High‐Energy‐Density Solid‐State Metal–Air Batteries: Progress, Challenges, and Perspectives

Abstract Next‐generation batteries have long been considered a transition to more sustainable storage technologies. Among them, metal–air batteries (MABs) with low cost, high safety, and environmental friendliness have shown great potential for future large‐scale applications. Motivated by the desirable characteristics, significant progress is made in suppressing serious parasitic reactions, improving electrochemical performance, and increasing the energy density in MABs. Compared to the widely reported liquid electrolyte strategy, solid‐state electrolytes (SSEs) can thoroughly solve the volatilization challenges of liquid electrolytes and protect the oxygen electrodes without the formation of diffusion‐blocking oxide phases. Notably, SSEs for MABs are still in their infancy, and many thorny challenges still need to be solved. In this review, the main electrochemical mechanism, key challenges, and some important progress are sorted out for solid‐state MABs, such as lithium–air, zinc–air, aluminum–air, and magnesium–air batteries. Besides their fundamental significance, these configurations are further compared in terms of energy density, cost, carbon footprint, energy consumption, rate performance, cycle performance, safety, and air stability of prevailing electrolytes.