Dendrite suppression by scalable acid treatment of zinc metal anodes for aqueous zinc-ion batteries

Aqueous zinc-ion batteries (ZIBs) are desirable energy storage devices because of their low cost, safety, abundant Zn reserve, and environmental friendliness. However, Zn dendrite growth remains the main reason limiting the life span of ZIBs. Herein, a quick, simple, and scalable hydrochloric acid (HCl) treatment is designed to suppress the formation of Zn dendrites on Zn metal anodes. Scanning electron microscopy and atomic force microscopy reveal that the initial surface structure of the Zn metal anode determines the subsequent plating/stripping behavior. By soaking the Zn foil in HCl for 5 s (HCl-5 Zn), microgrooves are formed on the surface, but longer immersion destroys the special structure. This special microgroove structure homogenizes the electric field on the surface of the Zn plate, giving rise to more uniform Zn deposition. Compared to the pristine and over-processed Zn electrodes, HCl-5 Zn shows less Zn nucleation and smaller plating overpotentials resulting in suppression of Zn dendrites. Furthermore, HCl-5 Zn tends to deposit on the (002) plane of Zn to improve the cycling stability of the cell compared to the (001) plane of Zn. The symmetrical cell composed of the HCl-5 Zn anode exhibits small voltage hysteresis and excellent cycling stability. The cycling characteristics and low voltage polarization are improved, as demonstrated by the assembled symmetrical and full batteries comprising the K_0.5V₂O₅@CC cathode. Moreover, the strategy is suitable for flexible batteries with hydrogel as the electrolyte. The results reveal a simple strategy to minimize dendrite formation and provide insights into the commercial development of ZIBs.