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

Abstract

AbstractLow 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.