Solid‐state Li–air batteries: Fundamentals, challenges, and strategies

The landmark Net Zero Emissions by 2050 Scenario requires the revolution of today's energy system for realizing nonenergy‐related global economy. Advanced batteries with high energy density and safety are expected to realize the shift of end‐use sectors toward renewable and clean sources of electricity. Present Li‐ion technologies have dominated the modern energy market but face with looming challenges of limited theoretical specific capacity and high cost. Li–air(O2) battery, characterized by energy‐rich redox chemistry of Li stripping/plating and oxygen conversion, emerges as a promising “beyond Li‐ion” strategy. In view of the superior stability and inherent safety, a solid‐state Li–air battery is regarded as a more practical choice compared to the liquid‐state counterpart. However, there remain many challenges that retard the development of solid‐state Li–air batteries. In this review, we provide an in‐depth understanding of fundamental science from both thermodynamics and kinetics of solid‐state Li–air batteries and give a comprehensive assessment of the main challenges. The discussion of effective strategies along with authoritative demonstrations for achieving high‐performance solid‐state Li–air batteries is presented, including the improvement of cathode kinetics and durability, solid electrolyte design, Li anode optimization and protection, as well as interfacial engineering.