Solution-processable multicolor TiO2/polyaniline nanocomposite for integrated bifunctional electrochromic energy storage device

We report a solution-processable nanocomposite film based on TiO2 and polyaniline (PANI) for high-performance electrochromic and energy storage via the combination of electrostatic spray deposition (ESD) and electropolymerization (EPM) techniques. This combined strategy provides an exciting method for high-performance metal oxide/conducting polymer composite with well-controlled morphology and structure. The obtained TiO2/PANI composite film with a sea urchin-like porous structure exhibits a unique electron donor–acceptor (D-A) structure, facilitating the electron transport from PANI to TiO2. As a result, the nanocomposite film presents excellent electrochemical performances in both electrochromic and energy storage aspects, such as large optical modulation up to 76.9 % at 600 nm, short switching time (<3.6 s), and high coloration efficiency (CE) of 78 cm2 C-1. Furthemore, an intelligent energy-storage indicator with energy level monitoring functionality is designed and constructed based on the multicolor composites, in which the energy-storage level can be visually detected in real-time by the different color variations. This work paves a way for developing multicolor nanomaterials in the field of bifunctional electrochromic energy storage.