Untying the Gordian knots of air-rechargeable aqueous Zn-based batteries based on an effective dead-zinc activation method

Abstract

Air-rechargeable aqueous Zn-based batteries (ARAZBBs) possess their typical air self-charge advantage. Unfortunately, their further development is beset by two major challenges: an ultrashort air-charge lifespan due to the formation of ‘dead Zn’ (basic zinc salt, BZS) deposited on the cathode surface and the severe corrosion of Zn anode due to continuous consumption of Zn during the air-charge process. Aiming at untying these Gordian knots, herein, an effective dead-zinc activation method of in-situ electrochemical conversion successfully activates ‘dead zinc’ in BZS and repairs the Zn anode simultaneously. Specifically, the specific discharge capacity of as-prepared nitrogen-doped hierarchically porous carbon (NHPC) declines rapidly from 132.4 to 36.8 mAh g⁻¹ at 0.2 A g⁻¹ after only the 5th air-charge due to a large amount of dead zinc formation. To recover these failed NHPC electrodes, we skillfully draw support from in-situ electrochemical conversion to successfully eliminate BZS on the NHPC during the galvanostatic charging process. More importantly, the method also recovers Zn resources from ‘dead zinc’ to well repair Zn anode, providing a viable solution to address the issue of continuous consumption of Zn. As a result, the air-rechargeable specific capacity of NHPC has been significantly improved from 36.8 to 118.9 mAh g⁻¹ at 0.2 A g⁻¹ by using this effective dead-zinc activation method. Meanwhile, related mechanisms to charge-storage, air-charge, and in-situ electrochemical conversion are clearly revealed by a series of in-/ex-situ tests. This work lays the foundation for the wider practical application of ARAZBBs.