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Ion beam assisted deposition of an organic light emitting diode electrode

Souza, Danilo Olzon Dionysio de; Chubaci, Jose Fernando Diniz; Matsuoka, Masao; Faria, Roberto Mendonça; Guimarães, Francisco Eduardo Gontijo
Fonte: ELSEVIER SCIENCE SA Publicador: ELSEVIER SCIENCE SA
Tipo: Artigo de Revista Científica
ENG
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This work presents the electro-optical characterization of metal-organic interfaces prepared by the Ion Beam Assisted Deposition (IBAD) method. IBAD applied in this work combines simultaneously metallic film deposition and bombardment with an independently controlled ion beam, allowing different penetration of the ions and the evaporated metallic elements into the polymer. The result is a hybrid, non-abrupt interface, where polymer, metal and ion coexists. We used an organic light emitting diode, which has a typical vertical-architecture, for the interface characterization: Glass/Indium Tin Oxide (ITO)/Poly[ethylene-dioxythiophene/poly{styrenesulfonicacid}]) (PEDOT:PSS) /Emitting Polymer/Metal. The emitting polymer layer comprised of the Poly[(9,9-dioctyl-2,7-divinylenefluorenylene)-alt-co-{2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene}] (PFO) and the metal layer of aluminum prepared with different Ar(+) ion energies varying in the range from 0 to 1000 eV. Photoluminescence, Current-Voltage and Electroluminescence measurements were used to study the emission and electron injection properties. Changes of these properties were related with the damage caused by the energetic ions and the metal penetration into the polymer. Computer simulations of hybrid interface damage and metal penetration were confronted with experimental data. (C) 2010 Elsevier B.V. All rights reserved.

Nanocompósitos de blendas poliméricas condutoras e óxidos de metais de transição; Nanocomposities of polimer blend and transition metal oxide

Ponzio, Eduardo Ariel
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 15/09/2006 PT
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No presente trabalho, é apresentado o desenvolvimento de novos nanocompósito híbridos orgânico-inorgânico, especificamente MnO2/Blendas poliméricas condutoras (BPC) e nanofibras de V2O5 e V2O5/Pani, com propriedades diferenciadas. Estes óxidos nanoestruturados com morfologia definida, bem como a sua combinação com matrizes de polímeros condutores, apresentaram as características necessárias para um bom desempenho como material para catodos de baterias secundárias de lítio e/ou supercapacitores. Através dos resultados obtidos, foi possível demonstrar, de maneira inequívoca, que é possível alcançar um nanocompósito de óxido de metal de transição/polímero condutor, eletroativo e com morfologia definida mediante a síntese por micela reversa. A caracterização das BPC (Pani/PMMA e Ppy/PMMA) mostrou suas vantagens como matrizes para suportar e dispersar nanopartículas de MnO2, evitando o uso de carbono para aumentar a condutividade eletrônica do óxido. Particularmente, a utilização de nanocompósitos MnO2/(Ppy/PMMA), como material para supercapacitores, demonstrou que a distribuição homogênea das nanopartículas de MnO2 na BPC favorece a rápida difusão dos íons, o que indica que as nanopartículas...

Desempenho de membranas híbridas  Nafion-TiO2 e  eletrocatalisadores de PtSnb/C em células a combustível do tipo PEM alimentadas com etanol e com H2/CO em alta temperatura; Performance of Nafion-TiO2 hybrid membrane and PtSn/C electrocatalysts in PEMFC fed with ethanol and H2/CO at high temperature

Isidoro, Roberta Alvarenga
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 17/12/2010 PT
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Este trabalho teve como objetivo sintetizar eletrólitos híbridos de Nafion-TiO2 e eletrocatalisadores de PtSn/C para a aplicação em células a combustível de oxidação direta de etanol (DEFC) em alta temperatura (130oC). Para tanto, partículas de TiO2 foram incorporadas in-situ em membranas comerciais de Nafion via processo sol-gel. Os materiais resultantes foram caracterizados por análise gravimétrica, absorção de água, DSC, DRX e EDX. Eletrocatalisadores baseados em platina-estanho dispersos em carbono (PtSn/C), de diferentes composições, foram produzidos pelo método de redução por álcool e utilizados como eletrodos anódicos. Os eletrocatalisadores foram caracterizados por DRX, EDX, XPS e MET. A avaliação eletroquímica dos eletrocatalisadores foi realizada por voltametria cíclica, varredura linear anódica de monóxido de carbono (stripping de CO) e cronoamperometria. Ânodos de PtSn/C e cátodos de Pt/C comercial foram dispostos juntamente com os híbridos Nafion-TiO2 para a formação do conjuntos membrana-eletrodos. A avaliação final dos materiais foi realizada por meios de curvas de polarização em células unitárias alimentadas com misturas padrão H2/CO ou etanol no ânodo e com oxigênio no cátodo no intervalo de temperatura de 80 a 130oC. As análises demonstraram que o uso de membranas híbridas diminuiu o crossover de combustível...

Síntese de filmes automontados de poli(o-metoxianilina) e nanopartículas de pentóxido de vanádio como cátodos em baterias de íon-lítio em líquido iônico; Self assembly of poly(o-methoxyaniline) and vanadium pentoxide nanoparticles as cathodes for lithium-ion batteries in ionic liquid

Nogueira, Filipe Braga
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 01/11/2012 PT
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O presente trabalho utilizou a técnica de automontagem camada-por-camada para produzir eletrodos híbridos de poli(o-metoxianilina) e nanopartículas de pentóxido de vanádio. Foram obtidos filmes acusticamente rígidos, homogêneos com relação à massa depositada e com crescimento linear com o número de bicamadas depositadas. A caracterização eletroquímica foi realizada por voltametria cíclica, onde esse filme apresentou alta capacidade de intercalação/desintercalação de íons lítio e de forma reversível. A capacidade eletroquímica desse filme foi então comparada com filmes automontados de poli(dialildimetilamônio)/V2O5 e polialilamina/V2O5. O filme de Poli(dialildimetilamônio) apresentou um crescimento irregular com dissolução das nanopartículas, o que resultou em uma capacidade eletroquímica extremamente inferior ao filme de poli(o-metoxianilina). O filme de polialilamina apresentou uma deposição mais eficiente de V2O5 que o filme de poli(o-metoxianilina), entretanto essa maior quantidade de pentóxido de vanádio não refletiu em um aumento da capacidade do eletrodo. Os resultados de espectroscopia de impedância eletroquímica mostram que o filme de polialilamina é significativamente mais resistivo que o filme de poli(o-metoxianilina). Essa diminuição da condutividade...

A micro-nano porous oxide hybrid for efficient oxygen reduction in reduced-temperature solid oxide fuel cells

Da Han; Liu, Xuejiao; Zeng, Fanrong; Qian, Jiqin; Wu, Tianzhi; Zhan, Zhongliang
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em 15/06/2012 EN
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Tremendous efforts to develop high-efficiency reduced-temperature (≤ 600°C) solid oxide fuel cells are motivated by their potentials for reduced materials cost, less engineering challenge, and better performance durability. A key obstacle to such fuel cells arises from sluggish oxygen reduction reaction kinetics on the cathodes. Here we reported that an oxide hybrid, featuring a nanoporous Sm0.5Sr0.5CoO3−δ (SSC) catalyst coating bonded onto the internal surface of a high-porosity La0.9Sr0.1Ga0.8Mg0.2O3−δ (LSGM) backbone, exhibited superior catalytic activity for oxygen reduction reactions and thereby yielded low interfacial resistances in air, e.g., 0.021 Ω cm2 at 650°C and 0.043 Ω cm2 at 600°C. We further demonstrated that such a micro-nano porous hybrid, adopted as the cathode in a thin LSGM electrolyte fuel cell, produced impressive power densities of 2.02 W cm−2 at 650°C and 1.46 W cm−2 at 600°C when operated on humidified hydrogen fuel and air oxidant.

A facile approach to nanoarchitectured three-dimensional graphene-based Li–Mn–O composite as high-power cathodes for Li-ion batteries

Zhang, Wenyu; Zeng, Yi; Xu, Chen; Xiao, Ni; Gao, Yiben; Li, Lain-Jong; Chen, Xiaodong; Hng, Huey Hoon; Yan, Qingyu
Fonte: Beilstein-Institut Publicador: Beilstein-Institut
Tipo: Artigo de Revista Científica
Publicado em 17/07/2012 EN
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We report a facile method to prepare a nanoarchitectured lithium manganate/graphene (LMO/G) hybrid as a positive electrode for Li-ion batteries. The Mn2O3/graphene hybrid is synthesized by exfoliation of graphene sheets and deposition of Mn2O3 in a one-step electrochemical process, which is followed by lithiation in a molten salt reaction. There are several advantages of using the LMO/G as cathodes in Li-ion batteries: (1) the LMO/G electrode shows high specific capacities at high gravimetric current densities with excellent cycling stability, e.g., 84 mAh·g−1 during the 500th cycle at a discharge current density of 5625 mA·g−1 (~38.01 C capacity rating) in the voltage window of 3–4.5 V; (2) the LMO/G hybrid can buffer the Jahn–Teller effect, which depicts excellent Li storage properties at high current densities within a wider voltage window of 2–4.5 V, e.g., 93 mAh·g−1 during the 300th cycle at a discharge current density of 5625 mA·g−1 (~38.01 C). The wider operation voltage window can lead to increased theoretical capacity, e.g., 148 mAh·g−1 between 3 and 4.5 V and 296 mAh·g−1 between 2 and 4.5 V; (3) more importantly, it is found that the attachment of LMO onto graphene can help to reduce the dissolution of Mn2+ into the electrolyte...

A Three-electrode Column for Pd-Catalytic Oxidation of TCE in Groundwater with Automatic pH-regulation and Resistance to Reduced Sulfur Compound Foiling

Yuan, Songhu; Chen, Mingjie; Mao, Xuhui; Alshawabkeh, Akram N.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
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A hybrid electrolysis and Pd-catalytic oxidation process is evaluated for degradation of trichloroethylene (TCE) in groundwater. A three-electrode, one anode and two cathodes, column is employed to automatically develop a low pH condition in the Pd vicinity and a neutral effluent. Simulated groundwater containing up to 5 mM bicarbonate can be acidified to below pH 4 in the Pd vicinity using a total of 60 mA with 20 mA passing through the third electrode. By packing 2 g of Pd/Al2O3 pellets in the developed acidic region, the column efficiency for TCE oxidation in simulated groundwater (5.3 mg/L TCE) increases from 44 to 59 and 68% with increasing Fe(II) concentration from 0 to 5 and 10 mg/L, respectively. Different from Pd-catalytic hydrodechlorination under reducing conditions, this hybrid electrolysis and Pd-catalytic oxidation process is advantageous in controlling the fouling caused by reduced sulfur compounds (RSCs) because the in situ generated reactive oxidizing species, i.e., O2, H2O2 and •OH, can oxidize RSCs to some extent. In particular, sulfite at concentrations less than 1 mM even greatly increases TCE oxidation by the production of SO4•−, a strong oxidizing radical, and more •OH.

Batteries used to Power Implantable Biomedical Devices

Bock, David C.; Marschilok, Amy C.; Takeuchi, Kenneth J.; Takeuchi, Esther S.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
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Battery systems have been developed that provide years of service for implantable medical devices. The primary systems utilize lithium metal anodes with cathode systems including iodine, manganese oxide, carbon monofluoride, silver vanadium oxide and hybrid cathodes. Secondary lithium ion batteries have also been developed for medical applications where the batteries are charged while remaining implanted. While the specific performance requirements of the devices vary, some general requirements are common. These include high safety, reliability and volumetric energy density, long service life, and state of discharge indication. Successful development and implementation of these battery types has helped enable implanted biomedical devices and their treatment of human disease.

Highly Flexible Self-Assembled V2O5 Cathodes Enabled by Conducting Diblock Copolymers

An, Hyosung; Mike, Jared; Smith, Kendall A.; Swank, Lisa; Lin, Yen-Hao; L. Pesek, Stacy; Verduzco, Rafael; Lutkenhaus, Jodie L.
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em 22/09/2015 EN
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Mechanically robust battery electrodes are desired for applications in wearable devices, flexible displays, and structural energy and power. In this regard, the challenge is to balance mechanical and electrochemical properties in materials that are inherently brittle. Here, we demonstrate a unique water-based self-assembly approach that incorporates a diblock copolymer bearing electron- and ion-conducting blocks, poly(3-hexylthiophene)-block-poly(ethyleneoxide) (P3HT-b-PEO), with V2O5 to form a flexible, tough, carbon-free hybrid battery cathode. V2O5 is a promising lithium intercalation material, but it remains limited by its poor conductivity and mechanical properties. Our approach leads to a unique electrode structure consisting of interlocking V2O5 layers glued together with micellar aggregates of P3HT-b-PEO, which results in robust mechanical properties, far exceeding the those obtained from conventional fluoropolymer binders. Only 5 wt % polymer is required to triple the flexibility of V2O5, and electrodes comprised of 10 wt % polymer have unusually high toughness (293 kJ/m3) and specific energy (530 Wh/kg), both higher than reduced graphene oxide paper electrodes. Furthermore, addition of P3HT-b-PEO enhances lithium-ion diffusion...

Doped LiFePO₄ cathodes for high power density lithium ion batteries

Bloking, Jason T. (Jason Thompson), 1979-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 56 leaves
ENG
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Olivine LiFePO4 has received much attention recently as a promising storage compound for cathodes in lithium ion batteries. It has an energy density similar to that of LiCoO 2, the current industry standard for cathode materials in lithium ion batteries, but with a lower raw materials cost and an increased level of safety. An inherent limitation of LiFePO4 acknowledged by researchers studying this material is that its low intrinsic electronic conductivity limits its applicability in commercial systems. Through a doping process, however, its electrochemical performance at high current rates can be improved to levels above that of commercially available lithium batteries. The increase in performance is brought about by a concurrent increase in the electronic conductivity and a reduction of the final particle size. The experimental data suggest that cells formulated with this doped cathode material may produce power densities high enough for consideration as a future battery system for hybrid electric vehicles and other high rate applications.; by Jason T. Bloking.; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2003.; Includes bibliographical references (leaves 53-56).

Optimizing Field Emission Properties of the Hybrid Structures of Graphene Stretched on Patterned and Size-controllable SiNWs

Lv, Shasha; Li, Zhengcao; Liao, Jiecui; Wang, Guojing; Li, Mingyang; Miao, Wei
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em 19/10/2015 EN
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Graphene is one of the ideal nanomaterials to be paired with silicon, and their complementary properties can be exploited in field emission (FE) devices. We reported an efficient way to produce and adjust the dimension of uniform protrusions within graphene. First, a multistep template replication process was utilized to fabricate highly periodic and well-aligned silicon nanowires (SiNWs) of different diameters (400, 500 and 600 nm). Then, large-scale and uniform graphene, fabricated by chemical vapor deposition (CVD), was transferred onto these size-controlled SiNWs to obtain the nanoscale and uniform undulations. As compared to the nanowires alone, the hybrid structures lead to higher FE performance due to electron conductivity enhancement, high-density emmison protrusions and band bending. These hybrid SiNWs/graphene structures could provide a promising class of field emission cathodes.

The stability and electronic properties of novel three-dimensional graphene-MoS2 hybrid structure

Tang, Zhen-Kun; Zhang, Yan-Ning; Zhang, Deng-Yu; Lau, Woon-Ming; Liu, Li-Min
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em 12/11/2014 EN
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Three-dimensional (3D) hybrid layered materials receive a lot of attention because of their outstanding intrinsic properties and wide applications. In this work, the stability and electronic structure of three-dimensional graphene-MoS2 (3DGM) hybrid structures are examined based on first-principle calculations. The results reveal that the 3DGMs can easily self-assembled by graphene nanosheet and zigzag MoS2 nanoribbons, and they are thermodynamically stable at room temperature. Interestingly, the electronic structures of 3DGM are greatly related to the configuration of joint zone. The 3DGM with odd-layer thickness MoS2 nanoribbon is semiconductor with a small band gap of 0.01–0.25 eV, while the one with even-layer thickness MoS2 nanoribbon exhibits metallic feature. More importantly, the 3DGM with zigzag MoS2 nanoribbon not only own the large surface area and effectively avoid the aggregation between the different nanoribbons, but also can remarkably enhance Li adsorption interaction, thus the 3DGM have the great potential as high performance lithium ion battery cathodes.

Facile and Gram-scale Synthesis of Metal-free Catalysts: Toward Realistic Applications for Fuel Cells

Kim, Ok-Hee; Cho, Yong-Hun; Chung, Dong Young; Kim, Min Jeong; Yoo, Ji Mun; Park, Ji Eun; Choe, Heeman; Sung, Yung-Eun
Fonte: Nature Publishing Group Publicador: Nature Publishing Group
Tipo: Artigo de Revista Científica
Publicado em 02/03/2015 EN
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Although numerous reports on nonprecious metal catalysts for replacing expensive Pt-based catalysts have been published, few of these studies have demonstrated their practical application in fuel cells. In this work, we report graphitic carbon nitride and carbon nanofiber hybrid materials synthesized by a facile and gram-scale method via liquid-based reactions, without the use of toxic materials or a high pressure-high temperature reactor, for use as fuel cell cathodes. The resulting materials exhibited remarkable methanol tolerance, selectivity, and stability even without a metal dopant. Furthermore, these completely metal-free catalysts exhibited outstanding performance as cathode materials in an actual fuel cell device: a membrane electrode assembly with both acidic and alkaline polymer electrolytes. The fabrication method and remarkable performance of the single cell produced in this study represent progressive steps toward the realistic application of metal-free cathode electrocatalysts in fuel cells.

Defect physics, delithiation mechanism, and electronic and ionic conduction in layered lithium manganese oxide cathode materials

Hoang, Khang
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
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Layered LiMnO$_2$ and Li$_2$MnO$_3$ are of great interest for lithium-ion battery cathodes because of their high theoretical capacities. The practical application of these materials is, however, limited due to poor electrochemical performance. We herein report a comprehensive first-principles study of defect physics in LiMnO$_2$ and Li$_2$MnO$_3$ using hybrid-density functional calculations. We find that manganese antisites have low formation energies in LiMnO$_2$ and may act as nucleation sites for the formation of impurity phases. The antisites can also occur with high concentrations in Li$_2$MnO$_3$; however, unlike in LiMnO$_2$, they can be eliminated by tuning the experimental conditions during preparation. Other intrinsic point defects may also occur and have an impact on the materials' properties and functioning. An analysis of the formation of lithium vacancies indicates that lithium extraction from LiMnO$_2$ is associated with oxidation at the manganese site, resulting in the formation of manganese small hole polarons; whereas in Li$_2$MnO$_3$ the intrinsic delithiation mechanism involves oxidation at the oxygen site, leading to the formation of bound oxygen hole polarons $\eta_{\rm O}^{+}$. The layered oxides are found to have no or negligible bandlike carriers and they cannot be doped n- or p-type. The electronic conduction proceeds through hopping of hole and/or electron polarons; the ionic conduction occurs through lithium monovacancy and/or divacancy migration mechanisms. Since $\eta_{\rm O}^{+}$ is not stable in the absence of negatively charged lithium vacancies in bulk Li$_2$MnO$_3$...

Estudios de materiales de cátodos híbridos y ánodos vítreos. Caracterización en celdas de ion litio; Study of Hybrid Cathode Materials and Vitreous Anodes. Characterization in Lithium Ion Cells

Jurado Egea, José Ramón; Cuentas Gallegos, A. K.; Colomer, María T.; Palacín, M. R.; Gómez-Romero, P.
Fonte: Sociedad Española de Cerámica y Vidrio Publicador: Sociedad Española de Cerámica y Vidrio
Tipo: Artículo Formato: 1109521 bytes; application/pdf
SPA
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[ES] Como parte de nuestros estudios de nuevos materiales de electrodos para aplicación en celdas reversibles de litio, hemos abordado el estudio de materiales vítreos e híbridos [1] como posibles alternativas a los materiales activos cristalinos, que ven frecuentemente limitada su capacidad como resultado de transiciones de fase irreversibles. Dentro de este trabajo se presentan aquí los resultados recientes sobre cátodos híbridos de PPi/MnO2 (PPi= polipirrol) y de PAni/V2O5 (PAni= polianilina), y de ánodos basados en vidrios en el sistema V-Ni-Te-O, así como de su combinación en celdas reversibles de ion litio. Hemos logrado obtener mediante reacción directa de pirrol con permanganato el híbrido PPi/MnO2, y hemos observado que en la síntesis de PAni/V2O5 existen factores que influyen positivamente en su comportamiento electroquímico.; [EN] This paper is based on new materials applied as electrodes in rechargeable lithium batteries. We have approached the study of glassy and hybrid materials as an alternative to crystalline active materials, which capacity is frequently limited by irreversible phase transitions. We present here our latest results on hybrid cathodes, PPy/MnO2 (PPy= PPi= polypirrol) and PAni/V2O5 (PAni= polyaniline)...

Materiales híbridos basados en fosfato de vanadilo y polímeros conductores como cátodos en baterias reversibles de litio; Hybrid Materials Based on Vanadyl Phosphate and Conducting Polymers as Cathodes in Rechargeable Lithium Batteries

Casañ Pastor, Nieves; Gómez-Romero, P.; Cuentas Gallegos, A. K.; Vijayaraghavan, V.
Fonte: Sociedad Española de Cerámica y Vidrio Publicador: Sociedad Española de Cerámica y Vidrio
Tipo: Artículo Formato: 283533 bytes; application/pdf
SPA
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[ES] El fosfato de vanadilo es bien conocido como una fase inorgánica laminar capaz de intercalar una gran variedad de moléculas orgánicas. Mediante la polimerización in-situ, de anilina o pirrol, en la fase inorgánica es posible preparar materiales híbridos orgánico-inorgánicos en los que el polímero queda intercalado. Se describe la síntesis y caracterización de este tipo de híbridos y algunos resultados preliminares de su aplicación como materiales activos de cátodo en celdas reversibles de litio.; [EN] Vanadyl phosphate is a well known layered inorganic phase, capable of intercalating a great variety of organic molecules. By means of an in-situ polymerisation of aniline or pyrrole between the layers of the inorganic phase, it is possible to obtain organic-inorganic hybrids. We describe the synthesis and characterization of these type of hybrids, and some preliminary results of their application as active cathodic materials for positive electrodes in reversible lithium cells.; Agradecemos la financiación de este trabajo a través de los proyectos MAT2001-709-C04-01 y MAT2002-04529-C03, y al Consejo Nacional de Ciencia y Tecnología de México (CONACYT) por la concesión de una beca predoctoral a A.KCuentas-Gallegos.; Peer reviewed

Triple hybrid materials: A novel concept within the field of organic–inorganic hybrids

Cuentas Gallegos, A. K.; Gómez-Romero, P.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artículo Formato: 579917 bytes; image/jpeg
ENG
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We explored a new approach within the field of hybrid materials, namely, an integration of an electroactive inorganic molecule into a conducting polymer that in turn is intercalated into an extended inorganic oxide. In particular we present the specific material formed by hexacyanoferrate-doped polypyrrole or polyaniline inserted in turn into layered V2O5. This novel kind of hybrid with three components interacting at a molecular level is what we have called, triple hybrid materials (THM). The synthetic approach was based on our earlier work on PAni/V2O5, PAni/HCF and PPy/HCF systems. The materials obtained were characterized by FTIR, XRD, TGA, elemental analyses, and ICP. The electrochemical properties of THMs as insertion cathodes in rechargeable Li cells were also explored. The initial specific charge was high for PPy/HCF/V2O5 system (160 Ah kg−1), giving a greater value than for their corresponding simple hybrids: PPy/HCF (69 Ah kg−1) and PPy/V2O5 (120 Ah kg−1). Repeated charge–discharge cycles showed a poor cyclability, which could be related to the voltage limit values during recharge, overoxidation of the polymer, or to the detrimental effect of structural water from THMs. Nevertheless, the present work showed a novel route towards a more complex and versatile electroactive hybrid design.; Partial financial support from the Ministry of Science and Technology (Spain) (Grant MAT2002-04529-C03) and from CONACYT (México) (fellowship to A.K. Cuentas-Gallegos) are gratefully acknowledged.; Peer reviewed

Integration of Hexacyanoferrate as Active Species in a Molecular Hybrid Material. Transport Properties and Application of PAni/HCF as Cathode in Rechargeable Lithium Batteries

Torres-Gómez, G.; Tejada Rosales, E. M.; Gómez-Romero, P.
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Artículo Formato: 579917 bytes; image/jpeg
ENG
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Especial Issue on Nanocomposite Materials.; The hybrid organic-inorganic material formed by polyaniline and the hexacyanoferrate anion (PAni/HCF) constitutes a molecular hybrid where the anchoring of the electroactive anion within the polymer leads to its application as a functional material that harnesses the activity of the molecular species. Transport measurements of the hybrid have been carried out, both by cyclic voltammetry at different scan rates and ac impedance spectroscopy. An apparent diffusion coefficient of 5 10-8 cm2/s and an activation energy of 15.5 kJ/mol (0.16 eV) have been obtained. The particular application of these hybrids to energy storage is shown here through their use as cathodes in lithium rechargeable cells. In this respect, the PAni/HCF hybrids show very good cyclabilities and high specific charges of up to 140 A.h/ kg, unprecedented for this type of hybrid materials; This work was funded by CICYT (Spain) (MAT98-0807-C02-02). We thank the Ministry of Education and Culture (Spain) for predoctoral fellowships awarded to G.T.G. and E.M.T.R.; Peer reviewed

Free Energies for Acid Attack Reactions of Lithium Cobaltate

Benedek, R.; van de Walle, A.
Fonte: Electrochemical Society Publicador: Electrochemical Society
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em //2008
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The attack of lithium-ion battery cathodes by stray aqueous HF, with resultant dissolution, protonation, and possibly other unintended reactions, can be a significant source of capacity fade. We explore the calculation of reaction free energies of lithium cobaltate in acid by a “hybrid” method, in which solid-phase free energies are calculated from first principles at the generalized gradient approximation + intrasite coulomb interaction (GGA+U) level and tabulated values of ionization potentials and hydration energies are employed for the aqueous species. Analysis of the dissolution of the binary oxides Li2O and CoO suggests that the atomic energies for Co and Li should be shifted from values calculated by first principles to yield accurate reaction free energies within the hybrid method. With the shifted atomic energies, the hybrid method was applied to analyze proton-promoted dissolution and protonation reactions of LiCoO2 in aqueous acid. Reaction free energies for the dissolution reaction, the reaction to form Co3O4 spinel, and the proton-for-lithium exchange reaction are obtained and compared to empirical values. An extension of the present treatment to consider partial reactions is proposed, with a view to investigating interfacial and environmental effects on the dissolution reaction.