The key to improving the performance of Li-air batteries: recent progress and challenges of the catalysts.

Li-air batteries are considered to be one of the most promising energy storage devices due to their high energy density and large specific capacity. But the high overpotential, the sluggish oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) kinetics, and the poor cycling stability critically restrict their practical applications. To overcome these problems, various catalysts and electrolyte mediators have been used and studied. However, for practical application, these catalysts still have some challenges and scientific problems that need to be solved. Specifically, the performance of lithium-air batteries faces three major problems of capacity, overpotential, and cycle life that need to be solved. Solid-phase catalysts and liquid-phase redox mediators have their own advantages and disadvantages in the performance and reaction mechanism of lithium-air batteries. This review comprehensively analyzes and summarizes the catalytic materials and electrolyte additives of different systems and discusses in depth the corresponding reaction mechanism and performance (including technical characteristics and application difficulty). Finally, according to the characteristics of catalysts and practical application difficulties, the development direction of lithium-air batteries is proposed. Li-air batteries need to exploit the advantages of catalysts and redox mediators in terms of stability and overpotential to improve the electrochemical performance of the battery. In the future, anode protection and air purification systems will be combined to achieve large-scale, long-cycle applications of lithium-air batteries.