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

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 served 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.