Optimizing the Spin States of Mesoporous Co3O4 Nanorods through Vanadium Doping for Long-Lasting and Flexible Rechargeable Zn–Air Batteries

High-performance rechargeable Zn–air batteries with long-life stability are highly desirable for the power application in electric vehicles and portable electronics for their great balance in capacity and safety. The key component of the Zn–air batteries is the bifunctional oxygen electrocatalyst that requires high intrinsic reversibility and durability. Spinel Co3O4 emerges as a promising nonprecious-metal catalyst for oxygen catalysis but limited by the inefficient catalytic performance with an undesirable eg0 configuration of Co3+ ions at the octahedral sites. Herein, a mesoporous vanadium-doped Co3O4 (V–Co3O4) electrocatalyst is developed, with an optimized eg occupancy of 1.010. By optimizing the spin states of Co3O4 through V-doping, V–Co3O4 exhibits a great bifunctional property that even outperforms Pt–IrO2. As a demonstration, both a liquid-state rechargeable Zn–air battery and an all-solid-state flexible cable-type Zn–air battery are fabricated using the V–Co3O4 electrocatalysts, offering a promising power source for the next-generation electronics.