemical performance. Together, the results presented herein should be of importance for developing new iron based materials for Li-ion batteries. / Av de idag tillgängliga teknologierna för elektrokemisk energilagring så har litium-jonbatterier de bästa egenskaperna när det gäller energiförluster och energilagringskapacitet. De har revolutionerat marknaden för portabel elektronik (telefoner, laptops etc.), och blir mer och mer viktiga för storskaliga tillämpningar såsom elbilar. För den typen av applikationer måste teknologin baseras på vanligt förekommande material och grundämnen, t.ex. järn. I den här avhandlingen har järnbaserade material för den positiva elektroden hos litium-jonbatterier studerats. Olika aspekter som påverkar spänningen och effektiviteten hos elektroderna har undersökts. Ett exempel på det är hur olika omgivningar kring järnatomerna i en förening påverkar spänningen hos ett batteri. För föreningen litiumjärnpyrofosfat visade det sig att sex närmaste grannar ger lägre spänning än fem närmaste grannar till järn. Dessutom har förändringar i föreningens struktur studerats då den används i ett batteri. Den här typen av grundforskning är viktig för förståelsen av nya elektrodmaterial i Li-jonbatterier. Ur en mer praktisk synvinkel så har elektroder baserade på en annan järnförening, litiumjärnsulfatfluorid, utvecklats. Ledningsförmågan hos dessa elektroder har förbättrats genom att belägga föreningen med ett ledande skikt, samt att mekaniskt pressa samman elektroderna genom mangling. Båda metoderna är viktiga för att tillverka välfungerande elektroder. Föreningen litiumjärnsulfatfluorid förekommer i två olika former, och en jämförelse av hur elektriskt ledande beläggningar påverkar de bägge materialen har också gjorts i den här avhandlingen. Tillsammans visar resultaten från de olika studierna på hur man kan arbeta och tänka kring utvecklingen av nya material för litium-jonbatterier.

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A síndrome de Li-Fraumeni (SLF) é uma síndrome rara de predisposição a câncer associada a mutações germinativas no gene supressor tumoral TP53. As vias de sinalização da proteína p53 estão envolvidas na regulação da apoptose, das paradas do ciclo celular, da senescência e do reparo de danos no DNA. As mutações em p53 mais comumente encontradas em tumores estão distribuídas ao longo do domínio de ligação ao DNA, incluindo a mutação G245S associada à SLF. No entanto, a mutação mais frequentemente associada à SLF nas regiões Sul e Sudeste do Brasil é a mutação R337H, que afeta o domínio de oligomerização de p53. Assim, o objetivo deste estudo foi analisar os efeitos em células de p53 mutantes associadas à síndrome de SLF na viabilidade em condições basais e na sobrevivência celular sob estresse genotóxico. Células p53 null da linhagem NCI-H1299 foram transfectadas com vetores para a expressão de p53 wt e das mutantes G245S e R337H, e ensaios celulares foram realizados. A mutante R337H inibiu a formação de colônias e diminuiu a viabilidade celular de forma similar ao observado para células com expressão p53 wt, enquanto G245S demonstrou menor influência sobre a viabilidade e sobre a proliferação das células. Após submetidas a estresse genotóxico induzido por meio de exposições à radiação UVC, células com expressão de R337H mostraram-se mais sensíveis à morte celular mesmo quando expostas à baixa dose de UVC. Já as células com a expressão de G245S apresentaram aumento nas taxas de apoptose tardia somente quando submetidas a altas doses de radiação de UVC, assim como nas células com expressão de p53 wt. Dessa forma, foram observadas atividades funcionais similares entre R337H e p53 wt quanto à influência sobre a viabilidade e sobre a proliferação celular, enquanto células com expressão de G245S apresentaram fenótipo celular mais próximo ao p53-null. Todavia, G245S demonstrou atividade próxima a de p53 wt ao conferir proteção às células contra morte induzida pela radiação UVC, e a mutante R337H gerou maior sensibilidade para morte celular em condições de estresse genotóxico. / Li-Fraumeni syndrome (LFS) is a hereditary cancer predisposition disorder associated with germline mutations in the TP53 tumor suppressor gene. The p53 signaling pathways are involved in the regulation of apoptosis, cell cycle arrest, senescence and DNA repair. The p53 mutations found in tumors are commonly distributed along the DNA binding domain, including the G245S mutation associated with LFS. However, the most frequent p53 mutation associated with LFS in Southeast and Southern Brazil is the R337H mutation, which affects the oligomerization domain of p53. Thus, the aim of this study is to analyze the effects of mutant p53 associated with LFS on cell viability at basal conditions and on cell survival in genotoxic stress. Null-p53 NCI-H1299 cell line were transfected with vectors for the expression of wild-type, G245S and R337H p53, and cell assays were performed. The R337H mutant inhibited the colony formation and decreased the cell viability similar to that observed in cells with wt p53 expression, while G245S demonstrated less influence on cell viability. After undergoing genotoxic stress induced by UVC radiation exposures, cells with R337H expression were more sensitive to cell death when exposed to low UVC dose. Cells with G245S expression showed an increase in late apoptosis rates only when subjected to high doses of UVC radiation, as well as cells with wt p53 expression. Thus, similar and functional activities were observed between R337H and wt p53 concerning influence on cell viability and proliferation, with the expression of G245S presented cellular phenotype closer to p53-null. However, G245S demonstrated to confer protection for cell death as seen for wt p53, whereas R337H generated increased of sensitivity to cell death under conditions of genotoxic stress.

Dans cette thèse, nous avons exploré toute une palette de composés à base de métaux de transition et de polyanions carboxylates (oxalates, malonates et carbonates) préparés via des procédés éco-efficaces. La synthèse du composé oxalate de fer (III) (Fe2(C2O4)3·4H2O) dont nous en avons élucidé pour la première fois la structure cristalline en combinant les techniques de diffraction des rayons X et neutrons, fait l'objet de la première partie de cette étude. Ce composé cristallise dans une maille triclinique (P -1) et il présente des propriétés électrochimiques intéressantes (98 mAh/g à 3.35 V vs. Li+/Li0). Dans cette quête pour de meilleurs matériaux, nous avons exploré la famille des oxalates Na2M2(C2O4)3·2H2O, dont la synthèse avait été déjà rapportée, mais sans qu'aucune activité électrochimique ne puisse être détectée. En revanche, le remplacement du groupement oxalate par un groupement malonate nous a permis d’obtenir pour la première fois plusieurs membres de la famille (Na2M(H2C3O4)2·nH2O (n=0, 2), M= Mn, Fe, Co, Ni, Zn et Mg) dont nous avons résolu leurs structures cristallines correspondantes. Cependant, comme dans le cas des oxalates, ces phases ne dévoilent aucune activité électrochimique vis-à-vis du lithium, bien qu'elles présentent des propriétés magnétiques intéressantes. Enfin nous avons conclu ce travail par la synthèse de composés appartenant à la famille des fluorocarbonates KMCO3F (M= Ca et Mn) en utilisant la voie tout solide. La phase au calcium, déjà rapportée dans la littérature, a fait l'objet d'une étude en température qui nous a permis de mettre en évidence pour la première fois la formation d'une phase haute température (KCaCO3F-HT), pour T≥320°C, dont nous avons résolu la structure. Finalement, l'utilisation du Mn au lieu du Ca a conduit à l'obtention d'une nouvelle phase (KMnCO3F) qui cristallise dans une maille hexagonale (P -6 c 2) / This thesis has focused on the exploration of new compounds based on 3d-metal and carboxylate polyanions (oxalates, malonates and carbonates) prepared through different sustainable synthetic approaches. In the first part, we report a new synthetic route to prepare the iron (III) oxalate compound (Fe2(C2O4)3·4H2O) and solve its crystal structure through combined X-ray and neutron powder diffraction. The compound crystallizes within a triclinic cell (P-1) and exhibits attractive electrochemical properties (98 mAh/g at 3.35 V vs. Li+/Li0). Motivated by this finding we pursued our quest for new positive electrode materials. We prepared by hydrothermal synthesis single crystals of sodium 3d-metal oxalates Na2M2(C2O4)3·2H2O, which are widely investigated in the literature for their magnetic properties. Unfortunately, these phases are electrochemically inactive versus lithium. Thereafter, we extended the synthesis towards the malonate family and we reported for the first time several members (Na2M(H2C3O4)2·nH2O (n= 0, 2), M= Mn, Fe, Co, Ni, Zn et Mg). These systems present rich crystal chemistry together with interesting antiferromagnetic properties but as in the case of the oxalates, they are not electrochemically active versus lithium. Finally, we synthesized two members of fluorocarbonates compounds KMCO3F (M= Ca and Mn) using solid state process. We succeeded in the preparation of the calcium member, already reported in the literature and we identified for the first time a phase transition at 320°C. The crystal structure of the high temperature phase (KCaCO3F-HT) was solved using neutron powder diffraction. A new manganese phase (KMnCO3F) was synthesized using the same technique and its crystal structure was solved by combining TEM, XR and neutrons powder diffraction techniques. This compound crystallizes within a hexagonal unit cell (P -6 c 2)

En raison de leur capacité théorique élevée, les batteries Li-air ont été considérées comme des dispositifs de stockage d'énergie prometteurs depuis leur invention. Cependant, la grande complexité de ces dispositifs a entravé leur application pratique. En plus, les résultats expérimentaux et les théories mécanistes rapportés dans la littérature sont épars et ajoutent des difficultés pour développer une compréhension globale de leurs principes de fonctionnement. Le travail accompli dans cette thèse repose sur la combinaison de deux approches : la modélisation et l'expérimentation, non pas dans le but d'avoir une adéquation parfaite entre simulation et expérience mais afin de mieux comprendre le lien entre les différents mécanismes mis en jeux. Un modèle de déchargé, basé sur une approche continuum et rassemblant théorie de la nucléation, description des réactions cinétiques et du transport de masse, a été développé. Le modèle permet d'étudier simultanément l'impact de la densité de courant, des propriétés de l'électrolyte et des propriétés de surface de l'électrode sur le procédé de décharge des batteries Li-air permettant ainsi une meilleure compréhension. De plus, le modèle de charge développé lors de cette thèse, met en lumière la corrélation entre la distribution des tailles de particules de Li2O2 et le profil de recharge obtenu. Finalement, afin d'étudier ces batteries au niveau mésoscopique, un modèle de cinétique Monte-Carlo a été créé et permet de comprendre les processus de décharge dans des espaces confinés / Due to their high theoretical capacity, Li-air batteries (LABs) have been considered as promising energy storage devices since their invention. However, the high complexity of these devices has impeded their practical application. Moreover, the scattered experimental results and mechanistic theories reported in literature, add difficulties to develop a comprehensive understanding of their operation principles. The work accomplished in this thesis constitutes an effort to entangle the complexity of LABs through the combination of modeling approaches with experiments, with the focus on getting better understanding about the mechanisms interplays, rather than pursuing a perfect quantitative match between simulation and experimental results. Based on continuum approach, a discharge model has been developed combining the nucleation theory, reaction kinetics and mass transport. This model converged the impacts of current density, electrolyte property and electrode surface property on the discharge process of LABs to a comprehensive theory. Furthermore, a charge model has been developed to address the important role of Li2O2 particle size distribution in determining the shape of recharge profile. In addition, to investigate the LAB system at mesoscale, a kinetic Monte Carlo (KMC) model has been build and the simulation results provided insights into the discharge process in confined environment at local level

New layered cathode materials, Li₀.₉Ni₀.₄₅Ti₀.₅₅O₂, were synthesized by means of ion-exchange from Na₀.₉Ni₀.₄₅Ti₀.₅₅O₂. The degree of cation disordering in the material depends critically on the synthesis conditions. Longer times and higher temperatures in the ion-exchange process induced more cation disordering. However, the partially disordered phase showed better capacity retention than the least disordered phase. First principles calculations indicated this could be attributed to the migration of Ti⁺⁴ into the Li layer during the electrochemical testing, which seems to depend sensitively on the Ni⁺² -Ti⁺⁴ configuration in the transition metal layer. The poor conductivity of this material could also be the reason for its low specific capacity according to the Density of States (DOS) obtained from first principles calculations indicating that only Ni participates in the electronic conductivity. / Singapore-MIT Alliance (SMA)

Efficient, cost effective, and environmentally friendly energy storage and conversion systems are highly desirable to meet ever increasing demands. Nanostructured materials have attracted great interest due to their many superior characteristics in these energy applications. These materials, typically nanoporous or nanostructured, exhibit faster charge transports, better contact, and sometimes new electrochemical reactivity, which leads to their high energy density, high power and/or great catalytic performances. A series of functional nanostructured materials have been fabricated with new synthetic schemes. Nanoporous materials technology and solid state electrochemistry have been attempted to be integrated in this study. New functional nanoporous materials have been sought for electrochemical purposes. By employing a simple dilution strategy, homogeneously sized, ordered mesoporous silica nanorods (SBA-15), spanning about 10 porous channels in width and ranging from 300 to 600 nm in length were prepared. By employing SBA-15 nanorods as a template, ordered mesoporous carbon (OMC) CMK-3 nanorods were prepared. These porous nanorods exhibit enhanced mass transfer kinetics in their applications owing to their short dimensions. To improve the electronic conductivity of OMC and exploit otherwise wasted copolymer surfactant cross-linked in the channels of as-synthesized SBA-15, direct graphitic mesoporous carbon (termed as DGMC) were synthesized from the copolymer surfactant by employing transition metals (Fe, Co, Ni) as a catalyst. DGMC exhibit three orders higher conductivity and better thermal stability than non-graphitic OMC materials. A series of nanostructured composites were fabricated by employing OMC as structure backbones and/or electronic conduits. DGMC/MoO2 as a Li ion battery anode exhibits a reversible capacity more than twice the value that a graphite anode can provide. Due to the confined and nanosized dimensions of the MoO2, the composite exhibits a cycle life with no capacity fading. Polymer modified OMC/sulfur interwoven nanostructures were prepared and applied as a cathode in Li-S batteries. The nanostructure displays all of the benefits of confinement effects at a small length scale. The nanostructure provides not only high electronic conductivity but also great access to Li+ ingress/egress for reactivity with the sulfur. The tortuous pathways within the framework and the surface polymer strongly retard the diffusion of polysulfide anions out from the channels into the electrolyte and minimize the loss of active mass in the cathode, resulting in a stabilized cycle life at reasonable rates. The Li-S batteries can supply up to near 80% of the theoretical capacity of sulfur (1320 mA∙h/g). This represents more than five times the specific capacity of conventional intercalation Li ion batteries. The assembly process for OMC/S is simple and broadly applicable, conceptually providing new opportunities for materials scientists for tailored design that can be extended to many different electrode materials. Size-controlled supported metal and intermetallic nanocrystallites are of substantial interest because of their wide range of electrocatalytic properties. These intermetallics are normally synthesized by high temperature techniques; however, rigorous size control at high temperature is very challenging. A simple and robust chemically controlled process was developed for synthesizing size controlled noble metal, or bimetallic nanocrystallites, embedded within the porous structure of OMC. The method is applicable to a wide range of catalysts, namely bimetallic PtBi but also including Pt, Ru, Rh and Pd. By using surface-modified OMC, nanocrystallites are formed with monodisperse sizes as low as 1.5 nm, that can be tuned up to 2 and 3.5 nm (equivalent to the channel size of OMC) by thermal treatment. The method is also tailored for the deposition of catalysts on conventional fuel-cell carbon supports. OMC-PtBi nanohybrids were investigated as catalysts for formic acid oxidation for the first time. OMC-PtBi catalysts show an absence of CO poisoning. The excellent catalytic properties can be attributed to the successful catalyst preparation and the faithful practice of the “ensemble effect” at the nanoscale level. A new agitation-friction methodology was developed to prepare the nano-OMC/S composite. The method is completely different from any conventional impregnation which requires the voluntary molecular mobility of guest phases. The method relies on frictional forces, and the hydrophobic attraction of the mixing components. This is the first example of a nanoporous solid which can be infiltrated by another solid phase at room temperature. The C/S nanocomposite exhibits not only better Pt ion sorption kinetics than its bulk counterpart, but also a higher pseudo-second-order rate constant than chitosan sorbents.

Efficient, cost effective, and environmentally friendly energy storage and conversion systems are highly desirable to meet ever increasing demands. Nanostructured materials have attracted great interest due to their many superior characteristics in these energy applications. These materials, typically nanoporous or nanostructured, exhibit faster charge transports, better contact, and sometimes new electrochemical reactivity, which leads to their high energy density, high power and/or great catalytic performances. A series of functional nanostructured materials have been fabricated with new synthetic schemes. Nanoporous materials technology and solid state electrochemistry have been attempted to be integrated in this study. New functional nanoporous materials have been sought for electrochemical purposes. By employing a simple dilution strategy, homogeneously sized, ordered mesoporous silica nanorods (SBA-15), spanning about 10 porous channels in width and ranging from 300 to 600 nm in length were prepared. By employing SBA-15 nanorods as a template, ordered mesoporous carbon (OMC) CMK-3 nanorods were prepared. These porous nanorods exhibit enhanced mass transfer kinetics in their applications owing to their short dimensions. To improve the electronic conductivity of OMC and exploit otherwise wasted copolymer surfactant cross-linked in the channels of as-synthesized SBA-15, direct graphitic mesoporous carbon (termed as DGMC) were synthesized from the copolymer surfactant by employing transition metals (Fe, Co, Ni) as a catalyst. DGMC exhibit three orders higher conductivity and better thermal stability than non-graphitic OMC materials. A series of nanostructured composites were fabricated by employing OMC as structure backbones and/or electronic conduits. DGMC/MoO2 as a Li ion battery anode exhibits a reversible capacity more than twice the value that a graphite anode can provide. Due to the confined and nanosized dimensions of the MoO2, the composite exhibits a cycle life with no capacity fading. Polymer modified OMC/sulfur interwoven nanostructures were prepared and applied as a cathode in Li-S batteries. The nanostructure displays all of the benefits of confinement effects at a small length scale. The nanostructure provides not only high electronic conductivity but also great access to Li+ ingress/egress for reactivity with the sulfur. The tortuous pathways within the framework and the surface polymer strongly retard the diffusion of polysulfide anions out from the channels into the electrolyte and minimize the loss of active mass in the cathode, resulting in a stabilized cycle life at reasonable rates. The Li-S batteries can supply up to near 80% of the theoretical capacity of sulfur (1320 mA∙h/g). This represents more than five times the specific capacity of conventional intercalation Li ion batteries. The assembly process for OMC/S is simple and broadly applicable, conceptually providing new opportunities for materials scientists for tailored design that can be extended to many different electrode materials. Size-controlled supported metal and intermetallic nanocrystallites are of substantial interest because of their wide range of electrocatalytic properties. These intermetallics are normally synthesized by high temperature techniques; however, rigorous size control at high temperature is very challenging. A simple and robust chemically controlled process was developed for synthesizing size controlled noble metal, or bimetallic nanocrystallites, embedded within the porous structure of OMC. The method is applicable to a wide range of catalysts, namely bimetallic PtBi but also including Pt, Ru, Rh and Pd. By using surface-modified OMC, nanocrystallites are formed with monodisperse sizes as low as 1.5 nm, that can be tuned up to 2 and 3.5 nm (equivalent to the channel size of OMC) by thermal treatment. The method is also tailored for the deposition of catalysts on conventional fuel-cell carbon supports. OMC-PtBi nanohybrids were investigated as catalysts for formic acid oxidation for the first time. OMC-PtBi catalysts show an absence of CO poisoning. The excellent catalytic properties can be attributed to the successful catalyst preparation and the faithful practice of the “ensemble effect” at the nanoscale level. A new agitation-friction methodology was developed to prepare the nano-OMC/S composite. The method is completely different from any conventional impregnation which requires the voluntary molecular mobility of guest phases. The method relies on frictional forces, and the hydrophobic attraction of the mixing components. This is the first example of a nanoporous solid which can be infiltrated by another solid phase at room temperature. The C/S nanocomposite exhibits not only better Pt ion sorption kinetics than its bulk counterpart, but also a higher pseudo-second-order rate constant than chitosan sorbents.

The thesis is composed of two topics : a charger circuit of Li-ion batteries for wireless biomedical systems and a capacitor-less low dropout regulator¡]LDO¡^. The first topic discloses a charger circuit of Li-ion batteries using 2P4M 0.35-£gm CMOS process, which comprises a small bias circuit, a comparator with hysteresis, a transistor voltage divider circuit, a power MOS, and a Li-ion charger with a cut-off voltage and a recharge voltage. The proposed design receives a 13.56 MHz carrier with 5¡Ó0.2 V amplitude to charge the Li-ion batteries with a small constant current. The second topic reveals a low dropout regulator ¡]LDO¡^ without capacitor load and ESR, including a bias circuit, an error amplifier, and a Flipped Voltage Follower circuit generating a stable output voltage independent on different loads. The proposed design improves the input voltage limitation of Flipped Voltage Follower by compensating phase margin such that the proposed design shows a good transient response and stability without any output capacitor. The proposed LDO is implemented by 1P6M 0.18-um CMOS process, which can operate correctly given an input voltage range from 3.3~4.2 V.

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.