Aqueous Electrolyte With Weak Hydrogen Bonds for Four‐Electron Zinc–Iodine Battery Operates in a Wide Temperature Range

Abstract

AbstractIn the pursuit of high‐performance energy storage systems, four‐electron zinc–iodine aqueous batteries (4eZIBs) with successive I−/I2/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 ZnCl2 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–H2O interaction, which strengthens the O─H covalent bond of water and intensifies the coordination with Zn2+. This synergistic effect substantially reduces water activity to restrain the I+ hydrolysis, facilitating I−/I2/I+ redox kinetics, mitigating I3− 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.