In Situ Anchoring Co-N-C Nanoparticles on Co4 N 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 Co4 N 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 Co4 N, 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.