A Prussian‐Blue Bifunctional Interface Membrane for Enhanced Flexible Al–Air Batteries

Abstract Flexible Al–air batteries have attracted widespread attention in the field of wearable power due to the high theoretical energy density of Al metal. However, the efficiency degradation and anodizing retardation caused by Al parasitic corrosion severely limit the performance breakthrough of the batteries. Herein, a Prussian‐blue bifunctional interface membrane is proposed to improving the discharge performance of hydrogel‐based Al–air battery. When a rational 12 mg·cm⁻² membrane is loaded, the effect of anticorrosion and activation is optimal thanks to the formation of a stable and breathable interface. The results demonstrate that a flexible Al–air battery using the membrane can output a high power density of 65.76 mW·cm⁻². Besides, the battery can achieve a high capacity of 2377.43 mAh·g⁻¹, anode efficiency of 79.78%, and energy density of 3176.39 Wh·kg⁻¹ at 10 mA·cm⁻². Density functional theory calculations uncover the anticorrosion‐activation mechanism that Fe³⁺ with a large number of empty orbitals can accelerate electrons transfer, and nucleophilic reactant [Fe^II(CN)₆]⁴⁻ promotes the Al³⁺ diffusion. These findings are beneficial to the inhibition of interfacial parasitic corrosion and weakening of discharge hysteresis for flexible Al–air batteries.