Zn Anode Structural Evolution in Aqueous and DES Electrolytes: A Comparative SEM and AFM Study

After 20 stripping/plating cycles at 1mA cm−2, the Zn//Zn half-cells utilizing aqueous solution and DES electrolyte were disassembled to investigate the structural evolution of the Zn anode using SEM and AFM. The observation results revealed that the surface morphology of the zinc metal in the aqueous solution was uneven, featuring zinc protrusions (Fig 4e) penetrating the glass fiber separator. Furthermore, the XRD spectrum (Fig) exhibited a significant presence of insulating by-products, such as Zn(OH)2, ZnO, and Zn5(OH)8Cl2·xH2O.

Conversely, the zinc metal anode in the DES-3 electrolyte showcased a uniform and dense deposition morphology, with minimal by-products detected in the XRD. AFM also indicated improved surface smoothness of the zinc anode in the DES-3 deep eutectic electrolyte, along with a considerably reduced overall thickness in comparison to the aqueous electrolyte.

Additionally, comparable phenomena were evident in both SEM and corresponding AFM images under the operating condition of 60℃, signifying severe corrosion and dendritic overgrowth of the zinc anode in the aqueous electrolyte, leading to a highly rough surface. However, the utilization of the DES-3 electrolyte ameliorated the roughness and unevenness of the zinc anode, exhibiting only a minor increment in comparison to the room temperature condition.