Shape-Controlled Zn Nanosheet Electrodeposition Revealed by in Situ Liquid-Phase Transmission Electron Microscopy

Electrodeposition is ubiquitous in the anode of rechargeable metal batteries and is controlled by both ion concentration and applied potential. Today, metallic zinc (Zn) is considered to be an ideal anode material, and an in-depth understanding of the Zn deposition process helps to maximize its capacity. Here, a self-designed electrochemical transmission electron microscope liquid cell was used to visualize the electrodeposition of Zn at a nanoscale in the ZnSO4 electrolyte. Shape-controlled electrodeposition in a liquid cell was achieved, and in situ observation confirmed that Zn deposits tend to form a 2D hexagonal structure by epitaxial or stacking growth. Zn ion diffusion and thus induced immediate nucleation was captured. Microscopic inhomogeneity of the electrochemical reaction may be related to ion concentration difference or charge distribution. A growth exponent far beyond the reaction-limited three-dimensional (3D) growth mode indicates that the Zn adatom diffuses rapidly to the nucleation site at the surface. These results provide details for the Zn anode during plating and stripping at the nanoscale, which may guide future Zn-based battery design.