Current-Controlled Zinc Electrodeposition Morphology in Ionic Liquid Electrolytes Using Microelectrode Arrays.

Understanding and controlling the microstructure of zinc (Zn) metal electrodeposits are critical for advancing the next generation of rechargeable Zn batteries. In this study, we develop microelectrode arrays to systematically investigate the relationship among current density, morphology, and Coulombic efficiency (CE) during Zn electrodeposition from an ionic liquid electrolyte. By independently controlling the current density or voltage on each microelectrode, we identify three key deposition regimes. At lower current densities, Zn electrodeposition forms soft, loosely packed mossy structures with moderate CE between 80 and 90%. Increased current densities yield more compact morphologies, representing a transition zone where growth becomes more uniform and achieves 98-99% CE. Under constant voltage deposition, the Zn salt in the electrolyte near the microelectrode depletes, leading to sharp, filament-like dendrites with CE below 50%. These findings demonstrate the ability to control Zn electrodeposition morphology in nonaqueous electrolytes while highlighting the diffusion-limited kinetics that dictate deposition behavior and reversibility. The methodology provides mechanistic insights and offers viable strategies for designing dendrite-free Zn anodes for stable and efficient ZIBs.