High Performance Multicolor Intelligent Supercapacitor and Its Quantitative Monitoring of Energy Storage Level by Electrochromic Parameters

The construction of an electrochromic supercapacitor device (ESD) with multicolor change, good energy storage capacity, cyclic stability, and the realization of the quantitative monitoring of energy storage level (ESL) of an ESD are very important to realize the practical application of the device. In this study, poly­(indole-5-carboxylic acid)/WO₃ (P5ICA/WO₃) nanocomposites with good electrochromic and supercapacitive properties are successfully prepared. The color of P5ICA/WO₃ nanocomposites can be reversibly changed among blue-green, yellow, and dark green. The specific capacitance of the prepared P5ICA/WO₃ composites is 30.2 mF cm^–2, indicating a good energy storage capacity. An all-solid ESD is constructed based on the prepared P5ICA/WO₃ nanocomposites and poly­(3,4-ethylenedioxythiophene) (PEDOT), which exhibits excellent capacitive and electrochromic performance, long-term charge/discharge stability, and electrochromic stability. The max specific capacitance of the ESD is 10.11 mF cm^–2, and the coloration efficiency is 608 cm² C^–1. The ESL of the ESD can be directly monitored through the color change during the charging and discharging process. Furthermore, in order to achieve the quantitative monitoring of the ESL, the relationship between ESL and electrochromic parameters (optical density) of the device is established. It is believed that this study may provide a strategy for the preparation of bifunctional electrode materials and expand the intelligent functions of the supercapacitor.