Integrated Electrode-to-Device Design via Combination of Grain Boundary Reconstruction and Dynamic Gas Management Toward Stable 3 Ah Aqueous Zinc-Iodine Pouch Cells.

Abstract

The substantial electrochemical performance gap between Ah-level pouch cells and laboratory-scale coin cells remains a critical bottleneck hindering the practical application of aqueous Zn-I₂ batteries. Herein, Zn anode degradation and cell-level gas accumulation, exacerbated under large-area-electrode conditions, are systematically identified as dominant failure mechanisms in high-capacity Zn-I₂ pouch cells. Accordingly, an integrated electrode-to-device strategy is proposed, combining Zn grain-boundary reconstruction with dynamic gas management. The intrinsically nonuniform grain boundary distribution in commercial zinc foil is confirmed to induce stripping heterogeneity and subsequent dendrite growth, while persistent H₂ evolution leads to cell swelling and electrolyte leakage, ultimately resulting in accelerated capacity fading. At the electrode level, a scalable electrodeposition strategy yields current-collector-integrated zinc anodes with refined grains and homogenized boundaries, effectively mitigating initial stripping heterogeneity and enhancing zinc utilization. At the device level, a selective H₂-expulsion window (LaNi-based hydrogen storage alloy nanoparticles embedded in a hydrophobic PTFE matrix) is integrated into the aluminum-plastic packaging, enabling efficient H₂ removal while blocking water vapor to maintain electrolyte stability. Leveraging this design, multilayer-stacked Zn-I₂ pouch cells with >3 Ah capacity and an ultra-low N/P ratio of 1.18 achieve over 600 stable cycles. This work offers a scalable, system-level solution toward practical aqueous Zn-based pouch cells.