Polyiodide Confinement by Starch Enables Shuttle-Free Zn-Iodine Batteries

Aqueous Zn-iodine (Zn-I-2) batteries have been regarded as a promising energy-storage system owing to their high energy/power density, safety, and cost-effectiveness. However, the polyiodide shuttling results in serious active mass loss and Zn corrosion, which limits the cycling life of Zn-I-2 batteries. Inspired by the chromogenic reaction between starch and iodine, a structure confinement strategy is proposed to suppress polyiodide shuttling in Zn-I-2 batteries by hiring starch, due to its unique double-helix structure. In situ Raman spectroscopy demonstrates an I-5(-)-dominated I-/I-2 conversion mechanism when using starch. The I-5(-) presents a much stronger bonding with starch than I-3(-), inhibiting the polyiodide shuttling in Zn-I-2 batteries, which is confirmed by in situ ultraviolet-visible spectra. Consequently, a highly reversible Zn-I-2 battery with high Coulombic efficiency (approximate to 100% at 0.2 A g(-1)) and ultralong cycling stability (>50 000 cycles) is realized. Simultaneously, the Zn corrosion triggered by polyiodide is effectively inhibited owing to the desirable shuttling-suppression by the starch, as evidenced by X-ray photoelectron spectroscopy analysis. This work provides a new understanding of the failure mechanism of Zn-I-2 batteries and proposes a cheap but effective strategy to realize high-cyclability Zn-I-2 batteries.

Automated summary

This study proposes a structure confinement strategy using starch to suppress polyiodide shuttling in Zn-I-2 batteries, resulting in a highly reversible and long-cycling Zn-I-2 battery with high Coulombic efficiency. The starch effectively inhibits Zn corrosion triggered by polyiodide, providing a cheap yet effective strategy for high-cyclability Zn-I-2 batteries.