Engineering of high entropy alloys for high-performance Zn–air batteries: Design, progress, and perspectives

Zn-air batteries (ZABs) have attracted much attention due to their high theoretical energy density (1086 Wh·kg^-1), high safety, low cost. However, the sluggish kinetics of the air-cathode reaction and its unsatisfactory long-term durability limit the large-scale application of ZABs. Therefore, exploring novel and efficient bifunctional catalysts to promote the kinetics and cycling stability of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is a straightforward and effective strategy for the construction of high-performance ZABs. High entropy alloys (HEAs) as a new type of emerging catalysts have garnered extensive attention owing to their unique physical-chemical properties. Despite some progress made, the design, fabrication and engineering of HEAs as bifunctional catalysts for ORR and OER as well as their applications in ZABs are still in an early stage. Therefore, it is vital to capture these latest research works and developments, which are not only instructive for researchers in this burgeoning field, but also crucial for the future synthesis and applications of HEAs. In view of this, this review timely summarizes the research progress and breakthroughs in the synthesis of HEAs and their applications in ZABs, focusing on different surface and structural engineering strategies, reaction mechanism studies and possible active sites identification as well as perspectives on future research directions.