Activating and Stabilizing a Reversible four Electron Redox Reaction of I−/I+ for Aqueous Zn‐Iodine Battery

We propose an efficient inter-halogen activation strategy together with an interlayer confinement design, which successfully triggers and stabilizes a highly reversible four-electron redox reaction from I⁻ to I⁺ for Zn-Iodine batteries. As a result, the specific capacity, output voltage and cycling performance of zinc-iodide battery are greatly improved.

Abstract

Low capacity and poor cycle stability greatly inhibit the development of zinc-iodine batteries. Herein, a high-performance Zn-iodine battery has been reached by designing and optimizing both electrode and electrolyte. The Br⁻ is introduced as the activator to trigger I⁺, and coupled with I⁺ forming interhalogen to stabilize I⁺ to achieve a four-electron reaction, which greatly promotes the capacity. And the Ni−Fe−I LDH nanoflowers serve as the confinement host to enable the reactions of I⁻/I⁺ occurring in the layer due to the spacious and stable interlayer spacing of Ni−Fe−I LDH, which effectively suppresses the iodine-species shuttle ensuring high cycling stability. As a result, the electrochemical performance is greatly enhanced, especially in specific capacity (as high as 350 mAh g⁻¹ at 1 A g⁻¹ far higher than two-electron transfer Zn-iodine batteries) and cycling performance (94.6 % capacity retention after 10000 cycles). This strategy provides a new way to realize high capacity and long-term stability of Zn-iodine batteries.

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