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Urbaniak J.,Poznan University of Technology | Skowronski J.M.,Poznan University of Technology | Olejnik B.,Central Laboratory of Batteries And Cells
Journal of Solid State Electrochemistry | Year: 2010

In the present work, a simple method of preparation of FeCl 4 -- graphite intercalation compounds from HCl/FeCl 3 solution with the aid of chemical oxidant is presented. Based on X-ray diffraction measurements it was concluded, that stages 8, 6, and 5 FeCl 4 --graphite intercalation compounds were obtained. The compounds thus obtained were thermally treated to obtain Fe 2O 3-exfoliated graphite composites. The dispersion of Fe 2O 3 in the exfoliated graphite flakes was examined with the aid of the energy dispersive X-ray analysis combined with a scanning electron microscopy. Electrochemical behavior of electrodes was investigated in 6 M KOH solution. Electrochemical investigations proved the formation of FeOOH on the surface of exfoliated graphite during the anodic process. Besides, electrochemical investigations showed that the lower limit potential strongly affects the redox behavior of the Fe 2O 3-EG electrode. © Springer-Verlag 2010. Source

Zalas M.,Adam Mickiewicz University | Walkowiak M.,Central Laboratory of Batteries And Cells | Schroeder G.,Adam Mickiewicz University
Journal of Rare Earths | Year: 2011

Modified with gadolinium-containing layer, nanoporous titania electrode and its application in dye-sensitized solar cells were reported. The electrode prepared was characterized with UV-Vis and X-ray diffraction (XRD) techniques. The amount of gadolinium was measured with inductively coupled plasma-optical emission spectrometry (ICP-OES) experiments. The modified electrode showed reduced N3 dye adsorption ability, but increased light conversion efficiency in comparison with the non-modified electrode. The overall conversion efficiencies, determined under 400 W/m2 irradiation with tungsten-halogen lamp at room temperature, were 0.55 for non-modified and 0.74 for modified electrodes. © 2011 The Chinese Society of Rare Earths. Source

Lota G.,Poznan University of Technology | Tyczkowski J.,Technical University of Lodz | Kapica R.,Technical University of Lodz | Lota K.,Central Laboratory of Batteries And Cells | Frackowiak E.,Poznan University of Technology
Journal of Power Sources | Year: 2010

The carbon material was modified by RF plasma with various reactive gases: O2, Ar and CO2. Physicochemical properties of the final carbon products were characterized using different techniques such as gas adsorption method and XPS. Plasma modified materials enriched in oxygen functionalities were investigated as electrodes for supercapacitors in acidic medium. The electrochemical measurements have been carried out using cyclic voltammetry, galvanostatic charge/discharge and impedance spectroscopy. The electrochemical measurements have confirmed that capacity characteristics are closely connected with a type of plasma exposition. Modification processes have an influence on the kind and amount of surface functional groups in the carbon matrix. The moderate increase of capacity of carbon materials modified by plasma has been observed using symmetric two-electrode systems. Whereas investigations made in three-electrode system proved that the suitable selection of plasma modification parameters allows to obtain promising negative and positive electrode materials for supercapacitor application. © 2009 Elsevier B.V. Source

Zalewska A.,Warsaw University of Technology | Walkowiak M.,Central Laboratory of Batteries And Cells | Niedzicki L.,Warsaw University of Technology | Jesionowski T.,Poznan University of Technology | Langwald N.,Warsaw University of Technology
Electrochimica Acta | Year: 2010

The aim of the presented work was to perform a preliminary study of the physicochemical and interfacial properties of hybrid organic-inorganic gel electrolytes for Li-ion batteries based on the PVdF/HFP polymeric matrix and surface-modified silicas. Two types of silica fillers of different grain sizes (>500 nm and ∼100 nm) were used as additives. The silica particles were modified by two different functional groups, i.e. methacryloxy and vinyl ones. The gel electrolytes based on PVdF/HFP copolymer were prepared according to the so-called Bellcore two-step process. The motivation of the present work was to study more deeply those systems in terms of morphology by means of scanning electron microscopy techniques. Fillers modified with identical functional groups but differing fundamentally in the manufacturing processes were compared in terms of the impact on morphology and electrochemical performance of the resulting membranes. Interfacial properties were examined by means of impedance spectroscopy technique using Swagelok-type cells with two lithium electrodes. © 2009 Elsevier Ltd. All rights reserved. Source

Sierczynska A.,Central Laboratory of Batteries And Cells | Lota K.,Central Laboratory of Batteries And Cells | Lota G.,Central Laboratory of Batteries And Cells | Lota G.,Poznan University of Technology
Journal of Power Sources | Year: 2010

Nickel hydroxide is used as an active material in positive electrodes of rechargeable alkaline batteries. The capacity of nickel-metal hydride (Ni-MH) batteries depends on the specific capacity of the positive electrode and utilization of the active material because of the Ni(OH)2/NiOOH electrode capacity limitation. The practical capacity of the positive nickel electrode depends on the efficiency of the conductive network connecting the Ni(OH)2 particle with the current collector. As β-Ni(OH) 2 is a kind of semiconductor, the additives are necessary to improve the conductivity between the active material and the current collector. In this study the effect of adding different carbon materials (flake graphite, multi-walled carbon nanotubes (MWNT)) on the electrochemical performance of pasted nickel-foam electrode was established. A method of production of MWNT special type of catalysts had an influence on the performance of the nickel electrodes. The electrochemical tests showed that the electrode with added MWNT (110-170 nm diameter) exhibited better electrochemical properties in the chargeability, specific discharge capacity, active material utilization, discharge voltage and cycling stability. The nickel electrodes with MWNT addition (110-170 nm diameter) have exhibited a specific capacity close to 280 mAh g-1 of Ni(OH)2, and the degree of active material utilization was ∼96%. © 2010 Elsevier B.V. Source

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