FRLP - I+D+i - CENTROS - CITEMA
Permanent URI for this communityhttp://48.217.138.120/handle/20.500.12272/1746
Browse
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 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.[1] 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 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 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 positive electrode of NiMH batteries with cobalt additives(Elsevier, 2014-02-18) Ortiz, Mariela; Real, Silvia; Castro, Élida BeatrizThe present paper shows the preparation and characterization of alkaline batteries cathodes formed by nickel hydroxide with the addition of cobalt. This additive was incorporated by two methods: on the electrode surface, using the electroless technique and by direct incorporation of cobalt powder in the active material. The electrochemical behavior of both nickel hydroxide electrodes was investigated and compared. The results indicate that active materials containing cobalt additive by the electroless technique exhibit an improvement on the electrochemical performance.