Self-assembled films from WO(3): Electrochromism and lithium ion diffusion

WO(3)/chitosan and WO(3)/chitosan/poly(ethylene oxide) (PEO) films were prepared by the layer-by-layer method. The presence of chitosan enabled PEO to be carried into the self-assembled structure, contributing to an increase in the Li(+) diffusion rate. On the basis of the galvanostatic intermittent titration technique (GITT) and the quadratic logistic equation (QLE), a spectroelectrochemical method was used for determination of the ""optical"" diffusion coefficient (D(op)), enabling analysis of the Li(+) diffusion rate and, consequently, the coloration front rate in these host matrices. The D(op) values within the WO(3)/chitosan/PEO film were significantly higher than those within the WO(3)/chitosan film, mainly for higher values of injected charge. The presence of PEO also ensured larger accessibility to the electroactive sites, in accordance with the method employed here. Hence, this spectroelectrochemical method allowed us to separate the contribution of the diffusion process from the number of accessible electroactive sites in the materials, thereby aiding a better understanding of the useful electrochemical and electrochromic properties of these films for use in electrochromic devices. (C) 2010 Elsevier B.V. All rights reserved.

Flexible thin-film lithium battery

Tese de Doutoramento Programa Doutoral em Engenharia Electr��nica e Computadores.

Lithium Containing Complex Metal Oxides and Metal phosphates:Investigations on their synthesis and various characterizations for rechargeable lithium battery applications

The work presented in the thesis is centered around two important types of cathode materials, the spinel structured LixMn204 (x =0.8to1.2) and the phospho -oIivine structured LiMP04 (M=Fe and Ni). The spinel system LixMn204, especially LiMn204 corresponding to x= 1 has been extensively investigated to understand its structural electrical and electrochemical properties and to analyse its suitability as a cathode material in rechargeable lithium batteries. However there is no reported work on the thermal and optical properties of this important cathode material. Thermal diffusivity is an important parameter as far as the operation of a rechargeable battery is concerned. In LixMn204, the electronic structure and phenomenon of Jahn-Teller distortion have already been established theoretically and experimentally. Part of the present work is an attempt to use the non-destructive technique (NDT) of photoacoustic spectroscopy to investigate the nature of the various electronic transitions and to unravel the mechanisms leading to the phenomenon of J.T distortion in LixMn204.The phospho-olivines LiMP04 (M=Fe, Ni, Mn, Co etc) are the newly identified, prospective cathode materials offering extremely high stability, quite high theoretical specific capacity, very good cycIability and long life. Inspite of all these advantages, most of the phospho - olivines especially LiFeP04 and LiNiP04 show poor electronic conductivity compared to LixMn204, leading to low rate capacity and energy density. In the present work attempts have been made to improve the electronic conductivity of LiFeP04 and LiNiP04 by adding different weight percentage MWNT .It is expected that the addition of MWNT will enhance the electronic conductivity of LiFeP04 and LiNiP04 with out causing any significant structural distortions, which is important in the working of the lithium ion battery.

Metal complexes with atropisomeric sulfur ligands in asymmetric hydroformylation X-ray structure of [Rh2(��-biphes)(cod)2] (H2biphes = 4,4���-biphenanthrene-3,3���-dithiol)

The addition of the atropisomeric racemic sulfur compound 4,4���-biphenanthrene-3,3���-dithiol (H2 biphes) to a dichloromethane solution of [{M(��-OMe)(cod)}2] (M = Rh, Ir, cod = cycloocta-1,5-diene) afforded the dithiolate-bridged complexes [{Rh2(��-biphes)(cod)2}n] (n = 2 5 or n = 1 6) and [{Ir2(��-biphes)(cod)2}n]��nCH2Cl27. When 1,1���-binaphthalene-2,2���-dithiol (H2 binas) reacted with [{Ir(��-OMe)(cod)}2], complex [Ir2(��-binas)(cod)2] 8 was obtained. Complexes 5 and 6 reacted with carbon monoxide to give the dinuclear tetracarbonyl complex [Rh2(��-biphes)(CO)4] 9. The reaction of 9 with PR3 provided the mixed-ligand complexes [{Rh2(��-biphes)(CO)2(PR3)2}2] �� xCH2Cl2 (R = Ph, x = 2 10, C6H11, x = 1 11) and [{Rh2(��-biphes)(CO)3(PR3)}2] �� CH2Cl212 (R = OC6H4But-o). The crystal structure of 6 was determined by X-ray diffraction. Reaction of the dithioether ligand Me2biphes with [Rh(cod)2]ClO4 in CH2Cl2 solution afforded the cationic complex [Rh(cod)(Me2biphes)]ClO4 �� CH2Cl213. Asymmetric hydroformylation of styrene was performed using the complexes described. The extent of aldehyde conversion ranges from 53 to 100%, with selectivities towards branched aldehydes in the range 51 to 96%. The enantioselectivities were quite low and did not exceed 20%.

Vibrational properties, crystal X-ray diffraction structure and quantum chemical calculations on a divalent sulfur substituted phthalimide: 1H-Isoindole-1,3(2H)-dione, 2-[(methoxycarbonyl)thio]

Structural and conformational properties of 1H-Isoindole-1,3(2H)-dione, 2-[(methoxycarbonyl)thio] (S-phthalimido O-methyl thiocarbonate) are analyzed using a combined approach including X-ray diffraction, vibrational spectra and theoretical calculation methods. The vibrational properties have been studied by infrared and Raman spectroscopies along with quantum chemical calculations (B3LYP and B3PW91 functional in connection with the 6-311++G** and aug-cc-pVDZ basis sets). The crystal structure was determined by X-ray diffraction methods. The substance crystallizes in the monoclinic P2(1)/c space group with a = 6.795(1), b = 5.109(1), c = 30.011(3) angstrom, beta = 90.310(3)degrees and Z = 4 molecules per unit cell. The conformation adopted by the N-S-C=O group is syn (C=O double bond in synperiplanar orientation with respect to the N-S single bond). The experimental molecular structure is well reproduced by the MP2/aug-cc-pVDZ method. (C) 2010 Elsevier B.V. All rights reserved.

Bamboo overabundance alters forest structure and dynamics in the Atlantic Forest hotspot

Funda����o de Amparo �� Pesquisa do Estado de S��o Paulo (FAPESP)

Quantitative structural analysis of the transition from LT-Li xCoO2 to HT-LixCoO2 using the rietveld method: Correlation between structure and electrochemical performance

A quantitative phase analysis was made of LixCoO2 powders obtained by two distinct chemical methodologies at different temperatures (from 400 to 700��C). A phase analysis was made using Rietveld refinements based on X-ray diffraction data, considering the Li xCoO2 powders as a multiphase system that simultaneously contained two main phases with distinct, layered and spinel-type structures. The results showed the coexistence of both structures in LixCoO 2 obtained at low temperature (400 and 500��C), although only the layered structure was detected at higher temperatures (600 and 700��C), regardless of the chemical powder process employed. The electrochemical performance, evaluated mainly by the cycling reversibility of Li xCoO2 in the form of cathode insertion electrodes, revealed that there is a close correlation between structural features and the electrochemical response, with one of the redox processes (3.3 v/3.9 v) associated only with the presence of the spinel-type structure. �� 2003 Elsevier B.V. All rights reserved.

Bamboo overabundance alters forest structure and dynamics in the Atlantic Forest hotspot

With fast growth rates and clonal reproduction, bamboos can rapidly invade forest areas, drastically changing their original structure. In the Brazilian Atlantic Forest, where recent mapping efforts have shown that woody bamboos dominate large areas, the present study assessed the differences in soil and vegetation between plots dominated (>90% of bamboo coverage) and not dominated (<10% of coverage) by the native Guadua tagoara. Surface soil was physically and chemically analyzed, and trees at three size classes (seedling, sapling, and adult) were counted, identified and measured. New inventories were conducted to assess recruitment, mortality, and damage rates. Bamboo plots had more fertile soils (higher bases saturation and lower potential acidity) due to the preferential occurrence of G. tagoara on more clayey soils. Bamboo-dominated plots had lower density of adult trees (diameter >5 cm) and lower species density. In addition, overall tree diameter distribution was very different between environments, with bamboo plots having greater concentration of small-sized trees. Such differences are probably related to the general tendency of higher mortality, recruitment, and damage rates in bamboo plots. Greater physical (wind and bamboo-induced damages) and physiological stress (heat and light) in bamboo plots are probable causes of bamboo-dominated plots being more dynamic. Finally, we discuss the differences between Atlantic and Amazonian Guadua-dominated forests, causes, and possible consequences of bamboo overabundance to the Atlantic Forest conservation. (C) 2012 Elsevier Ltd. All rights reserved.

The Equilibrium Structure of Lithium Salt Solutions in Ether-Functionalized Ammonium Ionic Liquids

Molecular dynamics simulations have been performed for ionic liquids based on a ternary mixture of lithium and ammonium cations and a common anion, bis(trifluoromethylsulfonyl)imide, [Tf2N](-). We address structural changes resulting from adding Li+ in ionic liquids with increasing length of an ether-functionalized chain in the ammonium cation. The calculation of static structure factors reveals the lithium effect on charge ordering and intermediate range order in comparison with the neat ionic liquids. The charge ordering is modified in the lithium solution because the coordination of [Tf2N](-) toward Li+ is much stronger than ammonium cations. Intermediate range order is observed in neat ionic liquids based on ammonium cations with a long chain, but in the lithium solutions, there is also a nonhomogenous distribution of Li+ cations. The presence of Li+ enhances interactions between the ammonium cations due to correlations between the oxygen atom of the ether chain and the nitrogen atom of another ammonium cation.

Storage stability of SBS/sulfur modified bitumens at high temperature: influence of bitumen composition and structure

Polymer modified bitumens, PMBs, are usually prepared at high temperature and subsequently stored for a period of time, also at high temperature. The stability of PMBs, in these conditions, has a decisive influence in order to obtain the adequate performances for practical applications. In this article the attention is focused in the analysis of the factors that determine the stability of styrene���butadiene���styrene copolymer (SBS)/sulfur modified bitumens when the mixtures are maintained at high temperature. Bitumens from different crude oil sources were used to prepare SBS/sulfur modified bitumens. Changes in the values of viscosity, softening point, as well as in the morphology of PMB samples, stored at 160 ��C, were related to the bitumen chemical composition and to the amount of asphaltene micelles present in the neat bitumen used in their preparation El trabajo se centra en el estudio de la influencia de la estructura /composici��n del bet��n sobre la compatibilidad del sistema bet��n/SBS. Cuatro betunes provenientes de dos crudos distintos se seleccionaron y sus mezclas se utilizaron para preparar betunes modificados con contenidos de SBS del 3% en peso

Enhanced 3-dimensional carbon nanotube based anodes for lithium-ion battery applications

A prototype 3-dimensional (3D) anode, based on multiwall carbon nanotubes (MWCNTs), for Li-ion batteries (LIBs), with potential use in Electric Vehicles (EVs) was investigated. The unique 3D design of the anode allowed much higher areal mass density of MWCNTs as active materials, resulting in more amount of Li+ ion intake, compared to that of a conventional 2D counterpart. Furthermore, 3D amorphous Si/MWCNTs hybrid structure offered enhancement in electrochemical response (specific capacity 549 mAhg���1 ). Also, an anode stack was fabricated to further increase the areal or volumetric mass density of MWCNTs. An areal mass density of the anode stack 34.9 mg/cm2 was attained, which is 1,342% higher than the value for a single layer 2.6 mg/cm2. Furthermore, the binder-assisted and hot-pressed anode stack yielded the average reversible, stable gravimetric and volumetric specific capacities of 213 mAhg���1 and 265 mAh/cm3, respectively (at 0.5C). Moreover, a large-scale patterned novel flexible 3D MWCNTs-graphene-polyethylene terephthalate (PET) anode structure was prepared. It generated a reversible specific capacity of 153 mAhg���1 at 0.17C and cycling stability of 130 mAhg ���1 up to 50 cycles at 1.7C.

Effect of the Electrolyte Formulation on the Performances of Edlc and Li-Ion Batteries

One of the most important components in electrochemical storage devices (batteries and supercapacitors) is undoubtedly the electrolyte. The basic function of any electrolyte in these systems is the transport of ions between the positive and negative electrodes. In addition, electrochemical reactions occurring at each electrode/electrolyte interface are the origin of the current generated by storage devices. In other words, performances (capacity, power, efficiency and energy) of electrochemical storage devices are strongly related to the electrolyte properties, as well as, to the affinity for the electrolyte to selected electrode materials. Indeed, the formulation of electrolyte presenting good properties, such as high ionic conductivity and low viscosity, is then required to enhance the charge transfer reaction at electrode/electrolyte interface (e.g. charge accumulation in the case of Electrochemical Double Layer Capacitor, EDLC). For practical and safety considerations, the formulation of novel electrolytes presenting a low vapor pressure, a large liquid range temperature, a good thermal and chemical stabilities is also required.<br/><br/>This lecture will be focused on the effect of the electrolyte formulation on the performances of electrochemical storage devices (Li-ion batteries and supercapacitors). During which, a summary of the physical, thermal and electrochemical data obtained by our group, recently, on the formulation of novel electrolyte-based on the mixture of an ionic liquid (such as EmimNTf2 and Pyr14NTf2) and carbonate or dinitrile solvents will be presented and commented. The impact of the electrolyte formulation on the storage performances of EDLC and Li-ion batteries will be also discussed to further understand the relationship between electrolyte formulation and electrochemical performances. This talk will also be an opportunity to further discuss around the effects of additives (SEI builder: fluoroethylene carbonate and vinylene carbonate), ionic liquids, structure and nature of lithium salt (LiTFSI vs LiPF6) on the cyclability of negative electrode to then enhance the electrolyte formulation. For that, our recent results on TiSnSb and graphite negative electrodes will be presented and discussed, for example 1,2.<br/><br/>1-C. Marino, A. Darwiche1, N. Dupr��, H.A. Wilhelm, B. Lestriez, H. Martinez, R. Dedryv��re, W. Zhang, F. Ghamouss, D. Lemordant, L. Monconduit ��� Study of the Electrode/Electrolyte Interface on Cycling of a Conversion Type Electrode Material in Li Batteries��� J. Phys.chem. C, 2013, 117, 19302-19313<br/><br/>2- Mouad Dahbi, Fouad Ghamouss, M��ri��m Anouti, Daniel Lemordant, Fran��ois Tran-Van ���Electrochemical lithiation and compatibility of graphite anode using glutaronitrile/dimethyl carbonate mixtures containing LiTFSI as electrolyte��� 2013, 43, 4, 375-385.

An effective three-dimensional ordered mesoporous CuCo₂O₄ as electrocatalyst for Li-O₂ batteries

<p>Three-dimensional ordered mesoporous (3DOM) CuCo₂O₄ materials have been synthesized via a hard template and used as bifunctional electrocatalysts for rechargeable Li-O₂ batteries. The characterization of the catalyst by X-ray diffractometry and transmission electron microscopy confirms the formation of a single-phase, 3-dimensional, ordered mesoporous CuCo₂O₄ structure. The as-prepared CuCo₂O₄ nanoparticles possess a high specific surface area of 97.1 m² g^{- 1} and a spinel crystalline structure. Cyclic voltammetry demonstrates that mesoporous CuCo₂O₄ catalyst enhances the kinetics for either oxygen reduction reaction (ORR) or oxygen evolution reaction (OER). The Li-O₂ battery utilizing 3DOM CuCo₂O₄ shows a higher specific capacity of 7456 mAh g^{- 1} than that with pure Ketjen black (KB). Moreover, the CuCo₂O₄-based electrode enables much enhanced cyclability with a 610 mV smaller discharge-recharge voltage gap than that of the carbon-only cathode at a current rate of 100 mA g^{- 1}. Such excellent catalytic performance of CuCo₂O₄ could be associated with its larger surface area and 3D ordered mesoporous structure. The excellent electrochemical performances coupled with its facile and cost-effective way will render the 3D mesoporous CuCo₂O₄ nanostructures as attractive electrode materials for promising application in Li-O₂ batteries.</p>

Synth��se de titanates de lithium nanostructur��s par plasma inductif pour les batteries lithium-ion

Le march�� des accumulateurs lithium-ion est en expansion. Cette croissance repose partiellement sur la multiplication des niches d���utilisation et l���am��lioration constante de leurs performances. En raison de leur durabilit�� exceptionnelle, de leur faible co��t, de leur haute densit�� de puissance et de leur fiabilit��, les anodes bas��es sur les titanates de lithium, et plus particuli��rement le spinelle Li4Ti5O12, pr��sentent une alternative d���int��r��t aux mat��riaux classiques d���anodes en carbone pour de multiples applications. Leur utilisation sous forme de nanomat��riaux permet d���augmenter significativement la puissance disponible par unit�� de poids. Ces nanomat��riaux ne sont typiquement pas contraints dans une direction particuli��re (nanofils, nanoplaquettes), car ces formes impliquent une tension de surface plus importante et requi��rent donc g��n��ralement un m��canisme de synth��se d��di��. Or, ces nanostructures permettent des r��ductions suppl��mentaires dans les dimensions caract��ristiques de diffusion et de conduction, maximisant ainsi la puissance disponible, tout en affectant les propri��t��s habituellement intrins��ques des mat��riaux. Par ailleurs, les r��acteurs continus reposant sur la technologie du plasma thermique inductif constituent une voie de synth��se d��montr��e afin de g��n��rer des volumes importants de mat��riaux nanostructur��s. Il s���av��re donc pertinent d�����valuer leur potentiel dans la production de titanates de lithium nanostructur��s. La puret�� des titanates de lithium est difficile �� jauger. Les techniques de quantification habituelles reposent sur la fluorescence ou la diffraction en rayons X, auxquelles le lithium ��l��mentaire se pr��te peu ou pas. Afin de quantifier les nombreuses phases (Li4Ti5O12, Li2Ti3O7, Li2TiO3, TiO2, Li2CO3) identifi��es dans les ��chantillons produits par plasma, un raffinement de Rietveld fut d��velopp�� et valid��. La pr��sence de ��-Li2TiO3 fut identifi��e, et la calorim��trie en balayage diff��rentiel fut explor��e comme outil permettant d���identifier et de quantifier la pr��sence de ��-Li2TiO3. Diff��rentes proportions entre les phases produites et diff��rents types de morphologies furent observ��s en fonction des conditions d���op��ration du plasma. Ainsi, des conditions de trempe r��ductrice et d���ensemencement en Li4Ti5O12 nanom��trique semblent favoriser l�����mergence de nanomorphologies en nanofils (associ��s �� Li4Ti5O12) et en nanoplaquette (associ��es �� Li2TiO3). De plus, l���ensemencement et les recuits augment��rent significativement le rendement en la phase spinelle Li4Ti5O12 recherch��e. Les recuits sur les poudres synth��tis��es par plasma indiqu��rent que la d��composition du Li2Ti3O7 produit du Li4Ti5O12, du Li2TiO3 et du TiO2 (rutile). Afin d���approfondir l���investigation de ces r��actions de d��composition, les param��tres cristallins du Li2Ti3O7 et du ��-Li2TiO3 furent d��finis �� haute temp��rature. Des mesures continues en diffraction en rayon X �� haute temp��rature furent r��alis��es lors de recuits de poudres synth��tis��es par plasma, ainsi que sur des m��langes de TiO2 anatase et de Li2CO3. Celles-ci indiquent la production d���un interm��diaire Li2Ti3O7 �� partir de l���anatase et du carbonate, sa d��composition en Li4Ti5O12 et TiO2 (rutile) sur toute la plage de temp��rature ��tudi��e, et en Li2TiO3 et TiO2 (rutile) �� des temp��ratures inf��rieures �� 700��C.

DEVELOPMENT OF LI+ AND NA+ CONDUCTING CERAMICS AND CERAMIC STRUCTURES FOR USE IN SOLID STATE BATTERIES

A solid state lithium metal battery based on a lithium garnet material was developed, constructed and tested. Specifically, a porous-dense-porous trilayer structure was fabricated by tape casting, a roll-to-roll technique conducive to high volume manufacturing. The high density and thin center layer (< 20 ��m) effectively blocks dendrites even over hundreds of cycles. The microstructured porous layers, serving as electrode supports, are demonstrated to increase the interfacial surface area available to the electrodes and increase cathode loading. Reproducibility of flat, well sintered ceramics was achieved with consistent powderbed lattice parameter and ball milling of powderbed. Together, the resistance of the LLCZN trilayer was measured at an average of 7.6 ohm-cm2 in a symmetric lithium cell, significantly lower than any other reported literature results. Building on these results, a full cell with a lithium metal anode, LLCZN trilayer electrolyte, and LiCoO2 cathode was cycled 100 cycles without decay and an average ASR of 117 ohm-cm2. After cycling, the cell was held at open circuit for 24 hours without any voltage fade, demonstrating the absence of a dendrite or short-circuit of any type. Cost calculations guided the optimization of a trilayer structure predicted that resulting cells will be highly competitive in the marketplace as intrinsically safe lithium batteries with energy densities greater than 300 Wh/kg and 1000 Wh/L for under $100/kWh. Also in the pursuit of solid state batteries, an improved Na+ superionic conductor (NASICON) composition, Na3Zr2Si2PO12, was developed with a conductivity of 1.9x10-3 S/cm. New super-lithiated lithium garnet compositions, Li7.06La3Zr1.94Y0.06O12 and Li7.16La3Zr1.84Y0.16O12, were developed and studied revealing insights about the mechanisms of conductivity in lithium garnets.