Dual-functional electrochromic supercapacitors with electrospun TiO2 ion storage layer

We have developed dual-functional electrochromic supercapacitors (ECSs) incorporating electrospun TiO2 nanofibers as an ion storage layer (ISL). The prepared ISL-ECSs exhibit excellent integrated electrochromic performances at low driving voltages due to high visible transparency and energy storage capabilities. This study describes direct electrospinning TiO2 on an FTO electrode and fabricating asymmetric electrochromic devices with viologen-based ion gel compositions. The electrospinning technique proved suitable for producing oxide nanostructures that facilitate efficient ion transport. The surface morphology of the fabricated nanoweb was analyzed using SEM and AFM images. The electrochromic performances were evaluated through cyclic voltammetry and spectroelectrochemical measurements, and charge storage properties were examined by galvanostatic charge-discharge curves. The optimized dual-functional devices demonstrated a large transmittance contrast of up to 87 %, high coloration efficiency of 175.7 cm2/C, areal capacitance of 20.53 mF/cm2, and good charging-discharging cyclic stability. Furthermore, the practical feasibility of the ISL-ECSs was demonstrated by evaluating their ability to serve as a power source for illuminating an LED lamp. The findings suggest the potential application of ISL-ECSs for dual-functional smart windows, in which the color intensity visualizes the realtime energy storage status.