Defect‐Engineered Carbon Fabric and Dual‐Additive Electrolyte Unlock Ultra‐Durable Flexible Iron‐Ion Hybrid Supercapacitors

Abstract The development of flexible energy storage systems combining high energy/power density and cost‐effectiveness remains a critical challenge. Herein, a groundbreaking flexible iron‐ion hybrid supercapacitor (IHSC) is proposed, featuring a carbon fabric (CF)‐based cathode and an iron‐anode composite, synergistically optimized through structural engineering and electrolyte stabilization. The cathode, derived from hydrothermally etched and annealed CF (AHCF), exhibits enriched nanopores (876.64 m 2 g −1 ) and defects, enabling rapid SO 4 2− ion transport and storage. The anode, AHCF‐Fe, mitigates volume expansion via robust Fe deposition on defect‐rich carbon substrates. A dual‐additive electrolyte (EDTA and NaBO 2 ) stabilizes Fe 2 ⁺ ions, optimizes pH (3.5), and suppresses corrosion, thereby achieving unparalleled electrochemical performance, with a peak energy density of 1.31 mWh cm −2 and a power density of 30.32 mW cm −2 . Notably, the IHSC exhibits a capacity retention of 94.54% capacity after 20 000 cycles at 20 mA cm −2 . Molecular dynamics (MD) and density functional theory (DFT) calculations confirm the ion diffusion kinetics and the mechanism of enhanced interfacial interactions. Demonstrating exceptional flexibility, the quasi‐solid‐state IHSC operates reliably under bending, sewing, and cutting, powering wearable electronics. This work pioneers a cost‐effective, high‐performance energy storage paradigm that combines battery‐level energy density with power delivery like supercapacitors, thus advancing flexible and sustainable electronics.