Dual-Function Electrochromic Supercapacitors Displaying Real-Time Capacity in Color.

Dual-function electrochromic supercapacitors (ECSs) indicating their real-time charge capacity in color are fabricated using tungsten trioxide (WO3) and Li-doped ion gels containing hydroquinone (HQ). The ECSs in this work can simultaneously serve as either electrochromic devices (ECDs) or supercapacitors, so the coloration/bleaching and charging/discharging characteristics are investigated between 0 and -1.5 V. At the optimal HQ concentration, a large transmittance contrast (~91 %), high coloration efficiency (~61.9 cm2/C), high areal capacitance (~13.6 mF/cm2), and good charging/discharging cyclic stability are achieved. By exploiting the elastic characteristics of the gel electrolytes, flexible ECSs are also fabricated on plastic substrates and exhibit good bending durability. Moreover, the practical feasibility is evaluated by demonstrating the use of the ECSs as an energy storage device and a power source.