The Mechanism of Zn Diffusion Through ZnO in Secondary Battery: A Combined Theoretical and Experimental Study

Zinc (Zn) deposition and dissolution are very important processes during the charge and discharge cycles of rechargeable Zn aqueous batteries (ZBs). During this process, an interfacial ZnO layer is formed on the surface of Zn electrode that can have profound effects on the formation and growth of Zn dendrites and ZB performance and stability. The present work seeks to understand the structure and stability of the ZnO interfacial layer and mechanisms of Zn diffusion through this layer. The density functional theory (DFT) calculations supported by the aberration-corrected scanning transmission electron microscopy (AC-STEM) are employed to understand the ZnO atomic structure and its chemo-mechanical properties. Owing to the polycrystalline nature of the ZnO layer, the Zn diffusion through the two subsystems, namely, ZnO grain and ZnO grain boundary (GB) are studied. The activation energy of Zn diffusion varies significantly depending upon the modeled structure and the number of Zn adatoms. The calculated elastic properties show the decrease of Young’s modulus with an increase of Zn adatoms. Our findings provide insights into developing mitigation strategies toward the suppression of Zn dendrites during electrodeposition.