Insights into the Geometric Properties and Electrochemical Behavior of Printable Zinc Powder Anodes

Zinc powder anodes offer enhanced flexibility and processing capabilities compared to traditional zinc foil anodes, making them ideal for smart wearable devices. However, their significantly increased surface area leads to severe side reactions, such as hydrogen evolution and corrosion, which cause rapid capacity decay. While previous studies have focused on surface modifications of zinc powder, the influence of intrinsic geometric properties on electrochemical performance remains underexplored. In this study, the isoperimetric principle is bridged with electrochemical kinetics to establish a design criterion for zinc powder electrodes. The findings demonstrate that maximizing the volume-to-surface ratio of zinc powder minimizes side reactions and improves performance. The effects of different geometric morphologies on anode behavior are systematically investigated, and the underlying electrochemical mechanisms are revealed. Large zinc powder (LZP) exhibits the smallest specific surface area for a given weight, leading to reduced side reactions and enhanced stability. A symmetric cell with the LZP anode achieves over 400 h of cycle life at 1 mA cm⁻², with a low overpotential, significantly outperforming cells with other zinc powders. Additionally, LZP ink shows excellent printability, facilitating the fabrication of wearable electrodes in diverse configurations. This work provides valuable insights into the intrinsic factors that influence zinc powder anodes, enhancing significant potential for wearable devices.