Insight into the corrosion microcell and passivation mechanisms of a Zn anode for aqueous zinc-ion batteries

Abstract

Zinc anodes suffer from severe corrosion together with uncontrolled passivation in aqueous electrolytes, which could be aggregated during cycling of aqueous zinc-ion batteries (AZIBs). Unfortunately, the intrinsic corrosion mechanism under an electric field and its correlation with the passivation reaction remain unclear. This work revealed the spontaneous microcell corrosion mechanism of a Zn anode in a static ZnSO₄ solution together with Zn dissolution and oxygen reduction via localized electrochemical analysis techniques (LEATs). It is found that the electric field could promote Zn corrosion, primarily attributed to the intensified stripping and plating heterogeneity. Synchronously, it is feasible for the high electrical field strength to trigger the heterogeneous passivation layer along with uneven Zn-ion deposition. To mitigate the self-corrosion of Zn efficiently, a zincophilic “corrosion-retarding” maskant was constructed at the Zn/ZnSO₄ interface via the incorporation of (1-(3-sulphonatopropyl)pyridinium) (SPP). A Zn//Zn symmetrical cell with SPP sustains a long-term cycling of 1300 h under a high areal capacity of 20 mA h cm⁻². Interestingly, Zn–I₂ full cells with ZnSO₄-SPP electrolyte could deliver a capacity of 138.9 mA h g⁻¹ at 5 A g⁻¹ after 20 000 cycles. This work provides a microscopic understanding of self-corrosion and passivation behavior of a Zn anode for rechargeable AZIBs.