The redox couple of I⁰/I⁻ in aqueous rechargeable iodine–zinc (I₂-Zn) batteries is a promising energy storage resource since it is safe and cost-effective, and provides steady output voltage. However, the cycle life and efficiency of these batteries remain unsatisfactory due to the uncontrolled shuttling of polyiodide (I₃⁻ and I₅⁻) and side reactions on the Zn anode. Starch is a very low-cost and widely sourced food used daily around the world. “Starch turns blue when it encounters iodine” is a classic chemical reaction, which results from the unique structure of the helix starch molecule–iodine complex. Inspired by this, we employ starch to confine the shuttling of polyiodide, and thus, the I⁰/I⁻ conversion efficiency of an I₂-Zn battery is clearly enhanced. According to the detailed characterizations and theoretical DFT calculation results, the enhancement of I⁰/I⁻ conversion efficiency is mainly originated from the strong bonding between the charged products of I₃⁻ and I₅⁻ and the rich hydroxyl groups in starch. This work provides inspiration for the rational design of high-performance and low-cost I₂-Zn in AZIBs.