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This paper describes the preparation and characterization of poly(ethylene oxide) (PEO)-lithium bis(perfluoroethylenesulfonyl)imide (LiBETI), LiN false(SO2CF2CF3)2 polymer electrolytes. The structural properties of Pfalse(EO)n LiBETI electrolyte tapes, investigated using X-ray diffraction (XRD) and differential scanning calorimetry (DSC), are correlated with their ionic conductivities. PEO-LiBETI complexes were found to have very high ionic conductivities due to their amorphous structure. © 2001 The Electrochemical Society. All rights reserved.

Oxidized and reduced cobalt(II) hexacyanoferrates were fabricated and characterized in the presence of alkali metal (Li+, Na+, K+, Cs+) and Co2+ countercations. Formal potentials of hexacyanoferrate(III,II) redox reactions are sensitive to the choice of electrolyte cation, and they correlate well with the sizes of hydrated Li+, Na+, and K+. Electrochemical quartz crystal microbalance measurements clearly indicate that countercations, presumably in partially dehydrated form, are incorporated into reduced cobalt(II) hexacyanoferrate(II). The color of the system reflects primarily the oxidation state of iron sites. But the color of the reduced form is also affected by the nature of an intercalated hydrated countercation. This observation is correlated with the reversible continuous thermochromism of K2CoII[FeII(CN)6]*nH2O that shall be attributed to the release of structural water molecules interacting with CoII during heating in the temperature range 25−85 °C. It is apparent from X-ray absorption near-edge structure (XANES) experiments that the chemical environment of cobalt(II) sites is influenced by the presence of hydrated alkali metal countercations. The results are consistent with the accommodation of countercations in the lattice cavities at interstitial positions. The structural environment of iron ions was the same in all systems studied except that a chemical shift was observed due to change of the oxidation state of iron.

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X-ray absorption spectroscopy (XAS) has been used to probe the local structure of doped vanadium pentoxide materials prepared through sol–gel processes. The doped samples have been analyzed at the vanadium K-edge as well as at the doping metal K-edge (copper and zinc). The presence of two metal sites gives two independent absorption signals, even if we are investigating the same compound; for this reason the reliability of the analysis is enhanced. The strategy in determining the local structure will be discussed. The local structural modifications resulting from low to high doping concentration in the best performing copper-doped V2O5 aerogel like material is reported. Similar measurements were done using zinc as doping metal, in both aerogel-like and xerogel form. The EXAFS analysis shows that the vanadium atomic environment is not altered by the doping metal insertion and that the doping metals (Cu and Zn) are found to be in the same site. Copper and zinc are 4-fold coordinated by almost coplanar oxygens in both xerogel and aerogel-like oxide hosts. The use of the metal–metal interaction while analyzing data concerning sample of high doping level played a key role in the determination of the preferred metal sites.

Cobalt(lI) hexacyanoferrate(lll,Il), a system analogous to prussian blue, is a unique electrochromic material: its color is not only dependent on the oxidation potential, but also on the nature of the countercations sorbed from electrolyte during reduction. The electrodeposition of cobalt hexacyanoferrate thin films, their voltammetric behavior and spectroelectrochemical identity are reported here in potassium and sodium electrolytes. The oxidized film is purple brown in both electrolytes, but following reduction, the system turns olive-brown in 1 M KCI and becomes green in 1 M NaCl.Much attention has been devoted lately to the preparation and characterization of thin films of metal hexacyanoferrates because of their interesting alkali-metal cation storage capabilities and possible applications in batteries, sensors, and electrochromic display devices. A number of reports emphasize the stability and long-term reversibility of electrochromic redox reactions using prussian blue, KFe"[F&(CN)6], and its metal (Fe10) substituted analogues.These structures are fairly open, since they typically feature cubic, or almost cubic, rigid frameworks with interstices spacious enough to easily accommodate the compensating countercations (particularly hydrated-K) which are necessary for charge balance during redox reactions.While many prussian blue analogs are known, the spectroelectrochemical properties of only few metal hexacyanoferrates have been well established and documented. Recently, the synthesis and electrochemical characterization of thin films of cobalt(ll) hexacyanoferrate(l 11,11) have been reported.125 These films show reversible electrochemical behavior, and they are stable during prolonged potential cycling in supporting electrolytes containing potassium or sodium. We demonstrate in this paper that cobalt hexacyanoferrate is electrochromic and its spectroelectrochromic responses are different in electrolytes containing potassium and sodium ions. Also, simple solution tests show that X2Co°[Fe"(CN)6] precipitates have different colors depending on a choice of the X alkali metal cation. We think that this concept may be of importance to the construction of multicolor display devices. ExperimentalElectrochemical measurements were done with Bioanalytical Systems Model 100 W analyzer. Quartz disks (diam, 22 mm), covered with Sn-doped indium oxide (resistance, 20 1 /L1), or Au-covered foil (gold thickness, ca. 50 nm) were applied as optically transparent electrodes for spectroelectrochemistry. Visible spectra were taken using Hewlett Packard 8452 diode array spectrophotometer.All chemicals were reagent grade and were used as-obtained from suppliers. Experiments were carried out at room temperature. All potentials are expressed vs. the saturated calomel electrode (SCE) reference. The electrode substrates were pretreated as described earlier.16 The potassium or sodium containing cobalt hexacyanoferrate films were grown by potential cycling (at 100 mV s) for 10 mm from 0.85 to 0 V in freshly prepared modification solutions...

Polarized X-ray absorption spectroscopy has been used to study the short-range structure of deposited films of V2O5 xerogel. The material is characterized by a layer of VO5 units with the V-O apical bond perpendicular to the basal (xy) plane. We have focused our attention along the z axis. Experiments were carried out by extended X-ray absorption fine structure (EXAFS) spectroscopy in a grazing incidence geometry and showed evidence for close interactions between neighboring layers of V2O5. The structure is described by two sheets of V2O5 facing each other. Fitting of the EXAFS data has confirmed the existence of a vanadium-vanadium interaction between two different V2O5 layers and an oxygen bridge between them.

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