Aqueous Electrolyte With Weak Hydrogen Bonds for Four‐Electron Zinc–Iodine Battery Operates in a Wide Temperature Range
Tingting Liu, Chengjun Lei, Huijian Wang, Jinye Li, Pengjie Jiang, Xin He, Xiao Liang
Abstract
Abstract In the pursuit of high‐performance energy storage systems, four‐electron zinc–iodine aqueous batteries (4eZIBs) with successive I − /I 2 /I + redox couples are appealing for their potential to deliver high energy density and resource abundance. However, susceptibility of positive valence I + to hydrolysis and instability of Zn plating/stripping in conventional aqueous electrolyte pose significant challenges. In response, polyethylene glycol (PEG 200) is introduced as co‐solvent in 2 m ZnCl 2 aqueous solution to design a wide temperature electrolyte. Through a comprehensive investigation combining spectroscopic characterizations and theoretical simulations, it is elucidated that PEG disrupts the intrinsic strong H‐bonds of water by global weak PEG–H 2 O interaction, which strengthens the O─H covalent bond of water and intensifies the coordination with Zn 2+ . This synergistic effect substantially reduces water activity to restrain the I + hydrolysis, facilitating I − /I 2 /I + redox kinetics, mitigating I 3 − formation and smoothening Zn deposition. The 4eZIBs in the optimized hybrid electrolyte not only deliver superior cyclability with a low fading rate of 0.0009% per cycle over 20 000 cycles and a close‐to‐unit coulombic efficiency but also exhibit stable performance in a wide temperature range from 40 °C to −40 °C. This study offers valuable insights into the rational design of electrolytes for 4eZIBs.