Amorphous Nb/Fe‐Oxide Ion‐Storage Films for Counter Electrode Applications in Electrochromic Devices

Abstract

The electrochromic properties of mixed Nb/Fe-oxide films with amorphous structure which were prepared via the solgel route were determined. Films with Nb/Fe molar concentration ratios 0.2:1, 0.4:1, and 1:1 exhibit ion-storage capacities up to 18 mC/cm 2 depending on Nb/Fe molar ratio. Electrochromically films behave as optically passive electrodes with a coloration efficiency of nearly zero at X > 480 nm, while at shorter wavelengths a relatively strong anodic coloring was observed, yielding negative coloration efficiencies up to -20 cm'/C. Coloring/bleaching changes of films are correlated with the ex situ IR spectroscopic measurements of charged/discharged films showing distortions of the film structure with Li + ion insertion/extraction reactions. Electrochemical stability of Nb/Fe (0.4:1)-oxide films was tested up to 2000 cycles in a sol-gel electrochromic device consisting of sol-gel-derived WO, films and hybrid organic/inorganic ionic conductor with ionic conductivity of about 10 -4 S/cm serving for lamination of the electrodes. ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 129.49.23.145 Downloaded on 2015-03-15 to IP

High Li+-Ion Storage Capacity and Double-Electrochromic Behavior of Sol−Gel-Derived Iron Oxide Thin Films with Sulfate Residues

“…Sputtered TiO 2 -CeO 2 films showed a capacity of 18 mC/cm 2 with high reversibility. 38 Orel et al 39 reported single-dipped SnO 2 /Mo films (100-200-nm-thick) with a high ion storage capacity of 20-30 mC/cm 2 while Nb-Fe mixed oxide films 7 were up to 18 mC/cm 2 . V 2 5 , which is ranked among the most promising ion storage films, typically possesses an ion storage capacity of up to 35 mC/cm 2 .…”

“…Iron(III) oxide thin films are widely used for their interesting properties, for example, as catalysts in dehydrogenation reactions, magnetic devices, temperature and humidity sensors, optical filters, potential use in nonlinear optics, and so forth. , Iron oxide could also be considered as a promising electrochromic (EC) material with regard to its many valence states, which could be easily changed by either heat treatment or potential cycling in electrochemical cells. However, few studies have been done on the electrochromic properties of iron oxide films in its pure 3-6 or mixed oxide forms. − …”

“…However, few studies have been done on the electrochromic properties of iron oxide films in its pure [3][4][5][6] or mixed oxide forms. [7][8][9][10] Fe 2 O 3 shows mixed cathodic/anodic electrochromism, which upon lithium intercalation, colors in the visible spectral region (450 < λ < 800 nm) and bleaches in the UV spectral region (300 < λ < 450 nm). 9 Its electrochromic mechanism is not well understood yet, but might be tentatively explained by band gap widening upon electrochemical reduction, analogous to that of V 2 O 5 .…”