Integrated electrochromic supercapacitors with visual energy levels boosted by coating onto carbon nanotube conductive networks

Conductive polymer polyaniline (PANI) demonstrates potential applications in developing integrated smart energy devices based on the bi-functional electrochromic optical modulation and electrochemical energy storage. One challenge is to improve the structural stability of PANI films in response to repeating doping and dedoping of anions during the electrochemical redox process. Herein, a facile and effective approach is developed for improving the electrochemical performance of PANI by coating onto the carbon nanotube (CNT) conductive networks. The introduction of CNT firstly provides multiple directions for electron transfer and thus enhances the charge capacity of PANI. Then, the polymerization of PANI onto the CNT (PANI@CNT) contributes to the formation of a 3D network film, which effectively reduces the structural failure caused by anions intercalation and extraction. Compared with compact PANI film, a substantial promotion of bi-function achieves in the porous PANI@CNT one, whose optical transmittance modulation increases to over 40% and the specific capacitance of the initial cycle is almost tripled. On the basis of reversible and stable chromatic transitions between different charged states, the PANI@CNT electrode is further developed to be a smart electrochromic supercapacitor exhibiting visual energy storage level. We expect that this work may lead to new designs of robust smart energy storage devices.