Multifunctional polyamides containing O, S heterocycle cores for electrochromic device : From colorless to dark and energy storage

Electrochromic supercapacitors (ECSCs) find extensive applications in flexible wearable, self-powered smart windows because of their visual energy storage characteristics. ECSCs simultaneously achieve rapid response, high transmittance and high specific capacity. Due to O, S heterocycle with more electron cloud which will bring more electroactive properties, two monomers and a series of polyamides (PAs) films containing furan, thiophene blocks (named as PA1, PA2, PA3, PA4, PA5 and PA6) are designed and synthesized. All the six PAs demonstrate a colorless to dark green/dark blue, while PA2 shows an initial optical contrast of 86 %, bleaching time (t b ) and coloring time (t c ) of 0.9 s and 1.2 s. Simultaneously PA2 delivers a specific capacitance of 197.2F g −1 at a current density of 1 A g −1 . When the current density rises to 20 A g -1 from 1 A g −1 , its capacitance retention rate remains at 79 % of its initial capacitance after undergoing 3000 charge–discharge cycles. ECSCs with PA1, PA2 assembled exhibit a ΔT of 70 % and 76 %. The ECSCs have a specific capacitance (60.1F g −1 and 69.1F g −1 at 1 A g −1 ), with 70 %, 69 % of initial specific capacitance following 2000 consecutive charge–discharge cycles. These PAs containing O, S heterocycle cores demonstrate promising prospect for ECSCs.