  Metal-air batteries are among the most promising next-generation energy
storage devices. Relying on abundant materials and offering high energy
densities, potential applications lie in the fields of electro-mobility,
portable electronics, and stationary grid applications. Now, research on
secondary zinc-air batteries is revived, which are commercialized as primary
hearing aid batteries. One of the main obstacles for making zinc-air batteries
rechargeable is their poor lifetime due to the degradation of alkaline
electrolyte in contact with atmospheric carbon dioxide. In this article, we
present a continuum theory of a commercial Varta PowerOne button cell. Our
model contains dissolution of zinc and nucleation and growth of zinc oxide in
the anode, thermodynamically consistent electrolyte transport in porous media,
and multi-phase coexistance in the gas diffusion electrode. We perform
electrochemical measurements and validate our model. Excellent agreement
between theory and experiment is found and novel insights into the role of zinc
oxide nucleation and growth and carbon dioxide dissolution for discharge and
lifetime is presented. We demonstrate the implications of our work for the
development of rechargeable zinc-air batteries.
