Synergistic boron-based nanocrystal and amorphous Ni–Fe–B catalyst for high-performance flexible zinc-air batteries

Abstract

Flexible zinc-air batteries (FZABs) are still limited by slow oxygen electrocatalysis and poor mechanical durability. In this work, we prepare a Ni–Fe–B catalyst with a nanocrystalline–amorphous composite structure through a two-step chemical reduction method. The amorphous Ni–B matrix stabilizes uniformly dispersed Fe nanocrystals, generating abundant unsaturated coordination sites and forming a mesoporous network (2–6 nm) that promotes the accessibility of active sites and facilitates mass transport. Boron-mediated electronic interaction between Ni and Fe modulates the surface electronic states, which lowers the interfacial charge-transfer resistance to 3–5 Ω cm² and improves the oxygen reduction reaction (ORR) activity, yielding a half-wave potential of 0.86 V vs. RHE, comparable to that of commercial Pt/C. When applied as the cathode in FZABs, this catalyst exhibits a peak power density of 224.9 mW cm⁻² and remarkable cycling stability, with a voltage decay rate of only 0.05 mV h⁻¹ over 100 h. The assembled battery also retains stable output under repeated bending between 0° and 180°, showing voltage fluctuations within 50 mV, thereby confirming excellent mechanical tolerance. This study demonstrates for the first time the use of bimetallic borides in FZABs and proposes a material design strategy that combines an amorphous host, a mesoporous structure, and bimetallic synergy to achieve high-performance, deformable zinc-air battery systems.