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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 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 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 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 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 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.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.