Constructing a stable cobalt-nitrogen-carbon air cathode from coordinatively unsaturated zeolitic-imidazole frameworks for rechargeable zinc-air batteries

Zeolitic-imidazole frameworks (ZIFs) derivations have widely emerged as an efficient air cathode of zinc-air batteries (ZABs) due to excellent bifunctional oxygen electrocatalysis performance. However, they are not stable enough for long-term operation of rechargeable ZABs because of weak association with current collector, especially under bending conditions for flexible ZAB devices. Here, we show that by purposely designing coordinatively unsaturated ZIFs via a facile morphology regulation, which can be chemically linked on acid-treated carbon cloth, a stable Co-N-C air cathode is therefore derived where Co nanoparticles (NPs) are uniformly confined within the Co-N-C matrix on carbon cloth (Co/Co-N-C/CC). Specifically, when without being stabilized from carbon cloth, the pyrolysis of ZIFs with different unsaturated coordination levels has a negligible impact on the bifunctional oxygen-catalyzed performance. The optimal Co/Co-N-C/CC catalyst assembled ZAB possesses a large open circuit voltage of 1.415 V and a high peak power density of 163 mW·cm⁻² as well as excellent cycling durability upon 630 discharge–charge cycles with 61% voltage efficiency remained, largely exceeding those of a benchmark Pt/C-IrO₂ catalyst assembled ZAB. The synergy between Co NPs and active Co-N-C sites via electronic interaction induces the outstanding bifunctional oxygen-catalyzed activity and cathode performance. The present work highlights the importance of unsaturated coordination structures in ZIFs precursors for the performance of derived nanostructures in integrated electrodes.