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 Co 3 O 4 emerges as a promising nonprecious-metal catalyst for oxygen catalysis but limited by the inefficient catalytic performance with an undesirable e g 0 configuration of Co 3+ ions at the octahedral sites. Herein, a mesoporous vanadium-doped Co 3 O 4 (V–Co 3 O 4 ) electrocatalyst is developed, with an optimized e g occupancy of 1.010. By optimizing the spin states of Co 3 O 4 through V-doping, V–Co 3 O 4 exhibits a great bifunctional property that even outperforms Pt–IrO 2 . 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–Co 3 O 4 electrocatalysts, offering a promising power source for the next-generation electronics.