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

Abstract

Flexible zinc-air batteries (FZABs) are limited by sluggish oxygen electrocatalysis and insufficient mechanical durability. Here, we report a Ni-Fe-B catalyst with a nanocrystalline-amorphous composite architecture synthesized via a two-step chemical reduction. The amorphous Ni-B matrix accommodates uniformly dispersed Fe nanocrystals, providing abundant unsaturated sites and constructing a mesoporous framework that enhances active-site exposure and facilitates mass transport. Boronmediated electronic coupling between Ni and Fe optimizes surface valence states and decreases interfacial charge-transfer resistance (85 Ω•cm2), thereby accelerating ORR kinetics. When employed as the cathode in FZABs, the catalyst achieves a peak power density of 224.9 mW cm⁻2 and remarkable durability, with a voltage decay of only 0.05 mV h⁻1 over 100 h. The device maintains stable output under repeated 0°-180° bending, with voltage fluctuations ≤ 50 mV, demonstrating excellent mechanical tolerance. To the best of our knowledge, this is the first report of bimetallic borides applied in FZABs. The synergistic integration of the amorphous boride host, mesoporous architecture, and bimetallic electronic modulation provides a general strategy for developing high-activity, long-life, and deformable zinc-air batteries as well as related boridebased electrocatalysts.