Molecular Bonding Engineering Enables Ultra‐Stable Electrochromic Energy Storage in Flexible PEDOT Devices

Abstract Wearable electronics require materials that can withstand mechanical deformation while retaining electrochemical and optoelectronic functionality. Conducting polymers (CPs) are attractive candidates due to their inherent flexibility and electronic conductivity. However, their practical application is often limited by poor long‐term stability and deteriorated performance, particularly under thermal or mechanical stress, owing to structural degradation and overoxidation at high potentials. Herein, a dual‐strategy molecular design is adopted to intrinsically stabilize poly(3,4‐ethylenedioxythiophene) (PEDOT) by combining deuterium substitution with Lewis acid‐assisted polymerization, which suppresses backbone vibrational energy and mitigates over‐oxidative degradation during redox cycling. The resulting deuterated PEDOT film demonstrates exceptional multifunctional performance, including <5% capacitance loss after 300 000 cycles, a high electrochromic contrast of 40.9% at 700 nm, and a specific capacitance of 317 F g −1 at 1 A g −1 . PEDOT‐D ‐based wearable electrochromic‐supercapacitor devices subsequently exhibit 14.3% transmittance at 550 nm, a specific capacitance of 39.7 F g −1 at 1 A g −1 , robust stability, and reliable operation from −25 to 50 °C. This work establishes a structurally grounded molecular strategy for advancing the durability of CPs, providing a rational design for next‐generation flexible energy systems that are mechanically robust, thermally adaptive, and optically responsive.