Organic small-molecule cathodes for aqueous zinc-ion batteries: design strategy, application and mechanism

Owing to its high safety, environmental friendliness and low cost, aqueous zinc-ion batteries (AZIBs) have been considered an effective alternative to other energy-storage batteries. Among the adopted cathode materials for AZIBs, organic small molecules (OSMs) show potential due to their renewable resources, diverse structures, easy preparation and fast kinetics. In this review, recent progress on OSMs as cathodes for AZIBs has been summarized, and various types of OSMs (including quinone-based, amide-based, nitrogen-containing, and related composites) have been discussed and compared in detail. The energy storage mechanism for these OSM cathodes and the relationship between their structure and performance have been deeply explored. Furthermore, the key problems of OSM cathodes in practical applications and the corresponding strategies for improving their application performance, in terms of molecular structure design and composite material modification, have also been discussed and illuminated. Finally, the future development and prospect of OSM cathodes for AZIBs are envisioned, aiming to provide a reference for promoting further research and application.