Development of a Stable Electrolyte for Dendrite Suppression and High‐Performance Zn–I ₂ Redox Flow Battery

ABSTRACT The zinc–iodide redox flow battery has gained importance due to its low cost, non‐corrosive nature, high solubility, high energy density, and high redox potential. However, low iodine utilization, the shuttle effect, Zn dendrite growth, and dead Zn formation at the anode, as well as imbalanced reaction kinetics, prevent it from achieving long‐term cycling stability. To address these issues, this work improves the performance of the Zn–I ₂ flow cell by adopting the safe, low‐cost bifunctional ammonium chloride as a neutral supporting electrolyte. NH ₄ Cl helps reduce I ₂ precipitation and polyiodide formation by forming an I ₂ Cl ⁻ complex. On the anolyte side, the electrolytes reduce the dendrite formation and increases stability. The ammonium chloride supporting electrolyte added on both sides, KI + NH ₄ Cl (catholyte) || ZnCl ₂ + NH ₄ Cl (anolyte) has shown promising stability over 1000 cycles at a current density of 30 mA cm ⁻² , with a coulombic efficiency (CE) and energy efficiency of 93.83% and ~75%, further the flow cell also delivered a maximum power density of 74.8 mW cm ⁻² , which is far better than the bare KI (catholyte) and ZnCl ₂ (anolyte) electrolyte‐based flow cell.