High‐Performance Aqueous Supercapacitors Based on a Self‐Doped n‐Type Conducting Polymer

Abstract Environmentally‐benign materials play a pivotal role in advancing the scalability of energy storage devices. In particular, conjugated polymers constitute a potentially greener alternative to inorganic‐ and carbon‐based materials. One challenge to wider implementation is the scarcity of n‐doped conducting polymers to achieve full cells with high‐rate performance. Herein, this work demonstrates the use of a self‐doped n‐doped conjugated polymer, namely poly(benzodifurandione) (PBDF), for fabricating aqueous supercapacitors. PBDF demonstrates a specific capacitance of 202 ± 3 F g⁻¹, retaining 81% of the initial performance over 5000 cycles at 10 A g⁻¹ in 2 m NaCl_(aq). PBDF demonstrates rate performances of up to 100 and 50 A g⁻¹ at 1 and 2 mg cm⁻², respectively. Electrochemical impedance analysis reveals a surface‐mediated charge storage mechanism. Improvements can be achieved by adding reduced graphene oxide (rGO), thereby obtaining a specific capacitance of 288 ± 8 F g⁻¹ and high‐rate operation (270 A g⁻¹). The performance of PBDF is examined in symmetric and asymmetric membrane‐less cells, demonstrating high‐rate performance, while retaining 83% of the initial capacitance after 100 000 cycles at 10 A g⁻¹. PBDF thus offers new prospects for energy storage applications, showcasing both desirable performance and stability without the need for additives or binders and relying on environmentally friendly solutions.