Morphological engineering of PTAm@CNTs cathode for high-rate potassium dual-ion battery

Redox-active polymers are regarded as one of the most promising electroactive materials for non-lithium electrochemical energy storage devices due to the inherent molecular flexibility that can tolerate the structure change during the charge/discharge process. Their diverse functional groups provide abundant active sites to accommodate large-sized electrolyte ions. In this work, for the first time, the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radical group, equipped at poly(TEMPO-acrylamide) (PTAm), is employed as an active cathode for potassium dual-ion batteries (KDIBs). Carbon nanotubes (CNTs) assist morphological engineering of the PTAm to create a conductive nanostructured composite, namely PTAm@CNTs. Systematic material characterizations and electrochemical evaluation suggest that the PTAm@CNTs nanocomposite possesses significant surface area and nanopores, enabling enhanced electronic and ionic conductivity. The PTAm@CNTs cathode reversibly stores hexafluorophosphate (PF₆⁻) anions in KDIBs, delivering high energy density, rate capability, and robust cycling stability. The fast reaction kinetics of nitroxide radicals (N–O^.), the redox-active groups on the PTAm, and their association with the PF₆⁻ anions contribute to the dual-ion storage. As a result, the PTAm@CNTs cathode delivers a high specific capacity of 108 mAh g⁻¹ at 2 A g⁻¹ (16.8C) over 300 cycles. The work suggests a promising pathway to design and synthesize functional organic electrode materials for potassium dual-ion batteries.