High-Performance Zinc–Iodine Batteries Enabled by β-Cyclodextrin Confinement of Iodide Species

Aqueous zinc–iodine (Zn–I 2 ) batteries are promising for energy storage due to their high energy density, safety, and low cost. However, the dissolution and shuttle effect of polyiodides (e.g., I 3 – and I 5 – ) lead to active material loss and zinc anode corrosion, resulting in rapid capacity decay and poor cyclability. Herein, β-cyclodextrin (β-CD) was employed as a cathode to trap iodide species due to its host–guest interactions with various ions. Unlike conventional designs, the active iodine is supplied solely by an I 2 /ZnI 2 catholyte, while the iodine-free β-CD cathode dynamically captures I 2 from the electrolyte via the generation of β-CD-I 2 inclusion complexes. This “solidification” of iodine in the hydrophobic cavity of β-CD disrupts the I 2 /I – /I 3 – equilibrium, significantly reducing the concentration of soluble I 3 – and suppressing the polyiodide shuttle. As a result, the Zn–I 2 battery achieves a high specific capacity of 308.4 mAh g –1 at a current density of 0.2 A g –1, while maintaining nearly 100% Coulombic efficiency and exceptional long-term cycling stability over 10,000 cycles at 5 A g –1 . This work presents an effective electrode–electrolyte design strategy for developing durable and high-performance zinc–iodine batteries.