Electrochromic Displays Based on V2O5 Electrodes

Cycling the DG device from Fig. 5.3b between — 1V and -I-1V gave rise to a color change from blue-gray to green-yellow as shown in Fig. 5.12c. Transmission spectra 

DG are juxtaposed with 10 that show approximately the same transmission values at A = 430 nm for the colored oxidized state. 

The contribution of faradaic and double-layer capacitances in the response of DG-structured V2O5 can be estimated by comparing the CV curves of devices that use RTIL electrolyte with and without lithium salt, shown in Fig. 5.14b. Since V2O5 does not react with either of the ions of pure RTIL, the lithium-free experiment tests the EDLC response. With lithium salt added, the significant increase in capacitive current and the appearance of peak pairs indicates that redox reactions are taking place. These faradaic processes are kinetically facile and thus considered pseudocapacitive, but phase transitions may occur. Although it is difficult to distinguish between redox and intercalation pseudocapacitance, the latter is likely to be present in DG bicontinuous materials. 

The overall performance of our V2O5-based supercapacitors is summarized in the Ragone plot describing the relation between energy density and power density (Fig. 5.15a) [51]. The highest obtained energy density of nontemplated vanadia supercapacitors is 1 Wh kg at a power density of 50 W kg , which drops to one-half at a power density of 0.4 kW kg . Such low values arise from the limited ion diffusion 

A commonly observed problem in nanostructured supercapacitors is their initial loss of capacitance during cycling, mainly caused by compaction of the material resulting in a reduced surface area exposed to electrolyte [65]. A performance 

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