Facet-Engineered Zn Nanosheet Arrays for High-Energy-Density Fiber-Shaped Zn-Air Batteries

Fiber-shaped zinc-air batteries (FZABs) hold great promise for wearable energy storage owing to their intrinsic safety, mechanical flexibility, and high theoretical energy density, yet their practical energy density remains fundamentally constrained by the low utilization of Zn anodes, originating from restricted interfacial accessibility and sluggish reaction kinetics, which lead to incomplete Zn stripping and "dead Zn" accumulation. Here, we address this critical challenge by developing a facet-engineered hierarchical fiber-shaped Zn anode (HF-Zn), in which vertically aligned nanosheet arrays are integrated onto a zincophilic polydopamine (PDA)-modified carbon fiber scaffold. The PDA interfacial layer enables uniform Zn nucleation and homogenized current distribution, directing the growth of (101)-dominant Zn nanosheets with intrinsically fast and reversible stripping/plating kinetics. Coupled with a porous conductive framework that promotes electrolyte penetration and charge transport, this design fundamentally improves Zn utilization. As a result, the assembled FZAB achieves a high specific capacity of 620 mAh g_{total Zn} ^-1 (DOD ≈ 75%) and an energy density of 271 Wh kg_{total device} ^-1, together with stable cycling over 53 h, surpassing those of previously reported FZABs. This work establishes a generalizable strategy for regulating Zn deposition and unlocking high-energy-density wearable Zn-air batteries.