In Situ Anchoring Co–N–C Nanoparticles on Co₄N Nanosheets toward Ultrastable Flexible Self-Supported Bifunctional Oxygen Electrocatalyst Enables Recyclable Zn–Air Batteries Over 10 000 Cycles and Fast Charging

Zn–air batteries (ZABs) are very promising for flexible energy storage, but their application is limited to the primary battery. Developing an efficient and non-noble metal cathode toward oxygen reduction/evolution reactions (ORR/OER) is of great significance for the commercial application of rechargeable ZABs. Herein, a flexible self-supported integrated bifunctional cathode is presented in which the Co–N–C nanoparticles are in situ anchored on Co₄N nanosheets via a facile and scalable strategy. Benefiting from integrated 3D architecture with adequate active sites, porous structure, high conductivity originating from the metal substrate, and the synergistic effects of Co–N–C and Co₄N, the cathode exhibits excellent bifunctional activity (low overpotential of 275 mV at 10 mA cm⁻² for OER, high half-wave potential of 0.833 V for ORR), and ultralong durability for ORR/OER in the alkaline medium. Impressively, this cathode enables the recyclable aqueous ZABs a record overall lifespan over 10 000 cycles at 20 mA cm⁻², and a superior fast-charging feature at an ultrahigh charging current density of 100 mA cm⁻². Furthermore, such a flexible integrated cathode can be directly used as a self-supported cathode for flexible solid-state ZABs, with excellent reversibility for 300 cycles, demonstrating its feasibility for practical application.