Browsing by Author "Visintin, Arnaldo"

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    Characterization of anodes for lithium ion batteries
    (Springer, 2015-08-14) Humana, Rita; Ortiz, Mariela; Thomas, Jorge; Real, Silvia; Sedlarikova, Marie; Vondrak, Jiri; Visintin, Arnaldo
    The 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.
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    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, Silvia
    Nowadays, 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.
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    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, Arnaldo
    The 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.
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    Nickel oxide performance as anode material for lithium ion batteries
    (IWLiME, 2016-11-01) Ortiz, Mariela; Visintin, Arnaldo; Real, Silvia
    Lithium 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.
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    Preparation and characterization of electrode materials in lithium batteries
    (Electrochemistry from Sensing to Energy Conversion and Storage, 2015) Ortiz, Mariela; Real, Silvia; Visintin, Arnaldo
    The 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.
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    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, Arnaldo
    The 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).
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    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, Arnaldo
    The 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.
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    Síntesis y estudio electroquímico de materiales de cátodo en baterías de ion litio
    (Congreso Argentino de Fisicoquimica y Química Inorgánica, 2015-04-12) Ortiz, Mariela; Visintin, Arnaldo; Real, Silvia
    En este trabajo se presenta la preparación de óxidos mixtos de Li-Ni-Co-Mn por síntesis hidrotermal, que permite obtener materiales altamente homogéneos a través de un proceso sencillo, de bajo costo y empleando bajas temperaturas. En la síntesis se emplean soluciones precursoras que contienen: Co, Ni, Mn; hidróxido de sodio y de litio; las mismas se introducen en un autoclave a 180 ºC y posteriormente, se realiza la combustión del precipitado obtenido en atmósfera de oxígeno. La caracterización del material preparado se realizó empleando técnicas ópticas (difracción de rayos X, microscopía electrónica de barrido y de transmisión). El desempeño electroquímico de estos óxidos mixtos como material activo en cátodos de baterías de ion-Litio se estudió empleando técnicas electroquímicas como: ciclos de carga-descarga, descargas galvanostáticas a diferentes corrientes, voltamperometría cíclica.
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    Study of the electrochemical behavior of different carbon materials as anode material for lithium ion batteries
    (Topical Meeting of the International Society of Electrochemistry, 2017-03-19) Ortiz, Mariela; Visintin, Arnaldo; Real, Silvia
    Since the lithium ion battery was first commercialized by the Sony Corporation in 1991, the development for improvement it is critical for advancements in a variety of applications ranging from hybrid electric vehicles to consumer electronic. Most lithium ion commercial battery use LiCoO2, LiNiO2 or LiFePO4 as cathode material, organic solvent as the electrolyte and carbon composites as anode material. The electrochemical reactions involve Li transfer and exchange of electron. A number of studies have so far been performed for providing a high performance carbonaceous material for the anode of Li-ion batteries. In this study, out of the many available carbonaceous materials we have selected some of them to prepared anodes material and study their electrochemical behavior and correlation to their physical, chemical and physic-chemical parameters.
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    Synthesis and electrochemical properties of Nickel oxide as anode for Lithium ion batteries
    (Topical Meeting of the International Society of Electrochemistry, 2017-03-19) Ortiz, Mariela; Visintin, Arnaldo; Real, Silvia
    Transition-metal oxides (MO, where M is Fe, Ni, Co and Cu) have been studied since these materials were proposed by Tarascon and co-workers [1-6]. These oxides can offer higher capacities (600-1000 mAh g-1) that graphite material (372 mAh g-1); in particular, NiO has high theoretical capacity values (718 mA h g-1 for 2Li+per NiO) also present many advantages such as natural abundance, low cost and environmental friendless In this contribution we would like to present the preparation and characterization of nickel oxide as anodes materials in lithium-ion batteries. 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, chargedischarge cycles, galvanostatic discharge at different currents, cyclic voltammetry and electrochemical impedance spectroscopy.