Constructing the Triple-Phase Boundaries of Integrated Air Electrodes for High-Performance Zn-Air Batteries

Rechargeable zinc (Zn)-air batteries receive research interest due to the high theoretical energy density, intrinsic safety, and excellent market competition. The design of the triple-phase (solid/liquid/gas) boundaries of the air electrode is the key to excellent performance. Although integrated air electrodes ensure the large active sites, rapid electron and species transport, and good stability during the long-term operation, the massive agglomeration of hydrophobic binder always leads to the reduction of triple-phase boundaries using conventional fabrication strategies. To address this issue, a novel strategy for constructing the triple-phase boundaries of an integrated Co3O4 electrode is proposed through hydrothermal treatment under a high temperature. The ultrasmall hydrophobic particles distribute extremely uniformly in Co3O4 nanowires, which do not cover the electrode surface and create good gas-phase boundaries, leading to a high-performance Zn-air battery with a high discharge voltage of 1.13 V and a low charge voltage of 2.06 V at even 10 mA cm(-2), a high peak power density of 51.7 mW cm(-2), and a small voltage gap increment of only 86 mV after 1000 cycles. This strategy greatly enhances the performance and durability of integrated air electrodes, raising the attention to boundary design for other electrochemical energy conversion and storage devices.