Wide Potential Window Supercapacitors Using Open‐Shell Donor–Acceptor Conjugated Polymers with Stable N‐Doped States

Abstract Supercapacitors have emerged as an important energy storage technology offering rapid power delivery, fast charging, and long cycle lifetimes. While extending the operational voltage is improving the overall energy and power densities, progress remains hindered by a lack of stable n‐type redox‐active materials. Here, a new Faradaic electrode material comprised of a narrow bandgap donor−acceptor conjugated polymer is demonstrated, which exhibits an open‐shell ground state, intrinsic electrical conductivity, and enhanced charge delocalization in the reduced state. These attributes afford very stable anodes with a coulombic efficiency of 99.6% and that retain 90% capacitance after 2000 charge–discharge cycles, exceeding other n‐dopable organic materials. Redox cycling processes are monitored in situ by optoelectronic measurements to separate chemical versus physical degradation mechanisms. Asymmetric supercapacitors fabricated using this polymer with p‐type PEDOT:PSS operate within a 3 V potential window, with a best‐in‐class energy density of 30.4 Wh kg⁻¹ at a 1 A g⁻¹ discharge rate, a power density of 14.4 kW kg⁻¹ at a 10 A g⁻¹ discharge rate, and a long cycle life critical to energy storage and management. This work demonstrates the application of a new class of stable and tunable redox‐active material for sustainable energy technologies.