Dendrite‐Free Zn Anode Modified with Prussian Blue Analog for Ultra Long‐Life Zn‐Ion Capacitors

Abstract The main challenge for aqueous zinc‐ion capacitors is the low stability of zinc anode. In this study, a Prussian blue analog (PBA) has been coated on the surface of zinc foil to create an inorganic protective layer. This layer features a three‐dimensional open microporous structure, which not only endows it with excellent pseudocapacitive properties but also serves as an effective barrier against dendrite growth. The presence of PBA coating can increase the nucleation point of zinc ions and provide a low‐energy barrier for the rapid migration of zinc ions. Hence, the PBA@Zn ||PBA@Zn symmetric cell exhibits exceptional cycling stability, enduring over 1400 h of operation at a current density of 1 mA cm −2 and a capacity of 1 mAh cm −2 . The PBA@Zn||AC capacitor demonstrated a discharge capacity of 46.23 mAh g −1 after 10 000 cycles at a current density of 1 A g −1 , with a capacity retention of 92.41%, whereas the discharge capacity of Zn||AC capacitor is only 16.02 mAh g −1 , with a capacity retention of 23.13%. The PBA@Zn||AC capacitor exhibited remarkable endurance and stability, retaining a substantial discharge capacity of 32.7 mAh g −1 after 10 000 cycles at 10 A g −1 . Density Functional Theory (DFT) calculations also show that PBA has a strong interaction with Zn and exhibits superior zincophilic ability. This study reports industrially applicable low‐cost Prussian blue analogs as artificial interfacial protective layers for improving the cycling stability of zinc anode with a low‐energy barrier for rapid migration of zinc ions especially at high current density.