New electropolymerized triphenylamine polymer films and excellent multifunctional electrochromic energy storage system materials with real-time monitoring of energy storage status

Multifunctional intelligent electrochromic energy storage with real-time monitoring of energy storage level by color change has become the extremely attractive researches for the development of electrochemical energy storage systems. Herein, three novel triphenylamine-based organic monomers with star-shaped donor–acceptor structure are designed and synthesized to successfully obtain the corresponding three polymer films with different and rich color switching by electrochemical polymerization via the coupling between peripheral triphenylamine groups. Based on these three polymer films as the electrodes, a fast switching electrochromic property with a large optical contrast of 80.5 % in the visible region and a high coloration efficiency of 277.21 cm2·C−1, which are one of the best results among TPA-based electrochromic materials, is achieved for the polymer pPh-4TPA with the pyrazino[2,3-g]quinoxaline acceptor core. Meanwhile, pPh-4TPA also shows high specific capacitance of up to 423F·g−1 (475F·cm−3), high capacity of 115.3 mAh·g−1 and unparalleled rate performance. The assembled asymmetric electrochromic energy storage devices based on pPh-4TPA polymer films exhibited maximum energy density of 105.12 Wh·kg−1 (107 mWh·cm−3) and power density of 45 kW·kg−1 (45.9 W·cm−3), which are both the highest energy and power densities among the pure organic electrochromic pseudocapacitors ever reported, simultaneously accompanied by reversible color changes in appearance during charging and discharging process.