Realizing High Performance Four‐Electron Zinc‐Iodine Batteries with Acidic Eutectic Electrolyte
Yi Yan, Yucong Jiao, Peiyi Wu
Abstract
Abstract Achieving multi‐electron redox reaction via halide ions and protons is promising for Zn─I 2 batteries, yet their practical application is hindered by halide ion and proton corrosion, sluggish iodine redox kinetics and poor redox reversibility. Here, a deep eutectic solvent (ZPDES) composed with concentrated ZnCl 2 and H 3 PO 4 is engineered as the electrolyte for high performance Zn‐I 2 batteries. The chloride atom (Cl) and active hydrogen of H 3 PO 4 in DES form hydrogen bonds (Cl⋯H─O) to mitigate the corrosion of Cl − and protons. Therefore, while achieving four‐electron transfer by Cl − , the protons in DES can accelerate redox reaction kinetics and reduce I 3 − formation for improved reversibility. Moreover, the proton can promote the (002) texture formation and reduce by‐products on Zn anode. As a result, the Zn─I 2 battery with ZPDES delivers a high specific capacity of 576 mA h g −1 at 0.5 A g −1 after 320 cycles, and maintains a capacity retention of 100% over 20,000 cycles at 7 A g −1 .