Unlocking the Role of Indium Ions to Stabilize Zinc Negative Electrodes in Highly Acidic Electrolytes for High-Voltage Aqueous Zn Batteries

Abstract

Operating Zn||MnO2 and Zn||PbO2 batteries in the highly acidic electrolytes enables much higher output voltages (up to ca. 2 V and 2.5 V, respectively) than the near-neutral systems, making them attractive for high-energy aqueous zinc-ion batteries. However, Zn electrodes suffer from the severe hydrogen evolution reaction (HER) and self-corrosion in acidic media, limiting the cycling stability. Here, we introduce the indium ion to stabilize the Zn electrodes in highly acidic electrolytes. During Zn plating, indium accumulates at the electrode surface to form a protective In–Zn alloy, which suppresses the HER via weakening the hydrated proton adsorption and promotes preferential growth of the Zn (002) facet, enabling highly reversible Zn plating/stripping. Moreover, the replacement deposition during rest can generate an indium-containing protection layer that mitigates the Zn self-corrosion. Consequently, Zn||Zn symmetric cells exhibit an extended cycling life approaching 3000 h (at pH 1.13), while acidic Zn||MnO2 coin cells deliver a record-high discharge plateau of ~1.95 V with stable cycling over 1100 cycles. Notably, the effectiveness of In3+ additives is validated in highly acidic Zn||PbO2 batteries, demonstrating the general applicability. This work provides a comprehensive understanding on the In3+-regulated interfacial chemistry for high-voltage Zn batteries in highly acidic electrolyte.