Revitalizing Prussian Blue Cathodes: Dynamic Self‐Healing in Dilute Aqueous Electrolytes for Ultra‐Stable Potassium‐Ion Batteries

The practical application of aqueous potassium‐ion batteries is critically hindered by the structural instability of Prussian blue analogue (PBA) cathodes. Here, an innovative and economically viable dynamic self‐healing strategy is presented to overcome this challenge. By introducing trace amounts of [Fe(CN) 6 ] 3− as a functional additive into a conventional dilute aqueous electrolyte, dissolved iron species are effectively captured and reincorporated into the potassium iron hexacyanoferrate (KFeHCF) cathode lattice, dynamically repairing structural vacancies during cycling. This simple approach endows the KFeHCF cathode with unprecedented electrochemical performance, including a high specific capacity of 197 mAh g −1 at 0.1 A g −1 and near‐perfect capacity retention over 7000 cycles at 1.5 A g −1 . A full potassium‐ion battery, pairing the self‐healed cathode with a perylenetetracarboxylic dianhydride (PNTCDA) anode, demonstrates an impressive energy density of 52 Wh kg −1 and retains 90% of its capacity after 3000 cycles. This work introduces a transformative pathway to stabilize PBA cathodes without resorting to complex modifications or costly high‐concentration electrolytes, significantly advancing the development of ultra‐stable, high‐performance aqueous energy storage systems.