Amorphous Metakaolin Interface Layer with Abundant Oxygen Vacancies Enabling High-Utilization Ah-Level Practical Zinc–Iodine Batteries

The intrinsically safe zinc–iodine (Zn–I2) battery is significantly constrained by the uncontrollable shuttle effect of polyiodide species and the accelerated parasitic reactions occurring on the Zn anode. To address the surface-determined degradation of Zn anode, interfacial modification presents a straightforward and effective mitigation strategy. Herein, we engineer an oxygen-vacancy-rich amorphous metakaolin (KL-Ameta) layer via thermal regulation to protect the Zn anode. This functional layer acts as a robust barrier against the dissolved polyiodides shuttle, blocking polyiodide migration and subsequent Zn anode corrosion. Furthermore, the unique amorphous structure and abundant defect sites of KL-Ameta synergistically homogenize the Zn2+ flux and electric field. Benefiting from the optimized interfacial kinetics, the KL-Ameta@Zn anode exhibits exceptional cycling stability for 1600 h at 5 mA cm–2 in a symmetric cell. Furthermore, the KL-Ameta@Zn||I2@AC full cell delivers an impressive lifespan of 39,800 stable cycles at 5 A g–1 with 96.92% capacity retention. Crucially, practical application is demonstrated in a 450 mAh pouch cell cycled steadily for 155 cycles. Even a 1 Ah pouch cell (9.5 cm × 9 cm) exhibits robust cycling capability under a high Zn anode utilization rate of 66.7%. This amorphous mineral engineering strategy provides a highly viable pathway for developing long-life and practical AZIBs.