engleski

Metal oxide nano-particles and nano-composite polymer electrolytes - electrodes and electrolytes in solar and galvanic cells of the second generation

(PEO)8ZnCl2 polymer electrolytes and nano-composites were prepared using PEO  -irradiated to selected doses and TiO2 nanograins. The influence of added nanosize TiO2 grains to polymer electrolytes and the effect of gamma -radiation from a Co-60 source were studied by small-angle X-ray scattering (SAXS) simultaneously recorded with differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) at synchrotron ELETTRA. Infrared (IR) and impedance spectroscopy (IS) were also performed (1). We observed changes between 293 K and 373 K for treated and as prepared polymer electrolyte in SAXS/DSC/WAXS spectra and during the phase transition to the superionic phase at 335 K. Above-mentioned treatments largely enhanced the conductivity of polymer electrolyte. Room temperature conductivity increase up to two orders of magnitude was achieved. Metal oxide nanostructured thin films were studied as electrodes for dye-sensitized solar cells and charge-discharge second generation batteries. We have studied materials based on titanium, cerium and vanadium (2). Materials based on titanium are nanocrystalline TiO2 thin films, which play an important role in new generation of photochemical solar cells. Dye-sensitised cell differ from the semiconductor devices that they separate the function of light absorption from charge carrier transport. This cell was made of relatively non pure material with a cheap preparation procedure and energy conversion efficiencies ranging from 7 to 12%. Average grain sizes and specific surface areas as a function of temperature for TiO2 samples annealed in oxydizing and non-oxydizing atmosphere were obtained by GISAXS measurements at synchrotron ELETTRA. Vanadium oxide, such as V2O5, has been extensively studied because it tends to form layered structure that allows the intercalation/de-intercalation of different ions between its layers. It can be used as catalysts, in electrochromic device, in an advanced electrochemical cell concept, especially in lithium batteries. We have also studied V/Ce films intercalated with Li+-ions. 2D-GISAXS measurements revealed morphology change upon the intercalation of Li+ ions. GIXR (grazing-incidence X-ray reflectivity) was used for determination of layer thickness. The conductivity of (PEO)8ZnCl2 polyelectrolytes films can be significantly increased by radiation processing of poly(ethylene oxide) and addition of TiO2 nano-grains. These treatments significantly increased conductivity of polyelectrolytes and lowered temperature of the phase transition.The results are stimulating for further research of PEO polyelectrolytes and nanocomposites and also gather information on underlying conductivity mechanisms. GISAXS at ELETTRA could be applied for determining grain size and porosity in TiO2, CeO2, V2O5 and V/Ce oxides on glass substrate as well as for following the process of intercalation of cations into the porous nanostructured films. The morphology obtained by modifying and choosing particular preparation is suitable for application in advanced electrochemical and efficient new solar cells. By means of electrical measurements, we have shown that polymer electrolyte (PEO)8ZnCl2 can be combined with V2O5-CeO2 at 38 at.% of V as intercalation cathode in order to obtain all solid-state rechargeable galvanic cell. Further optimisations of electrolyte and electrodes properties are in progress. References 1. A.Turković, M. Pavlović, P. Dubček, M. Lučić-Lavčević, B. Etlinger, S. Bernstorff, SAXS/DSC Study of Polymer Electrolyte for Zn Rechargeable Nanostructured Galvanic Cells, J. of Electrochemical Society 154 (6) (2007) 554-560. and ibid. Virtual Journal of Nanoscale Science & Technology 15 (2007), 17 ; 554-560. 2. A. Turković, SAXS Characterization of Mesoporous Thin Films: A Solar Energy Point, Chapter 11 in the Book: Solar Energy Research Technology and Applications, Editors William L. Olafsson, V.I. Bengsson, Nova Science Publishers, Inc. (2008).1-29.

nanocomposites; nanostructured metal oxide fims; galvanic cells

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