Indium−Vanadium Oxides Deposited by Radio Frequency Sputtering:  New Thin Film Transparent Materials for Li-Insertion Electrochemical Devices

Abstract

Thin films of mixed In/V oxides have been obtained by reactive RF sputtering. Their optical and electrochemical performances have been investigated in order to determine their possible applications in electrochromic devices as optically passive ion-storage layers. The targets used have been made of In 2 O 3 and V 2 O 5 powders mixed in different In/V ratios in a reactive sputtering atmosphere. Cyclic voltammetry and chronopotentiometry studies of these films have been performed. The films demonstrate high ion-storage capacity retained even after 1000 cycles without any significant degradation. Lithium diffusion coefficients, calculated by the potentiostatic intermittent titration technique (PITT), range around 10 -13 cm 2 s -1 . The optical measurements, taken in the UV-vis-NIR transmittance and reflectance modes, have demonstrated that films are electrochromic, but the presence of In enhances their transparency and optical passiveness. The photometric spectra evaluation by a computer fitting shows that the refractive index is lower for films with higher In content. This result is in good agreement with Rutherford backscattering spectroscopy (RBS) measurements. The material structure has been discussed on the basis of the above results, as a function of the measured thin film composition, and is corroborated by preliminary results of XPS surface analysis.

Surface evolution of Ni–V transparent oxide films upon Li insertion reactions

“…The presence of shake-up satellites is characteristic of Ni(II) paramagnetic species in octahedral and tetrahedral coordination, as reported in early literature findings, 21 where it has been shown that the satellite number, intensity and energy separation from main peaks are variable to a large extent in different species. Based on the phase diagram of the NiO-V 2 O 5 system 22 and on the experimental conditions for sample production adopted here, the present sample composition could be expected to be a mixture of Ni VO 3 and V 2 O 5 . V 2 O 5 has been characterized thoroughly by photoemission in several publications.…”

“…Relevant issues have been addressed on intercalated electrodes, by conventional or more recently synchrotron radiation-excited photoemission. 9,10 The versatility of XPS is exemplified in studies on the electronic structure of well-established electrochromic materials such as WO 3 , 11 on in situ investigations on largearea electrode materials 12 and on the determination of the surface composition of reactive electrodes as a consequence of the use of different electrolytes or solutions. 13 The aim of our paper is to monitor the evolution of some aspects of Li insertion reaction that are mostly relevant to the performance of an intercalation electrode.…”

Synthesis and electrochromic property of single-crystalline V 2 O 5 nanorod arrays by template-based deposition

“…A large surface area and easy transport are required to achieve high charge/discharge rate. 6,7 The diffusion coefficient of Li in V 2 O 5 is about 10 11 -10 13 cm 2 /sec 8,9 , which is relatively small, so that a large surface area and a short diffusion distance are desired to achieve such abilities. It is clear that nanostructures, such as nanorod arrays, are advantageous for these applications to make such properties improved.…”

Electroanalytical Methods Utilizing Small Signal Current or Potential Excitations for the Characterization of Porous Electrodes Comprising Insertion Materials

“…The time derivative of any variable is thus given, for example, as ∂c ∂τ = λjωc exp[ jωτ] [29] Because the terms exp[ jωτ] multiply all of the order λ terms in the equations, these terms can be omitted when writing down the equations for the order λ terms. With these notational changes, equations 20-26 can be replaced with…”