Aqueous Zn-ion batteries (AZIBs), being safe, inexpensive, and pollution-free, are a promising candidate for future large-scale sustainable energy storage. However, in a conventional AZIBs setup, the Zn metal anode suffers oxidative corrosion, side reactions with electrolytes, disordered dendrite growth during operation, and consequently low efficiency and short lifespan. In this work, we discover that purging CO2 gas into the electrolyte could address these issues by eliminating dissolved O2, inhibiting side reactions by buffering the local pH change, and preventing dendrite growth by inducing the in situ formation of a ZnCO3 solid electrolyte interphase layer. Moreover, the CO2-purged electrolyte could enable a highly reversible plating/stripping behavior with a high Coulombic efficiency of 99.97% and an ultralong lifespan of 32,000 cycles (1600 h) even under an ultrahigh current density of 40 mA cm-2. Consequently, the CO2-purged symmetrical cells deliver long cycling stability at a high depth of discharge of 57%, while the CO2-purged Zn/V2O5 full cells exhibit outstanding capacity retention of 66% after 1000 cycles at a high current density of 5 A g-1. Our strategy, the simple introduction of CO2 gas into the electrolyte, could effectively mediate the zinc anode's critical issues and provide a scalable and cost-effective pathway for the commercialization of AZIBs.
Keywords: CO2-purged electrolyte; Zn corrosion; aqueous Zn-ion batteries; dendrite-free anode; dissolved oxygen; solid interface layer.