Facile Polyiodides Conversion Enabled by Facet Engineering for Durable Zinc–Iodine Batteries

Abstract Aqueous zinc–iodine (Zn–I2) batteries are highly promising for grid-scale energy storage, yet their practical viability is severely plagued by the polyiodides shuttle effect and sluggish liquid–solid conversion kinetics, which fundamentally arise from the contradictory energetic demands between soluble intermediate confinement and solid-product desorption. Herein, we rationally construct a dual-facet spinel cobalt oxide to precisely decouple these competing interfacial behaviors. By regulating the proportional exposure of strongly coordinating (100) and weakly coordinating (111) facets, a tailored surface microenvironment is constructed that effectively circumvents the inherent thermodynamic trade-off, breaking the single adsorption limitation intrinsic to uniform catalysts. In situ iodine L3-edge X-ray absorption spectroscopy and three-dimensional synchrotron-based nanocomputed tomography reveal that this specific facet modulation substantially reduces the activation barrier for rate-determining polyiodides oxidation, facilitating spatially uniform solid-iodine deposition. Driven by these structural advantages, the assembled Zn–I2 batteries with c/o-Co3O4 deliver a high specific capacity of 161.1 mAh g–1 at 16 A g–1 and an ultralow capacity decay rate of 0.00055% per cycle after 50,000 cycles at 10 A g–1. Furthermore, the batteries also exhibit a broad operational temperature ranging from −30 to 60 °C, highlighting the strong potential for practical applications. This work provides a perspective on facet engineering for achieving wide-temperature-tolerant aqueous iodine storage.