Self-Activated Formation of Hierarchical Co3O4 Nanoflakes with High Valence-State Conversion Capability for Ultrahigh-Capacity Zn-Co Batteries

Cobalt-based materials are attracting increasing interest in alkaline Zn batteries due to the high theoretical capacity. However, the practical utilization is restricted by the poor microstructure and insufficient valence-state conversion. Herein, a self-activated formation of hierarchical Co3O4 nanoflakes with high valence-state conversion capability is designed. This electrode not only exhibits the optimized microstructure with large reaction surfaces, but also shows excellent valence-state conversion capability. Consequently, this battery delivers an ultrahigh capacity of 481.4 mAh g(-1) and an energy density of 818.3 Wh kg(-1) based on the active material, which shines among reported Co-based materials. Besides, the capacity can retain 41.9% with even 20x current density increases, and it can operate with a capacity decay of 20% after the 1000th cycle. This strategy greatly enhances the performance and durability of integrated air electrodes, raising the attention of boundary design for other electrochemical energy conversion and storage devices.

Automated summary

Cobalt-based materials are of interest for alkaline Zn batteries due to their high theoretical capacity, but face challenges in cyclic stability and capacity retention. By designing hierarchical Co3O4 nanoflakes with high valence-state conversion capability, the electrode demonstrated improved capacity and energy density, enhancing battery performance and durability.