Synergistic Co/Fe/Zn–N _<i>x</i> Active Sites on Microporous Carbon Nanotubes for High Power-Density Flexible Aqueous Magnesium–Air Batteries

Flexible magnesium-air batteries employing neutral electrolytes offer attractive energy-storage solutions for wearable electronics due to their favorable biocompatibility and competitive energy density. However, challenges (inadequate cyclic stability, sluggish oxygen reduction, and limited choice in compatible electrolytes and efficient cathode electrocatalysts) hinder their development. Herein, we demonstrate an advanced aqueous Mg-air battery featuring a novel cathode architecture: zinc-pored cobalt-iron (CoFe) alloy confined within nitrogen-doped carbon nanotubes, where Zn-induced micropores and N_<i>x</i>-coordinated Co/Fe/Zn enhance reversible oxygen reaction and accelerate discharge-product decomposition. With a poly(vinyl alcohol) (PVA)-NaCl hydrogel electrolyte, the resulting flexible Mg-air batteries achieved robust flexibility, stable open-circuit potential (1.68 V), high power density (21 mW cm^-2), and excellent durability (9 h). Practical application was verified through powering a rollable display wristband. This work establishes a viable pathway with interfacial engineering to realize high power-density aqueous Mg-air batteries in flexible electronics and deformable energy devices.