Design of electrochromic supercapacitor based on rGO–W18O49 nanowires/polyaniline

An electrochromic supercapacitor is a new type of multifunctional device. It can store energy, change its optical properties, and its color can intuitively reflect the energy storage of the device in real time. This study focused on W18O49 nanowires (WNS) and polyaniline (PANI) electrochromic materials and their thin-film electrodes. Graphene oxide was incorporated in the process of solvothermal preparation of WNS and graphene/W18O49 nanowires composite (rGO–WNS) was obtained. Compared with WNS, the electron transport capability of rGO–WNS is improved, which effectively reduce the discoloration time from 7 to 4 s and the coloring time from 10 to 2 s. In addition, the coloration efficiency has also improved from 45.37 to 52.72 cm−2·C−1, however, the optical modulation amplitude of the composite is reduced from 35 to 20% due to the obstruction of graphene to the transmittance. A characteristic pseudocapacitive behavior is observed for rGO–WNS and PANI electrodes, which were assembled in pairs to form an EC supercapacitor (ECSC) device. With the voltage increased from − 0.2 to 1.4 V, the color of ECSC varies among light green, dark green, light blue and dark blue.