Browsing by Author "Real, Silvia"
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Item Characterization of anodes for lithium ion batteries(Springer, 2015-08-14) Humana, Rita; Ortiz, Mariela; Thomas, Jorge; Real, Silvia; Sedlarikova, Marie; Vondrak, Jiri; Visintin, ArnaldoThe lithium-ion batteries are energy storage systems of high performance and low cost. They are employed in multiple portable devices, and these require the use of increasingly smaller and lighter batteries with high energy and power density, fast charging, and long service life. Moreover, these systems are promising for use in electric or hybrid vehicles. However, the lithium-ion battery still requires the improvement of the electrode material properties, such as cost, energy density, cycle life, safety, and environmental compatibility. These batteries use carbon as anode material, usually synthetic graphite, because of its high coulombic efficiency and acceptable specific capacity for the formation of intercalation compounds (LiC6). In this paper, the methodology used to prepare and characterize the reversible and irreversible capacity and cyclic stability of graphite materials as anodes in lithium-ion batteries of commercial carbon and shungite carbon is presented. The results obtained using electrochemical techniques are discussed. These electrodes exhibited good activation process and high-rate dischargeability performance. For carbon and shungite electrodes, the maximum discharge capacity values were 259 and 170 mA h g−1, respectively.Item Contribución de diferentes aditivos en el comportamiento electroquímico de electrodos de hidróxido de níquel(Mattear, 2014-05-13) Ortiz, Mariela; Real, Silvia; Castro, Élida BeatrizEl hidróxido de níquel es utilizado como material activo en electrodos positivos de las baterías alcalinas recargables de níquel. La capacidad de estas baterías depende de la capacidad específica del electrodo positivo y la utilización del material activo, por lo que numerosas investigaciones fueron realizadas con el objetivo de optimizar este electrodo. Entre las mejoras propuestas cabe mencionar el aumento de la conductividad y el potencial de evolución de oxígeno, mejorar la eficiencia de la carga y la inhibición del desarrollo de la fase γ–NiOOH. En consecuencia, es necesario incorporar diferentes aditivos al material activo. Los aditivos que más se destacan son: cobalto [1-2], materiales carbonosos [3], calcio [3], zinc [2] y nanomateriales [4]. En este trabajo estudiamos el comportamiento electroquímico del electrodo de hidróxido de níquel con cobalto (incorporado vía electroless) e hidróxido de níquel nanocristalino (agregado por mezcla directa con el material activo).Estos materiales compuestos se utilizaron para preparar dos electrodos que fueron caracterizados mediante técnicas ópticas y electroquímicas.Item Desarrollo y caracterización de materiales de electrodo para dispositivos electroquímicos basados en nuevos criterios de ingeniería de diseño, aplicaciones en sistemas de baterías del tipo Níquel Hidruro metálico(2013-03-21) Ortiz, Mariela; Real, Silvia; Castro, Élida BeatrizEste trabajo de Tesis Doctoral se enmarca en las líneas de investigación que desarrolla actualmente el grupo de investigación CAE (Conversión y Almacenamiento de Energía) del INIFTA (Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicadas) de la Universidad Nacional de La Plata. Los trabajos realizados han contribuido al desarrollo de los proyectos “Sistemas de Almacenamiento de Energía por Hidrógeno y Electrocatálisis” (PICTR/N 656), “Caracterización de nuevos materiales de electrodo para su empleo en dispositivos electroquímicos” (Proyecto Incentivos de la UTN/FR La Plata, 25/I040) y “Materiales metálicos y nanoestructurados para almacenamiento de hidrógeno en forma de hidruros” (PAE-PICT-2007-02164 ); el primero ya finalizado y los restantes actualmente en desarrollo. El objetivo principal de esta Tesis es contribuir al conocimiento de materiales aplicables a dispositivos electroquímicos de almacenamiento de energía, tanto desde un punto de vista básico, comprendiendo el comportamiento de los materiales empleados, como de aplicación, intentando desarrollar métodos sencillos y efectivos de preparación de electrodos y probando su uso en prototipos de baterías.Item Effect of cobalt electroless deposition on nickel hydroxide electrodes(Elsevier, 2014-02-21) Ortiz, Mariela; Castro, Élida Beatriz; Real, SilviaThe effects of cobalt additive on the positive electrode surface of nickel alkaline batteries are investigated. Electrode surface modifications by electroless cobalt deposits were made at different immersion times. The performance of nickel hydroxide electrodes was studied by optical techniques, such as scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX) and electrochemical methods as cyclic voltammetry, charge discharge curves and electrochemical impedance spectroscopy (EIS). According to these results, electroless cobalt deposits obtained with 5 min of immersion time in the electroless-bath exhibit a better electrode performance.Item Effect of different additives on the electrochemical behaviour of nickel hydroxide electrodes employed in batteries(Annual Meeting of the International Society of Electrochemistry, 2014-08-31) Real, Silvia; Ortiz, Mariela; Castro, Élida BeatrizNickel hydroxide is widely used as the active material in positive electrodes in most nickel-based rechargeable alkaline batteries. The theoretical capacity of nickel hydroxide is 289 mAhg-1. The capacity of these batteries depends on the specific capacity of the positive electrode and the utilization of the active material because of the positive electrode capacity limitation. The poor conductivity of active material requires the addition of some additives to increase conductivity and, additionally, to increase the oxygen evolution potential, the charge efficiency and to inhibit the development of γ-NIOOH phase. Many studies have been published on nickel hydroxide with different additives to obtain optimum performance; for example: cobalt [1-2], carbonaceous materials [3], calcium [3], zinc [2] and nanomaterials [4]. In this work, we have studied the electrochemical behaviour of nickel hydroxide electrodes containing additives as: cobalt (by electroless technique), nanosized Ni(OH)2 (by direct mix with active material) and MWCNTs (incorporated to active material during hydrothermal synthesis). Their electrochemical characterization was investigated by using cyclic voltammetry, charge-discharge cycling, and electrochemical impedance spectroscopy (EIS) techniques. The experimental EIS data are used to identify the model parameters by fitting the theoretical impedance function; this was derived from the physicochemical model based on the theory of porous electrodes with the charge/discharge processes occurring at the active material/electrolyte interface [5]. The results are found to be useful to determine the key factors responsible of the electrochemical performance of nickel hydroxide electrodes.Item Electrochemical characterization of MWCNT Ni(OH)2 composites as cathode materials(Springer, 2015-09-04) Ortiz, Mariela; Real, Silvia; Castro, Élida BeatrizThe hydrothermal method was used to synthesize multi-walled carbon nanotube/nickel hydroxide composites (MWCNT/Ni(OH)2). The structure and morphology of the prepared materials were characterized by X-ray diffraction and transmission electron microscopy. The electrochemical performance of cathodes prepared with multi-walled carbon nanotubes (MWCNT) loaded into the β-nickel hydroxide materials was investigated employing cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopic measurements. It is shown that the cathode active material utilization increases for MWCNT/ Ni(OH)2 obtained after 24 h of hydrothermal synthesis. These composites exhibit a fairly good electrochemical performance as cathode materials. Based on the results, this fact could be associated with the formation of a continuous conductive network structure in the hydroxide matrix. The analyses of impedance data, according to a physicochemical model, allow the improvement of a better understanding of the main structural and physicochemical parameters that control the electrochemical performance of these systems.Item Electrochemical characterization of Nickel Hydroxide electrodes with MWCNT(Anual Meeting of ISE, 2013-09-08) Ortiz, Mariela; Real, Silvia; Castro, Élida BeatrizAlkaline secondary batteries are widely required in the current market of electronic devices. Particularly, nickel hydroxide active material is the positive electrode in Ni/H2 and Ni/MH batteries. Due to their semiconductor nature, it becomes necessary to solve this limitation. A poor electrical contact yields ohmic overpotential and capacity loss at high currents. The carbon nanotubes (CNT) employed as additive was first studied by Lvetal. Who found that the addition of NTC may improve battery performance at high download speeds. However, discussions about the way that CNT affect structural and kinetic parameters are still acking. In this work, the addition of multiwall carbon nanotubes (MWCNT) is investigated. The active material was prepared by hydrothermal synthesis method. The characterization was performed by optical (SEM, TEM, XRD) and electrochemical techniques (charge‐discharge cycles, cyclic voltammetry, electrochemical impedance spectroscopy ‐ EIS). The EIS technique along with a physicochemical model developed in the laboratory, are powerful tools for the estimation of physicochemical and structural parameter such as: specific active area, effective conductivity and diffusion coefficient of H+[2]. This knowledge allows electrochemical performance optimization of the systems.Item Electrochemical characterization of nickel hydroxide nanomaterials as electrodes for NiMH batteries(Springer, 2016-08-23) Real, Silvia; Ortiz, Mariela; Castro, Élida Beatrizβ-Nickel hydroxide was successfully synthesized by a hydrothermal method. Nano-nickel hydroxide material was characterized by X-ray diffraction, infrared absorption spectroscopy, and transmission electron microscopy. They were employed as additives to the positive electrode of Ni-MH batteries. Working electrodes, with mixtures of commercial nickel hydroxide and nano-nickel hydroxide (0–10 wt.%) as active material, were prepared. Cyclic voltammetry, charge discharge profiles, and electrochemical impedance spectroscopy studies were carried out to evaluate the electrochemical performance of the nickel electrode, in 7 M KOH electrolyte, at 25 °C. The presence of nano-nickel hydroxide improves the electrochemical behavior of the active material. The electrochemical impedance spectroscopy (EIS) results were analyzed employing a modified version of previously developed physicochemical model that takes into account the main structural and physicochemical parameters that control these systems.Item Electrochemical performance comparison of MWCNTs Ni (OH)2 composite materials by two preparation routes(Springer, 2017) Ortiz, Mariela; Castro, Élida Beatriz; Real, SilviaCarbon materials are used to improve the nickel hydroxide electrode capacity in rechargeable alkaline batteries. Herein, we present the preparation of multiwall carbon nanotubes/nickel hydroxide composites (MWCNTs/Ni (OH)2) by two different routes. The first method consists of the direct incorporation of MWCNTs in the active material, and the second is based on the hydrothermal synthesis of β-nickel hydroxide, where MWCNTs are added to the precursor solutions. The electrochemical properties of the prepared positive electrodes containing MWCNTs/Ni (OH)2 composites are studied. Electrochemical results indicate that the active material with MWCNTs incorporated before the hydrothermal synthesis is capable of delivering a higher discharge capacity and exhibits a better reversibility than those composites prepared with MWCNTs after the hydrothermal route.Item Electrochemical performance of Carbon Sulfur as Lithium Sulfur battery cathodes(Topical Meeting of the International Society of Electrochemistry, 2017-03-19) Ortiz, Mariela; Visintin, Arnaldo; Real, SilviaNowadays, rechargeable batteries with higher energy density are required for our society due to the needs of cleaner and more efficient energy systems and with the objective of supplying the increasing technological demands. Commercial lithium batteries are systems based on intercalation compounds able to delivering specific energies about 150-200 WhKg-1, one-third of their theoretical energy ( ≈ 600 Wh kg-1). It is difficult for the reversible capacity of these intercalation compounds to be increased, thus the need to explore new cathodes formed by lighter materials and involving electrochemical reactions of more than one electron. An element satisfying these conditions is sulfur (with a theoretical capacity of 1675 mAhg-1 and a specific energy of 2600 WhKg-1). The lithium-sulfur battery has been investigated by different groups in past decades; however, there are serious drawbacks, which have not been overcome yet, so it limits the practical development of this system. Moreover, sulfur is much more abundant, inexpensive, and non-toxic compared to the transition-metal oxide cathodes. We present here the preparation of composites with carbon and sulfur materials in a single fabrication process: using S2C as the solvent. The characterization of the prepared material was performed using optical techniques (X-ray diffraction, scanning electron microscopy and transmission) and its electrochemical performance in lithium-sulfur batteries was studied using electrochemical techniques such as: charge-discharge cycles, galvanostatic discharges to different currents and cyclic voltammetry. The prepared composite materials delivered higher capacities in the first cycles (≈800 mAhg-1) and then it were stabilized at values around 60% of the initial capacity. Also, carbon electrochemical response was not observed, so its main function is to act effectively as an electron-conducting and support matrix.Item Estudio de diferentes aditivos en el electrodo de hidróxido de níquel(Jornada de Ciencia y Tecnología UTN-FRLP 2013, 2013-10-09) Ortiz, Mariela; Real, SilviaLa tendencia mundial de optar por tecnologías denominadas “limpias” conlleva a que se invierta en el desarrollo de fuentes energéticas alternativas. Dentro de estos dispositivos se incluye a las baterías alcalinas del tipo Ni-HyNi-HM, en las que el electrodo positivo tiene como material activo hidróxido de níquel. Si bien ha sido estudiado con agregados de diferentes aditivos (Co, Ca, Zn, C, materiales nano estructurados, etc.), los que contienen Co resultan ser los más exitosos debido a que: incrementa la reversibilidad del par redox Ni(OH)2/NiOOH, aumenta el sobrepotencial de evolución de oxígeno, mejora la conductividad y reduce el crecimiento de especies γ-NiOOH durante la carga.Item Estudio del agregado de cobalto vía “electroless” a electrodos de hidróxido de níquel(2013-04-09) Ortiz, Mariela; Castro, Élida Beatriz; Real, SilviaEl hidróxido de níquel es utilizado como material de cátodos en baterías alcalinas del tipo Ni/Cd, Ni/Fe, Ni/Zn, Ni/H, Ni/MH. Para mejorar las propiedades de este material y así su desempeño, en los dispositivos mencionados, se incorporan aditivos. En este trabajo se estudia la incorporación de cobalto sobre la superficie del material activo, Ni(OH)2, utilizando la técnica “electroless” variando el tiempo de inmersión: 5, 15 y 30 minutos. La caracterización de los electrodos se realizó empleando técnicas electroquímicas y ópticas.Item Hydrothermal synthesis of cathode materials for rechargeable lithium ion battery(Annual Meeting of the International Society of Electrochemistry, 2014-08-31) Ortiz, Mariela; Real, Silvia; Visintin, ArnaldoThe Lithium-ion batteries are electrochemical systems based on the use of intercalation compounds supported on porous structures with different characteristics. The Li-ion battery operates by intercalation of Li+ cations in materials, for migration from the cathode to the anode. Different materials are used as cathode, for example, mixed oxides of transition metals (LiMO2, where M: Mn, Co and / or Ni) [1-2], and lithium iron phosphate (LiFePO4) [3] or other materials [4-5]. In this paper the preparation of Li-Ni-Co-Mn oxides by hydrothermal synthesis is presented; being a simple, low cost and low temperatures process; that produces highly homogeneous materials. A solution containing nitrate of cobalt, nickel and manganese, sodium hydroxide and lithium are used as precursor solution; this is introduced into an autoclave at 180°C. Then the precipitates that have been obtained are combusted in an oxygen atmosphere. Optical techniques (as DRX, SEM and TEM) are used to characterize the prepared material. The electrochemical performance of mixed oxides as active cathode materials in lithium-ion batteries are studied by electrochemical techniques such as charge-discharge cycles, galvanostatic discharge at different currents, cyclic voltammetry and electrochemical impedance spectroscopy.Item Nickel oxide performance as anode material for lithium ion batteries(IWLiME, 2016-11-01) Ortiz, Mariela; Visintin, Arnaldo; Real, SilviaLithium ion batteries, as a rechargeable power source, have attracted much more attention due to their extensive applications in portable electronic devices and electric vehicles. Although most commercial Li-ion batteries use graphite as anode, a variety of materials have been investigated in order to increase the cell capacity, and therefore its specific energy. Some of these materials are transition metal oxides, which are able to store more Li per gram than graphite and to improve their specific capacities. In this respect, special attention has been given to Fe, Co, and Ni based oxides [1-3]. Particularly, NiO is one of the promising anode materials for Li -ion batteries because of its low cost, environmental friendless and high theoretical capacity values (718 mA h g-1 for 2Li+per NiO).Various NiO components with different structures such as mesoporous, nanosheet, networks, nanowall, nanotube and hollow microsphere have been successfully fabricated [4-5]. In this work, the preparation and characterization of nickel oxide as anodes materials in lithium-ion batteries are presented. Two processes are involved in the synthetic procedure; in the first step the nickel hydroxide was obtained by hydrothermal synthesis (4h, 180°C) and then the precipitated was washed with distilled water to remove the residual species. The second step consists of the material calcinations in air at 300ºC, for 4 (NiO-4h) and 24(NiO-24h) hours. The structural characteristics and electrochemical properties of the obtained nickel oxides are subsequently investigated by optical and electrochemical techniques such as: FTIR, SEM, charge-discharge cycles, galvanostatic discharge at different currents and cyclic voltammetry. The anode materials (NiO-4h and NiO-24h) were synthesized via a facile two-step route and exhibit a satisfactory specific capacity, cyclability and rate capability (Figure 1). These results indicate that the studied electrodes could be suitable as anodes in lithium ion batteries applications.Item Obtención y caracterización de Li(Ni1/3Co1/3Mn1/3)O2, material de cátodo en baterías de ion litio(JONICER, 2017-10-09) Gamba, Martina; Ortiz, Mariela; Suárez, Gustavo; Real, SilviaArgentina, junto con Bolivia y Chile conforman lo que se ha denominado el “Triángulo del litio”, concentrando entre los tres países el 55% de las reservas mundiales de litio y cerca del 85% de los depósitos de salmueras. El litio es un elemento fundamental en los sistemas de almacenamiento de energía actuales: las baterías de ion-litio están presentes en teléfonos celulares, computadoras laptop, cámaras fotográficas, en sistemas de transporte “verdes” como los vehículos eléctricos (VE) y VE híbridos. Un componente clave que limita el rendimiento de baterías es el material de intercalación del cátodo. Aunque existe gran variedad de sistemas, se conoce que la fase Li(Ni1/3Co1/3Mn1/3)O2 tiene una alta capacidad y excelentes características de ciclado y por ello se la utiliza ampliamente a nivel industrial. Existen diversas metodologías de síntesis. Entre ellas la reacción en estado sólido presenta como ventaja a la sencillez y facilidad de escalado.Item Preparación y caracterización de ánodos de baterías de ion Litio(J, 2013-10-09) Ortiz, Mariela; Real, SilviaEl uso de fuentes de energía, basadas en recursos renovables, ha sido ampliamente reconocido como la alternativa más viable para resolver problemas asociados con la combustión térmica convencional, tal es como su ineficiencia operacional, el agotamiento de las reservas de los combustibles fósiles y el aumento de la contaminación ambiental. En la actualidad, el mercado de las baterías empleadas en los dispositivos portátiles esta dominado por el uso de las baterías de ion-litio. Para satisfacer demandas que requieren alta potencia, como por ejemplo para su empleo en vehículos eléctricos o híbridos, se necesita aún lograr la optimización del comportamiento de las curvas de carga/descarga. Este estudio está dirigido a desarrollar, preparar y caracterizar materiales de ánodos con cinéticas rápidas y gran resistencia al ciclado para su uso en baterías de ion-litio.Item Preparación y caracterización del electrodo positivo de baterías de Ni-HM con aditivos de cobalto(HYFUSEN, 2013-06-09) Ortiz, Mariela; Castro, Élida Beatriz; Real, SilviaLa tendencia mundial de optar por tecnologías denominadas “limpias” conlleva a que se invierta en el desarrollo de tecnologías de fuentes energéticas alternativas. Dentro de estos dispositivos se incluye a las baterías alcalinas del tipo Ni-H y Ni-HM, en las que el electrodo positivo tiene como material activo hidróxido de níquel. Ha sido estudiado con agregados de diferentes aditivos (Co, Ca, Zn, C, materiales nanoestructurados, etc.), los que contienen Co resultan ser los más exitosos debido a que: incrementa la reversibilidad del par redox Ni(OH)2/NiOOH, aumenta el sobrepotencial de evolución de oxígeno, mejora la conductividad y reduce el crecimiento de especies γ-NiOOH durante la carga.Item Preparation and characterization of electrode materials in lithium batteries(Electrochemistry from Sensing to Energy Conversion and Storage, 2015) Ortiz, Mariela; Real, Silvia; Visintin, ArnaldoThe lithium batteries are electrochemical systems based on the use of intercalation compounds supported on porous structures. Different materials are used as cathodes: for example, mixed oxides of transition metals (LiMO2, where M: Mn, Co and / or Ni), and carbons materials (commercial carbon and Sungite carbon) are used as anodes. The preparation of anodes and cathodes materials are presented. Optical techniques (as DRX, SEM and TEM) are used to characterize the prepared material. The electrochemical performance are studied by electrochemical techniques: charge-discharge cycles, galvanostatic discharge at different currents and cyclic voltammetry.Item Preparation and characterization of graphite anode for lithium ion batteries(Advanced Batteries, Accumulators and Fuel Cells, 2014-08-24) Humana, Rita; Ortiz, Mariela; Thomas, Jorge; Real, Silvia; Visintin, ArnaldoThe lithium-ion batteries are energy storage systems of high performance and low cost for use in multiple portable devices. These require the use of increasingly smaller and lighter batteries with high energy and power density, fast charging and long service life. Moreover, these systems are promising for use in electric or hybrid vehicles. However, the successful use of the lithium in the field, requires improvements in relation to the properties of electrode materials, such as cost, energy density, cycle life, safety, and environmental compatibility. Currently, investigations are looking to improve the cell configuration by careful selection of the materials and components electrolytic. These batteries use carbon as anode material, usually synthetic graphite, because of its high coulombic efficiency and acceptable specific capacity for the formation of intercalation compounds (LiC6). Their low voltage increases the potential difference between the electrodes and therefore the energy density of the battery. In this paper, we present the methodology used to prepare and characterize the reversible and irreversible capacity and cyclic stability of graphite materials as anodes in lithium-ion batteries of commercial carbon (CR 1296) and Sungite carbon. We discuss the results obtained using electrochemical techniques for charging and discharging at different current densities, cyclic voltammetry and electrochemical impedance spectroscopy (EIS).Item Preparation and characterization of graphite anodes for lithium ion batteries(The Electrochemical Society, 2014) Humana, Rita; Ortiz, Mariela; Thomas, Jorge; Real, Silvia; Sedlarikova, Marie; Vondrak, Jiri; Visintin, ArnaldoThe lithium-ion batteries are energy storage systems of high performance and low cost. They are employed in multiple portable devices and these require the use of increasingly smaller and lighter batteries with high energy and power density, fast charging and long service life. Moreover, these systems are promising for use in electric or hybrid vehicles. However, the lithium-ion battery still requires to improve the electrode materials properties, such as cost, energy density, cycle life, safety, and environmental compatibility. These batteries use carbon as anode material, usually synthetic graphite, because of its high coulombic efficiency and acceptable specific capacity for the formation of intercalation compounds (LiC6). In this paper the methodology used to prepare and characterize the reversible and irreversible capacity and, cyclic stability of graphite materials as anodes in lithium-ion batteries of commercial carbon and Sungite carbon, is presented. The results obtained using electrochemical techniques, are discussed.