Bridging Materials and Energy Storage Mechanisms in Zn-I<sub>2</sub> Batteries

Zinc-iodine (Zn-I2) batteries have emerged as a compelling candidate for large-scale energy storage, driven by the growing demand for safe, cost-effective, and sustainable alternatives to conventional systems. Benefiting from the inherent advantages of aqueous electrolytes and zinc metal anodes, including high ionic conductivity, low flammability, natural abundance, and high volumetric capacity, Zn-I2 batteries offer significant potential for grid-level deployment. This review provides a comprehensive overview of recent progress in three critical domains: positive-electrode engineering, zinc anode stabilization, and in situ characterization methods. On the cathode side, anchoring iodine to conductive matrices effectively mitigates polyiodide shuttling and enhances the kinetics of I−/I2 conversion. Advanced in situ characterization has enabled real-time monitoring of polyiodide intermediates (I3−/I5−), offering new insights into electrolyte-electrode interactions and guiding the development of functional additives to suppress shuttle effects. For the zinc anode, innovations such as protective interfacial layers, three-dimensional host frameworks, and targeted electrolyte additives have shown efficacy in suppressing dendrite growth and side reactions, thus improving cycling stability and coulombic efficiency. Despite these advances, challenges remain in achieving long-term reversibility and structural integrity under practical conditions. Future directions include the design of synergistic electrolyte systems, and integrated electrode architectures that simultaneously optimize chemical stability, ion transport and mechanical durability for next-generation Zn-I2 battery technologies.