Facultad Regional La Plata

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Author: search.filters.author.Real, SilviaSubject: search.filters.subject.Batteries

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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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    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 Beatriz
    Nickel 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.
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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).