A zinc-air battery is a metal-air electrochemical cell in which a zinc anode is paired with a porous air electrode that reduces atmospheric oxygen, giving a theoretical energy density on the order of 1086 Wh kg^-1 and a nominal cell voltage near 1.65 V ^[1]. The cell is assembled in the discharged state and is normally operated with an alkaline aqueous electrolyte, so that discharge consumes zinc and oxygen and produces zincate species that precipitate as zinc oxide ^[2]. Two electrochemical steps limit performance: the oxygen reduction reaction on discharge and the oxygen evolution reaction on charge, both of which are slow and require bifunctional catalysts, so the same air electrode must catalyse both without being degraded by the high potentials reached during charging ^[2]. On the anode side, zinc dissolves and re-deposits unevenly during cycling, producing dendrites, shape change and passivation that shorten cycle life ^[3]. Electrically rechargeable systems, in which the air electrode operates in both directions, have been demonstrated, and alternative configurations separate the charge and discharge electrodes or replace the liquid electrolyte with a solid-state or gel membrane ^[4]. Measured round-trip efficiencies are typically 50–65% over tens to a few hundred cycles, and the values depend strongly on current density, depth of discharge and catalyst loading ^[4]. Energy densities reported for practical cells remain well below the theoretical figure because of the mass of the electrolyte, separator and current collectors ^[5].