Stable Three-Dimensional PEDOT Network Construction for Electrochromic-Supercapacitor Dual Functional Application

In view of that conducting polymers (CPs) have potential application in an energy storage system but suffer from poor stability during the charge-discharge process, we proposed a molecular expansion strategy to guide the design of stable electrochromic supercapacitors in this work. Two polymers P(BT-4Th) and P(BT-4EDOT) with a three-dimensional (3D) network structure were prepared by electrochemical polymerization in the neutral (DCM/ACN (v/v = 1:1) with 0.1 mol L-1 Bu4NPF6) and acidic (boron trifluoride ether (BFEE)) system. Comparatively, P(BT-4EDOT) with a good 3D porous structure that fully utilizes its exposed active sites exhibited both good electrical properties and excellent stability, including 55% optical contrast in the visible region, within 1 s response time, 355 cm(2) C-1 coloration efficiency, 210 F g(-1) specific capacitance, and 92% capacitance retention after 2000 cycles. The P(BT-4EDOT)-based electrochromic-supercapacitor device (ESD) also exhibited good capacitive performance (66 F g(-1)) and excellent stability (85.26% after 1000 cycles). Excitingly, the energy storage level of ESD could be directly monitored through color changes. All of these results showed that the 3D network structure can dramatically improve the internal utilization of CPs and thus improve their stability. And the molecular expansion strategy will spark ideas for the construction of high-stable ESD based on CPs.