Advances in bifunctional electrocatalysts towards high-performing Li-air batteries.

Abstract

The development of high-performance Li-air batteries (LABs) is an important quest for effectively utilizing high-energy density electric systems. One possible way to achieve this goal is by introducing novel bifunctional electrocatalysts at the battery cathode, enhancing the cycle life and the discharge capacity of the LABs by facilitating fast oxygen reaction kinetics. Understanding bifunctional catalysts' function and evolution is essential to developing a better-functioning LAB. In this review, we discuss the fundamentals, mechanisms, and key concepts related to LAB technology. We then provide critical discussions on recent advances in bifunctional catalysts used in LAB cathodes through material characterization, electrochemical analysis, battery performance, in-situ and ex-situ discharge product analysis, DFT calculations, and theoretical concepts to provide the most up-to-date, thorough, and broader discussion on the subject. These include the general and modified catalysts of carbon nanostructures, noble metals, transition metal oxides, nitrides, sulfides, and phosphides. Furthermore, special attention is given to techniques designed to enhance the catalytic activity of LABs through the modulation of electronic structures. Various facet engineering and eg electron engineering approaches are explored, including heteroatom doping, alloying, hybridization, stoichiometric optimization, and selective facet growth. Finally, we suggest potential prospective pathways for future research.