Polythiophene/WO3 composite electrochromic fiber devices with rapid color switching and supercapacitor application

The electrochromic supercapacitor is combined with flexible fibers and inorganic-organic composites. • This fiber exhibits excellent electrochromic performance and has a fast color response time of 0.3 s. • After the fibers are bent, their electrochromic and electrochemical properties remain stable. • The structure of "asymmetric devices" has enhanced the performance of electrochromic devices, with a capacitance of 136.95 F*g −1 . In this study, bilayer poly(3-methylthiophene) and WO 3 composites were polymerized on the surface of stainless steel fibers by electrochemical deposition method to form composite electrochromic fibers. The film layer formed by polythiophene is uniformly wrapped around the surface of stainless steel fibers, and tungsten trioxide forms a porous film on the outermost layer, providing interpenetrating channels for ions. The composite electrochromic fiber shows color changes of red to black within the voltage range of −1.5–1.5 V. Its coloring time is 0.55 s and bleaching time is 0.50 s. It has good stability and electrochemical performance. Moreover, the performance of electrochromic fiber remains unchanged in the bending state. More importantly, it has fast charging/discharging performance and high specific capacitance of 440 F·g −1 . The asymmetric electrochromic supercapacitor device can also achieve a high specific capacitance of 136.95 F·g −1 at a current density of 0.8 A·g −1 . The P3MeT/WO₃ asymmetric electrochromic supercapacitor retained 71% of its initial capacitance with a coulombic efficiency of 83.46% after 1000 cycles, demonstrating excellent capacitive performance and electrochemical stability. These results indicate that the electrochromic composite fibers offer broader application prospects in wearable supercapacitors.