A conjugated polymer with Electron-withdrawing cyano group enables for flexible asymmetric electrochromic supercapacitors

Abstract

Flexible electrochromic supercapacitors (ECSCs) consisting of conjugated polymer electrodes are promising for integrating optical modulation with sustainable energy storage. However, there remain formidable challenges to achieving long-term cycling stability while maximizing high device output voltage. Here, we design a new twisted conjugated polymer bearing dual-redox centers (thiophene and triphenylamine) and an electron-withdrawing cyano group. The as-prepared conjugated polymer showcases elevated discharge potential and highly efficient charge transport synchronously, attributed to the lowered energy of the lowest unoccupied molecular (LUMO) orbitals and twisted alignment of the polymer chain. Coupled with the transparent vanadium pentoxide (V2O5) nanowires ion-storage material, the flexible ECSC affords a high optical contrast of 67 %, wide voltage window of 2 V, large capacitance of 32.9 mF/cm2, and outstanding cycling durability (86 % capacitance and 96 % optical modulation retention after 7000 cycles at 0.2 mA/cm2). This molecular engineering strategy and insight illustrated by density functional theory (DFT) calculation together with electrochemical kinetics analysis provide another way along the route toward the synergetic improvement of electrochromic and energy storage performance.