Bio-inspired interface engineering of Ag₂O rooted on Au, Ni-modified filter paper for highly robust Zn–Ag₂O batteries

Flexible zinc–silver oxide (Zn–Ag₂O) batteries have attracted extensive attention for comfortable wearable electronics owing to their stable output voltage, inherent safety, and environmental benignity. However, they suffer from inferior specific capacity and poor mechanical stability due to the low utilization of Ag₂O cathodic material and weak interfacial adhesion of active material/substrate. Inspired by the nature of the tree root system, we develop an interface-engineered cathode, in which Ag₂O nanoparticles are rooted on an Au, Ni co-modified filter paper substrate (CFP) through an electroless plating followed by an in situ electrochemical oxidation. The staggered-stacked Ag₂O nanoparticles provide abundant electrochemically active sites and convenient ion diffusion paths, and the unique biological tree-root-like structure of the electrode material creates robust interlocking interfaces. A quasi-solid-state Zn–Ag₂O battery assembled with a tree-root-like Ag₂O/CFP cathode delivers a high areal specific capacity of 1.08 mAh cm⁻² and long-term cycling durability with a capacity retention of 77.3% even after 100 cycles. Moreover, the device presents good mechanical stability under various flexural deformations, including bending, folding, and twisting, and exhibits minimal capacity changes after 1000 bending cycles. These findings suggest that the bio-inspired interface-engineered electrode structure is an efficient approach for developing flexible batteries with excellent electrochemical performance and mechanical properties.