Organic pH Buffer for Dendrite‐Free and Shuttle‐Free Zn‐I2 Batteries

Abstract Aqueous Zn‐Iodine (I 2 ) batteries are attractive for large‐scale energy storage. However, drawbacks include, Zn dendrites, hydrogen evolution reaction (HER), corrosion and, cathode “shuttle” of polyiodines. Here we report a class of N‐containing heterocyclic compounds as organic pH buffers to obviate these. We evidence that addition of pyridine /imidazole regulates electrolyte pH, and inhibits HER and anode corrosion. In addition, pyridine and imidazole preferentially absorb on Zn metal, regulating non‐dendritic Zn plating /stripping, and achieving a high Coulombic efficiency of 99.6 % and long‐term cycling stability of 3200 h at 2 mA cm −2 , 2 mAh cm −2 . It is also confirmed that pyridine inhibits polyiodines shuttling and boosts conversion kinetics for I − /I 2 . As a result, the Zn‐I 2 full battery exhibits long cycle stability of >25 000 cycles and high specific capacity of 105.5 mAh g −1 at 10 A g −1 . We conclude organic pH buffer engineering is practical for dendrite‐free and shuttle‐free Zn‐I 2 batteries.